Method for measuring the potassium content of root vegetables and method for producing root vegetables

Abstract

To provide a method capable of measuring a potassium content in root vegetable hypocotyls in a non-destructive manner.SOLUTION: A method capable of measuring a potassium content in root vegetable hypocotyls includes the steps of; irradiating a hypocotyl of a test root vegetable with visible light between 400 and 1400 nm and light included in a near-infrared region; measuring reflectance intensity corresponding to two or more kinds of wavelengths included in the visible light and the near-infrared region between 400 and 1400 nm; calculating the reflectance; and measuring the potassium content of the test subject from the values. The root vegetable is preferably radish (Raphanus sativus var. sativus) or turnip (Brassica rapa var. rapa).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for measuring the potassium content of root vegetables, particularly in the hypocotyl, in a non-destructive manner. [Background technology]

[0002] The number of patients with chronic kidney disease in Japan is increasing year by year, and according to Non-Patent Literature 1, there are over 340,000 kidney disease dialysis patients with end-stage renal failure. Since chronic kidney disease cannot be cured with current medical treatments, kidney disease dialysis patients are subjected to strict dietary restrictions in addition to hemodialysis. Potassium is one of the nutrients that needs to be restricted in the intake of kidney disease dialysis patients. Because kidney disease dialysis patients cannot adequately excrete potassium from their bodies, if intake is not restricted, it can lead to hyperkalemia, which can result in arrhythmias and heart failure.

[0003] To alleviate some of the problems faced by kidney disease patients undergoing dialysis, "low-potassium vegetables" have been developed, which are cultivated to have a lower potassium content. To date, there have been reports of successful cases of reducing potassium content in leafy vegetables such as spinach (see Non-Patent Literature 2) and lettuce, as well as in fruits such as melons, strawberries, and root vegetables.

[0004] On the other hand, low-potassium leafy vegetables, primarily low-potassium lettuce, currently sold on the market are cultivated in plant factories where growing conditions such as temperature, sunlight, and humidity are kept uniform. While 100% inspection is desirable to guarantee quality, a decrease in potassium content is confirmed by random sampling at the time of shipment. Measuring potassium content through random sampling involves destructive procedures such as extracting juice from the plant and measuring potassium using an ion meter, or measuring potassium by ashing the plant and extracting potassium. Therefore, in order to aim for quality assurance through 100% inspection, it is necessary to develop a non-destructive and easy method for measuring potassium content.

[0005] Referring to Patent Document 1, there is an invention that describes a method for non-destructively measuring the potassium content of a melon by irradiating the melon rind with multiple wavelengths included in the visible light range of 500 nm to 800 nm and measuring the potassium content of the melon based on the reflected light intensity. In other words, Patent Document 1 non-destructively measures the potassium content of melons using the reflectance in the visible light range of 500 nm to 800 nm. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-135344 [Non-patent literature]

[0007] [Non-Patent Document 1] Hanabusa, Norio et al., Current Status of Chronic Dialysis Therapy in Japan (as of December 31, 2020), Journal of the Japanese Society for Dialysis Therapy, 2021, 54, pp. 611-657. [Non-Patent Document 2] Yosuke Tanigaki et al., Basic Research on Potassium Reduction in Root Vegetables 2, Abstracts of Presentations at the Matsuyama Conference of the Japanese Society of Biological and Environmental Engineering, 2017, pp. 80-81. [Non-Patent Document 3] Atsushi Ogawa et al., Establishment of a cultivation method for low-potassium spinach for kidney disease dialysis patients, Journal of the Crop Science Society of Japan, 2007, 76, pp. 232-237. [Overview of the project] [Problems that the invention aims to solve]

[0008] In Patent Document 1, it was found that using the reflectance range of 500 nm to 800 nm for melons, which are green in color, yielded a correlation with the potassium content. However, root vegetables such as radishes and turnips exhibit a variety of colors, including white, red, and purple, and even when examining the relationship between these colors and potassium content using reflectance in the 500nm to 800nm ​​range, a high correlation between the two was sometimes not obtained.

