Cooked rice modifier, cooked rice modification method, and modified cooked rice

Abstract

The present invention relates to: a cooked rice modifier that contains pectin methylesterase and an alkaline earth metal salt; a cooked rice modification method that includes bringing rice to contact with pectin methylesterase and an alkaline earth metal salt; and cooked rice that contains an alkaline earth metal salt and rice on which pectin methylesterase has been acted and that has improved texture.　According to the present invention, it is possible to improve the quality (such as firmness and grain distinctness) of rice cooked with an increased amount of water for the purpose of suppressing staling of the cooked rice. In particular, for cooked rice prepared by high-hydration rice cooking for the purpose of reducing the carbohydrate content of cooked rice, and the like, it is possible to provide a cooked rice modifier that can improve the texture by suppressing softening, and to improve the quality of cooked rice prepared with an increased amount of water. In particular, it is possible to improve the texture of cooked rice prepared by high-hydration rice cooking.

Description

Rice modification agent, method for modifying cooked rice, and modified cooked rice

[0001] The present invention relates to a rice modification agent, a method for modifying cooked rice, and modified cooked rice. The present invention relates to a rice modification agent that can improve the quality (hardness, grain looseness, etc.) of cooked rice with increased water addition during cooking, and particularly can suppress softening of cooked rice prepared with high water addition.

[0002] It is known that with the passage of time after cooking, starch retrogradation causes cooked rice to become dry and hard, thereby deteriorating its texture. In the food industry, increasing water addition during cooking is performed to suppress starch retrogradation of cooked rice. However, increasing water addition during cooking causes problems such as stickiness on the surface of cooked rice immediately after cooking, which deteriorates the texture, and the soft and sticky cooked rice immediately after cooking degrades the moldability of processed rice products such as rice balls and sushi. To solve the above problems, a quality improving agent for cooked rice containing α-amylase and / or glucosyltransferase and pectinase having pectin methylesterase activity has been proposed, which is disclosed to be capable of suppressing retrogradation of cooked rice without increasing water addition during cooking (Patent Document 1).

[0003] In addition, in response to the recent growing health consciousness, high-water addition rice cooking, which means cooking rice with increased water addition during cooking for the purpose of reducing the carbohydrate content of cooked rice, has attracted attention. High-water addition rice cooking can increase the moisture content contained in cooked rice and reduce the carbohydrate content of cooked rice, but cooked rice prepared by high-water addition rice cooking has the problem of becoming too soft, which impairs the texture. Therefore, there is a need for a quality modifying agent for cooked rice that can suppress softening and prevent texture deterioration of cooked rice prepared by high-water addition rice cooking.

[0004] Japanese Unexamined Patent Publication No. 2024-046208

[0005] Therefore, the present invention aims to improve the quality (hardness, grain shape, etc.) of cooked rice by increasing the amount of water added in order to suppress the aging of cooked rice, and in particular to improve the texture of cooked rice that has been cooked with a high amount of water added for the purpose of reducing the sugar content of cooked rice, by suppressing softening.

[0006] The inventors of this invention diligently studied to solve the above problems and found that by adding pectin methylesterase and alkaline earth metal salts during rice cooking, softening of rice cooked with high water content is suppressed and the texture of the rice is improved. Further investigation led to the completion of the present invention.

[0007] In other words, the present invention relates to the following: [1] A rice modifier containing pectin methylesterase and an alkaline earth metal salt. [2] The modifier according to [1], wherein the alkaline earth metal salt is one or more selected from the group consisting of calcium chloride, calcium hydroxide, calcium carbonate, calcium sulfate, calcium citrate, calcium gluconate, calcium acetate, calcium lactate, magnesium chloride, and magnesium sulfate. [3] The modifier according to [1] or [2], wherein the amount of pectin methylesterase per 1 g of rice is 0.01 U to 300 U. [4] The modifier according to [1] or [2], wherein the amount of pectin methylesterase per 1 g of rice is 0.05 U to 100 U. [5] The modifier according to any one of [1] to [4], wherein the amount of alkaline earth metal salt per 100 g of rice is 0.001 g to 2 g. [6] A modifier according to any one of [1] to [4], wherein the amount of alkaline earth metal salt per 100 g of rice is 0.005 g to 2 g. [7] A modifier according to any one of [1] to [6], further comprising one or more selected from the group consisting of dietary fiber and collagen. [8] A method for modifying cooked rice, comprising contacting rice with pectin methylesterase and an alkaline earth metal salt. [9] The method for modifying rice according to [8], wherein the alkaline earth metal salt is one or more selected from the group consisting of calcium chloride, calcium hydroxide, calcium carbonate, calcium sulfate, calcium citrate, calcium gluconate, calcium acetate, calcium lactate, magnesium chloride and magnesium sulfate.

[10] The method for modifying rice according to [8] or [9], wherein 0.01 U to 300 U of pectin methylesterase is contacted per 1 g of rice.

[11] The method for modifying rice according to [8] or [9], wherein 0.05 U to 100 U of pectin methylesterase is contacted per 1 g of rice.

[12] A modification method according to any one of [8] to

[11] , wherein 0.001 g to 2 g of an alkaline earth metal salt is brought into contact with 100 g of rice.

[13] A modification method according to any one of [8] to

[11] , wherein 0.005 g to 2 g of an alkaline earth metal salt is brought into contact with 100 g of rice.

[14] A modification method according to any one of [8] to

[13] , further comprising contacting with one or more selected from the group consisting of dietary fiber and collagen.

[15] Cooked rice with improved texture, containing rice treated with pectin methylesterase and an alkaline earth metal salt.

[16] Cooked rice according to

[15] , wherein the alkaline earth metal salt is one or more selected from the group consisting of calcium chloride, calcium hydroxide, calcium carbonate, calcium sulfate, calcium citrate, calcium gluconate, calcium acetate, calcium lactate, magnesium chloride, and magnesium sulfate.

[17] Cooked rice according to

[15] or

[16] , containing rice treated with 0.01 U to 300 U of pectin methylesterase per gram of rice.

[18] Cooked rice according to

[15] or

[16] , containing rice treated with 0.05 U to 100 U of pectin methylesterase per gram of rice.

