The present invention relates to a process for producing β-conglycinin
protein having a low hydration property, and β-conglycinin protein having a
low hydration property and low viscosity obtained by the process, and a food comprising
β-Conglycinin, which is fractionated from soybean proteins, is
known to be quite effective for improvement of serum lipid (AOYAMA, Biosci. Biotechnol.
Biochem., Vol.65, No. 5, 1071-1075 2001, and JP 2002-114694 A). It is very useful
if such β-conglycinin can be ingested in various forms including liquid foods
such as drinks and soup, gel foods, and dry foods or semi-dry foods, such as bread,
cookie and cake, tablets, and the like.
Many methods for obtaining β-conglycinin from soybeans have been
hitherto investigated. Among them, one proposed method is to utilize β-conglycinin
separated from β-conglycinin rich bred soybeans in meat, cheese, milk powder,
substitute foods such as coffee creamer, general foods such as nutrition bars, drinks,
powdery drinks and frozen desserts (US 6,171,640 B1).
However, the protein rich in β-conglycinin has a remarkably high
hydration property and viscosity as compared with a soybean protein isolate conventionally
used for various foods. Then, various problems are caused due to formation of so-called
undissolved lumps of a powder of the protein in various food processing using it.
For example, in case where the protein is processed and ingested as a liquid food
such as soup or miso soup, or a protein powder which is dissolved in water to drink,
it is very difficult to disperse and dissolve the protein because of undissolved
lumps thereof. In addition, a problem such as heavy mouth feel is caused because
of high viscosity. Further, in case of a flour food or a starchy food such as bread,
sponge cake or rice cracker, since β-conglycinin takes out water unevenly when
added in dough, insufficient water absorption of wheat flour is resulted. Then,
sometimes, formation of homogeneous dough is difficult, and molding is impossible
except that an amount of water to be added is increased, a special molder is used,
or manual molding is carried out because of remarkable increase in viscosity. Thus,
there are many cases that β-conglycinin is hardly processed as various foods,
and is hardly ingested in the form of foods because of its high hydration property
and high viscosity.
As to a soybean protein isolate, wherein undissolved lumps of its
powder upon dissolution in water are also problematic, though not to comparable
with that of β-conglycinin protein, JP 59-25650 A (Literature A) discloses
a technique for improving water dispersibility thereof in a solution by heating
a dispersion thereof at about neutral pH. (pH 5.8 to pH 6.2) and a high temperature
such as not lower than 120°C for 10 seconds or longer. However, this technique is
directed to a normal soybean protein isolate having β-conglycinin content of
about 30% or less and heating is conducted at a relatively high solubility pH range
far from the isoelectric point. Therefore, this is different from the present invention
directed to a protein having β-conglycinin content of 40% or more and heating
it in an acidic range including the isoelectric point. Further, in the above Literature
A, the dispersibility of the soybean protein isolate is further improved by incorporating
granulation using lecithin and a fat as binders. However, the use of a fat causes
flavor deterioration with time and, further, since β-conglycinin is effective
for improving serum lipid, the use of a fat in improvement of dispersibility should
be avoided as much as possible.
Thus, there has been no desired method for reducing a hydration property
and high viscosity and improving a water reconstitution property of β-conglycinin
protein without any problems in application and flavor.
An object of the present invention is to provide processed β-conglycinin
protein whose high hydration property and high viscosity, which are great obstacles
as to processing of β-conglycinin protein in the various form of foods or as
to ingestion, are improved.
Disclosure of the Invention
As a result of the investigation for improving a high hydration property
and high viscosity of a solution of β-conglycinin protein, the present inventors
have found that by heating an aqueous solution or paste of the protein under acidic
conditions, solubility is reduced even after putting pH of the solution back to
neutral conditions under which the protein is originally soluble, and as a result,
a highly hydration property and high viscosity of β-conglycinin protein is
reduced in a wide pH range to improve its water reconstitution property, thereby
easily processing the protein as various foods and easily ingesting the protein.
The present inventors further have investigated heating conditions of the protein
solution under acidic conditions and, as the result, completed the present invention.
The present invention relates to a process for producing processed
β-conglycinin protein having a low hydration property and low viscosity which
comprises heating a solution containing β-conglycinin protein under acidic
conditions to reduce the solubility of the protein. Further, the present invention
relates to the processed β-conglycinin protein obtained by the above process
and a food comprising it.
