U.S. DEPARTMENT OF AGRICULTURE
CONTENTS

ECONOMICS

SUGAR MAPLES

THE SUGAR GROVE

Sap yields

Summary

TAPPING THE TREE

Date of tapping

Selection of trees

Boring the taphole

Life of a taphole

Summary

SPOUTS AND BUCKETS

Sap spouts

Rainguards

Sap buckets

Summary

GATHERING THE SAP

Collecting tanks

Pipelines

Storage tanks

Summary

THE EVAPORATOR HOUSE

Location of building

Function of the evaporator house

Requirements of the evaporator house

Design of the evaporator house

Steam ventilation

Location of the evaporator

Air supply

Sirup processing room

Wood storage

Storage tanks

Summary

THE EVAPORATOR AND ITS FUNCTION

Design

Rule of 86

Changes in sap during its evaporation to sirup.

The evaporation time

Liquid level in the evaporator

Rates of evaporation

Summary

OPERATING THE EVAPORATOR

Starting the evaporator

Drawing off the sirup

Automatic drawofif valve

Finishing pan

Completion of run of sap

Cleaning the evaporator _'

Summary

OTHER TYPES OF EVAPORATORS

Steam evaporator

Vacuum evaporator

High-speed tube-type evaporator

Summary

FUEL

Wood

Oil

Summary

MAPLE SIRUP

Composition of sap and sirup

Color and flavor

Factors controlling color and flavor

Rules of sirupmaking

Grades of sirup

Summary

CONTROL OF FINISHED SIRUP

Viscosity of maple sirup

Old standards of finished sirup

Use of precision instruments

Elevation of the boiling point

Special thermometers

Hydrometers

Summary

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CLARIFICATION OF SIRUP 29

Sugar sand 29

Sedimentation 29

Filtration 29

Flat filters 30

Summary 30

STANDARDS FOR MAPLE SIRUP 31

For retail sale 31

United States standards for table maple sirup.. 31

Summary 32

CHECKING AND ADJUSTING THE DENSITY

OF SIRUP 32

Weight method 32

Refractometry method 32

Hydrometry method 32

The Brix scale 33

The Baume scale 33

Making the density measurement 33

Correcting for temperature 34

Adjusting the density of the sirup 36

Alligation (Pearson's square) 36

Summary 36

GRADING THE SIRUP BY COLOR 37

Color standards 37

U.S. color comparator 37

Use of the color comparator 37

Summary 38

PACKAGING 38

Stack burn 38

Control of micro-organisms 38

Size and type of package 38

Summary 39

MAPLE SUGAR 39

The equipment 39

The chemistry of maple sugar 39

Formation of crystal sugar 40

Invert sugar 40

Doctor 40

Summary 40

MAPLE CREAM OR BUTTER 41

Sirup for creaming 41

Invert-sugar content 41

Cooking and cooling 41

Creaming 42

Holding cream for delayed packaging 42

Packaging and storing maple cream 42

Summary 42

SOFT-SUGAR CANDIES 42

Cooking, cooling, and stirring 43

The bob 43

Crystal coating of candies 43

Packaging candies 44

Summary 44

MAPLE SPREAD 44

Summary 45

HIGH-FLAVORED MAPLE SIRUP 45

Atmospheric process 45

Pressure-cooking process 46

Uses of high-flavored sirup 46

Summary 47

CRYSTALLINE HONEY-MAPLE SPREAD 47

Summary 47

OTHER MAPLE CONFECTIONS 47

Rock candy 47

Hard sugar 48

Granulated or stirred sugar 48

Maple on snow 48

Summary 48

TESTING MAPLE SIRUP FOR INVERT SUGAR. 48

Preparing the sirup-and-water dilutions 49

Testing for color 49

Interpreting the color test 50

The simplified test 50

Summary 50

LITERATURE CITED 50

SUPPLEMENTAL READING 52
MAPLE-SIRUP PRODUCERS MANUAL

By C. O. Willits,

Eastern Utilization Research and Development Division,

Agricultural Research Service

No one knows who first discovered how to make

sirup and sugar from the sap of the maple tree.

Both products were well established items of barter among the Indians living in the area of the

Great Lakes and the St. Lawrence River, even

before the arrival of the white man (ü, S7) .^ ^

The maple crop has three claims to distinction :

(1) It is one of our oldest agricultural commodities; (2) it is one of the few crops whose production is solely American; and (3) it is the only

crop that must be processed on the farm before it

is in suitable form for sale.

Although maple-sirup production is recognized

as one of our oldest industries, relatively little

scientific work has been done to improve it. The

sap has been collected and converted to sirup in

much the same way since the development of atmospheric evaporation equipment about 1900.

This equipment was developed by Yankee ingenuity, not engineering studies. Today, a strong

research program dealing with the different

phases of maple-sirup production is being conducted by the Eastern Utilization Research and

Development Division of the united States Department of Agriculture and by the experiment

stations and agricultural colleges of Michigan,

New Hampshire, New York, Ohio, and Vermont.

As a result of this research a noticeable change

is occurring in the maple-sirup industry, and this

will be described throughout this handbook.

Maple sirup is a woodland crop. The trees

grow ibest at altitudes of 600 feet and above ; therefore, maple sirup is usually produced in the hilly

country. Its production is a vital part of the local

economy in dozens of communities from Maine

westward into Minnesota, and south to Indiana

and West Virginia (chart 1). The same type and

quality of maple products are produced throughout the area.

Annual production of maple sirup, like other

crops, is subject to yearly fluctuations caused by

climatic and economic conditions. Production in

the past has been affected by the cost or supply of

white sugar and by the supply of farm labor. In

1860, a record crop of 4,132,000 gallons of maple

sirup was produced. For the next decade the pribe

of cane sugar declined and so did production of

maple sirup, reaching a low of 921,000 gallons in

1869. As cane sugar became scarce during World

War I, production of maple sirup again rose,

slightly exceeding the 1860 record. An increase

occurred also during World War II. Since then,

there has been a decrease in production (table 1)

(4^,4?').

^ Also communication from J. A. Mason, the University

Museum, University of Pennsylvania.

^ Italic numbers in parentheses refer to Literature

Cited, p. 50. Chart 1.—A, Range of commercial production of maple sirup;

B, range of hard maple trees.
TABLE 1.—Production of maple sugar and sirup^ trees tapped^ average price received hy farmers^ and

imports^ selected years^ 1918-5Jt.

Trees

tapped

Production Price Imports for

consumption

Sugar Sirup

Total

product

in terms

of sugar 1

Average total production per tree

Per

pound

of

sugar

Per

gallon

of

sirup

Year

Sugar 2 Sirup ^

As sugar ^ As sirup 1

1918

Thousand

trees

17, 053

15, 198

13, 948

13, 158

12, 099

11,380

10, 046

8,257

8, 146

6,786

Thousand

pounds

11,383

5,227

3,585

2, 134

1,044

705

560

310

257

168

Thousand

gallons

4,141

3,370

3,504

3,712

2,444

2,770

2,987

1,351

2,024

1,730

Thousand

pounds

44, 511

32, 187

31,617

31, 830

20, 596

22, 865

24, 456

11, 118

16, 449

14, 014

Pounds

2.61

2. 12

2. 27

2.42

1.70

2.01

2.43

1.35

2.02

2.07

Gallons

0.33

.26

.28

.30

.21

.25

.30

. 17

.25

.26

Cents Dollars

Thousand

pounds

3,807

3,201

3,446

9,735

2,976

3,946

7, 121

4,207

6,549

6,643

Thousand

pounds

1922 _ _ * 1

1926 29.3

30.2

24.9

28. 4

37.7

65.5

77.8

85. 1

2. 12

2.03

1.33

1.61

2.26

3.30

4. 13

4.66

203

1930 _ _ 1,575

1934 1,316

1938 39

1942 4,791

1946 2,221

1950 5,282

19545 4,096

1 Assuming that 1 gallon of sirup is equivalent to 8 pounds of sugar.

2 Includes maple sirup through Sept. 21, 1922.

3 A gallon of sirup weighs about 11 pounds.

^ Included with maple sugar through Sept. 21, 1922.

5 Preliminary.

Agricultural Statistics, 1952 and 1955 (46y 47).

The decreased production since World War II

is not necessarily a trend. Rather it is a reflection

of the shortage of farm labor during this period.

Although the downward trend tends to exist in

the country as a whole, production of maple sirup

in Minnesota, Wisconsin, and Michigan has shown

a definite increase. In fact, based on the number

of tappable trees, production in these States could

exceed production in New York and the Northeastern States. For example, Michigan has onefifth of the total stand of maple trees.

Current surveys in the eastern maple-producing areas (47) ^ of the number of maple trees that

are tapped as well as the total number that are of

®Also unpublished estimates for 1948-52 of the Northeastern Forest Experiment Station (Ü. S. Forest Service),

Upper Darby, Pa.

TABLE 2.—Number of tappable maple trees^ and

number and percentage tapped^ Eastern States^

1951

State Tappable

trees ^

Tapped trees

Maine _

Number

53, 553, 000

1, 660, 000

11,913,000

12, 103, 000

73, 128, 000

33,553,000

25, 840, 000

13, 031, 000

Number

136, 000

28, 000

166, 000

261, 000

1,960,000

422, 000

3, 118,000

Percent

0.25

Maryland _ _ 1.7

Massachusetts

New Hampshire

New York_

1.4

2.2

2.7

Pennsylvania _ 1.3

Vermont- _ - - 12. 1

West Virginia

1 Larger than 10 inches d. b. h.

TABLE I>.—Rank• of States in production o/ maple sugar^ selected years^ 1916-5Jf.

Rank 1916 1921 1926 1931 1936 1941 1946 1951 1953 1954

1

2

N. Y.

Vt.

Ohio

Pa.

N. H.

Mich.

Wis.

Mass.

Maine

Md.

Vt.

N. Y.

Ohio

Mich.

N. H.

Pa.

Wis.

Mass.

Maine

Md.

N. Y.

Vt.

Ohio

Pa.

Mich.

N. H.

Mass.

Wis.

Maine

Md.

Vt.

N. Y.

Ohio

Pa.

Mich.

Wis.

N. H.

Mass.

Md.

Maine

Vt.

N. Y.

Ohio

Pa.

Mich.

Wis.

N. H.

Mass.

Md.

Maine

Vt.

N. Y.

Ohio

Pa.

Mich.

Mass.

N. H.

Wis.

Maine

Md.

Vt..

N. Y.

Ohio

Mich.

Pa.

N. H.

Mass.

Wis.

Maine

Md.

Vt.

N. Y.

Pa.

Mich.

Mass.

N. H.

Wis.

Maine

Md.

Ohio

Minn.

Vt.

N. Y.

Ohio

Pa.

Wis.

Mich.

N. H.

Mass.

Minn.

Md.

Maine

Vt.

N. Y.

3 __ _ _ Pa.

4___ Mich.

5

6

Ohio

N. H.

7 _____ Wis.

8--_ Mass.

9__ Maine

10 - - _ Md.

11 Minn.
tappable size show that the industry is not suffering from too few trees. Although many sugar

maples have been cut for lumber, vast stands still

exist and these can supply our maple-sirup needs.

Table 2 shows the number of maple trees of tappable size and the percentage that were tapped in

1951.

Table 3 shows the production of maple sirup by

the 11 principal States for selected years, 1916-54.

The chief functions of these associations are to

maintain adequate supplies, to promote sales, and

to maintain the quality of the products. A number of communities hold annual festivals to stimulate interest in maple products.

Also, the different States, in cooperation with

the Agricultural Eesearch Service and the Extension Service of the United States Department

of Agriculture, have set up a strong extension

program. This program has done much to bring

the results of research directly to maple producers. In New York, which has taken a lead

in this adult education program, it is not uncommon for more than a thousand producers to

attend the "maple sirup" schools held annually

throughout the State in the premaple season.

ECONOMICS

The maple season is short and comes in the

early spring when most other farm activities are

slowest, so it does not compete with them. Maple

sirup can be considered a byproduct of the farm.

However, surveys in New York {2, Ji)^ Ohio {18)^

Michigan (^^), and Wisconsin (^) have shown

that production of maple sirup is one of the farmer's most profitable enterprises, paying him as

much as $3 per hour for every hour spent, including time spent in cleaning the equipment and

collecting and boiling the sap.

Modernization of equipment has done much to

increase profits in maple-sirup production. This

includes the use of flue-type evaporators, oil as

fuel, mechanical tapping tools, and instruments

for judging finished sirup. All these tend to reduce labor costs and contribute to the production

of better grades of sirup that have a correspondingly greater value. Fixed costs, which normally

represent about 35 percent of the total, may lower

net income in groves where fewer than 500 buckets are hung.

The sirup can be sold immediately and so produce a ready source of cash, or it can be held for

a more favorable market or to supply raw material for production of other more profitable maple

products. If the sirup is held, it can be used as

collateral for short-term loans.

Since 1940 the proportion of the maple sirup

produced in the United States that has been sold

directly to the consumer by the producer has increased. This in many instances has resulted in

increased returns for him. To stabilize this expanded outlet, the producer has improved the

appearance of the package and the quality of the

sirup so that it meets State and Federal specifications. Many producers are converting their

sirup to confections such as "maple cream," pralines, and soft-sugar candies, which result in even

larger returns. Maple-sirup producers have

formed associations so they can pool their stocks.

SUGAR MAPLES

Only 2 of the 13 species of maples {Acer) native

to the United States are of importance in the production of sirup because of the sweetness (sugar

content) of their sap {3^ 13^ 46).

Acer saccharum Marsh, (better known as

sugar maple, hard maple, rock maple, or sugar

tree) furnishes three-fourths of all sap used in

the production of maple sirup. Although this

tree grows throughout the maple-producing areas

(Chart 1, A and B) the largest numbers are in

the Lake States and the Northeast. The tree

grows singly and in groups in mixed stands of

hardwoods. The trunk of a mature tree may be

30 to 40 inches in diameter. It is a prolific seeder

and endures shade well, but unfortunately it does

not grow rapidly. The tree is best distinguished

by its leaf (chart 2).

Acer nigrum Michx. F. (black sugar maple,

hard maple, or sugar maple) grows over a smaller

range than J.. saccharum. It does not grow as far

north or south, but it is more abundant in the

western part of its range. This tree is similar to

A, saccharum in both sap production and appearance. Its principal distinguishing feature is

the large drooping leaf of midsummer (chart 2).

Other species of maples commonly found in our

hardwood forests are the red maple {Acer rubrwn

L.) and the silver maple {A, saccharinum L.).

These trees, readily identified by their leaves

(chart 2), are not good sources of maple sirup

because their sap is less sweet and often contains

excessive amounts of sugar sand. The red maple,

the more common of the two, is easily identified

in the spring by the red color of its buds.
BLACK MAPLE SUGAR MAPLE

RED MAPLE SILVER MAPLE

Chart 2.—Leaves of the sugar maple (Acer saccfiorum Marsh.), red mapie U. rubrum U, silver maple iA. saccharînum U, and black maple

{A, nigrum Michx. F.).

but the cost of labor for collecting sap increases.

Figures 1 and 2 show a maple grove (bush)

with the large full crowns that are so important

to the production of large amounts of sweet sap.

For maximum returns, the grove should contain at least 500 trees of tappable size, that is,

10 inches in diameter at breast height (d. b. h.).

Groves with fewer than 10 maple trees per acre

are not profitable; 25 to 30 trees to the acre

is ideal (19).

Maples grown in the open, for example, along

the roadside (fig. 3), have large crowns and are

excellent sap producers (20). Because of their

shorter boles, roadside trees do not make as good

saw logs as trees that grow under crowded conditions. However, trees in a crowded stand have

smaller crowns and consequently they are not

good sap producers (figs. 4 and 5).

The ideal sugar grove requires not only a

planned spacing of the trees but also a good understory to protect the ground, keep it moist,

and permit the growth of seedling maples to reTHE SUGAR GROVE

Most maple-sugar groves, often called sugar

bushes, are parts of stands of old hardwood forests. In the ideal sugar grove most of the other

trees have been cut out and the maples have

been thinned sufficiently to allow the trees to develop a good crown growth. This should be done

according to a carefully planned program, with

the assistance of the State extension forester and

the State forester for the area. If the stand is

made up entirely of maples, approximately the

same volume of sap is produced per acre refardless of the size of the trees (21). As the numer of trees per acre increases, the size of the

crowns and boles and the yield per tree decreases.
place trees that have matured and can be cut for

lumber (figs. 6 and 7).

Sap Yields

The yield of sap in a sugar bush should be

expressed in terms of the number of tapholes

rather than the number of trees. The yield per

hole is independent of the number of holes per

tree and ranges from 5 to 15 gallons. It is not

uncommon for a taphole to produce from 40 to 80

gallons of sap and as much as 3 quarts of sirup

in a single year. The sugar content of the sap

produced by the different trees in a grove varies

considerably. The sap produced by the average ]

tree has a sugar content of 2° to 3"^ Brix.^ Fre- /

quently trees produce sap with a sugar content '

of less than 1° Brix, and occasionally a tree

produces sap with as much as 9° or even 11°

Brix.

The yield and sweetness of the sap produced

by a tree varies from year to year, but trees that

produce sap with a high sugar content and trees

that produce sap with a low sugar content maintain their relative positions from year to year.

It is important to know the exact sugar content

of the sap produced by each tree. Those trees

that produce sap low in sugar (1 percent or less)

should be culled. It is not difficult to measure

the sugar content of sap. All that is needed is

a sap hydrometer and a thermometer. These can

be bought from any maple-sirup equipment

house.

To make the reading, float the hydrometer in

the sap bucket (fig. 8) or in a hydrometer can

containing the sap (fig. 9). There should be no

ice in the sap. The temperature of the sap must

also be obtained so the hydrometer reading can

be corrected. Subtract 0.4° Brix for temperatures of 32° to 50° F., 0.3° Brix for temperatures

of 51° to 59° F., and 0.1° Brix for temperatures

of 60° to 68° F.

The hydrometer is usually calibrated from 0°

to 10° Brix, with divisions of 0.5°. A more accurate measurement can be obtained by using a

hydrometer with divisions of 0.1° (fig. 9), with

a refractometer, or by a quantitative chemical

analysis.

A taphole that produces 15 gallons of sap with

a sugar content of 2° Brix will yield 2.5 pounds

of sugar or one-third of a gallon of sirup, whereas a taphole that produces 15 gallons of sap with

a sugar content of 1° Brix will yield only 1.3

pounds of sugar, or less than one-fifth of a gallon

of sirup. The cost of producing the sirup from

both tapholes will be approximately the same.

^ The density of sap and sirup is due to a mixture of

dissolved solids and not just sugar. The physical instruments used to measure the density of sap and sirup

do not distinguish between the density due to sugar

and that due to other solids. The degrees Brix (° Brix)

means that the solution has the same density as a solution containing a percentage of sugar numerically equal

to the Brix value.

Trees producing sap with a sugar content of 10

percent would be especially profitable, as 15 gallons from 1 taphole will yield nearly 1% gallons

of sirup.

Eesearch is being conducted at the Universities

of Vermont and New Hampshire on the propagation of maple trees from selected high-yielding

trees (7). This research should eventually make

possible the setting out of maple orchards or

roadside trees that will produce sap with a high

sugar content.

Summary

1. Consult your State extension forester, farm

forester, and county agricultural agent and

work with them to develop a management plan

for your sugar grove. This plan should include

removing defective, diseased, and weed trees to

obtain maximum growth and sap production

from crop trees.

TAPPING THE TREE

The sap of the sugar maple, from which sirup

and sugar are made, appears to be different from

the circulatory sap of a growing tree. We know

little concerning this sap, or sweet water as it is

called in western Pennsylvania. Intensive study

of maple sap, being conducted at the University

of Vermont, should lead to a better understanding

of its nature, function, and source (Í4? J¿) • Maple trees will produce flows of sap any time

from late fall after they have losttheir leaves until

well into the spring, each time a period of freezing

is followed by a period of thawing. The sap will

now from a wound in the sapwood, whether the

wound is from a hole bored in the tree or from a

broken twig.

Date of Tapping

To establish a rule of thumb that can be used

to set the date when sugar maples should be tapped

is not a simple matter. The date should be early

enough to assure the collection of large early flows

of sap but not so early that only a small flow occurs followed by a long period of no flow. Michigan and New York provide sugarmakers with

radio weather forecasts of the correct tapping

dates {9)j and a similar service is being set up in

other maple-producing States including Massachusetts, Wisconsin, and Vermont. Generally,

trees should not be tapped according to a calendar

date. For example, in 1953 when this practice was

followed, many producers failed to collect the
early and largest flow of sap. In many instances

a third of the crop waslost.

The best plan is to watch the weather maps, beginning about the first or middle of February.

When the map shows a warm front moving across

the country from West to East, which will cause

the temperature to climb from below freezing at

night to 40° or 50° F. in the daytime for a period

of 2 or 3 days, the trees in a particular area should

be tapped before the warm front reaches that area.

In 1954, favorable weather occurred in most sections of the country about February 18,19, and 20,

whereas records show thatthe normal tapping date

for most areas is after the middle of March. To

take full advantage of these early flow periods the

sirup maker must be prepared. The trees must

be selected, all of the equipment must be clean,

sterile, and in order, and the evaporator house

must be ready to put into operation on 1 or 2 days'

notice.

Selection of Trees

The selection of the trees for tapping is of

greatest importance and can be done at any time

throughout the year. Culling low-yielding trees

must be done during the period of sap flow {19),

Trees selected for tapping should measure 10

inches or more in diameter 4i/^ feet above the

ground (10 inches d. b. h.) (fig. 10).

A good rule (^, 19) for determining the number

of tapholes that can safely be made in a single

tree is as follows :

Tapholes

Diameter of tree, per tree^

inches niimher

Less than 10 0

10 to 14 1

15 to 19 2

20 to 24 3

25 or more 4

* Number of buckets.

To undertap a tree reduces the potential size

of the crop without any benefit to the tree. On the

other hand, to overtap (fig. 11) may result in

serious damage to the tree. The extent of such

damage is the subject of a study being conducted

at Michigan State University.

Once the trees have been measured, it is well to

mark them so they will not have to be remeasured

each succeeding season. This can be done by painting a numeral or a series of dots on the tree or by

using paints of different colors, such as white for

1 taphole, yellow for 2 tapholes, etc.

Boring the Taphole

The taphole is made by boring with either a

%-inch or %6-inch fast-cutting wood bit. This

can be done either by hand, with a carpenter's

brace or breast drill, or with a motorized tool.

The brace (fig. 12) is slower than the breast drill

but less fatiguing. Some prefer the faster acting

machinist's drill (fig. 13).

For large operations, where the additional expense justifies its cost, a portable motor-driven

drill (fig. 14) not only speeds up the operation

but is far less fatiguing.

With a motorized tapping outfit one man can

drill holes as rapidly as a crew of three can set

the spouts and hang the buckets or bags. The development of this tool is one of the outstanding

mechanizations that have occurred in the indusThe hole is bored straight into the tree (preferably perpendicular to the tree) to a depth of 3

inches or until stained wood is reached. Studies

at Michigan State university have shown that a

taphole 3 inches deep (fig. 15) will produce up

to 25 percent more sap than a taphole only 2 inches

deep.

The position of the first taphole is selected

arbitrarily. The hole should be 2 or 3 feet above

the ground, or if there is snow on the ground, as

close as possible to this height. This low position is particularly well suited to the use of the

plastic bag. The compass location of the hole

is not important. Data obtained in New York

{4^3) and in Michigan ® have shown that the total

yield per season is essentially the same regardless of the compass location of the hole. Data

also show that the distance above ground level

has little effect on yield. The best practice is to

make the new hole on successive years 6 to 8

inches from the previous year's taphole, working up the tree in a spiral pattern until the hole

is at breast height (fig. 16). With this procedure, the producer may tap his tree year after

year in different quadrants and avoid striking

an old taphole or dead tissue that has been hidden

by new bark, either of which would result in a

smaller flow and poorer quality sap.

The time required for new bark to grow over

a taphole depends on the health and vigor of the

tree. It is not uncommon to find the hole nearly

covered in a year, as shown in figure 17. The

hole itself remains open, but fungus growth {S9)

that may occur in the new hole stains the wood

several inches above and below the hole and an

inch or less to the sides, as shown in figure 18

(cross section of a maple log) and in figure 19

(longitudinal split of a log).

Life of a Taphole

A taphole should be usable from the time it is

bored until the buds begin to swell and the sirup

acquires an unpalatable or buddy flavor. In

practice, this is seldom the case. Instead, the

taphole usually "dries up" within 3 or 4 weeks

after the hole is bored. This drying up is caused

by growth of micro-organisms in the taphole

rather than by air-drying of the wood tissue.

5 BOBBINS, P. W. POSITION OF TAPPING AND OTHER FACTORS AFFECTING THE FLOW OF MAPLE SAP. 1948. [UnpubUshed master's thesis. Copy on file in Library, Mich.

State Univ., East Lansing.]
When the microbial growth has reached a count

of 1 million per cubic centimeter, sap will no

>. longer flow from the hole, and it is said to be

dried up i(2If).

V In the past, a dried-up taphole was reamed to

cause it to flow again, for it was assumed that

^ ^ this procedure would remove the air-dried wood

tissue. Reaming was never successful and this

can be readily explained. Research has shown

.^ that the reaming bit did not sterilize the hole.

Only a layer of the microbial deposit was re-

>. moved, with the result that the remaining bacteria kept on growing and soon sufficient numbers

^ ^ were again produced to stop sap flow. Investigations being conducted at Michigan State University on the problem of taphole infection may

lead to ways by which the taphole can be maintained in a sterile condition throughout the sap

^ season. Until such information is available the

best practice is to keep the sap-collecting equip-

•- y ment sterile and clean.

'^ Summary

^ 1. Don't tap by the calendar. Follow your State's

^ maple weather reports.

2. Make 1 taphole in a tree 10 inches in diameter,

-m and 1 additional hole for each additional 5

inches of the tree's diameter.

8. Make the taphole with a %-inch or %ß-inch

fast-cutting (special) wood bit.

^ 4. Bore the hole straight into the tree to a depth

of 3 inches.

^ 5. The location of the taphole in respect to comy pass position and roots is unimportant.

6. Space the holes at least 6 inches apart (circum-

< ference of tree) and in a spiral pattern.

7. Use a power tapper if the grove is large

enough to justify the expense.

SPOUTS AND BUCKETS

^ Sap Spouts

The spout or spile has three important functions : (1) It conveys the sap from the taphole to

r a container; (2) it serves as a support on which

to hang the sap bucket or bag; (3) it keeps adventitious (wild or stray) bacteria from gaining

access to the moist taphole, which should reduce

^ infection.

Over the years a large number of sap spouts

have been designed and used, with special features

^. claimed for each. The earliest spouts were hollow

reeds, often a foot or more in length. Two reeds

inserted in adjacent tapholes carried the sap to

the same container (fig. 20).

There are only a few basic differences in the

design of the various sap spouts or spiles. Some

have a large opening at the delivery end. Others

have a hook to support the bucket and a hole for

attaching the bucket cover. On others the bucket

is supported directly on the spout. A few spouts

are shown in figure 21. All spouts have a tapered

shoulder so that when they are driven into position in the taphole, they form a watertight seal

with the bark and outer sapwood but leave a free

space between the sapwood and the spout (fig.

15). In setting the spout (fig. 22) care must be

exercised not to split the tree at the top and bottom of the taphole. Such a split results in leakage of the sap and often causes complete loss of

sap from that hole.

Rainguards

Heavy rains often occur during the sap season.

Rainwater picks up dirt and leaches tannins from

the bark. Both the dirt and the tannins, if permitted to get into the sap bucket, will lower the

grade of the sirup produced. Most sap spouts are

provided with "drip tips" to deflect runoff rainwater from the tree and prevent it from entering

the bucket. In heavy downpours, drip tips are

often inadequate. Use of a simple, homemade

rubber rainguard (fig. 23) will make it impossible

for the heaviest runoff rainwater to enter either

a sap bucket or bag.

To make a rainguard, cut a 2-inch square from

a thin sheet of rubber, such as an old inner tube.

Cut a %6-inch hole in the center of the square with

a leather punch. Slip the rainguard over the end

of the spout near the tree and set it far enough

forward so that when the spout is seated in the

taphole there will be a free space of i/4 to % inch

between the rubber guard and the bark of the tree.

