General Information

We may not have a definitive solution to the age-old riddle that has perplexed generations: Which came first, the chicken or the egg? But one thing we do know is that birds and eggs preceded man in the evolutionary chain, so they’ve definitely existed longer than historians.

Chickens are known to have been domesticated as early as 3200 B.C. by the East Indian’s who domesticated wild fowl. Egyptian and Chinese records also show that fowl were laying eggs for man in 1400 B.C. Europe has had domesticated hens since 600 B.C. There is some evidence of native fowl in the Americas prior to Columbus’ arrival. However, it is believed that, on his second trip in 1493, Columbus’ ships carried to the New World the first of the chickens related to those now in egg production.

Egg Collection and Washing

In most commercial operations, eggs drop automatically from the hens’ cages to a conveyor belt below where they are taken to a machine for washing.  To clean and sanitize the eggs, a machine washes them in water heated to more than 90°F with a special cleaning solution. Once the eggs are washed, they are rotated as they pass by to look for dirt spots.  If an egg is detected with dirt spots, the egg is routed back to the washer.  In some cases, oil is used to protect shell eggs and is applied in a manner that prevents egg contamination and preserves egg quality.

The contents of the egg are examined without cracking the shell. The condition of the shell, albumen and yolk are all checked. Inferior eggs are removed.

In modern operations, to detect shell cracks, eggs are checked sonically. In a matter of seconds, tiny probes tap each egg 16 times and ‘listen’ for the sound it makes. A fully intact egg has a high pitch and a sustained ring. A thud indicates a crack and the egg won’t be packed.

Once washed and determined whole, the eggs are packaged and shipped.  Each package must be determined to be clean and in good condition, mold free and without offensive odors, and sufficiently strong and durable to protect eggs from damage during normal distribution.  

Throughout the collection and washing process, eggs held prior to processing and packing for more than 24 hours after they are laid must be kept at an average temperature of 60° F or below, but must be brought to 45°F or colder within 36 hours after collection.  After being processed and packaged they must be kept at an average ambient temperature of 45°F or colder at all times, including while they are being transported.  At no time should the eggs be frozen. 

Egg Quality Grade and Weight

The interior and exterior quality of an egg, referred to as the grade (AA, A, B), is determined by a process called candling. The candling light allows the user to grade the interior quality of the egg.

The following combination of factors is used to determine the grade of an egg:

• Distinctness of the yolk shadow outline.The shadow of the yolk outline cast on the shell, when the egg is twirled in the candling process is one of the best indicators of interior quality. As the egg ages the whites lose carbon dioxide and moisture causing them to become thinner, allowing the yolk to spin more freely in the egg. This creates a more clearly defined shadow of the yolk, when the egg is candled.
• Air Cell. The size of the air cell is another factor used to determine the grade of the egg. When an egg is first laid, it has a very small air cell or none at all. As the internal temperature of the egg drops, the liquids contract more than the shell. As a result of this contraction, the inner membrane separates from the outer to form an air space. As the egg ages this air cell becomes bigger due to the escape of gas and evaporation of water from the egg.  Higher grade eggs have a very shallow air cell. In AA quality eggs, the air cell may not exceed 1/8 inch in depth. Eggs of A quality may have air cells over 3/16 inch in depth.  There is no limit on air cell size in Grade B.
• Blood and Meat Spots can also be detected by the candling light. The presence of large spots will downgrade an egg.
• Surface cracks on the shell are also easier to detect when candling.

Egg Weights

In the grading process, eggs are examined for both interior and exterior quality and are sorted according to weight (size). Grade quality and size are not related to one another. The weight standards are as follows:

• A dozen Jumbo eggs should weigh approximately 30 oz. or more
• A dozen Extra Large eggs should weigh approximately 27 oz. or more
• A dozen Large eggs should weigh approximately 24 oz. or more
• A dozen Medium eggs should weigh approximately 21 oz. or more

Egg Labeling

Retail egg packaging must contain all of the following components to meet requirements as stated in Wisconsin regulations ATCP 88 and 90.  Cartons must contain:

• a declaration of product identity
• a declaration of responsibility in the form of a packer identification number or shell egg handler registration number identifying the state of origin as follows:  WI##
• a declaration of responsibility may identify the individual name and address of the packer if they do not have a number assigned
• a declaration of net quantity
• nutrition labeling
• grade and size of the eggs in letters not less than 3/16 inch high 
• a “keep refrigerated” or an equivalent statement
• the date the eggs were packed
• an expiration date or “sell by” date not more than 30 days from the packing date OR a “use by” date
• a safe handling statement, such as “To prevent illness from bacteria: Keep eggs refrigerated, cook eggs until yolks are firm, and cook foods containing eggs thoroughly.” 

Shipping packaging must contain the same information on one end with all of the information in letters not smaller than ½ inch tall.

Exceptions to Egg Grading and Labeling Requirements

There are only two circumstances in which egg grading and labeling are not required by regulations; eggs being shipped from the producer to a packer are exempt as are eggs that a producer sells directly to household consumers on the premises where the eggs are produced.