Food Quality and Preference 18 (2007) 901–908
www.elsevier.com/locate/foodqual
Impact of ethanol on the perception of wine odorant mixtures
Elodie Le Berre a,b, Boriana Atanasova a,c, Dominique Langlois a,
Patrick Etiévant a, Thierry Thomas-Danguin a,*
a
Unité Mixte de Recherches FLAVIC, INRA, ENESAD, Université de Bourgogne, 17 rue Sully, BP 86510, 21065 Dijon Cedex, France
b
Department of Psychology, James Cook University, PO Box 6811 Cairns, Qld 4870, Australia
c
EA3248, Psychobiologie des émotions, UFR Sciences et Techniques, Parc Grandmont, 37200 Tours, France
Received 9 November 2006; received in revised form 15 February 2007; accepted 16 February 2007
Available online 13 March 2007
Abstract
Several studies have focused on perceptual interactions in binary odor mixtures, but few on more complex mixtures. The aroma of
wine is an example of a complex odor mixture. Our aim was to assess the impact of ethanol on the perception of mixtures of Woody
(whiskey lactone) and Fruity (isoamyl acetate) odorants commonly found, physico-chemically and perceptually, in wine. Physico-chemically, reduced whiskey lactone volatility was observed in hydro-alcoholic solutions. Perceptually, a synergy effect by the Woody on the
Fruity odor was observed in aqueous solutions, which disappeared with the addition of ethanol. Conversely, the Woody odor was
masked in both aqueous and dilute alcohol solutions. In addition, mixed Woody and Fruity odors were found to mask the so-called
Alcohol odor. These results underline the importance of perceptual interactions in the perception of wine bouquet.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Wine; Odor; Mixture; Ethanol; Perceptual interactions
1. Introduction
The emergence of new consumption trends, the constant
drop in regular wine consumption and the development of
a worldwide structural surplus are known to have faced the
wine industry with a wide range of problems (Descout
et al., 2003). Moreover, the harmful effects of alcohol on
health and behavior have led several countries to regulate
the consumption of alcohol, with age limits required for
the purchase of alcohol or maximum permitted alcohol
blood levels for driving. Another harmful effect of alcohol,
mediated by lactating mothers, is on breastfed infants (Little, Northstone, Golding, & Alspac, 2002; Mennella &
Beauchamp, 1991).
All these consequences of alcohol consumption have led
researchers and wine growers to seek to design low-alcohol
*
Corresponding author. Tel.: +33 (0)3 80 69 30 84; fax: +33 (0)3 80 69
32 27.
E-mail address: [email protected] (T. ThomasDanguin).
0950-3293/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.foodqual.2007.02.004
wines, which could let consumers continue to enjoy winedrinking, while avoiding the harmful effects of ethanol.
One difficulty here is to maintain the aromatic bouquet
of the wine, while reducing the alcohol content; few studies,
however, have looked at the perceptual impact of alcohol
content on the perception of wine flavor.
In 1994, Fischer and Noble studied 18 wines varying in
ethanol content (8%, 11%, 14% v/v), pH (2.9, 3.2, 3.8) and
(+)-catechin level (100 and 1500 mg/L). Twenty panelists
assessed sourness and bitterness intensities. The results
showed that an increase in ethanol content raised bitterness
intensity but had only a slight effect on sourness. Martin
and Pangborn (1970) and Vidal et al. (2004) observed the
same effect of ethanol on bitterness. Similarly, according
to Mattes and DiMeglio (2001), who worked on the oral
ethanol exposure effect on ratings for sucrose, NaCl, citric
acid and quinine hydrochloride, ethanol enhanced the bitter aftertaste of quinine although it suppressed its bitter
character when held in the mouth. Furthermore, according
to these authors, ethanol itself has a bitter taste at concentrations near threshold. Martin and Pangborn (1970) also
902
E. Le Berre et al. / Food Quality and Preference 18 (2007) 901–908
observed that alcohol slightly enhanced the sweetness of
sucrose and depressed the perceived intensity of salt and
sourness.
Few studies have been performed on aroma aspect and
possible perceptual interactions between wine aroma compounds in mixtures of more than two odorants (Escudero
et al., 2004; Lorrain et al., 2006), although there have been
some studies of a simpler model using binary mixtures.
Thus, Atanasova, Thomas-Danguin, Chabanet et al.
