Manufacturing method of packaged soybean rice

Abstract

To provide packaged soy rice in which aggregation due to pressurized heating treatment is suppressed so as to achieve excellent appearance and texture.SOLUTION: A method for producing packaged soy rice comprises a step for immersing soy rice in a soaking solution, a step for sealing the soaked soy rice and a filling liquid in a container, and a heating step for performing pressurized heating, wherein the pH values of the soaking solution and the filling liquid are 2.2 to 3.7, and the pH value of the packaged soy rice after the heating step is 5.3 to 6.7.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing retort-packaged soybean rice using artificial rice (soybean rice) made primarily from soybeans. [Background technology]

[0002] Rice, the staple food of the Japanese people, is relatively high in calories due to its high starch content. Therefore, patients with diseases such as obesity or diabetes may have to limit their rice intake, resulting in an increasing number of people who are unable to feel satisfied with their daily meals. Furthermore, in recent years, nutritional disorders associated with decreased food intake among the elderly, frailty (frailty), and muscle loss associated with aging (the onset of sarcopenia) have become problems, and the Ministry of Health, Labor, and Welfare's "Dietary Reference Intakes for Japanese (2020 Edition)" recommends consuming sufficient amounts of protein daily to prevent frailty in the elderly. Meanwhile, rice, the staple food of the Japanese people, is low in protein, and it is not possible to ingest the necessary protein from rice alone. Therefore, the applicant has proposed artificial rice (soybean rice), which is made primarily from soybeans, as an alternative to staple rice and is high in protein (Patent Document 1).

[0003] Soybean rice can be eaten by absorbing water in the same way as rice and then cooking it in a rice cooker or microwave oven, but for easier consumption, there is a demand for a form that can be eaten simply by reheating. Among cooked rice products, sealed cooked rice foods (packaged cooked rice) that can be eaten simply by reheating in a microwave or hot water and can be stored at room temperature for long periods are widely available as a convenient form of food. Known methods for producing this packaged cooked rice include a method in which cooked cooked rice is packed into a container in a sterile facility and then sealed (Patent Document 2), and a method in which rice and water are packed into a container, sealed, and then cooked and sterilized (Patent Document 3). However, there is no known method for producing artificial rice made primarily from soybeans that can be easily eaten and stored at room temperature for a long period of time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-82347 [Patent Document 2] Japanese Patent Application Publication No. 5-176696 [Patent Document 3] Japanese Patent Application Publication No. 9-149766 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a technology that can prevent soybean rice from sticking together in a retort-packaged product (hereinafter referred to as "packaged soybean rice") produced by sealing soybean rice soaked in water and water in a container and heating under pressure, as a form of soybean rice that can be easily eaten. Another object of the present invention is to provide packaged soybean rice that has an excellent appearance and texture by preventing sticking that occurs during the heating and pressurization treatment. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems and have found that the use of an acidic solution when soybean rice is soaked in water, and further using an acidic solution when the soybean rice and water are placed in a container and sealed after soaking, can prevent the binding of pressurized and heated packaged soybean rice. As a result, they have found that packaged soybean rice has excellent appearance and texture, and have completed the present invention.

[0007] The present invention was completed based on these findings and includes the following technical ideas. [1] A method for producing packaged soybean rice, comprising the steps of: a soaking step of soaking soybean rice in a soaking liquid; a packaging step of sealing the soybean rice after soaking and a filling liquid in a container; and a heating step of pressurizing and heating the soybean rice, wherein the pH of the soaking liquid and the filling liquid is 2.2 to 3.7, and the pH of the packaged soybean rice after the heating step is 5.3 to 6.7. [2] The method according to [1], which uses soybean rice obtained by a production method including a kneading step of adding water to raw materials containing soy flour, soy protein, and transglutaminase and kneading them together, a shaping step of extruding the kneaded mixture to obtain a rice-like product, and a drying step of heating and drying the rice-like product, wherein the temperature in the kneading step and the shaping step is 40°C or less, the temperature in the drying step is 30 to 100°C, and the raw materials are a mixture of soy flour and soy protein in a ratio of 30:70 to 90:10. [3] The manufacturing method described in [1] or [2], wherein the total amount of water absorbed by the soybean rice after soaking and the amount of the filling liquid is 1.5 to 2.8 parts by weight per 1 part by weight of the soybean rice. [4] The manufacturing method described in [3], wherein in the soaking step or the packaging step, a portion of the soybean rice is replaced with grain, and the dry weight ratio of the soybean rice to grain is 100:0 to 30:70. [5] The manufacturing method described in [2], wherein the soybean rice contains starch as a raw material. [Effects of the Invention]

[0008] According to the method of the present invention, an acidic solution is used when soybean rice is soaked in water, and an acidic solution is further used in the filling liquid when the soaked soybean rice and the filling liquid are sealed in a container. As a result, sticking of the packaged soybean rice caused by the pressurized heat treatment is suppressed, and packaged soybean rice with an excellent appearance and texture can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the embodiments of the present invention will be described, but the present invention is not limited to the following description.

