copy 2017 Japan Society for Food Engineering
Influence of Acidity Regulators on the Stability of a Soymilk Colloidal Dispersion System
Kanako SATO1 Shiori IDOGAWA12dagger Tomoyuki FUJII2
1 Taishi Food Inc 51-1 Shinden Furukawashimizu Osaki Miyagi 989-6228 Japan2 Graduate School of Agricultural Science Tohoku University
468-1 Aramaki Aza Aoba Aoba-ku Sendai Miyagi 980-0845 Japan
To elucidate the influence of acidity regulators on stability using a soymilk colloidal dispersion system a viscous model was constructed and its effectiveness was verified When the pH of soymilk was reduced using ascorbic acid the apparent viscosity of all soymilk increased significantly at approximately pH 58-59 this was found to be a universal phenomenon in the soymilk colloidal dispersion system When the pH decreased after addition of six types of acidity regulators to soymilk the apparent viscosity behaviors of the samples were similar Assuming that the bulkiness of the aggregate was proportional to the hydrogen ion concentration in the high pH range calculations were made by applying the extended equation obtained from the viscosity equation of Einstein and the Krieger-Dougherty equation A negative correlation was confirmed with the parameter hc representing the degree of bulkiness of the aggregate and the parameter Kc representing the degree of filling state of the gigantic aggregate Moreover the macroscopic aggregation behavior was similar even if the internal structure of the isolated aggregates dif fered depending on dif ferences in the crosslinking mechanism Because of the correlations between parameters this system for soymilk processing may have industrial applicationsKeywords soymilk pH colloidal dispersion system stability aggregation
Original Paper
1Introduction
Soymilk is a colloidal dispersion system in which pro-
tein particles and lipids are dispersed in a dissolved pro-
tein solution [1] Lipids exist as oil bodies consisting of
triacylglycerols whose surface is covered with phospho-
lipids and oleosin [2-4] The oil body extracted by grind-
ing the swollen soybean has proteins and cell wall com-
ponents adhering to surface of the oil body Then depos-
its such as protein are dissociated by heating and the oil
bodies are dispersed in soymilk as colloidal particles of
several hundreds of nanometers [5] The oil bodies in
soymilk are thought to prevent coalescence of oil bodies
due to the presence of oleosin as a result soymilk
becomes a stable colloidal dispersion system [6-8]
Thus it is necessary to elucidate the colloidal character-
istics of soymilk whose consumption is increasing in
Japan to improve and stabilize soymilk production and
develop novel soymilk processed products
In soymilk acids are generally used for food process-
ing based on their induction of gel-like coagulation by
addition to soymilk However the stability of colloids var-
ies depending on multiple factors such as pH heat elec-
trolytes and organic matter content [9-11] By evaluat-
ing the viscosity it thus becomes possible to quantita-
tively observe and evaluate the stability of colloids such
that it can be used as an indicator of the variation of daily
production and the quality control of the product at the
manufacturing site In a previous paper we evaluated pH
as a factor controlling stability and found that the appar-
ent viscosity and colloidal stability of soymilk were rap-
idly altered as the pH decreased due to addition of ascor-
bic acid solution [12] Thus the component composition
in soymilk was thought to affect the pH at which a rapid
viscosity increase occurred however the mechanisms
through which aggregation involving oil bodies and pro-
teins occurs have not yet been determined To clarify the
characteristics of soymilk colloid aggregation accompa-
nying a decrease in pH it is necessary to elucidate the
mechanism from the stage at which the soymilk particles
exist in an isolated state until the particles gather and
produce gigantic aggregates with a filled state or gel
The characteristics of acrylamide and agarose have been
studied extensively during gelation [13-15] and cross-
linking aggregation and coagulation are often observed
(Received 5 Apr 2017 accepted 17 Sep 2017)
daggerFax 0229-36-1702 E-mail s-itonotaishi-foodcojp
J-STAGE Published online on 17 Nov 2017
Japan Journal of Food Engineering Vol 18 No 4 pp 177 - 184 Dec 2017 DOI 1011301jsfe17491
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII178
copy 2017 Japan Society for Food Engineering
in many food manufacturing processes [16 17]
However few models have been developed to quantita-
tively describe the changes in viscosity accompanying
aggregation in foods characterized as multicomponent
dispersions
In soymilk oil bodies can be regarded as spheres cov-
ered with oleosin and if the size is sufficiently small the
oil bodies behave like rigid spheres in the dispersion
phase [18] Most of the proteins present in the continu-
ous phase in soymilk are globulin proteins mainly 11S
globulin (glycinin) and 7S globulin (β-conglycinin)
Each globulin is an association of subunits and the iso-
electric points of the proteins differ depending on the
subunits or polypeptides [19] Therefore depending on
the pH the surface potential of the protein changes and
the amount of protein participating in aggregation may
increase or decrease
In this study we hypothesized that aggregates were
formed because of the decrease in protein solubility as
the pH of soymilk decreased and approached the isoelec-
tric point of protein contained in soymilk Thus we con-
structed a viscous model combined with the extended
Einstein equation and the Krieger-Dougherty equation
and experimentally investigated the validity of the model
2Theory
A viscosity model combining Einsteinrsquos viscosity equa-
tion and Krieger-Doughertyrsquos viscosity equation was pre-
viously developed to analyze the viscous behavior of the
process of colloidal coagulation with a crosslinking agent
[20] In a system in which the rigid spheres are dis-
persed if the relative viscosity in the diluted state is ηr
and the volume fraction of the dispersed phase is φ the
following Einsteinrsquos viscosity equation [21 22] can be
established
ηr=1+25φ (1)
Einsteinrsquos viscosity theory is limited to the case in
which φ is suf ficiently small because hydrodynamic
interactions between dispersoids are not considered
Given that bulky aggregates are formed by adding an
acidity regulator under conditions of low pH and assum-
ing that the increase in the effective volume fraction
from the formation of aggregates is proportional to the
hydrogen ion concentration Einsteinrsquos viscosity equation
can be extended as follows
ηd=1+25timeshctimesC (2)
where hc denotes the bulkiness of the colloidal aggre-
gates and C denotes the hydrogen ion concentration
Furthermore under conditions of high pH assuming
that the bulkiness of the aggregates is proportional to
the hydrogen ion concentration the Krieger-Dougherty
equation [23] is expanded as a viscous model applicable
to the concentrated dispersion system and the following
equation is obtained
ηd=(1-KctimeshctimesC )-25Kc (3)
where Kc is the reciprocal of the closest packing ratio of
the disperse phase and is a parameter of the bulkiness of
the gigantic aggregate in the closest packed state
3MaterialsandMethods
31 Materials
The soybeans used in this study were produced in
America Canada Hokkaido Aomori Iwate and Miyagi
Soymilk was provided by Taishi Food Inc (Aomori
Japan) The moisture content was determined by micro-
wave drying (SMART TURBO CEM Japan KK Tokyo
Japan) and the protein content was determined by the
improved Dumarsquos method using a nitrogen analyzer
(SUMIGRAPH NC-220F Sumika Analysis Chemical
Service Ltd Tokyo Japan) The lipid content was deter-
mined by nuclear magnetic resonance (NMR SMART
TRAC CEM Japan KK) [24] The results are shown in
Table 1
Lactic acid malic acid hydrochloric acid ascorbic
acid citric acid and phytic acid (Wako Pure Chemical
Industries Ltd Osaka Japan) were used as acidity regu-
lators The concentration of each acidity regulator was
028 M
32 Measurementofviscosity
Soymilk heated to 25 was adjusted to pH 56-62 by
adding an acidity regulator The apparent viscosity η of
Table 1 Water protein and lipid contents of soymilk samples
Water[]
Protein[]
Lipid[] Harvest area
A 884 49 29 Miyagi Japan
B 890 51 30 USA
C 880 55 35 Canada
D 876 53 30 Hokkaido Japan
E 891 51 26 Aomori Japan
F 886 53 26 Iwate Japan
Soymilk stability 179
copy 2017 Japan Society for Food Engineering
soymilk was measured with a cone plate viscometer
(TPE-100 Toki Sangyo Co Tokyo Japan) at 25 using
a 1deg34primetimesR24 rotating cone at a shear rate of 1915 s-1
Soymilk was applied to the viscometer 30 seconds after
the addition of an acidity regulator and the value after 30
seconds from the start of measurement at a shear rate of
1915 s-1 was adopted The dimensionless viscosity
ηd was defined as the value obtained by dividing the
apparent viscosity η by the viscosityηc0 of the soymilk
before adding the acidity regulator
33 Calculationoftheviscosityparameter
The concentration of hydrogen ions contained in soy-
milk was calculated from the pH of soymilk Viscosity
parameters were obtained by applying a viscosity equa-
tion to measured values of the hydrogen ion concentra-
tion and dimensionless viscosityηd and fitting by a least
squares method (Office Excel 2002 Microsoft Co)
4ResultsandDiscussion
41 Changesinviscosityofsoymilkwith
decreasedpH
The change in the apparent viscosity of the six types of
soymilk when the pH was reduced with ascorbic acid is
shown in Fig 1 As the pH decreased the apparent vis-
cosity increased slightly up to approximately pH 60
When the pH was lower than 60 the apparent viscosity
increased gradually and when the pH was lower than 59
the apparent viscosity increased exponentially The soy-
milk from Miyagi prefecture (Soymilk A) showed an
acidic shift of 01 in pH Thus the apparent viscosity was
increased slightly to approximately pH 59 and a sharp
increase was confirmed when the pH was lower than pH
58 Although there was a difference in the degree of
change in viscosity depending on the type of soymilk the
increase in apparent viscosity when adding ascorbic acid
was a universal phenomenon in the soymilk colloidal dis-
persion system regardless of the variety of soymilk In
particular regarding the point of pH deviation in the vis-
cosity change in Soymilk A the possibility that the com-
ponent content influenced the viscosity (Table 1) was
examined based on a report showing that the lipid and
protein contents of soymilk affected the pH at which the
viscosity change was observed when ascorbic acid was
added to soymilk [12] and another report showing that
the solid concentration influenced the viscosity of the liq-
uid food [25] However no correlation between ingredi-
ents and viscosity was observed before the ascorbic acid
solution was added Proteins in soybeans have been
shown to differ in terms of the proportions of globulin-
containing protein in soymilk composed of different vari-
eties of soybean [26] As the pH decreases to near the
isoelectric point of the protein the structure of the pro-
tein can change and the protein may become insoluble
[19] Therefore differences in isoelectric point between
globulin proteins may affect changes in viscosity in dif-
ferent types of soymilk Because ash phosphorus and
potassium have been reported as soymilk components
[27] the pH decrease may also be affected
42 Analysisofchangesinviscosity
accompanyingthedecreaseinpHusing
differentacidityregulatorsandevaluation
ofviscositybehaviorsofpH-dependent
aggregationsystemsbytheextended
Krieger-Doughertyequation
Changes in viscosity with decreases in pH following
addition of six types of acidity regulators in soymilk pre-
pared from American whole soybeans (Soymilk B) are
shown in Fig 2 As observed following addition of ascor-
bic acid to the six types of soymilk the apparent viscosity
increased slightly as the pH decreased until reaching a
pH of approximately 60 and the viscosity increased
sharply when the pH was lower than 59 When lactic
acid was added the viscosity increased rapidly after the
pH was below 59 In the system in which other acidity
regulators were added the pH at which the apparent vis-
cosity exceeded 50 mPas was approximately pH 57 or
less however in the case of lactic acid this value was
slightly higher at pH 58 In addition the change in
apparent viscosity was slightly lower when phytic acid Fig 1 Apparent viscosities of the six types of soymilk
after addition of ascorbic acid
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII180
copy 2017 Japan Society for Food Engineering
solution and citric acid solution were added At approxi-
mately pH 59 there was almost no increase compared
with the apparent viscosity before addition of phytic acid
or citric acid and a rapid viscosity increase was observed
beginning at approximately pH 57 These results may be
explained by the chelating action of phytic acid and citric
acid [28] Aggregation of soymilk was caused not only by
the pH decrease but also by divalent cations [29] In
addition soybeans contained many minerals and soy-
milk also contained magnesium ions and calcium ions
[30] In particular phytic acid combined with calcium
and magnesium has been shown to affect the onset of
aggregation [31] The chelation of magnesium ions by
phytic acid and citric acid may suppress the onset of
aggregate formation as a result the apparent viscosity
may gradually increase
For each of the six types of acidity regulator the rela-
tionship between the concentration of hydrogen ions
contained in soymilk and the measured value of dimen-
sionless viscosityηd is shown in the plot in Fig 3 From
these results the viscosity parameter was calculated by
fitting to the extended Einstein equation and Krieger-
Dougherty equation (Eqs 2 3) When analyzing the vis-
cosity change accompanied by the pH decrease we con-
sidered that the charge state of the protein changed as
the soymilk pH decreased ie as the hydrogen ion con-
centration increased and bulky aggregates were formed
to increase the viscosity Therefore we attempted to ana-
lyze the viscosity change using the variable C of the
extended Krieger-Dougherty equation as the hydrogen
