Home Canning Magazine


Food Preservation - Spoilage Factors

All foods exposed to air at room temperature will spoil slowly unless preserved in some way.

Why food spoils

Food spoilage is the result of enzyme action and growth of microorganisms.

Enzymes

Enzymes are proteins found in all plants and animals. If uncooked foods are not used while fresh, enzymes cause undesirable changes in colour, texture and flavour. Enzymes are destroyed easily by heat processing.

Microorganisms

There are three types of microorganisms that cause food spoilage -- yeasts, molds and bacteria.

Clostridium botulinum is the spore-forming bacteria that is the cause of concern when home canning low acid foods. While the bacteria is destroyed at 100°C, it has the ability to form hardy spores that can survive boiling water processing. These spores can germinate and grow in a low acid environment in the absence of air. As they grow they give off a deadly toxin. Clostridium botulinum spores can be destroyed by heat processing at a temperature of 116°C. Foods that are low in acid such as meat, poultry, seafood or vegetables must be processed in a pressure canner in order to obtain temperatures of 116°C.

Clostridium botulinum is not a spoilage concern in high acid foods. The spores cannot grow or produce the deadly toxin in high acid foods. High acid foods can be safely heat processed in a boiling water canner.



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