Food Quality and Preference 73 (2019) 1–7
Contents lists available at ScienceDirect
Food Quality and Preference
journal homepage: www.elsevier.com/locate/foodqual
Modulation of sensory perception of cheese attributes intensity and texture
liking via ortho- and retro-nasal odors
T
⁎
Pengfei Hana, , Therese Farka, Rene A. de Wijkb,c, Natacha Roudnitzkya, Emilia Iannillia,
Han-Seok Seod, Thomas Hummela
a
Smell & Taste Clinic, Department of Otorhinolaryngology, Technical University of Dresden Medical School, Fetscherstrasse 74, 01307 Dresden, Germany
Top Institute Food and Nutrition, Consumer Science & Health, Wageningen, The Netherlands
c
Wageningen Food & Biobased Research, Consumer Science & Health, Wageningen, The Netherlands
d
Department of Food Science, University of Arkansas, 2650 North Young Avenue, Fayetteville, AR 72704, USA
b
A R T I C LE I N FO
A B S T R A C T
Keywords:
Cross-modal sensory enhancement
Orthonasal
Retronasal
Cheese
Texture
Congruency
Cross-modal sensory integration plays a key role in food flavor perception and acceptance during consumption.
The current study investigated the effect of a butter odor, delivered at various stages of the oral processing cycle,
on modulating the sensory properties of cheese. Twenty healthy volunteers (aged between 25 and 29 years, 12
women) were measured for their detection thresholds for the butter odor. In the sensory evaluation sessions,
participants chewed and swallowed three types of cheese (low-fat, 20% fat content, LF; a medium-fat, 30% fat
content, MF; high-fat, 40% fat content, HF, served in 16 × 16 × 12 mm3 cubes) while the butter odor was
presented ortho- and retronasally in two concentrations at various points of the oral processing cycle. After
swallowing, participants rated on a visual analogue scale for the intensities of cheese creaminess, butter note,
overall flavor, and the pleasantness for cheese texture. Enhancement of added butter odor on perceived sensory
attributes differed as a function of the delivery routes and timings. Creaminess intensity increased significantly
when butter odor presented retro-nasally at the start of chewing. Butter note was enhanced when the retro-nasal
odor was added during chewing. The texture pleasantness was increased with ortho-nasal odor presentation. In
addition, for the creaminess intensity and texture liking enhancement, the observed effects were more pronounced with butter odor presentation at the lower concentration. Taken together, these findings suggested the
importance of temporal congruency for cross-modal sensory enhancement in food flavor perception. The findings help to better understand flavor perception during oral processing of solid food and add value for future
development of foods with nutritional benefits.
1. Introduction
Flavor is one of the most important attributes of food evaluation.
Food flavor perception involves multisensory interaction in which signals from different sensory channels, including olfactory, gustatory,
mechanical, trigeminal and even auditory sources merge and form a
whole sensory percept (Seo & Hummel, 2017). Sensory signals from
different modalities often interact (enhancement or suppression) with
each other and modulate the whole flavor perception. Odors not only
contribute to the qualitative diversity of food but also interact with
other sensations and modulate the overall flavor perception. The most
studied cross-modal sensory enhancement is between odor and taste,
which often form the unitary flavor of food (Dalton, Doolittle, Nagata,
& Breslin, 2000), with a number of previous studies having shown odor
⁎
enhancement by taste (Green, Nachtigal, Hammond, & Lim, 2012;
Welge-Lussen, Husner, Wolfensberger, & Hummel, 2009) or taste enhancement by odors (Labbe, Damevin, Vaccher, Morgenegg, & Martin,
2006; Labbe, Rytz, Morgenegg, Ali, & Martin, 2007; Sakai,
Kobayakawa, Gotow, Saito, & Imada, 2001; Schifferstein & Verlegh,
1996) (Fig. 1).
The cross-modal sensory enhancement largely depends on the
quality and temporal congruency of individual sensory stimuli. The
quality congruency refers to the extent to which signals for distinct
modalities could be considered attributes to the same object. For example, the salty- or sweet-congruent odor could enhance the saltiness
and sweetness perception, respectively (Seo et al., 2013; Small et al.,
2004). In the opposite direction, Green et al. (2012) showed that sucrose, but not other tastants (NaCl, citric acid), significantly enhanced
Corresponding author.