ion concentration First in the range in which the hydro-
gen ion concentration was low fitting was performed on
the first equation of the extended Einstein equation (Eq
2) and measured values to find hc Next for all measured
values including the range with high hydrogen ion con-
centrations we fitted the second equation (Eq 3) of the
extended Krieger-Dougherty equation to obtain Kc The
obtained parameters hc and Kc are shown in Table 2 hc
was within the range of approximately 32times103 to 105times
103 M-1 for each type of acidity regulator and Kc was
within the range of approximately 4 to 18 The values
described from the extended Krieger-Dougherty equa-
tion using the hc and Kc values in the system of each pH-
adjusting agent are shown by solid lines in Fig 3 As a
result the solid line was almost near the plot of the mea-
sured value and the measured value could be described
well hc represents the bulkiness of the aggregate larger
hc values were associated with bulkier aggregates Kc
indicates the filling state of the gigantic aggregate
formed by agglomerates gathering and the reciprocal of
the maximum particle packing ratio As the value of Kc
increased the agglomerates were not densely packed
ie the bulkiness of the gigantic aggregate was high
Because the hc of citric acid was the largest of the six
acidity regulators citric acid was thought to significantly
enhance the aggregation in soymilk The molecular
weight and acid dissociation constant of the acidity regu-
lator are also shown in Table 2 but correlation with the
hc value was not found As the soymilk pH decreased the
charge state of the protein changed to form aggregates
However because the proteins contained in soymilk dif-
fered in their isoelectric points proteins participating in
aggregation seemed to change as the pH changed
However we found that one equation (Eq 3) could
describe the viscous behaviors of the soymilk aggrega-
tion system quite well due to the continuous pH decrease
accompanying the addition of the acidity regulators
Furthermore the system assumed that aggregate forma-
tion would progress with an increase in viscosity
Fig 2 Apparent viscosities of Soymilk B after addition of each acidity regulator
Table 2 The viscosity parameters hc and Kc and molecular weight (MW) and acid dissociation constant (pKa) for each acidity regulator
Acidity regulators hc
[times103 M-1]Kc
[-]MW[-]
pKa[-]
Lactic acid 775 79 901 39 [32]
Malic acid 829 70 1341 34 [32]
Hydrochloric acid 712 79 55 -80 [33]
Ascorbic acid 328 182 1761 41 [32]
Citric acid 1052 45 2101 31 [32]
Phytic acid 740 62 6600 19 [34]
Soymilk stability 181
copy 2017 Japan Society for Food Engineering
43 Relationshipbetweenparametersh cand
Kcintheaggregate-formingsystemdueto
thepHdecrease
The relationship between the viscosity parameters hc
and Kc obtained from the viscosity measured using six
types of soymilk and six acidity regulators is shown in
Fig 4 A negative correlation was found and the coeffi-
cient of determination (R2) was as high as 097
Fig 3 Dimensionless viscosities (ηd) of soymilk plotted against the concentration of hydrogen ions after addition of lactic acid (a) malic acid (b) hydrochloric acid (c) ascorbic acid (d) citric acid (e) and phytic acid (f) The solid line shows the viscous model combining the extended Krieger-Dougherty equation
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII182
copy 2017 Japan Society for Food Engineering
Therefore these data suggested that as the size of the
aggregate produced in the high pH range above approxi-
mately pH 60 increased the agglomerates became
denser and the bulk became smaller In contrast as the
size of the aggregate decreased bulky aggregates
became more bulky Additionally because the data were
plotted on the same curve regardless of the type of acid-
ity regulators even if the internal structure of the iso-
lated aggregate differed depending on the difference in
crosslinking mechanism the macroscopic aggregation
behaviors were thought to be similar
Even when coagulating with a crosslinking agent such
as magnesium chloride a negative correlation between
hc and Kc is obtained in previous work [20] In crosslink-
ing aggregation the interaction between colloidal parti-
cles is electrostatic interaction On the other hand in
acid aggregation physical interaction such as hydropho-
bic interaction is mainly The interactions acting between
colloidal particles in both are different As shown in Fig
4 the same tendency was observed even when acid
aggregation with hydrogen ion concentration as a vari-
able strongly suggesting that macroscopic aggregation
mechanism is similar in both acid aggregation and cross-
linking aggregation
Because there was a correlation between hc and Kc
viscosity could be predicted at low pH range below about
pH 59 by measuring changes in viscosity at a high pH
Accordingly it may be possible to predict aggregation
behaviors due to decreased pH in soymilk in the high pH
range and these results may be applied to control the
viscous quality of soymilk
5Conclusion
In this study when the pH of soymilk with different
primary producing areas was reduced using ascorbic
acid the apparent viscosity of all soymilk increased sig-
nificantly at approximately pH 58-59 this was found to
be a universal phenomenon in the soymilk colloidal dis-
persion system Even when the pH decreased following
the addition of six types of acidity regulators to soymilk
prepared from American whole soybeans the apparent
viscosity increased sharply when the pH was lower than
59 However because the apparent viscosity increase
was relatively moderate when phytic acid and citric acid
were added the chelating actions of phytic acid and citric
acid suppressed the initial formation of aggregates
Assuming that the bulkiness of the aggregate was pro-
portional to the hydrogen ion concentration in the high
pH range calculations were made by applying the
extended Krieger-Dougherty equation obtained from
Einsteinrsquos viscosity equation and the Krieger-Dougherty
equation a negative correlation was confirmed with the
parameter hc representing the degree of bulkiness of the
aggregate and the parameter Kc representing the degree
of filling of the gigantic aggregate Moreover the macro-
scopic aggregation behaviors were similar even if the
internal structure of the isolated aggregates dif fered
depending on the difference in crosslinking mechanism
Because of the correlation between hc and Kc viscosity in
the low pH range can be predicted by observing changes
in viscosity in the high pH range Based on these fea-
tures this process may have industrial applications In
future studies we will evaluate the rheological character-
istics of soymilk and assess the applications of these find-
ings in other systems with aggregation Furthermore
additional studies are needed to examine the aggregation
of soymilk particles and structure in greater detail
NOMENCLATURE
C hydrogen ion concentration M-1
Kc reciprocal of closest packing ratio -
hc parameter of bulkiness M-1
φ volume fraction -
η apparent viscosity mPas ηc0 initial viscosity mPas ηd dimensionless viscosity -
ηr relative viscosity -
Fig 4 Relationship between the viscosity parameters hc and Kc obtained from the viscosity measured using six types of soymilk and six acidity regulators
Soymilk stability 183
copy 2017 Japan Society for Food Engineering
Acknowledgements
This research was supported by a grant from the
Project of NARO Bio-oriented Technology Research
Advancement Institution (Project for Development of
New Practical Technology)
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16) J A Gerrard S J Meade A G Miller P K Brown S B
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copy 2017 Japan Society for Food Engineering
豆乳コロイド分散系の安定性に及ぼす pH調整剤添加の影響
佐藤加奈子 1井戸川詩織 12dagger藤井智幸 2
1太子食品工業株式会社2東北大学大学院農学研究科
豆乳はタンパク質溶液にタンパク質粒子と脂質が分散したコロイド分散系である豆乳中に含まれる脂質はオイルボディとして存在しており表面を覆うオレオシンによって合一が抑制され安定なコロイド分散系を形成していると考えられている豆乳の製造管理および豆乳加工品の開発のためには豆乳のコロイド特性の把握が重要と考えられるコロイドの安定性は pHや熱電解質有機物の添加などの要因で変動することが知られている筆者らはアスコルビン酸溶液の添加による pHの低下に伴って豆乳の見かけ粘度が急激に変化する挙動を確認しているオイルボディとタンパク質が関わる凝集体の生成により見かけ粘度が上昇すると考えられるが凝集の詳細は明らかになっていないpH低下に伴う豆乳コロイドの凝集挙動の詳細を明らかにするためには豆乳の粒子が孤立状態で存在している段階から粒子が集まり充填状態やゲル構造を伴う巨大凝集体を生成するまでのメカニズムに関する理解が求められる本研究では豆乳の pH低下によって豆乳中に含まれるタンパク質の等電点に近づくことでタンパク質溶解度が低下し凝集体が形成されると仮説を立て拡張アインシュタイン型の式とKrieger-Dougherty型の式とを組み合わせた粘性モデルを構築してその有効性を実験的に調べた原料産地が異なる 6種類の豆乳にアスコルビン酸溶液を添加してpH 56-62の pH調整豆乳とし円錐平板型回転粘度計を用いて見かけ粘度を測定したpHが低下するにしたがいおよそ pH 60までは見かけ粘度はやや微増するにとどまったがpHが 60より低くなると徐々に見かけ粘度が上昇しpHが 59より低くなると指数関数的に見かけ粘度が上昇したまた宮城県産大豆から調製した豆乳Soymilk AではpHがおよそ 01低い条件で同様の挙動がみられ品種の違いによるグロブリンタンパク質の含有割合の変化や灰分などの他成分による影響が考えられた6種類の pH調整剤をアメリカ産大豆から調製した豆乳Soymilk Bへ添加して見かけ粘度を測定したところ先述の実験と同様
におよそ pH 60までは pH低下に伴って微増しpHが59より低くなると急激に粘度が上昇する挙動を示したただしフィチン酸溶液およびクエン酸溶液の場合は粘度が顕著に変化する pHが低くこれはキレート作用によるものと示唆された
6種類の pH調整剤によるそれぞれの結果について豆乳に含まれる水素イオンの濃度を豆乳の pHから算出し無次元粘度ηdの実測値との関係を示したこのプロットに対し拡張 Krieger-Dougherty型の式に当てはめて粘性パラメータ hcKcを算出したhcは凝集体のかさ高さを表しhcの値が大きいほど凝集体がかさ高いことを示すKcは分散相の最密充填率の逆数であり巨大凝集体のかさ高さを示すつまり Kcの値が大きいほど凝集体が密ではなく巨大凝集体がかさ高いことを表す各 pH 調整剤の系において拡張 Krieger-Dougherty
式の適用妥当性を検討したところpH調整剤の添加に伴う連続した pH低下による豆乳の凝集形成系について1つの式で良好に記述できることがわかった
6種類の豆乳および 6種類の pH調整剤を用いて測定した粘度データから得られた粘性パラメータ hcと Kc
に負の相関が認められたつまりpH低下によって進行する凝集過程において高 pH領域にて生成される凝集体の大きさが大きいほど巨大凝集体が密に充填してかさが小さくなり逆に凝集体の大きさが小さいほど巨大凝集体はかさ高くなることが示唆されたまたpH調整剤の種類によらず同一の曲線上にプロットされたことから孤立状態にある凝集体の内部構造が架橋機構の違いにより異なっていてもマクロな凝集挙動は同様であることが示唆されたさらにhcと Kcに相関関係があるために高い pH領域で粘度変化を測定することによって低い pH領域での粘度が予測できることが示されたこのことは豆乳における pH低下による凝集挙動を高 pH領域で予想可能であることを表し豆乳の品質管理に応用できる可能性が期待される本研究は生研センター「革新的技術創造促進事業(事業化促進)」の支援を受けて行った
(受付 2017年 4月 5日受理 2017年 9月 17日)
1 989-6228 宮城県大崎市古川清水字新田 51-1
2 980-0845 仙台市青葉区荒巻字青葉 468-1
daggerFax 0229-36-1702 E-mail s-itonotaishi-foodcojp
和文要約
「日本食品工学会誌」 Vol 18 No 4 p 185 Dec 2017
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII178
copy 2017 Japan Society for Food Engineering
in many food manufacturing processes [16 17]
However few models have been developed to quantita-
tively describe the changes in viscosity accompanying
aggregation in foods characterized as multicomponent
dispersions
In soymilk oil bodies can be regarded as spheres cov-
ered with oleosin and if the size is sufficiently small the
oil bodies behave like rigid spheres in the dispersion
phase [18] Most of the proteins present in the continu-
ous phase in soymilk are globulin proteins mainly 11S
globulin (glycinin) and 7S globulin (β-conglycinin)
Each globulin is an association of subunits and the iso-
electric points of the proteins differ depending on the
subunits or polypeptides [19] Therefore depending on
the pH the surface potential of the protein changes and
the amount of protein participating in aggregation may
increase or decrease
In this study we hypothesized that aggregates were
formed because of the decrease in protein solubility as
the pH of soymilk decreased and approached the isoelec-
tric point of protein contained in soymilk Thus we con-
structed a viscous model combined with the extended
Einstein equation and the Krieger-Dougherty equation
and experimentally investigated the validity of the model
2Theory
A viscosity model combining Einsteinrsquos viscosity equa-
tion and Krieger-Doughertyrsquos viscosity equation was pre-
viously developed to analyze the viscous behavior of the
process of colloidal coagulation with a crosslinking agent
[20] In a system in which the rigid spheres are dis-
persed if the relative viscosity in the diluted state is ηr
and the volume fraction of the dispersed phase is φ the
following Einsteinrsquos viscosity equation [21 22] can be
established
ηr=1+25φ (1)
Einsteinrsquos viscosity theory is limited to the case in
which φ is suf ficiently small because hydrodynamic
interactions between dispersoids are not considered
Given that bulky aggregates are formed by adding an
acidity regulator under conditions of low pH and assum-
ing that the increase in the effective volume fraction
from the formation of aggregates is proportional to the
hydrogen ion concentration Einsteinrsquos viscosity equation
can be extended as follows
ηd=1+25timeshctimesC (2)
where hc denotes the bulkiness of the colloidal aggre-
gates and C denotes the hydrogen ion concentration
Furthermore under conditions of high pH assuming
that the bulkiness of the aggregates is proportional to
the hydrogen ion concentration the Krieger-Dougherty
equation [23] is expanded as a viscous model applicable
to the concentrated dispersion system and the following
equation is obtained
ηd=(1-KctimeshctimesC )-25Kc (3)
where Kc is the reciprocal of the closest packing ratio of
the disperse phase and is a parameter of the bulkiness of
the gigantic aggregate in the closest packed state
3MaterialsandMethods
31 Materials
The soybeans used in this study were produced in
America Canada Hokkaido Aomori Iwate and Miyagi
Soymilk was provided by Taishi Food Inc (Aomori
Japan) The moisture content was determined by micro-
wave drying (SMART TURBO CEM Japan KK Tokyo
Japan) and the protein content was determined by the
improved Dumarsquos method using a nitrogen analyzer
(SUMIGRAPH NC-220F Sumika Analysis Chemical
Service Ltd Tokyo Japan) The lipid content was deter-
mined by nuclear magnetic resonance (NMR SMART
TRAC CEM Japan KK) [24] The results are shown in
Table 1
Lactic acid malic acid hydrochloric acid ascorbic
acid citric acid and phytic acid (Wako Pure Chemical
Industries Ltd Osaka Japan) were used as acidity regu-
lators The concentration of each acidity regulator was
028 M
32 Measurementofviscosity
Soymilk heated to 25 was adjusted to pH 56-62 by
adding an acidity regulator The apparent viscosity η of
Table 1 Water protein and lipid contents of soymilk samples
Water[]
Protein[]
Lipid[] Harvest area
A 884 49 29 Miyagi Japan
B 890 51 30 USA
C 880 55 35 Canada
D 876 53 30 Hokkaido Japan
E 891 51 26 Aomori Japan
F 886 53 26 Iwate Japan
Soymilk stability 179
copy 2017 Japan Society for Food Engineering
soymilk was measured with a cone plate viscometer
(TPE-100 Toki Sangyo Co Tokyo Japan) at 25 using
a 1deg34primetimesR24 rotating cone at a shear rate of 1915 s-1
Soymilk was applied to the viscometer 30 seconds after
the addition of an acidity regulator and the value after 30
seconds from the start of measurement at a shear rate of
1915 s-1 was adopted The dimensionless viscosity
