JP7784091B2 - Carbon dioxide measuring device, ethanol concentration measuring device, carbon dioxide concentration measuring method, and ethanol concentration measuring method - Google Patents

Description

This disclosure relates to a carbon dioxide measurement device, an ethanol concentration measurement device, a carbon dioxide concentration measurement method, and an ethanol concentration measurement method.

In the brewing process of alcoholic beverages such as sake, the ethanol concentrations contained in the starter mash and moromi mash are measured as indicators for process control, quality control, etc. A standard method for analyzing ethanol is described in Non-Patent Document 1.
In addition to the above, Patent Documents 1 to 3 disclose methods that focus on the correlation between the amount of carbon dioxide produced and the amount of ethanol produced in alcohol (ethanol) fermentation.

National Tax Agency Specified Analysis Method (National Tax Agency Instruction No. 1, January 11, 1961; last revised: National Tax Agency Instruction No. 8, June 24, 2022)

Japanese Patent Application Publication No. 7-23764 Japanese Patent Application Publication No. 10-75766 Japanese Patent Application Laid-Open No. 2023-2080

The method disclosed in Non-Patent Document 1 requires sampling of the target material, and then measures the ethanol concentration of the pre-treated sample using instrumental analysis, etc. Pre-processing is time-consuming and labor-intensive, and the required equipment is highly specialized, requiring a great deal of experience and knowledge from the operator. Another problem is that the ethanol concentration in the target material cannot be determined in real time. Furthermore, because a specified amount of sampling (e.g., 600 ml per sampling) is required, this results in a corresponding reduction in the volume of the final product, and frequent sampling tends to be avoided.

Furthermore, the methods disclosed in Patent Documents 1 and 2 measure the amount of carbon dioxide generated using an airtight tank. Typically, open tanks are used in manufacturing processes, with raw materials being added through the opening as needed, and a paddle (or paddle rod) for stirring being inserted. Using an airtight tank poses the problem of interfering with the addition of raw materials and stirring (paddle insertion). Furthermore, fermentation in a closed system can lead to poor fermentation.

Furthermore, the method disclosed in Patent Document 3 requires a tank capable of monitoring changes in mass. Such tanks are not typically available at manufacturing sites, and application to existing manufacturing facilities is difficult due to cost and other factors.

As described above, there is a correlation between the amount of carbon dioxide produced and the amount of ethanol produced in alcoholic fermentation, and accurately measuring the amount of carbon dioxide produced has the same meaning as measuring the amount of ethanol produced in an alcoholic fermentation system.
Therefore, an object of the present disclosure is to provide a carbon dioxide measuring device that can solve at least one of the problems of the above-mentioned conventional techniques. In other words, an object of the present disclosure is to provide a carbon dioxide measuring device that is easy to use, has real-time performance, or is sampling-free, or that is applicable to an open system, or that can be easily applied to existing manufacturing facilities.
Another object of the present disclosure is to provide an ethanol concentration measurement device, a carbon dioxide concentration measurement method, and an ethanol concentration measurement method.

A first embodiment of the carbon dioxide measuring device disclosed herein is a carbon dioxide measuring device that measures the concentration of carbon dioxide generated from an object by bringing the end of a cylindrical probe into proximity with or in contact with the object. The carbon dioxide measuring device includes a first inlet for introducing a first gas into the probe and a second inlet for introducing a second gas, each of which is disposed at the end; a sensor that is housed midway along the length of the probe and measures the concentration; and an airflow unit that circulates a mixed gas of the first gas and the second gas in a direction from the end toward the sensor, with the second inlet being disposed closer to the sensor than the first inlet.

A first embodiment of the ethanol concentration measurement device disclosed herein is a carbon dioxide measurement device that measures the concentration of carbon dioxide generated from a target object, which may be a microbial culture medium or a fermentation medium obtained by fermenting a raw material, by contacting or inserting the end of a cylindrical probe into the liquid surface of the target object. The ethanol concentration measurement device includes a first inlet for introducing a first gas into the probe and a second inlet for introducing a second gas, both of which are disposed at the end of the probe; a sensor that is housed midway along the length of the probe and measures the concentration; an airflow unit that circulates a mixed gas of the first gas and the second gas in a direction from the end of the probe toward the sensor; and a controller. The second inlet is disposed closer to the sensor than the first inlet, and the controller calculates the ethanol concentration in the target object from the integrated amount of carbon dioxide calculated from the concentration and the gas flow rate due to the flow, based on a predetermined conversion formula.

