Cooked rice, method for producing the same, seasoning liquid for cooking rice, cooked rice improver, and method for using the same

Abstract

There is provided cooked rice containing 4 - α - glucanotransferase and satisfying at least one, preferably two or more of the following (A) to (D): SOLUTION: (A) Dryness of the surface is suppressed even after a long time has elapsed. (B) Aging is suppressed even after the lapse of a long time. (C) Even after a long period of time, the unfastening is excellent. (D) Excellent fresh flavor even after a long period of time. To provide cooked rice containing 4 - α - glucanotransferase and a method for producing the same, to provide a seasoning liquid for cooking rice and a cooked rice improver containing 4 - α - glucanotransferase, and to provide a method for improving at least one of loosening, deterioration and flavor of cooked rice after long-term storage by adding 4 - α - glucanotransferase and cooking the rice.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to cooked rice, a method for producing the same, a rice-cooking seasoning liquid, a cooked rice improving agent, and a method for using the same. [Background technology]

[0002] Recently, there has been an increase in the number of meals known as "take-home meals," in which prepared foods such as prepared meals, bento boxes, and sushi are purchased from supermarkets and convenience stores and eaten at home. Many take-home meals are consumed a long time (several to several tens of hours) after production before they reach the consumer's mouth. For this reason, there is a demand for long-life, pre-cooked foods that maintain a nearly freshly cooked taste for a long period of time, not only from the standpoint of taste and safety, but also from the standpoint of reducing food waste.

[0003] In particular, with cooked rice (white rice, rice balls, sushi rice, etc.), there has been a problem in that the surface becomes dry and stale over time from production or processing to consumption, and the freshly cooked flavor (the taste, deliciousness, and pleasant texture of freshly cooked rice) is no longer felt.

[0004] For this reason, in the production of cooked rice for ready-to-eat meals, high-water cooking is commonly performed, in which a large amount of water is added to cook the rice in order to maintain the flavor of the cooked rice even after a long period of time has passed. However, by adding more water, the surface of the cooked rice becomes sticky, sticks together, and forms lumps, which causes problems such as the rice not separating easily when eaten. Note that "sticky" refers to a state in which the rice has a lot of water and is sticky.

[0005] In other words, although cooking rice with a large amount of water can prevent the surface of cooked rice from becoming dry and aging after a long time to some extent, the cooked rice does not loosen up well, and as a result, the flavor of freshly cooked rice cannot be fully experienced.

[0006] Furthermore, ready-to-eat cooked rice, supplied to supermarkets and convenience stores, is typically cooked in large quantities (tens of kilograms per cooker) using industrial rice cookers. This results in inconsistent circulation of the ingredients (rice, water, ingredients, seasonings, etc.) inside the cooker, leading to temperature variations (temperature differences between the top and bottom of the cooker, making temperature control impossible). This results in inconsistent firmness and graininess of the cooked rice, and depending on the location inside the cooker, the surface of the cooked rice can become sticky or pasty, resulting in unsatisfactory flavor and texture. Furthermore, temperature variations can easily cause the cooker to burn, leading to reduced yields due to waste, increased workload during subsequent cooking, and deterioration of the cooker itself, all of which are productivity-related issues.

[0007] Known techniques for preventing deterioration in the texture of cooked rice include a method of adding a cooked rice improving agent containing an enzyme when cooking rice (see, for example, Patent Document 1).

[0008] Patent Document 1 discloses a method for improving cooked rice, which is characterized by adding enzymes such as amylase, protease, and lipase, as well as salt and cyclodextrin when cooking polished rice.

[0009] According to the technology of Patent Document 1, even when old rice is used, the rice is able to absorb water sufficiently to the center, and is fully gelatinized, improving the physical properties of cooked rice (hardness, adhesiveness, cohesiveness). However, this technology cannot improve the poor loosening of cooked rice after long-term storage, so there is a problem that the deliciousness of freshly cooked rice cannot be fully enjoyed after long-term storage. Furthermore, this technology cannot improve convection inside the pot. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 58-86050 Summary of the Invention [Problem to be solved by the invention]

[0011] The present disclosure addresses the problem of providing cooked rice containing 4-α-glucanotransferase, which satisfies at least one, and preferably two or more of the following (A) to (D): (A) Dryness of the surface is suppressed even after a long period of time has passed. (B) Retrogradation is suppressed even after a long period of time has passed. (C) Excellent loosening even after a long period of time has passed. (D) Excellent freshly cooked flavor even after a long period of time has passed. [Means for solving the problem]

[0012] As a result of extensive research to achieve the above-mentioned objectives, the inventors discovered that the cooked rice can be obtained by adding 4-α-glucanotransferase to cooked rice, and based on these findings, they have completed the present disclosure.

[0013] That is, the present disclosure relates to cooked rice containing (a) 4-α-glucanotransferase, which may further contain (b) α-amylase, and which may further contain (c) maltotriohydrolase.

[0014] The present disclosure also relates to (a) cooked rice obtained by adding 4-α-glucanotransferase and cooking the rice.

[0015] The present disclosure also relates to (a) a method for producing cooked rice, in which 4-α-glucanotransferase is added before or during cooking.

[0016] The present disclosure also relates to (a) a rice cooking seasoning or cooked rice improving agent containing 4-α-glucanotransferase.

[0017] The present disclosure also relates to (a) a method for improving at least one of the loosening, deterioration, and flavor of cooked rice after long-term storage by adding 4-α-glucanotransferase and cooking the rice.

[0018] The present disclosure also relates to a method for improving at least one of the loosening, deterioration, flavor, and uneven heating during cooking of cooked rice after long-term storage by adding (a) 4-α-glucanotransferase and (b) α-amylase, or the above-mentioned (a), (b), and (c) maltotriohydrolase and cooking the rice. [Effects of the Invention]

[0019] According to the present disclosure, cooked rice containing 4-α-glucanotransferase is provided that satisfies at least one, and preferably two or more of the following (A) to (D): (A) Dryness of the surface is suppressed even after a long period of time has passed. (B) Retrogradation is suppressed even after a long period of time has passed. (C) Excellent loosening even after a long period of time has passed. (D) Excellent freshly cooked flavor even after a long period of time has passed. The term "long time" used here refers to a state in which approximately 6 to 48 hours have passed, with the time immediately after production being set to 0 hours. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 10 is a diagram illustrating an image of temperature changes inside the oven when the convection rating is "3." [Figure 2] FIG. 10 is a diagram illustrating an image of temperature changes inside the oven when the convection rating is "2." [Figure 3] FIG. 10 is a diagram illustrating an image of temperature changes inside the oven when the convection rating is "1." DETAILED DESCRIPTION OF THE INVENTION

[0021] This embodiment will be described in detail below.

[0022] The cooked rice according to the first embodiment is characterized by containing 4-α-glucanotransferase.

[0023] The term "cooked rice" is not limited as long as it contains the specific enzymes described below, and examples include plain rice, sushi rice (vinegared rice), red rice, pilaf, fried rice, seasoned rice, steamed sticky rice, etc. Furthermore, foods that contain cooked rice as part of their diet, such as sushi and rice balls, are also included in the "cooked rice" of this embodiment.

[0024] The "sushi rice" may be produced by a conventional method, but is preferably one with an acidity of 0.15 w / v% to 0.40 w / v%. Acidity refers to the total content of organic acids (10 types: acetic acid, citric acid, tartaric acid, gluconic acid, malic acid, succinic acid, lactic acid, fumaric acid, adipic acid, and propionic acid), and can be measured using high-performance liquid chromatography or the like.

[0025] There are no restrictions on the type of rice used; any type of rice can be used, including japonica or indica, non-glutinous or glutinous, soft or hard, new or old, and regardless of the degree of polishing.

[0026] 4-α-glucanotransferase is classified as EC 2.4.1.25 and is an enzyme that catalyzes a reaction that converts starch into a branched starch by transferring three sugar units. The origin of the 4-α-glucanotransferase used in the present embodiment is not limited. It may also be a recombinant enzyme. Specific examples include "Glycotransferase 'Amano' L" and "Glycotransferase 'Amano'" manufactured by Amano Enzyme Inc.

[0027] By adding 4-α-glucanotransferase to cooked rice, the starch in the cooked rice changes to one with a branched chain structure. This allows moisture to penetrate deeply into the branched chains and the gaps between the branched chains, while retaining moisture within the starch. This is thought to prevent the cooked rice from becoming dry on the surface or from aging, even after long-term storage. Furthermore, the breakdown and transfer of starch into trisaccharide units reduces the starch-derived sticky substance (oneba) that covers the surface of the rice grains to some extent, lowering the viscosity of the cooking liquid. This is thought to reduce the adhesion between the rice grains and make them easier to separate. Furthermore, by adjusting the amount of 4-α-glucanotransferase, these effects can be further (in some cases significantly) improved.

[0028] In this embodiment, 4-α-glucanotransferase may be contained alone as an enzyme preparation, or may be contained in a rice cooking seasoning liquid or cooked rice improving agent, as described below.

[0029] The content of (a) 4-α-glucanotransferase in the cooked rice of this embodiment can be, for example, 0.0005% by mass or more, preferably 0.0006% by mass or more, even more preferably 0.0007% by mass or more, even more preferably 0.001% by mass or more, especially preferably 0.0013% by mass or more, and especially more preferably 0.0015% by mass or more, relative to the dried raw rice before washing and soaking, from the standpoint of preventing the surface of the cooked rice from becoming dry and aging over a long period of time, improving loosening, and maintaining the freshly cooked flavor.

[0030] Furthermore, the upper limit of the content of 4-α-glucanotransferase is not particularly limited, but from the viewpoint of solubility and miscibility with other ingredients such as water and seasoning liquid added during rice cooking, it can be, for example, 0.20% by mass or less, preferably 0.10% by mass or less, relative to the dried raw rice before washing and soaking.

[0031] Therefore, the content of (a) 4-α-glucanotransferase in cooked rice of this embodiment can be, for example, 0.0005% by mass to 0.20% by mass, preferably 0.0006% by mass to 0.20% by mass, more preferably 0.0007% by mass to 0.20% by mass, even more preferably 0.001% by mass to 0.20% by mass, particularly preferably 0.0013% by mass to 0.10% by mass, and especially more preferably 0.0015% by mass to 0.10% by mass, based on the dry raw rice before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0032] The cooked rice of this embodiment may contain α-amylase in addition to the above-mentioned 4-α-glucanotransferase, in order to further significantly improve the effect of preventing the surface of the cooked rice from becoming dry and aging over a long period of time, improving the loosening of the rice, and retaining the freshly cooked flavor, as well as to prevent uneven heating during cooking and improve convection.

