Texture improver for boiled rice product, and production method of boiled rice product

Abstract

To provide a texture improver for a boiled rice product, capable of preventing or reducing progress of aging through chilled thawing after freezing, and retaining excellent texture after chilled thawing, and to provide a production method of a boiled rice product using the same.SOLUTION: A texture improver for a boiled rice product contains an enzyme treated product of gelatinized cereals. The enzyme treated product is liquid, and a surface tension of a 2% (w / w) aqueous solution of the enzyme treated product is lower by 20% or more on the basis of a surface tension of distilled water. A production method of a boiled rice product includes a step of boiling the mixture of raw rice and the texture improver for a boiled rice product, or a step of mixing processed boiled rice and the texture improver for a boiled rice product. The boiled rice product thus obtained is effectively prevented from or reduced in hard and dry texture after chilled thawing.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a texture improver for cooked rice products and a method for producing cooked rice products using the same. [Background technology]

[0002] With the advancement of food preservation technology, various foods are flash-frozen, stored at sub-freezing temperatures (for example, -20°C), and then thawed at temperatures around 10°C (sometimes called chilled thawing) before being served to the public.

[0003] This freezing and thawing method is advantageous in that it not only allows the food to be stored for a long period of time, but also allows the food to be eaten directly by humans after thawing, and it is expected that its use will become increasingly widespread in the future.

[0004] However, it is not easy to include cooked rice products as a type of food. General cooked rice products are prone to damage and aging during thawing after freezing. For example, chilled thawing accelerates aging of the cooked rice, resulting in a hard and dry texture. For this reason, the aging of cooked rice cannot be sufficiently suppressed during thawing after freezing, and further technical improvements that are safe and efficient are desired. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention addresses the above-mentioned problems, and its object is to provide a texture improver for cooked rice products that can prevent or reduce the progression of aging during chilled thawing after frozen storage and can maintain a good texture even after chilled thawing, and a method for producing cooked rice products using the same. [Means for solving the problem]

[0006] The present invention provides a texture improver for cooked rice products, which contains an enzyme-treated product of pregelatinized grain, the enzyme-treated product being in a liquid state, and the surface tension of a 2% (w / w) aqueous solution of the enzyme-treated product being 20% ​​or more lower than the surface tension of distilled water.

[0007] In one embodiment, the enzyme-treated product is an amylase-treated product.

[0008] In one embodiment, the enzyme-treated product further comprises a product treated with at least one enzyme selected from the group consisting of protease, pectinase, cellulase, hemicellulase, β-glucanase, and pullulanase.

[0009] In one embodiment, the pregelatinized grain is at least one grain selected from the group consisting of pregelatinized non-glutinous rice, pregelatinized glutinous rice, and pregelatinized oats.

[0010] In one embodiment, the enzyme-treated product contains molecules with a molecular weight of 3,000 or less at a rate of 50% or more.

[0011] The present invention also provides a method for producing cooked rice products, which comprises the step of cooking a mixture of raw rice and the above-mentioned texture improver for cooked rice products.

[0012] The present invention also provides a method for producing cooked rice products, which comprises the step of mixing processed cooked rice with the above-mentioned texture improver for cooked rice products. [Effects of the Invention]

[0013] According to the present invention, the progression of aging in cooked rice products can be effectively prevented or reduced even when the cooked rice products are thawed under chilled conditions after frozen storage. Furthermore, cooked rice products treated with the texture improver for cooked rice products of the present invention are prevented or reduced from hardening after thawing under chilled conditions, and can provide a texture with good stickiness. [Brief explanation of the drawings]

[0014] [Figure 1]This graph shows the results of the maximum load (hardness) of measurement samples prepared from the frozen cooked rice (RC0) obtained in Comparative Example 4 and the frozen cooked rice (RE6) of Example 12 after frozen storage and thawing, and the results of the maximum load (hardness) of the sample when cooked rice on the day before preparing each of the frozen cooked rice (RC0) and (RE6) was used as the measurement sample. [Figure 2] This graph shows the results of the maximum adhesive force (stickiness) of measurement samples prepared from the frozen cooked rice (RC0) obtained in Comparative Example 4 and the frozen cooked rice (RE6) of Example 12 after frozen storage and thawing, and the results of the maximum adhesive force (stickiness) of the sample when cooked rice on the day before preparing each of the frozen cooked rice (RC0) and (RE6) was used as the measurement sample. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Texture improver for cooked rice products) The texture improver for cooked rice products of the present invention contains an enzyme-treated product of pregelatinized grain.

[0016] Pregelatinized grains refer to grains that contain crystalline starch (beta starch) converted into amorphous starch (gelatinized starch).

[0017] Examples of grains include cereals, pulses, and pseudocereals, and combinations thereof. Examples of cereals include rice (e.g., japonica, javanica, indica, and glaberrima), corn, wheat (e.g., barley, wheat, rye, oats, and Job's tears), millet, foxtail millet, and barnyard millet. Examples of pulses include soybeans, adzuki beans, mung beans, cowpeas, kidney beans, peanuts, peas, broad beans, lentils, chickpeas, and runner beans. Examples of pseudocereals include buckwheat.

[0018] In the present invention, the pregelatinized grains are preferably pregelatinized non-glutinous rice, pregelatinized glutinous rice, pregelatinized oats, or combinations thereof, because they are non-allergenic materials and are readily available due to their large global production volumes. Specific examples of pregelatinized grains include puffs made from grains using heating equipment such as a grain expander, extruder, or hot air roaster, cereals (such as puffed non-glutinous rice or oat), pregelatinized rice flour and pregelatinized glutinous flour made by grinding and powdering pregelatinized grains, and white rice steamed or cooked from raw rice.

[0019] The enzyme-treated product constituting the present invention is obtained by treating such pregelatinized grain with an enzyme, and is in the form of a liquid at room temperature, for example. Here, "liquid" can include any of a solution, emulsion, and suspension.

