The 1950s to the mid-1980s was the first period of development. This period began with the manufacture of simple air extractors. At that time, there were less than 20 companies producing vacuum equipment in the country, and the products were mainly medium and low-grade vacuum equipment, such as mirror coating machines and cigarette packaging machines. The late 1980s to the entire 1990s is the second period of China's vacuum industry development. During this period, the number of production enterprises increased to nearly 3,000, with 35,000 employees. After the "Seventh Five-Year Plan" and "Eighth Five-Year Plan" technical transformation, the overall level of the entire vacuum industry has been greatly improved. In terms of processing conditions, advanced production equipment such as CNC machine tools for machining centers and resin sand castings have begun to equip enterprises. By 1996, due to the pull of the magnesium smelting industry, the vacuum industry developed rapidly.
The main function of vacuum packaging is to remove oxygen to help prevent food from spoiling. The principle is relatively simple. The mold and spoilage of food are mainly caused by the activities of microorganisms, and most microorganisms (such as molds and yeasts) need oxygen to survive. Yes, and vacuum packaging uses this principle to extract oxygen in the packaging bag and food cells, so that microorganisms lose their living environment. Experiments show that when the oxygen concentration in the packaging bag is less than or equal to 1%, the growth and reproduction speed of microorganisms will drop sharply. When the oxygen concentration is less than or equal to 0.5%, most microorganisms will be inhibited and stop reproducing. (Note: Vacuum packaging cannot inhibit the growth of anaerobic bacteria and the deterioration and discoloration of food caused by enzyme reactions, so it needs to be combined with other auxiliary methods, such as refrigeration, quick freezing, dehydration, high temperature sterilization, irradiation sterilization, microwave sterilization, salt Pickled etc.)
In addition to inhibiting the growth and reproduction of microorganisms, vacuum deaeration has another important function to prevent food oxidation. Because fats and oils contain a large amount of unsaturated fatty acids, they are oxidized by the action of oxygen, which makes food taste and deteriorates. In addition, oxidation also causes Vitamin A and C are lost, and the unstable substances in food pigments are affected by oxygen to darken the color. Therefore, deoxygenation can effectively prevent food from spoiling.
In addition to the oxygen-removing and quality-preserving functions of vacuum packaging, vacuum inflatable packaging also has the functions of compression resistance, gas barrier, and preservation, which can more effectively maintain the original color, aroma, taste, shape and nutrition of food for a long time. value.
In addition, many foods are not suitable for vacuum packaging and must be vacuum-filled packaging. Such as crispy and fragile foods, foods that are easy to agglomerate, foods that are easy to deform and run out of oil, foods with sharp edges or corners or high hardness that will pierce the packaging bag. After the food is vacuum-inflated and packaged, the inflation pressure inside the packaging bag is stronger than the atmospheric pressure outside the packaging bag, which can effectively prevent the food from being crushed and deformed under pressure without affecting the appearance of the packaging bag and printing decoration.
The vacuum inflatable package is filled with a single gas such as nitrogen, carbon dioxide, and oxygen or a mixture of two or three gases after being vacuumed. Nitrogen is an inert gas, which plays a filling role and keeps positive pressure inside the bag to prevent air outside the bag from entering the bag and protect the food. The carbon dioxide can dissolve in various fats or water, and it can be turned into weakly acidic carbonic acid, which has the activity of inhibiting mold, spoilage bacteria and other microorganisms. The oxygen can inhibit the growth and reproduction of anaerobic bacteria and keep the freshness and color of fruits and vegetables. The high concentration of oxygen can keep fresh meats bright red.
