It Says "Use By Tomorrow," But You Don't Have To

expiration date “Use by,” “best by” and “sell by” dates (commonly referred to as expiration dates) are supposed to help consumers make good decisions about what foods to purchase, consume, and discard.   But many folks find them more confusing than helpful.  Moreover, these food expiration dates create anxiety, causing consumers to throw out a lot of perfectly good food.  


Fearing food poisoning, many consumers follow this familiar advice: “When in doubt, throw it out.”  That’s the most worry-free solution, but it certainly isn’t the thriftiest. 


True or False?  Test your knowledge, and then read on for the correct answers and explanations.  

1. Most food-borne illness is not caused by eating food that is “old.”

2. Bacteria generally don’t grow (or grow very slowly) on refrigerated foods.

3. Bacteria that make food taste, look, or smell bad are not likely to make you sick.

4. Bacteria don’t multiply in frozen food, but they don’t die off either.

Guess what?  All the statements above are true.  For explanations, read on.

Before you toss a recently expired unopened food, consider these facts:

- Most food-borne illness is NOT caused by food that is past its expiration date; it is caused by some sort of mishandling that results in contamination. If food is properly handled--cooked to a high enough temperature or kept at the correct cold temperature, washed thoroughly (if produce), prepared properly with clean hands, and not brought into contact with contaminated raw products after it is cooked--it will probably be safe to eat. 


- Food product dating is about quality, NOT safety. "Best if used by" means exactly that. It's the last date the item will be at its peak quality in terms of taste, texture, color, scent and/or nutritional value, according to its manufacturer. "Use by" is not a warning of impending doom if the product is not banished to the garbage can immediately.  


- Foods that are refrigerated at 40ºF or less are not likely to make you sick because most pathogens don’t grow at refrigerator temperatures, or they grow very slowly.  One exception is listeria, which is a problem for pregnant women and people with somewhat compromised immune function such as children, the elderly, and people undergoing chemotherapy treatments.  It is most likely to appear in cured meat products such as hot dogs and bologna.  


- Spoilage bacteria (the ones that make food taste bad and/or become slimy, discolored, and off-odored) are not the ones that make you sick.  Their growth precedes the growth of bacteria that cause illness because spoilage bacteria grow faster. Therefore, you’re likely to discard a food before it becomes dangerous to consume.


- Is it too old to eat? To some extent, you can trust your senses.  If a product looks, smells, and feels okay (isn’t slimy), it is probably safe to eat for 4-7 days after the expiration date, though it  may not be quite as good as before it “expired.”


- Check for mold, which can grow in the refrigerator and can cause illness. Most molds do not produce dangerous toxins, but you can’t tell by looking at them whether or not they do.  Therefore, if you see mold on a product, the safest response is to throw it out no matter what the expiration date is.  Pathogenic organisms that cause infections don’t have to be present in large numbers to make you sick.


- Food expiration dates refer to UNOPENED products.  Once you open a food, that date becomes meaningless.  How long will an edible item be good once it's opened?  To find the answer, type the name of the product into the search box on the home page of The site has information on hundreds of edible items. If the food you're wondering about is not covered on the site,  check the manufacturer's website or call the manufacturer.  Many companies have customer service recorded messages, and some even have live personnel answering consumer questions about the shelf life of their product(s).  


For additional information about product dating and food safety, use the links to the following FAQs:


FAQs about Bacteria

FAQs about Mold

FAQs about Product Dating



Susan Brewer, Ph.D.  University of Illinois, Department of Food Science and Human Nutrition



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