Method for producing soy protein composition and soy protein composition

Abstract

The present invention provides a method for producing a soy protein composition, which can produce a protein composition having a high protein content from soybeans without using organic solvents or chemicals such as acids and alkalis, and the soy protein composition. [Solution] A method for producing a soy protein composition, comprising a soy milk separation step in which soybeans are squeezed and separated into soy milk and okara, an enzymatic hydrolysis step in which a protease is added to the soy milk to hydrolyze the proteins contained in the soy milk, and a fermentation step in which a sugar-utilizing microorganism is added to the soy milk to utilize the sugars contained in the soy milk.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a soy protein composition having a high soy protein content, which is made from soybeans as a raw material, and to the soy protein composition. [Background technology]

[0002] Conventional methods for producing soy protein using soybeans as a raw material include: (A) a method in which defatted soybeans are added with water and crushed to form a slurry, the slurry is centrifuged to separate and remove the okara, an acid is added to the resulting water-soluble fraction (defatted soy milk) to adjust the pH to the isoelectric point to precipitate the soy protein, the supernatant (soy whey) is separated and removed to obtain an acidic slurry, an alkali is added to this acidic slurry to neutralize it, and the slurry is dried by spray drying or the like; and (B) a method in which concentrated soy protein is extracted with water, the okara is removed, and the resulting soy protein solution is dried by spray drying or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2007 / 66694 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional methods for producing soy protein compositions, when producing a protein composition with a high soy protein content, it was necessary to defatt the soy protein using an organic solvent such as hexane, followed by chemical treatment using an acid or alkali. However, such methods use organic solvents, acids, alkalis, etc., which impose a high environmental burden and may leave chemical-derived components in the product. In recent years, there has been a widespread demand for active protein intake from the perspective of maintaining health, and there is a demand for methods for producing soy protein compositions with a high soy protein content that do not require these chemical treatments.

[0005] An object of the present invention is to provide a method for producing a soy protein composition, which can produce a protein composition having a high soy protein content from soybeans as a raw material without using organic solvents or chemicals such as acids and alkalis, and to provide the soy protein composition. [Means for solving the problem]

[0006] The present invention provides the following (1) to ( 6 The present invention relates to a method for producing a soy protein composition according to any one of the above. (1) Whole soybeans with the husk removed a soybean protein composition having a soy protein content of 80% by mass or more, the method comprising: a soy milk separation step of squeezing soybeans and separating the juice into soy milk and okara; an enzymatic hydrolysis step of adding a protease to the soy milk to hydrolyze the proteins contained in the soy milk; and a fermentation step of adding a sugar-assimilating microorganism to the soy milk to assimilate the sugars contained in the soy milk, the method further comprising a centrifugation step of centrifuging the soy milk after the enzymatic hydrolysis step and the fermentation step. ( 2 ) a solid-liquid separation step of centrifuging the soy milk after the enzymatic decomposition step or the fermentation step to separate it into a supernatant and a precipitate, and a step of obtaining soy protein from the supernatant, ) A method for producing the soy protein composition described above. ( 3 ) the soy milk after the enzymatic decomposition step or the fermentation step is adjusted to a pH of 6.0 or less, and then the solid-liquid separation step is carried out; 2 ) A method for producing the soy protein composition described in ( 4 ) the method further comprising the steps of: a squeezed juice producing step of squeezing the precipitate after the solid-liquid separation step to obtain a squeezed juice; a squeezed juice separating step of centrifuging the squeezed juice to separate it into a supernatant and a precipitate; and a step of obtaining soy protein from the supernatant obtained by centrifuging the squeezed juice. 2 ) A method for producing the soy protein composition described in ( 5 ) In the squeezed juice producing step, the okara is added to the sediment and squeezed. 4) A method for producing the soy protein composition described in ( 6 ) In the squeezed juice separation step, the pH of the squeezed juice is adjusted to 6.0 or less, and then the squeezed juice is separated into a supernatant and a precipitate. 4 ) The soy protein composition described in The present invention also provides the following ( 7) The present invention relates to a soy protein composition. ( 7 ) Soy milk made by squeezing the juice from whole soybeans with the husks removed Adding proteolytic enzymes The aforementioned A soy protein composition in which the protein contained in soy milk is enzymatically hydrolyzed to liberate and remove lipids from the protein, sugars contained in the soy milk are removed by adding a sugar-utilizing microorganism to utilize the sugars contained in the soy milk, and the soy milk is then centrifuged to have a soy protein content of 80% by mass or more. [Effects of the Invention]

