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Aroma-taste interactions and heterogeneous spatial distribution of tastants were used as strategies for taste enhancement. This study investigated the combination of these two strategies through the effect of heterogeneous salt and aroma distribution on saltiness enhancement and consumer liking for hot snacks. Four-layer cream-based products were designed with the same total amount of sodium and ham aroma but varied in their spatial distribution. Unflavoured products containing the same amount of salt and 35% more salt were used as references. A consumer panel (n=82) rated the intensity of salty, sweet, sour, bitter and umami tastes as well as ham and cheese aroma intensity for each product. The consumers also rated their liking for the products in a dedicated sensory session. The results showed that adding salt-associated aroma (ham) led to enhancement of salty taste perception regardless of the spatial distribution of salt and aroma. Moreover, products with a higher heterogeneity of salt distribution were perceived as saltier (p<0.01), whereas heterogeneity of ham aroma distribution had only a marginal effect on both aroma and salty taste perception. Furthermore, heterogeneous products were as well liked by consumers compared to the homogeneous products.
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Food &
Function
PAPER
Cite this: DOI: 10.1039/c4fo01067a
Received 21st November 2014,
Accepted 14th March 2015
DOI: 10.1039/c4fo01067a
www.rsc.org/foodfunction
Combined heterogeneous distribution of salt and
aroma in food enhances salt perception
Marion Emorine,
a,b,c
Chantal Septier,
a,b,c
Isabelle Andriot,
a,b,c
Christophe Martin,
a,b,c
Christian Salles*
a,b,c
and Thierry Thomas-Danguin
a,b,c
Aromataste interactions and heterogeneous spatial distribution of tastants were used as strategies for
taste enhancement. This study investigated the combination of these two strategies through the eect of
heterogeneous salt and aroma distribution on saltiness enhancement and consumer liking for hot snacks.
Four-layered cream-based products were designed with the same total amount of sodium and ham
aroma but varied in their spatial distribution. Unavoured products containing the same amount of salt
and 35% more salt were used as references. A consumer panel (n= 82) rated the intensity of salty, sweet,
sour, bitter and umami tastes as well as ham and cheese aroma intensity for each product. The consu-
mers also rated their liking for the products in a dedicated sensory session. The results showed that
adding salt-associated aroma (ham) led to enhancement of salty taste perception regardless of the spatial
distribution of salt and aroma. Moreover, products with a higher heterogeneity of salt distribution were
perceived as saltier (p< 0.01), whereas heterogeneity of ham aroma distribution had only a marginal
eect on both aroma and salty taste perception. Furthermore, heterogeneous products were well liked by
consumers compared to the homogeneous products.
Introduction
High dietary salt (NaCl) intake is recognised as an important
causal factor in elevated blood pressure, the leading risk for
premature death in the developed and developing world.
1,2
Moreover, a high dietary salt intake is associated with several
health issues, including stroke, cardiovascular events, gastric
cancer, kidney disease and, indirectly, obesity.
3
Health
agencies throughout the world recommend a drastic reduction
in salt intake,
46
and actions with this aim have been pro-
moted in many countries.
7
However, salt is a multifunctional
component in food. It performs many functions that can be
interrelated and interdependent
8
such as preservation,
9
water-
binding, and texture processing.
10
In addition, reduction of
salt in food products changes the sensory properties of pro-
cessed food. Salt is not only a stimulus that elicits the percep-
tion of saltiness, but it also influences the overall flavour
perception.
11
A reduction in salt may influence the temporal
release of volatiles, which has been shown to be dependent
not only on the salt concentration but also on the hydrophobi-
city of the volatile compounds.
12
In many cases, lowering salt
content in foods is associated with a loss of liking and a
decrease in consumersacceptance of the product.
1315
More-
over, food flavour characteristics are very important in the
decision to purchase or repurchase a food.
16
Thus, the
reduction of salt content in processed food without loss of
consumer acceptability has become one of the major issues
for food manufacturers.
17,18
Among the strategies investigated to compensate for salt
reduction in food
19
is the manipulation of the delivery of taste
stimuli to enhance taste perception.
20
Indeed, as reported for
sweetness in liquid models,
21
salt perception in the mouth has
been found to be enhanced by pulsatile stimulations.
22
This
principle has been further extended to layered gels that alter-
nate between low and rich domains of tastants, showing that
heterogeneous distribution of tastants increases taste percep-
tion.
23,24
It has been proposed that a heterogeneous spatial
distribution of salt in complex food matrices could help in the
maintenance of salt perception in low-salt bread and hot
snacks.
25
Recently, a large contrast in salt concentration in a
hot served four-layered cream based food was reported to
enhance the perception of saltiness.
26
Moreover, it is
noteworthy that similar observations were reported on aroma
perception for a heterogeneous distribution of volatile
compounds in gels.
27,28
Another strategy currently under investigation to compen-
sate for sensory loss in low-salt food proposes to take advan-
a
CNRS, UMR6265 Centre des Sciences du Goût et de lAlimentation, F-21000 Dijon,
France. E-mail: salles@dijon.inra.fr; Fax: +33 380 69 32 27; Tel: +33 380 69 30 79
b
INRA, UMR1324 Centre des Sciences du Goût et de lAlimentation, F-21000 Dijon,
France
c
Université de Bourgogne, UMR Centre des Sciences du Goût et de lAlimentation,
F-21000 Dijon, France
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tage of the cross-modal interactions between odour and taste
to enhance taste intensity.
2931
The perception of flavour is
hence a multisensory process involving the integration of taste
and odour as a function of their congruency, relying on consu-
mersprevious food experiences, memory or culture.
32,33
Indeed, perceptual interactions can occur when taste and
odour are congruent, so that taste can modulate smell and vice
versa.
29,3436
Numerous studies have investigated tasteodour
interactions on sweet perception, but few have studied the salt
perception.
3739
It was recently demonstrated that salt-associ-
ated odour can increase the salt perception of water solutions
containing a low concentration of sodium chloride.
40
Odour-
Induced Saltiness Enhancement (OISE) was also found to be
operant in low-salt solid food matrices.
41
Until now, the strategies proposed to compensate for salt
reduction in food products could compensate for a 25% to
30% sodium reduction.
11
It is likely that a method to compen-
sate for higher reductions in the salt level in processed food
would rely on the combination of several strategies. In the
present study, we set out to examine whether the hetero-
geneous spatial distribution of salt associated with a hetero-
geneous spatial distribution of a salt-associated aroma would
enhance salty taste perception and significantly and additively
increase saltiness perception compared to results obtained for
a single strategy. Since we were interested in evaluating
whether such a combined strategy could help to maintain con-
sumer acceptability for low-salt everyday food, we performed
our sensory experiments with a panel of consumers rating
salty taste intensity and liking for hot-served multilayered-
cream-based model snacks which were designed with the
same total amount of sodium and salt-associated aroma but
varied in their spatial distribution.
Experimental
Materials
The multilayered model snack consisted of a four-layered
cream-based product (FLP) made of whipping cream (30% fat)
(LNA, Le Moulin Henry, France), pasteurised eggs (Blanchard,
Lannergat, France), Emmental cheese (Tippagral, Dijon,
France), modified food starch (Colflo 67, National Starch &
Chemical, Hamburg, Germany), T80 wheat flour (Elevia, Fay-
moreau, France), xanthan gum (Rhodigel Easy, Rhodia Food,
France), table salt (Salin du Midi, Aigues-Mortes, France), ham
aroma (Silesia, Gouvieux, France) and mineral water (Evian,
France). Dry ingredients were stored at room temperature and
wet ingredients were stored at 4 °C. The same batch of raw
materials was used to make all the products for both studies.
