Canned Food Basics

• All commercially canned foods are heat-processed to both seal their containers and kill harmful bacteria that can cause foodborne illness. Heat processing is completed based on the type of product and susceptibility to the growth of toxin bacteria Clostridium botulinum, or botulism, as they are commonly known. Temperatures needed to kill botulism spores are much higher than those needed to kill listeria. Cooking foods at 170 degrees Fahrenheit or higher is all that is needed to kill listeria; this is always exceeded on any canned product as part of the processing to seal jars and kill other spoilage-causing bacteria and yeast. Pasteurization is the lowest-temperature processing used in canned food production and requires that jars are heated to 180 F, killing all listeria bacteria in food.

Listeria Basics

• Listeria is most commonly found on fresh produce, ready-to-eat meats, unpasteurized dairy and cheeses, smoked seafood and raw sprouts. Because these items are not heat-processed or are processed in a contaminated facility, they are most commonly subject to contamination. Listeria bacteria continue to grow even upon refrigeration. Ingesting a product contaminated with listeria creates flulike symptoms that are worse in children and those with weakened immune systems. Fever, stiff neck, vomiting, diarrhea and weakness are symptoms of listeriosis.

Opened Canned Foods

• While the proper processing of canned foods kills all present spoilage-causing bacteria and makes the product sterile, it does not prevent it from contamination once opened. Once you open a canned food item, it can become contaminated with listeria in your kitchen. Practice safe handling by storing opened canned items in a separate covered plastic or glass container, using clean utensils to transfer foods and washing your hands before handling. Use all opened canned foods within two to three days of opening, and store them in the refrigerator.

Canned Food Safety

• While properly canned foods do not contain listeria, cans that are improperly processed or damaged could become contaminated. Home canned foods must be canned in a boiling water bath or pressure canner for the appropriate processing time based on U.S. Department of Agriculture recommendations to prevent spoilage and foodborne illness. Avoid using the open-kettle method of canning and steam processing, as these methods are not recommended by the U.S. Department of Agriculture. It is very unlikely that listeria could be present in an improperly canned good because of the relatively low amount of heat needed to kill them, but other spoilage bacteria and yeast can cause improperly canned items to spoil. If any canned food looks or smells bad, throw it out without tasting it.