Rice taste evaluation method, fertilizer, soil conditioner, and rice manufacturing method

Abstract

To provide a method for evaluating the taste of rice in an accurate and simple manner.SOLUTION: A rice taste evaluation method includes a step of measuring an α-glucosidase activity value in a rice sample.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating the taste of rice, a fertilizer, a soil conditioner, and a method for producing rice. [Background technology]

[0002] Methods for evaluating rice taste include the use of taste meters and midori meters. The method using a taste meter measures the protein and amylose content, and a low content indicates excellent taste. The method using a midori meter measures the thickness of the water-retaining film formed on the surface of rice after cooking, and a thicker film indicates excellent taste. However, the results of these evaluations are not sufficiently correlated with actual taste. Furthermore, reducing the protein content of rice by reducing nitrogen fertilizer results in a superior rating using a taste meter, but this method has issues such as reduced yield and increased susceptibility to heat damage.

[0003] Patent Documents 1 and 2 disclose methods for evaluating the taste of cooked rice based on the physical properties of the rice, but these methods require the rice to be cooked. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-185606 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-266742 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for accurately and simply evaluating the eating quality of rice. [Means for solving the problem]

[0006] The present inventors have discovered that the activity of α-glucosidase contained in rice is highly correlated with the taste, and have completed the present invention.

[0007] The present disclosure includes the following aspects. <1> A method for evaluating the taste of rice, comprising a step of measuring α-glucosidase activity in a rice sample. <2> Item 1. The rice taste evaluation method according to Item 1, wherein the rice sample is a water extract of rice. <3> The method further comprises a step of comparing the α-glucosidase activity between two or more rice samples and determining that the rice sample with a higher α-glucosidase activity has a better taste than the rice sample with a lower α-glucosidase activity. Item 1 or 2. The rice taste evaluation method according to item 1 or 2. <4> a solid support, and a detection portion containing a substrate for α-glucosidase, which is disposed on the solid support; Including, Chromatography strips for evaluating rice eating quality. <5> Further comprising a reference portion disposed on the solid support. Item 5. The chromatography strip according to Item 4. <6> Item 1: A step of obtaining color information from the detection portion of the chromatography strip according to Item 4 or 5; and Step 2: Estimating the taste based on the color information obtained in step 1 Including, A computer-implemented method for estimating rice eating quality. <7> Further, the method includes a step 3 of transmitting identification information of the rice sample and taste information of the rice to a server. Item 6. The method for estimating the taste of rice according to item 6. <8> A server that communicates with a user device over a network, a storage unit that stores identification information of the first rice sample and rice taste information received from the user device; a comparison unit that compares the identification information and rice taste information of the first rice sample stored in the storage unit with the identification information and rice taste information of the second rice sample previously stored in the storage unit; and A communication unit that delivers the comparison result to the user device. A server having: <9> The identification information is a cultivation location, a cultivation time, a variety, or a relative taste. Item 8. The server according to item 8. <10> A fertilizer or soil conditioner for increasing the alpha-glucosidase in rice. <11> A method for producing rice, comprising at least one step selected from the group consisting of threshing, drying, hulling, and polishing, characterized in that the step is carried out under low-temperature conditions. [Effects of the Invention]

[0008] According to the present invention, the eating quality of rice can be evaluated accurately and simply. [Brief explanation of the drawings]

[0009] [Figure 1] An example of a system configuration for implementing the taste estimation method will be described. [Figure 2] 1 shows an example of a hardware configuration of a server. [Figure 3] The functional configuration of the server is shown below. [Figure 4] This shows the relationship between rice taste and protein content. [Figure 5] The relationship between rice taste and α-amylase activity measured at 37°C is shown. [Figure 6] The relationship between rice taste and α-amylase activity measured at 60°C is shown. [Figure 7] The relationship between rice taste and α-glucosidase activity is shown. [Figure 8]A schematic diagram of the rice taste evaluation method using chromatography strips and a smartphone app is shown. DETAILED DESCRIPTION OF THE INVENTION

[0010] <<Rice taste evaluation method>> The rice taste evaluation method of the present invention is characterized by including a step of measuring the α-glucosidase activity in a rice sample.

