Microbial Screening And Identification Of Traditional Starter And The Impact On The Quality Of Mantou

Microorganisms in traditional starter cultures are investigated in this paper, includingmicroorganism separation, screening, identification and the effects of complex bacteria onquality and flavor of Mantou, basedly on foreign Sourdough research results. The aim is toprovide reference for industrial production of traditional starter cultures in Mantou. The mainresearch contents and conclusions are as follows:1. Firstly, the influence of commercial lactic acid bacteria on Mantou quality werestudied. Mantou by adding different lactic acid bacteria has very big positive impact on thedough fermentation characteristics, Mantou sensory evaluation and structure parameters.Lactic acid bacteria can improve dough fermentation performance, increase the doughproducing gas and hold breath performance. For that reason the dough more flexible and loose,Mantou taste and texture being better than the dry yeast Mantou. This is a theoretical basis foradding lactobacillus to increase steamed bread quality.2.27strains of lactic acid bacteria and25strains of yeast were screened from traditionalstarter cultures. Three strains of lactobacillus and three strains of yeast are chosen byre-screening and single factor experiments and use vacuum freeze-drying as powder. Bacteriapowder were directly added to Mantou. Through orthogonal experiment, determine the yeastY-3and lactobacillus L-25for optimal collocation. Strains identification results showed thatyeast Y-3for saccharomyces cerevisiae B, lactobacillus L-25for lactococcus lactis ss lactis.The research results show that the optimum process is saccharomyces cerevisiae B for0.15g,lactococcus lactis ss lactis for0.1g, fermentation time for60min and fermentation temperaturefor32℃.3. Solid phase micro extraction (SPME) for sample pretreatment, the volatile substanceof Mantou were analysed and identified by gas chromatography-mass spectrometry(GC-MS).Firstly, the best conditions of SPME-GC-MS were determined as follows:2g sample in15mLvessel, exposure for60min at60℃, and desorption for4min at250℃. Analyzing the volatilesubstances of Mantou fermented by lao jiao tou and yeast showed that flavor substances typemainly include alcohols, esters, aldehydes, ketones, benzene class, acyl compounds andheterocyclic compounds, but the flavor material composition, quantity and content aredifferences. The number and concentrations of alcohols and esters are higher in lao jiao toustarter Mantou. Through the study of flour and Mantou without yeast found that there are acertain amount of volatiles in flour, Mantou did not produce alcohols, alcohols and esters mostly produced during yeast fermentation. Not only the number of flavor volatiles weregrowing, but also the content and concentration had greatly improved of Mantou addingsaccharomyces cerevisiae B and lactococcus lactis ss lactis.4. The research of composite bacteria powder on the influence of Mantou aging draw theconclusion that flavor substances have decreased in storage process. Alcohols and carbonylcompounds volatilize slower, so content decreases speed also is slower. Ester and acylcompounds were greatly influenced by the ageing, reduce speed is faster. Complex bacteriafermenting Mantou is still able to maintain its flavor within3days. Storing1to2dayscomplex bacteria fermenting Mantou can still maintain its texture and taste, which is the poorafter two days.