[19] Cooked rice according to any one of

[15] to

[18] , containing 0.001 g to 2 g of alkaline earth metal salt per 100 g of rice.

[20] Cooked rice according to any one of

[15] to

[18] , containing 0.005 g to 2 g of alkaline earth metal salt per 100 g of rice.

[21] Cooked rice according to any one of

[15] to

[20] , further containing one or more selected from the group consisting of dietary fiber and collagen.

[22] Cooked rice according to any one of

[15] to

[21] , which is cooked with a water content of 180% to 200% by weight, and in which softening is suppressed.

[23] Cooked rice according to any one of

[15] to

[21] , which is cooked with a water content of 145% to 200% by weight, and in which the texture is improved.

[0008] The present invention can improve the quality (hardness, grain shape, etc.) of rice cooked with increased water content, and in particular, it can provide a rice modifier that can suppress softening in rice cooked with high water content and improve the texture of the rice. Furthermore, the present invention can improve the quality (hardness, grain shape, etc.) of rice cooked with increased water content, and in particular, it can provide a method for modifying rice that can suppress softening in rice cooked with high water content and improve the texture of the rice. Moreover, the present invention can provide rice with improved quality (hardness, grain shape, etc.) even when cooked with increased water content, and in particular, it can provide rice with improved texture and suppressed softening while being cooked with high water content. Therefore, the present invention can suppress the aging of rice and reduce the sugar content of rice.

[0009] Furthermore, the rice modifier and rice modifier method of the present invention can improve the quality (hardness, grain shape, etc.) of cooked rice not only when the amount of water is increased during cooking, but also when the amount of water is not increased significantly during cooking. Therefore, the present invention makes it possible to provide cooked rice with improved quality (hardness, grain shape, etc.) even when cooked with a small increase in water.

[0010] Figure 1 shows the hardness measurement results for each sample in Test Example 6. In the figure, "165% (-)" and "165% (+)" represent the cases where the rice was cooked with a water content of 165% by weight, without adding the rice modifier of Example 23, and with the rice modifier of Example 23 added, respectively. "200% (-)" and "200% (+)" represent the cases where the rice was cooked with a water content of 200% by weight, without adding the rice modifier of Example 23, and with the rice modifier of Example 23 added, respectively. Figure 2 shows the rate of increase in hardness for each sample stored for two days after cooking in Test Example 6. In the figure, "165% (-)" and "165% (+)" represent the case where rice is cooked with a water content of 165% by weight, without adding the rice modifier of Example 23, and the case where rice is cooked with the rice modifier of Example 23 added, respectively. "200% (-)" and "200% (+)" represent the case where rice is cooked with a water content of 200% by weight, and the case where rice is cooked with the rice modifier of Example 23 added, respectively.

[0011] The present invention provides a rice modifier (hereinafter also referred to as "the modifier of the present invention" in this specification). The modifier of the present invention contains pectin methylesterase and an alkaline earth metal salt.

[0012] In this specification, "rice modifier" refers to an additive added to rice or water to which rice has been added in order to improve the quality and texture of cooked rice. "Cooked rice" refers to a food prepared by adding water to rice and heating it by boiling, steaming, or other means. The rice used in preparing cooked rice is not particularly limited as long as it is a granular grain obtained by removing the outer husk from the husk, which is the fruit of the rice plant, and examples include Japonica rice (Oryza sativa subsp. japonica), Indica rice (Oryza sativa subsp. indica), and African rice (Oryza glaberrima). The modifier of the present invention can be used with both high-amylose rice with an amylose content of 25% by weight or more, and low-amylose rice with an amylose content of about 3% to 17% by weight, and can also be used with medium-grain Japonica rice from California (Calrose (amylose content = 19% by weight), etc.). Furthermore, since the effects of the present invention can be more clearly obtained, it is preferably used with high-amylose rice, and more preferably with non-glutinous rice (amylose content = 15% to 30% by weight).In this specification, "rice" refers to raw rice before heating for the preparation of cooked rice or rice during the heating process.

[0013] The pectin methylesterase contained in the modifier of the present invention is an enzyme that demethylates D-galacturonic acid methyl ester, which constitutes pectin, and is known to be produced by fungi such as Aspergillus niger. The pectin methylesterase contained in the modifier of the present invention is not particularly limited as long as it has sufficient enzyme activity to add the enzyme activity amount described below to 1 g of rice. Furthermore, the pectin methylesterase content in the modifier of the present invention is set to an amount that allows the enzyme activity amount described below to be added to 1 g of rice. The enzyme activity of pectin methylesterase can be determined by titrating the carboxyl group produced by the hydrolysis of pectin by pectin methylesterase with sodium hydroxide and measuring the amount of sodium hydroxide required to neutralize the carboxyl group. When pectin methylesterase is added to 1 g of pectin and reacted at pH = 4.5 and temperature = 50°C, the enzyme activity that decomposes the methyl ester of pectin and produces 1 μmol of carboxyl group in 1 minute is defined as 1 unit (U). In this invention, pectin methylesterase produced by Aspergillus niger or the like may be isolated, purified, and used, but commercially available enzyme preparations provided by various companies for food use can also be used.

[0014] The modifier of the present invention is preferably added in such an amount that the amount of pectin methylesterase per 1 g of rice is 0.01 U to 300 U, more preferably 0.5 U to 100 U, even more preferably 2.5 U to 100 U, even more preferably 2.5 U to 50 U, and even more preferably 5 U to 50 U.

