Filter Of Yeast Of Traditional Rice Koji And Its Influence On The Quality Of Chinese Steamed Bread

As one of the starter which used for making rice wine,traditional rice koji is not only rich in a variety of molds,but also rich in yeast.The research process was as follows: Firstly,the yeasts were isolated from traditional rice koji.Secondly,the fermentation characteristics of rice wine and dough with different species of yeast inoculated were studied.Thirdly,the quality and character of steamed bread fermented by different mixed yeasts were analyzed.This study provides some theoretical guidance for the research of compound yeast fermentation to make steamed bread.The main results from the study are as follows:A total of six kinds of traditional rice koji were selected in this study,and they were collected from Shaoguan,Guangdong province,Yanbian,Jinlin province,Yichang,Hubei province,Xiaogan,Hubei province,Fuzhou,Fujian province,respectively.A total of five kinds of yeasts were isolated from the traditional rice koji,including Wickerhamomyces anomalus(WA);Saccharomycopsis fibuligera(SF);Saccharomyces cerevisiae(SC);Candida glabrata(CG)and Cyberlindnera fabianii(CF).Among them,Saccharomycopsis fibuligera and Saccharomyces cerevisiae were existed in all the traditional rice koji,and accounted for a high proportion,which indicated that they were dominant yeast in traditional rice koji.The characteristics of rice wine with five kinds of single yeast inoculated were studied.The ability of S.cerevisiae to produce alcohol was better than the other four yeasts in the fermentation process of rice wine.The ability of S.fibuligera to produce amylase and protease was better than the other four yeasts in the fermentation process of rice wine.The rice wine with single yeast inoculated were unsuitable for steamed bread making,which made the dough had poor fermentation performance and less gas production.The characteristics of dough with single yeast and mixed yeast inoculated was studied.The dough had the highest total gas production and the highest maximum expansion height which inoculated with Saccharomyces cerevisiae.When the fermentation time was 0 h and 4h,the gas production capacity,fermentation expansion capacity and gas holding capacity of the mixed yeast fermented dough were better than those of the rice wine dough fermented with the same mixing method,but it was smaller than the dough fermented with mixed yeast rice wine.The extensibility of the dough fermented with mixed yeast is slightly worse than that fermented with mixed yeast rice wine.The final weakly bound water content in the dough with mixed yeast rice wine inoculated(JFC),which prepared by mixed fermentation of Sp.fibuligera(SF)and S.cerevisiae(SC)for 24 hours was higher than that of the mixed yeast dough,and the content of medium and strong bound water decreased significantly during the fermentation,and the gelatinization peak viscosity,valley viscosity,disintegration value,final viscosity and pick-up value of starch were relatively lower.The starch granules and gluten network in the dough inoculated with co-culture of W.anomalus,Sp.fibuligera and S.cerevisiae(WFC)were closely combined and have a better structure.The starch crystal in the dough were not influenced by the four kinds of mixed yeasts and rice wine.The volatile flavor components of steamed bread with mixed yeast and mixed rice wine were quite different.The hardness and chewiness of steamed bread made from the dough JFC were significantly lower than the other five kinds of steamed bread;The steamed bread made by the rice wine which inoculated with Sp.fibuligera and S.cerevisiae and fermented for 24 hours and produced by secondary fermentation had the highest sensory score and the best taste.