expiration dateBusiness Week reports that nervous folks are peering more closely at dates stamped on the produce they buy from supermarkets. But how helpful are these dates really?

Many of them are actually quite confusing. "Is a food fresh until Feb. 1, 2008, if that’s the date stamped on it, and then do you throw it out on Feb. 2?" asks Jeanne Goldberg, professor at the Friedman School of Nutrition Science & Policy at Tufts University. "It’s a very inexact science since those dates include a wide margin of safety."

DATE DATA. The dates, for one, mean quite different things. For instance, "sell by" is more a guide for the store to know how long it can display a product for sale. The "best before" or "best if used by" date refers to a quality or flavor of the food. "Use by" works more like an expiration date, similar to that on medicines, and taking them after the date is not recommended.

Worse, some dates can actually be quite misleading. Few folks, for instance, know when they buy meat, that even if the sell-by date is five days away, the refrigerator at home usually isn’t cool enough to keep the meat fresh for more than two days. Usually raw meat is kept around 30 degrees Fahrenheit, while the home refrigerator’s temperature is set around 40 degrees to keep other things in the fridge (like vegetables) from freezing. So, food safety experts suggest that whether it’s ground meat, or a pound of steak, or chicken, consumers either eat or freeze it within two days of buying.

Of course, even frozen meats don’t last forever. Some, like ground beef, need to be consumed within three months of being frozen (see BusinessWeek.com, "A Guide to Shelf Life"). "Ground meat spoils more quickly because there’s more surface area for bacteria to grow on,"  says Tufts’ Goldberg.