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JFS S: Sensory and Food Quality

Salt Reduction in Foods UsingNaturally Brewed Soy SauceSTEFANIE KREMER, JOZINA MOJET, AND RYO SHIMOJO

ABSTRACT: In recent years, health concerns related to salt/sodium chloride consumption have caused an increaseddemand for salt-reduced foods. Consequently, sodium chloride (NaCl) reduction in foods has become an importantchallenge. The more so, since a decrease in NaCl content is often reported to be associated with a decrease in con-sumer acceptance. The objective of the present study was to investigate whether or not it would be possible to reducethe NaCl content in standard Western European foods by replacing it with naturally brewed soy sauce. Three typesof foods were investigated: salad dressing (n = 56), soup (n = 52), and stir-fried pork (n = 57). In the 1st step, anexchange rate (ER) by which NaCl can be replaced with soy sauce without a significant change in the overall tasteintensity was established per product type, by means of alternative forced choice tests. In the 2nd step, the sameconsumers evaluated 5 samples per product type with varying NaCl and/or soy sauce content on pleasantness andseveral sensory attributes. The results showed that it was possible to achieve a NaCl reduction in the tested foodsof, respectively, 50%, 17%, and 29% without leading to significant losses in either overall taste intensity or productpleasantness. These results suggest that it is possible to replace NaCl in foods with naturally brewed soy sauce with-out lowering the overall taste intensity and to reduce the total NaCl content in these foods without decreasing theirconsumer acceptance.

PRACTICAL APPLICATION: Health concerns related to salt consumption cause an increased demand for salt-reduced foods. Consequently, the development of foods with reduced salt content without decreasing the consumeracceptance is an important challenge for the food industry. A new possible salt reduction approach is described inthe present article: The replacement of salt with naturally brewed soy sauce.

Keywords: odor-induced taste perception, saltiness enhancement, salt replacement, soy sauce, umami

Introduction

Sodium chloride (NaCl) is one of the most important ingredi-ents for many foods. It influences not only the flavor profile

of food products, but also their texture, and it plays an importantrole in the preservation of foods against microbes. However, NaClhas also been reported to increase the risk of hypertension andto be directly related to the development of cardiovascular disease(Weinsier 1976; Law 1997). Therefore, the World Health Organiza-tion (WHO) in 1990 recommended a limitation of the average NaClintake to 6 g per day for adults. Seventeen years later, WHO repeatedthis earlier warning and recommended an even lower daily sodiumintake of 5 g per day (WHO 2007). Consequently, the reduction ofNaCl content in food products has become an important challengefor the food industry. The more so, since a decrease in NaCl contentis very often reported to be associated with a decrease in consumeracceptance (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 potas-sium chloride (KCl) and calcium chloride (CaCl2). The second is tostrengthen other tastes to enhance perceived saltiness.

The former approach was performed for Feta cheese (Katsiariand 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 andMojet are with Wageningen Univ. and Research, Centre for Innovative Con-sumer Studies, Bornsesteeg 59, 6708 PD Wageningen, The Netherlands.Author Shimojo is with Kikkoman Europe R&D Laboratory B.V., NieuweKanaal 7, 6709 PA Wageningen, The Netherlands. Direct inquiries to authorKremer (E-mail: stefanie.kremer@wur.nl).

Guardia and others 2006). According to their studies, the alterna-tive salts may allow reduction of the NaCl content by up to 50%.However, as Jacobson (2005) pointed out, “the average sodium con-tent of processed foods decreased only by 0.3% per year between1983 and 2004.” This clearly suggests that the previous attemptsto reduce NaCl content have significant obstacles when applied toreal-life products. Two problems can be foreseen. First, KCl is in-applicable to nephritic patients whose potassium intake is strictlycontrolled. Second, manufacturers have to declare on their labelsthat alternative salts are included as additives. This might result inthe loss of customers who prefer a clean label.

