Vacuum packaging is a common way of food packaging, to extend the shelf life as a selling point, has been favored by numerous manufacturers and consumers. Many people believe that vacuum-packed food will not go bad within the shelf life, without paying attention to storage conditions. But in fact, vacuuming without refrigeration can be even more dangerous.
Vacuum pumping principle
Vacuum packaging is to remove the oxygen in the package and prevent the contents from changing. The principle is also relatively simple, because food mold spoilage is mainly caused by microbial activities, and most microorganisms (such as mold and yeast) need oxygen to survive, when oxygen concentration is less than 1%, the growth and reproduction of these microorganisms will be effectively inhibited. Vacuum packaging is to use this principle, to remove the oxygen in the packaging bag and food cells, so that microorganisms lose the living environment.
Vacuum packing is not foolproof
In fact, vacuum packed food is not absolutely safe. The safety of vacuum packaging is affected by many conditions. Any unqualified link will affect the safety of food. Any perishable food that needs to be refrigerated should still be refrigerated or frozen after vacuum packaging. Vacuum packaging is not an alternative to refrigeration or freezing. Vacuum packaging is to remove the air from a completely sealed packaging bag and complete the sealing process after reaching a predetermined vacuum degree, so that the items in the bag can be stored in a vacuum environment for a long time.
Vacuum packaging technology can not inhibit the reproduction of anaerobic bacteria and cause food spoilage. If sterilization is not thorough before vacuuming, some anaerobic bacteria remain on the food surface, then vacuuming packaging just provides a perfect anaerobic environment for these anaerobic bacteria, so that they grow and multiply in large numbers, the total number of bacterial colonies is likely to exceed the standard, and eventually lead to flatulence in the packaging.
The gas moisture in the air is permeable to packaging materials, and the permeability coefficient is closely related to the temperature. In general, the higher the temperature is, the greater the permeability coefficient is, the more serious the penetration of packaging materials is. Therefore, for the food packed in vacuum bags, it must be stored at low temperature. If it is stored at high temperature, the permeability of the bag will be seriously affected and the food will deteriorate. General vacuum packed food is stored below 10℃.
In addition, sous-vide food purchased through regular channels is pasteurized at super high temperature to kill the spores of botulinum toxin, thus extending the shelf life. But some "local food", "small restaurants" and other small shops, basically can not meet the above process, if these food is done on the same day to eat, will not appear botulinum toxin, and if the cooked food vacuum packaging, and then sent through the logistics, in line with the "normal temperature, no oxygen, no preservatives" botulinum attack conditions, the possibility of poisoning.
Choose safe vacuum packed food correctly
When buying vacuum food, the first thing to check is whether the bag is bulging. Whether the bag is bulging is the most intuitive and convenient way for consumers to judge whether the vacuum packaging of food deteriorates. Under normal circumstances, the air pressure in the packaged food bag should be the same as the outside world or less than the outside world after vacuuming. If the bag is swollen, it indicates that the air pressure in the bag is higher than the outside world, which indicates that new gases are produced in the sealed bag. These gases are the metabolites produced after a large number of microorganisms, because the metabolites of a small number of microorganisms are not enough to expand the bag.
Most of the bacteria or molds that may cause food spoilage (lactic acid bacteria, yeast, aerobacter, Bacillus polymyxis, Aspergillus and hundreds of others) will produce a large number of gases, such as carbon dioxide, hydrogen sulfide, ammonia, and alkyl, in the process of decomposing protein and sugar in food, and these gases will "blow" the packaging bag into a balloon. In the sterilization process of food before packaging, microorganisms and buds have not been completely killed. After the completion of packaging, microorganisms proliferate and become corrupt, which naturally leads to the problem of bulging packaging bags.
At the same time, when buying vacuum packed food, do not judge by the smell of food. If the taste of food spills out of the packaging, it means that the vacuum packaging itself is no longer vacuum, and there is air leakage. This means that bacteria can also "flow" freely.
In addition, to get a food package, the first thing to check its production license, SC code, production enterprise, ingredient list is complete. These certificates are like an "identity card" of food. Behind the certificates are the "past life" of food, where it came from and where it has been. The Food Safety Law clearly stipulates that the food production license number shall be marked on the food package. The number is composed of the letter "SC" and 14 Arabic digits. The "SC" code represents the unique license number of the enterprise, which can realize the traceability of the food.
Food manufacturers should pay attention to production
Firstly, it is necessary to choose a reliable vacuum bag packaging manufacturer to ensure that the raw material of the vacuum bag is food-grade plastic, ensure the physical properties of the vacuum bag, test the water permeability, air permeability and high temperature resistance of the vacuum bag, and ensure the quality of the vacuum bag.
Secondly, when vacuum operation is performed on food, it is necessary to pay attention to the hot sealing of food vacuum packaging bags. It is necessary to pay attention to the sealing parts without sticking grease, protein, food and other residues, so as to ensure that the sealing can be completely hot sealed. When heating sterilization treatment of vacuum packed packaging bags, the sterilization temperature and sterilization time should be strictly controlled to avoid excessive internal pressure of packaging bags due to high temperature, resulting in packaging bag sealing separation and rupture. Food vacuum packaging bags must be completely pumped, especially for fresh meat and unshaped food vacuum packaging. No residual gas can be allowed to prevent the residual gas from leading to spoilage of the food in the vacuum packaging bag.
