The chemical foundations of wine aroma - A role game aiming at wine quality, personality and varietal expression

Full text

 1

The chemical foundations of wine aroma: a role game aiming
at wine quality, personality and varietal expression
V. Ferreira, A. Escudero, E. Campo, J. Cacho
Laboratory for Flavour Analysis and Enology, Analytical Chemistry Department, Faculty of Sciences,
University of Zaragoza, 50009 Zaragoza, Spain. Corresponding author’s email: vferre@unizar.es
Abstract
is paper presents a revision of our knowledge and understanding about the chemical basis of wine aroma. One of the key points of the
present knowledge is the surprising aroma-buering eect played by ethanol and the major olatiles formed by fermentation. Such a
system has the ability to suppress the eect of many odourants added to it, particularly of those with uity characteristics. e ability of
the dierent odour chemicals to break such a buer, and hence transmit to the wine a dierent aroma nuance, is used as a classication
criterion of wine odourants. To our knowledge, there are only twele aroma chemicals that at the concentration at which they can be
naturally found in some wines, have the ability to break the buer without the support of additional odourants. ose aroma chemicals in
some wines can play a genuine role as aroma impact compounds. A second way to break the buer is by means of the concerted action of a
group of molecules sharing chemical and odour properties, and at least nine families of this type are described. e third way to break the
buer is by the concerted action of many chemicals sharing some similarity in any of their generic aroma descriptors. Of course, the buer
can be broken, but in a negative way, by many chemicals playing the role of o-avours whose nature and role are briey discussed. e
way in which the buer is broken in a given wine: by means of more or less impact compounds or families, or by means of large numbers
of subtle compounds, determines the complexity and aroma characteristics of the wine. Simple wines most usually have a single impact
compound determining the aroma properties. Some more complex wines can have several of them. Still more complexity is found in some
wines in which there are not impact compounds but in which the dierent sensory notes are the consequence of the concerted action of
dierent groups of molecules. Some of the most relevant associations between wine aroma chemicals to form important aroma nuances
of some wines, such as oral notes of some whites or dierent uity notes of red wines have been recently discoered and will be presented
here.
Introduction
Wine is a luxury product from which the consumer expects to
obtain a pleasure large enough to justify the large amount of money
invested. Such pleasure is linked to the dierent olfactory, taste and
chemoestesic sensations elicited during the act of drinking. is
pool of sensations must be balanced and should never be perturbed
by the presence of any spurious sensation. Aer all, nearly all those
sensations are caused by chemical molecules, since these are the target
of our chemical senses, which are the ones that aer a complicated
brain processing, make us perceive and feel. erefore, at the core of
the quality (or the lack of it) of a wine there are numbers of odour
and avour active molecules responsible, and the major challenge
for wine avour chemists is to know which are those molecules and
to understand the role they play in the nal perception.
In fact, avour chemists began very early to do their task, and
by the late eighties they had identied more than 800 compounds
in the volatile fractions of wines (Maarse and Vischer 1989). is
was a sort of bitter success, since so much of that information
was apparently mostly useless as was recognised at that time by a
relevant and honest researcher (Etievant 1991). e reasons for that
apparent failure were mainly three. e rst one is that researchers
at that time tried to identify all the molecules present in the
volatile fraction of wine instead of concentrating their eorts on
those ones that really have the power to impact the pituitary. e
second one is linked to the complexity of wine aroma and avour:
only in a limited number of cases can a single odour molecule be
explicitly recognised in the aroma or avour of the wine. It is not
surprising, therefore, that the major successes had come in the
identication of o-avours or in the identication of molecules
responsible for wines with very dierent characteristics (i.e.
Muscat). e third reason is that at that time it was very dicult to
get accurate quantitative data on some of the molecules present at
low concentrations.
All those limitations have been slowly and progressively
solved in the last 10 or 15 years. On the one hand, the systematic
development of GC-Olfactometric (GC-O) studies, together
with powerful chemical separation schemes, have made it possible
to screen from all the volatile compounds of wine, those ones that
really have the opportunity to be avour active (Guth 1997a,b,
Ferreira, V. et al. 1998, 2002, López et al. 1999, 2003, Kotseridis
and Baumes 2000, Cullere et al. 2004, Escudero et al. 2004, Campo
et al. 2005). On the other hand, a great progress has also been
made in the quantitative determination of some trace important
odourants (Allen et al. 1994, Tominaga et al. 1998, Ferreira, V. et
al. 2003, 2006, Schneider et al. 2003, Cox et al. 2005, Culleré et al.
2006, Tominaga and Dubourdieu 2006, Campo et al. 2007, Mateo-
Vivaracho et al. 2007). Finally, with the quantitative information at
hand, it has been possible to reconstitute the avour of some wines
(Guth 1997a,b, Ferreira, V et al. 2002, Escudero et al. 2004) and to
begin to study the kind of relationships existing between odourants
(Segurel et al. 2004, Campo et al. 2005, Cullere et al. 2007, Escudero
et al. 2007). It can be said, therefore, that we are nally beginning to
understand wine aroma, and the basics of such understanding will
be briey presented in this paper.
1. Chemosensory properties of the basic chemical
environment of wine odourants
Wine, in common to nearly all alcoholic beverages produced by
fermentation, has a quite denite chemical environment which
has a deep inuence on the perception of odour volatiles and it
is necessary to understand some basic things of this environment
before going on. Such a basic chemical environment is formed by
ethanol and the major volatile metabolites of fermentation, such as
the fusel alcohols, fatty acids and their ethyl esters, branched fatty
acids and their ethyl esters, fusel alcohol acetates, acetoin, diacetyl
and acetaldehyde.


2

Compound Signif Qualitative Effect
ethyl isovalerate NS NONE
ethyl 2-methylbutyrate NS NONE
ethyl isobutyrate NS NONE
ethyl butyrate NS NONE
ethyl acetate NS NONE
acetaldehyde NS NONE
diacetyl NS NONE
β-phenylethanol  Inappreciable
butyric acid  Inappreciable
isoamyl alcohol  inappreciable
ethyl octanoate  inappreciable
methionol  inappreciable
octanoic acid  inappreciable
hexanoic acid  inappreciable
ethyl hexanoate  inappreciable
isovaleric acid  inappreciable
isoamyl acetate  slightly less fruity
β-damascenone  slight decrease in intensity
Table 1. Effect of the omission in the mixture of wine major compounds (the aroma buffer)

0
2
4
6
8
10
12
0% 10% 12% 14.50% reference
% of ethanol
Fruitiness
-0.5
0
0.5
1
1.5
2
2.5
0,1 1.0 10.0
Concentration (ppm)
decanal
decanal + ethanol
eugenol + ethanol
eugenol
-
Intensity
-
Figure 1. Effect of ethanol on the perceived fruitiness of a mixture of nine ethyl esters

Figure 2. 


