Food Expiration Dates
Foodborne Illness
A foodborne illness is used to describe symptoms associated with eating food contaminated by bacteria. Some common types of bacteria that can contaminate food include: Escherichia coli (E. coli), Listeria monocytogenes, Salmonella, Campylobacter jejuni, Clostridium perfringens, Clostridium Botulinum and Shigella. Eating contaminated food may cause nausea, vomiting, diarrhea and/or fever. People with weakened immune systems or chronic diseases are most susceptible to severe illness and complications from a foodborne illness.
According to the CDC, more than 17,460 laboratory-confirmed cases of foodborne infections were reported in the U.S. during 2009. Incidence rates were highest among children under 4. However, people 50 and older were most likely to be hospitalized from foodborne illness.
Package Product Dates
Proper handling, cooking and storage of foods greatly reduces the risk for foodborne illness. Meats should be cooked thoroughly and leftovers refrigerated within two hours (one hour in hot temperatures). The refrigerator should be kept at 40 degrees F or lower and the freezer at 0 degrees or lower.
Shelf life of packaged products can vary considerably. Many packaged foods have dates on them, however these dates can be confusing. There is no uniform food dating system in the U.S. and the government only requires dating for infant formulas and some baby foods. In general, here are some guidelines on the different types of food dates:
Sell-by: The sell by date is a general guideline for stores to know how long to display the product. Ideally, consumers should purchase items before the sell-by date. However, most foods will still be good for several days after that date. Some products with an expiring sell-by date can be frozen to extend their shelf life. One caveat, however: Mandel Smith, Nutrition/Food Safety Educator with the Penn State Cooperative Extension in Collegeville, PA, warns that once a product is opened, it should be used within 5 to 7 days, regardless of the sell-by date.
Use-by: The use-by date refers to the end point at which the manufacturer has determined the product is no longer at peak freshness. It generally doesn’t refer to safety, but rather to quality. For example, cake mixes with an expired use-by date may not rise properly because the baking soda has become inactive. In many cases, however, products can often be used past their use-by date as long as they have been properly stored.
Best-if-used by: This is a variation on the use-by date that infers prime flavor or freshness if a product is used by the printed date.
Product code: The product code is not really a date, but rather a packing number for manufacturer and retailer reference. Sometimes a product’s freshness can be determined by a product code. However, in most cases, the number is used to help stores rotate stock and enable manufacturers to issue food recalls.
Specific Food Concerns
Smith reminds consumers that package dates are just a guideline for determining the safety and freshness of foods. Some items deserve specific mention:
Canned foods. Shelf life of canned foods varies considerably. High-acid foods, like tomatoes and pineapple, should be stored no longer than 12 to 18 months because the acidity degrades the seal of the can. Low-acid foods, however, can be kept anywhere from 2 to 5 years. Make sure canned goods are stored in a cool, dry place. It’s also a good idea to rotate stock, placing the freshest items in the back of the counter or cabinet and the oldest items in front (so they can be used first). If there are no dates on the cans, use a marking pen to indicate the purchase date. Discard any canned goods that have bulges at the seams or rust spots on the can. Home canned goods should be kept no longer than one year.
Rice/flour. White rice has an almost indefinite storage time. Brown rice, however, is a whole grain. Smith says the oil in brown rice can become rancid, so she recommends storing it for no more than 6 months. The same goes for whole wheat flour.
Packaged salads. Pay close attention to the dates on pre-bagged salads. Many are labeled with sell-by dates and will spoil quickly if not used within a day or two of that date.
Eggs. Most eggs sold in the grocery store are very fresh, typically reaching the shelves within a few days of leaving the farm. They usually have a sell-by date. However, the USDA says properly stored eggs can be kept for about 3 to 5 weeks. Keep the eggs in their original carton and place them in the coldest part of the refrigerator. Don’t take them out of the package and put them in the egg slots on the refrigerator door because that area gets too warm to prevent spoilage. Hard boiled eggs shouldn’t be kept longer than a week.
Milk, cream. Milk, cream and similar products are typically pasteurized to reduce spoilage. However, you still need to pay attention to the sell-by date. If properly stored and handled, a carton of milk will last 5 to 7 days after the sell-by date.
Fresh meats and seafood. These products have a very short shelf life. They should be cooked by the date on the package or frozen for longer storage.
AUDIENCE INQUIRYFor general information on safe food handling and storage:
Centers for Disease Control and Prevention, http://www.cdc.gov/foodsafety
USDA, Food Safety and Inspection Service, http://www.fsis.usda.gov
BIBLIOGRAPHYCarrasco E, et al., “Survey of Temperature and Consumption Patterns of Fresh-Cut Leafy Green Salads: Risk Factors for Listeriosis,” Journal of Food Protection, October 2007, Vol. 70, No. 10, pp. 2407-2412.
Cates SC, et al., “Consumer Knowledge, Storage, and Handling Practices Regarding Listeria in Frankfurters and Deli Meats,” Journal of Food Protection, July 2006, Vol. 69, No. 7, pp. 1630-1639.
Kosa KM, et al. “Consumer Knowledge and Use of Open Dates,” Journal of Food Protection, May 2007, Vol. 70, No. 5, pp. 1213-1219.
Lenhart, J., “Consumer Assessment of Safety and Date Labeling Statements on Ready-to-Eat Meat and Poultry Products Designed to Minimize Risk of Listeriosis,” Journal of Food Protection, January 2008, Vol. 71, No. 1, pp. 70-76.
Pouillot R, et al., “Estimating Parametric Distributions of Storage Time and Temperature of Ready-to-Eat Foods for U.S. Households,” Journal of Food Protection, February 2010, Vol. 73, No. 2, pp. 312-321.
