JP2021016346A - Soybean curd, raw soybean curd, food, and method for suppressing pore occurrence of soybean curd - Google Patents

Abstract

To provide soybean curd suppressed in pore occurrence at heating, and excellent in palate feeling.SOLUTION: There are provided: soybean curd which contains soybean protein-derived peptide showing a maximum peak within a dissolution time of 24-28 minutes in a peptide chromatograph obtained in a predetermined condition; and soybean curd which contains a partial decomposition product of protein selected from the group consisting of a subunit of β-conglycinin, b subunit, glycinin Acidic subunit, and glycinin Basic subunit.SELECTED DRAWING: None

Description

The present invention relates to tofu, raw tofu, foods, and a method for suppressing porosity of tofu.

Tofu is one of the widely used ingredients in cooking. However, tofu has a so-called "poor standing" problem in which fine holes are formed when heated.

For example, Patent Document 1 proposes a method for producing cut tofu in which porosity is suppressed.

JP-A-2010-75105

However, there is a further need for tofu in which porosity during heating is suppressed without impairing the texture and the like.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide tofu that suppresses porosity during heating and has an excellent texture.

The present inventors have found that tofu containing a specific peptide can solve the above-mentioned problems, and have completed the present invention. Specifically, the present invention provides:

(1) Tofu containing a peptide derived from soybean protein that shows a maximum peak at an elution time of 24 to 28 minutes in a peptide chromatograph obtained under the following conditions.
(Peptide chromatograph conditions)
Equipment used: High Performance Liquid Chromatograph (UHPLC), Shimadzu Corporation Detector: Fluorescence Detector Column: Product name "TSKgel G200SW 10 μm" (7.5 mm ID x 30 cm), Tosoh Column temperature: 25 ℃
Composition of elution buffer: 40% acetonitrile, 0.1% acetic acid Flow rate: 0.5 ml / min

(2) Tofu containing a partial decomposition product of a protein selected from the group consisting of a subunit of β-conglycinin, b subunit, glucinin Acidic subunit, and glucinin Basic subunit.

(3) The tofu according to (1) or (2), wherein the total amount of free amino acids is 200 mg / 100 g or more and 10000 mg / 100 g or less.

(4) The tofu according to any one of (1) to (3), which is made from soymilk of germinated soybean and / or soymilk treated with a proteolytic enzyme.

(5) The tofu according to any one of (1) to (4), which contains gluconolactone in an amount of 0.10% by mass or more.

(6) Raw tofu showing a breaking point after the following heating test and breaking stress test.
(Heating test)
The tofu is soaked in water and wrapped in a retort pouch (made of nylon poly (NYPE)), and allowed to stand at 1 atm and 90 ° C. for 20 minutes.
(Fracture stress test)
The tofu after the heating test is cut into a size of 10 mm × 10 mm × 10 mm, and this is placed on a sample table. Next, using a creep meter physical property test system (model: RE2-3305B, manufactured by Yamaden Co., Ltd.), a plunger of φ30 mm from the top surface was inserted into the tofu placed on the sample table at a speed of 1.0 mm per second. The breaking load is measured by penetrating at a strain rate of 85%.

(7) Retort-sterilized tofu showing a breaking point in the following breaking stress test.
(Fracture stress test)
Cut the tofu into a size of 10 mm × 10 mm × 10 mm and place it on the sample table. Next, using a creep meter physical property test system (model: RE2-3305B, manufactured by Yamaden Co., Ltd.), a plunger of φ30 mm from the top surface was inserted into the tofu placed on the sample table at a speed of 1.0 mm per second. The breaking load is measured by penetrating at a strain rate of 85%.

(8) A retort-sterilized food containing the tofu according to any one of (1) to (7).

(9) A method for suppressing tofu porosity using soymilk of germinated soybean and / or soymilk treated with proteolytic enzyme as a raw material.

According to the present invention, tofu having an excellent texture is provided by suppressing porosity during heating.

It is a figure which shows the result of the peptide analysis of the soybean raw material used in an Example. It is a figure which shows the result of the electrophoresis of the peptide contained in the soybean raw material used in an Example. It is a figure which shows the result of the breaking stress test after heating about the tofu produced in an Example. It is a figure which shows the state after heating about the tofu produced in an Example. It is a figure which shows the observation result of the cross section after heating about the tofu produced in an Example. It is a figure which shows the state after heating about the tofu produced in an Example.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not particularly limited thereto.

