INSTRUCTIONS FOR INSPECTION 

of 

CANNED 

MUSHROOMS 

For Use ol USDA Processed Foods Inspectors 

UNITED STATES DEPARTMENT OF AGRICULTURE 

AGRICULTURAL MARKETING SERVICE 

FRUIT AND VEGETABLE DIVISION 

PROCESSED PRODUCTS STANDARDIZATION AND INSPECTION BRANCH 

UNITED STATES DEPARTMENT OF AGRICULTURE 

Agricultural Marketing Service 

Fruit and Vegetable Division 

f'rocessed Products Branch 

BRANCH NOTICE NO. 2651 

February 1995 

SUBJECT: Instructions for Inspection of Canned Mushrooms, Corrected Pages 

TO: All Inspectors 

Please remove from the Instructions for Inspection of Canned Mushrooms pages i, ii, iii, 7, 8, 

31 and 32, replace them with the attached pages i, ii, 7, 8, 31, and 32 dated February 1995. 

These pages have been changed to address the use of citric acid as a packing medium in 

canned mushrooms. 

TillS BRANCH NOTICE MAY BE DISCARDED AFTER IT HAS SERVED ITS 

PURPOSE. 

{/Branch 

JJ=~~e~~ Chief 

Distribution:D 

Agriculture: Washington 

PREFACE 

These instructions- are designed primarily for Processed Fruit and Vegetable Inspectors 

of the U.S. Department of Agriculture. They are not intended to be a comprehensive 

treatise on the subject but give background information and guidelines to assist in the 

uniform application and interpretation of USDA grade standards and other similar 

specifications. 

These instructions are revised as necessary without public notice and no mailing list is 

maintained as a public advisory of such changes. 

The citation of any data, criteria, techniques, illustrations, copyrighted material, or pictorial 

representation accredited to private authorship is used with the permission of the 

individuals or sources cited. Unless a specific accreditation is referenced, the information 

herein has been compiled and/or developed from sources available to the public as well 

as from technical knowledge of personnel in the Department 

Compliance with the suggested guide-lines and other pertinent information herein does 

not excuse anyone from failure to comply with the Federal Food, Drug, and Cosmetic Act 

or any other applicable Federal or State laws and/or regulations. 

Except for official USDA inspection aids or devices and color guides (or standards) 

produced under license of the Department, the mention ·at any supplier, patented device, 

product, brand name, or equipment does not imply endorsement by the Department over 

any other similar, or equally effective, material. 

Information contained in this instruction is available to the public. Inquiries as to 

availability of portions of this instruction and copying or reproduction privileges should be 

addressed to: 

Chief, Processed Products Branch 

Fruit and Vegetable Division, AMS 

U.S. Department of Agriculture 

P.O. Box 96456, Room 0709, South Building 

Washington, DC 20090-6456 
Canned Mushrooms 

February 1995 

INSTRUCTIONS FOR INSPECTION OF CANNED MUSHROOMS 

TABLE OF CONTENTS 

PRODUCTION 

Page 

Importance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Recent Trends in Mushroom Production . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Producing Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Types and Varieties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Growing Requirements ....... : .................... , . . . . . . . . . . 2 

Harvesting and Delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

PREPARATION AND CANNING 

General .................................................. 4 

Cutting ................................................... 4 

Washing, Trimming and Sorting ................................. --~ 5 

S1z1ng ............................................ · ........ 5 

Slicing ................................................... 5 

Blanching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

Filling and Weighing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

Brining and Cooking ...................... ·. . . . . . . . . . . . . . . . . . . 7 ~ 

Use of Antioxidants .................. ·. . . . . . . . . . . . . . . . . . . . . . . . 7 

A. Citric Acid and Ascorbic Acid . . . . . . . . . . . . . . . . . . . . . . . . . 7 

B. Relationships of pH to Antioxidants . . . . . • . . . . . . . . . . . . . . . 7 

FOOD AND DRUG REQUIREMENTS 

General ......... ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Required Label Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

Standard of Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

Special Container Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 

INSPECTION OF THE PRODUCT 

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

Minimum Equipment and Inspection Material ...................... . 

Drained Weights .......................................... . 

A. General ...................................... . 

B. Drained Weight Procedure ......................... . 

C. Compliance with Drained Weight Requirements .......... . 

Product Description ........................................ . 

Color Types ............................................. . 

Styles .................................................. . 

Color ............................................... -.... . 

A. General ................... ' ............. ~ .... . 

ii 

10 

11 

11 

12 

12 

15 

15 

16 

19 

19 

/ 
TABLE OF CONTENTS (CONTINUATION) 

B. Instructions for Using USDA Canned Mushroom 

Colors . . . . . . 

Uniformity of Size and Shape 

Defects . . . . . 

Starts on 

Page 

19 

23 

24 

Foreign Material 29 

Character . . . . 29 

Summary of Scoresheets 30 

Certification . . . . 31 

Methods of Analysis . 31 

A. Extraction and Microscopic Examination for Maggots 31 

THIS INST}{UCTION DOES NOT ESTABLISH 

A NEW 01{ REVISED SUBSTANTIVE RULE 

- iii -

IMPORTANCE 

PRODUCTION 

Canned Mushrooms 

August 1972 

Mushrooms rank among the minor vegetables in volume of production 

and consumption. From 1950, however, the production and consumption 

has increased steadily. For example, during 1946 through 1954 the 

annual per capita consumption in the United States was 7 ounces. In 

the packing year 1968-1969 the annual per capita consumption was 18 

ounces. This latter figure compares with the annual per capita consumption in France of 35 ounces, although the total U.S. production 

far exceeds that of France. 

RECENT TRENDS IN MUSHROOM PRODUCTION 

In 1946 and 1947 the quantity of mushrooms used for soups exceeded that for canning or for the fresh market. Since then, the quantity 

of mushrooms used for canning has steadily increased (Table I). 

During the 1970-1971 season, the total mushroom production in 

the United States was 206.81 million pounds, of which 128.58 million 

pounds, or 62 percent, was produced in Pennsylvania. 

TABLE I 

Percent of Total Production Sold to Various Outlets 

Total 

Year Production Fresh Processed 

(Pounds) (Percent) (Percent) 

1946 62,788,000 32.0 68.0 

1947 62,500,000 40.0 60.0 

1948 65,000,000 30.8 69.2 

1961-62 165,000,000 30.5 69.5 

1968-69 189,000,000 29.7 70.3 

1969-70 193,000,000 32.2 67.8 

1970-71 206,810,000 28.2 71.8 

PRODUCING AREAS 

Mushrooms are produced largely in areas conveniently located 

with respect to a large market outlet for fresh mushrooms. Climate 

also helps to determine the areas of production. The Southern States 

are generally unsuited for the growing of this crop because it is 

difficult to maintain a low enough temperature for more than a few 

months each year without artificial air conditioning. 
PRODUCING AREAS (Continuation) 

Canned Mushrooms 

August 1972 

In Pennsylvania, which is the largest mushroom producing area 

in the entire country, production centers around Kennett Square in 

the southeastern part of the State. This location is convenient for 

distribution to the major consuming centers of the northeast. 

In New York, most of the crop is produced in Greene and Ulster 

Counties in the Hudson Valley between New York and Albany. 

