A

United States

Department of

Agriculture

Agricultural

Marketing

Service

Agricultural 

Handbook 

Number 75

Egg-Grading

Manual

i

Contents

I. Introduction ..........................................................................................................1

II. Production and Maintenance of Egg Quality.....................................................................2

Breeding........................................................................................................2

Hatching .......................................................................................................2

Brooding and Raising ..........................................................................................2

Housing .......................................................................................................3

Feeding ........................................................................................................3

Care of Eggs on the Farm .....................................................................................4

Egg-processing Facilities .......................................................................................4

Buildings and Premises ........................................................................................5

Washing, Grading, and Packing Operations and Equipment ..................................................6

Cooling Facilities ..............................................................................................9

Health and Cleanliness of Employees ........................................................................10

Distribution ..................................................................................................10

III. Structure, Composition, and Formation of the Egg ............................................................11

Physical Structure ............................................................................................11

Composition .................................................................................................11

Formation ....................................................................................................12

Formation of the Yolk ........................................................................................13

Formation of the White ......................................................................................13

Formation of the Shell Membranes...........................................................................14

Formation of the Shell........................................................................................14

Abnormalities ................................................................................................14

IV. Grading............................................................................................................15

Advantages of Grading .......................................................................................15

General Application ..........................................................................................16

V. Quality Factors ....................................................................................................17

Shell Color ...................................................................................................17

Classification of Exterior Quality .............................................................................17

Exterior Quality Factors......................................................................................17

Shell Shape and Texture ................................................................................17

Soundness of Shell ......................................................................................19

Shell Cleanliness ........................................................................................19

Classification of Interior Quality .............................................................................20

Interior Quality Factors ......................................................................................20
ii

Air Cell..................................................................................................20

Yolk .....................................................................................................22

White (Albumen) .......................................................................................24

Loss Eggs................................................................................................25

VI. U.S. Standards, Grades, and Weight Classes for Shell Eggs .................................................27

U.S. Standards for Quality of Individual Shell Eggs ..........................................................27

U.S. Consumer Grades and Weight Classes for Shell Eggs ...................................................28

U.S. Nest Run Grade and Weight Classes for Shell Eggs .....................................................30

Obsolete Grades and Weight Classes.........................................................................30

VII. Determining Interior Quality by Hand Candling...............................................................31

Hand Candling Booth ........................................................................................31

Hand Candling Light.........................................................................................31

Hand Candling Technique ...................................................................................32

VIII. Determining Interior Quality by the Breakout Method ......................................................34

Quality Control Program.....................................................................................34

Breakout Equipment .........................................................................................34

Procedure ....................................................................................................35

IX. Egg Grading and Certification Services........................................................................36

Federal-State Grading Programs..............................................................................36

Costs of Service...............................................................................................37

Cooperative Agreements .....................................................................................37

X. Official Grade Labeling and Identification......................................................................38

XI. Certification to Specific Purchase Requirements.............................................................41

Pasteurized Shell Eggs........................................................................................41

XII. Plant Sanitation and Good Manufacturing Practices (PSGMP) Program ..................................42

XIII. Legislation Affecting Grading and Marketing of Eggs ......................................................47

Federal Laws .................................................................................................47

Surveillance Inspections......................................................................................47

State Laws....................................................................................................47

XIV. Egg Quality Schools and Training Sessions ..................................................................49

Formal Training ..............................................................................................49

Informal Training.............................................................................................49

XV. Resource Materials Available..................................................................................50
1

I. Introduction

This manual is an aid in teaching both beginning and

experienced egg graders the correct interpretation and

application of the U.S. standards, grades, and weight

classes for eggs. It can serve as a guide in short courses or

grading schools when supplemented with lectures, group

discussions, and demonstrations. This manual should also

prove useful to those teaching or working in the production, processing, and marketing of eggs.

Although some of the material in this manual is not

directly related to the actual grading function, knowledge

of it will help graders do a better job in handling eggs and

in maintaining egg quality. Such information will give

graders a better understanding of their job, and will aid

them in acquiring the knowledge necessary to do their

jobs well.

This manual provides graders with an understanding of

egg marketing, the purpose of grading, production and

processing practices, and Federal-State grading programs.

An in-depth description of USDA’s egg grading and certification programs is provided for use by processors, marketers, volume food buyers, and retailers to enhance their

procurement and quality control activities.

Information is also included about the formation, 

structure, and composition of the egg. The egg is a biological structure used in nature for the reproduction of

the chicken. It protects the developing chick embryo,

provides it a complete diet, and serves as the principal

source of nutrition for the first few days of the chick’s

life. The egg also serves as one of the most nutritious

and versatile of human foods. Chickens produce eggs 

in abundance, making this source of food extremely

important throughout the world, nutritionally as well 

as economically.

The modern trend in production is toward large, highly

specialized flocks. The high-quality egg produced under

this system lends itself very well to the use of machineflash candling equipment or mass electronic scanning

devices to detect checks, irregular shells, dirts, meat and

blood spots, and loss eggs. For this reason, it is highly

desirable for graders to have a working knowledge of

these systems.

Descriptions of the various qualities of individual eggs

should assist the student grader in understanding egg

quality. However, it is imperative that the descriptions of

the different qualities be compared with eggs before the

candling light, and that the quality interpretations be

checked by experienced graders.

The importance of practice in candling cannot be stressed

enough. It is essential that student graders become thoroughly familiar with the descriptions of the different qualities because the final measure of their ability is the accuracy by which they interpret quality before the candling

light. Occasional comparisons of broken-out appearance

with candled appearance are also essential in developing

grading skill.

Egg quality and grading procedures are the “what” and

“how” of the job. Coupled with reasonably good judgment, practice, and guidance, graders should acquire the

necessary skills to rapidly determine the proper classification of shell eggs based on official standards of quality.
2

II. Production and Maintenance

of Egg Quality

Egg production has been, and continues to be, a major

agricultural industry in the United States. In 1999, total

egg production was almost 7 billion dozen. The north

central area continues to lead the Nation in production,

followed by the west and the middle Atlantic areas.

Producing and marketing this volume of quality eggs

have been accompanied by specialization in the areas of

breeding, hatching chicks, raising chickens, producing

eggs, and producing poultry meat. Large vertically integrated firms that perform several or all of these functions

have become most prominent. The average flock size for

an operation often exceeds 75,000 layers, with many

over 1 million.

Production is either “off-line” or “in-line.” Off-line production refers to processing operations that are not integrated with the laying facility. Off-line eggs are gathered

and shipped in from laying facilities at other locations. Inline production refers to processing operations where

eggs are laid, processed, packed, and shipped from one

location. Most production facilities today are large integrated in-line operations. An understanding of egg production practices will help processors and quality control

personnel contend with product quality issues.

Breeding

The White Leghorn is the predominant breed of layer

being raised, in part because it lays white-shell eggs.

Brown-shell eggs are available in some parts of the country, but white-shell eggs are more widely demanded by

consumers. Shell color and thickness, egg size, quality

and quantity of thick white, quantity of eggs produced,

and, to some extent, freedom from blood spots are

hereditary factors that affect overall egg quality. For

example, broken and cracked egg shells are directly related to shell thickness and strength, and have great economic impact on the industry. Also, a reduction in shell

quality is a direct result of increased egg production.

Over time, improvements in these hereditary factors

have been bred into the White Leghorn. Chicks or pullets for the initial flock or flock replacement should be

procured from a source that can give reasonable assurance that these factors have been carefully considered in

the breeding program.

Hatching

To promote improved breeding and production qualities

in poultry and to reduce losses from pullorum disease,

the industry established the National Poultry

Improvement Plan (NPIP) in 1935.

Today, NPIP is administered jointly by USDA’s Agricultural

Research Service and an official State agency in each of

the cooperating States. It operates according to regulations and standards developed to provide assistance to

breeders and hatcheries in producing birds free from eggtransmitted diseases. Procurement of chicks from “plan”

hatcheries assists the producer in the selection of desirable young stock. In 1989, NPIP developed a Salmonella

enteritidis (Se) control program to reduce the incidence of

Se in hatching eggs and chicks. Participants in this program follow designated control procedures and practices

at breeder farms and hatcheries.

Brooding and Raising

Some operators brood chicks and raise them to laying

age, while others purchase 16- to 20-week-old birds from

specialists in the pullet-raising field. The brooding period

usually involves the first 6 to 8 weeks of the chick’s life

and is the most critical period for the bird in reaching 

its full potential. Temperature, feed, water, and environmental stress must be controlled and monitored continuously. A properly managed feeding program assures uniform growth and a manageable egg production schedule.

The intensity and duration of light during the brooding

and growout period have a dramatic effect on growth and

sexual maturity. Today, most brooding and growout operations are environmentally controlled, which means the

lighting and other factors can be automatically controlled

for optimum development.

Years ago, many producers utilized the practice of culling

flocks. Culling is the careful evaluation, either visual or

physical, of a flock to remove birds that are diseased or

weak and cannot reach their full level of production.

Modern breeding and production technology has virtually eliminated the need for culling. Today, most layers are

kept in production for a laying period of 12 to 14 months

unless they are force molted.
3

Molting is the natural loss of feathers that generally

occurs annually late in the summer. During the molting

period, which usually lasts 45 to 60 days, egg production

stops and the chicken’s reproductive system rejuvenates.

Force molting is a controlled production practice that,

depending on the current economic situation, can have a

significant effect on production income. Cost of feed, egg

prices, and cost of layer replacements are factors that

must be considered before committing to a force molting

program. Force molting is usually induced by a withdrawal of feed followed by a low-protein, high-calcium

diet until production resumes.

Housing

Proper housing is essential for efficient egg production.

Birds that are comfortable are healthier than birds kept

under improper conditions, and production costs are

lower. Environmental temperature and air circulation

are critical, with the optimum temperature being

between 57 and 79 °F (13.9 and 26.1 °C).

Temperatures outside this range affect feed conversion,

egg production, egg quality, and water consumption.

Waterers and feeders, whether the manual or mechanical type, should be kept clean. Dirt and dust should be

held to a minimum. Controlled ventilation and, where

necessary, adequate insulation should be provided to

have the proper temperature and humidity conditions.

Overcrowding should be avoided, and the equipment

and facilities should be kept in good condition.

Currently, over 90 percent of all table eggs produced in

the United States are from caged layers, primarily

because of economics. Eggs produced in cages cost less

to produce than those in floor systems due to much

more intensive labor and floor space requirements with

the latter. Most new operations are environmentally

controlled multiple-level cage systems that are completely automated with mechanical feeding and watering equipment and conveyor belts that carry the eggs

out of the laying house. Environmental housing also

provides a method of controlling temperature, light,

and humidity. Additionally, controlled housing provides

protection from predators and disease-carrying rodents

and pests.

Feeding

Feeding shares the limelight with breeding in the production of high-quality eggs. With recent advances in

poultry nutrition and the use of computers for formulating, a dozen eggs can now be produced on less than 4

Figure 2. Automated multi-deck caged layer system. (CD 8202 3241 1143-89) Large-capacity feed tanks provide a continuous supply of feed to each layer 

house. (CD 8202 3241 1143-96)

Figure 1. Typical environmentally controlled layer house. (00-CN-0601)
4

pounds of feed. Feed formulas with varying protein levels are adjusted based on the season, age of the birds,

and the availability of specific grains.

Shell. The breaking strength of an egg shell is affected by

feed, breeding, age, freedom from disease, and hot weather. Today, the average commercial feed supplemented

with “grit” (calcium carbonate) usually has sufficient calcium, phosphorus, manganese, and vitamin D to produce

sound shells. The source of shell trouble is more frequently found in the other factors mentioned.

Yolk. Dark pigmentation in the yolk affects the acceptability of the egg in the top qualities. Rations high in yellow grains and green feeds produce dark yellow to orangecolored yolks. Rations high in green grasses, silage, and

cottonseed meal (gossypol not removed) will cause the

yolks to acquire a reddish or olive color. Off-flavors may

be from feed formulated with a poor-quality fish meal or

other contaminants in the feed.

White (Albumen). To be of top quality, eggs must

have a high percentage of thick albumen. A lack of this

factor can be attributed to breeding and disease of the

chickens, and to improper care of the egg after production. Low-quality whites can also be attributed to high

levels of ammonia gas in the laying house due to

improper ventilation.

Care of Eggs on the Farm

Immediately after it is laid, an egg begins to lose quality,

even if it is removed from the nest, cooled, packed, and

marketed promptly. Keeping temperature and humidity

conditions at an optimum level retards this loss in quality

to a large degree.

Although most eggs are produced by large in-line integrated operations, some are still produced from off-line

production facilities. At off-line sites, certain steps are necessary to maintain egg quality at the highest level. Some

of these steps are:

1. Gather eggs frequently (at least 3 times a day).

2. Handle the eggs carefully to prevent breakage.

3. Cool the eggs promptly and store them under the 

optimum temperature and humidity.

4. Pack the eggs in clean, cool packing materials.

5. Pack clean eggs separately from dirty eggs.

Egg-processing Facilities

The high-quality egg produced under today’s large-scale

integrated flock system lends itself well to handling and

processing by automatic equipment. In fact, most new

complexes are in-line systems designed to carry eggs from

the hen house to the carton in one continuous operation.

Figure 4. Layers grouped in wire cages with automatic water and feed dispensing. (CD 8202 3241 1143-90)
5

Eggs must be handled properly throughout each phase

of production, processing, and transportation to maintain quality.

Washing equipment washes, sanitizes, and dries eggs automatically. Grading equipment uses mass scanners to help

operators detect and remove dirties, checks, irregular shells,

meat and blood spots, and loss eggs. Automatic weighing

equipment individually weighs each egg and sorts the eggs

according to the official weight classes. Automatic packaging

equipment places the eggs into cartons, closes the cartons,

and stamps the cartons with a production code. Coolers

reduce the temperature of the eggs and maintain humidity

levels that minimize quality deterioration.

In addition to people doing quality control work, plants

occasionally conduct quality segregation by hand-candling. In these situations, adequate facilities and equipment must be provided in order to grade eggs with maximum efficiency. 

Buildings and Premises

Maintaining a sanitary food environment is an integral

part of processing quality eggs. The design of the building and layout of the premises should provide suitable

environmental conditions, permit adequate cleaning,

minimize contamination, prevent access and breeding of

pests, and provide an adequate space to accommodate

the processing operation.

The premises should be clean and free of trash, debris, and

old equipment and supplies to discourage and eliminate

the presence of insects and pests and reduce the possibility

of cross-contamination. Areas surrounding the plant should

be properly graded and free of standing water, free of tall

grass or weeds, and kept reasonably clean.

The floors, walls, and ceilings of buildings should be constructed of materials that are durable and smooth, 

and that can be kept clean, sanitary, and in good repair.

Processing room floors should be properly sloped for

drainage and constructed of materials that are smooth,

impervious to moisture, cleanable, and resistant to chemical cleaning compounds. Doors and windows leading to

the outside should be kept closed or fitted with tight-fitting

screens that remain closed when not in use. Adequate ventilation is to be provided to control humidity and provide

comfortable year-round working temperatures. 

All rooms should be kept clean and sanitary at all times.

Figure 6. Eggs are automatically transferred from off-line conveyor to conveyor

spools going through the egg washer. (CD 8202 3241 1143-31)

Figure 8. Eggs from multiple in-line and off-line systems are conveyed to centralized orientation area before entering washer. (CD 8202 3241 1143-80)

Figure 5. Flats of eggs are loaded onto the washing line at the off-line conveyor.