[0010] In this specification, "soybean rice" refers to artificial rice made primarily from soybeans, which is formed into rice grains and dried, and has the following characteristics (a), (b), or (c). (i) Soybean rice obtained by a production method comprising: a kneading step of adding water to and kneading raw materials containing soy flour, soy protein, and transglutaminase; a shaping step of extruding the kneaded mixture to obtain a rice-like product; and a drying step of heating and drying the rice-like product, wherein the temperature in the kneading step and the shaping step is 40°C or less, the temperature in the drying step is 30 to 100°C, and the raw materials are a mixture of soy flour and soy protein in a ratio of 30:70 to 90:10. (ii) Soybean rice obtained by the manufacturing method described in (i), wherein the raw material contains soybean flour and soybean protein in total as solids of 50 parts by weight or more per 100 parts by weight of the total raw material solids. (C) Soybean rice obtained by the manufacturing method described in (A) or (B), in which the raw material contains starch.

[0011] (I) Soybean rice production method First, the method for producing soybean rice will be described in detail. (soybean flour) The soybean flour used for soybean rice can be any ordinary soybean flour. Specifically, for example, it is prepared by crushing dehulled soybeans, appropriately heating them, and drying them. From the viewpoint of flavor, such as the unpleasant odor and taste characteristic of soybeans, it is preferable to use soybean flour in which enzyme activity such as lipoxygenase has been inactivated by heat treatment. The soybean raw material used for the soybean flour is not particularly limited, and whole soybeans, dehulled soybeans, cracked soybeans, etc. can be used. The type of soybean used for the soybean flour is not particularly limited and may be selected depending on the desired flavor, such as yellow soybeans, white soybeans, green soybeans, black soybeans, and kurakake soybeans. For example, from the viewpoint of color tone, white soybeans and yellow soybeans are preferred when a color tone similar to that of white rice is desired. Soybean flour is processed, for example, by dehulling soybeans, heating them, grinding them, and drying them. The heat treatment may be performed before, after, or after the dehulling process, or after the grinding process, and is not particularly limited. If pre-dehulled soybeans are used, the dehulling process is not necessary. The soybean dehulling treatment is not particularly limited, and any commonly used known method may be used. Specific examples include grinding, dry crushing, dry dehulling using a millstone, polishing, and flash heating, and may be carried out using a commercially available dehulling machine. When a heating method is used, the activity of enzymes such as lipoxygenase can be inactivated or suppressed by heating at the same time as the dehulling treatment. The heat treatment of soybeans is not particularly limited as long as it can inactivate or suppress the activity of enzymes such as lipoxygenase by heating, and any commonly used known method may be used. The heating method may be either dry heating or wet heating, and examples of dry heating include roasting and heating with hot air. The soybean grinding process is not particularly limited, and any commonly used known method may be used. Examples of grinding methods include dry grinding, wet grinding, and freeze grinding, and the grinding may be carried out using a commercially available grinder. The particle size of the resulting soybean flour is, for example, 100 μm or less, preferably 25 μm or less. From the viewpoint of improving the texture of the final soybean rice, a smaller particle size of the soybean flour is preferable. The amount of soybean flour used can be adjusted depending on the desired texture, flavor, and moldability of the soybean rice, and soybean rice with excellent taste, flavor, and texture can be obtained by adjusting the mixing ratio with the soybean protein described below.

[0012] (soy protein) The soybean protein used in soybean rice is not particularly limited, and for example, either isolated soybean protein or concentrated soybean protein can be used, or a combination of these can be used. Soy protein isolate is obtained by removing non-protein compounds from defatted soybeans, for example, by purifying the protein content to about 90% or more on a dry matter basis. Examples of soy protein isolates that can be used include commercially available products and those prepared using soy protein as a raw material. Soy protein concentrate is obtained by removing most of the fats and oils and water-soluble non-protein compounds from defatted soybeans, for example, by purifying the protein content to about 70% or more on a dry matter basis. Concentrated soy protein can be, for example, a commercially available product or one prepared using soy protein as a raw material. Soy protein can be in various forms, such as powder, granules, or fiber, but the soy protein used in soy rice is powder. Using granular or fibrous soy protein is undesirable because it results in uneven texture and appearance of the soy rice. The amount of soy protein used can be adjusted depending on the desired texture, flavor, and moldability of the soy rice, and soy rice with excellent taste, flavor, and texture can be obtained by adjusting the mixing ratio with the soy flour described above.

[0013] (mixture ratio of soy flour and soy protein) The mixing ratio of soy flour and soy protein can be adjusted depending on the texture, flavor, and moldability of the desired soy rice. When the auxiliary ingredients described below are not used, the mixing ratio of soy flour and soy protein in the raw material is preferably adjusted to a range of 30 parts by weight:70 to 90 parts by weight:10 parts by weight relative to the total raw material solids, as this provides good moldability. A more preferable ratio is 30 parts by weight:70 to 50 parts by weight:50 parts by weight, as this provides a better texture. If the mixing ratio of soy flour and soy protein is 25 parts by weight or less relative to the total raw material solids, the kneaded product obtained by mixing and kneading the soy flour and soy protein will not be sticky, and will not be able to be molded in the process of extruding the kneaded product to obtain a rice-like product, as described below, and this is unsuitable. Furthermore, if the amount of soybean flour exceeds 90 parts by weight relative to the total raw material solid content, the kneaded mixture will be too sticky, and the rice-shaped products extruded from the kneaded mixture will not break apart but will stick together, resulting in molding defects, making this unsuitable.

