Process Optimization And Spatial Heterogeneity Analysis Of Huang Jiu Inoculated With Raw Wheat Qu

"Using wheat to produce Qu,and using Qu to brew alcohol"is a characteristic of Chinese Huangjiu,and the quality of wheat Qu as a saccharification and fermentation agent has a great impact on the quality of the Chinese Huangjiu.Inoculating raw wheat Qu refers to using raw wheat as a material,and obtaining a saccharification and fermentation agent through inoculation of specific microorganisms and solid-state fermentation.During the fermentation process,physicochemical factors（such as temperature,moisture,gas composition,etc.）constantly affect the microbial structure,thereby affecting the quality of wheat Qu.Microbial communities exist with different compositions and characteristics depending on the distribution of physicochemical factors.Currently,research has been conducted on the microbial community structure of Huangjiu raw wheat Qu.However,under the background of the development of intelligent wheat Qu production,there is a lack of analysis methods based on mathematical statistics and simulation,which severely restricts the modernization of raw wheat Qu production.Therefore,this study aims to apply an method based on mathematical statistics and simulation to reveal the characteristics and variation rules of the microbial community structure of Huangjiu raw wheat Qu,and to analyze the relationship between the structure of the Huangjiu raw wheat Qu community and spatial heterogeneity.This is of great significance for promoting the modernization of Huangjiu raw wheat Qu production and improving the quality of Huangjiu.The main research content of this paper is as follows:（1）Optimization of the key fermentation process of inoculated wheat Qu.The effects of different fermentation temperature,fermentation time,moisture content and inoculation amount on microbial community and enzyme activity properties of wheat starter were analyzed the results showed that fermentation time had the greatest impact on microbial growth under various culture conditions,and excessive fermentation time could lead to microbial death.Therefore,the fermentation time was fixed at 96 hours.Based on the results of single-factor verification,response surface experiments were conducted to optimize the brewing conditions of inoculated wheat Qu.The optimal fermentation conditions were determined as follows:initial moisture content of 35%,total inoculation amount of 6%for Aspergillus oryzae Su-16,and fermentation temperature of 35℃.The highest enzymatic activities of amylase andα-glucosidase in inoculated wheat Qu produced under these conditions were 1099.8 U·g^-1 and 6.1U·g^-1,respectively,which increased by 38.6%and 106%,respectively,compared to traditional Chinese Huangjiu wheat Qu.The microbial population of the optimized inoculated wheat Qu was also measured,indicating that the balance between bacteria and fungi was achieved,and the enzymatic production capability was significantly enhanced.（2）Analyzing the heat and moisture transfer patterns within a Qu room during the fermentation process.A physical model of the Qu room was established using multiphysics simulation software（COMSOL Multiphysics）,and the velocity and temperature fields within the room were obtained through numerical calculations and simulations.To accurately describe and predict the temperature and flow fields within the Qu room,the three-dimensional model of the room was simplified to a two-dimensional model,and the mesh of the structural model was determined.The study found that there is a large temperature gradient in the different locations of the Qu during the fermentation process,with a maximum temperature difference of 4℃,approximately 0.13℃·cm^-1.Due to the existence of natural convection,there were differences in the velocity distribution between the upper,middle,and lower Qu layers,with the air velocity in the upper layer being relatively higher,reaching a maximum of 0.06 m·s^-1,while the air velocity in the lower layer was relatively lower,with a maximum of 0.01 m·s^-1.The study also analyzed the impact of heterogeneity in the production environment on the microbial community and physicochemical properties of the Qu,and determined the reasons for differences in quality during the fermentation process.The final results showed that there is a certain degree of coupling between heat and moisture transfer within the Qu room during the fermentation process,with the temperature exhibiting a pattern of being higher in the middle and lower on the sides,while the humidity showed a pattern of being higher at the bottom and lower at the top.（3）Validation of the simulation model.Based on the results of the above model simulation,two sets of experiments were conducted to verify the effect of the actual environmental distribution within the Qu room on the quality of the Qu,using the enzymatic activity of saccharifying enzymes and alpha-amylase,microbial quantity,and volatile flavor content as evaluation indicators.The results showed that,compared to the control group,the experimental group achieved a more favorable environment within the Qu room,with saccharifying activity increasing by 10.2%and liquefying activity increasing by 54.1%.This indicates that controlling the variation of environmental factors within the Qu room and reducing its heterogeneity is conducive to the growth of microorganisms in the Qu and to the stability of its quality.