(CD 8202 3241 1143-25) 

Figure 7. In-line conveyor moves eggs directly from laying houses to processing area. (CD 8202 3241 1143-72)
6

Waste collection and disposal is important in maintaining

an environment free of objectionable odors and pests.

Refuse containers used in the processing room should be

emptied and cleaned daily. Refuse generated from the

processing operation should be removed from the processing area daily, or more often if needed, and stored in

covered receptacles or compactors.

Separate areas should be provided for the storage of packing and packaging materials, chemical compounds, and

insecticides and rodenticides. Chemicals should be stored

separately from edible food areas and properly identified

to prevent any accidental contamination of the eggs. All

materials should be stored away from walls to facilitate

cleaning and pest control.

Washing, Grading, and Packing 

Operations and Equipment

Even with good farm-management practices and careful

handling, a small percentage of dirty eggs will be produced. Producers must bear in mind that dirty eggs are

covered with bacteria that will cause spoilage if they enter

the egg. Whether conducted at the production or processing site, washing must be performed in a manner that

will minimize the chances of bacterial penetration of the

shell. If these important facts are forgotten, and eggs are

washed carelessly, more damage can be done than by

leaving the dirt on the shell. Wetting a dirty shell provides

moisture in which bacteria may breed and assists their

growth and penetration through the shell. A washing

solution colder than the egg causes the egg content to

contract and thus allows polluted water to be drawn

through the shell. When washing eggs the following precautions should be followed:

1. Wash eggs with water at least 20 °F (11.1 °C) warmer

than the internal temperature of the eggs and at a minimum of 90 °F (32.2 °C).

2. Select a detergent or detergent sanitizer that is compatible with the wash water and one that will not give off

foreign odors that may be imparted to the egg.

3. Use only potable water with an iron content of less

than 2 parts per million (p/m) for washing and keep

wash water as clean as possible.

4. Rinse by spraying with water slightly warmer than the

wash water.

5. Use an approved sanitizer in the spray rinse.

6. Dry the eggs to remove any excess moisture prior 

to packaging.

Figure 9. Eggs are washed, rinsed, and sanitized using specially designed

in-line equipment that will remove dirt without damaging the shells or altering quality. (00CN0048)

Figure 10. After washing, eggs are dried with a high volume of filtered air to

remove excess moisture. (99-CS-1605)

Figure 11. After washing, eggs are sanitized with an approved chemical sanitizer to remove any remaining bacteria. USDA graders verify concentration of

sanitizing spray. (00CN0049)
7

After washing, eggs should be rinsed with a warm water

spray containing an approved chemical sanitizer to remove

any remaining bacteria. The strength of the sanitizing spray

should be no less than 50 p/m nor more than 200 p/m of

available chlorine or its equivalent.

Research has shown that during the washing process,

most of the outer cuticle on the egg shell is removed.

Removal of this cuticle increases the rate of carbon

dioxide and moisture loss of the internal egg contents. 

To reduce the rate of loss, spraying the eggs with a

light coating of food grade mineral oil is a common

practice. For best results, the entire oiling system,

including spray nozzles, filters, and oil storage reservoir, should be checked frequently to assure that the

equipment is functioning adequately and that the oil 

is free from contamination.

Most off-line eggs are packed in plastic filler flats, palletized, and transported to the processing facility. This

procedure provides the most efficient method of handling and cooling off-line eggs prior to processing.

Since plastic flats are used repeatedly to transport

unprocessed eggs, the incidence of bacterial cross-contamination is enhanced. To avoid cross-contamination

and the creation of an unsanitary condition, plastic flats

Figure 12. Food-grade mineral oil is pumped from reservoir (floor tank) to highpressure spray nozzles to provide a light coating over each egg. (00CN0050)

Figure 13. Automatic plastic egg flat washer washes, rinses, and stacks egg

flats for drying after each use. (00CN0051)

Figure 14. Plant personnel segregate broken and dirty eggs after the washing

cycle and prior to the candling operation. (CD 8202 3241 1143-1)

Figure 15. During candling, a wand-type pointer electronically marks eggs that

are dirty or cracked, or that contain blood spots. Newer equipment is capable

of automatically removing these eggs with minimal oversight. (99-CD-1606)
8

should be thoroughly cleaned and dried after each use.

To facilitate the cleaning process, modern processing

plants typically install and utilize plastic flat washing

and drying equipment.

All processing equipment should be designed and constructed of such materials and workmanship so as to be

smooth and easily cleanable, and to preclude the adulteration of eggs with foreign materials. Egg washing,

sanitizing, and oiling should be conducted according to

the procedures outlined in the current Regulations

Governing the Voluntary Grading of Shell Eggs (7 CFR

Part 56). All equipment and processing rooms should

be thoroughly cleaned at the end of each processing day

and should remain reasonably clean throughout the

processing shift.

The distance of processing equipment from walls and the

space between equipment should be enough to provide

room for cleaning, maintenance, and inspection. The

space will vary greatly depending on the type of operation and capacity needed for the amount of product handled. Sufficient overhead lights should be provided to

facilitate cleaning the room.

Figure 20. Packaged eggs leaving automatic packaging equipment are placed

into shipped cases. (CD 8202 3241 1143-32)

Figure 21. A computer attached to the processing system monitors and controls each phase of processing. (CD 8202 3241 1143-55)Figure 19. Eggs gently placed into carton or other packaging material. 

(CD 8202 3241 1143-28)

Figure 18. Packaging unit orients eggs with small end down and gently places

them into consumer cartons. (99-CS-1608)

Figure 16. In-line electronic scales weigh and sort individual eggs by weight classes so that they can be diverted to the proper packaging lines. (CD 8202 3241 1143-30)

Figure 17. Eggs are automatically conveyed to packaging unit. 

(CD 8202 3241 1143-27)
9

The candling area should be darkened to the extent necessary to do an efficient job. The extent of darkness will

vary depending on the type of processing equipment

used. The light rays from the mass scanning area should

be diverted away from the candler’s eyes. On high-production machines, it is generally best for a candler to also

have another type of job assignment to prevent eyestrain,

break the monotony, and improve efficiency of the candling operations.

Recent advances in processing technologies have resulted

in the development and use of candling equipment that

can electronically remove most under grade-type eggs.

After candling, individual eggs are weighed using

mechanical or electronic weighing equipment. Most

modern processing equipment integrates weighing as an

in-line component of the processing machine. The

weighed eggs are segregated by weight classes and conveyed to the applicable size packing line.

Packaging and packing are normally carried on in conjunction with the grading operation. Clean packaging and

packing materials should ensure adequate protection of

the product in the handling required in the grading station, distribution channels, and the retail store. Cartons

or filler flats of eggs should be placed on conveyors gently

and carefully moved to the packing station to minimize

any additional breakage.

Packaging materials should be new and free of mold,

mustiness, or any other off-odors or conditions. Packing

materials, such as wire or plastic baskets, or transport

containers such as metal racks, should be reasonably

clean and free of egg meat before use.

Cooling Facilities

After eggs are graded and packed in cases, they should

immediately be moved to the shipping room cooler and

held there until ready for distribution.

Cooler rooms should be free from objectionable odors

and mold and should be maintained in a sanitary condition at all times. The coolers must be capable of maintaining the temperature and humidity necessary for the

preservation of eggs. Coolers should be equipped with

thermometers and hygrometers to verify and monitor

temperature and humidity.

Figure 25. For ease of handling at retail, eggs are placed on portable shipping racks.

(CD 8202 3241 1143-41)

Figure 23. Processed eggs are placed in cooler in preparation for staging and

final shipment. (CD 8202 3241 1143-48)

Figure 24. Packaged eggs are loaded on a clean, refrigerated transport vehicle.

(CD 8202 3241 1143-34) 

Figure 22. Unprocessed eggs from an off-line system are accumulated in cooler prior to processing. (CD 8202 3241 1143-46)
10

Coolers for unprocessed eggs should be capable of maintaining an ambient temperature of 60 °F (15.6 °C) or

lower. Processed egg coolers must be capable of maintaining an ambient air temperature of 45 °F (7.2 °C) or lower.

All coolers should be capable of maintaining a relative

humidity of 70 to 85 percent.

Every reasonable precaution should be exercised to

prevent “sweating” of eggs (when there is condensation

or moisture on the shell) in order to avoid smearing

and staining the shell and to inhibit the growth of bacteria on the shell. Egg “sweating” is usually caused

when eggs are moved from a very cool environment to

an environment with a moderate temperature, i.e., from

the unprocessed-egg cooler to the processing room.

This is why it is impractical for unprocessed eggs to be

held in coolers for long periods of time with temperatures lower than 50 °F (10 °C).

Health and Cleanliness of Employees

Employees handling eggs should take every precaution to

prevent cross-contamination between production and

processing areas. Traffic patterns of employees should be

reviewed by management to avoid cross-contamination.

Employees assigned to work in production areas should

not be allowed to work in processing areas unless the

necessary facilities are available for cleaning and changing

clothes. Clean outer garments should be worn when

employees are processing eggs.

All employees should wash their hands before beginning

work and upon returning to work after using restrooms,

eating, smoking, or otherwise soiling their hands. Handwashing facilities should be provided in restrooms and

processing areas.

Persons afflicted with, or who are carriers of, a communicable disease should not be permitted in any room where

eggs are processed or otherwise handled. Persons with

discharging or infected wounds, sores, or lesions on

hands, arms, or other exposed portions of the body

should not be allowed to work in any processing room

where there is contact with eggs, processing equipment,

or packing or packaging supplies.

Distribution

Wholesale. Eggs for wholesale outlets should be packed

in new packaging and packing materials. The majority of

shipments today are by refrigerated truck. Trucks hauling

eggs must be refrigerated and well insulated on all surfaces

and doors to maintain quality during warm weather. The

loss of moisture during transportation can be minimized

by pre-cooling the transport vehicle prior to loading and

transporting the eggs. In addition, since wholesale eggs are

generally packed in fiberboard boxes with few, if any, vent

holes, it is extremely important to pre-cool the eggs to a

uniform temperature prior to loading.

A refrigerated truck should be used for summer deliveries

and a well-insulated truck for winter deliveries, equipped

with a warm-air heating unit for extreme conditions.

Truck beds should be equipped with racks to provide

uniform air circulation around the load. Before loading,

trucks should be checked to make sure that the interior is

clean and free from foreign odors, and that there are no

breaks in the walls, ceilings, or floor surfaces.

Retail. High-quality eggs that have been properly cared

for during packing and transportation are sometimes

handled carelessly by the retailer. Proper stock control

and care, including volume delivery, rotation of supply,

adequate refrigerated holding areas, and proper humidity, are necessary. Bulk stocks should be stored only

under refrigeration in a space that is free from volatile

odors of any kind. To promote consumer satisfaction,

eggs should be packed in attractive cartons, be uniform

in size and weight, and be of high interior quality.

Improper handling at any point during distribution and

marketing will result in lower overall quality and diminished consumer acceptance.
11

III. Structure, Composition, 

and Formation of the Egg

Physical Structure

An average chicken egg weighs about 57 grams 

or 2 ounces.

The parts of an egg are the yolk, the white, the shell

membranes, and the shell (figs. 26 and 27).

Yolk (Ovum). The yolk consists of the latebra, germinal

disc, concentric rings of yolk material, and vitelline membrane (a colorless membrane that surrounds and contains

the yolk). The yolk constitutes approximately 31 percent

of the total weight of the egg.

White (Albumen). The white consists of four distinct

layers which together constitute about 58 percent of the

weight of the egg.

The chalaziferous layer immediately surrounds the yolk

and is continuous with the chalazae (pronounced kahlay-za). This is a very thin, but firm, layer of white and

makes up 3 percent of the total white.

The inner thin layer surrounds the chalaziferous layer and

comprises about 17 percent of the white.

The firm or thick layer of white provides an envelope, or

jacket, that holds the inner thin white and the yolk. It

adheres to the shell membrane at each end of the egg.

Approximately 57 percent of the white is firm white.

The outer thin layer lies just inside the shell membranes,

except where the thick white is attached to the shell, and

accounts for about 23 percent of the total white.

Shell Membranes. The shell membranes are tough and

fibrous and are composed chiefly of a protein similar to

that in hair and feathers. The inner membrane is 

thinner than the outer, and together they are only about

24 ten-thousandths of an inch (0.00609 mm) thick.

Shell. The shell is composed of three layers and 

constitutes approximately 11 percent of the egg.

The mammillary or inner layer covers the outer shell

membrane. Next is the spongy layer, then the cuticle. 

Pores connect the surface and the mammilla.

The egg, as laid, normally has no air cell. The air cell

forms as the egg cools, usually in the large end of the egg,

and develops between the shell membranes. The air cell

is formed as a result of the different rates of contraction

between the shell and its contents.

Composition

The egg is an excellent source of high-quality protein 

and of certain vitamins and minerals. The chemical composition of the egg, including the shell, is summarized in

table 1.

White (Albumen). The egg’s protein content is complete;

it contains all of the essential amino acids in well-balanced proportions. Water is the major component of

albumen. The pH of albumen from a newly laid egg is

between 7 and 8.5 and, due to the loss of carbon dioxide,

will generally rise during storage.

The thick albumen is made up mainly of the proteins

ovomucin, ovalbumin, conalbumin, ovoglobulin, and

ovomucoid. Ovomucin gives structure to the thick albumen.

The thin albumen is composed mostly of the same proteins contained in the thick albumen, with the exception

of ovomucin.

Figure 27. Magnified radial section through the egg shell.

Figure 26. The parts of an egg.
12

The albumen also contains water-soluble B vitamins such

as riboflavin. Riboflavin gives the greenish tint to the

albumen.

Yolk. The major components of yolk are proteins and

lipids (fats). The important yolk proteins are ovovitellin

(about three-fourths of the yolk protein) and ovolivetin.

The fatty substances of the yolk are mostly triglycerides

(true fat) 65.5 percent, phospholipid 28.3 percent, and

cholesterol 5.2 percent. The pH of the yolk in a freshly

laid egg is generally about 6.0 but gradually increases to

about 7.0 during storage. Yolk pigments (mostly xanthophyll) come from green plants and yellow corn that the

birds eat.

The yolk contains most of the known vitamins with the

exception of vitamin C. The vitelline membrane is composed mostly of protein similar to that found in the shell

membranes and is fairly permeable to water. The higher

concentration of solids in the yolk causes the yolk to

increase in size and become less viscous because of the

inflow of water from the white as the egg ages.

The yolk contains iron, phosphorus, sulphur, copper,

potassium, sodium, magnesium, calcium, chlorine, and

manganese, all of which are essential elements.

Formation

The reproductive system of the hen is divided into two

main parts: Ovary and oviduct (fig. 28). Most female animals possess both a right and a left functioning ovary but

in the hen, the right ovary and oviduct normally remain

dormant and the left ovary and oviduct develop the egg.

Ovary. This is a cluster of developing yolks, each separate

from the others, attached to the middle part of the back

about midway between the neck and the tail. This organ

is fully formed, although very small, when the chick is

hatched. It contains approximately 3,600 to 4,000

minute ova (future yolks) each within its own sac or follicle.

