Manufacturing technology for cooked rice and rice balls made only from natural materials and having a high anti-corrosion delay effect.

Abstract

To provide a novel manufacturing technique for cooking rice, eliminating a certain heavy flavor in a taste caused by an addition of an antiseptic agent at rice cooking that is a shelf-life elongation technique generally often employed, which results in a difficulty to obtain a support by a consumer looking for a better taste, and to decrease a loss of purchasing opportunity due to a description of such an antiseptic agent in an ingredient list of a product, which is easily compared at purchasing by a consumer looking for a good taste and safety.SOLUTION: A rice cooking technique is developed in which a prescribed amount of plum vinegar is added to rice cooking water and rice is cooked so as to allow a satisfactory taste as well as a spoilage prevention / retardation effect for any rice cooking techniques, by using only natural materials without depending on a use of a chemical material such as an antiseptic additive or a special manufacturing method.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a manufacturing method having anti-corrosion delay of cooked rice. Specifically, it relates to a method for manufacturing "edible cooked rice manufactured without using any chemical substances", which extends the expiration date by suppressing the numerical value of the general bacterial count to 1 / 100 to 1 / 10,000 compared with the case where cooked rice manufactured by a normal method is stored at room temperature (25°C) for 48 hours (25°C).

Background Art

[0002] Conventionally, in order to improve the preservability of processed foods such as cooked rice and rice balls, many products have been produced using anti-corrosion additives such as amino acids represented by glycine.

[0003] The Tokyo Metropolitan Bureau of Health and Welfare is conducting an experiment on the antibacterial properties of pickled plums and the like placed on a petri dish coated with food poisoning bacteria. As a result, antibacterial properties were observed only around the pickled plums in the state of the pickled plums as they were, but antibacterial properties were not observed in the diluted 10-fold product. The results of this experiment are shown in a table.

Table 1

[0004] Also, in Non-Patent Document 1 shown below, it is confirmed that a certain anti-corrosion effect can be obtained by adding 3% or more of citrus vinegar by volume of rice to cooked rice or leftover rice after cooking. In this experiment, the state of spoilage of cooked rice stored in a constant temperature machine at 30°C was examined by adding 3% or more of citrus vinegar by volume of rice to cooked rice immediately after cooking, 6 hours after cooking, and 12 hours after cooking.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] The preservative effect of dried ume and ume vinegar has been passed down as a tradition since ancient times, but other than the previous experiment by the Tokyo Metropolitan Bureau of Health and Welfare, it is not known what kind of effect it has in what amount. In this experiment, as a result of culturing dried ume in a petri dish, it has been reported that the preservative effect was only observed around the area in contact with the dried ume. Also, nothing has been explained about the effect when cooked rice is in contact with dried ume or the effect of ume vinegar.

[0007] The paper in Non-Patent Document 1 examines whether adding vinegar to "cooked rice" after cooking has a preservative delay effect, but it is not a manufacturing technique for polished rice. Also, nothing has been explained about ume vinegar. From page 241 onwards in Non-Patent Document 1, it is believed that putting dried ume in bento rice or leftover rice has a preservative effect, but it has been reported that there was no preservative effect at all.

[0008] Conventionally, a method of making sushi vinegar rice by adding sushi vinegar to polished rice after cooking is known. However, this method requires the technique of evenly mixing the seasoning liquid into the polished rice, and it is easy to imagine that the flavor of the resulting sushi vinegar rice varies greatly depending on the skill of the cook. For example, in "NHK Asaichi" (broadcast on May 29, 2019), a recipe for "sushi vinegar rice that doesn't fail" is introduced. According to the explanation by Mr. Eiji Sugiyama of Koji Sushi in Ginza, who is the instructor, it is said that it takes 4 - 5 years of training as a sushi chef to make sushi vinegar rice. As can be seen, it takes a great deal of effort to manually make sushi vinegar rice with a good flavor by this method. Also, since the seasoning is directly mixed on the surface of the rice, when eating, one strongly feels the saltiness and sourness in the flavor, which is suitable for sushi but is imagined to be a major obstacle in terms of taste for use as polished rice. This is obvious from the fact that sushi vinegar rice is not used as a substitute for ordinary white rice for meals. Furthermore, in the method of adding the seasoning liquid after manufacturing the polished rice, the number of working processes and cooking utensils increases, so the risk of bacteria attaching and contaminating the polished rice increases.