[0015] The alkaline earth metal salt contained in the modifier of the present invention is a salt containing an alkaline earth metal ion as a constituent ion, and any edible salt can be used without particular limitations, with calcium salts and magnesium salts being preferred. Specifically, examples include inorganic calcium salts such as calcium chloride, calcium oxide, calcium hydroxide, calcium carbonate, calcium bicarbonate, calcium dihydrogen pyrophosphate, calcium sulfate, tricalcium phosphate, monocalcium phosphate, and dihydrogen phosphate; organic calcium salts such as calcium L-ascorbate, calcium citrate, calcium glycerophosphate, calcium gluconate, calcium L-glutamate, calcium acetate, calcium L-tartrate, calcium lactate, calcium pantothenate, calcium phytate, and calcium propionate; inorganic magnesium salts such as magnesium chloride, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium sulfate, trimagnesium phosphate, and monocalcium phosphate; and organic magnesium salts such as magnesium L-glutamate. For the purposes of the present invention, calcium chloride, calcium hydroxide, calcium carbonate, calcium sulfate, calcium citrate, calcium gluconate, calcium acetate, calcium lactate, magnesium chloride, magnesium sulfate, etc. are preferably used, and calcium carbonate, calcium sulfate, calcium gluconate, calcium lactate, and magnesium sulfate are more preferably used. In the modifier of the present invention, one alkaline earth metal salt may be selected and used alone, or two or more may be selected and used in combination. In the present invention, the alkaline earth metal salt may be produced and used by known chemical synthesis methods, neutralization reactions, etc., but commercially available products provided by various companies for food use can be used. In addition, foods or food additives that contain a large amount of alkaline earth metal salt, such as bittern, milk, and hard water, can also be used. The amount of alkaline earth metal salt in the modifier of the present invention is set so that the amount of alkaline earth metal salt described later can be added per 100 g of rice.

[0016] The modifier of the present invention is preferably added in such a way that the amount of alkaline earth metal salt per 100 g of rice is 0.001 g to 2 g, more preferably 0.005 g to 2 g, even more preferably 0.01 g to 1.5 g, and even more preferably 0.1 g to 1 g.

[0017] The modifier of the present invention may further contain dietary fiber. The dietary fiber that may be contained in the modifier of the present invention is a general term for indigestible components contained in food that are difficult to digest by human digestive enzymes. Preferably used in the modifier of the present invention are water-soluble dietary fibers, such as water-soluble polysaccharides derived from plants and mushrooms, such as guar bean enzyme hydrolysate, β-glucan, and gum arabic; water-soluble polysaccharides derived from algae, such as agarose, sodium alginate, carrageenan, fucoidan, porphyran, and laminaran; and indigestible dextrin. Plant storage carbohydrates such as glucomannan and inulin, which are nutritionally treated as dietary fiber, are also preferably used. In the modifier of the present invention, one type of dietary fiber may be selected and used alone, or two or more types may be selected and used in combination. In the present invention, dietary fiber may be extracted and purified from plants, mushrooms, algae, etc., but commercially available products provided by various companies for food use can be used. The dietary fiber content in the modifier of the present invention is set to an amount that allows for the addition of the amount of dietary fiber described later to 100g of rice.

[0018] The modifier of the present invention may contain collagen in place of or in addition to dietary fiber. The collagen that may be contained in the modifier of the present invention is the main component of the extracellular matrix of multicellular animals. In the present invention, one or more types of collagen with different molecular weights derived from various animals can be selected and used, but atelocollagen from which telopeptides have been removed by enzymatic treatment, gelatin with a modified three-dimensional structure, and collagen peptides that have been reduced in molecular weight by enzymatic treatment are preferably used. In the present invention, collagen can be extracted and purified from various animals and then treated with enzymes, etc., but commercially available products provided by various companies for food use can also be used. The collagen content in the modifier of the present invention is set to an amount in which the amount of collagen described later can be added per 100 g of rice.

[0019] The modifier of the present invention is preferably added so that the amount of dietary fiber per 100g of rice is 0.01g to 5g, and more preferably so that it is 0.1g to 2g. Furthermore, the modifier of the present invention is preferably added so that the amount of collagen per 100g of rice is 0.01g to 5g, and more preferably so that it is 0.1g to 2g.

[0020] The modifier of the present invention may contain, to the extent that it does not impair the characteristics of the present invention, excipients (e.g., sugars (glucose, lactose, corn starch, etc.), sugar alcohols (sorbitol, mannitol, etc.), binders (e.g., pregelatinized starch, partially pregelatinized starch, cellulose and its derivatives (crystalline cellulose, hydroxypropyl cellulose, etc.)), disintegrants (e.g., crospovidone, povidone, crystalline cellulose, etc.), lubricants (e.g., talc, magnesium stearate, etc.), thickening and stabilizing agents (e.g., xanthan gum, sodium carboxymethylcellulose, etc.), emulsifiers (e.g., glycerin fatty acid esters, sucrose fatty acid esters, saponins, lecithin, etc.), and preservatives (e.g., benzoic acid, sodium benzoate, sorbic acid, potassium sorbate, ε-polylysine). It may contain additives such as antioxidants (e.g., ascorbic acid, erythorbic acid, catechin, etc.), sweeteners (e.g., aspartame, acesulfame potassium, licorice extract, etc.), acidulants (e.g., citric acid, acetic acid, tartaric acid, etc.), bittering agents (e.g., caffeine, naringin, wormwood extract, etc.), seasonings (e.g., sugar, salt, soy sauce, mirin, miso, L-sodium glutamate, etc.), broths (e.g., kelp broth, bonito broth, mackerel broth, dried sardine broth, etc.), extracts (e.g., seafood extract, meat extract, vegetable extract, seaweed extract, yeast extract, etc.), colorants (e.g., annatto extract, turmeric extract, gardenia extract, etc.), and flavorings (e.g., synthetic flavorings such as ethyl aceto and anisaldehyde, spice extracts, natural flavorings such as laurel). The above-mentioned additives may be included one or more times as needed, and their amounts may be set in accordance with the normal usage amounts of such additives.

[0021] The modifier of the present invention can be in solid form such as powder, granules, tablets, etc., and can also be in liquid form such as solution, emulsion, suspension, or dispersion, by further containing water. Furthermore, it can be in solid form such as powder, granules, or granules, and can be prepared on demand by dissolving, dispersing, or suspending it in water or the like at the time of use. As water, purified water such as distilled water or ion-exchanged water, tap water, or other water suitable for food manufacturing can be used.

[0022] The modifier of the present invention can be manufactured by mixing pectin methylesterase and an alkaline earth metal salt, and optionally adding dietary fiber, collagen, the above-mentioned additives, water, etc., in accordance with general manufacturing methods for food products in solid form such as powder, granules, tablets, or liquid form such as solution, emulsion, suspension, or dispersion.

