Quick-frozen food means that the raw materials are properly pretreated and generally frozen below 15 minutes, so that the temperature can quickly pass through the temperature range of-1-5℃ within 30 minutes (also known as the maximum ice crystal formation zone), and the food will crystallize after freezing, and the storage and transportation temperature of the food should also be lower than-18℃. When food is frozen rapidly at ultra-low temperature, its tissue and cell structure will not change, and the activities of microorganisms and enzymes will not decrease. Temporarily inhibit, then seal and vacuum package (to prevent dry consumption, oil consumption, oxidation, etc.). ), and finally stored in the environment below-18 degrees for 300-600 days.
Quick-freezing technology can not only preserve the flavor and nutritional components of food, but also effectively inhibit the growth of microorganisms, making them dormant, and even some microorganisms die due to low temperature, thus effectively ensuring food safety. At the same time, the long-term freezing technology makes the activity of biological enzymes in a low-temperature inhibition state, which effectively inhibits the ability of biological enzymes to decompose protein and fat at low temperature, thus preventing food from spoilage.
The difference between quick freezing and freezing
Many consumers tend to confuse the two, but in fact these two concepts are completely different.
In the process of food freezing, the most critical link is the crystallization of water molecules inside and outside the cell. The size and distribution of ice crystals in food tissues have great influence on the quality of food. Food freezing technology is now generally divided into three types:
Slow freezing, such as household refrigerator. Slow freezing means that it takes several hours or even more than ten hours for the central temperature of food to reach the temperature required for food quality assurance, such as-18 degrees. Slow freezing will form large ice crystals in the tissue space outside cells, destroy the tissue structure of food and make food lose its toughness. In the end, the lock can't be realized, and the food can only be guaranteed not to go bad for a certain period of time.
Take medium-speed freezing as an example. Most frozen products enterprises use a fan to drive cold air (-15- 18 degrees) to flow, which can only be realized in a few hours. Medium-speed freezing usually refers to 30 minutes to 3-5 hours, and the temperature of the food center reaches the temperature required for food quality assurance, such as: MINUS 18 degrees. Medium-speed freezing technology can't pass through the "ice crystal formation zone" quickly because the cooling speed is not fast enough, thus destroying the microstructure of food. Once thawed, cell fluid will be lost, the original taste of food will be weakened, physical indicators such as taste will be reduced, and nutrition will be lost. However, the change of physical properties during medium-speed freezing is less than that during slow freezing. Therefore, in fact, medium-speed freezing can not keep fresh, but can only ensure that food does not deteriorate in a certain period of time.
Ultra-low temperature quick freezing, such as liquid ammonia refrigeration technology used in Haoyang quick-frozen food freezer, can make the food center temperature reach-0/8 degrees below zero required for food preservation in a few minutes to ten minutes. In the shortest time, let the temperature quickly pass through the largest crystallization area (ice crystal generation area-1℃ to -5℃), and the temperature will drop rapidly, so that the water molecules inside and outside the cell can generate a large number of crystals with smaller volume (less than 5 microns in diameter) (the shorter the time, the smaller the ice crystals), so that the water molecules can form fine crystals evenly distributed in the tissue without piercing the cell membrane (the diameter of animal cells). The integrity of food microstructure is guaranteed, the loss of cell fluid after thawing is very small, the reversibility is guaranteed to the greatest extent, and the taste, taste and nutrition of fresh food are maintained. Achieve the purpose of long-term preservation.
Fresh-keeping advantages of quick-frozen food
In order to keep food fresh for a long time, many people think of preservatives for the first time. But we all know that excessive inhalation of preservatives will bring a series of health problems, which is also the fundamental reason why preservatives have been criticized. Quick-frozen food can inhibit and kill all kinds of bacteria by ultra-low temperature, without adding any preservatives, so as to ensure that food can retain nutrition to the maximum extent without damaging human health and make food safe to eat for a long time!