[0009] This invention has been made in view of these circumstances and aims to resolve the above-mentioned problems. [Means for solving the problem]

[0010] The present invention provides a method for measuring the potassium content of root vegetables, which involves irradiating the hypocotyl portion of the root vegetable, with visible light and near-infrared light in the range of 400 to 1400 nm. The aforementioned root vegetable is either a radish (Raphanus sativus var. sativus) or a turnip (Brassica rapa var. rapa), The reflectance corresponding to two or more wavelengths of the aforementioned light is measured, and the reflectance is calculated from the reflectance, and the values ​​of the reflectance and the reflectance are used Therefore, using the reflectance and measured potassium content of multiple samples, a calibration curve prepared in advance was used. The method is characterized by measuring the potassium content of the root vegetables based on this. The present invention provides a method for measuring the potassium content of root vegetables, in which the potassium content is estimated by the following formula (1). K=a 1 ×R 1 +a 2 ×R 2 +a 3 ×R 3 …… +a n ×R n +b -- Equation (1) However, K is the estimated potassium content, R1, R2, R3...R n These represent the reflectance corresponding to n wavelengths included in the visible and near-infrared regions between 400 and 1400 nm, a1, a2, a3...a n And b are coefficients determined by the least squares method using measured reflectance and measured potassium content in a sufficiently large population. The present invention provides a method for measuring the potassium content of root vegetables. The two or more wavelengths mentioned above are selected based on their correlation with the measured potassium content in the population. It is characterized by the following: The present invention's method for producing root vegetables is characterized by measuring the potassium content of the root vegetables using the method for measuring the potassium content of root vegetables, and cultivating them after non-destructively confirming that they are low-potassium vegetables. [Effects of the Invention]

[0011] According to the present invention, the hypocotyl part of a root vegetable as a subject is irradiated with light in the visible light and near-infrared regions of 400 to 1400 nm, the reflection intensity corresponding to two or more wavelengths of the light is measured, the reflectance is calculated from the reflection intensity, and the potassium content of the root vegetable is measured based on the values of the reflection intensity and the reflectance, whereby a method for measuring the potassium content of a root vegetable capable of measuring the potassium concentration of the root vegetable nondestructively can be provided.

Brief Description of the Drawings

[0012] [Figure 1] It is a graph showing the relationship between the estimated value of the potassium content obtained from the reflectance of the hypocotyl of the variety "New Comet" of Hakusai radish according to an embodiment of the present invention and the measured value of the potassium content obtained by the destructive measurement method. [Figure 2] It is a graph showing the relationship between the estimated value of the potassium content obtained from the reflectance by non-destructive measurement of the hypocotyl of the variety "Ruby Comet" of Hakusai radish according to an embodiment of the present invention and the measured value of the potassium content obtained by the destructive measurement method. [Figure 3] It is a graph showing the relationship between the estimated value of the potassium content obtained from the reflectance of the hypocotyl of the variety "Isabel" of Hakusai radish according to an embodiment of the present invention and the measured value of the potassium content obtained by the destructive measurement method. [Figure 4] It is a graph showing the relationship between the estimated value of the potassium content obtained from the reflectance of the hypocotyl of the variety "Mifune" of turnip according to an embodiment of the present invention and the measured value of the potassium content obtained by the destructive measurement method.

Modes for Carrying Out the Invention

[0013] <Embodiment> Patients undergoing hemodialysis for kidney disease need to restrict their potassium intake. "Low-potassium vegetables" cultivated to have a reduced potassium content were developed to alleviate the problems faced by such patients undergoing hemodialysis for kidney disease. Low-potassium vegetables are guaranteed to have reduced potassium content through random sampling before shipment. However, random sampling does not guarantee quality, and 100% inspection, which involves destructive procedures to measure potassium content, is impossible. Therefore, there was a technical need to develop a non-destructive and easy method for measuring potassium content. Therefore, the inventors of this invention conducted diligent research and conceived the idea of ​​utilizing visible light and infrared light reflectance, which are used in the analysis of sugar content, etc. They established a non-destructive method for measuring potassium content in low-potassium root vegetables, and thus completed the present invention.

