Discriminating wine yeast strains and their fermented wines : an integrated approach

[摘要] The discrimination between wine yeast strains as well as between their fermented wineshas been investigated in this pilot study. The study was divided in two parts, the first toinvestigate the discrimination between wines fermented with five differentSaccharomyces cerevisiae yeast strains, analysed by gas chromatography (GC) andFourier transform infrared spectroscopy (FTIR) and the second part to investigatediscrimination between wine yeast strains in different liquid media and in dried formusing FTIR in transmission and attenuated total reflectance (ATR) modes.Wines from three cultivars (Clairette Blanche, Pinotage and Cabernet Sauvignon)that were fermented by five Saccharomyces cerevisiae yeast strains (VIN13, WE372,VIN13-EXS, VIN13-PPK and ML01) were analysed by GC and FTIR. This analysis wasdone on individual sample sets that consisted of the wines of each of the mentionedcultivars and also on samples drawn throughout the ageing process of these wines. Thedata obtained were analysed by PLS-Discrimination (PLS-discrim), a chemometricmethod. Using the data from both the analytical methods, discrimination was observedbetween wines fermented with different yeast strains in each of the two vintages (2005and 2006) for all the cultivars. When combining the data from the two vintages nodiscrimination could be observed between the fermented wines. The discrimination ofthe fermented wines was found to be similar when using data from GC and FTIR,respectively. Since analysis with FTIR is considerably faster than analysis by GC, itwould be recommended that FTIR is used for future studies of similar nature.Combining the samples into one set consisting of wines fermented with commercial wineyeast strains and wines fermented from closely related wine yeast strains (the parentalstrain and two genetically modified versions thereof (VIN13, VIN13-EXS and VIN13-PPK), those fermented with closely related stains did not show good discrimination fromeach other. Discrimination was found between wines fermented with geneticallymodified (GM) wine yeast strains and those fermented with non-GM wine yeast strains.This was done on a limited number of yeast strains and a larger study is needed toconfirm these results. As this is the first study of this nature and differences seen couldbe as result of the different phenotypes.It was shown that it is possible to use both FTIR-transmission and FTIR-ATR(attenuated total reflectance) to discriminate between different wine yeast strainphenotypes. It was shown that when using FTIR-transmission there is discriminationbetween yeast samples suspended in yeast-peptone-dextrose (YPD) and in water.Dried yeast samples could be discriminated when the yeast samples were in a granular, powder form or in a pellet form, using FTIR-ATR. It was possible to discriminatebetween the closely related yeast strain phenotypes using FTIR-ATR.In this pilot study it was shown that there can be discriminated between different wineyeast strains and also between the wines fermented with different wine yeast strains. Itis recommended that further studies be conducted to refine and expand the study.

[发布机构] Stellenbosch University