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).