Interestingly, Mojet and others (2004) found that the 5 basictastes, that is, umami, salty, sour, bitter, and sweet, interact witheach other. For example, they showed that umami enhancedperceived saltiness in foods. In their study, they used monosodiumglutamate (MSG) and inosine 5

′-monophosphate as umami sub-

stances. The study foresees that, in food products that contain alarge quantity of “natural” umami substance, NaCl content canbe decreased without diminished consumer acceptance. Anotherpossible approach to further reduce salt could be odor-inducedsaltiness enhancement (OISE) by a salty-congruent odor(Djordjevic and others 2004; Lawrence and others 2009). Well-selected odors might be used to compensate for NaCl reduction infoods. However, the sustainability of such an effect has still to beinvestigated. Naturally brewed soy sauce is one of the foods thatcontain high levels of naturally occurring umami substances, suchas amino acids and peptides (Skurray and Pucar 1988).

Soy sauce is a fermented sauce made from soybeans, grain, wa-ter, and salt, and was invented in Asia almost 2500 y ago. Nowadays,it is widely used both in Asian and in Western cuisines.

C© 2009 Institute of Food Technologists R© Vol. 74, Nr. 6, 2009—JOURNAL OF FOOD SCIENCE S255doi: 10.1111/j.1750-3841.2009.01232.xFurther reproduction without permission is prohibited

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The aim of the present study was to demonstrate whether or notit would be possible to reduce the NaCl content in standard WesternEuropean foods by replacing NaCl with naturally brewed soy saucewithout decreasing the consumer acceptance of these foods.

Materials and Methods

SubjectsPer product category (salad dressing, soup, stir-fried pork), 60

consumers, aged between 18 and 60 y, were selected by a local re-cruitment agency. All subjects were Caucasian and met the follow-ing criteria: healthy, not on a prescribed diet, not subject to foodallergies, and in good command of the Dutch language. On the daysof testing, not all recruited consumers were able to attend the ex-perimental sessions. Consequently, the actual numbers of subjectstested per category were 56, 52, and 57, respectively. Of the 56 con-sumers who evaluated the salad dressings, 28 were male and 28female (mean age 38, range 18 to 57 y) and of the 52 consumerswho evaluated the soups, 26 were male and 26 female (mean age38, range 18 to 56 y). Finally, of the 57 consumers who assessed thestir-fried pork, 26 were male and 31 female (mean age 39, range 18to 56 y).

Per product category, the consumers participated in 2 tastingsessions of approximately 60 min each. They received a fee for par-ticipation at the completion of the study.

SamplesCommercially 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 Kikkomanpowdered soy sauce KU-20 was used in the preparation of the soupsand stir-fried pork. Since both sauces were naturally brewed andconsequently no artificial glutamic acid salts such as monosodiumglutamate (MSG) were added, the sodium (Na) content present inthese soy sauces corresponded directly to their total NaCl content(1 g Na is correspondent to 2.54 g NaCl).

Salad dressingAbout 6.96 g of liquid Kikkoman soy sauce contained 1 g NaCl.

Prior to the preparation of the standard salad dressing, the 1st stepwas to dissolve 14.36 g NaCl in 85.64 g of water. This step was neces-sary, since a straight replacement of NaCl with soy sauce in a recipewould give too much difference in both weight and volume. Thesalad dressing was then prepared according to the following recipe:64 g olive oil, 22 g balsamic vinegar, 13.9 g NaCl/water solution, and0.1 g ground black pepper. This salad dressing was used as the stan-dard dressing in paired comparison tests with soy sauce variants. Ithad a NaCl content of 2% (w/w), which is in line with NaCl con-tent for commercial salad dressings reported in the Dutch Nutri-ent Database (Voedingscentrum 2001). For the 1st tasting session,this standard dressing and 5 soy sauce variants of the salad dressingwere prepared by replacing the NaCl with various concentrations ofsoy sauce (soy 1 to soy 5). NaCl content of the soy sauce variants was1.60% (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 basedon the results of a small pilot test conducted among colleagues atour department (n = 10). The aim of this pilot test was to ensurethat, within this soy sauce concentration range, one of the follow-ing 3 results can be expected to occur. First, that the overall tasteintensity of the soy sauce variant is stronger than that of the stan-dard salad dressing; second, that no difference in overall taste in-tensity can be observed; and, third, that the overall taste intensity

of the standard salad dressing is stronger than that of the soy saucevariant.