[0014] (Transglutaminase) The action of the transglutaminase used in soybean rice is to catalyze the formation of cross-links between glutamic acid residues and lysine residues through isopeptide bonds in the proteins contained in the soybean flour and soybean protein mentioned above, thereby polymerizing them and giving the proteins elasticity. The transglutaminase used for soybean rice may be any conventionally known transglutaminase, whether commercially available or prepared by a unique method. Examples include Activa TG-H, Activa TG-K, Activa TG-M, Activa TG-AK, Activa TG-B, and Activa TG-S (all manufactured by Ajinomoto Co., Inc.). These transglutaminases may be used alone or in combination of two or more. The amount of transglutaminase used can be adjusted depending on the desired texture of the soybean rice, and is not particularly limited. For example, 0.005 to 1.0 parts by weight may be used relative to the total solid content of the raw materials, and preferably 0.01 to 0.2 parts by weight can be added and used to impart elasticity to the texture of the soybean rice.

[0015] (auxiliary raw materials) The auxiliary ingredients used in soybean rice are not essential but can be used as appropriate for the purpose of improving the texture, flavor, moldability, and storage stability of the target soybean rice. The raw materials used as the auxiliary ingredients are not particularly limited, but starches such as rice flour and modified starch, thickening polysaccharides such as alginic acid, sugars other than starches such as monosaccharides and dextrin, and dietary fiber materials such as cellulose can be used.

[0016] (Starches) Although the starches used in soybean rice are not essential, their use can impart the soybean rice with the flavor and texture characteristic of cooked rice. The starches are not particularly limited in terms of their raw material or type, and examples thereof include grain starches such as rice flour, glutinous rice flour, corn starch, waxy corn starch, potato starch, sweet potato starch, tapioca starch, and cassava starch, and processed starches such as highly branched cyclic dextrin, heat-moisture treated starch, hydroxypropyl starch, starch acetate, hydroxyalkyl starch, and phosphate cross-linked starch, and at least one of these can be used as needed. The amount of starch used is not particularly limited, but if the flavor of cooked rice is particularly preferred, soybean rice with a flavor unique to cooked rice can be obtained by containing 3 parts by weight or more, preferably 5 parts by weight or more, and more preferably 10 parts by weight or more of starch relative to the total solid content of the raw material.

[0017] (Thickening polysaccharides) The thickening polysaccharide is not particularly limited, and examples thereof include sodium alginate, propylene glycol alginate, gum arabic, arabinogalactan, alginic acid, gum ghatti, curdlan, carrageenan, glucomannan, furcellaran, karaya gum, locust bean gum, xanthan gum, gellan gum, native gellan gum, guar gum, psyllium seed gum, tamarind seed gum, tara gum, tragacanth gum, pectin, pullulan, welan gum, cassia gum, gelatin, agar, etc. The use of thickening polysaccharides can impart elasticity and stickiness to the texture of soybean rice and improve its water retention.

[0018] (Dietary fiber material) Examples of dietary fiber materials include cellulose, polydextrose, indigestible dextrin, enzymatic hydrolyzate of guar gum, low-molecular-weight sodium alginate, psyllium husk, inulin, water-soluble soybean polysaccharides, gum arabic, corn fiber, etc. The use of dietary fiber materials can impart elasticity and stickiness to the texture of soybean rice and improve its water retention and flavor.

[0019] (Sugars other than starches) As the sugars other than starches, any sugars available for food can be used, including, for example, reduced starch syrups such as glucose, fructose, galactose, mannose, maltose, lactose, sucrose, trehalose, maltitol, and sorbitol. These sugars can impart effects such as making the soybean rice fluffy when cooked and when left for a while after cooking, as well as the effect of inhibiting protein hardening and starch retrogradation.

[0020] Soybean rice is made by kneading soy flour, soy protein, and transglutaminase with water, forming them into a rice-like product, and then heating and drying it to activate the transglutaminase, allowing it to act on the protein.

[0021] (Kneading process) First, the main ingredients, soy flour and soy protein, are uniformly mixed. If a secondary ingredient is used, it is mixed at the same time as the main ingredient. Next, transglutaminase is dissolved in cold water, and the solution and the powder mixture are mixed and kneaded. In the kneading step, the amount of water added during kneading can be set as appropriate. For example, when the total weight of the ingredients including water is 100 parts by weight, water is preferably added in the range of 30 to 60 parts by weight, more preferably 45 to 55 parts by weight. If the amount of water added is too high or too low, molding defects will occur in the molding step described below, and the desired rice-like product will not be obtained. Furthermore, if the amount of water added is too low, transglutaminase will not be able to act sufficiently in the drying step described below, and a desirable texture will not be obtained. The kneading step is carried out under conditions where the product temperature of the kneaded product is 40° C. or less so as not to accelerate the reaction between transglutaminase and protein. It is preferable that the main raw materials and auxiliary raw materials to be used as raw materials are cooled in a refrigerator in advance. The kneading method may be any method as long as the raw materials can be mixed uniformly, and the type of kneader is not particularly limited, but it is preferable to use a kneader equipped with a cooling chiller.

[0022] (molding process) The kneaded material obtained in the kneading step is fed to a screw extruder, and while being further kneaded, it is extruded and cut through a die attached to the tip of the extruder to form rice grain-like shapes. In this step, the kneaded material is compressed and extruded, thereby obtaining rice-like products with a dense structure. The type of extruder used for forming is not particularly limited, but a squeezer or extruder can be used, and preferably one equipped with a cooling chiller is preferred. The forming process is carried out under conditions where the temperature of the rice-shaped product is 40°C or less in order to avoid accelerating the reaction between transglutaminase and protein. If the temperature of the kneaded product exceeds 40°C during the preceding kneading and shaping processes, the activation of transglutaminase in the kneaded product will be accelerated, and the structured product will collapse upon extrusion, resulting in a decrease in the shape retention of the resulting rice-like product and the generation of many cracks and scraps. Furthermore, soybean rice will be imparted with excessive elasticity, making it impossible to obtain a desirable texture.