Sap Buckets

Three different types of containers have been

used to collect the sap from the spout: (1) The

wooden bucket, (2) the metal bucket, and (3) the

plastic bag. The wooden bucket, because of its

size and the care required to keep it watertight,

has largely disappeared from use. Zinc-coated

metal buckets of 15-quart capacity are the most

commonly used. Lead-coated metal (terneplate)

or lead-soldered buckets or buckets painted with a

lead paint should not be used because the lead may

be dissolved by the sap, and the sirup may contain

illegal amounts of lead. Aluminum buckets, use

of which is being subsidized in Canada, tend to

eliminate most of the objections to metal buckets.

All buckets should be provided with a cover to

keep out rain and falling debris. Covers are of

two general types: (1) Those that are attached to

the spout (fig. 24), and (2) those that are clamped

to the bucket (fig. 25).
The plastic sap bag (fig. 26), a recent development, is too new to be fully evaluated. Some of

its advantages and disadvantages are as follows :

Advantages: (1) Because of their small bulk,

they require minimum storage space, and they are

easily transported to the woods and hung. (2)

The bags have an adequate self-cover. (3)

Emptying the sap is a one-handed operation (fig.

27). The bags need not be removed from the

spout; they can be rotated on the spout. (4) Because the plastic bags are transparent to sunlight

radiation, which is lethal to micro-organisms (fig.

28), they tend to keep the sap sterile {23),

Sterile sap contributes to the production of highquality sirup.

Disadvantages: (1) The bags have not been in

use long enough to establish their life expectancy.

(2) The capacity of the bag may be inadequate

for a day's run. (3) The bags are subject to damage by rodents. (4) Washing and rinsing the

bags may be a problem.

Summary

1. Any of the commercially available spouts are

satisfactory.

2. Use only clean, sterile spouts.

3. Drive the spout into the taphole with a firm

enough blow to seat it securely, but do not drive

it so far as to cause a split in the bark and wood.

4. Use a 2- X 2-inch rubber runoff rainguard on

the spout.

5. Do not use buckets coated with lead paint or

with terneplate.

6. Use a bucket that will hold a normal day's run

of sap.

7. Use only covered sap buckets or bags.

GATHERING THE SAP

Gathering the sap (fig. 29) is the most expensive and laborious of all maple-sirupmaking

operations. Sap collection is handwork and accounts for one-third or more of the cost of sirup

production.

Much time can be saved if the trees on both

sides of a roadway that are to be serviced from

that roadway bear a distinguishing mark and

the trees to be serviced from an adjacent roadway bear another mark. This prevents visiting

the same tree from both roadways. Different

colored paints can be used to mark the trees.

Another timesaver requires punching a second

hole in the sap bucket opposite the first hole,

and painting a stripe from the hole to the bottom of the bucket. The buckets are hung first

from one hole (for example, with the stripe away

from the tree and plainly visible) ; then after

they are emptied, they are hung from the opposite hole. This makes it easy for the sap collector to tell whether or not a bucket has been

emptied and keeps him from skipping full

buckets as well as revisiting emptied buckets.

The only objection to this scheme is that a bucket

with holes on both sides holds less sap than a

bucket with one hole because it hangs from the

spout at an angle.

Collecting Tanks

Collecting tanks vary in size with the needs

of a particular sugar bush. The tanks usually

are provided with a strainer, baffled to prevent

loss of sap by splashing, and a drainpipe.

The method of hauling the tank is governed

by conditions in.the sugar bush. The tank can

be mounted on any of several types of carrier,

including stoneboat or skids, 2-wheel trailer,

high-wheeled wagon gear, and underslung rubbertired 2-wheel trailer (figs. 30-34, inch).

High mounting of the tank (figs. 31, 32, and

33) should be avoided, because of the labor required to lift the sap. usually an additional

worker is needed. The lowest mounting, such as

on a stoneboat or skids (fig. 30), requires the

least labor. A rig of excellent design is one with

a low-mounted sump tank (fig. 35) provided with

a self-contained power-driven pump to lift the

sap up to the large tank (fig. 36).

Pipelines

To eliminate the costly labor of collecting sap

by hand and to avoid the bad roads of the sugar

bush, some producers have installed pipeline systems. In these systems the sap is piped directly

from the tapholes to a storage tank. The first

pipeline systems did not become popular because

of the excessive cost of installing the intricate

piping system and also because poor-quality sirup

resulted if the sap fermented in the pipeline.

One factor that has made pipelines practical

is the development of plastic tubes. These can

be laid directly on the ground because sap

trapped in a low spot or sap in the line will not

burst the tube on freezing (fig. 37). The phenomenal growth in the use of pipeline systems

since the development of today's lightweight

plastic tubing can be attributed to: (1) The initial cost of plastic tubing is comparable to the

cost of buckets or plastic bags, (2) the cost of

collecting the sap and transporting it from the

tree to the storage tank is reduced, (3) seasonal

(daily) labor requirements are reduced, and (4)

no sap is lost by spillage or by dumping small

intermittent runs.

Because of the short time plastic pipeline systems have been in operation, no data are available

to show : (1) The life expectancy of the tubing as

8
affected by weathering either during the sap-flow

season or throughout the year, (2) whether fermentation will be retarded in the tubing, (3) how

the tubing can be sterilized if it becomes contaminated, (4) whether the tubing imparts any flavor

to or has any other harmful effect on the finished

sirup, and (5) how the tubing will perform if it

becomes covered with snow. These and many

other questions can be answered only after intensive studies have been made.

The use of pipelines is not limited to bushes located at an elevation above the evaporator house ;

they are equally useful for bushes at the same level

or at a level below the evaporator house. In the

latter, a pump is used. Several pump-operated

pipelines are in use in Ohio.

In installations where the sap must be pumped,

provision must be made for draining the pump

and the pipeline. The amount of trapped sap

should be kept as small as possible because it may

ferment during the period between runs and so

contaminate the next run. To prevent this, the

pipeline should be flushed with 5 to 10 gallons of

sap or water each time it is used, particularly if

it has been inactive for a day or more. The sap

or water used to flush the line must be discarded.

Some producers favor a partial pipeline system.

In one system of this kind, storage tanks are connected by pipelines to a large number of sapdumping stations throughout the sugar bush,

where the collecting pails are emptied. Another

type has fewer stations where gathering tanks are

emptied. Where tanks are used to transport the

sap to the evaporator house, they should be as large

as possible to reduce the number of trips that must

be made.

Storage Tanks

Storage tanks should be at least twice the capacity of collecting tanks. Where possible, the collecting tanks should empty into the storage tank

by gravity flow, as shown in figure 38. When this

is not practical, a sump tank from which the sap

is pumped to the storage tank can be used (fig. 39).

Summary

1. Use two gathering pails, one in each hand.

2. Mark all trees to be serviced from each roadway or mark buckets and punch a second hole so

that they can be rotated 180° each time after

emptying.

3. Use a large collecting tank.

4. Mount the collecting tank on low-riding gear.

5. Use plastic pipelines to transport sap whereever possible.

6. Use a ramp to elevate the collecting tank above

the storage tank, OR

7. Use a sump or receiving tank and pump the sap

up to the storage tank.

THE EVAPORATOR HOUSE

Location of Building

Originally, most evaporator houses were located

near the center of the sugar bush, to shorten the

distance the sap had to be hauled (fig. 40). With

the use of pipelines and large collecting tanks,

many producers today find it more profitable to

locate the evaporator house near the other farm

buildings and close to a traveled road (fig. 41).

This offers many advantages: (1) Water and

electric power are available, (2) laborious and

time-consuming travel to and from the evaporator

house is eliminated, and (3) full family participation is encouraged.

Function of the Evaporator House

The evaporator house, or sugar house as it

is often called, like the evaporator, has developed

without engineering design. In the early days of

the iron kettle, little thought was given to any

form of shelter. With the advent of the closed

fire pit and chimney, a lean-to type of shed was

used to protect both the sugarmaker and the boiling sap from the inclement weather which so

often occurs during the sirup season. The shed

shelter immediately introduced a new problem—

how to get rid of the steam from the boiling sap.

This was solved by completely enclosing the

evaporator and installing ventilators at the top.

These crude shelters were the forerunners of today's evaporator houses.

As the evaporator house is used only 4 to 6

weeks of the year, its cost must be kept low;

otherwise, the interest on the capital investment

is out of proportion to its use. Today the trend

is toward the construction of an evaporator house

that not only will permit the sanitary handling

of the sap and sirup, but in addition will provide a place to process and package the sirup, to

make confections, and to serve as a salesroom

for maple products.

Requirements of the Evaporator House

The evaporator house need not be elaborate. It

should be large enough to allow plenty of free

space (4 feet or more) on all sides of the evaporator, and it should be set on a foundation that

extends below the frostline. The house should

be of tight construction with provision for venting the steam and should have intakes to supply

air for the fire and to replace air that is exhausted

with the steam. Provision should also be made

for easy access to the fuel supply and sap-storage

tanks.

446270 0—58-
chimney

workbench

space for sirup filler,*;

sugar kitchen,^

reheating stove

packaging spoce^^

space heater«

hinged shutters, with ropes

to regulóte ventilation

•j^ ru$J- proof metal. hood

sop storage tank

(beyond)

wood fuel storoçie

wash sink

su^geâted oír inlet: 8 inch slot

along both sides* of pan

Chart 3.—A perspective drawing of an evaporator house with *'L*' to provide space for filtering and packaging sirup and making maple

confections.

Design of the Evaporator House

Chart 3 shows a suggested plan for an evaporator house with a wing in which the sirup can

be processed and maple products made.

The house itself is designed to contain only the

evaporator and workbench. The width (16 feet)

allows an aisle space of 5 feet on each side of an

evaporator 6 feet wide, to provide easy access

to all parts of the evaporator. The house is

equipped with a workbench along one wall. The

roof opening for the ventilator is two-thirds the

width and the same length as the evaporator. The

opening is provided with hinged shutters (sections

of the roof), which can be raised or lowered to get

the required ventilation.

Steam Ventilation

The steam hood.—The steam hood has nothing

to support so can be made of lightweight noncorroding material, such as aluminum or galvanized

sheets. The section between the stringers and the

roof openings is rectangular, with perpendicular

walls, and serves as a chimney. The dimensions

are the same as the roof opening. Below the

stringers the hood is flared out to project 1 foot

beyond the evaporator on all sides. The lower

edge of the hood is 6 feet from the floor to provide

adequate headroom. The flanged sections of the

hood are hinged to the chimney sections so they

can be raised or lowered to take care of the steam.

A strip of lightweight canvas, 1 to 3 feet wide,

attached to the lower edge of the hood (fig. 42)

will increase its efficiency. A small gutter i/^-inch

deep is attached to the lower edge of the hood to

collect the water that condenses on it. To make

the hood most effective, the distance between the

top of the evaporator pans and the bottom of the

hood curtain is narrow, about 2 feet. This requires that the evaporator arch be set higher from

the floor than has been the practice in the past.

Evaporator cover and steam ventpipe.—Instead of a steam hood, which requires large

amounts of outside air and a large opening in the

roof, an evaporator cover and steam ventpipe can

be used to remove steam from the evaporator

house. This simple and efficient system employs

the principal of the covered steam kettle. The

cover is fitted over the entire evaporator, with the

possible exception of the last section of the sirup

pan, and is connected with a steam ventpipe.

The cover is made of lightweight metal, and it

can be of arch, gable, or flattop design. If the

latter, the sides should be raised 4 to 6 inches to

provide free interconnecting space over the entire

top of the evaporator, as in the other designs. Inspection holes with covers should be provided in

the different areas of the cover, and especially

over the sap pan, to permit skimming of the sapr^

The steam ventpipe should be 8 to 10 inches in

diameter. It can be made of air-duct pipes similar

to those used in domestic heating systems. It

should be mounted in the cover over the sap pan

adjacent to the arch stack, and carried up through

the roof. It must be lagged with insulating material to prevent steam from condensing in the pipe.

Failure to do this will result in large amounts of

condensed steam running back into the evaporator.

10
Location of the Evaporator

The evaporator is located directly under the

rid^e of the roof and the opening of the hood.

Thi foundation for the evaporator arch is extended below the frostline; it is extended above

floor level sufficiently high so that the top of the

pans is at least 4 feet above the floor when the

arch and pans are in place. Setting the evaporator at this height, close to the hood, aids in

removal of steam, makes it easier to fire when

wood is the fuel, and brings the thermometers

closer to eye level. The house is floored, preferably with concrete.

In older installations, the foundation on which

the evaporator was mounted was much lower. To

make wood firing more convenient or to mount

the oil burner, a pit was dug in front of the firebox. To aid in reading the thermometers and to

provide depth below the sirup drawoff cocks, pits

were also dug on each side of the sirup pan.

If the sirup is only partly finished in the evaporator and evaporation is completed in a finishing pan, the finishing pan should also be in the

evaporator house.

Air Supply

When the evaporator is in operation, great

quantities of outside air are required for combustion of the fuel. For example, 150 cubic feet

of air per minute is required to burn seasoned

hard maple at the rate of one-fourth cord per

hour. Removal of the steam through the ventilator will require an additional 10 cubic feet of air

per minute per square foot of evaporator. For

example, an evaporator 4 feet wide and 12 feet

long requires 480 cubic feet of air per minute to

remove the steam through the ventilator.

If this air is supplied through an open door or

window the evaporator house will be very cold

and drafty. A more desirable method is to make

provision for delivering it where it is needed, as

indicated in chart 3. Ducts along both sides

of the evaporator supply the hood ventilation and

the combustion air. These ducts are 8 inches wide

and are open at the top and at the ends toward

the firebox. They run the entire length of the

evaporator. The incoming air supplied through

these ducts tends to keep the steam under the

hood. If the evaporator is covered and a steam

ventpipe is used, the fresh-air ducts will need

to supply air for combustion only.

oirup Processing Room

If the evaporator house consists of a single

room, it must have space for the filters and for

canning the sirup. A better plan is to process

the sirup in a second room built as an "L" to the

evaporator room (chart 3). This arrangement

does not add appreciably to the cost of construction, and the sirup can be processed under more

ideal working and sanitary conditions.

The processing room houses such operations as

filtering, heating, and packaging the sirup, and

making maple spread and other confections. The

equipment consists of a filter rack, stove for boiling the sirup (preferably heated with gas),

maple-cream beater, and sugar stirrers.

There should be a dishwashing sink and a

trough with cold running water in which sirup

that has been cooked for making maple cream

can be cooled rapidly. The room should be provided with adequate storage space for the cooking

utensils and the containers for the products.

If the evaporator house is to serve as a salesroom, space should be provided for the attractive

display of the products as well as for storage of

these products.

Wood Storage

When wood is the fuel, sheltered storage must

be provided in a convenient location so the wood

can be readily obtained by the fireman. Figure

44 shows a space for wood storage in front of the

evaporator house, which is the point closest to

the evaporator fire doors. This storage space will

hold enough wood for a run of sap. The supply

is replenished from a larger storage shed.

In some large operations, the wood is stored in

a separate building and is transported to the evaporator house by means of a truck mounted on

rails. Such an installation is shown in figure 43.

Storage Tanks

Storage tanks for sap must be located in a cool

place, never in the evaporator house where the

sap would be too warm. Warm sap favors the

growth of micro-organisms that produce unwanted fermentation.

When the contour of the ground will permit it,

the location of the tank underground has become

popular. However, it may be difficult to keep sanitary. If placed aboveground, the tank should

be insulated and covered (fig. 44). It should be

built so that its interior is readily accessible and

can be easily cleaned and rinsed. After each run

of sap the tank should be washed with a detergent

and thoroughly rinsed by hosing with clean fresh

water.

There must be some indicating device inside the

house to show the level (supply) of sap in the

tank. This device may be a simple sight glass (a

perpendicular glass tube connected to the feed line

of the evaporator) ; or it can be a float-and-weight

type, where a string attached to a float in the

tank is carried into the house, and a weighted

object is raised and lowered by means of guides

and puUies asthe level of the sap varies.

If the feed line from the tank to the house is

aboveground, it too must be well insulated. Nunierous cases have been reported where the sap

line, even when in operation, has frozen and shut

off the supply of sap, with the result that the

pans were burned.

n
Summary

1. If possible locate the evaporator house on

the main road close to the other farm buildings.

2. Build it large enough to provide at least 4

feet of free space on all sides of the evaporator.

3. Construct it so that it can be kept clean and

sanitary.

4. Provide a workbench along one wall.

5. Provide a steam vent.

6. Build a steam hood directly over the evaporator OK

7. Provide the evaporator with a cover and

steam ventpipe.

8. Elevate the evaporator arch on a foundation

which extends into the ground below the frostline.

9. Make floor of concrete or other easily cleaned

surface.

10. Provide ducts in the house for intake of outside air.

11. If possible, provide a separate but adjoining

room for processing the sirup and making

other maple products.

12. If possible, equip the house with running

water, electricity, and a gas fuel supply.

13. When wood is the fuel, provide adequate storage room for supplies of dry wood.

14. If possible, provide means for transporting the

wood to the evaporator.

15. Locate the sap-storage tanks outside the building.

THE EVAPORATOR AND

ITS FUNCTION

The maple-sirup evaporator is an open pan for

boiling water from the sap. Although the

primary purpose of the evaporator is to remove

water, it must do the job economically and in such

a way as to improve but never to impair the quality of the sirup that is being made.

Maple-sirup evaporators have gone through an

evolution in design. The first, used by the

Indians, was a hollowed log in which water was

evaporated from the sap by the addition of hot

stones. Later they used earthen vessels set in the

fire. These were followed by the metal kettles of

the white settlers. All of these were batch-type

evaporators, that is, the entire evaporation

process, from the first addition of sap to the last,

was done in one kettle, with sap both high and low

in sugar content being added. It might be many

hours before the sirup was finally drawn. As a

result, a dark strong-flavored sirup was produced.

The next improvement was the use of multiple

kettles (fig. 45).

The sap was partly evaporated in the first kettle, transferred to the second kettle for further

concentration, and then finally transferred to a

third and sometimes to a fourth kettle where

evaporation was completed. The multiple-kettle

method was a semicontinuous operation and resulted in an improved (lighter colored) sirup, as

the time of heating at near-sirup density could be

shortened.

The source of heat for all the early evaporators

was the open fire, which is poor in fuel economy.

The first major change in design of evaporators

was the introduction of the flat-bottom pan and

the enclosed firebox. The increased heating surface of the pan and the confined fire both increased

the efficiency of the fuel. This design was quickly

followed by partitioned pans which were the forerunner of flue-type evaporators.

A modern flue-type evaporator, the last major

change in design, was developed about 1900 (fig.

46). Use of "flues" or deep channels in the pans

and altering the firebox so that it arched the hot

gases between the flues, caused the hot gases and

luminous flames to pass between the flues before

escaping up the chimney and resulted in increased

fuel economy. Also, the rate of evaporation was

increased, which shortened the evaporation time,

improved the quality of the sirup, and lowered the

cost of production.

Design

The evaporator, which operates under atmospheric pressure, consists basically of two sections :

(1) The sap pan, in which the flues are located,

and (2) the sirup pan. The sections are separated

to facilitate their removal from the arch for cleaning and repair. Originally, a siphon was used to

connect the two pans (fig. 47). More recently,

rigid and semirigid pipe or tubing has been used

(fig. 48). So that the evaj)orators can be

operated in a continuous or semicontinuous manner, baffles or partitions are built in the pans to

form channels through which the sap flows as it is

being concentrated. The location of these partitions and the size and shape of the channels differ

with different manufacturers.

The sirup pan, often called the front pan, usually is located over the firebox. It is the pan in

which the concentration to sirup is completed.

This pan has a flat bottom to facilitate cleaning

and to permit evaporation of shallow layers of

sirup with less danger of burning.

The channels or flues in the sap pan can be narrower than in the sirup pan because the sap is

never concentrated enough to become viscous and

it flows readily. Use of narrow flues increases

the heating surface and thereby increases transfer of heat. Fresh sap is admitted to the sap

pan through a float valve, which is adjusted to

12
CD —

X

UJ

a

tr.

o_i

o

Ü

0.5

0RI6 0 30 60 90

BOILING TIME (MINUTES)

Choit 4.—Effect of length of boiling period on color formation (color index) in sap of different solids concentrations.

maintain the desired depth of liquid in the

* evaporator.

# Rule Of 86

The amount of water that has to be removed to

reduce sap to sirup varies with the density of

j^ the sap.

The "rule of 86" can be applied to deterniine

the number of gallons of a particular sap required

to produce 1 gallon of standard-density sirup

^ (65.5° Brix). Standard-density sirup contains

86.3 percent of solids (as su^ar) on a weightvolume basis. Since the density of sap is comj paratively low, its Brix value and percentage

of solids (weight-volume) are essentially the same.

Ç Therefore, the percentage of solids (weightvolume) of the sirup divided by the Brix value

• of the sap equals the number of gallons of sap

I required to produce 1 gallon of sirup. In prac-

^' tice the value of 86 can be used rather than 86.3,

^ and the equation is: a===pr From this number, 1 is subtracted to obtain the

number of gallons of water that must be evap-

^ orated from the sap. The following equation is

used :

86 .

a= X

where a=the number of gallons of water that

must be removed from sap to produce standard-density sirup.

X=the Brix value of the sap (to represent the solids content of the

sap).

Example : With sap having a density of 2.4° Brix,

a=^r-r— 1, or 36 — 1 =35, the number of gallons of

water that must be evaporated.

Changes in Sap During Its Evaporation

to Sirup

Development of the desired maple flavor and

color as well as undesirable flavors are the result

of browning reactions that occur while the sap is

boiling in the evaporator. (This is discussed

more fully on p. 23.) The extent to which these

reactions occur is determined in part by the

length of time the sap is boiled.

Chart 4 shows the effect of the length of the

boiling period on the amount of color {S2) produced in sap of different solids concentrations

(° Brix).® At low concentrations of sugar the

* To provide a basis for comparing color of maple saps

of different concentrations, color is expressed as ''color

index." Measurements to determine color index are

13
1.5

1.0 -,

0.5

X

üJ

O

z:

en

o

o

y-

/

-1 "--./

1 Color index ^^'^^ 1

f

III III III 1 1 1

10

8

X

o.

- 6

4

75

-50 f^.

LÜ

O

ÜJ

O

QQ U

40 60

TIME (MINUTES)

Chart 5.—Changes in Brix value, color, and pH that occur in sap during the evaporation period. A, The pH curve shows that soon after

evaporation begins the sap becomes alicaline, reaching a pH of 8 to 9; it then decreases in alkalinity until at the end of the period

it is about neutral. Little color is produced until after the sap reaches a pH of 8, at which point the rate of color production becomes

rapid. It becomes still greater as the concentration of the sap approaches that of finished sirup (30° Brix and above). B, Increase

in Brix value is slow at the beginning and becomes more rapid as evaporation progresses.

14
100

60 90

TIME (MINUTES)

150

Chart 6.—The average length of time (the time required to remove

50 percent of the water) that any lot of sap remains in the

sap pan (see dotted lines) is slightly less than 30 minutes. The

time can be shortened or lengthened by using sap of lower or

higher solids content (° Brix), by varying the depth of sap in

the eva|iorator, and by varying the intensity of the heat.

30 60 90 120

TIME (MINUTES)

Chart 7.—The average length of time (the time required to remove 50 percent of the water) that any lot of sap remains in

the sirup or front pan (see dotted lines) is a little more than 60

minutes. The time in this pan can also be shortened or lengthened by changing the Brix value of the sap entering the sirup

pan, by varying the depth of the sap, and by varying the intensity of the heat.

amount of color produced in a given boiling time

is small, whereas at higher concentrations it is

very much larger. The increasing rate of color

formation does not become appreciable until the

Brix value of the sap reaches 25° or more, and

this occurs after the sap reaches the sirup pan.

(See table 4.)

Other changes that occur in the sap as it boils

are shown in chart 5. The rate of color formation (Sß) is greatest as the sap approaches the

concentration of finished sirup. Thus, the length

of time that sap is heated in the sap pan (when

the Brix value is low) is relatively unimportant

in the formation of color. In the sirup pan, however, color development increases rapidly as concentration increases. The effect of holding the

made with monochromatic light in a spectrophotometer :

86. 3% Color index=A 1 cm

=A45o (86.3/bc)

where A450 is the observed absorbence at 450 ml. using

distilled water as the blank, b is the depth of the solution in centimeters, and c is the grams of solids as sucrose

per 100 ml. of solution as determined on a Abbé refractometer. The maximum color indices for table sirup

of various grades are: 0.510 for U. S. Grade AA (Light

Amber), 0.897 for U. S. Grade A (Medium Amber), and

1.45 for U. S. Grade B (Dark Amber).

boiling sap (sugar) in the sap and sirup pans

for different periods of time is shown in charts

6 and 7.

The curves show the average time (time required to remove 50 percent of the water) that

a lot of sap with an initial solids content of 2.5°

Brix remains in the sap pan is a little less than

30 minutes and in the sirup pan slightly more

than 60 minutes. The average time the sap is in

the evaporator is approximately I14 hours. To

make high-quality, light-colored sirup, the time

required to evaporate the sap to sirup must be

kept to a minimum. Conditions that affect the

boiling time are: (1) The design of the evaporator, (2) the amount of heat, (3) the efficiency of

the heat transfer, and (4) the depth of the boiling liquid. Once^an evaporator is selected and

purchased the sirupmaker controls only the

amount and steadiness of heat applied to the

pans and the depth of the boiling sap.

The Evaporation Time

From the time a unit of sap enters the sap pan

until it is removed from the sirup pan as sirup

is the evaporation time. Measurements of evaporation time should not be made until the evapo15
rator is operating steadily and sirup is being

drawn off. The evaporation time can be lengthened by increasing the level of liquid in the pans.

The lowest level of liquid will have the shortest

holdup time.

Liquid Level in the Evaporator

The depth of sap to maintain in the evaporator

is determined by a number of factors. Most important is the minimum depth that must be maintained to prevent scorchm^ the pans. Many

sirupmakers find that a liquid level of 1 inch in

the sirup pan is ideal. When the evaporator is

operating correctly with a steady source of heat,

there will be a slight gradient or decline in the

liquid level in the evaporator, the highest being

at the point of sap intake and the lowest at the

point of sirup drawoff. With uneven firing this

gradient is upset. During periods of low heat,

with the sap merely simmering, this gradient is

lost and the depth of the sap tends to become the

same and higher throughout the evaporator.

This also causes an intermixing of sap of

different concentrations which, together with an

average increase in the depth of sap, results in

a longer holdup time and production of darker

sirup. The lower the Brix value of the sap the

longer the holdup time becomes, since there must

be greater gradient in the sap levels. As the

minimum level at the point of sirup drawoff is

fixed to prevent burning the pans, the level at

the sap intake must be adjusted to keep the sap

proportionately deeper.

Rates of Evaporation

Eecent studies {40^ 60) indicate the changes in

density that sap undergoes in different parts of

the evaporator.

The solids concentration of the sap is about

doubled in the sap pan, that is, nearly 50 percent

of the water that is to be removed has been evaporated. By the time the sap reaches a concentration of only 19° Brix, 90 percent of this water has

been removed.

The changes in the concentration of a typical

sap (with a solids content of 2.5 percent) during

its evaporation are given in table 4. Chart 8

shows a 2-section evaporator with 3 channels in

the sap or flue pan and 4 in the sirup or front

pan and the points at which the concentration

measurements (table 4) were made.

To make 1 gallon of standard-density sirup

86 from this sap required^, or 34.3 gallons of sap,

and 33.3 gallons of water had to be evaporated.

The sap concentration was doubled (from 2.5°

to 5.0° Brix) in the sap pan. This removed 17.4

gallons of water or more than 52 percent of the

33.3 gallons of water that had to be removed to

make 1 gallon of sirup. By the time the solids

TABLE 4. — Changes in concentration of sap

( ° Brix) and water evaporated in a simulated

evaporator^ for each gallon of sirup produced

Section of evapoConcentration of

sap 1

Water evaporated

rator

Per section Total

Original sap

Sap pan:

7irst section

Second section

Third section

Sirup pan:

Fourth section. _ _

Fifth section

Sixth section

Seventh section-.

Finished sirup

"" Brix

2.5

3.0

3.7

5.0

8.0

19.0

42.0

54.0

65. 5

Gal'

Ions

Percent

GallonsPercent

5,77

5. 40

6. 16

6.45

6.26

2.48

.45

.28

17.35

16.24

18. 53

19. 40

18.83

7. 46

1. 35

.84

5. 77

11. 17

17.33

23 78

30.04

32. 52

33.97

33.25

17.34

33.59

52. 12

71.52

90.35

97.81

99, 16

100. 00

1 Percentage of sugar.

had increased to only 19° Brix, 90 percent of the

water had been removed, and this occurred by the

time the sap had progressed only halfway through

the sirup pan. Thus the remaining 10 percent of

the water was removed in the last half of the sirup

pan. This shows that most of the evaporation is

accomplished while the solids are at sufficiently

low concentrations to have little effect on the color

of the sirup. It also shows that sap must be kept

moving forward through the pan as it approaches

sirup concentration, so that it can be removed

from the evaporator as quickly as possible.