For the 2nd tasting session, 5 salad dressing variants were pre-pared, varying their table salt/soy sauce ratio (see Table 1). Allsalad dressing variants were prepared 24 h before serving, placed in100 mL plastic cups with air-tight lids, and stored overnight in afood grade refrigerator at 4 ◦C. Fifteen minutes before serving, allsalad dressings were taken out of the refrigerator and 30 g of thedressing were added per 200 g pre-cut salad and gently mixed in for3 min. Twenty-gram portions of the salads were then served in 50mL polystyrene cups.

SoupCream of tomato soup concentrate was obtained from a soup

producer (www.kleinstesoepfabriek.nl). It was produced under theorganic label “EKO” and did not contain NaCl or artificial gluta-mate. The recommended degree of dilution for this soup concen-trate was 1 L soup with 1 L water.

The soup was prepared according to the following recipe:50 g cream of tomato soup concentrate, 0.9 g NaCl, 49.1 g water.This soup was used as the standard in the paired comparisons. Ithad a NaCl content of 0.9% (w/w), which is in line with the NaClcontent for commercial soups reported in the Dutch NutrientDatabase (Voedingscentrum 2001).

For the 1st tasting session, this standard soup with NaCl and 5soy sauce variants of the soup was prepared; the latter were pre-pared by replacing the NaCl with various concentrations of soysauce (soy 1 to soy 5). Since 3.16 g of powdered Kikkoman soy saucecontain 1 g NaCl, the changes in weight/volume that occurred dur-ing this replacement were neutralized by the addition of less wa-ter. 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.

Table 1 --- Recipes for the salad dressing variants 1 to 5.

“Table salt” “Soy sauce” Total NaClpercentage percentage content

Variant Ingredients (g) (%) (%) (%, w/w)

1 Olive oil 64Balsamico 22Salt solution 13.9 100 --- 2.00Soy sauce ---Water ---Pepper 0.1

2 Olive oil 64Balsamico 22Salt solution 10.4 75 25 1.75Soy sauce 1.75Water 1.75Pepper 0.1

3 Olive oil 64Balsamico 22Salt solution 6.9 50 50 1.50Soy sauce 3.5Water 3.5Pepper 0.1

4 Olive oil 64Balsamico 22Salt solution 3.4 25 75 1.25Soy sauce 5.25Water 5.25Pepper 0.1

5 Olive oil 64Balsamico 22Salt solution --- --- 100 1.00Soy sauce 7Water 6.9Pepper 0.1

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Again, the range of these soy sauce concentrations was establishedby a small pilot test conducted among colleagues (n = 9) at our de-partment.

For the 2nd tasting session, 5 soup variants were prepared vary-ing in their table salt/soy sauce ratio (see Table 2). All soups wereprepared by a chef 20 min before serving and were kept warm in abain-marie at a temperature of 60 ◦C. Prior to serving, 30 mL of soupwere poured into 50 mL polystyrene cups and were served straightaway to the panelists.

Stir-fried porkFor the stir-fried pork, chops of belly/side pork were ordered

from a national meat supplier (DeliXL, Ede, the Netherlands). Themeat was cut into thin slices of equal size (1 × 2 cm), marinated bythe chef, and left to stand for 45 min before frying.

The pork was prepared for stir-frying according to the followingrecipe: 90.3 g sliced side pork, 0.7 g NaCl, 1 g potato starch, 3 g wheatgerm oil, 5 g white wine. This prepared standard pork had a NaClcontent of 0.7% (w/w), which is in line with the NaCl content formeat stir-fries reported in the Dutch Nutrient Database (Voedings-centrum 2001).

For the 1st tasting session, this standard pork with NaCl and 5soy sauce variants of the marinated meat were prepared; the latterwere prepared by replacing the NaCl with various concentrations ofsoy sauce powder (soy 1 to soy 5). Since 3.16 g of powdered Kikko-man soy sauce contained 1 g NaCl, the changes in weight/volumethat occurred during this replacement were neutralized by the ad-dition of less meat. The NaCl contents of the soy sauce variants were0.7% (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 wasestablished by a small pilot test conducted among colleagues (n =11) at our department.