[0033] (b) α-amylase is classified as EC 3.2.1.1 and is an enzyme that randomly hydrolyzes α-1,4 glycosidic bonds in starch, glycogen, etc. The α-amylase used in this embodiment may be of any origin and may be a recombinant enzyme. Specific examples include "Clystase (registered trademark)," "Clystase (registered trademark) L1," "Clystase (registered trademark) E5CC," "Biozyme A," and "Biozyme LC," all manufactured by Amano Enzyme Inc.

[0034] By adding α-amylase to cooked rice, starch and glycogen are broken down into polysaccharides, maltose, and oligosaccharides, which reduces the starch-derived mucus (oneba) that covers the surface of the rice grains and lowers the viscosity of the rice cooking liquid. This is thought to reduce the adhesion between rice grains and improve the rice's ability to separate. Furthermore, by reducing the adhesion between rice grains and lowering the viscosity of the rice cooking liquid, it is thought that temperature variations inside the rice cooker during cooking are less likely to occur and convection is improved. Furthermore, by adjusting the amount of α-amylase added, these effects can be further improved (in some cases significantly).

[0035] In this embodiment, α-amylase may be added to cooked rice as a single enzyme preparation. Alternatively, the above-described enzyme preparation containing 4-α-glucanotransferase and α-amylase may be mixed and added to cooked rice. Furthermore, 4-α-glucanotransferase and α-amylase may be added to and mixed with a rice cooking seasoning or cooked rice improving agent, which will be described later, and then added to cooked rice.

[0036] When cooked rice of this embodiment contains α-amylase, the content of α-amylase in the cooked rice is not particularly limited as long as it is contained simultaneously with 4-α-glucanotransferase. From the viewpoints of preventing the surface of cooked rice from becoming dry or aging over time, improving loosening, and maintaining the freshly cooked flavor, the content of α-amylase can be, for example, 0.0005% by mass or more, preferably 0.0006% by mass or more, more preferably 0.0007% by mass or more, even more preferably 0.001% by mass or more, particularly preferably 0.0013% by mass or more, and especially more preferably 0.0015% by mass or more, based on the dried raw rice before washing and soaking.

[0037] Furthermore, the upper limit of the α-amylase content is not particularly limited, but from the viewpoint of solubility and miscibility with other ingredients such as water added during rice cooking and seasoning liquid, it can be, for example, 0.20% by mass or less, preferably 0.10% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.04% by mass or less, of the dried raw rice before washing and soaking.

[0038] Therefore, the content of α-amylase in cooked rice can be, for example, 0.0005% by mass to 0.20% by mass, preferably 0.0006% by mass to 0.20% by mass, more preferably 0.0007% by mass to 0.10% by mass, even more preferably 0.001% by mass to 0.10% by mass, particularly preferably 0.0013% by mass to 0.05% by mass, and especially preferably 0.0015% by mass to 0.04% by mass, based on the dry raw rice before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0039] The cooked rice of this embodiment may contain maltotriohydrolase in addition to 4-α-glucanotransferase and α-amylase, in order to further significantly improve the effects of preventing the surface of the cooked rice from becoming dry and aging over a long period of time, improving the loosening of the rice, preserving the freshly cooked flavor, preventing uneven heating during cooking, and improving convection.

[0040] (c) Maltotriohydrolase is classified as EC 3.2.1.116 and is an enzyme that catalyzes the reaction of hydrolyzing α-1,4 glycosidic bonds in starch, glycogen, etc., and removing consecutive maltotriose units (trisaccharides formed by α-1,4 glycosidic bonds between three glucose molecules) from the non-reducing end of the chain. The origin of the maltotriohydrolase used in this embodiment is not limited, and it may be a recombinant enzyme. Specific examples include "AMT-1.2L" manufactured by Amano Enzyme Inc.

[0041] By adding maltotriohydrolase to cooked rice, starch is broken down into the trisaccharide maltotriose, which reduces the starch-derived mucus-like substance (oneba) that covers the surface of the rice grains and lowers the viscosity of the rice cooking liquid. This is thought to reduce the adhesion between rice grains and improve loosening. Furthermore, by reducing the adhesion between rice grains and reducing the viscosity of the rice cooking liquid, it is thought that temperature unevenness inside the rice cooker during cooking is reduced and convection is improved. Furthermore, it is thought that maltotriose produced by the breakdown of starch retains moisture and inhibits staling. Furthermore, by adjusting the content of maltotriohydrolase, these effects can be further improved (in some cases significantly).

[0042] In this embodiment, maltotriohydrolase may be contained alone as an enzyme preparation. Alternatively, the above-described 4-α-glucanotransferase, α-amylase, and maltotriohydrolase may be mixed together and contained in cooked rice as an enzyme preparation. Furthermore, 4-α-glucanotransferase, α-amylase, and maltotriohydrolase may be added to and mixed with a rice cooking seasoning or cooked rice improving agent, which will be described later, and then the resulting mixture may be contained in cooked rice.

[0043] When the cooked rice of this embodiment contains maltotriohydrolase, the content of maltotriohydrolase in the cooked rice is not particularly limited as long as it is contained simultaneously with 4-α-glucanotransferase and α-amylase. From the viewpoints of suppressing dryness and aging of the surface of cooked rice over a long period of time, improving loosening, and maintaining the freshly cooked flavor, the content of maltotriohydrolase can be, for example, 0.0005% by mass or more, preferably 0.0006% by mass or more, more preferably 0.0007% by mass or more, even more preferably 0.001% by mass or more, and particularly preferably 0.0013% by mass or more, based on the dry raw rice before washing and soaking.

[0044] Furthermore, the upper limit of the content of maltotriohydrolase is not particularly limited, but from the viewpoint of solubility and miscibility with other ingredients such as water added during rice cooking and seasoning liquid, it can be, for example, 0.20% by mass or less, preferably 0.10% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.04% by mass or less, relative to the dry raw rice before washing and soaking.

[0045] Therefore, the content of maltotriohydrolase in cooked rice can be, for example, 0.0005% by mass to 0.20% by mass, preferably 0.0006% by mass to 0.20% by mass, more preferably 0.0007% by mass to 0.10% by mass, even more preferably 0.001% by mass to 0.05% by mass, and particularly preferably 0.0013% by mass to 0.04% by mass, based on the dry raw rice before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0046] In the cooked rice of this embodiment, the total content of the (a) 4-α-glucanotransferase and (b) α-amylase, or the (a), (b) and (c) maltotriohydrolase, can be, for example, 0.003% by mass or more, preferably 0.004% by mass or more, even more preferably 0.005% by mass or more, even more preferably 0.006% by mass or more, particularly preferably 0.0065% by mass or more, and especially more preferably 0.007% by mass or more, relative to the dried raw rice before washing and soaking, from the viewpoints of preventing dryness and aging of the surface of the cooked rice over a long period of time, improving loosening, and maintaining the freshly cooked flavor.

[0047] Furthermore, the upper limit of the total content is not particularly limited, but from the viewpoint of solubility and miscibility with other ingredients such as water and seasoning liquid added during rice cooking, it can be, for example, 0.20% by mass or less, preferably 0.15% by mass or less, and more preferably 0.12% by mass or less, of the dry raw rice before washing and soaking.

[0048] Therefore, the total content in cooked rice can be, for example, 0.003% by mass or more and 0.20% by mass or less, preferably 0.004% by mass or more and 0.20% by mass or less, more preferably 0.005% by mass or more and 0.20% by mass or less, even more preferably 0.006% by mass or more and 0.20% by mass or less, particularly preferably 0.0065% by mass or more and 0.15% by mass or less, and especially preferably 0.007% by mass or more and 0.12% by mass or less, based on raw rice in a dried state before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0049] In the cooked rice of this embodiment, it is preferable to contain α-amylase in addition to 4-α-glucanotransferase from the viewpoints of preventing the surface of the cooked rice from becoming dry and aging over a long period of time, improving loosening, preserving the flavor of freshly cooked rice, preventing uneven heating during cooking, and improving convection. In this case, the respective contents of 4-α-glucanotransferase and α-amylase relative to the cooked rice, as well as the total content, are as described above.

[0050] Furthermore, when the cooked rice of this embodiment contains (a) 4-α-glucanotransferase and (b) α-amylase, the proportion of (a) in the total content of (a) and (b) can be, for example, 3% by mass or more, preferably 5% by mass or more, and more preferably 10% by mass or more, from the viewpoint of preventing the surface of cooked rice from becoming dry or aging over a long period of time, improving the loosening of the rice, and further enhancing the effect of retaining the freshly cooked flavor.

[0051] Furthermore, the upper limit of the proportion of (a) in the total content is not particularly limited, but can be, for example, 97% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less, from the standpoint of the desirability of the loosening method (loosening of the rice grains so that they crumble due to weak bonding between the grains is not desirable) and taste.

[0052] Therefore, the proportion of (a) in the total content of (a) and (b) can be, for example, 3% by mass or more and 97% by mass or less, preferably 5% by mass or more and 95% by mass or less, and more preferably 10% by mass or more and 90% by mass or less. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0053] As described above, when cooked rice contains only 4-α-glucanotransferase, the dryness and aging of the cooked rice surface are improved after a long period of time, the rice is more easily loosened, and the rice retains its freshly cooked flavor. By adding α-amylase to cooked rice in addition to 4-α-glucanotransferase at the above-described specified content and in the above-described ratio, the dryness and aging of the cooked rice surface are more effectively prevented after a long period of time, the rice is more easily loosened, and the rice retains its freshly cooked flavor. Furthermore, uneven heating during cooking is suppressed, and the effect of improving convection is more pronounced.

[0054] This is thought to be because, compared to when 4-α-glucanotransferase alone is added, the addition of α-amylase results in a greater number of "starch hydrolysates" produced by α-amylase starch hydrolysis, increasing the number of trisaccharide substrates available for 4-α-glucanotransferase to transfer. This results in the formation of more branched chain structures, increasing the total amount of moisture that can be retained between the branches, and significantly suppressing the dryness and staling of the cooked rice surface after long-term storage. Furthermore, the synergistic hydrolysis of starch by 4-α-glucanotransferase and α-amylase further reduces the starch-derived sticky substance (oneba) that covers the surface of the rice grains, further reducing the viscosity of the cooking liquid, which reduces the adhesion of the rice grains and makes the cooked rice easier to separate.

[0055] The proportion of (a) in the total content of (a) and (b) in cooked rice is not particularly limited as long as it is within the above-mentioned range. However, if it is outside the above-mentioned range, although the rice will be excellent in loosening, the rice grains may become too weakly bonded together and may loosen apart.