[0014] Specifically, the inventors cultivated radishes and turnips, which are low-potassium root vegetables, as shown in the examples described later. They then measured the potassium content of the hypocotyls of the root vegetables, which are the edible parts. To measure the potassium content of the hypocotyls of the root vegetables, the hypocotyl portion was dried, then subjected to dry ashing and extraction with nitric acid, and finally measured using an ICP emission spectrometer (ICP-OES) to non-destructively measure the reflectance in the visible light and near-infrared regions between 400 and 1400 nm according to the present invention. To address this, a calibration curve was created using the stepwise method of multiple regression analysis with potassium content measurement as the regression variable. Since radishes can be produced year-round, samples were prepared with staggered cultivation periods, and calibration curves were created and compared for each cultivation period. As a result, a significant correlation of 0.01% or higher was observed between potassium content and visible light and near-infrared light reflectance in all cultivation periods. In other words, it became possible to measure potassium content from visible light and infrared light reflectance.

[0015] The following describes in more detail the method for measuring the potassium content of root vegetables and the method for producing root vegetables according to embodiments of the present invention.

[0016] The method for measuring the potassium content of root vegetables according to this embodiment is characterized by irradiating the hypocotyl portion of the root vegetable, which is a test subject, with visible light and near-infrared light ranging from 400 to 1400 nm, measuring the reflectance corresponding to two or more wavelengths of light, calculating the reflectance from the reflectance, and measuring the potassium content of the root vegetable based on the values ​​of the reflectance and reflectance. In other words, the method for measuring the potassium content of root vegetables according to this embodiment involves irradiating the hypocotyl portion of the root vegetable with light included in the visible light and near-infrared region between 400 and 1400 nm. Then, the reflectance corresponding to two or more wavelengths included in the visible light and near-infrared region between 400 and 1400 nm is measured, the reflectance is calculated, and the potassium content of the sample is measured from these values.

[0017] More specifically, in the root vegetable potassium content measurement method according to this embodiment, the potassium content is estimated based on the following multiple regression model equation (1). K=a1×R1+a1×R1+a1×R1……+a n ×R n +b -- Equation (1) However, K is the estimated potassium content, R1, R2, R3...R n These represent the reflectance corresponding to n wavelengths included in the visible and near-infrared regions between 400 and 1400 nm, a1, a2, a3...a n And b are coefficients determined by the least squares method using measured reflectance and measured potassium content in a sufficiently large population.

[0018] Here, as these n wavelengths, there are two or more (n ≥ 2) wavelengths, and wavelengths that can characteristically explain at least the potassium content are used. Specifically, by reducing n from 1 to n in the above formula (1), wavelengths that are statistically significant enough may be used. In the examples described later, since they were set at intervals of 10 nm between 400 and 1400 nm, although there were 100 wavelengths (n = 100), it may be less, and even several dozen to, in some cases, two wavelengths may be sufficient. The reflectance of each wavelength can be measured using a spectrophotometer for visible light or infrared light.

[0019] Also, for the above a1, a2, a3……a n And a sufficiently large population for calculating b may be, for example, on the order of ten to several hundred, as long as there is a number of samples from which the correlation coefficient can be significantly calculated. For example, as shown in the examples below, a sufficient correlation can be obtained with a sample number of about twenty.

[0020] In the method for measuring the potassium content of root vegetables according to this embodiment, as the root vegetables to be measured, for example, as shown as a representative example in the examples described later, it is preferable to use white radish (Raphanus sativus var. sativus) or turnip (Brassica rapa var. rapa). In addition to the above, the method for measuring the potassium content of root vegetables according to this embodiment can be used for various types of root vegetables. Examples of other root vegetables include table beet (Beta vulgaris vulgaris L.), radish (Raphanus sativus var. hortensis), carrot (Daucus carota subsp. sativus), sweet potato (Ipomoea batatas), ginger (Zingiber officinale), burdock (Arctium lappa L.), lotus root (Nelumbo nucifera), potato (Solanum tuberosum L.), taro (Colocasia esculenta), and yam (Dioscorea), but other types of root vegetables may also be used. Specifically, root vegetables that are not green and have pigments on their surface may also be used.