[0007] According to the present invention, lipids and carbohydrates can be efficiently removed by enzymatically hydrolyzing and fermenting soy milk extracted from soybeans without using organic solvents or chemicals such as acids and alkalis, and a soy protein composition with a high soy protein content can be obtained. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a flowchart showing an example of producing a soy protein composition according to an embodiment of the present invention. [Figure 2] 1 is a flowchart showing another example of the production of a soy protein composition. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention relates to a method for producing a soy protein composition with a high soy protein content, using soybeans as a raw material, and to the soy protein composition. In particular, the method combines known food processing techniques, such as extraction and separation, with enzymatic hydrolysis and fermentation to remove fat, ash, and carbohydrates from raw soybeans, without using organic solvents such as hexane or chemicals such as acidic or alkaline chemicals, to produce a soy protein composition with a high concentration of soy protein. Furthermore, while the seed coat accounts for approximately 10% of the raw soybean material and is mostly composed of fiber (carbohydrates), the present invention removes approximately 10% of the carbohydrates from the raw material by dehulling during pretreatment, thereby increasing the protein concentration at the start of processing and enabling highly efficient recovery of soy protein. Below, an embodiment of the method for producing a soy protein composition according to the present invention is described.

[0010] The soy protein composition of this embodiment uses whole soybeans as a raw material. The whole soybeans used as a raw material are not particularly limited, and whole soybeans, full-fat soybeans, processed defatted soybeans, etc. can be used, but the following will be described using whole soybeans as an example of a raw material. The type of soybean is also not particularly limited, and white soybeans, yellow soybeans, mung soybeans, black soybeans, etc. can be used.

[0011] FIG. 1 is a flowchart showing an example of the production of a soy protein composition according to this embodiment. As shown in FIG. 1, in this embodiment, the raw material soybeans are first dehulled (step S101). There are a variety of products that use soybeans as a raw material, such as tofu, soy milk, natto, miso, soy sauce, and soybean oil, but dehulled soybeans are rarely used in these products. The method for dehulling soybeans is not particularly limited and can be appropriately selected from, for example, a method using a known dehulling device to rub soybeans against each other to dehull, a method using a roller or disc to apply friction to the surface of the soybeans to dehull, a method using a blade or roller rotating at high speed to dehull the soybeans against a wall, or other known methods. In this embodiment, a soy protein composition with a high protein content can be produced by producing a soy protein composition using dehulled soybeans in which the husks of soybeans, which contain almost no protein, have been removed.

[0012] Next, the dehulled soybeans are soaked in water or the like to absorb water (step S102). The temperature of the soaking water is not particularly limited, and water at room temperature or hot water may be used. The amount of water is preferably 2 to 3 times the total weight of the soybeans. The soaking time is also not particularly limited, and when water is used, the soybeans can be soaked for 2 to 24 hours, for example. Note that a pH adjuster such as sodium bicarbonate may be added to the soaking water as needed to improve the soybeans' water absorption.

[0013] The dehulled soybeans that have absorbed water are ground in a wet grinder to form a slurry (soybean soup), which is then squeezed out and separated into soy milk and okara (step S103). The crushing method is not particularly limited, and known wet grinders such as grinders, colloid mills, stone mills, disc mills, and homogenizers can be used. In this embodiment, the soybeans are crushed after absorbing water, but instead of this configuration, the soybeans can be crushed using a dry grinder such as a hammer mill before absorbing water, and the crushed soybeans can be allowed to absorb water.

