不同pH对模拟葡萄酒液中酵母自溶过程含氮组分变化的影响

Changes of Nitrogen Compounds in a Model Wine With Different p H During Yeast Autolysis

实验以酿酒酵母EC1118为研究对象,分别加入p H为2.8,3.0,3.2,3.4,3.6的葡萄酒模拟酒液中,并在40℃条件下进行加速自溶培养,跟踪测定了24,48,72,96,120h时的蛋白酶活、α-氨基氮、总氮及氨基酸含量。结果表明,酵母自溶过程中蛋白酶活力先增加后下降,48h酶活最高,72h后趋于稳定。α-氨基氮及总氮含量随时间增加,含量呈现升高的趋势;但随模拟酒液p H的增大,α-氨基氮含量升高,总氮下降。酵母自溶液中,Asp、Glu、Phe、Ala、Leu以及γ-氨基丁酸含量较高,且Ala和γ-氨基丁酸是最主要两种氨基酸,大约占了总氨基酸含量的50%。综上所述,可以推测出在自溶过程中,随时间的增加,酵母自溶程度逐渐增大;随模拟酒液p H的增加,酵母细胞自溶过程逐渐减缓。

Saccharomyces bayanus EC1118 was added into a model wine system with pH value of 2.8, 3.0, 3.2, 3.4, and 3.6, respectively. The model wines added with yeast EC1118 was cultivated in incubator of 40℃, in which protease activity, contents ofα-AN, total nitrogen and amino acids were detected at 24, 48, 72, 96 and 120h incubation period, respectively. It was found that the protease activity increased first and then declined, the highest activity appeared at 48h and a stable trend displayed after 72h. The contents of α-AN and total nitrogen increased gradually with the time going on;the content ofα-AN increased while that of total nitrogen decreased with the increase of pH value. Amino acid Asp, Glu, Phe, Ala, Leu, andγ-aminobutyric acid (GABA) presented the higher contents in the model systems, and Ala and GABA were the most important two amino acids in 18 amino acids detected which accounted for approximately 50%of total amino acids. Therefore it was suggested that the degree of yeast autolysis was enhanced with both the increase of incubation period and the decrease of pH value in the model wine system.