E-mail address: pengfeihan88@gmail.com (P. Han).
https://doi.org/10.1016/j.foodqual.2018.11.019
Received 13 September 2018; Received in revised form 29 October 2018; Accepted 21 November 2018
Available online 22 November 2018
0950-3293/ © 2018 Elsevier Ltd. All rights reserved.
Food Quality and Preference 73 (2019) 1–7
P. Han et al.
enhancement was largely attenuated when the odor was presented
before or after the delivery of taste with only one second of deviation
(Isogai & Wise, 2016).
Food odor does not only have an impact on taste perception, but
also on food texture. Previous research suggested that specific texture
sensations such as creaminess, a highly desirable food property, are
multi-modal percepts reflecting odor, taste, textural and, possibly, hedonic properties of foods (de Wijk, Terpstra, Janssen, & Prinz, 2006).
The interaction between odor and texture has been shown in previous
studies (Hollowood, Linforth, & Taylor, 2002; Pangborn, Gibbs, &
Tassan, 1978). Food texture (e.g. creaminess or thickness) is also important for overall food sensory characteristics, especially for certain
types of food such as milk products. It has been found that increased
viscosity of beverages reduces retronasal odor intensity (Pangborn
et al., 1978). Our previous work showed higher ratings for milk
thickness and creaminess when butter-like odor was presented retronasally at the time of swallowing (Bult et al., 2007; Roudnitzky et al.,
2011). This pointed towards the temporal congruency of odor-texture
enhancement in the late phase of oral processing. The first aim of the
current study was to investigate the modulation of added odor on
texture and flavor perceptions of a solid food – cheese. In addition,
unlike previous research, the current study allowed subjects to chew the
cheese ad libitum, trying to imitate eating situations in real life. A
butter-like odor was presented at various stages of the eating cycle at
the start of chewing, during chewing, and before swallowing, either
through the orthonasal or retronasal route; multiple sensory attributes
were rated. This study also tried to address the potential interaction
between odor-texture enhancement with odor concentration and cheese
type (e.g. fat level). We therefore included two concentrations of odor
based on the individual perceptual threshold and three types of cheese
with varied fat content (high-fat, medium-fat and low-fat cheese).
Fig. 1. Diagram showing the experimental procedure for one type of cheese
under one odor stimulus concentration. Cells in grey indicate the timepoints for
different conditions for odor stimuli and ratings for sensory attributes. Odor
stimulus was presented orthonasally for 3 s after food intake and before
chewing (Orthonasal 1, O1). Odor stimulus was presented retronasally for 3 s at
the three different instants: at the start of chewing (Retronasal 1, R1), half-way
between chewing and swallowing (Retronasal 2, R2), or during swallowing
(Retronasal 3, R3).
the perceived intensity of citral, vanillin, and furaneol – a strawberry
odor. Quality congruency also influences the pleasantness, intensity,
and familiarity of the flavor perception. A recent study showed the
odor-taste pairs were rated as more pleasant with increasing levels of
congruency (Amsellem & Ohla, 2016). In addition, the presence of a
congruent taste significantly increased the localization of retronasal
food odors to the tongue, known as the oral referral of retronasal odor
perception (Fondberg, Lundstrom, Blochl, Olsson, & Seubert, 2018;
Lim, Fujimaru, & Linscott, 2014; Lim & Johnson 2011; 2012). Neuroimaging studies also suggested a neural mechanism for the superadditive effect of multisensory integration, in which certain brain areas
(including insula, orbitofrontal cortex, amygdala and anterior cingulate
cortex) respond to stimuli of different modalities (e.g. odor, taste or
texture) and exhibit a larger response to their combinations than the
sum of responses to each individual stimulus (de Araujo, Rolls,
Kringelbach, McGlone, & Phillips, 2003; Onuma, Maruyama, & Sakai,
2018; Small et al., 2004; Verhagen & Engelen, 2006). The enhancement
of perceptual as well as neural responses depends on familiarity and
prior experiences with the stimulus (Frank & Byram, 1988; Small et al.,
2004). In addition, the quality congruency depends on the route of odor
delivery, especially for foods. For instance, a number of studies reported
the enhancement of taste intensity by odor delivered via the retronasal
route (Lawrence, Salles, Septier, Busch, & Thomas-Danguin, 2009;
Manabe, Ishizaki, Yamagishi, Yoshioka, & Oginome, 2014; Stevenson,
Prescott, & Boakes, 1999). This is due to the fact that retronasal odors
are more referred to the mouth to elicit flavor that represents known or
potential foods (Lim & Johnson, 2012).
