Canned Goods

Authors: Brandon Jahner (B.Y.U. Intern)
Brian A. Nummer, Ph.D. USU Food Safety Extension Specialist
September 2008

For the purpose of this fact sheet, “canned foods” refer to foods canned in liquid.  Dry pack canned goods are not included.  Canned foods are safe alternatives to fresh and frozen foods and help meet dietary needs and avoid preservatives. Proper storage can greatly increase the shelf life and quality of canned foods.

Quality & Purchase. Canned foods can either be purchased commercially or home canned.  Home canned foods should be canned using research-tested recipes and processes like those found in the USDA Complete Guide to Canning or in Extension publications.  Use only the best quality foods to can at home.  Home canning processes can never improve the quality of foods. Commercially canned foods are superior to home canned for food storage.  Commercial canners can closely control quality and safety to produce the best product.  Commercially canned foods for storage can be purchased at grocery stores and similar outlets.   Avoid budget resellers (e.g. scratch and dent sales, dollar stores, etc.).  Purchase canned foods in either cans or jars.  Avoid rusted, dented, scratched, or bulging cans. 

Packaging. Foods are commercially canned in glass jars with lids, metal cans, or special metal-Mylar®-type pouches.  All of these materials are suitable for food storage.  Home canners should only can in mason-style canning jars with two piece metal lids as recommended by the USDA Complete Guide to Canning.  Home canning in metal cans or metal-Mylar®-type pouches requires special knowledge and equipment.  Improper processing of home canned foods could lead to Clostridium botulinum food poisoning. 

Storage Conditions. Carefully label all home canned or commercially canned food containers.  We recommend labeling purchase date (month & year) on can lid with marker.  Store all canned food in cool, dark, dry space away from furnaces, pipes, and places where temperatures change like un-insulated attics. Do not allow sealed cans or glass jars to freeze. Freezing changes food textures, and leads to rust, bursting cans, and broken seals that may let in harmful bacteria. Always store metal cans off of the floor, especially bare concrete.  Moisture can wick up to cans and encourage rusting. 

Nutrition & Allergies.  Canned foods maintain mineral content for entire shelf life. Vitamins A & C will decrease rapidly after fruits and vegetables are picked and cooked. Vitamins are lost during heating processes; however, once canned, vitamin A & C loss slows to 5- 20% per year. Other vitamins remain close to fresh food levels. Salt or sugar are not necessary for safe canning and only added for flavoring. Be sure to label canned goods with ingredients when canning mixed foods like sauces.

Shelf Life. As a general rule, unopened home canned foods have a shelf life of one year and should be used before 2 years.  Commercially canned foods should retain their best quality until the expiration code date on the can.  This date is usually 2-5 years from the manufacture date.  High acid foods usually have a shorter shelf life than low acid foods.  For emergency storage, commercially canned foods in metal or jars will remain safe to consume as long as the seal has not been broken. (That is not to say the quality will be retained for that long).  Foods “canned” in metal-Mylar®-type pouches will also have a best-if-used by date on them.  The longest shelf life tested of this type of packaging has been 8-10 years (personal communication U.S. Military MRE’s).  Therefore, storage for longer than 10 years is not recommended.

Use from Storage. Always use FIFO (First-in, first-out), meaning use your oldest cans first.  Before opening, discard any badly dented, bulging, rusty, or leaky cans or jars that have broken seals. Open cans or jars to view and smell contents.  When opening, discard any can that spurts.  Discard contents (do not taste) if there is a strange odor or appearance.

Table 1. Canned food appearance defects

Defect

Cause

Safe to Consume

Brown color or dark color

Oxidation or chemical breakdown of food pigments

Yes

Soft food texture

Chemical breakdown of plant or animal tissue

Yes

Crystals in canned fish

Magnesium ammonium phosphate crystals naturally formed

Yes, crystals dissolve with heat

White crystals in some fruits like apricots or grape juice

The crystals are a natural acid-salt complex. 

Yes, if food has no off odors.

Food above the liquid level in home canned foods

 

Yes

 

If there is no strange appearance or odor, taste a sample.  For added safety, in the case of older canned foods, you may wish to boil the food for 10 minutes before tasting.  Discard if there is an off-flavor. High-acid foods may leach metal or metallic flavors from cans if food is stored in open cans; remove unused portions and store covered in the refrigerator. Low-acid foods should be heated to 165 degrees F° or boiled for 5 - 10 minutes before eating. Once opened canned foods may last between a day and a week depending on the food.

Reference

Andress, E. L. (Revised 2005). Preserving food: Using boiling water canners. Cooperative Extension Service University of Georgia, Athens:

Andress, E. L., & Harrison, J. A. (2006). So easy to preserve 5th edition Cooperative Extension Service, The University of Georgia, Athens.

Bingham, M. L., Pahulu, H. F., Ogden, L. V., & Pike, O. A. (2006). Quality of cornmeal stored long-term in a low oxygen atmosphere.

Jackson, J. M. (1979). Fundamentals of food canning technology. Westport Conn.: AVI Pub. Co.

Larson, C. M., Sloan, A. R., Ogden, L. V., & Pike, O. A. (2005). Effects of long-term storage on quality of retail-packaged pinto beans. Institute of Food Technologist Annual Meeting:

Lloyd, M. A., Ogden, L. V., & Pike, O. A. (2003). Quality of hermetically packaged nonfat dry milk in long-term storage Institute of Food Technologist Annual Meeting.

Long, K., & Crapo, C. (2004). Canning fish in quart jars. Cooperative Extension Service University of Alaska Fairbanks:

Lopez, A. (1981). A complete course in canning (11th Edition ed.)

Marchello, M., & Garden-Robinson, J. (2003). Preservation of game meats and fish. North Dakota State University:

McEwan, M. B., Ogden, L. V., & Pike, O. A. (2003). Effects on long-term storage on quality of regular and quick rolled oats Institute of Food Technology Annual Meeting.

Monroe, K. H., Brighton, K. W., & Bendix, G. H. (1949). The nutritive value of canned foods. Food Technology, 3, 292-299.

Reynolds, S., & Williams, P. (Revised 1999). In Andress E. L., Harrison J. A.(Eds.), So easy to preserve. Cooperative Extension Service. University of Georgia, Athens:

Rickman, J. C., Bruhn, C. M., & Barrett, D. M. (2007). Nutritional comparison of fresh, frozen, and canned fruits and vegetables II. vitamin A and carotenoids, vitamin E, minerals and fiber. Journal of the Science of Food and Agriculture, 87(7), 1185.

United States Department of Agriculture (Ed.). (Revised 1994). "Complete guide to home canning" agriculture information bulletin