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Effect of Fermentation Conditions on Yeast Growth and Quality of Ice Wine

Author: DuWenHua
Tutor: LiuZhongYi
School: Xiangtan University
Course: Chemical Engineering and Technology
Keywords: ice wine nutrient SO2 volatile acid yeast mortality trehalose fructose glucose
CLC: TS262.6
Type: Master's thesis
Year: 2013
Downloads: 64
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Abstract

In this paper, the changes of yeast mortality in ice wine fermentation broth, thechanges of the volatile acid content during ice wine fermentation and the changes oftrehalose, glucose and fructose content in ice wine were mainly investigated underconditions of different original sugar content, different adding amounts of SO2anddifferent periods of nutrients added. The objective was aimed to determine thesuitability of SO2added amount, the suitable ice grape sugar content, and adding ofnutrient supplements for yeast growth in ice wine brewing process.The changes of the volatile acid was investigated under conditions of differentoriginal sugar content and adding amounts of SO2during the fermentation process ofred ice wine. The results showed that under the same amount of SO2the higheroriginal sugar content of grape juice was, the higher volatile acid would be during thefermentation process of red ice wine.Under the same original sugar content of thegrape, when SO2dosage was between30mg/L to100mg/L, the volatile aciddecreased with the increase of SO2dosage. When SO2dosage was150mg/Lcompared to30mg/L, its volatile acid increased instead. Volatile acid generation andaccumulation is obviously influenced by original sugar content of grape juice andadding amount of SO2during the fermentation process of red ice wine.Yeast mortality in the fermentation process was investigated under conditions ofdifferent original sugar content, different adding amounts of SO2and different addingways of nutrition. The results showed that the change trends of yeast mortality in icewine fermentation broth decreased firstly and then increased gradually and finallybecame flat lastly; When other conditions are the same, such as the same period ofnutrients added, the same initial adding amount of SO2, yeast mortality increased asinitial sugar content of ice grape increased in ice wine fermentation broth; When theperiod of nutrients added and initial sugar content in ice wine fermentation broth arethe same, the initial adding amount of SO2was60mg/L compared to30mg/L, thedeath rate of yeast had significantly decreased; When the initial adding amount of SO2was100mg/L compared to30mg/L, the death rate of yeast slightly decreased; Whenthe initial adding amount of SO2was150mg/L compared to30mg/L, the death rate ofyeast increased instead; When initial sugar content in ice wine fermentation broth andinitial adding amount of SO2are same, different periods of nutrition added had little effect on death rate of yeast.The changes of trehalose, glucose and fructose content in ice wine wereinvestigated with different original sugar content, different adding amounts of SO2and different adding ways of nutrition. The results showed that in the same bottle ofice wine, trehalose, glucose, fructose content size relationships is fructose> glucose>trehalose; With the increase of initial sugar contentin fermentation broth, the trehalose,glucose and fructose content in ice wine increased; In ice wine fermentation broth thedifferent periods of added nutrition had no effect on trehalose, glucose, fructosecontent in ice wine; When the initial sugar content is same and without addingnutrition in fermentation broth, the initial SO2adding amount was60mg/L and100mg/L compared to30mg/L, the content of fructose, glucose decreased in ice wine,and when the initial SO2content was150mg/L compared to30mg/L in fermentationbroth, the content of trehalose, fructose, glucose increased in ice wine. The initialsugar and SO2content in the fermentation broth have significant effect on trehalose,fructose, glucose content in ice wine, so do the addition of nutrients.Under the premise of ensuring the quality of ice wine, A relatively low initialsugar content of ice grape juice should be choosed for fermentation; When the initialadding amount of SO2is60mg/L, which is most favorable for ice wine, because thereduction of volatile acid and yeast mortality is the largest, and the sugar content inice wine drop rarely; When original sugar content was430g/L to455g/L, nutritionshould be added in ice wine fermentation broth.

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