[0056] Furthermore, in the cooked rice of this embodiment, it is preferable to further contain maltotriohydrolase in addition to 4-α-glucanotransferase and α-amylase from the viewpoints of preventing the surface of cooked rice from becoming dry and aging after a long period of time, improving loosening, preserving the flavor of freshly cooked rice, preventing uneven heating during cooking, and improving convection. In this case, the respective contents of 4-α-glucanotransferase, α-amylase, and maltotriohydrolase relative to the cooked rice, as well as the total content, are as described above.

[0057] When the cooked rice of this embodiment contains (a) 4-α-glucanotransferase, (b) α-amylase, and (c) maltotriohydrolase, in order to suppress dryness and aging of the surface of the cooked rice over a long period of time, improve loosening, and further enhance the effect of retaining the freshly cooked flavor, the proportion of (a) in the total content of (a), (b), and (c) above can be, for example, 10% by mass or more, preferably 15% by mass or more, and more preferably 20% by mass or more.

[0058] Furthermore, the upper limit of the proportion of (a) in the total content of the above (a), (b), and (c) is not particularly limited, but can be set to, for example, 80% by mass or less, preferably 75% by mass or less, and more preferably 70% by mass or less, from the standpoint of the desirability of the loosening method (loosening of the rice grains so that they crumble due to weak bonding between the grains is not desirable) and taste.

[0059] Therefore, the proportion of (a) in the total content of (a), (b), and (c) can be, for example, 10% by mass or more and 80% by mass or less, preferably 15% by mass or more and 75% by mass or less, and more preferably 20% by mass or more and 70% by mass or less. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0060] As described above, when cooked rice contains only 4-α-glucanotransferase, the rice surface is less prone to dryness and aging after long periods of cooking, the rice is more easily loosened, and the rice retains its freshly cooked flavor. By adding α-amylase to cooked rice in the specified amount described above, and in the specified ratio of 4-α-glucanotransferase and α-amylase to cooked rice, the rice is more effectively prevented from dryness and aging after long periods of cooking, the rice is more easily loosened, and the rice retains its freshly cooked flavor. Furthermore, as described above, the rice is more effectively prevented from heating unevenly during cooking and the rice is more effectively convection-enhancing. Furthermore, by adding maltotriohydrolase to cooked rice in addition to 4-α-glucanotransferase and α-amylase, the above effects are even more significantly improved.

[0061] This is thought to be due to the different functions of each enzyme, but while 4-α-glucanotransferase decomposes starch into trisaccharides and transfers them as branched chains, the simultaneous inclusion of α-amylase increases the number of trisaccharide substrates that 4-α-glucanotransferase transfers compared to the presence of only 4-α-glucanotransferase, due to the presence of a large number of "starch hydrolysates" produced by α-amylase hydrolysis of starch. On the other hand, while maltotriohydrolase hydrolyzes starch into trisaccharide units, the coexistence of α-amylase is thought to result in the formation of more trisaccharides due to the presence of a large number of "starch hydrolysates" produced by α-amylase hydrolysis.

[0062] In other words, the number of trisaccharide substrates transferred by 4-α-glucanotransferase increases by adding both α-amylase and maltotriohydrolase compared to when only α-amylase is added, which is thought to make it easier to form branched chain structures. This combination of factors leads to the formation of more branched chain structures, which further increases the total amount of moisture that can be retained between the branched chains, and is thought to further significantly suppress the dryness and aging of the surface of cooked rice after long-term storage.

[0063] In addition, the synergistic hydrolysis by maltotriohydrolase in addition to 4-α-glucanotransferase and α-amylase further reduces the starch-derived mucus-like substance (oneba) that covers the surface of the rice grains, and the viscosity of the cooking liquid further decreases, which is thought to reduce the adhesion between the rice grains and make them even easier to separate.

[0064] The proportion of (a) in the total amount of (a), (b), and (c) is not particularly limited as long as it is within the above range, but if it is outside the above range, although the rice will be excellent in loosening, the rice grains may become too weakly bonded together and may fall apart. Also, if it is outside the above range, it may not be preferable from the viewpoint of improving the flavor, such as the taste and palatability, of the rice when eaten.

[0065] The cooked rice of this embodiment may contain any enzyme other than the above three types of enzymes, as long as it does not interfere with the above-mentioned effects. Specific examples include, but are not limited to, protease, glucoamylase, lipase, cellulase, glucose oxidase, xylanase, ribonuclease, transglutaminase, α-glucosidase, pullulanase, and cell wall-degrading enzymes.

[0066] Furthermore, in addition to the enzymes described above, the cooked rice of this embodiment can contain "other ingredients generally incorporated into foods," such as ingredients for seasonings and the like used in regular cooked rice, as well as ingredients, to the extent that the effects of the enzymes are not inhibited. Note that cooked rice of this embodiment that contains ingredients for seasonings and the like (seasoning ingredients) and "other ingredients generally incorporated into foods" can also be included in the "cooked rice" of this embodiment.

[0067] Examples of "other ingredients that are generally added to foods" include ingredients for seasoning, etc. (seasoning ingredients), such as water, salt, vinegar, sugars (including high-intensity sweeteners), oils and fats, organic acids, amino acid-based seasonings, nucleic acid-based seasonings, organic acid-based seasonings, flavor ingredients, umami seasonings, alcoholic beverages, fruit juice, spices, spice extracts, flavor oils, flavors, and other taste and flavor components, viscosity adjusters such as gums and starch, stabilizers, coloring agents, and additives such as calcium salts.

[0068] In addition to these ingredients, the cooked rice of this embodiment may contain ingredients such as vegetables (carrots, burdock, radish, etc.), grains (red beans, soybeans, etc.), meat, fish, etc. The amount of these ingredients and ingredients contained is not particularly limited and can be determined appropriately depending on the intended use of the cooked rice of this embodiment.

[0069] The "salt" may be salt itself, or a food containing salt. The food containing salt is not particularly limited, but examples include soy sauce, miso, and dashi.

[0070] The soy sauce is not particularly limited, but examples thereof include dark soy sauce, light soy sauce, white soy sauce, tamari soy sauce, re-brewed soy sauce, etc. These soy sauces may be used alone or in any combination and ratio of two or more kinds.

[0071] The miso mentioned above is not particularly limited, but examples include barley miso, rice miso, soybean miso, blended miso, and also red miso, white miso, light-colored miso, etc., which are named according to the color differences resulting from their manufacturing method. These miso may be used alone or in any combination or ratio of two or more types.

[0072] Examples of "vinegar" include brewed vinegar, which is produced using grains such as rice or barley or fruit juice as raw materials, and synthetic vinegar, which is produced by adding seasonings such as sugar to a diluted solution of glacial acetic acid or acetic acid, or by adding brewed vinegar to a diluted solution. Examples of brewed vinegar include rice vinegar, grain vinegar (brown rice vinegar, black vinegar, lees vinegar, malt vinegar, barley vinegar, soybean vinegar, etc.), fruit vinegar (apple vinegar, grape vinegar, white grape vinegar, citrus fruit vinegar (lemon, yuzu, kabosu, orange, mandarin orange, shikuwasa, grapefruit, calamansi, etc.), mango vinegar, strawberry vinegar, blueberry vinegar, pomegranate vinegar, peach vinegar, plum vinegar, pineapple vinegar, wine vinegar, balsamic vinegar, etc.), spirit vinegar produced by acetic acid fermentation using ethanol as a raw material, Chinese vinegar, sherry vinegar, etc. Synthetic vinegars include glacial acetic acid or acetic acid diluted with water. These vinegars may be used alone or in combination.

[0073] Examples of "saccharides" include sugar, maltose, fructose, isomerized liquid sugar, glucose, brown sugar, honey, starch syrup, dextrin, lactose, galactose, etc., as well as sugar alcohols such as sorbitol, maltitol, xylitol, etc. These saccharides may be used alone or in any combination or ratio of two or more.

[0074] Examples of "high-intensity sweeteners" include aspartame, acesulfame potassium, sucralose, neotame, licorice extract, stevia, and enzyme-treated products thereof. These high-intensity sweeteners may be used alone or in any combination or ratio of two or more.

[0075] Examples of "fats and oils" include soybean oil, soybean germ oil, rapeseed oil, corn oil, sesame oil, perilla oil, linseed oil, peanut oil, safflower oil, high oleic acid safflower oil, sunflower oil, cottonseed oil, grapeseed oil, macadamia nut oil, hazelnut oil, pumpkin seed oil, walnut oil, camellia oil, tea seed oil, perilla oil, olive oil, wheat germ oil, palm oil, algae oil, rice oil, almond oil, avocado oil, etc. These fats and oils may be used alone or in any combination or ratio of two or more.

[0076] Examples of "organic acids" include lactic acid, malic acid, citric acid, gluconic acid, succinic acid, tartaric acid, phytic acid, fumaric acid, phosphoric acid, etc. These organic acids may be used alone or in any combination of two or more kinds in any ratio.

[0077] Examples of "amino acid seasonings" include sodium L-glutamate, DL-alanine, glycine, L- or DL-tryptophan, L-phenylalanine, L- or DL-methionine, L-lysine, L-aspartic acid, sodium L-aspartate, L-arginine, etc. These amino acid seasonings may be used alone, or two or more may be used in any combination or in any ratio.

[0078] Examples of "nucleic acid seasonings" include 5'-inosinate disodium, 5'-guanylate disodium, 5'-uridylate disodium, 5'-cytidylate disodium, 5'-ribonucleotide calcium, 5'-ribonucleotide disodium, etc. These nucleic acid seasonings may be used alone, or two or more may be used in any combination or in any ratio.

[0079] Examples of "organic acid seasonings" include calcium citrate, trisodium citrate, potassium gluconate, sodium gluconate, succinic acid, monosodium succinate, disodium succinate, sodium acetate, potassium DL-hydrogen tartrate, potassium L-hydrogen tartrate, DL-sodium tartrate, L-sodium tartrate, potassium lactate, calcium lactate, sodium lactate, monosodium fumarate, and DL-sodium malate. These organic acid seasonings may be used alone, or two or more may be used in any combination or in any ratio. Using two or more organic acid seasonings in combination is preferred because the flavors of both seasonings are synergistically enhanced.

[0080] Examples of "flavoring ingredients" include bonito stock, kelp stock, vegetable extract, bonito extract, kelp extract, seafood extract, meat extract, etc. These flavoring ingredients may be used alone or in any combination or ratio of two or more.

[0081] Examples of "umami seasonings" include protein hydrolysates, yeast extracts, etc. Examples of "yeast extracts" include extracts obtained by decomposing yeast bodies using, for example, beer yeast, baker's yeast, Torula yeast, sake yeast, wine yeast, soy sauce yeast, etc. as raw materials, by autolysis or addition of enzymes, etc. These umami seasonings may be used alone, or two or more may be used in any combination or in any ratio.