[0023] The modifier of the present invention can improve the quality (hardness, grain shape, etc.) of cooked rice prepared by adding it to rice used in the preparation of cooked rice, and then adding water and heating it, i.e., by cooking the rice; or by adding it to water added to rice and then heating it, i.e., by cooking the rice; or by adding it to rice or water added to rice during the process of adding water and heating, i.e., during the cooking process. In particular, it can suppress softening in cooked rice prepared by cooking with a high water content, specifically with a water content of 180% to 200% by weight, and improve the texture of the cooked rice. As a result, it can suppress the deterioration of quality due to starch retrogradation when cooked rice is stored, and can also reduce the sugar content of the cooked rice.

[0024] In this specification, "cooking rice" refers to adding water to rice and heating it, and the methods of cooking include heating in water, i.e., boiling, as well as heating with steam, i.e., steaming. The rice cooking process may include a step of frying the rice before the boiling or steaming step, and a steaming step may include a step of steaming after the boiling step. Furthermore, in the rice cooking process, the boiling step may proceed when there is a lot of moisture, and the steaming step may proceed when there is less moisture.

[0025] The present invention also provides a method for modifying cooked rice (hereinafter also referred to as "the modification method of the present invention" in this specification). The modification method of the present invention comprises contacting rice with pectin methylesterase and an alkaline earth metal salt. In the modification method of the present invention, "cooked rice," "pectin methylesterase," "alkaline earth metal salt," and "rice" are as described above in the description of the modifying agent of the present invention. Furthermore, in the modification method of the present invention, "modification" means improving the quality and texture of cooked rice.

[0026] In the modification method of the present invention, means for bringing pectin methylesterase and alkaline earth metal salt into contact with rice include sprinkling or coating the rice with powdered pectin methylesterase and alkaline earth metal salt, adding powdered pectin methylesterase and alkaline earth metal salt to water added to the rice, adding powdered pectin methylesterase and alkaline earth metal salt to the rice together with water and mixing, immersing the rice in an aqueous solution, dispersion, or suspension of pectin methylesterase and alkaline earth metal salt, adding the rice to an aqueous solution, dispersion, or suspension of pectin methylesterase and alkaline earth metal salt and heating it, and adding pectin methylesterase and alkaline earth metal salt to the rice while it is being heated. From the viewpoint of ease of contact and modification efficiency, it is preferable to dissolve, disperse, or suspend powdered pectin methylesterase and alkaline earth metal salt in water, add and mix rice, and bring them into contact; add pectin methylesterase and alkaline earth metal salt after adding water to rice, mix and bring them into contact; immerse rice in an aqueous solution, dispersion, or suspension of pectin methylesterase and alkaline earth metal salt and bring them into contact; or add an aqueous solution, dispersion, or suspension of pectin methylesterase and alkaline earth metal salt to rice and heat to bring them into contact. Contact between pectin methylesterase and alkaline earth metal salt and rice may be performed before adding water to the rice, after adding water to the rice but before heating (i.e., before cooking), or during heating with water (i.e., during cooking), but it is preferable to add them to the water to which the rice is added before adding water to the rice, or after adding water to the rice but before heating (i.e., before cooking).

[0027] Pectin methylesterase and alkaline earth metal salts can be prepared as the modifiers of the present invention as described above and brought into contact with rice. Means of bringing the modifiers of the present invention into contact with rice include adding and mixing powdered, granular, or granular modifiers of the present invention with rice; adding and mixing powdered, granular, or granular modifiers of the present invention with water to rice; immersing rice in liquid modifiers of the present invention, or a solution, dispersion, or suspension of the modifiers of the present invention; adding liquid modifiers of the present invention, or a solution, dispersion, or suspension of the modifiers of the present invention to rice; adding solid or liquid modifiers of the present invention to water added to rice; and adding liquid modifiers of the present invention, or a solution, dispersion, or suspension of the modifiers of the present invention when heating rice. From the viewpoint of ease of operation and modification efficiency in bringing the modifier of the present invention into contact with rice, it is preferable to add the modifier of the present invention in powder, granular, or granular form to the rice and mix and bring it into contact; add the modifier of the present invention in powder, granular, or granular form to the rice together with water and mix and bring it into contact; add the rice to a liquid modifier of the present invention, or a solution, dispersion, or suspension of the modifier of the present invention, and mix and bring it into contact; add the modifier of the present invention after adding water to the rice and mix and bring it into contact; or immerse the rice in a liquid modifier of the present invention, or a solution, dispersion, or suspension of the modifier of the present invention and bring it into contact. Contact between the modifier of the present invention and the rice may be performed before adding water to the rice, after adding water to the rice but before heating (i.e., before cooking), or during heating with water added (i.e., during cooking), but it is preferable to add it to the water to which the rice is added before adding water to the rice, or after adding water to the rice but before heating (i.e., before cooking).

[0028] In the modification method of the present invention, it is preferable to contact the rice with pectin methylesterase in an amount of 0.01 U to 300 U per 1 g of rice, more preferably 0.5 U to 100 U, even more preferably 2.5 U to 100 U, even more preferably 2.5 U to 50 U, and even more preferably 5 U to 50 U. Furthermore, it is preferable to contact the rice with alkaline earth metal salt in an amount of 0.001 g to 2 g per 100 g of rice, more preferably 0.005 g to 2 g, even more preferably 0.01 g to 1.5 g, and even more preferably 0.1 g to 1 g. Even when pectin methylesterase and alkaline earth metal salt are brought into contact with rice as the modifiers of the present invention as described above, the amounts of pectin methylesterase and alkaline earth metal salt brought into contact with the rice should be within the ranges described above.

[0029] In the modification method of the present invention, contact between pectin methylesterase and alkaline earth metal salt and rice, or contact between the above-mentioned modifier of the present invention and rice, can usually be carried out at a temperature of 4°C to 80°C, preferably 10°C to 70°C, and more preferably 15°C to 60°C, before heating (before cooking). Furthermore, contact between pectin methylesterase and alkaline earth metal salt and rice, or contact between the above-mentioned modifier of the present invention and rice, can usually be carried out for 1 minute to 24 hours, preferably 5 minutes to 12 hours, and more preferably 10 minutes to 2 hours, and heating (cooking) can also be carried out immediately after contact.

