Measurement method, measurement device, and control system
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-02-09
- Publication Date
- 2026-08-13
Smart Images
Figure JP2026004659_13082026_PF_FP_ABST
Abstract
Description
Measurement method, measurement device, and control system
[0001] The technology disclosed in this specification relates to a technology for measuring the concentration of a specific substance contained in an object being fermented in a fermentation tank.
[0002] In order to control the fermentation state of an object (e.g., mash, etc.) being fermented in a fermentation tank, a technology for measuring the concentration of a specific substance (e.g., ethanol, etc.) contained in the object during fermentation has been developed. For example, Japanese Patent Application Laid-Open No. 2017-156185 discloses a technology for measuring the concentration of a substance (specifically, ethanol) in an object using transmission Raman spectroscopy. In Japanese Patent Application Laid-Open No. 2017-156185, a part of the object is taken out from the fermentation tank, and the taken-out part of the object is injected into a measurement cell. Then, Raman scattered light generated by transmitting excitation light through the object in the measurement cell is detected, and the concentration of the substance in the object is measured from the detected Raman scattered light.
[0003] In Japanese Patent Application Laid-Open No. 2017-156185, in order to measure the concentration of a substance in an object, a part of the object is taken out from the fermentation tank, and a part of the taken-out object is injected into a measurement cell. However, in order to measure the concentration of a substance in an object, it is necessary to take out a part of the object from the fermentation tank. Therefore, there was a problem that the object in the fermentation tank decreased when the concentration of the substance in the object was measured.
[0004] This specification discloses a technology that can accurately monitor the concentration of a substance contained in an object without taking out the object being fermented from the fermentation tank.
[0005] In a first aspect of the technology disclosed herein, the measurement method is a method for measuring the concentration of a substance contained in a fermenting object in a fermentation tank. The measurement method comprises a measurement step, a detection step, and a identification step. The measurement step is an irradiation step of irradiating the interface of the object in the fermentation tank with excitation light, wherein the excitation light is irradiated so as to converge at a focal position located between a first position located a first predetermined distance from the interface toward the object and a second position located a second predetermined distance from the interface toward the opposite side of the object. The detection step detects Raman scattered light produced when the excitation light is irradiated onto the interface. The identification step identifies the concentration from the detected Raman scattered light.
[0006] In the above measurement method, since the Raman scattered light generated when excitation light is irradiated onto the interface of the object in the fermentation tank is detected, there is no need to remove the object from the fermentation tank. Therefore, by measuring the concentration of the substance contained in the object, it is possible to avoid a decrease in the amount of object in the fermentation tank. Furthermore, by converging the excitation light to a focal point located between a first position located a predetermined distance from the interface towards the object and a second position located a predetermined distance from the interface away from the object, the intensity of the generated Raman scattered light can be increased, allowing for direct measurement of the concentration of the substance contained in the object. Therefore, the concentration of the substance contained in the object during fermentation can be measured without any time lag.
[0007] Furthermore, the measuring device disclosed herein measures the concentration of a substance contained in a material fermenting in a fermentation tank. The measuring device comprises a probe that irradiates the interface of the material in the fermentation tank with excitation light and detects Raman scattered light generated by the irradiation of the excitation light at the interface, and a identification unit that identifies the concentration from the Raman scattered light detected by the probe. The probe irradiates the excitation light so as to focus it at a focal position located between a first position located a predetermined distance from the interface toward the material and a second position located a second predetermined distance from the interface toward the opposite side of the material.
[0008] The above measuring device detects Raman scattered light generated when excitation light is irradiated onto the interface of the object in the fermentation tank. Therefore, it is possible to directly measure the concentration of substances contained in the object without removing it from the fermentation tank. For this reason, it can achieve the same effects as the measurement method described above.
[0009] Furthermore, the control system disclosed herein controls the fermentation state of the substance in the fermentation tank. The control system comprises the above-mentioned measuring device, a temperature sensor for detecting the temperature of the substance in the fermentation tank, a temperature adjustment device for adjusting the temperature of the substance in the fermentation tank, and a control device for controlling the temperature adjustment device based on the concentration measured by the measuring device and the temperature detected by the temperature sensor.
[0010] In the control system described above, the concentration of substances contained in the target material in the fermentation tank is measured using a measuring device that can directly measure the concentration of those substances. Based on the concentration measured by the measuring device, the temperature of the target material in the fermentation tank is adjusted. Therefore, the fermentation state of the target material in the fermentation tank can be automatically controlled.
[0011] A diagram showing the schematic configuration of the measuring apparatus according to Examples 1 and 2. A side view showing the tip of the probe. A flowchart showing an example of a method for measuring the concentration of substances contained in a fermenting object in a fermentation tank. A graph showing the intensity and regression coefficient of Raman scattered light with respect to the Raman shift generated when excitation light is irradiated onto sake mash in a fermentation tank, showing the graph for ethanol. A graph showing the intensity and regression coefficient of Raman scattered light with respect to the Raman shift generated when excitation light is irradiated onto sake mash in a fermentation tank, showing the graph for total sugar. A graph showing the change in ethanol concentration over time from the start of fermentation. A graph showing the change in total sugar concentration over time from the start of fermentation. A side view showing a modified probe. A side view showing another modified probe. A diagram showing another modified probe. A graph showing the Raman shift of Raman scattered light generated when excitation light is irradiated onto sake mash in a fermentation tank, showing the case when the excitation light is green light. A graph showing the relationship between the optical path length from the exit end of the probe to the interface and the peak height in the peak band E5 of Figure 11. This graph shows the Raman shift of Raman scattered light generated when excitation light is irradiated onto sake mash in a fermentation tank, and shows the case where the excitation light is ultraviolet light. This graph shows the relationship between the optical path length from the probe's exit end to the interface and the peak height in the peak band E5 of Figure 13. This graph shows the Raman shift of Raman scattered light generated when excitation light is irradiated onto sake mash in a fermentation tank, and shows the case where the excitation light is red light. This graph shows the relationship between the optical path length from the probe's exit end to the interface and the peak height in the peak band E6 of Figure 15. This block diagram shows the schematic configuration of the control system according to Example 2. This graph shows the AB line. This flowchart shows an example of a process for controlling the fermentation state of the mash in the fermentation tank.