The present disclosure provides a carbon dioxide measurement device that is simple, real-time, or sampling-free, or that can be applied to an open system, or that can be easily adapted to existing manufacturing equipment. The present disclosure also provides a method for measuring carbon dioxide concentration and a method for measuring ethanol concentration.

FIG. 1 is an explanatory diagram of a carbon dioxide measuring device. FIG. 2 is an enlarged view (schematic view) of a tip portion which is one end of a probe. FIG. 10 is a flow chart showing the procedure for measuring ethanol concentration and generating an alert. This is a probe image of the carbon dioxide measuring device used in the experiment. FIG. 10 is a diagram showing experimental results. 1 is a diagram showing the correlation between the alcohol concentration measurement result obtained by the sampling method (analysis method prescribed by the National Tax Agency) and the cumulative value of the amount of carbon dioxide (CO ₂ ) generated measured by a carbon dioxide measuring device.

A carbon dioxide measuring device according to a first embodiment of the present disclosure is a carbon dioxide measuring device that measures the concentration of carbon dioxide generated from an object by bringing the end of a cylindrical probe into proximity with or in contact with the object. The carbon dioxide measuring device includes a first inlet for introducing a first gas into the probe and a second inlet for introducing a second gas, each of which is disposed at the end; a sensor that is housed midway along the length of the probe and measures the concentrations; and an airflow unit that circulates a mixed gas of the first gas and the second gas in a direction from the end toward the sensor, with the second inlet being disposed closer to the sensor than the first inlet.

The probe provided in the carbon dioxide measuring device of the first embodiment has a first inlet and a second inlet at its end. The first inlet is located closer to the tip in the longitudinal direction than the second inlet, and a sensor is located within the probe on the opposite side in the longitudinal direction. Because the second inlet is located closer to the center in the longitudinal direction (closer to the rear end of the probe, in other words, the opposite end), when an object is brought into contact with the first inlet, the second inlet does not come into contact with the object and/or can be kept separated from the object.

When the first inlet is brought into proximity with or in contact with the object, a first gas containing carbon dioxide generated from the object enters the probe through the first inlet. In this state, the carbon dioxide concentration cannot be measured unless the inside of the probe is replaced with the first gas at least up to the position of the sensor. However, the carbon dioxide measuring device of the above embodiment includes an airflow unit that circulates gas inside the probe from the end toward the sensor, making it easy to measure the carbon dioxide concentration. When gas is drawn in by the airflow unit, the first gas reaches the sensor, and the carbon dioxide concentration is measured in real time.
Note that bringing a probe "close to" an object means that the probe is close to the object but not in direct physical contact with it, and "contact" means that the probe is in direct physical contact with the object. Note that "contact" can also include bringing the probe into close contact with the surface of the object and inserting the probe into the object from the surface.

The probe also includes a second inlet. The second inlet is located further rearward (opposite end) than the first inlet, and can be adjusted so that even when the first inlet is in contact with the object, the second inlet does not come into contact with the object. When gas is sucked in by the suction unit, the second gas is sucked in from the second inlet, which is not in contact with the object, and this gas mixes with the first gas just before the sensor and moves toward the sensor position. In other words, the second gas functions as a carrier for the first gas, and the carbon dioxide concentration in the mixed gas is measured at the sensor position.

With the carbon dioxide measuring device of the first embodiment configured in this way, even if a high concentration of carbon dioxide is generated from the object, the carbon dioxide reaches the sensor after being diluted with the second gas, so that even an inexpensive sensor can be used for measurement without saturating the sensor. As a result, the carbon dioxide measuring device can be provided at a lower cost.
In particular, high concentrations of carbon dioxide are generated from the mash during alcoholic fermentation, so if you try to measure this with a simple mechanism, you need to use an expensive sensor or measure the concentration by lowering it below the actual concentration in some way. In the carbon dioxide measuring device of this embodiment, by providing a second inlet and a suction unit, for example, the first gas (the carbon dioxide therein) is automatically diluted simply by suctioning to a constant flow rate, making it possible to measure using a general sensor. The carbon dioxide concentration in the first gas can be calculated from the sensor reading, the gas flow rate, etc. Furthermore, in calculating the carbon dioxide concentration in the first gas, parameters other than those described above (e.g., the hole diameters of the first inlet and the second inlet, etc.) may be used as necessary.