ηd was defined as the value obtained by dividing the
apparent viscosity η by the viscosityηc0 of the soymilk
before adding the acidity regulator
33 Calculationoftheviscosityparameter
The concentration of hydrogen ions contained in soy-
milk was calculated from the pH of soymilk Viscosity
parameters were obtained by applying a viscosity equa-
tion to measured values of the hydrogen ion concentra-
tion and dimensionless viscosityηd and fitting by a least
squares method (Office Excel 2002 Microsoft Co)
4ResultsandDiscussion
41 Changesinviscosityofsoymilkwith
decreasedpH
The change in the apparent viscosity of the six types of
soymilk when the pH was reduced with ascorbic acid is
shown in Fig 1 As the pH decreased the apparent vis-
cosity increased slightly up to approximately pH 60
When the pH was lower than 60 the apparent viscosity
increased gradually and when the pH was lower than 59
the apparent viscosity increased exponentially The soy-
milk from Miyagi prefecture (Soymilk A) showed an
acidic shift of 01 in pH Thus the apparent viscosity was
increased slightly to approximately pH 59 and a sharp
increase was confirmed when the pH was lower than pH
58 Although there was a difference in the degree of
change in viscosity depending on the type of soymilk the
increase in apparent viscosity when adding ascorbic acid
was a universal phenomenon in the soymilk colloidal dis-
persion system regardless of the variety of soymilk In
particular regarding the point of pH deviation in the vis-
cosity change in Soymilk A the possibility that the com-
ponent content influenced the viscosity (Table 1) was
examined based on a report showing that the lipid and
protein contents of soymilk affected the pH at which the
viscosity change was observed when ascorbic acid was
added to soymilk [12] and another report showing that
the solid concentration influenced the viscosity of the liq-
uid food [25] However no correlation between ingredi-
ents and viscosity was observed before the ascorbic acid
solution was added Proteins in soybeans have been
shown to differ in terms of the proportions of globulin-
containing protein in soymilk composed of different vari-
eties of soybean [26] As the pH decreases to near the
isoelectric point of the protein the structure of the pro-
tein can change and the protein may become insoluble
[19] Therefore differences in isoelectric point between
globulin proteins may affect changes in viscosity in dif-
ferent types of soymilk Because ash phosphorus and
potassium have been reported as soymilk components
[27] the pH decrease may also be affected
42 Analysisofchangesinviscosity
accompanyingthedecreaseinpHusing
differentacidityregulatorsandevaluation
ofviscositybehaviorsofpH-dependent
aggregationsystemsbytheextended
Krieger-Doughertyequation
Changes in viscosity with decreases in pH following
addition of six types of acidity regulators in soymilk pre-
pared from American whole soybeans (Soymilk B) are
shown in Fig 2 As observed following addition of ascor-
bic acid to the six types of soymilk the apparent viscosity
increased slightly as the pH decreased until reaching a
pH of approximately 60 and the viscosity increased
sharply when the pH was lower than 59 When lactic
acid was added the viscosity increased rapidly after the
pH was below 59 In the system in which other acidity
regulators were added the pH at which the apparent vis-
cosity exceeded 50 mPas was approximately pH 57 or
less however in the case of lactic acid this value was
slightly higher at pH 58 In addition the change in
apparent viscosity was slightly lower when phytic acid Fig 1 Apparent viscosities of the six types of soymilk
after addition of ascorbic acid
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII180
copy 2017 Japan Society for Food Engineering
solution and citric acid solution were added At approxi-
mately pH 59 there was almost no increase compared
with the apparent viscosity before addition of phytic acid
or citric acid and a rapid viscosity increase was observed
beginning at approximately pH 57 These results may be
explained by the chelating action of phytic acid and citric
acid [28] Aggregation of soymilk was caused not only by
the pH decrease but also by divalent cations [29] In
addition soybeans contained many minerals and soy-
milk also contained magnesium ions and calcium ions
[30] In particular phytic acid combined with calcium
and magnesium has been shown to affect the onset of
aggregation [31] The chelation of magnesium ions by
phytic acid and citric acid may suppress the onset of
aggregate formation as a result the apparent viscosity
may gradually increase
For each of the six types of acidity regulator the rela-
tionship between the concentration of hydrogen ions
contained in soymilk and the measured value of dimen-
sionless viscosityηd is shown in the plot in Fig 3 From
these results the viscosity parameter was calculated by
fitting to the extended Einstein equation and Krieger-
Dougherty equation (Eqs 2 3) When analyzing the vis-
cosity change accompanied by the pH decrease we con-
sidered that the charge state of the protein changed as
the soymilk pH decreased ie as the hydrogen ion con-
centration increased and bulky aggregates were formed
to increase the viscosity Therefore we attempted to ana-
lyze the viscosity change using the variable C of the
extended Krieger-Dougherty equation as the hydrogen
ion concentration First in the range in which the hydro-
gen ion concentration was low fitting was performed on
the first equation of the extended Einstein equation (Eq
2) and measured values to find hc Next for all measured
values including the range with high hydrogen ion con-
centrations we fitted the second equation (Eq 3) of the
extended Krieger-Dougherty equation to obtain Kc The
obtained parameters hc and Kc are shown in Table 2 hc
was within the range of approximately 32times103 to 105times
103 M-1 for each type of acidity regulator and Kc was
within the range of approximately 4 to 18 The values
described from the extended Krieger-Dougherty equa-
tion using the hc and Kc values in the system of each pH-
adjusting agent are shown by solid lines in Fig 3 As a
result the solid line was almost near the plot of the mea-
sured value and the measured value could be described
well hc represents the bulkiness of the aggregate larger
hc values were associated with bulkier aggregates Kc
indicates the filling state of the gigantic aggregate
formed by agglomerates gathering and the reciprocal of
the maximum particle packing ratio As the value of Kc
increased the agglomerates were not densely packed
ie the bulkiness of the gigantic aggregate was high
Because the hc of citric acid was the largest of the six
acidity regulators citric acid was thought to significantly
enhance the aggregation in soymilk The molecular
weight and acid dissociation constant of the acidity regu-
lator are also shown in Table 2 but correlation with the
hc value was not found As the soymilk pH decreased the
charge state of the protein changed to form aggregates
However because the proteins contained in soymilk dif-
fered in their isoelectric points proteins participating in
aggregation seemed to change as the pH changed
However we found that one equation (Eq 3) could
describe the viscous behaviors of the soymilk aggrega-
tion system quite well due to the continuous pH decrease
accompanying the addition of the acidity regulators
Furthermore the system assumed that aggregate forma-
tion would progress with an increase in viscosity
Fig 2 Apparent viscosities of Soymilk B after addition of each acidity regulator
Table 2 The viscosity parameters hc and Kc and molecular weight (MW) and acid dissociation constant (pKa) for each acidity regulator
Acidity regulators hc
[times103 M-1]Kc
[-]MW[-]
pKa[-]
Lactic acid 775 79 901 39 [32]
Malic acid 829 70 1341 34 [32]
Hydrochloric acid 712 79 55 -80 [33]
Ascorbic acid 328 182 1761 41 [32]
Citric acid 1052 45 2101 31 [32]
Phytic acid 740 62 6600 19 [34]
Soymilk stability 181
copy 2017 Japan Society for Food Engineering
43 Relationshipbetweenparametersh cand
Kcintheaggregate-formingsystemdueto
thepHdecrease
The relationship between the viscosity parameters hc
and Kc obtained from the viscosity measured using six
types of soymilk and six acidity regulators is shown in
Fig 4 A negative correlation was found and the coeffi-
cient of determination (R2) was as high as 097
Fig 3 Dimensionless viscosities (ηd) of soymilk plotted against the concentration of hydrogen ions after addition of lactic acid (a) malic acid (b) hydrochloric acid (c) ascorbic acid (d) citric acid (e) and phytic acid (f) The solid line shows the viscous model combining the extended Krieger-Dougherty equation
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII182
copy 2017 Japan Society for Food Engineering
Therefore these data suggested that as the size of the
aggregate produced in the high pH range above approxi-
mately pH 60 increased the agglomerates became
denser and the bulk became smaller In contrast as the
size of the aggregate decreased bulky aggregates
became more bulky Additionally because the data were
plotted on the same curve regardless of the type of acid-
ity regulators even if the internal structure of the iso-
lated aggregate differed depending on the difference in
crosslinking mechanism the macroscopic aggregation
behaviors were thought to be similar
Even when coagulating with a crosslinking agent such
as magnesium chloride a negative correlation between
hc and Kc is obtained in previous work [20] In crosslink-
ing aggregation the interaction between colloidal parti-
cles is electrostatic interaction On the other hand in
acid aggregation physical interaction such as hydropho-
bic interaction is mainly The interactions acting between
colloidal particles in both are different As shown in Fig
4 the same tendency was observed even when acid
aggregation with hydrogen ion concentration as a vari-
able strongly suggesting that macroscopic aggregation
mechanism is similar in both acid aggregation and cross-
linking aggregation
Because there was a correlation between hc and Kc
viscosity could be predicted at low pH range below about
pH 59 by measuring changes in viscosity at a high pH
Accordingly it may be possible to predict aggregation
behaviors due to decreased pH in soymilk in the high pH
range and these results may be applied to control the
viscous quality of soymilk
5Conclusion
In this study when the pH of soymilk with different
primary producing areas was reduced using ascorbic
acid the apparent viscosity of all soymilk increased sig-
nificantly at approximately pH 58-59 this was found to
be a universal phenomenon in the soymilk colloidal dis-
persion system Even when the pH decreased following
the addition of six types of acidity regulators to soymilk
prepared from American whole soybeans the apparent
viscosity increased sharply when the pH was lower than
59 However because the apparent viscosity increase
was relatively moderate when phytic acid and citric acid
were added the chelating actions of phytic acid and citric
acid suppressed the initial formation of aggregates
Assuming that the bulkiness of the aggregate was pro-
portional to the hydrogen ion concentration in the high
pH range calculations were made by applying the
extended Krieger-Dougherty equation obtained from
Einsteinrsquos viscosity equation and the Krieger-Dougherty
equation a negative correlation was confirmed with the
parameter hc representing the degree of bulkiness of the
aggregate and the parameter Kc representing the degree
of filling of the gigantic aggregate Moreover the macro-
scopic aggregation behaviors were similar even if the
internal structure of the isolated aggregates dif fered
depending on the difference in crosslinking mechanism
Because of the correlation between hc and Kc viscosity in
the low pH range can be predicted by observing changes
in viscosity in the high pH range Based on these fea-
tures this process may have industrial applications In
future studies we will evaluate the rheological character-
istics of soymilk and assess the applications of these find-
ings in other systems with aggregation Furthermore
additional studies are needed to examine the aggregation
of soymilk particles and structure in greater detail
NOMENCLATURE
C hydrogen ion concentration M-1
Kc reciprocal of closest packing ratio -
hc parameter of bulkiness M-1
φ volume fraction -
η apparent viscosity mPas ηc0 initial viscosity mPas ηd dimensionless viscosity -
ηr relative viscosity -
Fig 4 Relationship between the viscosity parameters hc and Kc obtained from the viscosity measured using six types of soymilk and six acidity regulators
Soymilk stability 183
copy 2017 Japan Society for Food Engineering
Acknowledgements
This research was supported by a grant from the
Project of NARO Bio-oriented Technology Research
Advancement Institution (Project for Development of
New Practical Technology)
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Res Bull 36 511-519 (2001)
33) B Tamamushi ldquoDictionar y of Physics and Chemistr y
(Rikagaku Jiten)rdquo (in Japanese) Iwanami Tokyo Japan
1981 pp 1577-1578
34) W J Evans E J McCourther R I Shrager Titration
studies of phytic acid J Am Oil Chem Soc 59 189-191
(1982)
copy 2017 Japan Society for Food Engineering
豆乳コロイド分散系の安定性に及ぼす pH調整剤添加の影響
佐藤加奈子 1井戸川詩織 12dagger藤井智幸 2
1太子食品工業株式会社2東北大学大学院農学研究科
豆乳はタンパク質溶液にタンパク質粒子と脂質が分散したコロイド分散系である豆乳中に含まれる脂質はオイルボディとして存在しており表面を覆うオレオシンによって合一が抑制され安定なコロイド分散系を形成していると考えられている豆乳の製造管理および豆乳加工品の開発のためには豆乳のコロイド特性の把握が重要と考えられるコロイドの安定性は pHや熱電解質有機物の添加などの要因で変動することが知られている筆者らはアスコルビン酸溶液の添加による pHの低下に伴って豆乳の見かけ粘度が急激に変化する挙動を確認しているオイルボディとタンパク質が関わる凝集体の生成により見かけ粘度が上昇すると考えられるが凝集の詳細は明らかになっていないpH低下に伴う豆乳コロイドの凝集挙動の詳細を明らかにするためには豆乳の粒子が孤立状態で存在している段階から粒子が集まり充填状態やゲル構造を伴う巨大凝集体を生成するまでのメカニズムに関する理解が求められる本研究では豆乳の pH低下によって豆乳中に含まれるタンパク質の等電点に近づくことでタンパク質溶解度が低下し凝集体が形成されると仮説を立て拡張アインシュタイン型の式とKrieger-Dougherty型の式とを組み合わせた粘性モデルを構築してその有効性を実験的に調べた原料産地が異なる 6種類の豆乳にアスコルビン酸溶液を添加してpH 56-62の pH調整豆乳とし円錐平板型回転粘度計を用いて見かけ粘度を測定したpHが低下するにしたがいおよそ pH 60までは見かけ粘度はやや微増するにとどまったがpHが 60より低くなると徐々に見かけ粘度が上昇しpHが 59より低くなると指数関数的に見かけ粘度が上昇したまた宮城県産大豆から調製した豆乳Soymilk AではpHがおよそ 01低い条件で同様の挙動がみられ品種の違いによるグロブリンタンパク質の含有割合の変化や灰分などの他成分による影響が考えられた6種類の pH調整剤をアメリカ産大豆から調製した豆乳Soymilk Bへ添加して見かけ粘度を測定したところ先述の実験と同様