Summary

1. Evaporators are of atmospheric or open-pan

design, usually with sections, and are made for

continuous or semicontinuous operation.

86

2. Eule of 86 : a== ^,

where a=the number of gallons of sap,

with an initial Brix value of X, required

to produce 1 gallon of standard-density

sirup.

3. Formation of color and flavor in maple sirup

occurs during evaporation of the sap. The

amount of these is related to the length of time

the sap is boiled in the evaporator, especially in

the sirup section.

4. The length of time the sap is in the evaporator

depends largely on the depth of the sap in the

evaporator. The depth of the sap in turn depends on the initial Brix value of the sap. The

higher the Brix value, the shallower is the

depth of sap required and the shorter is the required holdup time.

5. The rate of evaporation diminishes as the sap

approaches the solids concentration of standard-density sirup.

16
i —^

Lc\

4-^

—iS/rap Ou/-A\

4-

Chart 8. ^Top view of a simulated maple-sap evaporator having 3 channels in the sap pan and 4 channels in the sirup pan. Arrows

show direction of flow of the sap and the solid circles show the location of sap of difFerent sugar percentages {° Brix), as indicated in

table 4.

OPERATING THE

EVAPORATOR

Starting the Evaporator

The sap is run into the evaporator until the

bottom of the front pan is covered to a depth of

1 inch; then the fire is lit. As soon as the sap

begins to boil, the sap inlet ñoat valve is adjusted

to maintain the desired depth of liquid (i/^ to 1

inch) in the sirup pan. As water is evaporated,

the float valve will admit more sap^ (fig. 49).

If sirup has not been made previously, a series

of adjustments of the float will be necessary to be

sure the liquid in the sirup pan is always maintained at a depth of y^ to 1 inch at the point of

drawoff.

The constant addition of sap keeps the sap in

the sap pan dilute. It becomes progressively more

concentrated at points farther from the sap inlet.

The sirup drawoff is at the farthest point.

Saps of different solids concentrations (° Brix)

require different adjustments of the inlet-valve

regulator to maintain the same depth of sirup

in the front pan. The depth of sap in the §ap

pan must be greater for sap with a Brix value

of 1° than for sap with a Brix value of 2° and

it must be lower for sap with a Brix value of

3°. By checking the solids content of the sap

in the storage tank it is possible to set the float

valve to maintain the desired depth of sap in the

evaporator. The solids content of the sap

should be checked with a hydrometer every half

hour or whenever a new lot of sap is run into

the storage tank.

Drawing Off the Sirup

The best way to determine when sap has been

evaporated to standard-density sirup is by its

boiling point. The boiling point of standarddensity sirup is 7° F. above the boiling point of

water. This is discussed in detail in the section

"Elevation of the Boiling Point," page 26.

Any thermometer with a range of temperature up to 225° F. can be used to determine the

boiling point of sirup, if it has a sufficiently

open scale and is calibrated at intervals of 1°.

As soon as the boiling sirup reaches the proper

temperature, the drawoff valve is opened and

the finished sirup is removed. The temperature

of the boiling sirup should be watched closely to

be sure it neither rises above nor falls below the

proper temperature, and the rate of removal

should be regulated to maintain that temperature.

If the boiling sirup falls below the proper temperature, the drawoff valve should be closed immediately.

446270 0—58- 17
Automatic Drawoff Valve

An automatic sirup drawoff valve is now

available. It opens automatically when the sirup

reachers the proper temperature (7° F. above the

boiling point of water). The valve is operated

by a solenoid, which in turn is activated by a

thermoregulator. The thermoregulator is set by

hand to open or close the valve when the boiling

sirup goes above or below the proper temperature, and must be reset to compensate for changes

in barometric pressures.

This type of drawoff valve may be purchased

assembled and ready for use, or the various parts

may be purchased separately and assembled by

the user.

At the time of this writing, the author has had

insufficient experience with the autx)matic drawoff valve to make any recommendations regarding

its use.

Finishing Pan

Because of the difficulty of maintaining the

boiling sirup at exactly the right temperature for

continuous drawoff of standard-density sirup

(7° F. above the emact boiling point of water),

the use of a finishing pan is recommended.

When a finishing pan is used, the sap is drawn

from the evaporator at a concentration of 55° to

60° Brix (4° to 5° F. above the boiling point of

water). At this concentration, the density is not

critical and drawoff can be continuous. An automatic drawoff valve can be used. Evaporation

is then completed in a separate pan called the

finishing pan.

The dimensions of the finishing pan should be

approximately 2 feet by 3 feet. (The sugaringoff pan listed by most equipment manufacturers

is adequate.) The use of the finishing pan provides a means for the exact control of the finishing of the sirup without extending the total time

the sap is heated. When a finishing pan is used,

the following procedures should be observed:

(1) Do not finish more than 5 to 10 gallons of

sirup in a batch.

(2) When the sirup is finished, that is, when

it has reached the proper temperature (7° F.

above the exact boiling point of water) remove

the pan from the heat immediately, either by

lifting the pan free of the firebox, or, if it is heated by gas or oil, by extinguishing the flame or by

means of a damper arrangement bringing a current of cold air across the bottom of the pan. A

gas-fired burner is preferred since the heating

can be stopped immediately.

(3) Drain all of the finished sirup from the

pan. If any sirup is left in the pan, it will

darken the next batch.

Completion of Run of Sap

When the evaporation of a given run of sap has

been completed care must be taken or the pans

may be "burned."

If water is available, it can be VMM into the

storage tank as the last of the sap is being withdrawn. This permits the evaporation of all of the

sap to sirup without any loss of sap, and the pans

can be flooded with 3 to 5 inches of water before

the fire is extinguished.

If water is not available, the fires must be extinguished and evaporation stopped while there

is still enough sap in the storage tank to fill the

evaporator to a depth of 3 to 5 inches, because

enough heat will remain in the firebox and arch to

melt the solder and the thin metal of the pans if

the pans become dry before the firebox has cooled.

Cleaning the Evaporator

During the evaporation of sap to sirup, the salts

of calcium and magnesium are concentrated to a

point where they can no longer be held in solution.

They are then deposited as a precipitate called

sugar sand, mostly in the sirup pan. Like boiler

scale, sugar sand forms a hard, impervious layer

on the bottom and sides of the evaporator, and this

layer builds up with continued use. The scale cuts

down transfer of heat, which reduces the efficiency

of the evaporator, wastes fuel, and causes an undue

holdup of sirup in the evaporator. Sugar sand

also contains entrapped caramelized sugar, which

contributes to the production of dark-colored

sirup.

To remove sugar-sand scale is not easy and to

do so by physical means (scraping, scrubbing with

steel brushes, or chiseling) is almost impossible.

Removal becomes more difficult as tlie layer of

scale becomes thicker.

Because of the chemical similarity of sugar sand

to milkstone—^both are deposits of insoluble calcium salts—the same commercial preparations

used for removing milkstone from milk-processing

equipment can be used to remove sugar-sand scale.

One of the best of these is sulfamic acid, either

commercial grade or with modifier. Sulfamic acid

should be used on galvanized equipment only with

extreme care as it readily attacks the zinc coating.

Caution : The milkstone remover should be used

as directed by the manufacturer. Extreme care

should be taken to be sure that the remover has

been completely rinsed out of the evaporator pans

with water before they are used to evaporate more

sap. If rinse water is not available at the evaporator house, the evaporator pans should be taken

to a source of water supply.

If the pans have a heavy incrustation of scale,

a time should be selected when the milkstone remover (diluted according to the manufacturer's

directions) can be put in the pans to soak until the

scale softens. If the weather is cold, the pans with

the diluted solution should be set on the arch and

the solution should be heated but not boiled. Use

of excessively strong solutions of milkstone re18
mover or leaving it in the evaporator longer than

is required to soften the scale may damage the

tinned surface of the evaporator.

The best maintenance practice is to remove the

sugar-sand scale between each run. The deposit

will be thin, and swabbing the milkstone remover

on the pan with a cloth, allowing it to remain a

short time, and then completely rinsing the pan

with water will be sufficient to keep it clean and

bright.

The practice of periodically reversing the flow

of sap through the evaporator, according to the

manufacturer's directions, is recommended. This

practice will not prevent the formation of sugarsand scale, especially in the sirup pan, but it will

retard its formation. Another practice for cleaning the evaporator that has been used with some

success is that of running water through the entire evaporator for a long period of time.

At the end of the season the evaporator should

be cleaned and rinsed ; it should be stored in an

upside-down position preferably by mounting it

on sawhorses, or it can be leaned against the wall

of the evaporator house. An evaporator that is

stored in a dry place will not rust or deteriorate.

Summary

1. Use a flue-type open-pan evaporator.

2. Choose an evaporator of sufficient capacity

to handle a day's run of sap in 16 hours.

(Consult manufacturer's rated capacities.)

3. Operate the evaporator with a minimum

depth of sap. (Keep the depth of sirup at

point of drawoff between % and 1 inch.)

4. Keep the sap boiling rapidly at all times.

5. Keep the fire uniform.

6. Keep the fire doors closed except when adding

fuel.

7. Draw off the sirup as soon as it reaches the

proper temperature (7° F. above the boiling

point of water for that day).

8. Regulate the rate of sirup drawoff to the rate

of evaporation. Keep the temperature at exactly 7° F. above the boiling point of water.

9. With evaporators that cannot be operated so

that standard-density sirup can be drawn

continuously, draw the sirup when it is 50°

to 60° Brix (4° or 5° F. above the boiling point

of water). This will permit continuous

drawoff. Finish the low-Brix sirup by evaporating to standard density (65.5° Brix) in

batches in a finishing pan.

10. Clean the evaporators often to remove sugar

sand as it accumulates.

11. Be sure to rinse the evaporator pans

thoroughly with water after using a chemical cleaner to remove sugar-sand scale.

12. Keep the underside of the flues clean.

OTHER TYPES OF

EVAPORATORS

Other types of evaporators include the steam

evaporator (or a combination of oil-and-steam),

the vacuum evaporator, and a newly developed

rapid atmospheric evaporator (K. A. E.). They

are best suited to large-scale or central-station

(cooperative-plant) operation.

Steam Evaporator

The evaporation of maple sap with high-pressure steam is practiced by a few producers. Its

use, however, has never become widespread.

Steam evaporators have certain advantages as

well as some disadvantages, as follows:

Advantages: (1) The heat is steady so that

evaporation of the sap can be maintained at a

continuous and even rate. (2) The heat can be

supplied in steam coils, manifolds, or a jacketed

kettle. (3) The evaporator can be of smooth wall

construction; flues are unnecessary. (4) Scorching of sirup is minimized. (5) The evaporator

room can be separated from the boiler room and

so is easier to keep clean at all times.

Disadvantages: (1) A license may be required

to operate a steam boiler. (2) The boiler needs

periodic inspection and overhauling. (3) In

some areas the water is not suitable for use in a

steam boiler. (4) The initial cost of the steam

boiler may not be justified.

The approximate size of steam boiler (boiler

horsepower, b. h. p.) required to evaporate sap

to sirup can be calculated, as 1 b. h. p. will evaporate approximately 3.25 gallons of water (sap)

per hour. The value 3.25 varies slightly, depending on the temperature of the water as it enters

the boiler, the operating pressure of the boiler,

and the initial temperature of the sap. As indicated earlier, 33.25 gallons of water must be

evaporated from sap with an initial Brix value

of 2.5 to produce 1 gallon of sirup. This will

require 33.25-^ 3.25, or approximately 10 b. h. p.

to produce 1 gallon of sirup per hour.

A system that is proving successful is the combination of oil and steam. In this two-stage system, oil is used to evaporate the sap to about 30°

or 40° Brix in flue pans, and steam is used to complete the evaporation. This combination has all

the advantages of steam for finishing the sirup,

but requires a smaller, and therefore less expensive, steam boiler.

Vacuum Evaporator

Milk-concentration or evaporation plants in

maple-producing areas can be adapted for use in

evaporating maple sap. This was done during

19
the 1930's at Antigo, Wis., where a milk plant was

used for making sirup during part of the day in

the spring sirup season/

A practical procedure, and the one which was

used at Antigo, is as follows : The sap is concentrated in the conventional open-pan evaporator at

the farm site to between 25° and 30° Brix. Evaporation is completed in the vacuum evaporator at

a central or cooperative sirup-finishing plant.

This two-stage method of evaporation results in a

nearly colorless and flavorless maple sirup. Such

sirup would hardly find a market for direct use,

but it would be ideal for the production of highflavored sirup, as described on page 45.

A study at Cornell on the use of milk-plant

equipment during oiï-peak seasons for evaporating maple sap showed that this use was practicable but that the sirup produced had to be

treated by the high-flavoring process to obtain

marketable maple sirup (Iß). The fixed costs

chargeable to the use of the milk-plant equipment

would be negligible. However, means of transporting the perishable, partly concentrated sap

to the milk-concentrating plant would be required,

and the use of a central sirup-finishing plant

would require a new procedure of maple-sirup

production.

High-Speed Tube-Type Evaporator

The rapid atmospheric evaporator (R. A. E.),

which is designed to be operated with highpressure steam, is a new development (^i). Sap

that has been concentrated to a density of about

20° Brix can be converted to sirup in this highspeed tube-type evaporator in a few seconds. Because of the short heating time, little or no color

is developed in the final and critical stage of evaporation. Poor-quality sap, that would make a

dark-colored sirup in the conventional open-pan

evaporator, makes a lighter colored (higher quality) sirup when finished in the E. A. E. Highquality sap finished in the E. A. E. may make

sirup too light in color and too delicately flavored.

However, color and flavor can be developed by

holding the hot sirup for a short time in an insulated chamber attached near the outlet of the

E. A. E., or by the high-flavor process described

on page 45.

The E. A. E., like the vacuum evaporator, is

best suited to central-station or cooperative-plant

operation and its adoption by the maple industry

would require new marketing methods. The

E. A. E. is not a substitute for the open-pan evaporator; in fact, it functions best when used to

complete the evaporation of sap that has been

previously concentrated to a density of at least

20° Brix. Concentrating sap with an initial den-

^ Interdepartmental communication of Michigan CoUege

of Mining and Technology: Baggley, G. F., and Machwart, G. M. MAPLE SIRUP MANUFACTURE, USING A VACUUM

EVAPORATOR. 28 pp. 1947. [Processed.j

sity of 2.5° Brix to a density of 20° Brix removes

approximately 90 percent of the water that has to

be evaporated to make standard-density sirup. In

performing this important function the farmoperated open-pan evaporator would still do a

major part of the evaporation. However, finishing the sirup in the E. A. E. insures a better quality sirup from poor-quality sap.

Summary

1. The steam evaporator is expensive to install.

It provides a steady source of heat, and danger

of scorching is minimized. The sirup produced

is light colored and delicately flavored. A

combination oil-and-steam system (two-stage

method of evaporation) is proving successful;

it has all the advantages of steam but is less expensive to install.

2. The vacuum evaporator, which is limited to

large-scale or central-plant operation, is used

to complete the evaporation of sap that has

been partly concentrated on the farm. The

equipment used usually is idle milk-evaporation equipment. The sirup produced is bland

with essentially no maple flavor, but it is excellent for use in making high-flavored sirup.

3. A new rapid atmospheric evaporator

(R. A. E.) has been developed for use in the

second stage in a two-stage method of evaporation. This evaporator is also limited to largescale central-plant operation. The heating

time required by this high-speed tube-type

evaporator for the last and critical stage of

evaporation is so short that little color is imparted to the finished sirup, even sirup made

from late season or low-quality sap.

FUEL

Wood

The modern flue-type evaporator was designed

for burning wood. A wood fire carries a luminous flame throughout the entire length of the

arch. The flue area of the evaporator and that

portion which lies over the firebox are heated by

radiant as well as by convection heat that is liberated by the burning gases. The wood may be

sound cordwood, defective trees removed in improvement cuttings, or sawmill wastes—either

culls or slab.

In the evaporation of sap to sirup, the object is

to evaporate water in the shortest possible time.

Therefore, it is essential to use only dry sound

wood that will produce a hot fire. Wet or green

wood will not produce as much heat as the same

amount of dry wood. Poor-burning fuel results

20
in a slower boiling rate, which in turn causes the

sap to be held in the evaporator for a longer time

and results in a darker sirup.

A steady fire shortens the boiling time. The

best results are obtained by charging the firebox

first on one side and then the other, keeping the

fuel in the firebox at almost constant volume.

The fire doors should be closed immediately after

each charging of wood to reduce the intake of

cold air, which reduces the boiling rate of the sap

and increases its holdup time in the evaporator.

Likewise, draft doors that are open too wide will

admit more air than is required for combustion,

and the excess air has a cooling effect. Introduction of cold air beneath the evaporator pan in

either the firebox or the flue area not only reduces

the boiling rate but also tends to set up counter

currents in the flowing sirup in the different channels of the evaporator. This also contributes to

the production of a darker sirup.

The cost of wood fuel to produce a gallon of

sirup, based on data obtained in 1953 and 1955,

ranged from 15 to 65 cents, with an average of 45

cents. This represents less than 10 percent of the

cost of sirup production (^, Jß).

Oil

The use of oil for heating the evaporators has

been increasing steadily during the past few years.

Unquestionably, one factor has been the shortage

of labor; this would be a factor even if the cost

of oil were not favorable compared with the cost

of wood. Use of oil not only eliminates the need

of a fireman, but also eliminates the preseason

preparation of wood. Surveys in Wisconsin {4,2)

and New York {2) show that 35 percent of the

total labor in making maple sirup is spent in boiling the sirup ; therefore, elimination of a fireman

offers a real opportunity for economy. Surveys

{29) also show that the cost of oil (43 cents per

gallon of sirup produced) compares favorably

with the cost of wood.

Once oil-firing equipment has been installed and

put to use, its real advantage becomes apparent.

An oil fire provides the even, high temperature so

necessary for the production of high-quality sirup.

Present-day evaporators were designed for

wood, and conversion to oil merely by putting a

burner in the firebox of the evaporator has been

unsatisfactory in some instances because the two

fuels burn in different ways. The luminous flame

from wood extends the entire length of the arch,

whereas the flame from oil extends only a short

distance from the burner nozzle. Consequently,

the more successful installations of oil burners

have included specially built or rebuilt fireboxes

and arches. Such an installation is shown in

figure 50.

The evaporator pans are heated principally by

radiant heat, which travels in straight lines as

heat waves from its source. In oil firing, the heat

is propagated in the firebox and all of the luminous flame is limited to that area. To make full

use of the radiant heat, the firebox and the arch

must be rebuilt. The bed and slope of the arch

must be dropped so that most or all of the underside of both sap and sirup pans are in line with

the flame (chart 9).

The approximate size of oil burner (gallons

of No. 2 oil per hour) to use with a flue-type

evaporator can be calculated by dividing the

manufacturer's rated capacity of the evaporator

(gallons of sap per hour) by 10. Experimental

data have shown that under average operating

conditions 1 gallon of oil will evaporate 10 gallons of water (sap) in a flue-type evaporator.

Phillips and coworkers {29) found that use of

the flues in the sap pan as economizers is desirable

if maximum utilization of the B. t. u.'s of the oil

is to be achieved. Further, a perpendicular wall

at the back of the firebox is advisable. Unbumed

oil droplets impinge on this wall and ignite, instead of being drawn up the stack. Also, the

wall deflects the hot gases from the burner upward toward the pans. The burner is located well

below the pans to prevent insulating soot from

being deposited on them.

In other installations, the oil burner has been

mounted just a few inches below the pans. This

is satisfactory if sufficient air is supplied to permit complete combustion.

The brick used to line the arch must be a fireresistant type, and it must be nonporous, otherwise it will take up moisture during inactive

periods. This moisture may freeze and crack the

brick.

With either oil or wood, fuel costs are a small

part of the total cost of making sirup. Therefore, it is not good practice to make fuel economy

the major consideration. Kather, use the amount

of fuel that will evaporate the greatest number

of gallons of sap per hour. This will contribute

to the production of high-quality sirup.

Summary

1. Use only well-seasoned dry wood, either cord

or slab.

2. Keep a steady fire.

3. Fire first on one side of the firebox and then

on the other.

4. Keep the fire doors open only long enough to

charge the firebox.

5. Open the dampers and draft doors only enough

to furnish the air for combustion.

6. The use of oil as fuel is recommended if there

is a shortage of labor.

7. To use oil, the firebox and arch must be specially built or rebuilt.

8. Use only fire-resistant brick for lining the firebox.

9. The cost of fuel for making sirup is approximately the same for oil and wood.

21
Chart 9.-

OIL BURNING FURNACE

-Diagram showing an arch for oil-burner installation. With this design the radiant rays of the oil fire strike the underside of

the flues in the sap pan as well as the underside of the sirup pan.

MAPLE SIRUP

The characteristics of maple sirup are discussed

here so that the development of color and flavor

will be better understood.

Composition of Sap and Sirup

The composition of maple sap and sirup is given

in table 5. The analyses in this and subsequent

tables are not average values; they are analyses

of typical saps and sirups. Usually the composition of the sirup and sap are essentially the same,

except that on an "as is" basis the constituents of

the sirup show a 30r to 50-fold increase as a result

of the concentration of the sap to sirup. The

amounts of some of the constitutents, when expressed on a dry-weight basis, are less in sirup

than in sap because of their removal from solution

as insoluble sugar sand.

The different kinds of sugar in maple sap are

not numerous (33). Sucrose, the same sugar as

in cane sugar, comprises 96 percent of the dry

matter of the sap and 99.95 percent of the total

sugar (table 6). The other 0.05 percent is composed of raffinose together with 3 unidentified

oligosaccharides. Unfermented sap does not contain any simple or hexose sugars.

The sap contains a relatively large number of

nonvolatile organic acids (table 7), even though

they account for only a small proportion of the

solids (31). Malic acid exceeds all others by 10

times. One or more of these acids may play an

important role in the formation of "maple flavor."

The ash or mineral matter (table 8) accounts

for only 0.66 percent of the whole sirup, or 1 percent of the dry solids. Although the minerals

are only a minor part of the sirup, they have

been useful in establishing the purity of maple

sirup and they contribute an astringency to the

sirup that many find desirable.

Calcium, a part of the ash, is responsible for

the hard scale, calcium malate, which forms on the

pans and is known as sugar sand. The low

sodium and high potassium content of the ash

suggests the use of maple in dietary foods.

TABLE 5.—Gomposition of maple sap and sirup ^

Item

Sugars

Organic acids

Ash

Protein

Unaccounted for

Sap (dry

Sap weight)

Percent Percent

2. 00 97.0

.030 1. 5

. 014 . 7

. 008 . 4

. 009 . 4

Sirup

(dry

weight)

Percent

98. 0

. 3

. 8

. 4

. 5

1 Typical values, not averages. Maple sap and sirup

varies in composition betweeen rather wide limits.

22
TABLE 6.—Sugars in maple sap and sirup ^

Sugars

Hexoses

Sucrose

Raffinose and a glycosyl

sucrose

Oligosaccharide I ^

Oligosaccharide II ^

Oligosaccharide III ^

Sap

Percent

0

1. 44

. 00021

. 00018

. 00020

. 00042

Sap (dry

weight)

Percent

0

96.00

. 014

.013

. 014

.028

Sirup

(dry

weight)

free amino acids; nitrogen occurs only in the form

of peptids. Whether or not the nitrogenous matter enters into the formation of maple color or

flavor is an open question.

Color and Flavor

Percent Maple sap as it comes from the tree is a sterile,

Qûliq crystal-clear liquid with a sweet taste. None of

the brown color or flavor that we associate with

maple sirup is in the sap. This is easily demonstrated by collecting sap aseptically, freezing it,

and then freeze-drymg it. The solid so obtained

is white and has only a sweet taste. The typical

color and flavor of maple sirup are the result of

1 Typical values, not averages , chemical reactions, involving certain substances

.^aÄrC.Ul^"Vi'„Ä,a """' " ' m the s», br„„.ht about bA,at as the boils

[SI). Since at least one of the products ot the

TABLE "J,—Nonvolatile organic acids in maple sap reaction is the brown color, it is known as a

and sirup ^ browning reaction. Neither the exact nature oi

— this reaction nor the identity of the reacting subSirup (dry stances is known. Indications are that 1 or more

weight) of the 6 sugars and 1 or more of the 12 organic

acids in maple sap are involved in the browning

p . reaction.

0.141 Experimental evidence indicates that the color

! 015 and flavor of maple sirup are related to trióse

• 012 sugars. These sugars are not constituents of sap

• ^^^ when it comes from the tree but are formed as

006 a result of the two reactions shown in chart 10.

Acid

Malic -

Citric

Succinic

Fumarle

Glycolic or dihydroxybutyric

Unidentified acids I, II,

III, IV2

Unidentified acids V, VI,

VII3

Sap

Percent

0.021

.002

.0003

.0003

.000

Trace

0

Sap (dry

weight)

Percent

1.40

. 13

.02

.02

.00

Trace

0

Trace

Trace FORMATION OF TRIOSES

FROM SUCROSE

1 Typical values, not averages.

2 These occur in both sap and sirup.

3 These occur only in sirup.

HYDROLYSIS OF SUCROSE

TABLE 8.—Mineral composition of maple sap ^

Item Sap Dry weight

Soluble ash

Percent

0.38

.28

Percent

0.58

Tnsnliihlp. ash .42

Total ash .66 1.00

Pnifl.ssinm .26

.07

.02

.005

.003

Trace

.40

Calcium . 11

Silicon oxide .03

IVTansranese .008

Sodium .005

Maenesium Trace

0,2 H22O11

(SUCROSE)

FERMENTATION

OF SAP

ENZYMATIC

HYDROLYSIS

(HEXOSES)

-Ce H.gOç + CßHzOe

(GLUCOSE) (FRUCTOSE)

FISSION OF HEXOSES

1 Typical values, not averages.

The nitrogenous matter constitutes only a small

part of the total solids {SO) .^ Expressed as nitrogen, the sap contains only 0.0013 percent and the

sirup 0.06 percent. The sap does not contain any

8 Also unpublished data of Eastern Utilization Research and Development Division, U. S. Agricultural

Research Service.

TRIÓSE I GLUCIC ACID

HC = 0

1

HC = 0

1

HCOH +

1

:0H"

HC=0

HCOH

1

HC = 0

+ HgO

H COH

HCOHN

/^HOCH

^ALKALI FISSION

HCOH \^ HCOH H

1

H2COH HCOH + H" HCOH

1 c = o

j

+ HgO

H2COH

CH3

TRIÓSE n ACETOL

Chart 10.—Chemical reactions showing the formation of trioses

from the sucrose of sap. In the first reaction, 1 molecule of

sucrose is hydrolyzed by enzymes to yield 2 molecules of hexose

sugars. In the second reaction, these hexoses are broken by

alkaline fission into trioses.

23
The amount of invert hexose sugars is directly

proportional to the amount of fermentation that

has occurred. The first reaction is the bacterial

or enzymatic hydrolysis of the sucrose to form

invert sugar, a mixture of fructose and dextrose.

The second reaction is the alkaline degradation

of the fructose and dextrose to trioses (SS), The

latter reaction occurs while the sap is boiling in

the sap pan, where the alkalinity of the sap

reaches a pH of 8 to 9. These trioses are highly

active chemically. They can combine with themselves to form color compounds, and they can

react with other substances in the sap, such as

organic acids, to form the maple-flavor substances.

Experiments have also established that up to a

point the amount of color formed is proportional

to the amount of flavor formed. This makes

possible the evaluation of flavor in terms of color,

a measurable quantity. When the point is reached

at which the background flavor "caramel" begins

to be noticeably formed, this relationship no

longer holds.

Factors Controlling Color and Flavor

Factors that control color and flavor are: (1)

amount of fermentation, (2) pH of the boiling

sap, (3) concentration of the solids (sugars), (4)

time of heating (the time necessary to evaporate

sap to sirup), and (5) temperature of the boiling

sap {S2). The most important of these factors are

the time required to boil sap to sirup and the

amount of fermentation products in the sap. The

temperature of the sap under atmospheric pressure (open pan) boiling is fixed, and nothing can

be done about it. Neither can anything be done

about the pH changes in the boiling sap. At the

beginning of the evaporation the natural acidity

of fresh sap is lost and the sap becomes alkaline.