That is, the present invention relates to:
Best Mode for Carrying Out the Invention
- (1) A process for producing processed β-conglycinin protein which comprises
heating a solution or paste containing β-conglycinin protein under acidic conditions;
- (2) The process according to the above (1), wherein the acidic conditions are
those at pH 3.5 to 6.0;
- (3) The process according to the above (1), wherein the heating is carried out
at higher than 75°C but lower than 160°C;
- (4) β-Conglycinin protein having solubility of 70% or less in a neutral
solution which is obtained by the process according to any one of the above (1)
to (3); and
- (5) A food comprising β-conglycinin protein according to the above (4).
In the present invention, β-conglycinin substantially corresponds
to 7S globulin which is a globulin having an ultracentrifugal sedimentation coefficient
of molecular weight of 7S among of globulins, i.e., a generic name of soluble soybean
globular proteins. While β-Conglycinin generally consists of 3 subunits of
α, α' and β, β-conglycinin lacking a part of the subunits
may also be included. When an amount of β-conglycinin is referred to, it means
the total amount of the actually existing subunits of α, α' and β.
Further, in the present invention, β-conglycinin protein means the protein
containing more β-conglycinin than a conventional soybean protein isolate.
Usually, its purity in the protein exceeds 40%, and as the purity becomes higher,
β-conglycinin can be ingested more easily.
β-conglycinin protein to be used in the present invention may
be the protein obtained by any methods including the method of Thanh & Shibasaki
(J. Agric. Food Chem., 24, 117 1976) as well as other methods such as a fractionation
method utilizing the difference in isoelectric points (JP 55-124457 A), a fractionation
method utilizing the reactivity with calcium (JP 48-56843 A), a fractionation method
utilizing the difference in solubility depending on pH and ionic strength (JP 49-31843
A, JP 58-36345 A and JP 5-43597 A), and a fraction method utilizing a cryophilic
precipitation phenomenon and a reducing agent (JP 61-187755 A). In addition, β-conglycinin
protein obtained from β-conglycinin rich bred soybeans may also be used (Breeding
Science, 50, 101, 2000 and US 6, 171, 640 B1).
In addition to the above methods, the preferred protein to be used
includes β-conglycinin protein prepared according to a fractionation technique
of β-conglycinin from defatted soybeans with a phytase (SAITO, Biosci. Biotechnol.
Biochem., Vol.65, No. 4, 884-887 2001), and β-conglycinin protein having high
purity which is obtained by fractionation after warming a solution containing a
soybean protein to 30 to 75°C at pH 3.8 to 6.8 (WO 02/28198 A1). Alternatively,
the protein to be used can also be prepared by a similar method which can fractionate
β-conglycinin protein having high purity even in a lower pH range by controlling
ionic strength when warming under acidic conditions (Japanese Patent Application
No. 2002-328243). β-Conglycinin protein obtained by any methods including the
above-mentioned methods can be used for the solution containing β-conglycinin
protein to be used in the present invention. However, in case of using β-conglycinin
protein as foods, it is preferred to carry out the protein without using a reducing
agent because a wide range of applications can be expected.
For reducing the solubility, the solution or paste containing β-conglycinin
protein is heated under acidic conditions of pH 3.5 to 6.0. When pH is out of this
range, solubility is insufficiently reduced. Then, the high hydration property and
high viscosity are not improved. In addition, solubility is greatly reduced by heating
it in a pH range close to pH 4.5 to 5.0 which is the isoelectric point of β-conglycinin.
Accordingly, β-conglycinin protein having much lower solubility can be obtained
by heating at pH 3.8 to 5.8, particularly pH 4.0 to 5.6 though it depends on a heating
temperature. The optimal degree of reduction of solubility is different according
to a particular food using the protein.
Although a suitable heating temperature for reducing the solubility
depends on pH, it may be higher than 75°C, preferably higher than or 85°C, and more
preferably higher than or 95°C. When heating is carried out at a too low temperature,
it is difficult to improve the high hydration property. On the other hand, heating
at a too high temperature is not practical and, when the solution or paste is heated
at higher than 160°C, sometimes, it is scorched. This is not preferred. Further,
reduction of the solubility greatly depends on the factors of pH and temperature
and the influence of the factor of heating time is not so much. In general, heating
at a high temperature can be carried out for a shorter period of time, while heating
at a low temperature needs a longer period of time.
