JP7645767B2 - Digestion determination system and digestibility determination method - Google Patents

Description

Patent Act Article 30, Paragraph 2 applies 1. Publication name: Abstracts of General Lectures at the Japan Society of Brewing Science Conference Published date: September 1, 2021 Published address: The link has been removed as the conference has ended. (Link source: https://www.jozo.or.jp/gakkai/competition/y2021/) 2. Date held: October 1, 2021 Conference name: "Japan Society of Brewing Science Conference 2021" Venue: Online The link has been removed as the conference has ended. (Link source: https://www.jozo.or.jp/gakkai/competition/y2021/)

The present invention relates to a system and method for determining the digestibility of rice, and in particular to a system and method for determining the digestibility of rice using an alkaline decay method.

In sake production, rice aging is an important factor that determines the quality of the product. In the sake production process, alcoholic fermentation progresses using sugars generated by enzyme decomposition of steamed rice (steamed rice), which is the raw material for sake. Here, the ease with which steamed rice is decomposed by enzymes is called digestibility, and it is known that this digestibility also affects the degree of alcoholic fermentation and the final quality of sake. In addition, the phenomenon in which the crystal structure of steamed rice changes and the steamed rice becomes hard when steamed rice is left for a certain period of time is called rice aging. The digestibility of steamed rice, which is decomposed by enzymes in the fermentation process, is controlled by aging it to a certain extent before fermentation. Therefore, evaluating the digestibility of steamed rice (Brix value and aging rate) is important for sake quality control. Therefore, currently, before sake is produced, the digestibility of steamed rice that has been aged for three hours is analyzed according to the National Unified Analysis Method for Raw Rice for Sake Brewing. However, this analytical method is known to require preparation before measurement, to take a long time to measure, and to not accurately reflect the digestibility of rice during the fermentation process, which usually takes about 20 days.

As a result, a method has been proposed to evaluate the digestibility of rice by replacing the process of soaking the rice in water and then steaming it with a process of soaking the rice in an alkaline solution or urea solution, thereby shortening the measurement time. Examples of such a method include the methods described in Patent Document 1 and Patent Document 2.

The method described in Patent Document 1 involves soaking the rice to be evaluated in an aqueous urea solution or an aqueous alkali solution, evaluating its disintegration in these solutions, and using this evaluated disintegration as an index to evaluate the properties of the steamed rice, such as its enzymatic digestibility.

The method described in Patent Document 2 includes a gelatinization process in which rice is soaked in an alkaline solution or urea solution to gelatinize the rice, a separation process in which the solution is separated from the undissolved rice after the gelatinization process, a detection process in which the amount of dissolved starch is detected using an iodine-starch color reaction in the solution obtained in the separation process and the absorbance of the solution after the reaction, and an evaluation process in which the rice is evaluated based on the correlation between the amount of dissolved starch and the absorbance detected in the detection process and the physical properties of the rice (steamed rice digestibility, etc.).

JP 2017-161399 A Patent No. 6472001

Meanwhile, in sake manufacturing, from the perspective of reducing the burden on workers and minimizing variability in evaluations, methods for evaluating rice digestibility are required to meet four conditions: (1) they do not require complicated operations, (2) they require a short measurement time, (3) they can quantify digestibility, and (4) they can evaluate digestibility even for highly polished rice (rice with a low polishing rate).

However, in the method described in Patent Document 1, in order to evaluate the disintegrability of the rice to be evaluated, it is necessary to soak the rice in various solutions for at least about three hours. Therefore, it cannot be said that the above condition (2) is sufficient. Furthermore, in the method described in Patent Document 1, when evaluating the disintegrability of the rice to be evaluated in an aqueous solution, the degree of disintegration is judged visually, or the color of the solution after dyeing the dissolved starch is judged visually. Therefore, if the enzyme digestibility of steamed rice is evaluated using the evaluated disintegrability as an index, even if it can be quantified, there is a problem in terms of accuracy.

In addition, the method described in Patent Document 2 requires a separation step and the use of a starch iodine color reaction in the detection step, which requires complex operations.

Furthermore, in sake production, rice with a low polishing ratio is often used, but when assessing digestibility by soaking low polished rice in various solutions and observing the condition of the rice, it may not be possible to accurately assess digestibility due to the occurrence of cracks in the rice or the rice breaking or crumbling, splitting it into two or more fine grains.

In other words, the conventional methods described in Patent Documents 1 and 2 are insufficient to meet all four of the above conditions.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a digestibility assessment system that can numerically evaluate digestibility in a relatively short time without requiring complicated operations.

