08 July, 2011
Botulism Risk of Canned Beans
Food-borne botulism is increasingly uncommon, but it still occasionally occurs with improperly preserved food, such as beans. Botulinum toxin causes severe illness with paralysis, which can result in long-term illness or death. Proper food handling and preservation dramatically decrease your risk of exposure to botulism poisoning.
Clostridium Botulinum and Food-Borne Illness
Botulism is an illness caused by the nerve toxin produced by the bacterium Clostridium botulinum, widely found in soil and stream bottoms. Roughly 20 to 30 cases of food-borne botulism occur each year in the United States, most often from home canned foods, such as green beans and other vegetables, according to the Centers for Disease Control and Prevention. Extremely small amounts of toxin can cause severe symptoms, usually beginning within six to 36 hours of eating contaminated food. Early symptoms of botulism include double or blurred vision, drooping eyelids, slurred speech and muscle weakness, followed by paralysis and respiratory failure in severe cases. The fatality rate with advanced medical care is 5 percent or less, as opposed to a fatality rate of 50 percent from 50 years ago.
High-Risk Food Sources
Food-borne botulism results from eating improperly preserved foods that contain the botulinum toxin. Almost any food that has come in contact with soil could carry the bacteria, but poorly canned low acidity vegetables and processed meats encourage the growth of the bacteria and represent the greatest risk. Canned green beans, garbanzo and kidney beans, asparagus, corn, herbs and olives are just a few examples of vegetables commonly linked to botulism. The C. botulinum bacteria growing in the food produce the toxin, but food-borne botulism is not an infection and cannot be spread from person to person.
Preserving to Prevent Botulism
C. botulinum bacteria and their spores are very heat resistant and can survive food processing that would kill most other types of bacteria. Incomplete or irregular heating methods, more likely to be found in small home kitchens than commercial sites, can allow the bacteria to survive and produce toxin in the low-oxygen environment of canned foods. Adequate cooking times, appropriately high temperatures, maintaining the acid pH of canned food, use of preservatives and pressure cooking techniques are all important to lowering your risk of exposure to botulism.
Several simple steps can greatly reduce your risk of botulism from canned beans or other foods. Clean all your food carefully before processing or cooking, and be sure to follow all recommended processing steps, according to published guidelines when preserving food. Before eating canned foods, inspect the container for bulging, leakage, built-up pressure or strange odor. Any worrisome appearance or smell should prompt you to immediately throw the food away. The botulinum toxin itself is sensitive to heat, so cooking canned foods for at least 10 minutes at temperatures above 176 degrees Fahrenheit, and longer at higher elevations, will destroy the toxin, according to Colorado State University Extension. Following all these steps should greatly reduce your risk of botulism from canned beans, as well as other canned foods.
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