e presence of all these compounds in any alcoholic beverage
has two major impacts:
on the solubility and volatility of the odourants; and•
on the actual impact of the odourants on our •
chemoreceptor system.
In general, the presence of ethanol and of the other major
compounds increases the solubility of most aroma compounds,
in comparison to what is found in water solutions. Such increase
in solubility, in turn, causes the vapour pressure of the odourants
to decrease. ere is not a very large reduction (up to 40%,
depending on the odourant) on the amount of volatile in the
headspace (at equilibrium) of any alcoholic beverage (Tsachaki et
al. 2005). Surprisingly, ethanol can also improve the transference
of the volatiles into the headspace (in dynamic, non-equilibrium
conditions), but this eect is mostly cancelled by wine proteins and
is only noticeable in some old wines (Tsachaky et al. in preparation).
It can be said, therefore, that in most wines the amount of volatiles
reaching the pituitary during olfaction is below that found in
aqueous solutions containing equivalent amounts of volatiles.
But the major eect of ethanol is on the perception itself. ere
are several denitive experiences showing this. On the one hand,
ethanol has the ability to completely mask or suppress the fruity
notes of esters as can be seen in Figure 1 (Escudero et al. 2007). e
gure shows the intensity of the fruity note of solutions containing
a xed amount of nine fruity esters at dierent levels of ethanol.
In water, the smell of the mixture was much like the smell of an
apple beverage, however, as the level of ethanol increased, the apple
character was quickly lost and the fruitiness of the mixture became
barely perceptible up to the point at which the ester solution smelt
much like a simple hydroethanolic solution (i.e. the reference).
On the other hand, ethanol also has the power to enhance the
odour of some other volatiles, such as eugenol or decanal, as can
be seen in Figure 2. ese measurements were in this case taken by
Gas Chromatography-Olfactometry (GC-O) under two dierent
conditions. Dotted lines represent the normal GC-O measurements
of solutions containing three dierent levels of the two odourants,
using humidied air at the olfactory port. When a slight amount
of ethanol was added to the humidier (plain lines), the olfactory
signals increased in both cases (Petka et al. 2003).
e mixture of all the major fermentation compounds at the
concentrations at which they are usually found in wine has the
typical odour of alcoholic beverages that we oen dene as vinous.
It is slightly sweet, pungent, alcoholic and a little bit fruity. e key
point is that this mixture forms what we call an aroma buer. We
call it a buer because in some sense it resembles the buer systems
we usually use to x pH. ose buer systems have the ability to
counteract the eect of small additions of acid or of alkali, and
as such, the aroma buer has both the ability to counteract the
eect of the omission from the mixture of one of its components,
and also the ability to counteract the addition to the mixture of
many single odourants. Both eects can be seen in Tables 1 and 2.
Table 1 (Ferreira, V. et al. 2002) shows the eects of omission
from the mixture of one of the odourants. It should be remarked
that all of those compounds were at concentrations well above
threshold. However, in most cases, the omission from the mixture
had no eect, or a just noticeable eect that the judges were not
able to dene, as data in the table clearly shows. Only in the cases of
isoamyl acetate and β-damascenone were there slight eects on the
fruitiness of the mixture.
e eect of the addition of dierent aroma compounds to the
mixture is presented in Table 2 (Escudero et al. 2004). Results are
again really surprising. It can be seen that the addition of huge
amounts of some odourants has nearly no eect, or even that the
eect is not the perception in the mixture of the added odourant,
but a decrease on some of the basic attributes of the mixture (except
for isoamyl acetate). is buering eect is something challenging
for neurophysiologists and has such a deep inuence on the way
we should understand the hierarchical relationships between wine
odourants that can be used as a useful criterion to classify wine
odourants.

 3

Compound added (level and
relative increment) Effect Observations
 Slight 
β NONE
 Slight + banana
 NONE
 Slight 
 Slight 
 NONE
 Clear 
β NONE
Table 2. Sensory effects caused by the addition of some selected aroma compounds to the

0
1
2
3
4
5
6
7
10 100 1000 10000
Concentration (µg/L)
Odour Intensity
Secondary effect
Sweet-floral
(with help)
Sweet-floral
(alone)
Floral
Muscat
Very intense
muscat
NATURAL RANGE IN WINE
Intensity-
Concentration
plot
ADDITIVE
Secondary effect
Sweet-floral (with help)
Sweet-floral (alone)
Floral
Muscat
Very intense muscat
NATURAL RANGE IN WINE
Intensity-
Concentration
plot
RANGE AS
ADDITIVE
0
1
2
3
4
5
6
7
8
10 100 1000
Concentration (µg/L)
Intensity
No effect
Sweet -frutal
(with help)
Fruity (with
help)
Intensity -Concentration
plot
RANGE IN
WINE ADDITIVE
0
1
2
3
4
5
6
7
8
0
1
2
3
4
5
6
7
8
No effect
Sweet-floral
(with help)
Fruity
(with help)
Intensity–Concentration
plot
NATURAL
RANGE
IN WINE
RANGE AS
ADDITIVE
Figure 3.
sensory contribution of this compound to the aroma of wine at each concentration level
Figure 4.
superimposed the sensory contribution of this compound to the aroma of wine at each
concentration level
2. How can the aroma buffer be broken?
Fortunately, the aroma of many wines is very rich in aroma nuances
that are quite dierent to the basic ‘vinous’ aroma of the aroma
buer. is clearly means that some aroma molecules succeed in
some wines in breaking the buer and produce a dierent sensory
perception. Surely we are far from understanding why some
molecules can break the buer and others not but, by observation,
we have identied four dierent ways to break the buer:
single molecule at a concentration large enough, such as, for •
instance, linalool in Muscat wines;
group of molecules with close similarity in chemical and •
aromatic properties, such as, for instance, aliphatic γ-lactones
in some red wines;
large group of molecules with some similarity in a generic •
(non-specic) aroma descriptor (for instance sweet), such
as for instance linalool, γ-lactones and ethyl cinnamates in
some white wines; and
the association between an aroma enhancer and one or •
several aromatic molecules unable to break the buer
themselves. In this case, most oen, a new aromatic nuance
is formed.
e act of breaking the buer implies that a new aromatic
perception will be detected in the mixture. Such a new aromatic
perception is related to the aroma or group of aromas that are
able to break the buer. e new perception, however, can be the
specic aroma descriptor of the aroma breaking the buer, or just
one of the generic descriptors of that aroma. For instance, in some
wines linalool can be clearly perceived, i.e., in those wines linalool
is transmitting to the wine its specic odour nuances. However,
in some other wines, linalool just adds a oral (unspecic) odour
nuance. In these latter cases it is a generic descriptor of linalool that
is transmitted to the wine. ese ideas can be easily understood with
the help of Figures 3 and 4.
Figure 3 shows in schematic form the ability of linalool to transmit
its odour nuances to the wine as a function of concentration. As can
be seen, below 10 ppb linalool fails in being detected in the aroma
mixture (although it still could contribute to a generic sweet note
by association with many other compounds). Between 10 and 20
ppb it can be perceived but only if it is reinforced by the presence
of some other compounds sharing some similarity in aroma, such
as ethyl cinnamate. In this case its contribution to the aroma of
wine is generic and is limited to an unspecic sweet-oral aroma
nuance. Between 20 and around 50 ppb, it reaches enough power
so that it can be perceived independently of the presence of other
compounds. However, it only contributes to the wine a generic
sweet-oral note, i.e. one of its generic descriptors. Between 50
and 120 ppb it is responsible for a clear oral odour nuance. Only
beyond this point, the note becomes Muscat and the compound acts
as a genuine impact compound transmitting to the wine its specic
primary odour descriptors. It should be noted, in any case, that the
concentrations of linalool found in wine, even in Muscat wines, falls
below the level at which this compound is used as an additive by the
agro-food industry.
e second example is that of ethyl 2-methylbutyrate. is
compound, as the plot in Figure 4 shows, never reaches the level in
wine at which it is used as an additive by the industry. However, there
are many other compounds with chemical and aromatic similarity
in wine, such as ethyl isobutyrate, ethyl isovalerate and some other
branched esters recently discovered (Campo et al. 2007). erefore,
this compound will never transmit to wine its specic primary
odour descriptors. However, in association with its congeners and
with some other fruity compounds, it can be an active contributor
to the fruity notes of some wines.
With these ideas at hand we propose a classication of wine
aroma compounds.
3. Classification of wine aroma compounds
Aroma compounds in wine are going to be classied according to
the role they can play in wine.
Impact or highly active compounds, are the compounds which •
can eectively transmit their specic (impact) or primary (highly
active) aroma nuance to a given wine without the need of the
support of more aroma chemicals. An example is linalool.
Impact groups of compounds. ese are families of compounds •
usually having similar chemical structures (chemical
homologous series) and with quite close odour properties and
that can impart to the aroma of a wine the specic notes of the
family. An example is the γ-lactones.


