How Canning Preserves Foods

How Canning Preserves Foods

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.

Credit: NCHFP