(2005) highlighted perceptual interactions in binary
supra-threshold mixtures of Woody and Fruity wine odorants. The odor quality of the mixtures was found to be perceived as mainly homogeneous, with a perceptual
dominance of the Woody odor for iso-intense mixtures;
interactions depended on the perceived intensity of each
component. Another study notably found that a subthreshold Woody component enhanced the Fruity odor
(Atanasova, Thomas-Danguin, Langlois et al., 2005). In
more complex mixtures, a previous study by Moio, Schlich,
Issanchou, Etiévant, and Feuillat (1993) showed that when
the Woody odor raises in a wine, the complexity, and particularly the Fruity and Floral components of the bouquet
is reduced.
Furthermore, it is important to notice that temperature
is an important parameter that could affect wine bouquet.
Indeed temperature is particularly important for wine
drinkers, and often impacts on the perception of odorants
mixtures. Whelton and Dietrich (2004) especially found
that odor intensity was a function of both aqueous concentration and water temperature for water containing several
odorants.
Concerning the impact of ethanol on aroma perception, Pet’ka, Cacho, and Ferreira (2003) used wine-tasting
and GC–O procedures to assess the perceptual intensity
of eight aroma compounds, chosen as examples of chemical groups relevant to wine flavor research, at three
suprathreshold concentrations, with the same intensity
scale. The results showed that ethanol has an additive
effect on intensity and that adding ethanol at a low concentration (under 10%) could decrease aroma compound
detection thresholds. More recently, Grosch (2001)
observed that the less ethanol in a complex wine model
mixture, the greater the intensity of the Fruity and Floral
odors; this could be due to increased partial pressure of
the odorants with reduced ethanol concentration.
Thus, ethanol modifies the perception of wine aroma
compounds, but it remains to be established whether this
impact is only physico-chemical or also perceptual. Atanasova, Thomas-Danguin, Chabanet et al. (2005) demonstrated perceptual interactions between Fruity and
Woody components but did not study their impact with
ethanol, a major aroma compound in wine. The present
study therefore sought to assess the impact of ethanol in
both physico-chemical and perceptual terms: i.e., on the
volatility of Woody and Fruity aromas and on their olfactory perception, alone and in mixtures.
2. Materials and methods
2.1. Odorants
Two wine odorants were chosen to give a simple
model solution of wine aroma. One of these components,
b-methyl-c-octalactone (generally called whiskey lactone),
is mainly brought by oak wood, and was described as
‘‘Woody-Coconut”; the other is an ester, isoamyl acetate,
described as ‘‘Fruity-Banana”. Two types of mixture were
studied: the first combined the two odorants at four concentrations in an aqueous solution (MilliQ system, MilliporeÒ,
France); the second combined them at four concentrations
in a dilute alcohol solution (88% aqueous MilliQ system,
MilliporeÒ, France, and 12% anhydrous ethanol, Carlo
Erba) (Table 1). All odorants were obtained from Aldrich
(France) and presented no odorous impurities on gas chromatography–olfactometry (GC–O). The four concentrations of each odorant were in the same liquid-phase
concentration range as commonly found in red wine.
2.2. Stimulus delivery hardware
TeflonÒ bags (49 49 cm, 20 L capacity, equipped with
a TeflonÒ connector; Interchim France) were chosen to
deliver the odorants because of their suitability in flavor
analysis (Pet’ka, Etiévant, & Callement, 2000), and since
they allowed a large number of assessments over several
days without change in concentration (Atanasova, Langlois, & Etiévant, 2003). Two hundred and fifty milliliters
of odorous solution (aqueous or dilute alcohol) were first
introduced into the bag, which was then filled with 17 L
pure nitrogen. The bags were prepared 12 h before the first
Table 1
Gas-phase and liquid-phase concentrations of each concentration of odorants in aqueous and in dilute alcohol solution
Isoamyl acetate
C1
Whiskey lactone
C2
C3
Concentration in the liquid phase (mg/L)
Aqueous solution
0.38
Dilute alcohol solution
0.2
1.8
1.4
8.4
13.00
Concentration in the gas phase (lg/LN2)
Aqueous solution
2.24
Dilute alcohol solution
1.22
4.62
7.40
34.43
67.11
C4
C1
C2
C3
C4
39.00
38.00
4.00
7.00
10.00
17.00
25.00
46.00
63.00
90.00
146.68
147.09
0.18
0.14
0.36
0.31
0.92
1.15
1.65
1.63
E. Le Berre et al. / Food Quality and Preference 18 (2007) 901–908
measurement, to ensure equilibrium between liquid and gas
phases. Assessment was performed in a quiet, naturally lit
room at an ambient temperature (21 °C).
