Rice, production method thereof, rice modifier, method of improving loosening of rice, and use method for improving uneven heating inside pot when cooking rice

Abstract

To provide a technique for efficiently producing rice which, even after long storage after cooking, sufficiently retains the taste of freshly cooked rice, by improving the separation of the grains.SOLUTION: A rice modifier satisfies all of the followings (1) to (3) that: (1) the following (a) and (b) are satisfied: (a) glutaminase is contained by 0.01-10.0 wt.% in the rice modifier and (b) enzymatic activity of the glutaminase is 100 mU / g or more in the rice modifier; (2) pH of the rice modifier at 20°C is 4.6-9.0; and (3) dissociation type acetic acid concentration is 0.001-2.000 wt.%.SELECTED DRAWING: None

Description

Technical Field

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[0006]

[0001] The present invention relates to cooked rice, a method for producing the same, a cooked rice improver, a method for improving the looseness of cooked rice, and a method of use for improving uneven heating inside a rice cooker during cooking of cooked rice. Background Art

[0002] Recently, there has been an increase in the eating pattern called "ready-to-eat meals" where cooked rice such as onigiri, bento, and sushi is taken home from supermarkets or convenience stores and eaten. Therefore, the importance of technology for maintaining the deliciousness of cooked rice for a long time has been increasing.

[0003] As a technology for maintaining the deliciousness of cooked rice (such as plain cooked rice, onigiri, sushi rice, etc.) for a long time, for example, in Patent Document 1, there is disclosed a method for improving cooked rice, which is characterized by adding enzymes such as amylase, protease, and lipase, salt, and cyclodextrin when cooking polished rice. However, with this technology, the looseness of the cooked rice could not be sufficiently improved.

Prior Art Documents

[10] A method for producing cooked rice according to any one of the above, characterized in that edible oil is added to a mixture of raw rice and water before cooking, such that the amount added is 0.1 to 2 w / w% relative to the raw rice before water is added.

[11] A method for producing cooked rice according to any one of the above, characterized by cooling the cooked rice after it has been cooked.

[12] A method for improving the looseness of cooked rice, characterized by adding the rice improver described in any one of the above to a mixture of raw rice (excluding indica rice and feed rice) and water before cooking.

[13] A method for improving the looseness of cooked rice according to any one of the above, characterized in that edible oil is added to a mixture of raw rice and water before cooking, such that the amount added is 0.1 to 2 w / w% relative to the raw rice before water is added.

[14] A method for improving uneven heating inside a rice cooker during rice cooking, characterized by adding the rice cooker described in any one of the above to a mixture of raw rice (excluding indica rice and feed rice) and water before cooking. [Effects of the Invention]

[0007] The rice improver of the present invention provides rice that remains easy to separate even after being stored for a long time after cooking. [Modes for carrying out the invention]

[0008] In this specification, when specifying multiple upper and / or lower limits for a numerical range, even if not explicitly stated, the specification of a numerical range combining at least the maximum value of the upper limit and the minimum value of the lower limit is directly stated, and all numerical ranges obtained by combining any upper limit from among the upper limits and any lower limit from among the lower limits are included in one embodiment of the present invention. Also, in this specification, a numerical range connected by "~" means a numerical range that includes the numbers before and after "~" as the lower and upper limits. When multiple lower limits and multiple upper limits are shown separately, any lower and upper limits can be selected and connected by "~". In this invention, "wet mass conversion" (sometimes simply referred to as "wet mass basis") represents the content ratio of the target component in a sample, calculated by using the wet mass of the sample containing water as the denominator and the mass of the target component in the sample as the numerator. Furthermore, in the proportion specifications of this invention, when simply stated as "mass%" or "w / w%" without further specification, it represents the proportion "wet mass conversion".

[0009] <Rice> "Cooked rice" refers to rice that has been cooked from raw rice. Examples of cooked rice in this invention include plain white rice, sushi rice (vinegared rice), red bean rice, pilaf, fried rice, mixed rice, and sticky rice. Furthermore, in the case of foods that contain cooked rice as part of a larger food, such as sushi and rice balls, the cooked rice contained in those foods is included in the "cooked rice" of this embodiment. In addition, the claims and specification of this application refer to cooked rice obtained by cooking raw rice.

[0010] <Rice for ready-made meals> The type of food obtained by this food manufacturing method is not limited, but it is preferable that it be a ready-to-eat food that requires time from manufacturing or processing to consumption. In other words, a "ready-to-eat" food in this invention refers to a type of food that is purchased and eaten outside the home, such as bento boxes or side dishes purchased from a delicatessen, convenience store, or supermarket, or by using delivery services from a restaurant. These types of foods are sold in simple trays or containers, bottles, cans, pouches, and retort pouches. Generally, ready-to-eat meals and / or prepared foods are consumed several hours or more after being manufactured, and are stored at room temperature (10-25°C) or chilled (below 10°C) for several hours to about 100 hours. They can also be stored frozen (below -10°C) for about a year. Pouched products can be stored at room temperature or chilled for about 15-45 days or about 1-2 years. "Prepared rice for take-out" refers to rice that has been prepared to be eaten at home as a meal. Examples include white rice, sushi rice (vinegared rice), red bean rice, pilaf, fried rice, seasoned rice, and sticky rice sold at convenience stores and supermarkets, such as onigiri (rice balls), sushi, and bento boxes. Prepared rice for take-out often has a long shelf life from production to consumption, and may also be cooled after cooking for reasons of preservation and transportability. Therefore, it is important that it can maintain its excellent flavor and looseness for a long time. In addition, since prepared rice for take-out is often filled into containers, it is preferable that the rice is of a quality that makes it easy to loosen from the standpoint of packaging.

[0011] Furthermore, since rice for ready-to-eat meals is often cooked in large quantities (around 10 to 10 tens of kilograms per pot) using industrial rice cookers, the rice does not circulate properly inside the pot, resulting in uneven heating. This leads to inconsistent texture and grain separation in the cooked rice, and depending on its position inside the pot, the rice grains may stick together, forming clumps or a paste-like consistency, resulting in an unsatisfactory taste (flavor and texture) when eaten. In addition, uneven heating can easily cause the rice cooker to burn, leading to reduced yield due to waste, increased workload during subsequent pot cleaning, and deterioration of the rice cooker itself, all of which are problems for productivity. Therefore, reducing uneven heating is strongly desired in the production of rice for ready-to-eat meals.

[0012] <loosen up> In cooked rice, "looseness" refers to the fact that the rice grains are not easily bound together and separate easily. In cooked rice dishes such as rice balls and sushi, good looseness enhances consumer preference. Furthermore, in the case of cooked rice in bento boxes, good looseness is considered a desirable characteristic from the perspective of making it easier to fill the container with rice.

[0013] The ease with which cooked rice separates can be evaluated as a texture, for example, through sensory evaluation, such as "how weak the bond between rice grains is when placed in the mouth and felt on the tongue, front teeth, and upper palate." It can also be evaluated based on the number of small holes (like crab holes) in the cooked rice immediately after cooking, and how easily it can be handled with a rice paddle, as will be discussed later.

[0014] <The deliciousness of rice> In this invention, the "deliciousness" of cooked rice refers to the degree of likability judged comprehensively from the taste, texture, and flavor perceived when the rice is placed in the mouth, and can be evaluated, for example, by sensory evaluation. The goodness of the cooked rice's "separation" as mentioned above is also one of the factors that influence the "deliciousness" of the cooked rice.

[0015] <Crab hole> "Crab holes" refer to "holes that allow steam generated during cooking to escape," and can be visually inspected on the surface of cooked rice immediately after cooking to reveal cavities with roughly circular openings of 3 to 10 mm in diameter. If many crab holes are present on the surface of the cooked rice immediately after cooking in the rice cooker, it can be evaluated that the cooked rice has loosened well throughout and was cooked under good heating conditions.

[0016] <Shamoji Street> "Rice paddle ease" refers to "how easily cooked rice can be stirred inside the rice cooker after cooking." When rice separates well, the grains are less bound together, reducing the force required to stir and resulting in better rice paddle ease. Conversely, when rice separates poorly, it becomes difficult to stir. Also, less charring in the rice cooker improves rice paddle ease. Furthermore, good rice paddle ease makes it easier to pack the rice into bento boxes and other containers. Therefore, good rice paddle ease indicates that the cooked rice separates well overall, and can be evaluated as producing rice suitable for use in, for example, ready-to-eat meals.

[0017] <Uneven heating> In this invention, "uneven heating" refers to a condition where a temperature gradient occurs from the top to the bottom of the rice cooker, resulting in uneven quality of cooked rice. Heating changes the physical properties of components (such as starch) contained in the raw materials (rice, water, ingredients, seasoning liquid, etc.) inside the rice cooker, increasing their viscosity. When the viscosity increases, the raw materials inside the pot do not circulate properly, creating a temperature gradient from the top to the bottom of the pot. When such a temperature gradient occurs, the surface of the cooked rice sticks together, resulting in uneven quality of cooked rice, such as some parts becoming lumpy or others becoming paste-like. Uneven heating can be improved by reducing the temperature difference between the top and bottom of the pot during cooking. Conversely, if the temperature difference between the top and bottom of the pot is large, the heating conditions will not be appropriate, and the uneven heating will increase. In this invention, "top of the pot" and "bottom of the pot" refer to the position of the raw rice and the cooked rice (pre-cooked rice) mixed inside the pot. "Upper part of the pot" refers to the position on the hypothetical vertical line that passes through the center of the pot opening, starting from the liquid surface and corresponding to 1 cm below (i.e., the center of the pot and 1 cm below the liquid surface of the uncooked rice), and "Bottom of the pot" refers to the position on the hypothetical vertical line that starts from the bottom of the pot and corresponding to 2 cm above (i.e., the center of the pot and 2 cm from the bottom of the pot).

[0018] Uneven heating can be evaluated by measuring the temperature change at the top and bottom of the rice cooker pot during the process of rice changing from uncooked to cooked. For example, it can be evaluated by monitoring the temperature difference between the top and bottom of the rice cooker pot using a temperature measuring instrument (DATATRACE (memory thermometer) Micropack III). For instance, if the temperature at both the top and bottom of the rice cooker pot reaches 98°C within a predetermined time after the start of cooking, it can be evaluated as having little uneven heating. More specifically, the temperature at both the top and bottom of the pot may reach 98°C or higher within 2 to 20 minutes after the start of cooking. More specifically, the upper limit may be within 18 minutes, or within 16 minutes, or within 14 minutes, or within 12 minutes, or within 10 minutes, or within 8 minutes. The lower limit may be 3 minutes or more, or 4 minutes or more. Furthermore, if the temperature at both the top and bottom of the rice cooker pot remains above 98°C for a specified period of time from the start of cooking to the completion of cooking, it can be evaluated as having minimal uneven heating. Specifically, the time at which the temperature at both the top and bottom of the pot remains above 98°C may be between 8 minutes and 40 minutes. More specifically, the upper limit may be within 35 minutes, 30 minutes, 25 minutes, or 20 minutes. In addition, if the difference in the time at which the temperature at the top and bottom of the rice cooker pot remains above 98°C is within 7 minutes, it can be evaluated as having particularly minimal uneven heating.

[0019] <Raw rice> "Raw rice" refers to rice before cooking. In this invention, rice refers to brown rice (rice with the husk removed), white rice (rice with the bran removed), or a mixture thereof. From the viewpoint of the need to "improve the looseness of cooked rice," which is the objective of this invention, the raw rice used in this invention is preferably Japonica rice and preferably does not include Indica rice or feed rice.

