Method and device 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 the evaluation grains into contact with a solvent; a swelling step of swelling the evaluation grains through the contact step; a first volume measurement step of measuring the volume A of the evaluation grains after the swelling step; a heating step of applying heat to the evaluation grains; a second volume measurement step of measuring the volume B of the evaluation grains in the heating step; a heat swelling ratio calculation step of calculating the heat swelling ratio of the evaluation grains by dividing the volume B by the volume A; and an evaluation step of evaluating the amylopectin side chain structure on the basis of the temperature and the heat swelling ratio of the evaluation grains in the heating step.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for evaluating the characteristics of grains, more specifically, to a method for evaluating the amylopectin side chain structure contained in starch in grains, a method 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, a method for evaluating the moisture content or water absorption rate of grains, and an apparatus for carrying out said methods. [Background technology]

[0002] Sake is produced in a multiple parallel fermentation method in which alcohol fermentation and saccharification of the raw rice (enzymatic digestion of steamed rice) occur simultaneously in the mash. In this production, the degree of enzymatic digestion of the steamed rice affects the raw material utilization rate and the intensity of the flavor, so the solubility of the harvested raw rice (enzymatic digestibility of steamed rice) is important in sake production management in sake brewing.

[0003] The solubility of the raw rice can be changed by the amount of water absorption during pre-treatment of the raw rice, adjusting the product temperature during the production process, and other factors in addition to the inherent characteristics of the raw rice. Therefore, by knowing the solubility of the raw rice in advance, it is possible to adjust the pre-treatment of the raw rice and the production conditions in advance to obtain the desired enzymatic digestibility of the steamed rice during sake brewing. Furthermore, the moisture content of white rice before water absorption (also called the moisture content of white rice or white rice moisture) and the water absorption rate after water absorption, which affect the water absorption speed and water absorption rate of the raw rice, are also important brewing suitability indicators in production management.

[0004] It has been revealed that the properties of starch in the raw rice related to gelatinization and retrogradation are important factors that affect the enzymatic digestibility of steamed rice (Non-Patent Document 1).

[0005] The properties of starch in raw rice are closely related to the side chain structure of amylopectin contained in the starch, and therefore the side chain structure of amylopectin contained in starch is an indicator of the enzymatic digestibility of steamed rice (Non-Patent Documents 1 and 2).

[0006] On the other hand, because the analysis of amylopectin side chain structure and starch retrogradation characteristics is difficult and time-consuming, indicators closely related to the amylopectin side chain structure have been reported. For the evaluation of enzymatic digestibility related to changes in amylopectin side chain structure, a method of estimating the enzyme digestibility based on the weather conditions during rice cultivation (Non-Patent Documents 2 and 3) and a method of analyzing starch gelatinization characteristics by thermal analysis such as a differential scanning calorimeter (DSC) and a rapid visco analyzer (RVA) have been reported (Non-Patent Document 4).

[0007] Furthermore, for example, a disintegration test when rice grains are soaked in an alkaline solution has been reported as a method for estimating the enzymatic digestibility of steamed rice and a simple method for estimating the properties of starch (Non-Patent Document 5). In addition, because the method in Non-Patent Document 5 lacks quantitative capability, quantification of solubility estimation based on this method has also been considered. For example, it has been reported that the solubility of raw rice can be quantitatively evaluated easily and at low cost by determining the concentrations of the alkaline and urea solutions at which rice grains disintegrate (Patent Document 1 and Non-Patent Document 6).

[0008] On the other hand, the moisture content of polished rice is measured by a high-temperature drying method (135°C for 3 hours at normal pressure, or 105°C for 5 hours at normal pressure) or an electric resistance moisture meter, etc. It has been reported that the moisture content of polished rice affects the maximum amount of water absorption during water absorption (Non-Patent Document 7). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Special Publication No. 2014-534052 [Non-patent literature]

[0010] [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 [Non-Patent Document 7] Chieko Kumagai, Yoshihiro Kuroyanagi, and Kikuo Nojiro, "Study on Water Absorption of Rice for Sake Brewing (Part 1) Relationship between Water Content and Water Absorption Rate of White Rice for Sake Brewing", Journal of the Brewing Society of Japan, Vol. 71, pp. 718-722, 1976 Summary of the Invention [Problem to be solved by the invention]

[0011] Traditionally, evaluation of the suitability of raw rice for sake brewing, such as the enzyme digestibility of steamed rice, has often been carried out using the National Standard Analysis Method for Raw Rice for Sake Brewing.

[0012] However, this analysis method requires the adjustment of the moisture content of the rice and the polishing of the rice, which is time-consuming and labor-intensive, and it is not possible to analyze a large number of points. Therefore, there is a need to develop a simple and accurate method for evaluating the solubility of raw rice.

[0013] In addition, methods such as those described in Non-Patent Documents 2 and 3, which were developed as simple and highly accurate methods, are estimates based on weather conditions, so it may be difficult to obtain accurate weather conditions in the production area. In addition, in the thermal analysis described in Non-Patent Document 4, a process of crushing the sample without gelatinizing it is necessary, and the thermal analysis equipment is expensive. Furthermore, since the thermal analysis equipment measures one sample at a time, it takes time when there are many samples. In addition, in DSC and RVA, the sample is heated inside the equipment, so the state of sample change is unknown. In particular, there has been no equipment that can link information on the morphological changes of grain granules that occur with temperature changes.

[0014] Furthermore, although the methods described in Patent Document 1 and Non-Patent Document 3 provide information on changes in granular morphology, the degree of disintegration by alkali and urea is affected by the rice polishing ratio and rice moisture, so corrections are necessary when the rice polishing ratio and rice moisture vary significantly. Also, the observation of disintegration requires the preparation of reagents such as iodine, which can make the procedure complicated. Furthermore, no device has been seen to date that can simultaneously estimate gelatinization temperature, enzymatic digestibility of steamed rice (steamed rice digestibility), aging characteristics, and moisture content through test procedures.

[0015] Furthermore, the high-temperature drying method of measuring moisture content at 135°C for 3 hours at normal pressure and the method of drying at 105°C for 5 hours at normal pressure require grinding the rice and then drying it for several hours, which is time-consuming and labor-intensive.In addition, although the electrical resistance moisture meter is simple, it is necessary to obtain the appropriate moisture meter separately.

[0016] In addition, when it comes to water absorption characteristics, water absorption tests must be conducted in small lots, which poses challenges such as the need for special water absorption tubes, the effort required to test a large number of samples, and the need for skilled techniques to measure accurately, such as centrifugation.

[0017] Therefore, it is impossible to test the enzymatic digestibility, moisture content, and water absorption characteristics of steamed rice in one day. Although the ability to simultaneously evaluate these important characteristics in a short period of time would contribute to improving sake brewing technology, no such method or equipment exists yet.

[0018] In addition, the properties of cereal starch affect the manufacturing process of beer and shochu, as well as the quality and processing characteristics of other foods, so there is a great need for the development of a simple method for evaluating the thermal properties of starch. Even in such cases, since it is difficult to analyze the side chain structure of amylopectin, starch properties are evaluated using the aforementioned DSC, RVA, urea and / or alkali decay tests for the purpose of simplicity and speed. As mentioned above, these methods have many problems, so simpler methods are needed.

[0019] Therefore, an object of the present invention is to provide a method for evaluating the suitability of grains for sake brewing that can be easily carried out on site. [Means for solving the problem]

[0020] The inventors have investigated various means for solving the above-mentioned problems, and as a result have found that when rice is brought into contact with water to cause it to swell, and then heat is applied to the rice, the rice swells further, 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 the 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 the starch in the rice, thereby completing the present invention.

[0021] 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 contacting step of contacting the evaluation grain with a solvent; a swelling step of swelling the evaluation grain by the contact step; a first volume measurement step of measuring a volume A of the evaluation grain after the swelling step; a heating step of applying heat to the evaluation grain; a second volume measurement step of measuring a volume B of the evaluation grain in the heating step; A heat swelling ratio calculation step of calculating the heat swelling ratio of the evaluation grain by dividing the volume B by the volume A; an evaluation step of evaluating the amylopectin side chain structure based on the temperature of the evaluation grain in the heating step and the heat swelling ratio; The method includes: (2) The method according to (1), wherein the evaluation step is an evaluation step for evaluating the amylopectin side chain structure based on the thermal swelling ratio at the predetermined temperature. (3) The method according to (1), wherein the evaluation step is an evaluation step for evaluating the amylopectin side chain structure based on the temperature at which the predetermined thermal swelling ratio is reached. (4) The method according to (1) or (3), wherein the evaluation step is an evaluation step for evaluating the amylopectin side chain structure based on the temperature at which the thermal swelling ratio starts to increase. (5) The method according to any one of (1) to (4), wherein the solvent is water. (6) The solvent is water, the evaluation grain is white rice, and the evaluation step is a step of evaluating an amylopectin side chain structure based on the temperature at which the thermal swelling ratio reaches 120%, In the evaluation step, When the temperature is less than 58°C, the amylopectin side chain contained in the starch in the white rice is evaluated as being short, When the temperature is 58° C. or more and less than 63° C., the amylopectin side chains contained in the starch in the white rice are evaluated as being normal; When the temperature is 63° C. or higher, the amylopectin side chain contained in the starch in the white rice is evaluated as being long. A method according to any one of (1) and (3). (7) The number of grains evaluated is two or more; The evaluation step is a step of comparing the respective thermal swelling rates at the predetermined temperature, In the evaluation step, the larger the heat 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). (8) The number of grains evaluated is two or more; The evaluation step is a step of comparing the temperatures at which the predetermined thermal swelling ratio is reached, In the evaluation step, the lower the temperature, 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). (9) The evaluation step is a step of comparing the temperatures at which the thermal swelling ratio starts to increase, In the evaluation step, the lower the temperature, 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 (8). (10) The method according to any one of (1) to (9), further comprising a reference grain having a known amylopectin side chain structure as a comparison control. (11) The method according to any one of (7) to (10), wherein the solvent is water. (12) The method according to any one of (1) to (11), wherein the evaluation grain is rice. (13) The method according to any one of (1) to (12), wherein the solvent dissolves a compound having a starch gelatinizing action. (14) An apparatus for evaluating amylopectin side chain structures contained in starch in grains, comprising two or more containers of the same shape, two or more containers for placing grains of the same shape, a heating unit, a temperature measuring unit, and a measuring unit for measuring the volumetric change of the evaluation grains in the containers. (15) 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 (13), 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. (16) 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 (13), 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. (17) 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 starch obtained by any one of the methods described in (1) to (13), the steamed rice solubility during sake brewing of rice is evaluated based on the length of the amylopectin side chain contained in starch in rice. The method. (18) A method for evaluating the aging property of steamed rice, comprising the steps of: From the results of the evaluation of the amylopectin side chain structure contained in starch obtained by any one of the methods described in (1) to (13), 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. (19) A method for evaluating the moisture content or water absorption rate of grains, comprising the steps of: a first volume measurement step for measuring the volume a of the evaluation grain; a contacting step of contacting the evaluation grain with water after the volume measurement step I; a swelling step of swelling the evaluation grain by the contact step; A second volume measurement step of measuring the volume b of the evaluation grain after the swelling step; A non-heat swelling ratio calculation step of calculating the non-heat swelling ratio of the evaluation grain by dividing the volume b by the volume a; An evaluation step of evaluating the water content or water absorption rate based on the non-heated swelling rate The method includes: Effect of the Invention