Preparation of the four-layered products
Ten FLPs containing the same total amount of salt and ham
aroma, 5(w/w) and 0.5(w/w), respectively, were pro-
duced. The spatial distribution of salt and aroma was dierent
from one layer to another (Fig. 1). The products were coded
according to the distribution of salt (S) and ham aroma (A). In
the indices, the letter
H
refers to a homogeneous distribution
of stimuli, whereas the numbers
1
to
4
refers to the spatial
localisation of stimuli in the product; for example, S
1
A
4
refers
to the product with salt added in the top layer (1) and aroma
added in the bottom layer (4). Moreover, a FLP without added
ham aroma was used as an unflavoured reference (S
H
) and an
unflavoured FLP containing 35% more salt was used as a
saltier reference (S
H+
).
The FLPs were prepared according to a well-established pro-
cedure.
26
All the ingredients were mixed for 2 min (400 W
mixer, Seb, Selongey, France), the xanthan gum (Rhodigel
Easy, Rhodia Food, France) was added, and the dough was
mixed again for 2 min. The dough was spread in silicon
moulds (Flexipat, Demarle, Wavrin, France) and heated at
140 °C for 17 min in a vertical convection oven (Tecnox, Inox-
trend, Lucia Di Piave, Italy). Each layer (average thickness
0.5 cm) was chilled for 30 min at room temperature. The four
layers were piled-up, and in order to make the layers stick
together they were stored at 20 °C for 30 min. The four-
layered matrices were then cut into small pieces (2.5 × 2.5 cm;
9.5 g ± 0.5). The FLP samples were stored for 3 weeks at
20 °C, in aluminium trays closed on top with a cardboard lip,
until reheating on the day of analysis (sensory, liking and
physicochemical analyses).
Rheological measurements
To ensure that the various spatial distributions of salt and
aroma did not alter the rheological properties of the FLP,
Texture Profile Analysis (TPA) was performed on each product
(4 replicates) with a Texture Analyser TA HD plus (Stable Micro
Systems, England) at 21.5 °C.
On the day of analysis, the frozen FLP samples were pre-
pared in the same way as for sensory and liking evaluations
but they were allowed to cool until room temperature. The
samples were then placed at 21.5 °C for 20 min for tempera-
Fig. 1 Four-layered cream-based products. Black numbers on the left indicate the added salt concentration in each layer, grey italic numbers on
the right indicate the added ham aroma concentration in each layer.
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ture equilibration prior to analysis. The temperature of the
samples was controlled before TPA measurements.
Two-cycle compressions were performed at a constant
speed of 0.5 mm s
1
. The FLP samples were compressed with
a plate of 10 cm until a deformation rate of 75% of the initial
height was induced. After a backup at 1.5 mm s
1
, a second
cycle compression was run under the same conditions. The
developed forces were measured with a load cell (30 kg). The
obtained parameters were, as already described,
42
the hard-
ness (N), cohesiveness (dimensionless), springiness (mm) and
adhesiveness (N mm).
Salt concentration measurements
HPLC Ionic Chromatography (ICS Chain 3000, Dionex, Voisins
le Bretonneux, France) was used to determine the overall salt
content of the whole FLP and in each layer (in triplicate) to
check for between-layer salt diusion. Sodium was analysed
with an IonPac CS12A column 5 μm at 25 °C and detected by
conductivity with a CSRS 300 2 mm suppressor. A piece of
sample (1 g) was dispersed in 15 mL purified water (MilliQ
system, PureLab, ELGA, UK) using ultraturax® apparatus (Ika,
Werke, Sweden) at 13 500 rpm for 2 min, then centrifuged for
5 minutes at 10 000g(Dutscher, Brumath, France). The
obtained supernatant was diluted in MilliQ water and filtered
(filter pore size 0.45 μm, CIL, Sainte-Foy-la-Grande, France).
H
2
SO
4
(11 mM) was used as the eluent at a flow rate of 0.5 mL
min
1
. The injection loop was set at 20 µL. The system control
and data acquisition were performed using UCI-100 Chrome-
leon software (version 6.8, Dionex, Voisins le Bretonneux,
France).
Aroma concentration measurements
A headspace/solid phase micro-extraction/gas chromato-
graphy/mass spectrometry (HS-SPME-GC-MS) method was
used to evaluate the diusion of volatile components between
the four layers of the model snacks.
Samples. Among the twelve FLP products, five presenting
various spatial distributions of salt and ham aroma were
selected to characterise between-layer aroma diusion. More-
over, in order to increase sensitivity, the FLP recipe was modi-
fied as follows: a tracer, ethyl propanoate (Sigma Aldrich,
Saint-Quentin-Fallavier, France), was added to the ham aroma
at a concentration of 50 µL kg
1
while the ham aroma concen-
tration was increased up to 3(w/w). These FLPs (Table 2)
were prepared and cooked following the procedure previously
described (see the Preparation of the four-layered products
section). The concentration of the aroma compounds was
measured on the whole products and in each layer in order to
evaluate the overall aroma concentration and between-layer
aroma diusion. For a comparison between the dierent FLPs,
only the peak area of the aroma compounds was considered.
Analysis of aroma compounds. An optimisation of the
extraction conditions for the volatiles to be analysed was per-
formed in a preliminary study (not shown). The final con-
ditions were as follows. The odorant extractions were carried
out by placing 7 g of FLP mixed with 7 g of MilliQ water into
20 mL vials. Each FLP sample was prepared in triplicate. The
vials were immediately closed with a septum cap and placed in
the incubator of an automatic autosampler (GERSTEL MPS 2,
Gerstel Inc., Mülheim an der Ruhr, Germany) at 30 °C for
120 min. Subsequently, a DVB/CAR/PDMS (Stableflex 2 cm
50/30 µm) SPME fibre (Supelco Co. Bellefonte, USA) coated
with porous carbon was introduced into the vial and exposed
to the headspace of the samples for 45 min and then injected
into a gas chromatograph. All the odorant extractions were per-
formed using the same SPME fibre.
The SPME fibre was inserted into the splitless/split injector
(250 °C for 5 min in splitless mode, and an additional 10 min
in split mode in order to regenerate the fibre) of a gas
chromatograph (GC, HP6890 Hewlett-Packard, Palo Alto, CA)
equipped with a fused-silica capillary DB-WAX column (30 m,
0.32 mm i.d., film thickness 0.5 µm; Agilent, Folsom, CA,
USA). The linear velocity of the carrier gas, helium, was 44 cm
s
1
. The GC oven temperature was programmed from 40 °C to
240 °C at a rate of 3 °C min
1
and held at 240 °C for 10 min.
Mass spectrometry was performed on a mass selective detector
model MS 5973 (Agilent Technologies, Palo Alto, CA) operated
in electron impact mode (70 eV). The mass spectrometer
scanned masses from m/z29 to 350. The ion source tempera-
ture was set at 230 °C. The identification of the volatile com-
pounds was carried out by comparison of their mass spectra
with those of the standard compounds and with those from
the Wiley library and also by comparing their retention
indexes with those of standard compounds and data from the
literature. Linear retention indexes (RI) of the compounds
were calculated using a series of alkanes (C
10
C
30
) injected
under the same chromatographic conditions.
For quantification, the mass spectrometer was used in
selected ion monitoring (SIM) mode: ethyl propanoate, m/z75,
57, 102; limonene, m/z68, 93, 136; 2-acetylthiazole, m/z99,
127, 112; 2-methoxyphenol, m/z109, 81, 124. The quantifi-
cations were achieved with ion m/z68 for limonene, m/z75 for
ethyl propanoate, m/z99 for 2-acetylthiazole, and m/z109 for
2-methoxyphenol. These ions, which were not present in the
unflavoured reference (S
H
), were chosen for their relative ion
abundances and lack of interference with other compounds.