[0020] <Japonica rice> Examples of "Japonica rice" include Aichi no Kaori, Akita Komachi, Ichihomare, Oborozuki, Kaze Sayaka, Kinuhikari, Kirara 397, Ginga no Shizuku, Koshiibuki, Koshihikari, Kin-iro no Kaze, Sakihokore, Sasanishiki, Satoyama no Tsubu, Shinnosuke, Seiten no Hekireki, Date Masayume, Tsugaru Roman, Tsukiakari, Tsuyahime, Tentakaku, Ten no Tsubu, Donpishari, Nanatsuboshi, Nikomaru, Haenuki, Hatsushimo, Hitomebore, Hyakumangoku, Fusakogane, Fukkurinko, Tomitomi, Masshigura, Mineasahi, Mori no Kumasan, Yukiwakamaru, Yumeobako, Yumepirika, and Yumemizuho. Furthermore, this invention can be applied to rice whose taste has been improved by crossbreeding Japonica rice and Indica rice.

[0021] <Rice for feed> "Feed rice" refers to rice varieties cultivated primarily for use as animal feed, and is distinguished from staple rice cultivated primarily for human consumption. Examples of feed rice varieties include Akihikari, Fukuhibiki, Bekoaoba, Iwaidawara, Yumeaoba, and Momiroman. Furthermore, rice whose taste has been improved by crossbreeding staple rice and feed rice can be applied to this invention.

[0022] <Amylose content of raw rice> Generally, cooked rice made from rice with a high apparent amylose content is easily separated, and therefore the problem addressed by the present invention is small. Consequently, from the viewpoint of the need to "improve the separation of cooked rice," which is the problem addressed by the present invention, it is more useful to use the rice improver of the present invention on cooked rice made from rice with an apparent amylose content below a predetermined value. In the present invention, the apparent amylose content is the apparent amylose content measured by the absorption value of a single wavelength, using the iodine color reaction to determine the amount of the amylose-iodine complex in the endosperm starch contained in rice flour. The apparent amylose content can be measured by known methods, but for example, it can be measured according to Inatsu (1988) Research on quality improvement by improving the taste of Hokkaido-produced rice, Report of the Hokkaido Prefectural Agricultural Experiment Station, No. 66, pp. 1-89 (1988-03). Specifically, the present invention can be used more effectively by producing cooked rice using the rice improver of the present invention on rice whose apparent amylose content is below a predetermined value. More specifically, the rice may have an apparent amylose content of 0% to 30%. More specifically, the upper limit may be 28% or less, or 25% or less, or 20% or less. The lower limit may be 3% or more, or 5% or more.

[0023] <Rice Cooking> Cooking rice refers to the process of heating a mixture of raw rice and water that has been properly washed and then mixed with water.

[0024] <Rice improver> A rice improver is a food or beverage that has the effect of improving the quality of cooked rice. Rice improvers are usually used before or after cooking rice, but the rice improver of the present invention is used before cooking rice. The form of the rice improver of the present invention is not particularly limited, and may be in liquid or solid form (including pellet form, powder form, etc.), but it is preferable to be in liquid form from the viewpoint of ease of mixing after addition.

[0025] The timing for adding the rice improver of the present invention to raw rice before cooking may be immediately before mixing the raw rice with water (before adding water), immediately after adding water and starting soaking, or immediately after soaking the raw rice and starting cooking. However, it is preferable that the time between adding the rice improver and starting cooking is within a predetermined time.

[0026] The rice-improving agent of the present invention contains glutaminase. <Glutaminase> Glutaminase is a type of amide hydrolase enzyme that produces glutamic acid from glutamine through the following reaction. Note that glutaminase is a different enzyme from transglutaminase, which promotes cross-linking between glutamine and lysine residues. Glutamine + H2O → Glutamic acid + NH3 (Equation 1)

[0027] The glutaminase contained in the rice improver of the present invention includes those defined in the 9th edition of the Japanese Food Additives Compendium, but the origin of the glutaminase contained in the composition of the present invention is not particularly limited and may be derived from various natural materials containing glutaminase, synthesized, or used together. If derived from natural materials, the glutaminase contained in the various materials may be isolated and purified before use, or the material containing such glutaminase may be used as is. Furthermore, the glutaminase contained in the rice improver of the present invention may be, for example, a commercially available product (e.g., Amano Enzyme Co., Ltd., Glutaminase SD-C100S, etc.).

[0028] One of the features of the rice cooker improver of the present invention is that it contains a predetermined amount of glutaminase. By cooking rice in combination with a predetermined amount of glutaminase and the non-dissociated acetic acid described later, uneven heating inside the rice cooker can be improved, and rice with excellent loosening properties can be provided even after long-term storage. The principle is unknown, but it is possible that the non-dissociated acetic acid penetrates the rice during cooking and promotes the outflow of components that cause viscosity, and that the glutaminase decomposes these components from the initial stages of cooking, thereby improving uneven heating. Specifically, the rice improver of the present invention preferably satisfies the following (a) and / or (b), and more preferably satisfies both (a) and (b). (a) The glutaminase content in the rice improver is 0.01 to 10.0 w / w% (b) The enzyme activity of glutaminase in the rice improver is 100 mU / g or higher.

[0029] The glutaminase content in the rice improver in (a) above may be adjusted as appropriate so as to satisfy the enzyme activity in (b) below. In this invention, the glutaminase content refers to the content of glutaminase (CAS9001-47-2) as an enzyme. For example, it may be 0.01 to 10 w / w% in mass grams per 100 g of rice improver. More specifically, the lower limit may be 0.05 w / w% or higher, 0.1 w / w% or higher, 0.15 w / w% or higher, 0.2 w / w% or higher, 0.3 w / w% or higher, 0.4 w / w% or higher, 0.5 w / w% or higher, 0.6 w / w% or higher, 0.7 w / w% or higher, 0.8 w / w% or higher, 0.9 w / w% or higher, 1.0 w / w% or higher, 1.1 w / w% or higher, 1.2 w / w% or higher, 1.3 w / w% or higher, 1.4 w / w% or higher, 1.5 w / w% or higher, 1.9 w / w% or higher, or 2.4 w / w% or higher. Furthermore, while there is no upper limit, it may be, for example, 9.0 w / w% or less, 8.0 w / w% or less, 7.0 w / w% or less, 6.0 w / w% or less, 5.0 w / w% or less, 4.5 w / w% or less, 4.2 w / w% or less, 3.9 w / w% or less, 3.7 w / w% or less, 3.4 w / w% or less, 3.3 w / w% or less, 3.1 w / w% or less, 2.9 w / w% or less, 2.7 w / w% or less, 2.4 w / w% or less, 2.2 w / w% or less, 2.0 w / w% or less, 1.8 w / w% or less, 1.6 w / w% or less, 1.4 w / w% or less, 0.5 w / w% or less, or 0.30 w / w% or less. Furthermore, if the majority or all of the glutaminase activity is derived from the enzyme preparation, the glutaminase content may be 0.8 to 5.0 w / w%, preferably 0.9 to 4.5 w / w%, more preferably 1.0 to 4.0 w / w%, even more preferably 1.2 to 3.6 w / w%, even more preferably 1.6 to 3.4 w / w%, particularly preferably 1.8 to 3.2 w / w%, and especially preferably 2.0 to 3.0 w / w%.

[0030] It is preferable that the glutaminase enzyme activity in the rice improver described in (b) above is above a predetermined value, as this is necessary to achieve the effects of the present invention. In the present invention, "glutaminase enzyme activity" is defined as the amount of enzyme that produces 1 μmol of glutamic acid per minute, with 1 unit (1 U = 1000 mU). A known method can be used to measure glutaminase enzyme activity, but for example, it can be measured by adding 2.0 mL of 30 mM L-glutamine solution to 0.1 mL of enzyme solution appropriately diluted with 10 mM phosphate buffer (pH 7.0), reacting at 30°C for 30 minutes, and quantifying the produced glutamic acid using a known method (for example, using a glutamic acid measurement kit (manufactured by Seikagaku Corporation)). Specifically, the glutaminase enzyme activity in the rice improver may be 100 mU / g or more and 1000 U / g or less. More specifically, the lower limit may be 150 mU / g or higher, 200 mU / g or higher, 250 mU / g or higher, 300 mU / g or higher, 400 mU / g or higher, 500 mU / g or higher, 600 mU / g or higher, 650 mU / g or higher, 700 mU / g or higher, 800 mU / g or higher, 900 mU / g or higher, 950 mU / g or higher, 1000 mU / g or higher, 1200 mU / g or higher, 1500 mU / g or higher, 1700 mU / g or higher, 1800 mU / g or higher, or 2000 mU / g or higher. On the other hand, the upper limit may be 900 U / g or less, 800 U / g or less, 700 U / g or less, 600 U / g or less, 500 U / g or less, 400 U / g or less, 300 U / g or less, 200 U / g or less, 100 U / g or less, 90 U / g or less, 80 U / g or less, 70 U / g or less, 60 U / g or less, 50 U / g or less, 40 U / g or less, 30 U / g or less, 20 U / g or less, 10 U / g or less, 5 U / g or less, or 1 U / g or less. Furthermore, the glutaminase enzyme activity in the rice improver may be preferably 150 to 10,000 mU / g, more preferably 200 to 9,000 mU / g, even more preferably 300 to 7,000 mU / g, even more preferably 600 to 6,000 mU / g, particularly preferably 900 to 4,000 mU / g, and especially preferably 1,000 to 3,000 mU / g.

[0031] The rice improver of the present invention is preferable when its pH is above a predetermined value, as this is because it achieves the effects of the present invention. Although the principle is unknown, it is possible that when the pH of the rice improver is above a predetermined value, the ratio of undissociated acetic acid to dissociated acetic acid in the rice during the initial stages of cooking is maintained, and the undissociated acetic acid penetrates the rice during cooking, promoting the outflow of components that cause viscosity. Specifically, the pH of the rice improver of the present invention at 20°C may be normally 4.6 to 9.0, preferably 4.7 to 7.0, more preferably 4.8 to 6.5, even more preferably 4.9 to 6.4, even more preferably 5.0 to 6.3, particularly preferably 5.1 to 6.2, and especially preferably 5.2 to 6.1. More specifically, the upper limit is not limited, but for example, it could be 8.8 or less, 8.2 or less, 8.0 or less, 7.5 or less, 7.1 or less, 7.0 or less, 6.8 or less, 6.5 or less, 6.3 or less, 6.1 or less, 5.9 or less, 5.8 or less, 5.6 or less, or 5.5 or less. On the other hand, the lower limit is not limited, but for example, it could be 4.6 or more, 4.7 or more, 4.8 or more, 4.9 or more, 5.0 or more, 5.1 or more, 5.2 or more, 5.3 or more, or 5.4 or more.

[0032] Furthermore, one of the features of the rice improver of the present invention is that the concentration of non-dissociated acetic acid is within a predetermined range.

[0033] <Concentration of undissociated acetic acid> It is known that acetic acid molecules exist in resonance states in both dissociated and undissociated forms in aqueous solution. That is, if the concentration of dissociated acetic acid is [A-], the proton concentration is [H+], and the concentration of undissociated acetic acid is [AH], then the two forms coexist in equilibrium under the following conditions.

[0034] [AH] ⇔ [H+] + [A-] (Equation 2)

[0035] On the other hand, the non-dissociated acetic acid concentration [AH] can be determined from the pH and acetic acid concentration using the following formula. In this invention, the acetic acid concentration (sometimes referred to as acetic acid content) is measured by high-performance liquid chromatography in accordance with the measurement method for "organic acids" in the Japanese Food Standard Composition Table 2015 Edition (7th Revised Edition). That is, especially when a large amount of acetate salts such as sodium acetate is present, a value greater than the "acidity" determined by neutralization titration may be obtained.

