Fish proteins biological value

Proteins from animal sources Proteins from animal sources (meat, poultry, milk, fish) have a high quality because they contain all the essential amino acids in proportions similar to those required for synthesis of human tissue proteins (Figure 27.18). [Note Gelatin prepared from animal collagen is an exception it has a low biologic value as a result of deficiencies in several essential amino acids.]... 

If formula diets are not used, then the type of protein used is important due to considerations of biological value and digestibility. Milk, animal proteins, egg, certain legumes, and soy products are appropriate, rich sources. If lactose intolerance is encountered, then milk should be replaced with soy-based feeds or an alternative. Fish and vegetable oils are good sources of fats as they provide generous amounts of essential fatty acids and long-chain unsaturated fatty acids. 

The quality of different proteins can be expressed according to their chemical score, protein efficiency ratio (PER), biological value (BV), and net protein utilization (NPU). These parameters refer to the different tests used to define the protein s quality. The chemical score refers only to the property of the protein in question. The PER, BV, and NPU refer to relationship.s between the dietary protein and the consumer. The values of the PER, BV, and NPU depend on properties of both the protein in question and the needs of the animal. The chemical score, PER, BV, and NPU of proteins in various foods, including eggs, fish, rice, and maize, are listed in Table 8,1 3. 

Fish proteins contain all the essential amino acids and, like milk, eggs, and mammalian meat proteins, have a very high biological value (Table 3.11) [84]. 

Cereal grains are usually low in lysine and/or sulfur-containing amino acids (methionine and cysteine), whereas fish protein is an excellent source of these amino acids. A supplement of fish can therefore significantly raise the biological value in cereal-based diets. 

Blood meal is a chocolate-coloured powder with a characteristic smell. It contains about 800 g/kg of protein, small amounts of ash and oil, and about 100 g/kg of water. It is important nutritionally only as a source of protein. Blood meal is one of the richest sources of lysine and a rich source of arginine, methionine, cystine and leucine, but it is deficient in isoleucine and contains less glycine than fish, meat, or meat and bone meals. Owing to the poor balance of amino acids, its biological value is low in addition, it has a low digestibility. It has the advantage, in certain situations, that its protein has a very low rumen degradability (about 0.20). 

Lysine was isolated from casein by Drechsel in 1889. It makes up 7-9% of meat, egg and milk proteins. The content of this essential amino acid is 2-4% lower in cereal proteins in which prolamin is predominant. Crab and fish proteins are the richest sources (10-11%). Along with threonine and methionine, lysine is a limiting factor in the biological value of many proteins, mostly those of plant origin. The processing of foods results in losses of lysine since its 8-amino group is very reactive (cf. Maillard reaction). 

Biological value (BV) is the proportion of absorbed protein retained in the body. A protein that is completely useable (e.g. egg and human milk) has a BV of 0.9— 1 meat and fish have a BV of 0.75—0.8, wheat protein 0.5 and gelatine (which completely lacks tryptophan) a BV of 0. 

Great amount of marine fish species have been identified with potential nutraceutical and medicinal values. Consequently, a number of bioactive compounds have been identified including fish muscle proteins, peptides, collagen and gelatin, fish oil, fish bone. Bioactive peptides derived from various fish muscle proteins have shown various biological activities including antihypertensive, antibacterial, anticoagulant, anti-inflammatory, and antioxidant activities, and hence they may be a potential material for biomedical and... 

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