Method and kit for evaluating characteristics of grains

Abstract

To provide a method for evaluating the brewing suitability of grains that can be easily executed on site.SOLUTION: A method for evaluating an amylopectin side chain structure contained in starch in grains includes: a contact step of bringing evaluation grains into contact with each of A: a compound and solvent having starch gelatinization and B: the solvent; a swelling step of swelling the evaluation grains through the contact step; a swelling ratio calculation step of calculating a swelling ratio of the evaluation grains by dividing the volume of the evaluation grains brought into contact with A by the volume of the evaluation grains brought into contact with B after the swelling step; and an evaluation step of evaluating the amylopectin side chain structure on the basis of the solution concentration of the compound and the swelling ratio.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to methods and kits for evaluating the characteristics of grains, more specifically, to a method for evaluating the amylopectin side chain structure contained in starch in grains, and to methods for evaluating the retrogradation property of starch, the gelatinization temperature of rice, the enzymatic digestibility of steamed rice, the retrogradation property of steamed rice, and the solubility of steamed rice during sake brewing, as well as kits for carrying out said methods. [Background technology]

[0002] Sake is produced by a multiple parallel fermentation method in which dissolution and saccharification (enzymatic digestion) of raw rice and alcoholic fermentation occur simultaneously in the mash. The degree of saccharification of the raw rice affects the utilization rate of the raw rice and the aroma and flavor of sake, so the solubility of the raw rice (enzymatic digestibility of steamed rice) is important in the sake production process. For this reason, at sake production sites and in breeding sake rice varieties, the enzymatic digestibility of steamed rice is considered important when evaluating the suitability of raw rice for sake brewing. It has been revealed that the properties related to gelatinization and retrogradation of starch in the raw rice are important factors that affect the enzymatic digestibility of steamed rice (Non-Patent Document 1).

[0003] To date, methods for evaluating the solubility of raw rice have been reported, such as a method of estimation based on meteorological conditions (Non-Patent Documents 2 and 3) and a method based on thermal analysis (Non-Patent Document 4). These methods have the advantages of being simple and highly accurate.

[0004] It has also been reported that the solubility of rice can be estimated by the disintegration of rice grains when soaked in an alkaline solution (Non-Patent Document 5). Based on this method, studies are being conducted with the aim of quantifying solubility estimation. Rice grains were subjected to a disintegration reaction in alkaline or urea solutions of various concentrations, and the degree of disintegration of the rice grains and the coloring caused by iodine were observed. As a result, a strong correlation was observed between the concentration at which the rice grains disintegrated or the iodine solution turned deep blue, and the gelatinization temperature and enzymatic digestibility of steamed rice measured with a differential scanning calorimeter (DSC) or rapid visco analyzer (RVA). It has been reported that the solubility of raw rice can be easily and cheaply quantitatively evaluated by determining the concentration of the alkaline and urea solutions at which the rice grains disintegrate (Patent Document 1 and Non-Patent Document 6). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2014-534052 [Non-patent literature]

[0006] [Non-Patent Document 1] Okuda, M., Aramaki, I., Koseki, T., Inouchi, N. and Hashizume, K., "Structural and retrogradation properties of rice endosperm starch affect enyme digestibility of steamed milled-rice grains used in sake production", Cereal Chem, 2006, Vol. 83, pp. 143-151 [Non-Patent Document 2] Masao Okuda, Katsumi Hashizume, Yoshikoyo Numata, Midori Ueyo, Nami Goto, Shigeaki Mikami, "Relationship between meteorological data and suitability of raw rice for sake brewing," Journal of the Brewing Society of Japan, Vol. 104, pp. 699-711, 2009 [Non-Patent Document 3] Masao Okuda, Katsumi Hashizume, Midori Ueyo, Yoshikoyo Numata, Nami Goto, Shigeaki Mikami, "Rice ripening temperature and starch properties of sake rice during rice ripening and their variations between years and regions," Journal of the Brewing Society of Japan, 2010, Vol. 105, pp. 97-105 [Non-Patent Document 4] Okuda, M., Hashizume, K., Aramaki, I., Numata, M., Joyo, M., Goto-Yamamoto, N. and Mikami, S., "Influence of starch characteristics on digestibility of steamed rice grains under sake making conditions, and rapid estimation methods of digestibility by physical analysis", J.Appl.Glycosci., 2009, vol. 56, pp. 185-192. [Non-Patent Document 5] Masao Okuda, Midori Ueyo, Kei Takahashi, Nami Goto, Yukio Takagaki, Masaru Ikegami, and Yoshihito Nabekura, "Starch characteristics and enzyme digestibility of steamed rice produced in 2010 when the rice ripening period was hit by a record heat wave," Journal of the Brewing Society of Japan, 2013, Vol. 108, pp. 368-376 [Non-Patent Document 6] Masao Okuda, Midori Kamiyo, Hiroshi Fukuda, "Estimation of enzyme digestibility of steamed rice based on alkali and urea disintegration of raw rice for sake brewing," Journal of the Brewing Society of Japan, 2018, Vol. 113, pp. 315-330 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the case of estimation based on meteorological conditions as in Non-Patent Documents 2 and 3, it is sometimes difficult to obtain accurate information on the meteorological conditions of the production area, and in the case of thermal analysis as in Non-Patent Document 4, there is a problem that the equipment is expensive.

[0008] Furthermore, in the method using alkali or urea solution described in Patent Document 1 and Non-Patent Document 6 based on Non-Patent Document 5, the rice polishing rate and the moisture content of the rice (also called water content or moisture) to be evaluated affect the degree of rice disintegration caused by alkali and urea. In addition, further reagents such as iodine are required to observe disintegration. Therefore, even in such a method, there are significant issues in terms of simplicity, such as the standardization of the rice polishing rate and rice moisture, which requires a lot of effort, and the preparation of further reagents.

[0009] Therefore, an objective of the present invention is to provide a method for evaluating the starch characteristics and suitability for sake brewing of grains that can be easily performed on site. [Means for solving the problem]

[0010] The inventors have investigated various means for solving the above-mentioned problems, and as a result have found that rice swells when brought into contact with urea, and that this swelling property has a certain relationship with the gelatinization temperature of the rice, the enzymatic digestibility of steamed rice, and gelatinization retrogradation properties, such as the retrogradation properties of starch in rice and the retrogradation properties of steamed rice, i.e., the solubility of steamed rice during sake brewing, and further the amylopectin side chain structure contained in starch in rice, thereby completing the present invention.

[0011] That is, the gist of the present invention is as follows. (1) A method for evaluating an amylopectin side chain structure contained in starch in grain, comprising the steps of: A contact step of contacting the evaluation grain with the following A and B, A: Compounds and solvents that have starch gelatinizing properties B: the solvent a swelling step of swelling the evaluation grain by the contact step; a swelling ratio calculation step of calculating the swelling ratio of the evaluation grain after the swelling step by dividing the volume of the evaluation grain contacted with A by the volume of the evaluation grain contacted with B; and An evaluation step of evaluating the amylopectin side chain structure based on the solution concentration of the compound and the swelling ratio. The method includes: (2) The method according to (1), wherein the evaluation step is an evaluation step of evaluating the amylopectin side chain structure based on the swelling ratio at a predetermined solution concentration. (3) The method according to (1), wherein the evaluation step is an evaluation step for evaluating the amylopectin side chain structure based on the solution concentration until a predetermined swelling ratio is reached. (4) The method according to (1) or (3), wherein the evaluation step is a step of evaluating the amylopectin side chain structure based on the solution concentration at which the swelling ratio starts to increase. (5) The method according to any one of (1) to (4), wherein the compound having a starch gelatinizing effect is one or more compounds selected from the group consisting of urea, guanidine hydrochloride, and dimethyl sulfoxide. (6) The method according to any one of (1) to (5), wherein the solvent is water. (7) The compound having starch gelatinizing activity is urea, and the solvent is water; the evaluation step is a step of evaluating an amylopectin side chain structure based on the solution concentration at which the swelling ratio starts to increase, In the evaluation step, When the swelling ratio increase starting concentration is less than 2.5M, the amylopectin side chain contained in the starch in the evaluation grain is evaluated as being short; When the swelling ratio increase starting concentration is 2.5M or more and less than 3.1M, the amylopectin side chain contained in the starch in the evaluation grain is evaluated as being normal; When the swelling ratio increase starting concentration is 3.1M or more, the amylopectin side chain contained in the starch in the evaluation grain is evaluated as being long. A method according to any one of (1), (3) and (4). (8) The number of grains evaluated is two or more; The evaluation step is a step of comparing the swelling ratios of the respective solutions at a predetermined solution concentration, In the evaluation step, the larger the swelling ratio, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be. The method according to (1) or (2). (9) The number of grains evaluated is two or more; The evaluation step is a step of comparing the respective solution concentrations until the predetermined swelling ratio is reached, In the evaluation step, the lower the solution concentration, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be. The method according to (1) or (3). (10) The number of grains evaluated is two or more; The evaluation step is a step of comparing the respective solution concentrations at which the swelling ratio starts to increase, In the evaluation step, the lower the solution concentration, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be. A method according to any one of (1), (3), and (9). (11) The method according to any one of (1) to (10), wherein at least one of the evaluation grains is a reference grain whose amylopectin side chain structure is known. (12) The method according to any one of (8) to (11), wherein the compound having a starch gelatinizing effect is one or more compounds selected from the group consisting of urea, guanidine hydrochloride, and dimethyl sulfoxide. (13) The method according to any one of (8) to (12), wherein the solvent is water. (14) The method according to any one of (1) to (13), wherein the evaluation grain is rice. (15) A kit for evaluating the amylopectin side chain structure contained in starch in grains, comprising two or more containers of the same shape and a compound having a starch gelatinizing effect. (16) A method for evaluating retrogradation of starch, comprising the steps of: From the evaluation results of the amylopectin side chain structure contained in the starch obtained by any one of the methods according to (1) to (14), the retrogradation property of the starch is evaluated based on the length of the amylopectin side chain contained in the starch in the evaluation grain. The method. (17) A method for evaluating the gelatinization retrogradation characteristics of grains, comprising the steps of: From the evaluation results of the amylopectin side chain structure contained in the starch obtained by any one of the methods according to (1) to (14), the gelatinization retrogradation properties of the grain are evaluated based on the length of the amylopectin side chain contained in the starch in the evaluation grain. The method. (18) A method for evaluating the solubility of steamed rice during sake brewing, comprising the steps of: From the evaluation results of the amylopectin side chain structure contained in starch obtained by any one of the methods (1) to (14) when the evaluation grain is rice, the steamed rice solubility during sake brewing of rice is evaluated based on the length of the amylopectin side chain contained in the starch in the rice. The method. (19) A method for evaluating the aging property of steamed rice, comprising the steps of: From the evaluation results of the amylopectin side chain structure contained in starch obtained by any one of the methods (1) to (14) when the evaluation grain is rice, the retrogradation property of steamed rice is evaluated based on the length of the amylopectin side chain contained in the starch in the rice. The method. (20) A method for evaluating the gelatinization temperature of rice, comprising the steps of: From the evaluation results of the amylopectin side chain structure contained in starch obtained by any one of the methods (1) to (14) when the evaluation grain is rice, the gelatinization temperature of the rice is evaluated based on the length of the amylopectin side chain contained in the starch in the rice. The method. Effect of the Invention