[0014] Furthermore, the method of extracting juice after crushing soybeans to produce a slurry (soybean soup) is not particularly limited, and may be, for example, a method in which the slurry is filtered through a filter or cloth using a filtration-type juice extractor to separate the solid and liquid, a method in which the slurry is separated into solid and liquid using a decanter-type centrifuge, or a method in which the juice is extracted using a screw press or piston press. The slurry may be heated (for example, heated at 100°C for about 10 minutes) before juicing, but crushing and extracting the juice in an unheated state is preferable because this may cause protein denaturation. Furthermore, while the present embodiment has been described as an example of a method for producing soy milk from dehulled soybeans, the present invention is not limited to this method, and soybeans may also be crushed and extracted with the husks still attached, thereby separating the soybeans into soy milk and okara.

[0015] Next, an enzymatic hydrolysis treatment is performed to decompose the obtained soy milk with enzymes (step S104). Specifically, water is added to the soy milk separated in step S103, and proteolytic enzymes such as endoproteases, such as papain and pepsin, and / or exoproteases, such as aminopeptidase and carboxypeptidase, are added to the water-added soy milk. Endoproteases have high decomposition power, and exoproteases can improve taste. The enzymatic hydrolysis treatment separates soy protein and lipid, making it easier to remove the lipid. That is, in soy milk, soy protein and lipid form an emulsion, and it has been difficult to separate the soy protein and lipid by centrifugation alone. In this embodiment, the soy protein that forms an emulsion with lipid is enzymatically hydrolyzed, thereby demulsifying the emulsion of soy protein and lipid, and the soy protein and lipid can be separated by centrifugation, as described below.

[0016] The protease used in step S104 is not particularly limited, but a commercially available enzyme preparation for food use can be used. In addition to or instead of using a purified enzyme preparation, the soy milk can also be enzymatically hydrolyzed by adding foods such as enzymatically active mushrooms or fruits. The conditions for the enzymatic hydrolysis are not particularly limited, but the treatment can be carried out at a temperature appropriate for the enzyme used (for example, 45 to 55°C for papain) for 30 to 120 minutes.

[0017] After the enzymatic hydrolysis treatment, the soy milk is heated to inactivate the enzymes and sterilize the soy milk. The heating conditions are not particularly limited, and can be a temperature exceeding the inactivation temperature of the enzyme used or conditions that satisfy general food sterilization conditions. For example, the enzymes can be inactivated and the soy milk can be sterilized by heating at 90 to 100°C for 0 to 30 minutes.

[0018] Furthermore, in step S105, a process is carried out in which water-soluble carbohydrates in the soy milk are assimilated and removed using sugar-assimilating microorganisms. The sugar-assimilating microorganisms may be sugar-assimilating yeast or lactic acid bacteria that are generally used in food fermentation, and there are no particular restrictions on the type of microorganism.

[0019] Specifically, the sugar-utilizing yeast may be a bacterial species generally used in brewing or bread fermentation, such as yeasts such as Saccharomyces cerevisiae, Saccharomyces bayanus, Candida utilis, Kluyveromyces lactis, and Pichia pastoris, as well as commercially available brewer's yeast starters and dry baker's yeast.

[0020] Furthermore, as the sugar-utilizing lactic acid bacteria, species commonly used in the production of yogurt and cheese can be used, such as Lactobacillus casei, Lactobacillus plantarum, Lactobacillus helveticus, Lactobacillus bulgaricus, Lactobacillus gasseri, Lactobacillus acidophilus, Lactobacillus lactis, Lactobacillus salivarius, Lactobacillus gallinarum, Lactobacillus amylovorus, Lactobacillus brevis, Lactobacillus fermentum, Lactobacillus mali, Lactobacillus delbrueckii, Lactobacillus sanfranciscensis, Lactobacillus panis, Lactobacillus comensis, Lactobacillus italicus, Lactobacillus rhamnosus, Lactobacillus calvatus, and Lactobacillus Examples include the genus Lactobacillus such as Lactobacillus hilgardii, Lactobacillus reuteri, Lactobacillus pastorianus, Lactobacillus buchneri, Lactobacillus cellobiosus, and Lactobacillus fructivorans; the genus Streptococcus such as Streptococcus thermophilus, Streptococcus lactis, and Streptococcus diacetylactis; the genus Lactococcus such as Lactococcus lactis lactis and Lactococcus lactis cremoris; the genus Leuconostoc such as Leuconostoc mesenteroides cremoris and Leuconostoc lactis; and commercially available lactic acid bacteria starters.