[0030] The modification method of the present invention may further include contacting rice with dietary fiber and / or collagen. "Dietary fiber" and "collagen" are as described above in the description of the modifier of the present invention. Dietary fiber and / or collagen can also be contacted with rice as the modifier of the present invention as described above.

[0031] In the modification method of the present invention, it is preferable to contact the rice with dietary fiber such that the amount of dietary fiber per 100g of rice is 0.01g to 5g, and more preferably 0.1g to 2g. Also, in the modification method of the present invention, it is preferable to contact the rice with collagen such that the amount of collagen per 100g of rice is 0.01g to 5g, and more preferably 0.1g to 2g. Even when dietary fiber and / or collagen are contacted with rice as the modifier of the present invention as described above, the amounts of dietary fiber and / or collagen relative to the rice should be within the above-described ranges. The temperature and time when contacting the rice with dietary fiber and / or collagen are as described above for the contact between pectin methylesterase and alkaline earth metal salts and rice.

[0032] The modification method of the present invention can improve the quality (hardness, grain shape, etc.) of cooked rice prepared by adding more water than usual and heating it, i.e., cooked rice with increased water content. In particular, it can suppress softening in cooked rice prepared by high-water cooking, specifically with a water content of 180% to 200% by weight, and improve the texture of the cooked rice. As a result, it can suppress the deterioration of quality due to starch retrogradation when the cooked rice is stored, and it can also reduce the sugar content of the cooked rice.

[0033] Furthermore, regarding the "cooking of rice" in the modification method of the present invention, it is as described above for the modifying agent of the present invention.

[0034] Furthermore, the present invention provides cooked rice in which the quality (hardness, grain shape, etc.) is improved when prepared by adding more water than usual and heating, that is, when cooked with increased water content, and in particular, when prepared by high-water cooking, softening is suppressed and the texture is improved (hereinafter also referred to as "the cooked rice of the present invention" in this specification). The cooked rice of the present invention contains rice treated with pectin methylesterase and an alkaline earth metal salt. The "cooked rice," "pectin methylesterase," "rice," and "alkaline earth metal salt" in the cooked rice of the present invention are as described above in the modifier of the present invention.

[0035] The "rice treated with pectin methylesterase" contained in the cooked rice of the present invention refers to rice in which the pectin present on the surface of the rice has been partially demethylated by the action of pectin methylesterase after contact with pectin methylesterase. The means for contacting the rice with pectin methylesterase, the temperature at which contact occurs, and the contact time are as described above in the modification method of the present invention. In the "rice treated with pectin methylesterase" contained in the cooked rice of the present invention, the amount of pectin methylesterase that acts per gram of rice is preferably 0.01 U to 300 U, more preferably 0.5 U to 100 U, even more preferably 2.5 U to 100 U, even more preferably 2.5 U to 50 U, and even more preferably 5 U to 50 U.

[0036] The alkaline earth metal salt content in the cooked rice of the present invention is preferably 0.001 g to 2 g per 100 g of rice, more preferably 0.005 g to 2 g, even more preferably 0.01 g to 1.5 g, and even more preferably 0.1 g to 1 g. At least a portion of the alkaline earth metal salt contained in the cooked rice of the present invention is involved in crosslinking of carboxyl groups liberated by demethylation in pectin present on the surface of the rice.

[0037] The cooked rice of the present invention may further contain dietary fiber and / or collagen. The dietary fiber content in the cooked rice of the present invention is preferably 0.01g to 5g per 100g of rice, and more preferably 0.1g to 2g. The collagen content in the cooked rice of the present invention is preferably 0.01g to 5g per 100g of rice, and more preferably 0.1g to 2g.

[0038] The cooked rice of the present invention can be prepared by contacting rice with pectin methylesterase and an alkaline earth metal salt, and optionally with dietary fiber and / or collagen, followed by heating under hydration. The means for contacting the rice with pectin methylesterase and an alkaline earth metal salt, and optionally with dietary fiber and / or collagen, are as described above in the modification method of the present invention. Pectin methylesterase and an alkaline earth metal salt, or pectin methylesterase and an alkaline earth metal salt along with dietary fiber and / or collagen, can be contacted with rice as the modifying agent of the present invention as described above. The means for contacting the rice with the modifying agent of the present invention are also as described above in the modification method of the present invention.

[0039] The cooked rice of the present invention exhibits improved quality (hardness, grain structure, etc.) even when prepared by adding more water than usual and heating it, i.e., when cooked with increased water content. In particular, even when cooked with high water content, specifically with a water content of 180% to 200% by weight, the softening of the cooked rice is suppressed and the texture is improved. As a result, the deterioration of quality due to starch retrogradation during storage of the cooked rice can be suppressed, and a lower sugar content in the cooked rice can be achieved.

[0040] Regarding the cooked rice of the present invention, the "cooking" process is as described above for the modifier of the present invention.

[0041] The modifier and the modifying method of the present invention can be suitably applied not only when cooking rice with increased water content, but also when cooking rice with less water content. Therefore, in another embodiment, the present invention can provide cooked rice with improved quality (hardness, grain structure, etc.) when cooked with less water content. The present invention can be suitably applied when cooking rice with a water content of 145% to 200% by weight, and can also improve the quality of cooked rice when cooking with a water content of approximately 150% to 160% by weight, and when high-water cooking is performed with a water content of 180% to 200% by weight.

[0042] Hereinafter, the features of the present invention will be described in further detail with reference to working examples and test examples.