[0011] <Rice sample> The rice to be evaluated for taste according to the present invention is not particularly limited as long as it is common edible rice, and may be either Japonica rice or Indica rice. The rice sample for measuring α-glucosidase activity is not particularly limited as long as it contains components derived from the endosperm, and may be any of post-threshing unhulled rice, brown rice, and polished rice (brown rice from which the bran and germ have been removed, including partially cooked rice). Because α-glucosidase activity may be lost due to heating during the rice polishing process, it is preferable to use brown rice in order to accurately measure the α-glucosidase activity contained in rice.

[0012] To accurately measure the α-glucosidase activity of rice, it is preferable to use ground rice as the rice sample. To avoid denaturation of α-glucosidase due to heating, it is preferable to grind the rice while maintaining a temperature of 15 to 25°C. To accurately measure α-glucosidase activity, it is preferable to use a water extract of rice, and more preferably a water extract of ground rice. It is particularly preferable to use the water extract of ground rice obtained by soaking rice in water at 4°C for approximately 5 to 18 hours, grinding it, suspending it in water, and centrifuging it, and then using the supernatant.

[0013] <α-Glucosidase activity> α-Glucosidase is an enzyme that cleaves α-1,4 bonds in starch into glucose units. α-Glucosidase is generally found in large amounts in the inner layer of brown rice endosperm, and its optimum temperature is approximately 60°C. α-Glucosidase activity can be measured by a conventional method using an α-glucosidase substrate. Examples of α-glucosidase substrates include 4-nitrophenyl α-glucoside (PNPG). To reduce the influence of measurement errors, the α-glucosidase activity of a single rice sample may be measured multiple times, and the taste may be evaluated based on the average value.

[0014] When 4-nitrophenyl α-glucoside (PNPG) is used as a substrate, the amount of 4-nitrophenol (PNP) produced by the decomposition of PNPG by α-glucosidase can be measured by measuring the absorbance at a wavelength of 400 nm. A commercially available measurement kit that uses this principle is the Glycation Power Fractionation and Quantitative Analysis Kit (Kikkoman Biochemifa).

[0015] <Comparison of α-glucosidase activity values> In the present invention, although taste can be evaluated by measuring the α-glucosidase activity of a single rice sample, it is preferable to evaluate taste based on the α-glucosidase activity of two or more rice samples. Specifically, the α-glucosidase activity of two or more rice samples can be compared, and a rice sample with a higher α-glucosidase activity can be determined to have better taste than a rice sample with a lower α-glucosidase activity. When three or more rice samples are used, the α-glucosidase activity of each rice sample can be compared, and the rice sample with the highest α-glucosidase activity can be determined to have the best taste, and the rice samples can be ranked by taste in descending order of α-glucosidase activity.

[0016] The α-glucosidase activity of two or more rice samples can be compared relative to one another based on, for example, the amount of substrate degradation product described above, or absolute evaluation can be performed based on the absolute value of the α-glucosidase activity contained in the rice samples. The absolute unit of α-glucosidase activity is defined as 1 U, which is the activity that produces 1 μmol of 4-nitrophenol per minute. The α-glucosidase activity contained in the rice to be evaluated in the present invention is preferably 0.01 to 0.2 U per gram of rice, and more preferably 0.05 to 0.15 U per gram of rice.

[0017] Although not essential in this embodiment, the effectiveness of the rice taste evaluation method of the present invention can be confirmed by comparing it with the results of previously established taste evaluations, such as the following method developed by Hachidaime Gihee Co., Ltd. (1) Cooking rice (1-1) Weighing rice The conditions for milling are that the milling temperature must be within +15°C of the brown rice temperature, and that the average whiteness after milling is 42°C (low-temperature milling). One gou (150g) of rice milled within five days prior to the taste test is weighed out. (1-2) Measuring water for flooding For 150g of polished rice, prepare 190g of water for soaking. The water should have a hardness of 30 degrees and a temperature of 19°C. (1-3) Putting rice into the rice cooker Put the measured amount of rice into a 3-go rice cooker. Cook 1 go of rice in a 3-go rice cooker. Also, if you use an electric rice cooker, use the same "microcomputer rice cooker" for all of them. (1-4) Washed rice First add water, stir quickly and discard the water immediately to remove the bran (leaving it for too long will affect the taste). (1-5) Massage Immediately discard the water you added at first and knead the rice. This kneading process washes the rice. Knead 40 times. (1-6) Water change After 40 kneadings, the water is changed three times, which allows the rice bran to be properly removed. (1-7) Drainer Drain in a colander until the water is completely gone, being careful not to touch the rice. (1-8) Rice set Once the water has completely drained, place in a jar. (1-9) Addition of floodwater Add the water measured at the beginning. Since the rice absorbed 30g of water during the washing stage, add 190g of water, taking that into account. (1-10) Flooding Soak in water for 45 minutes. Regardless of the season, the soaking time should be 45 minutes. (1-11) Start cooking rice Press the "cook" button on the rice cooker. (1-12) Cooked rice Once the rice is cooked, the next step, cutting the rice, is carried out quickly. (1-13) Sushi rice cutting Quickly cut the rice into pieces. Place the rice scoop in a cross pattern and turn each quarter of the rice upside down. This allows the steam to escape while allowing air to enter the rice. If you neglect to cut the rice into pieces, the rice will have a mushy texture. (1-14) Completed Arrange and close the rice cooker lid.

