Research On Quality Improvement Technology Of Chinese Rice Wine Based On Nitrogen Source Control

The nitrogen metabolism of Chinese rice wine was affected by raw materials,fermentation strains,brewing process and climate.The level of nitrogen metabolism will also cause the changes in the quality of Chinese rice wine.In order to explore the effect of nitrogen metabolism level on the quality of rice wine during the fermentation,and to further clarify the quality improvement technology of Shaoxing rice wine,this experiment investigated the influence of different yeast strains,protease addition and glutinous rice protein components on nitrogen metabolism during rice wine fermentation.To clarify the regulation mechanism of different fermentation conditions on the nitrogen metabolism pathway of yeast,and further to evaluate the regulation of rice wine quality.The main research content,results and conclusions are as follows:(1)Four kinds of Saccharomyces cerevisiae were selected for the brewing experiment.The fermentation kinetic analysis revealed that different yeast strains have significant differences in amino acid assimilation and metabolic capacity(p <0.01).Among them,active dry yeast has stronger protein metabolism,and the types of volatile substances are rich in content.Rice wine which fermented by active dry yeast has rich fruity and milky flavor;85 # rice wine which fermented by yeast has strong floral and honey aromas,but the acidity is heavier;XZ-9 yeast fermentation produces refreshing rice wine flavor;XZ-10 yeast fermented rice wine has moderate flavor and no obvious odor.Different yeast strains can obviously change the nitrogen metabolism pathway and regulate the content and composition of nitrogen-containing metabolites in rice wine.Therefore,in the process of rice wine brewing,a new technology for improving the quality of rice wine can be constructed by optimizing the strain.(2)Active dry yeast is preferably used for rice wine brewing,and the nitrogen metabolism of yeast is intervened by adding three food-grade proteases.It is found that the addition of proteases increases the nitrogen source level,affecting the yeast glycolysis pathway,urea cycle and higher alcohol acetate synthesis pathways regulate the composition of protein metabolites and affect the quality of rice wine.Among them,flavor protease promoted yeast sugar metabolism,which increased the alcohol level by 5.6%,inhibited yeast arginine metabolism,and reduced the accumulation of urea in rice wine by 14.6%;it promoted isoamyl alcohol,ethyl acetate,and myristate ester,ethyl butyrate,ethyl palmitate and other flavor substances are generated,while inhibiting the production of 4-ethylguaiacol,weakening the spicy and irritating smell,creating a rich and harmonious aroma atmosphere for rice wine.Studies have shown that the addition of exogenous protease can be applied to the brewing of rice wine and can be used as a technical method to improve the quality of Shaoxing rice wine.(3)By adding two kinds of monomeric proteins(glutelin and albumin)for rice wine brewing,the difference of different glutinous rice protein components on the nitrogen metabolism of yeast and the effect of metabolic products on the quality of rice wine were studied.The results showed that changes in protein types and composition significantly affected yeast nitrogen metabolism and fermentation performance,which in turn affected rice wine quality.Among them,the addition of glutelin components can promote yeast sugar metabolism and increase ethanol yield,which is 10.3% higher than the control group;it inhibits arginine metabolism and reduces the accumulation of urea in the rice wine,which is 24.0% lower than the control group.The evaluation results show that increasing the gluten content gives the rice wine a rich and coordinated flavor,while the albumin increases the rice wine’s bitter taste and pungent odor.Therefore,the nitrogen metabolism and fermentation performance of yeast can be adjusted by changing the protein composition of glutinous rice,and the quality improvement technology of Shaoxing rice wine can be obtained from the perspective of regulating the protein composition of raw materials.