におよそ pH 60までは pH低下に伴って微増しpHが59より低くなると急激に粘度が上昇する挙動を示したただしフィチン酸溶液およびクエン酸溶液の場合は粘度が顕著に変化する pHが低くこれはキレート作用によるものと示唆された
6種類の pH調整剤によるそれぞれの結果について豆乳に含まれる水素イオンの濃度を豆乳の pHから算出し無次元粘度ηdの実測値との関係を示したこのプロットに対し拡張 Krieger-Dougherty型の式に当てはめて粘性パラメータ hcKcを算出したhcは凝集体のかさ高さを表しhcの値が大きいほど凝集体がかさ高いことを示すKcは分散相の最密充填率の逆数であり巨大凝集体のかさ高さを示すつまり Kcの値が大きいほど凝集体が密ではなく巨大凝集体がかさ高いことを表す各 pH 調整剤の系において拡張 Krieger-Dougherty
式の適用妥当性を検討したところpH調整剤の添加に伴う連続した pH低下による豆乳の凝集形成系について1つの式で良好に記述できることがわかった
6種類の豆乳および 6種類の pH調整剤を用いて測定した粘度データから得られた粘性パラメータ hcと Kc
に負の相関が認められたつまりpH低下によって進行する凝集過程において高 pH領域にて生成される凝集体の大きさが大きいほど巨大凝集体が密に充填してかさが小さくなり逆に凝集体の大きさが小さいほど巨大凝集体はかさ高くなることが示唆されたまたpH調整剤の種類によらず同一の曲線上にプロットされたことから孤立状態にある凝集体の内部構造が架橋機構の違いにより異なっていてもマクロな凝集挙動は同様であることが示唆されたさらにhcと Kcに相関関係があるために高い pH領域で粘度変化を測定することによって低い pH領域での粘度が予測できることが示されたこのことは豆乳における pH低下による凝集挙動を高 pH領域で予想可能であることを表し豆乳の品質管理に応用できる可能性が期待される本研究は生研センター「革新的技術創造促進事業(事業化促進)」の支援を受けて行った
(受付 2017年 4月 5日受理 2017年 9月 17日)
1 989-6228 宮城県大崎市古川清水字新田 51-1
2 980-0845 仙台市青葉区荒巻字青葉 468-1
daggerFax 0229-36-1702 E-mail s-itonotaishi-foodcojp
和文要約
「日本食品工学会誌」 Vol 18 No 4 p 185 Dec 2017
Soymilk stability 179
copy 2017 Japan Society for Food Engineering
soymilk was measured with a cone plate viscometer
(TPE-100 Toki Sangyo Co Tokyo Japan) at 25 using
a 1deg34primetimesR24 rotating cone at a shear rate of 1915 s-1
Soymilk was applied to the viscometer 30 seconds after
the addition of an acidity regulator and the value after 30
seconds from the start of measurement at a shear rate of
1915 s-1 was adopted The dimensionless viscosity
ηd was defined as the value obtained by dividing the
apparent viscosity η by the viscosityηc0 of the soymilk
before adding the acidity regulator
33 Calculationoftheviscosityparameter
The concentration of hydrogen ions contained in soy-
milk was calculated from the pH of soymilk Viscosity
parameters were obtained by applying a viscosity equa-
tion to measured values of the hydrogen ion concentra-
tion and dimensionless viscosityηd and fitting by a least
squares method (Office Excel 2002 Microsoft Co)
4ResultsandDiscussion
41 Changesinviscosityofsoymilkwith
decreasedpH
The change in the apparent viscosity of the six types of
soymilk when the pH was reduced with ascorbic acid is
shown in Fig 1 As the pH decreased the apparent vis-
cosity increased slightly up to approximately pH 60
When the pH was lower than 60 the apparent viscosity
increased gradually and when the pH was lower than 59
the apparent viscosity increased exponentially The soy-
milk from Miyagi prefecture (Soymilk A) showed an
acidic shift of 01 in pH Thus the apparent viscosity was
increased slightly to approximately pH 59 and a sharp
increase was confirmed when the pH was lower than pH
58 Although there was a difference in the degree of
change in viscosity depending on the type of soymilk the
increase in apparent viscosity when adding ascorbic acid
was a universal phenomenon in the soymilk colloidal dis-
persion system regardless of the variety of soymilk In
particular regarding the point of pH deviation in the vis-
cosity change in Soymilk A the possibility that the com-
ponent content influenced the viscosity (Table 1) was
examined based on a report showing that the lipid and
protein contents of soymilk affected the pH at which the
viscosity change was observed when ascorbic acid was
added to soymilk [12] and another report showing that
the solid concentration influenced the viscosity of the liq-
uid food [25] However no correlation between ingredi-
ents and viscosity was observed before the ascorbic acid
solution was added Proteins in soybeans have been
shown to differ in terms of the proportions of globulin-
containing protein in soymilk composed of different vari-
eties of soybean [26] As the pH decreases to near the
isoelectric point of the protein the structure of the pro-
tein can change and the protein may become insoluble
[19] Therefore differences in isoelectric point between
globulin proteins may affect changes in viscosity in dif-
ferent types of soymilk Because ash phosphorus and
potassium have been reported as soymilk components
[27] the pH decrease may also be affected
42 Analysisofchangesinviscosity
accompanyingthedecreaseinpHusing
differentacidityregulatorsandevaluation
ofviscositybehaviorsofpH-dependent
aggregationsystemsbytheextended
Krieger-Doughertyequation
Changes in viscosity with decreases in pH following
addition of six types of acidity regulators in soymilk pre-
pared from American whole soybeans (Soymilk B) are
shown in Fig 2 As observed following addition of ascor-
bic acid to the six types of soymilk the apparent viscosity
increased slightly as the pH decreased until reaching a
pH of approximately 60 and the viscosity increased
sharply when the pH was lower than 59 When lactic
acid was added the viscosity increased rapidly after the
pH was below 59 In the system in which other acidity
regulators were added the pH at which the apparent vis-
cosity exceeded 50 mPas was approximately pH 57 or
less however in the case of lactic acid this value was
slightly higher at pH 58 In addition the change in
apparent viscosity was slightly lower when phytic acid Fig 1 Apparent viscosities of the six types of soymilk
after addition of ascorbic acid
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII180
copy 2017 Japan Society for Food Engineering
solution and citric acid solution were added At approxi-
mately pH 59 there was almost no increase compared
with the apparent viscosity before addition of phytic acid
or citric acid and a rapid viscosity increase was observed
beginning at approximately pH 57 These results may be
explained by the chelating action of phytic acid and citric
acid [28] Aggregation of soymilk was caused not only by
the pH decrease but also by divalent cations [29] In
addition soybeans contained many minerals and soy-
milk also contained magnesium ions and calcium ions
[30] In particular phytic acid combined with calcium
and magnesium has been shown to affect the onset of
aggregation [31] The chelation of magnesium ions by
phytic acid and citric acid may suppress the onset of
aggregate formation as a result the apparent viscosity
may gradually increase
For each of the six types of acidity regulator the rela-
tionship between the concentration of hydrogen ions
contained in soymilk and the measured value of dimen-
sionless viscosityηd is shown in the plot in Fig 3 From
these results the viscosity parameter was calculated by
fitting to the extended Einstein equation and Krieger-
Dougherty equation (Eqs 2 3) When analyzing the vis-
cosity change accompanied by the pH decrease we con-
sidered that the charge state of the protein changed as
the soymilk pH decreased ie as the hydrogen ion con-
centration increased and bulky aggregates were formed
to increase the viscosity Therefore we attempted to ana-
lyze the viscosity change using the variable C of the
extended Krieger-Dougherty equation as the hydrogen
ion concentration First in the range in which the hydro-
gen ion concentration was low fitting was performed on
the first equation of the extended Einstein equation (Eq
2) and measured values to find hc Next for all measured
values including the range with high hydrogen ion con-
centrations we fitted the second equation (Eq 3) of the
extended Krieger-Dougherty equation to obtain Kc The
obtained parameters hc and Kc are shown in Table 2 hc
was within the range of approximately 32times103 to 105times
103 M-1 for each type of acidity regulator and Kc was
within the range of approximately 4 to 18 The values
described from the extended Krieger-Dougherty equa-
tion using the hc and Kc values in the system of each pH-
adjusting agent are shown by solid lines in Fig 3 As a
result the solid line was almost near the plot of the mea-
sured value and the measured value could be described
well hc represents the bulkiness of the aggregate larger
hc values were associated with bulkier aggregates Kc
indicates the filling state of the gigantic aggregate
formed by agglomerates gathering and the reciprocal of
the maximum particle packing ratio As the value of Kc
increased the agglomerates were not densely packed
ie the bulkiness of the gigantic aggregate was high
Because the hc of citric acid was the largest of the six
acidity regulators citric acid was thought to significantly
enhance the aggregation in soymilk The molecular
weight and acid dissociation constant of the acidity regu-
lator are also shown in Table 2 but correlation with the
hc value was not found As the soymilk pH decreased the
charge state of the protein changed to form aggregates
However because the proteins contained in soymilk dif-
fered in their isoelectric points proteins participating in
aggregation seemed to change as the pH changed
However we found that one equation (Eq 3) could
describe the viscous behaviors of the soymilk aggrega-
tion system quite well due to the continuous pH decrease
accompanying the addition of the acidity regulators
Furthermore the system assumed that aggregate forma-
tion would progress with an increase in viscosity
Fig 2 Apparent viscosities of Soymilk B after addition of each acidity regulator
Table 2 The viscosity parameters hc and Kc and molecular weight (MW) and acid dissociation constant (pKa) for each acidity regulator
Acidity regulators hc
[times103 M-1]Kc
[-]MW[-]
pKa[-]
Lactic acid 775 79 901 39 [32]
Malic acid 829 70 1341 34 [32]
Hydrochloric acid 712 79 55 -80 [33]
Ascorbic acid 328 182 1761 41 [32]
Citric acid 1052 45 2101 31 [32]
Phytic acid 740 62 6600 19 [34]
Soymilk stability 181
copy 2017 Japan Society for Food Engineering
43 Relationshipbetweenparametersh cand
Kcintheaggregate-formingsystemdueto
thepHdecrease
The relationship between the viscosity parameters hc
and Kc obtained from the viscosity measured using six
types of soymilk and six acidity regulators is shown in
Fig 4 A negative correlation was found and the coeffi-
cient of determination (R2) was as high as 097
Fig 3 Dimensionless viscosities (ηd) of soymilk plotted against the concentration of hydrogen ions after addition of lactic acid (a) malic acid (b) hydrochloric acid (c) ascorbic acid (d) citric acid (e) and phytic acid (f) The solid line shows the viscous model combining the extended Krieger-Dougherty equation
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII182
copy 2017 Japan Society for Food Engineering
Therefore these data suggested that as the size of the
aggregate produced in the high pH range above approxi-
mately pH 60 increased the agglomerates became
denser and the bulk became smaller In contrast as the
size of the aggregate decreased bulky aggregates
became more bulky Additionally because the data were
plotted on the same curve regardless of the type of acid-
ity regulators even if the internal structure of the iso-
lated aggregate differed depending on the difference in
crosslinking mechanism the macroscopic aggregation
behaviors were thought to be similar
Even when coagulating with a crosslinking agent such
as magnesium chloride a negative correlation between
hc and Kc is obtained in previous work [20] In crosslink-
ing aggregation the interaction between colloidal parti-
cles is electrostatic interaction On the other hand in
acid aggregation physical interaction such as hydropho-
bic interaction is mainly The interactions acting between
colloidal particles in both are different As shown in Fig
4 the same tendency was observed even when acid
aggregation with hydrogen ion concentration as a vari-
able strongly suggesting that macroscopic aggregation
mechanism is similar in both acid aggregation and cross-
linking aggregation
Because there was a correlation between hc and Kc
viscosity could be predicted at low pH range below about
pH 59 by measuring changes in viscosity at a high pH
Accordingly it may be possible to predict aggregation
behaviors due to decreased pH in soymilk in the high pH
range and these results may be applied to control the
viscous quality of soymilk
5Conclusion
In this study when the pH of soymilk with different
primary producing areas was reduced using ascorbic
acid the apparent viscosity of all soymilk increased sig-
nificantly at approximately pH 58-59 this was found to
be a universal phenomenon in the soymilk colloidal dis-
persion system Even when the pH decreased following
the addition of six types of acidity regulators to soymilk
prepared from American whole soybeans the apparent
viscosity increased sharply when the pH was lower than
59 However because the apparent viscosity increase
was relatively moderate when phytic acid and citric acid
were added the chelating actions of phytic acid and citric
acid suppressed the initial formation of aggregates
Assuming that the bulkiness of the aggregate was pro-
portional to the hydrogen ion concentration in the high
pH range calculations were made by applying the
extended Krieger-Dougherty equation obtained from
Einsteinrsquos viscosity equation and the Krieger-Dougherty
equation a negative correlation was confirmed with the
parameter hc representing the degree of bulkiness of the
aggregate and the parameter Kc representing the degree
of filling of the gigantic aggregate Moreover the macro-
scopic aggregation behaviors were similar even if the
internal structure of the isolated aggregates dif fered
depending on the difference in crosslinking mechanism
Because of the correlation between hc and Kc viscosity in
the low pH range can be predicted by observing changes
in viscosity in the high pH range Based on these fea-
tures this process may have industrial applications In
future studies we will evaluate the rheological character-
istics of soymilk and assess the applications of these find-
ings in other systems with aggregation Furthermore
additional studies are needed to examine the aggregation
of soymilk particles and structure in greater detail
NOMENCLATURE
C hydrogen ion concentration M-1
Kc reciprocal of closest packing ratio -
hc parameter of bulkiness M-1
φ volume fraction -
η apparent viscosity mPas ηc0 initial viscosity mPas ηd dimensionless viscosity -
ηr relative viscosity -
Fig 4 Relationship between the viscosity parameters hc and Kc obtained from the viscosity measured using six types of soymilk and six acidity regulators
Soymilk stability 183
copy 2017 Japan Society for Food Engineering
Acknowledgements
This research was supported by a grant from the