For the 2nd tasting session, 5 pork variants were prepared, vary-ing their table salt/soy sauce ratio (see Table 3). All pork vari-ants were prepared by a chef immediately before serving and werekept warm in a bain-marie at a temperature of 45 ◦C for ap-proximately 15 min. Five or 6 slices of stir-fried pork were placedin 50 mL polystyrene cups and were immediately served to thepanelists.

Table 2 --- Recipes for the soup variants 1 to 5.

“Table salt” “Soy sauce” Total NaClpercentage percentage content

Variant Ingredients (g) (%) (%) (%, w/w)

1 Concentrate 50Salt 0.9Soy sauce powder --- 100 --- 0.90Water 49.1

2 Concentrate 50Salt 0.68 75 25 0.87Soy sauce powder 0.59Water 48.73

3 Concentrate 50Salt 0.45Soy sauce powder 1.18 50 50 0.82Water 48.37

4 Concentrate 50Salt 0.23Soy sauce powder 1.77 25 75 0.79Water 48

5 Concentrate 50Salt --- --- 100 0.75Soy sauce powder 2.36Water 47.64

ProcedureThe tasting sessions were conducted in the sensory laboratory

of The Restaurant of the Future, Wageningen, The Netherlands. Perproduct type, 1st and 2nd panel sessions were held within 1 wk. Inthe 1st session, the subjects were asked to perform five 2-alternativeforced choice (2-AFC) tests. The aim of the 2-AFC tests was to es-tablish the exchange rate (ER) by which NaCl can be replaced withsoy sauce without a significant change in the overall taste intensity.To this end, the subjects were asked to compare the product withthe standard NaCl content with 1 out of 5 products with differentsoy sauce concentrations. They were asked to indicate which of the2 samples had the stronger overall taste. After the 1st session, theER was calculated from the results of the paired comparisons andthis ER was used to calculate the concentrations for the 2nd tastingsession. The aim was that the 100% soy variant used in the 2nd ses-sion would be perceived by consumers to taste equally intense asthe 100% NaCl variant (for more details, see the “Results and Dis-cussion” section).

In the 2nd session, panelists evaluated 5 samples with varying ta-ble salt and/or soy sauce content twice. The aim of the 2nd sessionwas to establish the optimal exchange rate (OER) by which NaCl canbe replaced with soy sauce in products without significant lossesin both overall taste intensity and in the degree of product liking.Per sample, pleasantness was always assessed first on a visual ana-logue scale. Next, the intensities of the following sensory attributes,“overall taste intensity,” “salty taste,” “sour taste” (salad dressingonly), “tomato taste” (soup only), “meat taste” (stir-fried pork only),were rated on the same visual analogue scales. The verbal anchorswere “very little/weak” and “very much/strong” and were placed at10% and 90% on the scale, respectively. All samples were coded withrandom 3-digit numbers and were presented in random order perperson. Panelists were instructed to rinse their mouth with waterand to eat cream crackers between the samples. The inter-stimulusinterval was 4 min.

Statistical analysisThe data from the 2-AFC tests were analyzed using beta-

binomial statistics. Analysis of variance (ANOVA) was performedon the ratings of pleasantness and attribute intensity. Once the

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F test indicated a significant difference between product means,post hoc LSD comparison of mean tests was performed to de-termine which means were significantly different. Significance ofdifferences was defined as P < 0.05. The ANOVAs and post hoctests were performed using SPSS v. 16.0 (SPSS Inc., Chicago, Ill.,U.S.A.).

Results and Discussion

Exchange rate (ER)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 soysauce variants was significantly perceived as stronger than that ofthe NaCl standard. No significant difference in overall taste inten-sity was reported for pair 5. Thus, a salad dressing prepared with 2%(w/w) NaCl tastes equally intense as a salad dressing prepared withsoy sauce with a NaCl content of 1% (w/w).

For pair 1 of the soup test, the overall taste of the soy sauce vari-ant was significantly perceived as stronger than the overall taste ofthe NaCl standard. For pair 2, no significant difference in overalltaste 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 equallyintense as the tomato cream soup prepared with soy sauce with aNaCl content of 0.75% (w/w).

For pair 1 and pair 2 of the stir-fried pork test, the overall taste ofthe soy sauce variant was significantly perceived as stronger thanthat of the NaCl standard. For pair 3, no significant difference inoverall 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

Table 3 --- Recipes for the stir-fried pork variants 1 to 5.

