JFS S: Sensory and Food Quality
Salt Reduction in Foods Using
Naturally Brewed Soy Sauce
STEFANIE KREMER, JOZINA MOJET, AND RYO SHIMOJO
ABSTRACT: In recent years, health concerns related to salt/sodium chloride consumption have caused an increased
demand for salt-reduced foods. Consequently, sodium chloride (NaCl) reduction in foods has become an important
challenge. The more so, since a decrease in NaCl content is often reported to be associated with a decrease in consumer acceptance. The objective of the present study was to investigate whether or not it would be possible to reduce
the NaCl content in standard Western European foods by replacing it with naturally brewed soy sauce. Three types
of foods were investigated: salad dressing (n = 56), soup (n = 52), and stir-fried pork (n = 57). In the 1st step, an
exchange rate (ER) by which NaCl can be replaced with soy sauce without a significant change in the overall taste
intensity was established per product type, by means of alternative forced choice tests. In the 2nd step, the same
consumers evaluated 5 samples per product type with varying NaCl and/or soy sauce content on pleasantness and
several sensory attributes. The results showed that it was possible to achieve a NaCl reduction in the tested foods
of, respectively, 50%, 17%, and 29% without leading to significant losses in either overall taste intensity or product
pleasantness. These results suggest that it is possible to replace NaCl in foods with naturally brewed soy sauce without lowering the overall taste intensity and to reduce the total NaCl content in these foods without decreasing their
consumer acceptance.
Introduction
S
odium chloride (NaCl) is one of the most important ingredients for many foods. It influences not only the flavor profile
of food products, but also their texture, and it plays an important
role in the preservation of foods against microbes. However, NaCl
has also been reported to increase the risk of hypertension and
to be directly related to the development of cardiovascular disease
(Weinsier 1976; Law 1997). Therefore, the World Health Organization (WHO) in 1990 recommended a limitation of the average NaCl
intake to 6 g per day for adults. Seventeen years later, WHO repeated
this earlier warning and recommended an even lower daily sodium
intake of 5 g per day (WHO 2007). Consequently, the reduction of
NaCl content in food products has become an important challenge
for the food industry. The more so, since a decrease in NaCl content
is very often reported to be associated with a decrease in consumer
acceptance (Sofos 1983; Breslin and Beauchamp 1997).
So far, there are 2 major approaches to reducing NaCl content.
The first is to replace NaCl with other types of salts, such as potassium chloride (KCl) and calcium chloride (CaCl 2 ). The second is to
strengthen other tastes to enhance perceived saltiness.
The former approach was performed for Feta cheese (Katsiari
and others 1997), Kefalograviera cheese (Katsiari and others 1998),
and meat products (Ruusunen and Puolanne 2005; Desmond 2006;
MS 20090214 Submitted 3/11/2009, Accepted 5/1/2009. Authors Kremer and
Mojet are with Wageningen Univ. and Research, Centre for Innovative Consumer Studies, Bornsesteeg 59, 6708 PD Wageningen, The Netherlands.
Author Shimojo is with Kikkoman Europe R&D Laboratory B.V., Nieuwe
Kanaal 7, 6709 PA Wageningen, The Netherlands. Direct inquiries to author
Kremer (E-mail: [email protected]).
R
Institute of Food Technologists
doi: 10.1111/j.1750-3841.2009.01232.x
C 2009
Further reproduction without permission is prohibited
Guardia and others 2006). According to their studies, the alternative salts may allow reduction of the NaCl content by up to 50%.
However, as Jacobson (2005) pointed out, “the average sodium content of processed foods decreased only by 0.3% per year between
1983 and 2004.” This clearly suggests that the previous attempts
to reduce NaCl content have significant obstacles when applied to
real-life products. Two problems can be foreseen. First, KCl is inapplicable to nephritic patients whose potassium intake is strictly
controlled. Second, manufacturers have to declare on their labels
that alternative salts are included as additives. This might result in
the loss of customers who prefer a clean label.
