FREE ACTIVE PEPTIDASES ARE DETECTED IN EMMENTALER JUICE EXTRACTED BEFORE RIPENING IN THE WARM ROOM

In Swiss-type cheese such as Emmental, proteolysis is one of the major phenomena occurring during ripening. Among the proteolytic agents inv olved in cheese ripening, the free enzymes originally present in milk and those arising from bacterial autolysis can act directly on the cas ein network. In order to understand the contribution of the bacterial enzymes and especially those arising from the thermophilic starters, t he juice of an Emmental cheese entering the warm room was extracted by pressure, then sterilized by filtration and incubated at 24 degrees C for 20 d under anaerobiosis. At different times, the peptides and fre e amino acids were determined in the sterile cheese juice. In parallel , in order to gather information about the nature of the enzymes prese nt, the sterile juice was also incubated with P-naphthylamide derivati ves as substrates. We have demonstrated a continuous increase in free NH2 groups and in free amino acids throughout the 20 d incubation time . The main peptidase activity was due to aminopeptidase(s) and X-proly l-dipeptidyl aminopeptidase(s) whose activities were recovered after n on-denaturing polyacrylamide gel electrophoresis. Most of the enzymes found in the juice would have their origin in thermophilic starters. A s they are generally intracellularly located, their release could be e xplained by the autolysis of these starters. Finally, the main free am ino acids released in the juice (Pro, Glu, Ala, Val, Leu and Lys) corr esponded to those previously found in Emmental cheese, suggesting that the enzymes detected in this study participate significantly in pepti de degradation during ripening.