Production in Ohio is scattered through the whole State. 

In Illinois, nearly all of the production is in the northeastern 

part of the State. 

In Michigan, the two major producing areas are in the extreme 

southwestern portion of the State, and in Macomb County, just north 

of Detroit. 

In California, practically all production is in coastal areas 

between San Francisco and San Diego. 

Canned mushrooms and mushroom products are also packed in the 

States of Oregon, Washington, New Jersey, Delaware, and Maryland. 

TYPES AND VARIETIES 

All cultivated mushrooms belong to the species Agaricus 

campestris. Various bracket fungi, puffballs, and other fungi have 

been used as food, but none have been grown commercially in this 

country. 

Mushrooms are classified as white, cream, or brown, depending 

on the color of the cap. Those grown for canning are almost 

exclusively of the white variety. In the East and Midwest the white 

variety is also the principal kind grown for fresh mushroom consumption, while in the West and in Canada a fair quantity of the 

cream variety is used. 

GROWING REQUIREMENTS 

Since mushrooms, like all fungi, do not possess chlorophyll with 

which to manufacture carbohydrates from co2 absorbed from the air, 

they must obtain carbohydrates and other nutrients by growing on 

organic material containing these ingredients. 

Compost is the favorite growing medium in commercial mushroom 

houses. 

- 2 -
GROWING REl,!UIREMENTS (Continuation) 

-

Canned -'"lushrooms 

August d7.:: 

~nlike plants possessing chlorophyll, mushrooms can grow in 

darkness. A cool, moist atmosphere is most favorable for their 

development. Caves and abandoned mines have been used extensively 

for the growing of mushrooms. 

Most mushrooms are grown in houses constructed especially for 

the purpose. Cinder blocks are a favorite construction material. 

The houses should be well insulated against cold in winter and heat 

in summer, and should have heating facilities for use in winter and 

means for keeping the air moist when the outside humidity becomes 

low. 

Most houses produce two distinct crops a year. Each crop consists of several "breaks". After the mushrooms are harvested the 

beds are covered with a new layer of "casing" soil and watered down 

for the next growth of mushrooms. After several such "breaks", the 

beds are cleaned out and filled with fresh compost. The entire cycle 

may be completed in as little as three months or even less, up to as 

long as seven months, depending largely on temperature. 

Higher temperatures usually mean a greater proportion of small 

mushrooms. 

Artificial air conditioning enables some growers to obtain 

three crops a year. 

The months of October to May, inclusive, are the months of 

heaviest production. Harvesting is light during the warm weather 

months. A few growers maintain production during the summer by means 

of artificial air conditioning. 

HARVESTING AND DELIVERY 

Most canners grow the greater part of the mushrooms they use, 

purchasing the remainder of their requirements from other growers. 

Some canners grow for canning exclusively; others grow both for the 

fresh market and for processing. 

Mushrooms are pulled from the beds with roots attached before the 

"veil" or membrane breaks open and exposes the "gills". Depending upon 

the contract between the packer and grower, the mushrooms may be 

delivered to the plant either with or without roots attached. In the 

latter case, the roots are ... cut from the mushrooms in the growing 

houses by the harvestors. In either case they are placed in baskets 

holding from three to as much as ten pounds for delivery to the plant, 

- 3 -
Canned ~lushrooms 

August 1972 

HARVESTJNG AND DELIVeRY (Continuation) 

Freshly harvested mushrooms with the root portion attached, will 

remain fresh longer than if the root portion has been removed. Mushrooms frequently grow in clusters which may contain from three to 

five or more units. The units may vary in size from tiny to large 

mushrooms in the same cluster which have developed from one root. 

Mushrooms deteriorate rapidly after picking, becoming discolored 

and wilted. They should be delivered to the cannery promptly after 

picking. When mushrooms cannot be processed promptly after delivery 

to the cannery, they should be placed in a refrigerated room at a 

temperature of 36° to 37° F. until needed. Refrigeration permits 

the supplies to be carried overnight to begin canning operations the 

following morning, or late weekend deliveries may be carried over to 

Monday morning. 

Mushrooms must be handled carefully at all times to avoid 

bruising, which results in dark discolored areas. 

PREPARATION AND CANNING 

GENERAL 

The following description of a canned mushroom operation is 

reasonably typical. The order, methods, and equipment may vary 

plant to plant. 

CUTTING 

from 

After delivery to the plant, the mushrooms which cannot be processed immediately are placed in refrigerated storage until they can 

be processed. 

The baskets of mushrooms are taken to the cutting line for removal 

of root stubs and stems. In most plants the cutting operation is 

performed mechanically, although some may still be cutting by hand. 

The stems may undergo one or two cuttings, depending on the style of 

mush~ooms desired, whether whole or buttons. 

In the case of whole mushrooms, only the root portion of the stem 

is removed by the mechanical cutters. 

If the style of buttons is desired, the cutters first remove the 

root portion of the stem which is carried away for waste. The rest 

of the stem is then removed by cutting immediately below the veil. 

This portion of the stem is used in the style of stems and pieces. 

- 4 -

( 
WASHING, TRIMMING, AND SORTING 

Canned Mushrooms 

August 1972 

After cutting, both the caps and stems are conveyed under a 

spray washer which removes the clinging bits of casing soil or other 

dirt. The mushrooms then pass over an inspection belt where seriously 

blemished mushrooms may be trimmed or sorted out. Misshapen, 

blemished, trimmed, and broken mushrooms are sorted out and placed 

with other mushroom material for the stems and pieces style. 

Mushrooms with partially open veils may be placed with the pieces 

material or may be added to the buttons or whole mushrooms intended 

for one of the sliced styles. 

SIZING 

Mushrooms intended for whole mushrooms or buttons are corc'Jeyed 

by means of water flume to the sizers. 

The mushrooms may be sized in a revolving drum sizer submerged 

in water. Rotary size graders which are not immersed in water may 

also be used. A submerged sizer minimizes bruising and gives the 

mushrooms an additional washing. The caps float upward from the sizer 

and each size is floated off into a separate holding tank. 

The buttons may be separated into six different sizes. The larger 

sizes are generally sliced and the smaller sizes packed as buttons. 

Price lists of packers may quote sizes in terms of number of 

buttons per 8-ounce can as 20/40, 40/60, 60/80, or 100/120. The same 

size designations apply when the mushrooms are packed in smaller 

sized cans. For example, the 40/60 size would pack between 20 to 30 

buttons in a 4-ounce can. 

SLICING 

Mushrooms intended for slicing are generally sliced prior to 

blanching; however, slicing may be performed after blanting. The 

mushrooms are passed through a mechanical slicer with circular knives 

which cut them into slices of predetermined thickness. A shaker 

screen removes the small pieces after slicing. 

Three styles of sliced mushrooms are produced: 1) Sliced Whole; 

2) Sliced Buttons; and 3) Random Sliced Whole. 

"Sliced Whole" style is prepared by aligning the mushrooms prior 

to slicing so that the mushroom is sliced lengthwise from stem to apex. 

- 5 -
SLICING (Continuation) 

Canned Mushrooms 

August 1972 

"Sliced Buttons" style is prepared by pos~t~oning the mushrooms 

prior to slicing so that the mushroom is sliced parallel to the 

longitudinal axis. 