[0018] (2) Taste evaluation The cooked rice is tasted by a panel of 9 to 19 people. It is preferable that the panelists are holders of the "Five-Star Rice Meister" certification provided by the Japan Rice Merchants Association. They are given a score of 1 to 10 for the following evaluation items (6 points is the standard, with higher points being given for superior and lower points for inferior), and the scores for all evaluation items are totaled. However, for gloss, sweetness, and smoothness, the scores for the evaluation items are multiplied by 2 before being totaled. The higher the total score, the better the taste is judged to be. (Evaluation items) Whiteness, aroma, stickiness, texture, gloss, sweetness, smoothness

[0019] Each step of the rice taste evaluation method of the present invention may be performed manually or automatically by a device. Devices for implementing the rice taste evaluation method of the present invention include dryer / conditioner machines, rice polishers, rice cookers, and automatic analyzers. The rice taste evaluation method of the present invention can be used to develop new taste meters that differ from conventional taste meters based on protein content and amylose content. Furthermore, the rice taste evaluation method of the present invention can be used in the development of fertilizers and soil conditioners, as well as rice polishers, rice cookers, and the like.

[0020] <<Chromatography Strips>> The chromatography strip of the present invention is characterized by comprising a solid phase support and a detection unit containing an α-glucosidase substrate arranged on the solid phase support, and is used to evaluate the taste of rice.

[0021] The solid support may be made of a material such as resin or glass that is generally used as a support for immunochromatography test strips, etc. A detection portion containing an α-glucosidase substrate is placed on the solid support.

[0022] The detection section is made of materials such as resin or filter paper, and is impregnated or immobilized with an α-glucosidase substrate. Examples of α-glucosidase substrates include 4-nitrophenyl α-glucoside (PNPG). When the detection section of the chromatography strip is brought into contact with a rice sample, the α-glucosidase activity in the rice sample decomposes the α-glucosidase substrate, and the color resulting from the degradation product is observed in the detection section.

[0023] The chromatography strip preferably further includes a reference portion disposed on the solid support. The reference portion is used to relatively measure the color change in the detection portion and is preferably made of the same material as the detection portion. The reference portion of the chromatography strip does not change color when contacted with a rice sample, allowing the α-glucosidase activity in the rice sample to be relatively measured by comparing it with the color change in the detection portion. The α-glucosidase activity of two or more rice samples can be compared using the chromatography strip, and it can be determined that a rice sample with a higher α-glucosidase activity has a better taste than a rice sample with a lower α-glucosidase activity. The color change in the detection portion can be observed visually or evaluated by analyzing images captured by a camera. When analyzing images captured by a camera, the taste of the rice can be estimated by a computer, as described below.

[0024] <<Method for estimating rice taste>> The method for estimating rice taste includes step 1 of acquiring color information from the detection section of a chromatography strip, and step 2 of estimating taste information based on the color information acquired in step 1, and is characterized by being implemented by a computer. This method is preferably implemented as application software on a computer. The computer that implements this method is not particularly limited as long as it is capable of performing steps 1 and 2, but examples include computers equipped with a camera and communication means, or computers connectable to a camera and communication means, and preferred are laptop personal computers, smartphones, and tablet devices.

