Convenient Synthesis of L-Ornithyltaurine-HCl and the Effect on Saltiness in a Food Material

Article abstract of DOI:10.1021/jf950711u

A new convenient synthesis of a salty peptide, ornithyltaurine (Orn-Tau), was designed. Compared with a conventional synthesis, the process was shortened by two steps and the purification was made much easier in the new one. Consequently, Orn-Tau was easily obtained and subjected to a further series of experiments. The product produced a good saltiness without Na⁺ in the presence of HCl, and the saltiness became stronger as the amount of added HCl increased. The best quality of saltiness was obtained by adding 1.2 equiv of HCl to the Orn-Tau solutions. The Orn-Tau·1.2HCl was equally salty to NaCl on a molar basis and also had an enhancing effect on saltiness of NaCl. The intake of Na⁺ could be cut by 95% in a model system and by 50% in a food material (soy sauce) by using Orn-Tau·1.2HCl, which have the most excellent saltiness and Na⁺ dietary effect of our NaCl substitutes at the present time.

Full text of DOI:10.1021/jf950711u

J. Agric. Food Chem. 1996, 44, 2481
−2485
2481
ARTICLES
Con ven ien t Syn th esis of L-Or n ith ylta u r in e‚HCl a n d th e Effect on
Sa ltin ess in a F ood Ma ter ia l
Kozo Nakamura,†,§ Rie Kuramitu,† Shirou Kataoka,† Daisuke Segawa,† Kouji Tahara,†
Masahiro Tamura,‡ and Hideo Okai*,†
Department of Fermentation Technology, Faculty of Engineering, Hiroshima University,
1-4-1 Kagamiyama, Higashihiroshima, Hiroshima 724, J apan, and Tokyo Research Laboratories,
Kowa Company, Ltd., 2-17-43 Noguchi-cho Higashimurayama, Tokyo 189, J apan
A new convenient synthesis of a salty peptide, ornithyltaurine (Orn-Tau), was designed. Compared
with a conventional synthesis, the process was shortened by two steps and the purification was
made much easier in the new one. Consequently, Orn-Tau was easily obtained and subjected to a
further series of experiments. The product produced a good saltiness without Na+ in the presence
of HCl, and the saltiness became stronger as the amount of added HCl increased. The best quality
of saltiness was obtained by adding 1.2 equiv of HCl to the Orn-Tau solutions. The Orn-Tau‚1.2HCl
was equally salty to NaCl on a molar basis and also had an enhancing effect on saltiness of NaCl.
The intake of Na+ could be cut by 95% in a model system and by 50% in a food material (soy sauce)
by using Orn-Tau‚1.2HCl, which have the most excellent saltiness and Na+ dietary effect of our
NaCl substitutes at the present time.
Keyw or d s: Salt substitute; L-ornithyltaurine; sodium ion dietary effect; new large scale synthesis
INTRODUCTION
the saltiness of the first finding, Orn-Tau‚HCl, is still
the best. We employed Orn-Tau‚HCl as a typical salty
compound without Na+ and examined its effect when
added to a practical food material. As a food material
for this study, soy sauce was selected. Soy sauce is one
of the most popular liquid fermentation seasonings
made from soybeans in J apan and is used not only as a
sauce for Sashimi, Susi, etc. but also as a base for most
J apanese foods. A typical J apanese person intakes
about 27mL of soy sauce containing about 16% (2.7 M)
NaCl everyday. In the soy sauce, many kinds of
constituents of food materials such as inorganic ions,
amino acids, sugars, acids, and alcohols were contained,
and so we might reasonably evaluate the effect on a food
material of Orn-Tau‚HCl.