It is during this alkaline phase of the pH cycle

that hexose sugars, if any are present, undergo

alkaline degradations. The sap then remains alkaline until sufficient organic acids are formed, by

the decomposition of the sap sugars, to make the

sap acid again.

The length of time the sap is boiled (the time

that it takes a unit of sap to traverse the evaporator and be drawn as sirup) is the most important

factor in development of color and flavor (S2),

The longer the boiling time the darker the sirup

and, conversely, the shorter the boiling time the

lighter the sirup. The effect of the boiling-point

factor is further augmented by the increasing

solids concentration as the sap is evaporated. This

was discussed previously in the section on evaporation. The relationship between the amount of

hexose sugars (invert sugar) produced during the

fermentation of the sap and the length of time the

sap is boiled is of the greatest importance. Thus

sirup made in exactly the same boiling time from

a series of saps of equal solids concentration (Brix

value) but with increasing amounts of invert sugar

will be progressively darker in color.

Rules of Sirupmaking

This leads to the following axioms that should

be followed in sirupmaking :

(1) Don't use fermented sap. To keep the sap

from fermenting, collect it often, don't allow it to

stand in the buckets or tanks, and keep it cold.

If there is a small flow of sap that does not warrant

collecting, dump it. Wash the sap-gathering

equipment (buckets, pails, and tanks) at least once

during a season.

(2) Speed should be the sirup producer's watchword, for speed has much to do with the color of

the finished sirup. The sooner sap is evaporated

after it has been obtained from the tree, the higher

the grade of sirup that will be produced. The

faster sap is evaporated to sirup, especially during

the last stages of the evaporation when the solids

concentration is highest, the lighter Avill be the

color and the higher the grade of the sirup.

(3) Cleanliness is a must in maple sirupmaking

for, aside from its esthetic aspects, cleanliness is

the only way that microbial contamination and

subsequent growth in the sap can be controlled.

Sirup made from sap in which growth of microorganisms has occurred tends to be dark-colored

and low in grade.

(4) By means of a hydrometer or other suitable instrument, measure and record the sugar

content of the sap produced by each tree and the

sap in the storage tanks.

Grades of Sirup

It is generally believed that the best sirup (that

is, sirup lightest in color and flavor) is made early

in the season during the first or second sap runs.

However, this is not always true, as was demonstrated in 1954 when sirup made early in the season was darker than some made later. The

important factor is the temperature. Warm

weather favors microbial growth, and the byproduct of this growth—invert sugar—affects the

color and grade of the sirup. It is only coincidental that the weather is usually cooler at the

beginning of the season and microbial growth is

low.

Sap that is essentially sterile contains very

little invert sugar, and little care is needed to

produce a light-colored, light-flavored, fancy

sirup. Sometimes, as in 1954, the weather at the

onset of the season is warm in most areas and

fermentation occurs. The result is that the firstrun sirup is darker than expected. Later in the

season, conditions reverse themselves and fancy

sirup is the rule, for with the cold weather little

or no fermentation of the sap occurs.

Making light-colored sirup with sterile sap that

is very low in invert sugar does not test a sirupmaker's skill. However, skill is required to produce light-colored sirup from sap rich in invert

sugar (with a high microbial count). This skill

is actually a measure of how fast the sirupmaker

can evaporate the sap to sirup.

24
Summary

1. Maple sap and sirup contain only sugar, pro-

^ tein, organic acids, ash, and less than 2 percent

of material not accounted for but which is of

great importance because it includes the color

^ and the flavor substances.

2. Sterile maple sap has neither color nor flavor.

-y 3. Experimental evidence indicates that the color

and flavor in maple sirup are related to trióse

sugars.

L Factors controlling the formation of color and

"^ flavor include fermentation, pH, solids conjt centration, length of boiling time, and the boiling temperature of the sap.

4 5. The shorter the boiling time, irrespective of

the quality of the sap, the lighter is the color of

sirup produced.

6. For best sirup—

(a) Use sap that has not fermented.

y (b) Use speed in collecting and in evaporating the sap.

^ (c) Keep equipment clean.

(d) Know the initial Brix value of the sap.

7. Higher grades of sirup are usually produced

earlier in the season than later on, because the

early season temperatures are usually lower

, and there is less chance of fermentation.

TABLE 9.—Viscosity ofsucrose solutions of various

densities at temperatutres of 68° and 140° F^

CONTROL OF

FINISHED SIRUP

Finishing the sirup is one of the most exacting

tasks in maple sirupmaking. The sirup must be

drawn from the evaporator or finishing pan at

just the right instant; otherwise its solids content

will be either too high or too low. To conform

with minimum Federal and State requirements,

sirup must have a solids content (density) of not

less than 65.46° Brix at a temperature of 68° F.

In this region, a little more or a little less evaporation has a relatively big effect on the concentration (table 4). Hence when using large evaporators capable of evaporating several hundreds of

gallons of water per hour, accurate control of

the sirup being drawn off is both important and

difficult.

Viscosity of IVIapie Sirup

Maple sirup with a density only 0.5° to 1° Brix

below standard-density sirup tastes thin. This is

due to the pronounced change in the viscosity of

sugar solutions with only slight change in concentration, especially in the range of standard-density sirup. At a temperature of 68° F., an

increase in the density of sirup from 0° to 20°

Density of solution (° Brix)

Viscosity at--

68° F. 140 ' F.

20

Centipoises

2.0

58.9

69.7

83.0

99. 8

121.0

148.2

164.3

193.3

229.4

290.5

372.7

Centipoises

0 8

60 9. 7

61 10. 9

62 ___ 12. 2

63 _ 13. 8

64 15. 7

65- - - - - 18. 0

65.5 19. 4

66 20. 7

67 24. 0

68 28. 0

69 33.0

1 Data from pp. 671, 674 of Circular C440 issued by the

National Bureau of Standards, TJ. S. Department of

Commerce.

Brix increases its viscosity only 2 centipoises

(table 9), whereas in the range of standard-density siruj) an increase of only 9° Brix (from 60°

to 69°) increases its viscosity 313.8 centipoises

(from 58.9 to 372.7). Thus, in this range only a

slight difference in density changes the viscosity

of the sirup sufficiently to be detectable to the

tongue.

As shown in the table, the viscosity of sirup is

lowered 16.1 centipoises if its density is only 0.5°

Brix below standard density, and 43.3 centipoises

if is is 1° Brix below standard density. The

tongue is sensitive enough to detect these differences. The lowered viscosity has a marked effect

on the keeping quality of the sirup and on its

acceptance by consumers.

Likewise, the tongue is sensitive to slight increases in the density of sirup above standard

density. An increase of only 0.5° Brix above

standard density increases the viscosity of sirup

19 centipoises, and the sirup acquires a thick,

pleasant feel to the tongue. Thus, the thicker the

sirup the better it tastes. However, sirup with a

density of more than 67° Brix crystallizes on

storage at room temperature, and 67° Brix therefore becomes the upper permissible density.

Sirup tastes best, based on its density, between

66° and 67° Brix at a temperature of 68° F.

At higher temperatures the viscosity of a sirup

solution is much lower, as shown in table 9, and

this accounts for the fact that all warm or hot

sirup appears and tastes thin.

Old Standards of Finished Sirup

In the past, the finishing point of sirup was determined by a number of methods, none of which

was highly accurate, and their use required skill

and artfulness. For that reason comparatively

few men have won the title of "sugarmaker."

446270 0—58 25
Typical of these methods was the "blow" test.

In this test, a small loop of wire was dipped into

the "sirup." When the film of sirup that formed

across the loop required a certain puff of breath

to blow it off, the sirup was considered finished.

Another method in more common usage was the

"apron" test. In this, a scoop was dipped into the

sirup and then held in an upright position to

allow the sirup to drain off. Formation of a

large, thin sheet or apron with the right shape

and other characteristics indicated that the sirup

was tinished.

Use of Precision Instruments

Precision instruments are now available by

which the finishing point of sirup can be determined easily and with a high degree of accuracy.

As concentration progresses, there is a progressive

increase in the boiling point, in density, and in

refractive index. These can be measured accurately with a thermometer, a hydrometer, and a

refractometer, respectively. However, only the

measurement of the elevation of the boiling point

is applicable to a sugar-water solution, such as

sap, while it is actively boiling.

Elevation of the Boiling Point

Chart 11 shows the changes in boiling-point

temperature for sugar solutions at different concentrations. When a sugar solution has been

evaporated to the concentration of standard-density sirup (65.46 percent of sugar or 65.46° Brix),

its boiling point has been elevated 6.85° F.

above the boiling point of water. Between 0°

and 27° Brix, there is only a slight elevation in

boiling point. However, as the solution nears the

concentration of standard-density sirup, a change

of only 2.5 percent in sugar concentration (from

64.5° to 67° Brix) raises the boiling point 1° F.

Hence, in this region the boiling-point method is

ideally suited to sirupmaking. Any Fahrenheit

thermometer calibrated in degree or half-degree

intervals and with a range that includes 225° F.

can be used. For greatest usefulness and accuracy the distances between degree lines should be

as open as possible.

Elevation of the boiling point as used here

means the increase in temperature (° F.) of the

boiling point of the sugar solution above the temperature of boiling pure water. Ife has nothing

to do with the specific temperature 212° F. except

when the barometric pressure is 760 mm. mercury.

Under actual conditions of sirupmaking the barometric pressure is seldom at 760 mm. ; therefore,

it is best not to associate the fixed value of 2i2° F.

with the boiling point of water.

A much safer and the recommended procedure

is to establish the temperature of boiling water

on the day and at the place sirup is being made.

To do this, merely heat water to boiling, insert the

bulb of a liquid stem thermometer or the stem of

a dial thermometer and note the temperature while

0 20 40 60

SUCROSE CONCENTRATION (PERCENT)

Chart 11.—Curve showing the relationship between the concentration of a sugar solution (sap) and the elevation of its boiling

point above the boiling point of water.

the watßi;is actually boiling. This is the trim temperature of boiling water for the barometric pressure at.that time and place. In practice, the boiling sap in the sap pan can be used to establish the

temperature of boiling water since, as was shown

in chart 11, at low-solids concentrations (up to

10° Brix) there is little elevation of the boiling

point. The boiling temperature of standarddensity sirup is then found by adding 7 to the

temperature of the boiling sap.

It is of the greatest importance to redetermine

the temperature of boiling water (sap) at least

once and preferably several times each day, especially if the barometer is changing as noted by

a change in the weather. The result of failure to

make frequent checks on the boiling point of water

is illustrated in the following examples :

On March 1, at Gouverneur, N. Y., the boiling

point of water was determined to be 210° F., which

established the boiling point of standard-density

sirup as 217°. On March 2, the producer neglected

to redetermine the boiling point of water, assuming it to be unchanged, and continued to use 217°

as the boiling point of sirup. Actually, the barometric pressure had fallen, which lowered the

boiling point of water to 208° and of standarddensity sirup to 215°. The sirupmaker, by using

the temperature of 217°, was boiling his sirup

26
Lu

hZ

i

oc

UJ

a

(fi

<

oc

z

o

<

o

o.

<

>

oc

Lu

H

<

BRIX (DEGREES)

Chart 12.—Change in the rate of loss of water by evaporation, with constant heat, as the concentration of sap increases. Boiling sap

with an initial density of 22° Brix loses 42 grams of water per minute, whereas sirup with a density of 65° loses only 15 grams

of water per minute, a threefold decrease in rate.

2^ too high, and the sirup contained 69.5 percent

of solids instead of 65.4 percent (chart 11). This

high-density sirup not only resulted in fewer gallons of sirup made, but the sirup crystallized in

storage since it was above 67"^ Brix.

If, on the other hand, the reverse had occurred,

the sirupmaker would have made sirup with a boiling point 2° F. too low. Such sirup would contam only 59.4 percent of solids as sugar. It would

not meet specifications for standard-density sirup,

would tend to spoil easily, and would have a low

viscosity and therefore would taste watery.

Special Thermometers

In sirupmaking, a knowledge of the boiling

point of standard-density sirup in ° F. is unimportant providing a temperature reference point

(the boiling point of water) is established and the

correct boiling point of sirup is located 7° above

it. On this basis, two special thermometers have

been developed for use in making sirup. One is

a liquid-stem thermometer with movable target

and the other is a dial thermometer with movable

dial.

Target thermometer.—The target thermometer (fig. 51) does not have any markings on the

stem. The degree lines on a movable target refer

to the boiling point of water, rather than to ° F.

as on the conventional Fahrenheit thermometer.

This thermometer is calibrated by placing the

bulb in either boiling water or boiling sap. The

target is moved by means of an adjusting screw

until the line "water boils" coincides with the

top of the mercury column. The line "sirup" is

exactly 7° above the line "water boils." This is

the boiling point of standard-density sirup for

that day and place. After adjustment, the thermometer is placed in the sirup pan adjacent to

the place where the sirup is drawn off. Unfortunately, atthis position, it is surrounded by steam

and is difficult to read (fig. 52).

27
Use of a flashlight to illuminate the thermometer and a large funnel to divert the steam will

make viewing easier. The funnel is held with

the tip toward the thermometer, and the thermometer is viewed through the funnel with the

aid of the flashlight. For maximum accuracy it

is desirable for any thermometer to have as great

a distance as possible between the "water boils"

line and "sirup" line. Since this is only 7° F.

the thermometer will have a very fine column of

liquid.

Dialthermometer.—The degree lines of the dial

thermometer (10), like the target thermometer,

refer to the boiling point of water (fig. 53).

This thermometer has a bimetallic element in the

first 3 or 4 inches of the stem. As the indicator

is a needle, the openness of scale is governed by

the length of the needle and the accuracy required. The scale is twice as open in a dial

thermometer 5 inches in diameter as in the target

thermometer.

The dial thermometer is calibrated by imniersing the part of its stem that contains the bimetallic element in boiling water or sap the same

distance that it is immersed in the sirup; when

the indicating needle comes to rest, the dial is

rotated by means of an adjusting screw until the

zero or "water boils" line coincides with the

pointer. Then the "sirup" line is located 7° F.

above the zero or "water boils" line to indicate

the boiling temperature of standard-density sirup

for that day and place.

The long straight stem of this thermometer is

inserted through the wall of the sirup pan and

sirup drawoff box so it will be parallel to the

bottom of the pan and entirely immersed in the

boiling sirup. The dial of the thermometer is

on the outside of the evaporator where it is out

of the steam and easy to read (fig. 53).

The physical factors that affect the finishing

of the sirup are in the sirupmaker's favor. These

are the rapid change in elevation of the boiling

point and the decrease in the rate of water loss

(by evaporation) as the sap approaches the concentration of standard-density sirup. The elevation of the boiling point, as has been discussed,

makes it possible to follow small changes in concentration by means of a thermometer. Also, as

shown in chart 12, with constant heat, the loss

of water per minute from boiling sap decreases

as the concentration increases. Therefore, as the

sap approaches the concentration of standarddensity sirup, loss of water per minute slows down

and the sirupmaker has a reasonable time in

which to adjust the drawoff valve.

temperature of the sirup being tested with the

hydrometer must be known so that the necessary

corrections can be made. The hydrometer and

refractometer are the only instruments that can

be used to measure the density of sirup that is

not in an actively boiling state.

A special hydrometer, the hydrotherm (chart

13), has a liquid thermometer built into it that

automatically locates the point on the hydrometer (top of thermometer liquid column) for

standard-density sirup. The accuracy of this

instrument depends on the relationship of lineal

expansion of the thermometer liquid to lineal displacement of the hydrometer stem by standarddensity sirup at different temperatures. In use,

sufficient time must be allowed for the thermometer of the hydrotherm to warm to the

temperature of the sirup.

Many sirupmakers use hydrometers successfully by standardizing their technique so exactly that they can reproduce the empirical conditions of the test each time, and so can test the

density of sirup that is near its boiling point

(210° F., hot test). For example, each mechanical operation (filling the hydrometer can, inserting the hydrometer, etc.) is standardized so

STANDARD

DENSITY

SIRUP

HYDROTHERM

FOR

MAPLE

SIRUP

THERMOMETER

Hydrometers

A hydrometer is not the ideal instrument for

judging the finishing point of sirup because it is

not calibrated at the temperature of boiling sirup

and it cannot be used to follow the concentration

of the sap continuously. For accuracy, the exact

Chart 13.—The hydrotherm, a special type of hydrometer. When

this instrument is placed in sirup, the top of the mercury column of the built-in thermometer automatically locates the point

on the hydrometer stem that corresponds to standard-density

sirup.

28
the same length of time is always used to make

the test and consequently the sirup cools for the

same length of time and to the same temperature (approximately 210°) each time the test

is made.

For those who prefer the hydrometer to test

the finishing point of sirup, the data in table 10

(p. 34) may be used. This table shows that standard-density sirup at a temperature of 210° F.

(hot test) is 58.8° Brix and 31.9° Baume.

Summary

1. Finished sirup must contain not less than 65.46

percent of solids (65.5° Brix) at a temperature

of 68° F.

2. Table sirup that is between 66° and 67° Brix

will have the best taste. Table sirup that is

below standard density will taste thin.

3. Use precision instruments to measure standard-density sirup.

4. The boiling temperature of standard-density

sirup is 7° F. above the temperature of boiling

water.

5. Use a thermometer to measure the temperature

of boiling sirup.

6. Calibrate the thermometer frequently with

reference to the boiling point of water.

7. Completely immerse in the boiling water or

sap the bulb of the stem of a liquid thermometer or that part of the stem of a dial

thermometer containing the bimetallic element.

8. To test hot sirup with a hydrometer, the temperature of the sirup must be noted and necessary temperature corrections applied to the observed hydrometer readings.

9. To test hot sirup with a hydrotherm, sufficient

time must be allowed for the hydrotherm to

come to the same temperature as the sirup in

which it is floated.

CLARIFICATION OF SIRUP

Sugar Sand

Sirup as it is drawn from the evaporator contains suspended solids, commonly known as sugar

sand. The amount and color of these solids vary

widely and depend on many factors. They are

primarily the calcium salts of malic acid. These

salts are precipitated because they become less

soluble (1) as the temperature of the sirup solution increases and (2) as its concentration increases. Sugar sand occurs in various forms,

ranging from an amorphous black oily substance

to a fine white crystalline material. Dark sugar

sand will usually cause the sirup to appear a

grade or two darker, whereas white sugar sand

will often cause it to appear lighter in color.

The amount and form of this precipitate in the

sirup is not always the same. Sap from a given

sugar bush varies from year to year and even

within the same sugar season.

Sirup to be sold for table use must be clear

(free of suspended matter) to meet Federal and

some State specifications. Sirup can be clarified

by sedimentation, filtration, or centrifugation.

On the farm, sedimentation and filtration are the

methods generally used.

Sedimentation

The sedimentation or settling method is the

simplest method of clarifying maple sirup, but

unfortunately it has several serious disadvantages. It cannot be used to clarify all sirup.

Some sirups contain suspended particles the size

and nature of which make them resistant to

settling. Clarification by sedimentation requires

a long time—days and sometimes weeks. The

sirup cools to room temperature and must be reheated to 180° F. before packaging to insure a

sterile pack.

To clarify by sedimentation the hot sirup is

first put through a coarse filter, such as several

layers of flannel or cheesecloth, to screen out large

particles of foreign matter. It is then transferred

to the settling tank. The tank should be of noncorrosive metal, and its height should be at least

twice its diameter. It should have a dustproof

cover and a spigot or other means of drawing off

the sirup about 2 inches above the bottom of the

tank. The sirup should be left in the tank until

samples that are withdrawn show it to be sparkling clear. It is then drawn from the tank, standardized, heated, and packaged. Sirup that has

failed to clarify after several weeks of standing

must be filtered. Because of the uncertainty of

the sedimentation method it is rapidly losing

favor.

Filtration

Filtration of maple sirup is not a simple procedure. As with sedimentation, the success and

ease of clarification by filtration depends on the

nature of the particles to be removed. It is best to

use two filters, a prefilter to remove the coarse

material and a thicker filter to remove the fine.

In the past, the most commonly used prefilter

was several layers of cheesecloth, outing flannel,

or similar cloth. Today a nonwoven rayon material called miracle cloth or maple prefilter paper

is used with considerable success. Following the

prefilter the sirup is run through a thicker filter,

usually a layer of wool felt.

The most common filtration assembly is a large

milk can in which is inserted a cone-shaped wool

felt bag (fig. 54) supported at the top of the can

29
with clothespins. Over this is placed the prefilter, also supported with clothespins and arranged to form a smaller cone within the felt.

Because sirup filters best when it is hot, it is

customary to set the milk can with its filters directly under the sirup drawoff valve of the evaporator or finishing pan so that the hot sirup runs

directly onto the filter. If the sirup cools off before it has all passed through the filters, the rate

of filtration will be slowed down. Several manufacturers of sirup equipment have developed

insulated boxes fitted with covers so that the sirup

will stay hot while filtering. Usually the boxes

are made to hold two or more filters to be used

in rotation.

Even when a prefilter is used, the felts soon

become heavily coated with sugar sand or filter

cake. This filter cake usually appears as a darkbrown mudlike substance and slows down the rate

of filtration. The filters have to be cleaned often

to maintain filtration at a rapid rate.

To clean the filters, the filter cake is scraped

off and the entrapped sirup is dissolved by dipping the bag in a pail of hot water or hot sap

taken from the evaporator. The water or sap can

be returned to the sap pan. Washing is completed by turning the bag inside out and washing

it several times in hot water. Soap or other

detergent should not be used because they add

ñavor to the sirup if they are not completely

rinsed out. The bag is then turned right side out

and the water is removed by passing it through a

clothes wringer. Prefilters can be cleaned in a

similar manner.

Flat Filters

A flat-type filter consists of a square felt filtering surface (fig. 55) instead of the cone. It was

first used in New York, and its use is gaining in

popularity elsewhere. The flat filter provides a

larger filtering area than the cone-shaped filter

during the entire filtering period ; distribution of

the filter cake over this larger area results in a

thinner layer, so the filters can be used for longer

periods before cleaning becomes necessary.

The felt sheet is supported in a shallow basket

of hardware cloth with 2-inch walls. The felt is

cut at least 4 inches larger than the bottom of the

basket, and the edges are turned up 2 inches to

form a shallow tray. The felt can be used 2 or

3 times longer between cleanings if the sirup is

first put through a prefilter, as described previously. The prefilter is mounted above the felt

and it is supported on a wire-screen basket the

same size as that used for the felt (chart 14).

The prefilter is cut to fit across the basket, but a

length of filter paper is left hanging over the edge

of the basket. As the prefilter becomes clogged,

a new filtering surface is provided by pulling the

prefilter part way across the basket (fig. 56).

The filters can be built in multiples over a common tank, as shown in figure 57. As one becomes

Roper filter

Suggested filter trays

heavy gage metal or

wood

'4

^Q--mch mesh,

alvanized hardware

cloth

Standard milk

can wash tank

SIRUP FILTER

Chart 14.—A flaMype felt filter assembly, constructed on a milkcan washer that serves as a temporary storage tank from

which the hot sirup can be drawn for packaging. Shortening

the legs and attaching castors or wheels permits the assembly

to be moved easily into place under the sirup drawofF spigot.

clogged with sugar sand, the assembly can be

moved so as to place a clean filter under the

spigot.

The flat prefilters and felts are cleaned in the

same way as the cone filters.

Summary

Sedimentation

1. Strain the sirup through a paper prefilter, or

cheesecloth.

2. Place sirup in settling tanks.

3. Allow it to stand until all suspended matter has

settled out. (Test by periodically drawing a

small sample from the tank spigot.)

4. Sedimentation is complete when the sirup is

crystal clear as it is drawn off.

5. If the sirup is still cloudy at the end of several

weeks, it can be clarified only by filtration.

Filtration (preferred method)

1. Run the hot standard-density sirup from the

evaporator or finishing tank directly on the

filters.

2. Use flat (preferably) or cone-shaped filters consisting of a prefilter (paper or flannel) above

the felt filter.

3. Change the prefilter and the felt filter as often

as necessary to maintain a rapid rate of filtration.

30
STANDARDS FOR

MAPLE SIRUP

For Retail Sale

The maple-sirup producer often finds it profitable to sell his sirup directly to the consumer. In

doing so, the farmer is not only a producer but he

is a food processor as well. As a food processor

he is expected to offer for sale a productthat meets

Federal and State requirements, and he must

package his sirup so that it will compare favorably in appearance and quality with other luxury

food items.

Vermont has taken the lead in the United

States and has enacted regulations governing the

sale and labeling of maple products (4S). Wisconsin (53) and New York (26) are among the

other States that are establishing similar regulations. To obtain information regarding your

State regulations governing the sale of maple

products write to the Division of Markets, Department of Agriculture, at your State capital.

These regulations protect the buyer and assure

him the product he has purchased meets certain

minimum standards, and they also protect the

producer against unfair competition.

The United States Standards for table maple

sirup (^4) are as follows :

UNITED STATES STANDARDS FOR

TABLE MAPLE SIRUP

Effective February 15, 1940

INTRODUCTION

Numbers in parentheses following grade terms indicate where such terms are defined under Definition of

Terms.

These standards are issued for the purpose of classifying maple sirup packed in containers for table use. It is

not intended that they shall apply to sirup which is

packed in drums or other large containers for later reprocessing. Another set of standards entitled ^'U. S.

Standards for Maple Sirup for Reprocessing*' has been

issued for this purpose.

GRADES

U. S. Grade AA {Fancy) TaMe Maple Sirup shall consist of maple sirup (1) which meets the following requirements :

The color shall not be darker than light amber as

represented by the color standards of the United States

Department of Agriculture.

The sirup shall not be cloudier than light amber cloudy

standard as represented by the standards of the United

States Department of Agriculture for cloudiness ( 2 ).

The weight shall be not less than 11 pounds per gallon of 231 cubic inches at 68° F. corresponding to 65.46"

Brix or 35.27° Baume (Bureau of Standards Baume scale

for sugar solutions, modulus 145).

The sirup shall possess a characteristic maple flavor,

shall be clean (3), free from fermentation, and free from

damage (4) caused by scorching, buddiness, any objectionable flavor or odor or other means. ( See Tolerance. )

U. 8. Grade A Tahle Maple Sirup shall consist of maple

sirup (1) which meets the requirements for U. S. Grade

AA (Fancy) Table Maple Sirup except for color and

cloudiness (2).

The color shall not be darker than medium amber as

represented by the color standards of the United States

Department of Agriculture.

The sirup shall not be cloudier than medium amber

cloudy standard as represented by the standards of the

United States Department of Agriculture for cloudiness

(2). (See Tolerance.)

U. S. Grade B TaMe Maple Sirup shall consist of maple

sirup (1) which meets the requirements for U. S. Grade

AA (Fancy) Table Maple Sirup except for color and

cloudiness (2).

The color shall not be darker than dark amber as represented by the color standards of the United States Department of Agriculture.

The sirup shall not be cloudier than dark amber cloudy

standard as represented by the standards of the United

States Department of Agriculture for cloudiness (2).

(See Tolerance.)

Unclassified Table Maple Sirup shall consist of maple

sirup which has not been classified in accordance with the

foregoing grades. The term "Unclassified" is not a grade

within the meaning of these standards but is provided

as a designation to show that no definite grade has been

applied to the lot.

Tolerance for Preceding Grades

In order to allow for variations incident to proper

grading and handling, not more than 5 percent, by count,

of the containers in any lot may have sirup below the

requirements for the grade, provided that no part of this

tolerance shall be allowed for defects causing serious

damage (5) and provided further that no tolerance is

permitted for sirup that is darker in color than that

which is required for the next lower grade.

Packing

Containers shall be clean and new in appearance. Tin

containers shall not be rusty.

In order to allow for variations incident to proper packing, not more than 5 percent, by count, of the containers

in any lot may fail to meet these requirements.

Definition of Terms

As used in these standards :

1. "Maple Sirup" means sirup made by the evaporation

of maple sap or by the solution of maple concrete (maple

sugar) and contains not more than 35 percent of water,

and weighs not less than 11 pounds to the gallon (231

cubic inches).

2. "Cloudiness" means presence in suspension of fine

particles of mineral matter, such as malate of lime,

"niter," "sugar sand," or other substances that detract

from the clearness of the sirup.

3. "Clean" means that the sirup shall be practically

free from foreign material such as pieces of bark, soot,

dust, and dirt.

4. "Damage" means any defect that materially affects

the appearance or the edibility or shipping quality of the

sirup.

5. "Serious damage" means any defect that seriously

affects the edibility or market value of the sirup. Badly

scorched sirup, buddy sirup, fermented sirup or sirup

that has any distasteful foreign flavor or disagreeable

odor shall be considered as seriously damaged.

