I recently got an e-mail from Scott who wrote, “I saw a TV show saying that the expiration date on mayonnaise is not real. . . Is this true? Also are the expiration dates on canned goods like tuna, soup, or tomato products really valid . . .?

I promised to look into it and the most reliable information I found is from the USDA. They say that the sell-by date is there to help the “purchaser to know the time limit to purchase or use the product at its best quality. It is not a safety date. After the date passes, while not of best quality, the product should still be safe for a period of time if handled properly.” Go to the USDA web site for more information and charts giving a time limit on the period of time different foods may be safe beyond the sell-by date.

I was surprised to find out that federal regulations only apply to baby formula and food. According to the USDA, “federal regulations require a “use-by” date on the product label of infant formula and the varieties of baby food under FDA inspection.”

Other dates are not controlled by federal regulations but are determined by the manufacturer. A “sell-by” date tells the store how long to offer the product for sale. A “best if used by” date is based on best flavor as determined by the manufacturer, not a safety date. A “use-by” date is the last date recommended by the manufacturer for use at peak quality.

The safe-use time for products varies. Many things go into the quality and safety of a stored product. Storage temperature is very important; storing in a cool, dry place prolongs product quality. Once opened, the way a product is handled is important. It is essential that you use a clean utensil when you dip into a product.  A spoon that has been used for tuna and is then used in mayonnaise reduces the safe life of the mayo to that of an opened can of tuna.