[0036] pH=4.76+log10 [A-] / [AH] (Formula 3)

[0037] One of the features of the rice improver of the present invention is that it contains a predetermined amount of non-dissociated acetic acid. By cooking rice in combination with a predetermined amount of glutaminase and non-dissociated acetic acid, uneven heating inside the rice cooker can be improved, and rice with excellent loosening properties can be provided even after long-term storage. The principle is unknown, but it is possible that non-dissociated acetic acid penetrates the rice during cooking, promoting the outflow of components that cause viscosity, and that glutaminase decomposes these components from the initial stages of cooking, thereby improving uneven heating. Specifically, the concentration of non-dissociated acetic acid in the rice improver of the present invention may be typically 0.001 to 2.000 w / w%, more preferably 0.005 to 1.800 w / w%, more preferably 0.008 to 1.700 w / w%, even more preferably 0.01 to 1.600 w / w%, even more preferably 0.050 to 1.550 w / w%, particularly preferably 0.100 to 1.450 w / w%, and especially preferably 0.300 to 1.300 w / w%. More specifically, the upper limit is not limited, but for example, it is 1.900 w / w% or less, 1.800 w / w% or less, 1.700 w / w% or less, 1.650 w / w% or less, 1.600 w / w% or less, 1.580 w / w% or less, 1.510 w / w% or less, 1.450 w / w% or less, 1.380 w / w% or less, 1.280 w / w% or less, 1.200 w / w% or less, 1.150 w / w% or less, 1.100 w / w% or less, 1.050 w / w% or less, 1.005 w / w% or less, 0.980 w / w% or less, 0.940 w / w% or less, and 0.920 w / w% or less. Furthermore, while the lower limit is not restricted, it is generally considered to be 0.001 w / w% or higher, 0.002 w / w% or higher, 0.005 w / w% or higher, 0.007 w / w% or higher, 0.01 w / w% or higher, 0.015 w / w% or higher, 0.02 w / w% or higher, 0.025 w / w% or higher, 0.03 w / w% or higher, 0.035 w / w% or higher, 0.04 w / w% or higher, 0.045 w / w% or higher, 0.048 w / w% or higher, 0.05 w / w% or higher, 0.053 w / w% or higher, and 0. The values ​​are 0.55 w / w% or higher, 0.100 w / w% or higher, 0.150 w / w% or higher, 0.180 w / w% or higher, 0.200 w / w% or higher, 0.210 w / w% or higher, 0.230 w / w% or higher, 0.240 w / w% or higher, 0.270 w / w% or higher, 0.300 w / w% or higher, 0.350 w / w% or higher, 0.400 w / w% or higher, 0.450 w / w% or higher, 0.500 w / w% or higher, 0.550 w / w% or higher, and 0.600 w / w% or higher.

[0038] A preferred feature of the rice improver of the present invention is that it contains both acetic acid and sodium acetate. By using a rice improver containing a predetermined amount of both acetic acid and sodium acetate, it is thought that the acetic acid in the cooked rice can more easily maintain its undissociated state, thereby making it easier to achieve the effects of the present invention. The acetic acid in the rice improver of the present invention may be contained in the food ingredients, extracted from the food ingredients, added as a compound, or a combination thereof. However, the rice improver of the present invention preferably contains vinegar, and more preferably contains both vinegar and sodium acetate. Furthermore, the ratio of the acetic acid content derived from sodium acetate to the total acetic acid content of the entire composition may be 30% by mass or more, more preferably 40% by mass or more, or 50% by mass or more, or 60% by mass or more, or 70% by mass or more, or 80% by mass or more, or 90% by mass or more. There is no particular upper limit, and it may usually be less than 100% by mass or less than 98% by mass. Furthermore, the acetic acid concentration derived from sodium acetate may be 1.9 to 11.9 w / w%, more preferably 2.1 to 11.0 w / w%, more preferably 2.2 to 10.0 w / w%, more preferably 2.3 to 9.5 w / w%, even more preferably 2.4 to 9.0 w / w%, even more preferably 2.6 to 8.8 w / w%, particularly preferably 2.8 to 8.5 w / w%, especially preferably 3.0 to 8.0 w / w%, or 4.0 to 7.5 w / w%, 4.3 to 7.0 w / w%. More specifically, the upper limit is not limited, but for example, it is 12.0 w / w% or less, 11.5 w / w% or less, 11.0 w / w% or less, 10.5 w / w% or less, 9.3 w / w% or less, 9.1 w / w% or less, 8.9 w / w% or less, 8.7 w / w% or less, 8.3 w / w% or less, 7.7 w / w% or less, 7.3 w / w% or less, 7.2 w / w% or less, 6.9 w / w% or less, 6.8 w / w% or less, and 6.7 w / w% or less.On the other hand, the lower limit is not limited, but it may be, for example, 2.1 w / w% or more, 2.2 w / w% or more, 2.3 w / w% or more, 2.4 w / w% or more, 2.7 w / w% or more, 2.9 w / w% or more, 3.1 w / w% or more, 3.2 w / w% or more, 3.3 w / w% or more, 3.5 w / w% or more, 3.7 w / w% or more, 3.9 w / w% or more, 4.1 w / w% or more, 4.3 w / w% or more, 4.5 w / w% or more, 4.7 w / w% or more, or 4.9 w / w% or more. Furthermore, the ratio of vinegar-derived acetic acid content to the total acetic acid content of the entire composition may be less than 50% by mass, and more particularly less than 40% by mass, or less than 30% by mass, or less than 20% by mass, or less than 15% by mass, or less than 10% by mass. The lower limit is not particularly limited and is usually greater than 0% by mass, or greater than 2% by mass, or greater than 5% by mass.

[0039] <Acetic acid content> The rice improver of the present invention may have an acetic acid content within a predetermined range. Specifically, the content may be 2.0 to 12.0 w / w%, more preferably 2.1 to 11.0 w / w%, more preferably 2.2 to 10.0 w / w%, more preferably 2.3 to 9.5 w / w%, even more preferably 2.4 to 9.0 w / w%, even more preferably 2.6 to 8.8 w / w%, particularly preferably 2.8 to 8.5 w / w%, especially preferably 3.0 to 8.0 w / w%, or 4.0 to 7.5 w / w%, 4.3 to 7.0 w / w%. More specifically, the upper limit is not limited, but for example, it is 12.0 w / w% or less, 11.5 w / w% or less, 11.0 w / w% or less, 10.5 w / w% or less, 9.3 w / w% or less, 9.1 w / w% or less, 8.9 w / w% or less, 8.7 w / w% or less, 8.3 w / w% or less, 7.7 w / w% or less, 7.3 w / w% or less, 7.2 w / w% or less, 6.9 w / w% or less, 6.8 w / w% or less, and 6.7 w / w% or less. On the other hand, the lower limit is not limited, but it may be, for example, 2.1 w / w% or more, 2.2 w / w% or more, 2.3 w / w% or more, 2.4 w / w% or more, 2.7 w / w% or more, 2.9 w / w% or more, 3.1 w / w% or more, 3.2 w / w% or more, 3.3 w / w% or more, 3.5 w / w% or more, 3.7 w / w% or more, 3.9 w / w% or more, 4.1 w / w% or more, 4.3 w / w% or more, 4.5 w / w% or more, 4.7 w / w% or more, or 4.9 w / w% or more. Furthermore, the acetic acid in the rice improver of the present invention may be partially contained in the form of an acetate salt. Specifically, the ratio of the acetic acid content measured by the high-performance liquid chromatography method of the present invention to the acidity determined by neutralization titration (acetic acid content / acidity determined by neutralization titration) may be 1.1 or higher, 1.2 or higher, 1.3 or higher, 1.4 or higher, 1.5 or higher, 1.6 or higher, 1.7 or higher, 1.8 or higher, 1.9 or higher, 2.0 or higher, 2.5 or higher, 3.0 or higher, 3.5 or higher, 4.0 or higher, 4.5 or higher, 5.0 or higher, 5.5 or higher, 6.0 or higher, or 6.5 or higher.

[0040] The rice improver of the present invention preferably has a specific gravity within a predetermined range at 20°C. Specific gravity is the ratio of the density (mass per unit volume) of a substance to the density of a reference water (at 4°C), and is a dimensionless quantity. Specifically, the specific gravity of the rice improver of the present invention at 20°C may be preferably 1.010 to 1.500, more preferably 1.020 to 1.450, even more preferably 1.030 to 1.420, even more preferably 1.040 to 1.400, particularly preferably 1.050 to 1.350, especially preferably 1.060 to 1.300, or 1.100 to 1.290. More specifically, the lower limit is not limited, but it may be 1.020 or higher, 1.030 or higher, 1.040 or higher, 1.050 or higher, 1.060 or higher, 1.070 or higher, 1.080 or higher, 1.090 or higher, 1.100 or higher, 1.100 or higher, or 1.150 or higher. The upper limit is not limited, but for example, it may be 1.500 or lower, 1.450 or lower, 1.400 or lower, 1.350 or lower, 1.300 or lower, or 1.250 or lower.

[0041] The rice improver of the present invention preferably contains a predetermined amount equivalent to salt.

[0042] <Salt equivalent amount> The salt equivalent in the rice improver of the present invention is calculated by multiplying the amount of sodium measured using atomic absorption spectrometry by 2.54, in accordance with the "salt equivalent" in the 2015 edition (7th revised edition) of the Standard Tables of Food Composition in Japan.

[0043] The salt equivalent in the rice improver of the present invention may be derived from sodium chloride or sodium acetate containing sodium salts, from sodium salts contained in food ingredients, from sodium salts extracted from food ingredients, from sodium salts added as compounds, or from a combination thereof. Generally, when sodium salts are added during cooking, the swelling of starch on the surface of the rice is suppressed, resulting in a hard, dry texture and consequently a deterioration in taste. However, in the rice improver of the present invention, the dryness of the rice surface caused by sodium salts is also improved by the effect of glutaminase. This is an extremely unusual effect for a method of cooking rice with added sodium salts. The detailed mechanism by which these effects are achieved is unknown, but it is presumed that the glutaminase effect of softening the rice and the sodium salt effect of hardening the surface of the rice, which seem contradictory at first glance, are exerted in an optimal balance. Furthermore, when the rice improver of the present invention contains a predetermined amount of salt equivalent, the rice becomes easier to scoop with a rice paddle.

[0044] The salt equivalent in the rice improver may be specifically 5.0 to 25.0 w / w%, more preferably 6.0 to 24.0 w / w%, even more preferably 7.0 to 23.0 w / w%, even more preferably 8.0 to 22.0 w / w%, particularly preferably 10.0 to 20.0 w / w%, and especially preferably 12.0 to 18.0 w / w%. Furthermore, there is no upper limit, but for example, it may be 26.0 w / w% or less, 25.0 w / w% or less, 24.0 w / w% or less, 23.0 w / w% or less, 22.0 w / w% or less, 20.0 w / w% or less, 19.0 w / w% or less, 18.0 w / w% or less, 17.5 w / w% or less, 17.0 w / w% or less, 16.0 w / w% or less, or 15.8 w / w% or less. On the other hand, the lower limit is not restricted, but it may be, for example, 1.0 w / w% or more, 2.0 w / w% or more, 2.5 w / w% or more, 3.0 w / w% or more, 3.5 w / w% or more, 4.0 w / w% or more, 6.0 w / w% or more, 7.5 w / w% or more, 8.0 w / w% or more, or 11.0 w / w% or more.