4

Subtle compounds or families. ese are the compounds or •
groups of compounds which fail in transmitting their specic
aroma nuances to the wine, but contribute decisively to the
development in wine of some secondary-generic aroma nuance
(for instance fruity, sweet) always with the necessary support
of other chemicals bearing a similarity in such odour notes.
Compounds in categories 1 and 2 in insucient concentration,
or even if present at high enough concentration, they co-occur
with many other powerful odourants (such as happens in
complex wines), may fall into this category.
Compounds forming the base of wine aroma. ese are the •
compounds, present in all wines at concentrations above their
corresponding odour thresholds which, however, are no longer
perceived as single entities because their aromas are fully
integrated to form the complex concept of wine aroma. Within
this group dierent roles can be found:
aroma enhancers; anda.
aroma depressors.b.
O-avours. ese are the compounds whose presence brings •
about a decrease in the general aroma quality of wine.
3.1 Impact compounds
According to our own research and from literature data, the
following compounds can act as impact compounds of some
particular wines.
Linalool. is was the rst identied aroma component able to •
exert an impact on Muscat wines (Cordonnier and Bayonove
1974, Ribéreau-Gayon et al. 1975). Its contribution to the
characteristic aroma of several wines made with grape varietals
from Galicia has been clearly demonstrated (Versini et al. 1994,
Campo et al. 2005, Vilanova and Sieiro 2006). Similarly, it also
contributes to the owery or even citrus notes of some other
white varietals (Arrhenius et al. 1996, Lee and Noble 2003,
Campo et al. 2005, Palomo et al. 2006).
cis-Rose oxide. is terpene of pleasant owery character was •
rst identied as a characteristic impact aroma compound of
wines made with Gewürztraminer (Guth 1997a). Later it has
been also found to be a key odourant in wines made with the
varietal Devin (Petka et al. 2006), and it has also been detected
in the hydrolysed fractions from precursors obtained from
dierent neutral grape varieties (Ibarz et al. 2006).
(E)-Whiskylactone. It is an impact compound in wines aged in •
oak wood (Boidron et al. 1988). Above a given concentration
it can produce an excessive and unpleasant woody character
(Pollnitz et al. 2000).
Sotolon (3-hydroxy-4,5-dimethyl-2(5H)-furanone) is also •
an impact compound in wines made with botrytized grapes
(Masuda et al. 1984), or wines from biological aging (Martin
et al. 1990, 1992, Moreno, et al. 2005), natural sweet wines
(Cutzach et al. 1998, 1999), Oporto (Ferreira, A. et al. 2003c)
or Madeira (Camara et al. 2004). Its level, in general, increases
with oxidation (Escudero et al. 2000a).
4-Mercapto-4-methylpentan-2-one has a characteristic scent •
of box tree which can be perceived in some wines made with
Sauvignon Blanc (Darriet et al. 1991, 1993, 1995) or Scheurebe
(Guth 1997b).
3-Mercaptohexan-1-ol has a smell reminiscent of green mango •
or box tree. It was rst identied in wines from Sauvignon Blanc,
Cabernet Sauvignon and Merlot (Bouchilloux et al. 1998) but
aerwards it was found in many others (Tominaga et al. 2000).
It is an impact compound of some rosé wines (Murat et al. 2001,
Ferreira et al. 2002) and of white wines made with Petit Arvine
(Fretz et al. 2005).
3-Mercaptohexyl acetate was rst found in wines from •
Sauvignon Blanc (Tominaga et al. 1996), but it can also be
found in many other wine types (Tominaga et al. 2000, Lopez et
al. 2003, Cullere et al. 2004, Gomez-Miguez et al. 2007). It has
been recently shown that it is the impact aroma compound of
the wines made with the Spanish variety Verdejo, imparting the
characteristic tropical fruit aroma nuance to the wine (Campo
et al. 2005).
Furfurylthiol (FFT, or 2-furanmethanethiol). is strong coee-•
smelling compound is formed by reaction between furfural from
the oak cask and sulydric acid formed during the fermentation
(Blanchard et al. 2001), and is able to transmit its aroma to
some types of wine. ere is not a lot of analytical data on the
occurrence of FFT because of diculties in its determination,
but it has been found at relatively high levels in aged wines from
Champagne (Tominaga et al. 2003) and in some other wines
(Tominaga and Dubourdieu 2006).
Benzylmercaptan (or benzenemethanethiol) is a compound •
with a powerful toasty aroma, and together with FFT can
impart smoky and empyreumatic nuances to some aged wines,
such as Champagne or Chardonnay sur lie (Tominaga et al.
2003a,b).
Dimethyl sulphide (DMS). is compound was identied some •
time ago in aged wines (Marais 1979) and apparently plays an
ambiguous role in wine aroma. Quite oen it is related to a defect
(sulfury odour) (Park et al. 1994, Ferreira, A. et al. 2003a), but
some other authors have demonstrated that it exerts a powerful
enhancing eect on the fruity note of some highly appreciated
red wines (Segurel et al. 2004, Escudero et al. 2007).
Methional (3-(methylthio)propanal) also plays an ambioguos •
role. In young white wines causes unpleasant odors (Escudero et
al. 2000), but in complex wines, such as some Chardonnays or
some great red wines, is a neat contributor to some appreciated
odour nuances (Ferreira, V. et al. 2005)
Diacetyl is another odourant playing a complex role on wine •
aroma. It was one of the rst identied wine aroma molecules
(Fornachon and Lloyd 1965), and it has oen been blamed as
the cause of a defect when it is present at high concentrations
(Clarke and Bakker 2004). Its sensory eect is extremely
dependent on the type of wine (Martineau et al. 1995b,
Bartowsky et al. 2002), its concentration is also time dependent
and related to the level of sulphur dioxide of in the wine (Nielsen
and Richelieu 1999). Diacetyl is responsible for the buttery
note appreciated in some Chardonnay wines (Martineau et al.
1995a, Bartowsky et al. 2002), and its role in the sweet notes of
some Port wines has also been suggested (Rogerson et al. 2001).
Several authors agree on its ambiguous character (Lonvaud-
Funel 1999, Bartowsky and Henschke 2004).
Isoamyl acetate. is is the only ester capable of imparting its •
characteristic aroma nuance to wines, sometimes too overtly.
In wines made with Tempranillo or Pinotage varieties it is a
characteristic aroma compound (Van Wyk et al. 1979, Ferreira
et al. 2000).
Rotundone, that is a sesquiterpene responsible for the spicy notes •
of Shiraz wines, as has been reported by Pollnitz et al. (2007).
All the aforementioned aromas, at lesser concentrations cannot
act as impact compounds or even as highly active aroma compounds,
but as contributors to a given aroma nuance. In this case its aroma
is not uniquely identiable, but a more generic aroma characteristic.
What is perceived, for instance, is its fruity character or its sweet
character, in association with fruity or sweet notes from other aroma
compounds in the mixture.

