Vacuum packaging machine function and working principle
Working process of vacuum packaging machine:1. Vacuum: the vacuum chamber is closed, the vacuum pump works, the vacuum chamber starts to evacuate, the packaging bag is vacuumed at the same time, the vacuum gauge pointer rises, and the rated vacuum degree is reached (controlled by the time relay ISJ). The vacuum pump stops working and the vacuum stops. While the vacuum is working, the two-position three-way solenoid valve IDT works, the heat sealing air chamber is vacuumed, and the heat pressing frame remains in place.
2. Heat sealing: IDT is disconnected, the outside atmosphere enters the heat sealing air chamber through its upper air inlet hole, and the heat sealing air chamber is inflated by the pressure difference between the vacuum chamber and the heat sealing air chamber, so that the upper heat pressing frame moves down and presses the bag mouth; at the same time, the heat sealing transformer works and starts sealing; at the same time, the time relay 2SJ works, and it acts after a few seconds, and the heat sealing ends.
3. Return air: the two-position two-way solenoid valve 2DT is open, the atmosphere enters the vacuum chamber, the vacuum gauge pointer returns to zero, the heat pressing frame is reset by the reset spring, and the vacuum chamber is opened.
4. Cycle: Move the above vacuum chamber to another vacuum chamber, that is, enter the next working process, and the left and right chambers work alternately and cyclically.
The main function of the vacuum packaging machine is to deoxygenate, which is beneficial to prevent food spoilage. Its principle is also relatively simple, because food mold and spoilage are mainly caused by the activities of microorganisms, and most microorganisms (such as molds and yeasts) need oxygen to survive. Vacuum packaging uses this principle to remove oxygen from the packaging bag and food cells, so that microorganisms lose their living environment. Experiments have shown that when the oxygen concentration in the packaging bag is ≤1%, the growth and reproduction rate of microorganisms will drop sharply. When the oxygen concentration is ≤0.5%, most microorganisms will be inhibited and stop reproducing.
Note: Vacuum packaging cannot inhibit the reproduction of anaerobic bacteria and food spoilage and discoloration caused by enzyme reactions. Therefore, 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, another important function of vacuum deoxygenation is to prevent food oxidation. Because oily foods contain a large amount of unsaturated fatty acids, they are oxidized by oxygen, causing the food to change taste and deteriorate. In addition, oxidation also causes the loss of vitamins A and C. The unstable substances in food pigments are affected by oxygen, causing the color to darken. Therefore, deoxygenation can effectively prevent food from deteriorating.
In addition to the deoxygenation and preservation functions of vacuum packaging, vacuum inflation packaging also has the functions of pressure resistance, air barrier, and preservation, which can more effectively keep the original color, aroma, taste, shape and nutritional value of food for a long time.
In addition, many foods are not suitable for vacuum packaging and must be vacuum inflation packaging. Such as crispy and fragile foods, foods that are easy to agglomerate, foods that are easy to deform and leak oil, foods with sharp edges or high hardness that will puncture the packaging bag, etc. After the food is vacuum-inflated and packaged, the inflation pressure in the packaging bag is greater than the atmospheric pressure outside the packaging bag, which can effectively prevent the food from being crushed and deformed under pressure and does not affect the appearance and printing decoration of the packaging bag.
Vacuum packaging is filled with nitrogen, carbon dioxide, oxygen or other single gases or a mixture of two or three gases after vacuuming. Nitrogen is an inert gas and plays a filling role, keeping the bag at a positive pressure to prevent air from entering the bag, thus protecting the food. Carbon dioxide can dissolve in various fats or water, and form weakly acidic carbonic acid, which has the activity of inhibiting mold, spoilage bacteria and other microorganisms. Oxygen can inhibit the growth and reproduction of anaerobic bacteria, keep fruits and vegetables fresh and colorful, and high concentration of oxygen can keep fresh meat bright red.
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