Food Safety Facts
A Fact Sheet for People Who Prepare Food

University of Maine Cooperative Extension
Bulletin #4273

Using Home-Preserved Food Safely

Preserving foods at home by canning, freezing or drying can save you money and provide nutritious meals for the future. However, home-preserved foods can spoil (see Bulletin #4277 "Can Home-Canned Foods Spoil?").  Spoiled foods may contain microorganisms that can make you sick. Food poisoning can cause vomiting, stomach cramps and flu-like symptoms. Children and elderly people may experience more severe symptoms, even death. This fact sheet will explain steps you can take to use home-preserved foods safely.

Canned Foods Examine them. Here are some tips on how to check canned foods.

Inspect the can before opening it.   If it is a glass jar, the metal lid should be firm and flat or curved slightly inward. There should be no sign of leakage around the rubber seal. If there is mold around the outside neck of the jar, there may be mold inside. Check for signs of "gassiness," including floating food, bubbles rising in the food or a swollen can lid.

As the jar is opened, notice whether there is an inrush or an outrush of air.  Air rushing out or liquid spurting out indicates spoilage.

Smell the contents at once.  The odor should be characteristic of the food. An "off" odor probably means spoilage (acid, acrid, sour, putrid, etc.).

Check the food carefully to see that it has a normal texture and color.  Liquids in all foods should be clear. Any change from the natural texture or color of the food indicates spoilage. Do not taste any questionable food.

Discard canned food with signs of spoilage.   If it is a high-acid food (fruit or tomatoes), throw it in the garbage or garbage disposal. If it is a low-acid food (vegetables, meat, fish, or poultry), it must be discarded more carefully because it could contain botulinal toxin. Be careful not to contaminate your work area by spilling the food. Wear rubber gloves when handling the food or containers. Then dispose of it in one of the following ways: 1) boil at full rolling boil for 20 minutes and discard; 2) burn; or 3) mix the food with 1 to 2 Tablespoons household lye or 1 cup chlorine bleach in a non-metal container, and let stand overnight. Flush it down the toilet or discard it in garbage or garbage disposal.

NOTE:  Any containers or utensils that come in contact with spoiled canned foods should be washed carefully. Use soap and hot water to wash containers used for high-acid foods. Containers that come into contact with low-acid foods should be sterilized with chlorine bleach or boiled for 20 minutes. Discard all lids, screw bands, washcloths, sponges and rubber gloves used while detoxifying low-acid foods.

As a safety precaution, boil all canned low-acid foods (meats, fish, poultry, vegetables), before tasting them. Boiling destroys any botulinal toxin, if it is present. Boil most vegetables for 10 minutes at a full, rolling boil. Boil thick vegetables (potatoes) for 20 minutes. Boil meat, fish and poultry for 15 minutes.

Frozen Foods

Food is safe from spoilage as long as it stays frozen. Microorganisms can start to grow as soon as food begins to thaw. To keep microbial growth at a minimum, thaw frozen foods in the refrigerator. Thawed food may be safely refrozen if ice crystals are still present in the food. However, refreezing often changes the quality of food (texture, color, flavor). Microorganisms that can make you sick may not be killed by freezing, so food that’s not safe to begin with won't be safe after it's frozen, either.

Dried Foods

Dried foods that take more than one to two hours to rehydrate or reconstitute, should be rehydrated either in the refrigerator or in simmering water to prevent the growth of microorganisms. Once vegetables are rehydrated, they will support the growth of Clostridium botulinum, so they must be handled safely. Discard any dried foods with signs of spoilage or mold.

By Mahmoud El-Begearmi, Extension professor, nutrition and food safety 

For more information about food safety, contact your University of Maine Cooperative Extension county office.

Published and distributed in furtherance of Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

Return to Publications Catalog Online Table of Contents
Return to Publications Homepage

Putting knowledge to work with the people of Maine

A Member of the University of Maine System
Last Modified: 08/12/08
These pages are currently being maintained from the
Communications Office, University of Maine Cooperative Extension.
Send comments, suggestions or inquiries to www-questions@umext.maine.edu  

COUNTY OFFICES | PROGRAMS | RESOURCES | PUBLICATIONS | NEWS AND EVENTS | UMAINE EXTENSION HOME  | UMAINE