Project of NARO Bio-oriented Technology Research
Advancement Institution (Project for Development of
New Practical Technology)
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5) S T Guo T Ono M Mikami Interaction between protein
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10) S G Garciacutea S Wold M Jonsson Effects of temperature on
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73 89-102 (1993)
12) K Oizumi S Idogawa Y Iwamoto K Ito T Fujii Influence
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Jpn Soc Food Sci Technol 63 142-149 (2016)
13) T Fujii T Yano H Kumagai O Miyawaki Dynamic light
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14) K Suzuki E Uchiyama A Kuroda T Momose M Tamura
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15) P J Flory ldquoPrinciples of polymer chemistryrdquo Cornell
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16) J A Gerrard S J Meade A G Miller P K Brown S B
Yasir K H Sutton M P Newberry Protein cross-linking
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17) D Saha S Bhattacharya Hydrocolloids as thickening
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Technol 47 587-597 (2010)
18) K Ito S Idogawa Elastic behavior of tofu emulsion gel (in
Japanese) Jpn J Food Eng 14 49-57 (2013)
19) Y Morita ldquoSoybean Protein (Daizu Tanpakushitu)rdquo Korin
Tokyo Japan 2000 pp 66-70
20) S Idogawa T Fujii Rheological analysis of the aggregation
behavior of a soymilk colloidal system Food Sci Technol
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24) G Cartwright B H McManus T P Leffler C R Moser
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28) P Ekholm L Virkki M Ylinen L Johansson The effect of
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copy 2017 Japan Society for Food Engineering
phytic acid and some natural chelating agents on the solu-
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29) T Ono S Kato K Mothizuki Influences of calcium and
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Comparison of bench and production scale methods for
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Res Bull 36 511-519 (2001)
33) B Tamamushi ldquoDictionar y of Physics and Chemistr y
(Rikagaku Jiten)rdquo (in Japanese) Iwanami Tokyo Japan
1981 pp 1577-1578
34) W J Evans E J McCourther R I Shrager Titration
studies of phytic acid J Am Oil Chem Soc 59 189-191
(1982)
copy 2017 Japan Society for Food Engineering
豆乳コロイド分散系の安定性に及ぼす pH調整剤添加の影響
佐藤加奈子 1井戸川詩織 12dagger藤井智幸 2
1太子食品工業株式会社2東北大学大学院農学研究科
豆乳はタンパク質溶液にタンパク質粒子と脂質が分散したコロイド分散系である豆乳中に含まれる脂質はオイルボディとして存在しており表面を覆うオレオシンによって合一が抑制され安定なコロイド分散系を形成していると考えられている豆乳の製造管理および豆乳加工品の開発のためには豆乳のコロイド特性の把握が重要と考えられるコロイドの安定性は pHや熱電解質有機物の添加などの要因で変動することが知られている筆者らはアスコルビン酸溶液の添加による pHの低下に伴って豆乳の見かけ粘度が急激に変化する挙動を確認しているオイルボディとタンパク質が関わる凝集体の生成により見かけ粘度が上昇すると考えられるが凝集の詳細は明らかになっていないpH低下に伴う豆乳コロイドの凝集挙動の詳細を明らかにするためには豆乳の粒子が孤立状態で存在している段階から粒子が集まり充填状態やゲル構造を伴う巨大凝集体を生成するまでのメカニズムに関する理解が求められる本研究では豆乳の pH低下によって豆乳中に含まれるタンパク質の等電点に近づくことでタンパク質溶解度が低下し凝集体が形成されると仮説を立て拡張アインシュタイン型の式とKrieger-Dougherty型の式とを組み合わせた粘性モデルを構築してその有効性を実験的に調べた原料産地が異なる 6種類の豆乳にアスコルビン酸溶液を添加してpH 56-62の pH調整豆乳とし円錐平板型回転粘度計を用いて見かけ粘度を測定したpHが低下するにしたがいおよそ pH 60までは見かけ粘度はやや微増するにとどまったがpHが 60より低くなると徐々に見かけ粘度が上昇しpHが 59より低くなると指数関数的に見かけ粘度が上昇したまた宮城県産大豆から調製した豆乳Soymilk AではpHがおよそ 01低い条件で同様の挙動がみられ品種の違いによるグロブリンタンパク質の含有割合の変化や灰分などの他成分による影響が考えられた6種類の pH調整剤をアメリカ産大豆から調製した豆乳Soymilk Bへ添加して見かけ粘度を測定したところ先述の実験と同様
におよそ pH 60までは pH低下に伴って微増しpHが59より低くなると急激に粘度が上昇する挙動を示したただしフィチン酸溶液およびクエン酸溶液の場合は粘度が顕著に変化する pHが低くこれはキレート作用によるものと示唆された
6種類の pH調整剤によるそれぞれの結果について豆乳に含まれる水素イオンの濃度を豆乳の pHから算出し無次元粘度ηdの実測値との関係を示したこのプロットに対し拡張 Krieger-Dougherty型の式に当てはめて粘性パラメータ hcKcを算出したhcは凝集体のかさ高さを表しhcの値が大きいほど凝集体がかさ高いことを示すKcは分散相の最密充填率の逆数であり巨大凝集体のかさ高さを示すつまり Kcの値が大きいほど凝集体が密ではなく巨大凝集体がかさ高いことを表す各 pH 調整剤の系において拡張 Krieger-Dougherty
式の適用妥当性を検討したところpH調整剤の添加に伴う連続した pH低下による豆乳の凝集形成系について1つの式で良好に記述できることがわかった
6種類の豆乳および 6種類の pH調整剤を用いて測定した粘度データから得られた粘性パラメータ hcと Kc
に負の相関が認められたつまりpH低下によって進行する凝集過程において高 pH領域にて生成される凝集体の大きさが大きいほど巨大凝集体が密に充填してかさが小さくなり逆に凝集体の大きさが小さいほど巨大凝集体はかさ高くなることが示唆されたまたpH調整剤の種類によらず同一の曲線上にプロットされたことから孤立状態にある凝集体の内部構造が架橋機構の違いにより異なっていてもマクロな凝集挙動は同様であることが示唆されたさらにhcと Kcに相関関係があるために高い pH領域で粘度変化を測定することによって低い pH領域での粘度が予測できることが示されたこのことは豆乳における pH低下による凝集挙動を高 pH領域で予想可能であることを表し豆乳の品質管理に応用できる可能性が期待される本研究は生研センター「革新的技術創造促進事業(事業化促進)」の支援を受けて行った
(受付 2017年 4月 5日受理 2017年 9月 17日)
1 989-6228 宮城県大崎市古川清水字新田 51-1
2 980-0845 仙台市青葉区荒巻字青葉 468-1
daggerFax 0229-36-1702 E-mail s-itonotaishi-foodcojp
和文要約
「日本食品工学会誌」 Vol 18 No 4 p 185 Dec 2017
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII180
copy 2017 Japan Society for Food Engineering
solution and citric acid solution were added At approxi-
mately pH 59 there was almost no increase compared
with the apparent viscosity before addition of phytic acid
or citric acid and a rapid viscosity increase was observed
beginning at approximately pH 57 These results may be
explained by the chelating action of phytic acid and citric
acid [28] Aggregation of soymilk was caused not only by
the pH decrease but also by divalent cations [29] In
addition soybeans contained many minerals and soy-
milk also contained magnesium ions and calcium ions
[30] In particular phytic acid combined with calcium
and magnesium has been shown to affect the onset of
aggregation [31] The chelation of magnesium ions by
phytic acid and citric acid may suppress the onset of
aggregate formation as a result the apparent viscosity
may gradually increase
For each of the six types of acidity regulator the rela-
tionship between the concentration of hydrogen ions
contained in soymilk and the measured value of dimen-
sionless viscosityηd is shown in the plot in Fig 3 From
these results the viscosity parameter was calculated by
fitting to the extended Einstein equation and Krieger-
Dougherty equation (Eqs 2 3) When analyzing the vis-
cosity change accompanied by the pH decrease we con-
sidered that the charge state of the protein changed as
the soymilk pH decreased ie as the hydrogen ion con-
centration increased and bulky aggregates were formed
to increase the viscosity Therefore we attempted to ana-
lyze the viscosity change using the variable C of the
extended Krieger-Dougherty equation as the hydrogen
ion concentration First in the range in which the hydro-
gen ion concentration was low fitting was performed on
the first equation of the extended Einstein equation (Eq
2) and measured values to find hc Next for all measured
values including the range with high hydrogen ion con-
centrations we fitted the second equation (Eq 3) of the
extended Krieger-Dougherty equation to obtain Kc The
obtained parameters hc and Kc are shown in Table 2 hc
was within the range of approximately 32times103 to 105times
103 M-1 for each type of acidity regulator and Kc was
within the range of approximately 4 to 18 The values
described from the extended Krieger-Dougherty equa-
tion using the hc and Kc values in the system of each pH-
adjusting agent are shown by solid lines in Fig 3 As a
result the solid line was almost near the plot of the mea-
sured value and the measured value could be described
well hc represents the bulkiness of the aggregate larger
hc values were associated with bulkier aggregates Kc
indicates the filling state of the gigantic aggregate
formed by agglomerates gathering and the reciprocal of
the maximum particle packing ratio As the value of Kc
increased the agglomerates were not densely packed
ie the bulkiness of the gigantic aggregate was high
Because the hc of citric acid was the largest of the six
acidity regulators citric acid was thought to significantly
enhance the aggregation in soymilk The molecular
weight and acid dissociation constant of the acidity regu-
lator are also shown in Table 2 but correlation with the
hc value was not found As the soymilk pH decreased the
charge state of the protein changed to form aggregates
However because the proteins contained in soymilk dif-
fered in their isoelectric points proteins participating in
aggregation seemed to change as the pH changed
However we found that one equation (Eq 3) could
describe the viscous behaviors of the soymilk aggrega-
tion system quite well due to the continuous pH decrease
accompanying the addition of the acidity regulators
Furthermore the system assumed that aggregate forma-
tion would progress with an increase in viscosity
Fig 2 Apparent viscosities of Soymilk B after addition of each acidity regulator
Table 2 The viscosity parameters hc and Kc and molecular weight (MW) and acid dissociation constant (pKa) for each acidity regulator
Acidity regulators hc
[times103 M-1]Kc
[-]MW[-]
pKa[-]
Lactic acid 775 79 901 39 [32]
Malic acid 829 70 1341 34 [32]
Hydrochloric acid 712 79 55 -80 [33]
Ascorbic acid 328 182 1761 41 [32]
Citric acid 1052 45 2101 31 [32]
Phytic acid 740 62 6600 19 [34]
Soymilk stability 181
copy 2017 Japan Society for Food Engineering
43 Relationshipbetweenparametersh cand
Kcintheaggregate-formingsystemdueto
thepHdecrease
The relationship between the viscosity parameters hc
and Kc obtained from the viscosity measured using six
types of soymilk and six acidity regulators is shown in
Fig 4 A negative correlation was found and the coeffi-
cient of determination (R2) was as high as 097
Fig 3 Dimensionless viscosities (ηd) of soymilk plotted against the concentration of hydrogen ions after addition of lactic acid (a) malic acid (b) hydrochloric acid (c) ascorbic acid (d) citric acid (e) and phytic acid (f) The solid line shows the viscous model combining the extended Krieger-Dougherty equation
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII182
copy 2017 Japan Society for Food Engineering
Therefore these data suggested that as the size of the
aggregate produced in the high pH range above approxi-
mately pH 60 increased the agglomerates became
denser and the bulk became smaller In contrast as the
size of the aggregate decreased bulky aggregates
became more bulky Additionally because the data were
plotted on the same curve regardless of the type of acid-
ity regulators even if the internal structure of the iso-
lated aggregate differed depending on the difference in
crosslinking mechanism the macroscopic aggregation
behaviors were thought to be similar
Even when coagulating with a crosslinking agent such
as magnesium chloride a negative correlation between
hc and Kc is obtained in previous work [20] In crosslink-
ing aggregation the interaction between colloidal parti-
cles is electrostatic interaction On the other hand in
acid aggregation physical interaction such as hydropho-
bic interaction is mainly The interactions acting between
colloidal particles in both are different As shown in Fig
4 the same tendency was observed even when acid
aggregation with hydrogen ion concentration as a vari-
able strongly suggesting that macroscopic aggregation
mechanism is similar in both acid aggregation and cross-
linking aggregation
Because there was a correlation between hc and Kc
viscosity could be predicted at low pH range below about
pH 59 by measuring changes in viscosity at a high pH
Accordingly it may be possible to predict aggregation
behaviors due to decreased pH in soymilk in the high pH
range and these results may be applied to control the
viscous quality of soymilk
5Conclusion
In this study when the pH of soymilk with different
primary producing areas was reduced using ascorbic
acid the apparent viscosity of all soymilk increased sig-
nificantly at approximately pH 58-59 this was found to
be a universal phenomenon in the soymilk colloidal dis-
persion system Even when the pH decreased following
the addition of six types of acidity regulators to soymilk
prepared from American whole soybeans the apparent
viscosity increased sharply when the pH was lower than
59 However because the apparent viscosity increase
was relatively moderate when phytic acid and citric acid
were added the chelating actions of phytic acid and citric
acid suppressed the initial formation of aggregates
Assuming that the bulkiness of the aggregate was pro-
portional to the hydrogen ion concentration in the high
pH range calculations were made by applying the
extended Krieger-Dougherty equation obtained from
Einsteinrsquos viscosity equation and the Krieger-Dougherty
equation a negative correlation was confirmed with the
parameter hc representing the degree of bulkiness of the
aggregate and the parameter Kc representing the degree
of filling of the gigantic aggregate Moreover the macro-
scopic aggregation behaviors were similar even if the
internal structure of the isolated aggregates dif fered
depending on the difference in crosslinking mechanism
Because of the correlation between hc and Kc viscosity in
the low pH range can be predicted by observing changes
in viscosity in the high pH range Based on these fea-
tures this process may have industrial applications In
future studies we will evaluate the rheological character-
istics of soymilk and assess the applications of these find-
ings in other systems with aggregation Furthermore
additional studies are needed to examine the aggregation
of soymilk particles and structure in greater detail
NOMENCLATURE
C hydrogen ion concentration M-1
Kc reciprocal of closest packing ratio -
hc parameter of bulkiness M-1
φ volume fraction -
η apparent viscosity mPas ηc0 initial viscosity mPas ηd dimensionless viscosity -
ηr relative viscosity -
Fig 4 Relationship between the viscosity parameters hc and Kc obtained from the viscosity measured using six types of soymilk and six acidity regulators
Soymilk stability 183
copy 2017 Japan Society for Food Engineering
Acknowledgements
This research was supported by a grant from the
Project of NARO Bio-oriented Technology Research
Advancement Institution (Project for Development of
New Practical Technology)
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(2009)
3) A H C Huang Oil bodies and oleosins in seeds Annu Rev
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4) J T C Tzen A H C Huang Surface structure and prop-
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(1992)
5) S T Guo T Ono M Mikami Interaction between protein
and lipid in soybean milk at elevated temperature J Agric
Food Chem 45 4601-4605 (1997)
6) D Iwanaga D A Gray I D Fisk E A Decker J Weiss D
J McClements Extraction and characterization of oil bod-
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7) M A Schmidt E M Herman Suppression of soybean oleo-