[0012] The present invention provides a method for evaluating the suitability of grains for sake brewing that can be easily carried out on site. [Brief description of the drawings]

[0013] [Figure 1] 1 is a photograph showing the results of evaluation of absorption and swelling of an aqueous urea solution by planar observation using a petri dish in Test 1-1. [Diagram 2] 1 is a photograph showing the results of evaluation of absorption and swelling of an aqueous urea solution by stereoscopic observation using a polystyrene bottle in Test 1-2. [Diagram 3] 1 is a graph showing the relationship between the urea concentration and the DSC gelatinization temperature and the RVA viscosity rise temperature in Test 1-2. [Figure 4] 1 is a graph showing the relationship between urea concentration and enzymatic digestibility of steamed rice in Test 1-2. [Diagram 5] 1 is a graph showing the relationship between urea concentration and aging rate in Test 1-2. [Figure 6] 1 is a photograph showing the results of evaluation of absorption and swelling rate based on different liquid volumes of urea aqueous solutions by stereoscopic observation using a test tube in Test 1-3. [Figure 7] 1 is a photograph showing the results of evaluation of absorption and swelling ratio based on the difference in reaction time with an aqueous urea solution by stereoscopic observation using a test tube in Test 1-3. [Figure 8-1] 11 is a photograph showing the results of evaluation of the absorption and swelling rate of an aqueous urea solution based on differences in rice by stereoscopic observation using a test tube in Test 1-3. [Figure 8-2] 11 is a photograph showing the results of evaluation of the absorption and swelling rate of an aqueous urea solution based on differences in rice by stereoscopic observation using a test tube in Test 1-3. [Figure 9-1] 1 is a graph showing the relationship between urea concentration and amylopectin short chain ratio in Tests 1-3. [Figure 9-2] 1 is a graph showing the relationship between the urea concentration and the DSC gelatinization temperature and the RVA viscosity rise temperature in Test 1-3. [Figure 9-3] 1 is a graph showing the relationship between urea concentration and enzymatic digestibility of steamed rice in Test 1-3. [Figure 9-4] 1 is a graph showing the relationship between urea concentration and aging rate in Tests 1-3. [Figure 10] Photographs showing the results of investigating the effect of white rice moisture in Test 1-3. [Figure 11] Photographs showing the results of investigating the effect of rice polishing ratio in Test 1-3. [Figure 12] 13 is a photograph showing the results of evaluation of the absorption and swelling rate of an aqueous DMSO solution and an aqueous guanidine hydrochloride solution by stereoscopic observation using a test tube in Test 2. [Figure 13] 13 is a photograph showing the results of evaluation of the swelling rate of long-grain rice, barley, and buckwheat by stereoscopic observation using a test tube in Test 3. [Figure 14] 1 is a graph showing the relationship between the urea concentration in Tests 1-3 and the retrogradation properties of starch examined in Test 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Preferred embodiments of the present invention will now be described in detail. In this specification, the features of the present invention will be described with reference to the drawings as appropriate. In the drawings, the dimensions and shapes of each part are exaggerated for clarity, and the actual dimensions and shapes are not accurately depicted. Therefore, the technical scope of the present invention is not limited to the dimensions and shapes of each part shown in these drawings. Note that the method and kit for evaluating grain characteristics of the present invention are not limited to the following embodiments, and can be embodied in various forms with modifications and improvements that can be made by those skilled in the art without departing from the gist of the present invention.

[0015] <Method for evaluating amylopectin side chain structure> The method of the present invention for evaluating the amylopectin side chain structure contained in starch in a grain includes a contacting step of contacting the evaluation grain with the following A and B, A: a compound having a starch gelatinizing effect and a solvent, B: the solvent, a swelling step of swelling the evaluation grain by the contacting step, a swelling ratio calculation step of calculating the swelling ratio of the evaluation grain after the swelling step by dividing the volume of the evaluation grain contacted with A by the volume of the evaluation grain contacted with B, and an evaluation step of evaluating the amylopectin side chain structure based on the solution concentration of the compounds and the swelling ratio.

[0016] Each step will be described in detail below.

[0017] (contact process) In the contacting step, the grain to be evaluated (hereinafter simply referred to as "grain") is contacted with A and B shown below, respectively. Here, A is a solution containing a compound having a starch gelatinizing effect and a solvent, and B is the same solvent as that used in A.

[0018] Here, the term "grain" used in this method is a general term for the seeds of plants that mainly contain starch. Grains include, but are not limited to, seeds of cereal crops, such as rice, barley, wheat, oats, foxtail millet, barnyard millet, millet, and corn. In the present invention, grains may be threshed or polished. For example, in the case of rice, it may be brown rice or polished rice. In addition, the polishing ratio of polished rice is not limited. For example, when using polished rice suitable for sake brewing, it is possible to use polished rice with the same polishing ratio as the rice used in sake brewing. For example, when using brown rice, it is possible to polish it to white rice for cooking using a test rice polishing machine or a home rice polishing machine before carrying out the evaluation. In addition, in addition to rice for making sake, it may be rice such as rice for making shochu, cooked rice, and rice for processing glutinous rice. The grain is usually a single grain, but may be a mixture of two or more different types of grains (e.g., rice and barley), or may be a mixture of two or more types of the same type of grain but different varieties (e.g., Yamada-nishiki and Nipponbare rice), or may be a mixture of two or more types of the same plant and variety but grown under different cultivation conditions such as cultivation time, place, and fertilizer (e.g., Yamada-nishiki rice grown in 2017 and 2018). When the grain is a mixture, the ratio of each grain in the mixture is not limited. As the grain, rice of a single variety, i.e., the same variety and cultivation conditions, is preferred.

[0019] By using rice as the grain, it is possible to evaluate one or more grain characteristics selected from the group consisting of rice gelatinization temperature, enzymatic digestibility of steamed rice, gelatinization retrogradation characteristics, such as the retrogradation characteristics of starch in rice and the retrogradation characteristics of steamed rice, and the solubility of steamed rice during rice sake brewing (also referred to in this specification as "characteristics such as rice gelatinization temperature"), i.e., the amylopectin side chain structure contained in starch in rice, particularly the length of the side chains, can be evaluated.

[0020] As the grain, one target may be used, but two or more different targets may also be used.

[0021] For example, when rice is used as the grain, two or more varieties of rice, such as Yamadanishiki and Nipponbare, may be used, and / or the same variety of rice grown under two or more different cultivation conditions, such as Yamadanishiki grown in 2017 and 2018, may be used.

[0022] By using two or more different targets for the grain, the characteristics of the grain can be evaluated by comparing each one, as described below.

[0023] The moisture content of the grain is not limited. The moisture content of the grain is usually 8% by weight to 17% by weight based on the total weight of the grain. It is preferable to measure the moisture content of the grain in advance.

[0024] A "compound having starch gelatinizing action" is a compound that has the action of changing starch into a paste-like form (also called "gelatinization") by contacting it with starch. Examples of compounds having starch gelatinizing action include, but are not limited to, urea, guanidine hydrochloride, dimethyl sulfoxide, etc. Compounds having starch gelatinizing action may be a mixture of two or more kinds. When the compound having starch gelatinizing action is a mixture, the ratio of each compound in the mixture is not limited. As a compound having starch gelatinizing action, urea is preferred.

[0025] By using a compound having a starch gelatinizing effect, the compound promotes the gelatinization of the starch contained in grains, and as a result, the compound and / or solvent are absorbed into the starch, causing the grains to swell.

[0026] The "solvent" is a medium for dissolving a compound having starch gelatinizing action in A, and is a compound for swelling the grain by being absorbed into the grain in contact with A and B. Examples of the solvent include water and alcohol, such as methanol, ethanol, and propanol. The solvent may be a mixture of two or more kinds. When the solvent is a mixture, the ratio of each compound in the mixture is not limited. As the solvent, water is preferable from the viewpoint of convenience of operation and environmental considerations.

[0027] A is a solution containing a compound having a starch gelatinizing effect and a solvent.

[0028] There is no limitation on the concentration of the compound having starch gelatinizing activity in A. The concentration of the compound having starch gelatinizing activity in A can be appropriately changed depending on the type of the compound having starch gelatinizing activity.

[0029] For example, when urea is used as the compound having starch gelatinizing action in A and water is used as the solvent, the concentration of urea in the aqueous solution of A is usually 1.0 mol / L (M) to 8.0 M, preferably 1.5 M to 5.0 M, and preferably 2.0 M to 5.0 M.

[0030] A may be a solution of two or more different concentrations of a compound having starch gelatinizing activity.

[0031] For example, when urea is used as the compound having starch gelatinizing action in A and water is used as the solvent, urea aqueous solutions having different concentrations of 2 or more, preferably 3 or more, preferably 5 or more, preferably 10 or more, preferably 100 or less, preferably 50 or less are used as A. Each of the two or more urea aqueous solutions is set to a stepwise different urea concentration, for example, set to a stepwise different urea concentration difference of 0.01M to 1M, preferably 0.05M to 0.5M, preferably 0.05M to 0.2M. The concentration difference between the highest concentration solution and the lowest concentration solution among the two or more urea aqueous solutions is not particularly limited, but can be exemplified as a range of 2.0M to 5.0M.

