Characterization of the purified actinidin as a plant coagulant of bovine milk

In this work, actinidin was characterized in view of its possible suitability as a coagulant enzyme in the manufacturing process of cheese. The results show that actinidin does exhibit milk-clotting activity, which is correlated with the enzyme concentrations. The combined use of urea and SDS-PAGE led to the conclusion that the milk clot is clearly separated from the whey proteins and corresponds to casein coagulum. Moreover, both the enzyme dependence on pH and temperature and the stability profiles are fully suitable with the chemical-physical conditions adopted during the cheese-making procedure. The analysis of the kinetic constants as well as the electrophoretic pattern of the hydrolysis products suggests that beta-casein is the preferred substrate of actinidin, whereas kappa-casein seems to be hydrolyzed only in a few large fragments.