Oviduct. This is a long, tubelike organ lying along the

backbone and attached to it loosely between the ovary

and the tail. It is approximately 25 to 27 inches (63.5 to

68.6 cm) long, and may be divided into five areas which

perform certain functions in completing the formation of

the egg. It is here that the white, shell membranes, and

shell are secreted.

TABLE 1. Chemical composition of the egg.

Figure 28. Enlarged drawings of a hen's reproductive system.

Percent Water Protein Fat Ash

Whole egg 100 65.5 11.8 11.0 11.7

White 58 88.0 11.0 0.2 0.8

Yolk 31 48.0 17.5 32.5 2.0

Calcium Magnesium Calcium Organic

carbonate carbonate phosphate matter

Shell 11 94.0 1.0 1.0 4.0
13

Formation of the Yolk

Each yolk within the ovary starts as a single cell (female

reproductive cell or germ) with the vitelline membrane

around it.

The yolk develops slowly at first by the gradual addition

of yolk fluid. Fat-soluble pigments, normally xanthophyll,

are transferred rapidly from the digestive tract to the

blood stream and then to the yolk. Occasionally, what

appears to be concentric layers of alternate dark- and

light-colored yolk fluid may be observed. However, modern feeding and production practices have reduced the

frequency of this occurrence.

The yolk matures as more yolk fluid is added. The germ

stays at the surface of the yolk, leaving a tubelike structure, the latebra, extending to the center of the yolk.

An accelerated stage occurs 8 to 10 days before ovulation.

This stage is initiated by the stimulating hormone of the

pituitary gland. The hormones secreted by the ovary in

turn stimulate the oviduct to activity. The rate of yolk

secretion increases rapidly from the 9th to 2nd day before

ovulation (0.5 to 2.8 grams of yolk per day) and decreases thereafter.

Ovulation is the release of a mature yolk (ovum) from the

ovary. Each developing yolk is enclosed in a yolk sac in

which many blood vessels are profusely distributed.

These blood vessels carry yolk-building substances to the

developing yolk. One particular area of the yolk sac is

free of blood vessels (stigma or suture line) and it is normally here that ovulation or release of the mature yolk

takes place. However, the rupture of the yolk sac and

release of the yolk sometimes occur at sites other than the

stigma, with the result that one or more blood vessels are

ruptured and blood spots occur on the yolk, or the white

becomes bloody.

Occasionally, reddish brown, brown, tan, or white spots,

commonly known as “meat spots,” may be found in the

egg. It has been demonstrated that meat spots may be

either blood spots which have changed in color due to

chemical action, or tissue sloughed off from the reproductive organs of the hen.

Ovulation occurs again about 30 minutes after an egg is

laid, during the laying clutch of a good producing hen.

Formation of the White

The first part of the oviduct, usually 3 or 4 inches (7.62

to 10.16 cm) long, is the infundibulum, commonly called

the funnel. It opens into the body cavity. When ovulation

occurs, the funnel engulfs the yolk and starts it on its way

down the oviduct.

Although the main function of the funnel is to pick up

the yolk, it also serves as a reservoir for male sperm

which, if present, fertilize the germ and set up embryonic

growth. The yolk moves through the infundibulum, or

funnel, to the magnum in about 15 minutes. Movement

is brought about by peristaltic action.

The magnum area is about 15 inches (38.1 cm) long and

the time required for the yolk to travel through its length

is about 3 hours. It is here that three of the four layers of

the white are formed, and where practically all the protein in the white is secreted.

The white contains ovomucin, secreted by the magnum

as fibers or strands, which makes the white thick. These

strands draw together as the developing egg continues its

spiral movement through the oviduct. From these strands

the chalaziferous layer and the chalazae are formed (1st

layer). The continued twisting and drawing together of

these strands tend to squeeze out thin white to form the

inner thin white (2nd layer). The remaining thick white is

a homogeneous gel (3rd layer).

The quality of the white is largely dependent on the

amount of ovomucin secreted by this part of the

oviduct. The portion of the gel immediately adjacent to

the yolk undergoes partial liquefaction before the egg

leaves the magnum.

The isthmus is a constricted area of the oviduct about 4

inches (10.16 cm) long, through which the developing

egg passes in about 1-1/4 hours. Here some water and

mineral salts are added and the two shell membranes

are deposited.

The uterus, a heavy-walled part of the oviduct, approximately 4 inches (10.16 cm) in length, is where the developing egg spends about 21 hours. Here, the outer thin

white (4th layer) and minerals pass through the shell

membranes by osmotic pressure, and the shell and shell

pigment are added. The water and solids of the white

ultimately become equally distributed in the various layers of the white.
14

Formation of the Shell Membranes

The shell membranes are added as the partly formed egg

enters the isthmus. The membranes are a closely knit lacelike nitrogenous compound similar to that present in the

chicken’s toe nails.

Formation of the Shell

Calcium carbonate comprises about 94 percent of the dry

shell. A hen may use as much as 47 percent of her skeletal calcium for egg shell formation. Two layers of the shell

are formed in the uterus.

The spongy layer consists of small calcite crystals that

are not arranged in any order, except in the outer portion of the layer where crystals are set at right angles to

the shell surface.

Pigment, if any, is laid down in the spongy layer of the

shell and is derived from the blood.

Pores are formed through the spongy layer connecting

some of the space between the knoblike mammilla with

the surface.

Moving finally into the vagina, a 2-inch (5.1 cm) area, the

fully formed egg enters the cloaca and the vent, and is

laid. When the egg is laid, the pores are filled by the

matrix material and covered by the cuticle.

Cuticle, which is sometimes erroneously referred to as

“bloom,” is of a chemical composition similar to the shell

membrane.

The time from ovulation to laying is usually slightly more

than 24 hours. About 1/2 hour after a hen has laid an

egg, she releases another yolk (ovulation), and it will,

likewise, travel the length of the oviduct.

Abnormalities

Double-yolked eggs result when two yolks are released

about the same time, or when one yolk is lost into the

body cavity for a day and is picked up by the funnel

when the next day’s yolk is released.

Yolkless eggs are usually formed around a bit of tissue

that is sloughed off the ovary or oviduct. This tissue stimulates the secreting glands of the oviduct and a yolkless

egg results.

An egg within an egg is due to the reversal of direction of

the egg by the wall of the oviduct. One day’s egg is added

to the next day’s egg and the shell is formed around both.

Blood spots are caused by a rupture of one or more

small blood vessels in the yolk follicle at the time of

ovulation. Since the albumen of freshly laid eggs is usually cloudy, the detection of small blood spots during

candling is difficult.

Meat spots have been demonstrated to be either blood

spots which have changed in color due to chemical

action, or tissue sloughed off from the reproductive

organs of the hen, although most meat spots are from

sources other than blood spots.

Soft-shelled eggs generally occur when an egg is prematurely laid, and insufficient time in the uterus prevents

the deposit of the shell.

Thin-shelled eggs may be caused by dietary deficiencies,

heredity, or disease.

Glassy- and chalky-shelled eggs are caused by malfunctions of the uterus of the laying bird. Glassy eggs are less

porous and will not hatch, but may retain their quality.

Off-colored yolks are due to substances in feed that cause

off-color.

Off-flavored eggs may be due to certain feed flavors or

improper storage practices.
15

IV. Grading

Grading generally involves the sorting of products according to quality, size, weight, and other factors that determine the relative value of the product. Egg grading is the

grouping of eggs into lots having similar characteristics as

to quality and weight.

The grading for quality of eggs is the classifying of the individual egg according to established standards. U.S. standards for quality of individual eggs have been developed 

on the basis of such interior quality factors as condition 

of the white and yolk, size of the air cell, and the exterior

quality factors of cleanliness and soundness of the shell.

These standards apply to eggs of the domesticated chicken.

Eggs are also classified according to weight (or size)

expressed in ounces per dozen. Although eggs are not

sold according to exact weight, they are grouped within

relatively narrow weight ranges or weight classes, the

minimum net weight per unit being specified. When

grading, eggs must meet minimum individual egg, carton, and case weight requirements.

Advantages of Grading

Grading aids orderly marketing by reducing waste, confusion, and uncertainty with respect to quality values. The

egg production pattern and the marketing system in the

United States are such that interstate trading and shipment occur constantly and in large volume. This situation

creates a need for uniform standards throughout the

country so that marketing may be facilitated and the efficiency of distribution increased.

Since eggs serve as a low-priced source of protein, the

production and consumption of eggs on a global basis

continues to expand. Currently, the United States is the

largest producer and exporter of eggs and egg products.

Grading according to uniform standards and certification

for specific requirements of a purchase contract ensure

importers and exporters that the product received is of

the quality and condition described in the contract

regardless of supplier.

Officials of USDA, and State and industry leaders,

encourage the use of uniform standards and grades for

eggs. Although all eggs reaching the consumer today are

graded and marked according to U.S. standards and

grades, only eggs packed in official USDA plants are graded by plant personnel authorized by the USDA.

Additionally, the USDA grader continuously samplegrades these eggs to determine if they are eligible to be

packed in cartons bearing the USDA grade shield. More

information on USDA grading and certification services is

provided in Sections IX through XII.

The primary advantage in using official standards and

grades for eggs is that they furnish an acceptable common language in trading and marketing the product, thus

making possible:

1. Impartial official grading that eliminates the need for

personal inspection of the eggs by sellers, buyers, and

other interested people.

2. Pooling of lots of comparable quality.

Figure 29. Individual eggs and consumer packages are check weighed by

USDA graders to verify minimum weight for the designated size. (00-CN-0602)

Figure 30. Bulk packages of eggs are check weighed on platform scales to verify

minimum net weight. Test weights are used to verify the accuracy of the scale. 

(00-CN-0603)
16

3. Development of improved quality at producer level

through “buying on grade” programs.

4. Market price reporting in terms understood by all

interested parties.

5. Negotiation of loans on generally accepted 

quality specifications.

6. A basis for settling disputes involving quality.

7. A basis for paying damage claims.

8. A basis for developing advertising.

9. A uniform basis for establishing brand names.

10. Establishment of buying guides for consumers.

General Application

Standards of quality have been developed as a means 

of classifying individual eggs according to various groups

of conditions and characteristics that experience and

research have shown to be desirable by producers, marketers, and consumers. The term “standardization”

implies uniformity, and uniformity in interpretation will

result if the same standard is used and is applied accurately in all instances.

Standards of quality are used as a basis for establishing

grades. Standards of quality apply to individual eggs;

grades apply to lots of eggs such as dozens, 30-dozen

cases, and carloads. As egg quality is unstable and grading procedures are largely subjective, it is necessary to

provide tolerances in grades for small percentages of eggs

of a quality lower than that comprising the major part of

the grade. The tolerances are provided to allow for errors

in judgment, differences in interpretation, and normal

deterioration in quality from the time of grading until the

eggs are sold to the consumer.

Grades differ from standards in that they provide tolerances for individual eggs within a lot to be of lower quality than the grade name indicates. Tolerances must be

within the capabilities of the industry to produce an

acceptable product at reasonable prices. Without tolerances, it would not be possible to produce cartoned eggs

at prices acceptable to consumers.

Once graders acquire a working knowledge of the standards of quality, accuracy in interpreting quality standards

and the ability to judge correct grade classification will

increase. In commercial operations, graders will make

many grading decisions each day and must develop an

ability to make instant decisions.

The greatest frequency of error is believed to occur in

instances of repeated indecision as to the placement of

individual eggs. It should be pointed out that mistakes

due to oversight, minor errors in decision, and differences

of opinion between graders or supervisors are factors that

are taken into consideration in the U.S. grades by providing tolerances. However, errors beyond the permitted tolerances result in the incorrect grading of the entire lot of

eggs. It is important that each grader’s decision of egg

placement be as accurate as possible.
17

V. Quality Factors

In acquiring skills in judging egg quality, it is helpful to

break the classification process down into steps, considering separately the various quality factors affecting the

shell, air cell, yolk condition, and condition of the white.

Graders can concentrate with greater ease when each factor is considered separately. Later, all factors should be

considered in combination.

Quality may be defined as the inherent properties of a

product that determine its degree of excellence. Those

conditions and characteristics that consumers want, and

are willing to pay for, are, in a broad sense, factors of

quality. The quality of an egg is determined by comparing

a number of factors. The relative merit of one factor alone

may determine the quality score of the egg, inasmuch as

the final quality score can be no higher than the lowest

score given to any one of the quality factors. Quality factors for eggs may be divided into two general groups:

Exterior and Interior.

Exterior quality factors are apparent from direct external

observation and should be the first point for evaluation.

Interior quality factors involve the contents of the egg as

they appear before a candling light, or when the eggs are

broken out and measured by the Haugh unit method

plus visual examination of the yolk. Both methods are

described in detail later in this manual.

Shell Color

Shell color does not affect the quality of the egg and is not

a factor in the U.S. standards and grades. Eggs are usually

sorted for color and sold as either “whites” or “browns.”

Eggs sell better when sorted and packed according to

color than when sold as “mixed colors.”

For many years, consumers in some areas of the country

have preferred white eggs, believing, perhaps, that the

quality is better than that of brown eggs. In other areas,

consumers have preferred brown eggs, believing they

have greater food value. These opinions do not have any

basis in fact, but it is recognized that brown eggs are

more difficult to classify as to interior quality than are

white eggs. It is also more difficult to detect small blood

and/or meat spots in brown eggs. Research reports and

random sample laying tests show that the incidence of

meat spots is significantly higher in brown eggs than in

white eggs.

Classification of Exterior Quality

The external factors of the egg shape, texture, soundness,

and cleanliness of the shell can be determined without

using the candling light, but soundness of shell should be

verified by candling. The method or place where this is

accomplished may vary with the type of candling and

processing equipment used.

In hand candling, the examination for shell cleanliness

and the removal of leakers, dented checks, and misshapen

eggs will be accomplished by using the case light.

In mass scanning, the segregation for these shell factors is

quite often the responsibility of a person who scans the

eggs for exterior factors prior to or immediately following

the candling operation. This should be done in a welllighted area.

Exterior Quality Factors

Shell Shape and Texture. The normal egg has an oval

shape with one end larger than the other, and it tapers

toward the smaller end. The ends of an egg are commonly called the large end (air cell end) and the small end.

Investigators measured both strength and appearance of

many eggs to develop the “ideal” egg shape. This ideal

egg shape is illustrated in figure 32. The shape of an egg

can be considerably different from the ideal (fig. 33), but

may still be considered practically normal. The grader

must keep a mental picture of the normal, or usual, shape

of an egg and compare each egg with that picture.

Eggs that are unusual in shape may have ridges, rough

areas, or thin spots (figs. 34 and 35).

Abnormal shells may result from improper nutrition, Figure 31. Eggs are usually sorted for color and packed separately as either

white or brown. (CD 8202 3241 1143-9)
18

disease, or the physical condition of the hen. Sometimes

a shell is cracked while the egg is still in the body of the

hen. These eggs, which are commonly referred to as

“body checks,” are repaired by an additional deposit of

shell over the cracked area, generally resulting in a

ridged area.

Shells with thin areas and some other types of defects are

usually weaker than normal shells, and the danger of

breakage en route to the consumer lowers the utility

value of the egg. Eggs of abnormal shape also lack consumer appeal.

