Is It Safe to Eat?

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What's On This Page

Don't Become A Statistic

Safety First

Handling Spoiled Canned Food

Detoxification Process

Reasons Home-Canned Food Spoils

How To Check for Spoiled Canned Foods

How to Guard Against Canned Food Spoilage

How Long Are Canned Foods Safe

Don't Become A Statistic

Safe CanningThe CDC estimates that foodborne diseases cause approximately 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths in the United States each year, these figures do not include mild cases of food poisoning were patients did not seek medical care, or misdiagnosed cases. Most cases of food poisoning are associated with inadequately processed, home-canned foods.

The most serious and deadly form of foodborne illness is botulism, a severe type of food poisoning caused by the ingestion of foods containing a potent toxin that affects the nervous system. Although incidence of the disease is low, the mortality rate is high. This toxin is destroyed in low-acid foods when they are processed at the correct time and temperature in pressure canners.

Safety First

Don't taste or use food that shows any kind of spoilage. Look closely at all jars before opening them. A bulging lid or leaking jar is a sign of spoilage. When you open the jar, look for other signs, such as spurting liquid and off-odors or mold. Spoiled canned foods should be discarded in a place where they will not be eaten by humans or pets. Spoiled meats, seafood and low-acid vegetables, should be detoxified to destroy any poisons that might be present before they are discarded because the contents are lethal and could cause life threatening illness or even that to people who might com in contact with it later.

Before eating canned foods, be sure of the following:

  • Food was processed following a current, tested recipe following the recommendations from University Extension services, the USDA or the latest edition of the Ball Blue Book.
  • Food was processed in a pressure canner with a gauge that was checked at the beginning of the canning season.
  • Time and pressure were properly adjusted for altitude.
  • Ingredients or proportions of a tested and approved canning recipe were NOT added, altered or changed.
  • Process times and pressures matched the size of jar, style of pack and kind of food being canned.
  • Jar lid is firmly sealed and concave (curved inward).
  • Nothing has leaked from the jar.
  • No liquid spurts out when jar is opened.
  • No unnatural or "off" odors can be detected

Handling Spoiled Canned Food

Look closely at all jars of food before opening them. Do not eat food which shows signs of spoilage. Do not taste foods that show signs of spoilage or foods from a jar with unsealed lids. All suspect jars of spoiled low-acid foods, including tomatoes, should be treated as containing botulism toxin.

Growth of spoilage bacteria and yeast produces gas which pressurizes the food, swells lids, and breaks jar seals. 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 cottony mold growth (white blue, black, or green) on the top food surface and underside of lid.

Detoxification Process

Carefully discard any jar of spoiled food to prevent possible illness to you, your family, and pets. Detoxify unsealed, open, or leaking jars of food before disposal to prevent the spread of toxin

 

  • If suspect glass jars are still sealed, place them in a heavy garbage bag. Close the bag, and place it in a regular trash container or bury it.
  • If suspect jars are unsealed, opened or leaking, detoxify (destroy bacteria and toxin) as follows before disposal.   Place suspect jars of food, including lids, on their sides in an 8-quart volume (or larger) stock pot. Wash your hands thoroughly in hot soapy water. Carefully add water to the pan until it is at least one inch above the containers. Avoid splashing the water. Place a lid on the pot. Heat to boiling, and boil rapidly for at least 30 minutes to insure detoxification and destroy all bacteria and toxin. Cool and drain water and dispose of the containers, lids and food in the trash, or bury in soil to prevent accidental poisoning.
  • Thoroughly scrub all counters, containers, and equipment that may have touched the food or containers, and other equipment or utensils used in the process with a solution of 1 part chlorine bleach to 5 parts water. Wet the surface with this solution and let stand 5 minutes before rinsing.
  • Wash clothing in hot water and soap.
  • Wash hands thoroughly in hot water and soap .
  • Place sponges , wash cloths and towels that were used in clean-up in a plastic bag and discard them in the trash. Boil all items in the water for 30 minutes. Cool and discard jar contents in garbage or bury in soil. This will prevent accidental poisoning.

How To Check for Spoiled Canned Foods

Improperly canned low-acid foods can contain botulinum toxin without showing signs of spoilage. Low-acid foods are considered improperly canned and not safe if any of the following are true:

  • The food was NOT processed in a pressure canner.
  • The gauge of the canner was inaccurate.
  • Up-to-date researched processing times and pressures were NOT used for the size of the jar, style of pack and kind of food being processed.
  • Ingredients were added that were NOT in an approved recipe.
  • Proportions of ingredients were CHANGED from the original approved recipe.
  • The processing time and pressure were NOT correct for the altitude at which the food was canned.

Because improperly canned low-acid foods can contain botulinum toxin without showing signs of spoilage, they should also be detoxified and then discarded.

Reasons Home-Canned Food Spoils

Time, energy and money are lost when food spoils. There are several reasons home-canned foods spoil. The most common ones are: failure to heat process the filled jars, processing by an incorrect method, processing for insufficient time, and failure of lids to seal.

