METHODS OF ANALYSES 

for 

TOMATO PRODUCTS 

FOR USE Of USDA PROCESSED FOODS .INSPECTORS 

UNITED STATES DEPARTMENT OF AGRICULTURE 

C~NSUMER AND MARKETING SERVICE 

\ FRUIT AND VEGETABLE DIVISION 

PROCESSED PRODUCTS STANDARDIZATION AMD INSPECTION BRANCH 
METHODS OF ANALYSES 

for 

TOMATO PRODUCTS 

FLY EGG AND MAGGOT DETERMINATION I 

TABLE OF CONTENI'S November 

1967 

These instructions with respect to Fly Egg and Maggot Determination in Tomato Products supersede: 

FLY EGG AND MAGGOT DETERMINATION - - - - July 1965 

Fly Egg and Maggot Determinations 

Supplements 1, 2, S 3 - - - - July 1966 

I BACKGROUND AND INCIDENCE . . . . . . 

II IDENTIFICATION AND CLASSIFICATION. 

III PRODUCT GROUPINGS OR CLASSIFICATIONS 

A 

B 

c 

D 

Canned Tomatoes . 

Comminuted Tomato Products. 11 Seeded11 Tomato Products. 

Specialty Products. o •••• 

N SAMPLING RATES 

A Lot Inspection 

B Inplant Inspection. 

V PREPARATION OF SAMPLE 

A Canned Tomatoes o • 

B Tomato Juice. . . . 

C Tomato Paste, or Tomato Puree (Tomato Pulp) 

Starting 

on Page 

1 

3 

4 

4 

4 

4 

5 

7 

8 

. 10 

or Concentrated Tomato Juice . . . . 10 

- i -
METHODS OF ANALYSES 

for 

TOMATO PRODUCTS 

FLY EGG AND MAGGOT DETERMINATION 

TABLE OF CONTENTS -- Continued 

D Tomato Catsup . 

E Tomato Sauce. 

F Pizza Sauce . 

G Chili Sauce . 

H Specialty Products ~Soups. 

VI EXTRACTION OF SAMPLE 

A 

B 

c 

D 

Equipment . • . . 

Preparation of Reagents and Materials . 

Pectolytic Enzyme . • . 

Bolting Cloth ..... 

Stereoscopic Microscope . 

Extraction Procedure. 

Recording Results 

VII MAGGOT RECOVERY. 

VIII LOT ACCEPTANCE • 

FLY EGG AND MAGGOT DILUTION CHART 

- ii -

November 

1967 

Starting 

on Page 

10 

10 

11 

11 

12 

13 

14 

14 

14 

15 

15 

16 

17 

18 

19 
P R E F A C E 

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 guide-lines to assist in the uniform application and 

interpretation of USDA grade standards and other similar 

specifications. 

These instructinns 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 Deparbment. 

Compliance with the suggested guide-lines and other pertinent 

information herein does not excuse any one 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 of any supplier, patented device, product, brandname, 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: 

November 1967 

Chief 

Processed Products Standardization 

and Inspection Branch 

Fruit and Vegetable Division, C&MS 

U. S. Departm~nt of Agriculture 

Hashington, D. C. 20250 

- iii -
INSTRUCTIONS FOR 

FLY EGG AND MAGGOT 

November 1967 

FLY EGG AND MAGGOT DETERMINATION 

I BACKGROUND AND INCIDENCE 

Canned tomatoes and tomato products are particularly susceptible 

to contamination by eggs and maggots of the Drosophila fly --

often referred to as fruit fly, vinegar fly, or some.times, gnat. 

Fly egg and/or maggot infestation has resulted in many Food 

and Drug seizures and other actions. It is one of the more 

serious contamination problems and one to which we must be 

ever alert. 

The majority of eggs laid by adult Drosophila in the field are 

deposited in fresh cracks in the fruit principally between 

6 to 8 A.M. and 4 to 8 P.M. when the light is not too strong 

nor the temperature too high or too low. The rate of egg 

deposition during these periods has been found to be 25 to 

35 times the rate during the rest of the day. The high rate 

of deposition may be extended on overcast days. 

