Because fish is rich in protein and various nutrients, and its acidity is very low, it is especially easy to breed bacteria, so it should be sterilized at high temperature and high pressure of115-121℃ when it is canned. Such a high temperature has little effect on protein, but it will cause a great loss of B vitamins. Therefore, the vitamin B 1 content of canned fish can be reduced to about half of that of fresh fish, and will be further reduced in long-term storage.
High temperature and high pressure heating makes fish bones brittle and soft, and a lot of calcium is dissolved out. Therefore, the calcium content of canned fish is more than 10 times higher than that of fresh fish, and there is no loss of minerals such as iron, zinc, iodine and selenium.
Eating canned fish has certain significance for supplementing minerals. However, if the fish used for canning are deep-sea fish polluted by lead and mercury, with the bones becoming brittle and soft, a lot of pollutants will be dissolved, which will increase the harm to human body. Compared with tuna, shark, perch, swordfish, pike, marlin and cod, salmon, trout and yellow croaker are safer.
In canned fish processed at high temperature and high pressure, protein, carbohydrates, minerals and other nutrients are basically unaffected, and there are few vitamins and fatty acids left.