Milk should not be frozen, because after freezing, the fat and protein in milk are separated, and the casein is powdered and coagulated, so the taste of milk will be significantly weakened, and the nutrients are not easily absorbed. Generally speaking, milk can be drunk after freezing. But after milk is frozen in the refrigerator, the nutritional value will be reduced. Because the main components of milk is protein, calcium and some animal-derived vitamins, and milk in the freezing process will have a small amount of vitamins are oxidized loss, protein will be denatured, but after thawing will restore the original state, calcium remains unchanged. So the nutritional value will be reduced, but does not affect consumption. Milk contains three kinds of water with different properties, among which free water is the most, not combined with other substances, and only plays the role of solvent. Crystallized water is water that exists as lactose crystals, and bound water is water that combines with proteins, lactose and salt and freezes without dissolving other substances. When milk is frozen, the free water freezes first, while the proteins, fats and other substances wrapped in it do not freeze. The longer the milk is frozen, the easier it is for the proteins to precipitate, solidify and deteriorate after thawing. So milk should not be frozen, the most suitable temperature to save milk is 2 ℃ -3 ℃.