Wine Chemistry and Biochemistry

(Steven Felgate) #1

364 M. Ugliano and P.A. Henschke


their hybrids withSaccharomyces cerevisiae, have improved ability to hydrolyse


S-cysteinylated conjugates to increase the concentration of the tropical fruity long-


chain polyfunctional thiols (Dubourdieu et al. 2006), and mask the green/vegetative


aromas, possibly due to methoxypyrazines (Bellon et al. 2008; Eglinton and Hen-


schke, unpublished). Consequently, selected strains ofSaccharomyces bayanus/


uvarumand hybrids are becoming useful for improving the flavour of Sauvignon


Blanc, Semillon, Chardonnay, Cabernet Sauvignon and Merlot wines.


Little information is yet available on otherSaccharomycessensu stricto species.


Saccharomyces paradoxuswines are augmented in ‘floral’ and ‘citrus’ attributes,


and contain lower concentrations of ethyl acetate, 3-methylbutanol, total volatile


esters, higher concentrations of total higher alcohols and variable formation of


volatile fatty acids, when compared to the reference strain ofSaccharomyces cere-


visiae(Orlic et al. 2007). No aroma descriptions have been published forSac-


charomyces kudriavzeviiwines but the one strain tested in a red and white juice


produced less total esters and more higher alcohols than the reference strain of


Saccharomyces cerevisiae(Gonz ́alez et al. 2007). TwoSaccharomyces kudriavzevii


xSaccharomyces cerevisiaehybrids (Lallemand W27 and W46) tended to show a


more moderate behaviour although with slightly higher amounts of higher alco-


hols than the reference yeast. Another hybrid (Maurivin AWRI 1503) has been


reported to produce ‘estery’, ‘floral’, ‘tropical’, ‘citrus’, ‘nutty’ and ‘waxy’ aromas


in Chardonnay wines, whereas aSaccharomyces cariocanusxSaccharomyces cere-


visiaehybrid (Maurivin AWRI 1502) gave a different profile described as ‘peach’,


‘pear’, ‘nectarine’, ‘violets’, ‘lemon fruit/zest’, ‘creamy’, ‘mineral’ and ‘match-
stick’; the non-Saccharomycesparents of these hybrids failed to ferment grape must


(Bellon et al. 2008; Henschke 2007).


8D.6.3 Mixed Cultures ofSaccharomyces


Winemakers have been combining strains ofSaccharomyces cerevisiaefor several


decades on the basis of observations that mixed-cultures produce more flavour diver-


sity and balanced wines, by introducing a greater range of flavour notes and moder-


ating the intensity of distinctive estery/fruity notes, such as pineapple and banana in


Chardonnay wines. Little research has, however, been conducted into the effects on


yeast growth, wine composition and flavour profiles resulting from fermentations


made with mixed cultures ofSaccharomycesstrains (Cheraiti et al. 2005; Favale


et al. 2007; Fleet 2003; Grossmann et al. 1996; Howell et al. 2004a, 2006). The


differences in yeast growth patterns of genetically distinct strains, that are observed


when they are cultivated individually and in mixtures, suggest that metabolic inter-


actions can occur between different yeasts, and that they can be antagonistic, neutral


or stimulatory.


Diffusable metabolites, such as acetaldehyde, are likely candidate effector


molecules. Acetaldehyde can, for example, be produced/utilised at different rates by


different strains, and can affect the redox status of each yeast, as has been observed

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