The digestibility determination system according to the present invention for achieving the above object has the following characteristic configuration:
A system for determining the digestibility of rice, comprising:
A soaking means for soaking raw rice in at least a gelatinizing solution;
An imaging means for capturing an image of the raw rice immersed in the gelatinization solution at a predetermined timing;
image data acquisition means for acquiring image data captured by the imaging means;
an index value calculation means for calculating an index value based on a change in the raw rice immersed in the gelatinization solution for determining the digestibility of the rice based on the image data;
a digestibility determination means for determining the digestibility of the rice based on the index value calculated by the index value calculation means and a predetermined correlation between the index value and the digestibility;
A brightness data acquisition means for acquiring brightness data of at least a portion corresponding to the raw rice from the image data,
the index value calculation means calculates, as the index value, at least one of an amount of increase in luminance and a rate of increase in luminance obtained from the luminance data at the predetermined shooting timing, starting from a predetermined time point;
The correlation is a correlation between the predetermined index value and a Brix value as the digestibility or a aging rate, which is a time rate at which the steamed rice is left to stand and the crystal structure changes to harden the steamed rice,
The predetermined index value is a value that is predetermined based on a change in the raw rice immersed in the gelatinization solution,
The digestibility is a Brix value or a aging rate of the raw rice in a steamed state, measured based on the National Unified Analysis Method for Raw Rice for Sake Brewing,
A change point calculation means for calculating a luminance change point based on the luminance data,
The photographing means photographs images of the raw rice continuously at a plurality of photographing timings,
the change point calculation means calculates the luminance change point at which an average luminance value becomes a minimum based on luminance data of image data at a plurality of shooting timings captured by the imaging means;
the index value calculation means calculates, as the index value, at least one of the amount of increase in luminance and the rate of increase in luminance, starting from the luminance change point;
The gelatinization solution is an alkaline solution .

In addition, the digestibility determination method according to the present invention for achieving the above object is characterized by the following configuration:
A method for determining the digestibility of rice, comprising the steps of:
A soaking step of soaking raw rice in at least a gelatinizing solution;
An imaging step of taking an image of the raw rice immersed in the gelatinization solution at a predetermined imaging timing;
an image data acquisition step of acquiring image data captured in the imaging step;
an index value calculation step of calculating an index value based on a change in the raw rice immersed in the gelatinization solution for determining the digestibility of the rice based on the image data;
a digestibility determination step of determining the digestibility of the rice based on the index value calculated in the index value calculation step and a predetermined correlation between the index value and the digestibility;
A brightness data acquisition step of acquiring brightness data of at least a portion corresponding to the raw rice from the image data;
the index value calculation step is a step of calculating, as the index value, at least one of a luminance increase amount and a luminance increase rate obtained from the luminance data at the predetermined shooting timing, starting from a predetermined time point;
The correlation is a correlation between the predetermined index value and a Brix value as the digestibility or a aging rate, which is a time rate at which the steamed rice is left to stand and the crystal structure changes to harden the steamed rice,
The predetermined index value is a value that is predetermined based on a change in the raw rice immersed in the gelatinization solution,
The digestibility is a Brix value or a aging rate of the raw rice in a steamed state, measured based on the National Unified Analysis Method for Raw Rice for Sake Brewing,
A change point calculation step of calculating a luminance change point based on the luminance data,
The photographing step includes photographing images of the raw rice continuously at a plurality of photographing timings,
The change point calculation step calculates the luminance change point at which an average luminance value becomes a minimum based on luminance data of image data at a plurality of shooting timings captured in the photographing step,
the index value calculation step calculates, as the index value, at least one of the luminance increase amount and the luminance increase rate, starting from the luminance change point;
The digestibility determination method is characterized in that the gelatinization solution is an alkaline solution .

According to the above-described characteristic configuration, raw rice soaked in an alkaline solution as a gelatinization solution is photographed, and the amount of brightness increase and the brightness increase rate obtained from the brightness data at a specified photographing timing, starting from a specified point in time, are calculated as index values.

Here, as a result of intensive research, the inventors of the present application found that there is a correlation between the amount of increase in brightness or the rate of increase in brightness obtained from brightness data of image data captured at a specific shooting timing starting from a specific time point, and the digestibility of rice. They obtained the knowledge that the digestibility of rice can be determined by utilizing this correlation, and completed the present invention.
In addition, it was found that when the predetermined index value is determined based on the change in raw rice when the raw rice is immersed in a gelatinization solution and the index value is the Brix value or aging rate of the raw rice in a steamed state measured based on the National Unified Analysis Method for Raw Rice for Sake Brewing, there is a correlation between the two, and when the luminance increase amount and luminance change point as the predetermined index values are calculated starting from the luminance change point, the digestibility of rice can be accurately determined based on the calculated index value. Furthermore, it has been confirmed by experiments that when an alkaline solution is used as the gelatinization solution, there is a high correlation between the index value and digestibility.

That is, in the above characteristic configuration, the digestibility of rice can be determined by the digestibility determination means (digestibility determination step) based on the amount of increase in luminance or the rate of increase in luminance as index values calculated by the index value calculation means (index value calculation step) starting from a point of change in luminance calculated based on image data obtained by continuously photographing images of raw rice at multiple shooting timings, and based on the correlation between the amount of increase in luminance or the rate of increase in luminance as predetermined index values and digestibility. Note that "digestibility" refers to the Brix value or the aging rate , which is the time rate at which steamed rice hardens due to a change in crystal structure when left to stand, and can be quantified.