[0023] (drying process) The rice-like formed product obtained in the forming process is dried at 100°C or less, which simultaneously enhances the activation of transglutaminase, and as the drying progresses, the rice-like formed product is dried to a predetermined dry state, while simultaneously deactivating or inactivating the transglutaminase. In the drying process, drying at 100°C or below not only produces a product with good color tone with little discoloration, but also enhances the reaction between transglutaminase and protein, which causes the proteins in the rice-like product to cross-link with each other and become polymerized, giving the soybean rice appropriate elasticity and improved shape retention, resulting in soybean rice with excellent texture and cooking resistance. The temperature in the drying step is 100°C or less, preferably 50 to 100°C, and drying for 30 to 210 minutes. More preferably, drying is performed at 60 to 90°C and for 35 to 90 minutes. This not only provides a product with good texture and color, but also has high drying efficiency and a short drying time, making it highly productive. While the lower limit temperature is not particularly limited, drying at a low temperature is not preferred because it results in poor drying efficiency and takes a long drying time. The predetermined dry state is preferably a moisture content of 12% by weight or less, more preferably 10% by weight or less, and even more preferably 8% by weight or less, which is preferable because reducing the moisture content can prevent deterioration and browning caused by microorganisms during storage. The dryer to be used is not particularly limited, but a hot air band dryer, a hot air flow dryer, a hot air shelf dryer, or the like can be used.

[0024] Thus, by the above method, it is possible to produce soybean rice that can be used as a substitute for cooked rice, which retains the shape of the rice grains without falling apart during cooking, has a hard and elastic texture similar to cooked rice, is high in protein and low in carbohydrates, and has excellent taste, flavor, and texture.

[0025] (II) Manufacturing method of packaged soybean rice Next, a method for producing packaged soybean rice using the soybean rice obtained above, which can be easily eaten and stored at room temperature for a long period of time, will be described in detail. (Soaking process) In the soaking process, the soybean rice is soaked in a soaking solution with an acidic pH to absorb the soaking solution. After soaking, the soybean rice is drained using a colander or the like to obtain soaked soybean rice.

[0026] The soaking solution is prepared by dissolving an acid in water to adjust the pH to an acidic level. The soaking solution can be appropriately adjusted to a pH range of 2.2 to 3.7 so that the pH of the packaged soybean rice is 5.3 to 6.7. For example, when adjusting the soaking solution to a pH of 3.5 using 10% (w / v) acetic acid (pH 2.3), 99 parts by weight of water can be added to 1 part by weight of 10% (w / v) acetic acid. If the pH of the soaking solution is lower than 2.2, the amount of water absorbed by the soybean rice decreases, resulting in a hard texture of the packaged soybean rice. If the pH of the soaking solution is higher than 3.7, the effect of inhibiting adhesion is weakened.

[0027] The acid used in the soaking solution may be any organic acid, inorganic acid, or salt thereof used in the food industry, and these acids may be synthetic, natural, or fermentation-produced acids, or may be salts of these acids or a combination of two or more acids. Examples of organic acids that may be used include acetic acid, gluconic acid, citric acid, lactic acid, fumaric acid, malic acid, and ascorbic acid, and examples of inorganic acids that may be used include phosphoric acid and hydrochloric acid.

[0028] The amount of water absorbed by the soaking liquid in the soaking step can be adjusted appropriately within the range of 0.8 to 1.2 parts by weight per 1 part by weight of soybean rice. The amount of soaking liquid is sufficient as long as it is 1.2 parts by weight or more per 1 part by weight of soybean rice, and may be adjusted to, for example, 2 to 5 parts by weight. The soaking time is sufficient as long as it is 30 minutes or more when the temperature of the soaking liquid is 15°C.

[0029] (packaging process) In the packaging step, the soaked soybean rice obtained in the soaking step and the filling solution having an acidic pH are placed in a heat-resistant plastic container and then sealed.

[0030] The filling liquid is prepared by dissolving an acid in water to adjust the pH to an acidic level. The pH of the filling liquid can be appropriately adjusted within the range of 2.2 to 3.7 so that the pH of the packaged soybean rice is 5.3 to 6.7. For example, when adjusting the filling liquid to pH 3.5 using 10% (w / v) acetic acid (pH 2.3), 99 parts by weight of water can be added to 1 part by weight of 10% (w / v) acetic acid. If the pH of the filling liquid is lower than 2.2, the amount of water absorbed by the soybean rice after soaking in the heating step described below will decrease, resulting in a hard texture. If the pH is higher than 3.7, the effect of inhibiting adhesion will be weakened. The pH of the filling liquid may be different from the pH of the soaking liquid.

[0031] The acid used in the filling solution may be any organic acid, inorganic acid, or salt thereof used in the food industry, and these acids may be synthetic, natural, or fermentation-produced acids, or may be salts of these acids or a combination of two or more acids. Examples of organic acids that may be used include acetic acid, gluconic acid, citric acid, lactic acid, fumaric acid, malic acid, and ascorbic acid, while examples of inorganic acids include phosphoric acid and hydrochloric acid. The acid used in the filling solution may be different from the acid used in the soaking solution.

