8D Yeasts and Wine Flavour 363
8D.6.2.2 Volatile Compounds
The aroma profile of wines made with strains ofSaccharomyces cerevisiae,selected
for (white) wine production, can be broadly classified into two groups, those that
are described as fruity/estery and others for which varietal character is enhanced.
The fruity/estery group can be further sub-divided into high and low ester pro-
ducers, with the latter group sometimes referred to as ‘neutral’ strains. This clas-
sification is based on sensory perception by winemakers world-wide and made
over several decades, and this information has been collated by various research
institutes and wine yeast producing companies. Nevertheless, this empirical based
information has some chemical basis,bearing in mind thevariability introduced
by fermentation conditions and must composition, especially nutrients that stimu-
late ester production (see for example Carrau et al. 2008; Delteil and Jarry 1992;
Dubourdieu et al. 2006; Dumont and Dulau 1997; Est ́evez et al. 2004; Houtman
and Du Plessis 1986; Lurton et al. 1995; Mateos et al. 2006; Loscos et al. 2007;
Miller et al. 2007; Rankine 1977; Reynolds etal. 2001; Soles et al. 1982; Swiegers
et al. 2008; Torrea et al. 2003; Ubeda-Iranzo et al. 2000; Vila et al. 2000; Vilanova
et al. 2007; Zeeman et al. 1982).
Examples of neutral yeasts are the various clones of the group that comprise
IOC Prise de Mousse, Lalvin EC1118, Mauurivin PDM, and many others. These
clones are highly versatile and can be usedin the production of every wine type,
from sparkling, dry white, red and ros ́e, sweet white and red, to botrytis-affected,
Eiswein and Ice-wine, excepting flor yeast wines. Estery yeasts typically produce
higher concentrations of some or most of the principal sensorially important esters
(ethyl acetate, 3-methylbutyl acetate, phenylethyl acetate, hexyl acetate and the
ethyl esters of hexanoic, octanoic, decanoic and dodecanoic acids) and average
concentrations of higher alcohols, which otherwise tend to mask aroma intensity
(van der Merwe and van Wyk 1981). Examples of estery yeast are Enoferm M1
and M2 (Lallemand), and Maurivin AWRI 350, AWRI 796 and AWRI R2 (Mauri
Yeast). Varietal enhancing yeast are those that, relative to ester production, enhance
the release and/or modification of grape-derived flavour compounds, to yield vari-
etal related aroma compounds, such as the fruity, long-chain, polyfunctional thiols
4-mercapto-4-methylpentan-2-one (4-MMP), 3-mercaptohexan-1-ol (3-MH) and 3-
mercaptohexyl acetate (3-MHA) (Dubourdieu et al. 2006; Swiegers et al. 2008).
The aroma profiles of non-Saccharomyces cerevisiaewines are distinctly dif-
ferent when compared toSaccharomyces cerevisiaewines. For example, Chardon-
nay wines made withSaccharomyces bayanusare more associated with savory-
and cooked-like aroma attributes including ‘cooked orange peel’, ‘honey’, ‘yeasty’,
‘nutty’ and ‘aldehyde’ whereasSaccharomyces cerevisiaearemoreestery/fruity
with ‘estery’, ‘ethyl acetate’, ‘floral’, ‘pineapple’, ‘peach’ and ‘citrus’ attributes
(Eglinton et al. 2000, 2005). These differences might be associated with higher
concentrations of phenyl ethanol, phenyl ethyl acetate, ethyl lactate and acetalde-
hyde, and lower ethyl acetate, acetic acid and the remaining higher alcohols pro-
duced bySaccharomyces bayanus(Antonelli et al. 1999; Eglinton et al. 2000;
Feuillat et al. 1997). In addition, strains ofSaccharomyces bayanus/uvarum,and