| Liquor brewing is a complex process of natural fermentation with multiple bacterial groups and interactions between different microbial flora and their metabolites.Finally,a fermented liquor with unique flavor and high quality is formed.During the brewing process,microorganisms are usually added such as Rhizopus and Aspergillus to strengthen the koji to improve the flavor and yield of liquor.However,there are few studies on the interaction between fungi and the mechanism of its mixed culture improving liquor quality is unclear.In order to explore the influence of the interaction of mold co-culture on the quality of liquor,the mold isolated and identified from Daqu was used as the material,Screening molds with high yields of esterase,saccharification and liquefaction were to study the conditions for improving the esterification power,saccharification power and liquefaction power of mold mixed culture.And apply it to strengthen Daqu brewing liquor,in order to provide some theoretical basis and guidance for food fermentation.The main conclusions are as follows:(1)With the help of fungal morphology and molecular biology techniques,22 strains of bacteria isolated and preserved in the laboratory from were identified,and 18 strains of Monascus,2strains of Aspergillus oryzae and 2 strains of Rhizopus were obtained.Among Monascus,Monascus M1 and M11 produced higher esterase activity,respectively: 137.74 U/g and 155.73U/g.Monascus M14 and M15 produced higher glucoamylase activities,respectively: 94 U/g and90 U/g.Monascus M7 and M15 produced higher liquefaction enzyme activities,respectively: 1.41U/g and 1.62 U/g.Aspergillus oryzae A1 and A2 produce esterase,saccharification and liquefaction,respectively: 64.37 U/g,70.05 U/g,110 U/g,82 U/g,1.59 U/g and 1.36 U/g.Rhizopus B1 and B2 produce esterase,saccharification and liquefaction,respectively: 82.83 U/g,64.43 U/g,138 U/g.110 U/g,2.43 U/g and 2.14 U/g.(2)The conditions of Monascus,Aspergillus oryzae and Rhizopus for producing esterase,saccharification and liquefaction were analyzed and optimized.The results showed that the optimum conditions for Monascus M1,M7,M11,M14 and M15 to produce esterase,saccharification and liquefaction as: the incubation time was 5 d,the incubation temperature was32 ?,and the inoculum amount was 3%.Under this condition,the esterification capacities of Monascus M1 and M11 were 137.27 U/g and 158.57 U/g,respectively.The saccharification capacity of Monascus M14 and M15 were 126 U/g and 116 U/g,respectively.The liquefaction powers of Monascus M7 and M15 were 1.34 U/g and 1.58 U/g,respectively.The optimal conditions for Aspergillus oryzae A1 and A2 and Rhizopus B1 and B2 to produce esterase,saccharification and liquefaction as: the incubation time was 4 d,the incubation temperature was30?and the inoculum amount was 3%.Cultivated under these conditions,the esterification power of Aspergillus oryzae A1 was 75.26 U/g,the saccharification power was 112 U/g,and the liquefaction power was 1.71 U/g.Aspergillus oryzae A2 esterification power was 77.37 U/g,saccharification power was 108 U/g,liquefaction power was 1.38 U/g;.The esterification power of Rhizopus B1 was 86.15 U/g,the saccharification power was 162 U/g,and the liquefaction power was 2.59 U/g.The esterification power of Rhizopus B2 was 72.42 U/g,the saccharification power was 130 U/g,and the liquefaction power was 2.22 U/g.on the basis of it to explore the optimal production conditions of esterase,glucoamylase and liquefaction enzyme in mixed culture of Monascus,Aspergillus oryzae and Rhizopus.The results showed at the culture time of 4 d,the culture time was 4 d,the culture temperature was 32?,and the inoculum amount was 3%.The inoculation ratio of Monascus: Aspergillus oryzae: Rhizopus was 2:2:1.Under these conditions,the esterification power of the mixed mold was 263.17 U/g,the saccharification power was 308 U/g,the liquefaction force was 4.12 U/g.Compared with mould alone,the activity of esterase production increased by 0.65 times,the activity of saccharification enzyme increased by0.9 times,and the activity of liquefaction enzyme increased by 0.59 times.(3)The mixed mold of Monascus,Aspergillus oryzae and Rhizopus was added to Tomur Peak Daqu according to the proportion of 10%,15% and 20% fermentation of liquor.With no mixed mold added as a control,the effect of fortified mold on the flavor and quality of liquor was explored,and the results showed that adding 15% mixed mold fermented liquor to Daqu with a storage period of 4 months.Compared with Dakoji-fermented liquor without mixed mold,the liquor yield and flavor substances were improved and the liquor fermented with mixed mold was ABV increased by 8% to 45.4 % vol.Flavor compounds were analyzed of liquor fermented mixed molds by HS-SPME-GC-MS technique and the results showed that the liquor with enhanced mixed mold Daqu fermentation increased added 23 flavor substances such as ethyl valerate,ethyl laurate,n-octanol,n-docosanol,etc.Enhanced Liquor Fermented by Mixed Mould Daqu a total of66 flavor substances were detected,including 38 kinds of lipid substances,9 kinds of acid substances,12 kinds of alcohol substances,and 7 kinds of other flavor substances.The isoamyl alcohol content was 43.4 mg/L,which was 1.15 times that of the control group.The contents of ethyl palmitate,1-butyl phthalate-2-isobutyl phthalate,dibutyl phthalate,ethyl hexanoate and ethyl acetate increased by 107.2%,193.5%,236.8%,119.1% and 50% compared with the control.To sum up,in view of the unclear mechanism of co-fermentation of liquor fermenting molds,There is a lack of researches on improving the quality of liquor by enhancing Daqu fermentation with Monascus,Aspergillus oryzae and Rhizopus,In this study,the factors affecting the enzyme production capacity of the mixed culture of mold were explored,optimized the culture conditions for the mixed culture of molds to produce enzymes and applied the results to fortified Daqu brewing liquor.It is preliminarily clarified that mixed molds strengthen Daqu fermentation.It can not only improve the liquor yield of liquor,but also make the liquor body and flavor substances richer.Therefore,it provides some guidance for the application of mold in liquor brewing and provides reference for the research on co-culture of other microorganisms. |
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