[0082] Examples of "alcoholic beverages" include sake, synthetic sake, mirin, shochu, wine, liqueur, Shaoxing wine, etc. These alcoholic beverages may be used alone or in any combination or ratio of two or more.

[0083] "Spices" refers to parts of plants (such as fruit, peel, flower, bud, bark, stem, leaf, seed, root, and rhizome) that have a distinctive aroma, pungent taste, and color and are added to food and drink for the purposes of flavoring, deodorizing, seasoning, coloring, etc., and includes spices and herbs. These spices may be used alone or in any combination or ratio of two or more.

[0084] Spices refer to the parts of spices that are used excluding the stems, leaves, and flowers, and examples include pepper (black pepper, white pepper, red pepper), garlic, ginger, sesame (sesame seeds), chili pepper, horseradish, mustard, poppy seeds, yuzu, nutmeg, cinnamon, paprika, cardamom, cumin, saffron, allspice, cloves, Japanese pepper, orange peel, fennel, licorice, fenugreek, dill seeds, Japanese pepper, long pepper, and olives.

[0085] Herbs are spices that use the stems, leaves, and flowers, and examples include watercress, coriander, shiso, celery, tarragon, chives, chervil, sage, thyme, laurel, chives, parsley, mustard greens, myoga, mugwort, basil, oregano, rosemary, peppermint, savory, lemongrass, dill, wasabi leaves, and Japanese pepper leaves.

[0086] The "spice extract" may be any extract of a food that is generally labeled as a "spice" or "spices," and examples thereof include chili pepper extract, mustard extract, ginger extract, wasabi extract, pepper extract, garlic extract, onion extract, Japanese pepper extract, etc. These spice extracts may be used alone, or two or more may be used in any combination or in any ratio.

[0087] Examples of "flavor oils" include ginger oil, garlic oil, mustard oil, onion oil, sesame oil, green onion oil, chive oil, parsley oil, perilla oil, wasabi oil, lemon oil, seafood oil, and meat oil. These flavor oils may be used alone or in any combination or ratio of two or more.

[0088] Examples of "flavors" include ginger flavor, garlic flavor, mustard flavor, onion flavor, sesame flavor, green onion flavor, chive flavor, shiso flavor, wasabi flavor, lemon flavor, etc. These flavors may be used alone or in any combination or ratio of two or more.

[0089] Examples of "viscosity modifiers" include alginic acid, sodium alginate, carrageenan, karaya gum, agar, cellulose, tamarind seed gum, pullulan, pectin, chitin, chitosan, starch, modified starch, starch hydrolysates, etc. These viscosity modifiers may be used alone or in any combination or ratio of two or more.

[0090] Examples of starch include wheat flour starch, corn starch, waxy corn starch, potato starch, rice starch, tapioca starch, and the like.

[0091] Furthermore, examples of the processed starch include crosslinked starch, oxidized starch, etherified starch, esterified starch, etc., which are obtained by subjecting the above-mentioned starch to a crosslinking treatment, esterification treatment, etherification treatment, oxidation treatment, etc.

[0092] Examples of starch hydrolysates include dextrin and maltodextrin obtained by hydrolyzing the above-mentioned starch or modified starch.

[0093] Furthermore, cooked rice may contain, instead of the enzyme, a liquid seasoning for cooking rice or a cooked rice improving agent according to the third and fourth embodiments described below.

[0094] In this embodiment, to incorporate the enzymes into cooked rice, the enzymes may be added to raw rice before or during cooking, as will be described in detail later. Although most of the enzymes are ultimately inactivated by cooking, it is believed that the enzymes act partially on rice starch during the temperature rise process, thereby exerting the aforementioned effects.

[0095] In this way, the cooked rice according to the first embodiment contains an enzyme containing 4-α-glucanotransferase, which improves at least one of the loosening, deterioration, and flavor of the cooked rice even after long-term storage. Furthermore, when the resulting cooked rice is mixed with sushi vinegar to make sushi rice, the load on the rice scoop can be reduced.

[0096] Here, "improved loosening" means that the rice grains are less likely to stick together and are easier to loosen, even after storage for 6 to 48 hours after cooking (or, in the case of processed foods containing cooked rice, after production).

[0097] "Improvement of deterioration" means that deterioration (dryness, aging) of cooked rice is improved (or suppressed) even after storage for 6 to 48 hours after cooking (or, in the case of processed foods containing cooked rice, after production). "Dryness" refers to the dryness of the surface of the rice grains. "Aging" refers to the powdery, crumbly texture of the cooked rice as a whole.

[0098] "Improved flavor" means that the deterioration of the desirable flavor of cooked rice, such as the taste and deliciousness of the rice, is suppressed and the freshly cooked flavor is maintained even after 6 to 48 hours of storage after cooking (or, in the case of processed foods containing cooked rice, after its manufacture). Also, if the cooked rice is sushi rice (vinegared rice), the taste (the acidity of the vinegar is perceived just right and is not overpowered) is also included in "flavor."

[0099] The cooked rice of the second embodiment is defined by the production method of the cooked rice of the first embodiment described above. That is, the cooked rice of the second embodiment is characterized by being obtained by adding 4-α-glucanotransferase and cooking the rice. Here, "cooked rice," "4-α-glucanotransferase," "α-amylase," and "maltotriohydrolase" are as explained above.

[0100] In the second embodiment, by adding 4-α-glucanotransferase and cooking rice, the starch in the cooked rice is converted to starch with a branched chain structure. This allows moisture to penetrate deeply into the branched chains and the voids between the branched chains, while retaining moisture within the starch. This is thought to prevent the cooked rice from becoming dry on the surface and aging even after long-term storage. Furthermore, as the starch is decomposed and transferred in trisaccharide units, the starch-derived mucus-like substance (stickiness) that covers the surface of the rice grains is reduced to a certain extent, lowering the viscosity of the rice cooking liquid. This is thought to reduce the adhesion between the rice grains and make them easier to separate. Furthermore, by adjusting the amount of 4-α-glucanotransferase added, these effects can be further (in some cases significantly) improved.

[0101] 4-α-glucanotransferase may be added alone as an enzyme preparation before cooking rice, or may be added as a rice cooking seasoning or rice improver, as described below, before cooking rice.

[0102] In the second embodiment, the amount of (a) 4-α-glucanotransferase added can be, for example, 0.0005% by mass or more, preferably 0.0006% by mass or more, even more preferably 0.0007% by mass or more, even more preferably 0.001% by mass or more, especially preferably 0.0013% by mass or more, and especially more preferably 0.0015% by mass or more, relative to the dried raw rice before washing and soaking, from the standpoint of preventing the surface of cooked rice from becoming dry and aging over a long period of time, improving loosening, and maintaining the freshly cooked flavor.

[0103] Furthermore, the upper limit of the amount of 4-α-glucanotransferase to be added is not particularly limited, but from the viewpoint of solubility and miscibility with other ingredients such as water and seasoning liquid added during rice cooking, it can be, for example, 0.20% by mass or less, preferably 0.10% by mass or less, relative to the dried raw rice before washing and soaking.

[0104] Therefore, the amount of (a) 4-α-glucanotransferase added in the second embodiment can be, for example, 0.0005% by mass to 0.20% by mass, preferably 0.0006% by mass to 0.20% by mass, more preferably 0.0007% by mass to 0.20% by mass, even more preferably 0.001% by mass to 0.20% by mass, particularly preferably 0.0013% by mass to 0.10% by mass, and especially more preferably 0.0015% by mass to 0.10% by mass, based on the amount of raw rice in a dry state before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0105] In the second embodiment, in order to further significantly improve the effect of preventing the dryness and aging of the surface of cooked rice over a long period of time, improving loosening, and retaining the freshly cooked flavor, as well as to suppress uneven heating during cooking and improve convection, α-amylase may be added together with the above-mentioned 4-α-glucanotransferase or separately from the 4-α-glucanotransferase.

[0106] (b) By adding α-amylase to cooked rice and cooking it, starch and glycogen are broken down into polysaccharides, maltose, and oligosaccharides, which reduces the starch-derived mucus (oneba) that covers the surface of the rice grains and lowers the viscosity of the cooking liquid. This is thought to reduce the adhesion between rice grains and improve the rice's ability to separate. Furthermore, by reducing the adhesion between rice grains and lowering the viscosity of the cooking liquid, it is thought that temperature variations inside the rice cooker during cooking are less likely to occur and convection is improved. Furthermore, by adjusting the amount of α-amylase added, these effects can be further improved (in some cases significantly).

[0107] Incidentally, α-amylase may be added alone as an enzyme preparation and then cooked. Alternatively, the aforementioned enzyme preparation containing 4-α-glucanotransferase and α-amylase may be mixed and added to raw rice before cooking. Furthermore, 4-α-glucanotransferase and α-amylase may be added to and mixed with a rice cooking seasoning or cooked rice improving agent, which will be described later, and then added to raw rice before cooking.

[0108] In the second embodiment, when α-amylase is added to cook rice, the amount of α-amylase added is not particularly limited as long as it is added in combination with 4-α-glucanotransferase. From the viewpoints of preventing dryness and aging of the surface of cooked rice over a long period of time, improving loosening, and maintaining the freshly cooked flavor, the amount of α-amylase added can be, for example, 0.0005% by mass or more, preferably 0.0006% by mass or more, more preferably 0.0007% by mass or more, even more preferably 0.001% by mass or more, particularly preferably 0.0013% by mass or more, and especially more preferably 0.0015% by mass or more, based on the dry raw rice before washing and soaking.

[0109] Furthermore, the upper limit of the amount of α-amylase to be added is not particularly limited, but from the viewpoint of solubility and miscibility with other ingredients such as water and seasoning liquid added during rice cooking, the amount can be, for example, 0.20% by mass or less, preferably 0.10% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.04% by mass or less, relative to the dried raw rice before washing and soaking.

[0110] Therefore, the amount of α-amylase added in the second embodiment can be, for example, 0.0005% by mass to 0.20% by mass, preferably 0.0006% by mass to 0.20% by mass, more preferably 0.0007% by mass to 0.10% by mass, even more preferably 0.001% by mass to 0.10% by mass, particularly preferably 0.0013% by mass to 0.05% by mass, and especially preferably 0.0015% by mass to 0.04% by mass, based on the amount of raw rice in a dry state before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0111] In the second embodiment, in order to further significantly improve the effects of preventing the surface of cooked rice from becoming dry and aging over a long period of time, improving loosening, preserving the freshly cooked flavor, and suppressing uneven heating during cooking and improving convection, maltotriohydrolase may be added in addition to 4-α-glucanotransferase and α-amylase.