Interestingly, Mojet and others (2004) found that the 5 basic
tastes, that is, umami, salty, sour, bitter, and sweet, interact with
each other. For example, they showed that umami enhanced
perceived saltiness in foods. In their study, they used monosodium
glutamate (MSG) and inosine 5 -monophosphate as umami substances. The study foresees that, in food products that contain a
large quantity of “natural” umami substance, NaCl content can
be decreased without diminished consumer acceptance. Another
possible approach to further reduce salt could be odor-induced
saltiness enhancement (OISE) by a salty-congruent odor
(Djordjevic and others 2004; Lawrence and others 2009). Wellselected odors might be used to compensate for NaCl reduction in
foods. However, the sustainability of such an effect has still to be
investigated. Naturally brewed soy sauce is one of the foods that
contain high levels of naturally occurring umami substances, such
as amino acids and peptides (Skurray and Pucar 1988).
Soy sauce is a fermented sauce made from soybeans, grain, water, and salt, and was invented in Asia almost 2500 y ago. Nowadays,
it is widely used both in Asian and in Western cuisines.
Vol. 74, Nr. 6, 2009—JOURNAL OF FOOD SCIENCE
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PRACTICAL APPLICATION: Health concerns related to salt consumption cause an increased demand for saltreduced foods. Consequently, the development of foods with reduced salt content without decreasing the consumer
acceptance is an important challenge for the food industry. A new possible salt reduction approach is described in
the present article: The replacement of salt with naturally brewed soy sauce.
Keywords: odor-induced taste perception, saltiness enhancement, salt replacement, soy sauce, umami
Salt reduction using soy sauce . . .
The aim of the present study was to demonstrate whether or not of the standard salad dressing is stronger than that of the soy sauce
it would be possible to reduce the NaCl content in standard Western variant.
For the 2nd tasting session, 5 salad dressing variants were preEuropean foods by replacing NaCl with naturally brewed soy sauce
pared, varying their table salt/soy sauce ratio (see Table 1). All
without decreasing the consumer acceptance of these foods.
salad dressing variants were prepared 24 h before serving, placed in
Materials and Methods
100 mL plastic cups with air-tight lids, and stored overnight in a
food grade refrigerator at 4 ◦ C. Fifteen minutes before serving, all
Subjects
salad dressings were taken out of the refrigerator and 30 g of the
Per product category (salad dressing, soup, stir-fried pork), 60 dressing were added per 200 g pre-cut salad and gently mixed in for
consumers, aged between 18 and 60 y, were selected by a local re- 3 min. Twenty-gram portions of the salads were then served in 50
cruitment agency. All subjects were Caucasian and met the follow- mL polystyrene cups.
ing criteria: healthy, not on a prescribed diet, not subject to food
allergies, and in good command of the Dutch language. On the days Soup
of testing, not all recruited consumers were able to attend the exCream of tomato soup concentrate was obtained from a soup
perimental sessions. Consequently, the actual numbers of subjects producer (www.kleinstesoepfabriek.nl). It was produced under the
tested per category were 56, 52, and 57, respectively. Of the 56 con- organic label “EKO” and did not contain NaCl or artificial glutasumers who evaluated the salad dressings, 28 were male and 28 mate. The recommended degree of dilution for this soup concenfemale (mean age 38, range 18 to 57 y) and of the 52 consumers trate was 1 L soup with 1 L water.
who evaluated the soups, 26 were male and 26 female (mean age
The soup was prepared according to the following recipe:
38, range 18 to 56 y). Finally, of the 57 consumers who assessed the 50 g cream of tomato soup concentrate, 0.9 g NaCl, 49.1 g water.
stir-fried pork, 26 were male and 31 female (mean age 39, range 18 This soup was used as the standard in the paired comparisons. It
to 56 y).
had a NaCl content of 0.9% (w/w), which is in line with the NaCl
Per product category, the consumers participated in 2 tasting content for commercial soups reported in the Dutch Nutrient
sessions of approximately 60 min each. They received a fee for par- Database (Voedingscentrum 2001).
ticipation at the completion of the study.
