Principle of vacuum bag.

Vacuum bag, also known as vacuum packaging, is based on the principle of atmospheric pressure, the main role of the vacuum bag is to deoxygenate, in order to help prevent food spoilage. Vacuum packaging is the process of pumping out the oxygen in the packaging bag and food cells with a pump, so that microorganisms lose their "living environment". Vacuum bags can also prevent food oxidation, so that food does not change taste, deterioration to reduce the loss of vitamin A and C.

Vacuum packaging materials commonly used double layer composite film or three layers of aluminum thin composite film made of three sealing bags. Vacuum packaging machine commonly used cavity type and external pumping type two models. China's vacuum packaging technology was developed in the early 1980s, and vacuum inflatable packaging technology began to be used in the early 1990s.

Vacuum packing is pumped vacuum, and then filled with nitrogen, carbon dioxide and other gases. Nitrogen is an inert gas, which plays a filling role, so that the vacuum bag maintains positive pressure to prevent the air outside the bag from entering the bag, and plays a protective role for food. Carbon dioxide has the active effect of inhibiting fungi, spoilage bacteria and other microorganisms. Some foods such as brittle and fragile food, easy deformation oil food, sharp edges or high hardness will puncture vacuum bags and other foods, after vacuum inflation packaging, the pressure of inflation in the vacuum bag is greater than the atmospheric pressure outside the bag, which can effectively prevent the food from crushing and deformation under pressure, and does not affect the appearance of the bag and printing and decoration. With the promotion of small vacuum bag packaging and the development of supermarkets, its scope of application will be more and more extensive, and some will gradually replace hard packaging.

Vacuum in addition to oxygen in addition to inhibiting the growth and reproduction of microorganisms, another important function is to prevent food oxidation, because fat foods contain a lot of unsaturated fatty acids, oxidized by the action of oxygen, so that food taste, deterioration. In addition, oxidation also causes the loss of vitamin A and vitamin C, and unstable substances in food coloring are affected by oxygen, which darkens the color. Therefore, deoxygenation can effectively prevent food deterioration and maintain its color, aroma, taste and nutritional value.