Although some eggs may be deposited in growth cracks which 

occur while the fruit is still attached to the plant, the 

primary attractant for egg deposition is fresh cracks with 

free 1uice, resulting from picking and handling or weather 

changes. Nearly all of the eggs found on the fruit at the 

canning plant have been laid in the fresh cracks after the 

fruit is picked. 

Some of the newer crack-resistant varieties of tomatoes have 

proven quite successful in decreasing the degree of fly egg 

deposition. 

Other practices which are significant contributions toward 

controlling the fly egg problem are: 

1) Use of clean, ~ containers in the fields during 

harvesting operations; 

2) Assurance that the containers (boxes or baskets) are not 

overfilled and that they are loaded and stacked on the 

truck in such a manner as to avoid breakage of the fruit 

during loading and in transit to the canning plant; 

-1-
FLY EGG AND MAGGOT 

November 1967 

3) Certainty that ~ picked tomatoes are permitted to 

remain in the field overnight when flies are present; 

4) Good sanitary practices and adequate washing and clean-up 

facilities in the plant; and 

5) Effective spraying or dusting with insecticides which are 

formulated and applied in conformance with USDA specifications. 

For a comprehensive discussion of the drosophila problem refer 

to the NCA bulletin on "Drosophila Control." 

-2-
II IDENTIFICATION AND CLASSIFICATION 

FLY EGG AND MAGGOT 

November 1967 

r!Y ~are tiny (approximately 0.25 mm. x 0.10 mm.) long-oval, 

symmetrical, yellow or whitish; covered with a transparent 

membrane; vinegar fly eggs have paired filaments near one end. 

Maggots are long, tapering or baggy, yellow or whitish, 

symmetrical and faintly segmented, without legs; with dark 

mouth hooks at one end. 

For the purpose of classification (in order to apply the guides 

which provide acceptance or rejection criteria) this type of 

infestation is considered under three (3) general categories: 

1) Fly eggs. 

2) Maggots 3 mm. or less in length. 

3) Maggots over 3 mm. in length. 

-3-
III PRODUCT GROUPINGS OR CLASSIFICATIONS 

FLY EGG AND MAGGOT 

November 1967 

The nature of tomato products varies as does the preparation of 

sample and the number of fly egg and maggot counts which are 

performed routinely. The final extraction method is stmilar 

in all cases. 

Processed tomato products are classified into these following 

general categories for purposes of relating stmilar items, 

preparing samples, and establishing mintmum numbers of 

extractions. 

A CANNED TOMATOES, and such related canned items as to 

include but are not limited to: 

Canned tomatoes with Puree 

Stewed tomatoes 

Canned tomatoes with Okra (or Okra with Tomatoes) 

Unpeeled tomatoes 

Diced, Sliced or Chunk Styles of Tomatoes 

B COMMINUTED TOMATO PRODUCTS, whether canned or otherwise 

processed, including but not limited to: 

Tomato Puree (Tomato Pulp) and Concentrated Tomato Juice 

Tomato Paste 

Tomato Juice 

Tomato Catsup 

Tomato Sauce 

C "SEEDED" TOMATO PRODUCTS, are those containing seeds, peel 

particles and condtments and which include but are not 

ltmited to: 

Pizza Sauce 

Chili Sauce 

D SPECIALTY PRODUCTS, in which tomato products are an 

tmportant ingredient, including but not limited to: 

Spaghetti with Tomato Sauce 

Pork and Beans with Tomato Sauce 

Bar-B-Que and Cocktail Sauces 

Tomato Soup 

Spaghetti Sauces 

Tomato Aspic 

-4-
* 

* 

IV SAMPLING RATES 

A LOT INSPECTION 

FLY EGG AND MAGGOT 

February 1971 

The following charts indicate the normal and tightened 

sampling rates for canned tomatoes and tomato products 

when these stated conditions apply: 

1) Normal rate -- is to be used when the individual 

sample units for fly egg and maggot determination 

contains no more than 1 maggot up to 2 mm or no 

maggots over 2 mm, or does not exceed 3/4ths of 

the limit specified for good commerical practice. 

2) Tightened rate -- is to be used when any individual 

sample unit for fly egg and maggot determination · 

exceeds the ltiit(s} for the normal rate given above. 