Issued : February 7,1940.

31
Summary

1. Sirup sold directly to the consumer must meet

State and Federal specifications.

2. The package and label must meet State and

Federal specifications.

3. Know your State law governing the retail sale

of maple products.

4. Federal specifications for table sirup are given

in this section.

CHECKING AND ADJUSTING THE DENSITY

OF SIRUP

The one specification that all grades of table

sirup must meet, irrespective of color or other considerations, is density. The minimum allowable

density of maple sirup is 11 pounds per gallon of

231 cubic inches at a temperature of 68° F., which

corresponds to 65.46° Brix or 35.27° Baume (Bureau of Standards Baume scale for sugar solutions,

modulus 145).

The density of sirup can be measured in three

ways: (1) Bj weight, (2) by refractometry, and

(3) by hydrometry.

Weight Method

Determination of the density of sirup by the

weight per unit of volume is not recommended as

a general testing procedure for farm use. This

test can be made only under the most exacting

conditions and with precision instruments. The

gallon measure must have a capacity of exactly

231 cubic inches, the temperature of the sirup

must be exactly 68° F., and the weight of the sirup

must be determined accurately to within 0.01

pound. If any one of these conditions (volume,

temperature, or weight) is in error, the measurement is valueless. For example, an exact gallon

of 231 cubic inches of sirup at 68° F., with a Brix

value of 63.5° weighs 10.90 pounds, whereas the

same volume of sirup at the same temperature

but with a Brix value of 67.5° weighs 11.10

pounds. Thus, two sirups could differ 4 percent

in their solids content and yet differ only 0.2

pound in weight, an amount not detected by

ordinary scales, so they would both appear to

weigh 11 pounds per gallon.

Refractometry Method

The determination of the density of sirup by

measuring its refractive index is the simplest of

the three methods. This method is not in general

use because it requires the use of a refractometer.

an expensive optical instrument. However, the

precision of the density measurement that can

be made with the refractometer makes it well

suited for use by Federal and State inspection

services and by judges of sirups placed in

competition.

Hydrometry Method

Hydrometry is the most generally used method

for measuring the density of cold sirup, and it

is best suited for use by the sirupmaker. All that

is required to make precise density measurements

is a relatively inexpensive but accurate hydrometer, a thermometer, and a hydrometer tube or

jar. The densit;^ of a liquid is measured by

means of a floating body. The hydrometer, a

partly immersed body, displaces a volume of

liquid having a mass equal to the weight of the

hydrometer. The level of the liquid surface on

the stem of the hydrometer is noted when the

hydrometer is at rest and floating freely in the

liquid, as shown in chart 15. The density value

HYDROMET.ER STEM

"A-

^

READING

•POINT

I^

Chart 15.—Hydrometer, an instrument for measuring cfensity.

The hydrometer can should be filled to the top and the hydrometer should be read by holding the top of the can at eye level.

is read from a scale sealed in the stem. The precision or accuracy of a hydrometer measurement

depends on the spacing of the markings on the

scale in the hydrometer stem, which in turn depends on the diameter of the stem. Thus, the

thinner the stem the farther apart the markings

(more open the scale) and the greater the ac32
curacy of the density measurements. Hydrometers for measuring density of sirup may have

the enclosed scale marked and calibrated with 1

of 3 systems or combination of these systems:

(1) Specific gravity, (2) Baume scale, or (3)

Brix scale (chart 16).

Both specific gravity and Baume value relate

the weight of a unit volume of the solution being

tested (maple sirup) to some other liquid used

as a standard; they give no direct information

regarding the solids content of the sirup being

tested.

HYD ROM ET ERS

BAUME

25

30

35

40

BAUME BRIX. BRIX.

VT.

60 F.

N. Y.

68°E 68 F.

Charf 16.—The three hydrometer scales used in testing sirup.

Left, Vermont Baume scale, marked for testing sirup at a temperaiure of 60° F.; standard-density sirup at this temperature

is indicated by the heavy line at 36°. Right, Brix scale,

marked for testing sirup at 68°; standard-density sirup at this

temperature is indicated by the heavy line at 65.46°. Center,

hydrometer v^ith double scale, marked for testing sirup at 68°;

standard-density sirup on the Baume scale of this hydrometer

is indicated by the heavy line at 35.27°. The double scale

requires a spindle so large in diameter that accurate readings

are difficult to make, since the scale must be compressed.

The Brix Scale

The Brix scale relates the density of sirup to

sugar solutions of the same density and known

percentages of sugar. The Brix value does not

express the true percentage of sugar in a solution

containing sugar plus other dissolved solids;

rather, it indicates what the percentage of sugar

would be if the density of the solution were due

only to dissolved sugar. The Brix scale is particularly well suited for measuring the density of

maple sirup because 98 percent of the dissolved

solids is sugar, and for practical purposes the

Brix value (°Brix) equals the percentage of

sugar in the sirup.

The approximate weight of sugar in any lot of

maple sirup, whether or not it is standard-density

sirup, can be found by multiplying the weight of

the sirup by its density (° Brix) and dividing by

100. This information is of great importance to

the producer who sells his sirup wholesale, since

the price is based on its solids (sugar) content.

Thus, 100 pounds of sirup at 64° Brix contains 64

pounds of sugar whereas 100 pounds of standarddensity sirup (65.5° Brix) contains 65.5 pounds

of sugar. Therefore, 100 pounds of the low-density sirup has a lesser value than 100 pounds of

standard-density sirup. Likewise, 100 pounds of

sirup with a density of 66.8° Brix contains 66.8

pounds of sugar, which is more than in 100

pounds of standard-density sirup, and it has a

greater value.

To obtain the weight of sugar in sirup when

density is measured by a hydrometer whose scale

is in specific gravity or ° Baume requires more

involved calculation, as neither scale has a direct

relationship to the amount of sugar present.

The Baume Scale

Even though the Baume scale does not express

directly the solids content of maple sirup and its

continued use cannot be recommended, its long

usage by the maple industry justifies the following explanation :

The Baume scale relates the density of a liquid

to that of a salt solution, but it is more convenient

to calculate the Baume value from specific-gravity tables. Thus, ° Baumé=sp.g. /íuj^ where

M=the modulus.

In the past, unfortunately, neither the temperature for which the Baume scale was calibrated nor

the modulus was standardized. Today, M is

standardized at 145. The temperature for calibration is standardized at 68° F. (except in Vermont). In Vermont the scale is marked at 36°

(for use at 60° F.), and standard-density sirup

will have a Baume reading of 36° when measured

at a temperature of 60°. In other States and for

Federal specifications the scale is marked at 35.3°

(for use at 68° F.). When this scale is used,

standard-density sirup will have a Baume reading

of 35.3° at a temperature of 68°. When using a

Baume hydrometer, caution must be exercised in

observing the temperature at which the scale is

to be used.

Making the Density Measurement

To make the measurement, fill the hydrometer

can to the top with sirup and hold it above the

finishing pan so that any sirup displaced by the

hydrometer will fall back in the finishing pan.

Hold a clean, dry hydrometer lightly in the hand

446270 O—58- 33
and let it sink into the sirup until it comes to rest

(fig. 58). Take care not to get any sirup on that

portion of the stem extending above the surface

of the sirup. This would add to the weight of

the hydrometer and make the sirup appear to be

of lower density.

After the hydrometer has come to rest, raise the

hydrometer can to eye level and obtain the density reading by sighting across the top of the jar

or cylinder and noting the point on the scale of

the hydrometer that is at the surface of the sirup.

This hydrometer reading is the apparent density

of the sirup.

However, maple sirup is a sugar-water solution

and it behaves like water, contracting and expanding with changes in temperature. Therefore,

standard-density sirup has different densities at

different temperatures. Table 10 shows the

TABLE 10.—Weight and hydrometer reading of

standard-density sirup at different temperatures

Temperature (° F.)

Weight

per gallon 1

Hydrometer reading

50

Pounds

11. 043

11. 038

11.035

11.028

11. 024

11.019

11.014

11. 009

11. 005

11. 000

10. 995

10. 991

10. 986

10. 981

10. 976

10. 972

10. 959

10. 948

10. 936

10. 923

10. 912

10. 900

10. 888

10. 878

10. 865

10. 855

10. 830

10. 807

10. 783

10. 760

10. 737

10. 715

10. 692

10. 669

° Brix

66.32

66.22

66. 13

66.04

65.94

65.85

65.75

65.65

65.55

65.46

65.37

65.27

65. 18

65.08

64. 99

64.90

64.66

64.43

64. 19

63.96

63.72

63.49

63.25

63.02

62.78

62. 55

62.08

61. 61

61. 14

60.67

60.20

59.73

59.26

58. 79

° Baume 2

35. 70

52 35. 65

54 35. 61

56 35. 56

58 35. 51

60 35. 46

62 35. 41

64 _ 35. 37

66 35.32

68 35.27

70 35. 22

72 35. 17

74 __ 35. 13

76 35.08

78 35. 03

80 34. 98

85 - _ - __ 34.86

90 34. 74

95 _ _ __ 34.62

100 34. 50

105 34.38

110 34. 26

115 34. 14

120_ 34. 02

125 _ _ _ 33. 90

130_ 33. 78

140 33. 44

150 _____ 33. 30

160 33.06

170 32.82

180 _ - --- 32. 58

190 - - -- - 32.34

200 32. 10

210 (hot test)_ 31.86

weight per gallon, the Brix value, and the Baume

value of standard-density sirup at temperatures

from 50° to 210° F. {38),

To determine whether or not the sirup is standard density, carefully measure the temperature of

the sirup in the hydrometer can; then locate the

hydrometer reading for standard-density sirup at

that temperature in table 10. If the observed

hydrometer reading is less than the value in the

table, the sirup is too thin; if the reading is

greater than that value, the sirup is too thick.

Correcting for Temperature

To determine the density (Brix or Baume

value) of sirup that is either warmer or colder

than the temperature for which the hydrometer

is marked for use, a correction must be made by

TABLE 11.—Amount to add to ( + ) or subtract

from ( — ) the observed reading on a hydrometer

marhed for use at 68"^ F. {Brix or Baume) and

on a hydrometer marked for use at 60° {Bamné)

to obtain the true density of maple sirup tested

at various temperatures

1 231 cubic inches.

2 M=145.

Temperature of

sirup tested (° F.)

Hydrometer

with Brix

scale—

Hydrometer with

Baume scale—

For use at

68° F.

For use at

68"^ F.

For use at

60° F.

50

° Brix

-0.86

-.61

-.39

-. 14

0

+.09

+ .33

+.56

+.80

+ 1.03

+ 1.27

+ 1. 50

+ 1.74

+ 1. 97

+ 2.21

+ 2. 44

+2.68

+ 2.91

+3. 15

+3.38

+ 3.62

+ 3.85

+ 4. 09

+ 4. 32

+ 4.56

+ 4.79

+5.03

+ 5. 26

+ 5. 50

+ 5.73

+ 5.97

+ 6.20

+ 6.44

+ 6.67

° Baume

-0.43

-.31

-.19

-.07

0

+ .05

+.17

+ .29

+.41

+.53

+ .65

+.77

+.89

+ 1.01

+ 1. 13

+ 1. 25

+ 1.37

+ 1. 49

+ 1. 61

+ 1.73

+ 1. 85

+ 1.97

+ 2. 09

+ 2.21

+ 2. 33

+ 2. 45

+ 2.57

+2.69

+ 2.81

+ 2. 93

+ 3.05

+ 3. 17

+ 3.29

+ 3.41

° Baume

-0.24

55 —. 12

60 - _-_ 0

65 + . 12

68 -

70 + .24

75 __ + . 36

80 + .48

85 +. 60

90 +.72

95 __- +.84

100 _ - + . 96

105 + 1.08

110 -- + 1. 20

115 + 1. 32

120 + 1. 44

125 _ _ _ + 1. 56

130 + 1.68

135 _ + 1.80

140 + 1.92

145 +2.04

150 + 2. 16

155 + 2.28

160 +2. 40

165 + 2.52

170 __ - + 2.64

175 + 2.76

180 + 2. 88

185 + 3.00

190 - + 3. 12

195 _ + 3.24

200 + 3. 36

205_ + 3.48

210 (hot test) + 3.60

34
adding to or subtracting from the observed density reading.

If the temperature of the sirup is between 50°

and 210° F. when tested, its approximate density

may be obtained by using the data in table 11.

The data show the amount that must be added

to ( + ) or subtracted from ( — ) the observed

reading on a hydrometer marked for use at 68°

F. (Brix or Baume) and on a hydrometer marked

for use at 60° (Baume), to obtain the true density

of the sirup.

The approximate density of maple sirup can

also be obtained by the following simple calculation: Determine the difference (° F.) between

the temperature of the test sirup in the cylinder

and the temperature at which the hydrometer is

marked for use (60° or 68°). Multiply this difference by 0.047 if the hydrometer has a Brix

scale (0.024 for Baume). Add the result to the

observed density for sirup warmer than the temperature for which the hydrometer is marked;

suh tract the result from the observed density for

sirup that is colder.

Example 1,—Suppose the temperature of the

sirup at the time of testing is 78°, and it is tested

with a hydrometer marked for use at 68° F.—a

difference of 10°. The observed hydrometer reading is 65.0° (Brix scale) and 35.0° (Baume scale).

The correction for the Brix scale is 0.047x10=

0.47°. Since the temperature of the test sirup is

higher than 68° F., the correction is added to the

observed reading. Therefore, the true density of

the sirup is 65 + 0.47 = 65.47° Brix.

The correction for the Baume scale (marked for

use at 68° F.) is 0.024X 10 = 0.24°. The true density would be 35.0 + 0.24=35.24° Baume.

Suppose the same sirup (at a temperature of

78°) is tested with a hydrometer with a Baume

scale marked for use at 60° F., a difference of 18°.

The correction is 0.024X18 = 0.43° Baume. The

true density of the sirup is 35.0°+ 0.43 = 35.43°

Baume.

TABLE 12.—Amount to add to ( + ) or suhtract from ( — ) the observed reading on a hydrometer with a

Brix scale marked for use at 68° F. {or 20° 0,) to obtain the true density of sirup tested at different

temperatures ^

Temperature of

sirup tested

Observed hydrometer reading

10 15 20 25 30 35 40 45 50 55 60 70

32.0° F.

41.0° F.

50.5° F.

51.8° F.

53.6° F.

55.4° F.

57.2° F.

59.0° F.

60.8° F.

62.6° F.

63.5° F.

64.4° F.

66.2° F.

(0° C.)__

(5° C.)_.

(10° C.)_

(11° C.)_

(12° C.)_

(13° C.)_

(14° C.)_

(15° C.)_

(16° C.)_

(17° C.)_

(17.5° C.)

(18° C.)_

(19° C.)_

-0. -0.49

-.47

-.38

-.35

-.32

-.29

-.26

-.22

-. 18

-. 14

-. 12

-. 10

-.05

-0.65

-.56

-.43

-.40

-.36

-.32

-.29

-.24

-.20

-. 15

-. 12

-. 10

-.05

-0.77

-.65

-.48

-. 44

-.40

-.35

-.31

-. 26

-.22

-. 16

-. 14

-. 11

-.06

-0.89

-.73

-.52

-.48

-.43

-.38

-.34

-.28

-.23

-. 18

-. 15

-. 12

-.06

-0.99

-.80

-.57

-.51

-.46

-. 41

-.36

-.30

-.25

-. 19

-. 16

-. 13

-.06

-1.08

-.86

-.60

-.55

-.50

-.44

-.38

-.32

-.26

-.20

-. 16

-. 13

-.07

-1. 16

-. 91

-.64

-.58

-.52

-.46

-.40

-.33

-.27

-.20

-. 17

-. 14

-.07

-1. 24

-.97

-.67

-.60

-.54

-.48

-. 41

-.34

-.28

-. 21

-. 17

-. 14

-.07

-1.31

-1.01

-.70

-.63

-.56

-.49

-.42

-.36

-.28

-. 21

-. 18

-. 14

-.07

-1.37

-1.05

-.72

-.65

-.58

-.51

-. 44

-.36

-.29

-. 22

-. 18

-. 15

-.08

-1.41

-1.08

-.74

-.66

-.59

-. 52

-.45

-.37

-.30

-.23

-. 19

-. 15

-.08

-1.44

-1. 10

-.75

-.68

-.60

-.53

-.46

-.38

-.31

-.23

-. 19

-. 15

-.08

-1. 49

-1. 14

-.77

-.70

-.62

-.55

-.47

-.39

-.32

-.24

-.20

-. 16

-.08

68.0° F. (20° C).

69.8° F.

71.6° F.

73.4° F.

75.2° F.

77.0° F.

78.8° F.

80.6° F,

82.4° F.

84.2° F.

86.0° F.

95.0° F.

104.0° F.

113.0° F.

122.0° F.

131.0° F.

140.0° F.

149.0° F.

158.0° F.

167.0° F.

176.0° F.

(21° C.)

(22° C.)

(23" C.)

(24° C.)

(25° C.)

(26° C.)

(27° C.)

(28° C.)

(29° C.)

(30° C.)

(35° C.)

(40° 0.)

(45° C.)

(50° C.)

(55° C.)

(60° C.)

(65° C.)

(70° C.)

(75° C.)

(80° C.)

+ 0.

+.

+.

+.

+.

+.

+.

+.

+.

+.

+.

+1.

+ 1.

+ 2.

+ 3.

+ 3.

+ 4.

+ 5.

+ 6.

+ 7.

+0.

+ .

+.

+.

+ 1.

+ 1.

+ 1.

+ 2.

+ 3.

+ 3.

+ 4.

+ 5.

+ 6.

+ 7.

+0.

+.

+ .

+.

+.

+.

+.

+.

+.

+.

+ 1.

+ 1.

+ 1.

+ 2.

+ 3.

+ 3.

+ 4.

+ 5.

+6.

+ 7.

+ 0.

+ .

+ .

+.

+.

+.

+ .

+.

+.

+ .

+ 1.

+ 1.

+ 2.

+2.

+3.

+ 3.

+4.

+ 5.

+ 5.

+ 6,

+0.

+.

+ .

+.

+.

+.

+.

+.

+ 1

+ 1.

+ 2

+2,

+ 3,

+ 3,

+ 4,

+ 5,

+5,

+ 6,

06

12

19

26

32

40

46

54

61

68

10

54

03

56

12

72

4

0

8

1.8

+0.

+. +. +.

+.

+ . +. +.

+ 1.

+ 1.

+2.

+ 2.

+ 3.

+ 3.

+ 4.

+ 5.

+ 5.

+ 6.

+0.

+. +. +. +. +. +. +. +. + .

+ 1.

+ 1.

+ 2.

+ 2.

+3.

+3.

+ 4.

+4.

+ 5.

+6.

+ 0.

+. +. + . +. + . +. +. + . +.

+ 1.

+ 1.

+ 2.

+ 2.

+ 3.

+ 3.

+ 4.

+ 4.

+ 5.

+ 6.

+0.

+. +. +. +. +. +. +. +. + .

+ 1.

+ 1.

+2.

+2.

+ 3.

+ 3.

+ 4.

+ 4.

+5.

+ 6.

+ 0.

+ . +. + . +. + . + . +.

+ 1.

+ 1.

+ 2.

+ 2.

+ 3.

+3.

+ 4.

+ 4.

+ 5.

+6.

+ 0.

+. +. +. +. + . +. + . +. +.

+ 1.

+ 1.

+2.

+2.

+ 3.

+ 3.

+ 4.

+ 4.

+ 5.

+ 6.

+0.

+ . +. + . +. +. +. + . +. +.

+ 1.

+ 1.

+ 2.

+ 2.

+ 3.

+3.

+4.

+ 4.

+ 5.

+ 6.

+ 0.

+ . +. +. + . +. +. +. +. + .

+ 1.

+ 1.

+ 2.

+ 2.

+ 3.

+ 3.

+ 4.

+ 4.

+ 5.

+ 5.

+0.09

+.16

+. 24

+.32

+.39

+. 48

+.56

+ .64

+.72

+.81

+ 1. 22

+ 1. 65

+ 2. 08

+ 2. 52

+ 2.97

+ 3. 43

+3.9

+ 4. 4

+ 5.0

+ 5.7

1 Adapted from a table on p. 624 of Circular C 440 issued by National Bureau of Standards, U. S. Department of

Commerce.

35
Example 2,—Suppose the temperature of the

sirup at the time of testing is 50° F. The observed hydrometer readings are 66.22° on the Brix

scale and 35.70° on the Baume scale.

The correction for the Brix scale marked for use

at 68° F., is 18X0.047=0.85°. The correction is

subtracted from the observed reading, since the

temperature of the test solution is below the temperature (68° F. ) marked on the hydrometer. The

true density of the sirup is 66.22°-0.85° =65.47°

Brix.

The correction for the Baume scale (marked for

use at 68° F.) is 0.024x18=0.43°. The true

density of the sirup is 35.70°-0.43° =35.27°

Baume.

If the same sirup (at a temperature of 50° F.) is

tested with a hydrometer with a Baume scale

marked for use at 60° F., the correction is lOX

0.024° = 0.24° Baume. The true density of the

sirup is 35.70-0.24=35.46° Baume.

For more exact measurements, some people may

prefer to use the corrections given in table 12. Although this table was prepared for a hydrometer

marked with a Brix scale for use at 20° C, it has

been adapted for a hydrometer marked with a

Brix scale for use at 68° F.

Adjusting the Density of the Sirup

Sirup with a density of more than 67° Brix at

a temperature of 68° F. (or more than 36° Baume

at 68° or 36.27° Baume at 60°) will crystallize on

storage and must be diluted. This can be done by

adding either sap or low-density (thin) sirup to

the high-density (thick) sirup. The amount of

sap or thin sirup to add can be calculated either

by alligation (Pearson's square) or by the trial

and error method. In the latter method, the

diluent (sap or low-density sirup) is added a little

at a time. After each addition the mixture is

stirred thoroughly, and the density is checked.

The need for thorough stirring cannot be overemphasized, because sirups of different densities are

not easily mixed. This addition and mixing is repeated until the sirup reaches standard density

(table 10).

Alligation (Pearson's Square)

Considerable time can be saved by calculating

the number of parts (by weight) of the heavy

sirup to mix with sap or thin sirup to obtain

standard-density sirup. A simple method' for

doing this is by alligation (Pearson's square).

Example 1.—Suppose sirup that tests 69° Brix

at 68° F. is to be diluted with sap (2.5° Brix) to

make standard-density sirup. The quantity of

each sirup to use can be determined by alligation,

as follows :

A=69° Brix

B = 2.5° Brix

= 63 parts of highdensity sirup

= 3.5 parts of sap

A = density of sirup; B= density of sap; C

= density of standard sirup (always the central

figure).

The difference between C and B = D (65.5 —

2.5 = 63). The difference between A and C =E

(69-65.5=3.5). If 63 parts by weight of 69°

Brix sirup and 3.5 parts by weight of 2.5° sap are

mixed, the density of the mixture will be exactly

65.5° Brix (standard density).

If the dense sirup in the above example is to

be diluted with thin sirup (63.3° Brix), the mixture of the two sirups which will be of standard

density (65.5° Brix at a temperature of 68° F.)

can be calculated by alligation as follows:

A=69 2.2 parts of highdensity sirup

E = 3.5 parts of lowdensity sirup

The difference between C and B = D (65.5 —

63.3=2.2). The difference between A and C =E

(69-65.5=3.5). Thus, if 2.2 parts by weight of

the 69° Brix sirup and 3.5 parts by weight of the

63.3° Brix sirup are mixed, the density of the

mixture will be 65.5° Brix (standard density).

Baume data may be used in the same way.

In practice, the density of sirup to be sold to

the consumer should be a little higher than the

minimum that meets specifications of standarddensity sirup (65.5° Brix at 68° F.). Sirup that

has a density of 66° Brix is more pleasing to the

taste because it has more body (viscosity) than

standard-density sirup and, since it is below 67°

Brix, it will not crystallize in storage.

Thin sirup can be used to dilute heavy sirup,

but this usage of thin sirup is limited, and the

best practice is to boil it until it reaches standard

density. If considerable boiling is required,

more sugar sand may form, which will require

refiltering the sirup. This reboiling may also

cause darkening and hence lowering of grade.

Summary

1. Do not check the density of sirup by weighing,

unless precision instruments are available.

2. The minimum allowable density is 65.46° Brix

(at 68° F.) or 35.27° Baume (at 68° F.) Bureau

of Standards Baume scale for sugar solutions,

modulus 145. Sirup that has a density of 66° to

36
66.5° Brix (at 68° F.) has a higher viscosity

and tastes better.

3. To test the density of sirup with a hydrometer,

fill the can or jar to the top \YÍth sirup.

4. Use only a clean, dry hydrometer.

5. Lower the hydrometer into the sirup carefully

until it comes to rest.

6. Hold the can so the top is at eye level and read

the value on the hydrometer scale at the surface

of the sirup. The value is the observed or apparent density of the sirup.

7. Determine the true density ( ° Brix or ° Baume)

of sirup tested at temperatures icarmer than the

temperature at Avhich the hydrometer is marked

for use by calculation, as follows :

TD (°Brix)=OD-f[0.047X(T-To)]

TD (°Baumé)=OD-i-[0.024X (T-To)]

and for sirup tested attemperatures colder than

the temperature at which the hydrometer is

marked for use, as follows :

TD (°Brix)=OD-[0.04Tx(To-T)]

TD (°Baumé)=OD-~[0.024X(To-T)]

where TD =true density; 0D= observed density ; 0.047 = correction factor for Brix reading ;

0.024 = correction factor for Baume reading;

T= temperature of sirup tested; and To = temperature at which hydrometer is marked for

use.

GRADING THE SIRUP

BY COLOR

Color Standards

Sirup should be graded before it is packaged.

Vermont producers are required to state on the

label the grade of sirup they are offering for sale

to consumers {IfS). The principal grade-determining factor is color.

The United States Department of Agriculture

color standards are designated "Light Amber,"

"Medium Amber," and "Dark Amber." These correspond to the Bryan Color numbers 6, 8, and 10.

The original IT. S. color standards were solutions of caramel in glycerin made according to

Balch's (7) revised spectrophotometric specifications for Bryan color numbers 6, 8, and 10. Master sets of these three solutions were supplied each

year for Federal and State inspection of maple

sirup. Unfortunately, the color of these caramel

solutions is not stable, and they should not be kept

for use as standards for more than 1 year.

U. S. Color Comparator

The United States Department of Agriculture

has developed a simple type of color comparator

with permanent standards of colored glass (ö).

These became the official USDA color standards

for maple sirup in 1950. The colors of the different grades of sirup are given in table 13. A thick

layer of the sirup to be tested is used in the comparator (fig. 59). This aids in precise gradmg

because the standards are widely spaced on a color

scale when viewed in this thickness. The square

shape of the container provides a field of view

of uniform thickness and color, a feature that

was not possible with the cylindrical bottles used

heretofore.

TABLE !?>.—Grade designations of maple sirup^ as

determined hy color

Grade designation Color Color index

range ^

U. S. Grade AA As light as or lighter 0-0.510

(New York than Light Amber.

Fancy or Vermont Fancy).

U. S. Grade A (New Darker than Light 0.510-0.897

York No. 1 or Amber but as light

. Vermont A). as or lighter than

Medium Amber.

U. S. Grade B (New Darker than Me- .897-1.455

York No. 2 or dium Amber but

Vermont B). as light as or

lighter than Dark

Amber.

Unclassified (New Darker than Dark Over 1.45

York No. 3 or Amber.

Vermont C).

^ For description of color index, see p. 15.

Use of the Color Comparator

The 3 clear blanks supplied with the kit are

placed in the compartments, in the back of the 3

standard glasses: Light, Medium, and Dark

Amber.

The sirup to be graded is poured into one of the

clean square glass bottles and placed in 1 of the

2 open compartments. The comparator is held at

a convenient distance from the eye and is viewed

toward the sky but away from the sun (fig. 60).

The color grade (classification) of the sirup is determined by comparing the sample with the standards. If the sample of sirup is cloudy, its true

color classification may be difficult to determine

as its brightness will be lowered. This cloudy effect can be compensated for if the clear blank

used behind the colored glasses is replaced by one

of the cloudy blanks (A, B, or C).

Information concerning the complete color comparator kit, including the comparator block with

glass standards and clear and cloudy blanks, may

be obtained by writing to the Eastern Utilization

Research and Development Division, U. S. Department of Agriculture, Philadelphia 18, Pa., or

to the Processed Products Standardization and

Inspection l^ranch, Agricultural Marketing Service, Washington 25, I). C.