[0032] By using solutions of a compound having starch gelatinizing activity at multiple concentrations, it becomes easier to quantitatively grasp the absorption and swelling properties of grains in the solutions of the compound having starch gelatinizing activity, and accordingly, it becomes possible to quantitatively evaluate said properties.

[0033] B is the same solvent as used in A.

[0034] By using B, which does not contain a compound having a starch gelatinizing effect, together with A, the influence of swelling caused only by the solvent can be eliminated from the swelling ratio in the swelling ratio calculation step.

[0035] There are no limitations on the method of contacting the grain with A and B. Examples of the contact method include putting the grain into A or B, putting A or B into the grain, spraying A or B onto the grain, etc. As for the contact method, putting the grain into A or B, or putting A or B into the grain is preferred from the viewpoint of operational convenience.

[0036] The grain that is brought into contact with A and the grain that is brought into contact with B are different of the same kind.

[0037] The amount of grain is not limited. The amount of grain to be contacted with one of A and B is the same for each, and is usually 0.3 g or more, preferably 0.3 g to 1.0 g.

[0038] There is no limitation on the volume of the solution A or the solvent B. The volume of the solution A or the solvent B is the same, and is usually 1.5 mL to 20 mL.

[0039] The ratio of the weight of solution A or solvent B to the weight of grain (weight of solution A or B / weight of grain) is not limited, but is usually at least 10, and preferably at least 12. Note that the amount of solution A or solvent B is sufficient to swell the grain, and there is no upper limit to the ratio.

[0040] The contact method is to put grain into A or B, or to put A or B into grain. When putting grain into a container, a container whose side projected area is smaller than its base area, a container whose side projected area is larger than its base area, etc. can be used. From the viewpoint of observing changes in the grain, it is preferable to use a container whose side projected area is larger than its base area.

[0041] (Swelling process) In the swelling step, the grains are swelled by the contact step.

[0042] Here, "swelling" refers to an increase in the volume of grains due to the absorption of a compound having starch gelatinizing activity and / or a solvent into the grains. Note that "swelling" includes not only an increase in volume, but also changes in the physical properties of the grains that accompany the increase in volume, such as an increase in the weight of the grains, a change in the refractive index, and a change in elasticity.

[0043] The time for the swelling step is not limited. The time for the swelling step is usually the time until the increase in volume due to swelling of the grain slows down, preferably until the increase in volume stops. The time for the swelling step is usually 3 hours to 48 hours, preferably 6 hours to 24 hours.

[0044] The temperature in the swelling step is not limited. The temperature in the swelling step is usually a temperature that does not affect the swelling caused by the compound having the starch gelatinizing effect of grains. The temperature in the swelling step is usually 10°C to 40°C, preferably 20°C to 30°C.

[0045] The conditions other than the time and temperature in the swelling step are also not limited. The conditions other than the time and temperature in the swelling step, such as the air pressure and humidity, may be the air pressure and humidity in the usual evaluation location. In addition, the swelling step may be performed with or without stirring, but it is preferable not to stir.

[0046] When using two or more different grains, it is preferable to match the conditions of the swelling process for each grain. Therefore, when evaluating two or more different grains, it is preferable to perform the evaluation at the same time, at the same place, and under the same conditions. However, this does not apply when the effect that may occur from changing the conditions of the swelling process is small or can be eliminated.

[0047] The swelling process causes the grains to absorb starch gelatinizing compounds and / or solvents therein and swell.

[0048] (Swelling ratio calculation process) In the swelling ratio calculation step, after the swelling step, the swelling ratio of the evaluation grain is calculated by dividing the volume of the evaluation grain in contact with A by the volume of the evaluation grain in contact with B. Therefore, the swelling ratio is expressed as (volume of evaluation grain in A) / (volume of evaluation grain in B) or {(volume of evaluation grain in A) / (volume of evaluation grain in B)}×100(%).

[0049] In the present invention, "volume" may be the volume of the evaluation grain itself, but from the viewpoint of ease of measurement, bulk volume is preferable. Therefore, the volume of the evaluation grain in A and the volume of the evaluation grain in B can be measured, for example, when the swelling step is carried out by placing the evaluation grain and A or B in a container such as a graduated cylinder on which a standard for measuring volume is written, by reading the graduation of the graduated cylinder that the evaluation grain reaches after swelling.

[0050] For example, if the swelling process is carried out by placing the evaluation grain and A in a cylindrical container with the same area as the bottom and top, and then placing the evaluation grain and B in another container of the same shape as the first container, the area of ​​the surfaces parallel to the bottom and top from the bottom to the top of the container will be the same as the bottom and top, so the swelling rate can be expressed as the ratio of the length from the bottom of the container where the evaluation grain in A reaches after swelling to the grain, to the length from the bottom of the container where the evaluation grain in B reaches after swelling to the grain.

[0051] The volume may be observed visually, or may be observed by computer analysis of images from photographs, videos, cameras, smartphones, etc., or by AI judgment based on image analysis.

[0052] In the swelling ratio calculation step, the swelling ratio is calculated based on the volume of the grain after the swelling step. However, as described above, the swelling of the grain may cause not only an increase in volume but also changes in physical properties, such as an increase in the grain's weight, a change in refractive index, and a change in elasticity. Therefore, the swelling ratio can also be calculated based on factors other than the volume of the grain after the swelling step, such as the grain's weight, refractive index, and elasticity.

[0053] By calculating the swelling ratio as described above, the influence of swelling caused only by the solvent can be removed from the swelling ratio as described above.

[0054] (Evaluation process) In the evaluation step, the amylopectin side chain structure is evaluated based on the solution concentration of the compound and the swelling ratio.

[0055] In one embodiment, the amylopectin side chain structure is evaluated based on the swelling ratio in a solution concentration of a compound having a predetermined starch gelatinizing action for one or more evaluation grains. In this case, the swelling ratio may be evaluated in a multi-stage evaluation, for example, in three or more stages. The solution concentration of the compound having a predetermined starch gelatinizing action may be multiple. By using multiple solutions, as described above, it becomes easier to quantitatively grasp the swelling property of the grain in the solution of the compound having a starch gelatinizing action, and the characteristic can be quantitatively evaluated accordingly. When there are two or more evaluation grains, the amylopectin side chain structure is evaluated by comparing the swelling ratios of each of the evaluation grains in a solution concentration of the compound having a predetermined starch gelatinizing action. In this case, the higher the swelling ratio of the evaluation grain, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be. In addition, a reference grain with a known amylopectin side chain structure that can serve as an indicator may be used as one of the evaluation grains. This allows the results of one or more evaluation grains to be compared to the results of a reference grain, where the amylopectin side chain structure is known. For example, if the swelling ratio of the evaluation grain is greater than that of the reference grain, the amylopectin side chains in the starch of the evaluation grain are assessed to be shorter than those of the reference grain. If the swelling ratio of the evaluation grain is similar to that of the reference grain, the amylopectin side chains in the starch of the evaluation grain are assessed to be similar to those of the reference grain. If the swelling ratio of the evaluation grain is smaller than that of the reference grain, the amylopectin side chains in the starch of the evaluation grain are assessed to be longer than those of the reference grain.

[0056] In one embodiment, the amylopectin side chain structure is evaluated based on the solution concentration of the compound having starch gelatinizing activity until a predetermined swelling ratio is reached for one or more evaluation grains. In this case, the solution concentration may be evaluated in a multi-stage evaluation, for example, three or more stages. The predetermined swelling ratio may be set, for example, when the volume of the evaluation grain contacted with A becomes 1.1 to 2.0 times, for example, 1.2 times, of the volume of the evaluation grain contacted with B. Alternatively, when a graduated test tube is used as a container for adding grains, the predetermined swelling ratio may be set when the volume of the evaluation grain contacted with A increases by 0.5 to 2 graduations, for example, 1 graduation, of the test tube from the volume of the evaluation grain contacted with B. The predetermined swelling ratio may be multiple. By using multiple swelling ratios, it becomes easier to quantitatively grasp the solution concentration of the compound having starch gelatinizing activity due to the change in swelling ratio, as described above, and it becomes possible to quantitatively evaluate the characteristics accordingly. Also, for example, as the predetermined swelling ratio, a minimum swelling ratio (i.e., swelling ratio (over 0%) at the solution concentration at which the swelling ratio starts to increase (swelling ratio increase start concentration)) and a maximum swelling ratio (i.e., swelling ratio at the solution concentration at which the swelling ratio stops increasing and no further swelling occurs (swelling ratio increase completion concentration)) may be set, and evaluation may be performed at a solution concentration midway between the swelling ratio increase start concentration and the swelling ratio increase completion concentration. When there are two or more evaluation grains, the amylopectin side chain structure is evaluated by comparing the solution concentrations of the compounds having starch gelatinization action until the predetermined swelling ratio is reached. In this case, the lower the solution concentration of the evaluation grain, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be. In addition, a reference grain with a known amylopectin side chain structure that can serve as an index may be used as one of the evaluation grains. This allows the results of one or more evaluation grains to be compared with the results of a reference grain with a known amylopectin side chain structure. For example, if the solution concentration of the evaluation grain is lower than that of the reference grain, the amylopectin side chains contained in the starch in the evaluation grain are evaluated to be shorter than those in the reference grain, and if the solution concentration of the evaluation grain is equivalent to that of the reference grain, the amylopectin side chains contained in the starch in the evaluation grain are evaluated to be equivalent to those in the reference grain.If the solution concentration of the evaluation grain is higher than that of the reference grain, the amylopectin side chains contained in the starch in the evaluation grain are estimated to be longer than those in the reference grain.

