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Date: May 1989 (Reviewed June 1996)

Source: University of Wisconsin

Botulism is a deadly form of food poisoning. It is caused by a toxin produced in food by a micro-organism which lives in soil all over the world. The organism has the ability to form a spore, or case, around itself that is resistant to heat and chemicals.

For botulism to occur, there must be several conditions. First of all, the spores must be present in a low-acid food. Then a person must can or process the foods in some way that removes air, but does not use enough heat to destroy the spores. In low-acid foods, and in the absence of oxygen, the spores grow and produce a toxin that is one of the most potent known. When there is enough acid present, as in most pickles or fruits, the spores cannot grow.

Foods commonly involved in botulism outbreaks are home canned low-acid vegetables, sauces and soups, meats, fish or poultry that have been insufficiently heated during canning. Examples of low-acid vegetables include peas, peppers, corn, lima beans, green beans and mushrooms. Mixtures of acid and low acid foods, such as salsa, are often low acid.

Botulism symptoms include difficulty in swallowing, speech and respiration and double vision. Death results from paralysis of respiratory muscles, unless the correct antitoxin is administered immediately.

To prevent botulism, discard all canned food that shows any signs of spoilage. Discard all bulging or swollen cans of food, and food from glass jars with bulging lids. Do not taste food from swollen containers, or food that is foamy or has a bad odor. Discard food in a way that prevents humans or animals from eating it.

Can low-acid foods at temperatures above the boiling point, and follow the recommended times for the size of container you use. This means you must can low-acid foods in a pressure canner. Do not can low-acid food in the oven, in a boiling water bath canner or by open kettle methods or in a microwave oven. If you know, or suspect, that home canned low-acid foods may not have been pressure canned long enough, discard them without tasting, and in a way that prevents humans or animals from eating them.

If you need additional information, please contact your county office of the NDSU Extension Service.

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