Revised - February 1971 

- 5 -
FLY EGG AND MAGGOT 

February 1971 

IV SAMPLING RATES (continued) 

A LOT INSPECTION (continued) 

CANNED TOMATOES 

No. I of Quality Samples as specified for single sampling plan in 

regulations I • Noaal 

6 

13 

21 

29 

38 

48 

60 

Each increment, or portion thereof, of 

. I • 

. I • 

3,000• 

cases in excess of maximum number of cases 

covered by 60 sample units 

TABLE II 

TOMATO PRODUCTS 

No •. of Quality Samples as specified for 

single sampling plan in regula~ions 

3 

6 

13 

21 

• I • 

• I • 

r • 

Each increment, or portion thereof, of 4,000, 

cases in excess of maximum number of cases 

covered by 21 sample units 

Addition and correction - February 1971 

- 6 -

1 

2 

3 

4 

5 

6 

7 

8 

1 

Normal 

1 

2 

3 

5 

1 

• I • 

• I • 

Tightened 

2 

3 

5 

6 

7 

9 

11 

13 

2 

Tightened 

2 

3 

5 

7 

2 

/ 
IV SAMPLING RATES (Continued) 

B INPLANT INSPECTION 

FLY EGG AND MAGGOT 

July 1968 

* General 

+ 

Inplant inspectors may determine fly egg counts on individual 

samples rather than composite sampling such as specified under 

lot inspection. Portions of production which fail the guide 

for good commerical practice will be considered an incomplete 

grade subject to further examination. Segregated portions of 

continuous production shall be examined on the tightened procedures for lot inspection. 

Sampling Plans 

There are three sampling plans for inplant inspection: 

1) Normal 

2) Reduced 

3) Tightened 

The sampling rate for the normal plan is one fly egg and maggot 

count every three hours for each source of continuous production. 

In most cases at the beginning of production the sampling rate will 

be on the normal plan. However, inspectors are permitted at any 

time to increase sampling rates in the event the raw product appears 

unsound or unsanitary situations arise. 

If, after analysis under the normal plan, five (5) consecutive 

samples contain individually less than 1/4 of the limit for fly 

eggs and no maggots, the inspector may apply a reduced rate of 

one (1) count every 6 hours. The normal plan is to be resumed 

if any sample exceeds this reduced limit. 

If at any time a sample exceeds 3/4ths of the limit for fly eggs 

or contains more than one maggot up to 2mm or any over 2mm, the 

tightened plan of one count per hour is to be applied for ea~ 

source of continuous production. 

The normal plan may be resumed from the tightened plan after 

three (3) consecutive samples individually contain no more than 

1/2 the guide for fly eggs and no maggots. 

Source of Samples 

Samples under inplant inspection may be drawn from many sources 

within an operation. The inspector may at his discretion draw 

samples at any point in the process where no further quality changes 

will occur. 

* - Changed, July 1968 

+ -Added, July 1968 - 7 -
V PREPARATION OF SAMPLE 

A CANNED TOMATOES 

FLY EGG AND MAGGOT 

November 1967 

1) Normally the size of the aliquot for canned 

tomatoes is 20 ounces of well mixed juice and 

the equivalents of a 2-1/2 can of tomato ingredients (loosely packed). 

This aliquot is composited as follows, depending 

upon the individual container size: 

CONTAINER SIZE Number of Containers 

8 OW1.ce Use 6 Containers Per Aliquot . . . . . 

10 OW1.Ce Use 5 Containers Per Aliquot 

It 303 and larger Use 3 Containers Per Aliquot • I • . . . 

Can sizes larger than #303: if composite yields 

less juice or tomato ingredient than specified 

above use entire amount available. 

Can sizes of less then #303 (other than 8 or 10 

ounce): use sufficient containers to make 48 to 

SO ounces net contents; or a sufficient number to 

give 20 ounces of juice and a No. 2-1/2 can of 

tomato ingredient. 

