Rice manufacturing method

Abstract

To provide a production method of rice which is excellent in handleability, does not generate an irritating odor like an acidic smell and is odorless, is safe and efficient, and also has an excellent bacteriostatic effect for rice-derived Bacillus subtilis.SOLUTION: Rice cooking is performed where fumaric acid is added at 0.03 to 0.2 mass% relative to a total amount of a cooked product of rice. Preferably, the rice cooking is performed where at least one selected from glycerin fatty acid ester, polyglyceryl fatty acid ester, and xanthan gum is additionally added.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing cooked rice, and more particularly, to a method for producing cooked rice that has no generation of irritating odors such as acidic odors or sour tastes and has an excellent bacteriostatic effect against Bacillus subtilis derived from rice.

Background Art

[0002] Conventionally, in cooked rice foods such as polished rice, rice balls, and glutinous rice, from the viewpoint of more thorough hygiene management, in order to suppress the growth of bacteria during storage and sales, there are many known techniques such as adding acidulants such as acetic acid and gluconic acid and pH adjusters.

[0003] For example, 1) a method for protecting cooked rice characterized by immersing washed polished rice in a 0.2 to 1.0% acetic acid solution and then cooking it by heating to allow acetic acid to penetrate to the center of the rice grains (see, for example, Patent Document 1), 2) when producing cooked rice by adding water to rice and heating it, adding an aliphatic organic acid (including this organic acid) excluding acetic acid, butyric acid, and other fatty acids and heating with the pH adjusted to 6.5 or less (see, for example, Patent Document 2), 3) a method for quality control of cooked rice characterized by immersing rice for cooking in an acetic acid solution to allow acetic acid to penetrate to the inside, treating it, and then neutralizing the acetic acid-treated rice with a solution containing an organic acid salt such as sodium citrate or sodium acetate, which is a food additive, to remove the smell and taste of acetic acid and improve the quality of the rice for cooking (see, for example, Patent Document 3), etc. are known.

[0004] In the above Patent Documents 1 to 2, the acetic acid used is excellent in terms of antiseptic power, but since it is a volatile acid, it tends to impart a unique irritating odor or sour taste to the cooked rice, and particularly, when reheating this type of cooked rice using a microwave oven or the like, there is a drawback that the acetic acid odor is more strongly generated and the flavor is deteriorated. In the case of the neutralization treatment of Patent Document 3, although it suppresses the generation of acetic acid odor, there are problems such as the complication of the treatment method, and at present, improvement is eagerly desired.

[0005] On the other hand, Bacillus subtilis is a bacterium found in soil and is present everywhere. In particular, it is commonly found in rice straw and is a type of putrefactive bacterium belonging to the Bacillus genus. This Bacillus subtilis forms an outer layer called a spore, which is heat-resistant, so it can survive the heat of cooking rice (100-120°C) and become active after cooking, causing discoloration and odor. Moreover, the troublesome thing is that it is not possible to visually check whether or not the rice is contaminated with these bacteria at the polishing stage. As Bacillus subtilis is a putrefactive bacterium, it is not very harmful to the human body, but in the food service industry, if the rice discolors and smells that much, fewer people will eat it, which can result in significant losses. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 53-94044 (Claims, Examples, etc.) [Patent Document 2] Japanese Patent Publication No. 4-183365 (Claims, Examples, etc.) [Patent Document 3] Japanese Patent Publication No. 7-250629 (Claims, Examples, etc.) [Disclosure of the Invention] [Problems that the invention aims to solve]

[0007] In view of the problems and current status of the above-mentioned prior art, the present invention aims to resolve these issues and provides a method for producing cooked rice that is easy to handle, does not have a sour taste, is odorless without generating any irritating odors such as acidic smells, is safe and efficient, and has an excellent bacteriostatic effect against Bacillus subtilis derived from rice. [Means for solving the problem]

