Isolation And Identification Of Yeast In The Old Yeast Of Shantou And Analysis Of Its Fermentation Characteristics

Chinese steamed bread starter is traditional Chinese dough fermented reagent. The steamed bread made by Chinese steamed bread starter has unique flavor, and consumers love it very much. In this study,14 Chinese steamed bread starters were collected from four provinces in Northwest China and their amino acid analysis, the growth curves, gas production, dough fermentation ability and nutrition value were investigated using analyses such as isolation and identification of microorganisms. Four conclusions had emerged from this study.Firstly, the total content of amino acids of Chinese steamed bread starter was relatively high, and contains 8 kinds of essential amino acids. However, the content of total amino acid, essential amino acids, and the amino acid score differed according to geographical region:Chinese steamed bread starter from Shaanxi scored highest (96.8 mg/g) followed by those from Qinghai, Ningxia and Xinjiang respectively, the lowest is Xinjiang for 80.8 mg/g.Secondly, among 36 strains of yeasts isolated from 14 Chinese steamed bread starter samples.33 strains were Saccharomyces cerevisiae,2 strains were Candida albicans, and the other one was Saccharomyces kudriavzevii.Thirdly, the longest logarithmic phase was found in yeast isolated from Shaanxi Province Chinese steamed bread starter (10 h), the next was that of Qinghai Province (9 h), which of Qinghai and Xinjiang yeast has a relatively large distribution range from 4 to 8h. Yeast has strong metabolism in Logarithmic phase and the morphology and physical properties are stable, it is helpful for the production of yeast metabolites in the industrialized production.Fourthly, significant differences were found in gas production and fermentation ability of yeast. Yeast isolated from samples collected in Shaanxi Province showed the strongest gas production, the highest value was 2-3 cm. The value for Ningxia and Xinjiang was 2-2.5 cm. The fermentation ability was strongest and the maximum value was 15 cm. That of samples collected in Qinghai Province has the second strongest ability and that of samples collected in Xinjiang showed weakest ability.Overall, Chinese steamed bread starter from Shaanxi Province has the highest value of amino acid content. Besides, the yeast isolated trom it has the longest logarithmic phase, the largest gas production and fermentation capacity, which has broad prospects for market development.