| 1.During the winemaking process,zymosan can enhance the stability and tartar of protein in wine,balance the composition of wine,stabilize polyphenols and color,and enhance the complexity of wine aroma.In the wine industry,the method with lees aging is commonly used in order to increase the content of zymosan.However,the release rate of polysaccharides during the aging process is slow,and this process is uncontrollable to some extent,and there are problems such as quality risks.Therefore,using commercial yeast to create a convenient,fast and safe method is particularly important for improving the quality of wine.In this experiment,yeast mannan,non-active yeast,yeast cell wall and yeast glucan were taken as the research objects,and the effects of different commercial polysaccharides on the quality of wines were evaluated during the mid-fermentation of Chardonnay dry white wines and the alcoholic fermentation.The main results are as follows:Yeast mannan,non-active yeast,yeast cell wall and yeast glucan were added during the middle period of alcoholic fermentation.Through determining the total acid,volatile acidity,chroma,light transmittance,browning index,total phenolics,protein content in the wine sample,we can confirm that the optimal added amounts of yeast mannan were 0.3g/L,non-active yeast,yeast cell wall and yeast glucan were 0.2g/L.The effect of yeast mannan was significant in polysaccharide treatment than the control,the total acid increased by 32.96%,volatile acid and total phenol decreased by 33.33% and 20.78%,and the color value,light transmittance,and browning index were respectively decreased 26.32%,4.34% and 61.06%.2.The adding of four kinds of polysaccharides during the middle period of alcoholic fermentation had a significant effect on the content of aroma substances.The content of ester compounds、dilute hydrazine、aldehydes and ketones increased,and the content of volatile acids decreased.Compared with the control,within the treatment group containing yeast mannan,the content of ester compounds increased by 26.54%,the content of volatile acids was reduced by 80.12%,and the content of indole and aldehydes and ketones increased by 55.85%.Combined with PCA we can get that yeast mannan contributed significantly more to the aroma than other treatments.3.Four types of zymosan were added before aging(after pouring),Through determining the basic physicochemical indexes such as total acid,volatile acidity,chroma,light transmittance,browning index,total phenol and protein content,it was clarified that the optimal added amount of yeast mannan,non-active yeast,yeast cell wall and yeast glucan before aging was 0.2 g/L.The effect of yeast mannan was significant,the total acid increased by 26.60%,the volatile acid and total phenolic reduction decreased by 51.40% and 25.93%.The chroma,light transmittance and browning index respectively decreased by 19.04%,24.88% and 43.96%.4.Four kinds of zymosan were added before aging(after pouring),and the aroma components and contents after 90 days of aging were analyzed.The differences between the wine samples of the treatment group and the control group were significant,the esters and aldehyde ketones in the treatment group were significantly increased.Combined with PCA,the experimental group with yeast mannan had the best effect.Sensory evaluation was performed on wines after aging 90 days,the results showed that the yeast mannose liquors had the lowest sourness score,and the color intensity,roundness,aroma strength and plumpness scores were highest scored.5.Adding the yeast mannan at two different periods has great different impacts on wine quality.The addition of zymosan during the middle fermentation has a positive effect on increasing the total acid content,reducing the chroma,browning index,and increasing the type and content of aroma substances.Adding zymosan before aging(after pouring)has a positive effect on reducing the volatile acid,improving the transparency light rate and enhancing protein stability. |
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