<Tofu of the present invention>
The tofu of the present invention contains peptides that meet the following requirements (P1) and / or (P2). Hereinafter, each of the following peptides is also simply referred to as "P1" and "P2".
(P1) A peptide derived from soybean protein that shows a maximum peak at an elution time of 24 to 28 minutes in a peptide chromatograph obtained under the following conditions.
(Peptide chromatograph conditions)
Equipment used: High Performance Liquid Chromatograph (UHPLC), Shimadzu Corporation Detector: Fluorescence Detector Column: Product name "TSKgel G200SW 10 μm" (7.5 mm ID x 30 cm), Tosoh Column temperature: 25 ℃
Composition of elution buffer: 40% acetonitrile, 0.1% acetic acid Flow rate: 0.5 ml / min
(P2) A partial decomposition product of a protein selected from the group consisting of the a subunit and b subunit of β-conglycinin, and the glucinin Acidic subunit and glucinin Basic subunit.

As a result of the studies by the present inventors, it was surprisingly found that the tofu containing the above peptide has suppressed porosity even after heating and has an excellent texture.

Both P1 and P2 have a molecular weight relatively smaller than that of proteins contained in a large amount in ordinary tofu. In the present invention, it is presumed that by blending a peptide having a small molecular weight in this way, protein denaturation and structural change of tofu due to heating are suppressed, and as a result, porosity is suppressed. In addition, P2 may be included in P1.

Regarding P2, the a subunit, b subunit, glucinin Acidic subunit, and glucinin Basic subunit of β-conglycinin have molecular weights of 72 kDa, 53 kDa, 37 to 42 kDa, and 20 kDa, respectively. Therefore, these partial decomposition products, P2, have a molecular weight smaller than the above molecular weight.

The lower limit of the content of P1 in the tofu of the present invention is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, based on the tofu. The upper limit of the content of P1 in the tofu of the present invention is preferably 10% by mass or less, more preferably 10% by mass or less, based on the tofu.

The lower limit of the content of P2 in the tofu of the present invention is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, based on the tofu. The upper limit of the content of P2 in the tofu of the present invention is preferably 10% by mass or less, more preferably 5.0% by mass or less, based on the tofu.

The tofu of the present invention is more likely to suppress porosity when it contains a relatively large amount of free amino acids. For example, the lower limit of the total amount of free amino acids in the tofu of the present invention is preferably 200 mg / 100 g or more, more preferably 600 mg / 100 g or more, still more preferably 600 mg / 100 g or more, with respect to the tofu, from the viewpoint that the porosity of the tofu is easily suppressed. It is 1000 mg / 100 g or more, and even more preferably 1500 mg / 100 g or more. The upper limit of the total amount of free amino acids in the tofu of the present invention does not have to be excessive, and is preferably 10000 mg / 100 g or less, more preferably 8000 mg / 100 g or less, still more preferably 5000 mg / 100 g or less, still more preferably 5000 mg / 100 g or less, based on the tofu. It is 3000 mg / 100 g or less.

When the tofu of the present invention contains a relatively large amount of free amino acids, the reason why porosity is more likely to be suppressed is presumed as follows. Among the proteins contained in soybean, which is a raw material of tofu, β-conglycinin is known to produce fibrous proteins, oligopeptides, etc. in the process of being decomposed by proteolytic enzymes. As a result of the studies by the present inventors, it has been found that such fibrous proteins, oligopeptides and the like may contribute to the construction of the network structure of tofu. The fact that the tofu of the present invention contains a relatively large amount of free amino acids means that the above-mentioned fibrous proteins, oligopeptides, etc. are also abundant, thereby constructing a strong tofu network structure. , It is considered that porosity is suppressed.

The lower limit of the total amount of free amino acids in the tofu of the present invention is preferably 200 mg / 100 g or more, more preferably 600 mg / 100 g or more, still more preferably 1000 mg / 100 g or more, and even more, from the viewpoint that the porosity of tofu is easily suppressed. It is preferably 1500 mg / 100 g or more. The upper limit of the total amount of free amino acids in the tofu of the present invention does not have to be excessive, and is preferably 10000 mg / 100 g or less, more preferably 8000 mg / 100 g or less, still more preferably 5000 mg / 100 g or less, still more preferably 5000 mg / 100 g or less, based on the tofu. It is 3000 mg / 100 g or less.