"Rai'dom Sliced Whole" style is prepared by slicing the mushroom 

in any direction. 

BLANCHING 

The mushrooms are flumed from the holding tanks or slicer to 

the blancher. 

The purpose of blanching is to shrink the mushrooms in order to 

obtain the proper fill. Shrinkage is due to loss of mushroom juice. 

Mushrooms may shrink as much as 30 to 40 percent in size in blanching. 

Mushrooms may be blanched by immersing in water at a temperature 

of 200° F. or more. The usual method, however, is to pass the mushrooms through a continuous steam blancher where they are exposed to 

live steam for a period of 5 to 8 minutes. In some cases the mushrooms may be filled into the cans and then blanched in the cans. 

Since iron tends to discolor mushrooms, the blancher should be 

made of stainless steel or other non-corrosive metal. 

During blanching, the color of some white varieties may change 

from near-white to a light tan or buff color. 

FILL~NG AND WEIGHING 

Whole or Button styles are generally filled into the can by hand 

while a semi-automatic filler is usually used for slices or stem and 

piece pack. After filling, the cans are moved by belt conveyor in 

front of the weighers, who weigh the individual cans and adjust the 

fill so that the finished product will meet the required minimum 

drained weight. 

As a safety factor, weighers generally overfill the cans, usually 

in accordance with a schedule of overfill weights which vary according 

to can size and style of pack. 

Cans may vary considerably in weight, particularly in the smaller 

sizes. Deficient drained weights have been found to be due in some 

cases to the use of an unusually light can as tare by the weigher. 

The weigher should choose a tare can of average weight. 

- 6 -
8:-:1:NING AND COOKING 

Canned Mushrooms 

February 1995 

After weighing, a salt tablet which may also contain ascorbic acid is added and 

cans are moved under taps of hot water, the temperature of which may range from 

190 to 200 degrees F. The taps are adjusted to fill cans to overflowing. A hot brine 

solution is sometimes used instead of the water and salt tablet. It is generally 

unnecessary to use an exhaust on the filled cans since a sufficiently high vacuum is 

obtained for most purposes by the addition of hot water. 

After closing, the cans are processed in retorts under steam pressure. After 

processing, the cans may be cooled by water in the retort or a cooling tank. The 

cans should be cooled to 90 to 100 degrees F., which checks the cook but leaves 

cans warm enough to dry off readily and prevent rusting. 

USE OF ANTIOXIDANTS 

A. Citric Acid and Ascorbic Acid 

The FDA Standard of Identity for Canned Mushrooms requires that mushrooms 

packed with the addition of organic acids (other than vinegar), such as citric acid, be 

packed in fully enamel-lined cans. Canned mushrooms cannot be packed in vinegar 

(acetic acid). Some applicants have submitted for grading imported canned mushrooms 

with added citric acid packed in partially enamel-lined cans. Also see the section, 

"Certification" (Page 31 of this manual). Canned mushrooms packed with the addition 

of ascorbic acid, in amounts permitted in the FDA Standard of Identity for Canned 

Mushrooms (up to 132 milligrams for each 100 grams (37.5 milligrams for each ounce) 

of drained weight], do not require full enamel lining. 

B. Relationships of pH to Antioxidants 

The pH value of canned mushrooms is considered to be an important index of 

the possible adulteration of the product with certain acids of tin salts. Fresh mushrooms 

packed with no added acid usually show that if the pH value is 6.0 or more, no citric 

acid has been added. The addition of citric acid very noticeably affects pH, whereas, 

the addition of normal quantities of ascorbic acid does not reduce the pH very much. 

Ascorbic acid in cans gradually diminishes through oxidation, whereas, the 

amount of citric acid changes very little over long periods of time. 

7 
Canned Mushrooms ( 

February 1995 

A pH value l:ielow 6.0 may indicate the presence of C02 in the water, or the 

addition of acid or salts of tin. When the pH is found to be as low as 4.5, the product 

may be considered to be off-flavor. 

FOOD AND DRUG REQUIREMENTS 

Although the Food and Drug Administration has promulgated standards of fill 

and identity (including label statement of optional ingredients) for canned mushrooms, 

no minimum standards of quality have been promulgated specifically for this product. 

Canned mushrooms are subject, however, to the same general requirements 

as other food products. They must be packed under sanitary conditions, must not 

be adulterated, or contaminated with decay, insects, or filth, and must be truthfully 

labeled. 

8 

( 
REQUIRED LABEL-STATEMENTS 

Canned Mushrooms 

August 1!::!72 

In addition to the name of the commodity, "mushrooms", the style 

must be shown as "buttons", "whole",- "stems and pieces", "slices" or 

"sliced", where applicable. The word "Random" in Random Sliced style 

(as in the USDA grade standards) is not required on labels, nor does 

it make any difference whether the style of pieces and stems is 

labeled Pieces and Stems or Stems and Pieces. 

Salt in sufficient quantity to season may be added to the product. 

When salt has been added, the label must bear a declaration of the 

fact. Ascorbic acid not to exceed 37.5 milligrams per ounce of 

drained weight may be added without specific declaration on the label. 

With respect to fill of container, a Drained Weight statement on 

the label is preferred by Food and Drug. However, a net weight 

statement in lieu of the drained weight statement is not considered 

illegal. 

STANDARD OF FILL 

The USDA grade standards outline in detail the Food and Drug 

requirements for standard of fill for canned mushrooms with respect 

to the mushroom ingredient. 

These required minimum drained weights are prescribed in the grade 

standards for the most common container sizes in use in 1962. Occasionally, the industry may introduce new container sizes for which 

specific drained weight requirements are not included in the grade 

standards. For container sizes other than those specified, the minimum drained weight must be equal to a percentage of the water capacity 

of the can, as shown below: 

Water Capacity 

of Container 

(ounces, Avoir.) 

Less than 11 oz. - - - - -

11 oz. or more, but less than 25 oz. 

25 oz. or more - - - - - - - - -

Minimum Drained 

Weight (Percent 

of Water Capacity) 

56% 

59% 

62% 

Water capacity is determined in accordance with the Food and Drug 

method outlined in "Title 21 Food and Drug, Part 10 General Regulations 

Relating to Definitions and Standards of Food". 1/ 

Containers which fail to meet the Food and Drug drained weight 

requirements (also as stated in the USDA grade standards) must bear 

the label declaration: 

"BELOW STANDARD IN FILL" 

See Processed Products Inspectors' copy of Food and Drug "Part 

27 Canned Fruits and Canned Fruit Juices, Definitions & Standards" 

- 9 -
SPECIAL CONTALNER SIZES 

Canned Mushrooms 

August 1:172 

In the case of mushrooms, the designation of can size is often 

misleading and differs from those used in other products. Thus, 

the designation of can sizes by ounces in connection with the word 

"mushroom" (as in 8 Z mushroom can) refers to the drained weight 

of mushrooms proper for the can size and not to the net weight of 

product nor fluid capacity of the container. 

When a new container size is encountered for which specific 

drained weights are not specified it is necessary to determine the 

water capacity of such container and then calculate the applicable 

drained weight. Inspectors and supervisors are cautioned not to 

take the word of the packer, applicant, or container manufacturer 

as to the water capacity of any container for which drained weights 

are not specified. 

