Characterisation of hybrid yeasts for the production of varietal Sauvignon blanc wine - A review

Abstract

The wine yeast Saccharomyces cerevisiae forms an integral part of wine production by converting relatively 'neutral' flavoured grape must into varietal aromatic wines. Additionally, non-Saccharomyces strains can be used with S. cerevisiae for the production of wines with more complexity. Yeast strains, to varying extents, produce and/or mediate the release of a whole range of key metabolites, which in turn contribute to enhanced aroma and flavour of the final wine, especially Sauvignon blanc. These metabolites viz. thiols are dependent on yeast-expressed enzymes during fermentation. Inoculation with an appropriate yeast will, therefore, lead to more commercial wine sales due to resultant wines with sought-after aroma and flavour. Likewise, inoculation with the incorrect yeast will have a negative effect on sales. It is also important to have quality control measures in place to ensure that the inoculated yeast strain quickly dominate, and is present throughout the fermentation process. Traditionally, the laborious contour clamped homogeneous electric field (CHEF) DNA karyotyping technique was shown to be reliable in this regard, however cutting-edge matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS) biotyping is proving to be a faster alternative. As both methods have advantages and disadvantages, they should be used in complementary as opposed to competitively. Standard chemical and descriptive sensory analyses of wine also serve as evaluation and/or characterisation tools of yeast starter cultures. Additionally, metabolomic and proteomic profiling using gas chromatography (GC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) of final wines was shown to be instrumental yeast evaluation tools. Therefore, this review highlights the importance and practicality of a more inclusive approach to evaluate and characterise novel yeast strains used for winemaking by deploying traditional and modern chemical and organoleptic evaluation techniques of wines in conjunction with cutting-edge omics approaches towards enhancing white wine varietal aroma.

Keywords: CHEF; Enzymes; Hybrid yeast; MALDI-TOF MS; Thiols; Wine organoleptic quality.