Study On The Control Technology Of Solid-state Bilateral Fermentation Saccharification Process

Baijiu is a typical representative of solid bilateral fermentation in China.Saccharification and fermentation are carried out at the same time,and are affected by the cooking process of grain raw materials,the temperature of fermented grains,and the acidity of fermented grains.The fermentation process proceeds spontaneously and is difficult to control.Most domestic Baijiu companies only focus on the extraction and determination of saccharification enzymes and saccharification products in Daqu and fermented grains,without in-depth research on the entire saccharification process.In this paper,the saccharification mechanism and control methods of liquor bilateral fermentation process were analyzed to improve the yield of liquor.The gelatinization rate of Baijiu grain raw materials under different cooking techniques was studied,and the optimal cooking process conditions were obtained.The effects of tannin content,gelatinization rate,temperature of fermented grains,lactic acid content and alcohol content on the bilateral fermentation of liquor were discussed on the basis of studying the enzymatic properties of Daqu glucoamylase.The main research conclusions are as follows:(1)Controlling the stewing process of grain raw materials can affect the subsequent saccharification and fermentation of Baijiu.By designing orthogonal experiments,the optimal stewing conditions for grain were determined as follows:water consumption of 90%,initial water temperature of 60?,grain soaking time of 180 min,and grain stewing time of 40 min.Under the optimized conditions,the degree of gelatinization was highly reached 61.63%.Among the influencing factors,the stewing time has the greatest impact on the gelatinization rate.In actual production,the stewing process must be combined with sensory evaluation,and the improvement of the gelatinization rate cannot be blindly pursued,which will cause serious damage to the physical and chemical properties of the grain.Tannin is the main component of sorghum,it can effectively degrade by heating the grains.(2)The glucoamylase in Daqu was extracted and studied on its enzymatic properties.It was found that the optimal reaction temperature of the glucoamylase was 50?.The optimum reaction pH is between 5 and 6.Using the Lineweaver-Burk double reciprocal method,the Michaelis-Menten equation of enzymatic hydrolysis kinetics was:v=0.2428[S]/18.4366+[S].The influence of factors such as gelatinization rate,mash temperature,lactic acid content and alcohol content on the saccharification process and the control method were explored through design experiments.The saccharification rate of grain raw materials with higher gelatinization rate is faster,and the saccharification rate of 60%gelatinization rate raw materials is 41.47%higher than that of 50%gelatinization rate raw materials in the first 4 hours.The suitable temperature for grain saccharification is in the range of 40-50?.At 50?,the grain saccharification rate can reach 0.2 mg·(g-1·h-1),which is 84.33%higher than that at 30?.The influence of acid on the grain saccharification process is mainly reflected in two aspects.On the one hand,adding a certain amount of lactic acid when moisturizing the grain can promote the gelatinization of the raw material within a certain range.When the lactic acid content of the grain is 0.04 mL·g-1,the grain paste saccharification rate increased by 7.5%year-on-year;On the other hand,after adding different contents of lactic acid after cooking,the saccharification rate gradually decreased with the increase of lactic acid content.When the grain lactic acid content was 0.04 mL·g-1,the saccharification rate decreased by 36.94%year-on-year.In actual production,the saccharification process can be controlled by changing the cooking process,temperature-controlled fermentation,and breeding strains that produce acid-resistant saccharification enzymes.(3)Simulated fermentation under solid-state conditions,and explored the effects of grain gelatinization,initial enzyme activity and yeast amount on fermentation.The results showed that:When the initial enzyme activity of the fermentation material is lower than 120 U·g-1 fermented grain,the initial enzyme activity is significantly related to the final output of alcohol.In the early stage of fermentation,the amount of alcohol production was significantly correlated with the initial number of yeasts,which was relatively obvious in the first 2 days.The wine yield of raw materials with different gelatinization rates has always been significantly different.At 7 days,the yield of grain materials with a gelatinization rate of 60%is 25.68%higher than that of grain materials with a gelatinization rate of 50%.Compared with normal fermentation,at 7 days,supplemented with yeast fermentation(adding 2*107 cfu·mL-1 yeast solution 10 mL per 100 g mash on the 4th day)compared with normal fermentation in saccharification After 7 days of fermentation,the wine yield rate increased by 16.8%.In the actual production,the saccharification process of grain can be controlled by controlling the proportion of saccharification enzyme producing strains in Daqu,changing the accumulation time of fermented grains and changing the cooking process of grain,so as to achieve the purpose of controlling the bilateral fermentation of Baijiu.