For the examinations, we had estimated that a
considerable amount of Orn-Tau‚HCl would be required,
which by a conventional synthesis would be difficult to
obtain. We sought to settle the problem by devising a
new convenient synthesis. The first problem was the
purification. After coupling dibenzyloxycarbonylorni-
thine [Z-Orn(Z)-OH] with taurine (H-Tau-OH), an ex-
traction with ethyl acetate was carried out for the
purification. However, owing to the sulfonyl group of
Tau, the extraction was very difficult even at pH 2. To
prevent a low yield, we might perform the extraction
many times under conditions of saturation with NaCl
at drastically low pH. These operations needed a large
amount of ethyl acetate and special excellent techniques
to avoid contamination of Na+ and deterioration of the
taste quality. At one time, a research group reported
that the saltiness of Orn-Tau was due to the contami-
nated Na+ (Huynh-ba and Philippossian, 1987). This
shows the difficulty of these operations. A second
problem is the coupling method of Z-Orn(Z)-OH and
Tau. In the conventional synthesis, an active ester
method was used for the coupling, because there are
In 1984, our research group reported that a series of
basic dipeptides, such as Orn-Tau‚HCl, ornithyl-â-
alanine‚HCl (OBA‚HCl), and some others, produced
saltiness (Tada et al., 1984). Since this finding, we have
continuously studied the properties of their salty taste
and attempted to find other new salty compounds. In
1988, we found a new salty compound with a more
simple structure, glycine ethyl ester‚HCl (Gly-OEt‚HCl)
(Kawasaki et al., 1988). The next year, it was found
that the saltiness of OBA and Gly-OEt was controlled
by the amount of HCl, and when 1.3 equiv of HCl was
added, the strongest saltiness was obtained. The salti-
ness of OBA‚1.3HCl was 1.4 times stronger than that
of NaCl on a molar basis. The saltiness of Gly-
OEt‚1.3HCl was stated to be equally salty to NaCl on a
molar basis. When both salty compounds were mixed
with NaCl, the sourness originated by HCl was de-
creased and taste qualities reached a practical level. In
these mixed solutions, the intake of Na+ could be cut
by 75% and 50% by using OBA‚1.3HCl and Gly-
OEt‚1.3HCl, respectively. Lys‚HCl and Orn‚HCl, though
themselves did not have saltiness, enhanced the salti-
ness of NaCl and the intake of Na+ could be cut by 25%
in the mixed solutions (Tamura et al., 1989). More
recently, we found that an O-aminoacyl sugar, which
is a complex of amino acids and sugars, had an excellent
enhancing effect of the NaCl saltiness and the intake
of Na+ could be cut by 90% (Tamura et al., 1993).
Though we have studied saltiness for more than 10
years and found some salty compounds described above,
† Hiroshima University.
‡ Kowa Co. Ltd.
§ Research Fellow of the J apan Society for the Promo-
tion of Science.
S0021-8561(95)00711-4 CCC: $12.00
© 1996 American Chemical Society

2482 J. Agric. Food Chem., Vol. 44, No. 9, 1996
Nakamura et al.
Sch em e 1
Ta ble 1. In flu en ce of HCl on th e Sa lty Ta ste of Or n -Ta u a
no appropriate sulfonyl-protecting groups without taste
deterioration. In the active ester method, synthetic
steps and operations increased.
In Scheme 1, a new synthetic route is shown. The
two problems are solved in this method. In this paper
we report the convenient synthesis and the taste
properties and effects on saltiness in soy sauce of the
Orn-Tau‚HCl.
HCl (equiv)
pH
scoreb
sourness
0
8.9
8.0
7.0
6.4
6.1
5.9
3.4
0
0
1
2
2.5
3
3.5
b
0.11
0.67
1.00
1.10
1.20
1.30
(
+
+
++
a
Concentration of Orn-Tau is 30 mM. Score shows saltiness
strength. Scores +3, +2, +1 are equal to the saltiness of 0.25%,
0.125%, 0.063% NaCl solutions, respectively.
MATERIALS AND METHODS
Ma ter ia ls. L-Ornithine (H-Orn-OH) was provided from
Ajinomoto Inc. and 4-(benzyloxycarbonyloxy)phenyldimethyl-
sulfonium methylsulfate (Z-DSP; Kouge et al., 1987) from
Sanshin Chemical Industrial Co., Ltd., Yamaguchi. Taurine
(H-Tau-OH) was purchased from Tokyo Kasei Kogyo Co., Ltd.
Water soluble carbodiimide (WSC‚HCl) and 1-hydroxybenz-
triazolehydrate (HOBt‚H2O) were from Kokusan Chemical
Works, Inc. Barium hydroxide octahydrate [Ba(OH)2‚8H2O],
palladium carbon, and all solvents were from Katayama
Chemical Industrial Co., Ltd. Commercial soy sauce and all
materials of soy sauce sample were prepared by Takeda
Syokuryo Co., Ltd.