[0021] The root vegetable production method according to this embodiment is a cultivation method in which the potassium content of the root vegetables is measured by a root vegetable potassium content measurement method, and the vegetables are cultivated after non-destructively confirming that they are low in potassium.

[0022] Specifically, in the cultivation method for root vegetables according to the embodiment of the present invention, it is preferable to use a hydroponic cultivation method that allows for easy modification of the nutrient composition of the growing medium during the cultivation period. In the root vegetable cultivation method of this embodiment, the potassium content of the hypocotyl can be reduced by using the 1K solution shown in the example described later and decreasing the potassium concentration in the culture solution partway through the cultivation period. Here, the hydroponic cultivation method according to the embodiment of the present invention is applicable to both young plants and plants of normal size. In other words, simply by replacing the nutrient solution with a low-potassium nutrient solution for root vegetables, it can be suitably used for hydroponic cultivation in facilities such as greenhouses and plant factories.

[0023] Furthermore, in this embodiment of hydroponic cultivation, after germinating the seeds of root vegetables, they are grown hydroponically using a standard hydroponic nutrient solution. At this time, the temperature, sunlight hours, electrical conductivity (EC), pH, etc. of the nutrient solution are adjusted as appropriate according to the type of root vegetable being cultivated. Furthermore, as a hydroponic cultivation method in this embodiment, cultivation may be performed using, for example, a spray hydroponic system or a flooded system. In the case of a flooded system, cultivation may be performed in a static state without creating a flow of nutrient solution, or in a flowing nutrient solution. This is also true for a specific period before harvest. Furthermore, the hydroponic cultivation method of this embodiment may be applied to conventional greenhouse hydroponic cultivation using sunlight, or to hydroponic cultivation in a plant factory using LEDs (Light Emitting Diodes), etc.

[0024] Furthermore, the root vegetables according to the embodiment of the present invention are characterized by being cultivated by the cultivation method described above for producing root vegetables. The components of root vegetables grown using the hydroponic cultivation method of this embodiment can be analyzed by the measurement method described above. This analysis makes it possible to distinguish them from root vegetables grown using conventional hydroponic cultivation methods that do not have a high potassium content.

[0025] By configuring it as described above, the following effects can be obtained. Traditionally, potassium content of low-potassium vegetables has been inspected through random sampling before shipment. However, from a quality assurance perspective, non-destructive, full-scale inspection is preferable. However, the method described in Patent Document 1 could only be used on green melons. In contrast, the potassium content measurement method for root vegetables according to this embodiment allows for the non-destructive measurement of the potassium content of root vegetables. Specifically, the potassium content in the hypocotyl, which is the edible part of the root vegetable, can be quantitatively measured non-destructively from the reflected light of a specific wavelength obtained by irradiating the root vegetable with light. Therefore, it can be used for quality inspection in the cultivation of low-potassium root vegetables for chronic kidney disease patients who have restrictions on potassium intake.

[0026] In addition, the root vegetable potassium content measurement method according to this embodiment allows for non-destructive measurement of potassium content simply by measuring the reflectance using a conventional small spectrophotometer or infrared spectroscopic sensor and applying it to a calculated multiple regression equation. This eliminates the need for special equipment, as described in Patent Document 1, and allows for easy inspection.

[0027] Traditionally, random sampling was used in the production of low-potassium vegetables. In contrast, by using the root vegetable potassium content measurement method according to this embodiment, it becomes possible to perform 100% inspection and guarantee quality before shipment. Furthermore, the method for measuring the potassium content of root vegetables according to this embodiment can non-destructively and quantitatively measure the potassium content of root vegetables and can be used for quality inspection in the cultivation of low-potassium root vegetables for chronic kidney disease patients who have restrictions on potassium intake. Therefore, the root vegetable production method according to this embodiment can also be used at cultivation sites before shipping low-potassium root vegetables. Furthermore, by incorporating it into a hydroponic cultivation system, it becomes possible to refer to the relationship between the cultivation conditions during cultivation and the potassium content, and to ship the vegetables earlier when the potassium content becomes low.