[0043] [Test Example 1] Study on the effect of the addition amount of pectin methylesterase on the quality and texture of cooked rice (1) Preparation of samples To raw rice (non-glutinous rice (Oryza sativa L.)), 1% by weight of calcium gluconate ("Calcium Gluconate", Fuso Chemical Industry Co., Ltd.) and 0.01% by weight to 2% by weight of pectin methylesterase ("Sumiteam PME", Shin Nihon Chemical Industry Co., Ltd.) (5,000 U / g) were added as shown in Table 2 and mixed. The water content was adjusted to 200% by weight, and the rice was cooked using a pot and an IH heater (heating for 30 minutes, steaming for 15 minutes) to prepare cooked rice (Examples 1 to 7). (2) Evaluation of quality and texture of cooked rice Sensory evaluation was performed on the hardness, sogginess, grain shape and overall preference of the prepared cooked rice. The sensory evaluation was conducted by 4 trained professional panelists, scored according to the evaluation criteria shown in Table 1, and the average value of the evaluation scores of the 4 panelists was calculated. The case where neither calcium gluconate nor pectin methylesterase was added and the water content was 165% by weight was set as a positive control, and the case where neither calcium gluconate nor pectin methylesterase was added and the water content was 200% by weight was set as a negative control. The evaluation results are also shown in Table 2.

[0044]

[0045]

[0046] (3) As shown in Table 2 of the results, when the water addition rate is 200% by weight, cooking rice with the addition of pectin methylesterase together with 1% by weight of calcium gluconate relative to rice improves the softness and watery texture of cooked rice, enhances the grain definition of rice, and improves the overall preference evaluation, compared with the negative control cooked at a water addition rate of 200% by weight. This effect was observed in a dose-dependent manner until the addition amount of pectin methylesterase per 1 g of rice reached 25 U, reached a plateau at 50 U, and decreased conversely at 100 U. From the above results of Test Example 1, it is suggested that when cooking rice with a high water content of 200% by weight, in order to suppress softening of cooked rice and improve texture, it is more preferable that pectin methylesterase added together with 1 g of calcium gluconate per 100 g of rice is 0.5 U to 100 U per 1 g of rice, and even more preferably 2.5 U to 50 U per 1 g of rice.

[0047] [Test Example 2] Examination of the influence of the addition amount of alkaline earth metal salt on the quality and texture of cooked rice (1) Sample preparation For raw rice (non-glutinous rice (Oryza sativa L.)), 25 U of pectin methylesterase per 1 g of rice and calcium gluconate in an amount of 0% by weight to 2.00% by weight relative to rice as shown in Table 3 were added and mixed, the water addition rate was adjusted to 200% by weight, and rice was cooked using a pot and an IH heater (heating for 30 minutes, steaming for 15 minutes) to prepare cooked rice (Comparative Example 1 and Examples 8 to 14). As pectin methylesterase and calcium gluconate, the same enzyme preparation and the same product as those in Test Example 1 were used. (2) Evaluation of quality and texture of cooked rice The quality and texture of the prepared samples were evaluated in the same manner as in Test Example 1. A positive control and a negative control were prepared in the same manner as in Test Example 1. (3) Results The evaluation results of the texture of cooked rice are also shown in Table 3.

[0048]

[0049] As shown in Table 3, the cooked rice of Comparative Example 1, which was treated with pectin methylesterase 25U alone on 1g of rice and then cooked with high water content, showed a slight improvement in softness and wateriness compared to the negative control. When calcium gluconate was added at a concentration of 0.005% by weight relative to the rice in addition to pectin 25U and cooked with high water content, the hardness, wateriness, and overall palatability were slightly improved compared to the cooked rice of Comparative Example 1 (Example 8). When the amount of calcium gluconate added was 0.01% by weight relative to the rice, the softness and wateriness were clearly improved, and the grain shape and overall palatability were also clearly improved (Example 9). Subsequently, the improvement in the texture of the cooked rice improved in a dependent manner with the amount of calcium gluconate added, but the overall palatability was found to plateau at 1.5% by weight relative to the rice (Example 13). The results from Test Example 2 suggest that, when cooking rice with a high water content of 200% by weight, the amount of calcium gluconate added along with 25 U of pectin methylesterase per gram of rice is very preferably 0.01% to 1.5% by weight relative to the rice, and even more preferably 0.1% to 1% by weight, in order to suppress the softening of the cooked rice and improve its texture.

[0050] [Test Example 3] Investigation of the effect of different types of alkaline earth metal salts on the quality and texture of cooked rice (1) Sample preparation Raw rice (non-glutinous rice (Oryza sativa L.)) was mixed with 25 U of pectin methylesterase per gram of rice and the alkaline earth metal salts shown in Table 4 in the amounts shown in Table 4. Cooked rice was prepared by adding water to 200% by weight and cooking it in a pot using an IH heater (heating for 30 minutes, steaming for 15 minutes) (Examples 15-22). The same enzyme preparations and products as in Test Example 1 were used for pectin methylesterase and calcium gluconate. The following products were used for the other alkaline earth metal salts. (i) Calcium chloride: "Calcium Chloride H", Tomita Pharmaceutical Co., Ltd. (ii) Calcium carbonate: "Mamacalso", Nitto Powdering Industry Co., Ltd. (iii) Calcium lactate: "Calcium lactate", Fuso Chemical Industry Co., Ltd. (iv) Calcium hydroxide: "Calcium hydroxide", Tomita Pharmaceutical Co., Ltd. (v) Calcium sulfate: "Calcium sulfate", Tomita Pharmaceutical Co., Ltd. (vi) Magnesium chloride: "Magnesium chloride S", Tomita Pharmaceutical Co., Ltd. (vii) Magnesium sulfate: "Magnesium sulfate (dried)", Tomita Pharmaceutical Co., Ltd. (2) Evaluation of the quality and texture of cooked rice The prepared samples were evaluated for quality and texture in the same manner as in Test Example 1. Positive controls and negative controls were prepared in the same manner as in Test Example 1. (3) Results The results of the evaluation of the texture of cooked rice are shown in Table 4.

[0051]

[0052] As shown in Table 4, when inorganic calcium salts (calcium chloride, calcium carbonate, calcium hydroxide, and calcium sulfate), organic calcium salts (calcium lactate), and magnesium salts (magnesium chloride and magnesium sulfate) were added in addition to calcium gluconate, cooking them together with pectin methylesterase suppressed the softness and wateriness of the rice during high-water cooking and improved the grain separation of the rice. However, when calcium chloride, calcium hydroxide, and magnesium chloride were used, the overall preference rating of the rice was low. This was considered to be due to the influence of the taste of the alkaline earth metal salts. Therefore, considering the influence on the taste of the rice, it was suggested that calcium gluconate, calcium carbonate, calcium lactate, calcium sulfate, and magnesium sulfate are preferably used.