[0008] As a result of diligent research into the above-mentioned conventional problems, the inventors investigated and conducted verification tests to see if fumaric acid, among the organic acids used as acidulants in food, could be used against Bacillus subtilis derived from rice. They found that a method for producing cooked rice for the above purpose could be obtained, and thus completed the present invention. In other words, the present invention is a method for producing cooked rice, characterized by adding 0.03 to 0.2% by mass of fumaric acid to the total amount of cooked rice during cooking. Preferably, at least one selected from glycerin fatty acid esters, polyglycerin fatty acid esters, and xanthan gum is added along with the above-mentioned fumaric acid. [Effects of the Invention]

[0009] The present invention provides a method for producing cooked rice that is easy to handle, has no sour taste, is odorless without generating any irritating odors such as acidic smells, is safe and efficient, and has an excellent bacteriostatic effect against Bacillus subtilis derived from rice. The object and effect of the present invention are recognized and obtained, in particular, by using the components and combinations indicated in the claims. Both the general description above and the detailed description below in this specification are illustrative and descriptive, and do not limit the present invention as described in the claims. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below. However, it should be noted that the technical scope of the present invention is not limited to each of the embodiments detailed below, but extends to the invention described in the claims and its equivalents. The present invention relates to a method for producing cooked rice, characterized by adding 0.03 to 0.2% by mass of fumaric acid to the total amount of cooked rice during cooking.

[0011] The fumaric acid used is a bacteriostatic component for Bacillus subtilis derived from rice during the production of cooked rice. Its structural formula is [HOOC-CH=CH-COOH (trans isomer)], and it is a water-insoluble crystalline powder. The fumaric acid used is not particularly limited, but preferably has a volume average particle size of 30 μm or less, more preferably 15 μm or less, and especially preferably 10 μm or less. Commercially available fumaric acid is ground using a dry or wet method to obtain the above preferred particle size. Alternatively, fumaric acid that has been crystallized to the preferred particle size during raw material production may be used.

[0012] The amount of fumaric acid used should be 0.03 to 0.2% by mass (hereinafter, "mass%" will be simply written as "%"), and more preferably 0.03 to 0.1% of the total amount of cooked rice. If the fumaric acid content is less than 0.03%, the effects of the present invention may not be achieved, while if it exceeds 0.2%, it will exhibit a sour taste, which is undesirable. In this invention, "total amount of cooked rice" means the total amount (100%) of rice, water, other food ingredients, added fumaric acid, and other additives used when cooking rice.

[0013] Furthermore, in the method of the present invention, it is preferable to add at least one selected from glycerin fatty acid ester, polyglycerin fatty acid ester, and xanthan gum along with the predetermined amount of fumaric acid, from the viewpoint of improving the solubility and dispersibility of fumaric acid. These ingredients are used as food additives, and their safety has been confirmed.

[0014] Considering the poor solubility of fumaric acid (solubility in water: 25°C, 0.63 g / 100 mL), the total content of the above-mentioned glycerin fatty acid ester, polyglycerin fatty acid ester, and xanthan gum is preferably 0.0001 to 0.05%, and more preferably 0.0005 to 0.01%, relative to the total amount of cooked rice.

[0015] More preferably, the fumaric acid used is an aqueous dispersion in which fumaric acid having a predetermined volume-average particle size is dispersed in glycerin fatty acid ester, polyglycerin fatty acid ester, and xanthan gum. Particularly preferably, the aqueous fumaric acid dispersion is used, which is the sum of the predetermined amount of fumaric acid with a volume-average particle size of 10 μm or less, 0.0002-0.002% xanthan gum, 0.001-0.005% glycerin fatty acid ester, and water used for cooking, relative to the total amount of rice to be cooked.