2.3. Tenax trap analysis
Tenax trapping was performed to measure odorant
headspace concentrations in the bags. The amount of each
odorant in the headspace sample was assessed using gas
chromatography with flame ionization detector (GCFID) and calibration curves. The samples were sucked up
on a Tenax trap at a constant flow of 300 ml min1 for
2–5 min according to the odorant concentration present
in the gas phase. In-trap humidity was eliminated by
nitrogen flow through the trap (100 ml min1 for 5 min).
Physico-chemical analyses were carried out using a Hewlett-Packard 5890 gas chromatograph (5890 Hewlett-Packard, Palo Alto, CA) equipped with a Tenax Cold Trap
injector (TCT, ChrompackÒ, Middelburg, The Netherlands), a DB-Wax silica capillary column (30 m; 0.32 mm
i.d.; 0.5 lm thickness (J&W Folsom, CA)), a Flame Ionization Detector (FID) and a sniffing port (Atanasova et al.,
2003). The chromatograph oven was programmed from
40 °C (1 min) to 230 °C at a rate of 5 °C min1. The carrier
gas was hydrogen. Acquisition used CoconutÒ software
and chromatogram integration used CocowinÒ software
(Almanza & Mielle, 1990).
2.4. Subjects
Fifteen volunteers (12 women and 3 men, ranging from
18 to 47 years old), with no self-reported sense-of-smell
problems or allergy, participated in the experiment. They
were selected from 33 candidates on criteria of availability
for the sessions, absence of anosmia to the odorants being
used, performance on the ETOC olfactory test (ThomasDanguin et al., 2003), and performance in (i) evaluating
the perceived intensity of different concentrations of 1butanol and of the study odorants (i.e. whiskey lactone
and isoamyl acetate) on a linear scale from ‘‘very slight”
to ‘‘very strong”, (ii) classifying different concentrations
of 1-butanol in increasing odor intensity order, and (iii)
generating terms when exposed to the study odorants. Subjects were not informed of the aim of the experiment. They
were asked to avoid smoking, drinking and eating at least
1 h before each session, and were paid for their participation (€8.10/h). At recruitment, subjects were informed that
they would have to smell different aroma compounds. They
were informed of the experimental protocol before the
beginning of the experiment.
2.5. Sensory experimental procedure
The sensory experimental procedure was in two parts:
one comprising three training sessions, and the second four
measurement sessions of about 2 h each, taking place on
separate days. Samples in bags could not be stored for
903
more than two weeks at room temperature and the number
of sample which could be evaluated in a session is limited.
As a consequence the first and second sessions (replication)
were dedicated to aqueous solutions measurements and the
third and fourth ones (replication) to dilute alcohol
solutions.
The three training sessions were devoted (i) to memorizing the 1-butanol scale (Atanasova, Langlois, Nicklaus,
Chabanet, & Etiévant, 2004), (ii) to determining and memorizing one term specific to each odorant, and (iii) to
assessing the perceived intensity of the extreme concentrations of pure odorants (lowest and highest concentrations
of each odorant, in aqueous and in dilute alcohol solvent).
These training sessions were fundamental to the subjects
for the memorization and the use of the 1-butanol scale.
Indeed, it was important that each subject memorized each
reference of the scale in order to evaluate more accurately
the samples during the measurements. Moreover, these
training sessions had for objective to learn to the subjects
to associate the odor of isoamyl acetate with the term
‘‘Banana” and the odor of whiskey lactone with the term
‘‘Coconut”, so that they could evaluate their presence in
the stimuli presented during the measurements.
In the measurement sessions, 26 stimuli were delivered
orthonasally to the subjects: four concentrations (C1, C2,
C3 and C4, presented in Table 1) of each of the two pure
odorants, and their 16 possible combinations, plus a blank
(aqueous solvent) and an alcohol (dilute alcohol solvent)
stimuli. Presentation order was balanced across the two
repetitions and was different for all subjects in a given
session.
Subjects had to assess overall perceived odor intensity,
and ‘‘Fruity-Banana” (isoamyl acetate), ‘‘Woody-Coconut” (whiskey lactone), and ‘‘Alcohol” odor intensities.