[0020] The enzyme used to treat pregelatinized grains includes amylase, i.e., the enzyme-treated product is an amylase-treated product.

[0021] Amylase is an enzyme that can hydrolyze glycosidic bonds in starch and convert them into glucose, maltose, oligosaccharides, etc., and includes α-amylase, β-amylase, glucoamylase, isoamylase, and combinations thereof. In the present invention, the amylase preferably includes α-amylase because it is an endo-type enzyme and can efficiently decompose starch into smaller molecules.

[0022] The amylase is preferably derived from a microorganism because it is readily available commercially. Examples of microorganisms that produce amylase include those derived from the genus Aspergillus or Bacillus. The amylase is preferably derived from Aspergillus oryzae and / or Bacillus subtilis because they have a proven track record of use in the food industry and their safety has already been fully confirmed.

[0023] The amount of amylase used is preferably 10 units (U) to 10,000 units (U), more preferably 50 U to 5,000 U, based on 100 g of pregelatinized grain to be treated. If the amount of amylase used is less than 10 U, the enzymatic reaction of the pregelatinized grain takes a long time, which may reduce industrial productivity. If the amount of amylase used is more than 10,000 U, the resulting enzyme-treated product does not further improve the texture of cooked rice products and may actually reduce productivity. Note that amylase activity can be calculated, for example, by using a 0.2% soluble starch solution as the substrate and defining the amount of enzyme required to decompose 1 μg of starch per minute as 1 unit (U).

[0024] By using the above-mentioned amylase in combination with other enzymes as auxiliary ingredients to treat gelatinized grains, the effect of the resulting enzyme-treated product in improving the texture of cooked rice products can be improved.

[0025] The other enzymes that serve as the auxiliary ingredients are those that can be commonly used in the food industry, and specific examples include proteases, pectinases, cellulases, hemicellulases, and pullulanases, as well as combinations thereof.

[0026] Protease is a general term for enzymes that catalyze the hydrolysis of peptide bonds, and specific examples include peptidases, proteinases, and combinations thereof. For example, proteases preferably have endo-peptidase activity or endo-proteinase activity, because they can efficiently decompose proteins into smaller molecules.

[0027] The protease is preferably derived from a microorganism because it is readily available commercially. Examples of microorganisms that produce proteases include microorganisms derived from the genus Aspergillus or Bacillus. The protease is preferably derived from the genus Bacillus because it has a proven track record in the food industry and its safety has already been fully confirmed.

[0028] The amount of protease that can be used is preferably 10 units (U) to 10,000 units (U), more preferably 50 U to 5,000 U, based on 100 g of pregelatinized grain to be treated. By using an amount of protease within this range, an enzyme-treated product with reduced molecular weight can be efficiently obtained. The activity of a protease can be calculated, for example, by using casein as a substrate and defining the amount of enzyme that increases the amount of a non-proteinaceous Folin's reagent coloring substance equivalent to 1 μg of tyrosine per minute as 1 unit (U).

[0029] Pectinases are also called pectin-degrading enzymes, and specific examples include polygalacturonase, pectin lyase, pectin esterase, and pectin methyl esterase.

[0030] Pectinase derived from microorganisms is preferred because it is readily available commercially. Examples of microorganisms that produce pectinase include Aspergillus and Rhizopus. Pectinase derived from Aspergillus niger is preferred because it has a proven track record in the food industry and its safety has already been fully confirmed.

[0031] The amount of pectinase that can be used is preferably 10 units (U) to 10,000 units (U), more preferably 50 U to 5,000 U, based on 100 g of pregelatinized grain to be treated. By using an amount of pectinase within this range, an enzyme-treated product with reduced molecular weight can be efficiently obtained. The activity of pectinase can be calculated, for example, by using a pectin solution as a substrate and defining the amount of enzyme that reduces the viscosity of the substrate by half in 10 minutes as 1 unit (U).

[0032] Cellulase is an enzyme that hydrolyzes glycosidic bonds in β-1,4-glucans such as cellulose, and is preferably derived from a microorganism because it is readily available commercially. Examples of microorganisms that produce cellulase include microorganisms derived from the genus Aspergillus or Trichoderma. Cellulase derived from the genus Aspergillus is preferred because it has a proven track record in the food industry and its safety has already been fully confirmed.

[0033] The amount of cellulase that can be used is preferably 10 units (U) to 10,000 units (U), more preferably 50 U to 5,000 U, based on 100 g of pregelatinized grain to be treated. By using an amount of cellulase within this range, an enzyme-treated product with reduced molecular weight can be efficiently obtained. Cellulase activity can be calculated, for example, by using an aqueous solution of carboxymethyl cellulose (CMC) as a substrate and defining the amount of enzyme that increases reducing sugars equivalent to 1 μmol of glucose per minute as 1 unit (U).

[0034] Hemicellulase is an enzyme capable of degrading polysaccharides other than cellulose and pectin that constitute the cell walls of land plant cells. Hemicellulase derived from microorganisms is preferred because it is readily available commercially. Examples of microorganisms that produce hemicellulases include those of the genera Aspergillus, Rhizopus, and Trichoderma. Hemicellulases derived from Aspergillus niger, Aspergillus oryzae, and Trichoderma reesei are preferred because they have a proven track record of use in the food industry and their safety has already been fully confirmed.

[0035] The amount of hemicellulase that can be used is preferably 10 units (U) to 10,000 units (U), more preferably 50 U to 5,000 U, based on 100 g of pregelatinized grain to be treated. By using an amount of hemicellulase within this range, an enzyme-treated product with efficiently reduced molecular weight can be obtained. The activity of hemicellulase can be calculated, for example, by using an aqueous solution of arabinoxylan as a substrate and defining the amount of enzyme that increases reducing sugars equivalent to 1 μmol of glucose per minute as 1 unit (U).

