Botulism is a rare, life-threatening paralytic illness caused by neurotoxins produced by an anaerobic, gram-positive, spore-forming bacterium, Clostridium botulinum. Classic symptoms of botulism include nausea, vomiting, fatigue, dizziness, double vision, drooping eyelids, slurred speech, difficulty swallowing, dryness of skin, mouth, and throat, lack of fever, muscle weakness, and paralysis.
Although the toxin is destroyed by heating to 85° C. for at least five minutes, the spores formed by the bacteria are not inactivated unless the food is heated under high pressure to 121° C. for at least twenty minutes. Most of the botulism events that are reported annually in the United States are associated with home-canned foods that have not been safely processed. Very occasionally, however, commercially- processed foods are implicated as the source of a botulism events, including sausages, beef stew, canned vegetables, and seafood products.
The canning process dates to the late 18th century in France when the Emperor Napoleon Bonaparte, concerned about keeping his armies fed, offered a cash prize to whoever could develop a reliable method of food preservation. Nicholas Appert conceived the idea of preserving food in bottles, like wine. After fifteen years of experimentation, he realized if food is sufficiently heated and sealed in an airtight container, it will not spoil. More than fifty years later, Louis Pasteur provided the explanation for effectiveness of canning when he was able to demonstrate that the growth of microorganisms is the cause of food spoilage.
An Englishman, Peter Durand, took the idea one step further and replaced the breakable glass bottles with cylindrical tinplate canisters (later shortened to “cans”). Durand did not can foods himself, but sold his patent to two other Englishmen, Bryan Donkin, and John Hall, who set up a commercial canning factory. By 1813, Donkin and Hall were busily producing their first canned goods for the British army, thus continuing the connection of canning to the military.
The basic principles of canning have not changed dramatically since Nicholas Appert and Peter Durand developed the process. Heat sufficient to destroy microorganisms is applied to foods packed into sealed, or “airtight” containers. The canned foods are then heated under steam pressure at temperatures of 240-250°F (116-121°C). The amount of time needed for processing is different for each food, depending on the food’s acidity, density, and ability to transfer heat.
Processing conditions are chosen and designed to be the minimum needed to ensure that the foods are made “commercially sterile,” while still retaining the greatest flavor and nutrition. All canning-processes must first be approved by the U.S. Food and Drug Administration. Once the cans are sealed and heat processed, the resulting canned food must maintain its high eating quality for more than two years and be safe to eat if the can is not damaged in any way. Historically, commercially canned food has a near-perfect track record, having caused only four outbreaks in over forty years.