Canned foods can remain usable for years when they are properly processed, sealed and stored. The U.S. Department of Agriculture says commercially canned low-acid foods, including vegetables and meat, can maintain their best quality for about two to five years when kept in a cool, dry place. High-acid foods such as fruits generally have a shorter recommended quality period.
That long shelf life makes canned foods useful for households that want foods that can be stored without refrigeration. But the safety and nutritional value of canned food depend on the product, processing method and storage conditions.
How canning preserves food
Canning preserves food by using heat to destroy microorganisms and enzymes that can cause spoilage, followed by sealing the food in a container to prevent contamination.
The exact temperature and processing time vary according to the type of food and the canning method. It is therefore inaccurate to say that all canned foods are heated to a single temperature of 250 degrees Fahrenheit.
Commercial canning is carried out using controlled processes designed to make the food safe and shelf-stable. Home canning requires following tested procedures because some foods, particularly low-acid vegetables, meat and poultry, can support the growth of Clostridium botulinum if they are not processed correctly.
What happens to the nutrients?
Canning does not simply remove all of a food’s nutrients. Some nutrients can be reduced by heat or by the handling of food during processing, while others remain relatively stable.
The nutritional profile can therefore differ between canned and fresh foods. Consumers should check the nutrition label rather than assume that a canned product has exactly the same nutritional value as its fresh counterpart.
The FDA recommends using nutrition labels to compare foods, paying particular attention to nutrients such as sodium and added sugars. Some canned vegetables are available in low-sodium or no-salt-added versions.
Home canning requires care
Improper home canning can create a serious risk of botulism, a potentially life-threatening illness caused by a toxin produced by Clostridium botulinum.
USDA guidance says the risk is greater when home-canned foods have not been processed according to safe canning procedures. Low-acid foods require particular care because the bacteria that cause botulism can survive inadequate processing.
Commercially canned food also should be inspected before use. USDA advises against eating food from cans that are leaking, bulging or badly dented, or containers that spurt liquid when opened or have other signs of spoilage. Suspect food should not be tasted.
Check the label
Canned food can be part of a practical food supply, but the fact that a product is canned does not automatically make it a healthier choice.
Some products contain significant amounts of sodium or added sugar. Reading the nutrition facts panel and ingredient list can help consumers compare products and choose options that fit their dietary needs. The FDA specifically recommends looking for lower-sodium or no-salt-added canned vegetables when appropriate.
For commercially canned foods, proper storage also matters. USDA recommends keeping unopened cans in a cool, clean and dry place and avoiding cans that show signs of damage or spoilage.