 5

3.2 Homogeneous aroma families
A particular case of additive (or eventually synergistic) action
is that of all of the groups of compounds which share aromatic
characteristics and share also common formation pathways ( Jarauta
et al. 2006). In this case it is possible to dene impact families of
odourants. e role of these families is less known, although the
concept is latent in the aroma groupings made by some authors
(Moreno et al. 2005) and has been the subject of research in two
recent PhD theses in our laboratory ( Jarauta 2004, Culleré 2005).
In this group dierent families can be identied.
Ethyl esters of fatty acids, responsible for fruity notes of some •
white wines (Ferreira, V. et al. 1995).
Aliphatic γ-lactones which contribute to the peachy aroma of •
some reds (Ferreira, V. et al. 2004, Jarauta 2004).
Volatile phenols such as guaiacol, eugenol, 2,6-dimethoxyphenol, •
isoeugenol and allyl-2,6-dimethoxyphenol.
Vanillas (vanillin, methyl vanillate, ethyl vanillate and •
acetovanillone).
Burnt-sugar compounds (furaneol, homofuraneol, maltol) •
(Jarauta 2004).
Fusel alcohol acetates. •
Aliphatic aldehydes with 8, 9 and 10 carbon atoms. •
Branched aldehydes 2-methylpropanal, 2-methylbutanal and •
3-methylbutanal (Culleré 2005).
Ethyl esters of branched or cyclic fatty acids (ethyl 2-, 3- and •
4-methylpentanoates and ethyl cyclohexanoate) (Campo et
al. 2006a,b) some of which have been recently identied. e
aroma of these compounds could act additively with that of
the other wine ethyl esters of branched acids (ethyl isobutyrate,
ethyl isovalerate and ethyl 3-methylbutyrate).
3.3 O avours
e rst thing that should be said is that the concept of o-avour
is a relative and sometimes slippery one, because it is, at least in part,
related to the previous experience and expectations of the consumer.
ere are many examples of this. For instance, many local producers
and ‘traditional’ consumers of Spanish wines from Rioja, became
so familiar with the presence of small amounts of ethyl phenols in
their wines, that for them the phenolic-note produced by those
compounds is something essential in the wines. e same is also
observed among producers of Beaujolais. Similarly, some producers
of wines from Sauvignon Blanc are quite happy with the earthy and
black-pepper notes introduced by methoxypyrazines. In some other
cases, however, there is a large world-wide consensus about the
negative role of some molecules, particularly if these are exogenous,
such as TCA. Our personal (and of course refutable) opinion on
this, is that all those aroma molecules that when removed from a
wine, lead to an improvement in its sensory characteristics should be
considered as the cause of defects. Clearly, eliminating ethyl phenols
would enhance the aroma and fruit character of many red wines,
and removing methoxypyrazines from some whites, will allow the
those wines to become more oral and fruity (Campo et al. 2005).
It also necessary to point out that some apparently ‘bad’ molecules
can sometimes play an interesting role on wine aroma. For instance,
DMS is a powerful enhancer of fruitiness in some red wines (Segurel
et al. 2004, Escudero et al. 2007). A second example, methional, in
young white wines can cause a clear depreciation in quality, yet can
play a very interesting role in the perception of complex – chocolate
– notes in reds (Ferreira, V. et al. 2005).
e third point that should be remarked on, is that in general, the
negative role of many aroma molecules is noted at concentrations
well below the level at which those molecules are clearly perceived in
wine. Before reaching such recognition threshold, the eect of these
molecules is to decrease on some positive sensory characteristics of
the wine, and sometimes even to unbalance the aroma of the wine.
And the nal comment that should be made about o-avours
is that sometimes the o-avours can be produced by relatively
large amounts of fermentation by-products (isoacids, acetoin,
vinylphenols, some alcohols) acting in a concerted way. is
phenomena has been recently described (Campo 2006) and
apparently could be one of the most important causes of low quality
observed in many wines. e existence of that concerted action
means that the individual compounds do not need to be present
at the concentrations at which they usually are considered a risk to
quality, which certainly challenges many of previously established
quality limits placed on these compounds.
e following list summarises those dierent compounds that
have been documented as potential wine o-avours.
a) Compounds made by micro-organisms from precursors present
in the wine or must.
e technical literature oen refers to some molecules as defects
or at least as quality depreciators without a clear scientic basis. We
are not able to trace the origin of some of these comments, but some
molecules such as biogenic amines, fusel alcohols, cis-3-hexenol
and methionol are oen cited as negative compounds (Swiegers et
al. 2005). e negative sensory role of some other molecules, such
as acetic acid, acetoin, the sulphur volatile compounds, is however
well known and will not be considered here. In addition to these
compounds, the following have been described:
Compounds responsible for mousy odour. Four dierent •
compounds have been identied: 2-acetyltetrahydropyridine
and 2-ethyltetrahydropyridine (Strauss and Heresztyn 1984),
2-acetylpyrroline (Herderich et al. 1995) and, more recently,
2-methoxy-3,5-dimethylpyrazine (Simpson et al. 2004), as
has been recently highlighted in a recent review (Snowdon
et al. 2006). ese compounds have a nasty odour which has
oen been erroneously (and still it is) assigned to acetamide.
Interestingly, those compounds are not clearly perceived via an
orthonasal response, but they are more easily perceived in the
mouth in the form of a long and unpleasant aertaste.
Horse-leather notes. is problem is basically caused by •
4-ethylphenol and 4-ethylguaiacol formed mainly by
Brettanomyces/Dekkera yeasts (Chatonnet et al. 1992, 1997,
Dias et al. 2003). is is one of the most evident problems of
many Spanish red wines.
Phenolic-pharmaceutical note. Some yeasts and bacteria have •
the ability to rst hydrolyse, and later decarboxylate, wine
cinnamic acids to form 4-vinylphenol and 4-vinylguaicol in
amounts sucient to impart this odour nuance to white wines
(Chatonnet et al. 1993, Dugelay et al. 1993).
b) Compounds formed by oxidation. Some powerful aroma
compounds can be formed upon white wine oxidation. ese
compounds are acetaldehyde, methional and phenyacetaldehyde
(Escudero et al. 2000a,b, Aznar et al. 2003, Ferreira, A. et al.
2003b,d, Ferreira et al. 2003), e latter compound is largely
responsible for the oxidative deterioration of red wines (Aznar et al.
2003). Other compounds which have also been found to be related
to sensory problems linked to wine oxidation are E-2-alkenals (E-2-
hexenal, E-2-octenal and E-2-nonenal), related with smells of paper,
cardboard or dust (Culleré 2005, Cullere et al. 2007).
c) Cork and cask related odour problems. e most
characteristic compound of the cork-related odour problems is


6

2,4,6-triclhoroanisole (TCA) (Buser et al. 1982). However, some
