| Yeast is the soul of the wine, and the flavor and quality of wine are affected by its fermentation characteristics. Generally, different types of yeasts are used to give the different taste and characteristic of wine. Nowadays imported active dry yeasts are widely used in most factories in our country. Due to the differences of natural environment and yeast evolution, the commercial yeasts might not be completely produced region style wine. Besides, they also caused homogeneity phenomenon of domestic wine in different regions to some extent. Therefore, it is necessary to screen excellent yeast strains used for wine production, which is adapt to particular regions and grapes in China.The product of “Changli wine" in Hebei province is the first certificate of original protection in our country, perhaps due to that the local climate, soil and grape varieties have cultivated the local yeast strains. Based on this, wild yeasts with excellent characteristics will be isolated from Changli region in this research, which provides the conditions for fermentation of high-quality wine with original characteristics.Ripened grapes Cabernet Sauvignon were randomly collected in Changli region. According to the individual and colony morphology, 33 typical characteristics of Saccharomyces cerevisiae strains were obtained from the surface of grapes fruits through enrichment in liquid YPD medium and followed by inoculating on WL flat medium after gradient diluted. S. cerevisiae strains of CLY03 and CLY04 with strong alcohol-producing capability and rapid fermentation were screened from them through the determination of triphenyltetrazolium choride(TTC) colorreaction and fermentation tube method Duchenne.With reference to the book <characteristics and identification of yeast handbook>, the ability of carbon source, nitrogen source assimilation, physiological-biochemical properties and the colony morphology and microscopic observation were determined in the experiment. Based on these results strain CLY03 and CLY04 were primarily identified as Hansenula and Saccharomyces, respectively.Through detection of tolerance test of the condition of 10~18 % alcohol concentration, pH 3.0~5.0, 20~30 % glucose concentration, 150~300 mg/mL sulfur dioxide concentration, 28°C~49°C, respectively, the result showed that both stains could ferment normally, and strain CLY04 in the time of beginning fermentation and gas filling was better than strain CLY03 in that aspect, yet the tolerance of high temperature of strain CLY03 was higher than that of strain CLY04, and the lethal temperature was 59°C and 52°C, respectively. The doubling time of strains CLY03 and CLY04 is short, they could rapidly be into the logarithmic phase after inoculation, and reached a higer cell concentration.Strains CLY03 and CLY04 had high ability for producing alcohol, the liquor alcohol content after the fermentation was 10.6% and 11.2%, respectively. In addition, the residual sugar content(3.92 g/L, 3.84 g/L) and volatile acid content(0.28 g/L, 0.24 g/L) were in the range of national standard. The organoleptic investigation score of wine fermented by strain CLY04 reached level B, and there were no significant differences in the colour and luster, clarity, aroma and taste of wine fermented by strain CLY04 and commercial strains. The color and luster of wine fermented by strain CLY03 was poorer than that of commercial strains, but the aroma is significantly superior to that of commercial strains. The typicality of wine fermented by strain CLY03 and CLY04 was significantly higher than that of commercial strains. Compared with the commercial strains fermentation, the wine fermented by strains CLY03 and CLY04 with quality and distinguishing feature in Changli region could be latent application value. |
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