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

Influence of Yeast Extracellular Enzymes on Formation of Ethyl Octanoate and Phenylethyl Acetate During Model Grape Juice Fermentation

分析两株优选非酿酒酵母胞外酶处理对酒精发酵过程中辛酸乙酯和乙酸苯乙酯生成的影响,旨在揭示其增香酿造的应用潜力。提取葡萄汁有孢汉逊和发酵毕赤两株酵母胞外酶,以模拟葡萄汁为发酵基质,添加目标香气成分对应糖苷底物,按照β-D-葡萄糖苷酶活5U/L的标准添加酵母胞外酶、AR2000酶和果胶酶制剂,酿酒酵母启动酒精发酵,每隔24h取样进行目标香气物质的GC-MS定量分析。结果表明,两株酵母胞外酶均表现出较高的风味酶活性,葡萄汁有孢汉逊胞外酶中α-L-阿拉伯糖苷酶、α-L-鼠李糖苷酶和β-D-半乳糖苷酶活性较高,发酵毕赤胞外酶中β-D-葡萄糖苷酶、酯酶和蛋白酶活性较高。发酵过程中辛酸与辛酸乙酯的最大生成区间是发酵的第4~8天,而后趋于下降,而苯乙醇和乙酸苯乙酯的最大生成区间是发酵的第6~14天,之后趋于平稳。相比于商业糖苷酶和果胶酶,葡萄汁有孢汉逊和发酵毕赤胞外酶促进辛酸乙酯和乙酸苯乙酯生成的效果更好,其中促进辛酸乙酯的生成量接近对应糖苷水解最大生成量的3倍;葡萄汁有孢汉逊和发酵毕赤酵母胞外酶促进苯乙醇的生成量远大于糖苷最大生成量,发酵结束时促进乙酸苯乙酯的生成量接近空白对照生成量的2倍。葡萄汁发酵过程中,优选酵母胞外酶处理主要是从促进酵母酯代谢的角度促进辛酸乙酯和乙酸苯乙酯的生成,且促进生成量远高于对应糖苷的水解生成量,因此有利于葡萄酒相关酯类的生成。

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 equivalentβ-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 ofα-L-arabinosidase,α-L-rhamnosidase,andβ-D-galactosidase in Hanseniaspora uvarum extracellular enzyme were higher,while those ofβ-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.