[0112] (c) By adding maltotriohydrolase to rice during cooking, starch is broken down into the trisaccharide maltotriose, which reduces the starch-derived mucilage (oneba) that covers the surface of the rice grains and lowers the viscosity of the cooking liquid. This is thought to reduce the adhesion between rice grains and improve loosening. Furthermore, by reducing the adhesion between rice grains and reducing the viscosity of the cooking liquid, it is thought that temperature variations inside the rice cooker during cooking are less likely to occur and convection is improved. Furthermore, it is thought that the maltotriose produced by the breakdown of starch retains moisture and inhibits staling. Furthermore, by adjusting the amount of maltotriohydrolase added, these effects can be further (in some cases significantly) improved.

[0113] Maltotriohydrolase may be added alone as an enzyme preparation to raw rice and then cooked. Alternatively, the aforementioned 4-α-glucanotransferase, α-amylase, and maltotriohydrolase may be mixed together to form an enzyme preparation, which may then be added to raw rice and then cooked. Furthermore, 4-α-glucanotransferase, α-amylase, and maltotriohydrolase may be added to and mixed with a rice cooking seasoning or cooked rice improving agent, which will be described later, and then the mixture may be added to raw rice before cooking.

[0114] In the second embodiment, when maltotriohydrolase is added to cook rice, the amount of maltotriohydrolase added is not particularly limited as long as it is added in combination with 4-α-glucanotransferase and α-amylase. From the viewpoints of preventing dryness and aging of the surface of cooked rice over a long period of time, improving loosening, and maintaining the freshly cooked flavor, the amount of maltotriohydrolase added can be, for example, 0.0005% by mass or more, preferably 0.0006% by mass or more, more preferably 0.0007% by mass or more, even more preferably 0.001% by mass or more, and particularly preferably 0.0013% by mass or more, based on the amount of dried raw rice before washing and soaking.

[0115] Furthermore, the upper limit of the amount of maltotriohydrolase to be added is not particularly limited, but from the viewpoint of solubility and miscibility with other ingredients such as water added during rice cooking and seasoning liquid, it can be, for example, 0.20% by mass or less, preferably 0.10% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.04% by mass or less, relative to the dried raw rice before washing and soaking.

[0116] Therefore, the amount of maltotriohydrolase added in the second embodiment can be, for example, 0.0005% by mass to 0.20% by mass, preferably 0.0006% by mass to 0.20% by mass, more preferably 0.0007% by mass to 0.10% by mass, even more preferably 0.001% by mass to 0.05% by mass, and particularly preferably 0.0013% by mass to 0.04% by mass, based on the amount of raw rice in a dry state before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0117] In the second embodiment, the total amount of (a) 4-α-glucanotransferase and (b) α-amylase, or (a), (b) and (c) maltotriohydrolase added can be, for example, 0.003% by mass or more, preferably 0.004% by mass or more, even more preferably 0.005% by mass or more, even more preferably 0.006% by mass or more, particularly preferably 0.0065% by mass or more, and especially more preferably 0.007% by mass or more, relative to the dried raw rice before washing and soaking, from the standpoint of preventing dryness and aging of the surface of cooked rice over a long period of time, improving loosening, and maintaining the freshly cooked flavor.

[0118] Furthermore, the upper limit of the total amount to be added is not particularly limited, but from the viewpoint of solubility and miscibility with other ingredients such as water and seasoning liquid added during rice cooking, it can be, for example, 0.20% by mass or less, preferably 0.15% by mass or less, and more preferably 0.12% by mass or less, of the dry raw rice before washing and soaking.

[0119] Therefore, the total amount added in the second embodiment can be, for example, 0.003% by mass or more and 0.20% by mass or less, preferably 0.004% by mass or more and 0.20% by mass or less, more preferably 0.005% by mass or more and 0.20% by mass or less, even more preferably 0.006% by mass or more and 0.20% by mass or less, particularly preferably 0.0065% by mass or more and 0.15% by mass or less, and especially preferably 0.007% by mass or more and 0.12% by mass or less, based on the amount of raw rice in a dry state before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0120] Furthermore, in the second embodiment, when rice is cooked by adding (a) 4-α-glucanotransferase and (b) α-amylase, the proportion of (a) in the total amount of (a) and (b) added can be, for example, 3% by mass or more, preferably 5% by mass or more, and more preferably 10% by mass or more, from the viewpoint of preventing dryness and aging of the surface of cooked rice after a long period of time, improving loosening, and further enhancing the effect of retaining the freshly cooked flavor.

[0121] Furthermore, the upper limit of the proportion of (a) in the total amount added is not particularly limited, but can be, for example, 97% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less, from the standpoint of the desirability of the loosening method (loosening of the rice grains so that they crumble due to weak bonding between the grains is not desirable) and taste.

[0122] Therefore, the proportion of (a) in the total amount of (a) and (b) added can be, for example, 3% by mass or more and 97% by mass or less, preferably 5% by mass or more and 95% by mass or less, and more preferably 10% by mass or more and 90% by mass or less. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0123] As described above, when rice is cooked with only 4-α-glucanotransferase added, the dryness and aging of the surface of cooked rice are suppressed after a long period of time, the rice is more easily loosened, and the freshly cooked flavor is maintained. By adding α-amylase in addition to 4-α-glucanotransferase in the specified amount described above, and with the 4-α-glucanotransferase and α-amylase in the specified ratio described above, not only are the dryness and aging of the surface of cooked rice suppressed after a long period of time, the rice is more easily loosened, and the freshly cooked flavor is maintained even more significantly, but uneven heating during cooking is suppressed and convection is more significantly improved.

[0124] This is thought to be because the addition of α-amylase results in a greater number of "starch hydrolysates" produced by α-amylase starch hydrolysis than when only 4-α-glucanotransferase is added, resulting in an increase in the number of trisaccharide substrates that 4-α-glucanotransferase can transfer. This leads to the formation of more branched chain structures, which increases the total amount of moisture that can be retained between the branches. This is thought to significantly suppress the dryness and staling of the cooked rice surface after long-term storage. Furthermore, the synergistic hydrolysis of starch by 4-α-glucanotransferase and α-amylase further reduces the starch-derived sticky substance (oneba) that covers the surface of the rice grains, further reducing the viscosity of the cooking liquid, which reduces the adhesion of the rice grains and makes the cooked rice easier to separate.

[0125] The proportion of (a) in the total amount of (a) and (b) added is not particularly limited as long as it is within the above-mentioned range. However, if it is outside the above-mentioned range, although the loosening effect will be excellent, the bonding between the rice grains may become too weak, causing the loosening to crumble.

[0126] In the second embodiment, when (a) 4-α-glucanotransferase, (b) α-amylase, and (c) maltotriohydrolase are added, in order to further suppress dryness and aging of the surface of cooked rice over a long period of time, improve loosening, and further enhance the effect of preserving the freshly cooked flavor, the proportion of (a) in the total amount of (a), (b), and (c) added can be, for example, 10% by mass or more, preferably 15% by mass or more, and more preferably 20% by mass or more.

[0127] Furthermore, the upper limit of the proportion of (a) in the total amount of (a), (b), and (c) added is not particularly limited, but can be set to, for example, 80% by mass or less, preferably 75% by mass or less, and more preferably 70% by mass or less, from the standpoint of the desirability of the loosening method (loosening of the rice grains so that they crumble due to weak bonding between the grains is not desirable) and taste.

[0128] Therefore, the proportion of (a) in the total amount of (a), (b), and (c) added can be, for example, 10% by mass or more and 80% by mass or less, preferably 15% by mass or more and 75% by mass or less, and more preferably 20% by mass or more and 70% by mass or less. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0129] As described above, adding α-amylase in addition to 4-α-glucanotransferase in the above-mentioned amount and ratio not only suppresses the dryness and aging of the surface of cooked rice over a long period of time, improves the loosening of the rice, and more significantly preserves the freshly cooked flavor, but also suppresses uneven heating during cooking and improves convection.These effects are even more significantly enhanced by adding maltotriohydrolase in the above-mentioned amount and ratio in addition to 4-α-glucanotransferase and α-amylase.

[0130] This is thought to be due to the different functions of each enzyme, but while 4-α-glucanotransferase decomposes starch into trisaccharides and transfers them as branched chains, the simultaneous addition of α-amylase increases the amount of "starch hydrolysates" produced by α-amylase hydrolysis compared to the addition of 4-α-glucanotransferase alone, which is thought to increase the amount of trisaccharide substrates that 4-α-glucanotransferase transfers. On the other hand, while maltotriohydrolase hydrolyzes starch into trisaccharide units, the coexistence of α-amylase increases the amount of "starch hydrolysates" produced by α-amylase hydrolysis, which is thought to result in the formation of more trisaccharides.

[0131] In other words, the addition of both α-amylase and maltotriohydrolase increases the number of trisaccharide substrates transferred by 4-α-glucanotransferase compared to the addition of α-amylase alone, which is thought to make it easier for branched chain structures to form. This combination of factors leads to the formation of more branched chain structures, which in turn increases the total amount of moisture that can be retained between the branched chains, which is thought to further significantly suppress the dryness and aging of the surface of cooked rice after long-term storage.

[0132] In addition, the synergistic hydrolysis by maltotriohydrolase in addition to 4-α-glucanotransferase and α-amylase further reduces the starch-derived mucus-like substance (oneba) that covers the surface of the rice grains, and the viscosity of the cooking liquid further decreases, which is thought to reduce the adhesion between the rice grains and make them even easier to separate.

[0133] The proportion of (a) in the total amount of (a), (b), and (c) is not particularly limited as long as it is within the above range, but if it is outside the above range, although the loosening effect will be excellent, the adhesion between the rice grains may become too weak, causing the rice to crumble. Furthermore, if it is outside the above range, it may be undesirable from the viewpoint of the effect of improving the flavor, such as the taste and palatability, of the rice when eaten.

[0134] Any enzyme other than the above three types of enzymes may be added as long as it does not interfere with the above-mentioned effects. The "any enzyme" is not particularly limited, but is as described above.

[0135] In the second embodiment, the rice cooking method may basically be a conventional method, except that the rice is cooked with the addition of the enzymes described above.

[0136] For example, the rice cooking method may include the steps of washing the raw rice, draining the rice using a colander or the like, soaking the rice in water, adding the enzyme to the rice, and cooking the rice by heating in a conventional manner after adjusting the amount of water to an appropriate level. The soaking step can also be omitted. If pre-wash rice, from which the bran has been removed in advance by physical processing, is used as the raw rice, the washing and draining steps are not necessary.