Syn th esis of Or n -Ta u . (a) General Procedures. All melt-
ing points are uncorrected. Thin-layer chromatography was
carried out on Merck silica gel G with two solvent systems:
(1) 1-butanol/acetic acid/pyridine/water (4:2:2:1 v/v); (2) chlo-
roform/methanol/acetic acid (50:10:2 v/v). Spots of materials
possessing a free amino group on a thin-layer plate were
detected by spraying ninhydrin and those of amino group
blocked materials by spraying 25% hydrogen bromide in acetic
acid and then ninhydrin. The optical rotations were measured
on a Union PM-101 polarimeter, and microanalyses were
carried out by Sanshin Chemical Industrial Co., Ltd., Yamagu-
chi. Prior to analyses, the compounds were dried over
phosphorus pentaoxide at 66 °C (2 mmHg) for 8 h.
(b) Orn-Tau (5). Z-Orn(Z)-OH (2) was prepared using
Z-DSP (Kouge et al., 1987). To an aqueous solution (100 mL)
of 2 (20.0 g, 50 mmol), H-Tau-OH (8.1 g, 65 mmol), and HOBt
(0.76 g, 5.0 mmol), was added triethylamine (6.9 mL, 50 mmol)
at room temperature. After 0.5 h of stirring, WSC‚HCl (12.4
g, 65 mmol) was added to the solution. After 8 h of stirring,
0.2 N aqueous solution of Ba(OH)2‚8H2O (125 mL, 25 mmol)
was added to the reaction mixture and the barium salt of the
protected dipeptide derivative was precipitated. The precipi-
tate was collected and washed with deionized water (2 L)
several times.
Ta ble 2. Str en gth of th e Sa lty Ta ste of Or n -Ta u ‚1.2HCla
Orn-Tau‚1.2HCl(aq) (mM)
scoreb
NaCl(aq) (mM)
scoreb
120 (2.88%, pH 5.1)
100 (2.40%, pH 5.2)
60 (1.44%, pH 5.3)
45 (1.08%, pH 5.4)
30 (0.72%, pH 5.3)
15 (0.36%, pH 5.4)
a
+6
107.0 (0.625%)
85.6 (0.5%)
64.2 (0.375%)
+6
+5
+4
+5
+4
+3.5
+3
42.8 (0.25%)
10.7 (0.063%)
b
+3
+1
+1
Threshold value of Orn-Tau‚1.2HCl is 7.5 mM. Score shows
saltiness strength. Scores of +6, +5, +4, +3, +2, +1 are equal to
the saltiness of 0.625%, 0.5%, 0.375%, 0.25%, 0.125%, 0.063% NaCl
solutions, respectively.
slightly produced by CO2 in the air, was filtered off, and the
filtrate was added to ether (250 mL). The precipitated product
was collected and dried under reduced pressure: yield 23.6 g
(82%); mp 89 °C; [R]25D -3.0 (c 1, DMF); Rf1 0.67, Rf2 0.15. Anal.
Calcd for C46H56O16N6S2Ba: C, 48.02; H, 4.91; N, 7.31.
Found: C, 47.89; H, 5.01; N, 7.21.
When not isolated, to a suspension of the precipitate in
water (200 mL) was added 1 N H2SO4(aq) (35 mL). The
mixture was stirred for 0.5 h and then hydrogenated in the
presence of palladium carbon at room temperature for about
6 h at atmospheric pressure. The catalyst and precipitation
of BaSO4 was filtered off and washed with water several times.
H2SO4(aq) (0.1 N, 92 mL) was added to the filtration until
formation of BaSO4 was complete. BaSO4 were removed and
the filtrate lyophilized. The final product was obtained as a
hygroscopic solid: yield 11.5 g (79%); hygroscopic; [R]25 -0.1
D
(c 1, H2O); Rf1 0.14, Rf2 0. Ba2+ in the final product was
spectrophotometrically determined by dimethylsulfonazo III
(Budesinsky et al., 1967).
P r ep a r a tion of Sa m p le Solu tion s. (a) Preparation of
Orn-Tau‚nHCl Solutions (n ) 0-1.3). Orn-Tau‚nHCl solu-
tions for sensory analyses were prepared by adding HCl
solutions to HCl-free Orn-Tau solutions (see Table 1). HCl-
free Orn-Tau was obtained by the new convenient synthesis.