[0016] In the method of the present invention, there are no particular restrictions on the rice used as the raw material for cooking rice, as long as it is the type of rice commonly used in rice-based foods. Non-glutinous rice, glutinous rice, polished rice, brown rice, japonica rice, indica rice, glutinous rice, etc., can be used regardless of their degree of polishing or variety, and multiple types of rice may be mixed and used. Furthermore, in the present invention, as long as 0.02 to 0.2% fumaric acid is added to the total amount of rice during cooking, there are no particular restrictions on the cooking method (cooking temperature, time, cooking machine, cooking means, cooking process, etc.). For example, rice can be cooked using a designated rice cooker with heating means such as electricity or gas for household or commercial use, or a commercial rice cooker. Furthermore, when manufacturing rice dishes other than white rice, such as mixed rice dishes, kamameshi (rice cooked in a pot), okowa (sticky rice), and sekihan (red bean rice), ingredients other than rice may be added to the rice food ingredients. Also, when packaging rice balls or the like in a resin packaging film, edible oils and fats may be added during cooking for release purposes. In other words, in the present invention, in addition to rice, other ingredients such as seasonings, carbohydrates (trehalose, isomerized sugar, glucose, lactose, fructose, etc.), edible oils and fats, spices, and broth may be used as ingredients for the cooked rice, as needed. Furthermore, the method of the present invention may include a step of placing or packaging the cooked rice in a container or packaging material. Such containers or packaging materials may be made of heat-resistant materials that can be heated by microwave. In other words, the cooked rice food contained or packaged in a container or packaging material is also within the scope of the products of the cooking method (method for producing cooked rice) that is the manufacturing method of the present invention.

[0017] In the method of the present invention, when cooking rice, fumaric acid is added in an amount of 0.03 to 0.2% based on the total amount of the cooked rice, and more preferably, the pH of the cooked rice obtained by the above cooking method is 5.0 or more, and particularly preferably, it is desirable to cook the rice so that the pH is 5 to 6.5. By setting the pH of the cooked rice to 5.0 or more, the cooked rice will not have a sour taste or an acid smell. On the other hand, by setting the pH of the cooked rice to 6.5 or less, the growth of various bacteria such as Bacillus subtilis can be suppressed. The adjustment of the pH range (5 to 6.5) of the cooked rice can be achieved by adding the respective contents of fumaric acid and acetic acid used, and further adding organic acid salts such as fumarate, citrate, malate, lactate, etc.

[0018] As described above, the cooked rice obtained by the method of the present invention is excellent in handling properties, has no sour taste, and has no pungent smell such as an acidic odor, is odorless, is safe and efficient, and has an excellent bacteriostatic effect against Bacillus subtilis derived from rice. The cooked rice cooked in this way is appropriately packed in a container as needed, and is used after passing through low-temperature distribution, etc., and is reheated in a microwave oven or the like as needed and then eaten.

Examples

[0019] Next, the present invention will be described in more detail with reference to the following Test Examples 1 to 3. 〔Test Example 1〕 To 150 g of rice (rice harvested in Reiwa 1st year, variety: Yume Tsukushi rice), 170 ml of water and 0.75 g of Test Solution Sample 1 having the following composition were added, and the rice was cooked using a rice cooker (NL-B805 type (0.54 L size), manufactured by Zojirushi Corporation). 10 g of the cooked rice was taken, and a preparation adjusted so that the number of Bacillus subtilis spores (spore-forming Bacillus subtilis: B. subtilis NBRC3134) was 300 CFU / 0.1 ml was added, and after storing at 25°C for 72 hours, the number of Bacillus subtilis was measured by the pour plate method. The control was 100% water (purified water). These results are shown in Table 1 below.

