the behavior of taste ingredients during desalination of

日本調理科学会誌Vo1.40,No.5,329～336(2007)〔Note〕

The Behavior of Taste Ingredients during Desalination

of Salted Pacific Herring Ovary (Kazunoko)

Atsuko Kasuga Eiko Ogiwara Yasuo Aoyagi

Desalination using salt water of a low concentration is called "Yobi-shio", and many cookbooks recommend the

use of salt to desalt. Analysis of sodium, potassium, magnesium, free amino acids and 5'-nucleotides was carried

out after the desalination using water and NaCl solution, to clarify whether the elution of taste ingredients caused

by diffusion was the only factor affecting the taste and what kinds of taste ingredients were affected during the

desalination of kazunoko. Sodium and magnesium eluted at lower contents in desalination using NaCl solution than

using water, but potassium was not affected. Free amino acids in the soaking solution increased with time and that

of desalted kazunoko decreased. The sum of the total free amino acids in desalted kazunoko and that of the soak-

ing solution with desalination using water after 15 hours was 1.8 times that of kazunoko, but that using 3% NaCl

was not increased at all. Moreover, the contents of total free amino acids in desalted kazunoko using water after

15 hours was twice that using 3% NaCl solution. Among these free amino acids, the hydrophobic amino acids

which are said to be bitter occupied 70%. These results indicate that free amino acids were produced by protease

during the desalination using water.

Key word: kazunoko, Pacific herring, desalination, yobi-shio, taste ingredient

Salted or dried roe of the Pacific herring (Clupea pal-

lasi) is called "kazunoko" in Japan. Salted kazunoko gen-

erally sells well in the market. Kazunoko with its distinc-

tive texture and taste is one of the foods considered to be

indispensable for the New Year holiday in Japan because

it is said to assure prosperity for a long time. The spawn

is generally full of protein and fat. Kazunko contains a

much higher content of Vitamin E, EPA and DHA than

the fish flesh from Pacific herring (Suzuki, 1994). Kazu-

noko, however, is rich in cholesterol. Furthermore, kazu-

noko is usually preserved in salt for storage, and exces-

sive intake of salt is also a concern.

When we make kazunoko with taste, we must first ex-

tract the salt. The desalination method for kazunoko var-

ies in each home. Some homes desalt it by draining the

water for several hours, and some homes desalt it by

changing the water several times overnight. According to

a Japanese cookbook dealing with kazunoko, many books

("Kihon no osechi to syougatsu no omotenashi", 2006 ; "O

syougatsuryouri to nabe", 2006 ; "Kazoku ga yorokobu

osechiryouri", 2006 ; Asada, 2006) recommend the use of

salt to desalt. However expression of the concentration of

salt as "a little" or "appropriate" is not clear. Thus, the to-

tal time of desalination varies from 6 to 48 hours, and the

times for exchanging the soaking solution vary from 0 to

several times. When kazunoko is sold in the market, a de-

salination method using salt water of seawater concentra-

tion is often displayed on the package. Moreover, Kawano

(2006) reported that soaking in salt water removes salt

quickly from the kazunoko. Kazunoko desalted using wa-

ter is sometimes said to taste bitter.