Examples of free amino acids and their contents that can be contained in the tofu of the present invention include the following.
Glutamic acid: 15-30 mg / 100 g
Alanine: 10-20 mg / 100 g
Aspartic acid: 0.5-3 mg / 100 g
Lysine: 2-5 mg / 100 g
Histidine: 2-5 mg / 100 g
Phenylalanine: 2-5 mg / 100 g
Methionine: 0.5-3 mg / 100 g
Threonine: 1.5-5 mg / 100 g
Leucine: 1-5 mg / 100 g
Isoleucine: 1-5 mg / 100 g
Valine: 1.5-5 mg / 100 g
Arginine: 20-50 mg / 100 g
Glycine: 2-5 mg / 100 g
Serine: 2-5mg / 100g
Tyrosine: 1.5-5 mg / 100 g

The tofu of the present invention tends to have a large amount of glutamic acid, alanine, threonine, and serine, which can affect the taste, among the above free amino acids. Therefore, the tofu of the present invention can be a tofu having a good palatability.

The isoelectric point of the tofu of the present invention may be 2.0 to 6.8. The isoelectric point is identified by acid titration.

(Soy milk)
The tofu of the present invention is made from soymilk obtained from soybeans. The soybean from which soymilk is derived is not particularly limited, but it is preferable to use germinated soybean as a raw material from the viewpoint that tofu containing P1 and / or P2 can be easily obtained. Moreover, as soymilk, soymilk of germinated soybean and / or soymilk treated with proteolytic enzyme is preferable.

In the present invention, the term "germinated soybean" means soybean that has undergone germination treatment, which will be described later, and includes soybean in which no bud (sprout) is clearly recognized.

As a result of the studies by the present inventors, germinated soybeans contain a large amount of peptides (P1, P2, etc.) and free amino acids having a smaller molecular weight than normal soybeans (soybeans that have not been germinated). Found. The same was found for soymilk and tofu made from germinated soybeans. Therefore, if soymilk of germinated soybean is used as a raw material, the tofu of the present invention can be easily produced.

As the germinated soybean, any soybean that has been subjected to germination treatment (treatment that promotes germination) can be used. As the germination treatment, a conventionally known method can be adopted, and examples thereof include a method in which soybeans are immersed in water and then exposed to the air. Other methods include the methods of Japanese Patent No. 5795676 and Japanese Patent No. 5722518.

The raw material of the tofu of the present invention preferably contains soymilk of germinated soybean. When soymilk obtained from ordinary soybeans (soybeans that have not been germinated) is used as the raw material for the tofu of the present invention, it may be mixed with soymilk of germinated soybeans, or P1 and soymilk obtained from ordinary soybeans may be used. / Or by adding P2, soymilk as a raw material for the tofu of the present invention can be easily prepared.

In the present invention, "proteolytic enzyme-treated soymilk" means soymilk obtained from any soybean and treated with proteolytic enzyme.

As a result of the studies by the present inventors, it is found that any soymilk (for example, commercially available soymilk) subjected to proteolytic enzyme also contains a large amount of small molecular weight peptides (P1, P2, etc.) and free amino acids. Found. Therefore, if soymilk treated with a proteolytic enzyme is used as a raw material, the tofu of the present invention can be easily produced.

The soybean from which the soymilk to be treated with the proteolytic enzyme is derived is not particularly limited, and either germinated soybean or soybean not subjected to the germination treatment can be used, and these can also be used in combination.

The proteolytic enzyme is not particularly limited as long as it can decompose the protein contained in soymilk. For example, enzymes such as protease and peptidase (gingibain, cysteine protease, etc.) can be mentioned. As the proteolytic enzyme, a refined product can be used, and a food containing the enzyme can also be used. Examples of foods containing proteolytic enzymes include raw ginger, papaya, kiwifruit, and juices thereof.

The conditions of the proteolytic enzyme (amount of enzyme used, temperature, time, etc.) are not particularly limited as long as the enzyme is not inactivated and the protein in soymilk can be sufficiently decomposed. For example, the temperature condition may be 10 to 50 ° C. The enzyme treatment time may be 1 to 72 hours.

