JP7390686B2 - Rice production method - Google Patents

Description

The technical field of the present specification relates to a method for producing rice.

Plasma technology is applied to electrical, chemical, and materials fields. Inside the plasma, ultraviolet rays and radicals are generated in addition to charged particles such as electrons and ions. It has been found that these have various effects on living tissues, including sterilization of living tissues.

It has also become clear that plasma is effective in growing agricultural crops. For example, Patent Document 1 discloses a technique for promoting the growth of rice by irradiating the rice with atmospheric pressure plasma. Patent Document 2 discloses a technique for producing a plasma-activated aqueous solution by irradiating an aqueous solution containing sodium L-lactate with plasma. It has been disclosed that the proportion of heart white rice in sake rice is increased by using a plasma-activated aqueous solution (paragraph [0083] of Cited Example 2).

JP 2020-18278 Publication Japanese Patent Application Publication No. 2020-18277

Shinshiro rice has a white opaque area in the central region of the rice grain. This white part contains starch, and rice grains with a lot of white part are said to be suitable for inlaying. For this reason, it is preferable that the ratio of Shinpaku rice is high in sake rice. On the other hand, when it comes to edible rice, it is said that complete rice without shinpaku etc. is of good quality. In other words, it is preferable that the proportion of white rice in edible rice be small.

The techniques described in Patent Document 1 and Patent Document 2 cannot reduce the proportion of white rice. In addition, with the techniques described in Patent Document 1 and Patent Document 2, it is difficult to increase or decrease the proportion of white white rice depending on whether the sake rice or the edible rice is used.

The problem to be solved by the technology of the present specification is to provide a rice production method capable of controlling increase/decrease in the ratio of white-heart rice.

The rice production method in the first aspect includes a plasma irradiation step of irradiating rice with atmospheric pressure plasma. In the plasma irradiation step, atmospheric pressure plasma is irradiated toward the flower spikelet or carob after flowering.

In this rice production method, the proportion of white rice can be controlled. In other words, it is possible to increase the ratio of Shinpakumai to sake rice, and decrease the ratio of Shinpakumai to table rice. Therefore, this rice production method is suitable for both sake rice and table rice.

The present specification provides a method for producing rice that can control increase or decrease in the proportion of white-heart rice.

Figure 1. A is a sectional view showing the configuration of the first plasma generation device, and FIG. B is a diagram showing the shape of the electrode. Figure 2. A is a sectional view showing the configuration of the second plasma generator, and FIG. B is a diagram showing the shape of the electrode. FIG. 3 is a diagram showing the growth of rice after flowering and the timing of plasma irradiation. It is a figure explaining the plasma irradiation method to rice. It is a graph showing the weight of one grain of brown rice and the proportion of white rice.

Hereinafter, specific embodiments will be described with reference to the drawings, taking a rice production method as an example. Note that the dimensions of the plasma generator are merely examples, and numerical values outside the illustrated numerical range may be used.

(First embodiment)
A first embodiment will be described. In the rice production method of the first embodiment, atmospheric pressure plasma is directly irradiated onto rice. Therefore, first, a plasma irradiation device that irradiates plasma will be explained.

1. Plasma device 1-1. First plasma generator Figure 1. A is a sectional view showing a schematic configuration of a plasma generator P10. Here, the plasma generator P10 is a first plasma generator that spouts plasma in a dotted manner. Figure 1. B is Figure 1. It is a figure showing the details of the shape of electrodes 2a and 2b of plasma generator P10 of A.

The plasma generator P10 includes a housing section 10, electrodes 2a and 2b, and a voltage application section 3. The housing portion 10 is made of a sintered body made of alumina (Al ₂ O ₃ ). The shape of the housing portion 10 is a cylindrical shape. The inner diameter of the housing portion 10 is 2 mm or more and 3 mm or less. The thickness of the housing portion 10 is 0.2 mm or more and 0.3 mm or less. The length of the housing portion 10 is 10 cm or more and 30 cm or less. A gas inlet 10i and a gas outlet 10o are formed at both ends of the casing 10. The gas inlet 10i is for introducing gas for generating plasma. The gas outlet 10o is an irradiation part for irradiating plasma to the outside of the housing part 10. Note that the direction in which the gas moves is the direction of the arrow in the figure.