Regarding the salt, desalination using salt water of a

low concentration is called "yobi-shio" or "mukae-shio" in

Japan. "Yobi-shio" has been performed with salted fish

such as salted salmon and salted mackerel, and with ka-

zunoko (Kawano, 2006). However, considering the phe-

nomenon of diffusion, it is unnatural that the desalination

effect is higher in salt water than in water. Shimizu and

Satomi (1933) had already clarified that "Yobi-shio" was

ineffective. Sakai et al. (Sakai and Miki, 1982 ; Sakai and

Suzuki, 1985) also reported that the mechanism of desalt-

ing from fish flesh depends on diffusion. However, "yobi-

shio" generally seems to be a suitable means, as disclosed

in the following reports. Sugita (1977) mentioned that, in

the case of desalination of salted salmon and salted cod-

fish with water, elution of a taste ingredient in addition to

salt occurs earlier in comparison with salt and that only

the surface salt elutes early. Kazunoko desalted using wa-

ter is sometimes said to taste bitter. We wondered

whether, during desalination of kazunoko, the elution

caused by diffusion was the only factor affecting the taste

and what kinds of taste ingredients were affected. There

are few reports of taste ingredients during the desalina-

* Junior College of Kagawa Nutrition University

** Kagawa Vocational College of Nutrition

*** Kagawa Nutrition University

inquiry Junior College of Kagawa Nutrition University

3-24-3 Komagome, Toshima-ku, Tokyo, Japan, 170-8481

TEL 03 (3576) 2964 FAX 03 (3576) 2964

(329)33

J. Cookery Sci. Jpn. Vol. 40 No. 5 (2007)

tion of kazunoko.

In this background, we examined the effect of "yobi-

shio" of kazunoko not only from the viewpoint of desalina-

tion but also from that of taste ingredients such as bitter-

ness and umami ingredients. After the desalination of

kazunoko with water and NaC1 solution, analysis of the

contents of sodium, potassium, and magnesium, free ami-

no acids was carried out. Moreover, sensory evaluation

was carried out to determine whether the panelists could

distinguish the seasoned kazunoko which was immersed

in seasoning solution after desalination with water and

NaCl solution.

Materials and Methods

1. Materials

Kazunoko of about 3 kg was purchased in 2005 and

2006 in a fish shop in Tokyo. All of them were Alaska .

products. They were cut into pieces of about 5 g to re-

move individual differences in form, size and salt concen-

tration and were to be desalted uniformly. They were

put in a plastic bag and stored in a refrigerator before

the experiments and sensory evaluation.

2. Reagents

The hydrochloric acid for the mineral analysis was of

super special grade, and the lanthanum chloride solution

and other mineral standard solutions were used as re-

agents for the atomic absorption analysis. The lithium ci-

trate buffer solution (pH 2.2, lithium ion concentration =

0.25 mol//), the buffer solution for the amino acid analy-

sis and the amino acid standard solutions were the re-

agents for amino acid analysis. All other reagents were of

super grade. These reagents were purchased from Wako

Pure Chemical Industries, Ltd. The water used in this ex-

periment was purified using Milli-Q Lab equipment (Ni-

hon Millipore K. K). The seasonings used for sensory

evaluation were as follows : Seafood flavor of Bonito fillet

extract (Honkatsuodashi, RIKEN VITAMINE Co., Ltd.),

Light soy sauce (Usukuchi shoyu, HIGASHIMARU

SHOYU Co., Ltd.), Alcohol-based seasonings (Takara

Hon-Mirin, TAKARA SHUZO Co., Ltd.), Japanese liquor

(Cooking Sake Fukuizumi, FUKUIZUMI SANGYO Co.,

Ltd.). The composition of the seasoning solution by vol-

ume ratio was Japanese-style broth (10 g seafood flavor

of Bonito fillet extract dissolved in 1,200 ml water) : light

soy sauce : boiling-off of alcohol-based seasonings : boil-

ing-off of Japanese liquor = 6 1 1 1.

3. Desalination methods of kazunoko

1) Investigation to determine how long and how many

timesaresuitableforexchangingthesoakingsolu-

tion,

About20g(4pieces)ofkazunokowereselectedat

randomandputintoa250-mZvolumeplasticbottlewith

100m乙ofwater.Afterlhour,theywereremovedfroln

thewater,placedinastaidessbasketwithoutstacking ,

anddrainedofwaterfor5m.in.Theywerethenplacedin

anotherbottlewithafresh100mZofwater .Rehydration

wascontinued,andtherehydrationprocedurementioned

abovewasrepeatedhourlyafterlto10hours.Another

periodofdesalinationwastriedtofindthemostconve-

nientdesalinationmethod.Onemethodwastochangethe

waterafter3,5,7,andghours,andtheotherwasto

changethewaterafter5and9hoursincomparisonwith

themethodinwhichwaterwasnotchanged.Alldesali-

nationswerecarriedoutatroomtemperaturearound24

℃withoutmovingthebottle.

2)Desalinationmethodforanalysis.