As a method for producing soymilk, a conventionally known method can be adopted. For example, a method in which soybeans are soaked in water and expanded, and then the fiber (okara) is removed to obtain soymilk. Soymilk may be sterilized if necessary.

<Tofu manufacturing method>
The tofu of the present invention can be obtained by adding a coagulant to soymilk, filling it in a mold as appropriate, or packaging it in a container. As the coagulant, those used in the production of tofu can be used. Other conditions are not particularly limited, and those usually used in the production of tofu can be adopted.

As a result of the studies by the present inventors, it has been found that when gluconolactone is used as a coagulant, tofu with more suppressed porosity during heating can be easily obtained. The lower limit of the amount of gluconolactone is preferably 0.10% by mass or more, more preferably 0.30% by mass or more with respect to tofu, from the viewpoint that tofu having an excellent texture and flavor can be easily obtained. The upper limit of the amount of gluconolactone is preferably 0.40% by mass or less, more preferably 0.35% by mass or less, from the viewpoint of not easily impairing the flavor of tofu. However, as the coagulant, a coagulant other than gluconolactone may be used, or a plurality of coagulants (for example, gluconolactone and other coagulants) may be used in combination.

In the production of tofu of the present invention, it is possible to obtain tofu having a good texture without containing the emulsifier used in the conventional production of tofu. Examples of such emulsifiers include glycerin fatty acid esters (monoglycerin fatty acid esters, diglycerin fatty acid esters, organic acid monoglycerides, polyglycerin fatty acid esters, polyglycerin condensed ricinoleic acid esters), sucrose fatty acid esters, sorbitan fatty acid esters, and propylene glycol fatty acids. Examples thereof include esters, stearoyl emulsions, yukka extracts, saponins, lecithins, polysorbates and the like. However, in the present invention, an embodiment containing such an emulsifier is not excluded. For example, the tofu of the present invention may contain the above emulsifier in an amount of preferably 0.5% by mass or less, more preferably 0.1% by mass or less, based on the tofu.

In the production of tofu of the present invention, it is possible to obtain tofu having a good texture without containing the thickener used in the conventional production of tofu. Examples of such a thickener include the following. Starch, caraginan, xanthan gum, native gellan gum, deacylated gellan gum, tamarind seed gum, guar gum, locust bean gum, tara gum, glucomannan, alginic acid, sodium alginate, curdran, arabic gum, agar, tragant gum, karaya gum, gati gum, purulan Thickening polysaccharides such as lambzan gum, psyllium seed gum, macrohomopsis gum, fermented cellulose, microfibrous cellulose, water-soluble cellulose ether (methyl cellulose, hydroxypropyl cellulose, hydroxymethylpropyl cellulose, etc.); corn starch, waxy corn starch, sweet potato starch , Wheat starch, Tapioca starch, Marin 薯 starch, Rice starch and other raw starch, and processed starch such as crosslinked, etherified, and esterified starches. However, in the present invention, the aspect in which such a thickener is contained is not excluded. For example, the tofu of the present invention may contain the above-mentioned thickener of preferably 0.5% by mass or less, more preferably 0.1% by mass or less, based on the tofu.

In the production of tofu of the present invention, it is possible to obtain tofu having a good texture without containing the protein auxiliary agent used in the conventional production of tofu. Examples of such a protein aid include proteins other than soymilk-derived proteins, and specific examples thereof include the following. Egg-derived proteins such as whey protein, egg protein, albumin; soybean protein; wheat protein; myosin protein; gelatin; collagen; plasma protein, etc. However, in the present invention, the aspect in which such a protein auxiliary agent is contained is not excluded. For example, the tofu of the present invention may contain the above-mentioned protein auxiliary agent in an amount of preferably 0.5% by mass or less, more preferably 0.1% by mass or less, based on the tofu.

The tofu of the present invention can be appropriately prepared as a retort-sterilized food product. In the present invention, "retort sterilization" means that the packaged food is subjected to pressure heat treatment under a temperature condition of about 100 to 150 ° C. In the present invention, the "food" may be tofu itself or a cooked product made from tofu (mapo tofu, hot and sour soup, sundubu, miso soup, etc.).

The tofu of the present invention can be prepared as an aseptically filled food (a food package in which the food product is sterilized and the packaging material is sterilized separately). However, the preparation of such products requires a great deal of equipment cost. According to the present invention, since a packaged product in which porosity is well suppressed can be obtained by simple retort sterilization, it is not necessary to perform aseptic filling in the production of the tofu of the present invention.

