Slide Show >>The latest spinach food scare, which has claimed at least one life and sickened 183 other people, took many by surprise. After all, previous E. coli bacteria outbreaks were mostly associated with raw meat.
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.
GOVERNMENT GUIDELINES. What does the government say? The Food & Drug Administration, which regulates packaged foods and drugs, only requires a use-by, or expiration, date on infant formula. That's because formula must contain a certain quantity of each nutrient that is described on the label. And if formula is stored too long, it loses its nutritional quality, and also separates or form lumps that will clog the bottle nipple.
The Agriculture Dept., which regulates fresh produce and meats, only requires labeling of the date when poultry is packed at the farm. However, many manufacturers are allowed to also add sell-by or use-by dates. "Grocery stores that grind their own meat can add their own package labels," says USDA spokesman Steve Cohen.
In fact, both the FDA and the USDA have a pretty laissez-faire attitude when it comes to food shelf-life labeling. That's not because they are not concerned for people's health. Mark Harrison, professor of food science at the University of Georgia, points out that most of these dates are not an indicator of safety, rather of quality. "Some foods spoil if not refrigerated quickly enough—but they won't kill you," says Harrison.
BACTERIA'S THREAT. Milk, for instance, starts deteriorating in quality quite quickly. Pasteurized milk usually remains fresh for five days after its sell-by date. However, if milk isn't refrigerated promptly, it will develop a sour taste and spoil, even though it might not necessarily be dangerous. Interestingly, milk can lose vitamins when exposed to light, which is why it usually comes in opaque plastic or paperboard.
The latest fad is drinking "raw milk," which people claim is tastier and healthier since it doesn't go through the pasteurization that they believe destroys some nutrients and the enzymes necessary to absorb calcium. However, the USDA claims that there is no significant difference in the nutritional value of pasteurized and unpasteurized milk, though pasteurized milk is a lot safer.
If a product already has harmful bacteria like salmonella or listeria in it, the bacteria will multiply and develop colonies within days, even in the refrigerator. Then it is dangerous to consume. "In cases where the bacteria is already there, the use-by dates become irrelevant because they can harm you much before then," says Bill Marler of Seattle law firm Marler Clark, food safety advocates that represent victims of food poisoning. Marler is representing 76 victims in the latest spinach E. coli outbreak, 22 of whom have had kidney failure.
MORE ADVICE THAN COMMAND. Salmonella and listeria can be fatal for young children, fetuses, and the elderly, and even healthy adults can get violently sick. These bacteria can usually be killed when food is cooked properly. However, listeria has turned up in cooked foods like cold cuts and others that are not heated properly like hot dogs. Soft cheeses like brie and camembert are also likely to carry listeria and should be eaten within three to four days of opening.
Many other foods, like potato chips or mayonnaise, that have oils or fat will go rancid and will taste bad before they can breed bacteria and hurt people. Surprisingly enough, eggs have a pretty long shelf life and can last as long as five weeks after the sell-by date if refrigerated properly.
Ultimately, most of these labels should be used more as a guide, rather than a hard and fast expiration date. And the confusion might even be a little deliberate on the part of the government. Says Harrision of the University of Georgia: "Once the consumer takes it home, not even the government can find out exactly what happened, which is why it's unlikely you will have a definite safety label on perishable food."
Click here to see the Guide to Shelf Life slide show.