In this way, according to the above characteristic configuration, the raw rice is immersed in a gelatinizing solution and gelatinized while being photographed, and an index value can be calculated based on the photographed image. Furthermore, the digestibility of the rice can be easily quantified and determined based on the calculated index value and the above correlation.

In addition, for example, when using index values obtained from the area of a single grain of rice in image data, such as the expansion rate or area increase of a single grain of rice, the rice may crack or break during observation and split into two or more fine grains, making it impossible to calculate an index value, or even if it can be calculated, it may be inappropriate, resulting in an inability to accurately evaluate digestibility. However, the above characteristic configuration uses brightness-related values, such as the brightness increase amount and brightness increase rate, as index values, and even if rice splits into fine grains, appropriate index values can be calculated and digestibility can be accurately evaluated. Splitting of rice during observation is particularly likely to occur with rice that has a low polishing rate, but the above characteristic configuration makes it possible to accurately evaluate digestibility even with rice that has a low polishing rate.

Thus, according to the above characteristic configuration, compared to the National Unified Analysis Method for Raw Rice for Sake Brewing, there is no need to perform complicated operations such as soaking sake rice in water for a long period of time or steaming the sake rice after soaking, and there is an advantage that the operation is simpler than the method described in Patent Document 2. Furthermore, in the above characteristic configuration, an index value is calculated based on an image of raw rice, and this index value is used to quantify digestibility. Therefore, there is an advantage that it is easier to improve accuracy than the method described in Patent Document 1, in which the index for evaluating digestibility is judged visually. In addition, because a value related to brightness is used as the index value, there is an advantage that digestibility can be accurately evaluated even for rice with a low polishing rate.

As described above, the digestibility assessment system and digestibility assessment method having the above-mentioned characteristic configuration can numerically evaluate digestibility in a relatively short time without requiring complicated operations. In addition, digestibility can be accurately evaluated even for rice with a low polishing rate.

Further, a further characteristic configuration of the digestibility determination system according to the present invention is as follows:
The digestibility determination means determines the digestibility of the rice based on the correlation between the luminance increase amount or the luminance increase rate as the predetermined index value starting from the luminance change point and the Brix value or aging rate after aging for a specified period of time, and the index value calculated by the index value calculation means.

As a result of extensive research, the inventors of the present application have succeeded in discovering that there is a particularly strong correlation between a predetermined amount of luminance increase or rate of luminance increase (index value) starting from a luminance change point and the Brix value or aging rate of rice after a specified period of aging, and have found that the digestibility of rice can be determined based on this correlation.

In other words, according to the above characteristic configuration, the digestibility of rice can be quantified as the Brix value or aging rate after aging for a predetermined period of time based on the correlation between the luminance increase amount or luminance increase rate as a predetermined index value starting from the luminance change point and the Brix value or aging time after aging for a predetermined period of time, and the calculated luminance increase amount or luminance increase rate.

1 is a diagram showing a schematic configuration of a digestibility determination system according to an embodiment. FIG. 2 is a functional block diagram showing a control device. 1 is a graph summarizing the relationship between luminance and the time elapsed from the start of the reaction. 11 is a graph summarizing the relationship between the amount of luminance increase and the time elapsed from the luminance change point. 11 is a graph summarizing the relationship between the luminance increase rate and the time elapsed from the luminance change point. 1 is a graph summarizing the relationship between Brix value and aging time. 11 is a graph showing the relationship between the amount of luminance increase 15 minutes after the luminance change point and Brix-0h. 1 is a graph showing the relationship between the luminance increase rate 30 minutes after the luminance change point and Brix-3h. 1 is a graph showing the relationship between the amount of luminance increase 45 minutes after the luminance change point and Brix-6h. 11 is a graph showing the relationship between the amount of luminance increase 5 minutes after the luminance change point and the aging rate. 1 is a graph showing the relationship between predicted values and actual measured values regarding Brix-0h. 1 is a graph showing the relationship between predicted and actually measured values for Brix-3h. 1 is a graph showing the relationship between predicted and actually measured values for Brix-6h.

The digestibility determination system and digestibility determination method according to one embodiment of the present invention will be described below with reference to the drawings.

Figure 1 shows a schematic configuration of a digestibility determination system 1 according to this embodiment. As shown in Figure 1, the digestibility determination system 1 includes an immersion device 2 (immersion means) that immerses raw rice R in a gelatinization solution, an image capture device 5 (image capture means) that captures images of the raw rice R immersed in the gelatinization solution at a predetermined timing, and a control device 10 that is composed of various functional parts that will be described later. In this embodiment, the raw rice R that is the subject of digestibility determination is raw rice for sake brewing.

