Limited enzymic hydrolysis of casein in the presence of ethanol

Abstract

Proteinases manifesting different specificity caused limited hydrolysis of casein in media containing 20–60% (v/v) ethanol. The activity of enzymes was maintained during casein breakdown; a weak activation was observed even for subtilisin DY and trypsin. Hydrolysis by subtilisin resulted in more bitter peptides with increased ethanol concentration, whereas trypsin and α-chymotrypsin action led to products with reduced bitterness. The limited casein digestion was connected with the formation of relatively stable polypeptide structures, containing in their interior peptide bonds susceptible to the enzyme action. A nonbitter casein hydrolysate (degree of hydrolysis 5%) was obtained by limited trypsin hydrolysis in the presence of 40–60% (v/v) ethanol. Using gel chromatography on Sephadex G-50, a decrease of the peptides with MW below 6 kDa in the product was observed, corresponding to the bland taste.