other molecules maybe also related to this problem, since dierent
authors have suggested the implication in the problem of molecules
such as guaiacol (Pena-Neira et al. 2000, Alvarez-Rodriguez et al.
2003), 2,4,6-tribromoanisole (TBA) (Chatonnet et al. 2004) or
2-methyoxy-3,5-dimethylpyrazine (Simpson et al. 2004). TCA,
however, seems to be the most important, because of its occurrence
and low odour threshold (Prescott et al. 2005). Another compound
causing problems, this time coming from green, unmatured wood is
E-2-nonenal, which can cause a smell of sawdust in wine (Chatonnet
and Dubourdieu 1998).
d) Age-related problems. e rst reported compound was TDN.
is compound can cause a kerosene-like o-odour in some wines
made with Riesling (Simpson 1978). is compound is formed from
wine carotenoids (Strauss et al. 1987, Winterhalter 1991). Recently,
a similar compound has been described, i.e. TBP (Cox et al. 2005).
In German wines, a dierent compound, 2-aminoacetophenone
has been reported as an o-avour caused by an untypical aging
(Rapp et al. 1993). is compound comes from indole-acetic acid
(Hoenicke et al. 2002).
e) Endogenous compounds. Alkyl-2-methoxypyrazines were rst
identied in extracts from Cabernet Sauvignon wines (Bayonove et
al. 1975), and their role in the vegetative, particularly green pepper,
notes of some of these wines was also demonstrated (Allen et al.
1991, Lacey et al. 1991, Noble et al. 1995, Deboubee et al. 2000).
ese compounds impart to the wine an earthy note that cause a
loss of quality. Isopropyl-2-methoxypyrazine can also be produced
by a beetle (Pickering et al. 2004, 2006).
ese lists give us a nearly complete picture about the players,
however, the following and key issue is the way in which these
compounds, i.e. the players interact to form dierent odour notes,
that is to say, the rules of the game.
4. Some examples about wine aroma formation
e key message coming out of this paper about the aroma of wine
is how the basic aroma buer produced by ethanol and the other
major fermentation volatiles, is broken. e way in which this
happens (through more or less impact compounds, or families,
or through large numbers of subtle compounds) determines the
complexity and aroma characteristics of wines.
4.1 Wines whose aromatic perception is driven mainly by a single
odour chemical
In general, these wines are simple and have a clear, simple and
distinctive aroma nuance caused by a chemical acting as a genuine
impact aroma compound. Its degree of complexity, of course, will
depend on the level of such a chemical, and on the presence of other
aroma compounds which can modify or add some more aroma
nuances.
e most typical and well known example of these kinds of
wines is Muscat. Some other examples are some rosé wines whose
aroma characteristics are due to the presence of high levels of
3-mercaptohexan-1-ol (Murat et al. 2001, Ferreira et al. 2002),
Sauvignon Blanc wines, whose aroma characteristics are due
mainly to 4-mercapto-4-methylpentan-2-one (Darriet et al. 1995)
or wines from Verdejo, whose aroma characteristics are due to
3-mercaptohexyl acetate (Campo et al. 2005). Other particular
examples of this type of wine are some Cabernet Sauvignon or
Cabernet Franc red wines made in some parts of New Zealand
or France and showing a very intense cassis aroma, nearly entirely
due to the presence of high levels of 3-mercaptohexyl acetate. Of
course if the wines are rich in some other compounds such as ethyl
esters of fatty acids, linalool or isoamyl acetate, the nal perception
will be more complex, and surely more appreciated. In the case of
Sauvignon Blanc wines, some producers nd value in the presence
of methoxypyrazines, which no doubt, adds some complexity (even
if this is controversial). Another case of simple wines that, nowadays,
are not very appreciated is that of white wines with large amounts of
isoamyl acetate, displaying a strong banana aroma. Finally, there are
some white wines with a simple fruity aroma which is mainly due to
the presence of high levels of ethyl esters of fatty acids.
4.2 Wines not having any genuine impact aroma compound
In this category we will nd some very interesting wines showing
complex aromas which cannot be attributed to a single chemical
identity. In the case of whites made with Macabeo or Chardonnay,
for instance, their aroma nuances are related to the simultaneous
presence of many relevant aroma families present at quite modest
concentrations. For instance, the owery notes of some of them can
be related to the simultaneous presence of small amounts of linalool,
γ-lactones, vanillins, ethyl cinnamates and nor-isoprenoids. eir
fruity notes are the result of a complex interaction between those
compounds and ethyl esters of fatty acids, fusel alcohol acetates
and small amounts of some cysteine-related mercaptans, such as
4-mercapto-4-methylpentan-2-one or 3-mercaptohexyl acetate and
eventually also to some aliphatic aldehydes (Escudero et al. 2004,
Loscos et al. 2007). In these cases, obviously, the quality vectors of
wine are extremely complex and multivariate.
4.3 Complex wines containing several potential impact compounds
Typical examples of wines in this category are some Chardonnays
fermented in barrel or aged sur lies. In this case, the levels of some
fermentation compounds are lower, and several powerful odourants
appear. ese are whiskylactones, of course, but also diacetyl,
methional and furfurylthiol. e aroma is still complex, since it
retains a large part of the compounds previously cited, but now
the typical woody notes, together with the creamy-buttery nuance
given by diacetyl and eventually a cauliower undertone given by
methional and a toasty-coee like note given by furfurylthiol can
be easily detected.
Other examples of these types of wines are Sherry-like or Sauterne-
like wines. In Sherry, acetaldehyde, diacetyl and several isoaldehydes
(isobutyraldehyde, isovaleraldehyde, 2-methylbutyraldehyde) act as
a family of impact compounds (Cullere et al. 2007), but they also
contain sotolon at high concentrations, which gives them their
characteristic nutty avour. In the case of Sauternes, there is large
variability between producers, but wines contain relatively high
levels of 4-mercapto-4-methylpentan-2-one, 3-mercaptohexan-1-ol,
phenylacetaldehyde and sotolon (Campo et al., in preparation).
4.4 Most complex wines. e case of big reds
Red wines are, by nature, much more complex since, among many
other factors, they contain quite large amounts of volatile phenols
which exert a suppression eect on fruity notes (Atanasova et al.
2004). is phenomenon is still more intense when the wines have
been aged in oak casks, increasing the levels of volatile phenols and
adding whiskylactones. In this chemical environment the perception
of the dierent notes, particularly fruity notes, is extremely
complex. In addition, great red wines do not have explicit or specic
odour nuances, but a large palette of many subtle odours. It is not
surprising, therefore, that in red wines, leaving aside whiskylactones,
most oen we do not nd genuine impact compounds, but relatively
large groups of compounds which contribute to the dierent