<Characteristics of tofu>
As described above, the tofu of the present invention suppresses porosity even when heated and has an excellent texture. Whether or not the porosity during heating is suppressed can be judged visually or by microscopic observation. The texture can be evaluated as the texture and smoothness when eating tofu.

The structural change of the tofu of the present invention is suppressed even when heated. Whether or not the structural change is caused by heating can be evaluated, for example, after the following heating test and by the breaking stress test.

The tofu of the present invention can be raw tofu that shows a breaking point after the following heating test and in the breaking stress test. The "raw tofu" means tofu that has not undergone heat treatment (for example, heat treatment at 90 ° C. or higher). The "breaking point" means the limit point at which the tofu is destroyed when an external force is applied to the tofu and the stress against the external force cannot be withstood.
(Heating test)
Soak the tofu in water and wrap it in a retort pouch (made by nylon poly (NYPE)) (trade name "Meiwapax BRS-1624S", made by Meiwapax Co., Ltd.) and leave it at 1 atm at 90 ° C for 20 minutes. ..
(Fracture stress test)
The tofu after the heating test is cut into a size of 10 mm × 10 mm × 10 mm, and this is placed on a sample table. Next, using a creep meter physical property test system (model: RE2-3305B, manufactured by Yamaden Co., Ltd.), a plunger of φ30 mm from the top surface was inserted into the tofu placed on the sample table at a speed of 1.0 mm per second. The breaking load is measured by penetrating at a strain rate of 85%.

When the tofu of the present invention is raw tofu, it can be used as it is, or it can be used for heating cooking. Examples of the heating cooking include heating through fire, hot water, oil, etc., heating using a microwave oven, and the like.

For example, the tofu of the present invention can be retort-sterilized tofu that shows a breaking point in the following breaking stress test.
(Fracture stress test)
Cut the tofu into a size of 10 mm × 10 mm × 10 mm and place it on the sample table. Next, using a creep meter physical property test system (model: RE2-3305B, manufactured by Yamaden Co., Ltd.), a plunger of φ30 mm from the top surface was inserted into the tofu placed on the sample table at a speed of 1.0 mm per second. The breaking load is measured by penetrating at a strain rate of 85%.

<Method of suppressing tofu porosity>
As described above, by using soymilk of germinated soybean and / or soymilk treated with proteolytic enzyme as a raw material, tofu with suppressed porosity can be obtained.

Further, in the production of tofu, by blending P1 and / or P2, tofu with suppressed porosity can be obtained. The blending amount of P1 and / or P2 can be appropriately adjusted according to the texture of the tofu to be obtained and the like.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples.

<Test 1: Amino acid analysis of tofu obtained from various soybean ingredients>
Amino acid analysis of tofu obtained from two kinds of soybean raw materials, that is, germinated soybean and normal soybean, was performed.

(1) Preparation of soybean raw material After washing "Toyomasari" from Hokkaido with 30 ppm sodium hypochlorite, sprinkling every 3 hours was repeated for 15 hours to prepare germinated soybeans. In addition, soybeans soaked in water for 15 hours from Hokkaido "Toyomasari" were usually used as soybeans.

(2) Preparation of soymilk The soybean raw material was swollen with water so as to have a mass of 2.25 times that of dried soybean. Next, the soybean raw material was ground while adding water about 2.5 times the mass of the swollen soybean raw material. The ground soybean juice was heated to extract proteins and other soluble components, which were then filtered. The filtrate was collected to obtain soymilk having a final solid content of 11.3%.

(3) Preparation of Tofu Groconodeltalactone (0.34% by mass with respect to soymilk) was added to each soymilk obtained in (2) above and coagulated to obtain tofu.