sin produces micro-oil bodies that aggregate into oil body
ER complexes Mol Plant 1 910-924 (2008)
8) C C Peng V S Lee M Y Lin H Y Huang J T Tzen
Minimizing the central hydrophobic domain in oleosin
for the constitution of artificial oil bodies J Agric Food
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9) E Tombaacutecz I Aacutebrahaacutem M Gilde F Szaacutentoacute The pH-depen-
dent colloidal stability of aqueous montmorillonite suspen-
sions Colloids Surf 49 71-80 (1990)
10) S G Garciacutea S Wold M Jonsson Effects of temperature on
the stability of colloidal montmorillonite particles at differ-
ent pH and ionic strength Appl Clay Sci 43 21-26 (2009)
11) C L Tiller C R OrsquoMelia Natural organic matter and col-
loidal stability models and measurements Colloids Surf A
73 89-102 (1993)
12) K Oizumi S Idogawa Y Iwamoto K Ito T Fujii Influence
of pH on the colloidal stability of soymilk (in Japanese) J
Jpn Soc Food Sci Technol 63 142-149 (2016)
13) T Fujii T Yano H Kumagai O Miyawaki Dynamic light
scattering analysis on critical behavior of cluster size dis-
tribution of polyacrylamide and agarose solutions near the
sol-gel transition point Food Sci Technol Res 6 94-98
(2000)
14) K Suzuki E Uchiyama A Kuroda T Momose M Tamura
Spherical gels of crosslinked polyacrylamide polymerized
in water diluent (in Japanese) Nippon Kagaku Kaishi 10
1756-1760 (1975)
15) P J Flory ldquoPrinciples of polymer chemistryrdquo Cornell
University Press 1953 p 688
16) J A Gerrard S J Meade A G Miller P K Brown S B
Yasir K H Sutton M P Newberry Protein cross-linking
in food Ann N Y Acad Sci 1043 97-103 (2005)
17) D Saha S Bhattacharya Hydrocolloids as thickening
and gelling agents in food a critical review J Food Sci
Technol 47 587-597 (2010)
18) K Ito S Idogawa Elastic behavior of tofu emulsion gel (in
Japanese) Jpn J Food Eng 14 49-57 (2013)
19) Y Morita ldquoSoybean Protein (Daizu Tanpakushitu)rdquo Korin
Tokyo Japan 2000 pp 66-70
20) S Idogawa T Fujii Rheological analysis of the aggregation
behavior of a soymilk colloidal system Food Sci Technol
Res 21 479-487 (2015)
21) A Einstein Uumlber die von der molekularkinetischen theorie
der waumlrme geforderte bewegung von in ruhenden fluumlssig-
keiten suspendierten teilchen Ann Physik 322 549-560
(1905)
22) A Einstein Berichtigung zu meiacutener arbeit eine neue
bestimmung der molekuumlldimensionen Ann Physik 34
591-592 (1911)
23) I M Krieger T J Dougherty A mechanism for non-
Newtonian flow in suspensions of rigid spheres Trans Soc
Rheol 3 137-152 (1959)
24) G Cartwright B H McManus T P Leffler C R Moser
Rapid determination of moisturesolids and fat in dairy
products by microwave and nuclear magnetic resonance
analysis J AOAC Int 88 107-120 (2005)
25) M Tezuka T Ono T Ito Properties of soymilk prepared
from soybeans of different varieties (in Japanese) J Jpn
Soc Food Sci Technol 42 556-561 (1995)
26) R Mujoo D T Trinh P KW Ng Characterization of stor-
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tionship to tofu yield and texture Food Chem 82 265-273
(2003)
27) T Ohara H Ohhinata H Karasawa T Matsuhashi
Contribution of chemical constituents in soymilk to the opti-
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39 586-595 (1992)
28) P Ekholm L Virkki M Ylinen L Johansson The effect of
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copy 2017 Japan Society for Food Engineering
phytic acid and some natural chelating agents on the solu-
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170 (2003)
29) T Ono S Kato K Mothizuki Influences of calcium and
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Biochem 57 24-28 (1993)
30) T D Cai K C Chang M C Shih H J Hou M Ji
Comparison of bench and production scale methods for
making soymilk and tofu from 13 soybean varieties Food
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(Rikagaku Jiten)rdquo (in Japanese) Iwanami Tokyo Japan
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34) W J Evans E J McCourther R I Shrager Titration
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(1982)
copy 2017 Japan Society for Food Engineering
豆乳コロイド分散系の安定性に及ぼす pH調整剤添加の影響
佐藤加奈子 1井戸川詩織 12dagger藤井智幸 2
1太子食品工業株式会社2東北大学大学院農学研究科
豆乳はタンパク質溶液にタンパク質粒子と脂質が分散したコロイド分散系である豆乳中に含まれる脂質はオイルボディとして存在しており表面を覆うオレオシンによって合一が抑制され安定なコロイド分散系を形成していると考えられている豆乳の製造管理および豆乳加工品の開発のためには豆乳のコロイド特性の把握が重要と考えられるコロイドの安定性は pHや熱電解質有機物の添加などの要因で変動することが知られている筆者らはアスコルビン酸溶液の添加による pHの低下に伴って豆乳の見かけ粘度が急激に変化する挙動を確認しているオイルボディとタンパク質が関わる凝集体の生成により見かけ粘度が上昇すると考えられるが凝集の詳細は明らかになっていないpH低下に伴う豆乳コロイドの凝集挙動の詳細を明らかにするためには豆乳の粒子が孤立状態で存在している段階から粒子が集まり充填状態やゲル構造を伴う巨大凝集体を生成するまでのメカニズムに関する理解が求められる本研究では豆乳の pH低下によって豆乳中に含まれるタンパク質の等電点に近づくことでタンパク質溶解度が低下し凝集体が形成されると仮説を立て拡張アインシュタイン型の式とKrieger-Dougherty型の式とを組み合わせた粘性モデルを構築してその有効性を実験的に調べた原料産地が異なる 6種類の豆乳にアスコルビン酸溶液を添加してpH 56-62の pH調整豆乳とし円錐平板型回転粘度計を用いて見かけ粘度を測定したpHが低下するにしたがいおよそ pH 60までは見かけ粘度はやや微増するにとどまったがpHが 60より低くなると徐々に見かけ粘度が上昇しpHが 59より低くなると指数関数的に見かけ粘度が上昇したまた宮城県産大豆から調製した豆乳Soymilk AではpHがおよそ 01低い条件で同様の挙動がみられ品種の違いによるグロブリンタンパク質の含有割合の変化や灰分などの他成分による影響が考えられた6種類の pH調整剤をアメリカ産大豆から調製した豆乳Soymilk Bへ添加して見かけ粘度を測定したところ先述の実験と同様
におよそ pH 60までは pH低下に伴って微増しpHが59より低くなると急激に粘度が上昇する挙動を示したただしフィチン酸溶液およびクエン酸溶液の場合は粘度が顕著に変化する pHが低くこれはキレート作用によるものと示唆された
6種類の pH調整剤によるそれぞれの結果について豆乳に含まれる水素イオンの濃度を豆乳の pHから算出し無次元粘度ηdの実測値との関係を示したこのプロットに対し拡張 Krieger-Dougherty型の式に当てはめて粘性パラメータ hcKcを算出したhcは凝集体のかさ高さを表しhcの値が大きいほど凝集体がかさ高いことを示すKcは分散相の最密充填率の逆数であり巨大凝集体のかさ高さを示すつまり Kcの値が大きいほど凝集体が密ではなく巨大凝集体がかさ高いことを表す各 pH 調整剤の系において拡張 Krieger-Dougherty
式の適用妥当性を検討したところpH調整剤の添加に伴う連続した pH低下による豆乳の凝集形成系について1つの式で良好に記述できることがわかった
6種類の豆乳および 6種類の pH調整剤を用いて測定した粘度データから得られた粘性パラメータ hcと Kc
に負の相関が認められたつまりpH低下によって進行する凝集過程において高 pH領域にて生成される凝集体の大きさが大きいほど巨大凝集体が密に充填してかさが小さくなり逆に凝集体の大きさが小さいほど巨大凝集体はかさ高くなることが示唆されたまたpH調整剤の種類によらず同一の曲線上にプロットされたことから孤立状態にある凝集体の内部構造が架橋機構の違いにより異なっていてもマクロな凝集挙動は同様であることが示唆されたさらにhcと Kcに相関関係があるために高い pH領域で粘度変化を測定することによって低い pH領域での粘度が予測できることが示されたこのことは豆乳における pH低下による凝集挙動を高 pH領域で予想可能であることを表し豆乳の品質管理に応用できる可能性が期待される本研究は生研センター「革新的技術創造促進事業(事業化促進)」の支援を受けて行った
(受付 2017年 4月 5日受理 2017年 9月 17日)
1 989-6228 宮城県大崎市古川清水字新田 51-1
2 980-0845 仙台市青葉区荒巻字青葉 468-1
daggerFax 0229-36-1702 E-mail s-itonotaishi-foodcojp
和文要約
「日本食品工学会誌」 Vol 18 No 4 p 185 Dec 2017
Soymilk stability 181
copy 2017 Japan Society for Food Engineering
43 Relationshipbetweenparametersh cand
Kcintheaggregate-formingsystemdueto
thepHdecrease
The relationship between the viscosity parameters hc
and Kc obtained from the viscosity measured using six
types of soymilk and six acidity regulators is shown in
Fig 4 A negative correlation was found and the coeffi-
cient of determination (R2) was as high as 097
Fig 3 Dimensionless viscosities (ηd) of soymilk plotted against the concentration of hydrogen ions after addition of lactic acid (a) malic acid (b) hydrochloric acid (c) ascorbic acid (d) citric acid (e) and phytic acid (f) The solid line shows the viscous model combining the extended Krieger-Dougherty equation
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII182
copy 2017 Japan Society for Food Engineering
Therefore these data suggested that as the size of the
aggregate produced in the high pH range above approxi-
mately pH 60 increased the agglomerates became
denser and the bulk became smaller In contrast as the
size of the aggregate decreased bulky aggregates
became more bulky Additionally because the data were
plotted on the same curve regardless of the type of acid-
ity regulators even if the internal structure of the iso-
lated aggregate differed depending on the difference in
crosslinking mechanism the macroscopic aggregation
behaviors were thought to be similar
Even when coagulating with a crosslinking agent such
as magnesium chloride a negative correlation between
hc and Kc is obtained in previous work [20] In crosslink-
ing aggregation the interaction between colloidal parti-
cles is electrostatic interaction On the other hand in
acid aggregation physical interaction such as hydropho-
bic interaction is mainly The interactions acting between
colloidal particles in both are different As shown in Fig
4 the same tendency was observed even when acid
aggregation with hydrogen ion concentration as a vari-
able strongly suggesting that macroscopic aggregation
mechanism is similar in both acid aggregation and cross-
linking aggregation
Because there was a correlation between hc and Kc
viscosity could be predicted at low pH range below about
pH 59 by measuring changes in viscosity at a high pH
Accordingly it may be possible to predict aggregation
behaviors due to decreased pH in soymilk in the high pH
range and these results may be applied to control the
viscous quality of soymilk
5Conclusion
In this study when the pH of soymilk with different
primary producing areas was reduced using ascorbic
acid the apparent viscosity of all soymilk increased sig-
nificantly at approximately pH 58-59 this was found to
be a universal phenomenon in the soymilk colloidal dis-
persion system Even when the pH decreased following
the addition of six types of acidity regulators to soymilk
prepared from American whole soybeans the apparent
viscosity increased sharply when the pH was lower than
59 However because the apparent viscosity increase
was relatively moderate when phytic acid and citric acid
were added the chelating actions of phytic acid and citric
acid suppressed the initial formation of aggregates
Assuming that the bulkiness of the aggregate was pro-
portional to the hydrogen ion concentration in the high
pH range calculations were made by applying the
extended Krieger-Dougherty equation obtained from
Einsteinrsquos viscosity equation and the Krieger-Dougherty
equation a negative correlation was confirmed with the
parameter hc representing the degree of bulkiness of the
aggregate and the parameter Kc representing the degree
of filling of the gigantic aggregate Moreover the macro-
scopic aggregation behaviors were similar even if the
internal structure of the isolated aggregates dif fered
depending on the difference in crosslinking mechanism
Because of the correlation between hc and Kc viscosity in
the low pH range can be predicted by observing changes
in viscosity in the high pH range Based on these fea-
tures this process may have industrial applications In
future studies we will evaluate the rheological character-
istics of soymilk and assess the applications of these find-
ings in other systems with aggregation Furthermore
additional studies are needed to examine the aggregation
of soymilk particles and structure in greater detail
NOMENCLATURE
C hydrogen ion concentration M-1
Kc reciprocal of closest packing ratio -
hc parameter of bulkiness M-1
φ volume fraction -
η apparent viscosity mPas ηc0 initial viscosity mPas ηd dimensionless viscosity -
ηr relative viscosity -
Fig 4 Relationship between the viscosity parameters hc and Kc obtained from the viscosity measured using six types of soymilk and six acidity regulators
Soymilk stability 183
copy 2017 Japan Society for Food Engineering
Acknowledgements
This research was supported by a grant from the
Project of NARO Bio-oriented Technology Research
Advancement Institution (Project for Development of
New Practical Technology)
References
1) T Ono M R Choi A Ikeda S Odagiri Changes in the
composition and size distribution of soymilk protein par-
ticles by heating Agric Biol Chem 55 2291-2297 (1991)
2) Y Chen S Yamaguchi T Ono The mechanism of the chem-
ical composition changes of yuba prepared by a laboratory
processing method J Agric Food Chem 57 3831-3836
(2009)
3) A H C Huang Oil bodies and oleosins in seeds Annu Rev
Plant Physiol Plant Mol Biol 43 177-200 (1992)
4) J T C Tzen A H C Huang Surface structure and prop-
erties of plant seed oil bodies J Cell Biol 117 327-335
(1992)
5) S T Guo T Ono M Mikami Interaction between protein
and lipid in soybean milk at elevated temperature J Agric
Food Chem 45 4601-4605 (1997)
6) D Iwanaga D A Gray I D Fisk E A Decker J Weiss D
J McClements Extraction and characterization of oil bod-
ies from soy beans a natural source of pre-emulsified soy-
bean oil J Agric Food Chem 55 8711-8716 (2007)
7) M A Schmidt E M Herman Suppression of soybean oleo-
sin produces micro-oil bodies that aggregate into oil body
ER complexes Mol Plant 1 910-924 (2008)
8) C C Peng V S Lee M Y Lin H Y Huang J T Tzen
Minimizing the central hydrophobic domain in oleosin
for the constitution of artificial oil bodies J Agric Food
Chem 55 5604-5610 (2007)
9) E Tombaacutecz I Aacutebrahaacutem M Gilde F Szaacutentoacute The pH-depen-
dent colloidal stability of aqueous montmorillonite suspen-
sions Colloids Surf 49 71-80 (1990)
10) S G Garciacutea S Wold M Jonsson Effects of temperature on
the stability of colloidal montmorillonite particles at differ-
ent pH and ionic strength Appl Clay Sci 43 21-26 (2009)
11) C L Tiller C R OrsquoMelia Natural organic matter and col-
loidal stability models and measurements Colloids Surf A
73 89-102 (1993)
12) K Oizumi S Idogawa Y Iwamoto K Ito T Fujii Influence
of pH on the colloidal stability of soymilk (in Japanese) J
Jpn Soc Food Sci Technol 63 142-149 (2016)
13) T Fujii T Yano H Kumagai O Miyawaki Dynamic light
scattering analysis on critical behavior of cluster size dis-
tribution of polyacrylamide and agarose solutions near the
sol-gel transition point Food Sci Technol Res 6 94-98
(2000)
14) K Suzuki E Uchiyama A Kuroda T Momose M Tamura
Spherical gels of crosslinked polyacrylamide polymerized
in water diluent (in Japanese) Nippon Kagaku Kaishi 10
1756-1760 (1975)
15) P J Flory ldquoPrinciples of polymer chemistryrdquo Cornell
University Press 1953 p 688
16) J A Gerrard S J Meade A G Miller P K Brown S B
Yasir K H Sutton M P Newberry Protein cross-linking
in food Ann N Y Acad Sci 1043 97-103 (2005)
17) D Saha S Bhattacharya Hydrocolloids as thickening
and gelling agents in food a critical review J Food Sci
Technol 47 587-597 (2010)
18) K Ito S Idogawa Elastic behavior of tofu emulsion gel (in
Japanese) Jpn J Food Eng 14 49-57 (2013)
19) Y Morita ldquoSoybean Protein (Daizu Tanpakushitu)rdquo Korin
Tokyo Japan 2000 pp 66-70
20) S Idogawa T Fujii Rheological analysis of the aggregation
behavior of a soymilk colloidal system Food Sci Technol
Res 21 479-487 (2015)
21) A Einstein Uumlber die von der molekularkinetischen theorie
der waumlrme geforderte bewegung von in ruhenden fluumlssig-