Under inplant inspection it is permissible to extract only the juice if the tomatoes have been lye 

peeled. Inspectors should check the peeled tomatoes 

in order to assure that no contamination is present 

and could contribute to higher counts. This can 

be accomplished by washing representative samples 

of peeled tomatoes off the canning tables and observing the washing for eggs and maggots. If the 

topping juice is of a lesser concentration than that 

of regular tomato juice use a 20 ounce aliquot or 

the equivalent of a full No. 2 can. In the event 

the topping juice is tomato juice puree or paste, 

prepare sample as prescribed for the individual 

product. 

- 8 -
V PREPARATION OF SAMPLE (Continued) 

A CANNED TOMATOES (Continued) 

FLY EGG AND MAGGOT 

February 1971 

2) After the aliquot has been prepared, pour it 

(tomatoes and juice) onto a U. S. Standard 8 -

mesh sieve, placed atop a funnel, which in turn 

rests in a No. 10 can. 

3) Rinse out draining pans and/or empty cans with 

minimum amount of warm water, adding such rinsings 

to the No. 10 can, straining through screen on 

doing so. 

4) Shake screen rather forcibly to effectively drain 

off all liquor and uniformly distribute tomatoes 

over the screen. 

5) Wash tomatoes with a fine but forceful spray (jet) 

of warm water, using as little water as necessary 

to accomplish an effective washing. 

6) Shake screen again, agitating the tomatoes so that 

different surfaces are exposed to insure that all 

portions of the tomatoes are washed. 

7) Repeat the washing procedure at least once or as 

many times as necessary to assure thorough washing 

of the tomato surfaces. 

8) Remove screen, tilt same, and allow any remaining 

free liquor to drain off into funnel or the No. 10 

can. 

9) Wash sides of funnel into the No. 10 can, _using 

minimum amount of water. 

10) Try to limit drained juice and washings to a 

volume not in excess of 1/2 the capacity of a No. 10 

can. This will permit the use of a single extracttion flask. 

No change in text 

- 9 -
* 

* 

FLY EGG AND MAGGOT 

February 1971 

B TOMATO JUICE 

c 

Take 100 grams of well-mixed tomato juice from ~ 

of three (3) containers of the same code, whenever 

possible. The entire 300 gram sample thus obtained 

is the aliquot to use in the examination of tomato 

juice for fly eggs and maggots. 

Proceed as under "Extraction of Sample." 

TOMATO PASTE, or 

TOMATO PUREE (TOMATO PULP), or 

CONCENTRATED TOMATO JUICE 

Take 100 grams of the well-mixed product from each 

of three (3) containers of the same code, whenever 

possible. Place in a suitable receptacle of such 

size as to permit addition of enough water to dilute 

sample to 5.5% natural tomato soluble solids --

Refractive Index 1.3410 @ 20° C. (See dilution 

chart Inspection Aid 77). From this diluted, 

thoroughly mixed sample, weigh out a 300-gram subsample to use in examining these products for fly eggs. 

Proceed as under "Extraction of Sample." 

D TOMATO CATSUP 

Take 100 grams of the well-mixed catsup from each 

of three (3) containers of the same code, whenever 

possible. Add 450 grams of wat~ (This will comprise 

a sample of 750 grams net weight.) From this diluted, 

thoroughly mixed sample, weigh out a 300-gram subsample to use in examining catsup for fly eggs. 

Proceed as under "Extraction of Sample." 

E TOMATO SAUCE 

Take 100 grams of the well-mixed tomato sauce from 

each of three (3) containers of the same code, whenever possible. Add 200 grams of wat~ (This will 

comprise a sample of 500 grams net weight.) From this 

diluted, thoroughly mixed sample, weigh out a 300-gram 

sub-sample to use in examining tomato sauce for fly 

eggs. 

Proceed as under "Extraction of Sample." 

Revised - February 1971 - 10 -
F PIZZA SAUCE 

FLY EGG AND MAGGOT 

November 1967 

1) Take 100 grams of well-mixed product from each of three 

(3) containers of the ~code and size whenever possible. 

2) Dilute sample with 200 grams of water. (This will 

comprise a sample of 500 grams net weight.) 

3) Weigh out 300 grams of the diluted, thoroughly-mixed 

product. 

