|Understanding and Increasing the Shelf Life of Canned Goods|
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 cooperative 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 percent per year. Other vitamins remain close to fresh food levels. Salt or sugar is 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 two years. Commercially-canned foods should retain their best quality until the expiration code date on the can. This date is usually two-five 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 eight-ten years (personal communication U.S. Military MREs). Therefore, storage for longer than ten 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 with 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.
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°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.
For more information on food safety, food preservation or food preparation, call Angela Treadaway, your Alabama Cooperative Extension System Regional Extension Agent in Food Safety/Preservation and Preparation at (205) 410-3696.
Angela Treadaway is a Regional Extension Agent in Food Safety. For any questions on food safety or preparation of vegetables, contact her at (205) 410-3696 or your local county Extension office.