Amino protein value, relation

The biological value of dietary proteins is related to the extent to which they provide all the necessary amino acids. Proteins of animal origin generally have a high biological value, whereas plant proteins may be deficient in lysine, methionine and tryptophan, and are generally less digestible than animal proteins. 

On the other hand, variation of pH in keratin solutions causes changes in amino-acid behavior related to the electronic charge response. Thus, if keratin solution has a pH below keratin s isoelectric point (reported at pH of 4), a cationic response can be expected, whereas higher values of pH produce an anionic performance. Therefore keratin has the capability of interact with different kind of species pollutants, including not only chromium but also other metals that could be removed. Besides the pH of pollutant solutions also plays an important role as was demonstrated ecently by Manrique-Juarez et al. In this study, the authors reported that pH has a strong influence on the morphology, mechanical properties and Cr(VI] removal efficiency, since if pH in keratin solution is 2.5, the protein separates from water solution, and therefore the polymerization reaction is affected producing a more closed cell in the membrane. The Cr(VI)... 

Biological value is stated as the proportion of the nitrogen intake that is actually retained and takes account of endogenous urinary and faecal nitrogen, whereas chemical score and the essential amino acid index are based on the proportion of the main limiting amino acid of the protein in relation to that in a standard protein. 

Proteins are important food components mainly due to their nutritional and functional value. Dietary proteins provide amino acids and nitrogen necessary for organisms. They also play a major role in determining the sensory and textural characteristics of food products. The functional properties are related to their ability to form viscoelastic networks, bind water, entrap flavors, emulsify fat and oil, and form stable foams [105]. 

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