Study On The Influence Of Baijiu Brewing Control Factors On The Solid-state Fermentation Process Of Saccharomyces Cerevisiae

Due to the openness of the traditional brewing process,the liquor fermentation process is spontaneous and difficult to control.There is a lack of research on the controllable factors of precise regulation of fermentation process and the influence mechanism of traditional fermentation mode of distiller’s grains recycling on alcohol fermentation metabolism.In order to improve the production efficiency and quality of Saccharomyces cerevisiae（Sc）fermentation in the process of liquor brewing,the solid-state fermentation of Sc was studied in this paper.The effects of glucoamylase,fermentation temperature,inoculation amount and initial acidity on the solid-state fermentation process of Sc were investigated.Saturated activated carbon was used to replace the role of carrying a lot of water in distiller’s grains,and lactic acid and phosphoric acid were used to replace the acidic substances in distiller’s grains.The effects of inoculation methods,sterilized Jiuqu and distiller’s grains reuse on the solid-state fermentation of Sc alcohol were explored.The main results of this paper are as follows:（1）The effects of various controllable factors on the solid-state fermentation process of Sc single strain were studied.The results showed that the optimum fermentation temperature range was 24～27°C.Considering the fermentation efficiency factor,the effects of other factors were explored at 30°C.The optimum glucoamylase content of fermented grains was 47.02 U·g^-1fermented grains.The optimum inoculation amount was 8.401 lg CFU·g^-1 fermented grains.The optimum acidity was less than 0.75 mmol·（10g）^-1 fermented grains.The amount of glucoamylase added basically did not affect the final alcohol yield,and the fermentation temperature,inoculation amount,and initial acidity all affected the final alcohol yield,the most important factor is temperature.Through comprehensive optimization,the optimum conditions for solid-state fermentation of alcohol were obtained:fermentation temperature 25°C,inoculum size 8.300 lg CFU·g^-1 fermented grains,acidity 0.15 mmol·（10g）^-1 fermented grains.Under these conditions,the alcohol yield could reach 11.98%vol.In addition,the regulation of controllable factors also affected the synthesis of flavor components in fermented grains.The increase of glucoamylase and inoculation amount and the total content of flavor components showed negative correlation and positive correlation respectively.Low temperature fermentation at 20°C was beneficial to the accumulation of esters.By adjusting the acidity of fermented grains by lactic acid,the synthesis of ethyl lactate and lactic acid content showed a positive correlation.In the actual production process,the quality of liquor fermentation can be improved by adjusting the controllable means of fermentation process.（2）The influence mechanism of inoculation method,sterilized jiuqu and distiller’s grains recycling on Sc solid-state alcohol fermentation process was analyzed at the laboratory level.The results showed that the two inoculation methods of liquid culture and dry yeast activation would affect the growth state of the cell and had no effect on the alcohol production.Starch in sterilized jiuqu can not be saccharified and utilized directly,but starch can be utilized and metabolized when sterilized jiuqu is processed by moistening grain and steaming grain.The water carried by distiller’s grains can reduce the inhibition of Sc products by diluting the alcohol concentration,so as to achieve the effect of increasing the total alcohol production.The moisture content of fermented grains increased from 31.49%to 56.65%,and the final alcohol production increased by 22.39%.And distiller’s grains can maintain the stability and fermentation activity of Sc strains under low sugar conditions;on the basis of acidity exploration,it was further found that the p H of fermented grains decreased from 3.62 to 3.08,and the final yield of alcohol decreased by 15.04%when different acidic substances in distiller’s grains were adjusted to the same acidity.In the actual production process,the liquor yield can be improved by reusing the jiuqu,ensuring the moisture content of fermented grains,and reducing the acidity of fermented grains（especially H⁺content）.（3）The effect of ester-producing yeast on Sc solid-state fermentation process was investigated.The results showed that the growth of Sc cell was inhibited during the mixed fermentation process,and the number of cell decreased from 8.328 lg CFU·g^-1 fermented grains to 7.648 lg CFU·g^-1 fermented grains,but the yield of alcohol was basically not affected.The flavor components produced during the fermentation process changed significantly,which significantly increased the content of esters,the content of ethyl acetate increased by 3.57 times,and the total content of higher alcohols decreased.Therefore,in the actual brewing process,the purpose of improving the quality of liquor brewing can be achieved by adding ester-producing yeast.