For the 1st tasting session, this standard soup with NaCl and 5
Samples
soy sauce variants of the soup was prepared; the latter were prepared by replacing the NaCl with various concentrations of soy
sauce (soy 1 to soy 5). Since 3.16 g of powdered Kikkoman soy sauce
contain 1 g NaCl, the changes in weight/volume that occurred during this replacement were neutralized by the addition of less water. The content of the soy sauce variants was 0.90% (w/w), 0.75%
(w/w), 0.60% (w/w), 0.45% (w/w), and 0.30% (w/w), respectively.
S: Sensory & Food
Quality
Commercially available liquid soy sauce Fancy grade (Kikkoman
Food Europe B.V.) was used in the preparation of the salad dressings
(per 100 g: energy 264 kJ/63 kcal, protein 8.8 g, carbohydrates 6.9 g,
fat 0.0 g, fiber 0.0 g, and sodium 5.76 g), whereas dried Kikkoman
powdered soy sauce KU-20 was used in the preparation of the soups
and stir-fried pork. Since both sauces were naturally brewed and
consequently no artificial glutamic acid salts such as monosodium
glutamate (MSG) were added, the sodium (Na) content present in Table 1 --- Recipes for the salad dressing variants 1 to 5.
“Table salt” “Soy sauce” Total NaCl
these soy sauces corresponded directly to their total NaCl content
percentage percentage
content
(1 g Na is correspondent to 2.54 g NaCl).
Variant Ingredients (g)
(%)
(%)
(%, w/w)
Salad dressing
About 6.96 g of liquid Kikkoman soy sauce contained 1 g NaCl.
Prior to the preparation of the standard salad dressing, the 1st step
was to dissolve 14.36 g NaCl in 85.64 g of water. This step was necessary, since a straight replacement of NaCl with soy sauce in a recipe
would give too much difference in both weight and volume. The
salad dressing was then prepared according to the following recipe:
64 g olive oil, 22 g balsamic vinegar, 13.9 g NaCl/water solution, and
0.1 g ground black pepper. This salad dressing was used as the standard dressing in paired comparison tests with soy sauce variants. It
had a NaCl content of 2% (w/w), which is in line with NaCl content for commercial salad dressings reported in the Dutch Nutrient Database (Voedingscentrum 2001). For the 1st tasting session,
this standard dressing and 5 soy sauce variants of the salad dressing
were prepared by replacing the NaCl with various concentrations of
soy sauce (soy 1 to soy 5). NaCl content of the soy sauce variants was
1.60% (w/w), 1.45% (w/w), 1.30% (w/w), 1.15% (w/w), and 1.00%
(w/w), respectively. This range of concentrations was chosen based
on the results of a small pilot test conducted among colleagues at
our department (n = 10). The aim of this pilot test was to ensure
that, within this soy sauce concentration range, one of the following 3 results can be expected to occur. First, that the overall taste
intensity of the soy sauce variant is stronger than that of the standard salad dressing; second, that no difference in overall taste intensity can be observed; and, third, that the overall taste intensity
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JOURNAL OF FOOD SCIENCE—Vol. 74, Nr. 6, 2009
1
2
3
4
5
Olive oil
Balsamico
Salt solution
Soy sauce
Water
Pepper
Olive oil
Balsamico
Salt solution
Soy sauce
Water
Pepper
Olive oil
Balsamico
Salt solution
Soy sauce
Water
Pepper
Olive oil
Balsamico
Salt solution
Soy sauce
Water
Pepper
Olive oil
Balsamico
Salt solution
Soy sauce
Water
Pepper
64
22
13.9
----0.1
64
22
10.4
1.75
1.75
0.1
64
22
6.9
3.5
3.5
0.1
64
22
3.4
5.25
5.25
0.1
64
22
--7
6.9
0.1
100
---
2.00
75
25
1.75
50
50
1.50
25
75
1.25
---
100
1.00
Salt reduction using soy sauce . . .