Sensory evaluations
This study was carried out in accordance with the relevant
institutional and national French regulations and legislation
(Comité de Protection des Personnes Est-1, France, no. 2011/
46, and the French Agency for the Safety of Healthcare Pro-
ducts, AFSSAPS, France, no. 2011-A00807-34) and with the
World Medical Association Helsinki Declaration as revised in
October 2008. All the subjects signed an informed consent
form and were compensated for their participation (10 euros
for a one-hour session). All sessions took place in an air-
conditioned (21 ± 1 °C) tasting room of the Chemosens platform
(INRA Dijon) with single booths equipped with FIZZ® software
(Biosystèmes, Couternon, France). During the sensory sessions
and before each tasting, the frozen samples were heated in a
vertical convection oven (Tecnox, Inoxtrend, Lucia Di Piave,
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Italy) for 4 min at 240 °C and served 1.5 min later at 55 °C. The
temperature of the samples was controlled using an electronic
temperature probe Checktemp1 Pocket Thermometer (HANNA
instruments, Dutcher, France).
Panel selection procedure. One hundred and twenty nine
consumers (84 women, 45 men, mean age 44) participated in a
preliminary selection test in which they were asked to evaluate
the taste and flavour intensity of cottage cheese samples.
These samples were made of cottage cheese (20% fat content,
Maîtres laitiers du Cotentin, Sottevast, France) in which one of
the following tastants or aromas was added: sodium chloride
(Cooper, Melun, France), saccharose (Cooper, Melun, France),
lactic acid (Fisher Scientific, Fair Lawn, NJ), anhydride caeine
(Cooper, Melun, France), monosodium glutamate (Cooper,
Melun, France), ham aroma (Silesia, Gouvieux, France) or
Emmental cheese aroma (Silesia, Gouvieux, France). Three
dierent concentrations for each tastant or odorant were used,
so that a total of 21 dierent cottage cheese samples were
tested by the panel. Participants were asked to rate the inten-
sity of tastes (salty, sweet, sour, bitter, umami) and aroma
(ham, Emmental cheese) on linear scales from 0 to 10 (0: very
weak, 10: very strong). The samples were evaluated according
to a monadic evaluation procedure and presented in a
balanced order according to a William Latin square design.
Panellists were asked to cleanse their mouth with Evian water
between each sample.
Points were attributed according to the correct rating
(expected ranking) of the 3 concentrations for each descriptor
as follows: 2 points when the 3 concentrations were rated in
the correct order, 1 point when 2 adjacent concentrations were
inverted, 0 points in other cases. To be selected for the study
on FLP, panellists had to obtain (i) at least 1 point for the salt
ranking test, (ii) at least a total of 7 out of 14 points (7 attri-
butes × 2 points), which is the maximum score for all tests,
and (iii) no more than 2 zero point instances among all tests.
Eighty-two consumers (58 women, 24 men, between 19 and 71
years of age, mean age 44) were finally selected for the sensory
study on FLP.
Selected participants declared that they were not suering
from food and other allergies and had no problem perceiving
taste or smell. They were requested not to smoke and eat one
hour before the sensory sessions.
Descriptive analysis. The 12 FLPs were evaluated in the
same session according to a monadic evaluation procedure
and presented in a balanced order according to a William
Latin square design. Red light was used to minimise visual
cues.
The 82 panellists were asked to eat the whole product
sample (2 samples of each product were served) and to rate
taste intensity (sour, bitter, salty, sweet and umami) and per-
ceived aroma intensity (ham and Emmental cheese) on linear
scales from 0 to 10 (0: very weak, 10: very strong). A warm-up
sample, i.e., the FLP with a homogeneous distribution of salt
and aroma (S
H
A
H
) was presented first in order to familiarise
panellists with the product and the task. This sample was not
included in the data analyses. Each panellist consumed a
maximum of 228 g of FLP for the session. A one-minute break
was imposed between each product, while panellists were
asked to cleanse their palate with apple in order to quickly
eliminate the fat layer coating the mouth and then with
mineral water (Evian, France) to cleanse apple particles.
Liking test. The liking test, carried out under the same con-
ditions as for the descriptive analysis, with the same batch of
products and with the same panel, took place 2 weeks later.
The participants were asked to eat the whole product and to
rate their liking on a linear scale from 0 to 10 (0: I do not like,
10: I like very much).
Data analyses
All data analyses were carried out using STATISTICA® Software
(version 10, StatSoft, France). Analyses of variance (ANOVA)
and multivariate analysis of variance (MANOVA) were carried
out with a general linear model (GLM). StudentNewman
Keuls (SNK) tests were used for post hoc multiple comparisons
of the means. For all data analyses, the eects were considered
significant when p< 0.05.
Results and discussion
Rheological properties
Measurements were carried out to control the influence of the
spatial distribution of salt and ham aroma on the rheological
properties of the FLP. A 2-way MANOVA was performed on the
4 measured rheological parameters (hardness, cohesiveness,
springiness and adhesiveness) with products and replications
as fixed factors. A weakly significant replication eect was
found (Wilksλ= 0.19, F(12, 79.7) = 2.2, p= 0.020), but not a
significant product eect. This result indicated that salt and
aroma distributions had no eect on the rheological pro-
perties of FLP. The replication eect could result from slight
inhomogeneity in the sample heating process, which could
have induced slight between-product dierences.
Salt concentration and diusion
The actual salt concentration in the FLPs was measured by
HPLC, which allowed for the assessment of salt diusion
within the products. The measured salt concentrations in the
dierent layers ranged between 3.3and 20.8according
to the product configuration (Table 1) while the salt concen-
tration in the cream-based product without added salt was
4(SD = 0.3). A 2-way ANOVA (replications and products as
fixed factors) on the overall salt concentration in the FLPs
revealed no significant replication eect, but a significant
product eect (F(11, 22) = 3.16; p= 0.011). Post-hoc multiple
comparisons of means indicated that, as expected, only the
35% more salted reference (S
+
) contained significantly more
salt than all the other samples (Table 1). ANOVA were also
carried out on the salt concentration in each layer of each
product (layer and replication as fixed factors). For each FLP,
no significant replication eect was found. For samples with
homogeneous salt distribution (S
H
,S
H+
,S
H
A
H
,S
H
A
1
,S
H
A
2
),
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Table 1 Salt concentrations measured, in triplicate, by HPLC in the whole four-layered cream-based products and in each layer. The nal salt concentrations were measured at the moment of
consumption, i.e., after pre-cooking, freezing, and nal baking. According to the StudentNewmanKeuls test, the same capital letters indicate no signicant dierence between products for
the overall salt concentration, whereas the same small letters indicate no dierence between layers for the nal salt concentration. sd: standard deviation
Product name Product design
Overall NaCl
concentration Layer 1 Layer 2 Layer 3 Layer 4
() sd NaCl ()* sd NaCl ()* sd NaCl ()* sd NaCl
a
()sd
Homogeneous salt distribution products
S
H
7.09
A
1.1 7.6
a
0.1 7.11
a
0.9 7.32
a
0.5 7.23
a
0.7
S
H
+ 11.1
B
1.8 12.33
a
0.6 13.08
a
1.8 12.15
a
3.3 11.99
a
0.5
S
H
A
H
7.52
A
0.4 8.53
a
0.6 7.32
a
0.2 7.37
a
0.4 8.39
a
1.0
S
H
A
1
7.44
A
0.4 8.64
a
0.6 7.78
a
0.2 7.87
a
0.6 9.57
a
1.1
S
H
A
2
8.86
A
0.7 8.98
a
0.5 8.18
a
0.5 8.63
a
0.6 9.07
a
0.8
Heterogeneous salt distribution products
S
1
A
H
7.66
A
1.2 12.5
a
1.4 8.37
b
0.7 4.20
c
0.1 3.32
c
0.1
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Table 1 (Contd.)