keiten suspendierten teilchen Ann Physik 322 549-560
(1905)
22) A Einstein Berichtigung zu meiacutener arbeit eine neue
bestimmung der molekuumlldimensionen Ann Physik 34
591-592 (1911)
23) I M Krieger T J Dougherty A mechanism for non-
Newtonian flow in suspensions of rigid spheres Trans Soc
Rheol 3 137-152 (1959)
24) G Cartwright B H McManus T P Leffler C R Moser
Rapid determination of moisturesolids and fat in dairy
products by microwave and nuclear magnetic resonance
analysis J AOAC Int 88 107-120 (2005)
25) M Tezuka T Ono T Ito Properties of soymilk prepared
from soybeans of different varieties (in Japanese) J Jpn
Soc Food Sci Technol 42 556-561 (1995)
26) R Mujoo D T Trinh P KW Ng Characterization of stor-
age proteins in different soybean varieties and their rela-
tionship to tofu yield and texture Food Chem 82 265-273
(2003)
27) T Ohara H Ohhinata H Karasawa T Matsuhashi
Contribution of chemical constituents in soymilk to the opti-
mum concentration of coagulant in coagulation process of
soymilk (in Japanese) Nippon Shokuhin Kogyo Gakkaishi
39 586-595 (1992)
28) P Ekholm L Virkki M Ylinen L Johansson The effect of
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII184
copy 2017 Japan Society for Food Engineering
phytic acid and some natural chelating agents on the solu-
bility of mineral elements in oat bran Food Chem 80 165-
170 (2003)
29) T Ono S Kato K Mothizuki Influences of calcium and
pH on protein solubility in soybean milk Biosci Biotech
Biochem 57 24-28 (1993)
30) T D Cai K C Chang M C Shih H J Hou M Ji
Comparison of bench and production scale methods for
making soymilk and tofu from 13 soybean varieties Food
Res Int 30 659-668 (1997)
31) K Saio E Koyama T Watanabe Protein-calcium-phytic
acid relationships in soybean Agr Biol Chem 31 1195-
1200 (1967)
32) S Y Park B I Lee S T Jung H J Park Biopolymer com-
posite films based on κ-carrageenan and chitosan Mater
Res Bull 36 511-519 (2001)
33) B Tamamushi ldquoDictionar y of Physics and Chemistr y
(Rikagaku Jiten)rdquo (in Japanese) Iwanami Tokyo Japan
1981 pp 1577-1578
34) W J Evans E J McCourther R I Shrager Titration
studies of phytic acid J Am Oil Chem Soc 59 189-191
(1982)
copy 2017 Japan Society for Food Engineering
豆乳コロイド分散系の安定性に及ぼす pH調整剤添加の影響
佐藤加奈子 1井戸川詩織 12dagger藤井智幸 2
1太子食品工業株式会社2東北大学大学院農学研究科
豆乳はタンパク質溶液にタンパク質粒子と脂質が分散したコロイド分散系である豆乳中に含まれる脂質はオイルボディとして存在しており表面を覆うオレオシンによって合一が抑制され安定なコロイド分散系を形成していると考えられている豆乳の製造管理および豆乳加工品の開発のためには豆乳のコロイド特性の把握が重要と考えられるコロイドの安定性は pHや熱電解質有機物の添加などの要因で変動することが知られている筆者らはアスコルビン酸溶液の添加による pHの低下に伴って豆乳の見かけ粘度が急激に変化する挙動を確認しているオイルボディとタンパク質が関わる凝集体の生成により見かけ粘度が上昇すると考えられるが凝集の詳細は明らかになっていないpH低下に伴う豆乳コロイドの凝集挙動の詳細を明らかにするためには豆乳の粒子が孤立状態で存在している段階から粒子が集まり充填状態やゲル構造を伴う巨大凝集体を生成するまでのメカニズムに関する理解が求められる本研究では豆乳の pH低下によって豆乳中に含まれるタンパク質の等電点に近づくことでタンパク質溶解度が低下し凝集体が形成されると仮説を立て拡張アインシュタイン型の式とKrieger-Dougherty型の式とを組み合わせた粘性モデルを構築してその有効性を実験的に調べた原料産地が異なる 6種類の豆乳にアスコルビン酸溶液を添加してpH 56-62の pH調整豆乳とし円錐平板型回転粘度計を用いて見かけ粘度を測定したpHが低下するにしたがいおよそ pH 60までは見かけ粘度はやや微増するにとどまったがpHが 60より低くなると徐々に見かけ粘度が上昇しpHが 59より低くなると指数関数的に見かけ粘度が上昇したまた宮城県産大豆から調製した豆乳Soymilk AではpHがおよそ 01低い条件で同様の挙動がみられ品種の違いによるグロブリンタンパク質の含有割合の変化や灰分などの他成分による影響が考えられた6種類の pH調整剤をアメリカ産大豆から調製した豆乳Soymilk Bへ添加して見かけ粘度を測定したところ先述の実験と同様
におよそ pH 60までは pH低下に伴って微増しpHが59より低くなると急激に粘度が上昇する挙動を示したただしフィチン酸溶液およびクエン酸溶液の場合は粘度が顕著に変化する pHが低くこれはキレート作用によるものと示唆された
6種類の pH調整剤によるそれぞれの結果について豆乳に含まれる水素イオンの濃度を豆乳の pHから算出し無次元粘度ηdの実測値との関係を示したこのプロットに対し拡張 Krieger-Dougherty型の式に当てはめて粘性パラメータ hcKcを算出したhcは凝集体のかさ高さを表しhcの値が大きいほど凝集体がかさ高いことを示すKcは分散相の最密充填率の逆数であり巨大凝集体のかさ高さを示すつまり Kcの値が大きいほど凝集体が密ではなく巨大凝集体がかさ高いことを表す各 pH 調整剤の系において拡張 Krieger-Dougherty
式の適用妥当性を検討したところpH調整剤の添加に伴う連続した pH低下による豆乳の凝集形成系について1つの式で良好に記述できることがわかった
6種類の豆乳および 6種類の pH調整剤を用いて測定した粘度データから得られた粘性パラメータ hcと Kc
に負の相関が認められたつまりpH低下によって進行する凝集過程において高 pH領域にて生成される凝集体の大きさが大きいほど巨大凝集体が密に充填してかさが小さくなり逆に凝集体の大きさが小さいほど巨大凝集体はかさ高くなることが示唆されたまたpH調整剤の種類によらず同一の曲線上にプロットされたことから孤立状態にある凝集体の内部構造が架橋機構の違いにより異なっていてもマクロな凝集挙動は同様であることが示唆されたさらにhcと Kcに相関関係があるために高い pH領域で粘度変化を測定することによって低い pH領域での粘度が予測できることが示されたこのことは豆乳における pH低下による凝集挙動を高 pH領域で予想可能であることを表し豆乳の品質管理に応用できる可能性が期待される本研究は生研センター「革新的技術創造促進事業(事業化促進)」の支援を受けて行った
(受付 2017年 4月 5日受理 2017年 9月 17日)
1 989-6228 宮城県大崎市古川清水字新田 51-1
2 980-0845 仙台市青葉区荒巻字青葉 468-1
daggerFax 0229-36-1702 E-mail s-itonotaishi-foodcojp
和文要約
「日本食品工学会誌」 Vol 18 No 4 p 185 Dec 2017
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII182
copy 2017 Japan Society for Food Engineering
Therefore these data suggested that as the size of the
aggregate produced in the high pH range above approxi-
mately pH 60 increased the agglomerates became
denser and the bulk became smaller In contrast as the
size of the aggregate decreased bulky aggregates
became more bulky Additionally because the data were
plotted on the same curve regardless of the type of acid-
ity regulators even if the internal structure of the iso-
lated aggregate differed depending on the difference in
crosslinking mechanism the macroscopic aggregation
behaviors were thought to be similar
Even when coagulating with a crosslinking agent such
as magnesium chloride a negative correlation between
hc and Kc is obtained in previous work [20] In crosslink-
ing aggregation the interaction between colloidal parti-
cles is electrostatic interaction On the other hand in
acid aggregation physical interaction such as hydropho-
bic interaction is mainly The interactions acting between
colloidal particles in both are different As shown in Fig
4 the same tendency was observed even when acid
aggregation with hydrogen ion concentration as a vari-
able strongly suggesting that macroscopic aggregation
mechanism is similar in both acid aggregation and cross-
linking aggregation
Because there was a correlation between hc and Kc
viscosity could be predicted at low pH range below about
pH 59 by measuring changes in viscosity at a high pH
Accordingly it may be possible to predict aggregation
behaviors due to decreased pH in soymilk in the high pH
range and these results may be applied to control the
viscous quality of soymilk
5Conclusion
In this study when the pH of soymilk with different
primary producing areas was reduced using ascorbic
acid the apparent viscosity of all soymilk increased sig-
nificantly at approximately pH 58-59 this was found to
be a universal phenomenon in the soymilk colloidal dis-
persion system Even when the pH decreased following
the addition of six types of acidity regulators to soymilk
prepared from American whole soybeans the apparent
viscosity increased sharply when the pH was lower than
59 However because the apparent viscosity increase
was relatively moderate when phytic acid and citric acid
were added the chelating actions of phytic acid and citric
acid suppressed the initial formation of aggregates
Assuming that the bulkiness of the aggregate was pro-
portional to the hydrogen ion concentration in the high
pH range calculations were made by applying the
extended Krieger-Dougherty equation obtained from
Einsteinrsquos viscosity equation and the Krieger-Dougherty
equation a negative correlation was confirmed with the
parameter hc representing the degree of bulkiness of the
aggregate and the parameter Kc representing the degree
of filling of the gigantic aggregate Moreover the macro-
scopic aggregation behaviors were similar even if the
internal structure of the isolated aggregates dif fered
depending on the difference in crosslinking mechanism
Because of the correlation between hc and Kc viscosity in
the low pH range can be predicted by observing changes
in viscosity in the high pH range Based on these fea-
tures this process may have industrial applications In
future studies we will evaluate the rheological character-
istics of soymilk and assess the applications of these find-
ings in other systems with aggregation Furthermore
additional studies are needed to examine the aggregation
of soymilk particles and structure in greater detail
NOMENCLATURE
C hydrogen ion concentration M-1
Kc reciprocal of closest packing ratio -
hc parameter of bulkiness M-1
φ volume fraction -
η apparent viscosity mPas ηc0 initial viscosity mPas ηd dimensionless viscosity -
ηr relative viscosity -
Fig 4 Relationship between the viscosity parameters hc and Kc obtained from the viscosity measured using six types of soymilk and six acidity regulators
Soymilk stability 183
copy 2017 Japan Society for Food Engineering
Acknowledgements
This research was supported by a grant from the
Project of NARO Bio-oriented Technology Research
Advancement Institution (Project for Development of
New Practical Technology)
References
1) T Ono M R Choi A Ikeda S Odagiri Changes in the
composition and size distribution of soymilk protein par-
ticles by heating Agric Biol Chem 55 2291-2297 (1991)
2) Y Chen S Yamaguchi T Ono The mechanism of the chem-
ical composition changes of yuba prepared by a laboratory
processing method J Agric Food Chem 57 3831-3836
(2009)
3) A H C Huang Oil bodies and oleosins in seeds Annu Rev
Plant Physiol Plant Mol Biol 43 177-200 (1992)
4) J T C Tzen A H C Huang Surface structure and prop-
erties of plant seed oil bodies J Cell Biol 117 327-335
(1992)
5) S T Guo T Ono M Mikami Interaction between protein
and lipid in soybean milk at elevated temperature J Agric
Food Chem 45 4601-4605 (1997)
6) D Iwanaga D A Gray I D Fisk E A Decker J Weiss D
J McClements Extraction and characterization of oil bod-
ies from soy beans a natural source of pre-emulsified soy-
bean oil J Agric Food Chem 55 8711-8716 (2007)
7) M A Schmidt E M Herman Suppression of soybean oleo-
sin produces micro-oil bodies that aggregate into oil body
ER complexes Mol Plant 1 910-924 (2008)
8) C C Peng V S Lee M Y Lin H Y Huang J T Tzen
Minimizing the central hydrophobic domain in oleosin
for the constitution of artificial oil bodies J Agric Food
Chem 55 5604-5610 (2007)
9) E Tombaacutecz I Aacutebrahaacutem M Gilde F Szaacutentoacute The pH-depen-
dent colloidal stability of aqueous montmorillonite suspen-
sions Colloids Surf 49 71-80 (1990)
10) S G Garciacutea S Wold M Jonsson Effects of temperature on
the stability of colloidal montmorillonite particles at differ-
ent pH and ionic strength Appl Clay Sci 43 21-26 (2009)
11) C L Tiller C R OrsquoMelia Natural organic matter and col-
loidal stability models and measurements Colloids Surf A
73 89-102 (1993)
12) K Oizumi S Idogawa Y Iwamoto K Ito T Fujii Influence
of pH on the colloidal stability of soymilk (in Japanese) J
Jpn Soc Food Sci Technol 63 142-149 (2016)
13) T Fujii T Yano H Kumagai O Miyawaki Dynamic light
scattering analysis on critical behavior of cluster size dis-
tribution of polyacrylamide and agarose solutions near the
sol-gel transition point Food Sci Technol Res 6 94-98
(2000)
14) K Suzuki E Uchiyama A Kuroda T Momose M Tamura
Spherical gels of crosslinked polyacrylamide polymerized
in water diluent (in Japanese) Nippon Kagaku Kaishi 10
1756-1760 (1975)
15) P J Flory ldquoPrinciples of polymer chemistryrdquo Cornell
University Press 1953 p 688
16) J A Gerrard S J Meade A G Miller P K Brown S B
Yasir K H Sutton M P Newberry Protein cross-linking
in food Ann N Y Acad Sci 1043 97-103 (2005)
17) D Saha S Bhattacharya Hydrocolloids as thickening
and gelling agents in food a critical review J Food Sci
Technol 47 587-597 (2010)
18) K Ito S Idogawa Elastic behavior of tofu emulsion gel (in
Japanese) Jpn J Food Eng 14 49-57 (2013)
19) Y Morita ldquoSoybean Protein (Daizu Tanpakushitu)rdquo Korin
Tokyo Japan 2000 pp 66-70
20) S Idogawa T Fujii Rheological analysis of the aggregation
behavior of a soymilk colloidal system Food Sci Technol
Res 21 479-487 (2015)
21) A Einstein Uumlber die von der molekularkinetischen theorie
der waumlrme geforderte bewegung von in ruhenden fluumlssig-
keiten suspendierten teilchen Ann Physik 322 549-560
(1905)
22) A Einstein Berichtigung zu meiacutener arbeit eine neue
bestimmung der molekuumlldimensionen Ann Physik 34
591-592 (1911)
23) I M Krieger T J Dougherty A mechanism for non-
Newtonian flow in suspensions of rigid spheres Trans Soc
Rheol 3 137-152 (1959)
24) G Cartwright B H McManus T P Leffler C R Moser
Rapid determination of moisturesolids and fat in dairy
products by microwave and nuclear magnetic resonance
analysis J AOAC Int 88 107-120 (2005)
25) M Tezuka T Ono T Ito Properties of soymilk prepared
from soybeans of different varieties (in Japanese) J Jpn
Soc Food Sci Technol 42 556-561 (1995)
26) R Mujoo D T Trinh P KW Ng Characterization of stor-
age proteins in different soybean varieties and their rela-
tionship to tofu yield and texture Food Chem 82 265-273
(2003)
27) T Ohara H Ohhinata H Karasawa T Matsuhashi
Contribution of chemical constituents in soymilk to the opti-
mum concentration of coagulant in coagulation process of
soymilk (in Japanese) Nippon Shokuhin Kogyo Gakkaishi
39 586-595 (1992)
28) P Ekholm L Virkki M Ylinen L Johansson The effect of
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII184
copy 2017 Japan Society for Food Engineering
phytic acid and some natural chelating agents on the solu-
bility of mineral elements in oat bran Food Chem 80 165-
170 (2003)
29) T Ono S Kato K Mothizuki Influences of calcium and
pH on protein solubility in soybean milk Biosci Biotech
Biochem 57 24-28 (1993)
30) T D Cai K C Chang M C Shih H J Hou M Ji
Comparison of bench and production scale methods for
making soymilk and tofu from 13 soybean varieties Food
Res Int 30 659-668 (1997)
31) K Saio E Koyama T Watanabe Protein-calcium-phytic
acid relationships in soybean Agr Biol Chem 31 1195-
1200 (1967)
32) S Y Park B I Lee S T Jung H J Park Biopolymer com-
posite films based on κ-carrageenan and chitosan Mater
Res Bull 36 511-519 (2001)
33) B Tamamushi ldquoDictionar y of Physics and Chemistr y
(Rikagaku Jiten)rdquo (in Japanese) Iwanami Tokyo Japan
1981 pp 1577-1578
34) W J Evans E J McCourther R I Shrager Titration
studies of phytic acid J Am Oil Chem Soc 59 189-191
(1982)
copy 2017 Japan Society for Food Engineering
豆乳コロイド分散系の安定性に及ぼす pH調整剤添加の影響
佐藤加奈子 1井戸川詩織 12dagger藤井智幸 2
1太子食品工業株式会社2東北大学大学院農学研究科
