Factors Affecting γ-aminobutyric Acid And Its Metabolic Control In Guangdong Hakka Rice Wine

Guangdong hakka rice wine is one of Low alcohol wine filled with nutrition and health. γ-aminobutyric acid(GABA) is a kind of functional ingredients of guangdong hakka rice wine. GABA could improve memory, lower blood pressure, activate liver and kidney, prevent arteriosclerosis and so on, which has a huge market potential. Therefore, it is necessary to make researches on GABA of guangdong hakka rice wine. To make researches of GABA of guangdong hakka rice wine, red koji used to brewing rice wine, rice materials, fermentation process conditions, microbial metabolism regulation were sudy at this article.(1) Effect of red koji on GABA of guangdong hakka rice wine. Koji fermentation performance and effect of red koji on fermentation and GABA content were study, microorganisms of red koji were isolated and identified by biochemical tests and 16 S r DNA molecular identification, and their ability to produce GABA was studied.The results showed that, saccharification and liquefying power of red koji were the highest, but esterification power was little low, saccharification and liquefying power of wheat koji were the lowest, esterification power of rice koji was high. During fermentation process of hakka rice wine, red koji has large effect on content of total sugar, total acid, p H, amino nitrogen, alcohol and GABA, and using red koji, wheat koji and rice koji mixed, the rice wine which had lower p H and alcohol, high total sugar, total acid, amino nitrogen and content GABA had vigorous metabolic activity of microorganisms, in particular, GABA content of using three kinds koji mixed was 2.16 times copared to only using wheat koji and rice koji mixed. Monascus, yeast and lactobacillus plantarum were separated from the red koji, and all of them had ability to produce GABA, for monascus 43.94mg/L reached the higest, followed by lactobacillus plantarum, and yeast 9.85mg/L was the least.(2) Effect of rice materials on GABA of guangdong hakka rice wine. Microstructure of glutinous rice, japonica rice, indica rice raw material and their cooked rice were analyzed by scanning electron microscope. The content of total sugar, total acid, amino nitrogen, GABA content and GAD Enzyme activity were respectively study in fermentation process of hakka rice wine brewed by glutinous rice, japonica rice and indica rice.The results showed that particles of glutinous rice were arranged in neat, particles of japonica rice were larger and IV stacked, and indica rice arranged very loose and had a clear gap. After cooking, glutinous rice and japonica rice became molten liquid, and pores of glutinous rice were small, quantity, dense and uniform, but indica rice still reserved some thickness solid substance and large particles not be gelatinized. Therefore, glutinous rice and japonica rice were easy to gelatinized when heated, which could absorb moisture, saccharify and ferment easily, thus glutinous rice and japonica rice could be used easily by microbial metabolic activities in the brewing process. From the indicators of total sugar, total acid and amino nitrogen, glutinous rice, japonica rice and indica rice were all suitable for hakka rice wine brewing, but content of total sugar and amino nitrogen of rice wine brewed by glutinous rice and japonica rice were higher, so microbial life activities in glutinous rice and japonica rice were more intense during fermentation during fermentation process; GABA content of rice wine brewed by glutinous rice was the higher, japonica rice was less, and indica rice was the least; After one month of storage, GABA content of rice wine brewed by glutinous rice reached 260.45mg/L, which was respectively 1.13 times of japonica rice and 1.44 times of indica rice. GAD activity of rice wine brewed by glutinous rice and japonica rice were strong and close, while GAD activity of indica rice was quite different and weak.(3) Effect of fermentation process conditions on GABA of guangdong hakka rice wine. Effect of red koji additive amount, temperature of main fermentation stage and time of main fermentation stage on GABA of hakka rice wine was studied, and fermentation process conditions were optimized by response surface methodology. The results showed that red koji additive amount, temperature of main fermentation stage and time of main fermentation stage had large effect on GABA of hakka rice wine. The model equations y=298.36+40.84*A +27.68*B+5.02*C- 14.10*A*B+ 11.71*A*C+ 52.21*B*C- 41.44*A2 –26.54*B2-30.01*C2(A for red koji additive amount, B for temperature of main fermentation stage, C for time of main fermentation stage)was get by optimizing red koji additive amount, temperature of main fermentation stage and time of main fermentation stage visa response surface methodology. The optimum fermentation conditions were red koji additive amount for 6.5%, temperature of main fermentation stage for 32℃, time of main fermentation stage for 6d, GABA content of guangdong hakka rice wine at those condition reached 309.09mg/L more higher than commercial hakka rice wine. Hakka rice wine brewed by above optimum fermentation conditions and commercial hakka rice wine of Huanglong were similar in taste.(4) Microbial metabolism regulation of GABA of guangdong hakka rice wine. Dynamic change of GABA and GAD enzyme were monitored during the whole fermentation process and main fermentation stage, and microbial metabolism to producing GABA was regulated by adding glutamate(Glu), alanine(Ala) and ascorbic acid. The results show that, during the fermentation process of hakka rice wine changed dynamically and GABA content increased rapidly in main fermentation stage, but GABA content fluctuated sharply when adding spirit and changed dynamically after. GABA content of hakka rice wine increased to 310 mg/L after 30 d fermention. GABA content and GAD enzyme activity increased greatly in main fermentation stage, which indicating microbial life activities more stronger and could produce more metabolites. Add appropriate amount of Glu and Ala could made effects on GABA of wine mash, and GABA content was high when adding 3%Glu in the second day. After 6d fermention, GABA content reached 403.63mg/L comparing CK group increased by 48.96%, which indicating Glu was a substrate for GAD enzyme to generated GABA, 3% of which added in the second day could significantly improve GABA content of hakka rice wine. Adding 1% Ala in the fourth day, GABA content reached 360.3mg/L comparing CK group increased by 32.97%, which indicating that Ala as product that GABA occured aminotransferase reactions, 1% of which added in the fourth day could promote the accumulation of GABA of hakka rice wine. Adding 1% ascorbic acid in the sixth day, GABA content and GAD enzyme activity respectively reached the highest for 355.2mg/L and 3.22μmol/h?ml, which indicating ascorbic acid could adjusted p H to make the p H within the most suitable range to improve activity of GAD and promote GABA accumulating better.