The carbon dioxide measuring device of the first embodiment can measure carbon dioxide simply by bringing a probe with an integrated sensor close to or in contact with an object in an open system. Furthermore, the carbon dioxide in the aspirated mixed gas can be monitored in real time by the sensor. Furthermore, since measurements can be made simply by bringing the probe close to or in contact with an object, no sampling is required (sampling-free). It can also be easily made portable, making it easy to apply to existing manufacturing equipment (for example, brewing tanks, etc.).

Furthermore, even if the amount of gas generated from the object is small, i.e., the amount of the first gas flowing into the probe is small, the proportion of the second gas flowing into the mixed gas increases accordingly, and the pressure inside the probe is kept constant, preventing the object from being sucked into the first inlet and causing clogging. In particular, when the object is a suspension such as "moromi" (unrefined soybean mash), clogging often occurs with conventional measurement probes, but this issue has also been improved with the carbon dioxide measuring device of this embodiment.

A carbon dioxide measuring device according to a second embodiment of the present disclosure is the carbon dioxide measuring device of the first embodiment, in which the air flow unit is positioned closer to the opposite end of the probe than the first inlet.

By positioning the airflow unit closer to the opposite end (rear end) than the first inlet, it becomes easier to form a gas flow (mixed gas flow) more efficiently within the probe, enabling more efficient measurements. Examples of airflow units include suction units such as pumps and air ejectors that form an airflow by sucking in mixed gas; blower units that transport mixed gas using centrifugal or axial fans; and discharge units that form an airflow by discharging compressed second gas from the second inlet. Any of these may be used.

In the case of a suction unit, the suction port is preferably located closer to the opposite end of the probe than the first inlet, and further closer to the rear end of the probe than the sensor.
In the case of a blower unit, it is preferable that the fan is disposed closer to the opposite end of the probe than the first inlet.
In the case of the discharge unit, it is preferable that the second gas is discharged from the second gas inlet. As already explained, the second inlet is disposed closer to the sensor (opposite end side) than the first inlet.

A carbon dioxide measuring device according to a third embodiment of the present disclosure is a carbon dioxide measuring device according to the first embodiment, in which the object is a liquid, the first inlet is in close contact with or inserted into the liquid surface of the object, and the first gas generated from the object is introduced, and the second gas with a known composition is introduced from the second inlet.

In the carbon dioxide measuring device of the third embodiment, a second gas of known composition is introduced through the second inlet. Therefore, the carbon dioxide concentration in the first gas can be calculated more accurately from the sensor reading, the gas flow rate, etc. Furthermore, when the airflow is generated by a blower unit or a suction unit, if the first inlet is brought into close contact with or inserted into a liquid object, a decrease in the probe internal pressure may cause the liquid to enter the probe and cause clogging.
However, in the carbon dioxide measuring device of this embodiment, the pressure inside the probe can be kept constant thanks to the contribution of the second inlet, so the liquid itself is not drawn into the probe, and there is no problem of the probe becoming clogged. For example, if the liquid is a fermented mash or the like that is a mixture of solid and liquid, simply sucking it with the probe would allow solids to enter the probe, causing clogging. The probe of the carbon dioxide measuring device of this embodiment is equipped with a second inlet for introducing a second gas of known composition, thereby suppressing clogging caused by reduced pressure inside the probe.

A carbon dioxide measuring device according to a fourth embodiment of the present disclosure is the carbon dioxide measuring device of the first embodiment, except that the first inlet is the open end of the probe and the second inlet is located on the side of the probe.

The probe provided in the carbon dioxide measuring device of the fourth embodiment is cylindrical with at least one open end, which serves as the first inlet. The second inlet is located longitudinally further toward the center from the open end, i.e., on the side closer to the sensor. With this configuration, simply bringing the open end close to or in contact with the object opens the second inlet to the object, making measurement even easier.

A carbon dioxide measurement device according to a fifth embodiment of the present disclosure is the carbon dioxide measurement device according to claim 1, in which a conduit for introducing the second gas is connected to the second inlet in the first embodiment.

Connecting a conduit to the second inlet can reduce the proportion of gas generated from the object in the second gas introduced from the second inlet. For example, when air is introduced as the second gas, connecting a conduit with an open end to the second inlet allows air to be introduced from a space farther away from the object, enabling more accurate measurement. That is, in this case, the side of the conduit opposite the second inlet is open to the atmosphere, and the second gas can be introduced into the probe from this open end.
Furthermore, when an introduction device (a cylinder or a gas generator) for a gas with a known composition (known carbon dioxide concentration) is used as the second gas, the degree of freedom in the layout of the device is further improved by connecting a conduit, making it easier to apply the device to existing manufacturing facilities.