Apart from quality congruency, the congruency in the temporal
dimension (e.g. timing of the delivery of sensory stimuli from different
sensory modalities) is also important for multisensory enhancement
(Isogai & Wise, 2016). Holding a subthreshold concentration of saccharine in the mouth decreased detection thresholds for a sweet almond
aroma, but odor thresholds were not affected when subjects expectorated the saccharine solution before sampling the odor (Pfeiffer,
Hollowood, Hort, & Taylor, 2005). Recently, Kakutani and colleagues
(Kakutani et al., 2017) compared the sweet taste intensity when a vanilla odor was presented synchronously with breathing via either orthonasal or retronasal route either before or after drinking the solution.
Taste enhancement was observed only when the odor was presented
retronasally and subjects exhaled after drinking the beverage, suggesting the importance of both the route of odor delivery and the
temporal synchrony between odor and taste for the enhancement
(Kakutani et al., 2017). Similar findings have been found for texture
enhancement by odor. Retronasal aroma increased rated creaminess of
dairy samples most when odor was presented during swallowing, less
when presented while subjects manipulated the dairy sample in the
mouth before swallowing, and not at all when the odor was presented
while the mouth was filling (Bult, de Wijk, & Hummel, 2007). In another study, the enhancement of sweetness and bitterness by “sweet”
and “bitter” odors was greatest with simultaneous presentation, and the
2. Materials and methods
2.1. Participants
Twenty young healthy participants (12 females and 8 males) aged
between 25 and 29 years took part in this study. Inclusion criteria were
a normal sense of smell, as ascertained using the “Sniffin’ Sticks” test
(Hummel, Sekinger, Wolf, Pauli, & Kobal, 1997), and self-reported
regular consumption of Gouda cheese. The study was carried out in the
Smell & Taste Clinic at the Department of Otorhinolaryngology of the
TU Dresden, and the protocol was approved by the local Medical Ethical
Committee (EK284122006). All participants were informed about the
experimental procedure and provided informed written consent before
participation.
2.2. Odor stimuli
The butter odor (Butter Buds Food Ingredients, Racine, WI, USA), a
natural cream flavor, was used as the odor stimulus. Two odor concentrations were selected for the study based on the individual
threshold levels of the participants: the low concentration (LC) was just
detectable for all subjects (5% above threshold – see below), whereas
the high concentration (HC) was clearly detectable for all participants
(twice the concentration of LC).
2.3. Cheese stimuli
The used cheeses were varieties of Gouda cheese ages less than two
months. Gouda is the most popular type of Dutch cheese and accounts
for approximately 50% of all Dutch cheeses. Three Gouda cheese products (Friesland Foods, Meppel, The Netherlands) varying in fat level,
i.e., low-fat (LF, 20% fat), medium-fat (MF, 30% fat), and high-fat (HF,
40% fat) cheeses, were used in this study. Using a cheese slicer (Genius,
Limburg, Germany), each cheese sample was broken into bite-size
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intensities and likings of cheese stimuli, principal component analysis
(PCA) on covariance matrix was conducted using XLSTAT statistical
software.
cubes (16 × 16 × 12 mm).
2.4. Procedure
Participants took part in three sessions. In the first session, detection
thresholds for butter odor were tested in an orthonasal way, using the
method of ascending limits. Odorous stimuli of 1000 ms duration were
presented to either left or right nostril (randomized selection) using a
computer-controlled olfactometer (Burghart OM6b; Burghart, Wedel,
Germany). Using the method of ascending limits the butter odor was
delivered in ascending concentrations starting from the lowest concentration (5% v/v), and increased in steps of 5%. Participants were
asked to answer “yes” or “no” whether an odor had been perceived or
not. When participants perceived the odor at a certain concentration,
they received the same concentration a second time. A threshold level
was defined as the concentration where a given stimulus had been
perceived twice in a row.
The second and third sessions lasted approximately two hours each,
during which all cheese stimuli were presented once in all experimental
conditions. Participants were asked to chew each cheese cube ad libitum
in the presence of either ortho- or retro-nasal odor at the low or high
concentration level. The odor presentation followed the same procedure described previously (Bult et al., 2007). In the orthonasal condition (O), the odor stimulus was presented immediately after the cheese
had been put into the mouth but before the onset of chewing (to mimic
the natural situation where cheese is smelled ortho-nasally when the
cheese is brought to the mouth). In the three retronasal conditions, the
odor stimulus was presented retronasally at three different moments: at
the start of chewing (R1), between the start and swallowing (R2), and
during swallowing (R3). Oral chewing activity was measured using
vibromyography (VMG) activity of the prelaryngeal, submandibular,
buccal, and temporal muscles (de Wijk, Polet, Bult, & Prinz, 2008).