When 4 was isolated, the washed precipitate was dissolved
in hot ethanol/water (50 mL, 9:1 v/v). BaCO3, which was

Effect of Orn-Tau‚HCl on Saltiness of Food
J. Agric. Food Chem., Vol. 44, No. 9, 1996 2483
Ta ble 3. Sa ltin ess of Or n -Ta u ‚1.2HCl w ith Ad d ed Na Cl
combination
Orn-Tau‚1.2 HCl
NaCl
pH
saltiness
100 mM (2.40%)
60 mM (1.44%)
30 mM (0.72%)
15 mM (0.36%)
0 mM (0%)
0.0% (0 mM)
5.2
5.2
5.3
5.3
6.7
+5, contains weak sourness
0.063% (10.7 mM)
0.125% (21.4 mM)
0.375% (64.2 mM)
0.5% (85.6 mM)
+5, contains very weak sourness
+5
+5
+5
Ta ble 4. Weigh t P er cen ta ge of Sod iu m Ion s in Sa m p le
Solu tion s Con ta in in g Or n -Ta u ‚1.2HCl a n d Sod iu m
Ch lor id e
Ta ble 5. Sa ltin ess a n d Ta ste Qu a lity of Or n -Ta u ‚1.2HCl
a d d in g Low -Sod iu m -Ch lor id e-Con ta in in g Soy Sa u ce
saltinessb/taste qualityc
concna
Na+ contentsa
(% w/w)
ratio of Na+b
(%)
(mM)
A
B
C
D
Orn-Tau‚1.2 HCl
NaCl (%)
192.6
171.2
149.8
128.4
107.0
85.6
64.2
42.8
21.4
10.7
8/++
9/+++
9.5/+++
9/+++
8/+++
7/+++
6/+++
5/+++
4/+++
3/+++
2/+++
1/+++
10/+++
9/+++
8/+++
7/+++
6/+++
5/+++
4/+++
3/+++
2/+++
1/+++
100 mM (2.40%)
60 mM (1.44%)
30 mM (0.72%)
15 mM (0.36%)
0 mM (0%)
0.0
0
1.7
5.8
20.1
39.4
0
4.3
15
51
100
7.5/++
7/++
8.5/+++
7.5/+++
6.5/+++
5.5/+++
5/+++
0.063
0.125
0.375
0.5
6.5/++
5.5/++
5/++
4.5/++
3.5/++
2.5/++
1.5/++
a
Na+ contents ) Na+/(NaCl + Orn-Tau) × 100. The weight
4/+++
of Na+ in each sample solution was divided by the total weight of
3/+++
additives. Ratio of Na+ ) Na+ contents/39.4 × 100. Ratio of the
b
2/+++
weight percentage of Na+ in the sample solution compared with a
solution containing only 0.5% of NaCl.
1/+++
a
b
Total concentration of NaCl and Orn-Tau. A, the ratio of
Orn-Tau to the total concentration is 60%; B, 50%; C, 33% (mol/
c
(b) Preparation of Mixed Solutions of Orn-Tau‚1.2HCl and
NaCl. Mixed solutions listed in Table 3 were prepared by
adding NaCl to Orn-Tau‚1.2HCl solutions.
mol); D, commercial soy sauce. Taste quality of the samples was
evaluated on
a scale of +++ and ++: +++, equivalent to
reference commercial soy sauce in quality; ++, slightly inferior
to commercial one.
(c) Preparation of Contents-Modified Soy Sauce Samples
Containing Orn-Tau‚1.2HCl. We requested a soy sauce mate-
rial containing only 6.4% NaCl for Takeda Syokuryo Co., Ltd.
(Muramatu et al., 1990). We called this soy sauce “pre-soy
sauce”. Though the glutamate and ethanol contents of pre-
soy sauce were a little higher than those of the commercial
soy sauce, pre-soy sauce amended to 16% NaCl had the same
taste and flavor as the commercial one (Muramatu et al.,
1993). NaCl and Orn-Tau‚1.2HCl were added to pre-soy sauce
to prepare contents-modified soy sauce with three additive
ratios (60%, 50%, and 33% mol/mol). The sample containing
Orn-Tau‚1.2HCl with additive ratio 60% was prepared as
follows: Orn-Tau‚1.2HCl was added to pre-soy sauce (NaCl
concentration is 1.12 M), and the Orn-Tau‚1.2HCl concentra-
tion of the sample was adjusted to 1.65 M. In this sample,
the total concentration of Orn-Tau‚1.2HCl and NaCl was 2.77
M, which was the same as the NaCl concentration of com-
mercially available soy sauce. The sample with additive ratio
50% was prepared as follows: NaCl was added to pre-soy sauce
so that the NaCl concentration became 1.38 M. Orn-
Tau‚1.2HCl was then added, and the Orn-Tau‚1.2HCl concen-
tration of the sample was adjusted to 1.39 M. Total concen-
tration of the two was 2.77 M. The sample with additive ratio
33% was also prepared in a similar way and contained 1.85
M NaCl and 0.92 M Orn-Tau‚1.2HCl. To apply these contents-
modified soy sauces to the sensory test, total concentrations
of NaCl and Orn-Tau‚1.2HCl were adjusted to the concentra-
tions shown Table 5.