In this embodiment, the soaking device 2 is composed of a mounting table 3 arranged in the measurement box B, a container 4 placed on the mounting table 3, and the like. Therefore, the soaking device 2 is capable of soaking the raw rice R in the gelatinization solution by putting the raw rice R and the gelatinization solution into the container 4. Specifically, in this embodiment, an alkaline solution is used as the gelatinization solution, and more specifically, a potassium hydroxide solution is used. When an alkaline solution is used as the gelatinization solution, the concentration of the alkaline solution is preferably 0.1 M to 3 M, more preferably 0.1 M to 0.6 M, and the concentration of the potassium hydroxide solution used in this embodiment is 0.35 M. In addition, the temperature at which the raw rice R is soaked in the gelatinization solution is preferably 10°C to 50°C, more preferably 20°C to 40°C, and in this embodiment, it is 30°C.

The photographing device 5 is disposed above the mounting table 3, and photographs the raw rice R in the container 4 at a predetermined photographing timing. In this embodiment, the photographing device 5 is a camera, and is configured to continuously photograph images of the raw rice R at multiple photographing timings. The photographing timings at which the photographing device 5 photographs the raw rice R are every 30 seconds from the time when the raw rice R and potassium hydroxide solution are put into the container 4 and soaking starts until a predetermined time has elapsed (at the start of soaking, 30 seconds after soaking starts, 1 minute after soaking starts, 1 minute 30 seconds after soaking starts, etc.).

As shown in FIG. 2, the control device 10 includes an image data acquisition unit 11 (image data acquisition means), an index value calculation unit 15 (index value calculation means), and a digestibility determination unit 16 (digestibility determination means). The control device 10 in this embodiment also includes a brightness data acquisition unit 13 (brightness data acquisition means) and a change point calculation unit 14 (change point calculation means). The control device 10 in this embodiment further includes an image processing unit 12 and a memory unit 17 in which a correlation between a predetermined index value and digestibility (hereinafter also referred to as "index value-digestibility correlation") and various information to be handled are stored.

The image data acquisition unit 11 is a functional unit that acquires image data of raw rice R photographed by the photographing device 5. Specifically, in this embodiment, a signal related to the image data transmitted from the photographing device 5 is received to acquire image data of raw rice R. The image data acquired by the image data acquisition unit 11 is appropriately stored in the storage unit 17.

The image processing unit 12 is a functional unit that processes the image data acquired by the image data acquisition unit 11. Specifically, in this embodiment, the image processing unit 12 performs processing to convert the image data acquired by the image data acquisition unit 11 into 256-level image data (grayscale image data) in which light areas are 255 and dark areas are 0.

The brightness data acquisition unit 13 is a functional unit that acquires brightness data from the image data at least for a portion corresponding to raw rice R. In this embodiment, the image data captured by the image capture device 5 is converted into grayscale image data by processing in the image processing unit 12. Therefore, the brightness data acquisition unit 13 in this embodiment acquires brightness data for a portion corresponding to raw rice R in the grayscale image data obtained by processing in the image processing unit 12.

The change point calculation unit 14 is a functional unit that calculates a luminance change point based on the luminance data acquired by the luminance data acquisition unit 13. In this embodiment, the luminance change point is calculated based on the luminance data of an area that includes only raw rice R in the grayscale image data obtained by converting image data of raw rice R captured at multiple capture timings. More specifically, the luminance change point is calculated as the time when image data was captured at which the average luminance value of the area corresponding to raw rice R in the grayscale image data becomes a minimum value.

The index value calculation unit 15 calculates the luminance increase amount and luminance increase rate obtained from the luminance data at a specified shooting timing, starting from a specified time point, as index values. Specifically, the index value calculation unit 15 of this embodiment calculates the luminance increase amount and luminance increase rate at a specified shooting timing point, starting from the luminance change point calculated by the change point calculation unit 14 (hereinafter also referred to as the "luminance increase amount starting from the luminance change point" and the "luminance increase rate starting from the luminance change point"). The luminance increase amount and luminance increase rate can be calculated, for example, by comparing the average luminance value of the area containing only raw rice R in the image captured at the shooting timing corresponding to the luminance change point with the average luminance value of the area containing only raw rice R in the image captured at the specified shooting timing.

The digestibility determination unit 16 is a functional unit that determines the digestibility of rice based on the index value (the amount of luminance increase and the rate of luminance increase from the luminance change point) calculated by the index value calculation unit 15 and a predetermined correlation between the index value and digestibility (index value-digestibility correlation).