“Table salt” “Soy sauce” Total NaClpercentage percentage content

Variant Ingredients (g) (%) (%) (%, w/w)

1 Pork meat 90.3Salt 0.7Starch 1 100 --- 0.70Wheat germ oil 3White wine 5Soy sauce powder ---

2 Pork meat 90.1Salt 0.53Starch 1 75 25 0.66Wheat germ oil 3White wine 5Soy sauce powder 0.4

3 Pork meat 89.9Salt 0.35Starch 1 50 50 0.60Wheat germ oil 3White wine 5Soy sauce powder 0.8

4 Pork meat 89.6Salt 0.18Starch 1 25 75 0.56Wheat germ oil 3White wine 5Soy sauce powder 1.2

5 Pork meat 89.4Salt ---Starch 1 --- 100 0.50Wheat germ oil 3White wine 5Soy sauce powder 1.6

as the stir-fried pork prepared with soy sauce with a NaCl contentof 0.5% (w/w).

These results can be translated into a NaCl reduction in thetested real food products of respectively 50%, 17%, and 29% with-out compromising the intensity of the overall taste.

Consequently, these ERs defined the soy sauce concentrationsthat were used for the preparation of the 100% soy sauce variantsserved in the 2nd tasting session.

Optimal exchange rate (OER)Figure 2 gives an overview of the pleasantness and attribute rat-

ings per product. First, no significant difference was observed forpleasantness, overall taste intensity, and sourness between the 5salad dressing variants with varying “table salt/soy sauce” ratios.Significant differences between the 5 dressing variants were ob-served for saltiness (P < 0.001). The 100% “table salt” dressing (vari-ant 1) and the 75/25% “table salt/soy” dressing (variant 2) wereperceived 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 vary-ing table salt/soy sauce ratios. The products differed significantlyin their overall taste intensity (P < 0.01). Variant 1 and variant 2of the soups (100% “table salt” and 75/25% “table salt/soy”) wereperceived as less strong in taste than the soup variants 3, 4, and5. Third, no significant difference was observed for pleasantness,overall taste intensity, saltiness, and meat taste between the 5 stir-fried pork variants with varying table salt/soy sauce ratios.

These results can be translated to a NaCl reduction in the testedreal food products of respectively 50%, 17%, and 29% without lead-ing to significant losses in either overall taste intensity or productpleasantness.

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Figure 1 --- 2-AFC test results for theoverall taste intensity of saladdressing, soup, and stir-fried pork(n.s. = not significant, ∗P < 0.05,∗∗P < 0.01, ∗∗∗P < 0.001).

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Figure 2 --- Pleasantness and attributeratings for salad dressing, soup, andstir-fried pork (dotted line = nosignificant difference, straight line =significant difference).

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NaCl reduction in foods using soy sauceIn the present study, it was demonstrated that it is possible to re-

place NaCl in a number of foods with naturally brewed soy sauceand to reduce the total sodium content in these foods without sig-nificantly lowering their consumer acceptance.

There are 2 possible explanations to put forward for the under-lying reasons for the salt reduction abilities of naturally brewed soysauce.

First, monosodium glutamate and 5′-ribonucleotides have been

reported to enhance other flavors in low salt lentil and mush-room soups (Roininen and others 1996). Similarly, Mojet and others(2004) demonstrated that umami tastants (monosodium glutamateand inosine 5

′-monophosphate) are able to enhance the perceived

saltiness of chicken broth. Thus, these taste–taste interactionsmight also have occurred in the present study, since soy sauce isknown to contain a large quantity of naturally occurring umamitastants (for example, glutamic acid) (Skurray and Pucar 1988;Populin and others 2007), leading to an enhancement in saltinessin salt-reduced soy sauce variants.

Second, the results of the present study are also consistent withprevious findings on OISE by a salty-congruent odor (Djordjevicand others 2004; Lawrence and others 2009). Hence, it might alsobe possible that in the present study soy sauce odor induced anenhancement of perceived saltiness, although it might be expectedthat the association between soy sauce odor and saltiness in a pop-ulation of almost completely nonusers of soy sauce might not bevery strong. In that case it will take probably more than 1 or 2sessions to establish an association between soy sauce odor andsaltiness.