Intensities were rated using a modified 1-butanol reference
scale procedure (Atanasova et al., 2004; Atanasova, Thomas-Danguin, Chabanet et al., 2005). The methodology
used was a direct line scaling technique based on five memorized references of 1-butanol intensity levels. These 1butanol references consisted of five concentrations, selected
in a preliminary experiment to cover the intensity range of
all odorants used in the present study (8; 182; 1130; 4124
and 11,259 mg/L) (Atanasova, Thomas-Danguin, Chabanet et al., 2005). These concentrations were carefully chosen so as to produce equal intervals in terms of perceived
intensity. Before each measurement session, subjects smelt
the five reference intensities of 1-butanol and were
instructed to memorize them. To overcome the risk of
adaptation and possible perceptual interactions between
the studied odorants and 1-butanol, subjects were allowed
to smell bags containing the 1-butanol reference odor only
at the beginning of each session and not during the assessment. During the experiment, subjects rated perceived
intensity on a 12 cm linear scale structured by five equally
spaced figures (1–5) corresponding to the five 1-butanol
reference intensities. The resulting intensity was expressed
as a score ranging from 0 to 10. The direct scaling
E. Le Berre et al. / Food Quality and Preference 18 (2007) 901–908
procedure, and the fact that the 1-butanol references elicited perceived intensities that were equidistant in terms of
intensity perception, confirmed that the scale respected
both interval and ratio properties, at least in the range used
by the subjects (Atanasova, Thomas-Danguin, Chabanet
et al., 2005).
Data were acquired by FIZZ software (Biosystèmes,
Couternon, France).
Hereinafter, ‘‘A” designates isoamyl acetate, ‘‘W” whiskey lactone, and the numbers 1, 2, 3 and 4 the four concentrations used per compound. Thus, ‘‘A1W4” refers to a
mixture of isoamyl acetate at concentration C1 and whiskey lactone at concentration C4; ‘‘AxW1” includes the
mixtures A0W1, A1W1, A2W1, A3W1 and A4W1. ‘‘BUT”
designates 1-butanol, ‘‘FR” Fruity odor and ‘‘WO”
Woody odor.
2.6. Data analysis
All statistical analyses used SAS software (SAS Institute
Inc., Cary, NC), release 8.2. Analysis of variance was performed with the GLM procedure.
3. Results and discussion
3.1. Physico-chemical analysis
Concentration in gas phase (µg/L)
The first analysis was intended to check for any physicochemical impact of adding ethanol on the gas-phase concentrations of whiskey lactone and isoamyl acetate. To
assess the impact of ethanol on gas-phase odorant release,
we sought to obtain the same gas-phase concentration in
both the dilute alcohol and aqueous solvents, changing
the concentration only in the liquid phase. This matching
procedure was intended to clarify the subsequent sensory
analysis. The gas- and liquid-phase concentrations of each
odorant concentration taken alone (‘‘out of mixture”: OM)
Isoamyl acetate
A A
160
140
120
100
80
B
60
C
40
20
0
D D
D D
A1Wx
A2Wx
Dilute alcohol solution
A3Wx
A4Wx
Aqueous solution
in the aqueous and in the dilute alcohol solvents are presented in Table 1.
To check that the gas-phase concentrations for both
odorants (isoamyl acetate and whiskey lactone) were the
same in both solvents, a two-way ANOVA (Solvent, Concentration) with interaction and a Newman–Keuls test for
multiple comparison were performed for each odorant.
The ANOVA indicated no significant effect of Solvent
for whiskey lactone: i.e., no significant difference in whiskey lactone gas-phase concentration over the aqueous
and the dilute alcohol solvent (all levels merged,
F = 0.30; p = 0.59). There was also no significant effect of
the Solvent*Concentration interaction (F = 1.17; p = 0.33):
i.e., no impact of the particular solvent on the gas-phase
concentration of whiskey lactone, whatever the whiskey
lactone concentration (Fig. 1, right-hand graph). As
expected, there was a significant effect of Concentration
(F = 128; p < 0.0001), and the Newman–Keuls test showed
that only the lowest two concentrations (AxW1 and
AxW2) did not significantly differ from each other
(Fig. 1, right-hand graph). More whiskey lactone had to
be added to the dilute alcohol solution to achieve the same
gas-phase concentration as in the aqueous solution (Table
1): i.e., the whiskey lactone partition coefficient between
liquid and gas phases was lower in the dilute alcohol than
in the aqueous solvent. Furthermore, the Henry slope for
whiskey lactone was lower in the dilute alcohol
(1.88E05) than in the aqueous solvent (2.56E05) and
the confidence intervals did not overlap ([1.72E05 to
2.04E05] and [2.30E05 to 2.81E05], respectively):
i.e., whiskey lactone was less volatile in presence of ethanol.