[0057] In one embodiment, the amylopectin side chain structure is evaluated for one or more evaluation grains based on the solution concentration of the compound having starch gelatinizing activity at which the swelling ratio starts to increase (swelling ratio increase starting concentration). In this case, the swelling ratio increase starting concentration may be evaluated in a multi-stage evaluation, for example, three or more stages. When there are two or more evaluation grains, the amylopectin side chain structure is evaluated by comparing the solution concentrations of the compounds having starch gelatinizing activity at which the swelling ratio starts to increase. In this case, the lower the swelling ratio increase starting concentration of the evaluation grain, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be. In addition, a reference grain with a known amylopectin side chain structure that can serve as an index may be used as one of the evaluation grains. This allows the results of one or more evaluation grains to be compared with the results of a reference grain with a known amylopectin side chain structure. For example, if the swelling ratio increase starting concentration of the evaluation grain is lower than that of the reference grain, the amylopectin side chains contained in the starch in the evaluation grain are evaluated to be shorter than those of the reference grain. If the swelling ratio increase starting concentration of the evaluation grain is equivalent to that of the reference grain, the amylopectin side chains contained in the starch in the evaluation grain are evaluated to be equivalent to those of the reference grain. If the swelling ratio increase starting concentration of the evaluation grain is higher than that of the reference grain, the amylopectin side chains contained in the starch in the evaluation grain are evaluated to be longer than those of the reference grain.

[0058] In one embodiment, urea is used as a compound having a starch gelatinizing effect, and water is used as a solvent, and the amylopectin side chain structure is evaluated for one or more evaluation grains based on the aqueous urea concentration at which the swelling ratio starts to increase (swelling ratio increase starting concentration). In this case, the swelling ratio increase starting concentration may be evaluated in a multi-stage evaluation, for example, in three or more stages. For example, when the grain is white rice and the swelling ratio increase starting concentration is less than 2.5M, the amylopectin side chains contained in the starch in the grain to be evaluated are short; for example, the short / long chain ratio of the amylopectin side chains fractionated using two gel filtration columns (Jorge Gel 10000 A°, 1000 A°, Alltech, Deerfiled, USA) after isoamylase treatment is evaluated as being 3.15 or more, or the proportion of DP (degree of glucose polymerization) 6 in the amylopectin measured using an HPAEC-PAD system (ICS-6000, Dionex, column: Carbopac PA1) after isoamylase treatment is evaluated as being 0.92 or more, or the proportion of DP6+DP7 is evaluated as being 2.87 or more. When the swelling ratio increase starting concentration is 2.5 M or more and less than 3.1 M, the amylopectin side chains contained in the starch in the evaluation grain are usually evaluated as, for example, the short chain / long chain ratio of the amylopectin side chains is 2.81 to 3.14, or the ratio of DP (degree of glucose polymerization) 6 in the amylopectin is 0.77 to 0.91, or the ratio of DP6 + DP7 is 2.60 to 2.86. When the swelling ratio increase starting concentration is 3.0 M or more, the amylopectin side chains contained in the starch in the evaluation grain are long, for example, the short chain / long chain ratio of the amylopectin side chains is evaluated as 2.80 or less, or the ratio of DP (degree of glucose polymerization) 6 in the amylopectin is evaluated as 0.76 or less, or the ratio of DP6 + DP7 is evaluated as 2.59 or less.

[0059] Furthermore, when the grain is rice, in the evaluation step, the properties of rice such as the gelatinization temperature can be evaluated based on the amylopectin side chain structure contained in starch in the rice evaluated based on the solution concentration of the compound and the swelling ratio. Since the solution concentration of the compound and the swelling ratio are also correlated with properties such as the gelatinization temperature, the properties of rice such as the gelatinization temperature can also be evaluated directly from the solution concentration of the compound and the swelling ratio. In the following aspects, the case where the grain is rice in the present invention is described in detail, but the grain is not limited to rice and may be other than rice.

[0060] In one embodiment, the amylopectin side chain structure is evaluated based on the swelling ratio in a solution concentration of a compound having a predetermined starch gelatinizing action for one or more evaluation target rices, and further, the gelatinization temperature and other properties of the rice are evaluated based on the evaluation results of the amylopectin side chain structure. In this case, the swelling ratio may be evaluated in a multi-stage evaluation, for example, in three or more stages. The solution concentration of the compound having a predetermined starch gelatinizing action may be multiple. By using multiple solutions, as described above, it becomes easy to quantitatively grasp the swelling property of rice in the solution of the compound having a starch gelatinizing action, and the properties can be quantitatively evaluated accordingly. When the evaluation target rice is two or more, the amylopectin side chain structure is evaluated by comparing the swelling ratios of each solution concentration of the compound having a predetermined starch gelatinizing action, and further, the properties of the rice such as the gelatinization temperature are evaluated based on the evaluation results of each amylopectin side chain structure. In this case, the higher the swelling ratio of the rice to be evaluated, the shorter the amylopectin side chain contained in the starch in the rice to be evaluated, and the shorter the amylopectin side chain, the lower the gelatinization temperature of the starch in the rice and the slower the retrogradation, the better the enzymatic digestibility of the steamed rice, the lower the retrogradation of the steamed rice, and the better the solubility of the steamed rice during sake brewing. In addition, as one of the rice to be evaluated, a reference rice may be used whose characteristics, such as the amylopectin side chain structure and / or rice gelatinization temperature, which can serve as an index, are known. This allows the results of one or more rice to be evaluated to be compared with the results of a reference rice whose characteristics, such as the amylopectin side chain structure and / or rice gelatinization temperature, are known. For example, if the swelling rate of the rice to be evaluated is greater than that of the reference rice, the amylopectin side chains contained in the starch in the rice to be evaluated are evaluated to be shorter than those of the reference rice, and based on the evaluation results, the starch in the rice is evaluated to have a lower gelatinization temperature than that of the reference rice and to be slower retrograding, the enzymatic digestibility of the steamed rice is better than that of the reference rice, the retrogradation property of the steamed rice is lower than that of the reference rice, and the solubility of the steamed rice during sake brewing is better than that of the reference rice. If the swelling rate of the rice to be evaluated is equivalent to that of the reference rice, the amylopectin side chains contained in the starch in the rice to be evaluated are evaluated to be equivalent to those of the reference rice, and based on the evaluation results, the properties of the rice, such as the gelatinization temperature, are also evaluated to be equivalent to those of the reference rice.If the swelling ratio of the rice to be evaluated is smaller than that of the reference rice, the amylopectin side chains contained in the starch in the rice to be evaluated are evaluated to be longer than those in the reference rice, and based on the evaluation results, the starch in the rice is evaluated to have a higher gelatinization temperature than that of the reference rice and to be easily aged, the enzymatic digestibility of the steamed rice is worse than that of the reference rice, the aging property of the steamed rice is higher than that of the reference rice, and the solubility of the steamed rice during sake brewing is worse than that of the reference rice. Note that, as mentioned above, the swelling ratio at a solution concentration of a compound having a specified starch gelatinizing effect is correlated with the gelatinization temperature and other properties of the rice, so that the evaluation of the amylopectin side chain structure may be omitted from the swelling ratio, and the gelatinization temperature and other properties of the rice may be evaluated directly.

[0061] In one embodiment, the amylopectin side chain structure is evaluated for one or more evaluation target rice grains based on the solution concentration of a compound having a starch gelatinizing effect until a predetermined swelling ratio is reached, and further, the properties of the rice such as the gelatinization temperature are evaluated based on the evaluation result of the amylopectin side chain structure. In this case, the solution concentration may be evaluated in a multi-stage evaluation, for example, three or more stages. The predetermined swelling ratio may be set, for example, when the volume of the evaluation grain contacted with A becomes 1.1 to 2.0 times, for example, 1.2 times, the volume of the evaluation grain contacted with B. Alternatively, when a graduated test tube is used as a container to which the grain is added, the predetermined swelling ratio may be set when the volume of the evaluation grain contacted with A increases by 0.5 to 2 graduations, for example, 1 graduation, of the test tube from the volume of the evaluation grain contacted with B. The predetermined swelling ratio may be multiple. By using a plurality of swelling ratios, as described above, it becomes easy to quantitatively grasp the solution concentration of the compound having starch gelatinizing action due to the change in swelling ratio, and the above-mentioned characteristics can be quantitatively evaluated accordingly. In addition, for example, as the predetermined swelling ratio, the minimum swelling ratio (i.e., the swelling ratio (more than 0%) at the solution concentration at which the swelling ratio starts to increase (swelling ratio increase start concentration)) and the maximum swelling ratio (i.e., the swelling ratio at the solution concentration at which the swelling ratio stops increasing and no more swelling occurs (swelling ratio increase completion concentration)) may be set, and the evaluation may be performed at the solution concentration at the midpoint between the swelling ratio increase start concentration and the swelling ratio increase completion concentration. When there are two or more rices to be evaluated, the amylopectin side chain structure is evaluated by comparing the solution concentrations of the compound having starch gelatinizing action until the predetermined swelling ratio is reached, and the characteristics of the rice, such as the gelatinization temperature, are further evaluated based on the evaluation results of each amylopectin side chain structure. In this case, the lower the solution concentration of the rice to be evaluated, the shorter the amylopectin side chains contained in the starch in the rice to be evaluated, and the shorter the amylopectin side chains, the lower the gelatinization temperature and the slower the retrogradation of the starch in the rice, the better the enzymatic digestibility of the steamed rice, the lower the retrogradation of the steamed rice, and the better the solubility of the steamed rice during sake brewing.In addition, as one of the rice to be evaluated, a reference rice may be used whose characteristics such as the amylopectin side chain structure and / or rice gelatinization temperature, which can serve as an indicator, are known.This allows the results of one or more evaluation rice samples to be compared with those of a reference rice sample having known properties such as amylopectin side chain structure and / or rice gelatinization temperature. For example, if the solution concentration of the evaluation rice sample is lower than that of the reference rice sample, the amylopectin side chains contained in the starch in the evaluation rice sample are evaluated to be shorter than those of the reference rice sample, and based on the evaluation results, the starch in the rice sample is evaluated to have a lower gelatinization temperature than that of the reference rice sample and to be slow to retrogradate, the enzymatic digestibility of the steamed rice sample is better than that of the reference rice sample, the retrogradation property of the steamed rice sample is lower than that of the reference rice sample, and the solubility of the steamed rice sample during sake brewing is better than that of the reference rice sample. If the solution concentration of the evaluation rice sample is equivalent to that of the reference rice sample, the amylopectin side chains contained in the starch in the evaluation rice sample are evaluated to be equivalent to those of the reference rice sample, and based on the evaluation results, the properties of the rice sample such as the gelatinization temperature are also evaluated to be equivalent to those of the reference rice sample. If the solution concentration of the rice to be evaluated is higher than that of the reference rice, the amylopectin side chains contained in the starch in the rice to be evaluated are evaluated to be longer than those in the reference rice, and based on the evaluation results, the starch in the rice is evaluated to have a higher gelatinization temperature than that of the reference rice and to be easily retrograded, the enzymatic digestibility of the steamed rice is worse than that of the reference rice, the retrogradation property of the steamed rice is higher than that of the reference rice, and the solubility of the steamed rice during sake brewing is worse than that of the reference rice. Note that, as described above, the solution concentration of the compound having a starch gelatinizing effect until a specified swelling rate is reached is correlated with the properties of rice such as the gelatinization temperature, so that the evaluation of the amylopectin side chain structure may be omitted from the solution concentration, and the properties of rice such as the gelatinization temperature may be evaluated directly.