A carbon dioxide measuring device according to a sixth embodiment of the present disclosure is the carbon dioxide measuring device of the first embodiment, in which the second gas is air.

By using air as the second gas, there is no need to connect any special mechanisms or equipment for supplying the second gas, making the device simpler and/or more compact. In particular, when the airflow unit is a suction unit or a blower unit, and a conduit with an open end is connected to the second inlet, this is advantageous in that the second gas can be supplied into the probe simply by placing the open end in the atmosphere. This makes the device simpler and easier to transport.

A carbon dioxide measuring device according to a seventh embodiment of the present disclosure is a carbon dioxide measuring device according to the fifth embodiment, in which the object is a liquid contained in an open container, and the second gas is taken in by the conduit from a space separated from the opening of the open container.

When the object is a liquid contained in an open container, when comparing the vicinity of the opening (e.g., directly above) with the peripheral area (e.g., the side of the container), the concentration of gas generated from the object is lower in the peripheral area.
The carbon dioxide measuring device of this embodiment is configured to take in the second gas from a space separated from the open portion of the open container through a conduit. Therefore, particularly when the second gas is air, the concentration of gas generated from the object contained in the second gas can be kept low. This makes it easier to obtain more accurate measurements.
In addition, if the air flow unit is a suction unit or a blower unit and the second gas is air, the side of the conduit opposite the second inlet can be opened to the atmosphere, which makes the device simpler and easier to transport.

The eighth embodiment of the carbon dioxide measuring device of the present disclosure is the carbon dioxide measuring device of the seventh embodiment, in which the target object is a microbial culture medium or a fermentation medium obtained by fermenting a raw material.

If the target substance is a microbial culture medium or a fermentation liquid obtained by fermenting raw materials, monitoring the amount of carbon dioxide generated from the target substance makes it possible to clearly understand the balance between the consumption and production of substrates and metabolic substances during the fermentation process. This balance is useful for managing the fermentation process. For example, if the target substance is mash during alcoholic fermentation, monitoring the amount of carbon dioxide makes it possible to estimate the alcohol concentration in the mash.

A carbon dioxide measuring device according to a ninth embodiment of the present disclosure is the carbon dioxide measuring device of the first embodiment, in which the first inlet is larger than the second inlet.

By making the first inlet larger, the proportion of the first gas in the mixed gas measured by the sensor increases. This makes it easier to obtain more accurate measurements. In particular, when the amount of carbon dioxide generated from the target object is small (for example, in the early stages of fermentation), reducing the amount of the second gas in the mixed gas allows for more accurate measurement of the amount of carbon dioxide.

A carbon dioxide measuring device according to a tenth embodiment of the present disclosure is a carbon dioxide measuring device according to any one of the first to ninth embodiments, which includes a controller, and which generates an alert when the concentration or a calculation result based on the concentration satisfies an alert condition.

When using the measurement results of carbon dioxide concentration for managing an object (for example, managing a fermentation process), generating an alert based on the concentration or calculation results can prompt the operator to check the status of the object. Furthermore, generating an alert for an increase in carbon dioxide concentration can also help prevent accidents such as suffocation. In managing a fermentation process, the cumulative amount calculated from the carbon dioxide concentration or the concentration of a specific substance in the object calculated from the cumulative value is related to the balance between the consumption and production of substrates and metabolic substances. Therefore, generating an alert when a specific alert condition is met can notify the operator of an abnormal fermentation.
The calculation result may be the amount of carbon dioxide generated, the cumulative amount, the amount of increase (decrease), or the derivative of the amount of increase (decrease), etc. Alternatively, it may be the amount of another substance calculated (converted) based on the measured value.

An eleventh embodiment of the carbon dioxide measuring device of the present disclosure is a carbon dioxide measuring device in the tenth embodiment, in which the calculation result includes the concentration and an integrated amount of carbon dioxide calculated based on the gas flow rate due to the distribution, or the concentration of a predetermined substance in the object calculated from the integrated amount.

The cumulative amount of carbon dioxide calculated from the carbon dioxide concentration and gas flow rate is likely to reflect changes in the target substance over time. Furthermore, the concentration of a specific substance in the target substance, such as the ethanol concentration, calculated from the cumulative amount is useful for understanding the balance between the consumption and production of substrates and metabolic substances during the fermentation (cultivation) process when the target substance is a microbial culture medium or a fermentation medium obtained by fermenting raw materials.

