Screening and application of wine yeasts at the eastern foot of Helan Mountain in Ningxia Hui Autonomous Region

Abstract:

[Background] The eastern foot of Helan Mountain in Ningxia was once regarded as the “golden zone” for wine grape growth and thus boasts high-quality wine. Wine produced in this area got the tile of geographical indication product and therefore this area was included in the protection catalogue for the product. [Objective] To screen excellent native yeast strains in Ningxia, compare and analyze the influence of each Saccharomyces cerevisiae strain on the aroma quality of Cabernet Sauvignon, and select strains with great influence on wine flavor according to sensory evaluation. [Methods] The 26S rDNA sequencing was performed on the 11 selected strains which featured rapid fermentation at the early stage and strong tolerance to high alcohol concentration, SO₂, glucose, and low acid environment for identification. The aroma compounds of Cabernet Sauvignon fermented by different strains were determined by head space-solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). [Results] Eleven yeast strains which were tolerant to 15% alcohol, 500 g/L glucose, 350 mg/L SO₂, and pH 3.0 were screened out, among which 10 (H5, G9, G3, X8, G14, L10, H3, X11, Z17, and Z24) were identified as S. cerevisiae and one (L1) was Pichia fermentans. Esters were the main aroma compounds of Cabernet Sauvignon, followed by alcohols. Among them, ethyl acetate, isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, 1-octene-3-alcohol and β-damascone had high odor activity values and contributed the most to the aroma of Cabernet Sauvignon, endowing the wine with pleasant apple aroma, banana aroma, mushroom aroma, anise aroma, and sweetness. Cluster analysis of aroma components of Cabernet Sauvignon samples fermented with different S. cerevisiae stains revealed that the wine samples fermented with G14 and H3 were the closest to the wine fermented with the commercial yeast XR and the three showed consistent influence on the characteristic aromas of Cabernet Sauvignon. [Conclusion] S. cerevisiae G14 and H3 have huge potential for brewing, particularly for wine fermentation, which can help improve the quality of wine in Ningxia.