[0062] In one embodiment, the amylopectin side chain structure is evaluated for one or more evaluation target rice varieties based on the solution concentration of the compound having starch gelatinizing activity at which the swelling ratio starts to increase (swelling ratio increase starting concentration), and the rice properties such as the gelatinization temperature are further evaluated based on the evaluation results of the amylopectin side chain structure. In this case, the swelling ratio increase starting concentration may be evaluated in a multi-stage evaluation, for example, three or more stages. When the evaluation target rice varieties are two or more, the amylopectin side chain structure is evaluated by comparing the solution concentrations of the compound having starch gelatinizing activity at which the swelling ratio starts to increase, and the rice properties such as the gelatinization temperature are further evaluated based on the evaluation results of each amylopectin side chain structure. In this case, the lower the swelling ratio increase starting concentration of the rice to be evaluated, the shorter the amylopectin side chain contained in the starch in the rice to be evaluated, and the shorter the amylopectin side chain, the lower the gelatinization temperature of the starch in the rice and the slower the retrogradation, the better the enzymatic digestibility of the steamed rice, the lower the retrogradation of the steamed rice, and the better the solubility of the steamed rice during sake brewing. In addition, as one of the rice to be evaluated, a reference rice may be used whose characteristics, such as the amylopectin side chain structure and / or rice gelatinization temperature, which can serve as an index, are known. This allows the results of one or more rice to be evaluated to be compared with the results of a reference rice whose characteristics, such as the amylopectin side chain structure and / or rice gelatinization temperature, are known. For example, if the swelling ratio increase starting concentration of the rice to be evaluated is lower than that of the reference rice, the amylopectin side chains contained in the starch in the rice to be evaluated are evaluated to be shorter than that of the reference rice, and based on the evaluation results, the starch in the rice is evaluated to have a lower gelatinization temperature than that of the reference rice and to be slow to retrogradate, the enzymatic digestibility of the steamed rice is better than that of the reference rice, the retrogradation property of the steamed rice is lower than that of the reference rice, and the solubility of the steamed rice during sake brewing is better than that of the reference rice. If the swelling ratio increase starting concentration of the rice to be evaluated is equivalent to that of the reference rice, the amylopectin side chains contained in the starch in the rice to be evaluated are evaluated to be equivalent to that of the reference rice, and based on the evaluation results, the properties of the rice, such as the gelatinization temperature, are also evaluated to be equivalent to those of the reference rice.If the swelling ratio increase starting concentration of the rice to be evaluated is higher than that of the reference rice, the amylopectin side chains contained in the starch in the rice to be evaluated are evaluated to be longer than that of the reference rice, and based on the evaluation results, the starch in the rice is evaluated to have a higher gelatinization temperature than that of the reference rice and to be easily retrograded, the enzymatic digestibility of the steamed rice is worse than that of the reference rice, the retrogradation property of the steamed rice is higher than that of the reference rice, and the solubility of the steamed rice during sake brewing is worse than that of the reference rice. Note that, as described above, the swelling ratio increase starting concentration is correlated with the properties of rice such as the gelatinization temperature, so that the evaluation of the amylopectin side chain structure may be omitted from the swelling ratio increase starting concentration and the properties of rice such as the gelatinization temperature may be evaluated directly.

[0063] In one embodiment, urea is used as a compound having a starch gelatinizing effect, and water is used as a solvent, and the amylopectin side chain structure is evaluated for one or more evaluation target rice grains based on the aqueous solution concentration of urea at which the swelling ratio starts to increase (swelling ratio increase starting concentration). In this case, the swelling ratio increase starting concentration may be evaluated in a multi-stage evaluation, for example, an evaluation in three stages or more. For example, when the grain is polished rice and the swelling ratio increase starting concentration is less than 2.5M, the amylopectin side chains contained in the starch in the evaluation rice are short, for example, the short chain / long chain ratio of the amylopectin side chains fractionated with two gel filtration columns (Jorge Gel 10000 A°, 1000 A°, Alltech, Deerfiled, USA) after isoamylase treatment is evaluated to be 3.15 or more, or .... The ratio of DP (degree of glucose polymerization) 6 in amylopectin measured by PA1) is evaluated as 0.92 or more, or the ratio of DP6 + DP7 is evaluated as 2.87 or more, and based on the evaluation results, the starch in the polished rice is evaluated as having a low gelatinization temperature and slow retrogradation, the enzymatic digestibility of the steamed rice is good, the retrogradation of the steamed rice is low, and the steamed rice solubility during sake brewing of the polished rice is evaluated as good. When the swelling ratio increase starting concentration is 2.5M or more and less than 3.1M, the amylopectin side chain contained in the starch in the evaluated rice is evaluated as normal, for example, the short chain / long chain ratio of the amylopectin side chain is evaluated as 2.81 to 3.14, or the ratio of DP (degree of glucose polymerization) 6 in amylopectin is evaluated as 0.77 to 0.91, or the ratio of DP6 + DP7 is evaluated as 2.60 to 2.86, and based on the evaluation results, the gelatinization temperature and other characteristics of the rice are also evaluated as normal. When the swelling ratio increase starting concentration is 3.1 M or more, the amylopectin side chains contained in the starch in the evaluation rice are evaluated as being long, for example, the short chain / long chain ratio of the amylopectin side chains is evaluated as being 2.80 or less, or the proportion of DP (degree of glucose polymerization) 6 in the amylopectin is evaluated as being 0.76 or less, or the proportion of DP6 + DP7 is evaluated as being 2.59 or less, and based on the evaluation results, it is evaluated that the starch in the white rice has a high gelatinization temperature and is easily aged, that the enzymatic digestibility of steamed rice is poor, that the aging tendency of steamed rice is high, and that the solubility of steamed rice during sake brewing from white rice is poor.As described above, the swelling ratio increase starting concentration is correlated with rice properties such as the gelatinization temperature. Therefore, it is possible to directly evaluate rice properties such as the gelatinization temperature from the swelling ratio increase starting concentration without evaluating the amylopectin side chain structure.

[0064] The gelatinization temperature of rice, the enzymatic digestibility of steamed rice, and the retrogradation property of steamed rice, which are correlated with the solution concentration of the compound and the swelling ratio in the present invention, can be measured as follows.

[0065] The gelatinization temperature of rice mentioned above typically refers to the gelatinization temperature measured by a differential scanning calorimeter (DSC) or a rapid visco analyzer (RVA).

[0066] The gelatinization temperature by DSC can be determined by the following method. Specifically, several mg of a sample is precisely weighed, and 2 to 4 times the weight of distilled water is added and mixed, and then sealed in a measurement cell. Distilled water is placed in a reference cell as a standard substance. The measurement conditions for DSC are to raise the temperature from about 20°C to about 120°C at a heating rate of about 5°C to 10°C per minute. As the temperature rises, starch gelatinization begins, and a peak is observed due to an endothermic reaction, and the gelatinization start temperature, gelatinization peak temperature, and gelatinization end temperature can be determined by a control analysis system. The gelatinization start temperature may be used as the gelatinization temperature, or the gelatinization peak temperature, which is not determined by the operator's judgment, may be used as the gelatinization temperature. The aging characteristics by DSC can be determined by storing the heated cell at 4°C to room temperature for about 1 to 2 weeks and then performing DSC analysis again, or by performing DSC analysis on the aged sample under the above conditions, and calculating the amount of aging from the endothermic enthalpy determined by the control analysis system from the amylopectin recrystallization peak observed due to the endothermic reaction.

[0067] The gelatinization temperature by RVA can be determined by the following method. Specifically, using an RVA (Rapid Visco Analyzer), a rice flour suspension is heated from about 50°C to about 95°C while rotating a paddle at a constant speed, and then held at about 95°C for several minutes. The temperature is then lowered to about 50°C and held at about 50°C for several minutes. This is the program used to measure the change in viscosity of the sample. As the temperature increases, starch gelatinization begins and an increase in viscosity is observed. The temperature at which the viscosity begins to increase, the peak viscosity, the breakdown, and the setback value can be determined by the control and analysis system. The pasting temperature (the temperature at which the viscosity begins to increase) is used as the gelatinization temperature.

[0068] The enzymatic digestibility of steamed rice means the ease of digestion by enzymes in the steamed rice state. Here, the enzymes are saccharification enzymes, and typically include one or more saccharification enzymes selected from α-amylase and glucoamylase. Therefore, the enzymatic digestibility of steamed rice can be evaluated using crude enzymes that include α-amylase, glucoamylase as another saccharification enzyme, and proteases and peptidases as proteolytic enzymes. Alternatively, the test may be performed using enzymes extracted from koji or koji itself.

[0069] The enzymatic digestibility of steamed rice using the crude enzyme can be evaluated by the following procedure. First, 10 g of polished rice is soaked in water overnight, drained the next day, and steamed for 45 minutes. The steamed rice is then cooled to room temperature, placed in a vinyl bag with a zipper, and left at 15°C for a certain period of time. It is then reacted with the enzyme solution of the crude enzyme. The reaction conditions are 15°C and 24 hours. After the reaction, the solid and liquid are separated by centrifugation or the like, and the Brix value (unit: ° or %) of the liquid portion is measured with a saccharometer. The obtained Brix value is regarded as the enzymatic digestibility of the steamed rice.