Since, in these previous studies on OISE, water solutions withlow NaCl content were used as model systems, the present studymight represent an indication for the existence of OISE in realfoods. Interestingly, for the salad dressing OISE could only be ob-served in the 75%/25% “table salt/soy sauce” variant, whereas forthe soup and meat OISE is observed in all 4 soy sauce-containingvariants. It seems that there are boundaries to the extent to whichOISE can compensate for actual NaCl reduction, as, in the 2nd tast-ing sessions, the perceived saltiness remained stable in the soupand meat (total NaCl reduction of, respectively, 17% and 29%) butnot in the salad dressings (total NaCl reduction of 50%). Therefore,OISE might not be the sole underlying reason for the NaCl reduc-tion abilities of naturally brewed soy sauce. Instead, it seems morelikely that both interaction mechanisms discussed previously haveoccurred simultaneously in the present study.

A decrease in NaCl content in foods is very often reported to beassociated with a decrease in consumer acceptance (Sofos 1983;Breslin and Beauchamp 1997). However, this loss in consumer ac-ceptance has not been observed in the present study. What is more,even though the perceived saltiness decreased alongside the de-creasing total NaCl content in the salad dressings (from variant1 to 5), this did not have a negative effect on the consumer ac-ceptance of these dressings. Hence, at least in the case of thesalad dressings, perceived saltiness seems not to be the crucial fac-tor in maintaining consumer acceptance. It has previously beenshown that monosodium glutamate can help to maintain high lev-els of acceptance in salt-reduced foods (Yamaguchi and Takahashi1984; Chi and Chen 1992). Therefore, it seems that the umamitastants (for example, glutamic acid) and/or soy sauce odorantsthat are present in naturally brewed soy sauce were able to main-tain the levels of consumer acceptance in the salt-reduced productvariants.

Interestingly, not only were no losses in consumer acceptanceobserved, but also no losses in overall taste were observed for the

foods tested in the 2nd sessions. Therefore, it seems that the es-tablishment of a product-specific ER might not only be a suitablemethod to prevent losses in overall taste, but also to ensure con-sumer acceptance. The more so, since for all 3 product types theestablished ER was shown to be equal to the OER.

In the present study, consumer acceptance was measured af-ter 1 exposure. This is a regular procedure in consumer research.However, the replacement of NaCl in Western European foods bysoy sauce might lead to subtle differences in the flavor profile ofthese reformulated products. These subtle differences in flavor pro-file might become more evident after repeated exposure and, inturn, might either increase or decrease product liking. Therefore, itseems advisable for food producers to also conduct repeated expo-sure tests to ensure the long-term acceptance of salt-reduced “soysauce foods.”

In the present study, it was shown for 3 different foods that it ispossible to reduce the total NaCl content through a replacementof NaCl with soy sauce. The underlying mechanisms responsiblefor the salt reduction ability of soy sauce therefore seem to be of ageneric nature. Interestingly, the extent to which the soy sauce wasable to compensate for NaCl reduction varied between the 3 testedfoods. The achieved NaCl reduction was highest in the salad dress-ing. Several explanations for this observation are possible. First,both quantity and quality of umami tastants/soy sauce odorantsmight vary at different temperatures. One could hypothesize thatthe heating process and/or higher serving temperatures change theamount or availability of tastants/odors present in the soy sauce(Paulus and Reisch 1980). Second, the odor profiles of liquid soysauce and dried powdered soy sauce differ in relation to their dif-ferent production processes (Ryo Shimojo, Kikkoman Europe, per-sonal communication). Third, both tomato soup and pork containnaturally present glutamates, which might have limited the NaClreduction abilities of the added soy sauce (Barylko-Pikielna andKostyra 2007). Finally, it is of course also possible that more thanone of the above-discussed explanations contributes to the differ-ent compensation potentials of soy sauce to replace NaCl in differ-ent foods.

Conclusions

The results of the present study strongly support the claim thatit is possible to replace NaCl in foods with naturally brewed soy

sauce without lowering the overall taste intensity and to reduce thetotal sodium content in these foods without decreasing their con-sumer acceptance.

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