[0025] In step 1, color information of the detection area of ​​the chromatography strip resulting from contact with the rice sample is obtained. The color information is preferably obtained by photographing the detection area with a camera. Examples of color information include images photographed by the camera, images obtained by processing the photographed images, and color data of the detection area obtained by processing the photographed images (e.g., RGB information, CMYK information, information defined in the Lab color space).

[0026] Although color information on the detection area can be obtained solely from the captured image of the detection area, it is preferable to obtain it by comparing the captured image of the detection area with the captured image of the reference area. By comparing with the captured image of the reference area, the influence of the camera's color balance and contrast, etc., can be reduced. For example, if the detection area of ​​a chromatography strip contains 4-nitrophenol glucose, the detection area will turn yellow due to the α-glucosidase contained in the rice sample. The intensity of the yellow color of the detection area can be calculated by comparing with the reference area.

[0027] In step 2, taste information is estimated based on the color information obtained in step 1. Examples of taste information include α-glucosidase activity and rice taste. Rice taste is expressed by any numerical value or grade. Methods for estimating taste include (i) a method of estimating taste based on a correspondence table between color information and rice taste created in advance, (ii) a method of estimating α-glucosidase activity based on a correspondence table between color information and α-glucosidase activity created in advance, and (iii) a method of estimating α-glucosidase activity based on color information and then estimating taste based on the estimated α-glucosidase activity.

[0028] Step 2 may be followed by step 3, in which identification information of the rice sample and rice taste information are transmitted to a server. The identification information may include the cultivation location, cultivation time, variety, relative taste, producer name, production method, etc. The identification information is preferably stored in a computer or on a medium that can be communicated from a computer before step 3.

[0029] FIG. 1 shows an example of a system configuration for implementing the taste estimation method of the present invention. A server 100 and multiple user devices 200 are connected to each other via the Internet. The user devices 200 are terminals for implementing the taste estimation method of the present invention, such as personal computers, smartphones, or tablet terminals. For example, at a farm or a distribution facility, a user operates the user device 200, and steps 1 and 2 are performed on the user device 200. The identification information of the rice sample and the rice taste information are transmitted from the user device 200 to the server 100 via the Internet. The server 100 stores the identification information and rice taste information of multiple rice samples.

[0030] <<Server>> The server of the present invention is a server that communicates with a user device via a network and is characterized by having a memory unit that stores the identification information and rice taste information of a first rice sample received from the user device, a comparison unit that compares the identification information and rice taste information of the first rice sample stored in the memory unit with the identification information and rice taste information of a second rice sample previously stored in the memory unit, and a communication unit that delivers the comparison results to the user device.

[0031] The user device may be a computer capable of implementing the rice taste estimation method described above, and is preferably a personal computer, a smartphone, a tablet terminal, or the like.

[0032] The storage unit stores the identification information of the first rice sample and rice taste information received from the user device. Examples of the storage unit include a memory device, a hard disk drive, and an optical disk drive. The taste information includes α-glucosidase activity and rice taste. The rice taste is expressed by an arbitrary numerical value or grade.

[0033] The comparison unit compares the identification information and rice taste information of the first rice sample stored in the memory unit with the identification information and rice taste information of the second rice sample previously stored in the memory unit. The second rice sample may be only one, or may be multiple rice samples whose taste was evaluated before the first rice sample. By storing the identification information and rice taste information of a large number of rice samples in the memory unit, the identification information and rice taste information of the second rice sample can be used as big data.

[0034] When the rice taste information is α-glucosidase activity, the comparison unit compares the α-glucosidase activity of the first rice sample with that of the second rice sample, and the relative taste of the first rice sample can be obtained as a comparison result. When the rice taste information is taste, the comparison unit compares the taste of the first rice sample with that of the second rice sample. As a result, it is possible to objectively measure, for example, whether taste changes depending on the cultivation season, even if the variety and cultivation location are the same.

[0035] The memory unit may store the identification information of past rice samples and rice taste information, as well as taste evaluations that are not based on α-glucosidase activity. Examples of such taste evaluation methods include the aforementioned method developed by Hachidaime Gihee Co., Ltd.

[0036] The communication unit transmits the comparison results obtained by the comparison unit to the user device. For example, by using the aforementioned chromatography strip and a smartphone as the user device, rice production and distribution sites can easily, quickly, and accurately evaluate rice taste and compare it with past evaluation results without using precision analytical equipment. Rice producers can easily learn the production and management conditions for rice with excellent taste, which promotes the production and distribution of rice with good taste. Rice producers can also use the present invention as a simple method for evaluating taste in the process of developing production and management conditions for rice with excellent taste.