[0020] Test solution sample 1: Fumaric acid (volume-average particle size of 10 μm, same applies below) 30.0% Xanthan gum 0.2% Glycerin fatty acid ester 0.5% Water (purified water) 69.3%

[0021] [Table 1]

[0022] As is clear from the results in Table 1 above, in test solution sample 1 containing 0.07% fumaric acid, no increase in the number of Bacillus subtilis spores was observed over time, confirming that it possesses excellent bacteriostatic effects. In the following test examples 2 and 3, the bacteriostatic effect on Bacillus subtilis at various concentrations of fumaric acid, as well as sensory evaluations (sourness, odor), were tested and evaluated. Note that the Bacillus subtilis spores used in test example 1 and the Bacillus subtilis solutions used in test examples 2 and below, described later, differ in whether or not they were added in a heat-resistant spore state.

[0023] [Test Example 2: Example 1 and Comparative Examples 1-4] 150g of rice (2019 harvest rice, variety: Yumetsukushi rice) was mixed with 170ml of water and organic acids (fumaric acid, acetic acid, citric acid, malic acid, lactic acid) at the concentrations shown in Table 1 below, and cooked using a rice cooker (NL-B805 model (0.54L size), manufactured by Zojirushi Corporation). 10g of cooked rice was taken out, and a solution of Bacillus subtilis containing the following bacterial species, adjusted to a concentration of 10-90 CFU / 0.1ml, was added. After storage at 25°C for 72 hours, the bacterial count was measured, and the effect of improving shelf life was evaluated. The bacterial count after storage at 25°C for 72 hours was in the range of 10 to the power of 5 (10 5 ) The following are passing grades (evaluation: ○), 10 5 The excess was marked with (Evaluation: ×). Furthermore, regarding the taste (sourness), five panelists tasted the product and conducted a sensory evaluation (if they detected sourness or a pungent odor: ×, if they did not detect sourness or a pungent odor: ○). Furthermore, the resulting cooked rice was measured using a pH meter: LAQUAact (manufactured by HORIBA) at a temperature of 25°C. For Bacillus subtilis derived from rice, B. subtilis NBRC3134 was used as the evaluation species. These results are shown in Table 2 below.

[0024] [Table 2] No additives: pH6.86

[0025] [Test Example 3: Examples 2-4 and Comparative Examples 1-4] 150g of rice, the same as in Test Example 1, was used to add 170ml of water and fumaric acid at the concentrations shown in Table 2 below, and cooked using the same rice cooker as in Test Example 1. 10g of cooked rice was taken out, and a Bacillus subtilis solution similar to that in Test Example 1, adjusted to 10-90 CFU / 0.1ml, was added. After storage at 25°C for 96 hours, the number of bacteria was measured, and the shelf-life improvement effect was evaluated in the same manner as in Test Example 1. Furthermore, taste (sourness) and pH were evaluated in the same manner as in Test Example 1 above. These results are shown in Table 3 below.

[0026] [Table 3]

[0027] As is clear from the results in Tables 1-3 above, it was confirmed that the optimal amount of fumaric acid to include is 0.03-0.20%. Furthermore, concentrations below 0.03% did not provide the desired shelf-life effect, while concentrations above 0.23% resulted in a sour taste. These findings demonstrate that by using a predetermined concentration of fumaric acid within the scope of the present invention, it is possible to obtain cooked rice that is easy to handle, has no sour taste, is odorless without generating any irritating odors such as acidic smells, is safe and efficient, and exhibits excellent bacteriostatic effects against Bacillus subtilis derived from rice. [Industrial applicability]

[0028] This provides a method for producing cooked rice that is easy to handle, has no sour taste, is odorless without producing any irritating acidic odors, is safe and efficient, and exhibits excellent bacteriostatic effects against Bacillus subtilis, a bacterium derived from rice.

Claims

1. A method for producing cooked rice, characterized by adding 0.07 to 0.2% by mass of fumaric acid as an active ingredient to the total amount of cooked rice, as a bacteriostatic component against spore-forming Bacillus subtilis, during the cooking of the cooked rice.

2. The method for producing cooked rice according to claim 1, characterized by adding at least one selected from glycerin fatty acid ester, polyglycerin fatty acid ester, and xanthan gum.

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