[0045] Furthermore, the amount of salt equivalent in the rice improver of the present invention can also be specified as the ratio of the amount of salt equivalent (w / w%) in the rice improver to the amount of glutaminase (w / w%) contained in the rice improver (amount of salt equivalent (w / w%) in the rice improver / amount of glutaminase (w / w%) contained in the rice improver).

[0046] The ratio of the salt equivalent amount (w / w%) in the rice improver of the present invention to the glutaminase content (w / w%) is preferably within a predetermined range. For example, this range is 0.1 to 730, 0.5 to 500, 0.7 to 300, 0.9 to 100, preferably 1 to 50, more preferably 1.2 to 30, even more preferably 1.5 to 25, even more preferably 2 to 15, particularly preferably 3 to 9, and especially preferably 4 to 8. The upper limit is not limited, but for example, it is 600 or less, 500 or less, 400, 300 or less, 200 or less, 100 or less, 80 or less, 60 or less, 51 or less, 37 or less, 35 or less, 30 or less, 25 or less, 24 or less, 20 or less, 18 or less, 14 or less, 12 or less, 10 or less, 9 or less, 8 or less, 7 or less, and 6 or less. On the other hand, the lower limit is not limited, but for example, it could be 0.15 or higher, 0.25 or higher, 0.35 or higher, 0.45 or higher, 0.7 or higher, 0.8 or higher, 0.9 or higher, 1.2 or higher, 1.4 or higher, 2.5 or higher, 3 or higher, 4 or higher, 5 or higher, 10 or higher, 15 or higher, or 20 or higher.

[0047] The rice improver of the present invention preferably contains a predetermined amount of carbohydrates.

[0048] <Carbohydrates> "Carbohydrates" are defined in the Food Labeling Standards based on Article 4, Paragraph 1 of the Food Labeling Act (Act No. 70 of 2013) as the amount of protein, lipids, dietary fiber, ash, and moisture remaining from the mass of the food in question. The carbohydrates contained in the rice improver of the present invention are preferably contained as soluble carbohydrates. In the present invention, "soluble carbohydrates" refers to carbohydrates that are soluble in water, and is a general term for monosaccharides and oligosaccharides (sugars in which 2 to 10 monosaccharides are linked together), and sugar alcohols. Therefore, starch, which has a much larger number of sugars linked together, is not included. Examples of soluble carbohydrates include glucose, fructose, galactose, sucrose, maltose, lactose, trehalose, sorbitol, etc. These may be contained as compounds alone, or they may be contained in sweeteners that contain them, such as brown sugar, honey, and starch syrup.

[0049] By incorporating carbohydrates into the rice improver of this invention, it is possible to prevent the rice from becoming too soft due to glutaminase, improve the texture and moldability of the rice, and obtain delicious rice even after long-term storage. The detailed mechanism by which these effects are achieved is unknown, but it is presumed that the water-retaining properties of carbohydrates contribute in some way. In addition, generally, when carbohydrates are added when cooking rice, there is a problem of the rice cooker pot burning, but by using the rice improver of this invention, the effect of "improving convection inside the pot during rice cooking," as described later, can suppress burning in the rice cooker pot. This is an extremely unusual effect for a method of cooking rice with added carbohydrates.

[0050] The carbohydrate content in the rice improver of the present invention is preferably below a predetermined value. Specifically, the carbohydrate content in the rice improver of the present invention may be preferably 0.5 to 50.0 w / w%, more preferably 1.0 to 40.0 w / w%, even more preferably 2.0 to 36.0 w / w%, even more preferably 3.0 to 29.0 w / w%, particularly preferably 4.0 to 27.0 w / w%, especially preferably 5.0 to 25.0 w / w%, or 13.0 to 25.0 w / w%. More specifically, the upper limit is not limited, but for example, it is 45.0 w / w% or less, 40.0 w / w% or less, 36.0 w / w% or less, 35.0 w / w% or less, 34.0 w / w% or less, 33.0 w / w% or less, 31.0 w / w% or less, 29.0 w / w% or less, 28.5 w / w% or less, 27.5 w / w% or less, 27.0 w / w% or less, 26.8 w / w% or less, and 26.3 w / w% or less. On the other hand, the lower limit is not limited, but it may be, for example, 0.5 w / w% or more, 1.0 w / w% or more, 1.5 w / w% or more, 2.0 w / w% or more, 2.5 w / w% or more, 3.0 w / w% or more, 3.5 w / w% or more, 4.0 w / w% or more, 6.0 w / w% or more, 7.0 w / w% or more, 7.5 w / w% or more, 8.0 w / w% or more, 9.0 w / w% or more, 10.0 w / w% or more, 11.5 w / w% or more, 12.0 w / w% or more, 12.5 w / w% or more, 13.0 w / w% or more, 13.5 w / w% or more, 14.0 w / w% or more, 16.0 w / w% or more, 17.0 w / w% or more, 17.5 w / w% or more, or 18.0 w / w% or more.

[0051] Furthermore, the rice improver of the present invention may preferably contain reduced starch syrup as the source of carbohydrates, from the viewpoint of suppressing deterioration of the taste of rice due to the taste of the sugar itself and obtaining the loosening effect of the present invention to a remarkable degree. Reduced starch syrup is a type of sugar produced by reducing starch syrup, which is obtained by hydrolyzing starch with acid or enzymes. When the rice improver of the present invention contains carbohydrates due to reduced starch syrup, preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, especially preferably 90% by mass or more, or 100% by mass of the carbohydrate content in the rice improver may be derived from reduced starch syrup. In addition, the content of reduced starch syrup may be 0.0 to 50.0 w / w%, and it is preferable that the above-mentioned upper and lower limits of carbohydrate content are satisfied.

[0052] Furthermore, the rice improver of the present invention may preferably contain soluble carbohydrates as the source of sugars, from the viewpoint of suppressing deterioration of the taste of rice due to the taste of sugar itself and obtaining the loosening effect of the present invention to a remarkable degree. When the rice improver of the present invention contains sugars from soluble carbohydrates, of the sugar content in the rice improver, preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, especially preferably 90% by mass or more, or 100% by mass may be derived from soluble carbohydrates. Furthermore, the soluble carbohydrate content may be 0.0 to 50.0 w / w%, and it is preferable that the above-mentioned upper and lower limits for carbohydrate content are also satisfied.

[0053] Furthermore, the above effects may be more favorably achieved when the carbohydrate content of the rice improver of the present invention is such that the ratio of the carbohydrate content (w / w%) contained in the rice improver to the glutaminase content (w / w%) contained in the rice improver (carbohydrate content (w / w%) / glutaminase content (w / w%) contained in the rice improver) is above a predetermined ratio. Specifically, the ratio of carbohydrate content (w / w%) to glutaminase content (w / w%) in the rice improver may be, for example, 0.1 to 300, 0.2 to 150, or 0.1 to 100, preferably 0.3 to 70, more preferably 0.5 to 60, even more preferably 1 to 50, even more preferably 2 to 30, particularly preferably 4 to 15, and especially preferably 6 to 12. More specifically, the lower limit is not limited, but may be, for example, 0.5 or more, 0.8 or more, 1 or more, 2 or more, 3 or more, 5 or more, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8 or more, 9 or more, 10 or more, 15 or more, 20 or more, 30 or more, or 40 or more. Furthermore, there is no upper limit, but for example, it may be 250 or less, 200 or less, 150 or less, 100 or less, 80 or less, 66 or less, 62 or less, 50 or less, 45 or less, 40 or less, 30 or less, 25 or less, 22 or less, 20 or less, 17 or less, or 15 or less. Also, the ratio of soluble carbohydrate content (w / w%) to glutaminase content (w / w%) of the rice improver may satisfy the above requirements. In addition, the ratio of reduced starch syrup content (w / w%) to glutaminase content (w / w%) of the rice improver may satisfy the above requirements.

[0054] Furthermore, it is preferable that the ratio of carbohydrate content (w / w%) to salt equivalent (w / w%) in the rice improver of the present invention is within a predetermined range. In this embodiment, both the synergistic effect of salt equivalent and glutaminase, and the synergistic effect of carbohydrates and glutaminase can be obtained, and it is particularly preferable because it can improve the dryness of the rice caused by the salt equivalent and the burning of the rice cooker pot caused by carbohydrates, which occur when glutaminase is not contained. Specifically, the ratio may be preferably 0.5 to 8, more preferably 0.5 to 7, even more preferably 0.5 to 6, even more preferably 0.5 to 5, particularly preferably 0.5 to 4, and particularly preferably 1 to 3. More specifically, the lower limit may be 0.1 or higher, 0.2 or higher, 0.3 or higher, 0.4 or higher, 0.5 or higher, 0.6 or higher, 0.7 or higher, 0.8 or higher, 0.9 or higher, 1.0 or higher, 1.5 or higher, 2.0 or higher, 2.5 or higher, or 3.0 or higher. The upper limit is not particularly limited, but may be, for example, 8.0 or lower, 7.0 or lower, 6.0 or lower, 5.0 or lower, 4.5 or lower, or 4.0 or lower. Furthermore, the ratio of soluble carbohydrate content (w / w%) to salt equivalent (w / w%) of the rice improver may satisfy the above requirements. In addition, the ratio of reduced starch syrup content (w / w%) to salt equivalent (w / w%) of the rice improver may satisfy the above requirements.

[0055] The rice improver in this invention may contain pH adjusters other than acetic acid and sodium acetate, as long as the objective of this invention is not impaired. The type of pH adjuster is not particularly limited, and commercially available pH adjusters, organic acids or their salts, and compositions containing organic acids or their salts can be used.

[0056] Examples of the aforementioned "organic acid" include lactic acid, malic acid, citric acid, gluconic acid, succinic acid, tartaric acid, phytic acid, fumaric acid, and phosphoric acid. These organic acids may be used individually or in any combination of two or more types.

[0057] Examples of the aforementioned "organic acid salts" include calcium citrate, trisodium citrate, potassium gluconate, sodium gluconate, succinic acid, monosodium succinate, disodium succinate, DL-potassium bitartrate, L-potassium bitartrate, DL-sodium tartrate, L-sodium tartrate, potassium lactate, calcium lactate, sodium lactate, monosodium fumarate, DL-sodium malate, and the like. These organic acid salts may be used individually or in any combination of two or more types.

[0058] The rice improver in the present invention may contain components other than those mentioned above, as long as they do not impair the purpose of the present invention. These components are supplied, for example, by various food ingredients or food additives. Food additives refer to substances used in the food manufacturing process by adding, mixing, impregnating, or other methods, and include, for example, excipients, binders, disintegrants, disintegration aids, lubricants, wetting agents, emulsifiers, edible oils and fats, etc.