4) Wash this sample through the 10-mesh sieve into a 2,000 

ml. beaker with a fine spray of warm water to remove 

seeds and peel. 

5) Transfer the seeds and peel so removed from the aliquot 

by the sieve into the black bottom pan and examine 

macroscopically for maggots. The strained aliquot 

thus obtained is used in determining number of fly eggs 

and maggots in this product. 

6) Proceed as under "Extraction of Sample." 

G CHILI SAUCE 

1) Take 100 grams of well~ixed product from ~ of three 

(3) containers of the ~code and size whenever possible. 

2) Dilute sample with 300 grams of water. (This will comprise a sample of 600 grams net weight.) 

3) Weigh out 300 grams of the diluted, thoroughly-mixed 

product. 

4) Wash this sample through the lO~esh sieve into a 

2,000 ml. beaker with a fine spray of w£rm water to 

remove seeds and peel. 

5) Transfer the seeds and peel so removed from the 

aliquot by the sieve into the black bottom pan and 

examine macroscopically for maggots. 

6) The strained aliquot thus obtained is used in determining number of fly eggs and maggots in this product. 

7) Proceed as under "Extraction of Sample." 

- ll -
H SPECIALTY PRODUCTS AND SOUPS 

Spaghetti Sauce (all styles) 

Pork and Beans with Tomato 

Sauce 

Bar-B-Que (and like) Sauces 

FLY EGG AND MAGGOT 

November 1967 

Spaghetti with Tomato Sauce 

Tomato Soup 

Cocktail Sauces 

Tomato Aspic 

As a general rule disregard testing of finished product. 

Under in-process inspection check tomato component prior 

!£ formulation and accept or reject. Under lot inspection 

disregard testing for fly eggs and maggots unless requested 

to do so, or circumstances would necessitate testing. 

Contact Washington office for advice on test procedure. 

- 12 -
VI EXTRACTION OF SAMPLE 

FLY EGG AND MAGGOT 

July :i.$\75 

~SuperF>ede8 Page 13 dated 6/75) 

- - - - ALL TOMATO PRODUCTS 

Kind and Size Where Obtain~d l/ . ----··· -------------------------------- 1) ltllO mI. beakers 

2) 2 - liter (pear-shaped) pyrex 

~eparatory funnels 

3) 50 ml. graduate (with 1 ml. 

graduations) 

4) Unleaded gasoline 

S) Klerzyme 200 

or 

~a) Pectinal 10-R 

._. 

6) Suitable suction apparatus 

--Buchner funnel, suction 

flask, pressure tubing, etc. 

7) Bolting Cloth -- 10XX --

Silk, black 

or 

7a) Bolting Cloth -- 10XX 

HC-3-132 Nitex 

Monofilament Nylon 

8) S & S No. 10 Ruled Black 

Filter Paper with blue lines 

9) Stereoscopic microscope 

1) Any reputa!J:Le chemical 

apparatus supply house. 

2) Any reputable chemical 

apparatus supply house. 

3) Any reputable chemical 

apparatus supply house. 

4) Any reputable gasoline 

dealer who sells this 

particular type of gasoline. 

5) Wallenstein Co. 

Division of Travenol Laboratories, Inc. 

Kingstree, South Carolina 29556 

Sa) Rohm & Haas Company 

Independence Mall, West 

Philadelphia, PA 19105 

6) Any reputable chemical 

apparatus supply house. 

I * 7) Xressilk Products 

525 Mpnf:e.r~ Pass Road 

Monterey Park, CA 91754 

7a) H. R. Williams Mill Supply Co. 

208 West 19th Street 

Kansas City. Missouri 64108 

Phone (816) 474-1511 

8) Schleicher & Schuell Co. 

Keene. New Hampshire 03431 

9) Any available source. 

l/ Except where no other material or equipment is suitable, the 

citation here does not endorse these products to the detrfment 

of others which may be of equal useability. 

• Corrected source of supply 

- 13 -
H. I'REPAH.i\TION OF REAGENTS AND MATERIALS ·-·-~· -

FLY EGG AND MAGGOT 

July 1575 

(Supereedes page 14 dated 6/75. 

