The protein content of fish flesh, in contrast to the fat content, is highly constant, independent of seasonal variations caused by the feeding and reproductive cycles.
The protein in fish muscle tissue can be differentiated into the following three groups:
1. Structural proteins – actin, myosin, tropomyosin and actomysin, which constitute 70-80 percent of the total protein content. It give the muscle its fiber-like structure and muscular activity.
2. Sarcoplasmic proteins – myoalbumin, globulin and enzymes, which are soluble in neutral salt. This fraction will comprise anything from 25 to 30 percent of the protein. The sarcoplasmic proteins consist largely of enzymes. The enzymes correspond to those do mammalian muscle tissue.
3. Connective tissue proteins (collagen), which constitute approximately 3 percent of the protein in teleosteii and about 10 percent in elasmobranchii. Collagen is the main component with a content of up to 90 percent and the remainder is elastin. These protein are easily solubulized by cooking.
Fish muscle can consist to main types, dark and white, depending on the life cycle of the species concerned.
The two muscle types are essentially similar in composition but the dark muscle has a higher content of heme pigments, such as myoglobin, for oxygen transport and more non-structural lipids, to provide energy; this reflects its role in active strong-swimming.
Fish proteins contain all the essential amino-acids and like milk, eggs and mammalian meta proteins, have a very high biological value.
The consumption of fish protein, independently of the effect exerted by fish fat, has been related to a decrease in the risk of atherogenic vascular diseases.
Fish protein
