Accumulation of short n-chain ethyl esters by esterases of lactic acid bacteria under conditions simulating ripening Parmesan cheese

EstA from Lactobacillus helveticus CNRZ32 (Lbh-EstA), EstB, and EstC from Lactobacillus casei LILA, and EstA from Lactococcus lactis MG1363 (Lcl-EstA) were evaluated for their ability to accumulate esters in a model system simulating Parmesan cheese ripening conditions (10 degrees C, 2 to 3% NaCl, pH 5.4 to 5.5, aw = 0.850 to 0.925) using Capalase K from kid goat as a positive control. All of the LAB esterases and Capalase K mediated the accumulation of esters in the model system in an enzyme specific manner, which was influenced by a, and selectivity for fatty acid chain-length. In general, enzyme mediated accumulation of ethyl esters was higher at aw values of 0.850 and 0.900 than at aw of 0.925, demonstrating that aw is a critical parameter influencing ester accumulation. The substrate selectivity of esterases, aw, and enzyme type may be important factors in the development of fruity flavors, as evidenced by results in this model system simulating Parmesan cheese ripening conditions.