This observation could be related to a higher solubility of
whiskey lactone in hydro-alcoholic wine model solution
(Barrera-Garcia, Gougeon, Voilley, & Chassagne, 2006).
For isoamyl acetate, an unexpected significant effect of
Solvent (F = 7.7; p = 0.007) was observed. The Newman–
Keuls test showed that gas-phase concentrations of isoamyl
acetate were significantly lower over the aqueous than over
the dilute alcohol solutions. Moreover, a significant effect
Concentration in gas phase (µg/L)
904
Whiskey lactone
1.8
A A
1.6
1.4
B
1.2
1.0
B
0.8
0.6
0.4
0.2
C C
C C
0.0
AxW1
AxW2
Dilute alcohol solution
Ax W3
Ax W4
Aqueous solution
Fig. 1. Mean gas-phase concentrations of isoamyl acetate (A) and whiskey lactone (W), per concentration level (e.g.: Isoamyl acetate A1Wx = mean gasphase concentration of isoamyl acetate for A1W0, A1W1, A1W2, A1W3 and A1W4). The difference between two modalities linked by the same letter is
not significant at 5%.
E. Le Berre et al. / Food Quality and Preference 18 (2007) 901–908
905
Table 2
Results of the two-way ANOVA performed on the Fruity odor intensity of isoamyl acetate and on the Woody odor intensity of whiskey lactone in
aqueous solution
Isoamyl acetate
Whiskey lactone
Source
ddl
F
p
Source
ddl
F
p
Model
Subject
Concentration level
19
14
5
47
9.7
153
<0.0001
<0.0001
<0.0001
Model
Subject
Concentration level
19
14
5
14
2.8
43
<0.0001
0.0005
<0.0001
8
6
4
D***
C***
2
A
A**
B***
0
Water
A1W0
A2W0
A3W0
A4W0
Whiskey lactone alone in aqueous solution
Intensity of the Woody odour
Intensity of the Fruity odour
Isoamyl acetate alone in aqueous solution
10
10
8
6
4
D***
2
A
B***
D***
C***
0
Water
A0W1
A0W2
A0W3
A0W4
Fig. 2. Mean Fruity odor intensity per isoamyl acetate concentration and mean Woody odor intensity per whiskey lactone concentration in aqueous
solution. The difference between two modalities linked by the same letter is not significant at 5%. Asterisks indicate values significantly different from 0
(* = p < 0.05; ** = p < 0.01; *** = p < 0.001).
of Concentration and of Solvent*Concentration emerged
(F = 461, p < 0.0001; F = 6.5, p < 0.0006, respectively).
The Newman–Keuls test showed, that, as with whiskey lactone, only the lowest two concentrations of isoamyl acetate
(A1Wx and A2Wx) did not significantly differ from each
other (Fig. 1, left-hand graph). Moreover, at the third level
(A3Wx), the gas-phase concentration of isoamyl acetate
was about twice as high over the dilute alcohol as over
the aqueous solution. This unexpected finding is to be
borne in mind when examining the sensory results. Moreover, the Henry slope for isoamyl acetate was also lower
in the dilute alcohol (3.64E03) than in the aqueous solution (3.86E03), although this time the confidence intervals did overlap ([3.42E03 to 3.87E03] and [3.66E03
to 4.06E03], respectively): i.e., there was no significant
difference in volatility between aqueous and dilute alcohol
solutions in the case of isoamyl acetate. It can thus be concluded that, under our experimental conditions, the partition coefficient for isoamyl acetate did not differ between
aqueous and dilute alcohol solutions.
Table 2 shows a significant effect of Concentration and
Subject for each odorant in the aqueous solution.
Fig. 2 shows that, as expected, each of the four concentrations of isoamyl acetate in aqueous solution was perceived as significantly different from the others. For
whiskey lactone, however, the highest two concentrations
were not perceived as significantly different. Comparing
the sensory and physico-chemical results, it can be seen
that the sensitivity ranges differed between human perception and the FID detector. For isoamyl acetate, the lowest
two concentrations could not be distinguished physicochemically but were clearly differentiated by the panel.