[0036] Pullulanase is an enzyme that hydrolyzes α-1,6 glucosidic bonds, and is preferably derived from a microorganism because it is readily available commercially. Examples of microorganisms that produce pullulanase include microorganisms derived from the genus Pullulanibacillus or Klebsiella. Pullulanase derived from the genus Klebsiella is preferred because it has a proven track record in the food industry and its safety has already been fully confirmed.

[0037] The amount of pullulanase that can be used is preferably 10 units (U) to 10,000 units (U), more preferably 50 U to 5,000 U, based on 100 g of pregelatinized grain to be treated. By using an amount of pullulanase within this range, an enzyme-treated product with reduced molecular weight can be efficiently obtained. The activity of pullulanase can be calculated, for example, by using an aqueous pullulan solution as a substrate and defining the amount of enzyme that increases reducing sugars equivalent to 1 μmol of glucose per minute as 1 unit (U).

[0038] In the present invention, the above-mentioned gelatinized grain is preferably an enzyme-treated product that has been treated with a combination of the enzymes amylase, protease, and at least one enzyme selected from hemicellulase, pectinase, and cellulase, because the main components of the raw grain and / or components unevenly distributed on the surface of the grain can be decomposed as substrates.

[0039] In producing the enzyme-treated product, the conditions for treating the pregelatinized grain with the enzyme are not particularly limited, as they vary depending on the type and amount of pregelatinized grain and / or enzyme used. The treatment is carried out, for example, by adding the enzyme to the pregelatinized grain, stirring as necessary, and exposing the mixture to a treatment temperature of preferably 10°C to 60°C. The treatment time also varies depending on the type and amount of enzyme used, and is not particularly limited, but is preferably 1 hour to 120 hours, more preferably 1 hour to 72 hours.

[0040] After the above treatment time has elapsed, the reaction product is subjected to enzyme inactivation by a method well known to those skilled in the art, and if necessary, a separation operation such as filtration may be carried out to obtain a liquid enzyme-treated product.

[0041] The enzyme-treated product is also a mixture with a characteristic molecular weight distribution, with molecules of molecular weight 3000 or less preferably contained at a ratio of 40% or more, more preferably 50% or more. By satisfying this molecular weight distribution range, the resulting cooked rice food can have physical properties suitable for improving the texture. In enzyme-treated products that satisfy this molecular weight distribution range, the enzymes have finely decomposed grain components, and the production of grain-derived sugars and oligosaccharides is promoted through the decomposition of, for example, starch and dietary fiber. The molecular weight distribution of the enzyme-treated product can be measured, for example, by size exclusion chromatography using HPLC.

[0042] When the enzyme-treated product constituting the texture improver for cooked rice products of the present invention is prepared into an aqueous solution with a concentration of 2% (w / w), its surface tension is at least 20%, preferably at least 23%, and more preferably at least 26% lower than the surface tension of distilled water. If the surface tension of a 2% (w / w) aqueous solution of the enzyme-treated product is lower than the surface tension of distilled water by less than 20%, the texture improvement effect of the resulting cooked rice product will be insufficient.

[0043] The enzyme-treated product constituting the texture improver for cooked rice products of the present invention also preferably has a refractive index sugar content (Brix sugar content) of 20 to 60, more preferably 25 to 55. If the refractive index sugar content of the enzyme-treated product is below 20, the decomposition of pregelatinized grains may be insufficient, resulting in an insufficient effect on improving the texture of cooked rice, or the enzyme-treated product may contain a large amount of water, resulting in a low proportion of active ingredients and making it industrially inefficient. If the refractive index sugar content of the enzyme-treated product is above 60, the free water required for the enzymatic reaction to decompose pregelatinized grains may be insufficient, and the enzymatic reaction may not proceed sufficiently. Such a refractive index sugar content can be measured using a commercially available refractometer.

[0044] The enzyme-treated product constituting the texture improver for cooked rice products of the present invention also preferably has a pH of 4.5 to 7.5, more preferably 5 to 7. If the pH of the enzyme-treated product is below 4.5 or above 7.5, the pH may be significantly different from the optimum pH of the enzyme used to produce the enzyme-treated product, or the enzyme may become unstable.

[0045] The texture improver for cooked rice products of the present invention may also contain an excipient. Examples of the excipient include, but are not limited to, dietary fiber, fermented grain products, and sugars, as well as combinations thereof.

[0046] Examples of dietary fiber include cellulose, inulin, hydrolyzed guar gum, and psyllium seed gum, and combinations thereof.

[0047] Examples of fermented grain products include mirin and sake lees, and combinations thereof.

[0048] Saccharides include sugars and sugar alcohols, and specific examples include trehalose, palatinose, sorbitol, and maltose, and combinations thereof.

[0049] The content of the excipient in the texture improver for cooked rice products of the present invention is not particularly limited, and an appropriate amount can be selected by those skilled in the art.

[0050] The texture improver for cooked rice products of the present invention may also contain other ingredients.

[0051] Other ingredients include antioxidants, emulsifiers, preservatives, stabilizers, sweeteners, colorants, coloring agents, seasonings, pH adjusters, acidulants, and processing aids, as well as combinations thereof. Specific examples of these other ingredients include, but are not limited to, salt, sugar, brown syrup, rice koji, fruit juice (e.g., pineapple juice powder and mango juice powder), ascorbic acid, sodium ascorbate, calcium ascorbate, tocopherol, dried egg white, propylene glycol alginate, alcohol preparations, acetic acid, calcium lactate, emulsified oils and fats, gardenia pigment, carotenoid pigment, aspartic acid, glycine, and propylene glycol. The content of other ingredients is not particularly limited, and an appropriate amount can be selected by one skilled in the art as long as it does not inhibit the effects of the auxiliary ingredients.

[0052] Furthermore, the texture improver for cooked rice products of the present invention may contain, as a solvent, for example, water (e.g., natural water, tap water, ion-exchanged water, distilled water), ethanol, or a combination thereof. The content of the solvent is not particularly limited, and an appropriate amount can be selected by those skilled in the art as long as it does not inhibit the effects of the enzyme-treated product.