37
Summary

1. Grade the color of the sirup by visually comparing it with color standards.

2. Use as standards either the U. S. Department

of Agriculture permanent glass standards (preferred) or suitable caramel-glycerin solutions.

3. Do not use caramel-in-glycerin standards that

are more than 1 year old.

4. Designate the color of the sirup as either Light

Amber, Medium Amber, Dark Amber, or

darker than Dark Amber.

5. Color is the grade-determining factor for table

sirups that meet all other requirements such as

density, flavor, and cloudiness.

PACKAGING

The graded and clarified sirup of correct density (between 65.5° and 67° Brix at a temperature

of 68° F.) is ready for packaging. If the temperature of the sirup when tested after filtering

is still above 180°, the sirup can be packaged immediately. If the sirup has cooled below 180° it

must be reheated. However, the sirup may become darkened if the temperature goes above 200°

when it is reheated.

As stated previously, maple sirup is a water

solution. Like w^ater, a given quantity of sirup

(by weight) expands and contracts with changes

in temperature. For this reason it is difficult to

package sirup accurately by volume. When the

package of hot sirup has cooled it may not contain exactly the specified volume.

On the other hand, the weight of a given quantity of sirup of standard density is the same regardless of the temperature of the sirup. For

this reason it is best to package maple sirup by

weight. The sirup can be w^eighed on ordinary

household scales. However, it is advisable to test

the scale before it is used. This can be done by

taking the scale to a grocery store and comparing

it with the grocer's certified scales. To do this,

weigh an object that weighs exactly 1, 2, or 10

pounds (such as a bag of sugar or a can of water)

on the grocer's scale. Then weigh it on the scale

being tested. If possible, adjust the household

scale to make it read correctly. If it cannot be

adjusted, make a calibration chart by recording

in one column the household scale reading and in

the other the corresponding true weight.

When packaging sirup by weight, allowance

must be made for the weight of the container.

The net w^eights most commonly used for standard-density sirup are :

1 gallon weighs 11 pounds; 1 quart weighs 2

pound, 12 ounces; and 1 pint w^eighs 1 pound,

6 ounces.

After the container is filled with the correct

weight of sirup, the closure is affixed and the container is laid on its side so that the hot sirup is

in contact with the closure and pasteurizes it.

After the containers have been on their sides 10

to 15 minutes they are ready for cooling.

Stack Burn

If packaged sirup is stacked while it is still hot

the same browning reaction that occurred in the

evaporator will continue and cause a darkening

of the sirup by as much as 1 or 2 grades. This

development of color in hot packaged sirup is

called "stack burn." To prevent stack burn, the

containers should be placed in cold w^ater or

spaced 3 or 4 inches apart to cool before stacking.

Control of Micro-Organisms

Standard-density sirup will not support active

growth of micro-organisms with the exception of

one type of yeast. Because of the possible contamination of sirup with this yeast no sirup that

is offered for sale to the consumer should be packaged cold. Instead the sirup must be heated to at

least 180° F., to destroy the yeast, and packaged

immediately.

Although everyone has seen mold growing on

sirup, mold will not grow in standard-density

sirup. These apparently contradictory statements are explained as follows: Maple sirup that

is cold-packed may contain mold spores. The

mold spores will remain in a resting state and will

not germinate as long as all the sirup is of standard density.

Sirup stored under ordinary conditions usually

undergoes some temperature change. When the

storage temperature becomes warm, some of the

water of the sirup is distilled up into the head

space. When the storage temperature falls this

vapor condenses into small drops of water that

run down onto the surface of the sirup, producing a layer of low-density sirup in which mold

spores can vegetate and grow.

Even though the sirup contains mold spores,

growth of mold can be prevented by momentarily

inverting the packaged sirup once or twice

weekly {22). This destroys the layer of dilute

sirup and therefore inhibits germination of the

mold spores.

Even though sirup is packaged under clean,

sanitary conditions, this does not guarantee that

the sirup will not become inoculated with microorganisms if it is packaged cold. Once a mold or

yeast has grown in the area where cold packaging

IS done, it is almost impossible to package sirup by

the cold method without its becoming infected.

Size and Type of Package

The size and type of package is important

when sirup is made for retail sale. The housewife dislikes to repackage sirup from a gallon

38
Container to smaller ones which can be used as

occasion demands. This has been demonstrated

by the growing tendency on the part of the public

to buy maple sirup in quart or even smaller

packages.

The consumer expects sirup to be as attractively packaged as other foods (fig. 61). The

day is gone when leftover mayonnaise jars, softdrink bottles, and the like are acceptable containers. When sold at roadside stands, sirup packaged in tin is attractive to the tourist regardless

of the size of the container, because he does not

have to take special care in storing it in the car as

with glass containers. Either glass or tin packages must be attractively labeled. The printed

label must be put on squarely, and the outside

must be clean. Many producers are finding that

cans with the labels lithographed on the tin make

an ideal package.

Summary

1. Package sirup hot (180° F. or above).

2. Do not reheat sirup above 200°.

3. Fill sirup package by weight rather than by

volume.

4. In packaging by weight, allow for the weight

(tare) of the container.

5. Use scales that have been tested and calibrated

against certified weights.

6. Avoid stack burn by cooling the packaged

sirup before close-stacking it.

7. Control mold growth in cold-packed sirup or

in sterile sirup that has been opened and exposed to infection by inverting the container once a week.

8. Yeast spoilage can be prevented only by hot

packing.

9. Package the sirup neatly in attractive containers.

10. Use quart and pint, as well as gallon, containers for packaging the sirup.

MAPLE SUGAR

Many producers are finding that the gross returns of their maple crop can be increased 20 to

160 percent by converting their sirup to sugar or

to confections such as maple cream, soft-sugar

candies, and maple spreads. The 8 pounds of

sugar in a gallon of sirup is worth 75 cents a

pound based on sirup selling at $6 per gallon.

This same weight of sugar, if converted to sugar

products can be sold at prices ranging from $1

to $2 per pound or a gross of $8 to $16 per gallon

of sirup. This increase in gross returns is commensurate with the additional labor involved in

converting sirup to sugar products.

The Equipment

The making of the different maple-sugar products is not difficult, nor does it require the use of

expensive or unusual equipment. It does require

the same type of care and sanitation that is expected of any candy company. Maple confections

can be made on a small scale in the home kitchen ;

for a larger operation a special room, either in

the home or a part of the evaporator house, is

preferable (fig. 62). Gas is the preferred fuel,

as it is easily controlled to give the right amount

of heat (fig. 63) ; bottled gas is available almost

everywhere.

The size of the equipment (kettles, mixers, and

pans) depends on the amount of sirup to be

processed. A thermometer with a range of 200°

to 300° F. is an absolute necessity; this can be

either the maple-sirup target or dial thermometer,

or a candy thermometer. Other equipment includes measuring cups, wooden ladles, wooden

paddles, and a household scale. Provision should

be made for cooling the sugar products. This is

especially desirable when making maple cream

or fondant. The cooler can be a trough with circulating cold water into which the pans of cooked

sirup are placed (fig. 64). A pan of chipped ice

or ice water may also be used.

The Chemistry of Maple Sugar

Maple sirup is essentially a solution of sucrose

in water. The amount of sugar that can be in

true solution in a given volume of water varies

with the temperature of the solution. Hot solutions can contain more and cool solutions less

sugar.

Maple-sirup solutions containing 67 percent of

sugar (67° Brix at 68° F.) are saturated at room

temperature. That is, no more sugar can be dissolved in the solution at that temperature. Sirup

that has been heated to 7.5° F. or more above the

boiling point of water will be supersaturated

when it cools to room temperature, that is, it will

contain more than 67 percent of sugar. This

supersaturated sirup, with its excessive sugar

content, is in an unnatural or abnormal condition,

and it tends to become normal again by ridding

itself of the excess sugar. The excess sugar is

thrown out of solution (precipitated), and sugar

crystals are formed.

To make any of the maple-sugar products it is

necessary first to make supersaturated sirup. The

degree of supersaturation increases as the boiling

temperature of the sirup is increased and more

water is evaporated from the sirup. When the

amount of supersaturation is small and cooling

is slow and accompanied by little or no agitation,

the state of supersaturation may persist for a long

time and very little sugar will be precipitated.

When the amount of supersaturation is appre39
ciable (such as occurs when sirup is boiled to 18°

F. or higher above the boiling point of water), the

sirup will appear to solidify on cooling. This

solid cake is mostly sugar, but some liquid sirup

(mother liquor) is mixed with the sugar.

Formation of Crystal Sugar

The crystalline or noncrystalline nature of the

precipitated sugar is determined by a number of

factors, all of which are influential in making the

desired type of confection (^7). These factors

include the degree of supersaturation, seeding, the

rate of cooling, and the amount and time of

stirring.

Large crystals, which represent one extreme,

are formed when slightly supersaturated sirup

(67° to 70° Brix) is cooled slowly and stored for

a long time without agitation. A glasslike noncrystalline sirup represents the other extreme.

This is formed when highly supersaturated sirup

(elevation of the boiling point, 18° F. or more)

is cooled rapidly well below room temperature

without stirring. The sirup becomes so viscous

that it solidifies before crystals can form and

grow. If the hot supersaturated sugar solution

is stirred while it is cooling the tendency to form

crystals increases. The mechanical shock of the

stirring causes crystal nuclei to form. Continued

stirring mixes the crystals throughout the thickened sirup causing them to grow. When the

number of crystals is relatively few, the large

crystals tend to grow larger at the expense of

the smaller ones. Thus, a grainy sugar tends to

become more grainy the longer it is stirred.

To produce maple sugar with a fine crystalline

structure, free of grittiness, all of the crystals

must be kept very small, even microscopic in size.

This is accomplished by suddenly cooling the hot,

highly supersaturated sirup so that a viscid, noncrystalline, glasslike mass is obtained. Then,

while it is still in this supersaturated state, fine

crystals, called seed, are added to serve as nuclei,

and stirring is begun. Since the mass is so highly

supersaturated not just a few crystals but literally

millions of tiny ones are formed at the same time,

and the result is a very fine-grained product.

Invert Sugar

Although sucrose is the only sugar in sap as

it comes from the tree, some of the sucrose is

changed into invert sugar as a result of microbial fermentation during handling and processing. Both sucrose and invert sugar are made

up of two simple sugars, dextrose and lévulose.

In sucrose these sugars are united chemically as

a single molecule; in invert sugar they occur as

separate molecules.

The presence of some invert sugar in maple

sirup to be made into maple sugar and maple

confections is desirable. Invert sugar tends to

reduce supersaturation, that is, more sugar can

40

be held in solution before crystallization occurs.

This helps to keep the product moist {17), Also

it helps in the promotion of exceedingly small

sugar crystals. The degree of these effects depends on the amount of invert sugar in the sirup.

Fortunately, most maple sirup contains an adequate amount of invert sugar. Occasionally,

however, maple sirup is found that has either too

little or too much invert sugar to permit making

a sugar product of the best quality. Too little

invert sugar in the sirup will cause the product

to be grainy; too much will prevent formation

of crystals (creaming). A simple chemical test

for use in determining the amount of invert sugar

in maple sirup is described on page 48. If the

amount of invert sugar in the sirup is so low that

a fine crystalline product cannot be made, a "doctor" solution is required {16).

Doctor

The "doctor" solution usually used is sirup rich

in invert sugar (more than 6 percent, as determined by the chemical test described on p. 48).

Sirup made from sap produced during a warm

spell usually contains a high percentage of invert

sugar. The addition of 1 pint of doctor sirup

to 6 gallons of maple sirup low in invert sugar

usually will correct the condition of coarse grain.

When sirup with a high content of invert sugar

is not available, the doctor solution can be prepared as follows : Two and one-half fluid ounces

of invertase (an enzyme that causes the inversion

of sucrose to invert sugar) is added to 1 gallon

of standard-density maple sirup; the mixture is

stirred thoroughly and allowed to stand at room

temperature (65° F. or above) for several days

during which time sufficient invert sugar will

form so that 1 pint of this solution can be used

to doctor 6 gallons of maple sirup low in invert

sugar.

Invertase may be purchased from any of the

larger candy companies.

Another type of doctor is an acid salt, such

as cream of tartar (potassium acid tartrate).

One-half teaspoon of cream of tartar added to 1

gallon of low-invert sirup just before it is boiled

will cause sufficient acid hydrolysis or inversion of

the sucrose to form the desired amount of invert

sugar.

Summary

1. Converting maple sirup to maple sugar is not

difficult nor does it require special equipment,

with the exception of a thermometer having

an upper range of 250° to e^00° F.

2. Sirup that is saturated in respect to sugar at

one temperature will be supersaturated when

cooled to another temperature.

3. Supersaturated sugar solutions tend to regain

their normal or saturated state by throwing

the excess sugar out of solution. This precipi-
4.

5.

tated sugar usually is in the form of crystals,

and the amount formed depends on the degree

of supersaturation.

The crystallinity of the precipitated sugar depends on the degree of supersaturation, the

rate of cooling the sirup, and the amount and

time of stirring.

Invert sugar, a product of fermentation of

sucrose, is a noncrystallizing sugar. Its presence in maple sirup influences the crystallization of maple sugar. Too much invert sugar

will tend to prevent crystallization of sugar

from a supersaturated sirup and too little will

cause the maple sugar to be coarse and gritty.

MAPLE CREAM

OR BUTTER

The amount of the maple sirup crop that is

being converted into maple cream or butter has

been increasing rapidly. Some producers have

built up so large a demand that they convert

their entire crop to cream. In 1954, one New

York producer made more than 2% tons of this

confection.

Maple cream (^7, ^^), a fondant type of confection, has a butterlike consistency. It is made

up of millions of microscopic-size sugar crystals

interspaced with a thin coating of saturated sirup

(mother liquor). The crystals are impalpable

to the tongue and give the cream a smooth, nongritty-texture. To make maple cream, it is necessary first to make a supersaturated sugar solution. This is cooled to room temperature so

quickly that crystals have no chance to form.

The cool glasslike mass is then stirred, which

produces the mechanical shock necessary to start

the crystallization. All of the crystals formed

are about the same size and very small.

Sirup for Creaming

For best results, U. S. Grade AA (Fancy) or

U. S. Grade A (ISTo. 1) maple sirup should be

used; it should contain less than 4 percent of invert sugar.

Invert-Sugar Content

The amount of invert sugar in the sirup selected for creaming should be determined by test,

as described on page 48. Sirup that contains

from 0.5 to 2 percent of invert sugar should make

a fine-textured cream that feels smooth to the

tongue. Sirup with from 2 to 4 percent of invert sugar can be made into cream by heating it

to 24° or 25° F. above the boiling point of water

(instead of the usual 20°). Sirup with more

than 4 percent of invert sugar is not suitable for

creaming. If used, it will not crystallize, or it

will crystallize only if heated to a much higherthan-normal temperature; however, the cream

will be too fluid and probably will separate a few

days after it is made.

For years, many people throughout the mapleproducing area have believed that maple cream

should be made only from first-run sirup and that

all first-run sirup will yield a good cream. This

is not the case. The amount of invert sugar in

the sirup determines its suitability for creaming,

not the run of sap from which the sirup is made.

The amount of invert sugar formed is directly

proportional to the amount of microbial fermentation of the sap, and this in turn is related to the

temperature. Unseasonably warm weather is not

uncommon during the first period of sap flow.

Warm weather favors fermentation of the sap,

and suificient invert sugar is produced to make

the early run sirup unsuitable for making into

cream.

As maple sirup for creaming normally contains an adequate amount of invert sugar, the use

of a "doctor" solution is not recommended. The

addition of or the formation of too much invert

sugar will ruin the sirup. Instead, select the

sirup for creaming on the basis of the quick test

for invert sugar.

Cooking and Cooling

The sirup is heated to a temperature 20*^ to 23°

F. above the boiling point of water. (The temperature of boiling water must be established at

the time the sirup is boiled for creaming.) The

boiling temperature determines the amount of

sirup (mother liquor) surrounding the crystals,

and this in turn governs the stiffness of the final

product. As soon as the sirup reaches the proper

temperature it should be removed from the heat

and cooled quickly. If the cooked sirup is left on

the hot stove (even with the heat turned off),

enough more water will be evaporated to produce

a more concentrated sirup than desired. Rapid

cooling prevents crystallization. To facilitat^e

cooling, the sirup is poured into large, flat-bottom

pans (the layer of sirup should be not more than

1 to 3 inches deep), and the pans are set in a

trough through which cold water (35° to 45° F.)

is flowing (fig. 65).

The thickened sirup is cooled to at least 70° F.,

and preferably to 50° or below. The sirup is sufficiently cool when the surface is firm to the touch.

Appearance of crystals during the cooling process

indicates either that cooling is too slow or that

the invert-sugar content of the sirup was too low

for the conditions of cooling used. This situation

can be corrected either by more rapid cooling

(thinner layers of sirup or more rapid flow of cold

water) or by increasing the invert-sugar content

of the sirup by use of a doctor as previously

described.

41
Creaming

The chilled, thickened sirup should be creamed

(either by hand or mechanically) in a room having a temperature of 70° F. or above. Many producers have developed their own mechanical cream

beaters (fig. 66)^ and there are a number of inexpensive ones on the market.

The homemade maple-cream beater (fig. 67)

consists of a pan approximately 13 inches in diameter that holds about 1% gallons of cooked

sirup. In this beater, the scrapers are held stationary and the pan revolves. In other beaters,

this procedure is reversed. Both types work

equally well.

A hardwood paddle having a sharp edge 2 or 3

inches wide is used for hand beating. The cooked

sirup is poured into a large flat pan, such as a

cookie tin. This is held firmly, and the thick sirup

is scraped first to one side of the pan and then the

other, mixing continuously so that no portion is

allowed to stay at rest. If stirring is stopped

some of the crystals will grow and cause the product to be gritty.

During the stirring operation the chilled sirup

will first tend to become fluid and then begin to

stiffen showing a distinct tendency to set. At this

time the batch will lose its shiny surface (fig. 67).

If creaming is stopped too soon, that is, while the

batch is too fluid, large crystals will form.

To hasten the creaming process a small amount

of "seed"—previously made cream-—can be added

to the glasslike chilled sirup just before beating.

The addition of 1 teaspoonful of seed for each

gallon of cooked sirup will provide crystals to

serve as nuclei for the more rapid formation of

crystals. Creaming may require from 1 to 2

hours, depending on the size of the batch, but the

use of seed will often shorten the time by half.

Holding Cream for Delayed Packaging

Often it is not convenient to package the cream

at the time it is made. In this case it can be stored

or aged for periods of 1 day to several weeks in

tightly covered glass or earthen vessels, preferably

under refrigeration. Many candymakers believe

that aging of a fondant is desirable because it permits an equalization of the crystals in the saturated sirup. After aging, the cream is remelted

for pouring and packaging by careful heating in a

double boiler (36). The temperature of the cream

during this reheating must not go above 150° F.

This can be controlled by not permitting the water

in the double boiler to go above that temperature.

If the temperature of the cream exceeds 150°,

too much sugar will be dissolved and large crystals may form when the remelted cream is cooled.

Packaging and Storing Maple Cream

Maple cream can be packaged in tin, glass, or

wax paper cups. Containers with wide mouths

are best for ease of filling. Care must be taken to

keep air bubbles from forming. This precaution

is of particular importance when the cream is

packaged in glass because the air bubbles are unpleasing in appearance and create the impression

the package is short in weight. Further, air

pockets provide a place where the separated

mother liquor can collect, and this also produces

an unpleasant appearance.

Freshly made cream should be packaged immediately, before it "sets up" (fig. 68). Kemelted

cream should be packaged while it is still warm

and fluid. Since maple cream is a mixture of

sugar crystals and saturated maple sirup, storing

the cream at temperatures above the 70° F. used

for creaming will cause more sugar to go into solution, and this increased volume of sirup will tend

to separate as an unattractive dark liquid layer

on the surface of the cream. This sirup layer will

also be formed if the cream is stored at uneven

temperatures.

For the best storage conditions keep the cream

at low temperature and constant humidity. If the

cream is packaged in moisture-proof containers,

glass, tins, or heavy waxed boxes, it can be stored

in refrigerators for long periods of time prior to

use, with little danger of the saturated sirup in

the cream separating.

Summary

1. Use U. S. Grade AA (Fancy) or U. S. Grade

A (No. 1) sirup.

2. The sirup must not contain more than 4 percent of invert sugar.

3. Heat the sirup to a temperature 20° to 23° F.

above the boiling point of water.

4. Cool the sirup rapidly to about 50° F.

5. Stir the thickened sirup continuously until

creaming is completed.

6. Freshly made cream can be packed immediately

or it can be aged before packaging.

7. Aged cream can be softened for pouring by

heating to temperatures not exceeding 150° F.

8. Store cream under refrigeration.

9. Causes of failure to cream :

(a) If the sirup contains too little invert

sugar or if it is not chilled sufficiently

before stirring, the cream will have a

gritty texture.

(b) If the sirup contains too much invert

sugar, it will not cream (crystallize).

SOFT-SUGAR CANDIES

Next to maple cream the making of soft-sugar

candies is gaining in popularity. Eight pounds

of soft-sugar candies can be made from 1 gallon

of sirup.

42
Soft-sugar candies contain little or no free

sirup so they are of stiffer consistency than cream.

Although the crystals in soft-sugar candies are

larger than in cream and are palpable to the

tongue, they should not be large enough to produce an unpleasant sandy effect. The candies

can be made from any of the top three grades of

sirup—U. S. Grade AA (Fancy), U. S. Grade A

(No. 1), and U.S. Grade B (No.2).

Cooking, Cooling, and Stirring

The sirup is cooked to a temperature 27° F.

above the boiling point of water (established for

that time and place). The pans of cooked sirup

should be cooled slowly (on a wooden-top table)

to a temperature of 155° F. (measured with a

thermometer). The thick sirup is then stirred,

either by hand with a large spoon (fig. 69) or

with a mechanical mixer (fig. 67).

While the sugar is still soft and plastic it is

poured or packed into rubber molds of different

shapes. This operation of packing the molds is

best done with a wide-bladed putty knife or spatula (fig. 70). Rubber molds for use in making

candies of different sizes and shapes can be purchased from any maple-equipment supplier.

The Bob

Another method of preparing the sugar so that

it can be run into the molds is used by commercial

confectioners. The soft sugar is set aside after

stirring to firm and age for a day. On the following day, it is mixed with an equal amount of

"bob," the two are stirred together, and the mixture is run into the rubber molds while it is still

fluid.

The bob (27) is sirup that is boiled to exactly

the same boiling point (27° F. above the boiling

point of water) as used in making the soft sugar.

As soon as the bob is made and while it is still

hot, the sugar made the previous day is added to

it, and the mixture is stirred enough to get uniformity but not enough to cause it to set up. The

hot bob partly melts the sugar and the resulting

semiliquid sugar can ba poured easily.

Ingenuity can be used in candymaking. For

example, one producer has developed the following semicontinuous process: The sirup is cooked

in a special vessel (fig. 71) from which the cooled

sirup is dispensed to a small mechanical agitator

(fig-T2).

Here the sirup is crystallized; while it is still

fluid it is run into the rubber molds, where it sets

up in 30 minutes to 1 hour. Candies formed by

pouring, rather than packing, have an attractive

glazed surface.

Crystal Coating of Candies

The candies can be prevented from drying by

coating them with a moisture-impervious shell

made from crystalline sucrose {S6). The effect

of crystal coating soft-sugar candies is shown in

figure 73. The crystallizing sirup is made as follows: Fancy maple sirup low in invert sugar is

heated to a temperature 10° to 11° F. above the

boiling point of water. This supersaturated sirup

should have a Brix value of 70° to 73° at a temperature of 68° F. One gallon of standarddensity sirup (65.5° Brix) will make 7 pints of

crystallizing sirup (70° to 73° Brix).

The hot, heavy sirup, in the vessel in which it

was boiled, is set aside to cool where it will not be

disturbed by jarring or shaking. To retard surface crystallization, the surface is covered with a

piece of damp cheesecloth or paper (preferably

the same kind used as a sirup prefilter, since it

has a high wet strength). The cloth or paper

must be in contact with the entire surface of the

sirup. If crystals form, they will be attached to

the cover and can be removed along with the

covering. These sugar crystals can be recovered

by rinsing the cover in hot water.

The candies to be coated should be dry (24 hours

old), and they can be coated by either of two

methods. In the first method, the candies are

loosely packed 2 or 3 layers deep in a tin pan, such

as a bread tin, which has a piece of i/^-inch mesh

hardware cloth in the bottom. The covering is removed from the cool (70° to 80° F.) crystallizing sirup, and if all the crystals are not removed

with the cover they are skimmed off. Enough of

the crystallizing sirup is poured over the candies

to cover them completely, and a paper cover is

placed on the surface.

The pans are gently set aside in a room with a

temperature of 65° to 80° F. for 6 to 12 hours, or

overnight. This is the crystallizing period. Sugar

comes out of the thick sirup and is deposited and

grows on the millions of tiny crystals on the surface of the candies. When sufficient sugar has

been deposited on the candies, the paper cover is

removed and the thick sirup is drained off. This is

done by covering the pan with a second piece of

hardware cloth and inverting the pan over a kettle to catch the sirup. The candies must be well

drained because any drops of sirup left on the

candies will dry as a glaze rather than as crystals.

After draining, the candies are spread out on

paper to dry. To facilitate even drying, each piece

is turned over at intervals of 1 or 2 hours. Crystal

coating of candies should not be attempted on a

damp or rainy day since the candies will not dry

properly.

In the second method the candies are packed

loosely in a shallow wire basket, the basket is submerged in the crystallizing sirup, and a paper

cover is placed on the surface, as in the first

method. Following the crystallizing period, the

cover is removed, the basket is raised from the

sirup and is held above the sirup by means of a

rack or other device until the candies have drained.

They are then spread out on paper to dry as before. A French fryer or blanching assembly of

43
kettle and wire basket is well adapted to this use

(fig. 74).

Packaging Candies

The packages have two functions : (1) To make

the candies as attractive as possible, and (2) to

keep them in good condition (fig. 75). Boxes, individual wrappings, and candy cups can be obtained from a confectioner's supply house. It is of

greatest importance that the net weight of the

candies be stated on the outside of the package.

This requires that the tare (weight of box) and

the net weight of the candies be determined for

each box, as shown in figure. 76.

Candies that have been cï-ystal-coated have relatively good shelf life, tending neither to take up

moisture nor to dry out. Candies that are not

crystal-coated may do either, depending on the

humidity of the room in which they are stored. In

a room of low humidity, they will lose moisture

and the dried-out areas will appear as white spots.

If the humidity is high the candies will take up

moisture, and moist areas or droplets of water will

appear on the surface of the candies. The droplets become dilute sugar solutions and are good

sites for growth of mold.

The best type of wrapper for the outside of the

candy package is one that is moistureproof, such

as metal foil or wax-coated paper, because a moistureproof wrapper tends to prevent changes in

the candies during storage. Unfortunately, most

wrappers are not completely moistureproof. They

reduce the gain or loss of moisture but do not prevent it, especially if the candies are stored under

excessively high or low moisture conditions or for

long periods.

Summary

Soft-sugar candies

1. Use any of the top three grades of sirup.

2. Heat the sirup to a temperature 27° F. above

the boiling point of water.

3. Cool the sirup slowly to 155° F.

4. Stir the thickened sirup until enough crystals

have formed to make a soft, plastic mass.

5. Immediately pour or pack the soft sugar into

molds, OE

6. Set it aside in a crock at room temperature

for 24 to 48 hours.

7. Concentrate an equal amount of sirup as

before.

8. As soon as the same elevation of boiling point

(27° F.) is reached add the hot concentrated

sirup (bob) to the aged soft sugar.

9. Stir only enough to mix and pour the semifluid sugar into the molds.

Crystal coating of candies

1. Make crystallizing sirup from top grades of

maple sirup.

44

2. Concentrate the sirup to 70° to 73° Brix by

heating it to a temperature 10° or 11° F. above

the boiling point of water.

3. Cool to room temperature.

4. Keep the surface of the sirup covered with

heavy paper, except when adding or removing

the candies.

5. Place the freshly made candies in the heavy

sirup and leave them in the sirup 6 to 12 hours.

6. Eemove the candies and completely drain the

sirup from them.

7. Place the candies on paper-covered trays and

turn each piece every hour until dry.

8. Don't attempt to crystal-coat candies during

damp or rainy weather.

MAPLE SPREAD

Maple cream, described on page 41, is not a

stable product when stored at room temperature

because saturated sirup (mother liijuor) tends to

separate from the cream and cover it with a sirup

layer.