For whiskey lactone likewise, the lowest two concentrations could not be distinguished physico-chemically but
were clearly differentiated by the panel, but the highest
two levels, in contrast, were distinguished physico-chemically but not by the panel. This could be due to a ceiling
effect in perception induced by the non-linear shape of
the stimulus–response curve of the odorants (Chastrette,
Thomas-Danguin, & Rallet, 1998).
3.2. Sensory analysis
3.2.1.2. In dilute alcohol solution. To study the impact of
ethanol perception on Woody and Fruity odor perception,
the Fruity (FR) and Woody (WO) odors perceived in dilute
alcohol (alc) and in aqueous solutions (water) were compared, by calculating the difference (DiffMed) between
odor intensities in the two solvents (DiffMed = IalcIwater).
To test for significant differences in the intensity of
Woody and Fruity odors perceived with and without ethanol, a two-way ANOVA (Subject, Concentration) and a
Newman–Keuls multiple comparison of means was performed on DiffMed. The analysis showed no significant
3.2.1. Perception of Fruity and Woody odors
3.2.1.1. In aqueous solution. The first step in the sensory
analysis was to measure the intensity of the various concentrations of isoamyl acetate and whiskey lactone, perceived
separately in aqueous solution. A two-way ANOVA (Subject, Concentration) with interaction and a multiple comparison of means by Newman–Keuls test were performed
for each odorant on the Fruity odor for isoamyl acetate
and on the Woody odor for whiskey lactone.
906
E. Le Berre et al. / Food Quality and Preference 18 (2007) 901–908
Whiskey lactone
Isoamyl acetate
0.9
A*
A*
IWOalc-IWOwater
IFR alc-I FR water
AB**
0.8
0.7
0.6
A**
1
A*
0.8
0.5
0.4
A
0.3
0.2
A
0.1
0.6
0.4
ABC
0.2
BC
A0W0
-0.2
0
A0W0
A1W0
A2W0
A3W0
A4W0
C
0
A0W1
A0W3
A0W4
A0W2
-0.4
Fig. 3. Mean differences between the Fruity odor perceived in dilute alcohol and in aqueous solvent per isoamyl acetate concentration (left-hand panel)
and between the Woody odor perceived in dilute alcohol and in aqueous solvent per whiskey lactone concentration (right-hand panel). The difference
between two modalities linked by the same letter is not significant at 5%. Asterisks indicate values significantly different from 0 (* = p < 0.05;
** = p < 0.01; *** = p < 0.001).
effect of Subject for both odorants (F = 1.48, p = 0.13 for
isoamyl acetate; and F = 1.08, p = 0.38 for whiskey
lactone).
Isoamyl acetate showed no difference in the effect of
concentration on the perception of the Fruity odor between
the aqueous and the dilute alcohol solutions (F = 1.41,
p = 0.23). Fig. 3 (left-hand panel) further shows that the
Fruity odor was more intense when perceived in the dilute
alcohol than in the aqueous solution (mean DiffMed = +0.5*). As it had been checked that the gas-phase
concentration of isoamyl acetate was the same above both
solvents (except for concentration A3W0), it may be concluded that the Fruity odor intensity increased in presence
of 12% ethanol in water as compared to water only. The
fact that the A3W0 mixture tended to elicit a higher perceived Fruity intensity in the dilute alcohol solution than
did A4W0 can be explained by the fact that, physico-chemically, the gas-phase concentration for A3W0 in the dilute
alcohol solution was about twice as high as in the aqueous
solution. Nevertheless, the difference between A3W0 and
A4W0 was not significant.
The Fruity odor of A0W0 was found to be more intense
in the dilute alcohol solution: i.e., ethanol itself obviously
had a Fruity odor as perceived by the subjects. Thus it cannot be said that a synergy occurred for the Fruity odor in
the dilute alcohol as compared to the aqueous solution.
Moreover, the intensity of the Fruity odor in the lowest
two isoamyl acetate concentrations (A1W0 and A2W0)
tended to be lower than that for Alcohol alone (A0W0).
