Study On Fermentation Process And Aroma Components Of Low-Alcoholic Mulberry Wine

Low-alcoholic mulberry wine is made by alcoholic fermentation of mulberry juice with alcohol content between 1.0-7.0%(v/v).It is nutritious and have numerous health benefits making it idea for health-conscious individual Presently grape wine yeast,which has high activity,fast fermentation rate,and high alcohol production is used to ferment mulberry wine.However,its high alcohol production makes it not suitable for brewing low-alcoholic mulberry wine.Besides,mulberry fruit has low aromatic profile which impacts on the final mulberry wine.In this regard,efforts are being made to improve on the quality of low-alcoholic mulberry wine.Consequently,it is important to employ a suitable yeast strain in the production of low alcoholic wine.In view of this,the study aimed at identifying suitable yeast for fermenting low-alcoholic mulberry wine.The study also sought to improve on the aroma of the wine through lactic acid fermentation and blending it with fermented malt liquid Combined fermentation of lactic acid bacteria and fermented malt,the aroma of low-alcoholic mulberry wine was improved,at the same time explored the better fermentation parameters of mulberry wine and malt fermentation liquid.This will provide theoretical basis for low-alcoholic mulberry wine production.The main research contents and conclusions are as follows:(1)Four stains,D1,Z5,Z8 and Z9,were isolated from mulberry fruit and cheese strain,which have low ethanol production capacity.Analyzing their homologous 18 SrDNA sequence and constructing phylogenetic tree,the strain D1 and Z5 were identified as Kluyveromyces lactis and Hanseniaspora uvarum respectively while strain Z8 and Z9 were Pichia fermentans.The yeast D1 was suitable for fermenting low-alcoholic mulberry wine by analyzing the indexes and sensory evaluation scores of the mulberry wines fermented with the different yeast strains.(2)Comparing the sensory scores of the low-alcoholic mulberry wine fermented with the different lactic acid bacteria,Lactobacillus paracasei was found to be the most suitable for producing low-alcoholic mulberry wine.A second order polynomial equation for the sensory scores and fermentation parameters for the low-alcoholic mulberry wine was established with response surface methodology.The data indicated that,the optimum fermentation parameters were: inoculum concentration(3.11%),initial soluble solids(16%)and fermentation temperature(31?).(3)Comparing the sensory scores of the different fermentation methods,CO fermentation with yeast 71 B and Lactobacillus paracasei was found to the most appropriate fermentation method.A second order polynomial equation for the sensory score and fermentation parameters of low-alcoholic mulberry wine were established with response surface methodology.The data indicated that the optimum fermentation parameters were: amount of inoculum(0.25 g/L),fermentation time(38.4 h),fermentation temperature(34.3?)and 12 % initial soluble solids.(4)It was better for improving the effects of alcohol aroma to blend mulberry wine and malt fermentation liquid with the ratio of 80:20.The aromatic profile and their quantities were significantly enhanced with the use of malt fermentation liquid.The difference between the activity of aroma components of the low-alcoholic mulberry wine before and after blending were hexyl acetate,ethyl phenylacetate,3-methyl-butanal,and nonanal,which made the blended low-alcoholic mulberry wine to have a more fruity and sweet aroma.The blending did not only retain the main aroma components of original low-alcoholic mulberry wine,but adds honey sweet,mellow and refreshing fruity aroma.This resulted in improving the flavor of low-alcoholic mulberry wine.(5)From the aroma values and the smell result of GC-O,the characteristic aroma components of the low-alcoholic mulberry wine after blending were determined.The aroma components were isoamyl alcohol,phenethyl alcohol,ethyl acetate,ethyl butyrate,ethyl butyrate,ethyl 2-methyl butyrate,isoamyl acetate,hexyl acetate,ethyl heptanoate,ethyl caproate,phenethyl acetate,3-methyl-butanal,nonanal,decyl aldehyde and ethyl phenylacetate,which resulted in a low-alcoholic mulberry wine with harmonized mellow,fruity and sweet honey.