[0021] These sugar-utilizing microorganisms may be used alone or in combination of two or more. Fermentation conditions are not particularly limited, and fermentation can be carried out at a temperature appropriate for each microorganism for the time required for the sugars to be consumed. For example, commercially available beer brewing yeast can be used for fermentation at 20 to 40°C for 12 to 48 hours. After fermentation is complete, the fermented liquid is heated to sterilize the sugar-utilizing microorganisms used in fermentation. The heating conditions are not particularly limited, as long as they are sterilization conditions for the sugar-utilizing microorganisms used. For example, heat sterilization can be carried out by heating at 90 to 100°C for 0 to 30 minutes.

[0022] In step S106, the soy milk fermented in step S105 is centrifuged to separate the soy milk into a supernatant containing soy protein and a precipitate containing lipids, fiber, and the cells of the sugar-utilizing microorganisms. The precipitate (lipids, fiber, and the cells of the sugar-utilizing microorganisms) is removed to obtain a supernatant containing soy protein. To separate the soy protein from the lipids, fiber, and sugar-utilizing microorganisms, the mixture is preferably centrifuged at a centrifugal force of 10,000 to 20,000 G, more preferably 12,000 to 18,000 G, and even more preferably 14,000 to 16,000 G.

[0023] Furthermore, it is preferable to adjust the pH of the soy milk before centrifuging. Specifically, the pH of the soy milk is preferably 4.0 or more and 6.0 or less, and more preferably 4.5 or more and 5.5 or less. This is because a pH below 4.0 results in a strong sour taste, impairing the flavor. Furthermore, a pH higher than 6.0 prevents good separation of soy protein and fat, making it impossible to obtain soy protein at a high concentration. The pH adjuster is not particularly limited, but it is preferable to use an edible agent such as fermented lactic acid or fruit juice. Furthermore, the centrifuge is not particularly limited as long as it is one commonly used in food processing, and the centrifugation conditions are also not particularly limited as long as they allow removal of lipids and fiber from the soy milk.

[0024] In addition, it is generally known that the isoelectric point of soy protein is around pH 5, and that soy protein tends to precipitate when the pH of soy milk containing soy protein is adjusted to 4.0 or higher and 6.0 or lower. However, in this embodiment, by reducing the molecular weight of soy protein through enzymatic hydrolysis, soy protein is less likely to precipitate even when the pH is adjusted to 4.0 or higher and 6.0 or lower, and soy protein can be recovered in a form contained in the supernatant after centrifugation (separated from precipitates such as fiber). Furthermore, when centrifugation is performed, a portion of the lipids contained in soy milk settles together with insoluble ash and carbohydrates (fiber), while the remainder separates as an oil layer above the supernatant containing soy protein. Therefore, in this embodiment, a three-phase separation centrifuge is used to recover the supernatant (middle layer) containing soy protein, thereby removing lipids, fiber, and cells of sugar-utilizing microorganisms.

[0025] In step S107, the supernatant containing soy protein obtained by centrifugation in step S106 is concentrated. The concentration method is not particularly limited, and a vacuum evaporation concentration device or a membrane concentration device commonly used in food applications can be used. The concentration is also not particularly limited, and any concentration suitable for the dryer in the subsequent drying step can be used. For example, the concentration can be 50% or less, preferably 40% or less, and more preferably 30 to 40% Brix.