The effect of the concentration of whiskey lactone on the
perception of the Woody odor differed significantly
between the two solvents (F = 4; p = 0.004). Fig. 3 (righthand panel) shows that the highest whiskey lactone concentrations (A0W3 and A0W4) were perceived as being
significantly more intense in the dilute alcohol solution
than was the A0W2 concentration or the Alcohol solution
(A0W0). Fig. 3 further shows that DiffMed for A0W0 did
not significantly differ from 0. Hence, it can be concluded
that ethanol does not provide a Woody odor. Moreover,
DiffMed for the lowest two whiskey lactone concentrations did not differ from 0. However, increasing the Woody
odorant concentration (A0W3 and A0W4) led to a signifi-
cant perceptual synergy effect on the Woody odor in the
presence of ethanol. As previously noted, the Woody intensity of A0W0 did not differ from 0, so that a definite synergy can be said to occur for the Woody odor in presence
of ethanol.
Taken together, these observations agree with the findings of Pet’ka et al. (2003), who demonstrated an additive
effect of ethanol on aroma intensity. In the present study,
the highest concentrations of Fruity and Woody odors
were perceived as being more intense in the dilute alcohol
than in the aqueous solution. Grosch (2001), on the other
hand, reported that the smaller the quantity of ethanol in
a complex wine model mixture, the higher the intensity of
the Fruity and Floral odors. This discrepancy may be
imputed to the fact that, unlike Grosch, the present study
did not concern complex wines but simpler mixtures.
3.2.2. Interactions in Woody/Fruity mixtures
Woody/Fruity interactions were studied by comparing
odors as perceived in a mixture (M) and as perceived out
of mixture (OM), for each solvent separately, and calculating the difference (DiffMix = IMIOM) in intensity.
First, to test for an effect of solvent (aqueous or dilute
alcohol) on odor as perceived in and out of mixture, a
four-way ANOVA (Subject, Solvent, FR-concentration
and WO-concentration) and Newman–Keuls multiple comparison of means were performed on ‘‘DiffMix”. A significant effect of Solvent emerged for both Fruity and Woody
odors (F = 8.2, p = 0.004; F = 13.8, p = 0.0002, respectively), and a three-way ANOVA (Subject, FR-concentration and WO-concentration) was therefore performed on
DiffMix for each solvent separately and for each odorant.
3.2.2.1. Interactions on the Fruity odor. In the aqueous solvent, the only significant difference the ANOVA revealed
was in Fruity odor perception according to Woody compound concentration (F = 3.26; p = 0.02).
Fig. 4 (left-hand panel) shows that, at low concentrations (AxW1 and AxW2), the presence of the Woody odor
induced a significant perceptual synergy of the Fruity odor,
becoming non-significant as the Woody concentration
increased. This is in agreement with Atanasova, Thomas-
E. Le Berre et al. / Food Quality and Preference 18 (2007) 901–908
Aqueous solution
0.5
907
Dilute alcohol solution
0.3
**
0.2
0.4
0.1
*
0.3
A4Wx
IFR M-I FR OM
IFR M-I FR OM
0
0.2
0.1
AxW4
A1Wx
A2Wx
A3Wx
A4Wx
-0.1
-0.2
-0.3
0
AxW1
AxW2
AxW3
AxW4
-0.4
-0.1
-0.5
-0.2
-0.6
***
Fig. 4. Graphs of the interactions on the Fruity odor in aqueous (left-hand panel) and dilute alcohol (right-hand panel) solutions. Asterisks indicate values
significantly different from 0 (* = p < 0.05; ** = p < 0.01; *** = p < 0.001).
Dilute alcohol solution
Aqueous solution
1
1
0.5
*
0.5
*
0
-0.5
*
*
-1
***
-1 .5
AxW1
AxW2
IW OM-I W OM
IW M-IW OM
0
-0.5
-1
**
AxW1
***
-1.5
***
***
AxW3
-2
-2.5
AxW4
A1
A2
A3
A4
Concentration of Isoamyl acetate
-2
-2.5
A1
A2
A3
AxW2
AxW3
AxW4
A4
Concentration of Isoamyl acetate
Fig. 5. Graphs of the interactions on the Woody odor in aqueous and dilute alcohol solutions. Asterisks indicate values significantly different from 0
(* = p < 0.05; ** = p < 0.01; *** = p < 0.001).
Danguin, Langlois et al. (2005), who demonstrated a synergy effect of the sub-threshold Woody odor on the Fruity
odor. Moreover, Atanasova (2004) demonstrated that the
probability of identifying the Fruity component was highest when the Woody component was sub-threshold or at
very low intensity. The present experiment shows that concentrations of the Woody component just above threshold
also enhanced the Fruity perception. Moreover, there was
a tendency for the highest whiskey lactone concentration
(AxW4) to mask the Fruity odor – in agreement with Moio
et al. (1993), who observed a decrease in Fruity odor perception as the Woody odor increased.