[0070] The retrogradation property of steamed rice means the ease with which steamed rice retrogrades. Specifically, the retrogradation property of steamed rice can be calculated according to the following formula. Staling of steamed rice (%) = 100 - (enzyme digestibility of steamed rice aged for 6 hours / enzymatic digestibility of steamed rice aged for 1 hour) x 100

[0071] Here, in the formula, "enzymatic digestibility of steamed rice aged for 6 hours" refers to the enzymatic digestibility of steamed rice when the time for leaving the rice at 15°C before reacting with the enzyme solution of the crude enzyme is set to 6 hours. Specifically, "enzymatic digestibility of steamed rice aged for 6 hours" can be obtained by the following procedure. First, 10 g of polished rice is soaked in water overnight, drained the next day, steamed for 45 minutes, cooled to room temperature, placed in a plastic bag with a zipper, and left at 15°C for 6 hours. After that, the rice is reacted with the enzyme solution of the crude enzyme for 24 hours at 15°C, and then the solid and liquid are separated by centrifugation or the like, and the Brix value of the liquid portion is measured with a saccharometer. The obtained Brix value is called "enzymatic digestibility of steamed rice aged for 6 hours".

[0072] Similarly, the "enzymatic digestibility of steamed rice aged for one hour" can also be determined by the following procedure. First, 10 g of polished rice is soaked in water overnight, drained the next day, and steamed for 45 minutes. The steamed rice is then cooled to room temperature, placed in a plastic bag with a zipper, and left at 15°C for one hour. After that, the rice is reacted with the enzyme solution of the crude enzyme for 24 hours at 15°C, after which the solid and liquid are separated by centrifugation or the like, and the Brix value of the liquid portion is measured with a saccharometer. The obtained Brix value is the "enzymatic digestibility of steamed rice aged for one hour."

[0073] The solubility of steamed rice during sake brewing refers to the solubility of rice in mash formed during sake brewing using rice as a raw material. Steamed rice is used for mash. The higher the solubility, the easier it is for steamed rice to dissolve in mash, and the lower the solubility, the harder it is to dissolve in mash and the easier it is for the grain shape to remain. The solubility of steamed rice during sake brewing depends on factors such as the amylopectin side chain structure contained in the starch in the rice, the gelatinization temperature of the rice, the retrogradation of the steamed rice, and the enzymatic digestibility of the steamed rice.

[0074] According to the present invention, the characteristics of grains, such as the gelatinization temperature of raw rice, which previously required a great deal of effort to determine, can be determined inexpensively, simply, and accurately using a small amount of sample. In other words, the suitability of sake rice for sake brewing, which could only be known after brewing, can now be known in advance, which can contribute greatly to sake production management and can be useful in improving the quality of sake. Furthermore, in the field of sake rice breeding and cultivation, the present invention can be applied to the selection of sake rice having the desired characteristics, such as solubility, and the improvement of cultivation methods, without the need to introduce expensive analytical equipment. Furthermore, the characteristics such as swelling ratio obtained by this evaluation method can contribute to the accumulation of new academic knowledge in the evaluation of rice variety characteristics, thereby contributing to the field of grain science.

[0075] Furthermore, the present invention also relates to a kit for evaluating the amylopectin side chain structure contained in the starch in the grain of the present invention. As described above, the kit of the present invention can also be used to evaluate the gelatinization temperature of rice, the enzymatic digestibility of steamed rice, the retrogradation property of steamed rice, and the solubility of steamed rice during sake brewing.

[0076] The kit of the present invention comprises two or more identical containers and a compound having a starch gelatinizing activity.

[0077] The number of containers of the same shape is not limited as long as the volume change of the grain contained therein can be observed. The containers of the same shape are preferably ones having a standard for measuring the volume, such as a graduated cylinder. The containers of the same shape are preferably transparent tubular containers such as test tubes and polystyrene bottles.

[0078] The compound having starch gelatinizing activity is as described above. The amount of the compound having starch gelatinizing activity is not limited as long as it is the amount necessary to swell grain. The compound having starch gelatinizing activity is preferably prepared, for example, tableted or divided into small portions, so that a certain concentration can be ensured, for example, by adding it to the container and further adding a solvent.

[0079] By using the kit of the present invention, it is possible to evaluate the amylopectin side chain structure contained in the starch in the grain of the present invention, and further to evaluate the gelatinization temperature of rice, the enzymatic digestibility of steamed rice, the retrogradation property of steamed rice, and the solubility of steamed rice during sake brewing. EXAMPLES

[0080] <Test 1. Evaluation of enzymatic digestibility of steamed rice by swelling with urea> (Test 1-1) Evaluation of absorption and swelling of urea aqueous solution by planar observation using a petri dish (method) The grains used for evaluation were Yamada Nishiki (Hiroshima) harvested in 2009 and 2010, with a polishing ratio of 70% and moisture content of 13.5%, and Gohyakumangoku (Niigata) harvested in 2018.

[0081] For each of the above sake rice varieties, the following evaluation indices for the enzymatic digestibility of steamed rice were measured: DSC gelatinization temperature (℃), RVA gelatinization temperature (℃), enzymatic digestibility of steamed rice left in the air for 1 hour, 3 hours, or 6 hours (digestibility of steamed rice left in the air for 1 hour, 3 hours, or 6 hours) (°Brix), and retrogradation (%). Each measurement was performed under the following conditions.

[0082] The DSC gelatinization temperature (℃) was analyzed using a DSC7000X manufactured by Hitachi High-Tech Science Corporation. First, approximately 3.5 mg of the sample was precisely weighed, mixed with 12 μL of distilled water, and sealed in a pressure-resistant cell. Next, the temperature was raised from 20°C to 120°C at a heating rate of 5°C per minute. 20 mg of alumina oxide was used as the reference material. The gelatinization onset temperature (T0), gelatinization peak temperature (T p ) was sought.

[0083] The RVA gelatinization temperature was analyzed using an RVA-TecMaster manufactured by Perten. A rice flour suspension (9% (W / W), total weight 28 g) was held at 50°C for 1 minute, then heated to 95°C at 5°C / min, held at 95°C for 5 minutes, then cooled to 50°C at 5°C / min, and held at 50°C for 6 minutes. The paddle rotation speed was kept constant at 160 rpm. The pasting temperature (temperature at which viscosity begins to increase) was calculated automatically by computer.

[0084] The digestibility (°Brix) of steamed rice left in the air for 1 hour, 3 hours, or 6 hours was measured as follows. First, 10 g of polished rice polished to 70% was placed in a wire mesh basket and soaked in water at 15°C for 15 to 20 hours, and then the soaked rice was drained. The soaked rice was steamed for 45 minutes using a small strainer (M-11, Eishin Denki Co., Ltd.). After steaming, the steamed rice was removed from the strainer, cooled to room temperature, and placed in a vinyl bag with a zipper and left at 15°C for 1 hour, 3 hours, or 6 hours. The left steamed rice was placed in 50 mL of enzyme solution (α-amylase 60 U / mL, glucoamylase 24 U / mL, peptidase (peptidase R, Amano Enzyme Co., Ltd.) 3 U / mL, 0.1 M succinate buffer pH 4.3) and enzymatically digested at 15°C for 24 hours. After the reaction was completed, the mixture was centrifuged at 2000×g for 10 minutes, and the °Brix of the supernatant was measured using a digital saccharometer (DIGITAL REFRACTOMETER PR-100, manufactured by Atago Co., Ltd.).

[0085] The retrogradation rate (%) was calculated from the following formula, taking the above-mentioned 1 hour steamed rice digestibility after leaving in the air as the steamed rice enzymatic digestibility (°Brix) of steamed rice aging for 1 hour, and the above-mentioned 6 hours steamed rice digestibility after leaving in the air as the steamed rice enzymatic digestibility (°Brix) of steamed rice aging for 6 hours. Staling of steamed rice (%) = 100-(enzymatic digestibility of steamed rice aged for 6 hours / enzymatic digestibility of steamed rice aged for 1 hour) x 100

[0086] Urea was used as a compound having a starch gelatinizing effect, and the absorption and swelling properties of an aqueous urea solution (urea absorption and swelling rate) of each of the above-mentioned sake rice varieties were evaluated according to the following procedure.

[0087] In the following urea absorption and swelling rate tests, sake rice samples were adjusted to a polishing ratio of 70% and a moisture content of 13.5%.

[0088] As the urea aqueous solutions, aqueous solutions with urea concentrations ranging from 2.2 M to 4.4 M in increments of 0.1 M were prepared.

[0089] The urea absorption and swelling ratio were evaluated by planar observation using a 12-well plate. The swelling ratio increase starting concentration was defined as the concentration at which the swelling ratio started to increase, calculated by dividing the volume of the target rice in contact with the urea aqueous solution by the volume of the target rice in contact with water.

[0090] 1.5mL to 3.5mL of urea solution was placed in a circular polystyrene dish with an inner diameter of 25mm and a height of 17mm, and Yamada-Nishiki harvested in 2009, which has a polishing ratio of 70% and a moisture content of 13.5%, giving good solubility, and Yamada-Nishiki harvested in 2010 and Gohyakumangoku harvested in 2018, which have poorer solubility than Yamada-Nishiki harvested in 2009, were evaluated. Sake rice samples were spread on the bottom of each dish, immersed in the urea solution, and left to stand at 30℃ for one day.

[0091] (result) The results are shown in Figure 1. As shown in Figure 1, in all samples, as the concentration increased, starch gelatinized and rice grains swelled. The swelling rate increase start concentration for Yamada-Nishiki harvested in 2009, which has good solubility, was 2.6M, while the swelling rate increase start concentration for Yamada-Nishiki harvested in 2010 and Gohyakumangoku harvested in 2018 was 3.4M. In other words, it was possible to evaluate the raw rice as being easy to dissolve when swelling started at low concentrations, and difficult to dissolve when swelling started at high concentrations. With regard to the liquid volume, it was observed that the liquid was completely absorbed as gelatinization occurred at 1.5mL to 3.5mL, but the swelling start concentration and the concentration at which the liquid was completely absorbed were lower for the 2009 harvest than for the 2010 harvest at all liquid volumes.

[0092] Therefore, it was found that by spreading rice on the bottom of a petri dish and observing the surface, the gelatinization characteristics and solubility of rice can be determined based on the degree of swelling of the rice grains that occurs during starch gelatinization and the degree of water absorption by the solution.

