Fermentation Characteristics Of Wild Yeast During Cold Maceration And The Effect On The Aroma Of Petit Manseng Wine

In order to explore the changing rules of aroma components during the cold maceration process,the isolation and identification of wild yeast on the grape,and the composition of the aroma components co-fermented by wild yeast with commercial yeast,using Petit Manseng wine grape variety as raw material.Different cold impregnation time was designed respectively,exploring the growth characteristics of different wild yeasts,wild yeasts were fermented independently or co-fermented with commercial yeast separately in simulated grape juice and Petit Manseng grape juice.Comparison of the varieties and contents of aromas produced by fermentation under cold maceration conditions and wild yeast in order to provide a theoretical basis for choosing the appropriate vinification to produce the high quality Petit Manseng dry white wine and amplification of yeast strain resources.Cold maceration for 0,1,3,5,and 7 days to make dry white wine.The effects of these treatments on volatile compounds in Petit Manseng dry white wines were also investigated by Headspace Solid-Phase Micro-Extraction(HS-SPME)coupled with GC-MS and combined with internal standard quantitative methods.The results are shown as follows.(1)Cold maceration treatment could increase the content and varieties of aroma substances in Petit Manseng grape juice,and the content of aroma substances is the highest in cold maceration 1 day,the most varieties of aroma substances were detected in cold maceration 7 days,and the 48 kinds of volatile aroma substances were detected after cold maceration treatment.(2)The content and varieties of aroma substances in the Petit Manseng dry white wine by cold maceration treating for 5 days reached the highest.Among them,[R-(R*,R*)]-2,3-Butanediol,phenylethyl alcohol,phenyl ethyl acetate,ethyl acetate,isoamyl acetate,ethyl 9-decenoate,ethyl octanoate,ethyl caprate and terpenoids,the increase in the content of these substances made a major contribution to the overall aroma enhancement of the Petit Manseng dry white wine of the cold maceration for 5days.The content of acid substances was low,and the aroma and taste were more harmonious and rounded.A total of 30 wild yeast strains in the paper,which were isolated from the Petit Manseng grape.the result showed that the selected yeast stains belonged to 9 species of8 denera: Pseudozyma aphidis,Rhodotorula sp.Rhodotorula glutinis,Papiliotrema laurentii,Cryptococcus laurentii,Hanseniaspora uvarum,Metschnikowia chrysoperiae,The growth curve is also studied.The 7 strains of wild non-Saccharomyces were fermented separately and 7 strains of yeast were mixed culture fermentation or co-fermented with commercial yeast separately in simulated grape juice and Petit Manseng grape juice.The results show:(1)In the 7 strains of wild non-Saccharomyces,the Hanseniaspora uvarum has the strongest ability to produce aroma substances by fermentation.Especially the production of phenyl ethyl alcohol,ethyl caprylate and ethyl caprylate with flowery and fruity aroma.(2)In simulated grape juice,the 7 strains of wild yeasts and mixed wild yeast were co-fermented with commercial yeasts.Among them,the Hanseniaspora uvarum could interact with commercial yeasts to produce higher content and species of aroma.(3)Wild non-Saccharomyces such as Cryptococcus laurentii,Hanseniaspora uvarum,Metschnikowia chrysoperiae,and 7 strains of wild yeast were mixed culture inoculation co-fermented with commercial yeasts in Petit Manseng grape juice.Compared with inoculating commercial yeasts separately,these operations could produce higher content and variety of aroma substances.