Sen sor y An a lysis. All samples were evaluated by a panel
of four or five people in terms of their characteristics and taste
strength. After rinsing the mouth, each person kept the
solution in his/her mouth for about 10 s to evaluate the
character and taste intensity of the sample. All panel mem-
bers gave the same evaluation for the taste characteristics,
while there were some personal variations in the taste strength
evaluation owing to personal and experimental conditions.
However, these personal deviations in the taste strength were
eliminated by tasting a standard NaCl solution and comparing
these results at the same time. The saltiness strength was
evaluated on a score of 0-10. Score 10 was judged to be
equivalent in salty taste to a reference 192.6 mM (1.125%)
NaCl. Score of from 9 to 1 indicated a descending degree of
saltiness, compared with the reference solution: score 9, 8, 7,
6, 5, 4, 3, and 2 meant that the saltiness of the sample solution
was the same as that of 171.2 mM (1.0%), 149.8 (0.875%), 128.4
mM (0.75%), 107.0 (0.625), 85.6 mM (0.50%), 64.2 mM (0.375),
42.8 mM (0.25%), and 21.4 mM (0.125%) NaCl, respectively;
score 1 was the saltiness of the threshold value of NaCl
(0.063%); score 0 indicated tastelessness or other tastes.
The quality of contents-modified soy sauce sample solutions
was evaluated. A sample solution was given a scale of +++
if the taste quality was judged equal to that of commercially
available soy sauce. Scale ++ indicates that the quality is a
little inferior to that of traditional soy sauce. The procedure
for the sensory analysis was described in our previous paper
(Ishibashi et al., 1987) in detail.
RESULTS AND DISCUSSION
New Con ven ien t Syn th esis of Or n -Ta u . A con-
ventional synthesis of Orn-Tau‚HCl is shown in Scheme
2. Even in 3 mmol scale, very careful techniques and
great cost were required to obtain such high yields.
Therefore, this method was not suitable for large scale
synthesis.
In the new method (Scheme 1), we could directly
couple Z-Orn(Z)-OH with H-Tau-OH by the WSC-HOBt
method (Konig et al., 1970). This coupling proceeded
readily in water without blocking the sulfonyl group and
side reactions did not occur. Subsequently, an aqueous
solution of Ba(OH)2‚8H2O was added to the reaction
mixture and Z-Orn(Z)-Tau-OH was selectively precipi-
tated as a barium salt [Z-Orn(Z)-Tau‚1/2Ba]. The pre-
cipitate washed several times with deionized water was
added to 1 N H2SO4(aq) (0.7 equiv of the starting
material) and then deblocked by hydrogenation. After
BaSO4 and the catalyst were removed, Ba2+ was com-
pletely precipitated as BaSO4 by adding 0.1 N H2SO4-
(aq). BaSO4 was filtrated off, and solid Orn-Tau was
obtained by lyophilization. Ba2+ was not detected in the
final product.
In this method, two problems in conventional syn-
thesis were solved and the following advantages for
large scale synthesis were found: All operations could
be performed in a water solvent system. Water is
superior to the other solvents from the point of safety,
cost, and easy control of the reaction condition by pH.

2484 J. Agric. Food Chem., Vol. 44, No. 9, 1996
Nakamura et al.