[0053] The texture improver for cooked rice products of the present invention contributes to improving the texture of various cooked rice products described below and can prevent or reduce the progression of aging of the cooked rice products during low-temperature storage. Therefore, it can be used, for example, for cooked rice products that are flash-frozen, stored at a freezing temperature (e.g., −20°C), and then thawed at a temperature around 10°C.

[0054] (Method of manufacturing cooked rice products) Next, the method for producing the cooked rice product of the present invention will be described.

[0055] In the method for producing cooked rice products of the present invention, for example, (a) raw rice and the texture improver for cooked rice products are cooked together, i.e., raw rice and the texture improver for cooked rice products are mixed with water to prepare a mixture, and then the mixture is cooked to produce a cooked rice product.

[0056] Alternatively, in the method for producing a cooked rice product of the present invention, for example, (b) processed cooked rice is mixed with the texture improver for cooked rice products. That is, after processing cooked rice is first prepared using raw rice or the like, the texture improver for cooked rice products (for example, a mixture of the texture improver for cooked rice products and water) is added to the processed cooked rice and mixed to produce a cooked rice product.

[0057] Alternatively, in the method for producing cooked rice products of the present invention, cooked rice that has been subjected to the above-mentioned operation (a) may be used as processed cooking water, and the cooked rice product may be produced by further performing the above-mentioned operation (b).

[0058] The raw rice may be any of the japonica, indica, or javanica varieties, and based on classification of processing such as polishing, may be polished rice, brown rice, germinated brown rice, germinated rice, no-wash rice, quick-cooking rice, or a combination thereof.

[0059] The raw rice is not particularly limited, but examples include those produced in Japan, and specific examples include Aichi no Kaori, Ai no Yume, Akane Sora, Akigeshiki, Akiho, Akita Komachi, Akita 39, Akitsuho, Aki Nishiki, Akineiro, Aki no Uta, Akibare, Akiroman, Akebono, Akogare, Asa no Hikari, Asahi, Asahi no Yume, Aji Kodama, Iya, Iya Minamitsuki, Iya no Kagayaki, Ayahime, Awaminori, Itadaki, Iwata 3, Iwata 11, Iwata 15, Iwatekko, Iwate 68, Iwahikari, Ukon Nishiki, LGC1, Ogon Nishiki, Oita 11, Ooseto, and Okiniiri. , Maiden Heart, Long Awaited, Owara Beauty, Kaga Hikari, Kaguya Hime, Kakehashi, Kagoshima No. 18, Kagoshima No. 22, Family Gathering, Kari no Mai, Kanto No. 29, Kibi no Hana, Kinuhikari, Kinu Musume, Kiyonishiki, Kirara 397, Kirari Miyazaki, Kirarin, Gin Oumi, Kin Nanpu, Koimusubi, Koimomiji, Koganemasari, Koganebare, Koshihibuki, Koshiji Wase, Koshihikari, Kokoromachi, Goropikari, Nishikai No. 232, Nishikai No. 248, Saga Urara, Saga No. 1, Sakihikari, Sasanishiki, Village Song, Sawa Kaori, Sawa no Hana, Sawa Pikari, Snow White, Snow Pearl, Final Performance, Star of the Earth , Wind of the Earth, Takaneminori, Freshly Fired, Dream of the Rice Paddies, Chiba 28, Chiyonishiki, Chiyohonami, Churahikari, Light of the Moon, Tsukushihomare, Tsukushiroman, Tsuyaotome, Dewa 75hikari, Angel's Poem, Tentakaku, Towa Nishiki, Togaotome, Tosa Nishiki, Tosapika, Todorokiwase, Tone no Megumi, Domannaka, Toyama 67, Toyonishiki, Dontokoi, Donpishari, Nakasei Shinsenbon, Naganohomare, Nagoriyuki, Nasuhikari, Natsushizuka, Natsu no Tayori, Natsuhikari, Nanatsuboshi, Nankai 157, Growing in the South, Nikomaru, Nishihomare, Nipponbare, Nebari Kachi 94, Norin 1, Norin 21, Norin 22, Norin 48, Noto Hikari, Haiminori, Haenuki, Hagi no Kaori, Hana Satsuma, Hana Kirari, Hatajirushi, Hatsushimo, First Star, Hanaechizen, Flower Dance, Hanabusa, Spring Sun, Clear Sky, Banbanzai, Barnyard Millet, Love at First Sight, Hiyokumochi, Biwa Minori, Fukuhikari, Fukuhibiki, Fukumirai, Fusaotome, Fusakogane, Fuji no Mai, Fukukkuriinko, Hourei, Hoshitarou, Star Dream, Smile, Hohohonoho, Maihime, Matsuyama Mitsui, Festival Clear, Manamusume, Mie no Mie, Mie no Yume, Miki Sayaka, Mizuho Gold, Mitsuhikari, Minamihikari, Mineasahi,Some of the names that are popular include Mine Hibiki, Minonishiki, Milky Queen, Milky Princess, Murasaki no Mai, Menkoina, Mori no Kuma-san, Yamauta, Yamagata 84, Yamahikari, Yamabiko, Yamahoushi, Yuwa Komachi, Yukigesho, Yuki no Sei, Yukihikari, Yukimaru, Yume Akogare, Yume Ikken, Yume Ippai, Yume Oumi, Yumegokochi, Yume Sayaka, Yume Shizuku, Yume Tsukushi, Yume no Hana, Yumehikari, Yume Hitachi, Yume Mizuho, ​​Yume Musubi, Yoneshiro, Lake 65, Wasejiman, and LGC Soft.

[0060] The raw rice may also be pre-mixed with other grains or legumes (e.g., barley, foxtail millet, barnyard millet, Job's tears, oats, soybeans, adzuki beans, kidney beans, buckwheat, sesame, and corn, and combinations thereof).