[0022] 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]

[0023] [Figure 1] 1. (A) is a schematic diagram and (B) is a photograph of the heating device used to observe the swelling of rice grains in a real-time evaluation of the swelling of rice grains by heating. [Diagram 2] 1. This is a photograph showing the change in swelling rate with heating for two types of white rice with different solubility (Yamada Nishiki and Gohyakumangoku (polished rice rate 70%) produced in 2018) in a real-time heating swelling evaluation of rice grains. The arrow (white) indicates the time when swelling begins (temperature at which the heating swelling rate begins to increase). [Diagram 3] 1. This is a photograph showing the change in swelling with heating for two types of polished rice with different moisture contents (Yamada-Nishiki rice produced in 2018 (polished rice ratio 70%, moisture contents 10% and 14%)) in a real-time evaluation of the swelling of rice grains by heating. The arrow (white) indicates the time when swelling begins (temperature at which the swelling rate begins to increase with heating). [Figure 4] 1. This is a photograph showing the change in swelling with heating for two types of polished rice (Yamada-Nishiki rice produced in 2018 (polished at 40% and 70%)) in a real-time evaluation of the swelling rate of rice grains when heated. The arrow (white) indicates the time when swelling begins (the temperature at which the swelling rate begins to increase when heated). [Diagram 5]2. Schematic diagram (A) and photograph (B) of the stepwise heating device used to observe the swelling of rice grains in the evaluation of the swelling of rice grains by stepwise heating. [Figure 6] 2. Photographs showing the change in swelling with heating for various types of polished rice in a test tube used in a stepwise heating swelling evaluation of rice grains. The arrow (white) indicates the time when swelling begins (the temperature at which the heat swelling rate begins to increase). [Figure 7] 2. A graph showing the correlation between the temperature at which the heat swelling rate begins to increase (as the rice grain swelling temperature) in the step-by-step heating swelling evaluation of rice grains, and the gelatinization temperature, enzymatic digestibility of steamed rice, conventional method, and aging characteristics. [Figure 8] 2. Photographs showing the change in swelling with heating for various types of polished rice using disposable microtubes in a stepwise evaluation of rice grain swelling by heating. The arrow (white) indicates the time when swelling begins (temperature at which the swelling rate begins to increase with heating). [Figure 9] 2. Photographs showing the change in swelling with heating for white rice with different moisture contents (Nihonbare, 2017 crop, 70% polishing rate) in a stepwise heating swelling evaluation of rice grains. The arrow (white) indicates the time when swelling begins (temperature at which the heating swelling rate begins to increase). [Figure 10] 2. Photographs showing the change in swelling with heating for rice with different polishing ratios (Yamada-Nishiki rice produced in 2017, polishing ratios 40%, 60%, and 70%) in a stepwise heating swelling evaluation of rice grains. The arrow (white) indicates the time when swelling begins (temperature at which the heat swelling rate begins to increase). [Figure 11] 3. Schematic diagram (A) and photograph (B) of the simultaneous heating device for multiple samples used to observe the swelling of rice grains in the simultaneous heating and swelling of multiple samples and to evaluate the water absorption and moisture content of white rice. [Figure 12] 3. Photographs showing the change in swelling with heating for white rice with a polishing ratio of 70% in simultaneous multi-sample heating swelling and evaluation of white rice water absorbency and moisture content. The arrow (white) indicates the time when swelling begins (temperature at which the heating swelling rate begins to increase). [Figure 13] 3. A graph showing the correlation between the temperature at which rice grains swell at a heat swelling rate of 120%, as determined from the results of Table 2 in the simultaneous heat swelling of multiple samples and the evaluation of white rice water absorption and moisture content, and the gelatinization temperature, enzymatic digestibility of steamed rice, conventional methods, and retrogradation characteristics. [Figure 14] 3. Photographs showing the change in swelling with heating for white rice with different moisture contents (Yamada-Nishiki rice produced in 2018, polishing rate 70%) in simultaneous multi-sample heating swelling and white rice water absorption and moisture content evaluation. The arrows (white) indicate the time when swelling begins (temperature at which the heating swelling rate begins to increase). [Figure 15] 3. Photographs showing the change in swelling with heating for 40% polished rice in simultaneous multi-sample heating swelling and evaluation of rice water absorption and moisture content. The arrow (white) indicates the time when swelling begins (temperature at which the heating swelling rate begins to increase). [Figure 16] 3. A graph showing the correlation between the temperature at which rice grains reach a heat swelling rate of 120% as the swelling temperature of rice grains in simultaneous heat swelling of multiple samples and evaluation of white rice water absorption and moisture content, and the gelatinization temperature, enzymatic digestibility of steamed rice, conventional method, and aging characteristics. [Figure 17] 3. A diagram showing the apparatus (A) and test scheme (B) used in the simultaneous heat swelling of multiple samples and in the evaluation of white rice water absorbency and moisture content. [Figure 18] 3. Photographs showing the change in swelling over time for white rice with different moisture contents in simultaneous heating and swelling of multiple samples, and white rice water absorption and moisture content evaluation, as well as graphs showing the time after water absorption, and the height and water absorption rate of the rice after water absorption. [Figure 19-1] 3. A graph showing the relationship between the non-heating swelling rate and water absorption rate after water absorption for each type of white rice in the simultaneous heat swelling test for multiple samples and the evaluation of white rice water absorption and moisture content. [Figure 19-2] 3. A graph showing the relationship between the non-heating swelling rate and water absorption rate after water absorption for each type of white rice in the simultaneous heat swelling test for multiple samples and the evaluation of white rice water absorption and moisture content. [Figure 20] 3. Photographs showing the non-heating swelling rate after water absorption for samples with different moisture contents in simultaneous heating and swelling tests of multiple samples and evaluation of white rice water absorption and moisture content. [Figure 21] 3. A graph showing the relationship between the non-heating swelling rate and moisture content after water absorption depending on the type of white rice or the rice polishing rate in the simultaneous heat swelling test on multiple samples and the evaluation of white rice water absorption and moisture content. [Figure 22]4. Photographs showing the change in swelling rate with heating for various types of brown rice (polished rice rate 90%) in the evaluation of brown rice. The arrow (white) indicates the time when swelling begins (temperature at which the swelling rate begins to increase with heating). [Figure 23] 4. A graph showing the correlation between the temperature at which the heat swelling rate begins to increase as the rice grain swelling temperature from the results of Figure 22 in the evaluation of brown rice, and the gelatinization temperature, enzymatic digestibility of steamed rice, conventional method, and aging characteristics. [Figure 24] 4. Photographs showing the change in swelling rate with heating of various types of brown rice after fine grinding in an evaluation of brown rice. The arrow (white) indicates the time when swelling begins (temperature at which the swelling rate begins to increase with heating). [Diagram 25] 4. A graph showing the correlation between the temperature at which the heat swelling rate begins to increase as the rice grain swelling temperature from the results of Figure 24 in the evaluation of brown rice, and the gelatinization temperature, enzymatic digestibility of steamed rice, conventional method, and aging characteristics. [Figure 26] 5. Photographs showing the change in swelling with heating in urea solution for various types of polished rice (produced in 2018, polishing rate 70%) in a simultaneous heating and swelling evaluation of multiple samples using urea solution. The arrow (white) indicates the time when swelling begins (temperature at which the heat swelling rate begins to increase). [Figure 27] 5. A graph showing the correlation between the temperature at which the heat swelling ratio begins to increase (as the rice grain swelling temperature) from the results of Figure 26 in the simultaneous heating and swelling evaluation of multiple samples using a urea solution, and the gelatinization temperature, enzymatic digestibility of steamed rice, conventional method, and retrogradation characteristics. [Figure 28] 3. A graph showing the correlation between the short-chain amylopectin percentage from the results in Table 2 in the simultaneous heating swelling of multiple samples and the evaluation of white rice water absorption and moisture content, and the gelatinization temperature, enzymatic digestibility of steamed rice, and retrogradation characteristics. [Figure 29] 3. A graph showing the correlation between the temperature at which rice grains reach a heat swelling ratio of 120% as the swelling temperature of rice grains from the results of simultaneous heat swelling of multiple samples and evaluation of white rice water absorption and moisture content in Table 2, or the gelatinization temperature measured by the conventional method, and the amylopectin short chain ratio. [Diagram 30]6. A graph showing the correlation between the temperature at which rice grains reach a heat swelling ratio of 120% as the swelling temperature in the results of Table 2 in the evaluation of starch retrogradation properties, or the gelatinization temperature measured by the conventional method, and starch retrogradation properties. [Diagram 31] 7. A graph showing the correlation between the temperature at which rice grains reach a heat swelling ratio of 110% as the swelling temperature in evaluating grains such as long-grain rice and wheat, and the gelatinization temperature measured using conventional methods. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] 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 device 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.

[0025] <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 a solvent, a swelling step of swelling the evaluation grain by the contacting step, a first volume measuring step of measuring the volume A of the evaluation grain after the swelling step, a heating step of applying heat to the evaluation grain, a second volume measuring step of measuring the volume B of the evaluation grain during the heating step, a heat swelling ratio calculation step of calculating the heat swelling ratio of the evaluation grain by dividing the volume B by the volume A, and an evaluation step of evaluating the amylopectin side chain structure based on the temperature of the evaluation grain during the heating step and the heat swelling ratio.

[0026] Each step will be described in detail below.

[0027] (contact process) In the contacting step, the evaluation grain (hereinafter also simply referred to as "grain") is brought into contact with the solvent.

[0028] 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.

[0029] By using rice as the grain, it is possible to evaluate one or more rice 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 sake brewing (in this specification, etc., this is also referred to as "characteristics such as gelatinization temperature of rice." When the rice is white rice, it is referred to as "characteristics such as gelatinization temperature of white rice."), that is, the amylopectin side chain structure contained in the starch in the rice, in particular the length of the side chains.

[0030] As the grain, one target may be used, but two or more different targets may also be used.

[0031] 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.