Desalinationofkazun .okowascarriedoutusingO.5%,1

%and3%NaClsolutionsassoakirlgsolutionsforanaly-

sisofsodiurnarldpotassium.Theseconcentrationswere

selectedforthefollowingtworeasonsthatthedesalina-

tlonuslngsaltwaterofseawaterconcentrationisdis-

playedonthepackageofkazunokoandthatHashimoto

andMurakami(2003)mentionedtheuseof1～4%salt

concentrationinthecaseof"Yobi-shio".

Foranalysisofmagnesiumandfreeaminoacids ,water

and3%NaClsolutionwereused・assoakingsolutions .

Eachsolutionwaschangedtwiceafter5and10hours ,

andthetotaldesalinationtimewas15hours.Allother

conditionswerethesameasmentionedabovein1).

4.Mineralcontent$

Thesodium,potassiumandmagnesiumcontentsof

eachsoakingsolutionelutedfromkazunokowerefiltered

withpaper5A(AdvantecTOYO,ToyoRoshiKaisha,

Ltd。)andthesolutionsweredilutedatappropriatetimes

withwater.Theywereanalyzedbythemethodde-

scribedintheStandardTablesofFoodCompositionin .

Japan,fifthrevisionandenlargededition(2005).ASpec-

traA55B(Varian,Ltd.)wasusedfortheatomicabsorp-

tlonspectrophotometeranalysis.Allthemeasurements

werecarriedoutinduplicateorsometimesintriplicate 。

5.Freeaminoacidcontents

Forthefreeaminoacidanalysisofthesolutions ,whole

sOlutionswerepassedthroughacolumn(2φ ×15cm)of

cationexchangeresins(IR120,0reganoCo.).Afterrins-

ingwith100mZofwater,freeaminoacidswereeluted

with2mol/乙ammoniasolution.Lithiumcitratebufferso一

34(330)

The Behavior of Taste Ingredients during Desalination of Salted Pacific Herring Ovary (Kazunoko)

lution (pH 2.2) was added up to an appropriate volume,

subsequently evaporating the solution to dryness. For the

free amino acid analysis of the desalted kazunoko, the

sample was homogenized (Polytron PT 10-35, Kinemati-

ka, Inc.) with 70% EtOH and the container filled to

200 ml with 70% EtOH. After being filtered with filter

paper (No. 3, Advantec TOYO) , 20 ml of the filtrate was

evaporated to a few ml and then defatted with diethyl

ether. Lithium citrate buffer solution (pH 2.2) was added

to an appropriate volume. The free amino acids were an-

alyzed using an amino acid analyzer (Hitachi Model 835).

6. Sensory evaluation

Desalination was planned with water and 3% NaC1 so-

lution at room temperature of around 24°C. A 5-times

amount of the solution vs. kazunoko was added to 216 g

(54 pieces) of samples in vinyl bags (32 cm x 38 cm).

Four vinyl bags containing the kazunoko and solution

were prepared, two bags for water and two bags for 3%

NaCl. All other conditions were the same as in the desali-

nation method for analysis. Next, the desalted kazunoko

samples were immersed in seasoning solution for 24

hours. For a sensory evaluation, the kazunoko samples

were separated from the seasoning solutions and were

then served on a plate.

The panel consisted of 18 males and females (1 : 2)

whose ages ranged from 20 to 50. They were the staff of

the cooking laboratory of the Kagawa Vocational College

of Nutrition. Three pieces of the kazunoko were served

in three sets of 54 paper dishes labeled "R", "5", and "T".

The triangle test was used to observe whether the panel-

ist could distinguish the taste of kazunoko which was im-

mersed in seasoning solution after desalination with wa-

ter and 3% NaC1 solution. Booths were used for the

sensory evaluations at 26°C.

7. Statistical analysis

The statistical analysis was carried out with binomial

distribution (p - 3) for the triangle tests and with two-

way layout analysis of variance for mineral and free ami-

no acids.

Results and Discussion

1. Investigation to determine how long and how many

times are suitable for exchanging the soaking solu-

tion.

We first performed this experiment to find which

method should be as easy and efficient as possible for de-

salination of our samples. Fig. 1 shows the sodium con-

tents of the soaking solution eluted from the kazunoko.

