不同酶水解对乳脂挥发性化合物的影响

Effect of Hydrolysis with Different Enzymes on the Volatile Compound Profile of Milk Fat

采用脂肪酶D、E及角质酶F、G水解3种不同的乳脂底物(黄油A、黄油B和稀奶油),测定水解前后乳脂酸值及挥发性化合物组成的变化。结果表明,脂肪酶D、E及角质酶F、G水解引起乳脂酸值的变化不同,质量分数50%的黄油A经脂肪酶E水解后酸值变化最明显,增加量大于40 mg/g。角质酶G仅发挥了极弱的水解作用,水解引起乳脂酸值的变化最小。乳脂底物经脂肪酶和角质酶水解后,挥发性化合物种类皆有明显增加。当以脂肪酶D为水解酶时,乳脂中辛酸含量最高(底物为质量分数93.3%的稀奶油时除外)。当以脂肪酶E为水解酶时,黄油A水解后丁酸、己酸、辛酸和癸酸含量相差不多,是含量最高的4种脂肪酸;黄油B水解后,其挥发性化合物中,以辛酸为主要产物;稀奶油水解后己酸含量最高。当以角质酶F为水解酶时,2种黄油水解后己酸含量最高;质量分数93.3%稀奶油水解后,己酸与辛酸是含量最多的2种脂肪酸;质量分数50%稀奶油水解后,癸酸含量最高。3种乳脂经3种不同酶水解后,挥发性化合物组成发生明显变化,丁酸、己酸、辛酸、癸酸4种游离脂肪酸含量增加。

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.