Study On The New Technology Of Mijiu-making By Enzymes

Chinese traditional fermented-Mijiu(rice wine,hereinafter referred to as Mijiu)has been favored by consumers in recent years due to its unique flavor and rich nutrition,and its development is relatively rapid.The traditional brewing process of Mijiu using rice qu as saccharification and fermentation starter,but the quality of qu is unstable,and the brewing process is relatively rough,which results in poor stability in quality of products,and limited production on a large scale.Based on the current status of Chinese traditional Mijiu,this study explored the application of enzymatic brewing technology in Chinese Mijiu,and used enzyme preparations and pure yeast to replace qu for brewing Mijiu.Through the analysis of the quality characteristics of traditional typical Mijiu,the screening of yeast and the application of various enzyme preparations,the new technology of Mijiu by enzymatic brewing was established,which provided a new way to get rid of the current problems in the Mijiu industry.It provided a basis for the establishment of scientific evaluation system for the Mijiu and the development of new products in China,and provided a reference for the mechanization and modernization of the Chinese Mijiu industry.The main findings of this paper are as follows:(1)The classification characteristics of traditional typical Mijiu and the target type of Mijiu produced by enzymatic process were clarified.Based on the cluster analysis of reducing sugar and alcohol content in Mijiu,10 traditional typical Mijiu samples in different regions were clearly divided into two categories,one with high alcoholicity and low sugar content,and the other with low alcoholicity and high sugar content,which basically reflects the fermentation degree of Mijiu.There were obvious differences in basic physicochemical parameters,taste characteristics and flavor components.The high alcoholicity and low sugar content type were the main target of enzymatic process,with the type had relatively complicated brewing process,and there were problems such as higher alcohols,relative lack of esters and volatile acids in flavor components,and taste defects in this type.(2)Mijiu yeast suitable for enzymatic fermentation was obtained.Several yeasts were isolated from traditional Mijiu qu and mash,Saccharomyces cerevisiae and Saccharomycopsis fibuligera were identified by 26S rDNA.Through screening,a strain of yeast YLJ5 with strong fermentation ability,good environmental tolerance and good low temperature fermentation performance was obtained for enzymatic brewing process.(3)The technological conditions of enzymatic brewing were determined.The crushed rice(27 meshes)was used,the ratio of material to water was 1:2,the thermostable a-amylase addition amount was 10 U·g-1,the liquefaction temperature was 95? and the liquefaction time was 20 min,the glucoamylase dosage was 250 U·g-1,the protease P1 was added in an amount of 1 U·g-1.The Mijiu brewed by the enzymatic method had an alcohol content of 18%vol and a reducing sugar content of less than 10 g·L-1;compared with traditional brewing,its taste characteristics were more balanced,and the content of volatile flavor components,especially esters,was significantly higher than that of traditional Mijiu,but the higher alcohols content was still high.The application of lipase in the enzymatic production of Mijiu can shorten the fermentation period,and had no significant effect on the physicochemical parameters,but it led to the increase of higher alcohols content in Mijiu.(4)In view of the high content of higher alcohols in enzymatic brewing,the low temperature enzymatic brewing technology of Mijiu was studied.The results showed that lowering the enzymatic fermentation temperature in a certain temperature range(20-30?)can reduce the formation of higher alcohols,and had no significant effect on fermentation rate and ethanol production.