Fig. 1 Sodium Contents of Soaking Solutions Eluted from the Kazunoko

Each value shows the sum of the sodium contents of soaking solution eluted from the kazunoko.

0 : water was not changed 0 : water was changed hourly

A : water was changed after 3, 5, 7, 9 hours

U : water was changed after 5, 9 hours

Each value showed the sum of the sodium contents elut-

ed. When the water was changed hourly, sodium was

eluted earliest from the kazunoko, and after 5 hours, the

sodium content reached equilibrium. When the water was

changed after 3, 5, 7 and 9 hours, equilibrium was

reached after 7 hours, and when the water was changed

after 5 and 9 hours, equilibrium was reached after 9

hours. When the water was not changed once, desalina-

tion was not performed sufficiently and equilibrium was

reached after 4 hours. Based on this experiment, a mini-

mum two changes of water and immersion for more than

7 hours is clearly desirable for desalination at 24t . Based

on this result, we decided that the desalination method.

for a later experiment was to change the water twice af-

ter 5 and 10 hours and the total desalination time was to

be 15 hours.

2. Mineral contents

The data showed the mineral contents of the soaking

solution eluted from the 100 g kazunoko, and each value

was the sum of the mineral contents eluted.

Fig. 2 shows the sodium contents eluted with different

NaC1 concentrations. When the desalination was carried

out with water, the highest amount of sodium content

was eluted. The second highest was with 0.5% NaC1 so-

lution and then with 1% and 3% NaC1 solution succes-

sively. From the variance of analysis, there was a signifi-

cant difference (p<0.01) between water and 3% NaC1,

and significant differences (p<0.05) between water and

0.5% NaCl, and between water and 1% NaCl. This result

(331) 35

Cookery Sci. Jpn. Vol. 40 No. 5 (2007)

Fig. 2 Sodium Contents of Soaking Solutions Eluted by Different NaC1 Concentrations

Each value shows the sum of the sodium contents of soaking solution eluted from the kazunoko.

Li- - - water 0 0.5% NaC1 : 1% NaCl A : 3% NaCI

There were significant differences at p<0.01 between A and L, rho.

There were significant differences at p<0.05 between GI and Gd, 0.

was expected based on the phenomenon of diffusion.

Many kinds of minerals taste bitter in addition to salty

(The Chemical Society of Japan, 1999). Bitter taste

seemed to be related to the sum of the diameter of the

anion and cation (Beets, M. G. J., 1978). Moreover, Ezaki

et al. (2004) reported that the components which affect

the taste of salt were MgC12 and KC1 and that the tastes

of MgC12 and KC1 were bitter. Therefore, we attempted

to measure the contents of potassium and magnesium.

Fig. 3 shows the potassium contents of the soaking solu-

tions eluted by different NaCl concentrations. The elution

curves for potassium were similar regardless of the con-

centration of NaCl. The potassium content of 100 g kazu-

noko was about 50 mg, and all potassium eluted into the

soaking solution after desalination using any solution.

Therefore, potassium did not seem to affect the taste of

desalted kazunoko.

Based on the results of Fig. 2, because there was a sig-

nificant difference (p<0.01) between water and 3%

NaCl, water and 3% NaCl solution were used as the soak-

ing solutions for a later experiment . Fig. 4 shows the

magnesium contents of the soaking solutions eluted with

different NaC1 concentrations. The magnesium content of

the soaking solution desalted using 3% NaC1 was lower

in quantity than that using water. There was a significant

difference (p<0.01) between water and 3% NaCl. This

result was caused by the phenomenon of diffusion, which

was also indicated in the case of sodium. The magnesium

content of kazunoko was about 19 mg. Though other fish-

Fig. 3 Potassium Contents of Soaking Solutions Eluted by Dif-

ferent NaCI Concentrations

Each value shows the sum of the potassium contents of soaking

solution eluted from the kazunoko.

Ll- - - : water • 0.5% NaCl

0- - : 1% NaCl A : 3% NaCl

Fig. 4 Magnesium Contents of Soaking Solutions Eluted by Dif- ferent NaC1 Concentration

Each value shows the sum of the magnesium contents of soaking solution eluted from the kazunoko.