[0061] The amount of cooked rice texture improver used in this cooking process is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, per 100 parts by mass of raw rice. If the amount of cooked rice texture improver used is less than 0.01 parts, the cooked rice product may not fully benefit from the texture improver, even if raw rice is cooked together with the cooked rice texture improver. For example, if the cooked rice product is flash-frozen, stored at a temperature below freezing, and then thawed at a temperature around 10°C (chilled thawing), the cooked rice product may deteriorate, resulting in a hard and dry texture. Alternatively, if the amount of cooked rice texture improver used exceeds 20 parts by mass, there is little change in the effect of preventing or reducing the progression of staling (i.e., texture improvement) in the resulting cooked rice product through chilled thawing after frozen storage, and production efficiency may actually decrease.

[0062] The water used for the rice cooking is not particularly limited, and any of natural water, tap water, well water, RO water, ion-exchanged water, distilled water, etc. may be used.

[0063] In order to further improve the texture when cooking rice, the mixture of raw rice, the texture improver for cooked rice products of the present invention, and water (i.e., the raw rice is soaked in water containing the texture improver for cooked rice products of the present invention) may be left to stand for a while without being cooked immediately.

[0064] For cooking rice, an industrial or household rice cooker is used. The conditions required for cooking rice are not particularly limited, and appropriate conditions can be selected by a person skilled in the art. After cooking, the rice may be steamed and loosened as necessary.

[0065] On the other hand, processed cooked rice includes white rice cooked from raw rice without adding the texture improver for cooked rice products; rice obtained by subjecting the white rice to additional cooking such as frying, baking or boiling; and rice obtained by subjecting raw rice to cooking other than rice cooking such as steaming or boiling.

[0066] When the texture improver for cooked rice products is added and mixed with processed cooked rice, the amount selected is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the processed cooked rice.

[0067] If the amount of cooked rice product improver added is less than 0.01 parts by mass, the effect of the cooked rice product texture improver may not be fully exerted in the resulting cooked rice product. For example, if the texture improver for cooked rice products is added to sushi vinegar and then mixed with white rice to produce vinegared rice, and the resulting vinegared rice is allowed to stand at 15°C for about an hour, the rice graininess may weaken. Alternatively, there may be little change in the texture improvement effect (e.g., graininess) in the resulting cooked rice product, and production efficiency may actually decrease.

[0068] If the amount of the improving agent for cooked rice products added exceeds 20 parts by mass, there is little change in the texture improving effect (for example, graininess) that accompanies an increase in the amount added, and production efficiency may actually decrease.

[0069] In this way, cooked rice products can be produced.

[0070] Cooked rice products that can be produced by the above method include cooked rice obtained by cooking polished rice, as well as brown rice, red rice, steamed rice, seasoned rice, pilaf, fried rice, dry curry, sushi rice, rice balls, etc.

[0071] The resulting cooked rice product is flash-frozen at a temperature of, for example, -40°C and stored at a normal freezing temperature (for example, -20°C). Then, by thawing the cooked rice in a chilled state at a temperature of, for example, around 10°C, the cooked rice product can be eaten directly by people without any subsequent cooking, such as heating. In this case, people can experience that the progression of aging has been prevented or reduced in the cooked rice product obtained by the method of the present invention. This prevents the processed cooked rice from drying out and hardening during storage at low temperatures, resulting in undesirable textures such as dryness and roughness.

[0072] Although the texture improver of the present invention has been described above from the perspective of improving the texture of cooked rice products, a preparation containing the enzyme-treated product can also function as a texture improver for processed grain foods.

[0073] Here, "processed grain foods" refers collectively to processed foods that use grains such as rice, wheat, barley, corn, buckwheat, soybeans, adzuki beans, rapeseed, sesame, sunflower, or other grains or their flour as ingredients. Examples of processed grain foods include noodles such as udon, soba, Chinese noodles, spaghetti, penne, macaroni, and lasagna; breads such as white bread, sweet buns, Danish pastries, cooked bread, and steamed buns; confectioneries such as biscuits, cookies, crackers, boro, rice crackers, wafers, donuts, karinto, baked buns, dorayaki, imagawayaki, taiyaki, steamed buns, and cakes (e.g., sponge cake, butter cake, waffles, pancakes, cream puffs, pies, and baumkuchen); premixes; and the like.

[0074] The texture of such processed grain foods can be improved by applying the texture modifier of the present invention to the raw materials used to obtain the processed grain foods, for example, before cooking by heating (for example, by immersing, coating, spraying, or kneading in the presence of water) or by applying the texture modifier after cooking by heating (for example, by adding, spraying, or applying the texture modifier of the present invention directly or after mixing with water or seasonings, etc.). [Example]

[0075] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0076] (1. Preparation of enzyme-treated solution and formulation sample) (Examples 1 to 6: Preparation of enzyme-treated solutions (LE1) to (LE6) and preparation samples (E1) to (E6)) 150 g (100 parts by weight) of raw rice (wash-free rice; Koshihikari rice from Niigata Prefecture) was placed in an electric rice cooker (Tiger Corporation, JKO-G) containing 225 g (150 parts by weight) of tap water. The rice was soaked at room temperature for 30 minutes and then cooked in the white rice mode to obtain white rice (gelatinized grain). The white rice was then thoroughly cooled, transferred to a Falcon tube (50 mL capacity), and the enzymes listed in Table 1 were added. The reaction was carried out at 45°C for 20 hours with stirring. The enzymes were dissolved in water equivalent to 10 parts by weight per 100 parts by weight of the white rice to be treated. After the reaction, the Falcon tube was immersed in an 80°C water bath for 30 minutes to heat sterilize the enzymes, yielding liquid enzyme-treated products (LE1) to (LE6).

