Effect of enzymatic modification on the biological activity and nutritive value of cow and buffalo casein

Buffalo and cow milk caseins were submitted to hydrolysis either with alpha -chymotrypsin or with pepsin. Enzymatic peptide modification (EPM) was carr ied out by using L-methionine ethyl ester in the reaction mixture. As catal yst, alpha-chymotrypsin or pepsin was used. The incorporation of methionine in to the peptide chains in the presence of alpha-chymotrypsin showed an o ptimum value at 0.14 g Met added to the reaction mixture/1 g hydrolysate in both cases. In the case of pepsin used as catalyst, the optimal Met-enrich ment was at 0.14 g Met added to the reaction mixture/1 g buffalo casein hyd rolysate and at 0.34 g Met/1 g cow casein hydrolysate. The covalent nature of the amino acid incorporation was confirmed by SDS - polyacryl amide gel electrophoresis in the presence of urea. Electrophoreti c patterns of the products indicate that transpeptidation plays an essentia l role in the EPM reaction. Antigenic character of the EPM-products was inv estigated in vitro by competitive indirect ELISA. Enzymatic peptide modification with methionine enrichment seems to be an ef ficient method for the reduction of the antigenic/potential allergenic char acter and for the improvement of the nutritive value of buffalo and cow mil k caseins.