Abstract: In this study, three different kinds of milk fat (two butters (A and B) and cream) were hydrolyzed respectively with two lipases (D and E) and two cutinases (F and G), and acid value and volatile compound profile before and after hydrolysis were compared. The results indicated that the variation of acid value after hydrolysis depended on the enzyme used. The largest increase in acid value of over 40 mg/g was observed after hydrolysis of 50% (m/m) butter A by lipase E. Cutinase G, however, very weakly hydrolyzed the milk fat and caused the smallest change in acid value. More volatile compounds were identified in hydrolyzed milk fat. Lipase D produced the highest content of octanic acid when hydrolyzing the butters and 50% (m/m) cream (except when using 93.3% (m/m) cream as substrate). After hydrolysis by lipase E, butyric acid, hexanoic acid, octanic acid and decanoic acid were the major compounds in the hydrolysate of butter A, whereas the most prominent volatile compounds in the hydrlysates of butter B and milk cream were octanic acid and hexanoic acid, respectively. After hydrolysis by cutinase F, hexanoic acid and octanic acid were the major volatile compounds in 93.3% (m/m) cream, while hexanoic acid and decanoic acid were major volatile compounds in the hydrolysates of butters and 50% (m/m) cream, respectively. The results showed that hydrolysis by lipases or cuitnases caused a significant change in the volatile compound profile of milk fat, not only producing new fatty acids, but also increasing the contents of butyric acid, hexanoic acid, octanic acid, and decanoic acid.

Key words: lipase, cutinase, acid value, solid-phase microextraction, volatile compounds