In addition, unscrupulous aquatic manufacturers will also use additives, such as prawns, have specialized synthetic medicament, hit up to the direct "beauty", to ensure that shrimp head will not turn black, always keep fresh and fresh look.
Added formaldehyde can make spoiled squid look fresh, but after a period of time, there will be odor, there are signs of corruption. Equally frightening is sodium benzoate, which is often overused when used by aquatic manufacturers, which is also harmful to the human body. Frozen seafood must be worse than live seafood?
Not necessarily! Freezing technology was born when seafood couldn't make it to the kitchen. Now the general freezing techniques are as follows: ship freezing: mostly done on board ocean fishing vessels, simply classified after capture and refrigerated in cold storage.
Shore freeze: more offshore fishing, crushed ice to maintain low temperature, and then sent to the processing plant to freeze, preservation effect is slightly poor. Also known as "land freeze". Raw frozen: seafood directly frozen, or simply treated after freezing. Frozen: shrimps, crabs, shellfish, etc., cooked (boiled) before freezing.
Ordinary freezing: freeze at-18 ℃. Low temperature freezing: at-35 ℃, 60 ℃, the preservation effect is good, keeping seafood quality to the maximum extent.
In addition, there are chunks (whole pieces frozen together), single freezing (the products are separated from each other after freezing), and semi-single freezing (the seafood is semi-fixed together with an ice tray). Among these freezing methods, low-temperature freezing technology is the best, which can lock the fresh taste and nutrition of seafood itself, keep the best quality, and be beneficial to long-term preservation.
Rapid freezing technology was developed in the United States after World War II, and up to now, there are basically three technologies:
1, Mechanical Food Frozen: like home refrigerators, ammonia is used as a refrigerant.
2,Absorb heat through a closed system. Ultra-low temperature food freezing: freezing with liquid nitrogen and other ultra-low temperature gases or liquids is now the most commonly used technology.
3, impingement food quick freezing: apparatus manufacturing high-pressure air flow for freezing.
Either way, food materials will produce ice crystals during freezing, and how they thaw will affect the loss of nutrients during thawing.
There are many factors that affect the fresh taste of high-quality seafood, and the quality of fresh seafood is not the same as that of fresh seafood.
Freezing logistics generally follows three 3T principles, Time (cold chain storage and circulation time), Temperature (temperature), Tolerance (products storage resistance). Norwegian research firm SINTEF has been testing the effects of different freezing and thawing techniques on the quality of fish and has proposed three key factors:
Once caught, fish will be frozen as soon as they are caught.
fish need to be kept in a stable low temperature without interruption.
thaw before sale. In this test, about 10 days after thawing, the fish were still of good quality.
This means that if they are frozen in the right way, they will be sterile, and touch, color, and persistence will remain of high quality. With the development of science and technology, new technology has been developed and applied to the fresh-keeping and transportation of seafood. Some colleges and universities have developed the technology of freezing in vivo, using low temperature to temporarily "dormant" the fish cells, but the survival time of the fish after resurrection is relatively short. How did thawing become technical work? Ice crystals are produced when seafood freezes, and incorrect thawing methods allow them to "go back and forth" to nourish them.
This process is explained in "The food is thawed, and when the temperature rises to a certain range (from 0 ℃ to 8 ℃, relative humidity is 70 ~ 90%), the melting water of the ice crystals inside the food cells can be recovered and absorbed into the cells, such as rapid thawing, and the water becomes the juice to flow out.
The water-soluble substances such as proteins, minerals, vitamins and the like in the flowing juice can cause the food flavor and the nutritional value to be lost." an article that parses the thawing method. After the chef, the cook was unfrozen with running water, unfrozen at a low temperature (frozen in a refrigerator), and naturally thawed.
When thawing, also ensure the independence of the ingredients, can not be pressed by other ingredients, or taste. But the thaw is slow, and large chunks of food can take days and could damage the ingredients. So when a large piece of food is thawed, it is recommended to use ice bath, but the food material must be packed with waterproof seal to avoid cross-contamination, and the water needs to be changed every 30 minutes.
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