The concentration of the solution or paste of β-conglycinin protein
at the time of heating is not particularly limited, but it may be 5 to 20%, preferably
5 to 15% and more preferably 5 to 10%. When the concentration is high, aggregation
lumps are formed by heating under the acidic conditions. Even when the concentration
is low, aggregation lumps may also be formed. Sometimes, the aggregation lumps as
such are problematic for processing after the heating under acidic conditions or
for processing the protein as a food. Then, preferably, the aggregation lumps formed
by heating under acidic conditions are ground by a wet grinder or the like.
Further, even if the aggregation lumps are ground by a wet grinder, etc., sometimes,
β-conglycinin protein obtained by drying which has reduced solubility contains
coarse particles. Then, the protein gives rough mouth feel, when the protein is
used in liquid foods such as drinks and soup. Thus, preferably, the solution is
homogenized by a high pressure homogenizer, etc.
β-Conglycinin protein prepared by one of the above methods has
a high hydration property, high viscosity and has solubility of 90% or more (see
hereinafter) in a neutral solution (pH 7.0) without heating under the acidic conditions.
However, the solubility in a neutral solution becomes 70% or lower when subjected
to heating under the acidic conditions. Thus, evident reduction of a hydration property
and viscosity can be recognized.
The solution or paste containing β-conglycinin protein having
reduced solubility obtained by the above treatment may be used as such, or after
concentration, neutralization or sterilization. Alternatively, from the view points
of storability and usability, it is practical to use the protein as dried β-conglycinin
protein having reduced solubility obtained by drying with a drier such as a spray
dryer after neutralization and sterilization. However, sometimes, when the solution
or paste containing β-conglycinin having reduced solubility is brought to pH
of higher than 6.0 and then sterilized at a high temperature, the solubility somewhat
increases, and the hydration property and viscosity revert. In that case, certain
treatment can be conducted in advance by taking such a phenomenon into account,
for example, the heating under acidic conditions is carried out under more stronger
From the practical viewpoint, examples the means for the above mentioned
concentration include so-called isoelectric separation wherein the resultant is
once diluted with water or desalinized to control its ionic strength to less than
0.2 and pH 4.0 to 5.0, followed by separation of an insoluble fraction. Then, water
is added thereto, the mixture is neutralized, sterilize by heating and dried. The
heating can be carried out by known HTST, UHT treatment and the like.
The solubility of β-conglycinin protein having reduced solubility
obtained by the above mentioned process is 70% or lower in a neutral solution (pH
7.0). As mentioned above, the protein having the solubility of 60% or lower, 50%
or lower, or 40% or lower can also be obtained by selecting heating conditions,
and can be appropriately selected according to particular use. If the solubility
is higher than 70%, such a protein is not suitable because it has an inferior water
reconstruction property and high viscosity at the time of processing it as various
foods of ingestion as foods.
The purity of β-conglycinin protein is not particularly limited
but, when the purity is 40% or higher, preferably 60% or higher and more preferably
70% or higher, β-conglycinin can be ingested or processed more efficiently.
Thus obtained β-conglycinin protein can be used for various foods such as tablets,
powdery drinks, foods such as baked confectionery, flour or starchy foods, various
premixes and the like.
Hereinafter, as examples of various foods containing β-conglycinin
protein, processing the protein as tablets, protein powders and rice cracker-like
foods is illustrated.
Tablets can be obtained by using a powdery mixture or a granulated
mixture containing β-conglycinin protein, filling the mixture into the mold
of a conventional tablet machine used for producing tablets and compressing it.
The content of β-conglycinin protein in tablets can be 80% by weight or lower.
When the content is higher than 80% by weight, hardness of tablets becomes insufficient
so that cracks are easily caused. Preferably, for ingestion of β-conglycinin,
β-conglycinin content is 20% by weight or higher, preferably 30% by weight
or higher, more preferably 40% by weight or higher. In addition to β-conglycinin
protein, tablets may further contain saccharides, and it is possible to produce
tablets having various hardness and mouth feel or flavors by appropriately selecting
saccharides. Further, tablets which are excellent in a luxurious property can be
obtained by addition of milk powder, cocoa powder, powdery juices, organic acids,
food flavors and the like, and, in order to improve a compression property, emulsifiers,
polysaccharides, silicon dioxide and the like can also be added.
Meanwhile, tablets containing β-conglycinin protein without the
processing of the present invention are difficult to eat because they stick to teeth
by chewing due to high viscosity. Further, because the bulk specific gravity of
β-conglycinin protein is low, when this powder is used mainly, weight per tablet
cannot be increased due to the relation to the mortar volume of a tablet machine.