Product name Product design
Overall NaCl
concentration Layer 1 Layer 2 Layer 3 Layer 4
() sd NaCl ()* sd NaCl ()* sd NaCl ()* sd NaCl
a
()sd
S
2
A
H
7.03
A
1.1 7.4
b
0.7 10.67
a
0.3 7.20
b
0.5 3.78
c
0.6
S
1,3
A
1,3
9.34
A
0.2 10.41
b
0.7 6.73
c
0.2 11.6
a
0.4 7.02
c
0.1
S
1
,-A
2,4
8.68
A
0.8 10.79
a
0.4 8.07
b
1.2 7.9
b
0.5 6.42
c
0.0
S
1
A
1
8.34
A
2.5 17.63
a
2.2 8.74
b
0.2 4.20
c
0.5 3.38
c
0.2
S
2
A
2
9.44
A
0.2 11.11
a
1.3 11.61
a
0.4 8.90
ab
0.3 4.85
b
0.4
S
1
A
4
8.82
A
1.4 20.84
a
1.8 8.21
b
0.8 4.43
c
0.6 3.92
c
0.4
a
Final NaCl concentration. For product design, salt and aroma contents are in .
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no significant layer eect was found (Table 1). For the samples
containing two salted layers (S
1,3
A
1,3
,S
1,3
A
2,4
), a significant
layer eect was found (F(3, 6) > 27.8, p< 0.00012). Post-hoc ana-
lysis showed that the actual salt distribution resulted in three
dierent concentration levels instead of the expected two. For
the products containing only one salted layer (S
1
A
H
,S
2
A
H
,
S
1
A
1
,S
2
A
2
,S
1
A
4
), the 2-way ANOVAs revealed significant
layer eects (F(3, 6) > 45.3; p< 0.0001). For the samples S
1
A
H
,
S
1
A
1
, and S
1
A
4
,post hoc analyses showed that the salted layer
(layer 1 or 4) was significantly dierent from the other three
layers in which no salt was added, but the just adjacent non-
salted layer was also significantly dierent from the other two
non-salted layers (Table 1). For the sample S
2
A
H
, the salted
layer (layer 2) contained significantly more salt than non-
salted layers 1 and 3, which were also significantly dierent
from the non-salted layer 4 (Table 1). For the sample S
2
A
2
, the
salted layer (layer 2) was significantly dierent only from layer
4 (Table 1). These results highlighted that salt diusion
occurred from the salted layer to the adjacent non-salted layers
depending on the salted layer position within the product.
However, despite salt diusion likely induced by the heating
process, the heterogeneity of salt distribution in the products
remained in conformity with the experimental design.
Aroma diusion
The actual aroma compound concentrations in the FLPs were
measured by HS-SPME-GC-MS. Moreover, as the heating
process can modify the initial spatial distribution of the
aroma, the actual aroma compound concentrations (related to
the peak area) were measured in each layer to check whether
heterogeneity of aroma distribution was maintained. A 2-way
MANOVA (replications and products as fixed factors) was
carried out on the peak area of the 4 monitored ions (m/z68,
m/z75, m/z99, m/z109) corresponding to the 4 aroma com-
pounds studied. No significant replication eect was found,
but a significant product eect was revealed (Wilksλ= 0.004,
F(16, 15.9) = 5.1, p= 0.001). Post-hoc tests indicated no signifi-
cant dierence between FLPs for the 2-acetylthiazole (m/z99)
and 2-methoxyphenol (m/z109). However, the S
1
A
4
product
tended to contain less ethyl propanoate (tracer, m/z75) than
the 4 other aromatised products (Table 2). In this product, and
compared to the S
1
A
1
one, no salt was added in the aroma-
tised layer resulting in the lowest salt concentration associated
with aroma compounds (Table 1). This could have aected the
aroma compound release by decreasing the release as a conse-
quence of a lower salting out eect.
4345
Moreover, such an
eect has likely been observed only for ethyl propanoate
because this aroma compound was added at a higher concen-
tration (tracer) and because the salting out eect has been
reported to depend on the polarity of the aroma com-
pounds.
12,46
Subsequently, 2-way MANOVA was performed for
each FLP on the 4 monitored ions with replication and layer as
fixed factors (Table 2). For FLPs with a homogeneous aroma
distribution (S
H
A
H
and S
1
A
H
models), no significant eect of
replication or layer factors was found. These results indicated
that no aroma diusion occurred between layers during
heating of the products with a homogeneous aroma distri-
bution, regardless of salt distribution. For FLPs with a hetero-
geneous aroma distribution (S
H
A
1
,S
1
A
1
,S
1
A
4
), 2-way
MANOVA yielded no significant eect of replication, but a sig-
nificant eect of the layer factor (Wilksλ> 0.00006, F(12, 8.2)
> 23.3, p> 0.0001). Post-hoc tests indicated that aroma com-
pounds diused dierently through the layers. For ethyl pro-
panoate (m/z75), the layer in which ham aroma was added
(layer 1) contained a higher concentration of this volatile com-
pound than the adjacent layer (layer 2) which itself contained
a higher concentration than the 2 remaining layers (layer 3
and 4). For limonene (m/z68), the diusion was the highest
since the adjacent layer (layer 2) contained a similar limonene
concentration as layer 1 in which this odorant had been
added. Layers 3 and 4 contained a significantly lower limonene
concentration, although not negligible, in comparison with
the concentration found in layer 1. For the 2-acetylthiazole
(m/z99) and 2-methoxyphenol (m/z109), post-hoc tests revealed
that only the layer in which ham aroma was added (layer 1)
contained a higher concentration of these volatile compounds
than the other 3 layers.
Overall, these results indicated that diusion of the volatile
compounds between layers during the heating process
occurred and depended mostly on the compound, namely its
chemical properties, but not on the salt concentration in the
layers. Because of this diusion process the initial design of
aroma distribution was only partially maintained after the
heating process so that the initial aroma concentration con-
trast was softened.
Sensory evaluation
Descriptive analysis. A series of mixed-eects ANOVA
(panellists as a random factor and products as a fixed factor)
were carried out, respectively, on sweetness, sourness, bitter-
ness, umami, saltiness, Emmental cheese and ham aroma
intensity ratings. No significant product eect was found for
sweetness (M= 1.43, SD = 1.74), bitterness (M= 1.20, SD =
1.74), sourness (M= 1.29, SD = 1.74), umami taste (M= 1.75,
SD = 2.04) and Emmental cheese aroma intensity (M= 2.70,
SD = 2.22). For ham aroma (M= 2.16, SD = 2.21) a significant
eect of the product factor (F(11, 883) = 6.25, p< 0.001) was
observed. Post-hoc tests showed that ham aroma was perceived
as more intense in products containing aroma, compared to
the reference lacking aroma (S
H
) (Fig. 2).