[0026] In step S108, the supernatant liquid concentrated in step S107 is dried to powder the soy protein composition. The method for drying the supernatant liquid is not particularly limited, and a general food dryer such as a spray dryer, freeze dryer, or vacuum dryer can be used.

[0027] Thus, the method for producing a soy protein composition according to this embodiment uses whole soybeans as a raw material. Soy milk is prepared from dehulled soybeans. The soy milk is then hydrolyzed with a protease to separate the proteins from the lipids that form an emulsion. Finally, the soy milk is fermented with a sugar-assimilating microorganism to assimilate and remove the carbohydrates. This process removes the carbohydrates and lipids contained in the soy milk without the need for conventional chemicals such as organic solvents or acids and alkalis. This allows for the production of a soy protein composition with a high soy protein content of 80% by mass or more, preferably 83% by mass or more, and more preferably 85% by mass or more, which is environmentally friendly and healthy. Furthermore, because the soy protein in the soy protein composition according to this embodiment is hydrolyzed by the enzymatic hydrolysis process, the resulting soy protein composition has a high solubility in water and is easily digested and absorbed.

[0028] The content of soy protein in the soy protein composition can be measured by known methods such as the Kjeldahl method, combustion method, Biuret method, Bradford method, Lowry method, infrared spectroscopy, and mass spectrometry.

[0029] Fig. 2 is a flow chart showing another example of producing a soy protein composition. In the method of producing a soy protein composition shown in Fig. 2, steps S201 to S206 are the same as steps S101 to S106 shown in Fig. 1, and therefore a description thereof will be omitted. In the example shown in Fig. 2, in order to increase the total amount of the soy protein composition, the bean lees obtained in step S203 and the precipitate obtained in step S206 are squeezed again, and soy protein is also recovered from the squeezed juice.

[0030] Specifically, as shown in Fig. 2, in step S207, the precipitate (including lipids, fibers, etc.) obtained by centrifugation in step S206 is squeezed. In particular, in this embodiment, the bean curd refuse obtained by squeezing in step S203 is mixed with the precipitate obtained by centrifugation in step S206, and the mixture is squeezed using a screw press or the like to obtain squeezed juice. By adding the bean curd refuse in this way, the bean curd refuse functions as an adsorbent for lipids, further facilitating the separation of lipids.

[0031] In step S208, the squeezed juice obtained in step S207 is centrifuged. Specifically, in step S208, similar to step S206, in order to separate the protein from the lipids and fiber, the squeezed juice is centrifuged using a centrifuge at a centrifugal force of, for example, 10,000 to 20,000 G, thereby separating the squeezed juice into a supernatant containing soy protein and a precipitate containing lipids and fiber. Also in step S208, similar to step S206, it is preferable to adjust the pH of the squeezed juice obtained in step S207 to not less than 4.0 and not more than 6.0, more preferably not less than 4.5 and not more than 5.5, and then centrifugal separation is performed on the pH-adjusted squeezed juice.

[0032] In step S209, the supernatant obtained from the centrifugation in step S206 is blended with the supernatant obtained from the centrifugation in step S208. Then, in steps S210 and S211, similar to steps S107 and S108 shown in Fig. 1, the supernatants blended in step S209 are concentrated, and the concentrated supernatant is dried and powdered. This results in a powdered soy protein composition.

[0033] Thus, in the example shown in Figure 2, not only the supernatant obtained by centrifugation in step S206, but also the bean lees obtained in step S203 and the precipitate obtained in step S206 are squeezed again, and soy protein is recovered from the squeezed juice, making it possible to increase the total amount of soy protein composition more than in the example shown in Figure 1. However, because the soy protein content in the soy protein composition is higher in the example shown in Figure 1, it is also possible to switch production methods depending on the application. [Example]

[0034] Examples of the method for producing the soy protein composition according to the present invention will be described below.