INSPECTION OF THE PRODUCT 

GENERAL 

The United States Standards for Grades of Canned Mushrooms 

describes and establishes requirements for the various quality factors 

under the different grade classifications and should be followed in 

the inspection of the product, except when another specification is 

cited. 

To uniformly apply the grade standards, be guided by the supervisor when in doubt as to the correct interpretation of any requirement. This is particularly important whenever unusual conditions are 

encountered or when any interpretation of a requirement will change 

the product from one grade to another. Quality requirements which 

involve judgement as to the extent to which the appearance and eating 

quality are affected should always be checked with the supervisor, 

unless certain of the proper interpretation. Refer to "General 

InsJ?ection Procedures" Section 130 of the Inspectors' Instructions 

for J?rocedures to follow when grading canned mushrooms. 

~UN I MUM EQUIP!v1ENT AND INSPECTION MATERIAL. 

The following list comprises minimum equipment and supplies 

needed for the inspection of canned mushrooms. 

1. Scale and pan provided with counter weights for taking tare of 

container and weights for range of containers of the product to 

be inspected. 

2. Trays, white, shallow for 16-ounce and smaller containers; deep 

trays for larger sizes. 

- 10 -
Canned Mushrooms 

August lY72 

MINIMUM EQUIPMENT AND INSPECTION MATERIAL (Continuation) 

3. Vacuum gauge. 

4. Headspace gauge. 

5. Can opener. 

6. Gram scales. 

7. Ruler. 

8. U.S. Standard No. 8 screen of proper diameter for container 

size for making drained weight determination. 

9. Color guides. 

10. Current U.S. Standards for Grades of Canned Mushrooms. 

11. Federal Specifications or other applicable purchase specifications. 

12. These Inspectors' Instructions and any supplemental instructions 

or memoranda on this product or related subject. 

13. Inspection Papers, such as, applicant's information, contract 

instructions, score sheets, and applicable work sheets for 

preparing certificates for typing. 

DRAINED WEIGHTS 

A. General 

The drained weights prescribed in the USDA grade standards are 

those required under the Federal Food, Drug, and Cosmetic Act. The 

method for ascertaining the drained weights is also prescribed in the 

grade standards and is the same as that prescribed in the Food and 

Drug standard of fill for canned mushrooms. 

Inspectors should be guided by the procedure that follows in 

ascertaining drained weights in order to minimize the introduction 

of unnecessary error in the drained weight results. 

- 11 -
B. Drained Weight Procedure 

Tare the dry sieves to the scale being used. 

Canned Mushrooms 

August 1972 

Place one hand on the completely loosened container lid, grasping the body of the container with the other hand. In one continuous 

motion tilt the container until the lip of the open can end just 

touches the mesh of the slightly inclined sieve; with the expelled lid 

remaining upright and stationary on the screen, draw the container 

away from the lid, permitting the product to flow out slowly, 

distributing it as evenly as possible over the screen. Make sure 

that all of the product is emptied onto the screen, leaving none 

adhering to the bottom or sides of the container. 

Permit the product to drain for exactly two minutes, rotating 

the sieve approximately 180 degrees at the end of one minute to permit any packing media which collects on the flange on the inside edge 

of the screen to drain off. 

Do not stir or otherwise disturb the product on the screen in 

any manner during this draining period. 

Weigh the product and record to the nearest·tenth (0.1) ounce. 

Since the sieve was previously tared, the weight registered on the 

scale will be the weight of the product only. 

Ascertain the drained weights for each sample unit in the sample 

in the manner prescribed. It is only necessary to shake off the 

excess packing media that may adhere to the sieve between drained 

weight determinations. It is not necessary to retare the sieves 

after the first tare adjustment of the scale. 

Calculate the average drained weight for the sample when one or 

more, but not all, of the sample units fail to meet the prescribed 

drained weight for the container size. 

C. Compliance with Drained Weight Requirements 

A lot of canned mushrooms will be considered as meeting the 

specified drained weight requirements if the following criteria 

are met: 

1. If the word "minimum" is stated on the label in conjunction 

with the drained weight declaration; or if a minimum drained weight 

is implied, all the sample units in the sample must be equal to or 

greater than the specified drained weight requirement. Such statements as the following would imply minimum drained weight: 

Example: Minimum Drained Weight 8 oz. 

or 

Drained Weight not less than 8 oz. 

or 

Drained Weight 8 oz. or over. 

- 1:; -
-

Canned Mushrooms 

August 1~72 

C. Compliance with Drained Weight Requirements (Continuation) 

2. If the word "minimum" is not stated on the label in conjunction with the drained weight declaration; or a minimum drained 

weight is not implied, the average drained weight of all the sample 

units in the sample must be equal to or greater than the drained 

weight requirement (designated as avg. in Table II of this 

instruction); and 

3. The number of sample units which fail to meet the required 

minimum drained weight for individuals (designated as Indv. in 

Table II of this instruction) does not exceed the applicable 

acceptance number specified in the single sampling plan contained 

in the Regulations Governing Inspection and Certification of 

Processed Fruits and Vegetables and Related Products. 

Canned mushrooms that fail to meet the drained weight requirements as outlined herein are certified as "Below Standard in Fill". 

NOTE: [See applicable inspector's "General Inspection Instruction 

File" for further certification information with respect 

to Substandard Fill.] 

- 13 -
TABLE II 

Canned Mushrooms 

August 1972 

Drained Weight Requirements for Canned Mushrooms 

Minimum Drained Weight, Ounces (Avoirdupois) Container 

size of All Sliced Style Whole 

Designation Styles including Buttons 

Stems & Pieces 

(Avg.) y (Indv.) y (Indv.) 1/ 

2z mushrooms 2.0 1.8 1.7 

2- 1 I 2 z g 1 as s 2.5 2.3 2.2 

3z mushrooms 3.0 2.7 2.7 

4z mushrooms 4.0 3.7 3.6 

8z mushrooms 8.0 7.6 7.5 

Jumbo 16.0 15.4 15.3 

No. 10 68.0 66.7 66.5 

1/ "Indv." means minimum drained weight for individual containers. 

ij "Avg." means the minimum average drained weight from all the 

containers in the sample. 

- 14 -
PRODUCT DESCRIPTION 

Canned Mushrooms 

August 1972 

The product description contained in the grade standards is an 

excerpt from the Federal Food and Drug Definitions and Standard of 

Identity for Canned Vegetables which pertains specifically to canned mushrooms. The definitions and standard of identity require 

that canned mushrooms be prepared from sound, succulent, fresh mushrooms by proper trimming, washing and sorting. This means that: 

1. With respect to soundness, the finished product must be 

practically free from decay or rot; 

2. With respect to succulence and freshness, the finished product 

may not be prepared from frozen, dehydrated, or otherwise processed 

mushrooms or from mushrooms that have been held in cold storage 

until they have become stale; and 

3. With respect to trimming, washing, and sorting, the root portion 

of the mushroom must be removed by cutting; the mushrooms must be 

washed in clean potable water to remove casing soils and any 

fungicides or insecticides that may be present; and the mushrooms 

must be properly sorted to remove any rot, decay, or insect damaged 

units and foreign material. 