Stir-fried pork
Procedure
The tasting sessions were conducted in the sensory laboratory
of The Restaurant of the Future, Wageningen, The Netherlands. Per
product type, 1st and 2nd panel sessions were held within 1 wk. In
the 1st session, the subjects were asked to perform five 2-alternative
forced choice (2-AFC) tests. The aim of the 2-AFC tests was to establish the exchange rate (ER) by which NaCl can be replaced with
soy sauce without a significant change in the overall taste intensity.
To this end, the subjects were asked to compare the product with
the standard NaCl content with 1 out of 5 products with different
soy sauce concentrations. They were asked to indicate which of the
2 samples had the stronger overall taste. After the 1st session, the
ER was calculated from the results of the paired comparisons and
this ER was used to calculate the concentrations for the 2nd tasting
session. The aim was that the 100% soy variant used in the 2nd session would be perceived by consumers to taste equally intense as
the 100% NaCl variant (for more details, see the “Results and Discussion” section).
In the 2nd session, panelists evaluated 5 samples with varying table salt and/or soy sauce content twice. The aim of the 2nd session
was to establish the optimal exchange rate (OER) by which NaCl can
be replaced with soy sauce in products without significant losses
in both overall taste intensity and in the degree of product liking.
Per sample, pleasantness was always assessed first on a visual analogue scale. Next, the intensities of the following sensory attributes,
“overall taste intensity,” “salty taste,” “sour taste” (salad dressing
only), “tomato taste” (soup only), “meat taste” (stir-fried pork only),
were rated on the same visual analogue scales. The verbal anchors
were “very little/weak” and “very much/strong” and were placed at
10% and 90% on the scale, respectively. All samples were coded with
random 3-digit numbers and were presented in random order per
person. Panelists were instructed to rinse their mouth with water
and to eat cream crackers between the samples. The inter-stimulus
interval was 4 min.
For the stir-fried pork, chops of belly/side pork were ordered
from a national meat supplier (DeliXL, Ede, the Netherlands). The
meat was cut into thin slices of equal size (1 × 2 cm), marinated by
the chef, and left to stand for 45 min before frying.
The pork was prepared for stir-frying according to the following
recipe: 90.3 g sliced side pork, 0.7 g NaCl, 1 g potato starch, 3 g wheat
germ oil, 5 g white wine. This prepared standard pork had a NaCl
content of 0.7% (w/w), which is in line with the NaCl content for
meat stir-fries reported in the Dutch Nutrient Database (Voedingscentrum 2001).
For the 1st tasting session, this standard pork with NaCl and 5
soy sauce variants of the marinated meat were prepared; the latter
were prepared by replacing the NaCl with various concentrations of
soy sauce powder (soy 1 to soy 5). Since 3.16 g of powdered Kikkoman soy sauce contained 1 g NaCl, the changes in weight/volume
that occurred during this replacement were neutralized by the addition of less meat. The NaCl contents of the soy sauce variants were
0.7% (w/w), 0.6% (w/w), 0.5% (w/w), 0.4% (w/w), and 0.3% (w/w),
respectively. Again, the range of these soy sauce concentrations was
established by a small pilot test conducted among colleagues (n =
11) at our department.
For the 2nd tasting session, 5 pork variants were prepared, varying their table salt/soy sauce ratio (see Table 3). All pork variants were prepared by a chef immediately before serving and were
kept warm in a bain-marie at a temperature of 45 ◦ C for ap- Statistical analysis
proximately 15 min. Five or 6 slices of stir-fried pork were placed
The data from the 2-AFC tests were analyzed using betain 50 mL polystyrene cups and were immediately served to the binomial statistics. Analysis of variance (ANOVA) was performed
panelists.
on the ratings of pleasantness and attribute intensity. Once the
Table 2 --- Recipes for the soup variants 1 to 5.
