Proteolytic System of Lactobacilli: A Case Study

The complex proteolytic enzyme systems of starter and non-starter lactic acid bacteria can complementarily act with rennet and/or indigenous milk proteinases in different phases of the long term process of cheesemaking and ripening. The overall reactions lead to a breakdown of casein into small peptides, amino acids, and primary as well as secondary products of metabolism.Enzyme modified cheese (EMC) supplemented with Neutrase ®0.5L,tends to induce accumulation of intense bitter peptides. This accumulation could be reduced by further treatment of the slurries with peptidases. When Neutrase and the crude enzyme extract from Lactobacillus casei ssp. casei LLG were added to the young or unripened cheese slurry followed by a controlled incubation process, an intense cheese flavor without bitterness was developed in three days.This study explains the important role of X-PDP in the debittering process of casein hydrolysates. The incubation of bitter EMC with cell free extract from Lactobacillus casei ssp. casei LLG has resulted in the debittering of EMC within a few hours. Strong evidence has been found to relate the debittering effect of crude extract to the action of X-PDP.