VMG measurements allowed direct identification of the onsets of
chewing and swallowing which served as triggers for odor delivery. The
inter-stimulus interval between cheese stimuli was approximately 4 min
to minimize adaptation. In addition to eight odor conditions (i.e., four
instants of odor presentation × two odor concentrations), a control
condition (C) was included without any odor presentation which was
also applied with any of the three cheese stimuli. Therefore, the total
number of stimulus conditions was 27 (i.e., 9 odor conditions × 3
cheese types) and each stimulus condition was tested in duplicate
through the second and third sessions.
Participants were asked to evaluate the intensities for cheese creaminess, butter note, overall flavor, and the pleasantness for cheese
texture. Ratings for cheese sensory attributes were performed using the
visual analogue scales (VAS): for intensity ratings the VAS ranged from
0 (not creamy / no butter note / no flavor) to 100 (very creamy / very
strong butter note / very strong flavor), and for the texture pleasantness
rating the VAS ranged from 0 (unpleasant) to 100 (pleasant) with a
central marker indicating neutral.
3. Results
3.1. Butter odor threshold
The averaged butter odor threshold 9.25 (SEM 1.63), with the 95%
CI 5.83 (lower CI) and 12.67 (upper CI) at 1000-ms stimulation. There
was a significant effect of gender on the threshold, showing that female
participants were more sensitive to butter odor than male participants
(F = 5.68, p = 0.03). There was no effect of nostril sides (F = 0.18,
p = 0.68) or interaction between gender and nostril side (F = 0.18,
p = 0.68) on butter odor threshold. Participants’ information and
threshold levels are shown in the Supplementary Table 1.
3.2. Creaminess
3.2.1. Low concentration level of butter odor
There was no significant interaction between odor condition and
cheese type in the ratings of creaminess intensity (F = 2.74, p = 0.22).
The odor condition had a significant impact on creaminess perception
(F = 2.74, p = 0.035). Post-hoc test showed that the creaminess intensity ratings in the R1 odor condition were greater than those in the
R3 odor condition (p = 0.01) (Fig. 2). Creaminess intensities significantly differed with a fat level of cheese stimuli (F = 45.51,
p < 0.001), with highest creaminess rating for HF, followed by MF and
the LF cheese stimuli.
3.2.2. High concentration level of butter odor
There was no significant interaction between odor condition and
cheese type in the ratings of creaminess intensity (F = 0.89, p = 0.53).
Creaminess intensities were not significantly different as a function of
odor condition (F = 0.14, p = 0.97) (Fig. 2), but differed in relation to
the fat level of cheese stimuli (F = 51.32, p < 0.001), with highest
creaminess ratings for HF, followed by MF and the LF cheese stimuli.
3.3. Butter note
3.3.1. Low concentration level of butter odor
There was no significant interaction between odor condition and
2.5. Statistical analysis
Data analysis was conducted using SPSS for WindowsTM (version
24.0, IBM SPSS Inc., Chicago, IL, USA), GraphPad Prism (Version 6,
GraphPad Software, Inc. La Jolla, CA), and XLSTAT statistical software
(Addinsoft, New York, NY, USA). To determine whether odor condition
(i.e., O, R1, R2, R3, and C) could affect attribute intensities and texture
likings of three types of cheese (i.e., LF, MF, and HF), a three-way
analysis of variance (ANOVA), treating “odor condition” and “cheese
type” as fixed effects and “participants” as a random effect, was performed as a function of odor concentration (i.e., L and H). Post-hoc
comparisons between independent variables were performed using
Tukey’s Honest Significant Difference (HSD) method. A statistically
significant difference was defined as p < 0.05. To examine associations
between odor condition (i.e., O, R1, R2, R3, and C) and attribute
Fig. 2. Mean ratings of creaminess intensity for cheese stimuli in the absence
(control) or the presence of butter odor. Odor stimulus at either a low or a high
concentration was presented via orthonasal (O1) or retronasal (R1, R2, and R3)
pathways. Error bars represent standard error of the means. Mean ratings with
different letters at either low or high concentration level represent a significant
difference at p < 0.05.
