New plant endopeptidases with potential application in cheesemaking

Results are given on the milk clotting properties and casein hydrolytic behaviour of partially purified extracts of four new cysteine plant endopeptidases: balansain, hieronymain, asclepain f, and philibertain g. Milk coagulation behaviour was different for the assayed proteases: balansain and hieronymain showed a similar performance, whereas asclepain f exhibited the lowest clotting activity; philibertain g exhibited the highest one when was previously incubated with cysteine. According to the relative ratio of clotting activity to proteolytic activity, balansain, philibertain g and hieronymain appear as possible vegetable rennets. Casein hydrolysates were produced with each enzyme and the hydrolysis pattern was analysed by tricine SDS-PAGE. The α _S2 - and α _S1 -casein fractions, associated with cheese texture, showed different degradation patterns: higher degradation kinetics was obtained for philibertain g, followed by balansain and hieronymain, whereas asclepain f showed the lowest activity. The β-casein fraction, related to bitterness, showed similar initial degradation kinetics for balansain and asclepain f; degradation was faster in the case of philibertain g and slower for hieronymain. In the case of the κ-casein fraction, involved in milk clotting, the most remarkable behaviour was that of hieronymain, as this casein fraction was quickly degraded by the protease.