[0032] The amount of the filling liquid is the sum of the amount of soaking liquid absorbed by the soybean rice after soaking in the soaking step (hereinafter referred to as "amount of water absorbed by the soybean rice after soaking") and the amount of the filling liquid (hereinafter referred to as "total liquid amount"), and can be adjusted so that the total liquid amount is in the range of 1.5 to 2.8 parts by weight per part by weight of soybean rice, but from the viewpoint of texture, it is preferable to adjust it in the range of 2.0 to 2.7 parts by weight. If the total liquid amount is less than 1.5 parts by weight, the texture of the packaged soybean rice becomes hard. If the total liquid amount is more than 2.8 parts by weight, the soybean rice after soaking cannot absorb the entire amount of the filling liquid, and the appearance and texture of the packaged soybean rice are significantly inferior.

[0033] (Heating process) In the heating step, the soybean rice sealed in the packaging step is subjected to a pressure heating treatment, thereby cooking the soybean rice and ensuring its shelf life at room temperature. The heating step imparts a desirable flavor, texture, and shelf life to the soybean rice, thereby completing the packaged soybean rice of the present invention with reduced sticking.

[0034] The heating temperature and time can be adjusted as appropriate as long as the soybean rice is cooked and sterilized under conditions that result in an F value of 4 or higher. For example, the heating temperature and time can be adjusted to 105°C to 130°C and 20 to 120 minutes, depending on the content volume of the packaged soybean rice in the final product and the amount of sterilization treatment.

[0035] (grain) In the present invention, the soybean rice can be partially replaced with grains such as rice during the soaking or packaging process. The dry weight ratio of soybean rice to grains is, for example, in the range of 100:0 to 30:70. The grains may be mixed in dry form or may be pre-absorbed. The amount of filling liquid can be adjusted appropriately depending on the type of grain used, the amount added, and whether or not it has absorbed water. Grains that can be used include rice, brown rice, barley, Job's tears, oats, glutinous barley, black rice, red rice, millet, foxtail millet, and barnyard millet, and a combination of multiple grains may also be used. When using grains, the amount of water required for normal rice cooking of the grain to be used can be confirmed in advance to determine the amount of filler liquid required for the grain to be mixed. For example, when using white rice, the amount of water required for cooking can be adjusted to the desired firmness, and can be appropriately adjusted within the range of 1.0 to 1.5 parts by weight per 1 part by weight of white rice. When 1 part by weight of white rice is soaked for 1 hour, the amount of water absorbed by the white rice is approximately 0.2 to 0.25 parts by weight. Therefore, when mixing white rice (dry), the amount of filler liquid should be approximately 1.0 to 1.5 times the amount of white rice, and when mixing soaked white rice, the amount of filler liquid should be approximately 0.75 to 1.3 times the amount of white rice. Furthermore, when brown rice is used, the amount of water required to cook 1 part by weight of brown rice can be adjusted to the desired firmness, and can be appropriately adjusted within the range of 1.0 to 2.0 parts by weight per 1 part by weight of brown rice. Since the amount of water absorbed by brown rice when 1 part by weight of brown rice is soaked for 5 hours is approximately 0.2 to 0.25 parts by weight, when mixing brown rice (dried), the amount of filler liquid should be approximately 1.0 to 2.0 times the amount of brown rice, and when mixing soaked brown rice, the amount of filler liquid should be approximately 0.75 to 1.8 times the amount of white rice.

[0036] Thus, the manufacturing method of the present invention can provide packaged soybean rice that has excellent appearance and texture by suppressing the adhesion that occurs when heated under pressure. [Example]

[0037] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, the following examples were carried out at room temperature (25°C ± 5°C) and atmospheric pressure. Unless otherwise specified, % described below means "% by weight."

[0038] (1) Soybean rice manufacturing method An example of a method for producing soybean rice used in the present invention will be described below.

[0039] <Examples 1 and 2, Comparative Examples 1 to 3> The following examples and comparative examples were carried out using the following raw materials and conditions unless otherwise specified. (Soybean rice production) First, the manufacturing method of Example 1 will be described below. The raw materials used were soybean flour, powdered soybean protein (isolated soybean protein, manufactured by Fuji Oil Co., Ltd.), and transglutaminase (manufactured by Ajinomoto Co., Inc.). Soybean flour was prepared by heating whole soybeans (Toyomasari soybeans from Hokkaido) in hot air at 115°C for 20 minutes, then dehulling the soybeans with a dehuller and grinding them with a grinder. The average particle size of the resulting soybean flour was 20-30µm. Next, 2000 g of soy flour and 2750 g of soy protein that had been refrigerated below 10°C were mixed together, and then 1 g of transglutaminase was dissolved in 5249 g of water at 10°C, and these were mixed and kneaded uniformly to obtain a kneaded mixture. At this time, the product temperature of the kneaded mixture was below 20°C. The kneaded mixture was then fed into a screw-type extruder equipped with a die at the end, and extruded while circulating chilled water (10°C) in the outer jacket of the extruder rotor. Simultaneously, the mixture was cut into rice-shaped extrusions. The product temperature of the rice-shaped extrusions was below 25°C. The size of the rice-shaped extrusions was adjusted to 7 mm in length, 2 mm in width, and 2-3 mm in thickness. The rice-like shaped product was then fed into a steam convection oven (Fujimak Co., Ltd., product number FCCM6) and dried on a hot air rack without humidification at 80°C (the oven's set temperature) for 45 minutes, then transferred to a tray and air-cooled to 35°C or below to obtain soybean rice. The moisture content of the obtained soybean rice was 10% to 14%. In Example 2, the same procedure as in Example 1 was carried out except that the raw soy protein was changed from isolated soy protein to concentrated soy protein (manufactured by Matsuda Sangyo Co., Ltd.), and a sample of Example 2 was obtained. As comparative examples, those using transglutaminase were prepared using only soy flour as the raw material (Comparative Example 1), those using only soy protein (Comparative Example 2), and those not using transglutaminase were prepared using soy flour and soy protein (Comparative Example 3). These were all prepared in the same manner as in Example 1 except for the raw materials.