For saltiness (M= 3.96, SD = 2.37), ANOVA yielded a signifi-
cant product factor eect (F(11, 884) = 7.33, p< 0.0001). To
assess the increase in perceived saltiness, we evaluated salti-
ness enhancement, which is the dierence calculated for each
panellist between (i) the score obtained for aromatised pro-
ducts or saltier reference (S
H+
) and (ii) the score obtained for
the reference lacking aroma (S
H
). The ANOVA on saltiness
enhancement indicated a significant panellist eect
(F(81, 891) = 7.30, p< 0.0001) as well as a significant eect of
products (F(11, 891) = 6.56, p< 0.0001). Means for saltiness
enhancement were significantly higher than 0 for all aroma-
tised products and the saltier reference (Fig. 3). Interestingly,
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Table 2 Quantication of the volatile compounds measured by HS-SPME-GC-MS on the whole four-layered cream-based products and in each layer. Mean values represent the peak area (arbi-
trary units ×10
3
) for each of the monitored ions: m/z68 for limonene, m/z75 for ethyl propanoate, m/z99 for 2-acetylthiazole, and m/zfor 109 for 2-methoxyphenol. According to the Student
NewmanKeuls test, the same capital letters indicate no signicant dierence between the products for the nal overall volatile compound concentration, and the same small letters indicate no
dierence between the layers for the nal overall volatile compound concentration. sd: standard deviation
a
Product
name Product design
Overall peak area (sd) Final peak area Layer 1 (sd) Final peak area Layer 2 (sd) Final peak area Layer 3 (sd) Final peak area Layer 4 (sd)
68 75 99 109 68 75 99 109 68 75 99 109 68 75 99 109 68 75 99 109
Homogeneous salt distribution product models
S
H
A
H
20.9
AB
15 415.9
AB
36.9
A
169.2
A
18.6 12 761.7 34.2 39.3 14.9 14 891.6 39.3 193.7 28.9 13 888.8 36.6 165.6 29.0 10 146.4 34.5 165.3
2.5 782.2 1.2 1.7 2.0 431.3 0.9 2.4 0.3 342.8 2.4 24.4 3.7 682.4 0.8 4.9 4.9 1070.9 0.6 4.0
S
1
A
H
15.2
B
18 444.4
A
52.1
A
221.5
A
10.1 14 324.6 46.5 49.3 16.2 16 236.9 49.3 223.1 16.0 16 564.7 54.9 259.0 11.6 17 969.2 59.7 318.7
2.9 868.9 1.8 5.4 0.6 1101.5 7.0 1.7 0.9 857.4 1.7 2.8 3.4 628.4 4.4 37.7 0.6 1140.3 6.2 43.9
Heterogeneous salt distribution product models
S
H
A
1
13.6
B
14 644.3
AB
43.3
A
186.5
A
21.2
a
19 133.0
a
117.0
a
714.6
a
9.3
b
14 195.6
b
37.4
b
121.3
b
14.4
ab
4664.2
c
10.1
b
23.5
b
9.5
b
3087.6
c
8.2
b
34.2
b
2.3 1565.6 4.4 19.9 2.9 841.0 16.7 150.0 0.4 985.3 2.5 9.3 2.8 34.7 0.7 3.1 0.9 141.8 0.7 3.4
S
1
A
1
18.2
B
17 129.7
AB
58.2
A
281.0
A
24.9
a
18 902.9
a
144.1
a
904.7
a
22.4
a
12 365.8
b
43.9
b
156.2
b
14.1
b
6446.7
c
10.5
b
21.5
b
12.9
b
4709.1
c
8.9
b
27.4
b
8.0 4556.5 12.7 81.9 1.2 1056.5 17.1 130.3 3.2 796.1 1.2 10.0 1.3 806.1 0.6 2.6 0.9 427.2 0.8 5.0
S
1
A
4
25.2
A
11 568.7
B
44.1
A
210.1
A
13.5
b
1651.9
c
8.4
b
34.0
b
33.1
ab
2127.7
c
6.7
b
24.8
b
36.1
ab
8533.4
b
31.3
b
118.0
b
47.2
a
14 293.3
a
117.3
a
725.5
a
0.3 726.4 7.8 46.3 1.8 251.8 1.0 0.5 2.2 167.9 0.7 2.3 0.3 263.5 2.4 16.6 9.6 274.6 19.6 144.4
a
For product design, salt and aroma contents are in .
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saltiness enhancement increased with the increasing hetero-
geneity of salt distribution. This was the case when salt was
concentrated in only one layer, especially the external layer (S
1
;
Fig. 3). Moreover, multiple comparisons of means revealed
that only when salt and aroma were concentrated in one exter-
nal but dierent layer (S
1
A
4
) the saltiness enhancement was
significantly higher compared to a homogeneous distribution
of the same amount of salt (S
H
). Conversely, the distribution
of salt and aroma in two layers (S
1,3
A
2,4
) did not produce
more enhancement compared to the homogeneous distri-
bution of both salt and aroma (S
H
A
H
).
Liking test. Liking scores ranged from 4.4 to 5.8, which
suggested that FLP samples were rather well accepted by con-
sumers, taking into account that ratings were performed
under laboratory conditions. Despite the low variability of the
liking scores (1.4 on a scale of 10), an ANOVA (panellists as
random factors, products as fixed factors) was carried out on
liking scores and revealed a significant eect of the product
factor (F(11, 902) = 3.1, p= 0.0005). However, post-hoc tests did
not show a significant dierence between products and the
references (S
H
) or with the saltier reference containing 35%
more salt (S
H+
) as reported in Fig. 4. A Pearson correlation was
carried out on the mean saltiness and liking ratings for all the
FLPs. Results indicated no correlation between saltiness and
liking ratings (r(12) = 0.038, p= 0.8).
General discussion
In the present study we investigated the combined eects of
heterogeneous salt and aroma distribution in hot-served
snacks on salty taste perception, with the aim to compensate
for salt reduction while maintaining consumer acceptability.
Heterogeneity of the distribution of tastants that enhanced
taste perception has been described in liquid solutions and
gels,
24,47
but few studies have investigated the influence of the
heterogeneous spatial distribution of salt on the salty taste of
solid food products.
25,48
Recently, a saltiness enhancement
was observed for layered snack foods served at a hot tempera-
ture that varied in salt distribution.
26
These authors high-
lighted that salt perception was primarily dependent on the
composition of the salty layer and that the final salt concen-
tration in the saltier layer was the key driver of enhanced
saltiness in layered cream-based products. In that case,
heterogeneous spatial distribution of salt was shown to com-
pensate for a decrease in 20% of the total amount of salt in
the product. In addition, odour enhancing taste perception
has been described in liquid solutions. Odours were reported
to enhance sweetness,
38,39
sourness,
49
bitterness
50
and salti-
ness.
40
The influence of adding salt-associated odours on salty
taste perception in solid food products has been investi-
gated.
41
They reported odour induced saltiness-enhancement
(OISE) for Comté cheese and sardine odours in model cheese,
Fig. 2 Perceived ham aroma intensity for each four-layered cream-
based product. Error bars represent the standard error of the means.
Same letters indicate that means are not signicantly dierent at a level
of 5%.
Fig. 3 Saltiness enhancement mean scores for each four-layered
cream-based product. Saltiness enhancement was calculated with this
equation for each participant: (score obtained for four-layered cream-
based products) (score obtained for the unavoured reference (S
H
)).
Error bars represent the standard error of the mean. The asterisks indi-
cate a signicant saltiness enhancement: ***p< 0.001; **p< 0.01;
*p< 0.05 (t-test). The same letters indicate that the means for saltiness
enhancement were not dierent at a signicance level of 5% (SNK).
Fig. 4 Mean liking scores for each four-layered cream-based product.
Error bars represent the standard error of the mean. *p< 0.05.
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which contribute to increased overall salty taste perception by
15%.
To our knowledge, no study has focused on OISE and
heterogeneous salt distribution as a combined strategy to com-
pensate for decreased saltiness in low-salt food products.
However, combining several compensation strategies was
found to be ecient to increase the percentage of salt
reduction that could be achieved without a loss of perceived
saltiness. For instance, tastetaste and odourtaste perceptual
interactions were successfully combined to significantly
enhance saltiness perception in water solutions containing
salt, citric acid and sardine aroma.
51
The results of the present
study confirmed the usefulness of coupling several strategies
since we were able to combine odour-induced saltiness
enhancement and heterogeneous spatial distribution of salt to
design a hot-served snack (S
1
A
4
) that was more salty and as
well liked as a standard snack containing 35% more salt (S
H+
).
Using warm food products to study food flavour perception
is always a challenge because the heating process influences
the taste and flavour perception. It was demonstrated that a
higher serving temperature lowered saltiness intensity; pro-
ducts can thus lose 10 to 20% of saltiness intensity according
to the type of food and the salt concentration.
