Wine Chemistry and Biochemistry

(Steven Felgate) #1

8D Yeasts and Wine Flavour 369


ester and higher alcohol production, and production of novel wine aromas; acetic


acid and acetaldehyde are highly variable amongst strains (Table 8D.6) (Ciani and


Maccarelli 1998; Henschke et al. 2002; Jolly et al. 2003b; Soden et al. 2000). Strain


selection and sequential fermentation withSaccharomyces cerevisiaeis especially


important to avoid acetoin and aldehyde off-flavours and to enhance floral and estery


aromas in low aromatic grape varieties.


Issatchenkia orientalis(anamorphCandida krusei)is occasionally isolated from


grape musts and the early stages of fermentation, in which it can tolerate up to


6.5 vol.% ethanol (Table 8D.6). It produces relatively high concentrations of esters,


higher alcohols and succinicacid together with moderate concentrations of acetic


acid and acetaldehyde. In sequential fermentation withSaccharomyces cerevisiaeit


produced good acidity, very low volatile acidity, intense fruity ester production, and


in some wines, a desirable ‘wild yeast’ fermentation character. A recently studied


isolate of this thermotolerant,acidphilic yeast was found to degradeL-malic acid,


and in cofermentation withSaccharomyces cerevisiaecould produce wine with


acceptable quality (Bellon et al. 2008; Henschke et al. 2002; Kim et al. 2008).


Appropriate selections of this yeast appear to offer white and red wine making


potential.


Metschnikowia pulcherrima (anamorphCandida pulcherrima)is commonly iso-


lated from grapes and musts, and can dominate in the early stages of fermentation.


In monoculture some strains produce very high concentrations of esters, especially


ethyl acetate, which has a fruity, solvent character, and ethyl octanoate (ethyl capry-


late) a fruity, pear-like aroma (Table 8D.6). Considerable 2-phenylethyl alcohol,
which has a rose aroma, and diacetyl a buttery aroma, can also be produced in high


concentrations. Wines made with this species are overly estery; however these char-


acteristics can be used to intensify wine aroma. However, having a low tolerance


to ethanol, this yeast has been used in coculture withSaccharomyces cerevisiae.


Surprisingly, the composition of volatile compounds varieslittle from thecorre-


spondingSaccharomyces cerevisiaestrain wines, but in sensory tests these wines


were preferred (Clemente-Jimenez et al. 2004; Jemec and Raspor 2005; Jolly


et al. 2003b; Zohre and Erten 2002). This yeast is a good example of how their char-


acteristics can be beneficially moderated by cofermentation withSaccharomyces


cerevisiae.


Hanseniaspora uvarum(anamorphKloeckera apiculata) is commonly the major


yeast present on the grape berry and in musts and juices, but due to low tolerance to


ethanol, populations decline quickly in the presence ofSaccharomyces cerevisiae.


Strains are typically characterised by low fermentative ability and high production


of acetic acid, ethyl acetate and acetaldehyde, which render such strains more suit-


able to vinegar production. Nevertheless, Ciani and Maccarelli (1998) surveyed 37


isolates and found considerable variability, with some strains producing concentra-


tions of these compounds approaching concentrations present in wines made with


Saccharomyces cerevisiae(Table 8D.6). Cofermentation fermentation withSaccha-


romyces cerevisiaecan produce wines with an acceptable balance of volatile and


non-volatile compounds and sensory scores (Ciani et al. 2006; Jemec and Ras-
por 2005; Jolly et al. 2003b; Zohre and Erten 2002).

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