[0032] 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.

[0033] The moisture content of the grain is not limited, and is usually 8% by weight to 17% by weight based on the total weight of the grain.

[0034] A "solvent" is a compound that is absorbed into the contacted grain to cause the grain to swell. 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 preferred from the viewpoint of ease of operation and environmental friendliness.

[0035] The solvent may dissolve the compound having starch gelatinizing activity, in which case the solvent acts as a medium for dissolving the compound having starch gelatinizing activity.

[0036] 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 (DMSO), and the like. Compounds having starch gelatinizing action may be a mixture of two or more kinds. When the compounds having starch gelatinizing action are a mixture, the ratio of each compound in the mixture is not limited. As a compound having starch gelatinizing action, urea is preferred.

[0037] By using a compound having a starch gelatinizing effect, the compound promotes the gelatinization of the starch contained in the grain and further the absorption of the compound and / or solvent into the starch in the heating process described below, causing the grain to swell at a lower temperature.

[0038] When a compound having starch gelatinizing activity is used, the concentration of the compound having starch gelatinizing activity in a solution containing a solvent and the compound having starch gelatinizing activity is not limited. The concentration of the compound having starch gelatinizing activity in the solution can be appropriately changed depending on the type of the compound having starch gelatinizing activity.

[0039] For example, when urea is used as the compound having a starch gelatinizing effect in a solution and water is used as a solvent, the concentration of urea in the aqueous solution of A is usually 0.01 mol / L (M) to 4.0M, preferably 1.0M to 3.0M.

[0040] The method of contacting the grain with the solvent is not limited. Examples of the contact method include putting the grain into the solvent, putting the solvent into the grain, spraying the solvent onto the grain, etc. As the contact method, putting the grain into the solvent or putting the solvent into the grain is preferred from the viewpoint of operational convenience.

[0041] The amount of grains is not limited. The amount of grains may be changed depending on the container in which the grains are placed. For example, in a test tube, the amount may be about 1 / 3 to 1 / 4 of a teaspoon, and in a microtube, it may be a few grains. The amount of grains to be contacted with one solvent is usually 0.3 g or more, preferably 0.3 g to 2.0 g.

[0042] The volume of the solvent is not limited, and is usually 1.5 mL to 20 mL.

[0043] (Swelling process) In the swelling step, the grains are swelled by the contact step.

[0044] Here, "swelling" means that the volume of the grain increases as a result of the grain absorbing a solvent and / or, in some cases, a compound having a starch gelatinizing effect. Note that "swelling" includes not only an increase in volume, but also changes in the physical properties of the grain that accompany the increase in volume, such as an increase in the weight of the grain, a change in the refractive index, and a change in elasticity.

[0045] 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 10 minutes to 24 hours, preferably 30 minutes to 2 hours.

[0046] The temperature in the swelling step is not limited. The temperature in the swelling step is usually a temperature that does not affect the initiation of further swelling in the heating step described below. The temperature in the swelling step is usually 5°C to 40°C, preferably 10°C to 25°C.

[0047] 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.

[0048] 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.

[0049] The swelling process causes the grains to swell by absorbing therein a solvent and / or optionally a compound having a starch gelatinizing action.

[0050] (First volume measurement process) In the first volume measurement step, the volume A of the evaluation grain after the swelling step is measured. In the present invention, the "volume" may be the volume of the evaluation grain itself, but from the viewpoint of ease of measurement, it is preferable to use the bulk volume. Therefore, for example, when the swelling step is carried out by placing the evaluation grain and a solvent in a container such as a graduated cylinder on which standards for measuring volume are written, the volume A of the evaluation grain after the swelling step can be measured by reading the graduation of the graduated cylinder that the evaluation grain after swelling reaches.

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

[0052] By measuring the volume A, in the heat swelling ratio calculation process described below, the influence of swelling due to the solvent in the swelling step and the influence of swelling due to starch gelatinization when a compound having starch gelatinization action is dissolved in the solvent can be excluded from the heat swelling ratio, and the heat swelling ratio due only to the heating step can be calculated.

[0053] (Heating process) In the heating process, heat is applied to the grain to be evaluated. Note that in the heating process, the temperature of the grain is increased by heating. Therefore, heating and warming are sometimes used interchangeably.

[0054] The method of heating the grain in the heating step is not limited. Examples of the heating method include heating with an external heating device, such as heating with a gas burner, electric stove, hot stirrer, heater, block heater, microwave heating device, etc., and heating through a medium, such as heating with a water bath or oil bath. When a block heater is used, in the steps after the heating step, for example, the test tube is removed stepwise from a temperature slightly lower than the temperature at which swelling begins, and the degree of swelling is observed. After the observation, the test tube is placed back in the heat block and heated, and the temperature and swelling state are observed. This is repeated to observe the degree of swelling. Alternatively, the temperature to be observed is determined in advance, samples are prepared for that number of points, and when the target temperature is reached, the sample container is removed and the swelling temperature is observed.

[0055] The temperature in the heating step is not limited. For example, the heating step is usually started from room temperature (10°C to 30°C) and heated to about 75°C to 90°C.

[0056] The time for the heating step is not limited. For example, the heating speed depends on the capacity of the heating device, but is scheduled to be completed within 1 minute to 2 hours, for example, 5 minutes to 40 minutes, or 10 minutes to 30 minutes.

[0057] For example, in the case of the heat block method, the heating step starts from room temperature and increases the temperature to about 75° C. to 90° C. The heating step lasts for about several tens of minutes to several hours, depending on the temperature increasing capacity of the heat block device.

[0058] The heating step heats the grain and the solvent, and once at a certain temperature, the grain begins to absorb more of the solvent from the heating energy, causing it to swell further.

[0059] (Second volume measurement process) In the second volume measurement step, the volume B of the evaluation grain is measured at a predetermined temperature in the heating step. The volume B of the evaluation grain can be measured, for example, by reading the scale of a measuring cylinder at which the evaluation grain reaches the predetermined temperature in the heating step, as described above.

[0060] As in the first volume measurement step, the volume B may be observed visually, or may be observed by computer analysis of images from photographs, videos, cameras, smartphones, etc., or may be observed by AI judgment based on image analysis.

[0061] By measuring the volume B, the volume of the grain after it has swelled due to the heating process is measured.

[0062] (Heat swelling ratio calculation process) In the heat swelling ratio calculation step, the heat swelling ratio of the grain to be evaluated is calculated by dividing the volume B by the volume A. Here, "heat swelling ratio" means the proportion of the grain that swells due to the heating step. Therefore, the heat swelling ratio is expressed as B / A, or B / A x 100 (%). For example, when the method of the present invention is carried out using a cylindrical container with the same area for the bottom and top, the area of ​​the surface parallel to the bottom and top between the bottom and top will be the same as the bottom and top, and therefore the heat swelling ratio can be expressed as the ratio of the length from the bottom in the container to the grain before the heating step to the length from the bottom in the container to the grain after the heating step.

[0063] In the heat swelling ratio calculation step, the heat swelling ratio is calculated based on the volume of the grain. Meanwhile, as described above, the grain may experience a change in physical properties, such as an increase in weight, a change in refractive index, or a change in elasticity, in addition to an increase in volume, due to swelling. Therefore, the heat swelling ratio can also be calculated based on, for example, the weight, refractive index, or elasticity of the grain before and after the heating step, other than the volume of the grain before and after the heating step.

[0064] By calculating the heat swelling ratio as described above, it is possible to calculate the heat swelling ratio due only to the heating step, excluding the influence of swelling due to the solvent in the swelling step and the influence of swelling due to starch gelatinization when a compound having starch gelatinization action is dissolved in the solvent, as described above.

[0065] (Evaluation process) In the evaluation step, the amylopectin side chain structure is evaluated based on the temperature of the evaluation grain in the heating step and the heat swelling ratio.

[0066] In one embodiment, the amylopectin side chain structure is evaluated for one or more evaluation grains based on the heat swelling ratio of the evaluation grain at a predetermined temperature in the heating step. In this case, the heat swelling ratio may be evaluated in a multi-stage evaluation, for example, three or more stages. The predetermined temperature may be more than one. By using the heat swelling ratios at multiple temperatures, as described above, it becomes easier to quantitatively grasp the swelling property of the grain due to temperature change, 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 respective heat swelling ratios at the predetermined temperatures. In this case, the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be shorter as the heat swelling ratio of the evaluation grain is larger. 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 heat swelling rate of the evaluation grain is greater 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. If the heat swelling rate 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 heat swelling rate of the evaluation grain is smaller 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 in the reference grain.

[0067] In one embodiment, the amylopectin side chain structure is evaluated for one or more evaluation grains based on the temperature of the evaluation grains in the heating step until the predetermined heat swelling ratio is reached. In this case, the temperature may be evaluated in a multi-stage evaluation, for example, three or more stages. The predetermined heat swelling ratio may be set, for example, when the volume B becomes 1.05 to 2.0 times, for example, 1.2 times, of the volume A. Alternatively, when a graduated test tube is used as a container to which the grain is added, the predetermined heat swelling ratio may be set, for example, when the volume B increases from the volume A by 0.5 to 2 graduations, for example, 1 graduation of the test tube. Note that the predetermined heat swelling ratio may be multiple. By using the temperatures at multiple heat swelling ratios, it becomes easy to quantitatively grasp the temperature of the grain due to the change in heat swelling ratio, as described above, and it becomes possible to quantitatively evaluate the above-mentioned characteristics accordingly. Also, for example, the minimum heat swelling ratio (i.e., the heat swelling ratio (over 0%) at the temperature at which the heat swelling ratio starts to increase (heat swelling ratio increase start temperature)) and the maximum heat swelling ratio (i.e., the heat swelling ratio at the temperature at which the heat swelling ratio stops increasing and no further swelling occurs (heat swelling ratio increase completion temperature)) may be set as the predetermined heat swelling ratio, and the evaluation may be performed at a temperature midway between the heat swelling ratio increase start temperature and the heat swelling ratio increase completion temperature. When there are two or more evaluation grains, the amylopectin side chain structure is evaluated by comparing the respective temperatures until the predetermined heat swelling ratio is reached. In this case, the lower the temperature of the evaluation grain, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be. Also, as one of the evaluation grains, a reference grain with a known amylopectin side chain structure that can serve as an index may be used. 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 temperature of the evaluation grain is lower than that of the reference grain, the amylopectin side chains in the starch in the evaluation grain are evaluated as being shorter than those in the reference grain, if the temperature of the evaluation grain is equivalent to that of the reference grain, the amylopectin side chains in the starch in the evaluation grain are evaluated as being equivalent to those in the reference grain, if the temperature of the evaluation grain is higher than that of the reference grain, the amylopectin side chains in the starch in the evaluation grain are evaluated as being longer than those in the reference grain.

