Regularity Of Wine Aroma Enhancement Using A Novel Hanseniaspora Uvarum And Its Glycosidase

Complex and typical aroma siginificantly contribute to wine sensory quality.Most wine-producing regions in China are located in the monsoon-climate areas,where the harvest is often put forward to avoid much rainfall during the ripenning season,resulting in an insufficient accumulation of flavor compounds in grape and weak typicality in reasulting wine.Besides,the main trend of using commercial yeasts as fermentation starter leads to wines with unitary styles.To improve the sensory quality of domestic wine,an indepth study on regulating wine aroma should be taken into consideration.Based on mixed fermentation,this study proposed to stimulate wine aroma release using a novel Hanseniaspora uvarum and its glycosidase.The main results are shown below:1.Modeling of yeast growth in mixed fermentation.A novel H.uvarum strain and a commercial S.cerevisiae starter were inoculated in synthetic cultures according to different time lag where the cultures by single strain as the control.Results showed that Logistic models used for predicting yeast biomass in fermentation were fitting,with R2 ranged between 0.960 and 0.998.Due to the “Starter Leading Effect” we proposed in sequential fermentation,the fermentation sustainability of H.uvarum were significantly improved by the extended inoculation time lag.All the mixed-fermentation treatment achieved alcoholic fermentation while H.uvarum alone could not complete the fermentation.2.Generation of yeast-derived aroma in mixed-culture.Volatile compounds obtained from fermented cultures were subjected to Solid phase microextraction-Gas Chromatography-Mass Spectrometer(SPME-GC-MS)analysis.The detected aroma compounds included 10 higher alcohols,6 volatile fatty acids,5 acetates,4 short-chain fatty acids ethyl esters,8 medium/long-chain fatty acid ethyl esters,2 other esters,4 carbonyl compounds and 7 benzene derivatives.Isoamyl alcohol,octanoic acid,ethyl acetate,ethyl butyrate,ethyl caprylate,ethyl lactate,2-furaldehyde and 2-phenylethanol were the main contributors to the differences of aroma amounts in different cultures.Hierarchical Cluster Analysis of aroma components suggested that mixed-fermentation with strong aroma producing ability was a potential candidate for wine fermentation application.3.Tolerance of glycosidase extract from H.uvarum to winemaking conditions.In order to evaluate its winemaking applicability,glycosidase extract was placed into different levels of stress conditions: glucose,ethanol,acidity and combined stressful condition,with a commercial glycosidase AR2000 as the comparison.The β-glucosidase activity obtained from different treatment confirmed that H.uvarum glycosidase performed well,even could possess more than 75% initial activity in extremely stressful conditions.The desired adaptation of H.uvarum glycosidase extract ensured its potential application in wine aroma enhancement.4.White wine aroma enhancement using H.uvarum and its glycosidase.Ecolly grape was consequently fermented,and the conventional approach that inoculation with single S.cerevisiae was served as contrast.The detected wine aroma compounds indicated that sequential fermentation and enzyme treatment were both able to encourage most varietal and fermentative aroma components;the effect of simultaneous fermentation was similar to that of contrast,only increasing a few varietal and fermentative aroma compounds.Sensory analysis demonstated that sequential fermentation and enzyme treatment could not only removed green odor that generated by conventional brewing but also improved floral and fruity characteristics.However,wine fermented by simultaneous inoculation harboured the risk of triggering microbial odor.5.Red wine aroma enhancement using H.uvarum and its glycosidase.Cabernet Sauvignon wine was elaborated using the same brewing process as that of Ecolly.As for aroma compounds,sequential fermentation specially increased the concentrations of acetates and some varietal aroma compounds,while enzyme treatment intensified the hydrolysis of aromatic glycosides.Simultaneous and conventional fermentation gave Cabernet Sauvignon wine more aroma compounds than that of Ecolly.For aroma characteristics,although conventional fermentation give wine intense berry characteristics,this process also encourage the risk of releasing microbial and green flavors;Sequential fermentation triggered the intense nail polish odor;Instead,wine treated by simultaneous inoculation presented mild and complex aroma characteristics,like fruity,dairy,spice and floral;Moreover,H.uvarum glycosidase enhanced aroma complexity,giving red wine intense floral,vegetal,berry and smoky aroma characteristics.