Water is the only packing media permittedunder the Food and 

Drug Standards of Identity for canned mushrooms without label 

qualification. Salt and mon·osodium glutamate may be added as 

seasoning ingredients, but must be declared on the label. 

The Definitions amd Standard of Identity specifically prohibit 

the use of certain additives and seasoning ingredients in canned 

mushrooms such as: 

Citric Acid 

Vinegar 

Spice 

Refined Sugar (Sucrose) 

Refined Corn Sugar (Dextrose) 

COLOR TYPES 

The grade standards provide for three separate color types of 

mushrooms. Two of these types, the white and the cream, are in the 

same category. No distinction is made between these two types due to 

the similarity in color of the finished product. In the raw state, 

there is a very distinct difference, the white mushrooms being al~ost 

snow white in color, and the cream mushrooms being a cream color. During 

and after processing, however, color changes occur in both the white 

and cream types to the extent that the color appearance of the two 

types is very similar. 

- 15 -
Canned Mushrooms 

August 1972 

COLOR TYPES (Continuation) 

In 

effort 

types. 

should 

the inspection and certification of canned mushrooms, no 

should be made to distinguish between the white and cream 

For color types, inspection documents and certificates 

show "white or cream". 

Inspectors should have little or no trouble distinguishing the 

brown color type mushrooms from the white and cream types. Separate 

provision is made for the brown color type in the grade standards 

and should be recorded on the inspection documents and certificates 

accordingly. 

STYLES 

The grade standards provide descriptions and objective requirements for the styles of canned mushrooms most commonly packed in 

this country. Other styles of lesser importance may also be packed 

occasionally, such as "minced", but are not provided for in the grade 

standards or considered as a style for canned mushrooms in the Federal 

Food and Drug Definitions. and Standards of Identity. 

The Federal Food and Drug Definitions and Standards of Identity 

for canned mushrooms provides for only one sliced stlye with no 

reference to the direction of the slice. For the purpose of establishing definitions and standards of identity for canned mushrooms, 

it was the intent of the industry and the Food and Drug Administration 

to permit the use of whole mushrooms, buttons, or a mixture of both 

in the preparation of the sliced style with no limitations as to the 

direction of the slice. 

In actual industry practice, however, more than one sliced style 

is packed, each serving a definite purpose. The styles of sliced 

whole and ?liced buttons are considered as premium packs, used more 

for garnish or decorative purposes, and are meant to be competitive 

in market value with each other. The style of random sliced whole is 

considered by many canners as a "relief" style to aid the plant in 

increasing production to get rid of a "glut" or over supply of mushrooms which is brought about by unseasonable warm weather. This 

latter style is intended to be used in the same manner as the style 

of stems and pieces as an ingredient in various sauces, gravies, 

and other foods. The chief difference between the random sliced 

whole, and stems and pieces styles is the amount of detached stem 

material permitted 1n the former style. In the case of the style 

of sliced whole, it is not uncommon to find some units with stems 

1/8 inch or less in length. In the style of sliced buttons, it is 

not uncommon to find a few sliced units with attached stems whiGh 

are more than 1/8 inch in length. For whole style some units may 

be present with attached stems less than 1/8 inch in length. Also, 

in the style of buttons, some whole mushrooms may be present with 

attached stems longer than 1/8 inch in length but not longer than 

1/4 inch in length. 

- 16 -

1 
STYLES (Continuation) 

Canned Mushrooms 

August 1~72 

In order to provide for uniformity in determining compliance 

with a specific style, the following guide will be applicable in 

addition to the requirements specified in the grade standards: 

1. Whole - Not more than 15 percent, by count, of the units 

may possess stems 1/8 inch or less in length measured as 

specified in the grade standards; 

2. Buttons - Requirements as specified in the grade standards; 

3. Sliced Whole - Not more than 15 percent, by weight, of the 

sliced units (with attached stem material) may possess 

attached stem material which is 1/8 inch or less in length; 

4. Random Sliced Whole - No limitations as to whether prepared 

from whole mushrooms or buttons or a mixture thereof. Other 

requirements as specified in the grade standards; 

5. Sliced Buttons - Not more than 15 percent, by weight, of 

the sliced units may possess attached stem material which 

is more than 1/8 inch in length but not longer than 1/4 inch; 

6. With respect to the requirements for styles specified in 

the grade standards as well as those specified herein, a 

sample unit that fails to meet such requirements is considered a deviant; and 

7. The number of deviants in the sample does not exceed the 

acceptance number for the applicable sample size in the 

single sampling plan contained in the Rules and Regulations 

Governing Inspection Inspection of Processed Fruits and 

Vegetables, and Related Products. 

- 17 -
STYLES (Continuation) 

Canned Mushrooms 

August 1~72 

A lot of canned mushrooms that fails to meet the acceptance 

criteria for a specified style as specified herein shall be 

designated as follows with respect to style: 

Failure to meet 

Single style of: 

Whole; Buttons 

Sliced Whole 

Random sliced 

Whole 

Sliced Buttons 

Reason for Failure 

Excessive units possess 

stems which are more 

than 1/8 inch (or 1/4 

inch) in length, or 1/8 

inch or less in length -

as applicable. 

Excessive random sliced 

units and/or deta~hed 

stem material exceeds 

5% but not more than 

15%, by weight. 

Detached stem material 

exceeds 15%, by weight. 

Excessive sliced units 

that possess attached 

stem material which is 

1/8 inch or less in 

length. 

I Excessive detached stem 

I material. 

l 

I 

I Excessive sliced units 

i that possess stem 

: material which is more 

! than 1/8 inch in length 

l 

- 18 -

Designate as: 

Mixture of styles; 

Whole and Buttons 

(specify predominant 

style first). 

Random sliced whole. 

Stems and Pieces. 

Mi~ture of styles; 

sliced whole and 

sliced buttons. 

(specify predominant 

style first). 

Stems and Pieces. 

Mixture of styles; 

sliced buttons and 

sliced whole. 

(specify predominant 

style first). 
COLOR 

A. General 

Canned Mushrooms 

August 1972 

The grade standards describe the minimum color requirements for 

the different color types under the various grade classifications. 

USDA color guides which illustrate the minimum limits for color in 

the A and B grade classifications are made available to each 

inspection field office as well as to the mushroom canning industry 

except Hawaii and Puerto Rico. Such color guides will aid 

inspectors in objectively evaluating the factor of color. 

In evaluating color of canned mushrooms, consideration must be 

given to the overall color appearance of the product as well as to the 

color of the individual units. In the case of the styles of whole 

and buttons, only the surface of the caps are considered for color~ 

In the case of the sliced styles, including sliced units in the 

style of stems and pieces consideration must be given to the surface 

of the cap as well as to the gills. 

Separate color requirements for cap surface and gills are provided 

for in the different grade classifications. In addition to the 

minimum color requirements for the cap surface and the gills, the 

grade standards specify that the contrast in color between the cap 

surface and the gills does not more than slightly affect the overall 

appearance for Grade A and does not seriously affect in Grade B. 

Generally, 30 days or more are required after packing for the 

color to become stabilized in canned mushrooms which are packed without the addition of ascorbic acid. With the use of ascorbic acid, 

however, the color will stabilize in less time. 

The limiting rule on color applies in both the Grade B and Substandard classifications. There should be no "Substandard" color in 

Grade A. 