[0068] In one embodiment, the amylopectin side chain structure is evaluated for one or more evaluation grains based on the temperature at which the heat swelling ratio of the evaluation grain starts to increase in the heating step (heat swelling ratio increase onset temperature). In this case, the heat swelling ratio increase onset temperature 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 respective temperatures at which the heat swelling ratio starts to increase. In this case, the lower the heat swelling ratio increase onset temperature of the evaluation grain, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated. 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 the reference grain with a known amylopectin side chain structure. For example, when the heat swelling ratio increase onset temperature of the evaluation grain is lower than the heat swelling ratio increase onset temperature of the reference grain, the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be shorter than that of the reference grain. If the temperature at which the swelling ratio of the evaluation grain begins to increase on heat 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 temperature at which the swelling ratio of the evaluation grain begins to increase on heat 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 in the reference grain.

[0069] In one embodiment, water is used as the solvent, polished rice is used as the evaluation grain, and the amylopectin side chain structure is evaluated for one or more evaluation polished rice grains based on the temperature at which the thermal swelling ratio of the evaluation grain reaches 120% in the heating step (120% thermal swelling ratio temperature). In this case, the 120% thermal swelling ratio temperature may be evaluated in a multi-stage evaluation, for example, in three or more stages. For example, when the temperature at which the heat swelling ratio reaches 120% is less than 58°C, the amylopectin side chains contained in the starch in white rice 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 ratio 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 ratio of DP6 + DP7 is evaluated as being 2.87 or more. When the temperature for 120% heat swelling is 58°C or higher but lower than 63°C, the amylopectin side chains contained in the starch in polished rice are usually evaluated as, for example, a short / long chain ratio of the amylopectin side chains being 2.81 to 3.14, or the ratio of DP6 in the amylopectin being 0.77 to 0.91, or the ratio of DP6+DP7 being 2.60 to 2.86. When the temperature for 120% heat swelling is 63°C or higher, the amylopectin side chains contained in the starch in polished rice are evaluated as long, and the short / long chain ratio of the amylopectin side chains being 2.80 or less, or the ratio of DP6 in the amylopectin being 0.76 or less, or the ratio of DP6+DP7 being 2.59 or less.

[0070] Furthermore, when the grain is rice, in the evaluation step, the properties of the rice, such as the gelatinization temperature, can be evaluated based on the amylopectin side chain structure contained in the starch in the rice, which is evaluated based on the temperature of the evaluation grain in the heating step and the heat swelling ratio. Since the temperature of the evaluation grain in the heating step and the heat swelling ratio are correlated with the properties of the rice, such as the gelatinization temperature, the properties of the rice, such as the gelatinization temperature, can also be evaluated directly from the temperature of the evaluation grain in the heating step and the heat swelling ratio. In the following aspects, the case in which 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.

[0071] In one embodiment, the amylopectin side chain structure is evaluated for one or more evaluation target rice grains based on the heat swelling ratio at a predetermined temperature in the heating process, and 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 heat swelling ratio may be evaluated in a multi-stage evaluation, for example, three or more stages. The predetermined temperature may be multiple. By using multiple temperatures, as described above, it becomes easy to quantitatively grasp the swelling property of the rice in the heating process, 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 heat swelling ratios of the evaluation grains at the predetermined temperatures in the heating process, and 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 heat 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 heat 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 to retrogradate, the enzymatic digestibility of the steamed rice is better than that of the reference rice, the retrogradation rate 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 heat 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 heat 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 heat swelling ratio at a specified temperature is correlated with the gelatinization temperature and other properties of rice, so that the evaluation of the amylopectin side chain structure may be omitted from the heat swelling ratio and the gelatinization temperature and other properties of rice may be evaluated directly.

[0072] In one embodiment, the amylopectin side chain structure is evaluated based on the temperature of the evaluation grain in the heating process until the predetermined heat swelling ratio is reached for one or more evaluation target rice, and the properties such as the gelatinization temperature of the rice are evaluated based on the evaluation result of the amylopectin side chain structure. In this case, the temperature may be evaluated in a multi-stage evaluation, for example, three or more stages. The predetermined heat swelling ratio may be set, for example, when the volume B becomes 1.05 to 2.0 times, for example, 1.2 times, of the volume A. Alternatively, when a graduated test tube is used as a container to which the grain is added, the predetermined heat swelling ratio may be set, for example, when the volume B increases by 0.5 to 2 graduations, for example, 1 graduation, from the volume A on the test tube. Note that the predetermined heat swelling ratio may be multiple. By using the temperatures at multiple heat swelling ratios, it becomes easy to quantitatively grasp the temperature of the grain due to the change in heat swelling ratio, as described above, and it becomes possible to quantitatively evaluate the properties accordingly. Furthermore, for example, the minimum heat swelling ratio (i.e., the heat swelling ratio (more than 0%) at the temperature at which the heat swelling ratio starts to increase (heat swelling ratio increase starting temperature)) and the maximum heat swelling ratio (i.e., the heat swelling ratio at the temperature at which the increase in the heat swelling ratio stops and no further swelling occurs (heat swelling ratio increase completion temperature)) may be set as the specified heat swelling ratio, and evaluation may be performed at a temperature that is midway between the heat swelling ratio increase starting temperature and the heat swelling ratio increase completion temperature. When two or more types of rice are evaluated, the amylopectin side chain structure is evaluated by comparing the respective temperatures until the specified heat swelling ratio is reached, and further the gelatinization temperature and other properties of the rice are evaluated based on the evaluation results of each amylopectin side chain structure. In this case, the lower the temperature 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 temperature of the rice to be evaluated is lower than the corresponding temperature 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 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 temperature of the rice to be evaluated is equivalent to the corresponding temperature 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 temperature of the rice to be evaluated is higher than the corresponding temperature 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 temperature at which a specified heat 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 temperature, and the properties of rice such as the gelatinization temperature may be evaluated directly.

[0073] In one embodiment, the amylopectin side chain structure is evaluated for one or more evaluation target rice grains based on the temperature at which the thermal swelling ratio of the evaluation target grains starts to increase in the heating step (thermal swelling ratio increase starting temperature), 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 thermal swelling ratio increase starting temperature may be evaluated in a multi-stage evaluation, for example, three or more stages. When there are two or more evaluation target rice grains, the amylopectin side chain structure is evaluated by comparing the respective temperatures at which the thermal swelling ratio of the evaluation target grains starts to increase in the heating step, 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 starting temperature of the increase in the heat swelling rate 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 temperature at which the swelling rate of the rice being evaluated begins to rise on heat is lower than that of the reference rice, the amylopectin side chains contained in the starch in the rice being evaluated are evaluated to be shorter than that of the reference rice, and based on the evaluation results, the starch in the rice being 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 being better than that of the reference rice, the retrogradation property of the steamed rice being lower than that of the reference rice, and the solubility of the steamed rice during sake brewing being better than that of the reference rice. If the temperature at which the swelling rate of the rice being evaluated begins to rise on heat is equal to that of the reference rice, the amylopectin side chains contained in the starch in the rice being evaluated are evaluated to be equal 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 equal to those of the reference rice.If the heat swelling ratio increase starting temperature 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 mentioned above, the heat swelling ratio increase starting temperature 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 heat swelling ratio increase starting temperature and the gelatinization temperature and other properties of the rice may be evaluated directly.

[0074] In one embodiment, water is used as a solvent, and the amylopectin side chain structure is evaluated for one or more evaluation grains based on the temperature at which the thermal swelling ratio of the evaluation grain reaches 120% in the heating step (120% thermal swelling ratio temperature). In this case, the 120% thermal swelling ratio temperature may be evaluated in a multi-stage evaluation, for example, in three or more stages. For example, when the temperature at which the heat swelling ratio reaches 120% is less than 58°C, the amylopectin side chains contained in the starch in the polished rice are evaluated as being 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 ratio of DP (degree of glucose polymerization) 6 in the amylopectin measured using an HPAEC-PAD system (ICS-6000, Dionex Corporation, column: Carbopac PA1) after isoamylase treatment is evaluated as being 0.92 or more, or the ratio of DP6 + DP7 is evaluated as being 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 steamed rice is good, the retrogradation of steamed rice is low, and the solubility of steamed rice during sake brewing of polished rice is evaluated as being good. When the 120% heat swelling temperature is 58°C or higher and lower than 63°C, the amylopectin side chains contained in the starch in white rice are evaluated as normal, for example, the short chain / long chain ratio of the amylopectin side chains is evaluated as 2.81 to 3.14, or the proportion of DP6 in the amylopectin is evaluated as 0.77 to 0.91, or the proportion 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 white rice are also evaluated as normal. If the temperature at which the heat swelling ratio reaches 120% is 63°C or higher, the amylopectin side chains contained in the starch in the white rice are evaluated to be long, for example, the short chain / long chain ratio of the amylopectin side chains is evaluated to be 2.80 or less, or the proportion of DP6 in the amylopectin is evaluated to be 0.76 or less, or the proportion of DP6 + DP7 is evaluated to be 2.59 or less, and based on the evaluation results, the starch in the white rice is evaluated to have a high gelatinization temperature and be easily aged, the enzymatic digestibility of steamed rice is poor, the aging tendency of steamed rice is high, and the solubility of steamed rice during sake brewing is evaluated to be poor.As described above, the 120% heat swelling temperature is correlated with properties such as the gelatinization temperature of polished rice. Therefore, it is possible to omit the evaluation of the amylopectin side chain structure from the 120% heat swelling temperature and directly evaluate properties such as the gelatinization temperature of polished rice.

[0075] The gelatinization temperature of rice, which is correlated with the temperature of the evaluation grain in the heating step and the heat swelling ratio, the enzymatic digestibility of steamed rice, and the aging property of steamed rice can be measured as follows.

[0076] 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).

[0077] 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 or alumina oxide is placed in a reference cell as a reference 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.

[0078] 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, held at about 95°C for several minutes, then cooled to about 50°C and held at about 50°C for several minutes. The viscosity change of the sample is measured according to a program. As the temperature increases, starch gelatinization begins and an increase in viscosity is observed. The viscosity increase start temperature, peak viscosity, breakdown, and setback value can be determined by the control analysis system. The gelatinization temperature is taken as the pasting temperature (the temperature at which viscosity increase begins).

[0079] 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.

[0080] 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.

[0081] 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

[0082] 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 defined as "enzymatic digestibility of steamed rice aged for 6 hours". 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."

[0083] 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.

[0084] Furthermore, the present invention also relates to an evaluation device for evaluating the amylopectin side chain structure contained in the starch in the grain of the present invention. As described above, the evaluation device 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.