Furthermore, because high pressure is required for obtaining hardness, this is not
preferable for a table machine. On the other hand, by subjecting the processing,
the bulk specific gravity of β-conglycinin can be increased, thereby avoiding
to stick to teeth by chewing and solving the above problems concerning to workability
and quality of tablets.
Powdery drinks can be obtained by mixing a powder containing β-conglycinin
protein with a powder containing other raw materials, and preferably granulating
the resulting mixture. Examples thereof include powder drinks using flavor agents
such as powdery soup, powdery miso soup, coffee powder and the like, and protein
powders having a higher content of β-conglycinin protein. The content of β-conglycinin
protein is not particularly limited, but the content can be 20% by weight or higher,
preferably 30% by weight or higher, and more preferably 40% by weight or higher
in view of efficient ingestion of β-conglycinin. In case of a protein powder,
for the purpose of ingesting the protein, the powder preferably contains 70% by
weight or more thereof based on the weight of raw materials. For powdery drinks,
there can be used powders of vegetables, potatoes, beans, cereals and the like,
powdery miso, soy sauce powder, seasonings, fruit juices, coffee powder, cocoa powder,
milk powder, saccharides, starches, flavors, acidulants and the like, without limitation.
When unprocessed β-conglycinin protein is used, the formation of undissolved
lumps can be improved by granulation, but the improvement becomes harder as the
content is increased. Particularly, when the amount of β-conglycinin protein
to be used exceeds 50% by weight, it is difficult to obtain an end product having
suitable properties because of difficulty in obtaining sufficient dispersibility,
and further an increase in viscosity by granulation.
On the other hand, when processed β-conglycinin protein is used,
and further it is granulated, powdery drinks having suitable dispersibility without
any increase in viscosity can be obtained even if it is used for a food highly a
high content thereof such as a protein powder.
Foods such as rice cracker-like foods can be obtained by heating hydrated
dough to expand (puff) it. In order to ingest β-conglycinin, the content of
β-conglycinin protein is suitably 20% by weight or higher, preferably 30% by
weight or higher, and more preferably 40% by weight or higher in the solids content.
Further, by adding other raw materials, the mouth feel and flavor can be controlled
and, in this case, the content of β-conglycinin protein is suitably 90% by
weight or lower. In a formulation, there can be added starchy substances such as
corn starch, waxy corn starch, potato starch, tapioca starch, wheat starch and rice
starch, modified starch thereof, cereal powders such as wheat flour and rice powder,
fats and oils and the like to improve a luxurious property. In addtion, for flavoring
dough, spices and seasonings can be added. When water is added to such a powder
mixture containing β-conglycinin protein to prepare dough, if unprocessed β-conglycinin
protein is used, undissolved lumps are formed and homogeneous dough cannot be obtained.
Particularly, a high content such as 50% by weight or higher in a solids content
is hardly obtainable. On the other hand, in case of the processed β-conglycinin
protein, undissolved lumps are scarcely formed, and the protein can be mixed with
a conventional vertical mixer to be used for normal mixing. However, a degree of
expansion tends to decrease in the case of processed protein and, when expansion
is insufficient, sometimes, the end product becomes too hard. In this case, it is
possible to optimize both water dispersibility and a degree of expansion by appropriately
replacing processed β-conglycinin protein with unprocessed β-conglycinin
Hereinafter, the present invention is specifically explained by Examples.
However, the technical scope of the present invention is not limited by these Examples.
- Solubility: An aqueous solution containing 1% by weight of a sample was adjusted
to pH 7.0 and the proportion of an amount of a protein in a supernatant obtain by
centrifugation at 8,000 g for 5 minutes to the total amount of the protein in the
aqueous solution was determined_by Kjeldahl method.
- SDS-polyacrylamide gel electrophoresis: A sample was analyzed by the method
by Laemmli (Nature, 227, 680 1970), with a gradient gel at gel concentration of
10 to 20%. The applied amount of protein was 5 µg.
- Phytic acid:, Phytic acid was determined according to the method by Alii Mohamed
(Cereal Chemistry, 63, 475-478 1986).
- Chloroform/methanol oil content: Fifty-fold of a mixture of chloroform/methanol
(2 : 1 by volume) was added to a dried sample to extract an oil fraction at 160°C,
followed by weighing the fraction to calculate chloroform/methanol oil content.
- Purity (SPE basis): The areas of the electrophoresis migration pattern obtained
by the above SDS-polyacrylamide gel electrophoresis were measured by a densitometer,
and the area proportion of the area of β-conglycinin fraction to the total
areas was calculated to obtain the purity (SPE basis). Herein, the content of β-conglycinin
means total amounts of α, α' and β subunits.