[0137] Furthermore, when the cooked rice is sushi rice (vinegared rice), the cooked rice after being cooked as described above can be used to produce sushi rice by a conventional method. For example, the method for producing sushi rice may include the steps of steaming the cooked rice, adding seasoned vinegar (sushi vinegar) containing vinegar, sucrose, salt, etc. to the cooked rice (vinegar-mixing), stirring the cooked rice to loosen it, and cooling the finished sushi rice. The acidity of the sushi rice is not particularly limited, but is preferably 0.15 w / v% or more and 0.40 w / v% or less. The term "acidity" is as described above.

[0138] In the second embodiment, rice may be cooked with a higher amount of water than usual. By adding more water to the cooked rice, it is expected that the aging of the starch contained in the cooked rice can be suppressed, but the cooked rice usually becomes sticky and difficult to separate. However, by adding the enzyme to the cooked rice and cooking it, the rice is better able to separate and the stickiness is suppressed, resulting in an even greater effect of suppressing aging.

[0139] Therefore, when the cooked rice is white rice, the amount of water added is generally about 1.3 to less than 1.5 times the dry mass of the raw rice, whereas in this embodiment, the amount of water added may be about 1.5 to 1.8 times the dry mass of the raw rice.

[0140] Furthermore, when the cooked rice is sushi rice, the amount of water added is generally about 1.2 to less than 1.3 times the dry mass of the raw rice, whereas in this embodiment, the amount of water added may be about 1.3 to 1.7 times the dry mass of the raw rice.

[0141] The enzymes are added "before cooking" or "during cooking." Specifically, they can be added at any time between the time when the rice has been drained after washing and before cooking substantially begins in the rice cooking process. Here, "when cooking substantially begins" means when the water temperature reaches 40°C or higher. From the viewpoints of preventing dryness and aging of the surface of cooked rice after a long period of time, improving loosening, preserving the flavor of freshly cooked rice, preventing uneven heating during cooking, and improving convection, it is preferable to add the enzymes before the water temperature reaches the optimal temperature for the enzymes. In particular, it is preferable to add the enzymes to the rice before or simultaneously with adding the amount of water specified above.

[0142] In the second embodiment, in addition to the enzymes, "other ingredients generally added to foods," such as ingredients for seasonings and the like used in regular cooked rice, and ingredients, can be added to the cooked rice to the extent that the effects of the enzymes are not inhibited. Note that cooked rice containing or containing "other ingredients generally added to foods," such as ingredients for seasonings and the like (seasoning ingredients) and ingredients, can also be included in the "cooked rice" of the second embodiment. Here, "other ingredients generally added to foods" are as explained above.

[0143] Furthermore, instead of the enzyme, a liquid seasoning for cooking rice or a cooked rice improving agent according to the fourth or fifth embodiment described below may be added.

[0144] The cooked rice according to the second embodiment is defined by a manufacturing method in which 4-α-glucanotransferase is added and the rice is cooked. Generally, enzymes, except those with particularly high heat resistance, are inactivated by cooking, making it impossible to identify their structure based on the enzyme activity in the final product. Furthermore, it would be extremely difficult and expensive to fully analyze and numerically express the structural or characteristic changes that the addition of enzymes causes to cooked rice compared to the absence of enzymes at the time of filing, making it impossible to comprehensively express the results in the claims. Therefore, it is impossible or impractical to directly identify the cooked rice according to the second embodiment based on its structure or characteristics.

[0145] Next, the method for producing cooked rice according to the third embodiment is characterized in that 4-α-glucanotransferase is added before or during cooking. Here, the amounts of "cooked rice," "4-α-glucanotransferase," "α-amylase," and "maltotriohydrolase" added, their ratios, and the effects of these enzymes are as described above.

[0146] In the third embodiment, the method for producing cooked rice can basically be the same as the conventional method for producing cooked rice, except that the above-mentioned enzyme is added before or during cooking, and is specifically as described in the second embodiment.

[0147] In the third embodiment, in addition to the enzymes, "other ingredients generally added to foods," such as ingredients for seasonings and the like used in ordinary cooked rice, and ingredients, can be added to the extent that the effects of the enzymes are not inhibited. Note that cooked rice containing ingredients for seasonings and the like (seasoning ingredients) and "other ingredients generally added to foods," such as ingredients, can also be included in the "cooked rice" of the third embodiment. Here, the "other ingredients generally added to foods" are as explained above.

[0148] Furthermore, instead of the enzyme, a liquid seasoning for cooking rice or a cooked rice improving agent according to the fourth or fifth embodiment described below may be added.

[0149] In this way, the cooked rice produced by the production method according to the third embodiment becomes the cooked rice according to the first or second embodiment, containing or having added thereto 4-α-glucanotransferase.

[0150] Next, the liquid seasoning for rice cooking according to the fourth embodiment contains 4-α-glucanotransferase as an active ingredient. Here, the effects of "4-α-glucanotransferase," "α-amylase," and "maltotriohydrolase" and the enzymes are as described above.

[0151] The liquid seasoning according to the fourth embodiment is used for producing cooked rice according to the first or second embodiment. That is, this liquid seasoning has an effect of improving at least one of loosening, deterioration, and flavor of cooked rice after long-term storage, and when added to cooked rice, it functions as a loosening improver, deterioration improver, or flavor improver for cooked rice after long-term storage.

[0152] The total content of the enzymes in the liquid seasoning of the fourth embodiment is not particularly limited. When the liquid seasoning contains (a) 4-α-glucanotransferase and (b) α-amylase, from the viewpoints of suppressing dryness and aging of the surface of cooked rice after a long period of time, improving loosening, preserving the freshly cooked flavor, and further suppressing uneven heating during cooking and improving convection, the proportion of (a) in the total content of (a) and (b) can be, for example, 3% by mass or more, preferably 5% by mass or more, and more preferably 10% by mass or more, from the viewpoints of suppressing dryness and aging of the surface of cooked rice after a long period of time, improving loosening, and preserving the freshly cooked flavor even more significantly.

[0153] Furthermore, the upper limit of the proportion of (a) in the total content is not particularly limited, but can be, for example, 97% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less, from the standpoint of the desirability of the loosening method (loosening of the rice grains so that they crumble due to weak bonding between the grains is not desirable) and taste.

[0154] Therefore, the proportion of (a) in the total content of (a) and (b) can be, for example, 3% by mass or more and 97% by mass or less, preferably 5% by mass or more and 95% by mass or less, and more preferably 10% by mass or more and 90% by mass or less. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0155] The proportion of (a) in the total content of (a) and (b) in the seasoning liquid is not particularly limited as long as it is within the above-mentioned range. However, if it is outside the above-mentioned range, although the loosening effect is excellent, the bonding between the rice grains may become too weak, and the rice may loosen and crumble.

[0156] When the seasoning liquid of the fourth embodiment contains (a) 4-α-glucanotransferase, (b) α-amylase, and (c) maltotriohydrolase, in order to suppress dryness and aging of the surface of cooked rice over a long period of time, improve loosening, and further enhance the effect of preserving the freshly cooked flavor, the proportion of (a) in the total content of (a), (b), and (c) can be, for example, 10% by mass or more, preferably 15% by mass or more, and more preferably 20% by mass or more.

[0157] Furthermore, the upper limit of the proportion of (a) in the total content of the above (a), (b), and (c) is not particularly limited, but can be set to, for example, 80% by mass or less, preferably 75% by mass or less, and more preferably 70% by mass or less, from the standpoint of the desirability of the loosening method (loosening of the rice grains so that they crumble due to weak bonding between the grains is not desirable) and taste.

[0158] Therefore, the proportion of (a) in the total content of (a), (b), and (c) can be, for example, 10% by mass or more and 80% by mass or less, preferably 15% by mass or more and 75% by mass or less, and more preferably 20% by mass or more and 70% by mass or less. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0159] The liquid seasoning of the fourth embodiment may contain any enzyme other than the above three types of enzymes, as long as it does not interfere with the above-mentioned effects. The "any enzyme" is as explained above.

[0160] The liquid seasoning of the fourth embodiment may contain, in addition to the enzyme, "other ingredients commonly added to foods," and preferably contains "seasoning ingredients." Specific examples of "seasoning ingredients" include, but are not limited to, water, salt, vinegar, sugars (including high-intensity sweeteners), oils and fats, organic acids, amino acid seasonings, nucleic acid seasonings, organic acid seasonings, flavor ingredients, umami seasonings, alcoholic beverages, fruit juices, spices, spice extracts, flavor oils, flavors, and other taste and flavor components, viscosity adjusters such as gums and starches, stabilizers, colorants, and additives such as calcium salts.

[0161] In addition to these ingredients, the seasoning liquid of the fourth embodiment may contain ingredients such as vegetables (carrots, burdock, radish, etc.), grains (red beans, soybeans, etc.), meat, and fish. The contents of these ingredients and ingredients are not particularly limited and can be determined appropriately depending on the intended use of the cooked rice of the first or second embodiment. Note that "other ingredients generally added to foods" such as these various seasoning ingredients and ingredients are as explained above.

[0162] The liquid seasoning of the fourth embodiment is a liquid seasoning for rice cooking that is added before or during rice cooking. The time of addition can be any time between the time when draining of water after washing the rice is completed and before cooking by heating is substantially started in the rice cooking process. Here, "cooking by heating is substantially started" means that the water temperature reaches 40°C or higher. Note that from the viewpoints of preventing dryness and aging of the surface of cooked rice after a long period of time, improving loosening, preserving the freshly cooked flavor, preventing uneven heating during cooking, and improving convection, it is preferable to add the liquid seasoning before the water temperature reaches the optimal temperature for the enzyme.

[0163] The amount of the rice-cooking liquid seasoning of the fourth embodiment added to cooked rice is not particularly limited. From the viewpoints of preventing dryness and aging of the surface of cooked rice over a long period of time, improving loosening, and maintaining the freshly cooked flavor, the total amount of (a) 4-α-glucanotransferase and (b) α-amylase, or (a), (b), and (c) maltotriohydrolase contained or added to cooked rice can be, for example, 0.003% by mass or more, preferably 0.004% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.006% by mass or more, particularly preferably 0.0065% by mass or more, and particularly preferably 0.007% by mass or more, based on the dry raw rice before washing and soaking.

[0164] The upper limit of the amount to be added is not particularly limited, but from the viewpoint of solubility and miscibility with other ingredients such as water added during rice cooking and seasoning liquid, the amount can be set so that the total amount of the above (a) and (b), or (a), (b) and (c) contained or added to cooked rice is, for example, 0.20% by mass or less, preferably 0.15% by mass or less, and more preferably 0.12% by mass or less, of the dried raw rice before washing and soaking.