[0085] The evaluation device of the present invention includes two or more containers of the same shape, two or more containers of the same shape for placing grain, a heating unit, a temperature measuring unit, and a measuring unit for measuring the volumetric change of the evaluation grain in the containers.

[0086] 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 marked with 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, polystyrene bottles, and microtubes. The containers may be disposable.

[0087] The two or more identical grain arrangement containers are separate from the container for the solvent, and are containers for arranging grains so that the two or more grains can come into contact with the solvent at the same time and start swelling. The two or more identical grain arrangement containers are not limited as long as the two or more grains can come into contact with the solvent at the same time and start swelling. For example, a container for arranging grains with a shutter unit attached can be mentioned. An example is a container in which the same number of grain arrangement containers of the same shape are attached to the top of each of containers containing two or more solvents, grains are placed in the grain arrangement containers with the shutter unit closed, and when the shutter unit is opened, the two or more grains fall naturally into the container containing the solvent at the same time, so that the two or more grains can come into contact with the solvent at the same time and start swelling. The two or more identical grain arrangement containers are preferably transparent tubular containers. The container may be disposable. It is not necessarily necessary to install the container when only the heating swelling rate is measured.

[0088] The heating unit is a device for heating the container to which the grains and the solvent have been added. Examples of the heating unit include external heating devices such as a gas burner, an electric stove, a hot stirrer, a heater, a block heater, a microwave heating device, and heating devices via a medium such as a water bath or an oil bath.

[0089] The temperature measuring unit is a device for measuring the temperature of the grain and the solvent, particularly the grain. Examples of the temperature measuring unit include contact thermometers, such as thermometers, digital thermometers, thermocouples, and non-contact thermometers, such as radiation thermometers.

[0090] The measuring unit is a device for measuring the volume change of the grain. Examples of the measuring unit include a video, a camera, and a smartphone.

[0091] By using the evaluation device 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.

[0092] The present invention further relates to a method for evaluating the moisture content or water absorption of a grain, the method including a volume measurement step I of measuring the volume a of the evaluation grain, a contacting step of contacting the evaluation grain with water after volume measurement step I, a swelling step of swelling the evaluation grain by the contacting step, a volume measurement step II of measuring the volume b of the evaluation grain after the swelling step, a non-heated swelling ratio calculation step of calculating the non-heated swelling ratio of the evaluation grain by dividing the volume b by the volume a, and an evaluation step of evaluating the moisture content or water absorption ratio based on the non-heated swelling ratio.

[0093] Each step will be described in detail below.

[0094] (Volume measurement process I) In the Ith volume measurement step, the volume a of the evaluation grain is measured. For example, as described above, when the Ith volume measurement step is performed by placing the evaluation grain in a container on which a standard for measuring volume, such as a graduated cylinder, is written, the volume a of the evaluation grain can be measured by reading the mark on the graduated cylinder that the evaluation grain reaches.

[0095] The grains to be evaluated are as defined in the above-mentioned method for evaluating the amylopectin side chain structure.

[0096] The volume a may be observed visually, or may be observed by computer analysis of images from photographs, videos, cameras, smartphones, etc., or may be observed by AI judgment based on image analysis.

[0097] By measuring the volume a, the non-thermal swelling ratio based only on the contact step and the swelling step can be calculated in the non-thermal swelling ratio calculation step described below.

[0098] (contact process) In the contacting step, the evaluation grain is contacted with water after the first volume measuring step.

[0099] The contact step can be carried out in the same manner as the contact step in the method for evaluating the amylopectin side chain structure.

[0100] The volume a in the first volume measurement step is the volume of the grain before the swelling step described below, i.e., the volume of the grain before swelling. Therefore, the first volume measurement step and the contacting step may be performed after the first volume measurement step, or after the contacting step, preferably immediately after the contacting step. The contacting step is preferably performed after the first volume measurement step.

[0101] (Swelling process) In the swelling step, the evaluation grain is swelled by a contact step.

[0102] The swelling step can be carried out in the same manner as the swelling step in the above-mentioned method for evaluating the amylopectin side chain structure.

[0103] 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.

[0104] (Volume measurement step II) In the second volume measurement step, the volume b of the evaluation grain is measured after the swelling step. For example, when the swelling step is carried out by placing the evaluation grain and a solvent in a container having a volume measurement standard such as a graduated cylinder, as described above, the volume b of the evaluation grain can be measured by reading the graduation of the graduated cylinder that the evaluation grain reaches after the swelling step.

[0105] The volume b can be measured in the same manner as the measurement of the volume a.

[0106] By measuring the volume b, the volume of the grain after it has been swollen by the swelling step is measured.

[0107] (Non-heat swelling ratio calculation process) In the non-heated swelling ratio calculation step, the non-heated swelling ratio of the grain to be evaluated is calculated by dividing the volume b by the volume a. Here, the "non-heated swelling ratio" refers to the proportion of the grain swollen by the contact step and the swelling step. The "non-heated" in "non-heated swelling ratio" indicates that the contact step and the swelling step are usually carried out without heating, for example, at 4°C to 25°C, and is added before the swelling ratio to distinguish it from the thermal swelling ratio in the evaluation method of the amylopectin side chain structure. Therefore, the non-heated swelling ratio is expressed as b / a or b / a x 100 (%). As described above, for example, when the method of the present invention is carried out using a columnar vessel having the same area of ​​the bottom and top, the area of ​​the surface parallel to the bottom and top between the bottom and top is the same as the bottom and top, so that the non-heated swelling ratio can be expressed by the ratio of the length from the bottom to the grain in the vessel before the solvent is added to the length from the bottom to the grain in the vessel after the swelling step.

[0108] In the non-heated swelling ratio calculation step, the non-heated swelling ratio is calculated based on the volume of the grain. Meanwhile, as described above, the grain may increase in volume and also change in physical properties, such as an increase in the grain's weight, a change in refractive index, and a change in elasticity, due to swelling. Therefore, the non-heated swelling ratio can also be calculated based on, for example, the weight, refractive index, elasticity, etc. of the grain before the contact step and after the swelling step, other than the volume of the grain before the contact step and after the swelling step.

[0109] By calculating the non-heated swelling ratio as described above, the non-heated swelling ratio resulting only from the contacting step and the swelling step can be calculated as described above.

[0110] (Evaluation process) In the evaluation step, the moisture content or water absorption rate is evaluated based on the non-heated swelling rate. Here, the "moisture content" refers to the proportion of moisture contained in the grain (weight moisture content), and the "water absorption rate" refers to the proportion of moisture that the grain can absorb (weight absorption rate).

[0111] In one embodiment, the moisture content or moisture absorption rate is evaluated for one or more evaluation target rice based on the unheated swelling rate. In this case, the unheated swelling rate may be evaluated in a multi-stage evaluation, for example, three or more stages. For example, when the unheated swelling rate of white rice is more than 136%, the moisture absorption rate is evaluated as high, 34% or more. When the unheated swelling rate is 126% or more and 136% or less (126% to 136%), the moisture absorption rate is evaluated as normal, for example, 27% to 33%. When the unheated swelling rate is less than 126%, the moisture absorption rate is evaluated as low, for example, 26% or less. For example, when the unheated swelling rate of white rice is less than 124%, the moisture content is evaluated as high, 14% or more. When the unheated swelling ratio is 124% or more and 147% or less (124% to 147%), the moisture content is evaluated as normal, for example, a moisture content of 10% or more and 14% or less (10% to 14%). When the unheated swelling ratio is more than 147%, the moisture content is evaluated as low, for example, a moisture content of less than 10%.

[0112] According to the present invention, the water content or water absorption rate can be evaluated from the non-heated swelling rate.

[0113] The moisture content and water absorption rate of grains, which are correlated with the non-heated swelling rate in the present invention, can be measured as follows.

[0114] The moisture content of the above-mentioned grains, especially rice, is measured by high-temperature drying methods (135°C 3 hours at normal pressure drying method, 105°C 5 hours at normal pressure drying method) or by electric resistance moisture meter, etc. Among them, the 135°C 3 hours at normal pressure drying method uses a vibrating sample mill, puts about 10g of sample into each container (made of alumina), processes for 5 minutes, weighs about 2g of the crushed sample into a weighing scale with a lid (diameter 50mm, depth 25mm), dries at 135°C for 3 hours, cools in a desiccator, and calculates the moisture content by subtracting the weight lost by drying from the weight of the rice before drying.

[0115] The water absorption characteristics mentioned above, in the case where the grain is white rice, are determined by precisely weighing out 10g of white rice, placing it in a pre-weighed immersion tube, immersing it in water at 15°C, leaving it at 15°C, and then immediately centrifuging the immersion tube together with the rice in a centrifuge at RCF (centrifugal force) x t (rotation time (minutes)) = 2,500gt to 3,000gt (1,500 rpm or more), and then immediately weighing the rice and calculating the water absorption rate (%) using the following formula. Water absorption rate (%) = (weight of sample after centrifugation (g) - sample (g)) / sample (g) × 100

[0116] The method of the present invention allows the solubility, moisture content, and water absorption properties of grains, particularly raw rice, which previously required a great deal of effort to determine, to be determined simultaneously and easily with a small amount of sample at low cost and with high accuracy. In other words, the suitability of sake rice for sake brewing can be known in advance, which was previously only possible after brewing, and this can contribute greatly to sake production management and can be used to improve the quality of sake. Furthermore, in the field of breeding and cultivating sake rice, this method can be applied to the selection of sake rice with the desired solubility and the improvement of cultivation methods, without the need for expensive analytical equipment. In addition, this method can be used as an evaluation method for grains other than raw rice for sake, such as raw materials for shochu. Furthermore, this method can be used as an analytical device for the swelling properties and water absorption properties of starch in academic research on grains containing starch, as well as in the food industry, in addition to rice. EXAMPLES

[0117] <1. Real-time evaluation of rice grain swelling upon heating> (method) The following samples were used: For samples with different solubility, we used Yamadanishiki rice with good solubility at 13.5% moisture (rice steamed and left in the air for 6 hours digestibility°Brix value 9.6) and Gohyakumangoku rice with less solubility than Yamadanishiki (rice steamed and left in the air for 6 hours digestibility°Brix value 7.1) (both harvested in 2018, polishing ratio 70%). For samples with different moisture content, we used rice with moisture contents of 10% and 14% (Yamadanishiki harvested in 2018, polishing ratio 70%). For samples with different polishing ratios, we used white rice with polishing ratios of 40% and 70% (Yamadanishiki harvested in 2018).

