Fish proteins composition

Discarded fish bones and cutoffs may contain considerable amounts of muscle proteins. These muscle proteins are nutritionally valuable and easily digestible with well-balanced amino acid composition (Venugopal et al., 1996). Therefore, fish proteins derived from seafood processing by-products can be hydrolyzed enzymatically to recover protein. Protein hydrolysates from several marine species have been analyzed for their nutritional and functional properties, and researches have mainly explored the possibility of obtaining biologically active peptides (Benkajul and Morrissey, 1997). Moreover, skipjack tuna muscle (Kohama et al., 1988), sardine muscle (Bougatef et al., 2008), and shark meat (Wu et al., 2008) have been used to separate potential peptides. 

Shulman, G.E. and Kulikova, N.I. (1966). On the specificity of protein composition of blood serum in fish (In Russian). Uspekhi Sovremennoy Biologii 62,42-60. 

The study of fish proteins were initiated by the Swiss physiologist Miescher (1897), who first isolated the protamines from the sperm cells of various fishes as early as 1868. The relatively simple amino acid composition of these proteins and their pharmacological action have since promoted extensive researches, first of aU by Kossel and co-workers, whose important... 

The comparative biochemistry of proteins is still in its beginning. Research was first directed towards the study of the protein components of mammals, but is now extending to other classes of vertebrates. In the case of fish, this study, of great economic importance, has been contributed to both by protein chemistry and technology. The main characteristics of fish protein are now satisfactorily defined, and a comparison of the highest and lowest classes of vertebrates is possible from the point of view of protein composition. 

Solubilization of Protein. Fish protein concentrate has high nutritional quality as determined both from its essential amino acid composition and from animal feeding experiments. Unfortunately, the concentrate is quite insoluble in water because of its denaturation by the solvent extraction method used in processing thus it contributes no functional properties to a food and must be used in bakery products primarily. A potentially useful method of solubilizing the protein is by proteolysis (9-12). As is the case with protein hydrolysates of casein and soybean protein, bitter peptides are formed during the hydrolysis. Papain and ficin produce more of these bitter peptides than does Pronase, for example (12). Pronase was found to produce a more brothy taste (13). A possible method of removing the bitter peptides is to convert the concentrated protein hydrolysate to plastein by further proteolytic enzyme action (14) to remove the bitter peptides. 

Table VI. Amino Acid Compositions of Low-Phenylalanine High-Tyrosine Plasteins from Soybean and Fish Proteins (wt %)...

Because we are not dealing with the assembly of sequences of building blocks which are covalently linked, we might expect somewhat different rules for the collocative process. Lipids, confined by natural or experimental means into an organization, may exhibit collocative properties of their own, and there is some evidence that this is so (MICHAELSON al., 1973 ISRAELACHVILI, 1973). I think that one experimental approach will consist of some sort of "fishing expedition" whereby highly purified membrane proteins are trolled through lipid solutions with the expectation that a specific bait (= membrane protein) will attract a specific catch (= lipid). One such, apparently successful, experiment has been reported (STRUVE fl., 1975). This is an appropriate juncture to turn to a discussion of the protein composition of the plasma membrane. 

Table 1.44. Amino acid composition (weight-%) of plasteins with high tyrosine and low phenylalanine contents from fish protein concentrate (FPC) and soya protein isolate (SPI)...

The protein-N content of fish muscle tissue is between 2-3%. The amino acid composition, when compared to that of beef or milk casein (Table 13.6), reveals the high nutritional value of fish proteins. The sarcoplasma protein accounts for 20-30% of the muscle tissue total protein. The contractile apparatus accounts for 65-75% protein the connective tissue of teleosts is 3% and of elasmobranchs, such as sharks and rays (skate or rocker), is up to 10%. The individual protein groups and their functions in muscle tissue of mammals (cf. 12.3.2) also apply to fish. 

The amino acid composition shows relatively high amounts of Arg (12%) and Lys (9%) and little Pro. The paramyosin molecule consists of two peptide chains (M ) 95,000-125,000), each of which is 120 nm long, has a helical structure and is twisted to a rod. In fact, two disulfide bonds contribute to the stability of the molecule. It forms the core in the thick filaments and is surrounded by myosin. In the production of gels, it influences the rheological properties and is the reason why gels made from mollusk meat are more elastic and more cohesive than gels made from fish protein. 

The protein composition of cereals is not snfflcient to sustain optimnm growth in most domestic animals. Thus, cereals are supplemented with protein meals that contain high amonnts of lysine and tryptophan. The most common protein meals are soybean, cottonseed, canola, and meat and fish meal. The use of meat and bone meal, and other animal protein meals snch as dried blood, is prohibited in several parts of the world because its consumption has been associated with mad cow disease. 

Haard NF (1995) Composition and nutritive value of fish proteins and other nitrogen compounds. In Ruiter A (ed.) Fish and Fishery Products Composition, Nutritive Properties and Stability, pp. 77-115. Wallingford CAB International. 

Legume forages, such as alfalfa or clover, are considered high quaHty, readily available protein sources. Animal sources of supplemental protein include meat and bone meal blood meal, 80% CP fish meal other marine products and hydroly2ed feathermeal, 85—90% CP. Additionally, synthetic amino acids are available commercially. Several sources (3,9,19) provide information about the protein or amino acid composition of feedstuffs. 

Although proteins and amino acids in the food influence the metabolism of the fish, they do not alter the amino acid composition of proteins in the body. In contrast, the lipids in the body of the fish are greatly influenced by the dietary lipids. In particular, it is the triacyl-glycerols (the main constituents of reserve energy) which are influenced by diet (Lovem, 1937,1942,1964 Kelly et al., 1958 Brockerhoff et al., 1963, 1964 Ackman, 1964, 1967 Ananyev, 1965 Ackman and Eaton, 1966, 1976). Food lipids also influence the structural lipids of the fish. 

Both marine and freshwater fish are often overfed in fish farms, so their own lipids are less likely to follow changes in the dietary lipid pattern. In the natural state, the influence of food on the lipids of the tissues is somewhat blurred by the fact that some of the tissue lipids are generated from carbohydrates and proteins in the diet and so synthesized de novo. In his classic work, Lovem (1964) showed that the impact of food on the fatty acid composition of herring lipids was most pronounced during intensive feeding. In winter, at the end of that period, the fatty acid composition became different from that of the zooplankton on which the fish had been feeding earlier. 

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