Study On Breeding Of Low-urea-Reducing Strains And Fermentation Technology Optimization Of Rice Wine

Rice wine contained lots of ethyl carbamate, the main precursor material of ethyl carbamate in rice wine was urea, the most of urea came from the yeast fermentation process. This essay researched by using breeding strains from nature screening, mutation screening, and optimizating the fermentation technology to reduce the content of urea. The results are as follows:1.8strains were screened from nature, one of them called4#was got by the comparison and analysis of the acid, alcohol resistant and fermentation ability of these strains, the ability of fermentation was excellent, and it’s urea production was less than others. The fermentation liquid indicators of4#were as follows:residual sugar content was12.57g/L, total acid was2.99g/L, nitrogen amino acid was0.48g/L, alcohol content was16.1%, production of urea was37.23mg/L,serially generated7times, urea production and ability of fermentation of each generation were basically at the same level, so it was stable in heredity.2. A yeast called4-3-14#was attained after the UV mutagenesis and gamma ray continuous mutation. First, a yeast called4-3#was attained after UV mutagenesis, the optimal dose of UV mutagenesis was90s, the death rate was82%, the urea content was reduced19.2%than that before. Then the4-3-14#was attained after gamma ray, the optimal dose of UV mutagenesis was500Gray, the death rate was84%, the urea content was reduced20.02%than4-3#. The4-3-14#generated serially7times, the ability of urea production and the ability of fermentation were unchanged, so it was stable in heredity.3. By changing the inoculation amount, adjusting the fermentation temperature, adding inorganic salt,this research optimized the brewing technology and reduced the urea content in rice wine, the results were as follows:the4-3-14#inoculation amount was1×108cell/mL, fermentation temperature was30℃, the urea content in wine was17.89mg/L when the KH2PO4content was15mmol/L and it decreased51.94%than4#.By these methods the safety was greatly improved in rice wine.