[0053] [Test Example 4] Examination of the effect of improving the quality and texture of cooked rice with different water content (1) Preparation of samples Raw rice (non-glutinous rice (Oryza sativa L.)) was cooked using a pot and an IH heater (heating for 30 minutes, steaming for 15 minutes) at the water content shown in Table 5, with or without the addition of calcium gluconate and pectin methylesterase as cookable rice modifiers. The amount of calcium gluconate and pectin methylesterase added was 1 g per 100 g of rice, and the amount of pectin methylesterase added was 25 U / g. The same enzyme preparations and products as in Test Example 1 were used for pectin methylesterase and calcium gluconate. (2) Evaluation of the quality and texture of cooked rice The prepared samples were evaluated for quality and texture (hardness and grain separation) in the same manner as in Test Example 1. Positive controls and negative controls were prepared in the same manner as in Test Example 1. (3) Results The results of the evaluation of the quality and texture of cooked rice are shown in Table 5.

[0054]

[0055] As shown in Table 5, when no rice modifier was added (indicated by "-" in Table 5), rice cooked with a water content of 130% by weight was perceived as very hard, and the grain separation was also perceived as very strong. Rice cooked with a water content of 150% by weight was also evaluated as quite hard, and the grain separation was also perceived as quite strong. However, at a water content of 200% by weight, the rice was perceived as soft, and the grain separation was weak. At a water content of 230% by weight, the rice was perceived as very soft, and the grain separation was also perceived as very weak. On the other hand, when rice was cooked with the addition of a rice modifier (indicated by "+" in Table 5), the hardness and grain separation of the rice were perceived as stronger at all water content levels from 130% by weight to 230% by weight. Even when cooked with 200% by weight of water, the rice was evaluated as quite hard, and the grain separation was clearly perceived. The results of Test Example 4 suggest that the modifier and modification method of the present invention can improve the hardness and grain shape of cooked rice over a wide range of water content. Therefore, it is suggested that when cooking rice with a higher water content than usual, i.e., when cooking with increased water content, it is possible to obtain cooked rice that is as hard as or better than cooked rice with a normal water content, and has a more clearly defined grain shape. Furthermore, it is suggested that the modifier has the effect of suppressing rice softening and improving texture in high-water-cooked rice with a water content of about 180% to 200% by weight.

[0056] [Test Example 5] Examination of the effect of rice type on the hardness of cooked rice (1) Preparation of samples Calcium gluconate and pectin methylesterase were added to each type of rice shown in Table 6 as a rice cooker, with the amount of calcium gluconate added being 1 g and the amount of pectin methylesterase added being 25 U / g per 100 g of rice. Cooked rice was prepared by adding 200% by weight of water and cooking it in a pot using an IH heater (heating for 30 minutes, steaming for 15 minutes). (2) Evaluation of the hardness of cooked rice Four panelists tasted the cooked rice prepared above and made their evaluation by consensus according to the evaluation criteria below. For each type of rice, the case in which it was cooked in the same way without adding a rice cooker was used as a negative control. <Evaluation Criteria> ××; Softer than the negative control ×; Same hardness as the negative control △; Slightly harder than the negative control 〇; Clearly harder than the negative control ◎; Very hard compared to the negative control (3) Results The evaluation results regarding the hardness of the cooked rice are shown in Table 6.

[0057]

[0058] By adding the rice modifier of the present invention during cooking, as shown in Table 6, softening during high-water cooking was suppressed regardless of the type of rice or the level of amylose content. The effect of suppressing rice softening due to high water content was more pronounced in rice with a high moisture content that is prone to softening.

[0059] [Example 23] Rice modifier calcium gluconate, pectin methylesterase, and inulin were mixed in a weight ratio of 2:1:2 to obtain the rice modifier of Example 23.

[0060] [Test Example 6] Investigation of the effect of a rice modifier on inhibiting the softening and aging of cooked rice (1) Preparation of the sample The rice modifier from Example 23 was added at a rate of 2.5 g per 100 g of raw rice (non-glutinous rice (Oryza sativa L.)) and mixed (amount of calcium gluconate and inulin added per 100 g of rice = 1 g each, amount of pectin methylesterase added per 1 g of rice = 25 U). Then, 165% by weight or 200% by weight of water was added, and cooked using a pot and an IH heater (heating for 30 minutes, steaming for 15 minutes) to prepare cooked rice. Cooked rice immediately after preparation and cooked rice after being stored at 20°C for 2 days were used as samples. (2) Measurement of cooked rice hardness For each sample, a Texture Analyzer ("TA.XT plus", Eiko Seiki Co., Ltd.) was used to measure the maximum compressive load when one grain of rice was compressed by 90% at 1 mm / sec using a 25 mm diameter acrylic cylindrical plunger (SMS P / 25P). The average value of N=30 was used as the maximum stress for comparison. The measurement results are shown in Figure 1. The rate of increase in hardness due to storage at 20°C for two days was also calculated and is shown in Figure 2. (3) Results As shown in Figure 1, when the cooked rice was cooked with the rice modifier of Example 23 added, the softening of the cooked rice due to cooking with a high water content of 200% by weight was suppressed. When the modifier of Example 23 was added, the cooked rice was clearly given hardness even when cooked with 165% by weight of water. On the other hand, as shown in Figure 2, hardening due to aging of cooked rice when stored at 20°C for two days was suppressed by adding the modifier of Example 23 and cooking the rice, and the increase in the hardness of the cooked rice after two days of storage was suppressed to a low extent in both the 165% by weight water content and the 200% by weight water content.

[0061] [Test Example 7] Examination of the effect of pectin methylesterase addition on the quality and texture of cooked rice when cooked with a moderate amount of water. Cooked rice was prepared in the same manner as in Test Example 1, except that the water content was 150% or 165% by weight and the amount of pectin methylesterase added was as shown in Table 7 (Examples 24-29). The hardness, wateriness, grain shape, and overall preference of the prepared cooked rice were evaluated in the same manner as in Test Example 1, and the evaluation results are also shown in Table 7.