The specifications of the U.S. standards provide for

degrees of variation:

Practically normal — A shell that approximates the usual

shape and is sound and free from thin spots. Ridges and

rough areas that do not materially affect the shape and

Figure 32. Ideal egg shape, usually found in AA or A quality. (BN-16548) Figure 33. Practically normal shape which may be found in AA or A quality. 

(BN-16549)

Figure 34. Practically normal shape, showing slight ridges and rough areas that

do not materially affect the shape and strength of the shell and are permitted

in AA or A quality. (BN-16550)

Figure 35. Abnormal shape having pronounced ridges and/or thin spots. 

(BN-16551)
19

strength of the shell are permitted (AA or A quality).

Abnormal — A shell that may be somewhat unusual

or decidedly misshapen or faulty in soundness or

strength or that may show pronounced ridges or thin

spots (B quality).

Soundness of Shell. The shell of an egg may be sound,

checked or cracked, or leaking.

Following are definitions of these shell factors:

Sound — An egg whose shell is unbroken.

Check — An individual egg that has a broken shell or a

crack in the shell but its shell membranes are intact and

its contents do not leak.

Leaker — An individual egg that has a crack or break in

the shell and shell membranes to the extent that the egg

contents are exuding or free to exude through the shell.

Leakers are classed as loss.

Checks are an unavoidable problem in the marketing of

eggs because eggs cannot be assembled, graded, packed,

transported, and merchandized without some breakage.

Such eggs will not keep well or stand even moderately

rough handling, and they should be diverted to immediate use or further processing.

Checks may range from eggs with plainly visible dented

cracks that are removed during the grading process to

very fine, hairlike cracks (blind checks) that often escape

detection because they cannot be seen. While many of

these checks become detectable as time passes (due primarily to contraction caused by cooling); most of the eggs

will have already moved into marketing channels, reaching the retail level within 1 to 3 days after being laid.

“Blind checks” are the most common, and frequently the

most difficult to detect in rapid candling, being discernible only before the candling light or by “belling.”

“Belling” is the practice of gently tapping two eggs together to assist in the detection of “blind checks” by sound.

Hand candlers follow this practice by candling the eggs in

order to verify and complete the findings arrived at by

sound.

With the use of automatic processing equipment, the

“belling” procedure is not used in examining the eggs for

checks, although electronic check detectors are now

available on new equipment. The candler must be 

especially attentive when these detectors are not being

utilized so that all checks are removed prior to packaging. Quite often a bubbly air cell in fresh eggs indicates a

“blind check”.

It is necessary to remove leakers and dented checks carefully to avoid causing further damage to them and to prevent dripping liquid from the leakers onto clean eggs,

onto the packaging material, or into the mechanism of

the candling equipment, therefore cross-contaminating

the eggs. This is necessary not only for bacteriological reasons, but for good housekeeping and appearance of the

packaged product, and to keep the mechanisms of automatic weighing equipment in proper adjustment.

Shell Cleanliness. In machine processing, the examination for cleanliness is most often done immediately following the washing operation, during the mass scanning

for interior quality, or after mass scanning prior to packaging. This operation should be in an area with sufficient

lighting and adequate space for removing these types of

eggs.

Freedom from stains and foreign material on the shell

must be considered in assigning a quality designation to

an individual egg. The following terms are descriptive of

shell cleanliness:

Clean — A shell that is free from foreign material and

from stains or discolorations that are readily visible. An

egg may be considered clean if it has only very small

specks, stains, or cage marks, if such specks, stains, or

cage marks are not of sufficient number or intensity to

detract from the generally clean appearance of the egg.

Eggs that show traces of processing oil on the shell are

considered clean unless otherwise soiled.

Dirty — A shell that is unbroken and has dirt or foreign

material adhering to its surface, has prominent stains, or

has moderate stains covering more than one-thirty-second of the shell surface if localized, or one-sixteenth of

the shell surface if scattered.

The illustrations in figure 36 are intended as a guide and

are not to be used as an actual measurement in grading.

Graders should learn to determine the area that constitutes these measurements and then judge eggs having

soiled shells against this mental picture.
20

Classification of Interior Quality

Even under the most favorable conditions, egg quality is

relatively unstable as the interior quality of the egg deteriorates from the time it is laid until it is consumed.

Sometimes quality changes render eggs useless for food

before they reach consumers. However, when eggs are

properly cared for, the quality decline can be minimized.

Quality decline is illustrated graphically in figure 37.

In grading eggs, and more specifically in classifying them

according to internal quality, the grader is merely trying

to group the eggs according to where each is located on

“quality hill.”

On the basis of internal quality, edible eggs are divided

into three groups as shown in figure 37. All eggs whose

candled characteristics fall between the top line and point

1 on the chart are in the highest quality class, or AA;

those between points 1 and 2 are in the next quality, or A;

and those between points 2 and 3 are in B quality. Those

at and below point X are inedible or loss.

It is relatively easy to place eggs properly if they are midway between the various points on “quality hill,” but

judgment and skill are required to place the eggs that are

at or near the quality division points in the correct group.

It becomes increasingly difficult when brown eggs or

mixed whites and browns are being candled. A primary

objective in candling is to have a clear mental picture of

the dividing line between the various quality classes, so

that the eggs may be properly placed in their respective

quality groups.

Good judgment in determining white and yolk condition

can be developed and maintained by occasionally having

graders break out an egg. Their estimate of the candled

quality should be checked with the broken-out appearance as compared with (1) the chart for scoring brokenout appearance (fig. 38) and (2) the Haugh unit value of

the broken-out egg. This value results from the correlation of the height of the thick white as measured by a

micrometer and the weight of the egg. More information

about candling eggs and Haugh units is contained in

Sections VII and VIII of this manual.

Interior Quality Factors

Air Cell. As already stated, when the egg is first laid, it

has no air cell at all or only a small one. Its temperature is

about 105 °F (40.6 °C) and, as the egg cools, the liquids

contract more than the shell. As a result of this contraction, the inner shell membrane separates from the outer

to form an air space.

Further increase in the size of the air cell beyond that

resulting from contraction is due to evaporation of

water from the egg. The rapidity with which this takes

place is due to many factors, such as age, shell texture,

temperature, and humidity. The air cell is normally at

the large end of the egg and is one of the first factors

observed in candling.

The air cell is the easiest quality factor to evaluate, as it can

be judged objectively by a simple measuring device — the

High

Intermediate

Low

QUALITY

TIME

NORMAL NEW - LAID EGG

EGG QUALITY DECLINE

X

LOSS

(1)

(2)

(3)

AA QUALITY

A QUALITY

B QUALITY

Figure 37. Chart demonstrating range of egg quality decline over time.

1 4 OF SHELL

SURFACE OF 

AN EGG

1

16

1

32

Figure 36. One thirty-second, one-sixteenth, and one-fourth of the shell surface

of an egg (areas shown are approximate).
21

Figure 38. The pictures on this chart demonstrate the interior quality of broken-out eggs for each of the designated grades as specified in the U.S. standards with

respect to white and yolk quality. Pictures 1, 2, and 3 represent the appearance of broken-out eggs of high, average, and low AA quality; 4, 5, and 6 represent high,

average, and low A quality; and 7, 8, and 9 represent high, average, and low B quality. (00CN0055)
22

air-cell gauge (fig. 39). In candling, the air cell is considered a relatively unimportant quality factor for determining internal quality when compared to the broken-out

appearance of an egg. However, the air cell is one of the

factors of the U.S. standards and, therefore, it can be the

determining factor in classifying the individual egg in

terms of quality. Depth is the only quality factor considered with the air cell. Movement is not considered a quality factor, and the air cell may show unlimited movement

and be free or bubbly in all qualities (AA, A, B).

The size of the air cell permitted in the various qualities is

as follows:

Quality Depth

AA l/8 inch (3.2 mm)

A 3/l6 inch (4.8 mm)

B No limit

The air-cell gauge may be used by the beginner learning

to judge the size of the air cell accurately at a quick

glance while candling. More experienced candlers 

occasionally use the gauge to verify the accuracy of 

their determinations.

The depth of the air cell is measured at the point of greatest distance between the top of the cell and an imaginary

plane passing through the egg at the lower edge of the air

cell where it touches the shell (fig. 39).

The following terms are descriptive of the air cell:

Depth of air cell (air space between shell membranes,

normally in the large end of the egg) — The depth of the

air cell is the distance from its top to its bottom when the

egg is held air cell upward.

Free air cell — An air cell that moves freely towards the

uppermost part in the egg as the egg is rotated slowly.

Bubbly air cell —A ruptured air cell resulting in one or

more small, separate air bubbles, usually floating beneath

the main air cell.

Yolk. The appearance of the yolk as the egg is twirled in

candling is one of the best indicators of the interior quality of shell eggs. The characteristics of the yolk are determined by the shadow that it casts upon the shell before

the candling light. The appearance of the yolk is dependent on the condition of the white. As the egg ages, the

rate of carbon dioxide and moisture loss in the white

increases and affects the condition of the white. However,

there are three factors about the yolk itself that are considered in judging egg quality by the yolk: distinctness of

yolk shadow outline, size and shape of yolk, and defects

and germ development.

Distinctness of yolk shadow outline. The distinctness

of the yolk outline or shadow outline is governed by

three factors:

Hold gauge over egg in front of light.

For information regarding the 

U.S. Standards and Grades For

Eggs, write: 

Poultry Programs, Grading Branch

AMS, U.S. Department of Agriculture

P.O. Box 96456

Washington, D.C. 20090-6456

OFFICIAL EGG AIR CELL GAUGE

FORM PY-35 (Rev. 6-99)

AA QUALITY

1/8 inch

A QUALITY

3/16 inch

3/8 inch

(over)

Hold gauge over egg in front of light

For information regarding the 

U.S. Standards and Grades For

Eggs, write: 

Poultry Programs; Grading Branch

AMS, U.S. Department of Agriculture

P.O. Box 96456

Washington, D.C. 20090-6456

OFFICIAL EGG AIR CELL GAUGE

FORM PY-35 (Rev. 4-93)

AA QUALITY

1/8 inch

A QUALITY

3/16 inch

3/8 inch

(over)

90° Point from which

to measure

air cell depth

Figure 39. Official air cell gauge and method for measuring depth of air cell. 
23

1. The thickness and consistency of the white. The

thicker the white, the less distinct the outline appears,

because the yolk is prevented from moving close to

the shell.

2. Condition of the yolk. This condition is determined

by the presence or absence of blemishes that show

up before the candling light as dark shadows on the

yolk, or the presence or absence of an off-colored

yolk appearance which shows as a grayish or greenish shadow.

3. Color of the yolk. It is difficult to determine the color

of the yolk before the candling light except off-color.

However, extremes in yolk color may influence the

candler’s judgment of the egg quality. An extremely

deep-colored yolk, under some conditions, would cast

a darker shadow before the candling light than would

a lighter yolk.

By concentrating on the yolk outline instead of the depth

of the yolk shadow, the grader will minimize the influence of yolk color on quality determinations. The color of

the yolk and the firmness of the white are two interacting

influences affecting the distinctness of the yolk shadow

outline; therefore, a grader cannot be reasonably certain

which is the more important factor in any specific case.

The principle of judging distinctness of the outline rather

than the depth of darkness of the shadow can be illustrated by holding a ball close to a wall so its shadow falls on

the wall, and then moving it a little farther away from the

wall. At the greater distance, the outline of the shadow is

less distinct.

The terms used to define the three degrees of distinctness

of yolk shadow outline in the U.S. Standards of Quality

for Shell Eggs are:

Outline slightly defined — A yolk outline that is indistinctly indicated and appears to blend into the surrounding white as the egg is twirled (AA quality). (fig. 40)

Outline fairly well defined — A yolk outline that is discernible but not clearly outlined as the egg is twirled (A

quality). (fig. 41)

Outline plainly visible — A yolk outline that is clearly

visible as a dark shadow when the egg is twirled 

(B quality). (fig. 42)

Size and shape of yolk. The yolk in a freshly-laid egg is

round and firm. As the yolk ages, the strength of the yolk

membrane weakens allowing water to be absorbed from

the white. This increases its size and weight and causes it

to stretch and weaken the vitelline membrane and to

assume a somewhat flattened shape on top and an “outof-round” shape generally, resembling a balloon partially

filled with water. Yolk size and shape are mentioned only

in the lowest quality classification for eggs - B quality -

where these factors become apparent. The terms used in

Figure 40. Yolk outline slightly defined. 

(99-CS-1610)

Figure 41. Yolk outline fairly well defined. 

(99-CS-1611)

Figure 42. Yolk outline plainly visible. 

(99-CS-1612)
24

the U.S. Standards of Quality for Shell Eggs to describe

yolk size and shape are:

Enlarged and flattened — A yolk in which the yolk

membranes and tissues have weakened and/or moisture

has been absorbed from the white to such an extent that

the yolk appears definitely enlarged and flat (B quality).

Defects and germ development. Relatively little is

known about the exact causes of most yolk defects other

than those due to germ development. Some of the causes

which have been advanced are: irregular deposits of light

and dark yolk; blemishes from rubbing; and development

of accumulations or clusters of the fat and oil in droplets.

The relative viscosity of the white has a direct bearing on

the accurate determination of defects on the yolk before

the candling light. Unless yolk defects are very prominent, it is difficult to detect them, particularly when the

egg has a thick or cloudy albumen. Germ development is

visible before the candling light and can generally be

detected as a circular dark area near the center of the yolk

shadow. If blood is visible, the egg must be rejected as

inedible.

The terms used to describe yolk defects are:

Practically free from defects — A yolk that shows no

germ development, but may show other very slight

defects on its surface (AA and A quality).

Serious defects — A yolk that shows well developed

spots or areas and other serious defects, such as olive

yolks, that do not render the egg inedible (B quality).

Clearly visible germ development — Development of the

germ spot on the yolk of a fertile egg that has progressed

to the point where it is plainly visible as a definite circular

area or spot with no blood in evidence (B quality).

Blood due to germ development — Blood caused by

development of the germ in a fertile egg to a point where

it is visible as definite lines or as a blood ring. Such an

egg is classified as inedible.

White (Albumen). Nearly all freshly-laid eggs contain

four layers of white — chalaziferous, inner thin, thick,

and outer thin. The appearance of the egg before the candling light is governed largely by the relative proportions

of the thick and outer thin layers of albumen. The albumen and yolk are very closely associated and any discussion of either factor, by necessity, involves the other.

However, there are two important considerations about

the albumen which are included in standards of quality:

condition, or viscosity, and clarity.

The condition of the albumen is determined in candling

by the intensity of the yolk shadow and the freedom of

movement of the yolk as the egg is twirled before the

candling light. These factors are related to the viscosity of

the albumen. Thick albumen permits only limited movement of the yolk, and an indistinct shadow results.

The reverse is true of thin albumen, which permits free

movement of the yolk, and a distinct shadow results. The

grader must judge from the behavior of the yolk how the

albumen will appear when the egg is broken out. Figure 37

shows the appearance of the albumen in broken-out eggs.

The following terms describe albumen:

Clear — Albumen that is free from discolorations or

from any foreign bodies floating in it. Prominent chalazas

should not be confused with foreign bodies such as spots

or blood clots (AA, A quality).

Firm — Albumen that is sufficiently thick or viscous to

prevent the yolk outline from being more than slightly

defined or indistinctly indicated when the egg is twirled.

With respect to a broken-out egg, a firm albumen has a

Haugh unit value of 72 or higher when measured at a

temperature between 45 and 60 °F (7.2 and 15.6 °C) 

(AA quality).