(4) Amino acid analysis The amino acid analysis of the tofu obtained above was performed under the following conditions to specify the amount of free amino acids. The results are shown in Table 1.
Equipment used: High Performance Liquid Chromatograph (UHPLC), Shimadzu Corporation Detector: Fluorescence Detector Column: "Inertil ODS-4 HP 3 μm" (100 mm L. x 3.0 mm ID), GL Sciences Column Temperature : 35 ° C
Composition of elution buffer: 15 mmol / L potassium dihydrogen phosphate, 5 mmol / L dipotassium hydrogen phosphate, water / acetonitrile / methanol = 15/45/40 (V / V / V)
Flow rate: 0 to 1.5 min 9.5%, 1.5 to 6.0 min 30%, 6.0 to 11.0 min 40%, 11.0 to 16.0 min 100%
Flow rate: 0.8 ml / min

As shown in Table 1, the tofu obtained from germinated soybean had a significantly higher amount of free amino acids than the tofu normally obtained from soybean.

The tofu obtained from germinated soybeans contained a large amount of glutamic acid, alanine, threonine, and serine, which could affect the taste, among the above free amino acids. Therefore, the tofu obtained from germinated soybeans was superior in taste to the tofu obtained from normal soybeans.

<Test 2: Peptide analysis of soybean raw material>
Peptide analysis of the soybean raw material used in Test 1 was performed under the following conditions. The result is shown in FIG.
Equipment used: High Performance Liquid Chromatograph (UHPLC), Shimadzu Corporation Detector: Fluorescence Detector Column: Product name "TSKgel G200SW 10 μm" (7.5 mm ID x 30 cm), Tosoh Column temperature: 25 ℃
Composition of elution buffer: 40% acetonitrile, 0.1% acetic acid Flow rate: 0.5 ml / min

In FIG. 1, the longer the elution time, the shorter the molecular weight. As shown in FIG. 1, germinated soybeans showed a maximum peak at an elution time of 24 to 28 minutes, and normal soybeans showed a maximum peak at an elution time of 22 to 28 minutes. For this reason, many peptides contained in germinated soybean had a smaller molecular weight than peptides normally contained in soybean.

Based on the results of FIG. 1, in FIG. 1, a peak fraction having an elution time of 24 to 28 minutes was extracted for germinated soybeans, and a peak fraction having an elution time of 22 to 28 minutes was extracted for normal soybeans, and electrophoresis was performed under the following conditions. Was done. The result is shown in FIG.

(Electrophoresis conditions)
All reagents used for polyacrylamide gel electrophoresis (SDS-PAGE) are manufactured by Wako Pure Chemical Industries.
The migration buffer was prepared as follows. Distilled water was added to 3 g of tris (hydroxymethyl) aminomethane, 14.4 g of glycine, and 1 g of sodium lauryl sulfate to make 1 L, and an electrophoresis buffer was obtained.
The sample addition solution was prepared as follows. Add distilled water to 1.0 M tris (hydroxymethyl) aminomethane pH 6.8 solution 0.5 ml, dithiothreitol 0.154 g, 10% sodium lauryl sulfate solution 2 ml, bulmuphenol blue 0.01 g, glycerol 1 ml to make 10 ml. , A sample addition solution was obtained.
100 mg of the sample was suspended in 1 ml of physiological saline and homogenized with an ultrasonic crusher (manufactured by Tomy Seiko Co., Ltd.). 1 μl of the sample addition solution was added to the homogenized 10 μl sample, and the mixture was kept warm at 95 ° C. for 10 minutes in an aluminum block constant temperature bath (manufactured by AS ONE Corporation). A gel having an acrylamide concentration of 12.5% was placed in a mini slab size electrophoresis device (manufactured by Atto Co., Ltd.), and an electrophoresis buffer was added to the anode and cathode sides. The warmed sample was subjected to an acrylamide gel, SDS-PAGE was performed at a constant voltage of 30 V, and the protein was stained with a 0.25% Coomassive brilliant blue solution to observe the migration results.

As shown in FIG. 2, in normal soybean, bands of a subunit, b subunit, and glucinin Acid subunit of β-conglycinin were clearly observed. On the other hand, in germinated soybean, these bands were not clearly observed, and it was found that the a subunit, b subunit, and glucinin Acidic subunit of β-conglycinin were partially decomposed.

<Test 3: Breaking stress test after heating>
The tofu produced in Test 1 was subjected to a heating test and a breaking stress test by the following methods. The result is shown in FIG.

(Heating test)
Each tofu was left to stand at 1 atm at 115 ° C. for 23 minutes in a state where the whole tofu was immersed in water and wrapped in a retort bag (made of nylon poly (NYPE)).