Add sJx (6) level teas~oonfuls of pectolytic enz)~~ (any 

type listed under "Equipment" is equally acceptable) to 

100 ml. of warm water, stirring well for two minutes. 

Allow to settle until diatomaceous earth settles t:o bottom, 

then pour off clear solution. 

Make up the solution in multiples of the above p~oportions. 

Prepare a fresh supply daily. 

Pectic jellies which may form when making extraction, 

particularly catsup, may be greatly reduced by including 

0.5 gram of potassium oxalate in the above solution. 

Bolting Cloth 

Black silk (or nylon) bolting cloth lOXX should be used 

(BXX can be substituted). 

Before cutting into the desired shape and size to fit the 

filtering (suction) apparatus it should be boiled in order 

to prevent shrinkage. 

If not a black color wheri purchased, the cloth should be 

dyed a dark blue (or black) to facilitate counting. The 

boiled, (dyed) cloth·may .. be ruled with red India ink or 

other permanent marking ink (such as white) with parallel 

lines 5 to 7 mm. apart. 

An alternate aid is to paint a Petri dish with a black 

enamel and after the paint is dry and hardened, score the 

surface with a knife or sharp instrument ruling it off in 

parallel lines 5 to 7 mm. apart. The bolting cloth may 

then be pressed to the inverted Petri dish and light shining 

through the scored lines will provide a guide during counting. 

Also, counting grids, used in many tomato packing plants for 

such analyses, are acceptable substitutes. 

Black Filter Paper 

Ruled black filter paper with blue lines may be used instead of 

bolting cloth. 

This filter paper is preruled, 7 em. (2-3/4 inches) in 

diameter and has the same porosity as the bolting cloth. 

The filter is used one time and discarded. 

No change in text. - 14 -
FLY EGG AND MAGGOT 

.1une l9oH 

Stereoscopic Microscope 

The usual binocular stereoscopic scope is satisfactory 

for counting eggs and maggotr.. Ordinarily 20 X magnification 

is sufficient. (Higher magnification may be used for 

identifying purposes). 

As sn aid in counting, the scope may be set up with a 

substage lamp beneath the ~tage and a spot light directing 

illumination from above. 

If the black Petri dish is used, the substage lamp will 

provide an excellent source of light that will make the 

ruled lines very distinct. 

C EXTRACTION PROCEDURE 

1) Mark code on a two (2) liter separatory funnel. 

2) Wash the prepared aliquot into 

rinsing container adequately. 

of pectolytic enzyme solution, 

for 15 minutes. 

separatory funnel, 

Add approximately 15 ml. 

mix well, and let stand 

3) Add approxtmately 30 ml. of white gasoline. Put 

stopper in place, invert the funnel and release pressure 

by opening stopcock momentarily. 

4) Shake the funnel, held horizontally, with a vigorous 

back and forth motion for ~ minute, releasing 

pressure as necessary. 

5) Add warm water to bring the level to the wide portion 

of the funnel. Mix thoroughly by swirling and 

inverting funnel several times. 

6) Mark ttme on funnel or use other means to adequately 

indicate ttme. 

7) Let stand 15 minutes, then drain off ~nto a 400 ml. 

~eaker approximately 20 ml. of the bottom liquid. 

8) R~peat swirling, standing for 15 minutes and draining 

2 mor.e tfmes. On the last draining, remove approxtmately 

200 ml. of the bottom liquid. 

No Change - June 1068 - 15 -

. -
C EXTRACTION PROCEDURE (Continued) 

FLY EGG A.ND MAGGOT 

June l96R 

9) Discard the contents of the separatory funnel at this time. 

NOTE: lf, after the first draining, the trapped-off liquid is 

f il tercd ilnd only one fly egg is recovered, the product rr:ay be 

regarded :ts within the ~tcccptanee level for fly eggs and the 

proPedure may be terminated at this point; provided a full 

"cout1t" of fly eggs is nnt required or requested. This criteria 

docs not apply to maggots regardless of their size. 

lC) Filter the trapped-off liquid obtained in Step 7 (under 

"Extraction of Sample") through the lOXX Bolting Cloth, 

usinP, suitable suction. 

ll) Count the fly eggs and ~tggots on the cloth using a 

stereoscopic microscope at approximately 20x magnification. 