A new semisolid dextrose-maple spread has

been developed which avoids this separation of

sirup. Also, it requires no beating or stirring.

The process for making the spread consists of

three simple steps: (1) The sirup is concentrated,

by heating, to a density of 70° to 78° Brix; (2)

part of the sucrose is converted to invert sugar

by enzymatic hydrolysis; and (3) the dextrose

(part of the invert sugar) is crystallized to form

a semisolid spread.

Standard-density maple sirup (65.5° Brix) is

heated to a temperature about 10° F. above the

boiling point of water (approximately 76° Brix),

and then cooled to 150° F. or below (tested with

a thermometer). While the sirup is still fluid,

invertase is added, at the rate of iy2 ounces per

gallon of sirup, and thoroughly mixed with the

sirup by stirring. The enzyme will be inactivated and hence ineffective if it is added

while the sirup is too hot (above 160° F.). The

enzyme-treated sirup is stored at room temperature for 1 or 2 weeks. At first crystals (sucrose)

appear, but they do not form a solid cake and, as

the hydrolyzing action of the enzyme progresses,

the crystals dissolve. The result is a crystal-free,

stable, high-density sirup (70° to 78° Brix) containing a large amount of invert sugar. It will

remain clear at ordinary temperatures. Because

of its high density, it makes an excellent topping

for ice cream and sirup for waffles or pancakes.

Maple spread is made by seeding this highdensity sirup with dextrose crystals. A crystalline

honey spread, a stock grocery item, is a convenient source of dextrose crystals for use in seeding
the first batch. For subsequent batches, crystals

from previously made lots of the maple spread

may be used as seed. The dextrose crystals are

added at the rate of 1 teaspoon per gallon of highdensity sirup, and thoroughly mixed with the

sirup. After uniform mixing, the sirup is poured

into packages and set aside at a temperature of

55° to 60° F. Within a few days a semisolid

spread is formed. It is stable at temperatures up

to 80° F. If refrigerated it will keep indefinitely

without any sirup separating.

Maple spread eliminates the laborious hand

beating or the expensive machine beaters required

for making maple cream. Furthermore, the yield

of maple spread per gallon of sirup is higher,

because it is made from sirup concentrated to between Y0° and 78° Brix, whereas sirup for maple

cream is concentrated to 80° Brix.

Summary

1. Use any of the three top grades of sirup.

2. Heat the sirup to a temperature 10° or 11° F.

above the exact boiling point of water (70° to

78° Brix).

3. Cool the thick sirup to 150° or below and add

11/2 ounces of invertase per gallon of sirup.

4. Store at room temperature for 2 weeks. The

resulting product is high-density sirup.

5. "Seed" the high-density sirup with dextrose

crystals from previous batches of spread or

from crystallized honey. Use 1 teaspoonful

per quart of sirup.

6. Mix the seed thoroughly through the sirup and

gour the mixture into the final package,

tore at 55° to 60° F. Within a few days the

dextrose crystals will grow to yield a plastic

spread.

HIGH-FLAVORED

MAPLE SIRUP

As stated earlier, the color and flavor of maple

sirup result from a type of browning reaction

that occurs between constituents of the maple sap

during the boiling process. Experiments have

shown that all of the potential flavor is not developed under these conditions {SI). To develop

maximum flavor, the browning reaction must be

carried further ; that is, the sirup must be heated

to a high temperature and for a longer time.

Unfortunately, high temperatures favor the

formation of "caramel" flavor. The presence of

large amounts of water favor caramel formation

and the presence of some caramel in the initial

sirup accelerates it {32), Therefore, only lightcolored sirup of the two top grades—U. S. Grade

AA (Fancy) or U. S. Grade A (No. 1)—should

be used in making high-flavored maple sirup. It

may be made by either the atmospheric process or

by the pressure-cooking process.

Atmospheric Process

The sirup is concentrated at amospheric pressure by heating to a boiling temperature of 250°

to 255° F. This reduces the water content of the

sirup to approximately 10 percent. The sirup is

held at this temperature for li/^ to 2 hours. It is

then cooled and water is added to replace that

lost in evaporation so that the sirup is again of

standard density.

Because of the low-moisture content of the

sirup during the cooking period, there is danger

of scorching if it is heated in a kettle on a stove

or other hot surface. It is recommended therefore that the high-flavoring process be conducted

with high-pressure steam in a steam-jacketed

kettle or in a kettle provided with a steam coil

(fig. 77 and chart 17).

TRAP

AW OFF

WATER

CONNECTION

Chart 17.—Kettle with steam coil that can be built in any tin

shop. It is not as convenient to use as a tilting-jacketed kettle, but very satisfactory results can be had with it. Like the

steam-jacketed kettle, it must be operated with high-pressure

steam and the condensed water must not be allowed to collect

in the coils. Provision should be made for running cold water

through the coils for cooling the sirup.

The first step of the process^—removal of the

water from the sirup—should be done as rapidly

as possible. Steam pressures from 30 to 100

pounds should be used. As soon as the sirup

reaches a boiling temperature of 252° F., the

steam pressure is reduced until only enough heat

is applied to maintain the temperature between

250° and 255°. Usually a steam pressure of 20

to 28 pounds is sufficient. A relatively tight

cover is placed over the kettle to serve as a reflux

condenser. Because of the high viscosity of the

sirup very little water will be vaporized.

45
A thermometer calibrated in 1-degree intervals

and with an upper range of 300° to 350"^ F. is

kept in the sirup during the high-flavoring

process. If the temperature of the sirup rises

above 255° during the holding period, the pressure of the heating steam should be decreased and

small amounts of water should be cautiously

added. The sirup should not be stirred or agitated in any way during the high-flavoring

process; to do so encourages the formation of

crystals, and the whole batch may set into a hard

cake.

At the end of the cooking period, the thick

supersaturated sirup is cooled to 200° F. Approximately 3 pints of water is added for each

gallon of sirup originally used to replace the

water lost in evaporation and restore the sirup to

standard density. Extreme caution must be exercised in adding the water because the water

will be converted to steam with explosive violence

if the sirup has not cooled to a temperature below

the boiling point of water.

As flavor and color develop in sirup to the

same degree, flavor development in the treated

sirup may be measured by measuring the increase

in its color. A sample of the high-flavored

standard-density sirup is weighed, and then diluted with a colorless cane-sugar sirup that has a

density of 65.5° Brix as measured with a hydrometer or refractometer. The colorless sirup is

added slowly, with thorough stirring, to the highflavored sirup until the mixture matches the color

of the original maple sirup. Then the mixture

is weighed. The increase in color and flavor is

determined by the ratio:

Weight of the mixed sirup

Weight of high-flavored sirup

This procedure can be used to follow the progress of the high-flavoring process, since different

lots of sirup of the same grade will develop

flavor at slightly different rates. A sample is removed periodically from the cooking sirup and

weighed. Enough water is added to restore that

sample to standard density (65.5° Brix), and it

is tested as described above. The tests are easy

to make using the 2-ounce French square bottles

supplied with the U. S. Color Comparator described on page 37. If the color test shows a

ratio of 4:1, the process is completed and the

color and flavor has been increased fourfold. The

high-flavor process and its end uses are shown

graphically in figure 78.

Pressure-Cooking Process

Many maple producers do not have highpressure steam equipment. They may make highflavored sirup by the process described in U. S.

Patent 2,054,873 {Jß),^ In this process, standard-

® This patent, which was issued to George S. Whitby

on Sept. 22, 1936, has expired. Therefore, the process is

available for free use by the public.

density sirup is heated in a closed vessel, such as

an autoclave or ordinary pressure cooker, at 15

pounds' pressure. Best results are obtained when

the sirup is heated to a temperature of 250° to

253° F., as in the atmospheric process.

In the pressure-cooking process the water content of the sirup is 34.5 percent during heating,

rather than 10 percent, as in the atmospheric

process. The higher water content favors the formation of caramel. However, the rate at which

caramel forms depends on the original caramel

content of the sirup. The higher the caramel content in the original sirup, the greater the amount

formed in the product. Since the amount of caramel in sirup is related to the amount of color, only

Ü. S. Grade AA (Fancy) or U. S. Grade A (No.

1) sirup should be used to make high-flavored

sirup by the pressure-cooking process. Darker

grades usually result in an unpalatable product.

The sirup is heated almost to boiling and immediately is transferred to jars, which are filled

to within one-half inch of the top. The lids are

set loosely in place, and the jars are placed in the

autoclave or pressure cooker which contains the

amount of water specified by the manufacturer.

The cover of the cooker is assembled, and steam is

generated according to the manufacturer's directions. The sirup is heated at 15 pounds' pressure

for approximately I14 hours. Then the pressure

is decreased slowly to zero without venting or

quenching. The containers must not be jarred or

the sirup may boil over.

High-flavored maple sirup made from U. S.

Grade AA or U. S. Grade A sirup by either of

the above processes will have a strong full-bodied

maple flavor that is 4 to 5 times that of the sirup

from which it was made, and it will be essentially

free from caramel.

Uses of High-Flavored Sirup

High-flavored sirup has a number of uses. Because it is rich in maple flavor it is ideal for making maple products. It is especially desirable for

use in making cream and candies. From 1 to 2

percent of invert sugar is formed in the highflavoring process. This is the optimum amount

to make perfect cream or soft-sugar candies without the need of a "doctor." High-flavored, highdensity maple sirup makes a superior topping for

ice cream.

Only high-flavored sirup should be blended

with other foods such as maple-flavored honey

and crystalline honey spreads. Regular maple

sirup usually does not have enough flavor to compete with or to break through the flavor of the

food to which it is added. An inexpensive table

sirup that has the full flavor of pure maple can be

made by blending 1 part of high-flavored standard-density maple sirup with 3 parts of canesugar sirup with a Brix value of 65.5°. Blended

sirup must be properly labeled when offered for

sale. The percentage of each ingredient must ap46
pear on the label, with the one in greater amount

appearing first.

Summary

Use either of the two top grades of sirup to

make high-flavored maple sirup, and make it by

either the atmospheric or the pressure-cooking

process.

Atmospheric process

1. Concentrate the sirup by heating to a temperature 40"" F. above the boiling point of water

(250° to 255° F.). Use only a steam kettle,

jacketed or with coils, for the processing.

2. Hold the thickened sirup at the final temperature of concentration for 11/^ to 2 hours.

3. Cover the kettle with a close-fitting lid and

reduce the steam pressure to keep the sirup simmering (approximately 24 or 26 pounds per

square inch),

4. Turn off the steam at the end of the processing

period and cool the thick sirup to between 180°

and 200° F.

5. Add water with caution and in small amounts

until the sirup is restored to standard density,

as measured by the hydrometer test.

Pressure-cooking process

1. Heat the sirup almost to boiling temperature

(210° to 215° F.).

2. Transfer to containers to fit the cooker (usually

1- or 2-quart jars).

3. Place the lids on the containers loosely, and put

them in the cooker.

4. Add water to the cooker according to the

manufacturer's directions, and secure the cooker

lid.

5. Bring the steam pressure in the cooker to 15

pounds per square inch. Hold at this pressure

for iy2 hours.

6. Allow the pressure to fall slowly ; do not vent

or quench.

7. When the pressure has fallen to zero, open the

cooker, remove the high-flavored sirup, and

seal the containers.

tain a large amount of invert sugar. These requirements are met by converting U. S. Grade B

(Vermont B or N. Y. No. 2) sirup to high-density

sirup by the enzyme treatment, as described on

page 40, except that the sirup is heated to a temperature 19° or 20° F. above the boiling point of

water. It is then cooled to 150° F. or lower, and

114 to 2 ounces of the enzyme is added per gallon

of sirup. The mixture is set aside at room temperature until the action has been completed,

usually about 2 weeks. The sirup may have the appearance of soft sugar.

The high-flavored, high-density maple sirup is

added to mild strained honey at the rate of 33

parts of maple to 67 parts of honey, by weight.

The mixture is crystallized by the Dyce process

(6"), as follows : The honey-maple mixture is seeded

with crystalline honey (available in most grocery

stores) or with some honey-maple spread from a

previous batch, at the rate of 1 ounce of seed to 1

quart of honey-maple mixture. After thorough

stirring, the seeded mixture is held at a temperature of 57° to 60° F. until crystallization is complete, usually 3 to 7 days. The resulting product

is smooth with a barely perceptible grainy character, spreads well, and has a very pleasing flavor.

This spread becomes liquid at temperatures above

85°. Therefore, it should be stored under refrigeration.

Summary

1. Use U. S. Grade B, Vermont B, or N. Y. No.

2 sirup.

2. Heat the sirup to a temperature 19° or 20° F.

above the boiling point of water (80° Brix).

3. Cool the thick sirup to below 150° F. and add

11/^ to 2 ounces of invertase per gallon of sirup.

4. Store at room temperature for 2 weeks to produce a high-density sirup.

5. Mix thoroughly 1 part of the high-density

sirup to 2 parts of mild-flavored honey.

6. Add seed (dextrose crystals) at the rate of 1

teaspoonful per gallon of mixture. Use previous batch of honey-maple spread or crystalline honey as seed.

7. Hold the seeded mix at 60° F. until the dextrose crystals grow to produce a semifluid

plastic (3 to 7 days).

8. Store under refrigeration.

CRYSTALLINE HONEYMAPLE SPREAD

The development of a maple-flavored crystalline

honey spread has produced a new farm outlet for

both maple and honey. This spread is made by

mixing honey with high-flavored maple sirup. The

maple flavor must be strong enough to break

through the honey flavor, and the sirup must conOTHER MAPLE

CONFECTIONS

Rock Candy

Production of rock candy usually is unintentional. Although it should not be considered a

product of maple sirup, this form of "maple

47
sugar" is easy to make, as follows : When maple

sirup is evaporated to a density between 67.5°

and 70° Brix (heated to 8° F. above the boiling

point of water), and the sirup is stored at room

temperature or lower, a few well-defined crystals

of sucrose (rock candy) appear. These continue

to grow in size, if the sirup is left undisturbed for

a long time.

Hard Sugar

Because it is not easily eaten, hard sugar is

not classified as a confection, and it is not often

made for retail sale. It was popular in the past

because it offered a convenient form for the safe

and stable storage of maple sirup. The hard

sugar cake could be broken up, melted in water,

and the solution boiled to bring it to sirup density. This sirup is called maple-sugar sirup to

distinguish it from sirup made directly from

sap.

Hard sugar is made by boiling maple sirup to a

temperature approximately 40° to 45° F. above

the boiling point of water. As soon as the sirup

reaches the desired temperature, it is removed

from the heat and stirred. Stirring is continued

until the sirup begins to crystallize and stiffen,

when the semisolid sirup is poured into molds.

If stirring is continued too long or if transfer of

the sugar to the molds is delayed, the sugar will

solidify in the cooking vessel.

Hard sugar, often called maple "concrete," is

the preferred form for holding commercial maple

sirup in storage.

Granulated or Stirred Sugar

Granulated (stirred) sugar is made by concentrating the sirup to the same density as for

making hard sugar (heating to between 40° and

45° F. above the boiling point of water). The hot,

partly crystallized, thickened sirup is transferred

from the kettle to a stirring trough, and it is

stirred continuously until granulation is achieved.

In days gone by, this form of maple sugar w^as

made by stirring it in a hollowed log usually

made from basswood.

Maple on Snow

This is a favorite of guests at a maple-sirup

camp. As in making stirred sugar, the sirup is

heated to a temperature 40° to 45° F. above the

boiling point of water. As soon as it reaches the

desired temperature it is poured immediately,

without stirring, on snow or ice. Because it is so

quickly cooled, the supersaturated solution does

not have a chance to crystallize and it forms a

thin, glassy taffylike sheet.

Summary

Rock candies

1. Use one of the top grades of maple sirup.

2. Heat the sirup to a temperaure 8° F. above the ^

boiling point of water (67.5° to 70° Brix).

3. Store several months at or below room temperature. ^

Hard sugar

1. Use any grade of sirup. ^

2. Heat the sirup to a temperature 40° to 45° F.

above the boiling point of water.

3. Remove from the heat and begin stirring the

hot thick sirup immediately.

4. Continue stirring until crystals form (sirup begins to stiffen).

5. Pour the partly crystallized sirup into molds to

harden.

Granulated (stirred) sugar

1. Use a top grade of sirup.

2. Heat the sirup to a temperature 40° to 45° F.

above the boiling point of water.

3. Pour the hot sirup immediately into a tray or ^

trough for stirring.

4. Begin stirring immediately and continue stirring until granulation is completed. ^

Maple on snow

1. Use the top grades of sirup. "*

2. Heat the sirup to a temperature 40° to 45° F. ^

above the boiling point of water.

3. Without stirring, pour the sirup immediately i

onto snow or ice; it will form a glassy, taffylike

sheet of candy.

TESTING MAPLE SIRUP

FOR INVERT SUGAR

A simple test for determining the invert-sugar

content of maple sirup has been adapted from a

standard test for determining the sugar in urine

(^5). Table 14 shows how much invert sugar can

be tolerated in sirup from which good cream can

be made. The table also shows the results of using

sirup containing too much invert sugar.

The test to find the amount of invert sugar in

sirup is made in 3 main steps: (1) Five sirup-andwater mixtures are prepared. In each mixture the

sirup is diluted with a different amount of water.

(2) Each dilution is color-tested for the presence

48
TABLE 14.—The relation hetween the invert-sugar

content of maple sirup and its suitability for

making maple cream

Invert-sugar

content of

sirup (percent)

Suitability for cream

0.5 to 2

2 to 4

The right amount of invert sugar for

making a fine-textured cream—one

that feels smooth to the tongue.

Can be made into cream if sirup is

4 or more

cooked until it is 2° to 4'' F. hotter

than temperature called for in standard recipes for cream.

Not suitable for cream. If used, sucrose

will not crystallize, or it will crystallize only if sirup is heated to a muchhigher-than-standard temperature.

Such cream will be too fluid and

probably will separate a few days

after it is made.

of invert sugar. Clinitest^^ tablets and a color

scale are used in making the test. (3) The invertsugar content of the sirup is determined by comparing the results obtained in step 2 with a specially prepared key (table 15). The equipment

required is shown in figure 79.

Preparing the Sirup-and-Water Dilutions

Stir the sirup to be tested thoroughly, and fill

a standard measuring cup exactly to the 1-cup

mark with sirup. Dilute this sirup with five successive additions of water, as follows :

l~and-12 dilution,—Pour 2 measured quarts

(8 cups) of water into a pail, and add the cupful

of sirup. Be sure to let most of the sirup drain out

of the cup. Use a third measured quart (4 cups)

of water to rinse the remaining sirup from the

cup : Fill the cup with water ; stir with a small

spoon, and then pour the water into the pail. Eepeat this rinsing of the cup and pour each rinsing

into the pail untir the quart of water is used.

Stir the sirup and water in the pail until

thoroughly mixed. Then dip a 4-ounce glass into

the dilute sirup and withdraw half a glassful.

Label this glass "12" and set it aside.

l-and-W dilution.—^Add 2 measured quarts (8

cups) of water to the dilute sirup remaining in

the pail, and stir until well mixed. Eemove half

a glassful and label it "20."

l-and~S2 dilution.—^Add 3 measured quarts (12

cups) of water to the dilute sirup remaining in

the pail and stir until well mixed. Eemove half

a glassful and label it "32."

1-and-Jft dilution.—Add 2 measured quarts (8

cups) of water to the contents of the pail and stir

until well mixed. Eemove half a glassful and

label it "40."

l-and~^60 dilution.—Add 5 measured quarts (20

cups) of water to the contents of the pail and stir

until well mixed. Eemove half a glassful and

label it "60."

Testing for Color

Make the color test as follows:

Place 5 test tubes in a test-tube holder. Fill a

clean, dry medicine dropper with the dilute sirup

from the glass labeled "60." Hold the dropper

upright above the test tube in the hole marked

"60" and drop exactly 5 drops of the dilution into

the test tube. Similarly, fill a separate clean, dry

medicine dropper with the dilute sirup from each

of the other 4 glasses, and drop exactly 5 drops

of each dilution into the test tube in the hole with

the number corresponding to the number of the

dilution. Then fill a clean medicine dropper with

water, and add 10 drops to each of the 5 test tubes.

Eemove 5 Clinitest tablets from their container

and place them on a clean piece of paper. Add 1

*^ Clinitest tablets (trade name) are inexpensive tablets

stocked by most drug stores. Anyone can buy them.

They are sold by the bottle or as part of a kit. A color

scale on a small card comes with the tablets ; this scale

is also used in the test.

TABLE 15.—Key table forinterpreting results of color test of five dilutions

[ — indicates negative reaction ; -f indicates positive reaction ; ± indicates doubtful reaction]

Reactions for 5 dilutions

Invert-sugar content of sirup Suitability of sirup for making into cream

12 20 32 40 60

±

+

+

+

+

+

+

±

+

+

+

±

+

+

+

Percent

Less than 2 _ _ _ _ Suitable.

4-

+

+

+

4-

4-

+

+

More than 2, less than 3

More than 2, less than 4

More than 3, less than 4

More than 3, less than 5

More than 4, less than 5

More than 4, less than 6

More than 5, less than 6

More than 5, less than 7

Above 6, may be 7 or more

Do.

Suitable, if sirup is heated 2 to 4 degrees higher

than usual in cream making.

Not suitable.

Do.

Do.

Do.

Do.

Do.

Do.

49
tablet to each tube, in order, starting with the

tube marked "60." The tablets, as they dissolve,

cause the contents of the tubes to boil. Do not

move the tubes while the solutions are boiling.

Fifteen seconds after boiling stops, add water to

the test tube marked ''60" until the tube is twothirds full. Then add the same amount of water

to the other 4 test tubes.

Interpreting the Color Test

To interpret the color test, compare the colors

in the test tubes with the two colors of the color

scale (supplied with the tablets) marked "trace"

and " +." Disregard everything else on the color

scale; the other colors and the labels on all the

colors have no relation to this test.

The comparison must be made in a room lighted

with an incandescent bulb. The colors cannot be

judged properly with either sunlight or fluorescent light. Values for invert sugar are assigned

to each tube according to the color developed, as

follows: Positive ( + ), negative (~), or doubtful (±).

If the color in the tube is the same blue or more

blue than the scale marked "trace," it is negative

( — ). If the color is the same yellow or more yellow than the scale marked " +," it is positive ( + ).

If the color is between "trace" and "-f," it is

doubtful {± ). The color value for each of the 5

tubes is written down in order with the value for

the l-and-12 dilution at the left.

To find the invert-sugar content of the sirup,

find in the Key Table the line that contains the

same combination of values as obtained in the

color test. As the table shows, sirup is most suitable for making into cream if all dilutions are

negative or if the first (l-and-12) dilution is

positive and all others are negative.

Special note,—If the first sirup tested proves

positive in some dilutions and negative in others,

the difference betw^een a positive and a negative

reaction is easily seen. It is possible, however,

that all dilutions will prove positive or all will

prove negative. If this happens, and the interpretation of the results is doubtful, it will be

helpful to have for comparison a solution that is

known to test positive.

To make such a solution, add 3 drops of corn

sirup to the 4-ounce glass containing the sample

of the l-and-60 dilution and place 5 drops of this

mixture in a clean test tube, add 10 drops of

water and 1 Clinitest tablet. After boiling has

stopped, add water until the tube is two-thirds

full. The color that develops will be the color

that indicates a positive reaction.

The Simplified Test

After the complete test has been done a number of times, it may be desirable to shorten the

process by making a color test of only the 1-and20 dilution. As the Key Table shows, sirup that

is negative for invert sugar in the l-and-20 dilution is suitable for making into cream. Sirup

that is positive in this dilution, contains too much

invert sugar to make good cream. Sirup that is

doubtful in this dilution can be made into cream

if it is heated to a higher temperature than

usual in creammaking.

Summary

1. Prepare 5 dilutions of the sirup to be tested :

l-and-12, l-and-20, l-and-30, l-and-40, and

l-and-60.

2. With a clean, dry medicine dropper transfer 5

drops of each dilution to 5 test tubes labeled to

correspond with the labels on the dilutions.

3. With a clean medicine dropper, add 10 drops of

water to each test tube.

4. Add 1 Clinitest tablet to each test tube, beginning with the one labeled l-and-60.

5. 15 seconds after boiling has stopped in the test

tubes, add enough w^ater to fill the tubes twothirds full.

6. In a room illuminated with an incandescent

bulb, compare the colors in the test tubes with

the two colors of the color scale marked "trace"

and" + ."

7. Assign values to the color formed in each test

tube to indicate the presence of invert sugar,

no invert sugar, and doubtful.

8. Write down in order the values assigned to the

5 test tubes, beginning with the value for the

l-and-12 dilution on the left.

9. Compare the 5 values with the Key Table

(table 15) to determine the invert-sugar content

of the sirup.

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AND CHEMICAL CHANGES. Food Res. 17 : 475-

481, illus.

HoBAN, N., and WILLITS, C. O.

1954. CONTRIBUTION TO THE CARBOHYDRATE CHEMISTRY OF MAPLE SAP AND SIRUP. FOOd ReS.

19: 597-602, illus.

ROBBINS, P. W.

1947. THE COST OF MAKING MAPLE SIRUP. Mich.

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SATTLER, L., and ZERBAN, F. W.

1949. UNFERMENTABLE REDUCING SUBSTANCES IN

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1401-1406 illus.

SCARBOROUGH, N. F.

1932. THE CRYSTALLISATION OF CONFECTIONERY.

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ScHUETTE, H. x\., and SCHUETTE, S. C.

1935. MAPLE SUGAR : A BIBLIOGRAPHY OF EARLY

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SNYDER, C. F., and HAMMOND, L. D.

1946. WEIGHTS PER UNITED STATES GALLON AND

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457, 28 pp. (Supersedes publications by

same authors: Nati. Biir. Standards Cir.

375, same title, 6 pp. 1929 ; and Nati. Bur.

Standards Letter Cir. LC-770, Expanded

Table of Weights Per United States Gallon

and Weights Per Cubic Foot of Sugar

(Sucrose) Soluti(ms at 20°C, 26 pp. 1944.

[Processed.])

(39) SPROSTON, T., Jr., and SCOTT, W. W.

1954. VALSA LEUCOSTOMOIDES, THE CAUSE OF DECAY

AND DISCOLORATION IN TAPPED SUGAR

MAPLES. Phytopathology 44: 12-13, illus.

(40) STROLLE, E. O., CORDING, J., Jr., and ESKEW, R. K.

1956. AN ANALYSIS OF THE OPEN-PAN MAPLE-SIRUP

EVAPORATOR. U. S. Agr. Rcs. Serv. ARS73-14, 14 pp., illus. [Processed.]

51
(41)

(42)

(43)

(44)

(45)

(46)

(47)

(48)

(49)

(50)

(51)

(52)

(53)

STBOLLE, E. O., ESKEW, R. K., and CLAFFEY, J. B.

1956. A NEW RAPID EVAPORATOR FOR MAKING HIGHGRADE MAPLE SIRUP. U. S. Agr. Res. Serv.

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TRENK, F. B., and MCNALL, P. E.

[1954.] COSTS OF PRODUCING MAPLE SYRUP IN WISCONSIN. [Wis, Agr. Expt. Sta.] 6 pp.,

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TRESSLER, C. J., and ZIMMERMAN, W. I.

1942. THREE YEARS' OPERATION OF AN EXPERIMENTAL

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UNITED STATES AGRICULTURAL MARKETING SERVICE.

1940. UNITED STATES STANDARDS FOR TABLE MAPLE

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UNITED STATES DEPARTMENT OF AGRICULTURE.

1949. TREES; THE YEARBOOK OF AGRICULTURE, 1949.

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1952. AGRICULTURAL STATISTICS 1952. 876 pp.

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1956. AGRICULTURAL STATISTICS 1955. 610 pp.

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1950. VERMONT MAPLE SIRUP GRADING AND MARKING

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1936. MANUFACTURE OF MAPLE PRODUCTS OF INTENSE

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WiLLITS, C. O.

[1953.] SOME CHANGES THAT SAP UNDERGOES IN A

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1956. WISCONSIN MAPLE PRODUCTS, PRODUCTION AND

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1952. MAPLE SYRUP AND SUGAR PRODUTION IN NEW HAMPSHIRE. N. H. Univ. [Agr.] Ext. Bul. 103, 28 pp.,

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1918. NEW BAUMÉ SCALE FOR SUGAR SOLUTIONS. U. S.

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1946. GREEN MOUNTAIN SAP. Farm Quart. 1 (4) : 38-

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1938. MAPLE SUGAR AND SIRUP. N. Y. Agr. Col. (Cornell) Ext. Bul. 397, 32 pp., illus. (Rev. 1944.)

