Improperly canned food can result in the growth of botulism or other microorganisms. Eating such foods can cause serious illness and even death. For this reason it is important to strictly adhere to canning procedures as well as standards of cleanliness.
Clostridium botulinum spores are everywhere and eating them is not harmful to humans. It is when they grow in astronomical numbers in an ideal environment, such as an improperly canned jar of food, then begin to die off that they become a problem. They actually produce a neuro-toxin. It is this neuro-toxin that causes the effects of botulism.
Yet botulism and molds, viruses and bacteria that might grow in canned food can be effectively and easily controlled merely by taking simple precautions. Properly heating the jars and the food within them as well as proper sealing is the solution.
Since Clostridium botulinum prefers a low acid environment, high acid foods can be canned under less restrictive conditions using a boiling water canner. These foods have a pH of 4.5 or less. They include: apples, apricots, berries, jams, jellies, peaches, pears, pickles, sauerkraut, tomatoes, and more.
High pH (meaning low in acid) fruits and vegetables require a special device for canning called the pressure canner. The pressure canner can also be used for canning the high acid foods. Low acid foods include: Asparagus, beans, beets, carrots, corn, mushrooms, peas, potatoes, pumpkin, spinach, squash, most any meat.
It is not generally difficult to detect when a canning job has gone bad (done properly - this will seldom happen). The first sign that a can of food is no good is that the lid will pop up (or bulge), also there might be seeping around the seal. Mold growing on the surface of the food is a sure sign of a problem. Also abnormal colors in the brine of food, cloudiness in the brine, a white colored film on the surface of the food can all be indications of contaminated food.
Do not eat contaminated food. It invariably will cause harm. Reheating the food, even boiling it for long periods is not a solution as botulism is not the living part of the Clostridium botulinum, but a byproduct of its life-cycle.
Some traditional methods are NOT recommended such as open kettle canning, paraffin wax sealing, oven or microwave canning.
A final helpful hint regarding safety: It is best to store canned foods at relatively low temperatures as this helps to prevent any activity by microorganisms that might have survived the heating process. Keeping cans in dark, cool places also helps to preserve vitamins and taste.
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