111- - - : water A- : 3% NaCl There were significant differences at p<0.01 between 71 and A

ery products include much more magnesium than kazu-

noko, they do not seem bitter. Furthermore , the magne-sium content of desalted kazunoko became lower than

kazunoko. The threshold of bitterness for magnesium sul-

fate, was reported (The Chemical Society of Japan , 1976) to be 4.6 mM, and this corresponds to 55 mg / 100 ml . The form of magnesium of desalted kazunoko was not

clear, but judging from the quantity, it seemed that the

quantity of magnesium in desalted kazunoko was not re-

lated to bitterness.

3. Free amino acid contents

Fig. 5 shows the free amino acid contents of the soak-

ing solution and desalted kazunoko per 100 g of kazunoko

after 5-, 10- and 15-hour desalination with water and 3

36 (332)


Fig. 5 Effect of Soaking Solution on the Free Amino Acid Contents

kazunoko : solution after 5 hours : solution after 10 hours ni : solution after 15 hours

control : salted kazunoko * : significant difference at p<0. 01

% NaCl. The content of the free amino acids in kazunoko

was 64.5 mg per 100 g, and this was selected as the con-

trol. When the desalination was carried out with water,

the total free amino acid contents of the rehydration wa-

ter increased with time, and that of the kazunoko de-

creased with time. After 15 hours, 50% of the total free

amino acids of the control remained in the desalted kazu-

noko. The sum of the total free amino acid contents of

the solutions and those of the desalted kazunoko after 15

hours was 1.8 times that of the control. This result sug-

gested that the production and elution of free amino acids

from the kazunoko occurred during the desalination.

There are some previous reports (Fujii, 1994 ; Makinod-

an, 1993 ; Kaneko, 1992) on enzyme reactions in food with

a high salt concentration. Fujii et al. (1994) reported that

a self-digestion enzyme produced free amino acids in

squid Shiokara during ripening. Makinodan (1993) re-

ported that the effect of bacteria on the ripening of "shio-kara" seemed to be negligible. Kaneko et al. (1992) also

reported that not only free amino acids but also oligopep-

tides were increased in the ripening of salted preserves

by a self-digestion enzyme. In desalted kazunoko, oligo-

peptides might increase and contribute to its taste in some part.

To prove that the increase in free amino acids was

never caused by microorganisms, we measured the pH

and microbial flora of the soaking solution after 0, 3, 5

hours desalination of kazunoko using water at 24°C. Oth-

er conditions were the same as in the analysis of free

amino acid. As a result, the pH was constant (pH 6.0),

and the viable cell counts were under 30 c. f. u./ m/ of

soaking solution (n = 3). Our experimentation showed

that microorganisms had almost no effect on the desalina-

tion of kazunoko using water at 24°C.

When the desalination using the 3% NaC1 solution was

carried out, the total free amino acid contents of the re-

hydration water decreased with time. The sum of the to-

tal free amino acid contents of the solution and that of

desalted kazunoko was not increased at all. After a 15-

hour desalination with 3% NaCl solution, about 70% of

the total free amino acid contents eluted into the solution,

and only 30% of the total free amino acids remained in

the desalted kazunoko. Comparing the desalination using

water with desalination using 3% NaC1 solution, the con-

tents of total free amino acids remaining in kazunoko de-

salted with water was twice that with 3% NaCl solution.

There was a significant difference (p<0.01) between de-

salted kazunoko using water and 3% NaCl. These results

suggested the effect of a protease during the desalination

with water. The fact that free amino acids were not in.-

creased between desalination with 3% NaC1 solution illus-

trates that the protease could not function in this solution.

Though desalination with 1% NaC1 solution was not tried,

NaC1 might interfere with the reaction of the protease.

Based on the contents of free amino acids, it was clear

that the desalination with water produced a much higher

content of free amino acids. Moreover, too long a desali-

nation time was unfavorable because free amino acids

eluted out of the kazunoko. However, depending on the

taste of the amino acids left in the desalted kazunoko, one

cannot determine how much amino acid is desirable.