Greater magnifications for identification purposes may be 

used, if necessary. 

D RECORDING RESULTS 

Record results on any suitable form which will enumerate number 

of fly eggs and maggots recovered per extraction. Treat each 

item individually. Recheck code marks to assure that they have 

been transcribed accurately. For classification purposes and 

application of guide, it will be necessary to determine and 

record length of any recovered maggots. 

* - Changed, June 1968 

- ] 6 -
* 

VII MAGGOT RECOVERY 

FLY EGG A~'D MAGGOT 

December 196 8 

The procedure for the macroscopic examination of Canned 

Tomatoes (and related products) is the basic sedimentation 

method. 

The liquid drained from the Tomatoes (including any seeds 

and peel which may be retained on the sieve when straining 

the aliquot for fly egg extraction) is placed in a black 

bottom pan and the can or container rinsed into the pan 

using tap water. 

Using a generous supply of water, the tomato material is 

floated off until the bottom of the pan can be readily 

examined. 

The water remaining in the pan is swirled and examined using 

a strong light. 

Maggots over 3mm. in length can be readily seen as they 

remain on the bottom of the pan and collect near the center 

as the water is swirled. However, sometimes when observing 

for maggots in a black pan, in order to confirm that an object 

is a maggot, it is necessary to place the object on the 

bolting cloth to observe under magnification. 

The best way to transfer maggots from the black pan to the 

cloth is by drawing the maggot into an eye dropper and depositing it on the cloth. 

Enumerate the number and size of maggots found. 

Do not attempt to count fly eggs by this method. 

(Ordinarily, we do not expect comminuted tomato 

products and juice to contain any large (over 

Jmm.) larvae or maggots since this type of 

infestation should be removed or disintegrated 

in the finishers and juice extractors.) 

* - Addition, December 1968 

- 17 -
VIII LOT ACCEPTANCE 

FLY F.GG AND MAGGOT 

December 1 lJ 68 

The geners.l policy that each code mark "stand on its own" 

is applicable to fly egg and maggot contamination as is 

the same policy on grade and other factors. Therefore, 

insofar as possible subs for extraction should be made 

up of a single mark. 

Notwith5tanding the foregoing there will be times when 

code marks are so numerous (under lot inspection) that it 

will not be practical to restrict an extraction to a single 

mark. In such cases one will not have sufficient information to draw valid conclusions on a single mark and the 

entire lot must be accepted or failed on the basis of the 

findings. 

A som~what similar situation exists when the lot consists 

of n1ultiple codes, each code being extracted separately 

and one or more marks exceed the guide. The entire lot 

should be failed and the packer allowed an option to 

segregate those marks which he thinks are acceptable. 

However, the "good" portion so segregated must be 

resampled and retested in order to provide assurance that 

the segregated portion is acceptable. One must keep in 

mind that the number of fly eggs recovered from a single 

code mark can vary considerably from test to test. Only 

by increasing the number of tests can one be reasonably 

sure of the estimate of the prevalence of contamination 

in the mark or the lot. 

-18 -
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CONSUMER AND MARKETING SERVICE 

FRUIT "'NO VEGETABLE DIVISION Ir\SPECTIO!'\ AID !'\0, ii 

REVISED 

FEBRUARY, 1971 

TOMATO PASTE AND TOMATO PUREE 

FLY EGG AND MAGGOT DILUTION CHART 

Examples: 

1) Natural tomato soluble solids of 300 gram sub- sample 

Add 600 mi. or water to get a dilution at 5.5%. 

2) Natural tomato soluble solids of 300 gram sub-sample 

Add 1880 mi. of water to get a dilution at 5.5%. 

25 30 35 

2600 

2500 

2~00 

2300 

200 

2100 

2000 

900 

800 

700 

600 

1500 

1400 

300 

1200 

100 

_:__:: 

1000 

900 

·-

00 

== are 16.5%. ==600 

= are 40.0%. ~ 500 

_1±1: 

300 

00 

so 55 

PERCENT NATURAL TOMATO SOLUBLE SOLIDS OF 300 GRAM SUB-SAMPLE