Variant
1
2
3
4
5
Ingredients
Concentrate
Salt
Soy sauce powder
Water
Concentrate
Salt
Soy sauce powder
Water
Concentrate
Salt
Soy sauce powder
Water
Concentrate
Salt
Soy sauce powder
Water
Concentrate
Salt
Soy sauce powder
Water
(g)
50
0.9
--49.1
50
0.68
0.59
48.73
50
0.45
1.18
48.37
50
0.23
1.77
48
50
--2.36
47.64
“Table salt”
percentage
(%)
“Soy sauce”
percentage
(%)
Total NaCl
content
(%, w/w)
100
---
0.90
75
25
0.87
50
50
0.82
25
75
0.79
---
100
0.75
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Again, the range of these soy sauce concentrations was established
by a small pilot test conducted among colleagues (n = 9) at our department.
For the 2nd tasting session, 5 soup variants were prepared varying in their table salt/soy sauce ratio (see Table 2). All soups were
prepared by a chef 20 min before serving and were kept warm in a
bain-marie at a temperature of 60 ◦ C. Prior to serving, 30 mL of soup
were poured into 50 mL polystyrene cups and were served straight
away to the panelists.
Salt reduction using soy sauce . . .
F test indicated a significant difference between product means,
post hoc LSD comparison of mean tests was performed to determine which means were significantly different. Significance of
differences was defined as P < 0.05. The ANOVAs and post hoc
tests were performed using SPSS v. 16.0 (SPSS Inc., Chicago, Ill.,
U.S.A.).
Results and Discussion
as the stir-fried pork prepared with soy sauce with a NaCl content
of 0.5% (w/w).
These results can be translated into a NaCl reduction in the
tested real food products of respectively 50%, 17%, and 29% without compromising the intensity of the overall taste.
Consequently, these ERs defined the soy sauce concentrations
that were used for the preparation of the 100% soy sauce variants
served in the 2nd tasting session.
Exchange rate (ER)
Optimal exchange rate (OER)
Figure 1 gives an overview of the results from the 2-AFC tests.
In pairs 1 to 4 of the salad dressing test, the overall taste of the soy
sauce variants was significantly perceived as stronger than that of
the NaCl standard. No significant difference in overall taste intensity was reported for pair 5. Thus, a salad dressing prepared with 2%
(w/w) NaCl tastes equally intense as a salad dressing prepared with
soy sauce with a NaCl content of 1% (w/w).
For pair 1 of the soup test, the overall taste of the soy sauce variant was significantly perceived as stronger than the overall taste of
the NaCl standard. For pair 2, no significant difference in overall
taste intensity was observed, whereas for pair 3, pair 4, and pair 5,
the salt standard was reported to have a stronger overall taste. Thus,
tomato cream soup prepared with 0.9% (w/w) NaCl tastes equally
intense as the tomato cream soup prepared with soy sauce with a
NaCl content of 0.75% (w/w).
For pair 1 and pair 2 of the stir-fried pork test, the overall taste of
the soy sauce variant was significantly perceived as stronger than
that of the NaCl standard. For pair 3, no significant difference in
overall taste intensity was observed, whereas for pair 4 and pair 5,
the salt standard was reported to have a stronger overall taste. Thus,
stir-fried pork prepared with 0.7% (w/w) NaCl tastes equally intense
Figure 2 gives an overview of the pleasantness and attribute ratings per product. First, no significant difference was observed for
pleasantness, overall taste intensity, and sourness between the 5
salad dressing variants with varying “table salt/soy sauce” ratios.
Significant differences between the 5 dressing variants were observed for saltiness (P < 0.001). The 100% “table salt” dressing (variant 1) and the 75/25% “table salt/soy” dressing (variant 2) were
perceived as saltier than the salad dressing variants 3, 4, and 5.