A carbon dioxide measuring device according to a twelfth embodiment of the present disclosure is a carbon dioxide measuring device according to any one of the first to ninth embodiments, which includes a controller, and the controller calculates the concentration of a predetermined substance in the object from an integrated amount of carbon dioxide calculated from the concentration and the gas flow rate due to the suction, based on a predetermined conversion formula.

The controller provided in the carbon dioxide measuring device of the twelfth embodiment has the function of converting the cumulative amount of carbon dioxide into the concentration of a specified substance contained in the target object based on a predetermined conversion formula. For example, if the target object is a culture medium for microorganisms or a fermentation medium obtained by fermenting raw materials, it is easier to understand the balance between the consumption and production of substrates and metabolic substances during the fermentation (cultivation) process. Specifically, it is easy to convert into the amount of another substance (for example, the ethanol concentration in the target object).

A carbon dioxide measuring device according to a thirteenth embodiment of the present disclosure is a carbon dioxide measuring device according to the twelfth embodiment, in which the target object is a culture medium for a microorganism or a fermentation medium obtained by fermenting a raw material, and the specific substance is ethanol.

The carbon dioxide measuring device of the thirteenth embodiment has the function of calculating the ethanol concentration in the target microbial culture solution or the fermentation solution obtained by fermenting a raw material based on the carbon dioxide concentration measurement results, making it suitable for use in managing the fermentation (cultivation) process. Simply by bringing the probe into close proximity to or in contact with the fermentation solution in an open system, the integrated value can be calculated from the carbon dioxide concentration measured in real time, thereby obtaining the ethanol concentration. The carbon dioxide device of this embodiment does not require sampling and can be easily applied to existing equipment.

The first ethanol concentration measurement device of the present disclosure is a carbon dioxide measurement device that measures the concentration of carbon dioxide generated from a target object, which is a microbial culture medium or a fermentation medium obtained by fermenting a raw material, by contacting or inserting the end of a cylindrical probe into the liquid surface of the target object. The ethanol concentration measurement device includes a first inlet for introducing a first gas into the probe and a second inlet for introducing a second gas, both of which are disposed at the end of the probe; a sensor that is housed midway along the length of the probe and measures the concentration; an airflow unit that circulates a mixed gas of the first gas and the second gas in a direction from the end toward the sensor; and a controller. The second inlet is disposed closer to the sensor than the first inlet, and the controller calculates the ethanol concentration in the target object from the integrated amount of carbon dioxide calculated from the concentration and the gas flow rate due to the flow, based on a predetermined conversion formula.

The ethanol measurement device of this embodiment can easily measure the ethanol concentration without sampling, simply by bringing the first inlet of the probe close to or in contact with the fermentation broth or the like. Furthermore, the mixed gas inside the probe is circulated by the airflow unit (typically sucked in by the suction unit), and the carbon dioxide concentration is measured by the sensor and appropriately converted into ethanol concentration, allowing for real-time measurements. Measurements can be easily made even when the fermentation broth or the like is open to the atmosphere, making it easy to apply to existing manufacturing equipment, etc. This ethanol concentration measurement device is preferably used to manage the fermentation (cultivation) process of fermentation broth or the like.

The carbon dioxide concentration measurement method of the first embodiment of the present disclosure is a method for measuring carbon dioxide concentration that includes measuring the concentration of carbon dioxide generated from an object using the carbon dioxide measurement device of the first embodiment.

The measurement method of this embodiment uses the carbon dioxide measurement device of the first embodiment, so carbon dioxide concentration can be easily measured without sampling by simply bringing the first inlet of the probe close to or in contact with the object. Furthermore, because the mixed gas inside the probe is circulated by the airflow unit and the carbon dioxide concentration is measured appropriately by the sensor, measurements can be performed in real time. Measurements can be easily performed even when the object is open to the atmosphere, and the method can be easily applied to existing manufacturing facilities, etc.

The ethanol concentration measurement method of the first embodiment of the present disclosure is a method for measuring ethanol concentration, which includes measuring the concentration of carbon dioxide generated from a target using the carbon dioxide measurement device of the first embodiment, and calculating the ethanol concentration contained in the target, which is a microbial culture medium or a fermentation medium obtained by fermenting a raw material, from the integrated amount of carbon dioxide calculated from the concentration and the gas flow rate due to the circulation based on a predetermined conversion formula.