When you can low-acid vegetables and meat, you must use a pressure canner. Because the pressure canner keeps steam confined until it builds up pressure, it can build up temperatures above the boiling point. You need these high temperatures to destroy botulism spores that can cause food poisoning in low-acid foods. At 10 pounds pressure at sea level used in home pressure canning, you will get a temperature of 240 degrees F. Adjustments need to be made as altitude increases. You must maintain the recommended pounds of pressure throughout the processing period. If at any time during processing the pressure drops, the food will not be adequately processed. Whenever pressure drops below the recommended processing level, bring it back up and re-time for the entire period needed for the particular food.

In many old canning books, there are no instructions for heat processing jars of food after filling. The older books describe a canning method called "open-kettle canning", and spoilage with this method is quite common. Because the filled jars are not pasteurized or sterilized by heating after the lids are put on, molds, yeasts and bacteria survive and can cause food to spoil. The lids may seal at first, but later on become unsealed, indicating that food is spoiling. Do not use this method for any home-canned food. When foods canned in a pressure canner spoil, it is usually due to one of the following reasons:

  • An inaccurate dial gauge
  • Failure to vent steam from the canner for 10 minutes before closing the petcock or placing the weighted pressure control on the canner. This allows air to remain in the canner and temperatures will be lower than needed.
  • Fluctuating heat under the canner
  • Processing for too short a time

If you used a boiling water bath canner and canned food spoils, the cause could be failure to have water hot when you placed the jars in the canner, not having enough water to cover the tops of the jars by at least an inch, processing for too short a time, or processing low-acid foods with this method.

How to Guard Against Canned Food Spoilage

It is possible for canned foods to spoil, either due to improper heat processing or damage to the container. Examine the container of food before you open it. Cans with bulging ends or leaks or bulging, or unsealed jar lids indicate the possibility of spoilage. When you open a can, spurting or frothy liquid, mold or off-odors indicate possible spoilage. Do not use canned foods that show any of these signs of spoilage. Dispose of the food without tasting it, and do it in a way that will prevent consumption by other people or by animals.

Canned low-acid foods can contain the deadly toxin caused by growth of Clostridium botulinum bacteria, without showing any visible signs of spoilage. The risk of botulism is greater with home-canned foods than it is with commercially-canned products. There is no danger of botulism if you can low acid foods at the correct pressure, and for a sufficient time in a pressure-canner. But, if you are uncertain that you followed such procedures, it is best to boil home-canned vegetables and meats for 10 minutes before tasting. If the lids on jars of these low-acid foods are not sealed, or if you know that such foods were canned in a boiling water bath canner, do not use them under any conditions. Dispose of improperly processed home-canned foods in away that will prevent consumption by humans or animals.

How Long Are Canned Foods Safe

Tightly sealed, cooled jars are ready to be stored. Wash the lid and jar to remove food residue; rinse and dry jars. Label and date jars, and store them in a cool, dark, dry place (50-70 degrees F is ideal). Do not store jars above 95 degrees F or near hot pipes, a range, a furnace, in an uninsulated attic, or in direct sunlight. Under conditions such as these, food will lose quality rapidly and may spoil. Dampness may corrode metal lids, break seals, and allow contamination and spoilage. Plan to use home-canned food within one year for optimum quality and nutritional value.

Canned foods, whether in tins or glass jars, won't keep forever. Commercial canners work under tightly controlled conditions with careful sanitation and just the right heat and timing periods, but there are still limits to how long food quality can be preserved. Home-canned foods, processed under less carefully controlled conditions, may have even shorter storage lives.

There are several factors that limit the shelf-life of canned foods. First, 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 also cause container problems.

Then there is can corrosion. In all foods, especially high-acid foods like canned tomatoes and fruit juices, the food continually reacts chemically with the metal container. Over several years, this can cause taste and texture changes, and eventually lower the nutritional value of the food.

High temperature over 100 degrees F are harmful to canned foods, too. The risk of spoilage jumps sharply as storage temperatures rise. In fact, canned goods designed for use in the tropics are specially processed. Even at prolonged storage temperatures above 75 degrees F, the rate of nutrient loss in canned foods increases. Light can cause color changes and nutrient losses in foods canned in glass jars.

Never use foods from containers with these spoilage warning signs--loose or bulging lids on jars; bulging, leaking or badly dented cans, or foods with a foul odor. To store canned food wisely, follow these guidelines:

  • Store them in a cool, clean dry place where temperatures are below 85 degrees. A range of 60-70 degrees is even better.
  • Store canned hams in the refrigerator for use within six to nine months.
  • Low-acid canned foods may be stored in a cupboard for as long as two to five years. For top quality use before one year.
  • Use high-acid foods within 12 to 18 months. Foods stored longer will still be safe to eat if the cans show no signs of spoilage or damage,but the foods may have deteriorated in color, flavor and nutritive value.

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