Collagen is a biomolecular

Collagen is a biomolecular, the main component of animal connective tissue, but also the mammalian body content of the largest, most widely distributed functional protein, accounting for 25% to 30% of the total protein, some organisms even as high as 80%. Animal tissue is the main way for people to obtain natural collagen and its collagen peptides, but because related animal diseases and certain religious beliefs limit the use of terrestrial mammal collagen and its products, it is now gradually turning to marine life development. The European Food Safety Authority (EFSA) has confirmed that even collagen from animal bone sources is not likely to be infected with mad cow disease and other related diseases.

Due to the differences in amino acid composition and crosslinking, aquatic animals, especially their processing waste - skin, bone, scale containing rich collagen has many animal collagen does not have the advantages, in addition to collagen from marine animals in some aspects significantly better than terrestrial collagen, such as low antigen, low allergy and other characteristics. Therefore, aquatic collagen may gradually replace terrestrial animal collagen. There are many types of collagen, and the common types are Type I,TypeII, TypeIII, TypeV and Type XI. Collagen has been widely used in food, medicine, tissue engineering, cosmetics and other fields because of its good biocompatibility, biodegradability and biological activity.

Collagen content in aquatic animals was higher than that of terrestrial animals, such as mackerel, mackerel and herring skins, with protein content of 25.9%, 23.6% and 29.8%, respectively, higher than that of their respective fish: 17.8%, 15.3% and 16.6%. The collagen content in fish skin can exceed 80% of its total protein, much higher than the rest of the fish body, studies have reported that collagen in the skin of real mackerel accounted for 80.5% of coarse protein, eel as high as 87.3%. Such high levels mean high yields, such as 42.5 per cent for mackerel, 40.7 per cent for Japanese sea otters, 53.6 per cent for sachets, 40.1 per cent for yellow sea bass and 43.5 per cent for mackerel (all in dry weights).

However, there are far fewer types of collagen, and the collagen types identified from fish are type I, type II and XI type of cartilage and ridge rope, and V type of muscle, which are widely distributed in dermis, bone, scale, , muscle, etc. The I.D. collagen contained in fish skins and bones is its main collagen. In addition, X.VIII collagen has been found, but the more abundant type III collagen in mammals has not been found in aquatic animals. Only the price of type I collagen is acceptable, and other types of collagen, such as III,IV,V., etc., are prepared only in research and are not suitable for mass production due to their high price.