The Effect And Mechanism Of The Flavor Of Sweet Rice Wine Prepared By Synergistic Fementation With Saccharomycopsis Fibuligera And Rhizopus

Sweet rice wine is a traditional Chinese fermented food,which is well-loved for its flavor.Traditional sweet koji is rich of microorganisms and has a great flavor,but the quality of the sweet wine is unstable and there are some safety problems.In order to solve the problems,this paper study on traditional sweet koji,determines the characteristics of each koji,and isolates the microorganisms,analyzes the aroma production performance.Finally,the co-culture between microorganisms is studied.The main conclusions are as follows:(1)Firstly,the flavor yeast in the traditional sweet koji was isolated and evaluated its safety.The determination of key flavor substances in traditional sweet wines showed that the total contribution rate of five flavor substances,butanol,?-phenethyl alcohol,ethyl acetate,ethyl butyrate and phenethyl acetate is 82.41%,the contribution rate of ethyl ester and ?-phenylethanol was 53.16%.The sensory evaluation and the highest comprehensive score are GX,SC,CQ and ZJ.Four strains with good aroma production were isolated from the sweet wine koj is with great flavor,GX-A,SC-B,and CQ-D are Saccharomycopsis fibuligera,ZJ-O is Cyberlindnera fabianii;The three strains of Saccharomycopsis fibuligera have good ability to produce ?-phenylethanol;Cyberlindnera fabianii ZJ-O has a good ability to produce ethyl acetate;and the four strains have good safety and can be used for traditional food fermentation.(2)The isolated yeast has a synergistic effect of enhancing aroma.With a single strain fermented sweet wine as a control,the main flavor substances ?-phenylethanol and ethyl acetate were measured to study the effect of synergistic fermentation of Saccharomycopsis fibuligera and Rhizopus on the flavor of sweet wine.According to the predicted resuLts of the model,combined with the feasibility of the actual process settings,when the inocuLation ratio of the three Saccharomycopsis fibuligera GX-A,SC-B,and CQ-D is 10:1:10,and the inocuLation amount is 1.2%(w/v),the Rhizopus R inocuLum is 1.2%(w/v),the fermentation temperature is 30?,and the fermentation time is 60 hours.The actual verification showed that the ethyl acetate content was 30.439 mg/L.The content of ?-phenylethyl alcohol is 395.170 mg/L.The fermented sweet rice wine has a strong floral and fruity aroma,indicating that the mixed fermentation of Saccharomycopsis fibuligera and Rhizopus can be significantly improved Sweet wine flavor.(3)Preliminary research on the synergistic aroma-enhancing mechanism of mixed bacteria fermentation.Firstly,the influence of different molecuLar weight metabolites on the growth of different strains was analyzed.The interaction of GX-A and SC-B can promote the growth of microorganisms,and the metabolites with molecuLar weights of 7.0-14.0 kD have stronger effect than that of metabolites with a molecuLar weight of less than 7.0 kD.The enzyme system of the bacteria in the fermentation process was further studied,and the resuLts showed that compared with the fermentation of a single strain,the activities of ?-phenylethanol metabolism related enzymes in the fermentation system of Saccharomycopsis fibuligera were increased,and the activities of aromatic aminotransaminase,pyruvate decarboxylase,alcoholdehy drogenase,glucose-6-phosphatedehy drogenase,isocitrate dehydrogenase,and malate dehydrogenase were 8.6755 umolPPA.h-1.mL-1?87.97 U/mg?97.99 U/mg?94.47 U/g?2.1334 U/g?351.10 U/g,351.10 U/g,indicating that mixed fermentation can increase the activity of enzymes related to ?-phenylethanol metabolism in the fermentation system.At the same time,the protein content of the mixed-bacteria fermented sweet rice wine with Saccharomycopsis fibuligera and Rhizopus is 12.85 mg/g,the protein content of the single-strain fermented sweet wine is 5.89 mg/g;the acid protease activity in the mixed-strain fermented sweet wine is 191.89 U/g,the acid protease activity of single strain fermented sweet wine is 127.83 U/g;the free amino acid content in mixed-strain fermented sweet wine is 4.08 g/100g,and the free amino acid content of single strain fermented sweet wine is 3.39 g/100g;Microbial interaction also promotes protein metabolism.The protein content,protease activity,and amino acid content in the mixed-bacteria fermentation system are higher than those of single-bacteria fermentation.