[0028] In the above embodiment, a multiple regression model was used to measure the potassium content of root vegetables, but it is also possible to use other statistical models, neural networks, kernel machines, and other machine learning methods. [Examples]

[0029] Next, the present invention will be further described with reference to examples based on the drawings, but the following specific examples are not intended to limit the present invention.

[0030] [Cultivating low-potassium root vegetables] The test materials included the varieties of radish (Raphanus sativus var. sativus) "New Comet" (manufactured by Takii Seed Co., Ltd.), "Ruby Comet" (manufactured by Takii Seed Co., Ltd.), and "Isabel" (manufactured by Kaneko Seed Co., Ltd.), and the variety of turnip (Brassica rapa var. rapa) "Mifune" (manufactured by Sakata Seed Corporation).

[0031] Seeds were placed on a petri dish lined with moistened filter paper and germinated in a room set at 22°C for 3 to 5 days. After germination, the seedlings were sandwiched between urethane sponges (22mm x 22mm x 27mm) with a slit in the center, and grown in a culture medium of "1K solution" as described below. When the roots had grown to over 10 cm, the plants were transplanted, still in their sponges, into a Satoyama-style hydroponic cultivation plant (W100-3 type, 750 mm x 750 mm x 3780 mm, manufactured by Satoyama Village Co., Ltd.) located inside a greenhouse. Harvesting took place when the hypocotyl had grown to over 3 cm. Since radishes can be produced year-round, we prepared samples with staggered cultivation periods and created calibration curves for each period for comparison.

[0032] The culture medium (1K solution) used in this example was prepared based on the culture medium composition for low-potassium spinach cultivation described in Non-Patent Literature 3, and the EC in the culture medium was adjusted to 1.3 using an EC control device (Ondine Hydrocontroller, manufactured by Hyoshin Machinery Industry Co., Ltd.). The basic concentration composition (1K solution) was: 1.50 mM KNO3, 1.50 mM NaNO3, 2.00 mM Ca(NO3)2·4H2O, 0.50 mM NH4H2PO4, 1.00 mM MgSO4·7H2O, 26.9 μM EDTA-Fe, 4.55 μM MnCl2·4H2O, 23.1 μM H3BO3, 0.38 μM ZnSO4·7H2O, 0.16 μM CuSO4·5H2O, 0.015 μM (NH4)6Mo7O 24 • It was represented as 4H2O.

[0033] According to Non-Patent Literature 2, it is known that the potassium content of the hypocotyl can be reduced by decreasing the potassium concentration in the culture medium during the cultivation period. Therefore, in this example as well, the culture medium was changed to one with a potassium concentration of "0" during cultivation, and the cultivation was carried out in a manner that varied the potassium content of the hypocotyls.

[0034] [Method for measuring potassium content] After measuring the fresh weight immediately after harvest, the samples were dried for 72 hours in a forced-convection constant-temperature dryer (SOFW450, manufactured by AS ONE Corporation) at 80°C. After measuring the weight after drying, the samples were crushed, and the entire amount was placed in a crucible and burned for 6 hours in a muffle furnace (FP412, manufactured by Yamato Scientific Co., Ltd.) at 550°C. The entire ashed sample was dissolved in 12 ml of 1N HNO3 and filtered through a cellulose filter with a pore size of 0.25 μm. The solution was diluted 20-fold with 1N HNO3, and the potassium concentration was measured using an ICP emission spectrometer (IRIS Adventure ICAP, manufactured by Jarrel Ash, Inc.). The measured elemental concentrations were converted to content (mg / 100g FW), which is the content per 100g of fresh weight.