The electrodes 2a and 2b are a pair of opposing electrodes arranged to face each other. The length of the electrodes 2 a and 2 b in the direction of the opposing surfaces is smaller than the inner diameter of the housing section 10 . For example, it is about 1 mm. The electrodes 2a and 2b are shown in FIG. As shown in B, a large number of recesses (hollows) H are formed on each of the opposing surfaces. Therefore, the opposing surfaces of the electrodes 2a and 2b have minute irregularities. Note that the depth of this recess H is approximately 0.5 mm.

The electrode 2a is arranged inside the housing section 10 and near the gas inlet 10i. The electrode 2b is arranged inside the housing section 10 and near the gas outlet 10o. Therefore, in the plasma generator P10, gas is introduced from the side opposite to the facing surface of the electrode 2a, and the gas is ejected to the side opposite to the facing surface of the electrode 2b. The distance between the electrodes 2a and 2b is, for example, 24 cm. The distance between the electrodes 2a and 2b may be smaller than this.

The voltage application section 3 is for applying an alternating current voltage between the electrodes 2a and 2b. The voltage applying unit 3 boosts the voltage to 9 kV using a commercial AC voltage of 60 Hz and 100 V, and applies a voltage between the electrodes 2a and 2b.

When a rare gas such as argon is introduced through the gas inlet 10i and a voltage is applied between the electrodes 2a and 2b by the voltage application section 3, plasma is generated inside the housing section 10. Figure 1. As shown by the diagonal line A, the region where plasma is generated is defined as a plasma generation region P. The plasma generation region P is covered by the housing section 10.

1-2. Second plasma generator Figure 2. A is a sectional view showing a schematic configuration of a plasma generator P20. Here, the plasma generator P20 is a second plasma generator that ejects plasma linearly. Figure 2. B is Figure 2. FIG. 3 is a partial sectional view taken in a cross section perpendicular to the longitudinal direction of the plasma generation region P of the plasma generation device P20 of FIG.

The plasma generator P20 includes a housing section 11, electrodes 2a and 2b, and a voltage application section 3. The housing portion 11 is made of a sintered body made of alumina (Al ₂ O ₃ ). A gas inlet 11i and a large number of gas ejection ports 11o are formed at both ends of the housing portion 11. The gas inlet 11i is shown in FIG. It has a slit shape whose longitudinal direction is the left and right direction of A. The slit width from the gas inlet 11i to just above the plasma generation region P (width in the left-right direction in FIG. 2B) is, for example, 1 mm.

The gas outlet 11o is an irradiation part for irradiating plasma to the outside of the housing part 11. The gas outlet 11o has a cylindrical shape or a slit shape. The gas ejection port 11o in the case of a cylindrical shape is formed in a straight line along the longitudinal direction of the plasma generation region. The inner diameter of the gas outlet 11o is within the range of 1 mm or more and 2 mm or less. Moreover, in the case of a slit shape, it is preferable that the slit width of the gas jet port 11o is 1 mm or less. As a result, stable plasma is formed. Further, the gas introduction port 11i is configured to introduce gas in a direction intersecting a line connecting the electrode 2a and the electrode 2b.

The electrodes 2a, 2b and voltage application section 3 are the same as those of the plasma generator P10 shown in FIG. Similarly, a voltage is applied between the electrodes 2a and 2b using a commercial AC voltage. Thereby, plasma can be ejected in a straight line.

Furthermore, the plasma generator P20 that ejects plasma in a straight line is shown in FIG. By arranging them in rows in the left and right direction of B, plasma can be ejected planarly over a certain rectangular area.

2. Plasma Generated by the Plasma Generator The plasma generated by the plasma generators P10 and P20 is non-equilibrium atmospheric pressure plasma. Here, atmospheric pressure plasma refers to plasma having a pressure within a range of 0.5 atm or more and 2.0 atm or less.

In this embodiment, Ar gas is mainly used as the plasma generating gas. Of course, electrons and Ar ions are generated inside the plasma generated by the plasma generators P10 and P20. Then, the Ar ions generate ultraviolet rays. Furthermore, since this plasma is released into the atmosphere, it generates oxygen radicals, nitrogen radicals, and the like.