[0093] (Test 1-2) Evaluation of absorption and swelling of urea aqueous solution by stereoscopic observation using a polystyrene bottle (method) The samples used were from different years, varieties, and production areas: Ginpu (Hokkaido), Yamadanishiki (Hyogo, Hiroshima), Ginginga (Iwate), Dewasansan (Yamagata), Nihonbare (Shiga, Hiroshima), Gohyakumangoku (Fukushima, Tochigi, Niigata, Fukui), and Nihonbare (Shiga) harvested in 2017 and 2018, Okuhomare (Fukui) harvested in 2018, and Yamadanishiki (Hiroshima) harvested from 2014 to 2016.

[0094] As samples with different moisture contents, we used polished rice samples of Nipponbare and Yamadanishiki varieties harvested in 2014 with moisture contents ranging from 10.1% to 14.9% and a polishing ratio of 70%.

[0095] For each of the above sample rice, the DSC gelatinization temperature (℃), retrogradation rate (%), and enzymatic digestibility (°Brix) of steamed rice left in the air for 6 hours were measured, which are existing indices for evaluating the enzymatic digestibility of steamed rice. Each measurement was performed under the conditions described above.

[0096] The absorption and swelling properties of the urea aqueous solution (urea absorption and swelling rate) of each of the sample rices were evaluated according to the following procedure.

[0097] In the following urea absorption and swelling tests, sake rice samples were adjusted to a polishing ratio of 70% and a moisture content of 13.5%.

[0098] As the urea aqueous solutions, aqueous solutions having urea concentrations in the range of 2.2 M to 4.2 M or 2.2 M to 5.0 M in increments of 0.1 M were prepared.

[0099] The swelling rate of rice was evaluated by placing 1 g of polished rice and 5 mL of urea solution in a 15 mL transparent polystyrene bottle and leaving it overnight at 30°C, and then evaluating the urea absorption and swelling rate.

[0100] (result) By using a 15 mL polystyrene bottle, it was possible to observe swelling in three dimensions. Using samples with different enzyme digestibility and DSC gelatinization temperatures of steamed rice, the urea concentration differed depending on the sample, but in all samples, it was observed that the rice grains absorbed the urea aqueous solution and swelled as the urea concentration increased (Figure 2). Furthermore, in all samples, a concentration was observed at which 5 mL of solution was completely absorbed (complete absorption concentration). Comparing the samples, the swelling ratio increase starting concentration and complete absorption concentration were low in samples with low gelatinization temperatures and high digestibility, while the swelling ratio increase starting concentration and complete absorption concentration were high in samples with high gelatinization temperatures and low digestibility (Figure 2).

[0101] To find a quantitative solution, the urea absorption and swelling rate were evaluated. The concentration at which the rice reached half its capacity, the concentration at which no liquid was visible when viewed from the side (complete absorption concentration (1)), and the concentration at which no liquid dripped from the rice when the polystyrene bottle was turned sideways (complete absorption concentration (2)) were evaluated. To examine whether the solubility of rice could be evaluated based on the determined concentration, the relationship between the DSC gelatinization temperature, the RVA viscosity rise temperature, and the enzyme digestibility of steamed rice was analyzed.

[0102] There was a correlation between the three concentrations that were determined. As shown in Figures 3 to 5, all of the determined concentrations showed a high correlation with the DSC gelatinization temperature, RVA viscosity rise temperature, enzymatic digestibility of steamed rice, and retrogradation of steamed rice. Therefore, it was found that the swelling property of rice correlates with the molecular structure, particularly the side chain structure, of the amylopectin contained in the starch in rice, and as a result, the enzymatic digestibility of steamed rice can be estimated with a high degree of accuracy.

[0103] (Test 1-3) Evaluation of absorption and swelling rate of urea aqueous solution by stereoscopic observation using test tubes (method) The samples used were from different years, varieties, and production areas: Yamadanishiki (Hiroshima) harvested in 2009, 2010, and 2014-2016; Ginpu (Hokkaido), Yamadanishiki (Hyogo, Hiroshima), Ginginga (Iwate), Dewasansan (Yamagata), Nihonbare (Shiga, Hiroshima), Gohyakumangoku (Fukushima, Tochigi, Niigata, Fukui), Nihonbare (Shiga), and Okuhomare (Fukui) harvested in 2018. As samples with different moisture contents, we used white rice made from Yamadanishiki rice harvested in 2018 with a moisture content of 10.2% to 15.0% and a polishing ratio of 70%. As samples with different polishing ratios, we used Yamadanishiki rice from the 2017 and 2018 harvests, with polishing ratios of 40% and 70%.

[0104] The side chain structure of amylopectin was analyzed as follows. 20 mg of rice flour defatted with methanol was mixed with 5 mL of distilled water and gelatinized in boiling water for 1 hour. 50 μL of 600 mM sodium acetate buffer (pH 4.0), 10 μL of 2% sodium azide, and 25 μL of 500 U isoamylase were added to 1 mL of the gelatinized solution, and the enzyme reaction was carried out at 40°C for 24 hours. 120 μL of a reducing agent (3% ammonia, 0.5% sodium tetrahydroborate) was added and reacted overnight, after which the reducing agent was added again and reacted for another 7 hours for reduction treatment. After reduction treatment, the mixture was freeze-dried, dissolved with 100 μL of 1N NaOH, added with 900 μL of distilled water, filtered through a filter, and subjected to HPLC analysis. HPLC was measured using an HPAEC-PAD system (ICS-6000, Dionex, column: Carbopac PA1). The mobile phase was 100 mM NaOH as solution B and 100 mM NaOH + 600 mM AcONa as solution C, and the gradient program was 0 min: solution B: solution C = 5:95-120 min: solution B: solution C = 20:80. From the relative values ​​of the peak areas from glucose polymerization degree (DP) DP6 to DP61, the glucose polymerization degrees DP6, DP7, DP6 + DP7, DP6 / DPΣ (6-24), (DP6 + DP7) / Σ (DP6-DP24), and Σ (DP6-DP8) were evaluated as indicators of the proportion of short chains in amylopectin.

[0105] For each of the above sake rice varieties, the DSC gelatinization temperature (℃), retrogradation rate (%), and steamed rice digestibility (°Brix) after leaving in the air for 6 hours were measured, which are existing indices for evaluating the enzymatic digestibility of steamed rice. Each measurement was performed under the conditions described above.

[0106] The swelling rate of rice was evaluated using 13 mL disposable tubes with an elongated shape to make it easier to observe the change in the shape of the rice grains. 4 mL to 12 mL of solution was placed in each tube, with the weight of rice being 0.8 g, and the tubes were left overnight at 30°C to evaluate the urea absorption and swelling rate.

[0107] (result) First, the amount of solution was examined at 4mL, 8mL, and 12mL using Yamada-nishiki rice harvested in 2009, which has good solubility, and Yamada-nishiki rice harvested in 2010, which has poor solubility. As shown in Figure 6, the range of concentration from gelatinization to complete absorption (complete absorption concentration) was wider for 8mL and 12mL than for 4mL. In the case of disposable tubes containing 8mL and 12mL of solution, the change in the height direction was clearer than in the case of a 15mL polystyrene bottle, and it was easier to judge the concentration, including intermediate concentrations, from the concentration at which the swelling rate began to increase to the concentration at which the rice was completely absorbed. In terms of the height of the rice in the disposable tube, the scale on the disposable tube indicated that the rice was 1.5mL to 2mL at a concentration at which the rice was not swelling, but was 6.0mL to 8.5mL at a concentration at which the urea solution was completely absorbed, which means that the rice had swelled about four times in the height direction.

[0108] Next, the effect of reaction time was examined using the same samples with 12 mL of solution. As shown in Figure 7, with the 2009 harvest, which has good solubility, swelling began to be clearly observed after 1 hour, and became almost constant after 5 hours. With the 2010 harvest, which has poor solubility, swelling did not progress after 1 hour, but became clear after 5 hours, and became almost constant after 8.5 hours. Therefore, a judgment was possible after about 6 to 9 hours, and it was also possible to make a judgment without any problems after 1 or even 2 days.

[0109] Using this method, when comparing samples from different varieties and origins with a rice polishing ratio of 70% and a moisture content of 13.5%, as shown in Figure 8 (Figures 8-1 to 8-2), the samples with low gelatinization temperatures and high digestibility had low concentrations at which the swelling ratio began to increase and the complete absorption concentration were low, while the samples with high gelatinization temperatures and low digestibility had high concentrations at which the swelling ratio began to increase and the complete absorption concentration were high.

[0110] In this experiment, as shown by the arrow, the urea concentration at which the height of the rice in each sample swelled by about 10% based on the height of the rice in water that did not contain urea, that is, the urea concentration at which the swelling rate reached 110% (110% swelling rate concentration) was measured. The complete absorption concentration was the concentration at which the aqueous solution was completely absorbed. The average value of the 110% swelling rate concentration and the complete absorption concentration was taken as the intermediate swelling concentration.

[0111] The relationship between urea concentration and the short chain ratio of amylopectin was analyzed. As a result, as shown in Figure 9-1, the urea concentration at 110% swelling ratio, intermediate swelling concentration, and complete absorption concentration all showed an extremely high negative correlation with the short chain ratio of amylopectin, and the lower the short chain ratio of amylopectin, the higher these concentrations were. In other words, it was found that the side chain structure of amylopectin can be evaluated by the urea swelling concentration.

[0112] Next, in order to examine the solubility of rice depending on the urea concentration, the relationship between the DSC gelatinization temperature, the RVA viscosity rise temperature, and the enzymatic digestibility of steamed rice was analyzed. As a result, as shown in Figure 9 (Figures 9-2 to 9-4), a high correlation was observed between the DSC gelatinization temperature, the RVA viscosity rise temperature, the enzymatic digestibility of steamed rice, and the aging property of steamed rice at any concentration. The enzymatic digestibility was measured when the steamed rice was left in the air for 1 hour, 3 hours, or 6 hours, and the longer the left in the air time, the higher the correlation. Since the influence of the starch molecular structure increases when the left in the air time is extended, it is considered that the method of the present invention can estimate the enzymatic digestibility influenced by the starch molecular structure. Even when compared with the DSC gelatinization temperature and the RVA viscosity rise start temperature, which can estimate the enzymatic digestibility, the estimation of the enzymatic digestibility by the method of the present invention was as accurate as that by the method of the present invention.

