Microbes Related to Canned Foods

Canning is intended to destroy harmful microbes in food, however, with improper handling, cans become bacterial breeding grounds. This occurs most frequently with home-canned vegetables that are initially contaminated by the soil in which they grow and subsequently heated to a temperature insufficient for killing the microbes. Negligence at commercial canneries occasionally results in contamination. Not all bacteria, though, is bad. In some cases, microbe growth in canned food is actually encouraged.

Clostridium Botulinum

• Known better as botulism, this microbe is the most common type of bacterium found in canned foods. Originally it was associated with eating bad sausage, hence the name, which comes from the Latin for sausage (botulus). Today, however, botulism is contracted most often from dirty vegetables. Symptoms include dizziness and fatigue, but death can result if not treated with an antitoxin. A good rule of thumb is to never eat from a can that is bulging, as this is an indication of bacteria releasing carbon dioxide.

Bacillus Stearothermophilus

• In 1968, researchers identified this flat sour spore as the cause of spoilage in many cans of Taiwanese asparagus. Bacillus stearothermophilus can survive in a range of climates from cold water to hot soil. In canned food, it causes the pH level to drop. With less acid to counter bacterial growth, microbes rapidly reproduce and sour the product.

Bacillus Coagulans

• This is another type of flat sour spore. Unlike bacillus stearothermophilus, it does not thrive in a wide range of environs, but does replicate itself in highly acidic canned foods. The National Canners Association started studying flat sour spores in the 1930s. Their increased understanding of these organisms helped increase the shelf life of canned food. While flat sour spores compromise the flavor of canned foods, this type of microbe poses no threat to human health.

Lactobacillus Brevis

• Sauerkraut isn't so sour without the help of microbes.

  Sometimes microbes are actually encouraged in the production of certain foods. Take, for example lactobacillus brevis, a type of lactic acid bacteria, which brings about the fermentation necessary to give sauerkraut and kimchi their mouth-puckering flavor. This probiotic actually has a positive effect on the human digestive system, though individuals with compromised immune systems are cautioned against over-consumption.