The plasma density of this plasma is within the range of 1×10 ¹⁴ cm ⁻³ or more and 1×10 ¹⁷ cm ^{−3 or} less. Note that the plasma density of plasma generated by dielectric barrier discharge is approximately 1×10 ¹¹ cm ⁻³ or more and 1×10 ¹³ cm ⁻³ or less. Therefore, the plasma density of the plasma generated by the plasma generators P10 and P20 is about three orders of magnitude higher than the plasma density of the plasma generated by dielectric barrier discharge. Therefore, more Ar ions are generated inside this plasma. Therefore, a large amount of radicals and ultraviolet rays are generated. Note that this plasma density is approximately equal to the electron density inside the plasma.

The plasma temperature at the time of plasma generation is within a range of about 1000K or more and 2500K or less. Further, the electron temperature in this plasma is higher than the gas temperature. Furthermore, although the electron density is within the range of 1×10 ¹⁴ cm ⁻³ to 1×10 ¹⁷ cm ⁻³ , the gas temperature is within the range of approximately 1000 K to 2500 K. The temperature of this plasma is the temperature in the plasma generation region P where plasma is generated. Therefore, by setting different plasma conditions and the distance from the gas outlet to the target object, the plasma temperature at the target object position can be made to be about room temperature.

3. Growth of rice after flowering and timing of plasma irradiation Figure 3 is a diagram showing growth of rice after flowering and timing of plasma irradiation. After flowering, rice has an endosperm tissue formation period and a ripening period. During the endosperm tissue formation period, endosperm tissue is formed. During the ripening period, sugar translocation and starch accumulation occur.

In the first embodiment, the ears of rice are irradiated with atmospheric pressure plasma after the rice has bloomed. In the first embodiment, atmospheric pressure plasma is irradiated toward the panicle after flowering. That is, plasma is irradiated to the panicle during the endosperm tissue formation period or the ripening period.

4. Rice production method 4-1. Germination process Germinate rice seeds. For this purpose, a water absorption process is performed in which rice seeds are soaked in water.

4-2. Seedling raising process Next, the germinated seeds are sown into seedlings. The seeds are then grown into seedlings.

4-3. Rice planting Plant well-grown seedlings in paddy fields. Alternatively, it may be grown inside an artificial climate machine.

4-4. Earing After that, the rice starts heading.

4-5. Flowering After heading, rice flowers.

4-6. Plasma irradiation process As shown in FIG. 4, a plasma irradiation process is performed on the panicle after flowering. Specifically, non-equilibrium atmospheric pressure plasma is directly irradiated toward the panicle or carob (K1) of the rice ear after flowering. The plasma irradiation step is carried out within 4 days after 0 days after flowering of the rice plants. The spikelets turn into carpus over time.

The plasma density time product when irradiating atmospheric pressure plasma to the panicles or panicles of rice ears is preferably 6×10 ¹⁶ sec·cm ⁻³ or more and 4×10 ¹⁷ sec·cm ⁻³ or less. This numerical range corresponds, for example, to the case where atmospheric pressure plasma with a plasma density of 2×10 ¹⁶ cm ⁻³ is irradiated for 3 seconds or more and 20 seconds or less. The plasma density-time product is a quantity that defines the approximate amount of plasma product that is irradiated onto the rice spikelet or carole.

Furthermore, the emission region of the atmospheric pressure plasma may or may not be in contact with the spikelet or the carob. The plasma irradiation distance is preferably 5 mm or more and 30 mm or less. The plasma irradiation distance is the distance from the irradiation port of the plasma generators P10, P20 to the spikelet or carole. The plasma irradiation distance may be outside the above range. This is because the plasma product is still irradiated to the rice spikelet or carol.

4-7. Harvesting After that, the seedlings are grown using normal growing methods and harvested.

5. Effects of direct irradiation of rice with plasma By irradiating the spikelets or panicles of rice ears with atmospheric pressure plasma within 4 days from day 0 after flowering of rice, the percentage of white rice is reduced. Therefore, the rice production method of the first embodiment is suitable for producing edible rice.

6. Modification 6-1. Miniaturized Plasma Generator The plasma generators P10, P20, etc. may be further miniaturized. By sufficiently reducing the size, a pen-shaped plasma generator can be manufactured. Even in that case, a plasma density equivalent to that of the plasma generators P10 and P20 can be obtained.

(Second embodiment)
A second embodiment will be described. The second embodiment differs from the first embodiment in the timing of the plasma irradiation process. Therefore, the different points will be explained.

