酵母胞外酶处理对模拟葡萄汁发酵过程中辛酸乙酯和乙酸苯乙酯生成的影响

To reveal the application potential of two yeast extracellular enzymes in winemaking for aroma enhancement, the influence of the formation of ethyl octanoate and phenylethyl acetate in model winemaking by enzyme treatment was evaluated. Extracellular extracts of Hanseniaspora uvarum and Pichia fermentans were prepared. The model grape juice with respective glycosides of target compounds was used as the fermentation medium, and then various enzyme preparations (yeast extracellular enzyme, commercial glycosidase, and pectinase) were added with equivalent β-D-glucosidase activity 5 U/L. Moreover, commercial Saccharomyces cerevisiae was inoculated to conduct the alcoholic fermentation. And fermentative juice sampled during fermentation were analyzed by GC-MS every 24 h to obtain aroma compounds. The results showed that both yeast extracellular extracts gave high activities of flavor enzymes. The activities of α-L-arabinosidase, α-L-rhamnosidase, and β-D-galactosidase in Hanseniaspora uvarum extracellular enzyme were higher, while those of β-D-glucosidase, esterase, and protease were higher in Pichia fermentans extracellular enzyme. The highest producing range of octanoic acid and ethyl octanoate was located from the 4th to 8th day during fermentation, and then the content declined. While the highest producing range of phenyl ethanol and phenylethyl acetate sited from 6th to 14th day during fermentation, and then stabilized. Comparing with AR2000 and pectinase, the enhancement of target esters by Hanseniaspora uvarum and Pichia fermentans extracellular enzyme was better. The enhancement of ethyl octanoate was nearly 3 times of the possible level of the respective glycoside hydrolysis. The improved content of phenyl ethanol by Hanseniaspora uvarum and Pichia fermentans extracellular enzyme was greater than the possible level of the respective glycoside hydrolysis, and the content of phenylethyl acetate in the end of fermentation by Hanseniaspora uvarum and Pichia fermentans extracellular enzyme was nearly 2 times of the level in control. During grape juice fermentation treated by Hanseniaspora uvarum and Pichia fermentans extracellular enzyme, the enhancement of ethyl octanoate and phenylethyl acetate was mainly at the promotion of yeast ester metabolism, and the promotion effect was much stronger than the hydrolysis of the respective glycosides, so yeast extracellular enzymes are helpful to produce relative wine esters.