In addition to this method, as described hereinafter, purity is also
determined as corrected purity by taking an amount of an intermingled oil body-associated
protein (SAMOTO, Biosci. Biotechnol. Biochem., Vol.62, No. 5 935-940 1998) into
consideration. However, the present invention refers to the purity of β-conglycinin
protein as that by SPE basis.
- Corrected purity: By taking the purity of a sample (SPE basis) as A%, the corrected
purity is calculated as the purity based on the total protein obtained by subtracting
the amount of oil body-associated protein from the SPE value as shown in the following
equation because oil body-associated protein corresponding to 10 times by weight
of the amount of chloroform/methanol oil content intermingles in the sample.
Corrected Purity (%) = (100(%) - Chloroform/methanol oil content (%) ×
10) × A(%) / 100
- Evaluation of water reconstruction property: Water (300 g) at 20°C was placed
in a 500 ml beaker, to this was added a dried powder of β-conglycinin (9 g)
with stirring at 300 rpm by an octagon stirrer (35 mm length x 7.5 mm diameter),
and the mixture was stirred for 5 minutes. Then, the mixture was poured on a 16
mesh sieve and dried weight of undissolved lumps of β-conglycinin remained
on the sieve was measured to determine the proportion of lumps. The smaller proportion
of undissolved lumps represents a better water reconstruction property. This was
expressed as follows: less than 1/4 as o○;
1/4 to less than 2/4 as ○; 2/4 to less than 3/4 as Δ; and more than or
3/4 as ×.
Soybeans were pressed and extracted to remove oil with n-hexane as
an extraction solvent. To 1 part by weight of the resultant low denaturation defatted
soybean was added 10 parts by weight of extraction water (50°C), and the mixture
was adjusted to pH 5.3 with hydrochloric acid and extracted for 30 minutes. This
extraction slurry was adjusted to pH 5.5 with caustic soda, and centrifuged by a
batch-wise centrifuge (3,000 g). The solution temperature at the time of centrifugation
was about 45°C. After adjusting a temperature of the soluble fraction obtained to
50°C, phytase of 8 units per protein weight (manufactured by NOVO, "PHYTASE NOVO
L") was added thereto, and the fraction was digested by the enzyme, cooled to about
20°C, adjusted to pH 4.9 with hydrochloric acid and centrifuged to obtain precipitated
curd of low phytic acid β-conglycinin (the process described in WO 02/28198
A1). The precipitated curd was homogenized with 5 times by weight of water (solid
content 6.7%), adjusted to pH 3.3, 3.8, 4.0, 5.0, 5.5, 5.8, 6.0 or 7.0 with caustic
soda or hydrochloric acid, and heated at 65°C, 85°C, 100°C or 140°C for 10 seconds,
then immediately spray-dried to obtain powdered β-conglycinin protein. Purity
of β-conglycinin of the powder obtained was 93%. Solubility (%) at pH 7.0 in
a neutral solution and a water reconstruction property of the powder of β-conglycinin
protein obtained by heating under respective conditions are shown in Table 1.
As seen from the above results, in case of heating under neutral or
strongly acidic conditions or at a temperature of 75°C or lower, the solubility
of β-conglycinin protein obtained is not reduced, while β-conglycinin
protein having the solubility of 70% or lower can be obtained by heating at a temperature
of higher than 75°C under acidic conditions.
Water was added to the precipitated curd of low phytic acid β-conglycinin
protein prepared according to the same manner as that of Example 1 and the mixture
was homogenized (solids content 14.2%), adjusted to pH 5.5 with caustic soda and
heated at 120°C for 10 seconds. Then, aggregating lumps formed were ground by Comitrol
(manufactured by URSCHEL LABORATRIES, INC.), and the resultant was adjusted to pH
6.0 with caustic soda, sterilized by heating at 142°C for 7 seconds, and immediately
spray-dried to obtain a powder of β-conglycinin protein. Purity of β-conglycinin
of the powder obtained was 93%, and the solubility at pH 7.0 was 34%.
