Research On The Yeast Species Constitution Of Grapes From The Main Original Wine Areas In China

258 natural yeast strains were isolated from the surface of grapes and grape juice, collected from the major wine grape cultivation areas in Xinjiang, Gansu, Shaanxi, Ningxia and Shandong Provinces in China. Then parts of the strains were selected according to morphologic characteristics, and were identified based on the 26S rDNA D1/D2 domain sequence analysis and physiological characterization, in order to clarify the diversity of yeast species and their distribution. Among them, 26 species belonging to 13 genera were recognized. The dominant genera identified were Hanseniaspora (5 species): H. uvarum, H. clermontiae, H. vineae, H. guilliermondii, H. opuntiae, respectively; Pichia (4 species): P. guilliermondii, P. galeiformi, P. fermentans, P. kluyveri, respectively; Candida (4 species): C. tropicalis, C. stellata, C. atmosphaerica, C. ethanolica, respectively; and Issatchenkia (2 species): I. orientalis, I. terricola, respectively. Hanseniaspora uvarum and Issatchenki orientalis were the most widely distributed species. The results showed that there were abundant yeast resources on the surface of the grapes. D1/D2 sequence variations were compared among the strains of Hanseniaspora uvarum from different areas.3 excellent yeast strains were obtained by the first screening of Durham tube method, second screening of endurance experiments and then the test of simulation fermentation. The 3 yeast strains used in this study were named ZYFJQ (GenBank accession number EF550180), isolated from the grape juice of Cabernet Gernischt(Vitis vinifera)in Changyu winery, Shandong; QM (EU376056) from the grape juice of Merlot in Qilian winery, Gansu, and YQY (EF585434) from the grape of Yuquanying farm in Ningxia, respectively. All the three strains have been identified by morphological, physiological and 26S rDNA D1/D2 sequence analysis, strains ZYFJQ and QM were Saccharomyces cerevisiae and YQY belonged to Hanseniaspora uvarum. Three strains can endure 16% (Vol) of alcohol, 400 mg/L of sulphur dioxide, 60 % of the glucose in medium. The test of simulation fermentation showed that the alcoholicity produced by yeast strain QM was 8% (Vol).Flavor substances are the important typical factors to determine the wine quality and style, and play a significant impact on the formation of the original wine type. Therefore, Three excellencent natural yeast strains ( QM, ZYFJQ, YQY) were used in pure and mixed inoculated fermentations for original dry red wine with two grape cultivar Cabernet sauvignon and Cabemet gemischt harvested from WuWei and Yantai, meanwhile the commercial yeast Saccharomyces cerevisiae RC212 was used as control. Flavor compounds produced in wines and in must were identified by GC-MS. The results of the chemical index and aroma-component analysis showed that the chemical index of the wines with natural selected strains were close to strain RC212, which could satisfy the demand of Chinese National Wine Standard, while the reducing sugar determined varied from 2.96 to 3.90 g/L, the titratable acid between 5.30 to 7.00 g/L, and the volatile acid in the 0.20 to 0.40 g/L. The alcohol produced by the mixed fermentation were similar to the pure fermentation, while the kind and content of aroma components increased by the mixed fermentation. The GC-MS results showed that the compounds in grape juice were mainly esters, and the volatiles of the fermented wine samples were found to be mainly alcohols, esters, acids and heterocyclic compounds, which could account for that screened strains had certain ability to produce aroma compounds. The test identified 38 kinds of fermented aroma, there were 15 and 9 kinds of compounds by strain QM and ZYFJQ pure fermentation, and when mixed with strain YQY, the type of compounds added to 19 and 14, respectively. 2-benzene ethanol constituted the main characteristics of wine aroma components, and the particular compounds were dianhydrodulcitol and furans.In the course of brewing, different yeast strains have apparently different contribution to the type and content of the wine aroma components. This showed that different yeast strains play an important part in the characteristics of the original wine style.