1. Rice production method 1-1. Plasma irradiation process In the second embodiment as well, a plasma irradiation process is performed on the panicle after flowering. Specifically, non-equilibrium atmospheric pressure plasma is directly irradiated toward the panicle or carob of the rice ear after flowering. The plasma irradiation step is carried out within 6 days and 20 days after flowering of the rice plants.

2. Effects of the Second Embodiment By irradiating the spikelets or panicles of rice ears with atmospheric pressure plasma during a period from 6 days to 20 days after flowering of rice, the percentage of white rice increases. Therefore, the rice production method of the first embodiment is suitable for producing sake rice.

3. Modifications Modifications of the second embodiment may also be used.

1. Rice In this experiment, Yamada Nishiki (a rice variety), which is suitable for sake brewing, was cultivated.

2. Experimental method: The raised rice seedlings were planted in rice fields, and after flowering, the rice ears were irradiated with atmospheric pressure plasma. Atmospheric pressure plasma was directly irradiated at different days after flowering. At that time, a plasma generator P20 was used. The plasma density in plasma generator P20 was 2×10 ¹⁶ cm ⁻³ . The plasma gas was argon gas. The plasma irradiation time was 10 seconds or 20 seconds.

Each grain of rice was marked with a marker. This landmark indicates the flowering date. This makes it possible to determine how many days after flowering each rice ear was irradiated with atmospheric pressure plasma.

3. Experimental Results There was almost no difference whether the plasma irradiation time was 10 seconds or 20 seconds.

FIG. 5 is a graph showing the weight of each grain of brown rice and the proportion of white rice. The horizontal axis in FIG. 5 is the number of days from flowering to plasma irradiation. The vertical axis of the upper graph in Figure 5 is the weight of one grain of brown rice. The vertical axis of the lower graph in FIG. 5 is the ratio of white spots. Note that the leftmost column in FIG. 5 shows the values for rice that was not irradiated with plasma.

As shown in Figure 5, there was no change in the weight of each grain of brown rice due to plasma irradiation.

When the rice was not irradiated with plasma, the percentage of white rice was about 30%. When the rice was irradiated with plasma one day after flowering, the percentage of white rice was about 20%. When the rice was irradiated with plasma 5 days after flowering, the percentage of white rice was about 30%. When the rice was irradiated with plasma 10 days after flowering, the percentage of white rice was about 48%. When the rice was irradiated with plasma 15 days after flowering, the percentage of white rice was about 45%.

When the plasma was irradiated within 4 days after 0 days after flowering of rice, the percentage of white rice decreased. On the other hand, when the plasma was irradiated from 6 days to 20 days after flowering of rice, the proportion of white rice increased.

3. Summary of experiments When rice is irradiated with atmospheric pressure plasma when it is in the early stages of endosperm tissue formation, the proportion of white-heart rice decreases. On the other hand, if atmospheric pressure plasma is irradiated during the period when rice finishes the endosperm tissue formation period, the percentage of white-heart rice increases. Furthermore, if atmospheric pressure plasma is irradiated when rice is in the ripening period, the percentage of white rice increases.

In this way, by directly irradiating the rice ears with non-equilibrium atmospheric pressure plasma according to the growth stage after flowering of the rice, it is possible to increase or decrease the percentage of white rice. In other words, the proportion of white rice can be controlled.

(Additional note)
The rice production method in the first aspect includes a plasma irradiation step of irradiating rice with atmospheric pressure plasma. In the plasma irradiation step, atmospheric pressure plasma is irradiated toward the flower spikelet or carob after flowering.

In the rice production method according to the second aspect, the plasma irradiation step is performed within 4 days after flowering on day 0.

In the rice production method according to the third aspect, the plasma irradiation step is carried out after 6 days after flowering.

P10, P20...Plasma generation device 10, 11...Casing portion 10i, 11i...Gas inlet 10o, 11o...Gas outlet 2a, 2b...Electrode P...Plasma generation region H...Concave portion (hollow)
K1... spikelet or carob

Claims (3)

It has a plasma irradiation process in which rice is irradiated with atmospheric pressure plasma,
In the plasma irradiation step,
A method for producing rice comprising irradiating atmospheric pressure plasma to the spikelets or carcasses after flowering. In the rice production method according to claim 1,
A rice production method comprising carrying out the plasma irradiation step within 4 days after flowering. In the rice production method according to claim 1,
A rice production method comprising carrying out the plasma irradiation step after 6 days after flowering.

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