Reasonably firm — Albumen that is somewhat less

thick or viscous than firm albumen. A reasonably firm

albumen permits the yolk to approach the shell more

closely, which results in a fairly well defined yolk outline when the egg is twirled. With respect to a brokenout egg, a reasonably firm albumen has a Haugh unit

value of 60 up to, but not including, 72 when measured at a temperature between 45 and 60 °F (7.2 and

15.6 °C) (A quality).

Weak and watery — Albumen that is weak, thin, and

generally lacking in viscosity. A weak and watery albumen permits the yolk to approach the shell closely, thus

causing the yolk outline to appear plainly visible and

dark when the egg is twirled. With respect to a brokenout egg, a weak and watery albumen has a Haugh unit

value lower than 60 when measured at a temperature

between 45 and 60 °F (7.2 and 15.6 °C) (B quality).

Blood spots or meat spots — Small blood spots (aggregating not more than one-eighth inch in diameter) are to

be classified as B* quality. Small meat spots (aggregating

not more than one-eighth inch in diameter) are to be

classified as B quality. If blood spots are larger, or show

diffusion of blood into the albumen surrounding them,
25

the egg shall be classified as loss. Blood spots shall not be

due to germ development. They may be on the yolk or

in the albumen. Meat spots may be blood spots which

have lost their characteristic red color, or tissue from the

reproductive organs. (figs. 43 and 44)

Bloody white — An egg which has blood diffused

through the albumen. Such a condition may be present

in freshly laid eggs. Eggs with bloody albumen are

classed as loss. (fig. 45)

Loss Eggs. The U.S. standards of quality also define certain eggs as “loss.”

Loss — An egg that is inedible, cooked, frozen, contaminated, sour, musty, or moldy, or an egg that contains a

large blood spot, large meat spot, bloody white, green

white, rot, stuck yolk, blood ring, embryo chick (at or

beyond the blood ring state), free yolk in the white, or

other foreign material.

Cooked eggs are eggs which have been subjected to heat

resulting in coagulation of the contents. Cooked eggs,

when held before the candling light, may be identified by

the presence of threadlike shadows in the white, indicating a slightly cooked egg, or a dark, opaque appearance,

indicating complete coagulation of the contents.

Musty eggs frequently appear clear and free from foreign

material when viewed before the candling light, and can

generally be detected only by the characteristic musty

odor emanating from the egg. Sources of contamination

may be a musty odor in the case or the nesting material,

or the presence of this odor on the shell itself.

It is said that certain bacteria that occasionally invade the

egg also give off this characteristic odor. Because this type of

loss is impossible to detect by visual observation, it is

important that the grader note the odor emanating from the

case and packing material immediately upon opening the

case.

Moldy eggs may be detected by observing mold spots on

the shell or by mold growth in checked areas of the shell,

or by mold growths (the odor of mold or must may or

may not be present) inside the egg itself when viewed

before the candling light. The use of dirty water for washFigure 43. Small blood spot. (99-CS-1613)

Figure 45. Bloody white. (99-CS-1615)

Figure 44. Candled and broken-out appearance of a large blood spot. 

(99-CS-1614)
26

ing eggs and dirty processing oil cooler than the egg, and

the storage of the egg in unusually high humidity encourage mold growth and mold penetration through the shell.

Advanced stages of mold growth throughout the entire egg

might have an appearance similar to that of black rot.

Large blood spots and bloody whites have already been

discussed. They appear as brilliant red in color or as a

dark gray in so-called meat spots, in contrast to the surrounding lemon-to-orange colored tinge of the yolk,

observed before the candling light.

Green whites can be detected by experienced graders

using the standard candling light. This type of loss is

caused by the Pseudomonas group of bacteria. Like sour

eggs, eggs with green whites will fluoresce under the

ultraviolet light when broken out. Eggs with green whites

may or may not have a sour odor.

Mixed rot occurs when the vitelline membrane of the

yolk breaks and the yolk mixes with the white, resulting

in a murkiness throughout the interior of the egg when

viewed before the candling light. (fig. 46)

A white rot, in its early stages, may be detected by the presence of threadlike shadows in the thin white. In later stages

the yolk appears severely blemished when viewed before

the candling light, and, when broken, shows a crusted

appearance. The content frequently gives off a fruity odor.

Black rots are generally opaque (with the exception of the

air cell) when viewed before the candling light. When

broken, the contents have a muddy brown appearance

and give off a repulsive, putrid odor. The bacteria most

frequently causing this type of loss belong to a group

named Proteus. However, when any rot is at an advanced

stage, it may appear “black” before the candling light.

Stuck yolk occurs when the yolk membrane becomes

attached to the shell membrane. It generally occurs in

storage eggs that have been left in a fixed position for a

long time. When the thick white becomes thin, the yolk

floats close to the shell and becomes attached to the shell

membrane. Before the candling light, the yolk appears

attached to the shell and snaps back to its attached position when the twirling motion of the egg is stopped. If

loosened from its position, the yolk membrane usually

breaks, permitting the yolk content to seep into the white.

The first stage of this condition is generally referred to as

“seeping yolk,” and later as “mixed rot” or “addled egg.”

Blood rings and embryo chicks are caused by germ

development, occurring in fertile eggs held at incubation

temperatures. At a rather early stage in incubation (after

24 hours) the embryo develops a circulatory system. If

the embryo dies at this stage, the blood drains to the

outer edge of the germ disc and forms the blood ring.

Before the candling light, it appears as a brilliant bloodred circle from one-eighth to three-eighths inch in diameter, depending on the stage of development.

If incubation temperatures are maintained for a longer

period, the embryo chick is formed by about the third

day, and eventually fills most of the egg. This can be

observed before the candling light as an actual outline 

of the embryo in the early stages.

Sour eggs are often difficult to detect by standard candling

methods. Generally, eggs in this condition show a weak

white and murky shadow around an off-center swollen

yolk. The bacteria causing sour eggs belong to a group

named Pseudomonas. These organisms produce a material

which fluoresces under ultraviolet light, giving off a green

sheen. The adoption of ultraviolet light in candling (black

light) has made the detection of this type of loss easier.

In addition to the eggs described above, eggs showing

severe shell damage, and eggs that are leakers, are also

classified as loss.

Eggs not classified as loss, but as “no grade,” include

eggs of possible edible qualities that have been contaminated by smoke, chemicals, or other foreign material

which has seriously affected the character, appearance, 

or flavor of the eggs.

High concentrations of fish oil or garlic fed to hens

impart their flavor to the eggs. Eggs exposed to foreign

odors after they have been laid may give off these odors.

Eggs stored near kerosene, carbolic acid, mold, must,

fruits, and vegetables, for example, readily absorb odors

from these products.

Figure 46. Candled and broken-out appearance of a mixed rot. (99-CS-1616)
27

VI. U.S. Standards, Grades, and

Weight Classes for Shell Eggs

The U.S. standards, grades, and weight classes for individual shell eggs are applicable only to eggs of the domesticated chicken that are in the shell.

U.S. Standards for Quality of Individual Shell Eggs

The standards described below are summarized in table 2

and are based on the candled appearance of the egg.

AA quality — The shell must be clean, unbroken, and

practically normal. The air cell must not exceed oneeighth inch (3.2 mm) in depth, may show unlimited

movement, and may be free or bubbly. The white must

be clear and firm, so that the yolk is only slightly defined

when the egg is twirled before the candling light. The

yolk must be practically free from apparent defects.

A quality — The shell must be clean, unbroken, and

practically normal. The air cell must not exceed three-sixteenths inch (4.8 mm) in depth, may show unlimited

movement, and may be free or bubbly. The white must

be clear and at least reasonably firm, so that the yolk outline is only fairly well defined when the egg is twirled

before the candling light. The yolk must be practically

free from apparent defects.

B quality — The shell must be unbroken, may be abnormal, and may have slightly stained areas. Moderately

stained areas are permitted if they do not cover more than

one-thirty-second (0.8 mm) of the shell surface if localized, or one-sixteenth (4.8 mm) of the shell surface if scattered. Eggs having shells with prominent stains or adhering dirt are not permitted. The air cell may be over threesixteenths inch (1.6 mm) in depth, may show unlimited

movement, and may be free or bubbly. The white may be

weak and watery, so that the yolk outline is plainly visible

when the egg is twirled before the candling light. The yolk

may appear dark, enlarged, and flattened, and may show

clearly visible germ development, but no blood due to

such development. It may show other serious defects that

do not render the egg inedible. Small blood spots or meat

spots (aggregating not more than one-eighth inch (3.2

mm) in diameter) may be present.

Dirty — An individual egg that has an unbroken shell

with adhering dirt or foreign material, prominent stains,

or moderate stains covering more than one-thirty-second

of the shell surface if localized, or one-sixteenth of the

shell surface if scattered.

Check — An individual egg that has a broken shell or a

crack in the shell, but its shell membranes are intact and

its contents do not leak.

Leaker — An individual egg that has a crack or break in

the shell and shell membranes to the extent that the egg

contents are exuding or free to exude through the shell.

SPECIFICATIONS FOR EACH QUALITY FACTOR

Quality Factor AA Quality A Quality B Quality

Shell Clean Clean Clean to

slightly 

stained.*

Unbroken. Unbroken. Unbroken.

Practically Practically Abnormal.

Normal. Normal.

Air Cell 1/8 inch or 3/16 inch or less Over 3/16 inch 

less in depth. in depth. in depth.

Unlimited Unlimited Unlimited

movement and movement and movement and

free or bubbly. free or bubbly. free or bubbly.

White Clear. Clear. Weak and 

Firm. Reasonably firm. watery.

Small blood and

meat spots

present.**

Yolk Outline slightly Outline fairly Outline plainly 

defined. well defined. visible.

Practically free Practically free Enlarged and

from defects. from defects. flattened.

Clearly visible 

germ

development

but no blood.

Other serious 

defects.

For eggs with dirty or broken shells, the standards of quality provide

two additional qualities. 

Dirty Check

Unbroken. Adhering dirt or Broken or cracked shell, but 

foreign material, prominent stains, membranes intact, not 

moderate stained areas in excess leaking.***

of B quality.

* Moderately stained areas permitted (1/32 of surface if localized,

or 1/16 if scattered.).

** If they are small (aggregating not more than 1/8 inch in diameter).

*** Leaker has broken or cracked shell membranes, and contents

leaking or free to leak.

TABLE 2. Summary of U.S.Standards for Quality of Individual Shell Eggs.
28

U.S. Consumer 

Grades and Weight Classes for Shell Eggs

Consumer Grades. The standards for shell eggs provide

for “origin” and “destination” consumer grades. “Origin

grading” is defined as a grading made on a lot of eggs at a

plant where the eggs are graded and packed.

Table 3 gives a summary of the consumer grades, while

table 4 gives the tolerance for individual cases within a lot.

U.S. Consumer Grade AA (at origin) shall consist of eggs

that are at least 87 percent AA quality. The maximum tolerance of 13 percent that may be below AA quality may

consist of A or B quality in any combination, except that

within the tolerance for B quality, not more than 1 percent may be B quality due to air cells over three-eighths

inch (9.5 mm), blood spots aggregating not more than

one-eighth inch (3.2 mm) in diameter, or serious yolk

defects. Not more than 5 percent (7 percent for Jumbo

size) checks are permitted and not more than 0.5 percent

leakers, dirties, or loss (due to meat or blood spots) in

any combination, except that such loss may not exceed

0.3 percent. Other types of loss are not permitted.

U.S. Consumer Grade AA (destination) shall consist of

eggs that are at least 72 percent AA quality. The remaining tolerance of 28 percent shall consist of at least 10 percent A quality and the remainder shall be B quality,

except that within the tolerance for B quality, not more

than 1 percent may be B quality due to air cells over

three-eighths inch (9.5 mm), blood spots aggregating not

more than one-eighth inch (3.2 mm) in diameter, or serious yolk defects. Not more than 7 percent (9 percent for

Jumbo size) checks are permitted and not more than 1

percent leakers, dirties, or loss (due to meat or blood

spots) in any combination, except that such loss may not

exceed 0.3 percent. Other types of loss are not permitted.

U.S. Consumer Grade A (at origin) shall consist of eggs 

that are at least 87 percent A quality or better. Within the

maximum tolerance of 13 percent that may be below A

quality, not more than 1 percent may be B quality due to air

cells over three-eighths inch (9.5 mm), blood spots aggregating not more than one-eighth inch (3.2 mm) in diameter,

or serious yolk defects. Not more than 5 percent (7 percent

for Jumbo size) checks are permitted and not more than 0.5

percent leakers, dirties, or loss (due to meat or blood spots)

in any combination, except that such loss may not exceed

0.3 percent. Other types of loss are not permitted.

TABLE 3. Summary of U.S. Consumer Grades for Shell Eggs.

U.S. consumer grade Quality required 1 Tolerance permitted2

(origin) Percent Quality

Grade AA 87 percent AA. Up to 13 ....................... A or B. 5

Not over 5................... Checks. 6

Grade A 87 percent A or better. Up to 13 ....................... B. 5

Not over 5 .................. Checks. 6

Grade B 90 percent B or better. Not over 10 ................ Checks. 

U.S. consumer grade Quality required 1 Tolerance permitted3

(destination) Percent Quality

Grade AA 72 percent AA. Up to 28 4

..................... A or B. 5

Not over 7................... Checks. 6

Grade A 82 percent A or better. Up to 18 ....................... B. 5

Not over 7 .................. Checks. 6

Grade B 90 percent B or better. Not over 10 ................ Checks. 

1 In lots of two or more cases, see table 4 for tolerances for an individual case within a lot. 2 For the U.S. consumer grades (at origin), a tolerance of 0.50 percent Leakers, Dirties, or Loss (due to meat or blood spots) in any combination is permitted, except

that such Loss may not exceed 0.30 percent. Other types of Loss are not permitted. 3 For the U.S. consumer grades (destination), a tolerance of 1 percent Leakers, Dirties, or Loss (due to meat or blood spots) in any combination is permitted, except

that such Loss may not exceed 0.30 percent. Other types of Loss are not permitted. 4 For U.S. Grade AA at destination, at least 10 percent must be A quality or better. 5 For U.S. Grade AA and A at origin and destination within the tolerances permitted for B quality, not more than 1 percent may be B quality due to air cells over 3/8

inch, blood spots (aggregating not more than 1/8 inch in diameter), or serious yolk defects. 6 For U.S. Grades AA and A Jumbo size eggs, the tolerance for Checks at origin and destination is 7 percent and 9 percent, respectively.
29

U.S. Consumer Grade A (destination) shall consist of

eggs that are at least 82 percent A quality or better.

Within the maximum tolerance of 18 percent that may be

below A quality, not more than 1 percent may be B quality due to air cells over three-eighths inch (9.5 mm),

blood spots aggregating not more than one-eighth inch

(3.2 mm) in diameter, or serious yolk defects. Not more

than 7 percent (9 percent for Jumbo size) checks are permitted and not more than 1 percent leakers, dirties, or

loss (due to meat or blood spots) in any combination,

except that such loss may not exceed 0.3 percent. Other

types of loss are not permitted.

U.S. Consumer Grade B (at origin) shall consist of eggs

that are at least 90 percent B quality or better, not more

than 10 percent may be checks, and not more than 0.5

percent leakers, dirties, or loss (due to meat or blood

spots) in any combination, except that such loss may not

exceed 0.3 percent. Other types of loss are not permitted.