[0040] (Cooked soybean rice) 400 g of water was added to 200 g of the soybean rice obtained in the Examples and Comparative Examples, and the rice was cooked in a rice cooker in the usual manner. After stirring well with a rice scoop, the rice was steamed in the rice cooker for 10 minutes.

[0041] (Evaluation of soybean rice) The soybean rice obtained in the Examples and Comparative Examples was evaluated for its formability during production and for its sensory evaluation (texture, appearance, taste, and flavor) after cooking. The sensory evaluation was conducted by five trained panelists who tasted the rice and evaluated it according to the following criteria, and the results were compiled. In the sensory evaluation, rice that was not cooked due to poor forming was marked with "-". The results are shown in Table 1. [Evaluation criteria for formability] ◎: The grain surface is smooth and can be molded without crumbling or cracking. ○: No crumbling or cracking and can be molded. △: It crumbles a little, but can be molded. ×: Unable to mold, or many crumbles and cracks. [Evaluation criteria for sensory evaluation] (Texture) ◎: It has a texture similar to cooked rice and is delicious. ○: The texture is decent and it's delicious. △: The texture is slightly bad and the taste is inferior. ×: The texture is bad and it's not tasty. (Appearance) 〇: Little discoloration, crumbling, or sticking, and looks good. △: There is a problem with either discoloration, crumbling during cooking, or adhesion, and the appearance is poor. ×: There are many problems with either discoloration, crumbling during cooking, or adhesion, and the appearance is poor. (Taste / Flavor) 〇: No burnt or bitter taste, with a delicious soybean flavor. △: Slightly burnt or bitter, or has little soybean flavor and is inferior in flavor. ×: Burnt, bitter and not tasty.

[0042] [Table 1] TIFF0007760564000001.tif72167

[0043] The results in Table 1 show that when soy flour was used alone without soy protein (Comparative Example 1), the dough was too sticky and poorly molded, while when soy protein was used alone without soy flour (Comparative Example 2), the dough was not sticky and could not be molded because it did not hold together. Furthermore, when transglutaminase was not used (Comparative Example 3), the rice was easily molded, but gelation occurred during cooking, resulting in poor texture and appearance. These results demonstrate that soy flour, soy protein, and transglutaminase are essential ingredients for the soy rice used in this invention. Although the stickiness and adhesiveness differ depending on the type of soy protein, both the isolated soy protein (Example 1) and the concentrated soy protein (Example 2) were able to provide a good texture.

[0044] <Example 1, Comparative Example 4>: Examination of the enzyme reaction process of soybean rice A test was conducted in which transglutaminase was activated and allowed to act in the kneading process of Example 1. Specifically, 2000 g of soy flour stored at room temperature and 2750 g of soy protein were powder-mixed, and then 1 g of transglutaminase was dissolved in 5249 g of water at 50°C, and these were mixed and kneaded uniformly. The product temperature immediately after kneading was 40°C. The kneaded product was placed in a bag, sealed, placed in an incubator, and maintained at 40°C for 1 hour. It was then fed to an extruder and dried to obtain a soybean rice sample of Comparative Example 4. The molding and drying processes were carried out under the same conditions as in Example 1. The results are shown in Table 2.

[0045] [Table 2] TIFF0007760564000002.tif46125

[0046] The results in Table 2 show that when transglutaminase was activated and allowed to act in the kneading process (Comparative Example 4), the rice-like shaped products crumbled and cracked, and the quality after cooking was also affected by the loss of shape and poor texture. This demonstrates that it is essential to activate and allow transglutaminase to act in the drying process for the soybean rice used in the present invention.

[0047] <Examples 3 and 4, Comparative Examples 5 and 6>: Examination of temperature conditions in the kneading and molding processes of soybean rice The temperature conditions of the kneaded product from the kneading process to the molding process were examined to determine the moldability of the rice-like shaped product. Specifically, the temperature of the water added was adjusted so that the product temperature from the kneading process to the molding process was 25°C (Example 3), 40°C (Example 4), 45°C (Comparative Example 5), or 50°C (Comparative Example 6). The process was completed within 20 minutes from the start of kneading to the end of molding, and the resulting granular shaped product was dried to obtain each soybean rice sample. The same procedures as in Example 1 were carried out except for the temperature conditions from the kneading process to the molding process. The results are shown in Table 3.

[0048] [Table 3] TIFF0007760564000003.tif46150

[0049] The results in Table 3 show that when the product temperature from the kneading process to the molding process was 40°C or higher (Example 4, Comparative Examples 5 and 6), the rice-like shaped product crumbled slightly, reducing moldability and resulting in a poor texture and appearance after cooking. In particular, when the product temperature was 45°C or higher (Comparative Examples 5 and 6), the transglutaminase was excessively activated and acted upon, resulting in the soybean rice being too elastic after cooking, resulting in a poor texture. These results demonstrate that for the soybean rice used in the present invention, it is essential to maintain the product temperature of the kneaded product from the kneading process to the molding process at 40°C or lower.