B. Instructions for using USDA Canned Mushroom Colors 

1. Explanation 

The USDA Colors for Canned Mushrooms are intended as an aid to 

provide greater uniformity in the interpretation of the color 

requirements for the different grade classifications specified in 

the United States Standards for Grades of Canned Mushrooms. The 

grades provide for degrees of uniformity as well as separate 

descriptions of the minimum color requirements for caps and gills 

of the mushrooms. · 

- 19 -
COLOR (Continuation) 

Canned Mushrooms 

August 1972 

The colors -- USDA 1 through USDA 5 -- consist of separate 

plastic slats (1" x 5"). They represent basic minimum colors for 

"White or Cream" color type mushrooms as: 

WHOLE and BliTTON 

styles 

Caps .. 

OTHER styles 

Caps 

(or portions). 

Gills. . . 

USDA 

1 

Grade 

A 

Grade 

A 

USDA 

2 

Grade 

A 

Grade 

A 

USDA 

3 

Grade 

A 

USDA 

4 

Grade 

B 

Grade 

B 

USDA 

5 

Grade 

B 

---- See page 22 for allowances for the respective grades 

2. Making color comparisons 

The evaluation of color should be made under adequate lighting 

conditions, preferably under constant laboratory lighting that 

approximates diffused north daylight (about 7500 degrees Kelvin). 

Color of the Canned Mushrooms should be evaluated as soon as 

possible after the containers have been opened. 

3. Care of colors 

The colors are made of a plastic material and should be handled 

with care to avoid scratching. They should be cleansed by rinsing 

in clear, warm water and dried with a soft cloth immediately after 

using. No abrasive cleanser should be used. They should be stored 

in a cool, dark place when not in actual use. 

4. Licensed supplier for colors 

These color guides may be purchased, and prices are available 

from the licensed supplier: 

Magnuson Enginaers, Inc. 

1010 Timothy Drive 

San Jose, CA 95133 

- 20 -
COLOR (Continuation) 

Canned Mushrooms 

August 1972 

5. Obtaining addition copies of Instructions and Standard 

Additional copies of these instructions and the United States 

Standards for Grades of Canned Mushrooms are available upon 

request from: 

Processed Products Standardization 

and Inspection Branch 

Fruit & Vegetable Division, C&MS 

U. S. Department of Agriculture 

Washington, D. C. 20250 
COLOR (Continuation) 

Canned Mushrooms 

August 1972 

MAXIMUM ALLOWANCES FOR COLOR VARIATION 

White or Cream Color Types 

CAPS ---

Darker and more tannish 

than USDA 1 

-- or --

More greyish-green than 

USDA 2 

GILLS ---

Darker in tannish-grey 

than USDA 3 

CAPS ---

More grey than USDA 4 but no 

darker or no more brownishgrey than USDA 3 

-- and --

Darker and more brown than 

USDA 4 

-- or --

Darker and more brown than 

USDA 4 , 

GILLS ---

Darker and more tannish-grey 

than USDA 5 

GRADE A 

WHOLE and BUTTON 

Styles 

( y count) 

10% 

GRADE 

WHOLE and BUTTON 

Styles 

(by count) 

10% 

and 

5% 

or --

10% ~';;, 

ALL OTHER 

Styles 

(by we~g t 

10% 

But no 

or more than 

total of 

10% 

10% such caps 

and gills 

combined 

B 

ALL OTHER 

Styles 

(by weight) 

10% 

-- and 

5% 

-- or 

10% But no more 

than total of 

10% 

such caps and 

j 10% gills combined 

The color of caps is based on surface of the cap or any portion of cap. 

When the cap and gills of a sliced unit vary from the color limits, such 

unit is considered in the allowance for either caps or gills, but-not 

both. 

TI1e foregoing allowances supplement the descriptive requirements for 

uniformity and typical color for the respective grades in the United 

States Standards for Grades of Canned Mushrooms. 

7' 
UNIFORMITY OF SIZE AND SHAPE 

Canned Mushrooms 

August 1972 

Mushrooms intended for the styles of whole, ~ut~~ns, sliced_ 

whole, or sliced buttons are very carefully size graded. A high 

degree of uniformity may be obtained by the methods of sizing in 

general use in the canning industry. 

Mushrooms intended for the styles of random sliced whole or 

stems and pieces are not size graded. Since th1s latter style 

consists chiefly of pieces of stems and caps, and may contain 

sliced units as well as whole mushrooms and buttons, it would not 

be reasonable to expect any degree of uniformity of size and shape. 

Consequently, this factor is not scored for the style of stems and 

pieces. 

A. Whole and Buttons 

Consideration is given to the uniformity of shape among the 

individual units, to the uniformity of size with respect to diameters 

among the individual units, and the manner in which the stem has been 

cut. 

In addition to the allowances specified in the grade standards 

for variation in diameters, the following allowances for variation 

in shape and irregular cut stems will be applicabl~: 

Grade A -- Not more than 10 percent, by count, of the 

units may be irregular in shape, and/or may 

possess stems which have been irregularly 

cut such that the appearance of the unit is 

seriously affected. 

Grade B -- Not more than 15 percent, by count, of the 

units may be irregular in shape, and/or may 

possess stems which have been irregularly cut 

such that the appearance of the unit is 

seriously affected. 

NOTE: A unit that is irregular in shape and possesses an 

irregularly cut stem that seriously affects the appearance 

of the unit is scored as one or the other irregularity but 

not both. 

- 23 -
UNIFORMITY OF -siZE AND SHAPE (Continuation) 

B. Sliced Whole, Sliced Buttons 

Canned Mushrooms 

August 1972 

For these two styles, consideration is given to the uniformity 

of shape among the individual units as well as uniformity of 

diameters of the center slices. Inspectors are cautioned that only 

the center slices, as defined in the grade standards, are considered in evaluating uniformity of diameter for these styles. 

In addition to the allowances for vfiation of diameter specified 

in the grade standards, the following allowances for irregular 

shaped units are applicable. 

Grade A -- Not more than 10 percent, by weight, of the 

units may be irregular in shape. 

Grade B -- Not more than 15 percent, by weight, of the 

units may be irregular in shape. 

Inspectors should note the partial limiting rule applicable to 

the factor of uniformity of size and shape. Canned mushrooms that 

score into the Grade B range for this factor but are otherwise Grade A, 

may still be classified as Grade A provided the total score is not 

less than 90 points. Canned mushrooms that score into the Substandard 

range for this factor, however, may not be classified above Grade B, 

and only then if all other factors are Grade B or better and the 

total score is not less than 80 points. 

DEFECTS 

Table III, which follows this section, is designed to assist 

inspectors in assigning score points to the factor of defects. Careful consideration should be given to the effect that a particular 

defect or a combination of defects may have on the overall appearance of the product. 

The following supplemental explanations of the various defects 

are intended to further assist inspectors in properly classifying 

as to type: 

A. Crushed or Broken 

In order to be considered crushed, a whole mushroom, button: or 

sliced unit must be crushed to the extent that the original shape 

has been destroyed. Units that have been "crowded" in the container 

to the extent that the original shape has been changed but may be 

restored are not considered as crushed. 