Here, the index value-digestibility correlation in this embodiment will be described. In the index value-digestibility correlation in this embodiment, "digestibility" refers to the Brix value or aging rate of raw rice R steamed, measured with reference to the National Uniform Analysis Method for Raw Rice for Sake Brewing, and more specifically, for multiple varieties of raw rice R, the Brix value measured with reference to the National Uniform Analysis Method for Raw Rice for Sake Brewing described later with different aging times and the aging rate calculated from the measured Brix value, and the Brix value of rice steamed after soaking raw rice R in water for a predetermined time and the aging rate calculated from the measured Brix value. In addition, the "predetermined index value" in the index value-digestibility correlation is a value determined in advance based on the change in raw rice R soaked in a gelatinization solution, and more specifically, the luminance increase amount and luminance increase rate calculated as described above for multiple varieties of raw rice R of the same lot as raw rice R subjected to the National Uniform Analysis Method for Raw Rice for Sake Brewing at the time when a predetermined time has passed from the luminance change point. In other words, the index value-digestibility correlation is an approximation of a graph plotting the relationship between the Brix value and aging rate when multiple varieties of raw rice R are aged for a certain period of time, and the amount of luminance increase and the rate of luminance increase at a certain period of time after the luminance change point. For example, an approximation of a graph plotting the relationship between the Brix value measured when the aging time is 0 hours (i.e., unaged) and the amount of luminance increase at 10 minutes after the luminance change point for multiple varieties of raw rice R is one of the index value-digestibility correlations.

Furthermore, among such index value-digestibility correlations, when the index value is the amount of increase in luminance, strong correlations were observed between the relationship between the Brix value at unaged time and the amount of increase in luminance 5 to 35 minutes after the luminance change point, the relationship between the Brix value after an aging time of 3 hours and the amount of increase in luminance 20 to 45 minutes after the luminance change point, the relationship between the Brix value after an aging time of 6 hours and the amount of increase in luminance 30 to 45 minutes after the luminance change point, and the relationship between the aging rate and the amount of increase in luminance 5 to 15 minutes after the luminance change point (see Table 1). Furthermore, when the index value is the luminance increase rate, a strong correlation was observed between the relationship between the Brix value at unaged time and the luminance increase rate 10 minutes after the luminance change point, the relationship between the Brix value at 3 hours of aging time and the luminance increase rate 5 to 40 minutes after the luminance change point, and the relationship between the Brix value at 6 hours of aging time and the luminance increase rate 30 to 45 minutes after the luminance change point (see Table 2). Therefore, by using these relationships as the index value-digestibility correlation, digestibility can be accurately determined from the index value calculated by the index value calculation unit 15.

The memory unit 17 is a functional unit that stores various information handled by the digestibility determination system 1. Specifically, in this embodiment, in addition to the index value-digestibility correlation, information acquired and calculated by various functional units (such as brightness data) can be stored. The index value-digestibility correlation may be stored in the memory unit 17 as an approximation formula, or data required to create the approximation formula may be stored in the memory unit 17, and an approximation formula may be appropriately created and used based on this data when determining digestibility.

Next, we will explain how to determine the digestibility of rice using the digestibility determination system 1 configured as described above.

First, about 60 grains of raw rice R are placed in a container 4 placed on a mounting table 3 in the measurement box B, and then potassium hydroxide solution as an alkaline solution is poured into the container 4 to soak the raw rice R in the potassium hydroxide solution (soaking process).

Next, images of the raw rice R are taken by the photographing device 5 every 30 seconds from the start of soaking the raw rice R until a predetermined time has elapsed (photographing process).

Next, the image of the raw rice R captured by the photographing device 5 is acquired by the image data acquisition unit 11 (image data acquisition process), and the acquired image data is converted into grayscale image data in the image processing unit 12.

Next, the brightness data of the area containing only raw rice R in the grayscale image data is acquired by the brightness data acquisition unit 13 (brightness data acquisition process), and then the brightness change point is calculated by the change point calculation unit 14 based on the acquired brightness data (change point calculation process).

Next, the luminance increase amount and luminance increase rate starting from the luminance change point at a specified shooting timing are calculated by the index value calculation unit 15 (index value calculation process). Note that in this example, as described above, there is a particularly high correlation among the index value-digestibility correlations, so the luminance increase amount starting from the luminance change point at the shooting timings 5, 15, and 45 minutes after the luminance change point and the luminance increase rate starting from the luminance change point at the shooting timing 30 minutes after the luminance change point are calculated.

Next, in the digestibility determination unit 16, the digestibility of the rice is determined based on the index value (luminance increase amount and luminance increase rate) calculated by the index value calculation unit 15 and the index value-digestibility correlation (digestibility determination process). That is, based on the relationship between the Brix value when not aged and the luminance increase amount 10 minutes after the luminance change point, the digestibility of the rice is quantified as the Brix value when not aged. Also, based on the relationship between the Brix value after 3 hours of aging and the luminance increase rate 30 minutes after the luminance change point, the digestibility of the rice is quantified as the Brix value after 3 hours of aging. Furthermore, based on the relationship between the Brix value after 6 hours of aging and the luminance increase amount 40 minutes after the luminance change point, the digestibility of the rice is quantified as the Brix value after 6 hours of aging. Also, based on the relationship between the aging rate and the luminance increase amount 5 minutes after the luminance change point, the digestibility of the rice is quantified as the aging rate.

As described above, the digestibility determination system and method according to this embodiment can quantify and determine the digestibility of rice as a Brix value or aging rate in a relatively short time without requiring complicated operations. In addition, because the index value is related to brightness, the digestibility can be accurately evaluated even for rice with a low polishing rate.