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Fig. 3. Mean ratings of butter notes intensity for cheese stimuli in the absence
(control) or the presence of butter odor. Odor stimulus at either a low or a high
concentration was presented via orthonasal (O1) or retronasal (R1, R2, and R3)
pathways. Error bars represent standard error of the means. Mean ratings with
different letters at either low or high concentration level represent a significant
difference at p < 0.05.
Fig. 4. Mean ratings of texture pleasantness for cheese stimuli in the absence
(control) or the presence of butter odor. Odor stimulus at either a low or a high
concentration was presented via orthonasal (O1) or retronasal (R1, R2, and R3)
pathways. Error bars represent standard error of the means. Mean ratings with
different letters at either low or high concentration level represent a significant
difference at p < 0.05.
cheese type in the intensity ratings of the butter note (F = 1.15,
p = 0.34). Butter note intensities significantly differed by odor condition (F = 6.50, p < 0.001), with the butter note intensity being significantly higher in all odor conditions as compared to control conditions (i.e., no odor), as shown in Fig. 3. In addition, perceived butter
note intensity was highest when the odor was delivered during chewing
(R2). Intensities of butter note during chewing (R2) was greater than
those before chewing (i.e., orthonasal condition, “O”) and in the control
condition (Fig. 3). Intensity ratings of butter note were significantly
greater in relation to the fat level of cheese stimuli (F = 11.29,
p < 0.001), with highest butter note ratings for HF, followed by MF
and the LF cheese stimuli.
cheese type in the pleasantness ratings of cheese texture (F = 0.84,
p = 0.57). Pleasantness ratings of cheese texture were not significantly
different by odor condition (F = 0.27, p = 0.90) (Fig. 4). Pleasantness
ratings of cheese texture significantly increased with a fat level of
cheese stimuli (F = 10.26, p < 0.001), with the highest texture liking
for FF, followed by MF and the LF cheese stimuli.
3.5. Overall flavor
3.5.1. Low concentration level of butter odor
A significant interaction between odor condition and cheese type
was observed in the intensity ratings of the overall flavor of cheese
stimuli (F = 2.48, p = 0.02). More specifically, a significant effect of
odor condition on overall flavor intensity was present with MF cheese
(F = 3.12, p = 0.02); the ratings for overall flavor intensity were significantly higher at O condition as compared to R1 (p = 0.03), but not
with LF (F = 2.13, p = 0.09) or HF (F = 0.53, p = 0.72) cheese stimuli
(Fig. 5). There was no significant effect of odor condition (F = 0.29,
p = 0.89) or cheese type (F = 2.60, p = 0.09) on intensity ratings of
3.3.2. High concentration level of butter odor
There was no significant interaction between odor condition and
cheese type in the intensity ratings of butter note (F = 0.63, p = 0.75).
Butter note intensities were significantly different by odor condition
(F = 6.24, p < 0.001). Similar to the trend at the lower concentration
level of butter note, butter note intensities in the control condition (i.e.,
no odor) were significantly lower than other conditions with butter
odor presentation, and butter note intensities in the R2 condition were
greater than those in the O and control conditions (Fig. 3). Intensity
ratings of butter note significantly increased with the fat level of cheese
stimuli (F = 7.09, p = 0.002), with highest butter note ratings for HF,
followed by MF and the LF cheese stimuli.
3.4. Pleasantness of cheese texture
3.4.1. Low concentration level of butter odor
There was no significant interaction between odor condition and
cheese type in the pleasantness ratings of cheese texture (F = 0.68,
p = 0.71). Pleasantness ratings of cheese texture were significantly
different as a function of odor condition (F = 2.86, p = 0.03), with
higher ratings of texture pleasantness in the O condition than in the R3
condition; there were no other pairwise differences between odor
conditions (Fig. 4). Pleasantness ratings of cheese texture significantly
increased with a fat level of cheese stimuli (F = 11.10, p < 0.001),
with the highest texture liking for FF, followed by MF and the LF cheese
stimuli.
Fig. 5. Mean ratings of overall flavour intensity for cheese stimuli varied in
their fat content (MF, medium-fat; HF, high-fat; LF, low-fat) in the absence
(control) or the presence of butter odor presented at a low concentration via
orthonasal (O1) or retronasal (R1, R2, and R3) pathways. Error bars represent
standard error of the means. Mean ratings with different letters at either low or
high concentration level represent a significant difference at p < 0.05.
