Development Of Summer-autumn Tea Daqu And Study On Mixed Solid State Fermentation Of Tea Liquor

In the process of brewing Chinese liquor,daqu is a source of microorganisms and crude enzymes,serves as a portion of materials and provides flavour substances for Chinese liquor.Daqu is a moulded cereal,which is prepared by natural inoculation of moulds,bacteria and yeasts.During Daqu-making process,the raw materials are typically milled,mixed with water,pressed into a brick-shaped block and then incubated under nonsterile conditions.As a result of fermentation,daqu is rich in a wide variety of microorganisms such as Bacillus,Acetobacter,Aspergillus,Mucor,and Saccharomyces and various enzymes including amylases,glucoamylase and proteases.Many substances including amino acids and carbohydrates are also accumulated in daqu during fermentation.Therefore,as a source of microorganisms and crude enzymes,as well as a portion of brewing materials,daqu is important in the production of Chinese liquor,and daqu plays a key role in forming the aroma of Chinese liquor.Therefore,daqu plays an important role in Chinese liquor production.Therefore,daqu plays an important role in Chinese liquor production.The content of polyphenols,anthocyanins and caffeine in summer-autumn tea is higher,the content of amino acids is lower,the ratio of phenol to ammonia is larger,the taste of bitter and astringent is heavier,the taste of fresh and refreshing is lower,the quality of tea is lower.However,it is rich in many beneficial ingredients,which has the effects of detoxification,antioxidant,anti-aging,anti-cancer and so on.It has broad application prospects.Summer-autumn tea is a new type of food resource,but few studies have been done to add summer-autumn tea to daqu.Because of the typical characteristics of tea flavor,this paper attempts to combine summer-autumn tea with traditional daqu to make a new type of tea daqu,and then applies summer-autumn tea daqu in the process of brewing solid liquor to obtain a kind of fermented tea liquor with unique aroma.In this paper,wheat and summer-autumn tea were used as raw materials to produce daqu with traditional processing technology.Based on the study of the main factors,such as the amount of summer-autumn tea,the amount of water,the time of making daqu and so on.On the basis of single factor experiment,orthogonal experiment was used to optimize the processing parameters of summer-autumn tea daqu,and the optimum processing technology was determined.The results showed that the physical and chemical indexes of summer-autumn tea were 667.7mg/(g·h),67g CO2/(100g·48h),0.7mmol/g acidity,and 0.6 water activity under the conditions of 30%addition of summer-autumn tea,38%addition of water and 15d preparation time.Conclusion by analysis of variance,summer-autumn tea adding amount on the influence of the saccharification power and fermentation power was the most obvious.There were significant differences in sensory characteristics between wheat daqu and different summer-autumn tea daqu.The number of bacteria in summer and autumn tea daqu was lower than that in wheat daqu,and the number of yeast in 15%tea daqu was higher than that in other daqu,while the difference between molds was not significant.PCA analysis of volatile components based on GC-MS method showed that wheat daqu and 15%summer-autumn tea daqu were significantly different from 30%and 50%summer-autumn tea daqu.Wheat daqu and 15%summer-autumn tea daqu were in the positive direction of the first principal component,while 30%and 50%summer-autumn tea daqu were in the negative direction of the first principal component.The contents of 6 amino acids such as serine,proline and glycine in wheat daqu are all higher than those in summer-autumn tea daqu,and the essence contents of seven amino acids such as aspartic acid,threonine and glutamate are all higher than those in wheat daqu.But the contents of other amino acids were not different The total amount of free amino acids in daqu with the addition of 30%summer and autumn tea was higher than that in other daqu.The addition of summer-autumn tea has a great effect on the stretching vibration of C=O bond,the shear vibration of C=H and the stretching vibration of sugar C-OH of alcoholic daqu.Using wheat,rice and summer autumn tea as raw materials,summer autumn tea daqu and jiuqu as starter,a fermented tea liquor was produced by using traditional solid-state fermentation technology.There were 17 kinds of free amino acids in fermented grains,and the total amount of free amino acids in fermented grains in 30%summer-autumn tea daqu was higher than that in other daqu.There are 34,45,37 and 35 volatile components in different fermented tea liquor,including alcohols,esters,ketones and aldehydes,aromatic groups,acids and other compounds.The content of total ester in the liquor brewed with tea daqu was higher than that in the liquor without adding summer-autumn tea daqu,and geranyl formate in summer and autumn tea daqu was further converted into citronella formate during brewing.