Screening Of The Dry White Wine Yeast Rich In Polysaccharide And Its Fermenting Capacity

The production of high-quality wine requires fine wine yeast strains, which can bring special characters and styles to the wine. The yeast polysaccharide can increase the stability of tartar, protein, and tannin and pigment, keep the balance of wine, enhance the round feeling after being tasted, and improve the complexity of flavor. However, studies on the yeast strains applied to winemaking in our own country such as screening and usage are few. Therefore, it's very important to screen the yeasts rich in polysaccharide for winemaking in China.The polysaccharide production rates of 120 Saccharomyces cerevisiae strains were preliminarily screened by the phenol-sulfuric acid method and three strains with higher polysaccharide production were achieved. The polysaccharide production rate of W-15, NX-4, and NE-18 were 2.23%,2.20%,2.17%, their rate were higher than the VL1 :2.15% and AWRI796:2.17%, respectively. After a series of experiments done by biochemical methods, physiological characteristics and molecular biology identification methods, these three strains were identified as Saccharomyces cerevisiae strains. The results of sequences analysis showed that the homology of W-15 was 99.6%, NX-4 was 100%, and NE-18 was 100%. Subsequent experiments on the fermentative properties of them, including the fermenting power, and resistant capability, demonstrated that the resistant capability of NE-18 was desirable for the requirements of dry white wine production, and the other two strains of NX-4 and W-15 could not match the standards of fermenting power.Subsequently, these three yeasts screened above together with other two active dry yeasts (as the control) were put in a small container to ferment at 18℃, and the results showed that, the fermentation speed and time of W-15 did not reach the level of active dry yeast,and the physical and chemical parameters of its wine could not meet the requirements of dry white wine; The fermentation speed of NX-4 was the same as VL1, and its fermentation time was the same as AWRI796; the fermentation speed of NE-18 was quicker than AWRI796, but slower than VL1, and its fermentation time was the same as VL1.After fermentation, the final wine was analyzed, demonstrating the yeast that had higher polysaccharide capacity in fermentation, had better protein stability, and tartaric cold-stability, together with the complexity of aroma components of this wine. After being evaluated by 22 professional winetasters, the results indicated that the sensory quality of NE-18 was the same as VL1, and better than NX-4 and AWRI796.Therefore, NE-18 is considered as the most desirable stain for the production of dry white wine with high quality.