Adaptability Of Yeast In Traditional Starter To Whole Wheat Dough Fermentation For Steamed Bread Making

Traditional starter culture can significantly enhance the nutrition,texture and flavor of product when they are used to ferment whole wheat dough.However,the microbial flora in traditional starter culture is complex and susceptible to various endogenous and exogenous factors,and most of them are spontaneous fermentation,which makes the quality of whole wheat steamed bread different.Therefore,the use of pure cultured strains for fermentation has gradually attracted attention.In this study,yeasts with dough fermentation advantages were isolated,purified,identified and screened from three traditional starters,Jiaozi,Laomian and Mijiuqu,and their adaptability in whole wheat dough fermentation was investigated in order to provide strain resources and theoretical basis for whole wheat dough fermentation and quality improvement of whole wheat steamed bread.17 strains of yeasts with different RAPD types were isolated,purified and identified from three traditional starter cultures by traditional isolation method and randomly amplified polymorphic DNA,including Saccharomyces cerevisiae,Torulaspora delbrueckii,Wickerhamomyces anomalus,Kazachstania humilis,Sterigmatomyces elviae,Candida glabrata,Saccharomycopsis fibuligera,at the same time,six kinds of bacteria were isolated,and Lactobacillus plantarum was the dominant lactic acid bacteria(LAB).The fermentation characteristics,gas production characteristics and tolerance of isolated yeasts were investigated to screen excellent yeasts.The results showed that 9strains of yeast(classified as S.cerevisiae and K.humilis)had better fermentation characteristics.Principal component analysis(PCA)showed that the characteristics of steamed bread fermented by yeast from the same starter were similar,but the flavor clustering was different.The yeast tolerance showed that the tested strain had good acid resistance,and the maximum alcohol tolerance was 10 %.According to the characteristics of dough fermentation and the similarity between strains,a S.cerevisiae C1 and a K.humilis LB4 were selected for subsequent research.There were significant differences in the consumption of carbon sources,phytic acid,total phenols and antioxidant properties between C1 and LB4 during the fermentation of whole wheat dough.The starch crystal form did not change during fermentation and there was no significant difference in the pasting properties,dough tensile properties,sulfhydryl and disulfide bonds between the two yeasts.The growth of C1 and LB4 was not inhibited by LAB,reaching 8.6 Lg CFU / g and 8.7 Lg CFU / g at 12 h,respectively.The p H of the dough decreased significantly,and more lactic acid and acetic acid were produced in the system.When the dough was fermented for 8 h,the tensile resistance was small,the dough extensibility was good,and the gluten network structure was continuous and uniform.After fermentation,dough produced more lipid molecules and organic acids than Jiaozi dough.These changes in the dough showed that C1 and LB4 could adapt to the whole wheat dough fermentation environment and had a synergistic effect with LAB.The specific volume of whole wheat steamed bread fermented by C1,LB4 single bacteria and mixed bacteria with lactic acid bacteria was more than 1.7 m L / g.The specific volume of LB4 steamed bread was higher,and the in vitro digestibility of steamed bread was better than that of commercial yeast.The presence of lactic acid bacteria makes the specific volume of steamed bread larger,but the height-diameter ratio is also lower,and the sensory score of C1 steamed bread is the highest.After the second fermentation,the specific volume of steamed bread increased,the hardness decreased,the mixed bacteria steamed bread became more erect,and the overall quality was better than that of the first fermentation steamed bread.