[0077] The pH of the resulting enzyme-treated solutions (LE1) to (LE6) was measured using a pH meter (LAQUA F-2000PI, manufactured by Horiba, Ltd.), and the refractive index sugar content (Brix sugar content) of the resulting enzyme-treated solutions (LE1) to (LE6) was measured using a refractometer (HAND REFRACTOMETER N2, manufactured by Atago Co., Ltd.).

[0078] The resulting enzyme-treated solutions (LE1) to (LE6) were diluted with distilled water to prepare 2% (w / w) aqueous solutions. These solutions were placed in 50 ml Falcon tubes and centrifuged (12,000 rpm, 10 minutes, twice) to remove solids. The surface tension of these solutions was measured using an automatic surface tensiometer, DyneMaster DY-300 (Kyowa Interface Science Co., Ltd.). Surface tension measurements were performed three times for each test group, and the average value was used as the surface tension (mN / m).

[0079] Meanwhile, instead of the enzyme-treated solutions (LE1) to (LE6), the surface tension of distilled water (this was designated Comparative Example 1) was measured in the same manner as above. Then, the surface tension reduction rate of a 2% (w / w) aqueous solution of the obtained enzyme-treated solution (hereinafter sometimes simply referred to as the "surface tension reduction rate") was calculated according to the following formula.

[0080]

number

[0081] Table 1 shows the surface tension values ​​and calculated surface tension reduction rates of the enzyme-treated solutions (LE1) to (LE6) and distilled water.

[0082] Next, vegetable oil (rapeseed oil) and tap water were added to the enzyme-treated liquids (LE1) to (LE6) obtained above according to the formulations shown in Table 2, and the mixture was heated to 60°C in a hot bath and emulsified by stirring at 8,000 rpm for 5 minutes in a homomixer to obtain formulation samples (E1) to (E6).

[0083] Furthermore, 10 mL of each of the resulting formulation samples (E1) to (E6) was sampled and centrifuged at 1,500 rpm for 5 minutes at room temperature. The emulsifying power of formulation samples (E1) to (E6) was calculated from the volume (mL) of the white layer as follows. The results are shown in Table 2.

[0084]

number

[0085] In addition, the enzyme-treated solution (LE1) obtained above was used for TSKgel G3000PW XL Molecular weight distribution was measured by size exclusion chromatography using two connected columns (7.8 mm diameter x 300 mm, manufactured by Tosoh Corporation). Standard solutions were prepared by dissolving P-100, P-50, P-10, and P-5 of Shodex Standard P-82 (manufactured by Showa Denko K.K.), as well as maltose and glucose, in 0.1 mol / L sodium nitrate solution to a concentration of 0.05% (w / v). Approximately 0.2 g of the enzyme-treated solution (LE1) was added to 10 mL of 0.1 mol / L sodium nitrate solution, left overnight at room temperature, and then filtered through a 0.45 μm membrane filter. The resulting solution was used as the sample solution. The standard and sample solutions were then injected into a high-performance liquid chromatograph (Shodex GPC-101, manufactured by Showa Denko K.K.) using a size exclusion column. The column temperature was 50° C., the mobile phase was a 0.1 mol / L sodium nitrate solution, the flow rate was 1.0 mL / min, and the sample injection volume was 100 μL. A differential refractometer (RI-71S manufactured by Showa Denko K.K.) was used as the detector.

[0086] The results were analyzed using the 480II Data Station GPC program (System Instruments Co., Ltd.). The molecular weight of each peak was estimated using a calibration curve prepared based on the elution time and molecular weight of molecular weight standards.

[0087] The results of the molecular weight distribution of the enzyme-treated solution (LE1) are shown in Table 3. These results indicate that the enzyme-treated solution (LE1) contains 50% or more molecules with a molecular weight of 3000 or less in the soluble components. It is clear that the other enzyme-treated solutions (LE2) to (LE6) were treated with a wider variety of enzymes than the enzyme-treated solution (LE1), and therefore had molecular weights that were equal to or greater than that of the enzyme-treated solution (LE1).

[0088] (Comparative Example 1: Preparation of Formulation Sample (C1)) Except for using distilled water instead of the enzyme-treated solution (LE1), the solution was added to vegetable oil (rapeseed oil) and tap water to obtain the formulation shown in Table 2 in the same manner as in Example 1, to obtain a preparation sample (C1). The emulsifying power of the obtained preparation sample (C1) was measured in the same manner as in Example 1. The results are shown in Table 2.

[0089] (Comparative Example 2: Preparation of Formulation Sample (C2)) Instead of the enzyme-treated liquid (LE1), glutinous rice syrup (manufactured by Ohsawa Japan Co., Ltd.) was used, and a Brix 40 sample was prepared in advance using distilled water so that the emulsified sample had a concentration of 5%. This was added to vegetable oil (rapeseed oil) and tap water in the formulation shown in Table 2 in the same manner as in Example 1, to obtain a formulation sample (C2). The emulsifying power of the obtained formulation sample (C2) was measured in the same manner as in Example 1. The results are shown in Table 2.

[0090] (Comparative Example 3: Preparation of enzyme-treated solution (LC1) and preparation sample (C3)) An enzyme-treated liquid (LC1), a liquid enzyme-treated product, was obtained in the same manner as in Example 1, except that the enzymes shown in Table 1 were added and reacted at 45°C for 30 minutes with stirring. Then, in the same manner as in Example 1, except that this enzyme-treated liquid (LC1) was used, it was added to vegetable oil (rapeseed oil) and tap water to obtain the composition shown in Table 2, to obtain a preparation sample (C3). The emulsifying power of the obtained preparation sample (C3) was measured in the same manner as in Example 1. The results are shown in Table 2.