[0009] The difficulties in making sushi rice described in the previous paragraph are shown in the American movie "Jiro Dreams of Sushi" which interviewed "Sukiyabashi Jiro", a sushi restaurant chosen by Prime Minister Shinzo Abe for a dinner reception to host President Obama, instead of a guesthouse. Based on the belief of the restaurant owner Jiro Ono that the taste of sushi depends most importantly on the sushi rice, the movie closely documents the apprentices who undergo grueling training. Although it may seem like just a matter of "mixing vinegar into the rice", the results can vary greatly depending on the cook, and in the recipe for sushi rice, adding only vinegar does not result in a well-balanced flavor, so a large amount of sugar has to be added. It is unclear whether this state has an anti-corrosion delay effect. Therefore, sushi rice is not made with the expectation of an anti-corrosion delay effect.

Summary of the Invention

Problems to be Solved by the Invention

[0010] <Individual Problem A> In the current commonly adopted manufacturing method of adding preservatives to cooked rice to extend the shelf life, a unique heavy flavor remains in the taste, making it difficult to gain support from consumers who seek deliciousness. Also, since preservatives have to be listed in the raw material section of the product, they are easily compared with other products by consumers who seek deliciousness and safety when purchasing, and it is expected that this will lead to a loss of purchasing opportunities. <Individual Problem B> Although it has already been stated in the section of Non-Patent Document 1 that adding 3% by weight of Mitsukan vinegar to rice results in rice with an anti-corrosion delay effect, the method of adding a seasoning liquid to the cooked rice after cooking is a job that requires professional skill as described above. Since it is affected by changes in the person doing the work and air conditioning conditions such as temperature and humidity, the reproducibility regarding taste becomes low. Therefore, the practicality and necessity of a rice cooking technology that is easily available to anyone and has extremely high reproducibility are high. <Individual Problem C> When processing cooked rice into rice balls, it is common to add a little salt to the rice, but this is also a job that requires skill like the sushi rice mentioned above. Making a product with a uniform taste by hand requires a high level of skill and education.

Means for Solving the Problems

[0011] In order to solve the above problem of <Individual Problem A>, without relying on the use of chemical raw materials such as preservatives or special manufacturing methods, a rice cooking technology has been developed that uses only natural materials, can achieve an anti-corrosion delay effect corresponding to any rice cooking method, and can obtain a satisfactory taste.

[0012] In order to solve the above problem of <Individual Problem B>, a highly reproducible rice cooking technology has been developed that can be easily cooked by anyone using existing rice cooking methods without special education.

[0013] Regarding the above problem of <Individual Problem C>, the cooked rice made by the umeboshi vinegar rice cooking technology with an anti-corrosion delay effect can feel an appropriate saltiness, and the sour taste is hardly felt, probably because it volatilizes during rice cooking. Also, it is a rice cooking technology that can be manufactured with high reproducibility and a simple process as in the previous item.

Effect of the Invention

[0014] Since the present invention is a technology for manufacturing cooked rice using only natural materials as raw materials, the flavor and taste are extremely natural, and there is no unique heavy flavor or aftertaste felt in the cooked rice manufactured by the method of adding preservatives. Also, the method of adding preservatives to cook rice is mainly carried out at the site of mass cooking, and there are few examples of adoption in households and small-scale business establishments.

[0015] The present invention is also epoch-making in that it can manufacture cooked rice with an anti-corrosion delay effect without using special equipment or technology. It is a rice cooking technology that can manufacture cooked rice with an anti-corrosion delay effect having the same quality and performance with extremely high reproducibility by simply cooking with umeboshi vinegar water made by adding a certain amount of umeboshi vinegar to tap water, and its manufacture can be easily carried out by anyone.

[0016] Regarding the production of onigiri using the cooked rice with an anti-corrosion delay effect of the present invention, the relationship between the cooked rice with an anti-corrosion delay effect and the ingredients used as the filling is clarified, and onigiri with an anti-corrosion delay effect can be manufactured by using pickles of dried vegetables such as umeboshi.