[0165] Therefore, the amount of seasoning liquid added to cooked rice can be such that the total amount of (a) and (b), or (a), (b) and (c), contained in or added to the cooked rice is, for example, 0.003% by mass to 0.20% by mass, preferably 0.004% by mass to 0.20% by mass, more preferably 0.005% by mass to 0.20% by mass, even more preferably 0.006% by mass to 0.20% by mass, particularly preferably 0.0065% by mass to 0.15% by mass, and especially preferably 0.007% by mass to 0.12% by mass, based on the dried raw rice before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0166] Furthermore, the amount of seasoning liquid added to cooked rice in the fourth embodiment is not particularly limited, but from the standpoint of preventing the surface of cooked rice from becoming dry and aging over a long period of time, improving loosening, and maintaining the freshly cooked flavor, the amount of 4-α-glucanotransferase contained or added to cooked rice can be, for example, 0.0005% by mass or more, preferably 0.0006% by mass or more, even more preferably 0.0007% by mass or more, even more preferably 0.001% by mass or more, especially preferably 0.0013% by mass or more, and especially more preferably 0.0015% by mass or more, relative to the dried raw rice before washing and soaking.

[0167] Furthermore, although there is no particular upper limit to the amount added, from the viewpoint of solubility and miscibility with other ingredients such as water and seasoning liquid added during rice cooking, the amount of 4-α-glucanotransferase contained or added in cooked rice can be, for example, 0.20% by mass or less, preferably 0.10% by mass or less, relative to the dried raw rice before washing and soaking.

[0168] Therefore, the amount of seasoning liquid added to cooked rice can be such that the content or amount of 4-α-glucanotransferase in the cooked rice is, for example, 0.0005% by mass to 0.20% by mass, preferably 0.0006% by mass to 0.20% by mass, more preferably 0.0007% by mass to 0.20% by mass, even more preferably 0.001% by mass to 0.20% by mass, particularly preferably 0.0013% by mass to 0.10% by mass, and especially preferably 0.0015% by mass to 0.10% by mass, based on the amount of 4-α-glucanotransferase added to the dried raw rice before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0169] When the seasoning liquid of the fourth embodiment contains α-amylase together with 4-α-glucanotransferase, the amount of the seasoning liquid added to cooked rice is not particularly limited, but from the viewpoints of preventing the surface of cooked rice from becoming dry and aging over a long period of time, improving loosening, and maintaining the freshly cooked flavor, the amount of 4-α-glucanotransferase contained or added in the cooked rice can be within the above range, and the amount of α-amylase contained or added in the cooked rice can be, for example, 0.0005% by mass or more, preferably 0.0006% by mass or more, even more preferably 0.0007% by mass or more, even more preferably 0.001% by mass or more, especially preferably 0.0013% by mass or more, and especially more preferably 0.0015% by mass or more, relative to the dried raw rice before washing and soaking.

[0170] Furthermore, although there is no particular upper limit to the amount added, from the viewpoint of solubility and miscibility with other ingredients such as water and seasoning liquid added during rice cooking, the amount of 4-α-glucanotransferase contained or added in cooked rice can be within the above range, and the amount of α-amylase contained or added in cooked rice can be, for example, 0.20% by mass or less, preferably 0.10% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.04% by mass or less, relative to the amount of dried raw rice before washing and soaking.

[0171] Therefore, the amount of seasoning liquid added to cooked rice can be such that the content or amount of 4-α-glucanotransferase in the cooked rice is within the above-mentioned range, and the content or amount of α-amylase in the cooked rice is, for example, 0.0005% by mass to 0.20% by mass, preferably 0.0006% by mass to 0.20% by mass, more preferably 0.0007% by mass to 0.10% by mass, even more preferably 0.001% by mass to 0.10% by mass, particularly preferably 0.0013% by mass to 0.05% by mass, and especially preferably 0.0015% by mass to 0.04% by mass, based on the dried raw rice before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0172] When the seasoning liquid of the fourth embodiment contains maltotriohydrolase together with 4-α-glucanotransferase and α-amylase, the amount of the seasoning liquid added to cooked rice is not particularly limited, but from the viewpoint of preventing the surface of cooked rice from becoming dry and aging over a long period of time, improving loosening, and maintaining the flavor of freshly cooked rice, the amount of 4-α-glucanotransferase and α-amylase contained or added in the cooked rice can be within the above-mentioned range, and the amount of maltotriohydrolase contained or added in the cooked rice can be, for example, 0.0005% by mass or more, preferably 0.0006% by mass or more, more preferably 0.0007% by mass or more, even more preferably 0.001% by mass or more, and particularly preferably 0.0013% by mass or more, relative to the dried raw rice before washing and soaking.

[0173] Furthermore, although there is no particular upper limit to the amount added, from the viewpoint of solubility and miscibility with other ingredients such as water and seasoning liquid added during rice cooking, the amount of 4-α-glucanotransferase and α-amylase contained or added in cooked rice can be within the above range, and the amount of maltotriohydrolase contained or added in cooked rice can be, for example, 0.20% by mass or less, preferably 0.10% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.04% by mass or less, relative to the amount of dried raw rice before washing and soaking.

[0174] Therefore, the amount of seasoning liquid added to cooked rice can be such that the content or amount of 4-α-glucanotransferase and α-amylase in the cooked rice is within the above-mentioned ranges, and the content or amount of maltotriohydrolase in the cooked rice is, for example, 0.0005% by mass to 0.20% by mass, preferably 0.0006% by mass to 0.20% by mass, more preferably 0.0007% by mass to 0.10% by mass, even more preferably 0.001% by mass to 0.05% by mass, and particularly preferably 0.0013% by mass to 0.04% by mass, based on the dried raw rice before washing and soaking. Ranges formed by any combination of the above upper and lower limits are also exemplified in the present specification.

[0175] Next, the cooked rice improving agent according to the fifth embodiment contains 4-α-glucanotransferase as an active ingredient. Here, the effects of "cooked rice," "4-α-glucanotransferase," "α-amylase," and "maltotriohydrolase" and these enzymes are as described above.

[0176] The cooked rice improving agent according to this embodiment is used for producing cooked rice according to the first or second embodiment. That is, when this cooked rice improving agent is contained in cooked rice, it has the effect of improving at least one of the loosening, deterioration, and flavor of cooked rice after long-term storage.

[0177] The total content of the enzymes in the cooked rice improving agent is not particularly limited. When the cooked rice improving agent contains (a) 4-α-glucanotransferase and (b) α-amylase, the proportion of (a) in the total content of (a) and (b), and when the cooked rice improving agent contains (a), (b), and (c) maltotriohydrolase, the proportion of (a) in the total content of (a), (b), and (c) are as explained in the fourth embodiment.

[0178] The cooked rice improving agent of the fifth embodiment may contain any enzyme other than the above three types of enzymes, as long as it does not interfere with the above-mentioned effects. The "any enzyme" is as explained above.

[0179] The cooked rice improving agent of the fifth embodiment may contain, in addition to the enzyme, other ingredients that are generally added to foods, such as seasoning ingredients, etc. Here, the "other ingredients that are generally added to foods" are as explained above.

[0180] The cooked rice improving agent of the fifth embodiment is used by adding it before or during cooking rice. The timing of addition is as explained above.

[0181] Furthermore, the amount of the cooked rice improving agent of the fifth embodiment added to cooked rice can be the same as that of the fourth embodiment.

[0182] Next, the sixth embodiment of the method for improving the quality of cooked rice after long-term storage involves adding 4-α-glucanotransferase and cooking the rice. Here, the effects of "cooked rice," "4-α-glucanotransferase," "α-amylase," and "maltotriohydrolase" and these enzymes are as described above.

[0183] In the sixth embodiment, by adding an enzyme and cooking the rice in the same manner as in the method for producing cooked rice according to the third embodiment, it is possible to achieve an improvement in the quality of cooked rice after long-term storage (improvement in at least one of loosening, deterioration, and flavor). Note that "improvement in loosening," "improvement in deterioration," and "improvement in flavor" are as explained above.

[0184] Furthermore, when at least 4-α-glucanotransferase and α-amylase are added as enzymes, in addition to the above-mentioned quality improvement effect, the effect of suppressing uneven heating during cooking can also be obtained.

[0185] "Uneven heating" refers to the phenomenon in which cooking with heat changes the components (starch, sugar, etc.) contained in the ingredients (rice, water, ingredients, seasoning, etc.) inside the rice cooker, causing an increase in viscosity, preventing the ingredients from convection properly inside the cooker, resulting in a temperature gradient (uneven temperature) inside the cooker, and the quality of the cooked rice (hardness, graininess, etc.) not being uniform, resulting in unevenness such as stickiness or pastiness. It is presumed that adjusting the amount of enzyme added to the cooked rice so that it falls within the specified range described above and cooking the rice improves convection, thereby improving uneven heating. The action of each enzyme is considered to be as described above.

[0186] The amounts of (a) 4-α-glucanotransferase, (b) α-amylase, and (c) maltotriohydrolase added and the total amount added in the sixth embodiment are as described in the second embodiment.

[0187] Furthermore, when rice is cooked with the addition of (a) 4-α-glucanotransferase and (b) α-amylase, the proportion of (a) in the total amount of (a) and (b) added, and when rice is cooked with the addition of (c) maltotriohydrolase together with (a) and (b), the proportion of (a) in the total amount of (a), (b), and (c) added, are as described in the second embodiment.

[0188] Instead of the enzyme, the liquid seasoning for rice cooking or the cooked rice improving agent according to the fourth or fifth embodiment may be added.

[0189] In the sixth embodiment, the rice cooking method may basically be the same as that conventionally practiced, except that the rice is cooked with the addition of the enzymes described above, and specifically as described above.

[0190] The timing of adding the enzyme is either "before cooking" or "during cooking," as explained above. [Example]

[0191] Hereinafter, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to these examples.

[0192] Evaluation test 1 (verification of the effect of enzyme combinations) Various enzyme preparations of α-amylase (A1: optimum temperature of approximately 70°C), maltotriohydrolase (A2: optimum temperature of approximately 50°C), and 4-α-glucanotransferase (A3: optimum temperature of approximately 50°C) were used as enzymes, and the quality improvement effects on cooked rice after long-term storage and the convection improvement effects during cooking were compared when these enzymes were added alone to cooked rice and when two or more types were added in combination.

[0193] 450 g of polished Koshihikari rice from Toyama Prefecture in 2019 was weighed, washed, and soaked (at room temperature for 1 hour). After soaking, water was added to the rice to a 1.40x water ratio (total water weight: 630 g). The enzymes shown in Table 1 were added at 0.0195 w / w% (87.75 mg total) per uncooked rice. The rice was then cooked in an induction cooker (JKT-G101, manufactured by Tiger Corporation) using the quick-cook setting. The cooked rice was cooled to 45°C in a vacuum cooler (CMJ-20QE, manufactured by Miura Corporation) and formed into 20 g sushi rice balls using a rice ball-forming machine (SSN-FRA, manufactured by Suzumo Instruments Co., Ltd.) (Examples 1 to 9).

