| This study select the high-temperature Daqu and fermented grains within rounds of Moutai-flavor liquor as the research objects to analyze the yeast of its process of dynamic change and functions. This would accumulate some basic datum for realizing the fermentation mechanism of Moutai-flavor liquor. The results are as follows:(1)The number of yeast exist in the high-temperature Daqu of Moutai-flavor liquor is 103cfu/g. These yeast might affect our cognization about the population dynamics of the yeast in fermented grains within rounds. Accumulation process can significantly increase the number of yeast in fermented grains and make the number of yeast stabilize in 106-107 cfu/g. It is obvious that accumulation process could reduce the influence that the quality of Daqu and environmental factors make to the population change of yeast in fermented grains within rounds before being in pits. In all the rounds, the population of yeast in 4th and 5th rounds that the quality of Moutai-flavor liquor is good is more than the rounds of behind that the quality of Moutai-flavor liquor is not good. In pits, we find the population of yeast in fermented grains in different places show that the upper > the middle > the lower, and the population in the upper of 3th, 4th, 5th rounds that the quality of Moutai-flavor liquor is good is more than the rounds of behind.(2)Through the morphology observation and the modern molecular biology methods, the yeast strains separated and screened from Daqu and fermented grains are classified as 9 genus and 13 species. There are 2 species or 2 genus exist in Daqu, including Debaryomyces hansenii and Saccharomycopsis fibuligera. There are 12 species or 8 genus exist in fermented grains, including Trichosporon coremiiforme, Schizosaccharomyces pombe, Saccharomycopsis fibuligera, Saccharomyces cerevisiae, Pichia kudriavzevii, Pichia membranifaciens, Pichia manshurica, Candida apicola, Trichosporonoides sp., Pichia farinosa var. farinose, Candida inconspicua, Issatchenkia orientalis. In this study, the Saccharomycopsis fibuligera strains are separated and detected from Daqu and fermented grains at the same time. It is obvious that the yeast in Daqu can enter into brewing process, but, in contrast, its contribution is more less than the yeast in the environment make to the production process of the liquor.(3)Through the analysis of functions of the yeast, the results showed that the yeast separated and screened from the production of maotai-flavor liquor have different abilities in alcohol-producing, fragrance-producing and polyols-producing. Among these strains, the FBKL2.0316(Saccha- romyces cerevisiae) and FBKL2.0320(Saccharomyces cerevisiae) show the good ability in alcohol-producing, and the FBKL2.0302(Saccharomycopsis fibuligera) and FBKL2.0315(Trichosporonoides sp.) all do well in fragrance –producing within the both liquid and solid conditions. Their solid fermentation products present faint scent smell and floral smell, respectively. Composition analysis results show that among the volatile fragrance compositions of FBKL2.0302 solid fermentation product the content of phenethyl alcohol is most, followed by 3-methyl-1-butanol, 3-methylbutanoic acid and 3-methylbutyl acetate, and so on. For FBKL2.0315, the most content of the composition is unknown, followed by 4-ethyl-2-methoxyphenol, 4-ethylphenol, phenethyl alcohol and linalool, and so on. According to the content, the phenethyl alcohol and the unknown composition would have the largest contribution to the flavor characteristics of the two yeast strains with its solid fermentation product, respectively. In addition, most of the yeast have the ability to produce polyols, and the common polyols products are D-Arabinitol and glycerin. |