[0035] (Test Example 1) In Test Example 1, whole soybeans were dehulled and then soaked overnight (approximately 15 hours) in 2-3 kg of water per 1 kg of dehulled whole soybeans to allow them to absorb water. The absorbed dehulled soybeans were then slurried in a mass colloidal wet grinder, and the slurry was then separated into soy milk and okara using a juice extractor (Yanagi Co., Ltd. Squeezer). Water was then added to the separated soy milk in an amount equal to or 1.5 times the amount of soy milk, followed by enzymatic hydrolysis with the addition of papain and exo-protease (Protease P6, Amano Enzyme). The enzymatic hydrolysis was carried out at 45-55°C for 60 minutes. After enzymatic hydrolysis, the soy milk containing the protease was heated at 90-100°C for 15 minutes to inactivate the protease, and then cooled.

[0036] Next, in Test Example 1, the pH of soy milk was adjusted, and the pH-adjusted soy milk was centrifuged to obtain a supernatant containing soy protein. This supernatant was then concentrated and dried to obtain a powdered soy protein composition. In Test Example 1, the Brix of the supernatant before concentration and the soy protein content in the soy protein composition after drying were measured. Table 1 below shows the measurement results of the pH of pH-adjusted soy milk after enzymatic hydrolysis (before centrifugation), the Brix of the supernatant after centrifugation, and the protein content after drying. In Test Example 1, the soy protein content in the soy protein composition was measured by the combustion method. In Test Example 1, the Brix of the supernatant was measured using a saccharometer (handheld refractometer).

[0037] [Table 1]

[0038] As shown in Table 1 above, in Example 1, the pH was 6.2, higher than 6, compared to Examples 2-4. In this case, the Brix of the supernatant was lower at 5.2% and the soy protein content after drying was also lower at 74.8% compared to Examples 2-4. In contrast, in Examples 2-4, the pH of the soy milk after pH adjustment was 6 or less. In this case, the Brix of the supernatant was higher at 5.8% and the soy protein content after drying was also higher at 80% or more compared to Example 1. In particular, in Examples 3 and 4, where the pH of the soy milk after pH adjustment was 5 or less, the soy protein content after drying was the highest at 81%. However, the protein composition of Example 4 had a strong sour taste and was less palatable than Example 3.

[0039] (Test Example 2) Furthermore, in Test Example 2, after enzymatic hydrolysis was carried out in the same manner as in Test Example 1, the soy milk was centrifuged to separate it into a supernatant (A) and a precipitate. The precipitate was then mixed with okara (soybean curd refuse) produced during the production of soy milk and squeezed to obtain a squeezed juice. The pH of the squeezed juice was then adjusted, and the pH-adjusted squeezed juice was centrifuged to obtain a supernatant (B) containing soy protein. Furthermore, the supernatants (A) and (B) were blended, and the blended supernatant (A+B) was concentrated and dried to obtain a powder. In Test Example 2, the Brix of the blended supernatant (A+B) before concentration and the soy protein content after drying were measured. Table 2 below shows the measurement results of the pH of the squeezed juice, the Brix of the supernatant before concentration, and the protein content of the soy protein composition after drying. In Test Example 2, as in Test Example 1, the soy protein content in the soy protein composition was measured by the combustion method, and the Brix of the supernatant was measured using a sugar content meter (handheld refractometer).

[0040] [Table 2]

[0041] As shown in Table 2 above, in Example 5, the pH was 6.2, higher than 6, compared to Examples 6-8. In this case, the Brix of the supernatant was lower at 5.4% and the soy protein content after drying was lower at 74.8% compared to Examples 6-8. In contrast, in Examples 6-8, the pH was 6 or less, and in this case, the Brix of the supernatant was higher at 6.0% and the soy protein content after drying was also higher at 80% or more compared to Example 5. In particular, in Examples 7 and 8, where the pH of the soy milk after pH adjustment was 5 or less, the soy protein content after drying was the highest at 81%. However, the protein composition of Example 8 had a strong sour taste and was less palatable than Example 7.