[0194] The sushi rice balls prepared as described above were stored at 20°C for 24 and 48 hours, assuming they were to be eaten as a takeaway meal, and then subjected to the following sensory evaluation test. The sensory evaluation was carried out by 10 expert panelists, who evaluated the loosening, condition of the rice grain surface (dryness), aging (gritty texture), and flavor (taste and deliciousness of freshly cooked rice) according to the following criteria, and average scores were calculated. Freshly cooked white rice that had been cooked for 2 hours was used as a control.

[0195] <Loosening (when you put it in your mouth, you can feel the strength of the rice grains sticking together with your tongue, front teeth, and upper palate)> 7: Much better than control 6: Better than control 5: Slightly better than the control 4: Equivalent to control 3: Slightly worse than control 2: Worse than control 1: Much worse than control

[0196] <Deterioration prevention: Dryness (the feeling of the surface of the rice grain when it is put in the mouth and reaches the tongue is dry) Dear Customer)> 4: Equivalent to control 3: Slightly drier than the control 2: Dryer than the control 1: Much drier than the control

[0197] <Deterioration prevention: Aging (the texture of rice felt during chewing is powdery and crumbly) )> 4: Equivalent to control 3: Slightly rougher than the control 2: More gritty than the control 1: Much rougher than the control

[0198] <The taste and deliciousness of rice> 4: Equivalent to control 3: Slightly worse than the control 2: Inferior to control 1: Very inferior to control

[0199] In addition, convection during cooking was evaluated by monitoring the temperatures at the top and bottom of the rice cooker using a convection measuring device (DATATRACE (memory thermometer) Micropack III). The evaluation criteria are shown in Figures 1 to 3. Figure 1 shows the temperature history inside the cooker when the convection rating is "3," Figure 2 shows a convection rating of "2," and Figure 3 shows a convection rating of "1." As in Figure 1, if the temperature rises smoothly at both the top and bottom of the cooker, the rating is 3. If the temperature rise stagnates during heating, as in the circled area in Figure 2, the rating is 2. If a sudden drop in temperature (more than 5°C) during heating is observed, as in the circled area in Figure 3, the rating is 1.

[0200] <Convection during cooking> 3: The temperature rises smoothly both at the top and bottom of the pot (see image in Figure 1). 2: Temperature rise stagnation is observed during heating (image in Figure 2) 1: A sudden drop in temperature (more than 5°C) is observed during heating (image in Figure 3).

[0201] [Table 1] In the table, the content of each enzyme is shown as mass % per raw rice.

[0202] The results after 24 hours of storage at 20°C are shown in Table 1. As can be seen from Table 1, cooked rice containing either α-amylase or maltotriohydrolase alone did not show any clear quality improvement effects compared to the control (cooked cooked rice). On the other hand, cooked rice containing 4-α-glucanotransferase alone showed quality improvement effects, such as improved loosening, suppression of deterioration (dry surface, aging), and improved flavor (maintaining the freshly cooked flavor), even after long-term storage.

[0203] Furthermore, cooked rice treated with a combination of maltotriohydrolase and 4-α-glucanotransferase showed some improvement in loosening, but no clear effect was observed in terms of preventing deterioration or improving flavor. In contrast, when α-amylase and 4-α-glucanotransferase were used in combination, quality improvement was observed even after long-term storage, and it was also effective in preventing uneven heating (improving convection).

[0204] Furthermore, it was found that the enzyme composition (Example 9) containing α-amylase, maltotriohydrolase, and 4-α-glucanotransferase in a mass ratio of 1:1:1 exhibited the most excellent quality improvement and convection improvement effects. Similar effects were also confirmed when the composition was stored at 20°C for 48 hours.

[0205] Evaluation test 2 (verification of the effect of enzyme content) In this test, rice containing three types of enzymes in a 1:1:1 ratio, which showed the highest effect in Evaluation Test 1, was prepared with varying contents as shown in Table 2, and the effects were compared.

[0206] As the enzyme, an enzyme composition of the same composition as in Example 9 was used, and the total amount added per raw rice was varied from 0.0039 w / w% to 0.1170 w / w%. Except for this, rice balls were prepared in the same manner as in Evaluation Test 1, and sensory evaluation was performed after storing them at 20°C for 24 hours and 48 hours (Examples 10 to 15).

[0207] [Table 2] In the table, the content of each enzyme is shown as mass % per raw rice.

[0208] The results after 24 hours of storage at 20°C are shown in Table 2. Table 2 shows that by adding a certain amount of enzyme to raw rice, excellent quality improvements can be achieved, such as improved loosening of cooked rice after long-term storage, suppression of deterioration (dry surface and aging), and improved flavor (maintaining the flavor of freshly cooked rice), and excellent effects can also be achieved in improving convection during cooking. Similar effects were confirmed when the rice was stored for 48 hours at 20°C.

[0209] Evaluation test 3 (verification of the effect of enzyme content ratio) In this test, rice containing all three enzymes was prepared with the ratio of each enzyme changed as shown in Table 3, and the effects were compared.

[0210] The total amount of enzymes added per uncooked rice was adjusted as shown in Table 3, and the ratio of each enzyme to the total amount added was varied. Except for this, rice balls of white rice were prepared in the same manner as in Evaluation Test 1, and sensory evaluations were performed after storing at 20°C for 24 and 48 hours (Examples 16 to 25). For reference, rice balls of white rice were prepared in the same manner without adding enzymes, and the results of similar evaluations are shown as Comparative Example 1.

[0211] [Table 3] In the table, the content of each enzyme is shown as mass % per raw rice.

[0212] Table 3 shows that adjusting the ratio of 4-α-glucanotransferase to the total enzyme content can improve the quality of cooked rice after long-term storage, inhibit deterioration (dry surface, aging), and improve flavor (maintain freshly cooked flavor), and also improve convection during cooking. Examples 16, 21, 22, and 25 showed good loosening, but tended to break apart. Similar effects were observed when the rice was stored at 20°C for 48 hours.

[0213] Evaluation test 4 (verification of the effect on vinegared rice) Using 450 g of polished rice and the enzyme content shown in Table 4, rice was cooked in the same manner as in Evaluation Test 1. 99 ml (220 ml / kg of raw rice) of sushi vinegar (acidity 2.87 w / v%) was added to the freshly cooked white rice and mixed with vinegar to obtain vinegared rice (acidity 0.26 w / v%). The composition of the sushi vinegar was 36% brewed vinegar (acetic acid acidity 6.46 w / v%), 55% sucrose, and 9% salt (all by mass).

[0214] Next, rice balls were prepared in the same manner as in Evaluation Test 1, and after storage at 20°C for 24 hours and 48 hours, sensory evaluations were performed (Examples 26 to 31). The sensory evaluation was performed by 10 expert panelists, who evaluated the loosening, condition of the rice grain surface (dryness), aging (crumbly feeling), flavor (taste of freshly cooked rice, deliciousness), and taste, and calculated the average score. As a control, freshly cooked vinegared rice that had been mixed with vinegar for 2 hours was used.

[0215] The taste was evaluated using the following criteria: <Taste (the acidity of the vinegar is just right and not too strong)> 4: Equivalent to control 3: Slightly worse than the control 2: Inferior to control 1: Very inferior to control

[0216] The lightness of the mixture when mixed with a rice paddle was also evaluated according to the following criteria: The control was cooked white rice (without enzymes added) to which the sushi vinegar was added and mixed with the vinegar (Comparative Example 2).

[0217] <Lightness when mixed with a rice paddle> 3: Much easier to stir than the control 2: Easier to stir than the control 1: Slightly easier to stir than the control

[0218] [Table 4] In the table, the content of each enzyme is shown as mass % per raw rice.

[0219] The results for 24 hours of storage at 20°C are shown in Table 4. Table 4 shows that, just like with white rice, adding enzymes to vinegared rice also has an excellent effect on improving the quality of cooked rice after long-term storage (improving loosening, inhibiting deterioration (dry surface, aging), and improving flavor (maintaining the freshly cooked flavor)). In particular, a high quality improvement effect was observed when α-amylase and 4-α-glucanotransferase were used in combination, and the effect was particularly remarkable when all three enzymes were used in combination. Similar effects were confirmed in the results for 48 hours of storage at 20°C. The results were also similar when the acidity of vinegared rice was evaluated at 0.2 w / v% and 0.4 w / v%.

[0220] Although the embodiments and examples of the present disclosure have been described in detail above, the specific configurations are not limited to these, and design changes that do not deviate from the gist of the present disclosure are included in the present disclosure.

[0221] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority based on Japanese Patent Application No. 2020-114281, filed with the Japan Patent Office on July 1, 2020, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. (a) Cooked rice containing 4-α-glucanotransferase.

2. The cooked rice according to claim 1, further comprising (b) α-amylase.

3. The cooked rice according to claim 2, further comprising (c) maltotriohydrolase.

4. The cooked rice according to any one of claims 1 to 3, wherein the content of any one or more of (a), (b), and (c) in the cooked rice is 0.0005% by mass or more with respect to raw rice.

5. The total content of (a) and (b), or (a), (b) and (c) in the cooked rice is 0.003% by mass or more with respect to raw rice. Cooked rice according to any one of claims 2 to 4.

6. The ratio of (a) to the total content of (a) and (b), or (a), (b) and (c) is 10% or more and 80% or less. Cooked rice according to any one of claims 2 to 5.

7. The cooked rice according to any one of claims 1 to 6, wherein the cooked rice is white rice or sushi rice.

8. (a) Cooked rice obtained by adding 4-α-glucanotransferase and cooking the rice.

9. (a) A method for producing cooked rice, in which 4-α-glucanotransferase is added before or during cooking.

10. (a) A seasoning liquid for cooking rice or a cooked rice improving agent containing 4-α-glucanotransferase.

11. (a) A method for improving at least one of loosening, deterioration, and flavor of cooked rice after long-term storage by adding 4-α-glucanotransferase and cooking the rice.

12. A method for improving at least one of the loosening, deterioration, flavor, and uneven heating during cooking of cooked rice after long-term storage, by adding (a) 4-α-glucanotransferase and (b) α-amylase, or the above-mentioned (a), (b), and (c) maltotriohydrolase, and then cooking the rice.

13. 13. The method for improving at least one of the loosening, deterioration, flavor, and uneven heating during cooking of cooked rice after long-term storage according to claim 12, wherein (a) and (b), or (a), (b) and (c) are added so that the total content of (a), (b), and (c) in the cooked rice is 0.003% by mass or more relative to the amount of raw rice.

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