U.S. Consumer Grade B (destination) shall consist of

eggs that are at least 90 percent B quality or better, not

more than 10 percent may be checks, and not more than

1 percent leakers, dirties, or loss (due to meat or blood

spots) in any combination, except that such loss may not

exceed 0.3 percent. Other types of loss are not permitted.

Additional tolerances. In lots of two or more cases:

For grade AA — No individual case may exceed 10 percent less AA quality eggs than the minimum permitted

for the lot average.

For grade A — No individual case may exceed 10 percent less A quality eggs than the minimum permitted for

the lot average.

For grade B — No individual case may exceed 10 percent

less B quality eggs than the minimum permitted for the

lot average.

For grades AA, A, and B, no lot shall be rejected or

downgraded due to the quality of a single egg except for

loss other than blood or meat spots.

Weight Classes. The weight classes for U.S. consumer

grades for shell eggs shall be as indicated in table 5, and

shall apply to all consumer grades.

A lot-average tolerance of 3.3 percent for individual eggs

in the next lower weight class is permitted, as long as no

individual case within the lot exceeds 5 percent.

TABLE 4. Tolerances for individual cases within a lot.

U.S. consumer Case Quality Origin Destination grade (percent) (percent)

Grade AA AA (min) 77 62

A or B 13 28

Check (max) 10 10

Grade A A (min) 77 72

B 13 18

Check (max) 10 10

Grade B B (min) 80 80

Check (max) 20 20

TABLE 5. Weight classes of U.S. Consumer Grades for Shell Eggs.

Size or weight class Minimum net weight Minimum net weight Minimum net weight per dozen (ounces) 30 per dozen (pounds) for individual eggs at rate per dozen (ounces)

Jumbo . . . . . . . . . . . . . . . . 30 56 29

Extra large . . . . . . . . . . . . . 27 50 1/2 26

Large . . . . . . . . . . . . . . . . . 24 45 23

Medium . . . . . . . . . . . . . . . 21 39 1/2 20

Small . . . . . . . . . . . . . . . . . 18 34 17

Peewee . . . . . . . . . . . . . . . 15 28 —
30

U.S. Nest Run Grade and Weight 

Classes for Shell Eggs

Table 6 summarizes the nest run grade described below.

U.S. Nest Run__% AA Quality shall consist of eggs of

current production of which at least 20 percent are AA

quality; and the actual percentage of AA quality eggs shall

be stated in the grade name. Within the maximum of 15

percent that may be below A quality, not more than 10

percent may be B quality for shell shape, for interior quality (including meat or blood spots), or due to rusty- or

blackish-appearing cage marks or blood stains; not more

than 5 percent may have adhering dirt or foreign material

on the shell one-half inch (12.7 mm) or larger in diameter; not more than 6 percent may be checks; and not

more than 3 percent may be loss. Marks that are slightly

gray in appearance and adhering dirt or foreign material

on the shell less than one-half inch (12.7 mm) in diameter are not considered quality factors. The eggs shall be

officially graded for all other quality factors. No case may

contain less than 75 percent A quality and AA quality

eggs in any combination.

The weight classes for the U.S. Nest Run grade for shell

eggs shall be as indicated in table 7.

Obsolete Grades and Weight Classes

Procurement grades and weight classes were eliminated

in 1981. Procurement Grade I was practically identical to

U.S. Consumer Grade A; thus the consumer grade standard could readily be used in place of the procurement

standard. The U.S. Department of Defense was the principal user of Procurement Grade I. Procurement Grade II

had not been used for a number of years.

Wholesale grades and weight classes were also eliminated

as their use diminished. Almost all eggs moving in commerce today are sold on the basis of the U.S. Consumer

Grades, U.S. Nest-Run Grade, company specifications, or

are sold without certification. “U.S. Trades,” “U.S. Dirties,”

and “U.S. Checks” were eliminated in 1981; “U.S.

Specials,” “U.S. Extras,” and “U.S. Standards” in 1995.

TABLE 6. Summary of U.S. Nest Run Grade for Shell Eggs. 

Nest-run grade, description 1 U.S. nest run ___ percent AA quality 2

Minimum percentage of quality AA quality 4 20

required (lot average) 3

A quality or better 5 85

Maximum percentage tolerance B quality for shell shape, pronounced

permitted (15 percent lot average) 3 ridges or thin spots, interior quality 

(including blood & meat spots) or 

cage marks 6 and blood stains 10

Checks 6

Loss 3

Adhering dirt or foreign material 

1/2 inch or larger in diameter 5

1 Stains (other than rusty or blackish appearing cage marks or blood stains) and adhering dirt and foreign material on the shell less than 1/2 inch in diameter

shall not be considered as quality factors in determining the grade designation.

2 The actual total percentage must be stated in the grade name.

3 Substitution of eggs of higher qualities for lower specified qualities is permitted.

4 No case may contain less than 10 percent AA quality.

5

No case may contain less than 75 percent A quality and AA quality eggs in any combination.

6 Cage marks which are rusty or blackish in appearance shall be considered as quality factors. Marks which are slightly gray in appearance are not considered

as quality factors.

TABLE 7. Weight classes for U.S. Nest Run Grade for Shell Eggs.

Weight classes Minimum average net weight on lot basis 30-dozen cases (pounds)

Class XL 51

Class 1 48

Class 2 45

Class 3 42

Class 4 39
31

VII. Determining Interior Quality

by Hand Candling

Hand candling was originally developed as a method of

sorting fresh eggs from storage eggs and for the detection

of incubator rejects. With the changes in production

practices and processing technologies, hand candling is

used very little in present commercial grading operations.

Automated equipment and mass scanning devices have

practically replaced these manual operations. However,

hand candling is still an excellent method for teaching

and demonstrating quality determination, and is used for

spot checking and verifying accuracy of mass scanning

personnel.

Hand Candling Booth

For purposes of quality control, there should be at least

one strategically located candling booth in each grading

plant. Ideally, the booth should be 8 feet (2.43 m) wide, 4

feet (1.22 m) deep, and 7 feet (2.13 m) high. The proper

type of candling booth needed for check grading or quality control is illustrated in figure 47. The candling booth

walls should be painted with a dark-colored flat finished

paint to avoid light reflection. The booth should include

an overhead light, exhaust fan, and at least two electrical

outlets. Grading and candling equipment provided with

the booth should include two hand candling lights, an

electronic individual egg scale graduated in 1/10 ounce (1

gram) increments or less, a scale graduated in 1/4 ounce

(1 gram) or less increments for verifying weights of consumer packages, a bulk scale graduated in 1/4 pound

(0.1 kg) increments or less for verifying weights of shipping containers, test weights for verifying the accuracy of

each scale, and breakout plates for periodic correlations of

the candled versus the broken-out appearance of eggs.

Hand Candling Light

There are many styles and types of candling lights commercially available in which the light intensity and the

size of the candling light opening vary considerably.

Most of these lights are satisfactory if they are adjusted

to provide comfort and proper illumination for the job.

It is largely a matter of becoming accustomed to the

type of light in use. The accuracy of the hand candling

results can be checked by breaking out an occasional

egg and comparing the broken-out quality with the

candled quality.

In hand candling operations, there should be no cross

beams of light between the candler and the candling

light. The candling light should be properly adjusted and

focused to give better and more uniform candling

results. The light should be at about elbow height for the

candler and placed so that the light does not shine in the

candler’s eyes.

Graders may adjust their quality interpretation slightly

according to different types of candling lights or varied

adjustments of the same light. In selecting a candling light,

therefore, it is best to select one type of light and keep it

Figure 47. Dimensions and layout of an ideal candling booth. Figure 48. Typical layout of USDA grader's candling booth and work area. 

(99-CS-1609)
32

clean and properly adjusted. Once a grader has adjusted

candled interpretation to a reasonably close correlation

with the broken out appearance of eggs, uniform grading

can be maintained with moderate supervision.

The opening that the egg is held up to for examination

should be no larger than 1 1/8 inches (2.86 cm) in diameter. The opening at the bottom of the light should be no

larger than necessary to provide sufficient illumination to

detect dirty eggs and to observe the condition of the

packing material. The light should be adjusted so that its

aperture is approximately on the level of the grader’s

elbows. The interior of the candling light should be kept

clean and free from dust to assure maximum light efficiency. If a lens and a reflector are used, they should be

freed periodically of the film-like coating that tends to

buildup over time. The reflector should be kept in adjustment and the silver surface should be intact.

Hand Candling Technique

Prior to actual candling, the grader should make a preliminary examination of the general appearance of the

eggs to be candled at the time the container is opened or

the flats are removed from the sample case. This preliminary examination is to initially segregate the eggs for

cleanliness. Eggs with only very small specks, stains, or

cage marks may be considered clean if such small specks,

stains, or cage marks are not of sufficient number or

intensity to detract appreciably from the appearance of

the eggs. While the eggs are still in standing position, the

grader should remove and candle the eggs with stained or

dirty shells. This procedure will assist in removing dirty

or stained eggs that are noticed at first glance.

The grader should remove the remaining eggs in the container, two eggs in each hand, for candling. On the way

to the candling aperture, the eggs in each hand should be

rotated under the light that illuminates the contents of the

sample, commonly referred to as a case light. As the eggs

are rotated, the grader should observe the shells for stains

or dirty conditions.

This operation (rotation and observation for cleanliness)

should be performed rapidly enough that the motion of

the hand from the case light to the candling aperture is

made in one sweeping motion. Any stained or dirty eggs

that are detected at this point should be candled and segregated before the candling of clean eggs is begun. When

the eggs are placed before the candling aperture, the

grader should remove previously undetected dirty or

stained shells.

The candling light must provide sufficient illumination to

detect checks and interior defects. Light reflection from

the bottom of the candling light is used to detect stained

and dirty shells.

When hand candling, the grader should always have

clean, dry hands to avoid staining shells. The candling

aperture should be of a material that will not mark or

stain the shell and will aid in minimizing breakage.

In determining interior quality by hand candling, it is customary to hold two eggs in each hand, supporting one egg

by the tips of the thumb and index finger and holding the

other against the palm with the other fingers. The small

ends of the eggs should point toward the palm of the

hand (fig. 49). After one egg in the hand has been candled, it is shifted back in a rotating motion to the palm of

the hand and the second egg is brought into candling

position. The eggs are viewed alternately before the light.

The uppermost egg in one hand is examined first, then

the uppermost egg in the other hand, and this procedure

is repeated after the position of the eggs in each hand has

been shifted. After the first egg is candled and the hand is

dropped slightly back and downward, the third and

fourth fingers are relaxed, letting the uncandled egg roll

downward slightly.

At the same time, the thumb and index and second fingers guide the candled egg into the palm of the hand.

The third and little fingers then roll the uncandled egg

into candling position between the thumb and index finger; meanwhile the little finger (fourth) and third finger

hold the candled egg in the palm. The position of the egg

Figure 49. USDA grader demonstrates the proper way to hold eggs 

while candling. (00CN0052)
33

is changed in one hand while one of the eggs held in the

other hand is being candled. During this finger-to-palm

rotation, proficient candlers carefully conduct the

“belling” process to detect “blind checks.”

The ability to quickly rotate two eggs in each hand

makes for more rapid work and should be practiced

until reasonable dexterity is acquired. In manipulating

eggs before the candling light, it is important that the

rotation of eggs in each hand and the twirling motion

before the light become mechanical. Dexterity in this

rotation operation permits the grader to concentrate

entirely on placing the egg before the light rather than 

on changing its position, on rotating the two eggs, or on

concern over dropping the eggs. It also helps the grader

develop a rhythm which improves uniform timing of

judgment, thereby making possible greater proficiency.

In order to obtain a proper view of the egg while candling, it is necessary to have the contents spinning within

the shell at the time of viewing. This can be achieved in

one smooth motion when the two eggs in the one hand

are being rotated and moved toward the aperture in the

candling light. The contents of the egg will be set in

motion by a movement of hand and wrist in an arc of

about 180° (3.06 rad).

Stopping the hand motion at the end of the arc without

moving the arm or body permits the contents to spin within the shell. The long axis of the egg should be at about a

45° (0.76 rad) angle to the candling aperture. The thumb

and index finger should be on opposite sides of the shell

without obstructing the grader’s view (fig. 50). After gaining

some experience in the candling operation, the grader will

learn to have the egg contents spinning at the exact instant

the egg is placed before the candling aperture.

Speed and accuracy in hand candling should be accompanied by careful handling of the product. When eggs

are returned into a carton or filler-flat, they should be

placed carefully, not dropped, and always packed with

the small end down.

Figure 50. USDA grader demonstrating the use of a hand candling light. 

(CD 8202 3241 1143-14)
34

VIII. Determining Interior Quality

by the Breakout Method

The breakout method of determining interior quality is

a way for graders and students to fine-tune their grading

skills. It enables them to make comparisons of brokenout egg appearance with candled appearance. The most

accepted and widely used method for determining albumen quality is measuring Haugh units. The Haugh unit

was developed by Raymond Haugh in 1937, and consists of a correlation of the height of the thick albumen,

the weight of the egg, and the internal egg temperature.

At one time, this method was part of USDA’s quality

control program.

Quality Control Program

Research workers and breeders experimented for years

on a more objective way of determining interior quality

based on the measurement of the height of the thick

albumen correlated with the weight of the egg.

Statistical analysis of the quality variation found in eggs

from flocks of uniform age managed under similar conditions showed that a small sample of eggs randomly

selected from these flocks each week was highly accurate in reflecting the average quality of the lot.

Based on the extensive research and the statistical

analyses, USDA implemented a quality control program in 1959. This program made possible the marketing of high-quality eggs from the controlled flocks

under the fresh fancy or AA label of identification. A

program to market grade A eggs under the quality

control program was also made available with less

stringent requirements than the fresh fancy or 

AA program.

A small sample of eggs was randomly selected from

flocks under the programs. These eggs were then broken

out, the height of the thick albumen was measured with

a micrometer, and the reading was correlated with the

weight of the eggs. This resulted in a Haugh unit figure

used to determine the quality of the egg. The higher the

Haugh unit, the higher the quality of the egg. While the

programs were excellent marketing tools for high-quality

eggs, their use was very limited. The fresh fancy quality

program practically ceased, and the grade “A” program

was not used. Special handling was required for these

programs, and additional equipment and facilities were

required beyond those for the regular voluntary programs. The use of these programs probably was restricted by their cost and the fact that producers and packers

did not receive premiums for the product sufficient to

justify the costs. Thus the programs were eliminated in

1981.

Breakout Equipment

For economy in time and preservation of the product, the

following equipment should be available to persons

engaged in breaking eggs for the purpose of measuring

the height of the thick albumen as well as the condition

of the yolk and albumen:

Figure 51. Egg breakouts are conducted on equipment which typically includes

a metal stand, glass top, and reflective mirror. (CD 8202 3241 1143-11)

Figure 52. USDA grader demonstrating the use of a Haugh meter by measuring

the height of the thick albumen. (CD 8202 3241 1143-17)
35

1. A flat glass surface approximately 12 by 18 inches

(30.5 by 45.7 cm) or larger. The glass should be

placed on a metal stand having adjustable legs for

leveling. A mirror of approximately the same size as

the glass is needed for observing the under side of the

egg. The stand should be set on a table of such height

that the dial of the micrometer will be at eye level

when in use.

