Production Of Hanseniaspora Uvarum Active Dry Powder And Its Application Effect On Winemaking Of Vitis Davidii FoЁx

In recent years,wild grapes have been widely used in winemaking.Vitis davidii Fo（?）x is an unique cultivar in the southern part of China.Its berry skin contains abundant anthocyanins,proanthocyanidins,resveratrol and other antioxidant substances that are benefit for human health.However,the extremely high acid content in berries lead to weak wine aroma characteristic.Non-Saccharomyces can enhance wine aroma and complexity through secreting various extracellular enzymes and producing great amount of secondary metabolites.Besides,dry powder form of non-Saccharomyces is convenient to inoculate,store and transport.The aim of this research is to optimize the production of Hanseniaspora uvarum active dry powder,and apply the product on the wine fermentation of Vitis davidii Fo（?）x to improve aroma quality.The main results are as follows:（1）The optimization of conditions in high-density culture of H.uvarum.Through comparing the effect of growth curve and centrifugal conditions（speed and time）on the centrifugal recovery rate,the highest recovery rate was 80.89%±9.43%whose optimal condition were:activation culturing for 22～24 h at 28℃,amplification culturing at 180r/min for 20～22 h,fermentation culturing at 150 r/min for 12～14 h,then centrifuged at7000 r/min and 4℃ for 20 min.（2）The protective effect of six single-protectants.Resuts showed that lactose,sucrose,trehalose,skim milk powder,glycerol and the sodium glutamate was capable of protecting yeasts.Three best protectants were selected to conduct Box-Benhnken test to optimize their individual composition,namely,10.07%lactose,10.13%skim milk powder and 6.22%glycerol.After undergoing a vacuum freeze drying,the survival rate of yeast obtained was82.30%±1.18%.The freeze-dried yeast powder was sealed in a foil pouch and stored at 4℃ for three months,viable cells of dry yeast was 85.83%.（3）The influence of mixed fermentation with H.uvarum and commercial Saccharomyces cerevisiae on the physicochemical characteristics of wine.Different treatments showed various effects on physicochemical indexes.All the mixed fermentations could improve the content of alcohol and volatile acid.Among which,sequential fermentation（H.uvarum was inoculated one day before S.cerevisiae）supremely increased the contents of total phenolic,total anthocyanin,total tannin,the proportions of polymeric anthocyanin,and co-pigmented anthocyanin.（4）Wine volatile analysis through GC-MS and aroma evaluation through sensory analysis.Mixed fermentations,especially the sequential fermentation when H.uvarum yeasts were inoculated two days before S.cerevisiae,significantly increased the total content of aroma components.The contents of higher alcohols,acetate esters and alcohol esters in such fermentation were significantly higher than that in pure S.cerevisiae fermentation.In addition,this fermentation also increased the content of C₆compounds,benzene derivatives,volatile phenols and C₁₃-norisoprenoids,resulting in an overall enhancement of aroma characteristics like tropical fruit,small berries and nuts.