The existing methods for testing proteolytic activity are time consuming, quite difficult to perform, and do not
allow real-time monitoring. Proteases have attracted considerable interest in winemaking and some yeast species
naturally present in grape must, such as Metschnikowia pulcherrima, are capable of expressing this activity.
In this study, a new test is proposed for measuring proteolytic activity directly in fermenting grape must, using
azocasein, a chromogenic substrate. Several yeast strains were tested and differences in proteolytic activity
were observed. Moreover, analysis of grape must proteins in wines revealed that protease secreted by
Metschnikowia strains may be active against wine proteins.