[0059] The rice cooker of the present invention is preferable because, in addition to the effects of the present invention, the amylase activity in the rice cooker is above a predetermined value, which improves the release of cooked rice from the pot. In the present invention, "amylase activity" refers to the activity that decomposes 1 ml of a 1% starch solution in 30 minutes at 40 °C and pH 5.0 using starch (soluble) as a substrate until the iodine coloration gives a transmittance of 66% at a wavelength of 670 nm and an optical path length of 10 mm, with 1 unit (1 U = 1000 mU). Amylase activity can be measured by known methods. (See https: / / www.jfrl.or.jp / storage / file / 222.pdf or https: / / web.archive.org / web / 20220918072602 / https: / / www.jfrl.or.jp / storage / file / 222.pdf, etc.). Specifically, the amylase activity in the rice improver may be between 100 mU / g and 1000 U / g. More specifically, the lower limit may be 150 mU / g or higher, 200 mU / g or higher, 250 mU / g or higher, 300 mU / g or higher, 400 mU / g or higher, 500 mU / g or higher, 600 mU / g or higher, 700 mU / g or higher, 800 mU / g or higher, 900 mU / g or higher, 1000 mU / g or higher, 1500 mU / g or higher, or 2000 mU / g or higher. On the other hand, the upper limit may be 900 U / g or less, 800 U / g or less, 700 U / g or less, 600 U / g or less, 500 U / g or less, 400 U / g or less, 300 U / g or less, 200 U / g or less, 100 U / g or less, 90 U / g or less, 80 U / g or less, 70 U / g or less, 60 U / g or less, 50 U / g or less, 40 U / g or less, 30 U / g or less, 20 U / g or less, 10 U / g or less, 5 U / g or less, or 1 U / g or less.

[0060] The amylase content in the rice improver can be adjusted as appropriate so as to satisfy the above-mentioned amylase activity. In this invention, the amylase content refers to the content of α-amylase (CAS9000-90-2) as an enzyme. For example, it may be 0.01 w / w% to 10 w / w% in mass grams per 100 g of rice improver. More specifically, the lower limit may be 0.05 w / w% or higher, 0.1 w / w% or higher, 0.2 w / w% or higher, 0.3 w / w% or higher, 0.4 w / w% or higher, 0.5 w / w% or higher, 0.6 w / w% or higher, 0.7 w / w% or higher, 0.8 w / w% or higher, 0.9 w / w% or higher, 1.0 w / w% or higher, 1.1 w / w% or higher, 1.2 w / w% or higher, 1.3 w / w% or higher, 1.4 w / w% or higher, 1.5 w / w% or higher, or 1.9 w / w% or higher. Furthermore, although there is no upper limit, it may be, for example, 9.0 w / w% or less, 8.0 w / w% or less, 7.0 w / w% or less, 6.0 w / w% or less, 5.0 w / w% or less, 4.5 w / w% or less, 4.2 w / w% or less, 3.9 w / w% or less, 3.7 w / w% or less, 3.4 w / w% or less, 3.3 w / w% or less, 3.1 w / w% or less, 2.9 w / w% or less, 2.7 w / w% or less, 2.4 w / w% or less, 2.2 w / w% or less, or 2.0 w / w% or less. In addition, the majority or all of the amylase activity in the rice improver may be derived from the enzyme preparation.

[0061] The rice cooker of the present invention is preferable because it has a predetermined enzyme activity, such as glutaminase, which reduces the viscosity of water during cooking and improves uneven heating inside the rice cooker. Specifically, the enzyme activity of the rice cooker may be less than or equal to a predetermined value when the supernatant is measured using a B-type viscometer (No. 1 rotor, 60 rpm, 20°C) after adding 0.1 w / w% of the rice cooker to polished Koshihikari rice with 400% water content, heating to 98°C at a heating rate of 12°C / min, and holding for 2 minutes. The viscosity of the present invention can be measured using a B-type viscometer (for example, "B-II" manufactured by Toki Sangyo Co., Ltd.). Specifically, an appropriate amount of the liquid to be measured, whose temperature has been adjusted to 20°C, is filled into the measuring container of the B-type viscometer, the container is set in the B-type viscometer, and the viscosity can be measured using the No. 1 rotor at a rotation speed of 60 rpm. Specifically, the viscosity may be between 0 cP and 100 cP. More specifically, the upper limit may be 95 cP or less, 90 cP or less, 85 cP or less, or 80 cP or less. The lower limit may also be 0 cP or more, 1 cP or more, 2 cP or more, 3 cP or more, 4 cP or more, or 5 cP or more. Furthermore, it is preferable that the enzyme activity of the rice improver of the present invention is such that the viscosity ratio of the rice improver-added section to the section without the rice improver (a configuration without enzyme activity) (viscosity of the rice improver-added section / viscosity of the rice improver-free section) is less than or equal to a predetermined value. Specifically, this ratio may be 0.0 or more and less than 0.8. More specifically, the upper limit may be less than 0.75, or less than 0.70, or less than 0.65, or less than 0.60. The lower limit is not particularly limited, but may be 0.0 or more, or 0.1 or more, or 0.2 or more, or 0.3 or more, or 0.4 or more, or 0.5 or more.

[0062] The rice improver of the present invention is preferably sterilized at a maximum temperature of less than 124°C during manufacturing in order to maintain its enzyme activity, and preferably does not have a sterilization process. Specifically, for example, if the Z value of the indicator bacteria is 10 minutes, it is preferable not to perform a sterilization process equivalent to 124°C for 1.5925 minutes. More specifically, it is preferable that the water activity of the rice improver of the present invention is 0.94 or less. The water activity value can be measured according to a standard method using a general water activity measuring device (for example, Novacina's "LabMaster-aw NEO" using an electrical resistance type (electrolyte type) humidity sensor). If the rice improver of the present invention is a packaged rice improver and its shelf life is 4 months or more at room temperature, it is preferable that the above provisions are satisfied.

[0063] The present invention also relates to a method for producing cooked rice using the cooked rice improver of the present invention. In this embodiment, the cooked rice improver of the present invention includes any combination of preferred embodiments of the cooked rice improver disclosed herein.

[0064] Furthermore, when producing cooked rice using the rice improver of the present invention, it is particularly preferable that the cooked rice be intended for consumption in a medium-sized portion of a meal. This is because cooked rice intended for consumption in a medium-sized portion of a meal is strongly desired to maintain excellent flavor and fluffiness for a long period of time, and to reduce uneven heating, and the effects of the rice improver of the present invention are particularly useful in these situations.

[0065] When producing cooked rice using the rice improver of the present invention, food additives and ingredients such as seasonings, spices, and colorings can be added to a mixture of raw rice and water, or to cooked rice, as long as the objective of the present invention is not impaired.

[0066] Examples of seasonings that can be added to a mixture of raw rice and water, or to cooked rice, include seasoned vinegar (e.g., general-purpose seasoned vinegar, seasoned vinegar for vinegared dishes, seasoned vinegar for sushi rice, seasoning liquid for pickling (e.g., pickles), sweet vinegar, etc.), seasonings for cooked rice, and seasonings containing dashi (broth).

[0067] In this specification, "spices" refers to parts of plants (such as fruits, pericarps, flowers, buds, bark, stems, leaves, seeds, roots, and rhizomes) that have a distinctive aroma, pungent taste, and color, and are incorporated into food and beverages for purposes such as flavoring, deodorizing, seasoning, and coloring. Spices include spices and herbs. Spices refer to spices excluding the stems, leaves, and flowers as usable parts. Examples of spices that can be added to a mixture of raw rice and water, or cooked rice, in this invention include pepper (black pepper, white pepper, red pepper), garlic, ginger, sesame (sesame seeds), chili peppers, horseradish, mustard, yuzu, nutmeg, cinnamon, paprika, cardamom, cumin, saffron, allspice, cloves, Japanese pepper, orange peel, fennel, licorice, fenugreek, dill seeds, kasho pepper, long pepper, and olives. Furthermore, herbs refer to spices that utilize the stems, leaves, and flowers. Examples include watercress, coriander, shiso, celery, tarragon, chives, chervil, sage, thyme, bay leaf, chives, parsley, mustard greens, Japanese ginger, mugwort, basil, oregano, rosemary, peppermint, savory, lemongrass, dill, wasabi leaves, and Japanese pepper leaves.

[0068] Examples of the ingredients mentioned above include vegetables (carrots, burdock root, radish, etc.), grains (adzuki beans, soybeans, etc.), meats, and fish. These ingredients may be used individually or in any combination or ratio.

[0069] The manufacturing method of the present invention is characterized by comprising the following steps (i), (ii), and (iii) using the rice improver described in this specification. (i) The step of preparing pre-cooked rice by adding the rice improver of the present invention in such a way that the following conditions (a) and / or (b) are satisfied. (a) The glutaminase content is 0.0005 w / w% or more relative to the weight of raw rice. (b) Glutaminase enzyme activity of 0.1 mU / g or higher relative to the weight of raw rice. (ii) A heating stage in which the rice prepared in stage (i) is heated to 98°C or higher at a bottom heating rate of 6.0°C / min or more. (iii) The warming stage after the heating stage involves keeping the cooked rice at a bottom temperature of 98°C or higher for at least 2 minutes. The manufacturing method of the present invention will be described in detail below.

[0070] Stage (i) The stage in which rice is prepared before cooking by adding a rice improver. In this stage (i), a composition that forms the basis of the rice of the present invention (referred to as "pre-cooked rice") is prepared by mixing raw rice, water, a rice improver, and other ingredients that may be used as ingredients of the present invention. One of the features of the rice before cooking in step (i) of this invention is that it contains a predetermined amount of glutaminase. By cooking rice in combination with a predetermined amount of glutaminase and non-dissociated acetic acid, uneven heating inside the rice cooker can be improved, and rice that is easy to fluff can be provided even after long-term storage. The principle is unknown, but it is possible that non-dissociated acetic acid penetrates the rice during cooking and promotes the outflow of components that cause viscosity, and that glutaminase improves uneven heating by decomposing these components from the initial stages of cooking. Specifically, the uncooked rice of the present invention preferably satisfies (c) and / or (d) below, and more preferably satisfies both (c) and (d). (c) The glutaminase content is 0.0005 w / w% or more relative to the weight of raw rice. (d) Glutaminase enzyme activity of 0.1 mU / g or more relative to the weight of raw rice.

[0071] The glutaminase content in cooked rice relative to the weight of raw rice in (c) above may be adjusted as appropriate so as to satisfy the enzyme activity in (d) below. In this invention, the glutaminase content refers to the content of glutaminase (CAS9001-47-2) as an enzyme. For example, it may be 0.0005 w / w% to 2.0 w / w% in mass grams per 100g of raw rice. More specifically, the lower limits are 0.0006 w / w% or higher, 0.007 w / w% or higher, 0.0008 w / w% or higher, 0.0009 w / w% or higher, 0.001 w / w% or higher, 0.003 w / w% or higher, 0.004 w / w% or higher, 0.005 w / w% or higher, 0.006 w / w% or higher, 0.007 w / w% or higher, 0.008 w / w% or higher, 0.009 w / w% or higher, 0.010 w / w% or higher, 0.011 w / w% or higher, 0.012 w / w% or higher, 0.013 w / w% or higher, 0.014 w / w% or higher, 0.015 w / w% or higher, and 0.016 w / w It may also be % or more, 0.017 w / w% or more, 0.018 w / w% or more, 0.02 w / w% or more, 0.05 w / w% or more, 0.08 w / w% or more, 0.1 w / w% or more, 0.14 w / w% or more, 0.2 w / w% or more, 0.3 w / w% or more, 0.4 w / w% or more, 0.5 w / w% or more, 0.6 w / w% or more, 0.7 w / w% or more, 0.8 w / w% or more, 0.9 w / w% or more, 1.0 w / w% or more, 1.1 w / w% or more, 1.2 w / w% or more, 1.3 w / w% or more, 1.4 w / w% or more, 1.5 w / w% or more, or 1.9 w / w% or more. Furthermore, there is no upper limit, but for example, it may be 2.0 w / w% or less, 1.5 w / w% or less, 1.0 w / w% or less, 0.5 w / w% or less, 0.4 w / w% or less, 0.3 w / w% or less, 0.25 w / w% or less, 0.20 w / w% or less, 0.15 w / w% or less, 0.10 w / w% or less, 0.05 w / w% or less, 0.03 w / w% or less, or 0.01 w / w% or less. Furthermore, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 100% of the glutaminase activity in the uncooked rice may be derived from the enzyme preparation. Also, if the majority or all of the glutaminase activity in the uncooked rice is derived from the enzyme preparation, the glutaminase content relative to the weight of raw rice may be 0.0005 to 0.20 w / w%, preferably 0.0007 to 0.17 w / w%, more preferably 0.0008 to 0.15 w / w%, even more preferably 0.001 to 0.13 w / w%, even more preferably 0.001 to 0.10 w / w%, particularly preferably 0.001 to 0.05 w / w%, and especially preferably 0.001 to 0.03 w / w%.