[0037] 2 shows an example of the hardware configuration of the server 100. The server 100 includes, as hardware components, a CPU 11, a main storage device 12, an auxiliary storage device 13, and a network interface 14. These hardware components are connected by a bus 15.

[0038] The auxiliary storage device 13 stores programs and data used by the CPU 11. Examples of the auxiliary storage device 13 include non-volatile memory and hard disk drives. The main storage device 12 provides a storage area for loading the programs stored in the auxiliary storage device 13 into the CPU 11. The main storage device 12 is preferably a semiconductor memory.

[0039] The CPU 11 loads programs and data stored in the auxiliary storage device 13 into the main storage device 12 and executes the processing. The network interface 14 inputs and outputs information between the network and the server. The network interface 14 may be either wired or wireless.

[0040] 3 shows an example of the functional configuration of the server 100. The server 100 has a storage unit 21, a comparison unit 22, and a communication unit 23. Within the server 100, the storage unit 21, the comparison unit 22, and the communication unit 23 are connected to each other. The communication unit 23 can be connected to an external network.

[0041] <<Fertilizer, soil conditioner>> In addition to the above, the present invention is widely applicable to techniques for maintaining or improving α-glucosidase activity in rice. Examples of such techniques include fertilizers and soil conditioners. Fertilizers and soil conditioners that increase α-glucosidase activity in rice are preferred. The present invention is also applicable to rice cultivation methods that increase α-glucosidase activity in rice.

[0042] <<Rice production method>> The rice production method of the present invention is characterized by comprising at least one step selected from the group consisting of threshing, drying, hulling, and rice polishing, and characterized by carrying out said step under low-temperature conditions. By treating rice under low-temperature conditions, the loss of α-glucosidase activity contained in harvested rice during rice treatment is prevented. Examples of rice obtainable by the production method of the present invention include brown rice, germ rice from which the bran has been removed, and polished rice from which the bran and germ have been removed. Low-temperature conditions are preferably 40°C or lower, more preferably 37°C or lower, even more preferably 35°C or lower, and even more preferably 30°C or lower. [Example]

[0043] Examples of the present invention will be described below, but the present invention is not limited to the following examples. (1) Methods for measuring enzyme activity and protein content We received three years' worth of brown rice, the taste of which had been evaluated in advance, from Yatsudaime Gibei Co., Ltd. For each brown rice sample, α-glucosidase activity, α-amylase activity, and protein content were measured using the following methods. All measurements were subjected to multiple comparisons (Tukey-Kramer test) to verify statistical significance.

[0044] (1-1) Method for measuring protein content A Vario Max cube (Elementar) was used to measure protein content. This device quantifies total nitrogen using the combustion method (modified Dumas method), which is the official method for quantifying nitrogen in foods and is a more accurate analytical method than the near-infrared quantification method used in existing taste analyzers. Protein content (%) was calculated by multiplying the measured total nitrogen content (%) by a protein conversion factor of 5.95 and converting it to a moisture content equivalent to 15%. Protein content measurements were performed three times for each brown rice sample.

[0045] (1-2) Method for measuring α-glucosidase activity 5 g of brown rice was added to 9 mL of distilled water, soaked overnight at 4°C, crushed using a Multi-Beads Shocker (Yasui Kikai), and then centrifuged at 18,000 g for 10 minutes.

[0046] The α-glucosidase activity in the supernatant (hereafter referred to as the rice sample) after centrifugation was measured using a saccharification power fractionation and quantification kit (Kikkoman Biochemifa). After preincubating 100 μL of substrate solution at 60°C for 5 minutes, 10 μL of rice sample was added to a 96-well microplate to initiate the reaction. After 30 minutes, 50 μL of stop solution was added to stop the reaction. A blank was prepared by adding the rice sample after the stop solution. Absorbance at 400 nm was measured using a microplate reader (Infinite M1000 Pro, TECAN), and the blank absorbance was subtracted. Absorbance values ​​were substituted into the equation for a calibration curve prepared separately using 4-nitrophenol, and the activity required to produce 1 μmol of 4-nitrophenol per minute was defined as 1 U. All enzyme activity measurements were performed four times for each brown rice sample, and each test result was the average of the four replicates.