[0042] Furthermore, when Test Example 1 and Test Example 2 are compared, the protein content after drying was approximately the same in Test Example 1, in which soy protein was obtained only from the supernatant obtained by centrifuging the enzymatically hydrolyzed soy milk, and Test Example 2, in which soy protein was also obtained from the squeezed juice of the precipitate obtained by centrifuging the enzymatically hydrolyzed soy milk. This shows that soy protein compositions with approximately the same protein content can be produced by producing a soy protein composition using the method of Test Example 2 if you want to increase the total amount of soy protein, or by producing a soy protein composition using the method of Test Example 1 if you want to simplify the production process.

[0043] (Test Example 3) In Test Example 3, a test was conducted to determine whether a soybean protein composition having a soybean protein content of 85 mass % or more could be obtained by the method for producing a soybean protein composition according to this embodiment. Specifically, as in Test Example 1, enzymatic hydrolysis using a protease was carried out, followed by enzyme inactivation and cooling. The pH was then adjusted to 5.0, and the pH-adjusted soy milk was centrifuged at 15,000 G to obtain a supernatant (A) containing soy protein and a precipitate. As in Test Example 2, the supernatant (A) and the precipitate were separated, and the precipitate was mixed with okara (soybean curd refuse) generated during soy milk production, and squeezed to obtain a squeezed juice. The pH of the squeezed juice was then adjusted, and the squeezed juice adjusted to pH 5.0 was centrifuged to obtain a supernatant (B) containing soy protein. Furthermore, the supernatants (A) and (B) were blended, and a commercially available sugar-utilizing beer brewing yeast was added to the blended supernatant (A+B), followed by fermentation at 30°C for 16 hours. After fermentation, the soy milk to which the sugar-utilizing yeast had been added was sterilized by heating at 90°C for 30 minutes. The soy milk was then centrifuged at 15,000 G using a high-speed centrifuge to separate the soy milk into a supernatant containing soy protein and a precipitate containing lipids, fiber, and saccharifying microorganisms, and the supernatant containing soy protein was collected. The collected supernatant was then concentrated using a vacuum evaporator to a Brix of 40%, and the concentrate was then dried using a spray dryer to obtain a powdered protein composition.

[0044] The content of each component of the powdered soy protein composition obtained in Test Example 3 (hereinafter referred to as the soy protein composition of Example 9) was measured. Table 3 shows the content of each component of the soy protein composition of Example 9. Table 3 also shows the analysis results of each component of the whole soybeans used as the raw material for reference. Table 3 below shows the measurement results of the component contents (wt%) of the raw whole soybeans and the soy protein composition of Example 9. In Test Example 3, the soy protein content was measured by the combustion method, as in Test Example 1. [Table 3]

[0045] As shown in Table 3 above, the raw whole soybeans had a low soy protein content of 41.1%, but a low fat content of 21.7% and a high carbohydrate content of 23.0%, indicating a high fat and carbohydrate content. In contrast, the soy protein composition of Example 9 had a low fat content of 1.7% and a low carbohydrate content of 7.5%, resulting in a high soy protein content of 85.3% by mass, achieving a soy protein content of 85% by mass or more in the soy protein composition. Thus, the results of Test Example 3 demonstrated that a soy protein composition with a high soy protein concentration, with a soy protein content of 85.3% by mass, can be obtained by subjecting soymilk produced from dehulled whole soybeans to an enzymatic hydrolysis step in which a protease is added to degrade the proteins contained in the soymilk, and a fermentation step in which a sugar-assimilating microorganism is added to the soymilk to assimilate the carbohydrates contained in the soymilk.

[0046] As described above, the method for producing a soy protein composition according to this embodiment includes a soy milk separation step in which soybeans are squeezed and separated into soy milk and okara, an enzymatic hydrolysis step in which a protease is added to the soy milk to hydrolyze the proteins contained in the soy milk in order to increase the soy protein content, and a fermentation step in which a sugar-assimilating microorganism is added to the soy milk to hydrolyze the carbohydrates contained in the soy milk, thereby making it possible to obtain a soy protein composition with a high soy protein content of 80% by mass or more, preferably 83% by mass or more, and more preferably 85% by mass or more. In particular, the method for producing a soy protein composition according to this embodiment combines known food processing techniques such as extraction and separation with enzymatic hydrolysis and fermentation to remove fat, ash, and carbohydrates from raw soybeans, without using organic solvents such as hexane or chemicals such as acidic or alkaline chemicals, to obtain a soy protein composition with a high concentration of soy protein.