[0072] It is preferable that the glutaminase enzyme activity of the uncooked rice in (d) above is above a predetermined value, as this is necessary to achieve the effects of the present invention. Specifically, the glutaminase enzyme activity in the uncooked rice may be 0.1 mU / g or more and 10 U / g or less relative to the weight of the raw rice. More specifically, the lower limit may be 0.3 mU / g or more, 0.5 mU / g or more, 0.7 mU / g or more, 0.9 mU / g or more, 1.0 mU / g or more, 1.1 mU / g or more, 1.2 mU / g or more, 1.3 mU / g or more, 1.4 mU / g or more, 1.5 mU / g or more, 1.6 mU / g or more, 1.7 mU / g or more, 1.8 mU / g or more, 1.9 mU / g or more, 2.0 mU / g or more, 3.0 mU / g or more, 4. The upper limit may be 0 mU / g or higher, 5.0 mU / g or higher, 9.0 mU / g or higher, 10 mU / g or higher, 20 mU / g or higher, 30 mU / g or higher, 40 mU / g or higher, 50 mU / g or higher, 60 mU / g or higher, 70 mU / g or higher, 80 mU / g or higher, 90 mU / g or higher, 100 mU / g or higher, 150 mU / g or higher, 200 mU / g or higher, 300 mU / g or higher, 400 mU / g or higher, or 500 mU / g or higher. On the other hand, the upper limit may be 9 U / g or lower, 8 U / g or lower, 7 U / g or lower, 6 U / g or lower, 5 U / g or lower, 4 U / g or lower, 3 U / g or lower, 2 U / g or lower, 1 U / g or lower, 0.9 U / g or lower, 0.8 U / g or lower, 0.7 U / g or lower, or 0.6 U / g or lower.

[0073] Furthermore, in the pre-cooked rice at stage (i), a rice improver may be used in such a way that one or more, preferably two or more, and more preferably all three of the following conditions (e) to (g) are satisfied. (e) Salt equivalent amount in raw rice before cooking is 0.01-2.5 w / w% (f) The amount of carbohydrates added to raw rice before cooking is 0.01-0.9 w / w% (g) The ratio of added carbohydrates to the amount of salt equivalent is 1 to 8 Furthermore, if one or more of the above (e) to (g) are satisfied, preferably two or more, and more preferably all three, the amount of salt equivalent to the raw rice before cooking may be particularly preferably 0.05 to 0.2 w / w%, the amount of carbohydrates added to the raw rice before cooking may be particularly preferably 0.05 to 0.2 w / w%, and the ratio of the amount of carbohydrates added to the amount of salt equivalent may be preferably 0.5 to 8, more preferably 0.5 to 7, even more preferably 0.5 to 6, even more preferably 0.5 to 5, particularly preferably 0.5 to 4, and especially preferably 1 to 3.

[0074] Furthermore, in step (i), the rice may be manufactured by adding edible oil before cooking. For example, in ready-to-eat rice, edible oil is sometimes added to improve the release of cooked rice from the pot. However, when edible oil is added during cooking, the edible oil itself causes the rice to become sticky, resulting in a poor texture and a significant decrease in taste. The rice of the present invention is cooked using glutaminase and edible oil in combination. The synergistic effect of glutaminase and edible oil significantly improves the loosening of the rice, resulting in rice with a greatly improved taste. This is an extremely unusual effect for rice containing edible oil. There are no particular restrictions on the edible oil to be added; for example, salad oil, rice oil, corn oil, safflower oil, olive oil, pork fat, beef fat, butter, etc. may be used, and commercially available "cooking oils" may also be used. In addition, these edible oils may be combined in any way.

[0075] When the cooked rice of the present invention contains edible oil by adding it before cooking, the amount of edible oil is preferably 0.1 to 2 w / w%, more preferably 0.15 to 1.5 w / w%, even more preferably 0.3 to 1.2 w / w%, even more preferably 0.35 to 1.0 w / w%, particularly preferably 0.40 to 0.90 w / w%, and especially preferably 0.45 to 0.80 w / w%, as an amount added in grams per 100g of raw rice before watering, from the viewpoint of improving the loosening effect of the cooked rice and minimizing the influence of the oil itself on the flavor of the cooked rice. Furthermore, the upper limit can be, for example, 2 w / w%, 1.8 w / w%, 1.6 w / w%, or 1.4 w / w%, and the lower limit can be, for example, 0.1 w / w%, 0.2 w / w%, or 0.4 w / w%.

[0076] Furthermore, the raw rice used in step (i) is not particularly limited, but from the viewpoint of making the present invention more useful, it may be raw rice other than indica rice and feed rice. Also, for the same reason, it may be raw rice with an apparent amylose content of 30% or less. That is, the rice improver of the present invention may be a rice improver used with raw rice other than indica rice and feed rice, or a rice improver used with raw rice with an apparent amylose content of 30% or less.

[0077] Furthermore, the addition of water in step (i) can be carried out under general conditions. In this invention, "addition of water" refers to adding water to raw rice, and the amount of water added refers to the mass of water relative to the mass of raw rice before water is added. The moisture in the water addition in this invention may come from ingredients containing moisture or rice improvers, may be added as water, may be moisture absorbed by the raw rice in the soaking process described later, or may be a combination of these. The amount of water added in step (i) can be adjusted arbitrarily, but it may preferably be 1.10 to 2.00 times the mass of raw rice before water is added, more preferably 1.12 to 1.90 times, even more preferably 1.15 to 1.80 times, even more preferably 1.17 to 1.70 times, particularly preferably 1.18 to 1.60 times, especially preferably 1.2 to 1.55 times, or 1.20 to 1.50 times. Furthermore, there are no particular restrictions on the upper limit, but for example, it may be 2.00 times or less, 1.90 times or less, 1.80 times or less, 1.75 times or less, 1.65 times or less, 1.55 times or less, 1.50 times or less, 1.45 times or less, or 1.40 times or less. Also, there are no particular restrictions on the lower limit, but for example, it may be 1.05 times or more, 1.10 times or more, 1.12 times or more, 1.13 times or more, 1.14 times or more, 1.15 times or more, 1.16 times or more, 1.17 times or more, 1.18 times or more, 1.19 times or more, 1.20 times or more, 1.21 times or more, 1.22 times or more, 1.23 times or more, or 1.24 times or more.

[0078] Furthermore, the raw rice used in step (i) may be raw rice that has been soaked in advance. "Soaking" refers to holding a mixture of raw rice and water for a specific time after adding water to the raw rice and before starting to cook it. In this invention, in order to make it easier for heat to penetrate to the center of the raw rice, soaked raw rice, which has been soaked for a predetermined time after adding water, may be used. Soaking the raw rice may be done, for example, by adding water to the raw rice, holding it for a specific time, and then cooking it as is, or by adding water to the raw rice, holding it for a specific time, discarding the water, adding water again, and then cooking it. When soaking, the weight of the raw rice before soaking can be measured in advance, and the amount of water absorbed by the raw rice by soaking can be determined by the difference between the weight of the raw rice before soaking and the weight of the raw rice after soaking. The soaking time is not particularly limited as long as water penetrates into the raw rice, but it may be, for example, 10 minutes to 48 hours, more preferably 15 minutes to 36 hours, even more preferably 20 minutes to 24 hours, even more preferably 25 minutes to 20 hours, particularly preferably 30 minutes to 16 hours, and especially preferably 45 to 12 hours. More specifically, the lower limit is not particularly limited, but may be, for example, 10 minutes or more, 20 minutes or more, 30 minutes or more, 40 minutes or more, 50 minutes or more, or 60 minutes or more. The upper limit is not particularly limited, but may be, for example, 48 hours or less, 36 hours or less, 24 hours or less, 30 hours or less, 24 hours or less, 20 hours or less, 16 hours or less, or 12 hours or less.

[0079] Furthermore, while the pre-cooked rice in step (i) can be under general temperature conditions, pre-cooked rice that has been heated to a predetermined temperature or higher may also be used. Specifically, the temperature of the pre-cooked rice may be between 20°C and 60°C. More specifically, the lower limit is not particularly limited, but may be 20°C or higher, 25°C or higher, 30°C or higher, 35°C or higher, or 40°C or higher. The upper limit is also not particularly limited, but may be 60°C or lower, 55°C or lower, or 50°C or lower.

[0080] Stage (ii) Pre-cooking rice heating stage In this stage (ii), the uncooked rice obtained in stage (i) is heated to 98°C or higher (this will be referred to as the "heating stage" as appropriate). One of the features of the heating stage in step (ii) of the present invention is that the heating rate of the bottom of the pot is above a predetermined value. Although the principle is unknown, it is thought that the rice cooker improver of the present invention improves uneven heating inside the rice cooker pot and allows for smooth heat convection inside the pot, so that not only the heating rate of the pot, which tends to increase relatively quickly because the temperature rises first inside the pot during the heating stage, but also the heating rate of the bottom of the pot, which rises later, can be set to above a predetermined value. Specifically, the pre-cooked rice in step (ii) may be heated to 98°C or higher at a bottom heating rate of 6.0°C / min or more and 25°C / min or less. More specifically, the lower limit is not particularly limited, but may be 6.5°C / min or higher, or 7.0°C / min or higher, or 7.5°C / min or higher, or 8.0°C / min or higher, or 8.5°C / min or higher, or 9.0°C / min or higher, or 9.5°C / min or higher, or 10.0°C / min or higher, or 11.0°C / min or higher, or 12.0°C / min or higher, or 13.0°C / min or higher, or 14.0°C / min or higher, or 15.0°C / min or higher. The upper limit is not particularly limited, but may usually be 23°C / min or lower, or 20°C / min or lower.

[0081] Furthermore, in step (ii) of the present invention, it is preferable that the cooking rice before cooking has a pot bottom heating rate of 100% or more, as well as a pot heating rate of 100% or more. Specifically, the pre-cooked rice in step (ii) may be heated to 98°C or higher at a pot temperature rise rate of 6.0°C / min or more and 25°C / min or less. More specifically, the lower limit is not particularly limited, but may be 6.5°C / min or higher, or 7.0°C / min or higher, or 7.5°C / min or higher, or 8.0°C / min or higher, or 8.5°C / min or higher, or 9.0°C / min or higher, or 9.5°C / min or higher, or 10.0°C / min or higher, or 11.0°C / min or higher, or 12.0°C / min or higher, or 13.0°C / min or higher, or 14.0°C / min or higher, or 15.0°C / min or higher. The upper limit is not particularly limited, but may usually be 23°C / min or lower, or 20°C / min or lower.