[0047] (1-3) Method for measuring α-amylase activity 5 g of brown rice was added to 9 mL of distilled water, soaked overnight at 4°C, crushed using a Multi-Beads Shocker (Yasui Kikai), and then centrifuged at 18,000 g for 10 minutes.

[0048] The α-amylase activity in the supernatant (hereafter referred to as the rice sample) after centrifugation was measured using an α-amylase assay kit (Kikkoman Biochemifa). 25 μL of substrate solution and 25 μL of enzyme solution were added to a 96-well microplate and pre-incubated at 37°C or 60°C for 5 minutes. The reaction was initiated by adding 20 μL of rice sample. After 60 minutes, the reaction was stopped by adding 100 μL of stop solution. A blank was prepared by adding the rice sample after the stop solution. Absorbance at 400 nm was measured using a microplate reader (Infinite M1000 Pro, TECAN), and the blank absorbance was subtracted. Absorbance values ​​were substituted into the equation for a calibration curve prepared separately using 2-chloro-4-nitrophenol. The activity required to produce 1 μmol of 2-chloro-4-nitrophenol per minute was defined as 1 U, and calculations were performed.

[0049] (2) Measurement results of enzyme activity and protein content (2-1) Protein content The left side of Figure 4 shows protein content. Protein content is measured in weight percent and was calculated assuming a rice moisture content of 15% by weight. The right side shows the relationship between taste, as previously evaluated using a sensory test method developed by Hachidaime Gihee Co., Ltd., and the average protein content of the rice samples. In the graph on the right side of Figure 4, different letters indicate statistically significant differences. The bars in the figure indicate standard errors. Brown rice samples in the figure are also symbolized, for example, as "Brown Rice 1." No clear correlation was observed between rice taste and protein content. In 2020, rice with poor taste had significantly higher protein content, but the difference was not large. Considering individual differences, it was considered impossible to evaluate taste based on protein content.

[0050] (2-2) Enzyme activity During the seed germination process, α-amylase is an important enzyme that randomly breaks down starch and supplies sugars to the embryo. It is involved in the sweetness of rice and the formation of a water-retaining film, and may affect the taste. Also, α-glucosidase, also known as maltase, is known to break down maltose into glucose. However, there are reports that in rice seeds, α-glucosidase is an enzyme that directly breaks down starch to produce glucose*1, *2). Therefore, we measured the activity of these two types of starch-degrading enzymes and examined the correlation with taste. Since α-amylase is known to have optimal temperatures of 37°C and 60°C, we measured the activity of each enzyme separately. *1) Nakai, H. et al. (2007), Biochimie, 89(1), 49-62. *2) Nakai, H. et al. (2006), Journal of Applied Glycoscience, 53(2), 137-142.

[0051] The left side of Figures 5 to 7 shows the α-amylase activity in the rice samples. The right side shows the relationship between the taste, which was evaluated in advance using a sensory test method developed by Yasadaime Gihee Co., Ltd., and the average α-amylase activity in the rice samples. Figure 5 shows the α-amylase activity measured at 37°C, and Figure 6 shows the α-amylase activity measured at 60°C. The left side of Figure 7 shows the α-glucosidase activity in the rice samples. The right side shows the relationship between the taste, which was evaluated in advance using a sensory test method developed by Yasadaime Gihee Co., Ltd., and the average α-glucosidase activity in the rice samples. On the right side of Figures 5 to 7, different letters indicate statistically significant differences.

[0052] The activity of α-amylase with an optimum temperature of 37°C tended to be higher in rice with poor eating quality, but no clear correlation with eating quality was found throughout the three-year test (Figure 5). The same was true for the activity of α-amylase with an optimum temperature of 60°C (Figure 6). On the other hand, α-glucosidase activity was high in rice with good eating quality in all three years of testing, and activity decreased significantly as eating quality deteriorated (Figure 7).

