Vacuum packaging is to extract all the air from the packaging container and seal it so as to keep the bag in a highly decompressed state. The scarcity of air is equivalent to the effect of hypoxia, so that microorganisms have no living conditions, so as to achieve the goal of keep meat & seafood fresh, extend food shelf life, no more fast rot . At present, the application of vacuum packaging are in plastic bags, aluminum foil packaging, glassware, plastic and its composite materials packaging, etc. Packaging materials can be selected according to the type of articles. Because fruits are fresh food and are still breathing, high hypoxia can cause physiological diseases, so the use of vacuum packaging for fruits is not popular.
Vacuum packaging is to protect products from environmental pollution and extend the shelf life of food, which can improve the value and quality of products. Vacuum packaging technology originated in the 1940s. Vacuum packaging machines developed rapidly since 1950s with the application of polyethylene films. From semi automatic chamber vacuum sealers to fully automatic thermoforming packaging machines, the technology has been improving since then. In the field of people’s life and work, various kinds of plastic vacuum packaging are applied everywhere. Portable, sealed, fresh-keeping, anticorrosive and rust-proof plastic vacuum packaging covers many fields, such as food, medicine, knitwear, precision product manufacturing, metal processing plants and laboratories. The application of plastic vacuum packaging is more and more extensive, which promotes the development of plastic vacuum packaging machine, and also puts forward higher requirements for it. Vacuum packaging mechanism: Its purpose is to reduce the oxygen content in packaging, prevent the mildew of packaged food from deteriorating, maintain the color and fragrance of food, and extend the shelf life. The main function of vacuum packaging is deoxygenation, in order to prevent food deterioration, its principle is relatively simple, because food mildew deterioration is mainly caused by the activities of microorganisms, and most microorganisms (such as molds and yeasts) need oxygen to survive, and vacuum packaging is the use of this principle, the packaging bag and food cells to extract oxygen, so that microorganisms lose.“ The living environment. Experiments show that when the oxygen concentration in the packaging bag is less than 1%, the growth and reproduction speed of microorganisms will decrease sharply. When the oxygen concentration is less than 0.5%, most microorganisms will be inhibited and stop breeding. (Note: Vacuum packaging can not inhibit the food deterioration and discoloration caused by anaerobic bacteria reproduction and enzymatic reaction, so it needs to be combined with other auxiliary methods, such as refrigeration, quick freezing, dehydration, high temperature sterilization, irradiation sterilization, microwave sterilization, salt pickling, etc.).
In addition to inhibiting the growth and reproduction of microorganisms, the other important function of vacuum oxygen is to prevent food oxidation, which is caused by the oxidation of unsaturated fatty acids in oily foods, which makes food taste and deteriorate. In addition, oxidation also causes the loss of vitamin A and C, and the effect of oxygen on unstable substances in food pigments, which darkens the color. Therefore, deoxygenation can effectively prevent food deterioration and maintain its color, aroma, taste and nutritional value.
The main function of vacuum air-filled packaging is not only the function of oxygen preservation, but also the function of anti-pressure, air-blocking and fresh-keeping. It can effectively keep the original color, fragrance, taste, shape and nutritional value of food for a long time. In addition, many foods are not suitable for vacuum packaging, but must be packed with vacuum inflation. For example, crunchy and fragile food, caking food, deformable and oily food, food with sharp edges or high hardness will puncture the packaging bags, etc. After food is packed by vacuum aeration, the air pressure inside the bag is stronger than that outside the bag. It can effectively prevent food from crushing and deformation without affecting the appearance of the bag and printing decoration. Air-filled packaging is filled with nitrogen, carbon dioxide, oxygen single gas or a mixture of two or three gases after vacuum. Nitrogen is inert gas, which fills the bag and keeps the positive pressure inside, so as to prevent air outside the bag from entering the bag and protect the food. Its carbon dioxide can dissolve in various kinds of fat or water, lead to weak acidity of carbonate, and inhibit the activity of microorganisms such as fungi and spoilage bacteria. Oxygen can inhibit the growth and reproduction of anaerobic bacteria, maintain the fresh and color of fruits and vegetables, and high concentration of oxygen can keep fresh meat bright red. Fruits and vegetables are fresh but nutritious.