The Research Of Effect Of Exopolysaccharide-producting Lactic Acid Bacteria On The Steamed Bread Quality

Traditional taste and flavor are two important features in industrialization of steamedbread. In this study, exopolysaccharide-producing lactic acid bacteria(LAB) was isolated fromtraditional starter cultures, and the effects of exopolysaccharide-producing LAB and itsexopolysaccharides(EPS) on the quality of steamed bread were also investigated. It willprovide basis for industrial production of steamed bread with traditional taste and flavor.The first task is to screen of microorganisms from traditional starter cultures of fivedifferent regions of Henan(Zhoukou, Shangqiu, Puyang, Nanyang,Xuchang) and blank dough.152strains microorganisms were obtained. A total of107LABs were isolate from sourdoughby H2O2enzyme test, gram staining experiments and PCR identifying. These LABs belong tofour genera and seven kinds. They respectively are Lactococcus(Latococcus qarvieae),Lactobacillus(Lactobacillus paralimentarius, Lactobacillus brevis, Lactobacillus planetarium,and Lactobacillus crustorum), Leuconostoc(Leuconostoc fallax), and Weissella(Weissellacibraria). Lactobacillus brevis account for24.3%of total strains, and Weissella cibrariaaccount for22.4%of total strains. Lactobacillus brevis and Weissella cibraria account for thelargest proportion of LABs that isolate from sourdough. The yield of Weissella cibraria EPSis higher than others. Its yield of EPS is0.18mg/mL. And The yield of Lactobacillus brevis is0.14mg/mL. Therefore choose Weissella cibraria and Lactobacillus brevis for the followingtests. Add them to the dough, and research the effects on steamed bread.The yield of Weissella cibraria EPS is up to0.18mg/mL; The yield of Lactobacillusbrevis EPS is0.14mg/mL; The yield of Lactobacillus crustorum EPS is0.05mg/mL; The yieldof Lactobacillus paralimentarius EPS is0.07mg/mL; The yield of Lactobacillus planetariumEPS is0.15mg/mL; The yield of Latococcus qarvieae EPS is0.13mg/mL; The yield ofLeuconostoc fallax EPS is0.1mg/mL. Optimize ferment conditions of Weissella cibraria andLactobacillus brevis. We can get the follow conclusions: The yield of Weissella cibraria EPSis0.28mg/mL under this conditions which select sucrose as carbon source, the best fermenttime is18～20h, the optimal pH is about6, the optimal incubation temperature is about30℃;The yield of Lactobacillus brevis EPS is0.2mg/mL under this conditions which select sucroseas carbon source, the best ferment time is about22h, the optimal pH is about6, the optimalincubation temperature is about35℃.Dough with Weissella cibraria fermentation8h、16h、24h and32h using as startercultures can significantly improve specific volume, white degree, texture and sensory scoresof steamed bread comparing to steamed bread without LABs. Dough with Lactobacillus brevis fermentation8h、16h、24h and32h using as starter cultures adversely affect the qualityof steamed bread. Weissella cibraria can improve the quality of steamed bread, andLactobacillus brevis adversely affects the quality of steamed bread. So we can add Weissellacibraria to dough, and avoid adding Lactobacillus brevis in the industrial production ofsteamed bread.During the process of fermentation of dough which adds exopolysaccharide-producingLAB will produce EPS. Respectively, add exopolysaccharide-producing LAB and its EPS todough, we can get the following conclusions: Adding Weissella cibraria and0.2%Weissellacibraria EPS can improve the texture of steamed bread(such as hardness, resilience andadhesion, ect), increase specific volume, white degree, and sensory scores of steamed bread,and slow the aging of steamed bread to some extent. The steamed bread with Lactobacillusbrevis is too hardness; the specific volume of the steamed bread is too small; the sensoryscores of the steamed bread is too low. Lactobacillus brevis has a negative impact on thequality of steamed bread. While adding0.2%Lactobacillus brevis EPS can improve thequality of steamed bread. This shows that the decreasing of steamed bread quality is due tometabolic activity of Lactobacillus brevis druing fermentation process, rather thanLactobacillus brevis EPS.