[0047] Furthermore, in this embodiment, the protein content of the soy protein composition can be further increased by using whole soybeans from which the soybean husks have been removed in the soy milk separation process. Specifically, the seed coats account for approximately 10% of the raw soybeans, and these seed coats are mostly composed of fiber (carbohydrates). In this embodiment, a pretreatment step of removing the seed coats from the raw soybeans removes approximately 10% of the carbohydrates from the raw soybeans from the beginning, thereby increasing the soy protein concentration in the raw material at the time of processing and enabling more efficient recovery of soy protein. Furthermore, in this embodiment, the protein content of the soy protein composition can be further increased by adjusting the soy milk after the enzymatic hydrolysis step or fermentation step to a pH of 6.0 or less before performing a solid-liquid separation step.

[0048] In addition, after the solid-liquid separation step, the precipitate obtained in the solid-liquid separation step is pressed to obtain a pressed juice, which is then centrifuged to separate it into a supernatant and a precipitate, and the supernatant is concentrated and / or dried, thereby increasing the total amount of the soy protein composition. Furthermore, when producing the pressed juice, the protein content of the soy protein composition can be further increased by adding okara to the precipitate and pressing it, or by adjusting the pH of the pressed juice to 6.0 or less and then separating the pressed juice into a supernatant and a precipitate.

[0049] Although the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the above-described embodiments. Various modifications and improvements can be made to the above-described embodiments, and such modifications and improvements are also included in the technical scope of the present invention.

Claims

1. A soy milk separation process in which whole soybeans with the soybean husks removed are squeezed and the juice is separated into soy milk and okara; an enzymatic degradation step of adding a protease to the soy milk to degrade proteins contained in the soy milk, and a fermentation step of adding a sugar-utilizing microorganism to the soy milk to utilize the carbohydrates contained in the soy milk, The method further comprises a centrifugation step of centrifuging the soy milk after the enzymatic decomposition step and the fermentation step. A method for producing a soy protein composition having a soy protein content of 80% by mass or more.

2. a solid-liquid separation step of centrifuging the soy milk after the enzymatic decomposition step or the fermentation step to separate it into a supernatant liquid and a precipitate; and obtaining soy protein from the supernatant.

3. 3. The method for producing a soy protein composition according to claim 2, wherein the soy milk after the enzymatic hydrolysis step or the fermentation step is adjusted to a pH of 6.0 or less before the solid-liquid separation step is carried out.

4. a squeezed juice producing step of squeezing the precipitate after the solid-liquid separation step to obtain a squeezed juice; a squeezed juice separation step of centrifuging the squeezed juice to separate it into a supernatant and a sediment; 3. The method for producing a soy protein composition according to claim 2, further comprising a step of obtaining soy protein from the supernatant separated in the squeezed juice separation step.

5. 5. The method for producing a soy protein composition according to claim 4, wherein the soybean lees are added to the sediment and pressed in the squeezed juice producing step.

6. 5. The method for producing a soy protein composition according to claim 4, wherein in the squeezed juice separation step, the pH of the squeezed juice is adjusted to 6.0 or less, and then the squeezed juice is separated into a supernatant and a sediment.

7. A soy protein composition having a soy protein content of 80% by mass or more, obtained by squeezing whole soybeans from which the husks have been removed and separating them into soy milk and okara, adding a proteolytic enzyme to enzymatically decompose the proteins contained in the soy milk to liberate and remove lipids from the proteins, adding a sugar-utilizing microorganism to utilize the carbohydrates contained in the soy milk to remove the carbohydrates, and then centrifuging the soy milk.

Images