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Organisms that cause food spoilage—molds, yeasts, and bacteria—are
always present in the air, water, and soil. Enzymes that may cause
undesirable changes in flavor, color, and texture are present in raw
fruits and vegetables.
When you can fruits and vegetables you heat them hot enough and long
enough to destroy spoilage organisms. This heating (or processing) also
stops the action of enzymes. Processing is done in either a
boiling-water-bath canner or a steam-pressure canner. The kind of canner
that should be used depends on the kind of food being canned.