The availability of ethanol: A decisive factor in the biosynthesis of ethyl esters in enzyme-modified cheese flavor.

Lactic acid bacteria (LABs) exhibit a strong acid-producing capability in the manufacturing of enzyme-modified cheese flavor (EMCF), but their limited ester synthesis ability resulted in EMCF having strong sour aroma with imbalance flavor. Strains with higher esterase activity were screened by simulated fermentation. Lacticaseibacillus casei exhibited greater activity in synthesizing ethyl hexanoate and ethyl octanoate, while Lactobacillus helveticus had a higher yield of ethyl acetate. The analysis of volatile compounds revealed that ethyl esters were not detected under the conditions of both fatty acids and esterases, indicating that ethanol served as a key substrate limiting the synthesis of esters. The addition of ethanol significantly increased both the variety and concentration of volatile compounds, especially acids, alcohols, and ethyl esters. Sensory analysis indicated that ethanol contributed to the development of fruity and wine aromas. EMCF exhibitd a softer flavor at 0.5 % ethanol addition, which providing practical insights for balancing EMCF flavor.