by Amanda Vittitow

Created on: January 11, 2009

USDA (United States Dept of Agriculture) graded eggs, which are usually in supermarkets, have to follow certain USDA rules and codes in order to have the freshest eggs on the shelves. On the side of the carton, there is a USDA grade shield that must have the date and location of where the eggs were packed. The consumer can use this information to learn more about the eggs they are buying.

The USDA assigns a plant number to each official plant where the eggs are packed. The number is always preceded by the letter "P" and must be stamped on the side of the carton.

The day of the year that the eggs are processed and put into the carton must be stamped on the carton with the USDA grade shield. This number can range from 001 (January 1st) to 365 (December 31st). Eggs are usually packed within 1-7 days after they are laid. In my example the pack date number is 311, meaning they were packed on the 311th day of the year or November 7th.

Egg processors typically print code dates on the carton as a way to keep up with rotating stock or controlling inventory in the supermarket. The use of code dates is optional, but if it's used, certain rules must be followed. If the expiration date is used, it must have the month and day format with "EXP" or "Sell By" in front of it. The expiration date in this case is "Dec 20."

Getting the eggs on the supermarket shelves can take different amounts of time depending on transportation and warehousing. The quality of the eggs depends on how they're handled during the shipment and storage process.

So how fresh are the eggs on the supermarket shelves? Pretty fresh. Still in doubt? Try this little test.

Submerge your egg into water and watch what it does. Does it lay flat? If it does, it's fresh and will have the best taste for being fried or scrambled. Does it stand up a little bit on one end? If it does, it's starting to get a little spoiled and will be best boiled or for baking. Does it stand vertically but still touch the bottom? Use it as soon as possible for boiling or baking. If you're going to use it for baking, you may want to break it into a separate bowl and check it. If the yolk has a green tint or if the entire egg has a funny odor, throw it out because it could be rotten. And lastly, does the egg float in the water? If it does, it's quite old and could possibly be rotten. Throw it out.

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