Michigan State University Extension
Preserving Food Safely - 01600937
10/13/97
Growth of the bacterium CLOSTRIDIUM BOTULINUM in canned
food may cause botulism--a deadly form of food poisoning.
These bacteria exist either as spores or as vegetative
cells. The spores, which are comparable to plant seeds, can
survive harmlessly in soil and water for many years. When
ideal conditions exist for growth, the spores produce
vegetative cells which multiply rapidly and may produce a
deadly toxin within 3 to 4 days of growth in an environment
consisting of:
* a moist, low-acid food.
* a temperature between 40 and 120 degrees Fahrenheit.
* less than 2 percent oxygen.
Botulinum spores are on most fresh food surfaces.
Because they grow only in the absence of air, they are
harmless on fresh foods.
Most bacteria, yeasts and molds are difficult to
remove from food surfaces. Washing fresh food reduces their
numbers only slightly. Peeling root crops, underground stem
crops, and tomatoes reduces their numbers greatly.
Blanching also helps, but the vital controls are the method
of canning and making sure the recommended research-based
process times are used.
The recommended processing times ensure destruction of
the largest expected number of heat-resistant microorganisms
in home-canned foods. Properly sterilized canned food will
be free of spoilage if lids seal and jars are stored below
95 degrees Fahrenheit. Storing jars at 50 to 70 degrees
Fahrenheit enhances retention of quality.