Michigan State University Extension
Preserving Food Safely - 01600936
10/13/97
The high percentage of water in most fresh foods makes
them very perishable. They spoil or lose their quality for
several reasons:
* growth of undesirable microorganisms--bacteria,
molds, and yeasts.
* activity of food enzymes.
* reactions with oxygen.
* moisture loss.
Microorganisms live and multiply quickly on the
surfaces of fresh food and on the inside of bruised, insect-
damaged, and diseased food. Oxygen and enzymes are present
throughout fresh food tissues.
Proper canning practices include:
* carefully selecting and washing fresh food.
* peeling some fresh foods.
* hot packing many foods.
* adding acids (lemon juice or vinegar) to some
foods.
* using acceptable jars and self-sealing lids.
* processing jars in a boiling-water or pressure
canner for the correct period of time.
Collectively, these practices remove oxygen; destroy
enzymes; prevent the growth of undesirable bacteria, yeasts,
and molds; and help form a high vacuum in jars. Good
vacuums form tight seals which keep liquid in and air and
microorganisms out.