[0012] The main features of the embodiments described below are listed below. Note that the technical elements described below are independent technical elements that exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing.
[0013] In a second aspect of the technology disclosed herein, in the first aspect described above, the irradiation step may involve using a probe that emits excitation light toward the interface, thereby emitting the excitation light toward the interface. The probe may include an incident end into which the excitation light is incident, an outgoing end that emits the excitation light, and a light guide that guides the excitation light incident at the incident end to the outgoing end. The optical path length from the outgoing end of the probe to the interface may be 66.7% or more and 120.0% or less of the distance from the outgoing end to the focal point.
[0014] With this configuration, the Raman scattered light generated when excitation light is irradiated onto the interface can be efficiently focused at the output end. Therefore, the concentration of substances contained in the target object can be determined with high accuracy.
[0015] In a third aspect of the technology disclosed herein, in the second aspect described above, the wavelength of the excitation light may be greater than or equal to the wavelength of ultraviolet light and less than or equal to the wavelength of red light.
[0016] With this configuration, the concentration of a substance contained in an object can be measured by using excitation light having wavelengths between ultraviolet light and red light.
[0017] In a fourth aspect of the technology disclosed herein, in the second aspect described above, the object may be sake mash. The wavelength of the excitation light may be greater than or equal to the wavelength of ultraviolet light and less than or equal to the wavelength of green light.
[0018] With this configuration, the concentration of substances contained in sake mash can be accurately measured by using excitation light with wavelengths ranging from ultraviolet light to green light.
[0019] In a fifth aspect of the technology disclosed herein, in any one of the second to fourth aspects described above, the probe may be provided with a cover that covers the exit end of the probe. The irradiation process may be carried out with the cover in contact with the object. The interface may be the contact surface between the cover and the object.
[0020] With this configuration, the probe, equipped with a cover, can be immersed in the object inside the fermentation tank while controlling the focal position where the excitation light converges. This makes it possible to measure the concentration of substances contained in the object inside the fermentation tank.
[0021] In a sixth aspect of the technology disclosed herein, in any one of the first to fifth aspects described above, the object may be moromi (fermented mash).
[0022] In a seventh aspect of the technology disclosed herein, in any one of the first to sixth aspects described above, the substance may be at least one of ethanol, total sugar, and glucose.
[0023] (Example 1) The measuring device 10 according to the example will be described with reference to the drawings. As shown in Figure 1, the measuring device 10 is used to measure the concentration of substances contained in the object 4 that is fermenting in the fermentation tank 2. The fermentation tank 2 is made of an impermeable material. Note that in Figure 1, the inside of the fermentation tank 2 is shown for easier viewing of the drawing. In this example, sake is brewed in the fermentation tank 2, and the object 4 is the mash used to brew sake. In this example, the measuring device 10 is used to measure the concentration of ethanol and the total sugar concentration contained in the mash in order to confirm the fermentation state of the mash in the fermentation tank 2.
[0024] The measuring device 10 comprises a light source 12, a probe 20, a detector 30, and a control unit 32. The light source 12 is configured to emit laser light. In this embodiment, the light source 12 is a semiconductor laser device that emits excitation light of a specific wavelength (in this embodiment, a wavelength of approximately 532 nm). The light source 12 is connected to a fiber 14a and emits excitation light to the probe 20 via the fiber 14a.
[0025] The probe 20 comprises a main body 22, a tip 24, and a cover 26. The main body 22 is cylindrical, with a fiber 14a connected to one end (end 23 in Figure 1) and a tip 24 connected to the other end. The excitation light emitted from the light source 12 is emitted from the end 23 through the fiber 14a into the interior of the main body 22. In other words, the end 23 is the incident end of the excitation light in the probe 20. The main body 22 is configured to guide the excitation light incident at the end 23 to the tip 24.
[0026] The tip portion 24 extends from the main body portion 22 toward the tip (end portion 25 in Figure 1). The tip portion 24 guides the excitation light that has passed through the main body portion 22 to the end portion 25 and irradiates the excitation light from the end portion 25. A lens (not shown) is arranged on the tip portion 24 so that the excitation light emitted from the end portion 25 converges at a predetermined focal position (described later). In other words, the end portion 25 is the emission end of the excitation light in the probe 20. Light guide portions 22a are formed inside the main body portion 22 and the tip portion 24 to guide the excitation light incident from the end portion 23 (i.e., the incident end) to the end portion 25 (i.e., the emission end).
