Evaluation Of Fermentation Characteristics For Wild Yeast Strains And Brewing On The Original Wine Of Gansu

146 yeast strains were separated from Gansu province in China and used in the experiment. 24 strains with high fermentation capacity and thick flavour were screened out by Durham tube method. The results of resistance evaluation of some strains(tolerant to high concentration of SO2, NaCl, high temperature and acidity , as well as glucose and alcohol) showed that 23 strains could grow in high concentration of SO2 over 650 mg/L, 17 strains grow in high concentration of NaCl over 280g/L , 8 strains grow at 50℃, 9 strains grow at pH1.5～12.5, 23 strains grow in 650 g/L glucose medium and 6 strains could grow in 18%(vol)alcohol medium. The results of the formulation fermentation showed that strains QCH7,HYHT6,HYHP3C,HYHT1C,were short for fermenting primary period, that GS38A alcoholicity was 8%(Vol), and SQ4 is thick aroma.Three natural yeast strains(GS13F,GS38A,HYHP3C)were used in single or combination for original dry red wine fermentation with two grape cultivar Cabernet sauvignon and Cabemet gemischt harvested from Wuwei , commercial yeast RC212 as the control. The results of the chemical index and aroma-component analysis with GC-MS showed that the chemical index of the wine with natural strains could satisfy the demand of China wine standard, that the alcoholicity of the wine with strain GS38A(7.2%)was close to that of RC212(8.0%), that most aroma components were from fermentative process, that GS13F produced more suitable and more kinds of aroma components,the main aroma components were n-Amyl acetate(27.54%),2-Phenylethyl acetate(15.67%)and 2-Phenylethanol(9.85%).In combining with GS38A and RC212, the characteristic of producing aroma components of GS13F was complemented with the high alcoholicity of GS38A or RC212,and the aroma type and content increased, the wines tasted more rich and harmonious, suggesting their potentiality in producing original wine. Meanwhile, Two Cabernet sauvignon grapeberry material(harvested from WuWei and YanTai ) were used for dry red wine fermentation with two natural wine yeast strains(GS13F and GS38A). aroma-component analysis for the grape bunch and wine respectively, The results showed that 8 aroma-components were found in each grapes for each area, but the type and content were significant different. The main aroma components of the grape harvested from WuWei were Dimethyl phthalate(68.48%)and Diethyl phthalate(10.05%),while the main aroma components of the grape harvested from YanTai were Dimethyl phthalate (46.62%)and 2-Phenylethanol(7.69%). The type and content of aroma components of wine were largely decided by aroma components of grape. In the course of brewing, different yeast strains have apparently different contribution to the aroma components type and content of the wine.8 yeast strains were identified based on the combination of morphology and 26S rDNA Dl/D2 domain sequence analysis, the 4 species of them (or variety)belonging to 4 genera. The dominant genera identified were Candida and Kodamaea .