Fish is rich in nutrition, not only because of its high protein content, easy to digest, contains B vitamins and calcium, zinc, selenium, iodine and other minerals, but also because the fat is rich in the imiate 3 fatty acids, to prevent cardiovascular and cerebrovascular diseases and promote intellectual development. However, if the fish can be made into canned food, will its nutritional value change?

Fish are rich in protein and a variety of nutrients, the acid is very low, especially easy to propagate bacteria, so when can be canned at 115 - 121 C under high temperature and high pressure sterilization. Such a high temperature has little effect on protein, but can cause a large loss of B vitamins. Therefore, the vitamin B1 content of canned fish can be reduced to about half of that of fresh fish, and it will be further reduced in long-term storage.

However, it is necessary to have the advantages and disadvantages of all things. High temperature and high pressure heat makes the fish bones crisp and soft, so that calcium can be dissolved in large quantities. As a result, the calcium content of canned fish is more than 10 times higher than that of fresh fish, and iron, zinc, iodine, selenium and other minerals are not lost. Therefore, eating canned fish has a certain significance for mineral supplement. However, if the fish used to make cans is a deep-sea fish that has been contaminated with lead and mercury, as the bones become crisp and softened, the contaminants in the fish will dissolve in large quantities and increase the harm to the human body. Compared with tuna, sharks, sea bass, swordfish, barracuda, marlin, COD and other easily polluted fish, salmon, trout, and yellow fish are more safe.

According to the different processing methods, canned fish can be divided into three categories: braised pork, tomato juice, fresh fried, steamed, smoked, oil immersed and water soaked. Generally speaking, water-soaked fish with low fat content, and can basically maintain the natural fatty acid ratio of fish, is the most worthy of selection. You can make fish salad with fish sauce and seasoning and mix with vegetables.  The salt content of tomato juice products is high, but the acidity of tomato juice is good for the preservation of B vitamins, and it is also a good choice. Although the smoke, fresh and red fever and other varieties are rich in flavor, after the frying, the fish's omamiga 3 Series fatty acids are destroyed, the fat content is greatly increased, most of the B vitamins are destroyed and the nutritional value is not high, and the toxic carcinogens such as benzo and pyrene may also be produced in the process of frying and fumigation, so as to make food safe. The sex is greatly reduced. Most of the canned oil can not be fry and smoked at high temperature, and the safety is high.

The shelf life of canned fish is as high as 24 months. Many consumers think this is because it contains preservatives. In fact, it is not. Canned food is a kind of important food processing method, which is to put the raw material in the airtight container through the exhaust. It is treated with high temperature to kill all kinds of microbes and bacteria, destroy the activity of the enzymes, prevent the external pollution and the oxygen entering, so that the food can keep stable and edible for a long time. Therefore, most canned fish do not contain preservatives, consumers can rest assured that they eat.

But take care when eating canned fish, not more than 2 cans per week (about 225 grams of fish per can); among them, fish and smoked fish should not be more than 1 cans; pregnant women, milk mothers and children do not eat as much as possible. The people who eat canned fish should pay attention to a balanced diet, eat more fresh vegetables, fruits and beans, and potato, in order to improve the anti pollution ability, so as to avoid the adverse effects on health of a large number of canned fish for a long time.

When eating canned fish, be careful not to exceed two boxes a week.