Slate has an interesting article about food expiration dates and their meaning — which can be somewhat slippery. The basic idea is this: You don’t have to throw out food just because its past the “Sell By” date. You should inspect your food to see if it has spoiled and try to make a rational decision.
Is the food slimy and smelly? Don’t eat it.
The fact is that expiration dates mean very little. Food starts to deteriorate from the moment it’s harvested, butchered, or processed, but the rate at which it spoils depends less on time than on the conditions under which it’s stored. Moisture and warmth are especially detrimental. A package of ground meat, say, will stay fresher longer if placed near the coldest part of a refrigerator (below 40 degrees Fahrenheit), than next to the heat-emitting light bulb. Besides, as University of Minnesota food scientist Ted Labuza explained to me, expiration dates address quality—optimum freshness—rather than safety and are extremely conservative. To account for all manner of consumer, manufacturers imagine how the laziest people with the most undesirable kitchens might store and handle their food, then test their products based on these criteria.
With perishables like milk and meat, most responsible consumers (those who refrigerate their groceries as soon as they get home, for instance) have a three-to-seven-day grace period after the “Sell by” date has elapsed. As for pre-packaged greens, studies show that nutrient loss in vegetables is linked to a decline in appearance. When your broccoli florets yellow or your green beans shrivel, this signals a depletion of vitamins. But if they haven’t lost their looks, ignore the printed date.
You should not, however, feel free to behave like my father, who has a complete inability to tell if milk has gone bad. Having coffee over there is always an adventure.
Ignore Expiration Dates [Slate] (Thanks, Cy!)