[0017] According to the present invention, by cooking rice with a seasoning liquid added with ume vinegar during rice cooking, it is possible to easily produce rice with extremely high reproducibility in flavor and texture. In addition, there is no need to introduce special manufacturing equipment for rice cooking, and it can be manufactured in exactly the same way as cooking conventional white rice, so there is no need to provide special education to cooks. Furthermore, since the cooked rice already has the effect of delaying spoilage, it can proceed to the next process immediately, so the risk of bacteria attachment and contamination is the same as that of white rice, and there is no need to take special measures. Also, the ume vinegar contained in the rice cooking water is absorbed throughout the inside of the rice grains, and the rice balls made from the cooked rice are different from the rice with vinegar added after cooking as in the conventional method in that the state of penetration into the inside of the rice is different.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

[0019] The present invention will be described below. Regarding the preparation of the sample, 150g of raw rice was polished from brown rice (rice harvested in 2021) from a single source rice produced in Toyama Prefecture per cup. The cooking water was made by diluting plum vinegar (salt concentration 20.0% (measured by the Mohr method), pH about 2) used to pickle Nankou plums produced in Kishu with tap water. The diluted plum vinegar water (pH about 3) was added to about 196-200g of raw rice and cooked. This is shown in Table 2. In addition, in the specification of this application, "raw rice" is used to mean rice that has not been cooked or roasted, and refers to rice in a polished state. [Table 2]

[0020] We decided to use the salt concentration of the plum vinegar water as an indicator to compare the level of dilution required to delay preservation when cooking rice. Specifically, the values ​​of diluted plum vinegar water were compared based on the salt concentration after dilution (undiluted solution / dilution ratio). Plum vinegar is a by-product of making umeboshi (pickled plums) by pickling plums with salt, and since plum vinegar is not the only product produced, the salt concentration varies depending on the production lot and production location. For this reason, we measured the salt concentration of the plum vinegar and used the amount of salt as an indicator to provide a standard when using different types of plum vinegar. In actual cooking, the ratio of water content to the weight of raw rice is usually changed depending on the rice variety, dryness, and season, so we decided to compare the weight of the plum vinegar with raw rice, but rather based on the salt concentration of the plum vinegar water used for cooking. This has the advantage of making it easier to use, as the same flavor of cooked rice can be obtained regardless of the amount of water added when cooking. The undiluted plum vinegar reported here was in a single container.

[0021] According to the Ministry of Agriculture, Forestry and Fisheries' crop survey for 2020, the total plum harvest volume in Japan was about 71,100 tons, with Wakayama Prefecture ranking first with 41,300 tons (58%), Gunma Prefecture in second place with 5,190 tons, and Fukui Prefecture in third place with 1,500 tons. Wakayama Prefecture, which ranked first, boasts an overwhelming production volume, eight times that of the second place and 28 times that of the third place. The main variety produced in Wakayama Prefecture is a large, thick-fleshed variety called Nanko-ume, which was discovered in 1902 and is similar to apricots, and many of the pickled plums sold in the market are pickled Nanko-ume. For this reason, the plum vinegar used as the sample was Kishu-produced plum vinegar, which is mass-produced, has stable quality, is of the same quality, and is easily re-obtainable.

[0022] For raw rice, we purchased 2021 brown rice directly from farmers, stored it, and polished it recently before using it. In reality, rice loses moisture over time after harvest, and its quality varies depending on the storage method, so we used raw rice that was stored as brown rice and polished just before or a few days before using it. In actual manufacturing, the period during which new rice can be used is limited, so we did not use new rice.

[0023] For the experiment on the relationship between the anti-corrosion delay effect and the salt concentration, the one obtained by stirring table salt with tap water was used. The mixing ratio of the samples was the same as that in Table 2.

[0024] The analysis of the samples was entrusted to the Toyama Prefectural Food Research Institute, a public third-party institution. The samples were analyzed by culturing those stored at a constant temperature of 25°C on a standard agar medium for the analysis of the total viable count based on the Food Sanitation Law.