[0053] Low enzyme activity is prone to measurement errors and is difficult to measure stably and accurately. Comparing the activities of α-amylase and α-glucosidase, α-glucosidase activity is several dozen times higher than α-amylase activity, making stable and accurate measurement possible. It has also been reported that α-amylase is localized to the periphery of rice grains, while α-glucosidase is widely distributed in the center, along with starch.*3) This indicates that α-glucosidase is deeply involved in starch degradation in brown rice. In fact, the peak gelatinization temperature coincides with the optimal temperature for α-glucosidase.*3) These findings demonstrate a strong correlation between rice taste evaluation and α-glucosidase activity. Considering the high activity and enzyme localization, α-glucosidase activity is useful as an accurate and stable indicator of rice taste evaluation. *3) Tsuyukubo, M et al., (2010) Food Science and Technology Research, 16(6), 523-530.

[0054] (3) Method for estimating rice taste Figure 8 shows a simple method for estimating rice taste. Brown rice is ground in a manual mill, taking care to avoid raising the temperature. A level spoonful (0.5 g) of the powder is placed in a 1.5 mL microtube. 0.9 mL of tap water is added to the microtube and mixed vigorously. After leaving the mixture to stand for a while, a test strip soaked in the reaction solution is immersed in the supernatant, then immediately removed and incubated at room temperature. The test strip has a resin attached to its tip containing two solutions: the lower resin contains 10 mM 4-nitrophenyl α-glucoside (PNPG), a substrate for α-glucosidase, in 10 mM acetate buffer (pH 5.0), at a concentration of 10 mM; the upper resin contains only 10 mM acetate buffer (pH 5.0). The test is measured for exactly five minutes at room temperature, and after five minutes, the tip of the test paper is photographed using a dedicated smartphone app. The color of the upper resin is used as a reference, and the α-glucosidase activity is quantified based on the intensity of the yellow color of the lower resin, which is used as the taste value. Brown rice information such as cultivation location and variety can be registered in advance in the smartphone app, and this data, along with the taste value, can be stored in the cloud, making it useful for analyzing taste by region, variety, and year. This analysis will reveal the production and management conditions for rice with high taste values, making a significant contribution to revitalizing the distribution of rice with good taste. [Industrial Applicability]

[0055] According to this invention, rice retailers and distributors can reliably provide rice with excellent taste. Consumers can obtain rice that is objectively excellent in taste, regardless of the place of origin, variety, or "taste ranking" evaluation. Furthermore, producers can identify the reliable characteristics of rice with excellent taste, enabling them to cultivate rice that improves its taste index. Furthermore, research into breeding and cultivation methods for rice with excellent taste will be promoted. [Explanation of symbols]

[0056] 11 CPU 12 Main storage 13 Auxiliary storage device 14 Network Interface 15 Bus 100 servers 21 Memory section 22 Comparison section 23 Communications Department 200 User Device

Claims

1. A method for evaluating the taste of rice, comprising a step of measuring α-glucosidase activity in a rice sample.

2. The method for evaluating the taste of rice according to claim 1, wherein the rice sample is a water extract of rice.

3. The method further comprises a step of comparing the α-glucosidase activity between two or more rice samples and determining that the rice sample with a higher α-glucosidase activity has a better taste than the rice sample with a lower α-glucosidase activity. The method for evaluating the taste of rice according to claim 1 or 2.

4. a solid support, and a detection portion containing a substrate for α-glucosidase, which is disposed on the solid support; Including, Chromatography strips for evaluating rice eating quality.

5. Further comprising a reference portion disposed on the solid support. The chromatography strip according to claim 4.

6. A step 1 for acquiring color information from the detection portion of the chromatography strip according to claim 4 or 5; and Step 2: Estimating taste information based on the color information acquired in step 1 Including, A computer-implemented method for estimating rice eating quality.

7. Further, the method includes a step 3 of transmitting identification information of the rice sample and taste information of the rice to a server. The method for estimating rice taste according to claim 6.

8. A server that communicates with a user device over a network, a storage unit that stores identification information of the first rice sample and rice taste information received from the user device; a comparison unit that compares the identification information and rice taste information of the first rice sample stored in the storage unit with the identification information and rice taste information of the second rice sample previously stored in the storage unit; and A communication unit that delivers the comparison result to the user device. A server having:

9. The identification information is a cultivation location, a cultivation time, a variety, or a relative taste. The server of claim 8.

10. A fertilizer or soil conditioner for increasing the α-glucosidase in rice.

11. A method for producing rice, comprising at least one step selected from the group consisting of threshing, drying, hulling, and polishing, wherein the step is carried out under low-temperature conditions.

Images