[0118] The heating device shown in Figure 1 was used to observe the swelling of rice grains. Test tubes (external dimensions φ18mm x 105mm) or 2mL microtubes were used as sample containers. When using test tubes, 8mL of water was added for 1 / 3 of a small spoonful of rice (1.3g-1.4g). When using 2mL microtubes, 1.6mL of water was added for 15 grains of rice. The water bath was a 300mL beaker filled with enough water to fully immerse the sample in the test tube.

[0119] After adding water to the rice, the rice was left to stand for 30 minutes to an hour, after which heating was started with a gas burner. Swelling was judged by visual inspection or by looking at stored images taken with a video camera or digital camera to read the temperature at which swelling began. The temperature at which the heat swelling ratio began to increase was used as the rice grain swelling temperature to investigate whether it was possible to evaluate the gelatinization characteristics of rice and the enzymatic digestibility of steamed rice. Note that "rice grain swelling temperature" refers to the temperature at which a specified heat swelling ratio is reached. The series of test procedures were carried out at room temperature of approximately 16°C to 26°C, in an environment without humidity control.

[0120] (result) As shown in Figure 2, for both varieties, as the temperature increased, starch gelatinized and the rice grains swelled. For Yamadanishiki, rapid swelling began to be observed above 57°C, and when it reached 58°C, clear swelling could be confirmed as indicated by the arrow. In contrast, Gohyakumangoku swelled at higher temperatures than Yamadanishiki, and clear swelling was observed around 62°C, as indicated by the arrow. In other words, Yamadanishiki, which dissolves easily, swelled at low temperatures, while Gohyakumangoku, which dissolves less easily than Yamadanishiki, swelled at high temperatures. Similar trends were observed for other varieties, so it was possible to evaluate the solubility of rice used for sake brewing based on the swelling temperature of the rice grains. The heating time to 80°C was short, approximately within 20 minutes, making it possible to evaluate solubility in an unprecedentedly short time, even including the pretreatment of the rice.

[0121] Next, the effect of moisture content on this method was evaluated at moisture contents of 10% and 14% (Yamada-Nishiki rice harvested in 2018, polishing ratio 70%). As shown in Figure 3, although the amount of water absorbed before heating differed, in terms of the rice grain swelling temperature, swelling began to occur rapidly in both cases above 57°C, as indicated by the arrow, and clear swelling was observed in both samples at 58°C. In this way, this method was not affected by the moisture content of the rice.

[0122] Furthermore, the effect of rice polishing ratio on this method was evaluated using white rice (Yamada Nishiki, harvested in 2018) with polishing ratios of 40% and 70%. As shown in Figure 4, although the amount of water absorbed before heating differed, in terms of the rice grain swelling temperature, swelling began to occur rapidly in both cases above 57°C, as indicated by the arrow, and clear swelling was observed in both samples at 58°C. This demonstrated that this method is not easily affected by the rice polishing ratio.

[0123] From the above, this method was less affected by moisture content and rice polishing ratio, and it was possible to evaluate the gelatinization properties of rice and the enzymatic digestibility of steamed rice in a cheap, rapid and simple manner.

[0124] <2. Evaluation of rice grain swelling by stepwise heating> (method) The following samples were used: As samples with different solubilities, we used polished rice (produced in 2018) with a moisture content of 13.5% and a polishing ratio of 70%, which shows the gelatinization temperature and enzyme digestibility value of steamed rice in Table 1. As samples with different moisture content, we used polished rice samples with moisture contents of 11.0% to 15.5%. As samples with different polishing ratios, we used polished rice with polishing ratios of 40%, 60%, and 70%.

[0125] [Table 1]

[0126] For each of the above sake rice varieties, the gelatinization temperature (℃) using a differential scanning calorimeter (DSC), steamed rice digestibility (Brix) after leaving in the air for 1, 3, and 6 hours, and retrogradation rate (%) were measured, which are existing indicators of steamed rice enzymatic digestibility. Each measurement was performed under the following conditions.

[0127] The gelatinization temperature (℃) of DSC (DSC = Differential Scanning Calorimeter) was analyzed using a DSC7000X (Hitachi High-Tech Science Corporation). Approximately 3.5 mg of the sample was precisely weighed, mixed with 12 μL of distilled water, and sealed in a pressure-resistant cell. 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 a reference material. The gelatinization onset temperature (T0), gelatinization peak temperature (T p ) was sought.

[0128] RVA (Rapid Visco Analyser) gelatinization temperature was analyzed using an RVA-TecMaster (Perten). Rice flour suspension (9% (w / w), total weight 28 g) was heated 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 constant at 160 rpm. Pasting temperature (temperature at which viscosity begins to increase) was calculated automatically by computer.

[0129] The digestibility (Brix) of steamed rice left in the air for 1 hour, 3 hours, or 6 hours was measured based on the enzymatic digestibility of the steamed rice. 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 Electric 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 succinic acid 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.).

[0130] The aging of steamed rice (%) was calculated from the following formula, taking the aging rate as the above-mentioned 1 hour left in the air digestibility as the steamed rice enzymatic digestibility (Brix) of steamed rice aging for 1 hour, and the above-mentioned 6 hours left in the air digestibility 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

[0131] The stepwise heating device shown in Figure 5 was used to observe the swelling of rice grains. Test tubes (external dimensions φ18 mm × 105 mm) and 2 mL microtubes were used as sample containers. When using test tubes, 8 mL of water was added to 1 / 3 of a small spoonful of rice (1.7 g to 1.8 g). 9 mL of water was added to the reference test tube. After leaving it at 30°C for 1 hour, heating began. To determine swelling, the temperature was measured for the sample containing only water along with the set temperature. After the set temperature of 50°C, the temperature was increased stepwise by 2°C, and the temperature at which swelling began was read as the swelling temperature. We investigated whether it was possible to evaluate the gelatinization characteristics of rice and the enzymatic digestibility of steamed rice by the swelling temperature. The series of test operations was carried out in an environment with no humidity control, at room temperature of about 16°C to 26°C.

[0132] (result) Using test tubes, we evaluated rice (produced in 2018) with different gelatinization temperatures and enzyme digestibility values ​​of steamed rice with a polishing ratio of 70% and moisture content of 13.5%, as shown in Table 1. As shown in Figure 6, rice grain swelling was observed in all samples as the temperature increased, but the temperature at which swelling began was different between samples. The temperature at which the heat swelling rate began to increase was read as the rice grain swelling temperature, as indicated by the arrow. As shown in Table 1, the read values ​​ranged from 55°C for Ginpu (Hokkaido) and Yamadanishiki to 67°C for Gohyakumangoku and Okuhomare. The rice grain swelling temperature evaluated with this device showed an extremely high correlation with the gelatinization temperature (Figure 7A), enzyme digestibility of steamed rice (Figures 7B and 7C), and steamed rice aging characteristics (Figure 7D), measured by DSC and RVA, as shown in Figure 7. Samples with good solubility swell at low temperatures, and samples with poor solubility swell at high temperatures, so this method was able to evaluate the enzyme digestibility of steamed rice along with the starch gelatinization temperature. As shown in Figures 7C and 7D, the accuracy was equivalent to that of conventional thermal analysis devices, and the accuracy of this device was high.

[0133] Next, a similar experiment was carried out using a disposable 2 mL microtube, as shown in Figure 8. Swelling could be observed using a disposable 2 mL tube, just as with the test tube. Using a disposable tube reduces the labor required for the test, as it is not necessary to wash the test tube after the test. Another advantage is that the amount of water used is small, so the temperature rise time is short and satisfactory.

[0134] Next, the effect of moisture on this device was evaluated using white rice samples with moisture contents of 11.0% to 15.5%. As shown in Figure 9, although the amount of water absorbed before heating differed, the temperature at which the rice grain began to increase in the thermal swelling ratio, as indicated by the arrow, was consistent regardless of the moisture content, and was not affected by moisture.

[0135] In addition, to evaluate the effect of rice polishing ratio on this method, evaluation was carried out using white rice with polishing ratios of 40%, 60%, and 70%. As shown in Figure 10, although the amount of water absorption differed, the temperature at which the heat swelling rate begins to increase (as the rice grain swelling temperature) was consistent regardless of the polishing ratio, and was not affected by the polishing ratio.

[0136] From the above, this method was able to evaluate the gelatinization characteristics of rice, and the enzymatic digestibility and aging characteristics of steamed rice in a cheap, rapid and simple manner without being affected by the moisture content of white rice or the degree of polishing.

[0137] <3. Simultaneous heating and swelling of multiple samples and evaluation of rice water absorption and moisture content> (method) The following samples were used: As samples with different solubilities, we used polished rice (produced in 2018) with different gelatinization temperatures and steamed enzyme digestibility values ​​with a polishing ratio of 70% and moisture content of 13.5%, as shown in Table 2. As samples with different moisture contents, we used polished rice with moisture contents of 9.5% to 15.8%. As samples with different polishing ratios, we used polished rice with polishing ratios of 40%, 60%, and 70%.

[0138] [Table 2]

[0139] 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.

[0140] To observe the swelling of rice grains, the multiple sample simultaneous heating device shown in Figure 11 was used. Test tubes (external dimensions φ12mm x 105mm) were used as sample containers. Water was added to about 95% of the test tube's height for 1 / 4 of a small spoonful of rice (1.3g to 1.5g), and heating began after 30 minutes to an hour. When evaluating the water absorption rate before heating, the procedure was as follows.

[0141] (1) Determination of swelling due to heating While looking at the stored images taken with a video camera or a digital camera, the temperature at which swelling began was read as the rice grain swelling temperature. We investigated whether it was possible to evaluate the gelatinization characteristics of rice and the enzymatic digestibility of steamed rice using the rice grain swelling temperature. The above series of test operations were carried out in an environment with no humidity control at room temperature of about 16°C to 26°C.

[0142] (2) Analysis of water absorption characteristics and moisture content before heating Using only the test tube part of Figure 11A, a device was installed as shown in Figure 17 so that rice grains were simultaneously immersed in water. First, as shown in Figure 17, rice was placed in a test tube filled with water and in a rice placement container with the shutter closed (Figure 17(i)). When the water absorption started, the shutter was opened (Figure 17(ii)), so that multiple samples were simultaneously immersed in water (Figure 17(iii)). The state of the rice grains swelling over time from the point when the rice was immersed in water was observed (Figure 17(iv)). The above-mentioned rice was used as the sample. The operation was also performed in a 15°C constant temperature room without humidity control. The observation of the water absorption process of rice before heating was performed was performed by measuring the height of the rice grains during each process from images of the rice before, during, and after soaking, and the non-heating swelling rate was calculated. The relationship between the water absorption rate of rice measured in advance using a method based on the National Unified Analysis Method for Raw Rice for Sake Brewing described above and the moisture value of white rice was examined.

