Last week’s column reminded me of a question that I’ve been wanting to ask you for a long time. Is there a way to tell from the egg carton how old the eggs are?

According to the U.S. Department of Agriculture, many eggs reach stores only a few days after the hen lays them. If you have a carton that shows a voluntary USDA grade shield, you can determine the date the eggs were packed. When the USDA grade shield is present on the carton, the carton also must be labeled with the date and location of where the eggs were packed. This information is typically stamped on one end of each carton of eggs.

• Code dates. Egg processors typically print dates commonly called code dates on cartons for purposes of rotating stock or controlling inventory. “Sell by,” “Exp.” and “best if used before” are examples of terminology used for code dating.

If an expiration date is used, it must be printed in month/day format and preceded by the appropriate prefix, which may be “Sell by,” “Exp.” and “Not to be sold after.” Expiration dates can be no more than 30 days from the day the eggs were packed into the carton.

Another type of code dating used indicates the recommended maximum length of time that the consumer can expect eggs to maintain their quality when stored under ideal conditions. Terminology such as “use by,” “use before,” and “best before” indicates a period that the eggs should be consumed before overall quality diminishes. Code dating using these terms may not exceed 45 days including the day the eggs were packed into the carton.

• Pack date. The day of the year the eggs are processed and placed into the carton also must be shown on each carton with the USDA grade shield. The number is a three-digit code that represents the consecutive day of the year. For example, Jan. 1 is shown as “001” and Dec. 31 as “365.” Typically, eggs are packed within one to seven days of being laid. For example, if the pack date is “218,” it means the eggs were packed on the 218th day of the year or Aug. 5.

Why does a hard cooked egg white turn brown?

This is a result of a chemical reaction within the food called the Maillard Reaction. The Maillard Reaction produces a brown color when certain chemical reactions occur between sugars and proteins. It helps produce a golden crust in baked goods, the browning of meat, and the rich dark color of roasted coffee. While these are positive results, the Maillard Reaction also can produce negative results. An example is during the storage of dry milk. A dark color is a sign the milk has been stored too long.

In eggs, the egg proteins react with the small amount of carbohydrates in the egg. This may occur if the eggs are overcooked. To prevent the color change, follow these steps to hard boil eggs:

• Place eggs in a single layer in pan.
• Cover the eggs with water and bring to a boil.
• Remove from heat and let stand for 15 to 20 minutes.
• Cool the eggs immediately in cold water.
• Chill completely before removing shells.

The color change is not harmful and the eggs are safe to eat.