[0113] Next, the effect of the moisture content of the rice was examined (Figure 10). The degree of increase in swelling ratio differed depending on the moisture content of the rice, and when comparing solutions with the same urea concentration, there was a tendency for the swelling ratio to be high for rice with a low moisture content and low for rice with a high moisture content. On the other hand, the concentration at which the swelling ratio began to increase was determined to be about 0.2 M higher for Nipponbare at around 15.5% compared to 14% or less, possibly due to poor water absorption, but was almost constant at 14% or less regardless of moisture content.

[0114] Next, the effect of rice polishing ratio was examined at rice polishing ratios of 40% and 70%. The results showed that the swelling ratio increase concentration and complete absorption concentration were consistent regardless of rice polishing ratio (Figure 11).

[0115] Therefore, it was found that the method of the present invention makes it possible to estimate the enzymatic digestibility of steamed rice with high accuracy by determining the concentration at which the swelling ratio begins to increase, regardless of the moisture content of white rice and the rice polishing rate.

[0116] <Test 2. Evaluation of steamed rice digestibility by determining swelling ratio with guanidine hydrochloride and DMSO> (method) The samples used were Yamadanishiki rice from 2009, with a polishing ratio of 70% and moisture content of 13.5%, which has good solubility, and Yamadanishiki rice from 2010 and Gohyakumangoku rice from 2018, which have poorer solubility than Yamadanishiki rice from 2009. 0.8 g of rice grains and 12 mL of aqueous solutions of guanidine hydrochloride and DMSO with graded concentrations were added to a 13 mL disposable tube and mixed. After keeping the mixture at 30°C for two days, the swelling property of the rice was observed and the concentration at which the swelling ratio began to increase was determined.

[0117] (result) As shown in Figure 12, swelling of rice grains was observed in all samples as the concentration increased, but while the 2009 Yamadanishiki, which has good solubility, began to increase in swelling rate at low guanidine hydrochloride and DMSO concentrations, the 2010 Yamadanishiki and 2018 Gohyakumangoku, which have poor solubility, began to increase in swelling rate at higher solution concentrations. In other words, even when guanidine hydrochloride or DMSO was used as a compound with starch gelatinization, it was possible to evaluate the raw rice as being easy to dissolve steamed rice in cases where the swelling rate began to increase at low concentrations, as with urea, and difficult to dissolve steamed rice in cases where the swelling rate began to increase at high concentrations. In other words, it was possible to evaluate the solubility of steamed rice not only by using urea as a compound with starch gelatinization, but also by using compounds with starch gelatinization such as guanidine hydrochloride and DMSO.

[0118] <Test 3. Evaluation of grains such as long grain rice and wheat> (method) Grains such as long-grain rice and wheat were evaluated. As samples with different gelatinization temperatures, the gelatinization characteristics of four long-grain white rice samples (varieties: Saliqueen, Basmati, Hoshiyutaka, Yumejuiro, polishing ratio 91%) and four barley samples (one polished barley sample, and buckwheat) were evaluated. The DSC gelatinization temperature (°C) of each of the above samples was measured under the conditions described above.

[0119] The swelling rate was evaluated using a 13 mL disposable tube with an elongated shape to make it easier to observe the change in the shape of the grain. 0.8 g of grain and 12 mL of solution were placed in the disposable tube and left at 30°C overnight, and the urea absorption and swelling rate were evaluated.

[0120] (result) The degree of swelling differed depending on the sample, but the results of measuring the swelling onset concentration with this kit showed that for long-grain rice, samples with low DSC gelatinization temperatures, such as samples A to D in Figure 13, had a low swelling onset concentration, while samples with high DSC gelatinization temperatures had a high swelling onset concentration. For barley and buckwheat, too, samples with low gelatinization temperatures, such as samples E to H in Figure 13, had a low swelling onset concentration, while samples with high gelatinization temperatures had a high swelling onset concentration.

[0121] In other words, even for long-grain rice and barley other than Japonica rice, the correlation coefficient between the swelling onset concentration and the gelatinization temperature measured by DSC showed an extremely high correlation of 0.95.

[0122] In other words, the present invention made it possible to grasp the tendency of gelatinization properties for grains that contain starch. In other words, the present kit can be used to evaluate the gelatinization properties of starch for grains that contain starch, not just rice.

[0123] <Test 4. Evaluation of starch retrogradation properties> (method) Starch retrogradation characteristics were evaluated using 8 or 10 samples from the samples that were observed for swelling of rice grains in Test 1-3. Starch retrogradation characteristics were analyzed by DSC to measure the peaks resulting from the recrystallization of amylopectin in retrograded starch. The samples were evaluated for retrograded starch in the following two ways. In the first case, white rice flour (10 samples) was heated from 20°C to 120°C at a heating rate of 5°C per minute by DSC. After the measurement, the cells were stored at 4°C for 13 days and then analyzed by DSC again under the same conditions. 20 mg of alumina oxide was used as the reference material. The endothermic enthalpy (J / g) of the peak due to the recrystallization of amylopectin was calculated automatically by computer. The degree of retrogradation of starch was determined by the amount of endothermic enthalpy after retrogradation as an index of starch retrogradation. The ratio of the amount of enthalpy after retrogradation divided by the heat of fusion of amylopectin in raw starch was determined as the degree of amylopectin retrogradation. Secondly, steamed rice (8 samples) was left at 15℃ for 24 hours, then dehydrated with ethanol three times and acetone once, and evaluated by DSC. The endothermic enthalpy after retrogradation was used as an index of starch retrogradation.

[0124] (result) Figures 14A and B show the results of evaluating the retrogradation characteristics of starch and amylopectin, which accounts for the majority of starch retrogradation, for samples that were stored for 13 days after DSC measurement of white rice flour. Figure 14C shows the results of evaluating the retrogradation characteristics of starch during storage in steamed rice. As shown in Figures 14A to C, in all cases, the retrogradation characteristics of starch showed an extremely high correlation with the 110% swelling ratio concentration, intermediate swelling concentration, and complete absorption concentration. In other words, it was made clear that the higher the urea swelling concentration, the more likely it is that retrogradation will progress.

[0125] The aging characteristics can be evaluated by actually aging the material and then evaluating the degree of aging. However, if data matching the aging conditions is accumulated in advance, it is possible to evaluate the aging characteristics from the urea swelling concentration.

Claims

1. A method for evaluating an amylopectin side chain structure contained in starch in grain, comprising the steps of: A contacting step of contacting the evaluation grain with the following A and B, A: Compounds and solvents having starch gelatinizing properties B: the solvent a swelling step of swelling the evaluation grain by the contact step; a swelling ratio calculation step of calculating the swelling ratio of the evaluation grain after the swelling step by dividing the volume of the evaluation grain contacted with A by the volume of the evaluation grain contacted with B; and An evaluation step of evaluating the amylopectin side chain structure based on the solution concentration of the compound and the swelling ratio. The method includes:

2. The method according to claim 1 , wherein the evaluation step is an evaluation step for evaluating an amylopectin side chain structure based on the swelling ratio at a predetermined solution concentration.

3. The method according to claim 1 , wherein the evaluation step is an evaluation step for evaluating an amylopectin side chain structure based on the solution concentration until a predetermined swelling ratio is reached.

4. The method according to claim 3 , wherein the evaluation step is a step of evaluating an amylopectin side chain structure based on the solution concentration at which the swelling ratio starts to increase.

5. The method according to claim 1, wherein the compound having starch gelatinizing activity is one or more compounds selected from the group consisting of urea, guanidine hydrochloride and dimethyl sulfoxide.

6. The method of claim 1 , wherein the solvent is water.

7. the compound having starch gelatinizing activity is urea, and the solvent is water; the evaluation step is a step of evaluating an amylopectin side chain structure based on the solution concentration at which the swelling ratio starts to increase, In the evaluation step, When the swelling ratio increase starting concentration is less than 2.5 M, the amylopectin side chain contained in the starch in the evaluation grain is evaluated as being short; When the swelling ratio increase starting concentration is 2.5M or more and less than 3.1M, the amylopectin side chain contained in the starch in the evaluation grain is evaluated as being normal; When the swelling ratio increase starting concentration is 3.1 M or more, the amylopectin side chain contained in the starch in the evaluation grain is evaluated as being long. The method according to claim 4.

8. The number of evaluation grains is two or more, The evaluation step is a step of comparing the swelling ratios of the respective solutions at a predetermined solution concentration, In the evaluation step, the larger the swelling ratio, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be. The method of claim 2.

9. The number of evaluation grains is two or more, The evaluation step is a step of comparing the respective solution concentrations until the predetermined swelling ratio is reached, In the evaluation step, the lower the solution concentration, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be. The method according to claim 3.

10. The evaluation step is a step of comparing the respective solution concentrations at which the swelling ratio starts to increase, In the evaluation step, the lower the solution concentration, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be.

10. The method of claim 9.

11. The method according to any one of claims 1 to 10, wherein at least one of the evaluation grains is a reference grain for which the amylopectin side chain structure is known.

12. The method of claim 1 , wherein the evaluation grain is rice.

13. A kit for evaluating the amylopectin side chain structure contained in starch in grains, comprising two or more identically shaped containers and a compound having a starch gelatinizing effect.

14. A method for evaluating the solubility of steamed rice during sake brewing, comprising the steps of: From the results of the evaluation of the amylopectin side chain structure contained in the starch obtained by the method according to claim 12, the steamed rice solubility during sake brewing of rice is evaluated based on the length of the amylopectin side chain contained in the starch in the rice. The method.

15. A method for evaluating the retrogradation property of steamed rice, comprising the steps of: From the evaluation results of the amylopectin side chain structure contained in the starch obtained by the method according to claim 12, the retrogradation property of the steamed rice is evaluated based on the length of the amylopectin side chain contained in the starch in the rice. The method.

16. A method for evaluating the gelatinization retrogradation characteristics of grain, comprising the steps of: From the results of evaluating the amylopectin side chain structure contained in the starch obtained by the method according to claim 1, the gelatinization retrogradation properties of the grain are evaluated based on the length of the amylopectin side chain contained in the starch in the grain. The method.

Images