[0027] As shown in Figure 2, in this embodiment, the effective diameter D of the end portion 25 is approximately 10 mm. The excitation light emitted from the end portion 25 is emitted so as to converge at a predetermined focal position F. In this embodiment, the focal position F is set at a position where the length L1 (hereinafter also referred to as focal length L1) from the end portion 25 to the focal position F is approximately 7.5 mm. In this embodiment, the focal length L1 is shorter than the effective diameter D of the end portion 25, but the configuration is not limited to this. The effective diameter D and focal length L1 are not particularly limited as long as the value obtained by dividing the focal length L1 by the effective diameter D (the so-called F value) is 2.8 or less.
[0028] The cover 26 is attached to the end of the main body 22 on the tip end 24 side. The cover 26 is cylindrical and covers the end 25 of the tip end 24 so that it does not come into contact with the object 4. Therefore, the excitation light emitted from the end 25 passes through the cover 26 and is irradiated onto the object 4 from the tip of the cover 26. In this embodiment, the cover 26 extends about 8 mm from the tip of the tip end 24 (i.e., the end 25), and the optical path length L2 of the excitation light covered by the cover 26 from the end 25 is about 8 mm. That is, the optical path length L2 is about 106.7% of the focal length L1. The axial length of the cover 26 is about the same as the focal length L1. That is, the position of the tip of the cover 26 (i.e., the interface of the object 4) is about the same as the focal position F. Therefore, the cover 26 is located near the focal position F.
[0029] When measuring the object 4, the probe 20 is immersed in the object 4. Since the probe 20 is equipped with a cover 26, the end 25 does not come into contact with the object 4, and an interface is formed between the object 4 and the cover 26. Hereinafter, the length from the exit end of the probe 20 to the interface of the object 4 may be referred to as the optical path length L2. When excitation light is irradiated from the end 25 of the probe 20 while the probe 20 is immersed in the object 4, the excitation light is irradiated to the interface with the object 4 (in other words, the boundary portion between the object 4 and the cover 26). Then, the Raman scattered light generated by the irradiation of the interface of the object 4 with the excitation light is incident on the end 25. As shown in Figure 1, a light guide portion 22b is formed inside the tip portion 24 and inside the main body portion 22 to guide the Raman scattered light incident from the end 25 to the end 23. The Raman scattered light passes through the light guide 22b and enters the fiber 14b from the end 23, where it is detected by the detector 30. The Raman scattered light detected by the detector 30 is output to the control unit 32.
[0030] The control unit 32 is composed of a microcomputer (microprocessor) consisting of a CPU, ROM, RAM, etc. The control unit 32 is connected to the detector 30 and acquires detection data of Raman scattered light detected by the detector 30. From the detection data of Raman scattered light, the control unit 32 identifies the concentrations of substances contained in the object 4 (for example, ethanol concentration and total sugar concentration).
[0031] In this embodiment, the probe 20 is equipped with a cover 26. Therefore, by immersing the probe 20 in the object 4, an interface is created between the probe and the object 4. By using the probe 20, the focal position F of the excitation light can be adjusted to a predetermined position, and the Raman scattered light of the object 4 inside the fermentation tank 2 can be acquired. Therefore, the object 4 undergoing fermentation inside the fermentation tank 2 can be measured directly without removing a part of the object 4 from the fermentation tank 2.
[0032] Next, a method for measuring the concentration of substances contained in the object 4 being fermented in the fermentation tank 2 using the measuring device 10 of this embodiment will be described.
[0033] As shown in Figure 3, first, the installation process is performed (S12). The installation process is the process of installing the probe 20. Specifically, the cover 26 of the probe 20 is immersed in the object 4 inside the fermentation tank 2. This positions the end portion 25 inside the object 4. In addition to the cover of the probe 20, a portion of the tip portion 24 of the main body portion 22 may also be immersed in the object 4 inside the fermentation tank 2.
[0034] Next, the irradiation process is performed (S14). The irradiation process is the process of irradiating the object 4 with excitation light emitted from the light source 12. Specifically, the light source 12 is turned on. As a result, excitation light is emitted from the light source 12, and the excitation light passes through the fiber 14a and the light guide portion 22a of the probe 20 and is emitted from the end portion 25. The excitation light emitted from the end portion 25 is irradiated to the interface between the object 4 and the cover 26 inside the fermentation tank 2.
[0035] Next, the detection process is performed (S16). The detection process is the process of detecting Raman scattered light with the detector 30. The Raman scattered light generated by irradiating the interface of the object 4 is focused at the end 25, passes through the light guide portion 22b and fiber 14b of the probe 20, and is detected by the detector 30. The detector 30 outputs the detection data of the detected Raman scattered light to the control unit 32.
[0036] Next, a specific step is performed (S18). The specific step is a step in which the control unit 32 identifies the concentrations of substances contained in the object 4 (in this embodiment, the ethanol concentration and the total sugar concentration) from the detection data of Raman scattered light acquired in step S16. Specifically, the control unit 32 identifies the peaks of ethanol and total sugar from the Raman scattered light spectrum using a spectral preprocessing method. The type of spectral preprocessing method is not particularly limited, and for example, baseline correction (e.g., Asymmetric least squares smoothing method), smoothing (e.g., Savitzky-Golay method), differential calculus, cosmic ray correction which is a problem in Raman measurement, extraction of the optimal wavelength, etc. can be used. Next, the control unit 32 estimates the concentrations of ethanol and total sugar by performing regression analysis using the spectral information mainly consisting of the identified peak values of ethanol and total sugar, with the chemical analysis values as the training values.