(Breakdown stress test)
Each tofu after the heating test was cut into a size of 10 mm × 10 mm × 10 mm and placed on a sample table. Next, using a creep meter physical property test system (model: RE2-3305B, manufactured by Yamaden Co., Ltd.), a plunger of φ30 mm from the top surface was inserted into the tofu placed on the sample table at a speed of 1.0 mm per second. The breaking load was measured by penetrating at a strain rate of 85%.

As shown in FIG. 3, the tofu obtained from germinated soybean showed a breaking point. On the other hand, the tofu normally obtained from soybeans collapsed as soon as an external force was applied and did not show a breaking point. In addition, the tofu normally obtained from soybean was sponged and no breaking stress was observed. From this, it was found that the tofu obtained from germinated soybean maintains the three-dimensional structure that affects the appearance and texture of the tofu even after heating.

<Test 4: Observation of tofu cross section>
The tofu produced in Test 1 was heated at 90 ° C. for 20 minutes, and then the cross section was observed by the following method. The results are shown in FIGS. 4 and 5. FIG. 4 shows the state of tofu (before cutting) after heating. The upper part (A) of FIG. 5 is the observation result of the cross section with the naked eye, and the lower part (B) is the observation result of the cross section by the electron microscope.

As shown in FIGS. 4 and 5, tofu normally obtained from soybeans showed porosity after heating. On the other hand, the tofu obtained from germinated soybeans did not show any porosity after heating, and a fine mesh structure was constructed.

<Test 5: Tofu heating test-1>
The tofu produced in Test 1 was filled in a container for retort pouch (made of nylon poly (NYPE)), heated at 110 ° C. to 121 ° C. for 7 minutes, and evaluated from each viewpoint according to the following criteria. The results are shown in Table 2.

(Evaluation criteria)
◎: Very good ○: Good △: Neither ×: Bad

As shown in Table 2, the tofu obtained from germinated soybean was superior to the tofu obtained from normal soybean in all aspects, not only in appearance and texture.

Although the data is not shown, when the mapo tofu was cooked and evaluated using the tofu prepared in Test 1, the same results as in Table 2 were obtained. Further, the same results as in Table 2 were obtained even after the mapo tofu cooked using the tofu prepared in Test 1 was packed in a pouch and sterilized by retort pouching and heated in a microwave oven or the like.

<Test 6: Various evaluations of tofu obtained from soymilk treated with proteolytic enzymes>
Two kinds of soymilk raw materials, that is, soymilk obtained from normal soybeans (commercially available) and soymilk obtained by subjecting the soymilk to enzyme treatment were prepared, and amino acid analysis of the tofu obtained from these soymilks was performed. ..

(1) Preparation of Proteolytic Enzyme Derived from Ginger Juice 200 g of ginger (raw twisted ginger) was crushed and squeezed to obtain ginger juice. The obtained ginger juice was centrifuged at 2000 rpm for 20 minutes, and the supernatant was filtered. To the filtrate, 473 μl of 0.1 mM mercaptopropionic acid and ascorbic acid (0.2% with respect to the filtrate) were added. Hereinafter, the obtained solution was used as a proteolytic enzyme derived from ginger juice. It is known that ginger juice contains proteolytic enzymes such as gingibain and cysteine protease.

(2) Enzyme treatment of soymilk Commercially available soymilk (Sujata solid content, 12%) was usually used as soymilk obtained from soybeans. 0.06 ml of a ginger juice-derived proteolytic enzyme was added to 60 ml of the soymilk, and the mixture was left in a constant temperature bath at 37 ° C. for 48 hours. Hereinafter, the soymilk obtained from this step is also referred to as "enzyme-treated soymilk".
In addition, 0.06 ml of sterilized distilled water was added to 60 ml of commercially available soymilk (Sujata solid content, 12%) as a target group, and the mixture was left in a constant temperature bath at 37 ° C. for 48 hours. Hereinafter, the soymilk obtained from this step is also referred to as "normal soymilk".
Both the enzyme-treated soymilk and the normal soymilk were adjusted with sterile distilled water so that the final solid content was 11.3%.

(3) Preparation of Tofu Groconodeltalactone (0.34% by mass with respect to soymilk) was added to each soymilk obtained in (2) above and coagulated to obtain tofu.

