Fatty acids released from milk fat by lipoprotein lipase and lipolytic psychrotrophs

The ability of 13 different strains of psychrotrophs to release free fatty acids in milk was evaluated by using GC analysis. The 13 strains could be categorized into 3 groups: Group 1 consisted of bacteria that grew well and released large quantities of free fatty acids, group 2 consisted of bacteria that grew well but released low amounts of free fatty acids, and group 3 consisted of bacteria that did not grow well nor released large quantities of fatty acids. In group 1, 3 strains were determined to be highly lipolytic, releasing short-chain fatty acids in amounts greater than reported threshold values. Group 3 consisted of 2 strains, which did not grow well in beat-treated milk, and the subsequent release of free fatty acids was minor during the 10-d monitoring time. The other 8 strains tested showed no specific pattern of fatty acid release and quantities of short-chain fatty acids were not large, despite the ability to grow to high numbers in the treated milk. This work indicates that the lipolytic activity of psychrotrophs common in raw milk is specific to the species and a general prediction of free fatty acid release may not be possible.