[0050] <Example 1, Comparative Example 7>: Examination of the necessity of drying treatment of soybean rice A test was conducted in which transglutaminase was activated and allowed to act on the rice without heat drying in the drying step of Example 1. Specifically, the rice-like product obtained after the molding step was placed in a bag, sealed, and then placed in an incubator. After the product temperature reached 55°C, the bag was maintained for 60 minutes to activate and allow transglutaminase to act on the rice, yielding a soybean rice sample of Comparative Example 7. The conditions for the kneading and molding steps were the same as those for Example 1. The results are shown in Table 4.

[0051] [Table 4] TIFF0007760564000004.tif40116

[0052] The results in Table 4 show that when no drying treatment was performed (Comparative Example 7), the quality of the cooked rice was somewhat high in cracks and had a crumbly, brittle texture. It was found that for the soybean rice used in the present invention, it is essential to keep the soybean rice in a dry state during the drying process.

[0053] <Examples 5 to 8, Comparative Example 8>: Examination of the mixing ratio of soy flour and soy protein in soybean rice Tests were conducted on the raw materials of Example 1, with the mixing ratio of soy flour and soy protein varied. Specifically, only the mixing ratio of soy flour and soy protein was increased or decreased, and the water and transglutaminase were used in the same manner as in Example 1, to obtain each soybean rice sample. The conditions for the kneading, molding, and drying processes were the same as in Example 1. The results are shown in Table 5. In Table 5, each value indicates the weight percentage per total weight of the raw materials, and the value in parentheses indicates the ratio of soy flour to soy protein.

[0054] [Table 5] TIFF0007760564000005.tif58161

[0055] From the results in Table 5, when the soy flour mixing ratio relative to the total raw material solids was 25% by weight or less (soy protein 75% by weight or more) (Comparative Example 8), the dough was not sticky enough to hold together and could not be shaped. Also, when the soy flour mixing ratio relative to the total raw material solids was 90% by weight or more (soy protein 10% by weight or less) (Example 8), the dough was too sticky, causing the extruded grains to stick together, resulting in products with poor shaping ability, texture, and appearance.

[0056] <Examples 9 to 15, Comparative Examples 9 and 10>: Examination of drying temperature for soybean rice In the drying process of Example 1, tests were conducted in which the drying temperature and time were changed. Specifically, soybean rice samples were obtained by drying at each temperature until the moisture content was 8% by weight or less. The conditions for the kneading and molding processes were the same as in Example 1. The results are shown in Table 6.

[0057] [Table 6] TIFF0007760564000006.tif39159

[0058] The results in Table 6 show that when the drying temperature exceeded 100°C (Comparative Examples 9 and 10), discoloration and burning occurred, resulting in poor appearance. When the drying temperature was in the range of 60 to 90°C (Examples 11 to 14), the texture, appearance, taste, and flavor were all excellent.

[0059] Example 16: Examination of modified starch from soybean rice A test was conducted in which a portion of the soy flour and soy protein in the raw materials of Example 1 was replaced with modified starch. Specifically, 1590 g of soy flour and 2170 g of soy protein were powder-mixed with 1000 g of modified starch (heat-moisture treated starch, manufactured by Matsutani Chemical Industry Co., Ltd.), and the process was then repeated as in Example 1 to obtain a soybean rice sample of Example 16. The conditions for the kneading, molding, and drying processes were the same as in Example 1. The results are shown in Table 7. In Table 7, each value indicates the weight percentage per total weight of the raw materials, and the values ​​in parentheses indicate the proportions of soy flour, soy protein, and modified starch.

[0060] [Table 7] TIFF0007760564000007.tif72113

[0061] The results in Table 7 show that the use of processed starch makes it possible to produce soybean rice with excellent formability, texture, taste, and flavor.

[0062] (2) Manufacturing method of packaged soybean rice An example of the method for producing packaged soybean rice according to the present invention will now be described.

[0063] <Examples 17 to 20, Comparative Example 11>: Study of pH of immersion liquid and filling liquid Unless otherwise specified, the following examples and comparative examples were carried out using the soybean rice obtained in Example 16 under the following conditions.

[0064] [Manufacturing method] The manufacturing method of Example 17 will be described below. 250 g (2.5 parts by weight) of soybean rice was added to 100 g (1 part by weight) of soybean rice soaking solution, prepared by dissolving acetic acid in water and adjusting the pH to 3.73, and the rice was soaked for 60 minutes to allow it to absorb water. The soybean rice that had absorbed water was placed in a colander, left to stand for 5 minutes, and then drained to obtain soybean rice after soaking. The weight of the soybean rice after soaking was measured, and the amount of soybean rice absorbed after soaking (amount of water absorbed by the soybean rice after soaking) was measured. After soaking, 99.0 g of the soybean rice and 69.0 g of a filling solution prepared by dissolving acetic acid in water and adjusting the pH to 3.73 were packed into a container and sealed. Next, the product was pressurized and heated in a retort sterilizer to an F value of 8, and then cooled to 35°C or below to obtain packaged soybean rice. For Examples 18 to 20, the same procedures as in Example 17 were carried out, except that the pH of the soaking liquid and the filling liquid was changed to 3.50 (Example 18), 3.27 (Example 19), and 3.04 (Example 20), respectively, and packaged soybean rice for each was obtained. For Comparative Example 11, packaged soybean rice was obtained, similar to Example 17, except that water (pH 7.59) was used instead of acetic acid for the soaking liquid and the filling liquid. At this time, the pH of the soaking liquid and the filling liquid was 7.59.

