Q14: Enzymes involved in the formation of ethyl esters leading to... - Fundamentals of Dairy Microbiology & Raw Milk Quality - ICAR AIEEA PG Dairy Science 09 July 2023 (Shift 1) Paper | Agrigyan

Enzymatic synthesis of ethyl esters in milk:
The development of fruity off-flavors in milk and dairy products (such as in defects caused by psychrotrophs like Pseudomonas fragi) is caused by the synthesis of volatile ethyl esters (principally ethyl butyrate and ethyl hexanoate):

• Lipases (glycerol ester hydrolases) hydrolyze milk fat triglycerides to liberate short- and medium-chain free fatty acids (butyric, caproic, and caprylic acids).
• Esterases (carboxylesterases / alcohol acyltransferases) subsequently catalyze the esterification of these liberated free fatty acids with ethanol to form aromatic ethyl esters, imparting a distinct fruity/strawberry/pineapple odor.