52
Moreover,
heating induces many chemical and textural modifications
that particularly increase the diusion of water and volatile
compounds. This is a common issue in layered food products
with a heterogeneous distribution of water soluble com-
ponents (i.e., salt) and aroma compounds (i.e., volatiles)
because heterogeneity can be disrupted during the heating
process. Indeed, heating of snack foods was reported to induce
salt diusion which was a limiting factor for maintaining
heterogeneous salt distribution and therefore for the enhance-
ment of salt perception.
26
In the present study, diusion of
salt from the layers in which salt was concentrated to the salt-
free adjacent layers was also observed. For example, in the
S
1
A
1
product up to 50% of the salt added in the upper layer
diused to the adjacent salt layers. Nevertheless, even after
diusion was boosted by the heating process, the dierences
in salt concentrations remained significant in all the layered
configurations, which ensured sucient heterogeneity of salt
spatial distribution to induce saltiness enhancement. Indeed,
saltiness enhancement was significantly higher for the 5 pro-
ducts with added salt located in only one layer, especially
when the salt was concentrated in an external layer, which con-
firmed previously obtained data.
26
Diusion was also important for the added aromas, but
depended on their chemical nature. For instance, in the S
1
A
1
product the diusion from the layer containing the added
ham aroma into the other 3 layers was approximately 6040%
for the limonene and the ethyl propanoate. Hence, probably as
a consequence of aroma compound diusion boosted by the
heating process, we found no significant enhancement of ham
aroma intensity induced by the initial heterogeneous spatial
distribution of aroma compounds (Fig. 2). The diusion issue
could explain the dierence between our results and those
reported by others, which showed that heterogeneity of the
spatial aroma distribution in gels increased perceived aroma
intensity.
27,28
Nevertheless, added ham aroma significantly
contributed to enhanced saltiness regardless of its spatial dis-
tribution (Fig. 3). Therefore, the combined strategy allowed
compensation for a higher amount of salt reduction compared
to the heterogeneous distribution of salt alone.
26
Moreover,
because ham aroma intensity was quite low in the present
study as a consequence of aroma diusion in the products,
one can expect a greater enhancing eect of aroma by either
increasing aroma intensity and/or by limiting aroma com-
pound diusion.
Beyond taste and flavour perception, liking is the main
driver of food acceptability. For our experimental hot-served
snacks we obtained quite high liking scores (approximately
5 of 10).
53
We did not find that products with a heterogeneous
distribution of salt and/or aroma compounds were signifi-
cantly less appreciated (Fig. 4) which is in line with the results
of other studies using heterogeneous spatial distribution of
tastants in food products.
26,48
However, it is possible that, due
to the rather limited number of subjects included in the liking
experiment, small dierences in liking may have been under-
estimated. Therefore, our results suggest that the combination
of heterogeneous distribution of salt associated with odour-
induced saltiness enhancement does not alter food liking and
is a suitable strategy to maintain flavour intensity and
especially saltiness in low-salt food without loss of acceptabil-
ity, even after a 25% decrease of salt. Moreover, such a strategy
may be extended to compensate for sugar and fat reduction,
which could help manufacturers follow public health agencies
recommendations in terms of reductions in salt, sugar or
fat while maintaining a good acceptability of food products for
consumers.
Acknowledgements
The authors are very grateful to Céline Lafarge (AgroSup Dijon,
France) for assistance in the texture profile analysis measure-
ments, as well as to Karine Gourrat and Etienne Semon (Plat-
form Chemosens, CSGA, Dijon, France) for assistance in the
aroma diusion measurements. The authors also acknowledge
the Regional Council of Burgundy and FEDER for their finan-
cial participation in this study.
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... However, this effect is very dependent on the food matrix composition [27]. In cream-based food systems, a promising strategy combining olfactory-induced saltiness enhancement and heterogeneous distribution of stimuli was found to compensate for over a 35% decrease in salt content while maintaining saltiness intensity and consumer acceptability in hot snacks [22,28]. Only these authors reported a significant additive effect between the use of congruent aroma and heterogeneous distribution of salt for the enhancement of saltiness intensity, although the observed perceptual effect was limited because of salt and aroma compound diffusion between the different layers of the food. ...
... Surprisingly, no significant effect of aroma compound distribution on overall aroma intensity was observed. Furthermore, heterogeneous products were well liked by consumers compared to the homogeneous products [22,28]. In addition, in a composite food such as pizza, by modifying the salt content of each ingredient (ham, tomato, mozzarella, and dough), the overall salt content can be reduced by 30% while obtaining a salty perception higher than that of the control product [29]. ...
... Overall, the previous findings of [28] suggested that either saltiness in products with heterogeneous salt distribution counteracted aroma perception at a perceptual level or saltiness distribution modified aroma compound release because of the salting-out effect. Thus, we aimed to test the hypothesis that heterogeneous salt concentrations modify aroma compound release and further perception. ...
... Arranging different concentrations of tastants in layers within a food structure can alter the sensory profile, thereby allowing a reduction in the tastant without affecting desirable sensory perceptions. This spatial distribution has been demonstrated with sugar in gels [4][5][6], salt in bread [7] and cream-based snacks [8], and fat in gels [9] and sausages [10]. Bread samples with a heterogeneous distribution of salt permitted a reduction of up to 28% overall salt content without compromising saltiness intensity [7]. ...
... Samples with 43.56% sugar (HLH, HHL) were comparable in sweetness to a conventional 51.52% sugar chocolate (HHH). Similarly, cream-based snacks with a 35% reduction in salt and saltassociated aroma were found to be saltier than the reference snack when the salty aroma layer was at the bottom and the saltier layer was at the top [8]. In contrast, sweetness intensity was not different among four four-layered gels with different layering arrangements and an overall 10% (w/w) sugar concentration [5]. ...
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Labelling and information have been shown to increase acceptance of novel food technologies. The novel technology of 3 Dimensional Printing (3DP) of foods is not well known among consumers. The study aim was to investigate the effect of the 3DP label and benefits information on consumer acceptance and perception of plausible 3DP foods. Commercially available foods, such as milk chocolate swirls, gummy candy carrots, and baked potato Smiles®, represented 3DP benefits, and each was evaluated in a sensory panel. Participants rated acceptance and perceived quality after each of three product presentations; first labeled “conventional”, then labeled “3D printed”, and again labeled 3D printed after information presentation. Participants indicated product preference after the third presentation. Food Technology Neophobia (FTN), attitude, and previous 3DP knowledge were queried. Quality rating of chocolate swirls and gummy candy carrots increased when labeled as 3DP versus conventional; information did not further increase quality ratings. Participants preferred 3DP chocolate swirls and gummy candy carrots to conventional in the final evaluation. Label and information did not change flavor, texture, or overall acceptance ratings for any product. Attitude towards 3DP of foods increased with lower FTN. Future studies could tailor information to consumer interests and knowledge gaps that highlight relevant benefits of 3DP.
... Arranging different concentrations of tastants in layers within a food structure can alter the sensory profile, thereby allowing a reduction in the tastant without affecting desirable sensory perceptions. This spatial distribution has been demonstrated with sugar in gels [4][5][6], salt in bread [7] and cream-based snacks [8], and fat in gels [9] and sausages [10]. Bread samples with a heterogeneous distribution of salt permitted a reduction of up to 28% overall salt content without compromising saltiness intensity [7]. ...
... Samples with 43.56% sugar (HLH, HHL) were comparable in sweetness to a conventional 51.52% sugar chocolate (HHH). Similarly, cream-based snacks with a 35% reduction in salt and saltassociated aroma were found to be saltier than the reference snack when the salty aroma layer was at the bottom and the saltier layer was at the top [8]. In contrast, sweetness intensity was not different among four four-layered gels with different layering arrangements and an overall 10% (w/w) sugar concentration [5]. ...