(4) Amino acid analysis The amino acid analysis of the tofu obtained above was performed under the following conditions to specify the amount of free amino acids. The results are shown in Table 3.
Equipment used: High Performance Liquid Chromatograph (UHPLC), Shimadzu Corporation Detector: Fluorescence Detector Column: "Inertil ODS-4 HP 3 μm" (100 mm L. x 3.0 mm ID), GL Sciences Column Temperature : 35 ° C
Composition of elution buffer: 15 mmol / L potassium dihydrogen phosphate, 5 mmol / L dipotassium hydrogen phosphate, water / acetonitrile / methanol = 15/45/40 (V / V / V)
Flow rate: 0 to 1.5 min 9.5%, 1.5 to 6.0 min 30%, 6.0 to 11.0 min 40%, 11.0 to 16.0 min 100%
Flow rate: 0.8 ml / min

As shown in Table 3, the tofu obtained from the enzyme-treated soymilk had a significantly higher amount of free amino acids than the tofu normally obtained from the soymilk.

<Test 7: Tofu heating test-2>
The tofu produced in Test 6 was filled in a container for retort pouch (made of nylon poly (NYPE)), heated at 110 ° C. to 121 ° C. for 7 minutes, and evaluated from each viewpoint according to the following criteria. The results are shown in Table 4 and FIG.

(Evaluation criteria)
◎: Very good ○: Good △: Neither ×: Bad

As shown in Table 4 and FIG. 6, the tofu obtained from the enzyme-treated soymilk had significantly suppressed the occurrence of porosity as compared with the tofu obtained from the normal soymilk.

Although the data is not shown, when the mapo tofu was cooked and evaluated using the tofu prepared in Test 1, the same results as in Table 2 were obtained. Further, even after the mapo tofu cooked using the tofu produced in Test 6 was pouch-packed and retort-sterilized and heated in a microwave oven or the like, the same results as in Table 4 and FIG. 6 were obtained. Was done.

Claims (9)

Tofu containing a peptide derived from soybean protein that shows a maximum peak at an elution time of 24 to 28 minutes in a peptide chromatograph obtained under the following conditions.
(Peptide chromatograph conditions)
Equipment used: High Performance Liquid Chromatograph (UHPLC), Shimadzu Corporation Detector: Fluorescence Detector Column: Product name "TSKgel G200SW 10 μm" (7.5 mm ID x 30 cm), Tosoh Column temperature: 25 ℃
Composition of elution buffer: 40% acetonitrile, 0.1% acetic acid Flow rate: 0.5 ml / min A tofu containing a partial decomposition product of a protein selected from the group consisting of the a subunit, b subunit, glucinin Acidic subunit, and glucinin Basic subunit of β-conglycinin. The tofu according to claim 1 or 2, wherein the total amount of free amino acids is 200 mg / 100 g or more and 10000 mg / 100 g or less. The tofu according to any one of claims 1 to 3, which is made from soymilk of germinated soybean and / or soymilk treated with a proteolytic enzyme. The tofu according to any one of claims 1 to 4, which contains gluconolactone in an amount of 0.10% by mass or more. Raw tofu showing a breaking point after the following heating test and breaking stress test.
(Heating test)
The tofu is soaked in water and wrapped in a retort pouch (made of nylon poly (NYPE)), and allowed to stand at 1 atm and 90 ° C. for 20 minutes.
(Fracture stress test)
The tofu after the heating test is cut into a size of 10 mm × 10 mm × 10 mm, and this is placed on a sample table. Next, using a creep meter physical property test system (model: RE2-3305B, manufactured by Yamaden Co., Ltd.), a plunger of φ30 mm from the top surface was inserted into the tofu placed on the sample table at a speed of 1.0 mm per second. The breaking load is measured by penetrating at a strain rate of 85%. Retort-sterilized tofu that shows the breaking point in the following breaking stress test.
(Fracture stress test)
Cut the tofu into a size of 10 mm × 10 mm × 10 mm and place it on the sample table. Next, using a creep meter physical property test system (model: RE2-3305B, manufactured by Yamaden Co., Ltd.), a plunger of φ30 mm from the top surface was inserted into the tofu placed on the sample table at a speed of 1.0 mm per second. The breaking load is measured by penetrating at a strain rate of 85%. A retort-sterilized food containing the tofu according to any one of claims 1 to 7. A method for suppressing tofu porosity using soymilk of germinated soybean and / or soymilk treated with proteolytic enzyme as a raw material.