[0082] Furthermore, in step (ii), the time required for both the pot top temperature and the pot bottom temperature to reach 98°C may be within a predetermined time after the start of cooking. Specifically, the time required for both the pot top temperature and the pot bottom temperature to reach 98°C may be 3 minutes or more and 15 minutes or less after the start of cooking. More specifically, there is no particular limit to the upper limit, but it may be 14 minutes or less, or 13 minutes or less, or 12 minutes or less, or 11 minutes or less, or 10 minutes or less, or 9 minutes or less, or 8 minutes or less. There is no particular limit to the lower limit, but it may be 3 minutes or more, 4 minutes or more, or 5 minutes or more.

[0083] Furthermore, it is preferable to start step (ii) within a predetermined time after the preparation of pre-cooked rice in step (i). Although the principle is unclear, it is thought that if too much time passes after adding the rice improver, the texture will soften due to the enzymatic reaction, resulting in a decrease in taste. Specifically, the time from adding the rice improver to adding the rice improver to the pre-cooked rice and starting cooking may be 0 minutes or less, or 80 minutes or more. More specifically, the upper limit may be 80 minutes or less, or 70 minutes or less, or 60 minutes or less, or 50 minutes or less, or 40 minutes or less, or 30 minutes or less, or 20 minutes or less, or 15 minutes or less, or 10 minutes or less, or 5 minutes or less, or 1 minute or less, or 0.5 minutes or less, and the lower limit may be 0 minutes or more, or 0.1 minutes or more, or 0.2 minutes or more.

[0084] Stage (iii) A warming stage in which the cooked rice after the heating stage is kept at a bottom temperature of 98°C or higher. In this stage (iii), the cooked rice obtained in stage (ii) after the heating stage is maintained at 98°C or higher (this will be referred to as the "warming stage" as appropriate). In the heat retention stage of step (iii) of the present invention, one of its features is that the cooked rice after the heating stage is kept at a pot bottom temperature of 98°C or higher for a predetermined period of time or longer. Although the principle is unknown, it is thought that the rice improver of the present invention improves uneven heating inside the rice cooker pot and allows for smooth heat convection inside the pot, thereby ensuring a heat retention time of 98°C or higher for a predetermined period of time or longer, even for the pot bottom temperature, which is relatively difficult to raise. Specifically, in step (iii), the cooked rice after the heating stage may be kept at a bottom temperature of 98°C or higher for 2 minutes to 120 minutes. More specifically, the lower limit is not particularly limited but may be 3 minutes or more, or 4 minutes or more, or 5 minutes or more, or 6 minutes or more, or 7 minutes or more, or 8 minutes or more, or 9 minutes or more, or 10 minutes or more, or 11 minutes or more, or 12 minutes or more, or 13 minutes or more, or 14 minutes or more, or 15 minutes or more. The upper limit is not particularly limited but may be 100 minutes or less, or 80 minutes or less, or 60 minutes or less, or 50 minutes or less, or 40 minutes or less.

[0085] Furthermore, in the heat retention stage of step (iii) of the present invention, in addition to maintaining the cooked rice at a pot bottom temperature of 98°C or higher for a predetermined time or longer after the heating stage, the rice may also be maintained at a pot top temperature of 98°C or higher for a predetermined time or longer. Specifically, in step (iii), the cooked rice after the heating stage may be kept at a temperature of 98°C or higher above the pot for 2 minutes to 120 minutes. More specifically, the lower limit is not particularly limited but may be 3 minutes or more, or 4 minutes or more, or 5 minutes or more, or 6 minutes or more, or 7 minutes or more, or 8 minutes or more, or 9 minutes or more, or 10 minutes or more, or 11 minutes or more, or 12 minutes or more, or 13 minutes or more, or 14 minutes or more, or 15 minutes or more. The upper limit is not particularly limited but may be 100 minutes or less, or 80 minutes or less, or 60 minutes or less, or 50 minutes or less, or 40 minutes or less. Furthermore, it is preferable that the time during which both the kettle top temperature and the kettle bottom temperature are 98°C or higher is for a predetermined period of time or longer. Specifically, the time during which both the kettle top temperature and the kettle bottom temperature are 98°C or higher may be 10 minutes or more and 100 minutes or less. More specifically, the lower limit is not particularly limited, but it may be 11 minutes or more, or 12 minutes or more, or 13 minutes or more, or 14 minutes or more, or 15 minutes or more. Also, the upper limit is not particularly limited, but it may be 90 minutes or less, or 80 minutes or less, or 60 minutes or less, or 50 minutes or less, or 40 minutes or less, or 30 minutes or less.

[0086] Furthermore, it is preferable that the difference in time between the top temperature and the bottom temperature of the pot being 98°C or higher is within a predetermined time. Although the principle is unknown, it is thought that the rice cooking agent of the present invention improves uneven heating inside the rice cooking pot, and because heat convection inside the pot is carried out smoothly, the top temperature, which rises first inside the pot during the heating stage, and the bottom temperature, which usually rises later, rise in conjunction, thereby reducing the difference in time. Specifically, the difference in time between the top temperature and the bottom temperature of the pot being 98°C or higher may be 0 minutes or more and 15 minutes or less. More specifically, there is no particular limit, but the upper limit may be 14 minutes or less, or 13 minutes or less, or 12 minutes or less, or 11 minutes or less, or 10 minutes or less, or 9 minutes or less, or 8 minutes or less, or 7 minutes or less. There is no particular limit to the lower limit, but it may be 1 minute or more, or 2 minutes or more. Furthermore, it is preferable that the time during which both the top and bottom temperatures of the pot are 98°C or higher is 15 minutes or more, and that the difference between the time during which both temperatures are 98°C or higher is within a predetermined time, in order to produce high-quality cooked rice. Specifically, it is more preferable that the time during which both the top and bottom temperatures of the pot are 98°C or higher is 15 minutes or more, and that the difference between the time during which both temperatures are 98°C or higher is within 10 minutes.

[0087] Furthermore, the method for producing cooked rice according to the present invention may include a step of cooling the cooked rice after cooking. In this embodiment, it is preferable to lower the temperature of the cooked rice to 50°C or below. The cooling step can be carried out using a commercially available vacuum cooler (for example, GMJ-20QE manufactured by Miura Co., Ltd.).

[0088] Furthermore, the cooked rice of the present invention may be maintained at a temperature range of 0°C to 40°C for a predetermined period of time or longer after cooking is complete and before consumption. Specifically, it may be maintained at a temperature range of 0°C to 40°C for 8 hours to 72 hours after cooking is complete and before consumption. The lower limit is not particularly limited, but may be 10 hours or more, or 12 hours or more, or 14 hours or more, or 16 hours or more. The upper limit is not particularly limited, but may be 68 hours or less, or 60 hours or less, or 54 hours or less, or 48 hours or less, or 40 hours or less, or 36 hours or less, or 32 hours or less, or 36 hours or less, or 24 hours or less. Moreover, the present invention is particularly useful in embodiments in which the temperature range for which the rice is maintained after cooking is 0°C to 30°C, and especially 0°C to 20°C, for the above period of time.

[0089] The present invention also relates to a method for improving the looseness of cooked rice, a method for improving uneven heating inside a rice cooker during rice cooking, and a method for reducing scorching inside a rice cooker during rice cooking, using the rice cooker improver of the present invention.

[0090] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. [Examples]

[0091] Evaluation Test 1 (Verification of the effects of adjusting glutaminase, pH, and undissociated acetic acid concentration) Acetic acid, brewed vinegar, sodium acetate, and glutaminase enzyme preparation were diluted with tap water as appropriate to achieve the composition shown in Table 1. Furthermore, the amylase activity of the rice improver was adjusted using a commercially available enzyme preparation to 0.1 U / g or higher. The rice improver was then prepared by sterilization at 90°C or higher as appropriate (Comparative Example 1, Examples 1-6). Comparative Example 1 was used as a control in evaluation tests 1-4. <Enzyme activity of rice improver> The enzyme activity of the rice improver was evaluated by adding 0.1 w / w% of the rice improver to polished Koshihikari rice with 400% water content, heating it to 98°C at a heating rate of 12°C / min, and holding it for 2 minutes. The viscosity of the supernatant was then measured using a B-type viscometer (No. 1 rotor, 60 rpm, 20°C). Specifically, using a B-type viscometer (e.g., "B-II" manufactured by Toki Sangyo Co., Ltd.), an appropriate amount of the sample liquid, temperature-adjusted to 20°C, was filled into the measuring container of the B-type viscometer. The container was then set in the B-type viscometer, and the viscosity was measured using the No. 1 rotor at a rotation speed of 60 rpm. If the viscosity was 100 cP or less, it was evaluated as ○; otherwise, it was evaluated as ×. Furthermore, if the viscosity ratio of the rice improver-added group to Comparative Example 1 (viscosity of the rice improver-added group / viscosity of Comparative Example 1) was less than 0.8 times, it was evaluated as ○; otherwise, it was evaluated as ×.

[0092] 450g of polished Koshihikari rice from Toyama Prefecture (visual amylose content 17.1%) was weighed, washed, and then soaked in enough water to completely submerge the raw rice at room temperature (20°C) for 60 minutes. After soaking, the soaking water was discarded, and a rice improver and water were added to the soaked raw rice so that the water ratio relative to the weight of the raw rice before water addition (450g) was 1.40 times (total water mass 630g), and the glutaminase content relative to the weight of the raw rice before water addition was as shown in Table 1. Within 30 minutes of adding the rice improver and water, cooking was started in the quick-cook mode of an IH rice cooker (Tiger Corporation: JKT-G101) to obtain cooked rice (Comparative Example 1, Examples 1-6).

[0093] From the start to the end of cooking, the temperature change at the top and bottom of the rice cooker pot was measured using a temperature measuring device (DATATRACE (memory thermometer) Micropack III) to evaluate the unevenness of heating during cooking. If the rate of temperature rise to 98°C or higher at the top and bottom of the pot was 6.0°C / min or more, it was rated ○; otherwise, it was rated ×. In addition, if the time at which the temperature was maintained above 98°C at the top and bottom of the pot was 10 minutes or more, it was rated ○; otherwise, it was rated ×. Furthermore, if the difference in the time at which the temperature was maintained above 98°C at the top and bottom of the pot was 7 minutes or less, it was rated ◎; if it was between 7 minutes and 15 minutes, it was rated ○; otherwise, it was rated ×.

[0094] After the rice cooking was complete, the number of small holes (crab holes) in the cooked rice was visually counted and evaluated on a 5-point scale as follows. <Number of crab holes> 5-star rating (30+ items) Rating 4: 20-30 items Rating 3: 10-20 items Rating 2: 0-10 items Rating 1: 0

[0095] After the rice cooking was complete, the cooked rice was stirred with a rice paddle, and the ease with which the rice could be stirred was evaluated on a four-point scale, as shown below, using Comparative Example 1 as a control. <The charm of Shamoji Street> Rating 4: Much better than the control group Rating 3: Better than the comparison Rating 2: Slightly better than the control Rating 1: Equivalent to the control group

[0096] After the cooked rice was cooled to 45°C using a vacuum cooler (GMJ-20QE, manufactured by Miura Industries Co., Ltd.), 20g rice balls were formed using a rice ball molding machine (SSN-FRA, manufactured by Suzumo Kiko Co., Ltd.).

[0097] The rice balls prepared as described above were stored at 20°C for 3 hours and then at 20°C for 24 hours, simulating consumption during the day, before being subjected to the following sensory evaluation test. In the sensory evaluation, 10 expert panelists evaluated the looseness of the cooked rice and its deliciousness (the degree of likability judged from the overall taste, texture, and flavor perceived when placed in the mouth), using Comparative Example 1 as a control, and calculated the arithmetic mean.

