There are finite limits to how long food can be preserved. Storing canned food faces several factors which limit the shelf-life over time.
1. Factors that limit shelf life
Cans or jars with metal lids are susceptible to rust. If the rust becomes deep enough, tiny holes open in the can or lid that may let bacteria inside.
Can corrosion can occur when food reacts chemically with a metal container, especially high-acid food like canned tomatoes or fruit juices. Over several years, this causes taste and texture changes. It eventually lowers the nutritional value of the food.
High temperatures, over 100 degrees Fahrenheit, are harmful to canned foods. The risk of spoilage jumps up sharply as storage temperatures rise. At prolonged storage temperatures above 75 degrees, nutrient loss in canned foods increases.
Light can cause color changes and nutrient losses in foods canned in glass jars.
Never consume food from containers with these spoilage warning signs: loose or bulging lids on jars; bulging, leaking or badly dented cans, especially along the top, side and bottom seams, or foods with a foul or musty odor.
2. How to store canned food wisely
Store food in a cool, clean, dry place where temperatures are below 85 degrees. Temperatures between 50-70 degrees are good. Avoid freezing temperatures.
Temperatures over 100 degrees Fahrenheit are harmful to canned foods also.
Rotate foods so the oldest is used first. Try not to keep canned foods more than one year.
Use canned meats and seafood within 12 months.
Use low-acid canned foods within 8-12 months.
Use high-acid foods within 12 to 18 months. Foods stored longer will be safe to eat if the cans or jar show no signs of spoilage or damage. Food may deteriorate in color, flavor and nutritive value after 12 months.
Canned fruit juices can be stored up to 3 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.
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; U.S. Military MRE’s. Storage for longer than 10 years is not recommended.
Dry pack canned goods have longer shelf lives.
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.
3. Commercial vs. home canned food
Commercially canned foods have superior shelf life when compared to home canned food. Commercial processers and 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 with short shelf life canned goods. Avoid rusted, dented, scratched, or bulging cans.
Home canned foods should be canned using research-tested recipes and processes like those found in the USDA Complete Guide to Canning or in University extension publications. Use only the best quality foods to can at home. Home canning processes can never improve the quality of foods. But they can extend the season of larger fresh harvests.
Commercially canned foods are available 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 food poisoning.
5. 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 should only be added for flavoring. Be sure to label canned goods with ingredients when canning mixed foods like sauces.
6. Rotate Food from storage
Always use FIFO (first-in, first-out), meaning use the 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.
7. What to do with contaminated food
Wear disposable rubber or heavy plastic gloves. Carefully place the suspect jars and lids on their sides in an 8-quart volume or larger stock pot, pan, or boiling-water canner. For food with metal cans; dispose of these by placing them in a plastic bag before putting them in the trash.
Wash your hands with gloves thoroughly. Carefully add water to the pot and avoid splashing the water. The water should completely cover the containers with a minimum of a 1-inch level above the containers. Place a lid on the pot and heat the water to boiling. Boil 30 minutes to ensure detoxifying the food and all container components. Cool and discard the containers, their lids, and food in the trash or dispose in a nearby landfill.
Contact with botulin toxin can be fatal whether it is ingested or enters through the skin. Take care to avoid contact with suspect foods or liquids. Wear rubber or heavy plastic gloves when handling suspect foods or cleaning up contaminated work surfaces and equipment.
A fresh solution of 1 part unscented liquid household chlorine bleach (5 to 6% sodium hypochlorite) to 5 parts clean water should be used to treat work surfaces, equipment, or other items, including can openers and clothing, that may have come in contact with suspect foods or liquids. Spray or wet contaminated surfaces with the bleach solution and let stand for 30 minutes.
Wear gloves and wipe up treated spills with paper towels being careful to minimize the spread of contamination. Dispose of these paper towels by placing them in a plastic bag before putting them in the trash. Apply the bleach solution to all surfaces and equipment again, and let stand for 30 minutes and rinse.
As a last step, thoroughly wash all detoxified counters, containers, equipment, clothing, etc. Discard gloves when cleaning process is complete. Bleach is an irritant itself and should not be inhaled or allowed to come in contact with the skin.