Concerning the compositions of free amino acids, Table

1 shows the free amino acid composition of the soaking

solution and desalted kazunoko using water and 3% NaC1

per 100 g of kazunoko. In kazunoko = control) , the total

free amino acid content was 64.5 mg, and the largest con-

tent of amino acid was leucine (13.2 mg) and then valine,

alanine and isoleucine (6.5 mg, 6.3 mg, 6.2 mg). These

hydrophobic amino acids occupied 60% of the total free

amino acids. After 15-hour desalination, the ratio of the

free amino acids in desalted kazunoko using water re-

sembled that using 3% NaCl solution, and leucine, phenyl-

alanine and isoleucine were the main amino acids. The

contents of hydrophobic acids in kazunoko desalted with

water and with 3% NaC1 solution were 22.6 mg and

11.9 mg respectively, and they occupied about 70% of

each of the total free amino acids. When the desalination

was carried out using water, the production and elution

(333) 37

I Cookery Sci. Jpn. Vol. 40 No. 5 (2007)

Table 1. Free Amino Acid Composition of Soaking Solution and Desalted Kazunoko

mg/100 g of salted kazunoko

Control : salted kazunoko before desalination

of free amino acids from the kazunoko occurred. Espe-

cially, the leucine, phenylalanine, lysine and arginine con-

tents of the sum of the solutions and desalted kazunoko

were 2.3-2.8 times that of the control. Suzuki and

Suyama (1983) reported that taurine and glutamic acid

were major constituents of the free amino acids in fish

eggs, and taurine contents were 27.6-341 mg and glu-

tamic acid contents were 12.2-52.0 mg/100 g eggs.

They also reported that the total amino acids in the eggs

spawned in seawater were two to six times those of oth-

ers. In our examination, we did not show the taurine con-

tents because its retention time was very short. Howev-

er, if any, its content seemed to be only a few mg/ 100 g

in kazunoko. Our results were not consistent with theirs.

The reason seemed to be that kazunoko was, strictly

speaking, not fish eggs but ovaries and that various pro-

cessing methods such as removing blood and preserva-

tion with salt were performed.

As for the taste, especially a bitter taste, the "Amino

Acid Handbook" (2003) reported that the absolute

threshold and the differential threshold for leucine, phe-

nylalanine and isoleucine was 380 mg/100 ml 10%, 150

mg/100 ml 20% and 90 mg/100 ml 15%, respectively.

All analyzed data for kazunoko and desalted kazunoko

were lower than these thresholds. However, kazunoko

desalted with water is sometimes said to taste bitter.

Kawai (2003) reported that bitterness is reduced by so-

dium and is difficult to detect. Because there is scarcely a

salt taste in kazunoko desalted with water, bitterness

may be noticed. Moreover, a mixture of hydrophobic ami-

no acids and minerals such as potassium and magnesium

is expected to have some influence on the bitter taste . As for the Umami taste, the content of glutamic acid in

kazunoko was 2.7 mg, and after 15 hours, that of desalted

kazunoko decreased to 1.1 mg with water desalination

and to 0.3 mg with 3% NaC1 desalination. These contents

were very low compared with the data that the glutamic

acid of "Ikura" (salted roe of salmon or trout) was

18.6 mg/100 g (Fushiki, 2003). As the absolute threshold

of monosodium-glutamate is 30 mg/ d/ ("Amino Acid

Handbook", 2003), desalted kazunoko never has the

Umami taste. Besides, we also analyzed 5'-nucleotides

such as 5'-GMP, 5'-IMP (data are not shown) , but they

could scarcely be found. Fushiki (2003) mentioned the 5'-

IMP contents of various marine products. The 5'-IMP

content of "ikura" was 2.7 mg/100 g, that of sea urchin

was 2 mg and that of shellfish such as scallops and short-

neck clams was scarcely detected. If 5'-IMP might exist

in desalted kazunoko, a synergism with glutamic acid

would be expected. The data for Umami components in

kazunoko and desalted kazunoko have never been report-

ed until now.

4. Sensory evaluation

The triangle test was used to prove whether the panel-

38 (334)


ists could distinguish the taste of kazunoko which was

desalted with water from that with 3% NaC1 solution.

The panelists who gave the correct answer in the trian-

gle test were only 4 of the 18 people. Most of them could not distinguish the taste of desalted kazunoko by the two

desalination methods. If a significant difference was rec-

ognized, we intended to ask for further discussion regard-

ing which method of desalination was preferable.