[0037] Figures 4 to 7 show the experimental results of measuring the ethanol concentration and total sugar concentration in the sake mash in the fermentation tank 2 using the measuring device 10. In the experiment, the average values of 10 measurements taken each day from the start of fermentation are shown. The arrows in Figures 4 and 5 indicate the points where the peaks for ethanol and total sugar overlap. As shown in Figure 4, the peak bands E1 to E4 for ethanol could be identified from the Raman shift. Also, as shown in Figure 5, the peak bands S1 to S6 for total sugar could be identified from the Raman shift. Furthermore, Tanks 1 and 2 in Figures 6 and 7 show the measurement results of the target material 4 fermented in different fermentation tanks 2 over time. As shown in Figure 6, the ethanol concentration increased as fermentation progressed, and the increase decreased on the 16th day from the start of fermentation. Also, as shown in Figure 7, the total sugar concentration reached its peak about 2 days from the start of fermentation and continued to decrease thereafter. These results are consistent with the fermentation process of the mash. Thus, it was confirmed that the ethanol concentration and total sugar concentration of the mash can be measured accurately using the measuring device 10 of this embodiment.
[0038] In this embodiment, by using the probe 20, excitation light can be irradiated onto the fermenting material 4 in the fermentation tank 2. Therefore, the concentration of a substance contained in the material 4 can be measured without removing a portion of the material 4 from the fermentation tank 2. For example, conventionally, a portion of the material 4 in the fermentation tank 2 was removed, and after filtering the removed portion of the material 4 to remove impurities, the concentration of a specific substance contained in the material 4 was measured. With this method, it takes time from the time the material 4 is removed from the fermentation tank 2 until the measurement results are obtained, so it was not possible to quickly perform measures to change the fermentation state of the material 4 in the fermentation tank 2 (e.g., adding water or changing the temperature) in accordance with the fermentation state of the material 4. In addition, by performing measurement processing such as filtration on a portion of the removed material 4, the components of the material 4 at the time of measurement become different from those of the material 4 in the fermentation tank 2, which leads to the problem of errors between the concentration of a specific substance contained in the material 4 in the fermentation tank 2 and the measurement results. In this embodiment, the material 4 in the fermentation tank 2 is measured directly using the probe 20. Therefore, no time lag occurs, and the substance 4 in the fermentation tank 2 can be measured without changing its composition. As a result, the fermentation state of the substance 4 in the fermentation tank 2 can be grasped quickly and accurately, and measures to change the fermentation state of the substance 4 in the fermentation tank 2 (e.g., adding water or changing the temperature) can be carried out quickly and appropriately. As a result, it becomes easier to adjust the fermentation state of the substance 4 to produce a high-quality fermented product. In addition, because the probe 20 is equipped with a cover 26, the optical path length L2 for irradiating the substance 4 with excitation light can be appropriately adjusted, and the Raman scattered light can be sufficiently focused at the end 25 of the probe 20. This makes it possible to directly measure the concentration of a specific substance contained in the substance 4 in the fermentation tank 2 without removing the substance 4 from the fermentation tank 2.
[0039] Furthermore, in this embodiment, since the target substance 4 in the fermentation tank 2 can be measured directly, the amount of target substance 4 in the fermentation tank 2 does not decrease due to measurement. For example, conventionally, a portion of the target substance 4 in the fermentation tank 2 was taken out for measurement, so the amount of target substance 4 in the fermentation tank 2 decreased each time it was measured. Especially in the early stages of fermentation, the target substance 4 contains a lot of solid matter (for example, in the case of sake mash, the main ingredients such as rice), so it was necessary to take out a large amount of target substance 4 for measurement. As a result, it was not possible to frequently measure the concentration of a specific substance contained in the target substance 4, and the concentration of a specific substance contained in the target substance 4 was measured at intervals (for example, once every one or two days) from the start to the end of fermentation. Alternatively, it was necessary to prepare a larger amount of target substance 4 to account for the loss of target substance 4 for measurement. In this embodiment, since it is not necessary to take out the target substance 4 from the fermentation tank 2 for measurement, the amount of target substance 4 in the fermentation tank 2 does not decrease due to measurement. As a result, the concentration of a specific substance contained in the target substance 4 can be measured frequently. For example, it is possible to continue measuring continuously without interruption from the start to the end of fermentation. Therefore, the concentration of specific substances contained in object 4 can be measured frequently, making it easier to produce high-quality fermented products.
[0040] The shape of the cover 26 is not limited to those shown in Figures 1 and 2. For example, as shown in Figure 8, the cover 126 of the probe 120 may be a roughly frustoconical shape, with the cross-sectional area decreasing towards the tip. In this case as well, when the probe 120 is immersed in the object 4, an interface is created between the object 4 and the cover 126 (more specifically, between the object 4 and the tip of the cover 126). This allows for measurement of the object 4 inside the fermentation tank 2. The cover 126 may also be equipped with a reflective material (for example, gold) on its inner surface. By providing a reflective material on the inner surface of the cover 126, Raman scattered light that is off-axis from the optical axis of the probe 120 is reflected by the reflective material, making it easier to concentrate a large amount of Raman scattered light at the end 25. In addition, gases 6 such as carbon dioxide may be generated inside the fermentation tank 2 due to the fermentation of the object 4. Because the cover 126 is roughly frustoconical in shape, when the gas 6 floats up and comes into contact with the cover 126, it is less likely for the gas 6 to accumulate at the bottom surface of the cover 126 (the tip of the cover 126). Therefore, the excitation light can be irradiated onto the object 4 without being obstructed by the gas 6.