- =-+ -
DEFECTS (Continuation) 

Canned Mushrooms 

August 1972 

A broken unit is a unit that has been severed into two or more 

entirely separate parts. Two or more pieces from broken units that 

may be pieced together so as to approximate one whole unit (one 

whole mushroom, one whole button, or one whole slice, as applicable) 

is considered as one "broken unit". A unit that is only partially 

broken (i.e. not separated into two or more entirely separate parts) 

is not considered broken. 

B. Damaged mushrooms 

1. Discoloration 

The presence of very light sta1n1ng or surface discoloration 

which does not extend into the flesll of the mushroom should be considered only under the factor of color. 

Discoloration may be caused by bruising of the flesh in rough 

nandling or by contact with the soil in which the mushrooms are grown 

or by oxidation when the mushrooms are not handled promptly after 

picking. Discoloration may also be due to pathological injury caused 

by the development of fungus (brown spot) or b~cterial spot which may 

result in the development of yellow or brown spots (rust) or pits on 

the cap or stem. When such ~athological injury has progressed to 

the stage that decay or rot is present it is to be considered as 

foreign material. 

2. Mechanical injury 

Trimming on the cap of whole mushrooms or buttons which destroys 

the contour of the cap should be classified as a defect. Knife marks 

on stems or cuts which give a ragged appearance to the stem should also 

be classified in this category. Knife marks resulting from the preparation of sliced whole or sliced button mushrooms are not considered 

as mechanical injury. 

c. Serious damage 

When dark brown or black discolored areas extend into the flesh 

such discolored areas should be classified as damage and may be scored 

as damaged or seriously damaged, depending upon the extent of the 

effect upon the appearance or eating quality of the unit. No more than 

an occasional stem should show dark discoloration or deep staining 

from contact with the mushroom growing bed. 

Damage to mushrooms caused by discoloration, mechanical damage, 

pathological inJury, or damage by other means causing damage to the 

extent that the appearance or eating quality of the unit is seriously 

affected should be classified as serious damage. 

~- _.::: -
DEFECTS (Continuation) 

Canned Mushrooms 

August 1972 

Separate allowances are provided in the grade standards for 

crushed or broken and damaged under each of the grade classifications. 

The allowances provided for damaged and seriously damaged, however, 

are inclusive. For example, the maximum allowances penni tted in 

Grade A provide for a grand total of 10 percent by weight as follows: 

5 percent, by weight, may be crushed or broken; and 

in addition, a total of 5 percent, by weight, may 

be damaged and seriously damaged; but no more than 

1 percent, by weight, may be seriously damaged. 

The grade standards further provide that even though the product is within the limitations for the specified allowances, if 

the defects that are present either singly or in combination affect 

tne appearance of the product in excess of the degree permissible 

for the indicated grade, the product must be assigned the score 

points within the grade classification indicated by the appearance 

rather than the specified allowances. 

- 26 -
TABLE III 

Canned Mushrooms 

August 1972 

SCORING GUIDe AND SUMMARY OF ALLOWANCE FUR DEFECTS 

Maximum Allowances 

Grade Classi- Score 

fication Points All Styles 

except . I stems & p1eces; 

All Styles 

Crushed or Damaged & 

broken seriously Seriously 

damaged damaged y 

I (Percent by (Percent by (Percent by 

weight) weight) weight) 

30 0 0 But 0 

no 

29 1 1 more 0 

A thf!.n 

28 3 3 0.5 

27 5 5 1 

26 6 1.2 

But 

B 25 8 8 no 1.5 

more 

24 10 10 than 2.0 I 

SStd -23 Fails to meet requirements for Grade B 

1/ One unit in a container is permitted to be seriously damaged: 

Provided, that the total number of such seriously damaged units 

in all of the containers comprising the sample is within the 

percentage permitted for such defect. 

- 27 -
Canned ~Jshrooms 

August 1972 

DEFECTS (Continuation) 

0~ Extraneous material 

The grade standards do not provide allowances for harmless 

extraneous material. Since mushrooms are grown under highly controlled conditions it is not likely that such extraneous material 

as weeds, blades of grass or other harmless vegetable material 

would be encou~ered in the finished product. 

Occasionally, however, certain extraneous materials are 

encounterea in canneci mushrooms. In this respect in order to 

establish guidelines for gooa commercial practice, harmless 

extraneous material in canned mushrooms may be defined as that 

material related to the mushroom plant or to the growing of the mushroom 

which is harmless, and by its very nature, when present within certain 

limitations is not objectionable. Such material may include but is 

not limited to: 

l. Attached or loose root material with no adhering grit, soil, or 

compost; and 

2~ Small pieces of straw. 

For the purpose of ascertaining the grade of a sample when harmless extraneous material is present in canned mushrooms, the following 

administrative guide is applicable: 

' Harmless I 

extraneous ! Grade A Grade B SStd. 

material I 

I 

Attached or Average of 1 piece Average of 2 pieces Fails Grade 

loose root per approx. 100 oz. per approx. 100 oz. B 

material net contents. net contents. 

with no I 1/ 1/ 

adhering I grit, soil, 

or compost 

Small pieces Average of 1 inch Average of 1-1/2 Fails Grade 

of straw in length per inches in length B 

approx. 100 oz. per approx. 100 

net contents. oz. net contents. 

1/ y -

1 I Equlvalent to the net welght of a No. 10 can. 

' - 2 0 -
, 

FOREIGN MATERIAL 

Canned Mushrooms 

August 1972 

The best of commercial practices does not give absolute assurance 

that foreign material will be completely eliminated from the finished 

product. However, when good processing procedures are practiced, such 

material can be held to a minimum to the extent that its presence 

will not affect the appearance or eating quality of the product. 

Foreign material in canned mushrooms may be considered as any 

material that seriously affects the appearance or eating quality 

of the product (except that which is considered a defect and allowances provided for in the grade standards), and any other material 

which by its very nature, is objectionable. Such material includes 

but is not limited to: 

1. Grit, soil or compost; 

2. Wood splinters; 

3. Rot or decay; 

4. Insects·or insect fragments; and 

5. Maggots. 

Most of the aforementioned foreign material may be detected upon 

visual examination during the regular grading process. An exception 

would be the presence of maggots (See Methods of Analysis "Extraction 

and Microscopic Examination for Maggots in Canned Mushrooms") 

CHARACTER 

Mushrooms which have been harvested and canned promptly should be 

tender and have a noticeable crispness of texture when chewed. Toughness of the mushrooms, together with a stale flavor, is indicative of 

raw stock which has been held for several days under unfavorable 

storage conditions before canning. 

Mushrooms for canning should be harvested while the veils are closed. 

Frequently, the veil in whole mushrooms may be partially broken open 

during the blanching operation or during processing. Dpen veils are 

scored only in the styles of Whole and Buttons. Inspectors are cautioned 

to use good judgement in classifying a whole mushroom or button as to 

open or closed veils. The grade standards define a closed veil by 

specifying that the membrane which extends from the inner edge of the 

cap to the stem practically covers the gills. This means, to be-considered a closed veil, there may be a rupture in the veil that :i:s only 

slightly noticeable-probably was due to blanching rather than maturity. 

fne larger sized mushrooms may possess slightly longer ruptures than the 

small sizes and still be no more than slightly noticeable. In order to 

provide for uniformity in scoring open veils, be guided by the follo~ing: 

- !~ -
CHARACTER (Continuation) 

Canned Mushrooms 

August 1972 

Consider a unit to possess an open veil if the length of the 

veil opening exceeds: 

1/8 inch for No. 0 and No. 1 mushrooms; 

3/16 inch for No. 2 and No. 3 mushrooms; and 

1/4 inch for No. 4 and larger. 