[0143] (result) The amylopectin side chain structure was investigated for 10 samples from Table 2. The proportion of short chain amylopectin showed a high correlation with the starch gelatinization temperature, the enzymatic digestibility of steamed rice, and the retrogradation characteristics of steamed rice, as shown in Figure 28. In other words, a high proportion of short chain amylopectin resulted in a low gelatinization temperature, high enzymatic digestibility of steamed rice, and a slower retrogradation rate.

[0144] Next, all the samples in Table 2 were tested using the simultaneous swelling evaluation device for multiple specimens shown in Figure 11. Rice and water were placed in a test tube or the like, and swelling was observed in a water bath while heating with a hot stirrer.

[0145] Figure 12 shows an example of simultaneous heating and swelling evaluation of multiple samples of white rice with a polishing ratio of 70%. An arrow is attached to the test tube in which the rice grains began to swell. Using the test tube scale as a guide, the temperature at which the rice had swelled to about one-fifth of its original height (heat swelling rate of 120%) was read as the rice grain swelling temperature, as shown in Table 2. The rice grain swelling temperature read by this device showed an extremely high correlation with the short-chain amylopectin ratio, as with the gelatinization temperatures measured by DSC and RVA, as shown in Figure 29.

[0146] In addition, the rice grain swelling temperature measured by this device showed a very high correlation with the gelatinization temperature (Fig. 13A), enzymatic digestibility of steamed rice (Fig. 13B and 13C), and retrogradation characteristics of steamed rice (Fig. 13D) measured by DSC and RVA, as shown in Fig. 13. Samples with a high proportion of short chains of amylopectin and good solubility swell at low temperatures, while samples with poor solubility swell at high temperatures. This revealed that this device can simultaneously evaluate the starch gelatinization temperature, enzymatic digestibility, and retrogradation characteristics of steamed rice as well as the amylopectin side chain structure in multiple samples. As shown in Figs. 13C and 13D, the accuracy of this device was comparable to and superior to that of conventional evaluation devices such as DSC and RVA. When measuring with this device, the water absorption time before heating is about 30 to 60 minutes, and heating is completed within 1 hour, so the solubility of multiple samples can be evaluated simultaneously in a total of 1 to 2 hours. This evaluation time was unprecedentedly rapid. Since the device is inexpensive, by adding more devices, it becomes possible to continuously measure more samples simultaneously.

[0147] Next, the effect of moisture content on thermal swelling was examined using polished rice samples with moisture content of 10.3% to 15.0%. As shown in Figure 14, although the amount of water absorbed before heating differed, the temperature at which the thermal swelling rate began to increase was consistent regardless of moisture content, as indicated by the arrows, and the rice was not easily affected by moisture.

[0148] As raw rice for sake brewing is highly polished, a similar evaluation was performed using white rice polished to 40% as shown in Figure 15. As with the 70% polishing ratio, samples with good solubility swelled at low temperatures and samples with poor solubility swelled at high temperatures when heated. As with the 70% polishing ratio, the rice grain swelling temperature (temperature at which the heat swelling rate reached 120%) measured by this method showed an extremely high correlation with the gelatinization temperature (Figure 16A) measured by DSC and RVA, the enzymatic digestibility of steamed rice (Figures 16B and 16C), and the aging characteristics of steamed rice (Figure 16D), as shown in Figure 16. As with the 40% polishing ratio, samples with good solubility swelled at low temperatures and samples with poor solubility swelled at high temperatures, as with the 70% polishing ratio, so it was revealed that the enzymatic digestibility and aging characteristics of steamed rice, as well as the starch gelatinization temperature, can be simultaneously evaluated by this device for multiple samples, regardless of the polishing ratio, within the range of rice polishing ratios used in sake brewing. As shown in Figures 16C and 16D, the accuracy of this device was equivalent to and superior to that of conventional evaluation devices such as DSC and RVA.

[0149] It has been reported that the moisture content of polished rice affects the maximum amount of water absorbed during water absorption (Non-Patent Document 7). Looking at rice grains before swelling in Figure 14, it can be seen that the lower the moisture content of the rice, the more swollen the rice is before heating. This suggests the possibility that the water absorption rate of rice can be evaluated by evaluating the degree of swelling of rice. In other words, rice is allowed to absorb water before swelling by heating, and it was thought that if the swelling during water absorption was also evaluated, the water absorption characteristics and moisture content of polished rice could also be evaluated. The scheme for this is shown in Figure 17B.

[0150] Using the device shown in Figure 17A, the increase in the volume of rice grains during water absorption was measured using samples of Yamada-Nishiki rice with different polishing ratios and different moisture contents. When rice grains are immersed in water, they swell, and it was revealed that the volume of the rice grains changes over time, as shown in Figure 18A. Moreover, it was observed that the lower the moisture content of the polished rice, the greater the swelling. Figure 18B shows the swelling change as measured over time by the non-heated swelling rate of rice grains. Meanwhile, Figure 18C shows the water absorption rates of these samples, which were determined in advance by allowing them to absorb water for the same period of time based on the National Unified Analysis Method for Raw Rice for Sake Brewing. Looking at Figures 18A to 18C, it was observed that the lower the moisture content of the polished rice and the better the water absorption, the greater the swelling.

[0151] Therefore, rice with different moisture content, polishing ratio, and variety was used to absorb water using this method, and the relationship between the swelling change of the rice during absorption and the water absorption rate, which was previously determined by absorbing water for the same period of time based on the national unified analysis method for raw rice for sake brewing, was examined. Figure 19 (Figures 19-1 and 19-2) shows the relationship for all samples (Figure 19-1A), Yamada-nishiki with a polishing ratio of 70% (Figure 19-1B), Nipponbare (Figure 19-1C), Gohyakumangoku (Figure 19-1D), Yamada-nishiki with a polishing ratio of 40% (Figure 19-2E), Yamada-nishiki with a polishing ratio of 60% (Figure 19-2F), Yamada-nishiki with a polishing ratio of 40% to 70% (Figure 19-2G), and Nipponbare (Figure 19-2H). The moisture content of each rice was 9.6% to 15.1%. The relationship between the non-heating swelling rate of rice grains due to water absorption and the water absorption rate was somewhat variable for all samples in Figure 19-1A, but an extremely high correlation was observed when the variety was limited as in Figures 19-1B to 19-2H. The non-heating swelling rate can be determined by measuring the height of rice grains if a container with a constant bottom area is used. In other words, it was found that the water absorption rate can be estimated by measuring the change in height of rice grains from the bottom of a test tube due to the swelling of rice grains during soaking. To apply this knowledge to determining the target value of water absorption time, for example, if the target water absorption time is 30%, the height of rice with a water absorption rate of 30% can be obtained from the regression equation shown in Figure 19, and the time to reach this height can be measured with the device in Figure 17A to determine the target water absorption time.

[0152] The unheated swelling rate of rice grains after water absorption was observed for samples with different moisture contents. Figure 20 shows the results of an investigation using white rice samples with moisture contents of 9.6% to 15.8% for Yamada-Nishiki and Nipponbare rice (polished rice ratio 70%) harvested in 2017 and 2018. In all samples, the rice absorbed water, the rice grains swelled, and the unheated swelling rate in the test tube increased, but the unheated swelling rate differed depending on the moisture content. The lower the moisture content, the more the rice grains swelled and the higher the unheated swelling rate, and the higher the moisture content, the less the rice grains swelled and the lower the unheated swelling rate. Figure 21 shows the relationship between the unheated swelling rate after water absorption and the moisture content. For both varieties, an extremely high correlation was observed between the moisture content and the unheated swelling rate after water absorption. In other words, if the relationship between the unheated swelling rate and moisture content is determined for each variety, it becomes possible to estimate the moisture content of white rice as well as the water absorption characteristics, which are important when processing raw materials, from the unheated swelling rate prior to evaluating the heat swelling rate.

[0153] From the above, it was clarified that the scheme in Figure 17B can evaluate the water absorption characteristics and moisture content from the degree of swelling at the stage where polished rice is absorbed into water, and then by heating it, it is possible to simultaneously evaluate the enzymatic digestibility and retrogradation characteristics of steamed rice for multiple samples from the temperature at which the heat swelling rate begins to increase, as well as the starch gelatinization temperature. The entire process can be completed in as little as two hours, which is faster than any other device that has been used up to now.

[0154] <4. Evaluation of brown rice> (method) The following samples were used: As samples with different gelatinization temperatures and enzyme digestibility values ​​of steamed rice, we evaluated brown rice (harvested in 2018) from the varieties shown in Table 2: Ginpu (Hokkaido), Yamadanishiki (Hiroshima), Dewasansan (Yamagata), Ginginga (Iwate), Gohyakumangoku (Tochigi), Gohyakumangoku (Niigata), Gohyakumangoku (Fukui), and Okuhomare (Fukui). The brown rice was either polished to a polishing ratio of 91% using a small-scale test rice polisher (Kett Scientific, Pearlest) or ground in a blender for 10 seconds before use.

[0155] To observe the swelling of rice grains, a simultaneous heating device for multiple samples as shown in Figure 11 was used. Swelling was judged by reading the temperature at which swelling began while viewing stored images taken with a video camera or digital camera. We investigated whether it was possible to evaluate the gelatinization characteristics of rice and the enzymatic digestibility of steamed rice by the swelling temperature. Test tubes (external dimensions φ12mm x 105mm) were used as sample containers. Water was added to about 95% of the height of the test tube for 1 / 4 of a small spoonful of rice (1.3g-1.5g), and heating was started after 1 hour. The series of test operations was carried out at room temperature of about 16℃-26℃, in an environment without humidity control.

[0156] (result) Brown rice does not absorb water easily even when soaked in water. Therefore, when the sample is brown rice, it is preferable to polish it to the same level as cooked rice or raw rice for sake brewing using a rice polishing machine for rice cooking or a rice polishing machine for testing, or to cut it into half grains or finely grind it in a simple mill and use the ground product for testing.

[0157] Figure 22 shows the results of a heating swelling evaluation of eight varieties of brown rice after they were polished for eating using a home rice polisher. The results of measurements using this device for samples with a polishing ratio for eating showed an extremely high correlation with the gelatinization temperature (Figure 23A) measured by DSC and RVA, the enzymatic digestibility of steamed rice (Figures 23B and 23C), and the retrogradation characteristics of steamed rice (Figure 23D), as shown in Figure 23. For samples with a polishing ratio of 90%, the heating swelling temperature shifted higher than for samples with a polishing ratio of 40% to 70%, but the tendency of differences between samples was the same as for samples with a polishing ratio of 40% to 70%, with samples with good solubility swelling at low temperatures and samples with poor solubility swelling at high temperatures.