Tablets (tablet confectionery)
The precipitated curd of low phytic acid β-conglycinin protein
prepared according to the same manner as that in Example 1 was homogenized with
5 times by weight of water (solids content 6.7%), adjusted to pH 5.5 with caustic
soda and heated at 120°C for 10 seconds. Then, aggregating lumps formed were ground
by Comitrol (manufactured by URSCHEL LABORATRIES, INC.), and the resultant was adjusted
to pH 6.0 with caustic soda and sterilized by heating at 142°C for 7 seconds, and
immediately spray-dried to obtain a powder of β-conglycinin protein (T-1: solubility
at pH 7.0 was 38%). A mixture of 32 parts by weight of T-1 obtained and 68 parts
of malt sugar was granulated by a fluidized bed with 15 parts of a 0.2% by weight
guar gum aqueous solution as a binder. To the granules obtained were added 3 parts
of DK ester F-20W (manufactured by DAI-ICHI KOGYO SEIYAKU CO., LTD.), 1 part of
powdered lemon juice, 0.5 part of powdered lemon flavor and 1 part of citric acid,
and the resultant mixture was applied to a tablet machine to prepare tablets of
20 mm diameter (1.7 g/tablet). The tablets obtained had no problem of powder fluidity
and molding at the time of compression and was well to be chewed with no sticking
to teeth. On the other hand, for comparison, the precipitated curd was homogenized
with 5 times weight of water (solids content 6.7%), without heating under acidic
conditions, adjusted to pH 7.0 with caustic soda. Then, similarly, the resultant
was subjected to heat sterilization and spray drying to obtain unprocessed powder
of β-conglycinin protein (C-1: solubility at pH 7.0 was 99%). By using this
powder, similarly, tablets of 20 mm diameter were prepared, but it was very difficult
to chew with sticking to teeth.
In view of the above results, it has been shown that tablets having
good mouth feel can be obtained by using processed β-conglycinin protein.
The precipitated curd of low phytic acid β-conglycinin protein
prepared according to the same manner as that of Example 1 was homogenized with
5 times by weight of water (solids content 6.7%), adjusted to pH 5.8 with caustic
soda and heated at 120°C for 10 seconds. Then, aggregating lumps formed was ground
by a commit roll (manufactured by URSCHEL LABORATRIES, INC.), and the resultant
was further homogenized with a high pressure homogenizer (manufactured by IZUMI
FOOD MACHINERY CO., LTD., 150 kgf/cm2), adjusted to pH 6.0 with caustic
soda, sterilized by heating at 142°C for 7 seconds, and immediately spray-dried
to obtain a powder of β-conglycinin protein (T-2; solubility at pH 7.0 was
68%). A mixture of 90 parts by weight of T-2 thus obtained or C-1 β-conglycinin
protein obtained in Example 3, 9 parts of malt sugar and 1 part of cocoa flavor
was granulated in a fluidized bed with 10 parts of a 4% by weight aqueous Ryoto
Sugar ester S-570 solution (manufactured by MITSUBISHIKAGAKU FOODS CORPORATION)
as a binder to prepare a protein powder. To 100 g of water was added 5 g of the
protein powder and the mixture was lightly stirred. As a result, the protein powder
prepared using T-2 was dispersed uniformly and with no rough mouth feel, while the
protein powder prepared using C-1 could not be dispersed uniformly with undissolved
Rice cracker-like foods
A mix composed of 70 parts of T-1, C-1 or a 1 : 1 mixture of T-1 and
C-1, 25 parts of rice flour and 5 parts of "Norisio" (trade name) seasoning powder
was placed in a mixer. To this was gradually added 200 parts of water and the resultant
was kneaded to prepare dough. The dough obtained was divided into 8g portions, and
they were subjected to sandwich-baking by sandwiching between iron plates maintained
at 180°C and heating for 6 minutes to expand the dough, and dried for 3 hours under
air-blowing conditions with air at 50°C to prepare a rice cracker-like food.
When T-1 and the 1 : 1 mixture of T-1 and C-1 were used, uniform dough
was prepared. On the other hand, when C-1 was used, dough was not uniform with many
undissolved lumps. Further, as to expansion by sandwich-baking, the dough using
T-1 was a less expansion, while the dough using the 1 : 1 mixture of T-1 and C-1
was suitably expanded. As to mouth feel, the product using the 1 : 1 mixture of
T-1 and C-1 showed suitably crispy mouth feel, and it was most preferred one. On
the other hand, the product using T-1 is somewhat hard and has less desired mouth
feel. In view of the above results, the use of processed β-conglycinin protein
makes the preparation of dough be easy and further a rice cracker-like food having
suitable mouth feel can be obtained.
According to the present invention, by heating a solution or paste
containing soybean β-conglycinin protein under acidic conditions, it is possible
to provide soybean β-conglycinin protein whose high hydration property and
high viscosity, which are problematic in various food processing using it or at
the time of ingestion thereof, are improved.