3.4.2. High concentration level of butter odor
There was no significant interaction between odor condition and
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Fig. 6. Bi-plots of principal component analysis (PCA) showing the associations of four odor conditions with creaminess, butter note, and overall flavor intensities
and texture pleasantness of cheese stimuli as a function of odor concentration level: low (A) and high (B) concentration levels of butter odor.
overall flavor.
The enhancement of perceived cheese attributes by added butter
odor is in line with the temporal congruency for cross-modal sensory
perceptions. First, creaminess ratings increased when the butter odor
was presented retro-nasally at the start of chewing (R1). This finding is
in line with the temporal congruency theory for cross-modal sensory
integration, in which the enhancement of cheese sensory attributes by
retronasal odors depends on a temporal binding window (Isogai & Wise,
2016). This is the point when the cheese interacts with oral surface and
saliva, and the initiation of the physical breakdown (de Wijk et al.,
2006). Similar findings were observed for liquid dairy products (i.e.
milk) (Bult et al., 2007). Other studies found higher ratings of fatty
intensity without nose clips compared with nose clips on, indicating the
role for retronasal odor perception on texture perception (Zhou, Shen,
Parker, Kennedy, & Methven, 2016). In addition, human neuroimaging
study showed retronasal odor stimulation was related to brain activation at the base of the central sulcus, corresponding to the primary
representation of the oral cavity, possibly reflecting that retronasal
odors are referred to the mouth (Small, Gerber, Mak, & Hummel, 2005).
Another study reported the enhanced activation of the mechanosensory
area in response to sweetened milk when a butter note odor was presented via retronasal route (Iannilli et al., 2014). Moreover, the textural
and olfactory inputs converge in the insular cortex which serves as the
neural mechanism for the cross-modal sensory enhancement (Rolls,
2012; Small, 2012).
The butter note intensity peaked when the odor was presented
retronasally while the cheese was being chewed but before swallowing
(R2 condition). This timing is mainly followed by an exhalation where
the volatile compounds travel to the olfactory receptor via the retronasal route (Roudnitzky et al., 2011). Butter note is mainly contributed
by diacetyl which is released from the cheese during chewing (Curioni
& Bosset, 2002). This finding suggests that the butter note is perceived
while the cheese is under oral processing and the key volatile and nonvolatile compounds are released from the cheese-saliva bolus (Feron
et al., 2014). As for the texture pleasantness, an increased rating was
observed when butter odor was presented orthonasally at the lower
concentration. This mimics the situation in which the cheese odor
reaches the consumers’ nose before chewing the cheese. This suggests
an influence of odor on the expectation of texture pleasantness. Again,
this finding is in line with previous findings showing that odors can
affect texture attributes and vice versa (Bult et al., 2007). However, the
enhancement of perceived cheese creaminess and overall flavor intensity was more pronounced when the butter odor was presented at
the lower concentration. This might be due to the higher odor
3.5.2. High concentration level of butter odor
There was no significant interaction between odor condition and
cheese type in the intensity ratings of the overall flavor of cheese stimuli (F = 0.94, p = 0.48). Intensity ratings of the overall flavor did not
differ in relation to the odor condition (F = 1.27, p = 0.29) or the
cheese type (F = 2.63, p = 0.09).
3.6. Associations of odor condition with attribute intensity and liking
Biplot representations of the principal component analysis (PCA)
performed for the low and high odor concentration levels are shown in
Fig. 6. The first principal component (PC1) accounting for 64.09% and
79.22% of the total variance is related to the temporal congruency
(timing of odor presentation), and separated butter note from other
sensory attributes. The second component (PC2) accounted for 26.20%
and 20.05% of the total variance and suggested an overall enhancement
of the cheese sensory attributes by added odor (Fig. 6).
The PC1 in both low and high odor concentration conditions mainly
represents information linked to butter note intensity. At both odor
concentration levels, there was a positive association between butter
note intensity and added odor via retronasal route especially at R2
(Fig. 3A and 3B). When cheese was consumed in the presence of butter
odor at a low concentration level, the creaminess intensities were more
associated with retronasal odors presented at the onset of chewing (R1)
(Fig. 3A), however, the added odor (R1) at the high concentration had
little impact on the creaminess intensity (Fig. 3B). Additionally, we saw
more differentiation between attributes and conditions in the low
compared to the high odor concentration.