[0062]

[0063] As shown in Table 7, when rice was cooked with a water content of 150% by weight, adding 0.1 U of pectin methylesterase per 1 g of rice, along with 1 g of calcium gluconate per 100 g of rice, improved the evaluation of grain texture and overall preference. Adding 0.25 U and 0.5 U of pectin methylesterase per 1 g of rice, along with 1 g of calcium gluconate per 100 g of rice, respectively, improved the evaluation of hardness and grain texture, improved wateriness, and improved overall preference. Furthermore, when rice was cooked with a water content of 165% by weight, adding 0.1 U, 0.25 U, and 0.5 U of pectin methylesterase per 1 g of rice, along with 1 g of calcium gluconate per 100 g of rice, respectively, improved the evaluation of hardness and grain texture, improved wateriness, and improved overall preference. The results from Test Example 7 suggest that even when cooking rice with a water content of 150% to 165% by weight, adding the modifier of the present invention during cooking improves the quality of the cooked rice (hardness, wateriness, grain separation) and enhances its palatability.

[0064] As described in detail above, the present invention can improve the quality (hardness, grain shape, etc.) of rice cooked with increased water content, and in particular, it can provide a rice modifier that can suppress softening in rice cooked with high water content and improve the texture of the rice. Furthermore, the present invention can improve the quality (hardness, grain shape, etc.) of rice cooked with increased water content, and in particular, it can provide a method for modifying rice that can suppress softening in rice cooked with high water content and improve the texture of the rice. Moreover, the present invention can provide rice with improved quality (hardness, grain shape, etc.) even when cooked with increased water content, and in particular, it can provide rice with improved texture and suppressed softening while cooked with high water content. Therefore, the present invention can suppress the aging of rice and reduce the sugar content of rice.

[0065] In another embodiment, the present invention can provide a rice modifier that can improve the quality (hardness, wateriness, grain separation, etc.) of rice cooked with a moderate amount of water, and can improve the texture of the rice. Furthermore, in another embodiment, the present invention can provide a method for modifying rice that can improve the quality (hardness, wateriness, grain separation, etc.) of rice cooked with a moderate amount of water, and can improve the texture of the rice. Moreover, in another embodiment, the present invention can provide rice cooked with a moderate amount of water, in which the quality (hardness, wateriness, grain separation, etc.) has been improved.

[0066] This application is based on Japanese Patent Application No. 2025-056847, which is entirely contained herein.

Claims

1. A rice modifier containing pectin methylesterase and alkaline earth metal salts.

2. The modifier according to claim 1, wherein the alkaline earth metal salt is one or more selected from the group consisting of calcium chloride, calcium hydroxide, calcium carbonate, calcium sulfate, calcium citrate, calcium gluconate, calcium acetate, calcium lactate, magnesium chloride, and magnesium sulfate.

3. The modifier according to claim 1 or 2, wherein the amount of pectin methylesterase per 1 g of rice is added to be 0.01 U to 300 U.

4. The modifier according to claim 1 or 2, wherein the amount of pectin methylesterase per 1 g of rice is added to be 0.05 U to 100 U.

5. The modifier according to claim 1 or 2, wherein the amount of alkaline earth metal salt per 100 g of rice is 0.001 g to 2 g.

6. The modifier according to claim 1 or 2, wherein the amount of alkaline earth metal salt per 100 g of rice is 0.005 g to 2 g.

7. The modifier according to claim 1 or 2, further comprising one or more selected from the group consisting of dietary fiber and collagen.

8. A method for improving cooked rice, comprising contacting rice with pectin methylesterase and an alkaline earth metal salt.

9. The modification method according to claim 8, wherein the alkaline earth metal salt is one or more selected from the group consisting of calcium chloride, calcium hydroxide, calcium carbonate, calcium sulfate, calcium citrate, calcium gluconate, calcium acetate, calcium lactate, magnesium chloride, and magnesium sulfate.

10. The modification method according to claim 8 or 9, wherein 0.01 U to 300 U of pectin methylesterase is brought into contact with 1 g of rice.

11. The modification method according to claim 8 or 9, wherein 0.05 U to 100 U of pectin methylesterase is brought into contact with 1 g of rice.

12. The modification method according to claim 8 or 9, wherein 0.001 g to 2 g of an alkaline earth metal salt is brought into contact with 100 g of rice.

13. The modification method according to claim 8 or 9, wherein 0.005 g to 2 g of an alkaline earth metal salt is brought into contact with 100 g of rice.

14. The modification method according to claim 8 or 9, further comprising contacting the material with one or more selected from the group consisting of dietary fiber and collagen.

15. Rice with improved texture, containing rice treated with pectin methylesterase and alkaline earth metal salts.

16. The cooked rice according to claim 15, wherein the alkaline earth metal salt is one or more selected from the group consisting of calcium chloride, calcium hydroxide, calcium carbonate, calcium sulfate, calcium citrate, calcium gluconate, calcium acetate, calcium lactate, magnesium chloride, and magnesium sulfate.

17. The cooked rice according to claim 15 or 16, which contains rice that has been treated with 0.01 U to 300 U of pectin methylesterase per gram of rice.

18. The cooked rice according to claim 15 or 16, which contains rice that has been treated with 0.05 U to 100 U of pectin methylesterase per gram of rice.

19. Cooked rice according to claim 15 or 16, containing 0.001 g to 2 g of alkaline earth metal salt per 100 g of rice.

20. Cooked rice according to claim 15 or 16, containing 0.005 g to 2 g of alkaline earth metal salt per 100 g of rice.

21. The cooked rice according to claim 15 or 16, further comprising one or more selected from the group consisting of dietary fiber and collagen.

22. Cooked rice according to claim 15 or 16, wherein the cooked rice is prepared with a water content of 180% to 200% by weight, and softening is suppressed.

23. Cooked rice according to claim 15 or 16, wherein the water content is 145% to 200% by weight, and the texture is improved.

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