2. A standard individual egg scale that indicates the

weight in ounces per dozen for each egg. A test weight

should be used to check the scale at the start of the

breaking operation and any time the scale is moved.

3. A knife and breaking tray obtained from an equipment supplier of egg-breaking equipment is very convenient for opening the eggs.

4. A Haugh meter that has a provision for setting the egg

weight and provides a direct Haugh unit reading.

5. A squeegee is handy to move the broken egg from the

glass surface to a suitable container.

6. Containers for collecting and holding egg shells and

liquid egg contents.

Procedure

Comparable results can be obtained only if uniform procedures are used. Since eggs for top quality must have

practically normal shells, the grader should select only

such eggs when obtaining the sample for breakouts. The

eggs must be cooled to an internal temperature between

45 and 60 °F (7.2 and 15.6 °C) . Additionally, the internal temperatures of the eggs selected for the breakout

must be uniform to provide accurate and consistent

results.

Care must be taken in using the breaking knife so the

thick albumen is not ruptured. Consistent results can best

be obtained by using a breaking knife. Blunt edges, such

as a table edge, may cause the shell to splinter, with the

possibility of puncturing the thick albumen. The egg

should be held as near the glass as possible and the contents emptied very gently from the shell.

In some eggs, the envelope of thick albumen is rather

firmly attached to the shell membrane in the small end of

the egg. When this is noted, rupture of the thick albumen

can generally be prevented by slowly raising the half

shell. Haugh units should not be measured or recorded

when the thick albumen or yolk membrane has ruptured.

The surface on which the egg contents are placed must

be level. One egg at a time should be broken since it is

important to measure the albumen height immediately

after breaking. A delay of a few minutes can make a significant difference in the Haugh unit reading.

If a micrometer is used for measuring Haugh units, it

must be checked before using. Set it on the glass and turn

the measuring rod down until it touches the surface of

the glass on which the broken-out egg will be placed. To

be sure that the rod is actually touching the surface of the

glass, push the edge of a thin sheet of paper against the

intersection of the rod and the glass. The face of the

micrometer is then turned so that the indicator will read

zero. The procedure should be repeated from time to

time during the breaking operation to be sure that the

micrometer is properly adjusted.

When determining albumen quality with a Haugh meter

or micrometer, select a flat area in the surface of the

widest expanse of the thick albumen for measurement.

Eggs with a very high albumen will not have a flat surface

and in such cases a point about halfway between the yolk

and the edge of the widest expanse of thick albumen

should be selected. Care should be taken to avoid measuring areas over an air bubble or chalaza. The measuring

rod should be rolled down slowly until it makes contact

with the surface of the albumen and should be raised and

cleaned before placing over the next egg to be measured.
36

IX. Egg Grading and Certification

Services

Federal-State Grading Programs

For over 70 years, USDA in cooperation with the various

States has conducted a voluntary Federal-State egg-grading service. The legislation authorizing this service provides that it be conducted on a self-supporting basis

financed from fees charged to the applicants.

The grading service is based on the U.S. standards for

quality of individual shell eggs and the U.S. grades and

weight classes for consumer and nest run grades of shell

eggs. In addition, contract purchase specifications serve as

another basis for performing grading or inspection of lots

of eggs tendered for delivery under purchase agreements.

The various purchase specifications are, of course, based

on the U.S. standards for quality of individual shell eggs.

Although the first quality standards for individual eggs

were developed in 1925, the first standards for grades

and weight classes were enacted under the Agricultural

Marketing Act of 1946. It was during this period that the

U.S. Government became involved in developing grade

standards for numerous agricultural products. The application of standardized requirements for eggs became

essential in fair trade and, subsequently, impacted the

economical spectrum within the industry.

In the early days of the Federal-State grading service for

poultry and eggs, the work consisted largely of examining

eggs and poultry purchased by the U.S. Navy, to determine compliance with procurement specifications.

Grading and inspection service of this type was gradually

extended to other Government agencies and private institutions that purchased eggs and poultry products.

Grading offices were established at the important terminal

markets along the east and west coasts, as well as in the

inland terminal markets, such as St. Louis, MO., and

Chicago, IL. These offices, in addition to providing grading service for eggs, poultry, and poultry products, handled the market news reporting activities which began at

about the same time.

The growth of the service was slow at first, but expansion

continued at a steady pace during the thirties. The most

rapid expansion occurred during World War II in connection with Government buying programs for the

Armed Forces, and it was during this period that resident

grading programs developed into major importance.

The use of the services and the volume of products

inspected and graded continued to expand after the end

of hostilities. This expansion was due in part to the pricesupport programs that followed and to the fact that firms

had previous experience with Federal-State grading and

inspection programs and were continuing to use them in

their processing and marketing programs.

Under these programs, a qualified USDA-licensed grader,

whose duties included the grading of shell eggs in accordance with U.S. standards, was placed in the processing

plant. With the advent of this “resident grader” type of

service, the volume of products graded on a “fee basis”

became proportionately less important, considering the

overall volume officially graded. Resident services are

usually performed by graders who are assigned to a specific plant on either a full-time or part-time basis.

Today, resident graders are used in the production areas,

as well as in the distribution centers. Resident grading

offers several advantages over the terminal market or fee

type of grading service:

1. Graders are constantly available to grade and certify the

pack, whether in cartons or loose.

2. Grading is likely to be more uniform because the grader is continuously available to check the accuracy of

the candlers and processing equipment.

3. By constantly sampling product and monitoring the

grading operation, graders can detect quality problems

before large amounts of product are packed and rejected.

4. Depending on the volume of product graded, cost of

resident grading service is usually substantially less per

unit than intermittent fee grading.

5. Only resident plants are allowed to identify product

with the USDA grade shield.

Grading service can also be provided on a “temporary

plant” as-needed basis when requested by the applicant. Temporary plants must meet the same minimum

facility, operating, and sanitary requirements specified

in the regulations for resident service. All processing,

grading, and packing of product identified with the

grade shield must be completed under the supervision

of the assigned grader.

Fee grading is performed when an applicant requests

grading of a particular lot of eggs, often for verification of

grade, size, or compliance with other contract require-
37

ments. Requests for this type of service are usually made

on an irregular basis and the charges are based on the

time needed to perform the work.

USDA’s grading services for shell eggs are permissive, in that

individuals, firms, or Governmental agencies that desire

these services may request them on their own volition.

Application for grading service is usually made by telephoning the local USDA grading office or by contacting

the Federal-State supervisor’s office. Prospective applicants

for egg grading services may also contact USDA in

Washington, DC, regarding the availability of grading

service in their areas. Services are performed on the basis

of the Regulations Governing the Voluntary Grading of

Shell Eggs and the U.S. Standards, Grades, and Weight

Classes for Shell Eggs.

Today, voluntary egg grading and certification services are

administered by the Poultry Programs, Grading Branch of

USDA’s Agricultural Marketing Service (AMS). Grading

and certification is performed by USDA-licensed graders

who are supervised by the State, regional, and national

supervisors of the service. Graders may be either State or

Federal employees.

Costs of Service

The legislation that authorizes Federal-State grading programs provides that the costs of the service be covered by

fees charged to firms who use the service. Schedules of

charges have been established to cover these costs.

Included as cost items are the salaries and fringe benefits

of the graders who perform the service, travel costs

incurred in connection with grading activities, clerical

assistance in maintaining necessary office records, supervisory costs at the field level, and administrative and overhead costs at the Washington level.

Fees for grading service performed on a resident or continuous grading basis are based on the cost to USDA of

furnishing the grader or graders to the plant, plus an

overhead administrative charge based on the volume of

the product handled in the plant to cover supervisory

and other costs. Salaries of Federal resident graders are

based on the U.S. Government’s General Schedule (GS)

rates. The charges for grading shell eggs on a temporary

plant fee basis are based on the time required to render

the service. The fee schedules are updated from time to

time as costs change. Whether the grading is done on a

fee basis or a resident basis, the cost will generally average

only a fraction of a cent per dozen eggs.

Cooperative Agreements

The Federal-State egg grading service is conducted

under cooperative agreements between USDA and one

or more cooperating parties within most of the States.

The agreements are usually made with State departments of agriculture.

State colleges and extension services often cooperate in

the educational aspects of the grading program by providing training for prospective graders and by explaining the

Federal-State program to producers, handlers, and consumers.

State departments of agriculture are usually responsible

for the administrative phases of the program within their

States. These responsibilities may vary from State to State.

There are two main types of agreements — State Trust

Fund and Federal Trust Fund. Under the State Trust

Fund agreement, fees charged are collected and held in

trust by the State. The applications for service are

between the State and the individual firms, and the resident graders are State or Federal employees. To cover the

cost of the Federal supervision of the program and

Federal graders working within the State, the cooperating

State periodically reimburses USDA from the State Trust

Fund.

Under the Federal Trust Fund agreement, the contracts

for services are between USDA and the individual firms,

and the fees are collected and held in trust by USDA. The

employees doing resident grading work are Federal or

State employees, and the State is periodically paid an

amount out of the trust fund that is in accordance with

the terms of the agreement.
38

X. Official Grade Labeling 

and Identification

Several requirements must be met before packaged eggs

may be grade labeled with the official grade shield:

1. The eggs must be graded by and identified under the

supervision of a licensed grader. The eggs may be graded by an authorized company employee, but then

must be check-graded by the supervising grader.

2. Eggs to be packed in packages and marked U.S. grade

AA, U.S. grade A, or U.S. grade B must be packed from

eggs of current production. Current production means

that the eggs are not older than 30 days when packed.

3. Once packed and shipped for consumer sales, officially

graded and identified eggs may not be regraded,

repackaged, or redated.

4. Eggs must be packed in establishments meeting the

facility and operating requirements set forth in the

USDA regulations.

The greatest use of the grading program is in the grade

labeling of individual consumer packages of eggs to

inform consumers of the quality. The regulations provide

for the approval of grade labels that are used in the program. The grademark used on officially graded product is

contained in a shield design (figs. 54, 55, and 56). The

shield contains the letters “USDA” and the grade. The size

may also appear in the shield. The shield is usually printed

in a prominent place on the consumer package.

Under the Federal-State grading program, provisions are

made for the grade identification of the packaged product, whether packed bulk in 15- or 30-dozen cases, 1-

dozen cartons, or other consumer-sized packages. Usually

the official grademark is applied to cases of bulk-packed

eggs by means of a rubber stamp (fig.57). The stamp also

specifies the date the eggs were graded and the plant

number. When packed in cases, each case is sealed with

either paper or plastic tape, and the stamp is placed on

one end of the case partially on the tape and partially on

the case or adjacent to the tape.

Figure 53. For marketing purposes, the official grademark may be preprinted on

shipping cases. (00CN0053)

Figure 57. Official grademark applied to cases of bulk packed eggs by means

of a rubber stamp. (00-CN-0604)
A A

GRADE

Shell Eggs 

Produced From

USDA

Figure 65.

CERTIFIED

PASTEURIZED

USDA

Figure 64.

CE RTIFICAT E N O.

P - 42

GRADED FOR

EXPORT

U. S. D. A.

Figure 62.

P - 42

AS STAT E D O N

CE RTIFICATE

U. S. D. A.

O FFICIALLY CE RTIFIED

Figure 63.

INSP EC T E D FOR

P-42

CONTRACT COMPLIANCE

U. S. D. A.

Figure 61.

P-42

USDA

LOT U. S. D. A.

SAMPLE GRADE

U.S. A GRADE

P-42

Figure 59. Figure 60.

GRADE

A

USDA

GRADE

P-42

USDA

A

Figure 54. Figure 55.

USDA

A A

GRADE

Figure 56.

39
40

When using the official grademark, the date of grading,

corresponding to the consecutive calendar day of the year

when the eggs were actually packed into the consumer

package, must also be shown on the package. The use of

expiration dates on consumer packages by the packer or

retailer is optional. When used, the expiration date must

bear an appropriate qualifying prefix such as “EXP” or a

preprinted statement such as “Sell by,” “Not to be sold

after date on top or end” or “Last sale date on end” (fig.

58). All expiration dates are calculated from the date the

eggs are packed into the consumer package and may not

exceed 30 days, including the date of pack.

Terminology such as "Use before," "Use by," "Best before,"

or other similar language generally indicates the maximum time frame for expected quality. The dates associated with these prefixes must be calculated from the date

the eggs are packed into the consumer package and may

not exceed 45 days, including the date of pack.

The USDA Sample Grade stamp (fig. 59) is used to identify shipping containers of loose-packed or cartoned eggs

that were not packed under USDA supervision. The

words “USDA Sample Grade” and the Grade AA, A, or B

designation indicate that a representative sample of the lot

meets the grade requirements. The date of grading and

the number of the official plant where the product was

sample-graded by USDA are also shown. If not samplegraded in an official USDA plant, the stamp will show a

grader number instead of a plant number.

The USDA Lot stamp (fig. 60) is used on containers of

eggs to be identified with a consumer grademark at a

later date. The eggs are to be processed under continuous

USDA supervision and must meet all the processing

requirements outlined in the regulations. The lot number

used in the stamp is the consecutive day of the year the

eggs were packed. The number of the plant where the

eggs have been processed is also shown.

The USDA Contract Compliance stamp (fig. 61) is used to

identify shell eggs which comply with written contract or

specification requirements. The eggs may or may not have

been processed and graded in an official USDA plant

depending on the terms of the contract. Compliance is determined on a sample-graded basis by either a resident grader

or a fee grader. The date of grading or a certificate number

appears in the stamp, as well as a plant or grader number. A

grading certificate should accompany the eggs upon delivery.

The USDA Graded for Export stamp (fig. 62) is used to

identify product packed for export shipments under the

Export Enhancement Program, or for commercial export

sales. The eggs may or may not have been processed and

graded in an official plant depending on the terms of the

contract. Compliance is determined on a sample-graded

basis by either a resident grader or a fee grader. A grading

certificate is provided, and should accompany the eggs

upon delivery. The certificate number appears in the

stamp as well as a plant or grader number.

In lieu of stamping each case, some truck shipments of

officially graded consumer-packaged or loose eggs may be

sealed by the grader and the seal number recorded on a

grading certificate. The buyer and seller rely on the certificate to give the grade and percentages of the various qualities of the eggs in the shipment.

The USDA Officially Certified as Stated on Certificate

stamp (fig. 63) is used on containers of shell eggs that

have been certified as “disease free,” for condition, or for

other types of certifications where the grade and size are

not referenced on the certificate. The certification information is recorded on a certificate, and the certificate

number is shown in the stamp.

The USDA Certified Pasteurized stamp (fig. 64) is used

to identify pasteurized eggs that have been processed in

accordance with established pasteurization processing

requirements.

The Produced From ____ Shell Eggs stamp (fig. 65) is

used to identify pasteurized eggs that have been produced

from officially graded eggs identified as U.S. Consumer

Grade A or Grade AA.

Figure 58. Labeling on consumer cartons of officially identified eggs must

include the lot number and official plant number. Expiration dates are optional

but, if included, must be preceded by "EXP" or words of similar meaning. 