[0041] Furthermore, as shown in Figure 9, the probe 220 may also be further equipped with a secondary cover 28 that covers the outer circumference of the cover 126. The secondary cover 28 has a shape that allows liquid to pass through but makes it difficult for solids to pass through. For example, the secondary cover 28 may be filter paper or filter cloth that prevents impurities in the object 4 from passing through, or it may be a mesh-like stainless steel cap. By providing the secondary cover 28 to the probe 220, impurities in the object 4 are less likely to come into contact with the cover 126. Therefore, the excitation light can be irradiated onto the object 4 without being blocked by impurities. The secondary cover 28 may also be attached to the outer circumference of the cylindrical cover 26 shown in Figures 1 and 2.
[0042] Alternatively, an integrating sphere (not shown) may be installed on the inner wall of the cylindrical cover 26 shown in Figures 1 and 2. By installing an integrating sphere, Raman scattered light can be efficiently focused at the end 25.
[0043] Further, as shown in FIG. 10, the probe 320 may measure the object 4 from the side surface of the fermentation tank 2. In this case, a measurement window 2a is provided on the side surface of the fermentation tank 2. The opening for providing the window 2a is closed by a light-transmissive member (for example, glass or the like). Note that a lid that can be opened and closed (that is, a member having no light transmissivity (not shown)) may be installed on the window 2a, and measurement may be possible by opening the lid. When measuring, the cover 326 of the probe 320 is installed so as to contact the light-transmissive member that closes the opening of the window 2a. For this reason, the dimensions of the cover 326 are designed in consideration of the thickness of the light-transmissive member of the window 2a. That is, the dimensions of the cover 326 are designed such that the sum of the dimensions of the cover 326 and the thickness of the light-transmissive member of the window 2a becomes the optical path length L2. For example, when the optical path length L2 is set to about 106.7% of the focal length L1, the dimensions of the cover 326 are designed such that the optical path length L2 from the emission end of the probe 320 to the inner surface of the window 2a (the interface with the object 4) becomes about 106.7% of the focal length L1.
[0044] Further, in this embodiment, the optical path length L2 is about 106.7% of the focal length L1, and the excitation light is irradiated so as to converge at the focal position F located at approximately the same level as the interface of the object 4. However, the present invention is not limited to such a configuration. For example, the excitation light may be irradiated so as to converge at the focal position F located between the first position located on the object 4 side by a first predetermined distance from the interface of the object 4 and the second position located on the side opposite to the object 4 by a second predetermined distance from the interface of the object 4. For example, the optical path length L2 may be set to a length of 66.7% or more and 120.0% or less of the focal length L1. By setting the optical path length L2 to 66.7% or more and 120.0% or less of the focal length L1, even when measuring an object 4 with low permeability such as mash, the Raman scattered light generated by irradiating the interface of the object 4 can be sufficiently condensed. Further, the optical path length L2 may be 80.0% or more of the focal length L1, or may be 106.7% or less of the focal length L1.
[0045] Figures 11 to 16 show the experimental results of measuring the ethanol concentration in the sake mash in the fermentation tank 2 using the measuring device 10. In the experiment, a probe 320 was used to measure the target object 4 from the side of the fermentation tank 2. The focal length L1 of the probe 320 was set to 7.5 mm. In addition, multiple probes 320 with different optical path lengths L2 from the output end of the probe 320 to the inner surface of the window 2a (the interface with the target object 4) were used. Specifically, 13 types of probes 320 with optical path lengths L2 of 1 mm, 3 mm, 5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 9 mm, 11 mm, 13 mm, 15 mm, and 17 mm were used.
[0046] Figures 11 and 12 show experimental measurement results using a light source 12 that outputs green light at approximately 532 nm with a laser intensity of 150 mW. Figures 13 and 14 show experimental measurement results using a light source 12 that outputs ultraviolet light at approximately 360 nm with a laser intensity of 50 mW. Figures 15 and 16 show experimental measurement results using a light source 12 that outputs red light at approximately 785 nm with a laser intensity of 650 mW.
[0047] As shown in Figure 11, the peak band E5 of ethanol was identified from the Raman shift in measurements using green light. Figure 12 shows the relationship between the optical path length L2 and the peak height in the peak band E5 in measurements using green light. Furthermore, as shown in Figure 13, the peak band E5 of ethanol was also identified from the Raman shift in measurements using ultraviolet light. Figure 14 shows the relationship between the optical path length L2 and the peak height in the peak band E5 in measurements using ultraviolet light. In addition, as shown in Figure 15, it was difficult to clearly identify the peak band E5 of ethanol (see Figures 11 and 13) from the Raman shift in measurements using red light, but the peak band E6 could be identified. Figure 16 shows the relationship between the optical path length L2 and the peak height in the peak band E6 in measurements using red light.
