There are limits to how long food quality can be preserved
Why? Several factors limit the shelf-life of canned foods.
- Cans or metal lids on glass jars can rust. When rust is deep enough, tiny holes open in the can or lid that may let spoilage agents in. Shipping accidents that dent or crush cans cause problems.
- Can corrosion. Food reacts chemically with the metal container, especially high-acid food like canned tomatoes and fruit juices. Over several years, this causes taste and texture changes. It eventually lowers the nutritional value of the food.
- Temperatures over 100 degrees F are harmful to canned foods. The risk of spoilage jumps sharply as storage temperatures rise. At prolonged storage temperatures above 75 F, nutrient loss in canned foods increases. Light can cause color changes and nutrient losses in foods canned in glass jars.
To store canned food wisely, follow these guidelines
- Store in a cool, clean, dry place where temperatures are below 85 F (between 50-70 F is good) but not freezing temperatures.
- Rotate foods so the oldest is used first. Try not to keep canned foods more than 1 year.
- Use canned meats and seafood within 3 years of the date on the package.
- Use low-acid canned foods like vegetables and soup within 3 years of the date on the package.
- Use high-acid foods like fruit, pickles and tomatoes within 2 years of the date on the package.
- Canned fruit juices can be stored up to 1 year.
- Foods stored longer will be safe to eat if the cans do not show signs of spoilage or damage, but the foods may deteriorate in color, flavor and nutritional value.
If lids are tightly vacuum-sealed on cooled jars:
- Remove screw bands.
- Wash the lid and jar to remove food residue.
- Rinse and dry jars.
- Label and date the jars.
- Store them in a clean, cool, dark, dry place.
- Don’t store jars above 95 F. Don’t store near hot pipes, a range, a furnace, in an uninsulated attic, or in direct sunlight. Under these conditions, food will lose quality in a few weeks or months and may spoil.
- Dampness may corrode metal lids, break seals, and allow recontamination and spoilage.
Accidental freezing of canned foods will not cause spoilage unless jars become unsealed and recontaminated. However, freezing and thawing may soften food. If jars must be stored where they may freeze, wrap them in newspapers, place them in heavy cartons, and cover with more newspapers and blankets.
Identifying and handling spoiled canned foods
Do not taste food from a jar with an unsealed lid or food which shows signs of spoilage. You can more easily detect some types of spoilage in jars stored without screw bands. Growth of spoilage bacteria and yeast produces gas which pressurizes the food, swells lids and breaks jar seals.
Spoilage warning signs
Never use foods from containers with these signs:
- Loose or bulging lids on jars.
- Bulging, leaking or badly dented cans (especially along the top, side and bottom seams).
- Foul odor.
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Check each jar thoroughly
- As each stored jar is selected for use, examine its lid for tightness and vacuum. Lids with concave centers have good seals.
- Next, while holding the jar upright at eye level, rotate the jar and examine its outside surface for streaks of dried food originating at the top of the jar.
- Look at the contents for rising air bubbles and unnatural color.
- While opening the jar, smell for unnatural odors and look for spurting liquid and cotton-like mold growth (white, blue, black or green) on the top food surface and underside of lid.
Carefully detoxify and discard spoiled food
Carefully discard any jar of spoiled food to prevent possible illness to you, your family and pets. You must detoxify the container, lid and all the contents before disposal. Follow this process if you suspect spoiled food:
- Place container with contents and lid on their sides in an 8-quart or larger stock pot, pan or boiling-water canner.
- Wash your hands thoroughly.
- Add water to the pot so it is 1 inch or more above everything in the pot. Avoid splashing the water.
- Place a lid on the pot and heat the water to boiling.
- Boil 30 minutes to ensure detoxification of the food, container and lids.
- Cool and discard the food, container and all container components, such as lids, in the trash or bury in soil.
- Take care that animals or children can’t get in contact with the disposed food and containers.
- Thoroughly wash all counters, containers and equipment including can opener, clothing and hands that may have been in contact with the food or containers.
- Discard any sponges or washcloths used in cleaning.
- Place everything in a plastic bag and discard in the trash where they’re unreachable by animals and children. This will prevent accidental poisoning.
Estimating the amount to can
The amount of food to can or freeze for your family should be decided by your family. The following formula might be helpful in calculating your needs:
- Determine serving size (see suggested serving size list below).
- Multiply serving size by the number of family members who will be eating this food.
- Then multiply this by your estimate of the number of servings per week, per person.
- Multiply this figure by 52 weeks to get a total amount necessary to preserve in one year.
- To get this amount in quarts, divide the number by 4.
- Fruit - ½ cup suggested serving.
- X 4 family members = 2 cups.
- 2 cups X 3 servings per week per person = 6 cups/week.
- 6 cups X 52 weeks/year = 312 cups.
- Divided by 4 = 78 quarts.
Suggested serving size for different foods:
- Fruits - ½ cup.
- Juices - 1 cup.
- Vegetables - ½ cup.
- Meat and seafood - ½ cup.
- Soups - 1 cup.
- Sauces - ½ cup.
Reviewed in 2018