Biological value of protein

The initial Schiff base is digestible but after the Amadori rearrangement, the products are not metabolically available. Since lysine is the amino acid most likely to be involved and is an essential amino acid, Maillard browning reduces the biological value of proteins. Interaction of lysine with lactose renders the adjacent peptide bond resistant to hydrolysis by trypsin, thereby reducing the digestibility of the protein. 

Zduhczyk, Z., Juikiewicz, J., Flis, M. and Frejnagel, S. (1996) The chemical composition and nutritive value of low-alkaloid varietiesofwhitelupin.2.Oligosaccharides, phytates, fatty acids and biological value of protein. Journal of Animal and Feed Science 5, 73-82. 

All nutrients (except water) may undergo either chemical or physical changes during processing that render them inactive or less bioavailable. This occurs for macro- as well as micronutrients. During browning, the amino acid lysine can react with carbohydrates to lower the biological value of protein. 

The loss of nutritive value when protein or protein-rich foods are heated or stored in the presence of carbohydrates has been studied by a large number of groups (8,10,12,18,29,30). A decrease in the digestibility of proteins and in the availability of amino acids and carbohydrates after the Maillard reaction is shown in Table II. It can be concluded from this that the biologic value of proteins has also decreased. For example, in Table in one can see significant decreases in amino acids of egg albu-t... 

Digestibility of proteins Availability of amino acids Availability of carbohydrates Biologic value of proteins... 

Oser, B.L. An integrated essential amino acid index for predicting the biological value of proteins. In Protein and amino acid nutrition 66. (Albanese, A.A., ed.). New York Academic Press 1959... 

Horigome, T. and Kandatsu, M. (1968). Biological value of protein allowed to react with phenolic compounds in presence of o-diphenol oxidase. Agric. Biol. Chem. 32 1093... 

The nature and extent of the chemical changes induced in proteins by food processing depend on a number of parameters, for example, composition of the food and processing conditions, such as temperature, pH or the presence of oxygen. As a consequence of these reactions, the biological value of proteins may be decreased ... 

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