[0048] Furthermore, as shown in FIGS. 12, 14, and 16, a first threshold value T1 and a second threshold value T2 are shown. The first threshold value T1 indicates a lower limit value capable of specifying the peak band E5 or E6 of ethanol from the Raman shift. For example, in FIGS. 12, 14, and 16, the first threshold value T1 is a value of 15% of the peak height when the optical path length L2 is 7 mm. The second threshold value T2 indicates a value capable of accurately specifying the peak band E5 or E6 of ethanol from the Raman shift. For example, in FIGS. 12, 14, and 16, the second threshold value T2 is a value of 40% of the peak height when the optical path length L2 is 7 mm.
[0049] As shown in FIGS. 12, 14, and 16, when any of green light, ultraviolet light, and red light is used and the optical path length L2 is 5 to 9 mm, the peak height was greater than the first threshold value T1. The focal length L1 is 7.5 mm. For this reason, it was confirmed that when the optical path length L2 is 66.7% to 120.0% of the focal length L1, the ethanol concentration can be measured regardless of the wavelength of the light.
[0050] Also, when any of green light, ultraviolet light, and red light is used and the optical path length L2 is 6 to 8 mm, the peak height was greater than the second threshold value T2. For this reason, it was confirmed that when the optical path length L2 is 80.0% to 106.7% of the focal length L1, the ethanol concentration can be measured more accurately regardless of the wavelength of the light.
[0051] Further, when the object 4 is sake moromi, it was confirmed that the ethanol concentration can be measured without using the light source 12 that outputs light with a high laser intensity by using the light source 12 that outputs light having a wavelength between green light and ultraviolet light.
[0052] Furthermore, in this embodiment, the object 4 was mash for brewing sake, but the configuration is not limited to this. The object 4 may be, for example, mash for brewing other alcoholic beverages (e.g., wine). Alternatively, the object 4 may be mash for brewing fermented products other than alcoholic beverages (e.g., miso). In this case, by appropriately setting the wavelength of the excitation light emitted from the light source 12, the concentration of the substance contained in the object 4 can be measured with greater accuracy. For example, if the object 4 is wine mash, it is preferable to use a light source 12 that emits near-infrared laser light with a wavelength of approximately 785 nm or approximately 1064 nm.
[0053] Furthermore, in this embodiment, the concentration of ethanol and the total sugar concentration of the target substance 4 were specified, but the embodiment is not limited to this configuration. For example, the concentration of glucose in the target substance 4 may be specified. Alternatively, the concentration of organic acids (e.g., lactic acid, succinic acid, malic acid, etc.) indicating the acidity of the target substance 4 may be specified, or the concentration of amino acids (e.g., arginine, tyrosine, serine, leucine, glutamic acid, etc.) indicating the amino acid content may be specified.
[0054] (Example 2) Alternatively, as shown in Figure 17, the fermentation state of the object 4 in the fermentation tank 2 may be controlled by a control system 100 equipped with the measuring device 10 of Example 1 described above. The control system 100 controls the fermentation state of the mash for brewing sake in order to brew sake.
[0055] The control system 100 includes a measuring device 10, a temperature sensor 40, a temperature adjustment device 42, a water addition device 44, and a control device 50. The measuring device 10 has substantially the same configuration as the measuring device 10 of the above-described embodiment 1. Therefore, a detailed description of the measuring device 10 is omitted. In this embodiment, the measuring device 10 measures the ethanol concentration and total sugar concentration of the mash from Raman scattered light. The control unit 32 of the measuring device 10 may be provided separately from the control device 50 in the measuring device 10, or the control device 50 may be configured to also function as the control unit 32.
[0056] The temperature sensor 40 is installed inside the fermentation tank 2 and detects the temperature of the mash inside the fermentation tank 2. The temperature sensor 40 outputs the detected temperature of the mash to the control device 50.
[0057] The temperature control device 42 is configured to adjust the temperature of the mash in the fermentation tank 2. Specifically, the temperature control device 42 heats or cools the mash in the fermentation tank 2. The temperature control device 42 is controlled by the control device 50.
[0058] The water addition device 44 adds water to the fermentation tank 2. The water is added to the mash when the ethanol concentration of the mash fermenting in the fermentation tank 2 is high. The water addition device 44 is controlled by the control device 50.
[0059] The control device 50 is composed of a microcomputer (microprocessor) consisting of a CPU, ROM, RAM, etc. The control device 50 includes a storage unit 52, a timing unit 54, and an arithmetic unit 56.
[0060] The memory unit 52 stores the weight of the mash and the volume of water used during brewing, as well as the volume of additional water added by the additional water addition device 44. The memory unit 52 also stores a reference AB line. As shown in Figure 18, the AB line 60 is a straight line connecting the highest Baume point and the end of fermentation, with the alcohol content of the mash on the horizontal axis and Baume on the vertical axis. Baume represents the specific gravity of the mash. In sake brewing, the saccharification of rice starch by koji enzymes and alcoholic fermentation by yeast proceed simultaneously. The relationship between the alcohol content of the mash and Baume allows us to understand the balance between saccharification and fermentation. The highest Baume is the highest Baume value during brewing. In sake brewing, saccharification precedes fermentation, so the highest Baume is often reached around the fourth day after brewing (i.e., the start of fermentation). The reference AB line is an AB line that shows the brewing process (hereinafter also referred to as the ideal brewing process) when very high-quality sake was brewed in past brewing. The control system 100 controls the fermentation state to follow the reference AB line, thereby controlling the brewing process to produce high-quality sake.