[0035] [Method for measuring spectral reflectance] Harvested samples were separated into stems, leaves, hypocotyls, and roots, and the visible and near-infrared light reflectance of the hypocotyls was measured. A small spectrophotometer (Spectro 1™, Variable, Inc.) was used to measure visible light reflectance (400nm-700nm), and an ultra-compact near-infrared spectroscopic sensor module (NIRONE S 1.4, Spectral Engines GmbH) was used to measure infrared light reflectance (1100nm-1350nm). For each sample, the reflectance at 400nm-700nm and 1100nm-1350nm was measured in three replicates each under conditions of 10nm intervals.

[0036] The stepwise method (variable addition / removal method) of multiple regression analysis was used for statistical analysis. Potassium content was used as the dependent variable, and spectral reflectance at 10 nm intervals in the 400 nm to 700 nm and 1100 nm to 1350 nm ranges were used as independent variables. Statistical analysis was performed using the statistical software JMP 16 (SAS Institute Inc.). The p-value for adding or removing variables was set to 0.25, and a calibration curve was created.

[0037] [Test Results] Figure 1 shows the relationship between the estimated potassium content obtained from non-destructive reflectance measurements and the measured potassium content obtained by destructive measurement methods for the radish variety "New Comet".

[0038] The correlation coefficient was 0.820 (n=120), indicating a significant correlation between the two at the 0.01% level.

[0039] Figure 2 shows the relationship between the estimated potassium content obtained from non-destructive reflectance measurements and the measured potassium content obtained by destructive measurement methods for the radish variety "Ruby Comet".

[0040] The correlation coefficient was 0.864 (n=21), indicating a significant correlation between the two at the 0.01% level.

[0041] Figure 3 shows the relationship between the estimated potassium content obtained from non-destructive reflectance measurements and the measured potassium content obtained by destructive measurement methods for the radish variety "Isabel".

[0042] The correlation coefficient was 0.865 (n=18), indicating a significant correlation between the two at the 0.01% level.

[0043] Figure 4 shows the relationship between the estimated potassium content obtained from non-destructive reflectance measurements and the measured potassium content obtained by destructive measurement methods for the turnip variety "Mifune".

[0044] The correlation coefficient was 0.856 (n=39), indicating a significant correlation between the two at the 0.01% level.

[0045] These results revealed that potassium content in the hypocotyl of root vegetables can be measured from the reflectance of visible and near-infrared light.

[0046] It goes without saying that the configuration and operation of the above embodiment are examples and can be modified as appropriate without departing from the spirit of the present invention. [Industrial applicability]

[0047] This invention can be used for high-precision quality inspection in the cultivation of low-potassium root vegetables for patients with chronic kidney disease, and can be applied industrially.

Claims

1. The hypocotyl portion of the root vegetable, which is the test subject, is irradiated with visible light and near-infrared light in the range of 400 to 1400 nm. The aforementioned root vegetable is a radish (Raphanus sativus var. sativus) or a turnip (Brassica rapa var. rapa), The reflectance corresponding to two or more wavelengths of the aforementioned light is measured, and the reflectance is calculated from the reflectance. The potassium content of the root vegetable is measured based on the reflectance and reflectance values ​​of the aforementioned reflectance and reflectance, using a calibration curve prepared in advance with the reflectance and actual potassium content measured for multiple samples. A method for measuring the potassium content of root vegetables, characterized by the features described above.

2. The potassium content is estimated by the following formula (1): K=a 1 ×R 1 +a 2 ×R 2 +a 3 ×R 3 ... +a n ×R n +b -- Formula (1) However, K is the estimated potassium content, R 1 , R 2 , R 3 ...R n This shows the reflectance corresponding to n wavelengths included in the visible light and near-infrared region between 400 and 1400 nm, and a 1 a 2 a 3 ...a n And b are coefficients determined by the least squares method using measured reflectance and measured potassium content in a sufficiently large population. The method for measuring the potassium content of root vegetables according to feature 1.

3. The two or more wavelengths are selected based on their correlation with the measured potassium content in the population. The method for measuring the potassium content of root vegetables according to feature 2.

4. The potassium content of the root vegetable is measured by the method for measuring the potassium content of root vegetables according to any one of claims 1 to 3. Cultivate vegetables after non-destructively confirming that they are low in potassium. A method for producing root vegetables characterized by the following.

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