The fresh start remains the same &; Keep delicious
Ultra-low temperature freezing technology can reduce the central temperature of seafood to -60℃ in a short time and realize complete freezing. It can quickly and effectively cool the food, completely solidify the water, prevent the quality change caused by fluidity, ensure that the nutrition and water of seafood are not lost, achieve the nondestructive effect, and ensure that the taste of food is completely preserved. The thawed food is no different from fresh food, maintaining the original color, fragrance and quality of seafood.
Independent packaging &; Low temperature sterilization
The FDA stipulates that fish (seafood) must be frozen at -35℃ 15 hours or at -20℃ for 7 days before being eaten raw. In the ultra-low temperature freezing environment, it can effectively prevent bacterial invasion. Seafood must be processed in advance and quickly frozen in prime time. Ultra-low temperature can kill bacteria and parasites, and can be stored at -60℃ after sterilization to ensure the safety and quality of seafood. Independent packaging, perfect preservation.
Zero loss &; cold chain transportation
For some seafood that is far away or difficult to preserve, it will cause a lot of losses in the process of long-distance transportation, which will make it lose its delicious food experience. However, fresh meat can be kept delicious, nutritious and healthy through the whole process of preservation in the ultra-low temperature freezer at -60℃.
For example, bluefin tuna, which we are familiar with, met us in the form of ultra-low temperature freezing. At the same time, the shelf life of ultra-low temperature frozen seafood is more than double that of fresh or ordinary frozen products, which is more conducive to storage and preservation.
The ultra-low temperature cold chain can effectively ensure the food safety of the "first mile" and the "last mile" on the table, and ensure that all links of fishing, processing, storage, transportation, distribution and retail are at -60℃, thus effectively ensuring food safety and taste.
Mature ultra-low temperature cold chain operation, the cost will only be slightly higher than ordinary cold chain, but lower than fresh transportation, and almost no damage, greatly improving the value of food, but also retaining the proper taste of food. Therefore, in general, ultra-low temperature food will be enjoyed by consumers at a more civilian price, and its quality is no different from that of fresh products that were particularly expensive and particularly "high-end" in the past.
Thawing mode
(1) Natural Thawing: If thawed at room temperature for 2 hours, naturally thawed seafood will re-release its seawater flavor and umami flavor, and the biggest feature is that it can taste the seawater flavor of its origin.
(2) mineral water thawing: put it into mineral water to thaw 1 hour, which can thaw the product faster and make the meat more delicious and tender. (Not suitable for tuna, soaking for too long will affect the taste)
(3) Thawing plate thawing method: Parents who often eat ultra-low temperature frozen products can go to the online mall to buy household thawing plates, preferably coated with silver ions, which can prevent bacteria and sterilization. Just tear off the frozen product and put it on the thawing plate to thaw. The process is about 1 hour.
How to choose quick-frozen food
1. Select the frozen food with the freezing condition below-18℃.
The quick-frozen flour and rice food should be kept at the freezing condition of-65438 08℃. If there is no freezer in the store or the freezing temperature of the freezer can't reach-18℃, the product quality can't be guaranteed and it is not suitable for purchase.
2. Choose the frozen food closest to the production date.
Try to choose the food closest to the production date. The closer to the production date, the higher the freshness of food and the less the loss of nutrients.
3. Choose quick-frozen food with no frost and ice on the surface.
If frozen food is not thawed during production, transportation and storage, there will be no water, so there will be no frost or even freezing. Frost and ice will only be produced during repeated freezing and thawing. Moreover, it will destroy food nutrition to varying degrees, so we should first choose frost-free and ice-free quick-frozen food.
4. Choose big brands of frozen food.
Big brands also mean big manufacturers, large-scale and relatively standardized production and operation equipment. In particular, quick-frozen food also involves cold chain transportation. Only by standardizing the production and circulation fields can the entrance be safe.