[0025] As the cooked rice for the test samples, those made in the shape of a triangular rice ball called the Kanto type were used as samples. The size was 70 - 100 g of cooked rice as one sample. Therefore, regardless of whether the sample was "cooked rice" or "rice ball", the surface areas and shapes of all samples were stored to be of the same degree and compared.

[0026] Regarding the "rice ball", which is a processed food with the seeds as ingredients in the rice ball shape of cooked rice where the anti-corrosion delay effect was observed, its anti-corrosion effect was also examined.

[0027] As samples with the anti-corrosion delay effect, there were pickled ume and pickles. The raw material of the pickled ume was the wild ume type, and the red pickled ume made by pickling the high-salt-concentration pickled ume of Himi Inazumi Ume, an ancient variety in our country, made by the traditional manufacturing method since the Edo period, with red shiso was used. For daikon radish and shiitake mushrooms, those soaked in a seasoning liquid without chemical preservatives such as amino acids represented by glycine after being dried at low temperature were used.

[0028] As samples without the anti-corrosion delay effect, those obtained by cooking bonito flakes, eggs, meat, and pickles simply soaked in a seasoning liquid without sufficient drying deteriorated faster than in the case of only cooked rice.

[0029] An anti-corrosion delay effect was observed in the cooked rice cooked with ume vinegar water with a salt concentration of 1.31% or more. No anti-corrosion delay effect was observed in the cooked rice cooked with salt water at a concentration of 3.5%.

[0030] Examples and comparative examples of the present invention will be described below. In this specification, in addition to each example and each comparative example, the one cooked with only tap water is set as a "reference example". The time results of the viable bacteria analysis test of this "reference example" cooked with only tap water, each example, and each comparative example are used as evaluation indicators.

[0031] First, Comparative Example 1 will be described. Comparative Example 1 is a case where rice is cooked with ume vinegar water obtained by diluting 20% salt concentration ume vinegar with tap water so that the salt concentration of the ume vinegar water is 0.99%. This is ume vinegar water obtained by adding 190.6 grams of water to 9.9 grams of ume vinegar so that the salt concentration becomes 0.99%. When comparing the increase in the number of bacteria over time between this Comparative Example 1 and the one cooked with only tap water (reference example), no significant difference was observed between the two. The salt concentration of the ume vinegar water was expressed by rounding off the third digit after the decimal point. The test results of the general viable bacteria count analysis are shown in FIG. 1. The black circles in FIG. 1 represent the test results of Comparative Example 1, and the white circles represent the test results of the reference example. Note that the vertical axis in FIG. 1 represents the number of viable bacteria. Due to test conditions, the line of 100 at the detection limit value and the two types of microbial standard criteria for total vegetables defined in the old "Hygiene Regulations" (abolished in June 2020, Ministry of Health, Labour and Welfare Ordinance), 1 million cells / g for unheated products and 100,000 cells / g for heat-treated products, the line of 100,000 with a stricter numerical value for heat-treated products is entered in the graph as the desired upper limit value. Also, the horizontal axis represents the elapsed time since the start of the test (the same applies to the axis display of the graphs showing the following test results). When the pH of the ume vinegar used in the test was measured with pH test paper 0 - 14 from Merck KGaA, Germany, the ume vinegar stock solution showed approximately pH 2. This solution was prepared immediately before cooking rice to obtain ume vinegar water for cooking rice. The test was conducted without air conditioning in a normal equipment room without isolation. The utensils used were a bamboo rice washing basket (3-go bamboo basket), a general synthetic resin white cutting board, a wooden triangular rice ball mold made of Kiso hinoki (one-piece), and a general synthetic resin rice scoop. The utensils were not disinfected specifically, but those washed the day before and dried naturally were used. The cooking process was carried out after washing the above-mentioned utensils by hand. The cooked rice was molded into a rice ball mold and transferred to a plastic container for storage. The rice cooker used was a household pressure IH rice cooker, TIGER JKP-G 5-go cooker. The above conditions were the same as those in the following examples unless otherwise specified. The completed cooked rice was molded into a rice ball mold and then three pieces each were put into commercially available disposable transparent salad containers for each sample item, which was regarded as one sample. After molding into a rice ball mold, it was quickly cooled in an isolation room without air conditioning and without people entering or leaving. The analysis request times were three times: at the initial stage (time 0 hours from the start of inspection), 48 hours later, and 72 hours later. Regarding the quality of the analysis, the samples were stored at a constant temperature of 25°C as the content conformed to the analysis of the total viable count based on the Food Sanitation Law. An experiment was conducted to see how much anti-corrosion quality could be obtained for cooked rice and the like cooked without boiling disinfection or alcohol disinfection. The results showed that there was no significant difference between the rice cooked with tap water and the rice cooked with ume vinegar water with a salt concentration of 0.99%. After 48 hours, the total viable count of both was about 1 million, which was close to the limit value of the bacterial count suitable for edible as shown in the Food Sanitation Law. The initial total viable count was 600 for the rice cooked with tap water and 400 for the rice cooked with ume vinegar water with a salt concentration of 0.99%, which were fairly good test results. However, the difference was about the measurement error level, and it could be read that the rice cooked with ume vinegar water with a salt concentration of 0.99% did not have anti-corrosion performance immediately after production. After 72 hours passed, it was determined to be spoiled due to the occurrence of mold and abnormal odor.