To clarify the reason why the panelists could not dis-

tinguish between the two desalination methods, the free

amino acids compositions were analyzed (data are not

shown) . The contents of free amino acids in the season-

ing solution were extremely high, and so, those of the

seasoned kazunoko immersed in that solution increased

more than 10 times after desalination. As a result, it be-

came clear that desalination with or without NaCl did not

have any relation to the taste of the kazunoko samples

which were immersed in seasoning solution.

Conclusions

When the percentage of NaC1 solution was increased in

desalination, less sodium and magnesium were eluted.

This allowed us to reconfirm that "yobi-shio" was ineffec-

tive for quick desalting. However, "yobi-shio" consider-

ably influenced the behavior of free amino acids during

the desalination. The sum of the total free amino acids of

desalted kazunoko and that of the soaking solution with

water after 15 hours was 1 .8 times that of kazunoko be-

fore desalination. However, when using the 3% NaC1, free

amino acids were not increased at all. Moreover, the con-

tent of total free amino acids in kazunoko dessalted with

water after 15 hours was twice that desalted with 3%

NaCl solution. Free amino acids seemed to be produced

during the desalination by protease. Among these free

amino acids, the hydrophobic amino acids which are said

to be bitter occupied 70%. The content of glutamic acid

which is said to have a Umami taste was very low, al-

though the content of glutamic acid during desalination

using water was slightly higher than that with 3% NaCl.

Therefore, the content of glutamic acid of desalted kazu-

noko did not affect the Umami taste without 5'-nucleo-

tides. Other Umami contents, namely 5'-nucleotides, were

scarcely found before and after desalination with any so-

lutions ; in other words, 5'-IMP was not produced during

the desalination.

In conclusion, we could clarify that "yobi-shio" of kazu-

noko did not increase the speed of desalination and that it

not only decreased the amount of elution of taste ingredi-

ents by diffusion but also controlled the action of prote-

ase.

Acknowledgments

We thank Keiko Ryuushi for her skilful assistance.

References

Ajinomoto Co., INC. (2003) , Amino Acid Handbook, Kogyo Chosakai Publishing Inc., Tokyo, p 47

Asada M., (2006) "Dentou no osechi", Graph-sha Ltd., Tokyo, pp. 20

Beets M. G. J., (1978) , Structure-activity relationships in hu- man chemoreception, Applied Science Publishers, London,

pp. 259 Ezaki S., Iiyama S. and Toko K., (2004) , Quantitative evalua-

tion of taste of salt using potentiometric taste sensor., TECHNICAL REPORT OF THE INSTITUTE OF ELECTRON-

ICS, INFORMATION AND COMMUNICATION ENGINEERS', 104, No. 300 (20040909) , 65-68

Fujii T., Matsubara M., Ito Y. and Okuzumi M., (1994) , Micro- bial contributions on ripening of squid Shiokara, Nippon Su-

isan Gakkaishi, 60, 265-270 Fushiki T., (2003) , "Shokuhin to aji", KORIN PUBLISHING

CO., LTD., Tokyo, pp. 156-160 Hashimoto T. and Murakami M., (2003) , "Shio no kagaku",

Asakura Publishing Co., Ltd., Tokyo, pp. 163 Kaneko K., Tsuji K., Kim C-H., Kikuchi S., Sahara K., Sumino

T., Aida K. and Kaneda T., (1992) , Comparative study on content and composition of oligopeptides, free amino acids,

5'-ribonucleotides and free sugars in salted preserves produced in Korea and Japan., Nippon Shokuhin Kogyo Gak-

kaishi, 39, 1069-1076 Kawai M., (2003) , "Aminosan no aji sono 2", Ajico News, No.

