【作者】 祖显生；

【导师】 刘树文；

【作者基本信息】 西北农林科技大学 ， 葡萄与葡萄酒学， 2008， 硕士

【摘要】 优质葡萄酒需要具有产区特征、能够体现葡萄酒特色和风格的优良酵母菌种,因为酵母多糖可以增强葡萄酒的酒石、蛋白和色素单宁的稳定性,平衡葡萄酒的各个组份,增强酒的圆润感和后味,增加葡萄酒香气的复杂性。然而在目前,我国在葡萄酒酵母的研究和利用方面还处于起步阶段。因此,筛选具有我国产地特色的高产多糖酵母菌株对我国葡萄酒尤其是白葡萄酒的生产具有重要的意义。试验采用苯酚-硫酸法对120株酵母产多糖的能力进行初步筛选,获得3株多糖产率高于对照或与对照相当的菌株,即:W-15、NX-4、NE-18,它们的多糖产率分别为2.23%、2.20%、2.17%,高于对照菌株VL1和AWRI796的多糖产率2.15%和2.17%。该3株菌株形态学、生理生化以及分子生物学鉴定的(Saccharomyces cerevisiae)菌株,测序结果的同源率为99.6%(W-15),100%(NX-4),100%(NE-18)。菌株发酵力和耐受性试验的结果显示:W-15和NX-4在起酵速度和发酵的持久力方面不符合工业生产的要求;而NE-18的耐受性符合干白葡萄酒在发酵过程中对耐受性的要求。随后,在18℃的条件下,以2株工业菌株为对照,将初筛获得的3株酵母同时进行小容器发酵试验,结果表明:W-15的起酵速度和发酵用时都不及对照菌株,W-15的理化指标当中残糖量不符合国家标准;NX-4的起酵速度与对照菌株VL1相当,发酵用时与对照菌株AWRI796相当;NE-18的发酵速度低于对照菌株VL1,高于对照菌株AWRI796,发酵用时与对照菌株VL1相当。最后,对利用筛选菌株发酵所得酒进行相关试验结果发现:酵母的产多糖能力越强,发酵得酒的蛋白质稳定性和酒石酸冷稳定性越好酒样的香气也越复杂,所含芳香类化合物的种类越多、浓度越高;感官品评结果表明,NE-18发酵得酒的感官品质与活性干酵母VL1相当,优于NX-4和对照菌株AWRI796,而NE-18所得酒比其它三株酵母发酵得酒更能保持葡萄品种本身的香气。研究结果:NE-18菌株的各方面性能符合选育目标,适于优质干白葡萄酒生产的要求。更多还原

【Abstract】 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.更多还原