Example 1

Example 2

Example 3

Example 4

Example 5

Example 6

[0032] From here, the examples and comparative examples of onigiri with ingredients will be described.

Example 7

Example 8

Example 9

Example 10

[0033] When the results of the above-mentioned examples and comparative examples are tabulated, they are as shown in Table 3 and Table 4. Table 3 is a table of the analysis results of the general viable bacteria count of the cooked rice sample (a sample with cooked rice shaped into an onigiri). Table 4 is a table of the analysis results of the general viable bacteria count of the onigiri sample with ingredients. In the table, the ○ mark for the test results represents those with an evaluation result suitable for consumption after 48 hours, and the × mark represents those with an evaluation result not suitable for consumption after 48 hours.

Table 3

Table 4

Claims

1. A method for producing cooked rice for making meals, which comprises adding ume vinegar to the cooking water of raw rice and then cooking the rice, wherein the salt concentration of the ume vinegar in the cooking water is 1.31% or more.

2. The method for producing cooked rice for making meals according to Claim 1, wherein the salt concentration of the ume vinegar in the cooking water is 1.63% or more.

3. The method for producing cooked rice for making meals according to Claim 1, wherein the salt concentration of the ume vinegar in the cooking water is 2.19% or more.

4. The method for producing cooked rice for making meals according to any one of Claims 1 to 3, which does not contain chemical preservatives such as amino acids represented by glycine.

5. Cooked rice obtained by adding ume vinegar to the cooking water of raw rice and then cooking the rice, or a rice ball made from such cooked rice, wherein the salt concentration of the ume vinegar in the cooking water is 1.31% or more, and which satisfies the criterion that the total viable count at the time of 48 hours elapsed in a test of culturing on an agar medium and measuring the total viable count after storing at a constant temperature of 25°C is less than 100,000 cells / g.

6. Cooked rice in which the ume vinegar in the cooking water has been absorbed throughout the entire interior of the rice grains and then cooked, or a rice ball made from such cooked rice, wherein the salt concentration of the ume vinegar in the cooking water is 1.31% or more, and which satisfies the criterion that the total viable count at the time of 48 hours elapsed in a test of culturing on an agar medium and measuring the total viable count after storing at a constant temperature of 25°C is less than 100,000 cells / g.

7. A rice ball made from cooked rice obtained by adding ume vinegar to the cooking water of raw rice and then cooking the rice, wherein the salt concentration of the ume vinegar in the cooking water is 1.31% or more, and the ingredients in the cooked rice of the rice ball are any one of dried pickles, umeboshi, dried daikon radish pickles, and dried shiitake mushroom pickles, and which satisfies the criterion that the total viable count at the time of 48 hours elapsed in a test of culturing on an agar medium and measuring the total viable count after storing at a constant temperature of 25°C is less than 100,000 cells / g.

8. The rice ball according to any one of Claims 5 to 7, which does not contain chemical preservatives such as amino acids represented by glycine.

Images