 7

odour nuances. Up to this date we have identied several major
contributors to the fruity notes of red wines:
e concerted action of ethyl esters, including here several •
recently discovered branched ethyl esters, with nor-isoprenoids
(β-damascenone and β-ionone) and with the enhancing eect
of DMS, can give to the wine berry fruit notes (Escudero et al.
2007).
e concerted action of ve γ-lactones (γ-octa, nona, deca, •
undeca and dodecalactones) that can be responsible for the
peach notes of some reds, particularly from certain areas of
Spain and Portugal (Jarauta et al. 2006).
e concerted action of furaneol, homofuraneol, maltol, •
sotolon, nor-isoprenoids and methional that can be responsible
for some cherry and chocolate notes of some reds (Ferreira et
al. 2005).
Conclusion
e complexity of wine aroma is in accordance with its chemical
complexity. As happens in complex perfumes, and far from the
articially avoured products, wine aroma is the result of complex
interactions between many odour chemicals. Only in some particular
and simple cases it is possible to nd genuine impact compounds
able to transmit to the product their primary sensory descriptors. In
the most complex and most valuable products, however, the sensory
notes are created by the concerted action of many molecules, many
of which, surprisingly, are at concentrations near threshold. As the
most important aroma compounds are known and as today there are
analytical techniques available for their determination, it is a matter
of time to achieve the go on unscrambling and understanding of the
dierent aroma nuances of the most valuable products, and dening
their vectors of quality.
Acknowledgements
is work has been supported by the Spanish MYCYT, projects
AGL2004 06060/ALI and AGL2007 65139/ALI. E.C. got a grant
from the Spanish FPI program. All the sta of the Laboratory for
Flavour Analysis and Enology have participated in this project.
References
Alvarez-Rodriguez, M.L; Belloch, C.; Villa, M.; Uruburu, F.; Larriba, G.;
Coque, J.J.R. (2003) Degradation of vanillic acid and production of
guaiacol by microorganisms isolated from cork samples. Fems Microbiol.
Lett. 220: 49–55.
Allen, M.S.; Lacey, M.J.; Harris, R.L.N.; Brown, W.V. (1991) Contribution
of methoxypyrazines to Sauvignon Blanc wine aroma. Am. J. Enol. Vitic.
42: 109–112.
Allen, M.S.; Lacey, M.J.; Boyd, S. (1994) Determination of methoxypyrazines
in red wines by stable isotope dilution gas chromatography-mass
spectrometry. J. Agric. Food Chem. 42: 1734–1738.
Arrhenius, S.P.; McCloskey, L.P.; Sylvan, M. (1996) Chemical markers for
aroma of Vitis vinifera var Chardonnay regional wines. J. Agric. Food Chem.
44: 1085–1090.
Atanasova, B.; omas-Danguin, T.; Langlois, D.; Nicklaus, S.; Etievant, P.
(2004) Perceptual interactions between fruity and woody notes of wine.
Flavour Fragrance J. 19: 476–482.
Aznar, M.; Lopez, R.; Cacho, J.; Ferreira, V. (2003) Prediction of aged red
wine aroma properties from aroma chemical composition. Partial least
squares regression models. J. Agric. Food Chem. 51: 2700–2707.
Bartowsky, E.J.; Francis, I.L.; Bellon, J.R.; Henschke, P.A. (2002) Is buttery
aroma perception in wines predictable from the diacetyl concentration?
Aust. J. Grape Wine Res. 8: 180–185.
Bartowsky, E.J.; Henschke, P.A. (2004) e ‘buttery’ attribute of wine-
diacetyl-desirability, spoilage and beyond. Int. J. Food Microbiol. 96:
235–252.
Bayonove, C.; Codonnier, R.; Dubois, P. (1975) Etude d’une fraction
caractéristique de l’arôme du raisin de la variété Cabernet-Sauvignon; mise
en évidence de la 2--méthoxy-3-isobutylpyrazine. C. R. Acad. Sci. Paris
(SerieD) 281: 75–78.
Blanchard, L.; Tominaga, T.; Dubourdieu, D. (2001) Formation of furfurylthiol
exhibiting a strong coee aroma during oak barrel fermentation from
furfural released by toasted staves. J. Agric. Food Chem. 49: 4833–4835.
Boidron, J.N.; Chatonnet, P.; Pons, M. (1988) Inuence du bois sur certaines
substances odorantes des vins. Conn. Vigne Vin 22: 275–294.
Bouchilloux, P.; Darriet, P.; Henry, R .; Lavigne-Cruege, V.; Dubourdieu, D.
(1998). Identication of volatile and powerful odorous thiols in Bordeaux
red wine varieties. J. Agric. Food Chem. 46: 3095–3099.
Buser, H.R .; Zanier, C.; Tanner, H. (1982) Identication of
2,4,6-trichloroanisole as a potent compound causing cork taint in wine.
J. Agric. Food Chem. 30: 359–362.
Camara, J.S.; Marques, J.C.; Alves, M.A.; Ferreira, A.C.S. (2004) 3-hydroxy-
4,5-dimethyl-2(5H)-furanone levels in fortied Madeira wines:
Relationship to sugar content. J. Agric. Food Chem. 52: 6765–6769.
Campo, E.; (2006) La base química del aroma de vinos blancos de variedades
españolas y de diversos vinos especiales. University of Zaragoza. Zaragoza,
PhD esis.
Campo, E.; Ferreira, V.; Escudero, A.; Cacho, J. (2005) Prediction of the wine
sensory properties related to grape variety from dynamic-headspace gas
chromatography-olfactometry data. J. Agric. Food Chem. 53: 5682–5690.
Campo, E.; Ferreira, V.; Lopez, R .; Escudero, A.; Cacho, J. (2006a).
Identication of three novel compounds in wine by means of a laboratory-
constructed multidimensional gas chromatographic system. J. Chromatogr.
A 1122: 202–208.
Campo, E.; Cacho, J.; Ferreira, V. (2006b) Multidimensional chromatographic
approach applied to the identication of novel aroma compounds in wine.
Identication of ethyl cyclohexanoate, ethyl 2-hydroxy-3-methylbutyrate
and ethyl 2-hydroxy-4-methylpentanoate. J. Chromatogr. A 1137:
223–230.
Campo, E.; Cacho, J.; Ferreira, V. (2007) Solid phase extraction,
multidimensional gas chromatography mass spectrometry determination of
four novel aroma powerful ethyl esters - Assessment of their occurrence and
importance in wine and other alcoholic beverages. J. Chromatogr. A 1140:
180–188.
Clarke, R.J.; Bakker, J. (2004) Wine avour chemistry (Oxford, UK: Blackwell
Publishing).
Cordonnier, R.; Bayonove, C.L. (1974) Mise en evidence dans la baie de
raisin, var. Muscat d’Alexandrie, de monoterpenes lies revelables par
une ou plusieurs enzymes du fruit. C.R. Acad. Sci. Paris (Serie D) 278:
3387–3390.
Cox, A.; Capone, D.L.; Elsey, G.M.; Perkins, M.V.; Seon, M.A. (2005)
Quantitative analysis, occurrence, and stability of (E)-1-(2,3,6-
trimethylphenyl)buta-1,3-diene in wine. J. Agric. Food Chem. 53:
3584–3591.
Culleré, L. (2005) Contribución al estudio de los componentes carbonílicos
del vino. Nuevos métodos de análisis y caracterización de su papel sensorial,
Universidad de Zaragoza, Zaragoza. PhD esis.
Cullere, L.; Escudero, A.; Cacho, J.; Ferreira, V. (2004) Gas chromatography-
olfactometry and chemical quantitative study of the aroma of six premium
quality Spanish aged red wines. J. Agric. Food Chem. 52: 1653–1660.
Culleré, L.; Cacho, J.; Ferreira, V. (2006) Validation of an analytical method
for the solid phase extraction, in cartridge derivatization and subsequent
gas chromatographic-ion trap tandem mass spectrometric determination of
1-octen-3-one in wines at ng L-1 level. Anal. Chim. Acta 563: 51–57.
Cullere, L.; Cacho, J.; Ferreira, V. (2007) An assessment of the role played by
some oxidation-related aldehydes in wine aroma. J. Agric. Food Chem. 55:
876–881.
Cutzach, I.; Chatonnet, P.; Henry, R.; Pons, M.; Dubourdieu, D. (1998) Etude
sur l’arôme des vins doux naturels non muscatés. 2e partie: Dosages de
certains composés volatils intervenant dans l’arôme des vins doux naturels
au cours de leur élevage et de leur vieillissement. J. Int. Sci. Vigne Vin 32:
211–221.
Cutzach, I.; Chatonnet, P.; Dubourdieu, D. (1999) Study of the formation
mechanisms of some volatile compounds during the aging of sweet fortied
wines. J. Agric. Food Chem. 47: 2837–2846.
Chatonnet, P.; Dubourdieu, D. (1998) Identication of substances responsible
for the ‘sawdust’ aroma in oak wood. J. Sci. Food Agric. 76: 179–188.
Chatonnet, P.; Dubourdieu, D.; Boidron, J.N.; Pons, M. (1992) e origin of
ethylphenols in wines. J. Sci. Food Agric. 60: 165–178.
Chatonnet, P.; Dubourdieu, D.; Boidron, J.N.; Lavigne, V. (1993) Synthesis
of volatile phenols by Saccharomyces cerevisiae in wines. J. Sci. Food Agric.
62: 191–202.
Chatonnet, P.; Viala, C.; Dubourdieu, D. (1997) Inuence of polyphenolic
components of red wines on the microbial synthesis of volatile phenols.
Am. J. Enol. Vitic. 48: 443–448.