[0061] The timing unit 54 measures the elapsed time since the start of fermentation. The calculation unit 56 controls various operations of the control system 100 and calculates various values for controlling the fermentation state of the mash in the fermentation tank 2 by the control system 100. For example, the calculation unit 56 calculates the water intake ratio, which will be described later. The calculation unit 56 also determines the set temperature of the mash and the amount of additional water to be added, which will be described later.
[0062] Next, the process by which the control system 100 controls the fermentation state of the mash in the fermentation tank 2 will be described. As shown in Figure 19, first, the calculation unit 56 causes the measuring device 10 to perform measurements (S110). Note that the measurement method of the measuring device 10 can be used as described in the above-described embodiment 1, so a detailed explanation will be omitted. In this embodiment, the measuring device 10 measures the ethanol concentration and total sugar concentration of the mash. The control device 50 also causes the measuring device 10 to perform measurements continuously until the end of fermentation. That is, the control device 50 continues to monitor the ethanol concentration and total sugar concentration of the mash using the measuring device 10 until the end of fermentation. Note that the control device 50 may also cause the measuring device 10 to perform measurements continuously at predetermined intervals (for example, every hour) until the end of fermentation. When the measurement by the measuring device 10 is completed, the calculation unit 56 obtains the measured values (i.e., ethanol concentration and total sugar concentration) from the measuring device 10 (S120).
[0063] Next, the calculation unit 56 determines whether or not the fermentation of the mash has finished based on the measurements obtained in step S120 (i.e., ethanol concentration and total sugar concentration) (S130). Specifically, the calculation unit 56 determines that the fermentation of the mash has finished if the ethanol concentration is higher than a predetermined value and the total sugar concentration is lower than a predetermined value. The calculation unit 56 may also consider the elapsed time measured by the timing unit 54 (i.e., the number of fermentation days) when determining whether or not the fermentation of the mash has finished. If the fermentation of the mash has finished (YES in S130), the process of controlling the fermentation state of the mash in the fermentation tank 2 (the process in Figure 19) is terminated.
[0064] If the fermentation of the mash is not yet complete (NO in S130), the fermentation state of the mash is appropriately adjusted in order to further ferment it. In this case, the calculation unit 56 obtains the temperature of the mash in the fermentation tank 2 detected by the temperature sensor 40 (S140). The calculation unit 56 also obtains the number of fermentation days from the timing unit 54 (S150).
[0065] Next, the calculation unit 56 calculates the water ratio (S160). The water ratio is the ratio of water to the weight of the mash at the time of preparation. The calculation unit 56 uses the weight of the mash at the time of preparation, the volume of water at the time of preparation, and the amount of additional water added to the fermentation tank 2, which are stored in the memory unit 52, to calculate the water ratio.
[0066] Next, the calculation unit 56 determines the set temperature and the amount of additional water to be added using the various numerical values obtained in steps S120 and S140 to S160 (S170). Specifically, first, the calculation unit 56 calculates the alcohol content and Baumé from the ethanol concentration and total sugar concentration of the mash obtained in step S120. Then, the calculation unit 56 determines whether the calculated alcohol content and Baumé lie on the reference AB line 60 stored in the memory unit 52.
[0067] If the calculated alcohol content and Baumé point are located on the reference AB line 60, the calculation unit 56 determines that the mash is fermenting in a state close to the ideal brewing process. For this reason, the calculation unit 56 determines the set temperature of the mash and the amount of additional water to be added in order to maintain the current fermentation state. For example, the calculation unit 56 decides to maintain the current temperature of the mash. Alternatively, the calculation unit 56 decides to add no additional water or to add only a small amount of additional water. The amount of additional water to be added in the case of adding only a small amount of additional water is predetermined based on past experience, for example, and stored in the memory unit 52. The amount of additional water added in this case may vary depending on the number of fermentation days, or it may be the same amount regardless of the number of fermentation days.
[0068] If the calculated alcohol content and Baumé are not located on the reference AB line 60, they may be located in region 62 or region 64 in Figure 18. When the calculated alcohol content and Baumé are located in region 62, the Baumé is greater than the value in the ideal brewing process relative to the alcohol content. This means that saccharification is proceeding ahead of fermentation. Therefore, the calculation unit 56 determines the set temperature of the mash and the amount of additional water to be added in order to promote fermentation. Specifically, the calculation unit 56 determines the set temperature so that the temperature of the mash is higher than the current temperature. The difference from the current temperature of the mash (i.e., how many degrees higher to raise it) is set in advance based on past experience and stored in the memory unit 52. This difference may be a different value depending on the number of fermentation days, or it may be the same value regardless of the number of fermentation days. The calculation unit 56 also decides whether to add no additional water or to add only a small amount of additional water. The amount of additional water to be added when adding only a small amount is set in advance based on past experience, for example, and stored in the memory unit 52. The amount of water added at this time may vary depending on the number of fermentation days, or it may be the same amount regardless of the number of fermentation days.
[0069] If the calculated alcohol content and Baumé value fall within region 64, the Baumé value relative to the alcohol content is lower than the value in the ideal brewing process. This means that fermentation is proceeding ahead of saccharification. Therefore, the calculation unit 56 determines the set temperature of the mash and the amount of additional water to be added in order to suppress fermentation. Specifically, the calculation unit 56 determines the set temperature so that the temperature of the mash is lower than the current temperature. The difference from the current temperature of the mash (i.e., how many degrees lower to make it) is set in advance based on past experience and stored in the memory unit 52. This difference may be a different value depending on the number of fermentation days, or it may be the same value regardless of the number of fermentation days. The calculation unit 56 also decides not to add any additional water (i.e., the amount of additional water to be added is zero).
