Effect Of Glutathione-enriched Inactive Dry Yeast On Quality Characteristics Of Kiwi Wine

In recent years,kiwi wine,as a kind of deep-processed product of kiwi fruits,has shown great economical and nutritional potential.However,there are still many problems related to current kiwi wine products,such as dissatisfactory color and excessive acidity.Gutathione(GSH)is a tripeptide with strong antioxidant ability,and has been widely used in wine quality improvement studies.Neverthless,the permitted addition dose of pure GSH is restricted,so it is meaningful to evaluate the effect of glutathione-enriched inactive dry yeast(g-IDY),a potential substitute for GSH,on wine quality.In present study,‘Xuxiang' kiwi fruit was used as raw material to be fermented with or without pomace.Different concentrations of g-IDY were added in kiwi juice before alcoholic fermentation or kiwi wine before aging.The effects of g-IDY on quality characteristics of kiwi wine were evaluated and main findings are as follows:(1)The addition of g-IDY into kiwi juice enhanced the content of GSH in kiwi wine and significantly improved the color of kiwi wine.The addition of 300 mg/L g-IDY into wine fermented with pomace had the most obvious effect.Moreover,the addititon of g-IDY improved the antioxidant ability and total phenol content of kiwi wine,but had no obvious influence on contents of individual phenolic compounds.PCA showed that g-IDY had better effect in wine fermented with pomace.(2)The addition of g-IDY enhanced most of amino acid and volatile compound content in kiwi wine.PCA showed that esters mainly contributed to the volatile contents in wine fermented with pomace,while in wine fermented through pure juice,they were alcohols and terpenes.Compared to wine fermented with pomace,wine fermented through pure juice was more likely to be influenced by g-IDY.PLS regression showed that the amino acid content in kiwi wine was closely correlated with the volatile composition contents,and E-nose showed excellent ability to predict the contents of esters and total volatile compounds in kiwi wine.(3)The addition of high level g-IDY into kiwi wine significantly improved the color of kiwi wine after aging for six months and mainly effected on the decrease of yellow tint.Esters and alcohols mainly contributed to the volatile contents in kiwi wine after aging.The addition of high level g-IDY into wine fermented with pomace enhanced the concentrations of esters and terpenes of kiwi wine after aging.Nevertheless,g-IDY might be responsible for the decrease of fatty acid content in kiwi wine after aging.(4)The aroma analysis showed that g-IDY increased the proportion of fruity aroma in kiwi wine aroma.The sensory analysis showed that the addition of g-IDY improved the clarity and color of kiwi wine,notably in case of fermentation with pomace.All the above findings suggest that g-IDY could effectively improve the quality of kiwi wine.Moreover,the addition dose,time and fermentation process had different influence on the g-IDY activity in kiwi wine.These results provide new direction for kiwi winemaking development,and reliable theoretical knowledge for the application of g-IDY in winemaking industry.