8

Chatonnet, P.; Bonnet, S.; Boutou, S.; Labadie, M.D. (2004) Identication
and responsibility of 2,4,6-tribromoanisole in musty, corked odours in
wine. J. Agric. Food Chem. 52: 1255–1262.
Darriet, P.; Lavigne, V.; Boidron, J.; Dubourdieu, D. (1991) Caracterisation de
l’arome varietal des vins de Sauvignon par couplage chromatographique en
phase gazeuse-odometrie. J. Int. Sci. Vigne Vin 25: 167–174.
Darriet, P.; Tominaga, T.; Demole, E.; Dubourdieu, D. (1993) Mise en
évidence dans le raisin de Vitis vinifera var. Sauvignon d’un précurseur de
la 4-mercapto-4-méthylpentan-2-one. C.R. Acad. Sci. Paris (Serie D) 316:
1332–1335.
Darriet, P.; Tominaga, T.; Lavigne, V.; Boidron, J.N.; Dubourdieu, D. (1995)
Identication of a powerful aromatic component of Vitis vinifera L. var.
Sauvignon wines: 4-mercapto-4-methylpentan-2-one. Flavour Fragrance J.
10: 385–392.
Deboubee, D.R.; Van Leeuwen, C.; Dubourdieu, D. (2000) Organoleptic
impact of 2-methoxy-3-isobutylpyrazine on red Bordeaux and Loire wines.
Eect of environmental conditions on concentrations in grapes during
ripening. J. Agric. Food Chem. 48: 4830–4834.
Dias, L.; Dias, S.; Sancho, T.; Stender, H.; Querol, A.; Malfeito-Ferreira, M.;
Loureiro, V. (2003) Identication of yeasts isolated from wine-related
environments and capable of producing 4-ethylphenol. Food Microbiol.
20: 567–574.
Dugelay, I.; Gunata, Z.; Sapis, J.C.; Baumes, R.; Bayonove, C. (1993) Role of
cinnamoyl esterase-activities from enzyme preparations on the formation of
volatile phenols during winemaking. J. Agric. Food Chem. 41: 209–2096.
Escudero, A.; Cacho, J.; Ferreira, V. (2000a) Isolation and identication of
odorants generated in wine during its oxidation: a gas chromatography-
olfactometric study. Eur. Food Res. Technol. 211: 105–110.
Escudero, A.; Hernandez-Orte, P.; Cacho, J.; Ferreira, V. (2000b) Clues about
the role of methional as character impact odorant of some oxidized wines. J.
Agric. Food Chem. 48: 4268–4272.
Escudero, A.; Gogorza, B.; Melús, M.A.; Ortín, N.; Cacho, J.; Ferreira, V.
(2004) Characterization fo the aroma of a wine from Maccabeo. Key role
played by compounds with low odor activity value. J. Agric. Food Chem.
52: 3516–3524.
Escudero, A.; Campo, E.; Fariña, L.; Cacho, J.; Ferreira, V. (2007) Analytical
characterization of the aroma of ve premium red wines. Insights into the
role of odor families and the concept of fruitiness of wines. J. Agric. Food
Chem. 55: 4501–4510.
Etievant, P.X. (1991) Wine. In: Volatile compounds in foods and beverages,
Maarse, H. (ed.) New York, N.Y.: Marcel Dekker: 483–546.
Ferreira, A.C.S.; Rodrigues, P.; Hogg, T.; De Pinho, P.G. (2003a) Inuence
of some technological parameters on the formation of dimethyl sulde,
2-mercaptoethanol, methionol, and dimethyl sulfone in port wines. J.
Agric. Food Chem. 51: 727–732.
Ferreira, A.C.S.; Hogg , T.; de Pinho, P.G. (2003b) Identication of key
odorants related to the typical aroma of oxidation-spoiled white wines. J.
Agric. Food Chem. 51: 1377–1381.
Ferreira, A.C.S.; Barbe, J.C.; Bertrand, A. (2003c) 3-hydroxy-4,5-dimethyl-
2(5H)-furanone: A key odorant of the typical aroma of oxidative aged Port
wine. J. Agric. Food Chem. 51: 4356–4363.
Ferreira, A.C.S.; Oliveira, C.; Hogg, T.; de Pinho, P.G. (2003d) Relationship
between potentiometric measurements, sensorial analysis, and some
substances responsible for aroma degradation of white wines. J. Agric. Food
Chem. 51: 4668–4672.
Ferreira, V.; Fernandez, P.; Pena, C.; Escudero, A.; Cacho, J.F. (1995)
Investigation on the role played by fermentation esters in the aroma of
young Spanish wines by Multivariate-Analysis. J. Sci. Food Agric. 67:
381–392.
Ferreira, V.; Lopez, R.; Escudero, A.; Cacho, J.F. (1998) e aroma of
Grenache red wine: hierarchy and nature of its main odorants. J. Sci. Food
Agric. 77: 259–267.
Ferreira, V.; Lopez, R .; Cacho, J.F. (2000) Quantitative determination of the
odorants of young red wines from dierent grape varieties. J. Sci. Food
Agric. 80: 1659–1667.
Ferreira, V.; Ortín, N.; Escudero, A.; López, R.; Cacho, J. (2002) Chemical
characterization of the aroma of grenache rosé wines. Aroma extract
dilution analysis, quantitative determination and sensory reconstitution
studies. J. Agric. Food Chem. 50: 4048–4054.
Ferreira, V.; Jarauta, I.; López, R.; Cacho, J. (2003) Quantitative determination
of sotolon, maltol and free furaneol in wine by solid-phase extraction and
gas chromatography-ion-trap mass sepectrometry. J. Chromatogr. A 1010:
95–103.
Ferreira, V.; Jarauta, I.; Ortega, C.; Cacho, J. (2004) A simple strategy for
the optimization of Solid-Phase-Extraction procedures through the use of
solid-liquid distribution coecients. Application to the determination of
aliphatic lactones in wine. J. Chromatogr. A 1025: 147–156.
Ferreira, V.; Torres, M.; Escudero, A.; Ortín, N.; Cacho, J. (2005) Aroma
composition and aromatic structure of red wines made with Merlot. In:
State of the art in avour chemistry and biology. Proceedings from the 7th
Wartburg Symposium, Hofman, P.S.T. (ed.) Deutsche Forsch. Lebensm.
Garching: 292–299.
Ferreira, V.; Cullere, L.; Loscos, N.; Cacho, J. (2006) Critical aspects of
the determination of pentauorobenzyl derivatives of aldehydes by gas
chromatography with electron-capture or mass spectrometric detection -
Validation of an optimized strategy for the determination of oxygen-related
odor-active aldehydes in wine. J. Chromatogr. A 1122: 255–265.
Fornachon,.J.C.M; Lloyd, B. (1965) Bacterial production of diacetyl and
acetoin in wine. J. Sci. Food Agric. 16: 710–716.
Fretz, C.B.; Luisier, J.L.; Tominaga, T.; Amado, R. (2005) 3-mercaptohexanol:
An aroma impact compound of Petite Arvine wine. Am. J. Enol. Vitic. 56:
407–410.
Gomez-Miguez, M.J.; Cacho, J.F.; Ferreira, V.; Vicario, I.M.; Heredia, F.J.
(2007). Volatile components of Zalema white wines. Food Chem. 100:
1464–1473.
Guth, H. (1997a) Identication of character impact odorants of dierent
white wine varieties. J. Agric. Food Chem. 45: 3022–3026.
Guth, H. (1997b) Quantitation and sensory studies of character impact
odorants of dierent white wine varieties. J. Agric. Food Chem. 45:
3027–3032.
Herderich, M.; Costello, P.J.; Grbin, P.R.; Henschke, P.A. (1995) Occurrence
of 2-acetyl-1-pyrroline in mousy wines. Natural Product Letters 7:
129–132.
Hoenicke, K.; Borchert, O.; Gruning, K.; Simat, T.J. (2002) ‘Untypical
aging o-avor’ in wine: Synthesis of potential degradation compounds of
indole-3-acetic acid and kynurenine and their evaluation as precursors of
2-aminoacetophenone. J. Agric. Food Chem. 50: 4303–4309.
Ibarz, M.J.; Ferreira, V.; Hernandez-Orte, P.; Loscos, N.; Cacho, J. (2006)
Optimization and evaluation of a procedure for the gas chromatographic-
mass spectrometric analysis of the aromas generated by fast acid hydrolysis of
avor precursors extracted from grapes. J. Chromatogr. A 1116: 217–229.
Jarauta, I. (2004) Estudio analítico de fenómenos concurrentes en la
generación del aroma durante la crianza del vino en barricas de roble con
diferentes grados de uso. Nuevos métodos de análisis de importantes aromas
y caracterización de su papel sensorial, University of Zaragoza, Zaragoza.
PhD esis.
Jarauta, I.; Ferreira, V.; Cacho, J. (2006) Synergic, additive and antagonistic
eects between odorants with similar odour properties. In: Flavour
science: Recent advances and trends, Bredie, W.L.P.; Petersen, M.A. (eds)
Amsterdam: Elsevier: 2005–2208.
Kotseridis, Y.; Baumes, R. (2000) Identication of impact odorants in
Bordeaux red grape juice, in the commercial yeast used for its fermentation,
and in the produced wine. J. Agric. Food Chem. 48: 400–406.
Lacey, M.J.; Allen, M.S.; Harris, R.L.N.; Brown, W.V. (1991) Methoxypyrazines
in Sauvignon Blanc grapes and wines. Am. J. Enol. Vitic. 42: 103–108.
Lee, S.J.; Noble, A.C. (2003) Characterization of odor-active compounds
in Californian Chardonnay wines using GC-olfactometry and GC-mass
spectrometry. J. Agric. Food Chem. 51: 8036–8044.
Lonvaud-Funel, A. (1999) Lactic acid bacteria in the quality improvement
and depreciation of wine. Antonie Van Leeuwenhoek Int. J. Gen. Molec.
Microbiol. 76: 317–331.
López, R.; Ferreira, V.; Hernández, P.; Cacho, J.F. (1999) Identication of
impact odorants of young red wines made with Merlot, Cabernet Sauvignon
and Grenache grape varieties: a comparative study. J. Sci. Food Agric. 79:
1461–1467.
Lopez, R .; Ortin, N.; Perez-Trujillo, J.P.; Cacho, J.; Ferreira, V. (2003) Impact
odorants of dierent young white wines from the Canary Islands. J. Agric.
Food Chem. 51: 3419–3425.
Loscos, N.; Hernandez-Orte, P.; Cacho, J.; Ferreira, V. (2007) Release and
formation of varietal aroma compounds during alcoholic fermentation
from nonoral grape odorless avor precursors fractions. J. Agric. Food
Chem. (in press).
Maarse, H.; Vischer, C.A. (1989) Volatile compounds in food. Alcoholic
beverages. Qualitative and quantitative data (A.J. Zeist, e Netherlands:
TNO-CIVO, Food Analysis Institute).
Marais, J. (1979) Eect of storage time and temperature on the formation of
dimethyl sulde and on white wine quality. Vitis 18: 254–260.
Martin, B.; Etievant, P.; Henry, R.N. (1990) e chemistry of sotolon: a key
parameter for the study of a key component of or sherry wines. In: Flavour
science and technology, Bessière, Y.; omas, A.F. (eds) Chicherster; U.K.:
Wiley: 53–56.