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Sugar-reduced chocolates with desirable sensory qualities and sweetness can be created using a 3D printer by layering chocolates with different sugar concentrations. This study aimed to evaluate the temporal sensory profile, perceived sweetness intensity, and acceptance of prototype sugar-reduced and non-sugar-reduced 3D printed chocolates. A consumer panel (n = 72) evaluated the sensory profiles of six-layered chocolates. Sensory profiles were determined by temporal dominance of sensations (TDS), overall sweetness by a five-point intensity scale, overall liking by the nine-point hedonic scale, and differences among chocolates over time were visualized by principal component analysis (PCA). Layering by 3D printing achieved a 19% reduction in sugar without changes in the perceived overall sweetness and overall liking. Layering order of high and low sugar chocolate influenced the perceived overall sweetness and temporal sensory profiles of 3D printed chocolates with different total sugar concentrations. The dominance of attributes associated with milk chocolate was observed to increase sweetness perception while the dominance of attributes associated with dark chocolate was observed to decrease overall sweetness perception. Three-dimensional food printing technology is progressing rapidly, and further sugar reduction could be achieved with refined research methods.
... In order to promote healthier dietary patterns, food manufactures continue to develop reduced sugar and fat products without sacrificing sensory properties such as taste and texture. During (Emorine et al., 2013(Emorine et al., , 2015. They demonstrated that a large contrast in salt concentrations within one bite was required to enhance saltiness, and that salt-associated aromas (ham aroma) could contribute to saltiness enhancement. ...
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In many parts of the world, sodium consumption is higher than recommended levels, representing one of the most important food‐related health challenges and leading to considerable economical costs for society. Therefore, there is a need to find technical solutions for sodium reduction that can be implemented by food producers and within food services. The aims of this review are to discuss the barriers related to sodium reduction and to highlight a variety of technical solutions. The barriers relate to consumer perception, microbiology, processing, and physicochemistry. Existing technical solutions include inhomogeneous salt distribution, coated salt particles, changing particle sizes and forms, surface coating, multisensory combinations, sodium replacements, double emulsions, adapted serum release by microstructure design, and adapted brittleness by microstructure design. These solutions, their implementation and the associated challenges, and applicable product categories are described. Some of these solutions are ready for use or are in their early development stages. Many solutions are promising, but in most cases, some form of adaptation or optimization is needed before application in specific products, and care must always be taken to ensure food safety. For instance, further research and innovation are required in the dynamic evolution of saltiness perception, consumer acceptance, the binding and migration of sodium, juiciness, microbiological safety, and the timing of salt addition during processing. Once implemented, these solutions will undoubtedly support food producers and food services in reducing sodium content and extend the application of the solutions to different foods.
Chapter
The reduction dietary intake of sodium is considered one of the greatest demands worldwide in order to decrease the risk of hypertension and cardiovascular diseases, responsible for a high mortality rate worldwide. The main source of sodium in the diet comes from sodium chloride (NaCl), the edible salt most commonly used in foods. Sodium chloride has many technological functions which include preservative effects resulting from the reduction of water activity, improving functional properties of many classes of proteins and the excellent sensory properties, especially its salty taste. Solutions to replace and/or reduce NaCl content in foods consider the use of substitute chloride salts such as KCl, CaCl2, MgCl2, natural flavor enhancers, and new process technologies in combination with other barriers to meet physicochemical, microbiological, sensory stability. These topics will be discussed in detail throughout this chapter.
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This narrative historical review examines the wide range of approaches that has been trialled/suggested in order to reduce the consumption of salt. While sodium is an essential micronutrient, there is widespread evidence that high levels of consumption are leading to various negative health outcomes. This review summarises the evidence relating to the various approaches that have been put forward to date to help reduce salt consumption over the years, while also highlighting a number of important questions that remains for future research. Solutions to reducing salt consumption include everything from the gradual reduction in salt in foods through to the reduction in the number/size of holes in saltshakers (what one might consider a behavioural nudge). Physico-chemical solutions have included salt replacers, such as monosodium glutamate (MSG) through to the asymmetric distribution of salt in processed (e.g., layered) foods. A wide range of sensory approaches to modulating expected and perceived saltiness have also been suggested, including the use of salty aromas, as well as suggesting the use of colour cues, sonic seasoning, and even textural primes. It is currently unclear whether different salty aromas can be combined to increase odour-induced taste enhancement (OITE) effectiveness. In the years ahead, it will be interesting to assess how long such solutions remain effective, as well as whether different solutions can be combined to help reduce salt consumption without having to compromise on taste/flavour
Chapter
Multimodal interactions are central in food flavor construction and modulation. Two main types of mechanisms underpin these interactions. First, physicochemical mechanisms drive chemical stimuli release as a function of food composition and structure, and food oral processing. Second, perceptual mechanisms result from sensory information integration from the receptors to the brain. In this chapter, we propose a review of multimodal interactions in the context of food flavor construction and modulation. Starting from pieces of evidence for the integration of olfactory and gustatory information at sub- and suprathreshold levels, we review the mechanisms underpinning aroma–taste interactions, as well as the neurophysiological bases of perceptual flavor integration. Then, we focus on the impact of olfactory, gustatory, and trigeminal interactions on food flavor perception. Afterward, we present interactions between aroma, taste, and texture while summarizing the possible mechanisms, and considering the mutual influence of texture on aroma and taste.
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Odor-induced taste enhancement (OITE) is a phenomenon derived from the integrative processing of odor and taste in the brain. In summarizing the published research articles on OITE, the current review discusses the effects of odor concentration, odor perceptual routes (orthonasal or retronasal), and the odor-taste congruency on OITE. In addition, the review highlights the neural mechanisms of OITE by presenting human neuroimaging research results related to the brain processing of taste intensity, taste quality of odors, and taste-odor interactions. Finally, the paper discusses the implication of OITE on nutritional and clinical applications. The identification of odor molecules with potent taste enhancement effects and the application of OITE in the food industry and clinical populations are necessary for future research.
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High dietary intake of sodium is associated with several non-communicable diseases and depleting immunity. In recent years, with emergent regulations and increasing awareness about the role of diet on human health, there has been significant research and commercial interest in salt reduction approaches. Nevertheless, lowering the level of salt while maintaining the physicochemical properties, sensory attributes and microbial stability of food products is a challenging task for the food industry. This review analyses scientific literature and details the various techniques that have been used for the effective reduction of sodium levels in food products. These include various physical and chemical modifications, apart from psychological approaches, and novel non-thermal processing techniques. The work presents a comprehensive understanding of recent advancements in lowering salt content, with implications on their effects on the properties and consumer acceptance of foods. Some approaches have been proven to be realistic and sustainable. Importantly, a combination of different strategies can overcome the drawbacks of conventional methods and facilitate the development of high-quality foods. However, numerous challenges need to be addressed for the production of shelf-stable low-salt products. Future research works must consider these novel concepts and focus on commercial-level applications.
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This study investigated the relationship between perception of an odour when smelled and the taste of a solution to which the odour is added as a flavorant. In Experiment 1 (E1) sweetness, sourness, liking and intensity ratings were obtained for 20 odours. Taste ratings were then obtained for sucrose solutions to which the odours had been added as flavorants. Certain odours were found to enhance tasted sweetness while others suppressed it. The degree to which an odour smelled sweet was the best predictor of the taste ratings. These findings were extended in Experiment 2 (E2), which included a second tastant, citric acid, and employed four odours from E1. The most sweet smelling odour, caramel, was found to suppress the sourness of citric acid and, as in E1, to enhance the sweetness of sucrose. Again, odours with low sweetness suppressed the sweetness of tasted sucrose. The study demonstrated that the effects of odours on taste perception are not limited to sweetness enhancement and apply to sour as well as sweet tastes. The overall pattern of results is consistent with an explanation of the taste properties of odours in terms of prior flavour‐taste associations.