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1949. DEPTH OF TAPPING IN RELATION TO YIELD OF MAPLE

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1949. MAPLE SIRUP AND SUGAR. N. Y. Agr. Col. (Cornell) Ext. Bul. 397, rev., 32 pp., illus. [First

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DAMBACH, C. A.

1944. COMPARATIVE PRODUCTIVENESS OF ADJACENT GRAZED

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DANSEREAU, P.

1944. L'INDUSTRIE DE L'éRABLE. Université de Montréal,

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1912. MICRO-ORGANISMS OF MAPLE SAP. Vt. Agr. Expt.

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ENGLAND, G. M. and TOMKINS, E. H.

1956. MARKETING VERMONT'S MAPLE SYRUP. Vt. Agr.

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FABIAN, F. W. and BUSKIRK, H. H.

1935. AÍ5R0BACTER AËROGENES AS A CAUSE OF ROPINESS IN

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FiNLAY, M. C.

[1934.] OUR AMERICAN MAPLES AND SOME OTHERS. NeW

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1949. MAPLE—THE MYSTERY TREE. Naturc Mag. 42 I

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GOING, M.

1917. IN THE MAPLE SUGAR SEASON. Canad. Forestry

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GROSE, L. R.

192(). MAPLE SUGAR IN COLONIAL TIMES. Auier. Forests

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HAYWARD, F. W.

1946. THE STORAGE OF MAPLE SIRUP. N. Y. State Agr.

Expt. sta. Bul. 719, 8 pp., illus.

and PEDERSON, C S.

1946. SOME FACTORS CAUSING DARK-COLORED MAPLE SIRUP.

N. Y. state Agr. Expt. Sta. Bul. 718, 14 pp., illus.

52
HERBERT, P. A.

1924. THE WEATHER AND MAPLE SUGAR PRODUCTION,

Mich. Agr. Expt. Sta. Quart. Bui. 7: 60-62, illus.

HERR, C. S.

1938. MAPLE SYRUP AND SUGAR PRODUCTION IN NEW

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pp., illus.

HILLS, J. L.

1904. THE MAPLE SAP FLOW. Vt. Agr. Expt. Sta. Bui.

105, pp. [1931-222, illus.

HITCHCOCK, J. A.

1928. ECONOMICS OF THE FARM MANUFACTURE OF MAPLE

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96 pp., illus.

1929. COST AND PROFIT IN THE SUGAR ORCHARD. Vt. Agr.

Expt. sta. Bui. 292, 19 pp., illus.

1937. THE GRAZING OF MAPLE SUGAR ORCHARDS. Vt. Agr.

Expt. Sta. Bui. 414, 14 pp., illus.

HUFFMAN, R. E., DEVAULT, S. H., and CODDINGTON, J. W.

1940. AN ECONOMIC STUDY OF THE MAPLE PRODUCTS INDUSTRY IN GARRETT COUNTY, MARYLAND. Md. Agr.

Expt. Sta. Bui. 431, pp. 165-215, illus.

HuTOHiNS, MRS. H.

1900. PIONEERING [IN MICHIGAN] GATHERING SAP AND

GOING TO MILL. (A poem.) In [Mich. Hist.

Comn.,], [Mich.] Hist. Collect, (1897-98) 28:638-

640. ( Collections and Researches made by Michigan Pioneer and Historical Society.)

JONES, C. H.

1938. THE EXCLUSION OF LEAD FROM MAPLE SAP. (PROGRESS REPORT), vt. Agr. Expt. Sta. Bui. 439, 7 pp.

and BRADLEE, J. L.

1933. THE CARBOHYDRATE CONTENTS OF THE MAPLE TREE.,

Vt. Agr. Expt. Sta. Bui, 358, 147 pp., illus.

EDSON, A. W., and MORSE, W. J.

1903. THE MAPLE SAP FLOW. Vt. Agr. Expt. Sta. Bui. 103,

pp. [411-184, illus.

KELLEY, M. C.

1933. SAP, SUGAR AND SHEEPSKINS. Amcr. Forcsts

39 : 114-115, 144, illus.

1936. SAVING THE SUGAR ORCHARD. Amer. Forests 42 : 221,

242, illus.

MCINTYRE, A. C.

1932. THE MAPLE PRODUCTS INDUSTRY OF PENNSYLVANIA.

Pa. Agr. Expt. Sta. Bui. 280, 47 pp., illus.

MCKAY, A. W.

1922. MARKETING VERMONT MAPLE-SAP PRODUCTS. Vt.

Agr. Expt. sta. Bui. 227, 48 pp., illus.

MARVIN, J. W. and ERICKSON, R. O.

1956. A STATISTICAL EVALUATION OF SOME OF THE FACTORS

RESPONSIBLE FOR THE FLOW OF SAP FROM THE SUGAR

MAPLE. Plant Physiol. 31: 57-61.

[MARYLAND UNIVERSITY AGRICULTURAL EXTENSION SERVICE and GARRETT COUNTY MAPLE PRODUCTS ASSOCIATION.]

1931. MAPLE SUGAR AND SIRUP RECIPES. Md. UniV.

[Agr.] Ext. Cir. 87,9 pp.

MOORE, H. R., ANDERSON, W. R., and BAKER, R. H.

1951. OHIO MAPLE SYRUP SOME FACTORS INFLUENCING

PRODUCTION. Ohio Agr. Expt. Sta. Res. Bui. 718,

53 pp., illus.

BAKER, R. H., and DILLER, O. D.

1948. THE FARM SUGAR BUSH. OMo Farm and Home

Res.' [Ohio Expt. Sta.] 33 (251) : 40-45, illus.

MORROW, R. R.

1952. CONSISTENCY IN SWEETNESS AND FLOW OF MAPLE

SAP. Jour. Forestry 50: 130-131.

MURPHEY, F. T.

1937. THE MAPLE SYRUP CROP. Pa. State Col. Ext. Cir.

186, 28 pp., illus.

NEARING, H., and NEARING, S.

[1950.] THE MAPLE SUGAR BOOK. 271 pp., iUUS. NeW

York and Toronto.

NEW HAMPSHIRE MAPLE PRODUCERS ASSOCIATION, INC.

1956. NEW HAMPSHIRE MAPLE SYRUP, ITS CARE AND USE.

[Rev. ed.], 15 pp. Concord, N. H. (1953 ed. is

titled "Care and Use of Maple Syrup.")

ORMSBEE, C. O.

1920. EVERY STEP IN MAPLE SUGAR MAKING. Rural New

Yorker 79: 343-344, 409, 519-520, 576, 625, illus.

1923. THE MAPLE SUGAR INDUSTRY, THE TREE THAT MADE

VERMONT FAMOUS, AND HOW ITS DELECTABLE JUICE

IS HARVESTED. Sci. Amer. 129: 176, 214r-215, illus.

ORTON, V.

1941. SUGARING. Sat. Evening Post 213 (38) : [14]-15,

104, 106, 108-109, illus.

PEARL, M.

1952. VERMONT MAPLE RECIPES. 87 pp., illUS. Burlington, Vt.

PEFFER, E .L., and BLAIR, M. G.

1949. TESTING OF HYDROMETERS. [U. S.] Nati. Bur.

standards Cir. 477, 9 pp., illus.

PENNSYLVANIA DEPARTMENT OF FORESTS AND WATERS.

DIVISION OF FOREST RESEARCH.

1952. "COMMON TREES" OF PENNSYLVANIA. 55 pp., illus.

[Harrisburg.]

ROBBINS, P. W.

1944. SMOKE IN THE SUGAR BUSH. Couutry Gent. 114

(2) : 22, 25-26, illus.

1949.

SEARS,

1943.

SMITH,

1919.

SNELL,

1913.

1947. MAKING MAPLE SYRUP. Pa. State Col. Ext. Cir.

310, 36 pp., illus.

PRODUCTION OF MAPLE SYRUP IN MICHIGAN. Mlch.

Agr. Expt. Sta. Cir. Bui. 213, 28 pp., illus.

P. B.

GRAZING VERSUS MAPLE SYRUP. Scieuce 98: 83-84.

R. H.

TAPPING NATURE'S SUGAR BUSH. Couutry Gent. 84

(4) : 13, 63-64, illus.

J. F.

THE ANALYSIS OF MAPLE PRODUCTS. I. AN ELECTRICAL CONDUCTIVITY TEST FOR PURITY OF MAPLE

SYRUP. Jour. Indus, and Engin. Chem. 5: 740-

747, illus.

1916. THE ANALYSIS OF MAPLE PRODUCTS, V. MISCELLANEOUS OBSERVATIONS ON MAPLE SYRUP [TO FIND]

NEW METHODS OF DETECTING ADULTERATION. Jour.

Indus, and Engin. Chem. 8: 144-148.

and SCOTT, J. M.

1914. THE ANALYSIS OF MAPLE PRODUCTS. III. THE RANGE

OF VARIATION OF ANALYTICAL VALUES IN GENUINE

MAPLE SYRUPS. JouT. ludus. and Engin. Chem.

6: 216-222.

SPENCER, J. B.

1923. THE MAPLE SUGAR INDUSTRY IN CANADA. (THIRD

EDITION.) Canada Dept. Agr. Bui. (n. s.) 30, 43

pp., illus.

STEVENSON, D. D., and BARTOO, R. A.

1940 COMPARISON OF THE SUGAR PER CENT OF SAP IN

MAPLE TREES GROWING IN OPEN AND DENSE GROVES.

Pa. State Forest School Res. Paper 1, 3 pp.

[Processed.]

SY, A. P.

1908 HISTORY, MANUFACTURE AND ANALYSIS OF MAPLE

PRODUCTS. Franklin Inst. Jour. 166: 249-280,

321-352, 433-445, illus.

TOWLE, D. S.

1946. SAP WEATHER. Amer. Mus. Nat. Hist., Nat. Hist.

55: [1101-112, illus.

VERMONT DEPARTMENT OF AGRICULTURE.

1941. VERMONT MAPLE SUGAR AND SYRUP. Vt. Dcpt. Agr.

Bui. 38, rev., 41 pp., illus. [First printed 1930

(revision of Bui. 21) ; recent revisions of Bui.

38: 1941, 1949, and (condensed versions) 1952

and 1955.]

53
WEBBER, L. E., and SEELEY, L. E.

1950. OPERATION OF MAPLE SAP EVAPORATORS USING OIL

BURNERS. N. H. Engin. Expt. Sta. Engin. Pub. 9,

7 pp., illus.

WEIR, J. G.

1932. CARE OF THE SU«AR BUSH. Vt. Agr. Col. Ext. Cir.

71, 15 pp., illus.

1933. SUGGESTIONS FOR MAKING HIGH QUALITY MAPLE

SYRUP, vt. Agr. Col. Ext. Cir. 73, 16 pp., illus.

WlLLITS, C. O.

1938. THE PAINTING OF SAP BUCKETS AND OTHER EQUIPMENT USED IN THE PRODUCTION OF MAPLE SYRUP.

N. Y. State Agr. Expt. Sta. Cir. 182, 4 pp.

WiLLiTS, C. O., and TRESSLEE, C. J., Jr.

1939. THE PREPARATION AND PAINTING OF MAPLE-SUGARPRODUCING EQUIPMENT. Jour. Agr. Res. 59: 151-

158, illus.

WiNCH, F. E.

[1954.] TAP YOUR TREES. N. Y. State Col. Agr. [Cornell] Ext. Serv. [5] p. folder, illus. (Coop. Ext.

Work in Agr. and Home Econ.)

and MORROW, R. R.

[1957.] MAPLE SIRUP AND OTHER MAPLE PRODUCTS. N. Y.

State Col. Agr. [Cornell] Ext. Serv. Bui. 974, 44

pp., illus.

WOODS, J. B.

1945. MAPLE SUGAR OR MAPLE LOGS? Auier. Forests

51: 544-547, illus.

54
Figure 1.—Grove of maple trees with large crowns so important

for large yields of sweet sap.

Figure 2.—Same grove shown in figure 1 after defoliation, showing the branch structure of trees with large crowns.

Figure 3.—Large-crowned maples, typical of roadside trees.

55
Figure 4.—Trees in a crowded stand liave small crowns and small

boles. This grove requires thinning before it will be a profitable

source of maple sap.

Figure 5.—Mixed stand of crowded trees. Some trees have long

boles and small crowns. They will make good saw logs but are

poor sap producers.

Figure 6. An ideal spacing of maple trees, favoring the growth of large crowns. However, the grove shows the effect of heavy grazing,

a practice not to be recommended since it results in a reduction of sapwood production, stag-headness, loss of reproduction, and root

damage due to compacting of the ground.

56
Figure 7.—Removing overmature trees that produce sap low in sugar content, to encourage growtli of young stocl<.

to avoicJ some of tlie sap stain and diseased wood associated with old tapholes.

The high cut is made

Figure 8.—Measuring the sugar content (° Brix) of the sap from

a single taphole.

Figure 9.—Measuring the sugar content (° Brix) of sap with a

precision hydrometer, one calibrated in 0.1°. When there is

insufficient sap in the bucket to provide the necessary depth for

such a measurement, the sap is transferred to a hydrometer can,

where the measurement can be made.

57
v^v^;l^a9HQi^HI"

n wSk w

':'. i|ï ¡i \líí' 4!ir».1

a

I^KI^m

^^^^^^^^Mfe-'T-.í^- T.n^:.-'^ - •"'^^"^-?^C'''"í;~ ^f^^^i^^^^^¡^B

Figure 10.—Measuring tlie diameter of the tree to determine

the number of taplioles the tree will support.

Figure 11.—Example of overtopping (8 buckets on a 4-bucket

tree). Note attempt to tap over large roots.

Figure 12.—Boring the taphole at convenient breast height.

The hole is 6 inches from that of the previous season.

Figure 13.—To speed tapping operations, many producers prefer

to use the faster acting machinist's breast drill.

58
Figure 14.—For large maple groves, the power-operoied drill is

preferred.

Figure 16.—Tapholes arranged in a spiral obout the tree.

Figure 15.—The taphole is bored into the tree to a depth of 3

inches.

Figure 17.—In a healthy, vigorously growing tree, the taphole

will be completely covered with new wood and bark in 1

year.

59
Figure 18.—Cross section of maple log showing stained area

caused by fungus growth in old tapholes. The stains show

the exact contour of the holes including the area entered by

the screw of the bit. The stains do not indicate whether the

holes lie above or below the plane of the cut. Note that the

stain is confined to the width of the taphole, which indicates

that lateral damage to the tree is restricted to within V}

inch of either side of the hole, but damage may extend several

inches above and below the hole, as shown in figure 17.

"r-t f* "" '^p?" "^' *"

if'

1("f ?" 'T

f

I Í

Figure 19. A split section of a tapped maple log showing the longitudinal stain area above and below the taphole and the new

growth of bark that covered the outside end of the hole (left-hand piece).

60
Ë ^^

Figure 20.—Reed sap spouts, the forerunner of our metal spouts. Figure 21.—Wood and metal sap spouts.

Figure 22.—Setting the sap spout; care must be taken to seat the

spout firmly in the hole so that a watertight seal is made

with the sapwood and bark. If the spout is driven in too

deeply, the taper will split the wood and bark, and sap

will be lost. To strike the bark a sharp blow will damage

the tree and often kills an area for several inches.

Figure 23.—Rubber rainguard to prevent water from reaching the

sap bucket.

61
:.;|

^.'W |||S^ ^M% - 3^^^S^^^V^ #r^^

' i11!'' •

i^i.ü.'

Figure 24.—Sap-bucket cover attached to the spout by means

of a pin. With this type of cover, the bucket must be lifted

free of the spout for emptying.

Figure 25.—The clamp-on type of cover stays fixed to the bucket

and is not easily blown ofF. With this type of cover, a bucket

that is attached to the spout by means of a hook must be lifted

free of the hook for emptying. However, a bucket that hangs

on the spout by means of a large hole that will slip over the

spout can be emptied by rotating the bucket and cover on the

spout.

Figure 26.—The plastic sap bag: The amount of sap is easily

seen and accumulations of sap, even from short runs over a long

period of time, lend to remain sterile because of the transmitted ultraviolet rays of daylight. The bag has its own

plastic cover. Since the spout is completely covered it is free

from contamination.

Figure 27.—Emptying the plastic bag by rotating it on the sap

spout makes it a one-handed operation.

62
MAPLE SAP SAMPLES COLLECTED

SIMULTANEOUSLY FROM ONE

NONSTERILE SPILE

IN SAP BUCKET IN PLASTIC BAG

Figure 28.—Sap from a single faphole was diverted so that

one-half ran into a plastic bag and the other half into a

metal bucket. One week later samples of the sap from the

two containers were taken. The sap in the bucket was cloudy

because of 144 million bacteria per milliliter, whereas the sap

in the plastic bag was clear and had less than 3,000 bacteria

per milliliter.

Figure 29.—The collection of sap is the most expensive and

laborious operation involved in maple-sirup production. Usually two gathering pails are used to collect the sap from the sap

bags or buckets, and the sap is then carried by hand to the

gathering tanks.

Figure 30.—Collecting tank mounted on a stoneboat. This low-type mounting avoids lifting of the pails for emptying, but a great deal

of power is wasted in dragging the stoneboat.

63
^^ :'ï^^'. ^^ñM

Figure 31.—Collecting tank mounted on a truck body. This type of assembly

does not require special rigs, but an additional man is needed to empty

the pails into the tank.

Figure 32.—Collecting tank mounted on a trailer.

Again, an additional man is required to empty the

pails into the tank.

Figure 33.—Mounting the collecting tank on a wagon

bed is the most common practice. Low wheels make

filling of the tank easier. The wheels can be easily

interchanged with runners for use under all ground

conditions.

Figure 34.—For large operations or for collection from roadside trees extending along several miles of roads, the large tank trailer is desirable.

64
Figure 35.—Sap ¡s easily poured from buckets into a low

sump tank, from which it is pumped into the large

tank.

Figure 36.—The sap is lifted from the sump by means of a pump.

Power for the pump can be supplied by a takeoff from the tractor or

truck engine or by a small gasoline motor.

Figure 37. The use of pipelines to carry sap to the evaporator house saves time. With a lateral system of dumping stations, the use of

gathering tanks can be eliminated in some locations. The pipeline also makes accessible some maple groves that would be impossible

to reach by tractor or truck.

65
Figure 38.—The ramp on which the collecting tank is hauled must be high enough to allow gravity emptying.

Figure 39.—When it is not practical to build a ramp for emptying the collecting tank by gravity, it can be emptied into a sump tank from

which the sap can be pumped to the main storage tank.

66
Figure 40. Evaporator house located in center of sugar bush. Before the days of pipelines and large hauling fanks, the house was built

close to the sap supply to shorten the hauling distance.

Figure 41.—The trend today is to locate the evaporator house near the other farm buildings and on an improved road.

67
Figure 42.—Heavy cloth or canvas is attaclied to tlie lower edge of the hood to bring the hooded area closer to the evaporator.

Figure 43.—Wood truck with flanged wheels runs on roils to transport wood from large storage shed to the evaporator fire doors.

68
iN:?»t¡

Figure 44.—Sap-storage tank, which is a converted milk-storage

tank. When the storage tank is mounted outside aboveground it should be well insulated.

Figure 45.—Multiple-kettle method of making maple sirup, in

this method, which was the forerunner of today's continuous

evaporators, the sap was partly evaporated in the first kettle,

then transferred to the second and third kettles, and finally

to the fourth kettle, where evaporation was completed. (Courtesy of Prof. W. W. Simonds of Pennsylvania Slate University.)

Figure 46.—A modern flue-type evaporator. These are made in sizes up to 6 by 20 feet and have evaporating capacities up to 200

gallons of sap per hour.

69
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i

/

^ J jh-^**^^

^Bé^K ^3 Ä//^

y/if/ff frW^^

411 iÍMí

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Figure 47.—The siphon used to move the sap from the sap (flue)

pan to the sirup (front) pan.

!V

Figure 48.—A semirigid connection between the flue and

sirup pans.

Figure 49.—The float valve, which ad¡usts the depth of liquid in

the evaporator, is mounted on the sap pan. Different devices

are used to obtain precise settings of the valve.

Figure 50.—The installation of oil as fuel for the evaporator

usually requires reconstruction of the arch so that heat from

the oil flame can be fully utilized.

70
CAKE

SUGAR

CREAM

SOFT SUGARI *

n

WATER

BOILS

TUB

,SUGAR

SYRUP

Figure 51.—Maple-sirup target thermometer showing the movable

target on which are etched the markings "water boils," "sirup,"

and others.

Figure 52.—The target thermometer in place in the boiling sirup.

The fine mercury column is difficult to see because of the

steam. The boiling sirup being tested must be deep enough

to cover the bulb of the thermometer. The thermometer must

be in boiling sirup and as close to the point of sirup drawoff

as possible.

Figure 53.—The dial maple-sirup thermometer, like the target

thermometer, has markings to indicate "O" or "water boils,"

"sirup," "soft tub," and "cake sugar." The sensitizing element that moves the needle is in the first 3 inches of the stem.

The dial thermometer is mounted through the drawoff box on

the outside of the evaporator with the stem and its sensitizing

element projecting through the wall of the sirup pan. The

stem is placed one-fourth inch above and parallel to the bottom

of the pan. It must extend at least 3 inches into the area of

boiling sirup, adjacent to the point of sirup drawoff.

71
Figure 55.—A flat type of felt filter, with a flour bag used as a

prefllter.

Figure 54.—Flannel prefllter and felt fliter for maple sirup,

mounted on a milk can.

Figure 56.—The prefllter will clog with sugar sand before the

felt filter; to replace the clogged area the prefllter is pulled

forward until a clean area is in place.

Figure 57.—The use of a multiple fliter assembly permits moving

a clean fliter under the sirup drawoff as each one becomes

clogged.

72
Figure 58.—Measuring the density of sirup: The hydrometer is

carefully placed in the sirup and after it has come to rest the

scale is read. This is the apparent density (Brix value or

Baume value). The temperature of the sirup is then obtained,

so that the density reading can be corrected, if necessary.

Figure 59.—Color grading kit. The kit consists of the official USDA permanent glass color standards mounted in a comparator. The 3

clear blanks are in position in the comparator; 3 blanks (A, B, and C) of different degrees of turbidity, are on the right. The sirup

sample (in the bottle to left of comparator) is inserted in 1 of the 2 openings in the comparator for vievtring.

Figure 60.—Grading the color of maple sirup with the USDA permanent glass color comparator. The sirup is poured into a

rectangular bottle and placed in one of the open chambers in

the comparator. The sirup and color standards are viewed toward the sky (away from the sun, preferably toward the north

sky), and the sample of sirup is moved from one viewing compartment to the other until a match or near-match with one of

the color glasses is reached. If the sirup is cloudy, the clear

blank behind the colored glass which most nearly matches the

sirup should be replaced by the turbid blank (A, B, or C) that

gives the best match both in brightness and in color. Because

cloudiness in maple sirup can cause an apparent upgrading or

downgrading of the sirup, failure to use the turbid blanks may

result in grading the sirup incorrectly.

^M

73
,1^

S

Figure 61.—Exhibit of pacltaged sirup in labeled bottles and lithographed cans.

Figure 62.—For large operations, it is desirable to carry out the making

of maple confections in a separate room; this may be part of the

evaporator house.

Figure 63.—Gas, whether supplied from tanks or from

mains, is an ideal form of heat for cooking maple

products; the heat is easily controlled and can be stopped

the instant cooking is completed. Here, sirup is being

cooked for making maple cream.

74
Figure 64.—A trough with flowing cold water for cooling the thickened sirup quickly.

Figure 65.—Sirup that has been concentrated for creaming is poured immediately into large flat-bottom pans, which are set in flowing

cold water to cool to well below room temperature. The sirup is sufficiently cool when the surface is firm to the touch.

75
Figure 66.—Homemade cream beaters in which the stirrers are held stationary and the pan is rotated at approximately 70 r. p.

Figure 67.—During the creaming operation, the butterlike mass at

first has a shiny surface. When the surface becomes dull,

creaming is complete.

Figure 68.—The finished or remelted cream is sufficiently fiuid to

be poured into containers. Use wide-mouth jars to make filling

and emptying easier.

76
Figure 69.—The thick supersaturated sirup is stirred to form sugar

crystals and to cause them to grow sufficiently large to be

palpable but not large enough to be gritty.

Figure 70.—The partially crystallized sirup is paci<ed into molds

while it is still plastic. In a few hours crystallization is complete, and the candies are firm and can be removed from the

molds.

Figure 71.—A special candy cooking kettle has one end shaped like a funnel and is provided with a spout and shutoff. After the cooked

sirup has coaled but while it is still fluid, the kettle is mounted in an upended position and the sirup is run out through the shutoff.

77
Figure 72. A continuous candy beater of simple design. The cool<ed sirup is run in a small stream from the cooking kettle to the beater,

which consists of a turning worm in a metal trough. The turning worm beats the sirup, crystallizing it, and then drives the semiliquid sirup to the drawoff cock which controls the flow of the sirup into the molds.

Figure 73.—Crystal-coated candies: left. Freshly made uncoated

candies. Center, uncoated candies that have been stored 3

months at room temperature; the white blotches that produce

the unattractive appearance are caused by drying. Right, these

candies, made at the same time as those ir. the center, were

coated with sugar crystals which prevented loss of moisture,

and they have kept the appearance of fresh candies.

Figure 74.—A French fryer or blanching assembly provides a

practical means for crystal coating maple candies. The candies

are placed in the basket for crystallizing in the thick sirup and

are left in the basket to drain. The drained sirup is caught in

the sirup pan for reuse.

78
Figure 75.—The candies are placed in individual paper cups and then fitted into a special box, mal<ins a neat and attractive package.

Figure 76. The candies are weighed before packaging to be sure their net weight will be at least as much as stated on the package.

79
Figure 77.—A steam-jacketed kettle is an ideal cooker for the

high-flavoring process. A kettle with a capacity of 10 gallons

has a number of uses. It can be used as a finishing pan and

as a candy kettle. To use the kettle efficiently, a supply of highpressure steam is required. Provision must be made to discharge the condensed water; a water-logged kettle will not

heat properly. The jacket should be connected to a cold water

line to permit cooling of the sirup and for controlling the rate

of boiling.

A NEW MAPLE PRODUCT

PURE M¿Pi.e SIRUP

BRIX «•

MM ritoti 30 M Q4L% M^tE SAC

I GALLON

HtGH FLAVORED MAPLE SIRUP

FOUR-FOLD ORIGINAL FLAVOR

CORN OR CANE SUGAR SIRUP MMAPLE SiRüP BLEND

I40RMAL MAPLE PLAVOR

TAatE SIRDf.ie 07 »OTTLEi

Figure 78.—A schematic drawing showing the high-flavoring process and its use in making blended sirup and as a food

flavoring.

80

Figure 79.—Equipment required for testing maple sirup for invert sugar: One 16-quart pail, 1 long-handled spoon, 1 teaspoon, 5 glass tumblers (4-oz. size) 1 test-tube holder, paper,

Clinitest tablets, color scale, 7 medicine droppers, 6 test tubes

Vj-inch in diameter and 3 or 4 inches long, 1 cupful of the

sirup to be tested, 1 transparent measuring cup, 1 quart measure, 1 medicine glass, and 1 package of gummed labels.

U. S. GOVERNMENT PRINTING OFFICE; 1957 O -446270
ACKNOWLEDGMENTS

The author wishes to acknowledge the technical assistance of M. C.

Audsley, W. L. Porter, J. Naghski, T. S. Michener, A. J. Mernia, and

other personnel of the Engineering and Developments Section of the

Eastern Utilization Research and Development Division ; the suggestions

and practical information obtained from F. E. Winch, Jr., Cornell University, and F. B. Trenk, University of Wisconsin ; the research work of

J. W. Marvin and his associates at the University of Vermont and of

P, W. Bobbins and his students at Michigan State University ; and the

facilities made available by the following maple-sirup producers, processors, and equipment manufacturers: Sipple and Sons, The Clark Estate,

C. H. Hubbel, Robert Diamond, Schonagel Brothers, The Carey Maple

Sugar Co., United Maple Products, American Maple Products, Geo. H.

Soule Co., The Vermont EvaporatorCo., and The Leader Evaporator Co.

NOTE: The Eastern utilization Researcli and Development Division is located at Pliiladelphla

18, Pa.

Washington, D. O. Issued January 1958

For sale by the Superintendent of Documents, U. S. Government Printing Office

Washington 25, D. C. - Price 60 cents