Screening Low-methanol And High Total Esters’ Yeast And Study On Its Fermentative Process

It could increase liquor flavor of esters liquor quality and competition of Enterpriseproducts by brewing of adding esters yeast. It was important for consumer’s health to decreasemethanol in liquor, because the methanol was one of the toxic substances in liquor. It wasrealistic meaning for consumer and enterprise to increase ester and decrease methanol in liquor.Now there was few report on decreasing methanol in liquor by studying yeast metabolism. Soit was the technology of increasing ester and decreasing methanol by screaning strain andoptimizing brewing process.1. The liquor was brewed with beerwort by the LM-1of Saccharomyces cerevisiaemutated and breeded, as a parent strain. The relative content of methanol in liquor was188.21mg/L, tested by the headspace gas chromatography. The total esters was0.43g/L, tested byReflux saponification method. Another parent strain HTE-2was screened from aroma koji. Therelative content of methanol was305.12mg/L and the total esters was0.43g/L in liquorbrewed by HTE-2.2. The new Saccharomyces cerevisiae PF1of low methanol and high total esters wasscreened by the technology of inactivation biparental haploid protoplast fusion with parentstrains of LM-1and HTE-2. The relative content of methanol in liquor brewed by PF1was190.82mg/L and the total esters was0.70g/L, compared the liquor brewed by LM-1with therelative content of methanol188.21mg/L and the total esters0.43g/L increasing62.8%. Theexperiment result by analysising liquor component showed that the ability of producingalcohol acid ester and consumpting sugar by PF1fermentation was excellent. The experimentresult by5passages showed that the heredity ability of PF1was stalibity.3. The optimization brewing condition by PF1was emperature22℃time5d sugar150g/L pH4.0inoculums2%, by experiment with five factors of emperature time sugar pH andinoculums. The relative content of methanol in liquor brewed by PF1with optimum conditionwas169.90mg/L and the total esters was1.06g/L, compared liquor brewing by initialcondition with the relative content of methanol188.21mg/L decreasing11%and the totalesters0.70g/L increasing51.4%. Then the optimium condition of brewing by PF1was obtained by Box-Behnken response surface analysis through three factors and three levels,temperature19.07℃, Brix17.34%, pH4.35. The relative content of methanol in brewedliquor with the optimum condition was169.08mg/Land the total esters were1.096g/L.4. The liquor would be semisolid brewed by PF1with rice. First PF1was cultivated to2x108cfu/mL. Then the new koji of PF1koji was cultivated with koji: bran: PF1=2g:1g:2ml. The PF1koji without bran was cultivated with koji: PF1=2g:1g, as comparison. The ricewas brewed by PF1koji and bran. The relative content of methanol in liquor brewed by PF1koji was287.73mg/L, decreasing23.4%, and the content of total esters was0.62g/L,increasing37.1%. So It had a very significant effect on increasing ester decreasing methanolin the liquor brewed by PF1koji. The liquor was tested ester methanol and sensory evaluation,brewed by PF1koji with different grain materials. It had low methanol high ester in liquorbrewed with rice wheat. At the same time, the liquor had good sensory evaluation with esteraroma mellow. So the high quality liquor could be brewed by PF1koji with rice wheat.