Study On The Enhancement Of Wine Aroma Using Wild Non-saccharomyces And Their Glycosidase

China lies to the west of the Pacific Ocean.More than half part of the wine producing districts of China have climates with much rain in summer and autumn.Grapes cannot reach full maturity in most years.Therefore,the grapes cannot attain their optimal winemaking quality,lacking aromatic characteristics and olfactometric traits of typical wines in Mediterranean Climate.Glycosidic precursors are present in fruit juices,musts,and wines,which are flavorless and non-volatile.The main factor that determines varietal aroma characteristics is enzymatic hydrolysis.In this study,based on aroma compounds of winearoma characteristics,an aroma enhancing winemaking process using wild non-Saccharomyces and their glycosidases to improve aroma quality of Chinese wine with geography indication was developed.1.Non-Saccharomyces were screened and obtained.In order to study the evolution of yeast species associated with spontaneous fermentation,wild yeasts in three wine regions were screened and identified.A total of 296 yeast isolates were initially classified based on morphology in YunNan Province.The yeast communities had different species diversity.Ten species from eight genera were identified.They were Saccharomyces Cerevisiae.Hanseniaspora uvarum、Hanseniaspora Guilliermondii、Pichia kluyveri、Candida speciesIssatchenkia Orientalis、Metschnikowia、Schizosaccharomyces、Pichia、Membranefaciens and Rhodutorula species,accounting for 45.3%、18.2%、8.8%、8.1%、6.1%、5.4%、4.1%、3.7%、2.7%and 0.34%,respectively.A total of 189 yeast isolates were initially classified and eight species from eight genera were identified in Heibei and Heinan Province.They were Metschnikowia、Saccharomyces cerevisiae、Hanseniaspora uvarum、Issatchenkia orientalis、Pichia kluyveri、Pichia membranefaciens、Candida species and Rhodutorula species,representing 0.53%、48.7%、20.6%、2.6%、19.1%、2.1%、4.8%and 1.6%,respectively.Most of these non-Saccharomyces yeasts are active during the early fermentation stages,whereas the process is eventually completed by Saccharomyces cerevisiae.In addition,after fermentation,some non-Saccharomyces were still detected.2.A new method called the Semiquantiative Colorimetric Method that rapidly screens high p-glycosidase-producing strains was developed.Using this method,four yeast strains with high β-glycosidase activity(Hanseniaspora uvarum,Rhodutorula species,Pichia membranefaciens,and Schizosaccharomyces)were screened.To test the reliability and accuracy of our developed method,β-glycosidase activities from the 37 strains were measured by the p-NP(p-nitrophenol)method.Based on the β-glycosidase activities,a linear regression equation was generated.According to the results,the Semiquantitative Colorimetric Method had a good linear correlation with the p-NP method(quantitative method).Therefore,the developed method can be used for screening native yeast strains with glycosidase activity.It is particularly suitable for performing large-scale screenings.3.The conditions of extracting glucosidase were optimized and effects of Winemaking Conditions on β-glucosidase Activity were evaluated.Typical winemaking conditions(e.g.,high sugar and ethanol levels,low pH values,and high polyphenol concentrations)may inhibit the activity of grape and microbial β-glycosidases.Therefore,to enhance wine aroma it is crucial to select β-glycosidases from yeasts that are suitable for winemaking.Compared with other three yeasts,the β-glycosidase activity from Hanseniaspora uvarum had suitable characteristics for winemaking conditions.4.The Aroma enhancement ability of Hanseniaspora Uvarum selected and itsβ-glycosidases was studied.An aroma enhancing winemaking process using Hanseniaspora uvarum and its β-glycosidase was developed.The results showed that Hanseniaspora uvarum and its β-glycosidase selected can enhance the sensory quality and aroma compounds of wines,and treating must was better than treating grape and the mixed fermentation was superior to the pure fermentation."AI1"(β-glycosidase treating must)和 "AI5"(the mixed fermentation 1:1)were optimal treatments.