Below, we explain the experiments conducted to obtain the index value-digestibility correlation.

[Calculation of index values (luminance increase amount and luminance increase rate)]
A total of six samples were prepared - Yamadanishiki, Gohyakumangoku, and Miyamanishiki - with rice polishing rates of 50% and harvested in 2019 and 2020. 60 grains of each of these samples were immersed in a potassium hydroxide solution (0.35 M) at 30°C, and images were taken every 30 seconds. Based on the images, the brightness of areas containing only raw rice was obtained.

Next, the luminance change point was calculated based on the luminance of the area containing only raw rice. Figure 3 is a graph showing the relationship between the luminance of the area containing only raw rice for each sample and the time elapsed from the start of the reaction.

As can be seen from Figure 3, the brightness of the area containing only raw rice gradually decreased for all samples until approximately the same amount of time had elapsed from the start of the reaction, and then began to increase. The points at which the brightness changed for each sample (time elapsed from the start of the reaction) were 13.5 min for Yamadanishiki, 13.5 min for Gohyakumangoku, and 19.5 min for Miyamanishiki produced in 2019, and 15 min for Yamadanishiki, 13.5 min for Gohyakumangoku, and 16.5 min for Miyamanishiki produced in 2020.

Next, based on the brightness of the acquired area containing only raw rice, the brightness increase amount and brightness increase rate for each sample were calculated starting from the brightness change point. Figure 4 is a graph showing the relationship between the calculated brightness increase amount and the time elapsed from the brightness change point, and Figure 5 is a graph showing the relationship between the calculated brightness increase rate and the time elapsed from the brightness change point. Note that the brightness increase amount in Figure 4 and the brightness increase rate in Figure 5 are the average values for 60 grains of raw rice in each sample. As can be seen from Figures 4 and 5, there is a tendency for the brightness increase amount and brightness increase rate to increase as time passes from the brightness change point for each sample.

In this way, the amount of luminance increase and the rate of luminance increase from the luminance change point were calculated for each sample. This calculated index value is the "predetermined index value" in the index value-digestibility correlation function.

[Measurement of digestibility (Brix value and retrogradation rate)]
For the above six types of samples, the Brix value as a measure of digestibility was calculated by changing the aging time in accordance with the National Unified Analysis Method for Raw Rice for Sake Brewing, and the aging rate was calculated based on the calculated Brix value.
First, three sets of 10 g each of the six types of samples were immersed in water to absorb water for 15 to 20 hours, and then steamed for 45 minutes.
In addition, a 0.1 M succinic acid solution and a 0.1 M sodium succinate solution were mixed to prepare a 0.1 M succinic acid buffer solution of pH 4.3. Next, this succinic acid buffer solution was mixed with α-amylase at 60 u/mL and protease at 3000 u/mL to obtain an enzyme buffer solution.
Next, of the three sets, one of the sets was steamed, and after the rice temperature had cooled to room temperature, 50 mL of enzyme buffer was added, and the rice was vigorously shaken for 10 seconds, and then allowed to stand at 15° C. for 24 hours for digestion. If necessary, 0.5 mL of toluene was added as a preservative. Meanwhile, the other two sets were aged for 6 or 3 hours immediately after steaming, and then digested in the same manner as above.
After digestion, the digestive fluid was centrifuged to obtain a filtrate, and the Brix value of this filtrate was measured to obtain the Brix value before aging (Brix-0h), the Brix value after aging for 3 hours (Brix-3h), and the Brix value after aging for 6 hours (Brix-6h). In addition, the aging rate of each sample was calculated based on the Brix values of each sample (Brix-0h, Brix-3h, Brix-6h).
The aging rate was calculated based on the following formula 1.
(Equation 1)
Aging rate=100-(Brix-6h/Brix-3h)×100
Fig. 6 is a graph summarizing the relationship between the Brix value and the aging time of each measured sample. The aging rate of each sample was 20.9% for Yamada Nishiki, 22.5% for Gohyakumangoku, and 26.0% for Miyamanishiki produced in 2019, and 21.6% for Yamada Nishiki, 16.7% for Gohyakumangoku, and 9.1% for Miyamanishiki produced in 2020.