豆乳はタンパク質溶液にタンパク質粒子と脂質が分散したコロイド分散系である豆乳中に含まれる脂質はオイルボディとして存在しており表面を覆うオレオシンによって合一が抑制され安定なコロイド分散系を形成していると考えられている豆乳の製造管理および豆乳加工品の開発のためには豆乳のコロイド特性の把握が重要と考えられるコロイドの安定性は pHや熱電解質有機物の添加などの要因で変動することが知られている筆者らはアスコルビン酸溶液の添加による pHの低下に伴って豆乳の見かけ粘度が急激に変化する挙動を確認しているオイルボディとタンパク質が関わる凝集体の生成により見かけ粘度が上昇すると考えられるが凝集の詳細は明らかになっていないpH低下に伴う豆乳コロイドの凝集挙動の詳細を明らかにするためには豆乳の粒子が孤立状態で存在している段階から粒子が集まり充填状態やゲル構造を伴う巨大凝集体を生成するまでのメカニズムに関する理解が求められる本研究では豆乳の pH低下によって豆乳中に含まれるタンパク質の等電点に近づくことでタンパク質溶解度が低下し凝集体が形成されると仮説を立て拡張アインシュタイン型の式とKrieger-Dougherty型の式とを組み合わせた粘性モデルを構築してその有効性を実験的に調べた原料産地が異なる 6種類の豆乳にアスコルビン酸溶液を添加してpH 56-62の pH調整豆乳とし円錐平板型回転粘度計を用いて見かけ粘度を測定したpHが低下するにしたがいおよそ pH 60までは見かけ粘度はやや微増するにとどまったがpHが 60より低くなると徐々に見かけ粘度が上昇しpHが 59より低くなると指数関数的に見かけ粘度が上昇したまた宮城県産大豆から調製した豆乳Soymilk AではpHがおよそ 01低い条件で同様の挙動がみられ品種の違いによるグロブリンタンパク質の含有割合の変化や灰分などの他成分による影響が考えられた6種類の pH調整剤をアメリカ産大豆から調製した豆乳Soymilk Bへ添加して見かけ粘度を測定したところ先述の実験と同様
におよそ pH 60までは pH低下に伴って微増しpHが59より低くなると急激に粘度が上昇する挙動を示したただしフィチン酸溶液およびクエン酸溶液の場合は粘度が顕著に変化する pHが低くこれはキレート作用によるものと示唆された
6種類の pH調整剤によるそれぞれの結果について豆乳に含まれる水素イオンの濃度を豆乳の pHから算出し無次元粘度ηdの実測値との関係を示したこのプロットに対し拡張 Krieger-Dougherty型の式に当てはめて粘性パラメータ hcKcを算出したhcは凝集体のかさ高さを表しhcの値が大きいほど凝集体がかさ高いことを示すKcは分散相の最密充填率の逆数であり巨大凝集体のかさ高さを示すつまり Kcの値が大きいほど凝集体が密ではなく巨大凝集体がかさ高いことを表す各 pH 調整剤の系において拡張 Krieger-Dougherty
式の適用妥当性を検討したところpH調整剤の添加に伴う連続した pH低下による豆乳の凝集形成系について1つの式で良好に記述できることがわかった
6種類の豆乳および 6種類の pH調整剤を用いて測定した粘度データから得られた粘性パラメータ hcと Kc
に負の相関が認められたつまりpH低下によって進行する凝集過程において高 pH領域にて生成される凝集体の大きさが大きいほど巨大凝集体が密に充填してかさが小さくなり逆に凝集体の大きさが小さいほど巨大凝集体はかさ高くなることが示唆されたまたpH調整剤の種類によらず同一の曲線上にプロットされたことから孤立状態にある凝集体の内部構造が架橋機構の違いにより異なっていてもマクロな凝集挙動は同様であることが示唆されたさらにhcと Kcに相関関係があるために高い pH領域で粘度変化を測定することによって低い pH領域での粘度が予測できることが示されたこのことは豆乳における pH低下による凝集挙動を高 pH領域で予想可能であることを表し豆乳の品質管理に応用できる可能性が期待される本研究は生研センター「革新的技術創造促進事業(事業化促進)」の支援を受けて行った
(受付 2017年 4月 5日受理 2017年 9月 17日)
1 989-6228 宮城県大崎市古川清水字新田 51-1
2 980-0845 仙台市青葉区荒巻字青葉 468-1
daggerFax 0229-36-1702 E-mail s-itonotaishi-foodcojp
和文要約
「日本食品工学会誌」 Vol 18 No 4 p 185 Dec 2017
Soymilk stability 183
copy 2017 Japan Society for Food Engineering
Acknowledgements
This research was supported by a grant from the
Project of NARO Bio-oriented Technology Research
Advancement Institution (Project for Development of
New Practical Technology)
References
1) T Ono M R Choi A Ikeda S Odagiri Changes in the
composition and size distribution of soymilk protein par-
ticles by heating Agric Biol Chem 55 2291-2297 (1991)
2) Y Chen S Yamaguchi T Ono The mechanism of the chem-
ical composition changes of yuba prepared by a laboratory
processing method J Agric Food Chem 57 3831-3836
(2009)
3) A H C Huang Oil bodies and oleosins in seeds Annu Rev
Plant Physiol Plant Mol Biol 43 177-200 (1992)
4) J T C Tzen A H C Huang Surface structure and prop-
erties of plant seed oil bodies J Cell Biol 117 327-335
(1992)
5) S T Guo T Ono M Mikami Interaction between protein
and lipid in soybean milk at elevated temperature J Agric
Food Chem 45 4601-4605 (1997)
6) D Iwanaga D A Gray I D Fisk E A Decker J Weiss D
J McClements Extraction and characterization of oil bod-
ies from soy beans a natural source of pre-emulsified soy-
bean oil J Agric Food Chem 55 8711-8716 (2007)
7) M A Schmidt E M Herman Suppression of soybean oleo-
sin produces micro-oil bodies that aggregate into oil body
ER complexes Mol Plant 1 910-924 (2008)
8) C C Peng V S Lee M Y Lin H Y Huang J T Tzen
Minimizing the central hydrophobic domain in oleosin
for the constitution of artificial oil bodies J Agric Food
Chem 55 5604-5610 (2007)
9) E Tombaacutecz I Aacutebrahaacutem M Gilde F Szaacutentoacute The pH-depen-
dent colloidal stability of aqueous montmorillonite suspen-
sions Colloids Surf 49 71-80 (1990)
10) S G Garciacutea S Wold M Jonsson Effects of temperature on
the stability of colloidal montmorillonite particles at differ-
ent pH and ionic strength Appl Clay Sci 43 21-26 (2009)
11) C L Tiller C R OrsquoMelia Natural organic matter and col-
loidal stability models and measurements Colloids Surf A
73 89-102 (1993)
12) K Oizumi S Idogawa Y Iwamoto K Ito T Fujii Influence
of pH on the colloidal stability of soymilk (in Japanese) J
Jpn Soc Food Sci Technol 63 142-149 (2016)
13) T Fujii T Yano H Kumagai O Miyawaki Dynamic light
scattering analysis on critical behavior of cluster size dis-
tribution of polyacrylamide and agarose solutions near the
sol-gel transition point Food Sci Technol Res 6 94-98
(2000)
14) K Suzuki E Uchiyama A Kuroda T Momose M Tamura
Spherical gels of crosslinked polyacrylamide polymerized
in water diluent (in Japanese) Nippon Kagaku Kaishi 10
1756-1760 (1975)
15) P J Flory ldquoPrinciples of polymer chemistryrdquo Cornell
University Press 1953 p 688
16) J A Gerrard S J Meade A G Miller P K Brown S B
Yasir K H Sutton M P Newberry Protein cross-linking
in food Ann N Y Acad Sci 1043 97-103 (2005)
17) D Saha S Bhattacharya Hydrocolloids as thickening
and gelling agents in food a critical review J Food Sci
Technol 47 587-597 (2010)
18) K Ito S Idogawa Elastic behavior of tofu emulsion gel (in
Japanese) Jpn J Food Eng 14 49-57 (2013)
19) Y Morita ldquoSoybean Protein (Daizu Tanpakushitu)rdquo Korin
Tokyo Japan 2000 pp 66-70
20) S Idogawa T Fujii Rheological analysis of the aggregation
behavior of a soymilk colloidal system Food Sci Technol
Res 21 479-487 (2015)
21) A Einstein Uumlber die von der molekularkinetischen theorie
der waumlrme geforderte bewegung von in ruhenden fluumlssig-
keiten suspendierten teilchen Ann Physik 322 549-560
(1905)
22) A Einstein Berichtigung zu meiacutener arbeit eine neue
bestimmung der molekuumlldimensionen Ann Physik 34
591-592 (1911)
23) I M Krieger T J Dougherty A mechanism for non-
Newtonian flow in suspensions of rigid spheres Trans Soc
Rheol 3 137-152 (1959)
24) G Cartwright B H McManus T P Leffler C R Moser
Rapid determination of moisturesolids and fat in dairy
products by microwave and nuclear magnetic resonance
analysis J AOAC Int 88 107-120 (2005)
25) M Tezuka T Ono T Ito Properties of soymilk prepared
from soybeans of different varieties (in Japanese) J Jpn
Soc Food Sci Technol 42 556-561 (1995)
26) R Mujoo D T Trinh P KW Ng Characterization of stor-
age proteins in different soybean varieties and their rela-
tionship to tofu yield and texture Food Chem 82 265-273
(2003)
27) T Ohara H Ohhinata H Karasawa T Matsuhashi
Contribution of chemical constituents in soymilk to the opti-
mum concentration of coagulant in coagulation process of
soymilk (in Japanese) Nippon Shokuhin Kogyo Gakkaishi
39 586-595 (1992)
28) P Ekholm L Virkki M Ylinen L Johansson The effect of
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII184
copy 2017 Japan Society for Food Engineering
phytic acid and some natural chelating agents on the solu-
bility of mineral elements in oat bran Food Chem 80 165-
170 (2003)
29) T Ono S Kato K Mothizuki Influences of calcium and
pH on protein solubility in soybean milk Biosci Biotech
Biochem 57 24-28 (1993)
30) T D Cai K C Chang M C Shih H J Hou M Ji
Comparison of bench and production scale methods for
making soymilk and tofu from 13 soybean varieties Food
Res Int 30 659-668 (1997)
31) K Saio E Koyama T Watanabe Protein-calcium-phytic
acid relationships in soybean Agr Biol Chem 31 1195-
1200 (1967)
32) S Y Park B I Lee S T Jung H J Park Biopolymer com-
posite films based on κ-carrageenan and chitosan Mater
Res Bull 36 511-519 (2001)
33) B Tamamushi ldquoDictionar y of Physics and Chemistr y
(Rikagaku Jiten)rdquo (in Japanese) Iwanami Tokyo Japan
1981 pp 1577-1578
34) W J Evans E J McCourther R I Shrager Titration
studies of phytic acid J Am Oil Chem Soc 59 189-191
(1982)
copy 2017 Japan Society for Food Engineering
豆乳コロイド分散系の安定性に及ぼす pH調整剤添加の影響
佐藤加奈子 1井戸川詩織 12dagger藤井智幸 2
1太子食品工業株式会社2東北大学大学院農学研究科
豆乳はタンパク質溶液にタンパク質粒子と脂質が分散したコロイド分散系である豆乳中に含まれる脂質はオイルボディとして存在しており表面を覆うオレオシンによって合一が抑制され安定なコロイド分散系を形成していると考えられている豆乳の製造管理および豆乳加工品の開発のためには豆乳のコロイド特性の把握が重要と考えられるコロイドの安定性は pHや熱電解質有機物の添加などの要因で変動することが知られている筆者らはアスコルビン酸溶液の添加による pHの低下に伴って豆乳の見かけ粘度が急激に変化する挙動を確認しているオイルボディとタンパク質が関わる凝集体の生成により見かけ粘度が上昇すると考えられるが凝集の詳細は明らかになっていないpH低下に伴う豆乳コロイドの凝集挙動の詳細を明らかにするためには豆乳の粒子が孤立状態で存在している段階から粒子が集まり充填状態やゲル構造を伴う巨大凝集体を生成するまでのメカニズムに関する理解が求められる本研究では豆乳の pH低下によって豆乳中に含まれるタンパク質の等電点に近づくことでタンパク質溶解度が低下し凝集体が形成されると仮説を立て拡張アインシュタイン型の式とKrieger-Dougherty型の式とを組み合わせた粘性モデルを構築してその有効性を実験的に調べた原料産地が異なる 6種類の豆乳にアスコルビン酸溶液を添加してpH 56-62の pH調整豆乳とし円錐平板型回転粘度計を用いて見かけ粘度を測定したpHが低下するにしたがいおよそ pH 60までは見かけ粘度はやや微増するにとどまったがpHが 60より低くなると徐々に見かけ粘度が上昇しpHが 59より低くなると指数関数的に見かけ粘度が上昇したまた宮城県産大豆から調製した豆乳Soymilk AではpHがおよそ 01低い条件で同様の挙動がみられ品種の違いによるグロブリンタンパク質の含有割合の変化や灰分などの他成分による影響が考えられた6種類の pH調整剤をアメリカ産大豆から調製した豆乳Soymilk Bへ添加して見かけ粘度を測定したところ先述の実験と同様
におよそ pH 60までは pH低下に伴って微増しpHが59より低くなると急激に粘度が上昇する挙動を示したただしフィチン酸溶液およびクエン酸溶液の場合は粘度が顕著に変化する pHが低くこれはキレート作用によるものと示唆された
6種類の pH調整剤によるそれぞれの結果について豆乳に含まれる水素イオンの濃度を豆乳の pHから算出し無次元粘度ηdの実測値との関係を示したこのプロットに対し拡張 Krieger-Dougherty型の式に当てはめて粘性パラメータ hcKcを算出したhcは凝集体のかさ高さを表しhcの値が大きいほど凝集体がかさ高いことを示すKcは分散相の最密充填率の逆数であり巨大凝集体のかさ高さを示すつまり Kcの値が大きいほど凝集体が密ではなく巨大凝集体がかさ高いことを表す各 pH 調整剤の系において拡張 Krieger-Dougherty
式の適用妥当性を検討したところpH調整剤の添加に伴う連続した pH低下による豆乳の凝集形成系について1つの式で良好に記述できることがわかった
6種類の豆乳および 6種類の pH調整剤を用いて測定した粘度データから得られた粘性パラメータ hcと Kc
に負の相関が認められたつまりpH低下によって進行する凝集過程において高 pH領域にて生成される凝集体の大きさが大きいほど巨大凝集体が密に充填してかさが小さくなり逆に凝集体の大きさが小さいほど巨大凝集体はかさ高くなることが示唆されたまたpH調整剤の種類によらず同一の曲線上にプロットされたことから孤立状態にある凝集体の内部構造が架橋機構の違いにより異なっていてもマクロな凝集挙動は同様であることが示唆されたさらにhcと Kcに相関関係があるために高い pH領域で粘度変化を測定することによって低い pH領域での粘度が予測できることが示されたこのことは豆乳における pH低下による凝集挙動を高 pH領域で予想可能であることを表し豆乳の品質管理に応用できる可能性が期待される本研究は生研センター「革新的技術創造促進事業(事業化促進)」の支援を受けて行った
(受付 2017年 4月 5日受理 2017年 9月 17日)
1 989-6228 宮城県大崎市古川清水字新田 51-1
2 980-0845 仙台市青葉区荒巻字青葉 468-1
daggerFax 0229-36-1702 E-mail s-itonotaishi-foodcojp
和文要約
「日本食品工学会誌」 Vol 18 No 4 p 185 Dec 2017
Kanako SATO Shiori IDOGAWA Tomoyuki FUJII184
copy 2017 Japan Society for Food Engineering
phytic acid and some natural chelating agents on the solu-
bility of mineral elements in oat bran Food Chem 80 165-
170 (2003)
29) T Ono S Kato K Mothizuki Influences of calcium and
pH on protein solubility in soybean milk Biosci Biotech
Biochem 57 24-28 (1993)
30) T D Cai K C Chang M C Shih H J Hou M Ji
Comparison of bench and production scale methods for
making soymilk and tofu from 13 soybean varieties Food
Res Int 30 659-668 (1997)
31) K Saio E Koyama T Watanabe Protein-calcium-phytic
acid relationships in soybean Agr Biol Chem 31 1195-
1200 (1967)
32) S Y Park B I Lee S T Jung H J Park Biopolymer com-
posite films based on κ-carrageenan and chitosan Mater
Res Bull 36 511-519 (2001)
33) B Tamamushi ldquoDictionar y of Physics and Chemistr y
(Rikagaku Jiten)rdquo (in Japanese) Iwanami Tokyo Japan
1981 pp 1577-1578
34) W J Evans E J McCourther R I Shrager Titration
studies of phytic acid J Am Oil Chem Soc 59 189-191
(1982)
copy 2017 Japan Society for Food Engineering
豆乳コロイド分散系の安定性に及ぼす pH調整剤添加の影響
佐藤加奈子 1井戸川詩織 12dagger藤井智幸 2
1太子食品工業株式会社2東北大学大学院農学研究科
豆乳はタンパク質溶液にタンパク質粒子と脂質が分散したコロイド分散系である豆乳中に含まれる脂質はオイルボディとして存在しており表面を覆うオレオシンによって合一が抑制され安定なコロイド分散系を形成していると考えられている豆乳の製造管理および豆乳加工品の開発のためには豆乳のコロイド特性の把握が重要と考えられるコロイドの安定性は pHや熱電解質有機物の添加などの要因で変動することが知られている筆者らはアスコルビン酸溶液の添加による pHの低下に伴って豆乳の見かけ粘度が急激に変化する挙動を確認しているオイルボディとタンパク質が関わる凝集体の生成により見かけ粘度が上昇すると考えられるが凝集の詳細は明らかになっていないpH低下に伴う豆乳コロイドの凝集挙動の詳細を明らかにするためには豆乳の粒子が孤立状態で存在している段階から粒子が集まり充填状態やゲル構造を伴う巨大凝集体を生成するまでのメカニズムに関する理解が求められる本研究では豆乳の pH低下によって豆乳中に含まれるタンパク質の等電点に近づくことでタンパク質溶解度が低下し凝集体が形成されると仮説を立て拡張アインシュタイン型の式とKrieger-Dougherty型の式とを組み合わせた粘性モデルを構築してその有効性を実験的に調べた原料産地が異なる 6種類の豆乳にアスコルビン酸溶液を添加してpH 56-62の pH調整豆乳とし円錐平板型回転粘度計を用いて見かけ粘度を測定したpHが低下するにしたがいおよそ pH 60までは見かけ粘度はやや微増するにとどまったがpHが 60より低くなると徐々に見かけ粘度が上昇しpHが 59より低くなると指数関数的に見かけ粘度が上昇したまた宮城県産大豆から調製した豆乳Soymilk AではpHがおよそ 01低い条件で同様の挙動がみられ品種の違いによるグロブリンタンパク質の含有割合の変化や灰分などの他成分による影響が考えられた6種類の pH調整剤をアメリカ産大豆から調製した豆乳Soymilk Bへ添加して見かけ粘度を測定したところ先述の実験と同様
におよそ pH 60までは pH低下に伴って微増しpHが59より低くなると急激に粘度が上昇する挙動を示したただしフィチン酸溶液およびクエン酸溶液の場合は粘度が顕著に変化する pHが低くこれはキレート作用によるものと示唆された
6種類の pH調整剤によるそれぞれの結果について豆乳に含まれる水素イオンの濃度を豆乳の pHから算出し無次元粘度ηdの実測値との関係を示したこのプロットに対し拡張 Krieger-Dougherty型の式に当てはめて粘性パラメータ hcKcを算出したhcは凝集体のかさ高さを表しhcの値が大きいほど凝集体がかさ高いことを示すKcは分散相の最密充填率の逆数であり巨大凝集体のかさ高さを示すつまり Kcの値が大きいほど凝集体が密ではなく巨大凝集体がかさ高いことを表す各 pH 調整剤の系において拡張 Krieger-Dougherty
式の適用妥当性を検討したところpH調整剤の添加に伴う連続した pH低下による豆乳の凝集形成系について1つの式で良好に記述できることがわかった
6種類の豆乳および 6種類の pH調整剤を用いて測定した粘度データから得られた粘性パラメータ hcと Kc
に負の相関が認められたつまりpH低下によって進行する凝集過程において高 pH領域にて生成される凝集体の大きさが大きいほど巨大凝集体が密に充填してかさが小さくなり逆に凝集体の大きさが小さいほど巨大凝集体はかさ高くなることが示唆されたまたpH調整剤の種類によらず同一の曲線上にプロットされたことから孤立状態にある凝集体の内部構造が架橋機構の違いにより異なっていてもマクロな凝集挙動は同様であることが示唆されたさらにhcと Kcに相関関係があるために高い pH領域で粘度変化を測定することによって低い pH領域での粘度が予測できることが示されたこのことは豆乳における pH低下による凝集挙動を高 pH領域で予想可能であることを表し豆乳の品質管理に応用できる可能性が期待される本研究は生研センター「革新的技術創造促進事業(事業化促進)」の支援を受けて行った
(受付 2017年 4月 5日受理 2017年 9月 17日)
1 989-6228 宮城県大崎市古川清水字新田 51-1
2 980-0845 仙台市青葉区荒巻字青葉 468-1
daggerFax 0229-36-1702 E-mail s-itonotaishi-foodcojp
和文要約
「日本食品工学会誌」 Vol 18 No 4 p 185 Dec 2017
copy 2017 Japan Society for Food Engineering
豆乳コロイド分散系の安定性に及ぼす pH調整剤添加の影響
佐藤加奈子 1井戸川詩織 12dagger藤井智幸 2
1太子食品工業株式会社2東北大学大学院農学研究科
豆乳はタンパク質溶液にタンパク質粒子と脂質が分散したコロイド分散系である豆乳中に含まれる脂質はオイルボディとして存在しており表面を覆うオレオシンによって合一が抑制され安定なコロイド分散系を形成していると考えられている豆乳の製造管理および豆乳加工品の開発のためには豆乳のコロイド特性の把握が重要と考えられるコロイドの安定性は pHや熱電解質有機物の添加などの要因で変動することが知られている筆者らはアスコルビン酸溶液の添加による pHの低下に伴って豆乳の見かけ粘度が急激に変化する挙動を確認しているオイルボディとタンパク質が関わる凝集体の生成により見かけ粘度が上昇すると考えられるが凝集の詳細は明らかになっていないpH低下に伴う豆乳コロイドの凝集挙動の詳細を明らかにするためには豆乳の粒子が孤立状態で存在している段階から粒子が集まり充填状態やゲル構造を伴う巨大凝集体を生成するまでのメカニズムに関する理解が求められる本研究では豆乳の pH低下によって豆乳中に含まれるタンパク質の等電点に近づくことでタンパク質溶解度が低下し凝集体が形成されると仮説を立て拡張アインシュタイン型の式とKrieger-Dougherty型の式とを組み合わせた粘性モデルを構築してその有効性を実験的に調べた原料産地が異なる 6種類の豆乳にアスコルビン酸溶液を添加してpH 56-62の pH調整豆乳とし円錐平板型回転粘度計を用いて見かけ粘度を測定したpHが低下するにしたがいおよそ pH 60までは見かけ粘度はやや微増するにとどまったがpHが 60より低くなると徐々に見かけ粘度が上昇しpHが 59より低くなると指数関数的に見かけ粘度が上昇したまた宮城県産大豆から調製した豆乳Soymilk AではpHがおよそ 01低い条件で同様の挙動がみられ品種の違いによるグロブリンタンパク質の含有割合の変化や灰分などの他成分による影響が考えられた6種類の pH調整剤をアメリカ産大豆から調製した豆乳Soymilk Bへ添加して見かけ粘度を測定したところ先述の実験と同様
におよそ pH 60までは pH低下に伴って微増しpHが59より低くなると急激に粘度が上昇する挙動を示したただしフィチン酸溶液およびクエン酸溶液の場合は粘度が顕著に変化する pHが低くこれはキレート作用によるものと示唆された
6種類の pH調整剤によるそれぞれの結果について豆乳に含まれる水素イオンの濃度を豆乳の pHから算出し無次元粘度ηdの実測値との関係を示したこのプロットに対し拡張 Krieger-Dougherty型の式に当てはめて粘性パラメータ hcKcを算出したhcは凝集体のかさ高さを表しhcの値が大きいほど凝集体がかさ高いことを示すKcは分散相の最密充填率の逆数であり巨大凝集体のかさ高さを示すつまり Kcの値が大きいほど凝集体が密ではなく巨大凝集体がかさ高いことを表す各 pH 調整剤の系において拡張 Krieger-Dougherty
式の適用妥当性を検討したところpH調整剤の添加に伴う連続した pH低下による豆乳の凝集形成系について1つの式で良好に記述できることがわかった
6種類の豆乳および 6種類の pH調整剤を用いて測定した粘度データから得られた粘性パラメータ hcと Kc
に負の相関が認められたつまりpH低下によって進行する凝集過程において高 pH領域にて生成される凝集体の大きさが大きいほど巨大凝集体が密に充填してかさが小さくなり逆に凝集体の大きさが小さいほど巨大凝集体はかさ高くなることが示唆されたまたpH調整剤の種類によらず同一の曲線上にプロットされたことから孤立状態にある凝集体の内部構造が架橋機構の違いにより異なっていてもマクロな凝集挙動は同様であることが示唆されたさらにhcと Kcに相関関係があるために高い pH領域で粘度変化を測定することによって低い pH領域での粘度が予測できることが示されたこのことは豆乳における pH低下による凝集挙動を高 pH領域で予想可能であることを表し豆乳の品質管理に応用できる可能性が期待される本研究は生研センター「革新的技術創造促進事業(事業化促進)」の支援を受けて行った
(受付 2017年 4月 5日受理 2017年 9月 17日)
1 989-6228 宮城県大崎市古川清水字新田 51-1
2 980-0845 仙台市青葉区荒巻字青葉 468-1
daggerFax 0229-36-1702 E-mail s-itonotaishi-foodcojp
和文要約
「日本食品工学会誌」 Vol 18 No 4 p 185 Dec 2017