209, p. 1 Kawano T., (2006) , Encyclopedia of Cooking Techniques &

Science, Ishiyaku Publishers, Inc., Tokyo, pp. 192 "Kazoku ga yorokobu osechiryouri" , (2006), SHUFU-TO- SEIKATSU SHA Ltd., Tokyo, pp. 11

"Kihon no osechi to syougatsu no oinotenashi", (2006) , GAK- KEN CO., Ltd., Tokyo, pp. 12

Makinodan Y., Nakagawa T. and Fujita M., (1993), Effect of cathepsins on textural change during ripening of Ika-shio-

kara (salted squid preserves) , Nippon Suisan Gakkaishi, 59, 1625-1629

"Osyougatsuryouri to nabe" , (2006), THE ORANGE PAGE, Inc., Tokyo, pp. 8

Report of the Subdivision on Resources, The Council for Sci- ence and Technology, Ministry of Education, Culture, Sports,

Science and Technology, Japan, (2005) Sakai M. and Mild M., (1982), Transfer rates of salts in fish

flesh, Nippon Shokuhin Kogyo Gakkaishi, 29, 490-495 Sakai M. and Suzuki A., (1985) , Transfer rates of salt in fish

and into flesh through skin, Nippon Shokuhin Kogyo Gak- kaishi, 32, 480-485

Shimizu W. and Satorni T. (1933) , "Shionuki no kenkyuu, yobi- shio no kouka ni tsuite", Suisan Seizou Kaishi, 1,18-22

Sugita K., (1977) , "Shio to mikaku", "Syoku no kagaku", 39, 56-61

(335) 39

J. Cookery Sci. Jpn. Vol. 40 No. 5 (2007)

Suzuki K., (1994), "Gyoran no eiyouka to sono tokusei", "Syoku no kagaku", 195, 42-46

Suzuki T. and Suyama M., (1983), Free Amino Acids and Phosphopeptides in the Extracts of Fish Eggs , Bulletin of

the Japanese Society of Scientific Fisheries , 49, 1747-4753 The Chemical Society of Japan, (1976), "Aji to nioi no

kagaku", "KAGAKU SOSETSU", Japan Scientific Societies

Press, Tokyo, pp. 130 The Chemical Society of Japan, (1999) , "Aji to nioi no bunshi-

ninshiki", "KIKAN KAGAKU SOSETSU", Japan Scientific So- cieties Press, Tokyo, pp. 76

(Received Nov, 1, 2006 Accepted Jul, 18, 2007)

数の子の塩抜き過程における味成分の挙動

春日敦子　荻原英子　青柳康夫

和文抄録

低濃度の食塩水を用いた脱塩は"呼び塩'と言われ,多くの料理本では数の子の塩抜きに塩を用いることを薦めている。

塩漬け数の子の脱塩中に,拡散による味成分の溶出のみが数の子の味に影響する要因であるのか,またどのような味成分

が影響を及ぼされるかを明らかにするために,数の子を水と食塩水を用いて脱塩し,ナトリウム,カリウム,マグネシウ

ム,遊離アミノ酸,5'-ヌクレオチドの分析を行った。ナトリウム,マグネシウムは,水よりも食塩水を用いた脱塩の方

が溶出量は少なかったが,カリウムは食塩濃度とは関係がなかった。脱塩中に浸漬液中の遊離アミノ酸は時間と共に増加

し,数の子中の遊離アミノ酸は減少した。水で15時間脱塩した時の,数の子と浸漬液中の総遊離アミノ酸含量の合計は,

脱塩前の塩漬け数の子の総遊離アミノ酸含量より 1 . 8 倍多かったが , 3 % 食塩水を用いて脱塩した時は全く増加していな

かった。さらに ,水で 1 5 時間脱塩した時の数の子中の総遊離アミノ酸含量は , 3 % 食塩水を用いて脱塩したときより 2

倍多かった。これらの遊離アミノ酸の中では ,味が苦いと言われる疎水性アミノ酸が 7 0 % 占めていた。これらの結果は ,,

遊離アミノ酸が水を用いた脱塩中にプロテアーゼによって生成されたことを示唆している。

キーワード:数の子,ニシン,脱塩,呼び塩,味成分

*女子栄養大学短期大学部

亭毒香川栄養専門学校

榊香川栄養専門学校

§連絡先女子栄養大学短期大学部〒170 -8481東京都豊島区駒込3-24-3

TELO3(3576)2964FAXO3(3576)2964

40 (336)

the behavior of taste ingredients during desalination of

Documents