[0091] [Table 1]

[0092] [Table 2]

[0093] [Table 3]

[0094] (2. Preparation of frozen cooked rice) (Comparative Example 4: Preparation of frozen cooked rice (RC0) (additive-free group)) 150 g (100 parts by mass) of raw rice (wash-free rice; Koshihikari rice from Niigata Prefecture) was placed in an electric rice cooker (JKO-G, manufactured by Tiger Corporation) containing 240 g (160 parts by mass) of tap water, soaked at room temperature for 30 minutes, and then cooked in the white rice mode. The cooked rice was immediately transferred to a container and cooled to a core temperature of 30°C. The rice was then covered and flash-frozen at -40°C for 2 hours to obtain frozen cooked rice (RC0).

[0095] (Comparative Example 5: Preparation of frozen cooked rice (RC1) using glutinous rice syrup) 1.8 g (1.2 parts by mass) of glutinous rice syrup (manufactured by Ohsawa Japan Co., Ltd.) was added to an electric rice cooker (JKO-G manufactured by Tiger Corporation) containing 240 g (160 parts by mass) of tap water, and the mixture was uniformly dispersed and dissolved with a spoon. Next, frozen cooked rice (RC1) was obtained in the same manner as in Comparative Example 4, except that 150 g (100 parts by mass) of raw rice (wash-free rice; Koshihikari produced in Niigata Prefecture) was added.

[0096] (Comparative Example 6: Preparation of frozen cooked rice (RC2) using enzyme-treated liquid (LC1)) 3.0 g (2.0 parts by mass) of the enzyme-treated liquid (LC1) (texture modifier) ​​obtained in Example 3 was added to an electric rice cooker (JKO-G, manufactured by Tiger Corporation) containing 240 g (160 parts by mass) of tap water, and the mixture was uniformly dispersed and dissolved with a spoon. Next, frozen cooked rice (RC2) was obtained in the same manner as in Comparative Example 4, except that 150 g (100 parts by mass) of raw rice (wash-free rice; Koshihikari produced in Niigata Prefecture) was added.

[0097] (Example 7: Preparation of frozen cooked rice (RE1) using enzyme-treated solution (LE1)) 3.0 g (2.0 parts by mass) of the enzyme-treated liquid (LE1) (texture modifier) ​​obtained in Example 1 was added to an electric rice cooker (JKO-G, manufactured by Tiger Corporation) containing 240 g (160 parts by mass) of tap water, and the mixture was uniformly dispersed and dissolved using a spoon. Next, 150 g (100 parts by mass) of raw rice (wash-free rice; Koshihikari rice from Niigata Prefecture) was added and soaked at room temperature for 30 minutes, after which the rice was cooked in the white rice mode. The cooked rice was immediately transferred to a container and cooled to a core temperature of 30°C. The rice was then covered with a lid and flash-frozen at -40°C for 2 hours to obtain frozen cooked rice (RE1).

[0098] (Example 8: Preparation of frozen cooked rice (RE2) using enzyme-treated liquid (LE2)) Cooked rice was cooked in the same manner as in Example 7, except that 3.0 g (2.0 parts by mass) of the enzyme-treated liquid (LE2) (texture modifier) ​​obtained in Example 2 was used instead of the enzyme-treated liquid (LE1), and then transferred to a container and flash-frozen to obtain frozen cooked rice (RE2).

[0099] (Example 9: Preparation of frozen cooked rice (RE3) using enzyme-treated liquid (LE3)) Cooked rice was cooked in the same manner as in Example 7, except that 3.0 g (2.0 parts by mass) of the enzyme-treated liquid (LE3) (texture modifier) ​​obtained in Example 3 was used instead of the enzyme-treated liquid (LE1), and then transferred to a container and flash-frozen to obtain frozen cooked rice (RE3).

[0100] (Example 10: Preparation of frozen cooked rice (RE4) using enzyme-treated liquid (LE4)) Cooked rice was cooked in the same manner as in Example 7, except that 3.0 g (2.0 parts by mass) of the enzyme-treated liquid (LE4) (texture modifier) ​​obtained in Example 4 was used instead of the enzyme-treated liquid (LE1), and then transferred to a container and flash-frozen to obtain frozen cooked rice (RE4).

[0101] (Example 11: Preparation of frozen cooked rice (RE5) using enzyme-treated liquid (LE5)) Cooked rice was cooked in the same manner as in Example 7, except that 3.0 g (2.0 parts by mass) of the enzyme-treated liquid (LE5) (texture improver) obtained in Example 5 was used instead of the enzyme-treated liquid (LE1), and then transferred to a container and flash-frozen to obtain frozen cooked rice (RE5).

[0102] (Example 12: Preparation of frozen cooked rice (RE6) using enzyme-treated liquid (LE6)) Cooked rice was cooked in the same manner as in Example 7, except that 3.0 g (2.0 parts by mass) of the enzyme-treated liquid (LE6) (texture modifier) ​​obtained in Example 6 was used instead of the enzyme-treated liquid (LE1), and then transferred to a container and flash-frozen to obtain frozen cooked rice (RE6).

[0103] (3. Evaluation of frozen cooked rice) (Frozen storage method) Next, the resulting frozen cooked rice (RC0 to RC2 and RE1 to RE6) was placed in a freezer and stored at −20° C. for 7 days.

[0104] (sensory evaluation) Thereafter, the frozen cooked rice (RC0 to RC2 and RE1 to RE6) was taken out of the freezer and thawed for 16 hours at 7° C. The resulting cooked rice was subjected to a sensory evaluation from the following viewpoints while still uncooked.

[0105] (1) Hardness The thawed cooked rice was tasted by 10 experts, who then discussed and evaluated it according to the following criteria. The results are shown in Table 4: (4 points) Moderately soft and judged to be good. (3 points) Although it is somewhat hard, it is judged to be sufficiently durable for distribution on the market as a product. (2 points) It was determined that the product would be too hard and would only be distributed to a limited extent on the market. (1 point) It was very hard and we decided that it would be difficult to distribute it on the market as a product in this state.