[0070] Next, the calculation unit 56 controls the temperature control device 42 so that the mash reaches the set temperature determined in step S170 (S180). The calculation unit 56 also causes the amount of additional water determined in step S170 to be added to the additional water addition device 44 (S190). After that, the process returns to step S110 and steps S110 to S190 are repeated until the fermentation of the mash is complete.
[0071] In this embodiment, the set temperature of the mash in the fermentation tank 2 is adjusted and additional water is added to the fermentation tank 2 based on the measured values (specifically, the ethanol concentration and total sugar concentration of the mash) measured by the measuring device 10. This allows for the automatic execution of measurements to confirm the fermentation state of the mash, temperature adjustment of the mash in the fermentation tank 2, and addition of additional water to the fermentation tank 2. This reduces the burden on the operator. Furthermore, the control system 100 adjusts the fermentation state of the mash to follow the reference AB straight line 60. This makes it easier to brew high-quality sake.
[0072] In this embodiment, the set temperature and the amount of added water determined in step S170 were predetermined based on past experience, but the configuration is not limited to this. For example, the set temperature and the amount of added water determined in step S170 may be determined by machine learning, using the changes in set temperature and the amount of added water for each fermentation day in past brewing processes as training data. Since known methods can be used for machine learning, a detailed explanation will be omitted.
[0073] Furthermore, the control system 100 may also include a rice starch digest addition device that adds rice starch digest, obtained by saccharifying rice starch with enzymes, to the fermentation tank 2. In sake brewing, sugar may become insufficient towards the end of the brewing process. In such cases, rice starch digest may be added to the fermentation tank 2 (a so-called four-stage brewing process). In step S170, if the calculation unit 56 determines that the alcohol content and Baumé are located in region 64 of Figure 18, and that there is a sugar shortage in the fermentation tank 2 based on the Baumé reading, it may control the rice starch digest addition device to add rice starch digest to the fermentation tank 2.
[0074] Furthermore, in this embodiment, the control system 100 automatically controlled the fermentation state of the mash for brewing sake, but the system is not limited to this configuration. For example, the control system 100 may automatically control the fermentation state of the mash for brewing other alcoholic beverages (e.g., wine). For example, since no additional water is added when brewing wine, the control system 100 does not need to be equipped with an additional water addition device 44 when controlling the fermentation state of wine mash. Also, the control system 100 may automatically control the fermentation state of the mash for brewing fermented products other than alcoholic beverages (e.g., miso).
[0075] The specific examples of the technology disclosed herein have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described above. Furthermore, the technical elements described herein or in the drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated herein or in the drawings achieves multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness.
Claims
1. A method for measuring the concentration of a substance contained in an object being fermented in a fermentation tank, comprising: an irradiation step of irradiating the interface of the object in the fermentation tank with excitation light, wherein the excitation light is irradiated so as to converge at a focal position located between a first position located a first predetermined distance from the interface toward the object and a second position located a second predetermined distance from the interface toward the opposite side of the object; a detection step of detecting Raman scattered light generated by the irradiation of the excitation light on the interface; and a identification step of determining the concentration from the detected Raman scattered light.
2. The measurement method according to claim 1, wherein in the irradiation step, the excitation light is emitted to the interface using a probe that emits the excitation light toward the interface, the probe comprises an incident end into which the excitation light is incident, an outgoing end that emits the excitation light, and a light guide portion that guides the excitation light incident at the incident end to the outgoing end, and the optical path length from the outgoing end of the probe to the interface is 66.7% or more and 120.0% or less of the distance from the outgoing end to the focal position.
3. The measurement method according to claim 2, wherein the wavelength of the excitation light is greater than or equal to the wavelength of ultraviolet light and less than or equal to the wavelength of red light.
4. The measurement method according to claim 2, wherein the object is sake mash, and the wavelength of the excitation light is greater than or equal to the wavelength of ultraviolet light and less than or equal to the wavelength of green light.
5. The measurement method according to any one of claims 2 to 4, wherein the probe is provided with a cover that covers the output end of the probe, the irradiation step is performed with the cover and the object in contact, and the interface is the contact surface between the cover and the object.
6. The measurement method according to any one of claims 1 to 5, wherein the object is moromi (fermented mash).
7. The measurement method according to any one of claims 1 to 6, wherein the substance is at least one of ethanol, total sugar, and glucose.
8. A device for measuring the concentration of a substance contained in a material being fermented in a fermentation tank, comprising: a probe that irradiates excitation light onto the interface of the material in the fermentation tank and detects Raman scattered light generated by the irradiation of the excitation light onto the interface; and a identification unit that identifies the concentration from the Raman scattered light detected by the probe, wherein the probe irradiates the excitation light so as to focus it at a focal position located between a first position located a first predetermined distance from the interface toward the material and a second position located a second predetermined distance from the interface toward the opposite side of the material.
9. A control system for controlling the fermentation state of a substance in a fermentation tank, comprising: a measuring device according to claim 8; a temperature sensor for detecting the temperature of the substance in the fermentation tank; a temperature adjustment device for adjusting the temperature of the substance in the fermentation tank; and a control device for controlling the temperature adjustment device based on the concentration measured by the measuring device and the temperature detected by the temperature sensor.