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Effects of inhomogeneous spatial distribution of aroma compounds were investigated on the perceived aroma intensity and human eating behavior using polysaccharide gels as a food model. Gels tested were structured using gel-in-gel configuration to create different degrees of inhomogeneous spatial aroma distribution, and their pH values were set at neutral (6.7 - 6.8). There were no differences in mechanical properties between the structured gels. A greater degree of inhomogeneous spatial aroma distribution increased the perceived aroma intensity, increased the duration of oral processing and suprahyoid musculature activity during oral processing, decreased the particle size of the bolus, and increased the saliva content in the bolus. Effects of pH were compared with our previous report using the same experimental design but different pH (approximately 4.2), confirming a similar trend in the results. A strategy of food structure design for enhanced perceived aroma intensity and human eating behavior was suggested regardless of gel pH.
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Activity coefficients at infinite dilution in water have been determined for some aroma compounds detected in brown crab liquid effluent produced during boiling (1-octen-3-ol, 1-penten-3-ol, 3-methylbutanal, hexanal, benzaldehyde, 2,3-pentadione, and ethyl acetate) by using the headspace gas chromatography technique (HSGC). Experimental data have been obtained over the temperature range of (40 to 50) °C. In this work, activity coefficients at infinite dilution for different kinds of systems have been considered: one component solute + water and multicomponent solute + water. No significant differences were observed between activity coefficients obtained in these two kinds of systems. Additionally the effect of salt concentration at 40 °C has been studied by varying the salt concentration from (0 to 1.71) mol·kg–1. Experimental data were fitted as a function of salt concentration by using the Setschenow equation, obtaining the salting-out coefficient.
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Effects of inhomogeneous spatial aroma distribution in food gels were investigated for the enhancement of perceived intensity and the muscle activity during oral processing. A polysaccharide mixture was used as the gel matrix, in which small cubes from the same gelling agent were dispersed at 50% weight ratio. Degree of inhomogeneous spatial aroma distribution was arranged by its concentration in both the matrix and the dispersed gels although the overall aroma concentration within one gel sample was constant. There were no differences in mechanical properties between structured gel samples. A greater degree of inhomogeneous spatial aroma distribution increased perceived intensity, increased the duration of oral processing and the suprahyoid musculature activity, decreased the particle size of the expectorated bolus before swallowing, and increased the saliva content in the bolus using healthy adults as subjects. Importance of food structure design for enhanced perceived aroma intensity and human eating behavior was suggested. Results from this study can contribute to the food structure design, particularly for foods for the elderly or people with chewing and swallowing difficulties, because the texturally soft gels used can serve as a model of these foods in that they do not necessarily require chewing for size reduction and are often easy to form a bolus before swallowing. Because of some heterogeneity of food structure (fabricated by bi-phase gel in this study), perceived aroma intensity is increased, and people eat proactively. Gel technology that stimulates the five human senses may be a key for food texture innovation, for which the manufacturers should manipulate gelling and thickening polysaccharides as a texture modifier.
Article
The present study investigated the role that congruency between tastes and odors plays in two types of taste–odor interactions: retronasal odor enhancement by taste and retronasal odor referral to the mouth. In the first experiment, subjects rated (1) the intensities of sweetness, sourness, bitterness, and specific odor of aqueous samples of 3 tastants (sucrose, citric acid, caffeine) and 2 odorants (citral, coffee odor), both alone and in taste–odor mixtures, and (2) the degree of congruency of all possible taste–odor pairs. The results showed that only sucrose significantly enhanced the perceived intensities of citrus and coffee odors (Tukey’s test, p < 0.05), while citric acid and caffeine failed to enhance or even suppressed the odors. In the second experiment, the returning subjects were asked (1) to report the perceived locations of the odors after inhaling 3 odorants (citral, “sweet” and “bitter” coffee odors) through the mouth alone or in the presence of either water or various tastes in the mouth, and (2) to rate the degree of congruency between tastes and odors. The data showed that a highly congruent taste or taste mixture significantly increased localization of odors to the mouth (χ2, p < 0.05). These findings suggest that taste–odor congruency is a necessary but not sufficient condition for retronasal odor enhancement. In contrast, taste–odor congruency is a critical component for retronasal odor referral, and the degree of congruency modulates the degree of odor referral to the mouth. The results and implications of the study findings are discussed in terms of cognitive and perceptual factors of flavor perception.
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The effects of the lipid/protein ratio (20/28, 24/24, 28/20) and salt content of model cheeses were investigated simultaneously with respect to chewing behaviour, swallowing events and in vivo aroma release. Chewing parameters were measured by electromyography. Swallowing events were recorded manually. In vivo aroma release was investigated using nose-space on-line atmospheric pressure chemical ionisation–mass spectrometry. The values for chewing activity and time before swallowing were higher with lower lipid/protein ratios and lower salt contents, due to the greater mechanical resistance of the model cheeses. The corresponding microstructure was made up of smaller and more circular fat droplets in a stronger protein network. Furthermore, the maximum intensity and in-mouth release rate of aroma decreased as the lipid/protein ratio fell. This could be explained by a retention effect of the proteins, which was stronger than the chewing effect. A rise in salt content triggered more rapid aroma release from the protein phase of the model cheese to the oral cavity, and thence to the nasal cavity. The larger fat droplet size in salt-supplemented model cheeses slowed down the transfer of aroma release and the levels of aroma release after swallowing were higher. A more rapid swallowing was observed for model cheeses containing added salt and with a higher L/P ratio. It is suggested that this was due to greater salivation and lubrication. Moreover, the number of swallows was positively correlated to the total amount of aroma release. Copyright © 2013 John Wiley & Sons, Ltd.
Article
Two sensory studies were carried out to compare the taste intensity, the perceived fluctuation of taste intensity and the consumer preference of food products with homogeneous and inhomogeneous distributions of tastants using 2-alternative forced choice tests. The first study evaluated pairs of gels, breads and sausages (1 homogeneous product and 1 inhomogeneous product). The second study evaluated 4 types of gel and 4 types of sausage (1 homogeneous product and 3 inhomogeneous products varying in the magnitude of tastant concentration differences).
Article
Three main principles towards sodium reduction in food products can be discriminated: chemical stimulation to increase the saltiness perception peripherally, cognitive mechanisms towards increasing awareness or shifting the saltiness preference, and designed product structures that attempt to optimize the delivery of salt to the taste buds. Such designed product structures affect the way salt is released from the product structures or transported to the taste receptors during mastication and may be based on the format or the spatial distribution of the salt, its encapsulation methods or the bulk texture of the product. This review provides an overview of the different principles for sodium reduction in food products, with further elaboration on the third principle which has gained increasing attention in the past few years. In particular, the different methods and mechanisms underlying these product structure designs and their reported successes and challenges are discussed.
Article
Health issues have led worldwide organisations to encourage the food industry to reduce salt in processed foods. Therefore, different strategies for salt reduction have been investigated. Here, the effect of heterogeneous salt distribution on saltiness perception intensity was assessed to compensate for salt reduction in snack foods. Two models of hot-served baked foods were developed. One model is made of two layers that vary in composition (cream-based and cereal-based layers) and salt (NaCl) concentration; the other one is made of four cream-based layers that vary in salt concentrations. Consumer panels rated the saltiness intensity for each product and their liking for the four-layer products only.A significant enhancement of saltiness was observed in samples with a heterogeneous salt distribution for both types of snacks. In the bi-layer products, salt perception was more dependent on the salt concentration in the cream-based layer than in the cereal-based layer. Moreover, a large contrast in the salt concentrations was required to enhance salt perception for the four-layer products.Our results show that heterogeneous salt distribution is a powerful strategy to compensate for salt reduction in foods and to design healthier products while optimising taste.