Clostridium Botulinum (Spore Growth & Toxin Production)

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When home canned food is not sealed accurately and/or not processed properly, botulism (a deadly  type of food poisoning) can occur. By following a safe canning recipe, processing your jars using the correct method and processing for the time described in the recipe, then storing jars safely in a cool, dark and dry place, your jars of preserves and pressure canned food will retain flavour, freshness and prevent spoilage and prevent contamination during storage.
The bacterium spores of Clostridium botulinum is commonly found in soil and on the surface of fresh produce. As the spores multiply in an anaerobic ("no-oxygen") environment, the bacterium is harmless on fresh produce. However, the spores can survive dormant for several years in soil and water until conditions change.
When the bacterium is in an ideal environment they will produce vegetative cells, which produce the deadly botulin toxin within a few days. The botulin toxin is what causes botulism. The ideal environment for bacterium growth is one that is:
  • anaerobic (less than 2% oxygen)
  • temperature 40-120°F (5-49°C)
  • low acid (pH >4.6)   
Washing fruits and vegetables removes only a small amount of the bacteria, moulds and yeasts that are naturally found on fresh food. Peeling root vegetables greatly reduces their number. As vegetables are low acid, processing root vegetables at the correct temperature and length of time in a pressure canner is the best way to remove the risk of food poisoning in home canned food, or pickling vegetables instead (making them a high acid food).

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