[Correlation between index value and digestibility]
The index value-digestibility correlation can be obtained based on the index value and digestibility calculated as described above.
That is, for each elapsed time from the luminance change point, the luminance increase amount or luminance increase rate starting from the luminance change point is on the horizontal axis, and the Brix value (Brix-0h, Brix-3h, Brix-6h) or aging rate is on the vertical axis, and the approximation equation of the graph plotting each sample data is the index value-digestibility correlation.
7 to 10 show examples of graphs plotting data of each sample. FIG. 7 is a graph plotting data of each sample with the luminance increase amount at the time when 15 minutes have passed from the luminance change point as the horizontal axis and Brix-0h as the vertical axis. FIG. 8 is a graph plotting data of each sample with the luminance increase rate at the time when 30 minutes have passed from the luminance change point as the horizontal axis and Brix-3h as the vertical axis. FIG. 9 is a graph plotting data of each sample with the luminance increase amount at the time when 45 minutes have passed from the luminance change point as the horizontal axis and Brix-6h as the vertical axis. Furthermore, FIG. 10 is a graph plotting data of each sample with the luminance increase amount at the time when 5 minutes have passed from the luminance change point as the horizontal axis and the aging rate as the vertical axis.
Table 1 summarizes the correlation coefficients of the relationship between the amount of luminance increase starting from the luminance change point and digestibility, and Table 2 summarizes the correlation coefficients of the relationship between the rate of luminance increase starting from the luminance change point and digestibility.

As can be seen from Table 1, there is a very strong correlation between the amount of luminance increase from 5 to 35 minutes after the luminance change point and Brix-0h, the amount of luminance increase from 20 to 45 minutes after the luminance change point and Brix-3h, the amount of luminance increase from 30 to 45 minutes after the luminance change point and Brix-6h, and the amount of luminance increase from 5 to 15 minutes after the luminance change point and the aging rate.

Also, as can be seen from Table 2, there is a very strong correlation between the relationship between the luminance increase rate 10 minutes after the luminance change point and Brix-0h, the relationship between the luminance increase rate from 5 to 40 minutes after the luminance change point and Brix-3h, and the relationship between the luminance increase rate from 30 to 45 minutes after the luminance change point and Brix-6h.

As such, the above-mentioned relationship is a particularly significant one among the index value-digestibility correlations. Therefore, when it is necessary to more accurately determine the digestibility of rice, it is preferable to use a particularly significant relationship such as the above-mentioned as the index value-digestibility correlation in the digestibility determination system 1.

[Evaluation of relationship with actual measured values]
For each of the above samples, the predicted values (predicted Brix-0h value, predicted Brix-3h value, predicted Brix-6h value) determined by the digestibility determination system were evaluated for their relationship with the actual values (actual Brix-0h value, actual Brix-3h value, actual Brix-6h value) calculated in accordance with the National Unified Analysis Method for Raw Rice for Sake Brewing. Figures 11 to 13 are graphs showing the results. As can be seen from these figures, the predicted values and actual values are in good agreement, and this digestibility determination system can accurately evaluate the digestibility of rice.

[Another embodiment]
[1] In the above embodiment, a potassium hydroxide solution is used as the gelatinizing solution, but the present invention is not limited to this. As the gelatinizing solution, a sodium hydroxide solution, a lithium hydroxide solution, a rubidium hydroxide solution, a cesium hydroxide solution, a calcium hydroxide solution, a strontium hydroxide solution, a potassium thiocyanate solution, a potassium iodide solution, an ammonium nitrate solution, a calcium chloride solution, a guanidine hydrochloride solution, a dimethyl sulfoxide solution, a urea solution, or the like can be used.

[2] In the above embodiment, the raw rice R is immersed in the gelatinization solution without performing any pre-processing, but this is not limited to the above. For example, the immersion device 2 may be configured to immerse the raw rice R in water and then immerse the raw rice R in the gelatinization solution.

[3] In the above embodiment, the image capturing device 5 captures images of raw rice R continuously at intervals of 30 seconds, but this is not limited to the above. The intervals at which the image capturing device 5 captures images may be set as appropriate.

[4] In the above embodiment, the amount of luminance increase and the luminance increase rate starting from the luminance change point are used as index values, but the present invention is not limited to this, and at least one of these two index values may be calculated. Also, in the above embodiment, the amount of luminance increase starting from the luminance change point at the shooting timing 5, 15, and 45 minutes after the luminance change point and the luminance increase rate starting from the luminance change point at the shooting timing 30 minutes after the luminance change point are calculated, but the present invention is not limited to this. For example, the amount of luminance increase starting from the luminance change point at the shooting timing 20 minutes after the luminance change point may be calculated as an index value.

[5] In the above embodiment, the amount of luminance increase and the rate of luminance increase starting from the luminance change point are used as index values, but the present invention is not limited to this, and the amount of luminance increase and the rate of luminance increase starting from the start of the reaction may be used as index values. In this case, the photographing device 5 may be configured to photograph images of the raw rice R at the start of the reaction and at a certain photographing timing a predetermined time after the start of the reaction, rather than photographing images of the raw rice R continuously. Even in this case, the amount of luminance increase and the rate of luminance increase can be calculated as index values based on the image at the start of the reaction and the image photographed at the certain photographing timing, and digestibility can be determined using the index value-digestibility correlation.

[6] In the above embodiment, the change point calculation unit 14 is provided, but this is not limited to this, and it may be provided in a form that does not include these. In addition, in the above embodiment, the image processing unit 12 and the memory unit 17 are provided, but this is not limited to this, and it may be provided in a form that does not include these. Note that if a form that does not include the memory unit 17 is adopted, the index value-digestibility correlation can be appropriately obtained from an external server via, for example, an electric communication line, etc., to determine digestibility.