[0065] [pH measurement] The pH was measured using a pH meter (Horiba Ltd., product number D-51) connected to a pH electrode (Horiba Ltd., product number 9615S). When measuring solids, the pH electrode was inserted into the solid.

[0066] [Evaluation of packaged soybean rice] The packaged soybean rice obtained in the Examples and Comparative Examples was heated in a microwave oven (Sharp Corporation, Model RE-S203-H) at 600 watts for 30 seconds and subjected to a sensory evaluation (adhesion, texture, taste, and flavor). The sensory evaluation was conducted by five trained panelists who tasted the rice and evaluated it according to the following criteria. The results were summarized. The results are shown in Table 8. [Evaluation criteria for sensory evaluation] (binding) 〇: The whole is not solidified, can be loosened with a little force using chopsticks, and looks good. △: The whole thing is a little hard, but it can be loosened with chopsticks and looks pretty good. ×: The whole is strongly hardened and looks bad. (Texture) 〇: Moderately soft, with a texture similar to cooked rice, and delicious. △: A little hard, but the texture is good and it's tasty. ×: Hard. The core remains. Not tasty. (Taste / Flavor) 〇: No sourness, delicious with a soybean flavor. △: There is a slight sourness, but it has a delicious soybean flavor. ×: It has a strong sour taste and is not tasty.

[0067] [Table 8] TIFF0007760564000008.tif97159

[0068] From the results in Table 8, when the pH of the packaged soybean rice was between 5.50 and 6.64, sticking was suppressed, resulting in packaged soybean rice with a good appearance, texture, taste, and flavor. On the other hand, when the pH was 6.86 or higher (Comparative Example 11), although the taste and flavor were excellent, sticking occurred, the whole product was strongly hardened, and the texture was poor.

[0069] <Examples 21 to 26>: Examination of acid type and pH The type and pH of the acid used in the soaking solution and the filling solution were investigated. Specifically, packaged soybean rice was obtained in the same manner as in Example 17, except that the acid used in the soaking solution and the filling solution was changed to citric acid (pH 3.03 in Example 21, pH 2.23 in Example 22), fermented lactic acid (pH 3.21 in Example 23, pH 2.34 in Example 24), or glucono-delta-lactone (pH 3.00 in Example 25, pH 2.27 in Example 26), and various measurements and evaluations were similarly performed. The results are shown in Table 9.

[0070] [Table 9] TIFF0007760564000009.tif81156

[0071] The results in Table 9 show that even when acids other than acetic acid were used in the soaking solution and filling solution, sticking was suppressed, and packaged soybean rice with a good appearance, texture, taste, and flavor was obtained.

[0072] <Examples 27-28>: Examination of grain mixing In the packaging process, we investigated replacing a portion of the soybean rice after soaking with grains such as rice. In Example 27, 41.7 g of soybean rice after soaking, 49.4 g of grains (a 2.5:1 mixture of unabsorbed white rice and unabsorbed brown rice), and 74.9 g of filler liquid were packed into a container and sealed. In Example 28, 79.0 g of soybean rice after soaking, 22.0 g of grains (a mixture of unabsorbed white rice and unabsorbed brown rice), and 65.0 g of filler liquid were packed into a container and sealed. Except for the above changes, packaged soybean rice was obtained in the same manner as in Example 18, and various measurements and evaluations were similarly performed. The results are shown in Table 10.

[0073] [Table 10] TIFF0007760564000010.tif85109

[0074] The results in Table 10 show that even when soybean rice and grains were added in a ratio of 0.30:0.70, sticking was suppressed, and packaged soybean rice with grains was obtained that had a good appearance, texture, taste, and flavor (Example 27).

Claims

1. a soaking step of soaking the soybean rice in a soaking liquid; a packaging step of sealing the soybean rice and the filling liquid in a container after soaking; a heating step of pressurizing and heating the mixture, The pH of the soaking liquid and the filling liquid is 2.2 to 3.7, and the pH of the packaged soybean rice after the heating step is 5.3 to 6.7; a kneading step of adding water to a raw material containing soybean flour, soybean protein, and transglutaminase to prepare the soybean rice, and kneading the raw material; a molding step of extruding the kneaded mixture to obtain rice-shaped molded products; a drying step of heating and drying the rice-shaped product; the temperatures in the kneading step and the molding step are 40°C or less, the temperature in the drying step is 30 to 100°C; A method for producing packaged soybean rice, characterized in that the raw material is obtained by a production method in which the mixing ratio of soybean flour to soybean protein is 30:70 to 90:

10.

2. The manufacturing method described in claim 1, wherein the soybean rice contains starches as raw materials.

3. The method according to claim 1 or 2, wherein the total amount of water absorbed by the soybean rice after soaking and the filling liquid is 1.5 to 2.8 parts by weight per 1 part by weight of the soybean rice.

4. The method according to claim 3, wherein in the soybean rice soaking step or the packaging step, a portion of the soybean rice is replaced with grains, and the dry weight ratio of the soybean rice to grains is 100:0 to 30:70.

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