In the case of a single unit which possesses more than one opening, the combined lengths of such openings should not exceed the 

above guide for a single opening. 

SlJ111MARY OF SCORE SHEET 

Before preparing the certificate, the score sheet should be 

carefully analyzed to see that the ratings and notations are in 

good order. Sign and date the score sheet. 

- 30 -
CERTIFICATIONCanned Mushrooms 

February 1995 

In the certification of a lot of canned mushrooms that fails to meet the acceptance 

criteria for the specified style, the grade certificate should show in the body opposite 

"Style" that the lot fails requirements for the particular style, the reason for failing, and 

state whether the lot is a mixture of styles or meets requirements for a different style 

than for which the lot was offered. Flag the grade statement with usee Style Above". 

EXAMPLE: Lot Offered for Buttons - Fails. 

In the body of the certificate: 

Style: Fails to meet requirements for the style of Buttons account 

presence of excessive whole mushrooms. 

Grade Statement: 

Grade: 

Mixture of Styles - Whole and Buttons. 

U.S. Grade A or U.S. Farcy 

Average Score: 91 points. 

"SEE STYLE ABOVE" 

EXAMPLE: Lot Offered for Sliced Whole- Fails. 

In the body of the certificate: 

Style: Fails requirements for the style of Sliced Whole account 

detached stem material exceeds 5 percent, by weight. 

Meets requirements for the style of Random Sliced Whole. 

(or) 

Style: Fails requirements for the style of Sliced Whole account 

presence of excessive sliced buttons. 

Mixture of Styles - Sliced Whole & Sliced Buttons. 

Grade Statement: Same as above. 

Canned mushrooms, which do not meet the FDA Standard of Identity for added citric 

acid packed in cans lacking full enamel lining, should be certified as follows: 

Under Grade Statement: 

Grade: Fails Standard of Identity for Canned Mushrooms 

account addition of citric acid in cans lacking full 

enamel lining. 

31 
METHODS OF ANALYSIS 

Canned Mushrooms 

February 1995 

Extraction and Microscopic Examination for Maggots in Canned Mushrooms 

1 . Explanation 

Maggots in canned mushrooms have not been recognized as a problem in our 

inspection of this product. However, recently it has been established that maggots, 

under certain conditions, may be present in canned mushrooms. Maggots are more 

likely to be found in stems and pieces style, and in a product having a poor 

appearance (presence of pathological injury, external or internal dark brown or black 

spots). 

2. Sampling Rates 

All lots of mushrooms offered for inspection should be examined for maggots. 

The number of samples checked for maggots should be as follows: 

Drawn for Quality Examine for Maggots 

3 1 

6 1 

13 or more Same as deviant number 

If maggots are found during the examination of sample units, refer to the acceptance 

criteria found in File Code 172-A-1, Table 1 . 

When a history has been established for an individual plant, the frequency of 

maggot determinations, if the data warrants it, may be reduced. For example: When 

1 0 consecutive lots are free of maggots, the frequency of analyses may be reduced to 

one analysis for each four lots examined. 

3. Method 

(a) Reagents and Apparatus 

(i) Crystal Violet -- saturated aqueous solution or crystal. 

(ii) Sodium Hypochlorite solution (NaOCI) -- commercial product containing 

Ca. 5.25% (Hilex, Chlorox, Etc.) 

(iii) Aerator -- rubber slip on kitchen aerator with lower screen removed. 

(iv) High speed blender with voltage regulator for controlling speed.-

(v) 8-inch sieves, Nos. 20, 40, and 140. 

(vi) Stereoscopic wide-field microscope (20X magnification with additional 

magnification to 40X for verification). 

32 

\ 
~lliTHODS OF ANALYSIS (Continuation) 

(b) Sample preparation 

Canned Mushrooms 

August 1972 

The standard analytical sample is 100 grams of product plus the 

screened-off material from a proportionate amount of packing media. 

For container sizes smaller than 4-oz. mushroom can, combine the contents of enough cans to make 100 grams. The entire contents of a 

4-oz. can should be taken for the sample. 

For larger can sizes, 100 grams of drained product is used plus 

the screened material from a proportionate amount of the drained 

liquid. 

EXAMPLE: A 16-oz. can of product will contain about 8-oz. of packing media. 

Pour approximately 4-oz. of the product and 4-oz. of 

drained liquid onto an 8-mesh screen. The drained 

liquid and any material passing through the screen 

should be dyed, filtered, and examined separately. 

Any maggots or mites found in this e~amination should 

be included in the total count. For analysis of the 

product, 100 g. of the drained material should be 

taken. 

(c) Extraction and examination 

(i) Place 100 g. drained mushrooms into high speed blender cup. 

(ii) Add 300 ml H20 and operate blender at speed of 3,000-3,500 

rpm for 30-35 seconds. 

This step is very critical and a voltage regulator will 

have to be used with the blender. Usually a setting 

of about 30-35 on a Varivac voltage regulator will produce 

the correct speed. Care must be exercised to avoid overpulping the product. If this occurs, excessive plant 

material will accumulate on the filter papers making it 

impossible to find the maggots. Attain proper speed 

quickly by boosting setting 1.5 to 2 times the desired 

setting on the variable transformer for a few seconds 

at the start. Fragments of the blended mushrooms should 

be no longer than a small raisin. Some mushrooms, particularly soft broken pieces, require a minimum of blending. 

Larger firm whole units may require longer. Through 

experience, the analyst will learn when the blending is 

complete. 

- 33 -
METHODS OF ANALYSIS (Continuation 

Canned Mushrooms 

August 1972 

(iii) Pour mixture into a 600 ml beaker and add 15 ml 

saturated aqueous crystal violet or approximately 100 mg 

of powdered crystal violet, stir and heat to boiling. 

(iv) Pour stained mixture into a nested set of 8-inch Nos. 

20, 40, and 140 sieves. 

(v) Rinse tissue 2-3 minutes with spray of tap water from 

aerator and discard material on No. 20 sieve. 

(vi) Wash mushroom tissue and maggots, if any, on the No. 40 

and 140 sieves to edge of sieve and remove excess stain 

with tap water from aerator. 

(vii) Using wash bottle containing NaOCl solution and gentle 

spray of tap water from aerator, alternately spray 

tissue with water and NaOCl solution until stain has been 

removed from mushroom tissue. 

(v1ii) Hold a forward-tilted sieve over beaker; wash material 

into beaker by directing a spray of water through the 

back side of the sieve into beaker. 

Several small washings are desirable, resulting in an 

accumulation of about 300 ml water in the beaker. Avoid 

spilling any material in this transfer. 

(ix) Transfer contents of beaker to ruled filter paper, with 

suction. 

Avoid obscuring maggots and/or mites with mushroom tissue. 

Use as many papers as are necessary to avoid piling up 

too much material on a single paper. 

(x) View prepared filter paper under microscope and record 

result. 

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