In the dilute alcohol solution, the ANOVA revealed a
difference in Fruity odor perception according to Fruity
odor concentration (F = 6.04; p = 0.0006).
Fig. 4 (right-hand panel) shows significant Fruity odor
masking only for the highest isoamyl acetate concentration
(A4Wx). Since there is, as noted above, a synergy effect of
the Woody odor in the dilute alcohol solution (Fig. 3), the
Woody odor tends to dominate and thus mask the Fruity
odor, especially at its highest concentration. At the lowest
Fruity odor intensities, however, there is no influence of
Woody component concentration in the mixture.
3.2.2.2. Interactions on the Woody odor. In the aqueous solvent, the ANOVA revealed a difference in Woody odor
perception induced by the presence of the Fruity component (F = 5.24; p = 0.002).
Fig. 5 (left-hand panel) shows a significant masking
effect on the Woody odor in the aqueous solution with
the highest Fruity odor concentrations (A3Wx and
A4Wx): the more isoamyl acetate (Fruity odor) in the mixture, the more the Woody odor is masked.
In the dilute alcohol solution (Fig. 5, right-hand panel)
interactions on the Woody odor were more complex. The
ANOVA showed a significant effect of Fruity and of
Woody odor concentration (F = 12, p < 0.0001; F =
! 21.11, p < 0.0001, respectively). It seems that, at least
for the highest whiskey lactone concentrations (AxW3
and AxW4), the more isoamyl acetate (Fruity odor) in
the mixture, the more the Woody odor was masked, as likewise observed in the aqueous solution.
3.2.2.3. Interactions on the alcohol odor. To study the effect
of Woody and Fruity mixtures on the Alcohol odor, a
three-way ANOVA (Subject, FR-concentration and WOconcentration) and a Newman–Keuls multiple comparison
of means were performed. Concerning the perception of
the Alcohol odor in Woody–Fruity mixtures, the ANOVA
found no effect of isoamyl acetate or whiskey lactone concentrations (F = 0.15, p = 0.9; F = 0.35, p = 0.8, respectively). However, a significant Alcohol-masking effect (the
mean of the difference between the intensity of the Alcohol
OM
odor in and out of the mixture: I M
A I A ¼ 1:1 ) was
observed: in presence of isoamyl acetate and whiskey lactone, the Alcohol odor of ethanol was less perceived.
908
E. Le Berre et al. / Food Quality and Preference 18 (2007) 901–908
4. Conclusion
Physico-chemical and perceptual interactions between
Woody and Fruity odors in aqueous and dilute alcohol
solutions were studied under laboratory conditions using
physico-chemical and psychophysical methods. The physico-chemical results showed both chemical and sensory
interactions between the three components. There was a
significant difference in whiskey lactone (Woody component) volatility between the aqueous and the dilute alcohol
solutions, which did not seem to be the case for isoamyl
acetate (Fruity component). Perceptually, adding ethanol
to Woody/Fruity mixtures did not seem to change the perceptual interactions effects observed in the aqueous solution, but rather showed a tendency to reinforce them.
The sensory data showed a significant synergy effect of
just-above-threshold Woody odor on the lowest Fruity
odor concentrations in the aqueous solution, with a tendency to a masking effect on the highest Fruity odor
concentration. This masking effect was reinforced in the
dilute alcohol solution, which could be explained by the
synergic effect of ethanol on the Woody odor. On the other
hand, significant Woody odor masking by the Fruity odor
was observed in the aqueous solution; this effect was maintained in presence of ethanol, but only for the highest
Woody odor levels. Moreover, significant Alcohol odor
masking by the Fruity and Woody odors was observed in
the dilute alcohol solution. Taken together, these results
demonstrate that a reduction in alcohol content in wine
can affect the aromatic bouquet, especially by reinforcing
perceptual interactions between Woody and Fruity wine
odorants but also by modifying their chemical proportions.
Acknowledgements
This work was carried out with the financial support of
INRA, the Burgundy Regional Council and the ‘‘Agence
Nationale de la Recherche” under the ‘‘Programme National de Recherche en Alimentation et nutrition
humaine”, Project ‘‘ANR-05-PNRA-011, VDQA”.
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