Screening, identification and fermentability of yeast isolated from traditional sourdough in Henan

In order to obtain special yeast strains for sourdough, yeasts were isolated from traditional sourdough in Zhengzhou, Nanyang, Anyang, Zhoukou, Shangqiu and Sanmenxia by the method of traditional cultivation and separation methods. These tested strains were identified by molecular biology techniques and their fermentability were researched. The results showed that 9 strains were isolated and purified. 1 strain was identified as Saccharomycopsis fibuligera and 8 strains were identified as Saccharomyces cerevisiae. The 9 strains had different acid and ethanol tolerance. Strain Y2-1 had better tolerance, which could tolerate pH 1.5 and ethanol 16%. With the extension of fermentation time, the titration acidity of dough with different yeast addition showed an overall upward trend, while the pH value showed an overall downward trend. The volumes of the doughs increased gradually. Strains Y2-1 could increase the volume of dough by 1.23 times after fermentation for 3 h. To sum up, S. cerevisiae Y2-1 had better tolerance and the fermentation ability was the strongest, which could be used as an excellent strain to provide theoretical support for the development of direct delivery starter.