(CD 8202 3241 1143-8)
41

XI. Certification to Specific

Purchase Requirements

Poultry Programs provide certification services, as well as

grading services. These certification services provide volume

food buyers with the ability to tailor their purchase specifications to meet their unique needs. Volume food buyers

include food service operators, retailers, brokers, wholesalers, and exporters. Certification involves determining

compliance with the specific requirements in a purchase

contract, and then issuing a contract acceptance certificate

verifying compliance. Demand for this type of certification,

or contact acceptance service, continues to expand.

Basically, contract acceptance involves the review and

acceptance of eggs that have specific desirable attributes

required by the buyer. These certification-type examinations usually include grade and other quality factors that

may be specific for the intended use of the product. 

These product-specific certification services are available

to volume purchasers of eggs and can include:

1. Independent, third party certification of egg quality

based on U.S. or other standards.

2. Certification that purchases meet contract specifications

for quality, grade, weight, quantity, temperature, packaging and packing, transportation, or other desired

product characteristics.

3. Assurance of product quality on a continuous basis

regardless of supplier.

4. Continuous monitoring of plant facilities and processing equipment to ensure appropriate sanitary standards

are met.

5. Assurance that plants use only USDA approved chemicals, compounds, insecticides, and rodenticides according to manufacturers’ instructions.

6. Identification of eggs with a USDA plant number 

and code date to facilitate an immediate traceback, 

if necessary.

7. Establishment of a common language that enables buyers and sellers to communicate about egg quality and

other characteristics without actually seeing the product.

8. Establishment of a basis for fair, competitive bidding

between suppliers.

USDA grading specialists can help food purchasers prepare explicit egg specifications and then certify that purchases comply with these specifications. This assures purchasers that they are getting what they order, results in

overall higher quality eggs, permits long-range meal planning, and eliminates controversies between the buyer and

seller over compliance of the product.

Pasteurized Shell Eggs

The pasteurization of shell eggs is a recently developed

process intended to destroy any harmful viable microorganisms, specifically Salmonella enteritidis, that may be present in the egg. In 1997, a notice published in the Federal

Register advised that AMS will provide a voluntary certification program for pasteurized shell eggs. Once a processor's

pasteurization process is reviewed and approved by the

Food and Drug Administration (FDA), the processor may

request that AMS provide certain official marking and identification services that would assist them in marketing their

products.

Since FDA is responsible for the definitions and labeling of

foods such as eggs, shell egg processors must first receive

FDA authorization to use the term "pasteurized" in conjunction with their shell egg labeling. FDA's criterion for

pasteurization is a 5 log reduction in total Salmonella

count. Processors must demonstrate the effectiveness of

their pasteurization process by obtaining and providing

FDA with data that shows their process results in the

required reduction. Additionally, they must demonstrate

that, after pasteurization, product integrity can be ensured

through the packaging, packing, and marketing processes.

Upon satisfying these requirements, processors are

authorized to state that their products are USDA Certified

Pasteurized provided that an AMS grader monitors the

pasteurization process to ensure it is conducted in accordance with established requirements. For products in

compliance with these requirements, the shield-shaped

certified as pasteurized symbol may be placed on the

packing and packaging material (fig. 64).

Processors who do not wish to have their pasteurization

process monitored and certified by AMS have the option

of certifying that the pasteurized eggs are produced from

officially graded eggs identified as U.S. Consumer Grade

A or Grade AA. (fig. 65).
42

XII. Plant Sanitation and Good

Manufacturing Practices Program

(PSGMP)

As previously noted, USDA’s Agricultural Marketing

Service, Poultry Programs administers a voluntary egg

grading service to processors who request it. Under this

service, USDA graders continuously monitor the grading

and packing of eggs to ensure that they meet the applicable quality and size standards. In addition, plant processing equipment, facilities, sanitation, and operating procedures are checked and verified according to regulation

requirements. By meeting these requirements, eggs

packed at official plants are eligible to carry the USDA

grade shield.

More emphasis is being placed on food quality, associated quality systems based on the Hazard Analysis and

Critical Control Point (HACCP) system, and the

International Standards Organization (ISO) 9000 quality

principles. Poultry Programs has developed a sanitation

and good manufacturing practices program for use by

egg processors based on these principles. Facility and

operational requirements for this program are more comprehensive than the basic requirements for the traditional

resident grading program. Processors who consistently

meet minimum program requirements are entitled to use

the verification shield (fig. 68) on packing and packaging

materials.

The primary objectives of the PSGMP program are as follows:

1. Provide a comprehensive sanitation and quality program for official plants that supplements the voluntary

egg grading service.

2. Provide a sanitation and quality program that is universally recognized and accepted by major volume food

buyers and retailers.

3. Provide participants a method to convey to customers

their commitment to quality and sanitation through

use of the PSGMP verification shield.

Criteria for determining initial acceptance into the program are based on good manufacturing and sanitary practices typically associated with processing eggs and quality

assurance. The PSGMP program monitors over 80 prerequisite control points encompassing all phases of processing, storage, and transportation. Participating plants are

required to develop and follow a quality manual that

addresses each of the control points by stating how they

are monitored, the frequency of monitoring, the responsible person for monitoring, and any deviation procedures.

Figure 66. USDA graders conduct pre-operational sanitation checks of equipment prior to processing. (00CN0054)

Figure 67. USDA grader verifies that chemical compounds used in official plants

are approved and used according to manufacturers' instructions. (00-CN-0605)
43

For participating firms, monthly audits are conducted to

determine compliance with the control points listed on

the Audit of Sanitation and Operating Procedures for

Shell Egg Processing Plants worksheet (fig. 69). The audit

includes a general sanitation inspection of premises, facilities, and equipment for cleanliness along with a review of

washing, packing, cooling, and storage practices.

Continued participation in the PSGMP program is contingent upon maintaining a satisfactory level of compliance.

Each area of operation is assessed to determine its level of

significance, and subsequently designated either minor,

major, or critical. Upon completion of each audit, USDA

personnel will review the overall assessment with plant

management and establish time frames for correcting

non-complying items. When areas of non-compliance are

found, the participant is expected to immediately address

the issues and correct the deficiencies within the established time frames.

Figure 68. The PSGMP program logo designates that the participating plant has,

on a continuous basis, met all of the specified program requirements.
44

Figure 69 A.
45

Figure 69 B.
46

Figure 69 C.
Section XIII. Legislation Affecting

Grading and Marketing of Eggs

Much legislation has been enacted to regulate the sale of

shell eggs. The laws apply to the edibility of the product

and to its quality and grade. Both Federal and State laws

are applicable to eggs, but practically all of those pertaining to candling and grading have been enacted by

the States.

Federal Laws

The Farm Products Inspection Act of 1917 provided the

original authority for establishing grades and grading

service for voluntary use. Beginning in 1925, this authority was provided each year by an act of Congress that also

provided the USDA appropriations.

The Agricultural Marketing Act of 1946 contains the

authority under which the present grading service is

performed and authorizes the development of standards. The U.S. standards for quality of individual shell

eggs serve as a basis not only for establishing U.S.

grades, but also for developing State standards and

grades.

The Egg Products Inspection Act (EPIA)(Public Law 91-

597), which became law in 1970, provides for the uniformity of standards and grades. The Act states: “For eggs

which have moved or are moving in interstate or foreign

commerce, no State or local jurisdiction may require the

use of standards of quality, condition, weight, quantity, or

grade which are in addition to or different from the official Federal standards.” This has prompted States with

egg laws in which the standards and grades differ somewhat from the official Federal standards and grades to

amend their laws to comply with the Federal standards. A

provision on labeling prohibits States from requiring

labeling on eggs from other areas to indicate the State or

other geographic area of production or origin. This provision does not apply to Alaska, Hawaii, Puerto Rico, or the

Virgin Islands.

The Federal Food, Drug, and Cosmetic Act, and the regulations for its enforcement, apply to all food products in

interstate commerce, including shell eggs. This act is

designed to prevent the shipment of adulterated and misbranded foods. In applying this act to such eggs, a small

tolerance for loss eggs is permitted, as it would be rather

difficult, costly, and impractical to eliminate all loss eggs

from wholesale quantities of eggs.

The Federal Trade Commission has responsibility for regulating the business practices engaged in by firms marketing eggs in interstate or foreign commerce.

Surveillance Inspections

EPIA also controls the disposition of certain undergrade

eggs to prevent their getting into consumer channels.

These eggs are defined in the act as “restricted eggs”

and include checks, dirty eggs, incubator rejects, inedibles, leakers, and loss eggs. Checks and dirties can

move to official USDA egg breaking plants where they

can be handled and processed properly. All other

restricted eggs must be disposed of in a way that prevents their use as human food. They could be denatured with a color dye or other approved materials and

be used in animal foods.

The EPIA provides for inspections of shell egg handlers to

control the disposition of restricted eggs and to assure

that the eggs sold to consumers contain no more restricted eggs than permitted in U.S. Consumer Grade B. Shell

egg handlers include firms that grade and pack eggs for

the ultimate consumer, commercial distribution, and

hatcheries. Each handler is required to register with the

USDA.

Under this program, quarterly visits are made to each

producer/packer and yearly visits are made to hatcheries.

The visits are conducted by either a State or Federal shell

egg surveillance inspector to verify that shell eggs packed

for consumers are in compliance, that restricted eggs are

handled properly, and that adequate records are being

maintained as required.

State Laws

In 1919, the first State egg laws were enacted in South

Dakota, Iowa, and Illinois. The earliest regulations mainly

prohibited the sale of inedible eggs. Since then, egg laws

have been enacted in all of the 50 States. The laws regulate the labeling, grading, and marketing of eggs and reference the U.S. standards, grades, and weight classes. The

47
48

inspection of eggs at retail outlets for grade and weight

compliance is basically the responsibility of State regulatory agencies under State egg laws.

New York was one of the first States to enact a law

requiring that eggs be labeled by quality and size. New

York egg producers hoped that proper labeling for

quality, coupled with an intensive consumer education

program, would cause consumers to be willing to pay

more for top quality. They believed that local producers

would benefit because of the higher yield of top quality

eggs that packers could obtain from their eggs. Today,

most States have labeling requirements and require

licenses or permits for the sale of eggs.

The provisions of the EPIA concerning standards, grades,

and labeling have helped to ensure the free movement of

eggs in interstate commerce, and eliminate features in

State egg laws that tend to act as trade barriers.
49

XIV. Egg Quality Schools and

Training Sessions

Egg quality schools and training sessions are an effective

means for students, quality control personnel, graders,

and managers to learn about egg quality, standards, hand

candling techniques, and egg processing practices. These

sessions can be formal or informal depending on the level

and extent of training desired.

Formal Training

In regards to formal training, the National Egg Quality

School is one of the most extensive egg training programs

currently conducted. This annual school is sponsored by

United Egg Producers, State departments of agriculture,

agricultural colleges and universities, and State poultry

and egg associations. Curriculum covered during the 4-

day session includes egg formation, abnormalities, interior and exterior quality, conserving egg quality, and

HACCP development. The training includes individualized “hands-on” laboratory sessions, as well as classroomtype lectures. The instruction staff includes leading university scientists, experienced State and Federal egg

graders, and qualified industry representatives. Additional

information concerning this school can be obtained by

contacting:

National Egg Quality School

United Egg Producers

P.O. Box 170

Eldridge, IA 52748

Telephone: (319) 285-9100

Fax: (319) 285-9109

Informal Training

Informal training can be conducted on-site at the processing plant or at other locations where the essential equipment and facilities are available and where there is sufficient space for classes and laboratory practice sessions.

Informal training can be conducted by plant personnel or

other outside sources. Additionally, AMS Poultry

Programs offers an egg quality training service that can

accommodate specific training needs of the applicant.

This service is conducted by technical supervisors who

are egg grading experts and whose assistance can range

from developing agenda material to conducting the entire

training session.

Regardless of the type or source of training, the information contained in this manual can serve as the course outline. It can be presented as a 1-day refresher course for

egg graders, or expanded into a 2- to 5-day school allowing each topic to be covered in greater detail. The school

should be supplemented with appropriate slides, videos,

and other visual aids. Laboratory classes and hand-candling sessions are also valuable components to any egg

quality school. The instructors responsible for setting up

the hand-candling session should include a wide variety

of qualities within the various lots of eggs candled. The

selection and arrangement of the eggs for student practice

and testing is important in determining the students’

comprehension and will influence the overall success of

the school.

In addition to hand-candling demonstrations, the laboratory session should include classification with respect to

quality factors and weight classes. Each student should

classify the various lots of eggs as the instructor corrects

or adjusts interpretation and technique. After the student

becomes reasonably accurate in interpreting each quality

factor, combined lots of various qualities can be candled

and graded.

Each student should also be familiar with the use of a

micrometer to measure the height of the thick albumen

to determine quality by the break-out method.

For further information and training aids contact:

National Supervisor, Shell Eggs

Grading Branch, Poultry Programs

USDA - AMS - STOP 0258

1400 Independence Avenue, SW

Washington, DC 20250-0258

Telephone: (202) 720-4411

Fax: (202) 690-3165
50

XV. Resource Materials Available

The following materials are free, unless otherwise noted.

For prices and other information, call (202) 720-3506.

Publications available on the Internet are marked accordingly. Send orders to:

USDA-AMS-Poultry Programs-STOP 0259

1400 Independence Avenue, SW

Washington, DC 20250-0259

Regulations Governing the Voluntary Grading of Shell Eggs, 7

CFR Part 56

www.ams.usda.gov/poultry/regulations

U.S. Standards, Grades, and Weight Classes for Shell Eggs,

AMS 56

www.ams.usda.gov/poultry/standards

Egg-Grading Manual, AH-75 (for sale)

Guide to the uniform application of U.S. standards,

grades, and weight classes for shell eggs. Also provides

current and historical perspectives pertaining to grading,

production, and the processing of eggs. Training aid for

graders, students, quality control personnel, processing

personnel, and volume food buyers. 2000.

U.S. Standards for Quality of Individual Shell Eggs, AMS 605

(for sale)

Photos illustrating interior and exterior quality factors

used as the basis for U.S. standards and grades for shell

eggs. Chart, 15x22 inches, 4 color. 1992.

Guidelines for Operating Under the Plant Sanitation and

Good Manufacturing Practices (PSGMP) Program 

Buy Quality Eggs with Confidence, AMS-625

Egg certification services for volume food buyers. Twopage color flyer. 1996.

Quality Eggs for Volume Buyers, AMS-626

Egg certification services for volume food buyers. 12-

panel folder. 1996.

Specifications for Shell Eggs

A guide to egg certification services with detailed egg

specifications for volume food buyers.

Shedding Light on the Grademark

Videos show USDA graders performing various egg grading and certification services, and processors, retailers,

and volume food buyers discussing how they utilize and

benefit from these services. AMS-629 outlines information presented in the videos.

Video - 7-minute VHS format (for sale)

Video - 15-minute VHS format (for sale)

AMS-629 - 12-page brochure, 1998.

How to Buy Eggs, G264

General consumer information regarding egg wholesomeness, nutritive value, standards, buying and storage tips,

and safe handling. 12-page brochure. 1995.

www.ams.usda.gov/howtobuy

Photographs in this manual and about related topics are

available from:

USDA, OC, STOP 1390

1400 Independence Avenue, SW

Washington, DC 20250-1390

(202) 720-4022

www.usda.gov/oc/photo/opchomea.htm
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color,

national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases

apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille,

large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 14th and

Independence Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity

provider and employer.

Revised July 2000

Material in this manual is not copyrighted and may be reproduced with or without credit