Proteins, fish

The mmen is not functional at birth and milk is shunted to the abomasum. One to two weeks after birth, the neonate consumes soHd food if offered. A calf or lamb that is nursing tends to nibble the mother s feed. An alternative method of raising the neonate is to remove it from its mother at a very young age, <1 week. A common example of an early weaning situation is the dairy calf that is removed from the cow soon after birth so that the cow s milk supply might be devoted entirely to production. In this instance, the neonate requires complete dietary supplementation with milk replacer. Sources of milk replacer protein have traditionally included milk protein but may also include soybean proteins, fish protein concentrates, field bean proteins, pea protein concentrates, and yeast protein (4). Information on the digestibiUty of some of these protein sources is available (4). 

A pepsin hydrolysate of flounder fish protein isolate has been used as the substrate (40% w/v) for plastein synthesis, using either pepsin at pH 5 or alpha chymotrypsin at pH 7, with an enzyme—substrate ratio of 1 100 w/v at 37°C for 24 h (151). The plastein yields for pepsin and alpha chymotrypsin after precipitation with ethanol were 46 and 40.5%, respectively. 

In general, nonconventional protein foods must be competitive with conventional plant and animal protein sources on the bases of cost delivered to the consumer, nutritional value to humans or animals, functional value in foods, sensory quality, and social and cultural acceptability. Also, requirements of regulatory agencies in different countries for freedom from toxins or toxic residues in single-cell protein products, toxic glycosides in leaf protein products, pathogenic microorganisms, heavy metals and toxins in fish protein concentrates, or inhibitory or toxic peptide components in synthetic peptides must be met before new nonconventional food or feed protein products can be marketed. 

In terms of amino acids bacterial protein is similar to fish protein. The yeast s protein is almost identical to soya protein fungal protein is lower than yeast protein. In addition, SCP is deficient in amino acids with a sulphur bridge, such as cystine, cysteine and methionine. SCP as a food may require supplements of cysteine and methionine whereas they have high levels of lysine vitamins and other amino acids. The vitamins of microorganisms are primarily of the B type. Vitamin B12 occurs mostly hi bacteria, whereas algae are usually rich in vitamin A. The most common vitamins in SCP are thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, choline, folic acid, inositol, biotin, B12 and P-aminobenzoic acid. Table 14.4 shows the essential amino acid analysis of SCP compared with several sources of protein. 

We have demonstrated that addition of lysine to soy protein causes a significant increase of serum cholesterol and development of atherosclerosis. Another approach to this question was to feed three proteins of animal origin that contained almost identical amounts of lysine but different amounts of arginine. We used fish protein (lysine, 6.81 arginine, 4.74 L/A ratio, 1.44), casein (lysine, 6.91 arginine, 3.65 L/A ratio, 1.89), and milk protein (lysine, 6.61 arginine, 2.71 L/A ratio, 2.44) (14). The proteins... 

Cholesterol (mg/dl) Fish protein 238 + 40 Casein 530 + 76 Milk protein 462 + 62... 

Figure 3. Spectra of ethylisocyanide-ferrocytochrome P-450 complexes, rainbow trout. Conditions were as in Figure 2, except rainbow trout hepatic microsomes were used. (A) Microsomes from rainbow trout treated with (j-naphthoflavone (100 mg/kg sacrificed 4 days later). Protein concentration, 1.4 mg/mL total P-450 concentration, 0.48 fi.M. (B) Microsomes from control fish. Protein concentration, 0.93 mg/mL, total P-450 concentration, 0.22 /iM.

Solubilization of fish protein concentrates, recover oil or meat scraps from inedible parts Waste product conversion to feed, digestive aid... 

Further, fish protein hydrolysates contain hormone-like peptides and growth factors that accelerate calcium absorption (Fouchereau-Peron et ah, 1999). These peptides are capable of binding to the cell surface receptors on osteoclasts and have a role in calcium metabolism by decreasing the number of osteoclasts. Therefore, these peptides could be used in the treatment of osteoporosis and Paget s disease. Further,... 

Fouchereau-Peron, M., Duvail, L., Michel, C., Gildberg, A., Batista, I., and Gal, Y. I. (1999). Isolation of an acid fraction from a fish protein hydrolysate with a calcitonin-gene-related-peptide-like biological activity. Biotechnol. Appl. Biochem. 29, 87-92. 

Fujita, H. and Yoshikawa, M. (1999). LKPNM A prodrug-type ACE-inhibitory peptide derived from fish protein. Immunopharmacology 44,123-127. 

Gildberg, A., Bogwald, J., Johansen, A., and Stenberg, E. (1996). Isolation of acid peptide fractions from a fish protein hydrolysate with strong stimulatory effect on Atlantic salmon (Salmo solar) head kidney leucocytes. Comp. Biochem. Physiol. 11, 97-101. 

Rajapakse, N., Jung, W. K., Mendis, E., Moon, S. H., and Kim, S. K. (2005a). A novel anticoagulant purified from fish protein hydrolysate inhibits factor XHa and platelet aggregation. Life Sci. 76, 2607-2619. 

Samaranayaka, A. G. P. and Li-Chan, E. C. Y. (2008). Autolysis-assisted production of fish protein hydrolysates with antioxidant properties from Pacific hake (Merluccius productus). Food Chem. 107, 768-776. 

Development of Bioactive Peptides from Fish Proteins and Their Health Promoting Ability... 

V. Future Trends of Peptides from Fish Proteins 244... 

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. 

Peptides isolated from various fish protein hydrolysates have shown a different biological activities such as antihypertensive, antioxidative, antithrombotic, and immunomodulatory activities. 

Peptides derived from fish proteins have shown the ability of exerting potent antioxidative activities (Table 15.1) in different oxidative systems (Rajapakse et ah, 2005). Currently, an increasing interest exists to explore natural antioxidative substances without side effects and the identified antioxidative activities have potential to develop safe and nonhazardous natural antioxidants for the complications arose from oxidation of biomolecules. Je et ah (2007) purified an antioxidative peptide from tuna backbone protein and identified as VKAGFAWTANQQLS (1519Da) which was very important regarding the functional foods. It was reported that the derived peptides were good radical scavengers and antioxidant. 

TABLE 15.1 Potential bioactive antioxidative peptides derived from various fish proteins... 

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