Second, no significant difference was observed for pleasantness,
saltiness, or tomato taste between the 5 soup variants with varying table salt/soy sauce ratios. The products differed significantly
in their overall taste intensity (P < 0.01). Variant 1 and variant 2
of the soups (100% “table salt” and 75/25% “table salt/soy”) were
perceived as less strong in taste than the soup variants 3, 4, and
5. Third, no significant difference was observed for pleasantness,
overall taste intensity, saltiness, and meat taste between the 5 stirfried pork variants with varying table salt/soy sauce ratios.
These results can be translated to a NaCl reduction in the tested
real food products of respectively 50%, 17%, and 29% without leading to significant losses in either overall taste intensity or product
pleasantness.
S: Sensory & Food
Quality
Table 3 --- Recipes for the stir-fried pork variants 1 to 5.
Variant
1
2
3
4
5
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Ingredients
(g)
Pork meat
Salt
Starch
Wheat germ oil
White wine
Soy sauce powder
Pork meat
Salt
Starch
Wheat germ oil
White wine
Soy sauce powder
Pork meat
Salt
Starch
Wheat germ oil
White wine
Soy sauce powder
Pork meat
Salt
Starch
Wheat germ oil
White wine
Soy sauce powder
Pork meat
Salt
Starch
Wheat germ oil
White wine
Soy sauce powder
90.3
0.7
1
3
5
--90.1
0.53
1
3
5
0.4
89.9
0.35
1
3
5
0.8
89.6
0.18
1
3
5
1.2
89.4
--1
3
5
1.6
JOURNAL OF FOOD SCIENCE—Vol. 74, Nr. 6, 2009
“Table salt”
percentage
(%)
“Soy sauce”
percentage
(%)
Total NaCl
content
(%, w/w)
100
---
0.70
75
25
0.66
50
50
0.60
25
75
0.56
---
100
0.50
Salt reduction using soy sauce . . .
S: Sensory & Food
Quality
Figure 1 --- 2-AFC test results for the
overall taste intensity of salad
dressing, soup, and stir-fried pork
(n.s. = not significant, ∗ P < 0.05,
∗∗
P < 0.01, ∗∗∗ P < 0.001).
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Salt reduction using soy sauce . . .
Figure 2 --- Pleasantness and attribute
ratings for salad dressing, soup, and
stir-fried pork (dotted line = no
significant difference, straight line =
significant difference).
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Quality
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NaCl reduction in foods using soy sauce
In the present study, it was demonstrated that it is possible to replace NaCl in a number of foods with naturally brewed soy sauce
and to reduce the total sodium content in these foods without significantly lowering their consumer acceptance.
There are 2 possible explanations to put forward for the underlying reasons for the salt reduction abilities of naturally brewed soy
sauce.
First, monosodium glutamate and 5 -ribonucleotides have been
reported to enhance other flavors in low salt lentil and mushroom soups (Roininen and others 1996). Similarly, Mojet and others
(2004) demonstrated that umami tastants (monosodium glutamate
and inosine 5 -monophosphate) are able to enhance the perceived
saltiness of chicken broth. Thus, these taste–taste interactions
might also have occurred in the present study, since soy sauce is
known to contain a large quantity of naturally occurring umami
tastants (for example, glutamic acid) (Skurray and Pucar 1988;
Populin and others 2007), leading to an enhancement in saltiness
in salt-reduced soy sauce variants.
Second, the results of the present study are also consistent with
previous findings on OISE by a salty-congruent odor (Djordjevic
and others 2004; Lawrence and others 2009). Hence, it might also
be possible that in the present study soy sauce odor induced an
enhancement of perceived saltiness, although it might be expected
that the association between soy sauce odor and saltiness in a population of almost completely nonusers of soy sauce might not be
very strong. In that case it will take probably more than 1 or 2
sessions to establish an association between soy sauce odor and
saltiness.
