Question

describe the principal on which the following methods of food preservation are based : 1) boiling, 2) canning,3) freezing, 4) dehydration

Answer 1

a) Boiling kills of bacteria because bacteria spoils food.

All acidic foods- fruits, pickled vegetables, sugar preserves, and tomatoes with a little added acidity (lemon juice, vinegar, or citric acid) - may be safely processed in a boiling water bath. In boiling water bath canning, it is the acidity of the ingredients as much as the heat of the processing that safely preserves the food.

b) Canning, or jarring is one of the most popular food preservation methods, and it has the advantage of letting you store food at room temperature for many months.

c) freezing prevents degradation from inadequate preparation and cooking. so that the food can last for a long time.

d) Dehydration is pretty straight forward and involves reducing the water content of food. Removing moisture from food inhibits various bacteria and molds from growing and spoiling it. The water content of food is typically very high - 80% to 95% for various fruits and vegetables. Dehydration reduces the water content down to 10-15%.