4. Discussion
The present study confirmed the effects of an added butter odor on
perceived creaminess, butter note, total flavor and the texture pleasantness for cheese with different levels of fat contents. The odor presentations varied in pathways (either ortho- or retro-nasal) and timings
(at the start of chewing, during chewing or during swallowing). The
results demonstrated enhancement of creaminess ratings and butter
note intensity, as well as texture liking by the added odor which varied
with the timing of presentation, and cheese type (fat content). In addition, the observed effects were more pronounced when the odor was
added at a lower odor concentration.
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Conflicts of interests
concentration being perceived as less pleasantness (Sano, Tsuda,
Sugano, Aou, & Hatanaka, 2002).
Results from the current study suggested the enhancement of perceived cheese sensory attributes were dependent on the added odor
concentration, with higher effectiveness at lower compared to higher
butter odor concentrations. This was also reflected in a more differential pattern between attributes and conditions in the low compared to
the high odor concentration in PCA result. It was possible that the
higher odor concentration, twice as high as the detective threshold,
evoked irritation, which may, in turn, diminish the effect of odor-taste
enhancement. Besides, higher odor concentration may be also related to
changed quality (Gross-Isseroff & Lancet, 1988) or valence perceptions
(Rouby, Pouliot, & Bensafi, 2009). Previous studies have reported the
taste enhancement by odor at relatively lower rather than higher concentration levels (Labbe et al., 2007; Seo et al., 2013).
Findings from the current study may have implications for developing novel foods with nutritional benefits. For example, it has been
shown that oro-sensory cues (such as creaminess) increased the satiating effect of a protein-rich beverage (Bertenshaw, Lluch, &
Yeomans, 2013). Thicker products were able to generate expectations
that they are more filling compared to their thinner counterparts
(Hogenkamp, Stafleu, Mars, Brunstrom, & de Graaf, 2011; McCrickerd,
Chambers, Brunstrom, & Yeomans, 2012). Moreover, stronger sensory
attributes could also contribute to satiety through a top-down modulation of hormone release (Yeomans, Re, Wickham, Lundholm, &
Chambers, 2016), which may reduce the excessive consumption of
high-fat foods. Therefore, the odor-enhanced texture perception may
help to formulate foods with With increased satiating properties, but
without adding calories (de Graaf, 2012). This provides insights to
formulating food products with low calories density while preserving
pleasantness and having higher satiating properties (Campbell,
Wagoner, & Foegeding, 2017; Saint-Eve, Lauverjat, Magnan, Déléris, &
Souchon, 2009). However, results from the current study also indicate
that odor enhancing is highly specific and depends on factors such as
the fat content of the food, the type, and concentration of the odor.
The current study has some limitations. First, the study was performed in young participants with a narrow age range, in order to
minimize potential effects of age on olfactory function, and, hence, on
sensory evaluation. However, the results may not be representative of
the general population. The participants were not trained so that individual differences regarding the interpretation of certain sensory attributes may confound the results. For example, while the flavor is
commonly known as the integration of taste, aroma, and trigeminal
sensations, it is often confused with orthonasal olfactory perception;
evaluation of selected sensory attributes in the current study emerged
from integrated sensations of visual, olfactory, gustatory, and tactile
cues (Chen & Eaton, 2012). A group of experienced panelists would
make the findings more reliable. Second, since the study used a single
odorant with butter note, it is possible that the effect of butter odor is
potent and specific for certain sensory attributes; it may be weak for
others, given the complexity of cheese flavor. Future studies could use
other key odors derived from cheese that contribute to certain sensory
characteristics. Third, although we controlled the timing of odor delivery, the oral processing was ad libitum which may result in different
levels of flavor release between conditions. Besides, 5% of butter odor
was assigned for the threshold level for most of the participants, which
also the lowest concentration level used for the threshold testing.
Therefore, it was possible that the actual threshold level was below
than 5%, which may result in different outcomes. Lastly, tiredness due
to long testing duration and satiety effect with cheese consumption over
time may have impacted on the results shown here.
In conclusion, the current study adds to the increasing knowledge
that sensory perception can be modified substantially by adding an
odor which is an expression of the intimate connection between all the
sensory channels involved in flavor perception.
The authors declare no conflict of interest.
Acknowledgements
This study was supported by a grant from the Deutsche
Forschungsgemeinsschaft to TH (DFG HU411/18-1).
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.foodqual.2018.11.019.
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