Since, in these previous studies on OISE, water solutions with
low NaCl content were used as model systems, the present study
might represent an indication for the existence of OISE in real
foods. Interestingly, for the salad dressing OISE could only be observed in the 75%/25% “table salt/soy sauce” variant, whereas for
the soup and meat OISE is observed in all 4 soy sauce-containing
variants. It seems that there are boundaries to the extent to which
OISE can compensate for actual NaCl reduction, as, in the 2nd tasting sessions, the perceived saltiness remained stable in the soup
and meat (total NaCl reduction of, respectively, 17% and 29%) but
not in the salad dressings (total NaCl reduction of 50%). Therefore,
OISE might not be the sole underlying reason for the NaCl reduction abilities of naturally brewed soy sauce. Instead, it seems more
likely that both interaction mechanisms discussed previously have
occurred simultaneously in the present study.
A decrease in NaCl content in foods is very often reported to be
associated with a decrease in consumer acceptance (Sofos 1983;
Breslin and Beauchamp 1997). However, this loss in consumer acceptance has not been observed in the present study. What is more,
even though the perceived saltiness decreased alongside the decreasing total NaCl content in the salad dressings (from variant
1 to 5), this did not have a negative effect on the consumer acceptance of these dressings. Hence, at least in the case of the
salad dressings, perceived saltiness seems not to be the crucial factor in maintaining consumer acceptance. It has previously been
shown that monosodium glutamate can help to maintain high levels of acceptance in salt-reduced foods (Yamaguchi and Takahashi
1984; Chi and Chen 1992). Therefore, it seems that the umami
tastants (for example, glutamic acid) and/or soy sauce odorants
that are present in naturally brewed soy sauce were able to maintain the levels of consumer acceptance in the salt-reduced product
variants.
Interestingly, not only were no losses in consumer acceptance
observed, but also no losses in overall taste were observed for the
foods tested in the 2nd sessions. Therefore, it seems that the establishment of a product-specific ER might not only be a suitable
method to prevent losses in overall taste, but also to ensure consumer acceptance. The more so, since for all 3 product types the
established ER was shown to be equal to the OER.
In the present study, consumer acceptance was measured after 1 exposure. This is a regular procedure in consumer research.
However, the replacement of NaCl in Western European foods by
soy sauce might lead to subtle differences in the flavor profile of
these reformulated products. These subtle differences in flavor profile might become more evident after repeated exposure and, in
turn, might either increase or decrease product liking. Therefore, it
seems advisable for food producers to also conduct repeated exposure tests to ensure the long-term acceptance of salt-reduced “soy
sauce foods.”
In the present study, it was shown for 3 different foods that it is
possible to reduce the total NaCl content through a replacement
of NaCl with soy sauce. The underlying mechanisms responsible
for the salt reduction ability of soy sauce therefore seem to be of a
generic nature. Interestingly, the extent to which the soy sauce was
able to compensate for NaCl reduction varied between the 3 tested
foods. The achieved NaCl reduction was highest in the salad dressing. Several explanations for this observation are possible. First,
both quantity and quality of umami tastants/soy sauce odorants
might vary at different temperatures. One could hypothesize that
the heating process and/or higher serving temperatures change the
amount or availability of tastants/odors present in the soy sauce
(Paulus and Reisch 1980). Second, the odor profiles of liquid soy
sauce and dried powdered soy sauce differ in relation to their different production processes (Ryo Shimojo, Kikkoman Europe, personal communication). Third, both tomato soup and pork contain
naturally present glutamates, which might have limited the NaCl
reduction abilities of the added soy sauce (Barylko-Pikielna and
Kostyra 2007). Finally, it is of course also possible that more than
one of the above-discussed explanations contributes to the different compensation potentials of soy sauce to replace NaCl in different foods.
T
Conclusions
he results of the present study strongly support the claim that
it is possible to replace NaCl in foods with naturally brewed soy
sauce without lowering the overall taste intensity and to reduce the
total sodium content in these foods without decreasing their consumer acceptance.
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