 9

Martin, B.; Etievant, P.X.; Quere, J.; Schlich, P. (1992). More clues about
sensory impact of sotolon in some or sherry wines. J. Agric. Food Chem.
40: 475–478.
Martineau, B.; Henick-Kling, T.; Acree, T. (1995a) Reassessment of the
inuence of malolactic fermentation on the concentration of diacetyl in
wines. Am. J. Enol. Vitic. 46: 385–388.
Martineau, B.; Acree, T.E.; Henick-Kling, T. (1995b) Eect of wine type
on the detection threshold for diacetyl. Food Research International 28:
139–143.
Masuda, M.; Okawa, E.; Nishimura, K.; Yunome, H. (1984) Identication
of 4,5-dimethyl-3-hydroxy-2(5H)-furanone (Sotolon) and ethyl
9-hydroxynonanoate in botrytised wine and evaluation of the roles of
compounds characteristic of it. Agric. Biol. Chem. 48: 2707–2710.
Mateo-Vivaracho, L.; Cacho, J.; Ferreira, V. (2007) Quantitative
determination of wine polyfunctional mercaptans at nanogram per liter
level by gas chromatography-negative ion mass spectrometric analysis of
their pentauorobenzyl derivatives. J. Chromatogr. A 1146: 242–250.
Moreno, J.A.; Zea, L.; Moyano, L.; Medina, M. (2005) Aroma compounds as
markers of the changes in sherry wines subjected to biological ageing. Food
Control 16: 333–338.
Murat, M.; Tominaga, T.; Dubourdieu, D. (2001) Mise en évidence de
composés clefs dans l’arôme des vins rosés et clairets de Bordeaux. J. Int. Sci.
Vigne Vin 35: 99–105.
Nielsen, J.C.; Richelieu, M. (1999) Control of avor development in wine
during and aer malolactic fermentation by Oenococcus oeni. Appl.
Environ. Microbiol. 65: 740–745.
Noble, A.C.; Elliott-Fisk, D.L.; Allen, M.S. (1995) Vegetative avor and
methoypyrazines in Cabernet-Sauvignon. ACS Symp. Ser. 596: 226–234.
Palomo, E.S.; Perez-Coello, M.S.; Diaz-Maroto, M.C.; Vinas, M.A.G.;
Cabezudo, M.D. (2006) Contribution of free and glycosidically-bound
volatile compounds to the aroma of muscat ‘a petit grains’ wines and eect
of skin contact. Food Chem. 95: 279–289.
Park, S.K.; Boulton, R.B.; Bartra, E.; Noble, A.C. (1994) Incidence of volatile
sulfur-compounds in California wines – a preliminary survey. Am. J. Enol.
Vitic. 45: 341–344.
Pena-Neira, A.; de Simon, B.F.; Garcia-Vallejo, M.C.; Hernandez, T.; Cadahia,
E.; Suarez, J.A. (2000) Presence of cork-taint responsible compounds in
wines and their cork stoppers. Eur. Food Res. Technol. 211: 257–261.
Pet’ka, J.; Cacho, J.; Ferreira, V. (2003) Comparison of avour perception
routes in a synthetic wine model and with GC-olfactometric data. In
Oenologie2003, 7th International Symposium of Oenology ; Lonvaud-
Funel, A. (ed.) Lavoisier (París): Bourdeaux: 563–565.
Petka, J.; Ferreira, V.; Gonzalez-Vinas, M.A.; Cacho, J. (2006) Sensory and
chemical characterization of the aroma of a white wine made with Devin
grapes. J. Agric. Food Chem. 54: 909–915.
Pickering, G.; Lin, J.; Riesen, R .; Reynolds, A.; Brindle, I.; Soleas, G. (2004)
Inuence of Harmonia axyridis on the sensory properties of white and red
wine. Am. J. Enol. Vitic. 55: 153–159.
Pickering, G.; Lin, J.; Reynolds, A.; Soleas, G.; Riesen, R. (2006) e
evaluation of remedial treatments for wine aected by Harmonia axyridis.
Int. J. Food Sci. Technol. 41: 77–86.
Pollnitz, A.P.; Capone, D.L.; Seon, M.A. (2007) Spicy aroma in Shiraz. In
Blair, R.J.; Williams, P.J.; Pretorius, I.S. (eds) Proceedings of the thirteenth
Australian wine industry technical conference; 29 July–2 August 2007;
Adelaide; SA : Australian Wine Industry Technical Conference Inc.,
Adelaide, SA (in press).
Pollnitz, A.P.; Pardon, K.H.; Seon, M.A. (2000) 4-Ethylphenol,
4-ethylguaiacol and oak lactones in Australian red wines. Aust. Grapegrower
Winemaker 438: 47–50.
Prescott, J.; Norris, L.; Kunst, M.; Kim, S. (2005) Estimating a ‘consumer
rejection threshold’ for cork taint in white wine. Food Quality Pref. 16:
345–349.
Rapp, A.; Versini, G.; Ullemeyer, H. (1993) 2-Aminoacetophenone – causal
component of untypical aging avor (naphthalene note, hybrid note) of
wine. Vitis 32: 61–62.
Ribéreau-Gayon, P.; Boidron, J.N.; Terrier, A. (1975) Aroma of muscat grape
varieties. J. Agric. Food Chem. 23: 1042–1047.
Rogerson, F.S.S.; Castro, H.; Fortunato, N.; Azevedo, Z.; Macedo, A.; De
Freitas, V.A.P. (2001) Chemicals with sweet aroma descriptors found in
Portuguese wines from the Douro region: 2,6,6-Trimethylcyclohex-2-ene-
1,4-dione and diacetyl. J. Agric. Food Chem. 49: 263–269.
Schneider, R .; Kotseridis, Y.; Ray, J.L.; Augier, C.; Baumes, R. (2003)
Quantitative determination of sulfur-containing wine odorants at sub
parts per billion levels. 2. Development and application of a stable isotope
dilution assay. J. Agric. Food Chem. 51: 3243–3248.
Segurel, M.A.; Razungles, A.J.; Riou, C.; Salles, M.; Baumes, R.L. (2004)
Contribution of dimethyl sulde to the aroma of Syrah and Grenache Noir
wines and estimation of its potential in grapes of these varieties. J. Agric.
Food Chem. 52: 7084–7093.
Simpson, R.F. (1978) 1,1,6-Trimethyl-1,2-dihydronaphthalene – important
contributor to bottle aged bouquet of wine. Chem. Ind.: 37–37.
Simpson, R.F.; Capone, D.L.; Seon, M.A. (2004) Isolation and identication
of 2-methoxy-3,5-dimethylpyrazine, a potent musty compound from wine
corks. J. Agric. Food Chem. 52: 5425–5430.
Snowdon, E.M.; Bowyer, M.C.; Grbin, P.R.; Bowyer, P.K. (2006) Mousy o-
avor: A review. J. Agric. Food Chem. 54: 6465–6474.
Strauss, C.R.; Heresztyn, T. (1984) 2-Acetyltetrahydropyridines – a cause of
the mousy taint in wine. Chem. Ind.: 109–110.
Strauss, C.R.; Wilson, B.; Anderson, R.; Williams, P.J. (1987) Development
of precursors of C-13 nor-isoprenoid avorants in Riesling grapes. Am. J.
Enol. Vitic. 38: 23–27.
Swiegers, J.H.; Bartowsky, E.J.; Henschke, P.A.; Pretorius, I.S. (2005) Yeast
and bacterial modulation of wine aroma and avour. Aust. J. Grape Wine
Res. 11: 139–173.
Tominaga, T.; Dubourdieu, D. (2006) A novel method for quantication of
2-methyl-3-furanthiol and 2-furanmethanethiol in wines made from Vitis
vinifera grape varieties. J. Agric. Food Chem. 54: 29–33.
Tominaga, T.; Darriet, P.; Dubourdieu, D. (1996) Identication del’acétate
de 3-mercaptohexanol, composé a forte odeur de buis, intervenant dans
l’arôme des vins de Sauvignon. Vitis 35: 207–210.
Tominaga, T.; Murat, M.L.; Dubourdieu, D. (1998) Development of a
method for analyzing the volatile thiols involved in the characteristic aroma
of wines made from Vitis vinifera L. cv Sauvignon Blanc. J. Agric. Food
Chem. 46: 1044–1048.
Tominaga, T.; Baltenweck Guyot, R.; Des Gachons, C.P.; Dubourdieu, D.
(2000) Contribution of volatile thiols to the aromas of white wines made
from several Vitis vinifera grape varieties. Am. J. Enol. Vitic. 51: 178–181.
Tominaga, T.; Guimbertau, G.; Dubourdieu, D. (2003a) Role of certain
volatile thiols in the bouquet of aged Champagne wines. J. Agric. Food
Chem. 51: 1016–1020.
Tominaga, T.; Guimbertau, G.; Dubourdieu, D. (2003b) Contribution of
benzenemethanethiol to smoky aroma of certain Vitis vinifera L. wines. J.
Agric. Food Chem. 51: 1373–1376.
Tsachaki, M.; Linforth, R .S.T.; Taylor, A.J. (2005) Dynamic headspace
analysis of the release of volatile organic compounds from ethanolic systems
by direct APCI-MS. J. Agric. Food Chem. 53: 8328–8333.
Van Wyk, C.J.; Augustyn, O.P.H.; De Wet, P.; Joubert, W.A. (1979) Isoamyl
acetate, a key fermentation volatile of wines of Vitis vinifera cv. Pinotage.
Am. J. Enol. Vitic. 30: 167–173.
Versini, G.; Orriols, I.; Dallaserra, A. (1994) Aroma components of Galician
Albarino, Loureira and Godello wines. Vitis 33: 165–170.
Vilanova, M.; Sieiro, C. (2006) Determination of free and bound terpene
compounds in Albarino wine. J. Food Comp. Anal. 19: 694–697.
Winterhalter, P. (1991) 1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN)
formation in wine .1. Studies on the hydrolysis of 2,6,10,10-tetramethyl-
1-oxaspiro 4.5 dec-6-ene-2,8-diol rationalizing the origin of TDN and
related C-13 norisoprenoids in Riesling wine. J. Agric. Food Chem. 39:
1825–1829.