Determination and characterisation of milk-clotting activity of two Solanum tuberosum aspartic proteases (StAPs)

To identify new coagulant enzymes as rennet substitutes, the aim of this study was to determine and to characterise the milk-clotting activity (MCA) of two potato aspartic proteases (StAPs). Both enzymes exhibited MCA in a dose-dependent manner. Optimum MCA values were determined at pH 5 and 30 °C. The ability of StAPs to degrade casein subunits was also evaluated. β-Casein was preferentially hydrolysed by both StAPs, followed by αS-casein and, to a lesser extent, κ-casein. These results confirmed the suitability of StAPs for producing curd and the possibility of using these proteases in artisanal cheese production.