Sch em e 2
Our synthetic process was shortened by two steps
compared to the conventional one, and the purification
was made much easier. The final product did not
contain any counteranion such as HCl and so was an
ideal sample for the examinations to determine the taste
properties of Orn-Tau.
sourness of 60 mM Orn-Tau‚1.2HCl almost completely
disappeared when 0.063% NaCl was added. In other
words, the saltiness of 0.063% NaCl (score +1) was
increased to +5 by adding 60 mM Orn-Tau‚1.2HCl. We
calculated how much the proportion of Na+ was reduced
by adding Orn-Tau‚1.2HCl. The results are sum-
marized in Table 4. In a solution containing only 0.5%
NaCl, the weight percentage of Na+ is 39.4%. In the
case of solution of 60 mM Orn-Tau‚1.2HCl and 0.063%
of NaCl, the weight percentage of Na+ is 1.7% of the
total amount of additives. The weight percentage of
Na+ in the solution containing 60 mM Orn-Tau‚1.2HCl
and 0.063% NaCl is only 4.3% of that containing 0.5%
NaCl. Therefore, the percentage of Na+ can be reduced
by around 95% in this model system.
Effect on Sa ltin ess in P r e-Soy Sa u ce of Or n -
Ta u ‚1.2HCl. To determine the effect on a practical food
material, we added the Orn-Tau‚HCl to pre-soy sauce
and prepared contents-modified soy sauce samples
containing Orn-Tau‚1.2HCl. By comparing commer-
cially available soy sauce and the contents-modified soy
sauce samples, we examined the Na+ dietary effect and
the influence of Orn-Tau‚1.2HCl on the quality of soy
sauce.
Results of sensory analysis of the samples are listed
in Table 5. The 60% additives ratio samples produced
almost the same saltiness as did the commercially
available soy sauce in low concentration. In high
concentration, however, the saltiness and taste quality
were not satisfied. The deterioration of taste quality
was mainly caused by the sourness of Orn-Tau‚1.2HCl,
and it is thought that the saltiness was diminished by
influence of constituents in pre-soy sauce. When 50%
and 33% additive ratio samples were tasted, the same
level of saltiness and taste quality as those of com-
mercially available soy sauce were reproduced. We
judged that taste quality of 50% additive ratio sample
reached a practical level. In a food material, using Orn-
Tau‚1.2HCl, Na+ from NaCl could be reduced 50% from
that of commercially available soy sauce.
Ta ste Beh a vior of Or n -Ta u . (a) Optimum HCl
Equivalent for Orn-Tau Saltiness. For evaluating the
character and taste strength, 30 mM Orn-Tau solutions
containing 0-1.3 equiv of HCl were prepared. We
carried out sensory analyses of these solutions and
found that solutions containing <0.67 equiv of HCl did
not produce the salty taste. At pH 7, Orn-Tau contain-
ing 0.67 equiv of HCl produced a very weak salty taste
and the saltiness strength became stronger as the
amount of HCl was increased. However, when more
than 1.3 equiv of HCl was added, it was difficult to
discriminate the saltiness from the sourness originating
from HCl. We obtained the strongest saltiness by
adding 1.3 equiv of HCl, but Orn-Tau having 1.2 equiv
of HCl produced the most excellent saltiness, which
contained a slightly sour taste (see Table 1). Orn-
Tau‚1.2HCl was equally salty as NaCl on a molar basis.
This taste behavior is similar to OBA, except for the
minimum equivalent of HCl for saltiness production
(Tamura et al., 1989). The saltiness quality of Orn-
Tau‚1.2HCl is much superior to that of OBA‚1.3HCl,
and the saltiness was still excellent even in high
concentration compared with other NaCl substitutes
(Table 2). It is thought that this difference is caused
by a sulfonic acid group of Orn-Tau, which is the only
difference between Orn-Tau and OBA.
In the new synthesis of Orn-Tau, contamination of
Na+ could be held to a minimum and Orn-Tau exhibited
excellent salty taste. It was confirmed that the saltiness
of Orn-Tau was produced without Na+.
(b) Taste Behavior of Mixed Solutions of Orn-Tau‚
1.2HCl and NaCl. We prepared mixed solutions of Orn-
Tau‚1.2HCl and NaCl in several ratios as shown in
Table 3. These ratios were employed according to the
results of sensory analysis of OBA as previously re-
ported (Tamura et al., 1989). From the results of
sensory analysis, it was found that all mixed solutions
of each series possessed the same saltiness strength and
the sourness arising from excess HCl was weakened by
adding NaCl even though the pH was still acidic. The
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Received for review October 26, 1995. Accepted April 23,
1996.X
J F950711U
X Abstract published in Advance ACS Abstracts, Au-
gust 1, 1996.