[0106] (2) Stickiness The thawed cooked rice was tasted by 10 experts, who then discussed and evaluated it according to the following criteria. The results are shown in Table 4: (4 points) It has moderate stickiness and is judged to be good. (3 points) It was judged to be somewhat sticky and to be able to withstand market distribution as a product. (2 points) It is not very sticky and feels rough. We have determined that even if it is distributed on the market as a product, its distribution will be limited. (1 point) It had no stickiness at all and felt very rough, so I decided that it would be difficult to distribute it on the market as a product.

[0107] (3) Graininess The thawed cooked rice was tasted by 10 experts, who then discussed and evaluated it according to the following criteria. The results are shown in Table 4: (4 points) The original rice texture (grainy texture) was similar to that of unprocessed cooked rice (RC0) and was good. (3 points) Although the graininess is slightly weak, it is judged to be sufficiently durable for distribution on the market as a product. (2 points) It was determined that the grain was clearly weak and that even if it were to be distributed in the market as a rice product, it would only be distributed to a limited extent. (1 point) There was a significant difference in graininess compared to additive-free cooked rice (RC0), and it was determined that it would be difficult to distribute the product on the market as it was.

[0108] (4) Flavor The thawed cooked rice was tasted by 10 experts, who then discussed and evaluated it according to the following criteria. The results are shown in Table 4: (4 points) The flavor was the same as that of cooked rice that had not been frozen or thawed (storage period 0 days). (3 points) The flavor was slightly inferior to cooked rice that had not been frozen or thawed (storage period 0 days), but it was judged to be sufficiently suitable for distribution on the market as a product. (2 points) It was determined that the flavor was clearly weak and that even if it were to be distributed on the market as a rice product, it would only be distributed to a limited extent. (1 point) There was a significant difference in flavor compared to cooked rice that had not been frozen or thawed (storage period 0 days), and it was determined that it would be difficult to distribute the product on the market in this state.

[0109] [Table 4]

[0110] As is clear from Table 4, the frozen cooked rice (RE1) to (RE6) obtained in Examples 7 to 12 all had higher scores in hardness, stickiness, and flavor compared to the frozen cooked rice (RC0) of Comparative Example 4. Furthermore, the graininess of the frozen cooked rice (RE1) to (RE6) obtained in Examples 7 to 12 was comparable to that of the frozen cooked rice (RC0) of Comparative Example 1.

[0111] In particular, compared to frozen cooked rice (RE1) (Example 7) made using an enzyme-treated liquid (LE1) treated only with amylase (α-amylase and β-amylase), frozen cooked rice (RE6) made using an enzyme-treated liquid (LE6) treated with amylase, hemicellulase, cellulase, and protease was found to be good in all aspects of hardness, stickiness, graininess, and flavor.

[0112] (Mechanical measurement of hardness and stickiness of frozen cooked rice) The frozen cooked rice (RC0) obtained in Comparative Example 4 and the frozen cooked rice (RE6) in Example 12 were stored frozen as described above (storage at -20°C for 7 days), and then thawed at 7°C for 24 hours to obtain cooked rice, which was used as a measurement sample. The maximum load (hardness) and maximum adhesive force (stickiness) of these measurement samples were measured using a texture analyzer (EZ Test EZ-SX, manufactured by Shimadzu Corporation) as follows.

[0113] 20 g of the measurement sample, adjusted to 20°C, was placed in a cylindrical container with a diameter of 3.5 cm and a height of 2.5 cm. The container was then fixed to the perforated stage of the texture analyzer, and the maximum load (hardness) and maximum adhesive force (stickiness) of each sample were measured by compressing the sample using a cylindrical tool with a diameter of 10 mm as the plunger at a speed of 100 mm / sec and a compression ratio of 30%. The results are shown in Figures 1 and 2.

[0114] 1, the frozen cooked rice (RC0) obtained in Comparative Example 4 and the frozen cooked rice (RE6) in Example 12 both had increased hardness after frozen storage and thawing compared to cooked rice obtained on the day of cooking. Here, it can be seen that the frozen cooked rice (RE6) in Example 12 had a lower hardness and was better than the frozen cooked rice (RC0) obtained in Comparative Example 4.

[0115] 2, the stickiness of the frozen cooked rice (RC0) obtained in Comparative Example 4 after frozen storage and thawing was reduced compared to cooked rice obtained on the day of cooking. In contrast, the stickiness of the frozen cooked rice (RE6) in Example 12 after frozen storage and thawing was equal to or greater than that of cooked rice obtained on the day of cooking. [Industrial Applicability]

[0116] The present invention is useful, for example, in the food industry that handles cooked rice and household seasonings; in restaurants, lunchbox stores, and other food service establishments; and in retail stores such as convenience stores, supermarkets, and department stores.

Claims

1. The texture improver for cooked rice products contains an enzyme-treated product of pregelatinized grain, the enzyme-treated product is in a liquid state, and the surface tension of a 2% (w / w) aqueous solution of the enzyme-treated product is 20% or more lower than the surface tension of distilled water.

2. The texture improver for cooked rice products according to claim 1, wherein the enzyme-treated product is an amylase-treated product.

3. The texture improver for cooked rice products according to claim 1, wherein the enzyme-treated product further comprises a product treated with at least one enzyme selected from the group consisting of protease, pectinase, cellulase, hemicellulase, β-glucanase, and pullulanase.

4. 2. The texture improver for cooked rice products according to claim 1, wherein the pregelatinized grain is at least one grain selected from the group consisting of pregelatinized non-glutinous rice, pregelatinized glutinous rice, and pregelatinized oats.

5. The texture improver for cooked rice products according to claim 1, wherein the enzyme-treated product contains molecules having a molecular weight of 3,000 or less in a proportion of 50% or more.

6. A method for producing a cooked rice product, comprising: A method comprising the step of cooking a mixture of raw rice and the texture improver for cooked rice products according to any one of claims 1 to 5.

7. A method for producing a cooked rice product, comprising: A method comprising the step of mixing processed cooked rice with the texture improver for cooked rice products according to any one of claims 1 to 5.

Images