[7] In the above embodiment, the raw rice R to be judged for digestibility is raw rice for sake brewing, but this is not limited to this.

The configurations disclosed in the above embodiments (including other embodiments) can be applied in combination with configurations disclosed in other embodiments, provided no inconsistencies arise. Furthermore, the embodiments disclosed in this specification are merely examples, and the present invention is not limited thereto, and can be modified as appropriate within the scope of the purpose of the present invention.

The present invention can be used in a digestibility assessment system that can numerically evaluate digestibility in a relatively short time without requiring complicated operations.

1: Digestibility determination system 2: Soaking device (soaking means)
5: Photographing device (photographing means)
11: Image data acquisition unit (image data acquisition means)
13: Luminance data acquisition unit (luminance data acquisition means)
14: Change point calculation unit (change point calculation means)
15: Index value calculation unit (index value calculation means)
16: Digestibility determination section (digestibility determination means)

Claims (3)

A system for determining the digestibility of rice, comprising:
A soaking means for soaking raw rice in at least a gelatinizing solution;
An imaging means for capturing an image of the raw rice immersed in the gelatinization solution at a predetermined timing;
image data acquisition means for acquiring image data captured by the imaging means;
an index value calculation means for calculating an index value based on a change in the raw rice immersed in the gelatinization solution for determining the digestibility of the rice based on the image data;
a digestibility determination means for determining the digestibility of the rice based on the index value calculated by the index value calculation means and a predetermined correlation between the index value and the digestibility;
A brightness data acquisition means for acquiring brightness data of at least a portion corresponding to the raw rice from the image data,
the index value calculation means calculates, as the index value, at least one of an amount of increase in luminance and a rate of increase in luminance obtained from the luminance data at the predetermined shooting timing, starting from a predetermined time point;
The correlation is a correlation between the predetermined index value and a Brix value as the digestibility or a aging rate, which is a time rate at which the steamed rice is left to stand and the crystal structure changes to harden the steamed rice,
The predetermined index value is a value that is predetermined based on a change in the raw rice immersed in the gelatinization solution,
The digestibility is a Brix value or a aging rate of the raw rice in a steamed state, measured based on the National Unified Analysis Method for Raw Rice for Sake Brewing,
A change point calculation means for calculating a luminance change point based on the luminance data,
The photographing means photographs images of the raw rice continuously at a plurality of photographing timings,
the change point calculation means calculates the luminance change point at which an average luminance value becomes a minimum based on luminance data of image data at a plurality of shooting timings captured by the imaging means;
the index value calculation means calculates, as the index value, at least one of the amount of increase in luminance and the rate of increase in luminance, starting from the luminance change point;
The digestibility determination system , wherein the gelatinization solution is an alkaline solution . The digestibility determination system of claim 1, wherein the digestibility determination means determines the digestibility of the rice based on the correlation between the brightness increase amount or the brightness increase rate as the predetermined index value with the brightness change point as the starting point and the Brix value or the aging rate after aging for a specified period of time, and the index value calculated by the index value calculation means. A method for determining the digestibility of rice, comprising the steps of:
A soaking step of soaking raw rice in at least a gelatinizing solution;
An imaging step of taking an image of the raw rice immersed in the gelatinization solution at a predetermined imaging timing;
an image data acquisition step of acquiring image data captured in the imaging step;
an index value calculation step of calculating an index value based on a change in the raw rice immersed in the gelatinization solution for determining the digestibility of the rice based on the image data;
a digestibility determination step of determining the digestibility of the rice based on the index value calculated in the index value calculation step and a predetermined correlation between the index value and the digestibility;
A brightness data acquisition step of acquiring brightness data of at least a portion corresponding to the raw rice from the image data;
the index value calculation step is a step of calculating, as the index value, at least one of a luminance increase amount and a luminance increase rate obtained from the luminance data at the predetermined shooting timing, starting from a predetermined time point;
The correlation is a correlation between the predetermined index value and a Brix value as the digestibility or a aging rate, which is a time rate at which the steamed rice is left to stand and the crystal structure changes to harden the steamed rice,
The predetermined index value is a value that is predetermined based on a change in the raw rice immersed in the gelatinization solution,
The digestibility is a Brix value or a aging rate of the raw rice in a steamed state, measured based on the National Unified Analysis Method for Raw Rice for Sake Brewing,
A change point calculation step of calculating a luminance change point based on the luminance data,
The photographing step includes photographing images of the raw rice continuously at a plurality of photographing timings,
The change point calculation step calculates the luminance change point at which an average luminance value becomes a minimum based on luminance data of image data at a plurality of shooting timings captured in the photographing step;
the index value calculation step calculates, as the index value, at least one of the luminance increase amount and the luminance increase rate, starting from the luminance change point;
The method for determining digestibility , wherein the gelatinization solution is an alkaline solution .

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