[0158] Figure 24 shows the results of evaluating the swelling of eight varieties of brown rice after they were finely ground for 10 seconds using a simple mill. As shown in Figure 25, the brown rice ground samples also showed extremely high correlations with the gelatinization temperature (Figure 25A) measured by DSC and RVA, the enzymatic digestibility of steamed rice (Figures 25B and 25C), and the retrogradation characteristics of steamed rice (Figure 25D).

[0159] In the case of ground brown rice samples, the heating swelling temperature shifted higher than when the rice polishing ratio was 40% to 70%, but the tendency of the difference between samples was similar to that in the case of rice polishing ratios of 40% to 70%, with samples with good solubility swelling at low temperatures and samples with poor solubility swelling at high temperatures.

[0160] In other words, even when using brown rice, it was possible to obtain a similar tendency to the results for white rice in Figure 12 through simple processing. In other words, when using brown rice, evaluation is possible with this device after a short period of polishing and grinding, without the need for extensive polishing as in the case of sake brewing.

[0161] This shows that when evaluating grain starch samples other than rice that have poor water absorption, it is possible to use this device to evaluate swelling if the sample is processed, for example by crushing, to make it easier for water absorption and swelling to occur.

[0162] <5. Simultaneous heating and swelling evaluation of multiple specimens using urea solution> (method) The following samples were used: As samples with different gelatinization temperatures and enzyme digestibility values ​​of steamed rice, we evaluated white rice (harvested in 2018) with a polishing ratio of 70% and a moisture content of 13.5% from the varieties shown in Table 2: Ginpu (Hokkaido), Yamadanishiki (Hiroshima), Dewasansan (Yamagata), Ginginga (Iwate), Gohyakumangoku (Tochigi), Gohyakumangoku (Niigata), Gohyakumangoku (Fukui), and Okuhomare (Fukui).

[0163] To observe the swelling of rice grains, a multiple sample simultaneous heating device as shown in Figure 11 was used. Swelling was judged by reading the temperature at which swelling began while looking at stored images taken with a video camera or digital camera. We investigated whether it was possible to evaluate the gelatinization characteristics of rice and the enzymatic digestibility of steamed rice by the swelling temperature. A test tube (outer dimensions φ12mm x 105mm) was used as the sample container. Water was added to 1 / 4 of a small spoonful of rice (1.3g-1.5g) until the test tube was 95% of its height, and heating was started after 30 minutes to 1 hour. The series of test operations was carried out in an environment with room temperature of 16℃-26℃ and no humidity control.

[0164] (result) When using water for thermal swelling evaluation, the water in the water bath will begin to boil if heating is continued, so it is safe to measure up to about 80°C to 90°C. For samples that do not swell sufficiently unless heated to a high temperature, or when shortening the measurement time, using a urea or guanidine hydrochloride solution can lower the swelling temperature and shorten the measurement time.

[0165] Figure 26 shows an example of a heating swelling evaluation using a 2.0M urea solution. It can be seen that swelling occurred at a temperature 10°C or more lower than when water was used. As shown in Figure 27, the swelling temperature showed an extremely high correlation with the gelatinization temperature (Figure 27A) measured by DSC and RVA, the enzymatic digestibility of steamed rice (Figures 27B and 27C), and the retrogradation characteristics of steamed rice (Figure 27D). When a urea solution was used, the swelling temperature was lower than when water was used, but the tendency of the difference between samples was the same as when water was used, with samples with good solubility swelling at low temperatures and samples with poor solubility swelling at high temperatures. This demonstrated that starch characteristics and the solubility of steamed rice could be evaluated even when a urea solution was used.

[0166] Therefore, if a solution that gelatinizes starch, such as a dimethyl sulfoxide solution or a guanidine hydrochloride solution, is used in addition to a urea solution, the heating temperature can be lowered and the measurement time can be shortened.

[0167] <6. Evaluation of starch retrogradation characteristics> (method) Eight or ten samples were used from the varieties shown in Table 2. The swelling of rice grains was observed using the multiple sample simultaneous heating device shown in Figure 11. Starch retrogradation characteristics were analyzed by DSC, using peaks derived from the recrystallization of amylopectin in retrograded starch. Retrograded starch samples were evaluated 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 using DSC. After the measurement, the cells were stored at 4°C for 13 days and then analyzed again under the same conditions using DSC. 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 endothermic enthalpy after retrogradation as an index of starch retrogradation. The ratio of the enthalpy after retrogradation divided by the heat of fusion of amylopectin in raw starch was used 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.

[0168] (result) Figures 30A and B show the results of evaluating the starch retrogradation characteristics of samples obtained by DSC measurement of white rice flour and storing them for 13 days, as well as the retrogradation characteristics of amylopectin, which accounts for the majority of starch retrogradation. Figure 30C shows the results of evaluating the starch retrogradation characteristics of steamed rice when stored. As shown in Figures 30A to C, in all cases, the starch retrogradation characteristics showed an extremely high correlation with the rice grain swelling temperature. This correlation was about the same as the correlation with the gelatinization temperature measured by DSC measurement. In other words, it was clear that the higher the swelling temperature, the more likely it is that retrogradation will progress.

[0169] It is possible to evaluate the aging characteristics by actually aging the material and then evaluating the degree of aging. However, if data matching the aging conditions are accumulated in advance, it is possible to evaluate the aging characteristics in a short time from the swelling ratio onset temperature by this measurement method.

[0170] <7. Evaluation of cereals such as long grain rice and wheat> (method) Long-grain rice and grains such as wheat were evaluated. As samples with different gelatinization temperatures, the gelatinization characteristics of seven long-grain white rice samples (varieties: Saliqueen, Basmati, Kalasas, two samples of Hoshiyutaka, two samples of Yumejuiro, polishing ratio 91%), four barley samples (polished barley), and seven grain starch samples (three potato starch samples, two corn starch samples, one sweet potato starch sample) were evaluated. The long-grain rice was used as is. The barley was milled in a mill for 10 to 15 seconds before use.

[0171] For swelling observation, a simultaneous heating device for multiple samples shown in Figure 11 was used. Swelling was judged by reading the temperature at which the swelling rate reached 110% while viewing the stored images taken by a video camera. We investigated whether it is possible to evaluate the gelatinization characteristics of grains such as long-grain rice and wheat by the swelling temperature. Test tubes (external dimensions φ12mm x 105mm) were used as sample containers. Water was added to about 95% of the height of the test tube for 1 / 4 small spoonful (1.3g-1.5g) of long-grain rice and barley, and 1g of starch powder, and heating was started after more than 2 hours had passed. The series of test operations was carried out at room temperature of about 16℃-26℃ and in an environment without humidity control.

[0172] (result) Figure 31 shows the results of a heating swelling evaluation of long-grain rice, polished barley, and grain starch powder. It was possible to evaluate the swelling of long-grain rice as is, just like short-grain rice, but in the case of grains other than rice, the degree of swelling was low when the grains were left as is, just like when brown rice was evaluated, so they were simply crushed before evaluation. Also, because starch extracted from grains and powder samples are often used, evaluation of starch and powder samples was also carried out.

[0173] Although the degree of swelling differed depending on the sample, the swelling onset temperature measured with this device showed an extremely high correlation with the gelatinization temperature measured by DSC for long-grain rice and barley, as shown in Figure 31. Furthermore, for the extracted starch powder, regardless of the type of grain, there was a high correlation between the swelling onset temperature and the gelatinization temperature measured by DSC. In other words, even for grains such as long-grain rice and wheat, it was possible to grasp the tendency of gelatinization characteristics with simple processing. In other words, it is possible to evaluate the gelatinization characteristics of starch not only for rice but also for grains that contain starch with this device.

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 a solvent; a swelling step of swelling the evaluation grain by the contact step; a first volume measurement step of measuring a volume A of the evaluation grain after the swelling step; a heating step of applying heat to the evaluation grain; a second volume measuring step of measuring a volume B of the evaluation grain in the heating step; A heat swelling ratio calculation step of calculating the heat swelling ratio of the evaluation grain by dividing the volume B by the volume A; and an evaluation step of evaluating the amylopectin side chain structure based on the temperature of the evaluation grain in the heating step and the heat 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 thermal swelling ratio at a predetermined temperature.

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 temperature at which the predetermined thermal swelling ratio is reached.

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

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

6. the evaluation grain is white rice, and the evaluation step is an evaluation step of evaluating an amylopectin side chain structure based on the temperature at which the heat swelling ratio reaches 120%, In the evaluation step, When the temperature is less than 58° C., the amylopectin side chain contained in the starch in the white rice is evaluated as being short, When the temperature is 58° C. or more and less than 63° C., the amylopectin side chains contained in the starch in the white rice are evaluated as being normal; When the temperature is 63° C. or higher, the amylopectin side chain contained in the starch in the white rice is evaluated as being long. The method according to claim 5.

7. The number of evaluation grains is two or more, The evaluation step is a step of comparing the respective thermal swelling rates at the predetermined temperature, In the evaluation step, the larger the heat 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.

8. The number of evaluation grains is two or more, The evaluation step is a step of comparing the temperatures at which the predetermined thermal swelling ratio is reached, In the evaluation step, the lower the temperature, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be. The method according to claim 3.

9. The evaluation step is a step of comparing the temperatures at which the thermal swelling ratio starts to increase, In the evaluation step, the lower the temperature, the shorter the amylopectin side chain contained in the starch in the evaluation grain is evaluated to be. The method according to claim 8.

10. The method of claim 7 , wherein the solvent is water.

11. The method according to any one of claims 1 to 10, further comprising a reference grain having a known amylopectin side chain structure for comparison.

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

13. The method of claim 1 , wherein the solvent dissolves a compound having a starch gelatinizing effect.

14. An apparatus for evaluating amylopectin side chain structures contained in starch in grains, comprising two or more containers of the same shape, two or more containers for placing grains of the same shape, a heating unit, a temperature measuring unit, and a measuring unit for measuring the volumetric change of the evaluation grains in the containers.

15. A method for assessing the retrogradation of starch, comprising the steps of: From the evaluation results of the amylopectin side chain structure contained in the starch obtained by the method of claim 1, 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.

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 evaluated grain. The method.

17. 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.

18. A method for evaluating the retrogradation property of steamed rice, 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 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.

19. A method for evaluating the moisture content or water absorption rate of grain, comprising the steps of: A first volume measurement step of measuring the volume a of the evaluation grain; a contacting step of contacting the evaluation grain with water after the volume measurement step I; a swelling step of swelling the evaluation grain by the contact step; A volume measurement step II of measuring the volume b of the evaluation grain after the swelling step; A non-heat swelling ratio calculation step of calculating the non-heat swelling ratio of the evaluation grain by dividing the volume b by the volume a; An evaluation step of evaluating the water content or water absorption rate based on the non-heated swelling rate The method includes:

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