Effect Of The Key Enzymes About Esters In Saccharomyces Cerevisiae On Relevant Volatile Compounds In Wine

As vital compounds in wine aroma,esters play a key role in wine quality.The activity of three key enzymes(alcohol acetyltransferases,esterase synthesis and hydrolysis enzymes)of seven wild saccharomyces cerevisiae strains and five commercial saccharomyces cerevisiae strains was investigated by simulating the metabolic pathway of acetate esters in vitro,for revealing the relationship between these key enzymes and esters content.Seven wild saccharomyces cerevisiae strains and five commercial saccharomyces cerevisiae strains were inoculated to simulate grape juice medium and “Chardonnay” grape juice,respectively.Volatile substances(mainly esters)in two batches of wine samples were detected by HS-SPME and GC-MS immediately after alcohol fermentation.The results indicated:1.For the most of saccharomyces cerevisiaes strains,the activity of alcohol acetyltransferases was higher than esterase synthesis enzymes,and the activity of esterase hydrolysis enzyme was higher than esterase synthesis enzyme;the difference of the esterase hydrolysis enzymes activity and alcohol acetyltransferases activity among saccharomyces cerevisiaes strains was big,while the difference of esterase synthesis enzymes among these strains was small.Besides,the activity of three key enzymes of wild saccharomyces cerevisiae strains was not lower than commercial strains.2.For simulate grape juice medium,the activity of esterase hydrolysis enzyme played a decisive role on the content of acetate esters,followed by alcohol acetyltransferase,while the effect of esterase synthesis enzyme was relatively smaller;in addition,when the activity of esterase synthesis and hydrolysis enzymes was certain,the relationship between alcohol acetyltransferase activity and acetate esters content was roughly positive,in other words,the higher alcohol acetyltransferase activity,the more acetate esters content.3.The analysis result of “Chardonnay” grape juice corresponded with simulate medium even though complicated volatile substances in “Chardonnay” wine influenced the content of acetate esters.The screening of local saccharomyces cerevisiaes is one of the solutions to solve the serious homogeneity in wine quality.The traditional screening method according to wine aroma has many shortcomings,such as time consuming,heavy workload,variable factors and so on.The relationship between key enzymes activity and products content in this paper can provide theoretical basis for new methods of screening saccharomyces cerevisiae.Besides,it has important reference value and practical significance for improving the quality of aroma and wine.