[0098] <Flaked rice> Rating 7: Much better than the comparison Rating 6: Better than the comparison Rating 5: Slightly better than the comparison. Rating 4: Equivalent to the control group Rating 3: Slightly worse than the comparison. Rating 2: Worse than the comparison Rating 1: Much worse than the comparison

[0099] <The deliciousness of rice> Rating 7: Much better than the comparison Rating 6: Better than the comparison Rating 5: Slightly better than the comparison. Rating 4: Equivalent to the control group Rating 3: Slightly worse than the comparison. Rating 2: Worse than the comparison Rating 1: Much worse than the comparison

[0100] [Table 1]

[0101] Table 1 shows that rice improvers containing glutaminase and with adjusted pH and non-dissociated acetic acid concentration can produce rice that is easy to separate and delicious. Similar evaluations were obtained even after storage at 20°C for 3 hours. Furthermore, in the test group with adjusted amylase activity, the rice's ability to separate from the pot improved.

[0102] Evaluation Test 2 (Verification of the effect of a rice improver with adjusted salt content) In this study, acetic acid, brewed vinegar, sodium acetate, glutaminase enzyme preparation, and sodium chloride were diluted with tap water as appropriate to achieve the composition shown in Table 2. Furthermore, a commercially available enzyme preparation was used to adjust the amylase activity of the rice improver to 0.1 U / g or higher. Finally, the rice improver was prepared by sterilizing it at 90°C or higher as appropriate.

[0103] The aforementioned rice improver was added using the same process as in Evaluation Test 1, so that the glutaminase content relative to the weight of raw rice before water was as shown in Table 2, to obtain cooked rice (Comparative Example 2, Examples 7-12).

[0104] The cooked rice obtained by the above process was evaluated in the same manner as in Evaluation Test 1.

[0105] [Table 2]

[0106] Table 2 shows that by using a rice improver with adjusted salt content, we were able to obtain rice that was easier to separate, tastier, and easier to handle with a rice paddle. Similar evaluations were obtained even after storage at 20°C for 3 hours. Furthermore, in Example 12, some respondents reported a salty taste derived from the salt. Additionally, in the test group where amylase activity was adjusted, the rice's ability to separate from the pot improved.

[0107] Evaluation Test 3 (Verification of the effect of adjusting the carbohydrate content in rice improvers) In this study, acetic acid, brewed vinegar, sodium acetate, glutaminase enzyme preparation, and reduced starch syrup were diluted with tap water as appropriate to achieve the composition shown in Table 3. Furthermore, a commercially available enzyme preparation was used to adjust the amylase activity of the rice improver to 0.1 U / g or higher. Finally, the rice improver was prepared by sterilizing it at 90°C or higher as appropriate.

[0108] The aforementioned rice improver was added using the same process as in Evaluation Test 1, so that the glutaminase content relative to the weight of raw rice before water was as shown in Table 3, to obtain cooked rice (Comparative Example 3, Examples 13-18).

[0109] The cooked rice obtained by the above process was evaluated in the same manner as in Evaluation Test 1.

[0110] [Table 3] Table 3 shows that adjusting the carbohydrate content in the rice improver resulted in rice that was easier to separate and tastier. Similar evaluations were obtained even when stored at 20°C for 3 hours. In Comparative Example 3, scorching of the rice cooker pot was observed. Furthermore, in Example 18, some participants reported tasting a sweetness derived from reduced starch syrup. Additionally, in the test group where amylase activity was adjusted, the rice's ability to separate from the pot improved.

[0111] Evaluation Test 4 (Verification of the effects when the salt equivalent and carbohydrate content of the rice improver are adjusted, when the specific gravity of the rice improver is adjusted, when the amylase activity of the rice improver is adjusted, and when oil is added before cooking) In this study, acetic acid, brewed vinegar, sodium acetate, glutaminase enzyme preparation, sodium chloride, and reduced starch syrup were diluted with tap water as appropriate to achieve the compositions shown in Tables 4-1 and 4-2. In Examples 21-28, rice improvers were prepared by adjusting the amylase activity of the rice improver to 0.1 U / g or higher using a commercially available enzyme preparation. In this study, the rice improvers were not subjected to sterilization treatment at temperatures above 90°C.

[0112] Cooked rice was obtained by adding the aforementioned rice improver in the same process as in Evaluation Test 1, such that the glutaminase content relative to the weight of raw rice before water was as shown in Tables 4-1 and 4-2 (Examples 19-28). In Comparative Example 4 and Examples 26-28, commercially available edible oils and fats were added before cooking, such that the content relative to the weight of raw rice before water was as shown in Table 4-2.

[0113] The cooked rice obtained by the above process was evaluated in the same manner as in Evaluation Test 1.

[0114] [Table 4-1] [Table 4-2]

[0115] Tables 4-1 and 4-2 show that by adjusting the salt equivalent and carbohydrate content of the rice improver, and further adjusting the specific gravity of the rice improver, it was found that rice that separates well and tastes good could be obtained. Similar evaluations were obtained even when stored at 20°C for 3 hours. In Comparative Example 4, there was an opinion that the texture was unpleasant due to the edible oils. Furthermore, in the test group with adjusted amylase activity, the separation of the rice from the pot was improved compared to the test group without amylase activity.

Claims

1. A cooked rice improver that satisfies all of the following (1) to (3), wherein the carbohydrate content is 0.5 to 50.0 w / w%, and 40% by mass or more of the carbohydrates in the cooked rice improver are derived from reduced starch syrup. (1) Satisfy the following (a) and / or (b): (a) The content of glutaminase in the cooked rice improving agent is 0.01 to 10.0 w / w% (b) The glutaminase enzyme activity in the cooked rice improving agent is 100 mU / g or more. (2) The pH of the cooked rice improving agent at 20°C is 4.6 to 9.

0. (3) The concentration of undissociated acetic acid is 0.001 to 2.000 w / w%.

2. 2. The cooked rice improving agent according to claim 1, which has a specific gravity at 20°C of 1.010 or more.

3. 3. The cooked rice improving agent according to claim 1, wherein the salt equivalent amount is 5.0 to 25.0 w / w%.

4. 3. The cooked rice improving agent according to claim 1 or 2, having an acetic acid content of 2.00 w / w% or more and 12.00 w / w% or less.

5. A solid cooked rice improver that is diluted to satisfy all of the following (1) to (3): (1) Satisfy the following (a) and / or (b): (a) The content of glutaminase in the cooked rice improving agent is 0.01 to 10.0 w / w% (b) The glutaminase enzyme activity in the cooked rice improving agent is 100 mU / g or more. (2) The pH of the cooked rice improving agent at 20°C is 4.6 to 9.

0. (3) The concentration of undissociated acetic acid is 0.001 to 2.000 w / w%.

6. A rice improver as described in claim 5, having a specific gravity of 1.010 or more at 20°C after dilution.

7. A cooked rice improver as described in claim 5 or 6, wherein the salt equivalent amount after dilution is 5.0 to 25.0 w / w%.

8. A rice improver as described in claim 5 or 6, having an acetic acid content after dilution of 2.00 w / w% or more and 12.00 w / w% or less.

9. A rice improver as described in claim 1 or 5, which contains sodium acetate.

10. A rice improver as described in claim 1 or 5, which has amylase activity.

11. A method for producing the cooked rice improving agent according to claim 1 or 5, comprising sterilization at a maximum temperature of less than 124°C.

12. 6. A method for producing the cooked rice improving agent according to claim 1 or 5, characterized in that the method does not include a sterilization treatment step during production.

13. A method for producing cooked rice, comprising cooking rice using the cooked rice improving agent according to claim 1 or 5.

14. The method according to claim 13, wherein the cooked rice is cooked rice for quick meals.

15. The method of claim 13, further comprising storing cooked rice at 25°C or below after production until consumption.

16. A method for producing cooked rice, comprising cooking rice using a cooked rice improver that satisfies all of the following (1) to (3), and further comprising a step of storing the cooked rice at 25°C or below after production until consumption. (1) Satisfy the following (a) and / or (b): (a) The content of glutaminase in the cooked rice improving agent is 0.01 to 10.0 w / w% (b) The glutaminase enzyme activity in the cooked rice improving agent is 100 mU / g or more. (2) The pH of the cooked rice improving agent at 20°C is 4.6 to 9.

0. (3) The concentration of undissociated acetic acid is 0.001 to 2.000 w / w%.

17. A method for producing cooked rice comprising the following steps (i) to (iii). (i) preparing pre-cooked cooked rice by adjusting the following (c) and / or (d) to satisfy (e): (c) The glutaminase content is 0.0005 w / w% or more based on the weight of raw rice. (d) glutaminase enzyme activity of 0.1 mU / g or more based on the weight of raw rice (e) The concentration of undissociated acetic acid is 0.00003 w / w% or more based on the weight of raw rice. (ii) A temperature-raising step in which the pre-cooked cooked rice of step (i) is heated to 98°C or higher at a pot bottom temperature-raising rate of 6.0°C / min or higher. (iii) A heat-retaining step in which the cooked rice after the temperature-raising step is kept at a pot bottom temperature of 98 ° C. or higher for 2 minutes or more.

18. The method according to claim 17, wherein step (i) comprises adding edible oil or fat to cooked rice before cooking in an amount of 0.1 to 2 w / w% based on the weight of raw rice.

19. The method according to claim 17 or 18, wherein step (ii) is started within 80 minutes after the production of uncooked cooked rice in step (i).

20. The method according to claim 17 or 18, wherein step (i) comprises a step of blending salt so that the amount of salt equivalent to the weight of raw rice is 0.01 to 2.5 w / w%.

21. The method according to claim 17 or 18, wherein step (i) comprises a step of blending sugars so that the amount of sugar added is 0.01 to 0.9 w / w% relative to the weight of raw rice.

22. The method according to claim 17 or 18, wherein the rate of temperature rise in the kettle in step (ii) is 6.0°C / min or more.

23. The method according to claim 17 or 18, wherein in step (iii), the cooked rice after the temperature-raising step is maintained at a temperature above the pot of 98°C or higher for 2 minutes or more.

24. 19. The manufacturing method according to claim 17 or 18, wherein in step (iii), the cooked rice after the temperature raising step is kept warm so that the difference between the time for which the cooked rice is kept at a temperature of 98°C or higher at the bottom of the pot and the time for which the cooked rice is kept at a temperature of 98°C or higher at the top of the pot is 15 minutes or less.

25. A method for improving the loosening of cooked rice, comprising cooking rice using a cooked rice improver that satisfies all of the following (1) to (3): (1) Satisfy the following (a) and / or (b): (a) The content of glutaminase in the cooked rice improving agent is 0.01 to 10.0 w / w% (b) The glutaminase enzyme activity in the cooked rice improving agent is 100 mU / g or more. (2) The pH of the cooked rice improving agent at 20°C is 4.6 to 9.

0. (3) The concentration of undissociated acetic acid is 0.001 to 2.000 w / w%.

26. A method for improving at least one of uneven heating inside a rice cooker, convection inside the rice cooker, and burning of food inside a rice cooker during cooking, comprising cooking rice using a rice improver that satisfies all of the following (1) to (3): (1) Satisfy the following (a) and / or (b): (a) The content of glutaminase in the cooked rice improving agent is 0.01 to 10.0 w / w% (b) The glutaminase enzyme activity in the cooked rice improving agent is 100 mU / g or more. (2) The pH of the cooked rice improving agent at 20°C is 4.6 to 9.

0. (3) The concentration of undissociated acetic acid is 0.001 to 2.000 w / w%.