The measurement method of this embodiment uses the carbon dioxide measurement device of the first embodiment and obtains the ethanol concentration in the target object from the integrated amount. Therefore, the ethanol concentration can be easily measured without sampling by simply bringing the first inlet of the probe close to or in contact with the fermentation broth or the like. Furthermore, the mixed gas inside the probe is circulated by the airflow unit, and the carbon dioxide concentration is measured by the sensor and appropriately converted into ethanol concentration, so measurements can be performed in real time. Measurements can be easily performed even when the fermentation broth or the like is open to the atmosphere, and the method can be easily applied to existing manufacturing facilities. This measurement method is preferably used for managing the fermentation (cultivation) process of fermentation broth or the like.

Embodiments of a carbon dioxide measuring device will be described below with reference to the drawings. Figure 1 is an explanatory diagram of a carbon dioxide measuring device 100. The carbon dioxide measuring device 100 includes a cylindrical probe 10, a sensor 16, and a suction unit 20.

The probe 10 is cylindrical and open at both ends. The tip 10A is provided with a first inlet 12, which is an open end. The central portion 10B houses a sensor 16. The open end of the rear end 10C is airtightly connected to a tube 20A connected to a suction unit 20.

Figure 2 is an enlarged view (schematic diagram) of the tip 10A, which is one end of the probe 10. The tip 10A of the probe 10 is open and serves as the first inlet 12. On the other hand, a second inlet 14 with a smaller diameter than the first inlet 12 is provided on the side. A conduit 18 is airtightly connected to the second inlet 14. The second inlet 14 is located closer to the central portion 10B than the first inlet 12.

The material of the probe 10 is not particularly limited as long as it has the airtightness required for measuring the carbon dioxide concentration. Metal, glass, plastic, etc. can be used. When the object is food or the like, the probe 10 may be made of stainless steel, which makes it easier to keep the probe 10 clean.
The probe 10 may be formed as a single unit, or may be divided into a plurality of sections that are assembled to form a completed unit.

A sensor 16 is located in the central section 10B of the probe 10. The sensor 16 is capable of measuring carbon dioxide concentration and is connected to a controller (not shown) via a wired or wireless connection. In this example, the power supply for driving the sensor 16 is housed in the central section 10B in line with the sensor 16, but it may also be located outside the probe 10 and connected to the sensor 16 from outside the probe 10.

Any known carbon dioxide concentration sensor can be used as sensor 16, including non-dispersive infrared (NDIR), tunable diode laser absorption spectroscopy (TDLAS), and photoacoustic sensors.

A tube 20A is airtightly connected to the open end of the rear end 10C of the probe 10. The other end of the tube 20A is connected to the suction unit 20, so essentially, one end (tip end 10A) of the probe 10 is open.

The length and size (diameter) of the probe 10 are not particularly limited and can be adjusted appropriately depending on the shape and size of the object 40 to be applied, the depth of the container (open container 32) in which it will be placed, and other factors. For example, if the object 40 is a liquid and the open container 32 is 2 to 5 m in diameter and 2 to 5 m in height, the length is preferably 0.3 to 1.5 m, and more preferably 0.55 to 0.9 m, to make it easier to insert the probe 10 through the opening 30.

Furthermore, the inner diameter of the probe 10 is not particularly limited. However, in the carbon dioxide measuring device 100, as shown in FIG. 2 , the inner diameter of the probe 10 is directly related to the diameter of the first inlet 12. Therefore, the inner diameter is appropriately selected in accordance with the required sensitivity, measurement range, and the like. That is, if the inner diameter of the probe 10 (the diameter of the first inlet 12 in the carbon dioxide measuring device 100) is smaller than that of the second inlet 14, the proportion of the first gas FL1 drawn in will inevitably decrease. Accordingly, the carbon dioxide concentration in the mixed gas FL3 will also decrease. Therefore, if the measurable range of the sensor 16 is constant, it becomes easier to measure a range in which the carbon dioxide concentration generated by the target is higher. On the other hand, if the inner diameter of the probe 10 is larger than the diameter of the second inlet 14, it becomes easier to measure a range in which the carbon dioxide concentration generated by the target is lower.
In one embodiment, the inner diameter of the probe 10 is preferably 10 to 100 mm, more preferably 13 to 50 mm.

The width of the sensor 16's measurable range depends on the sensor 16's type, etc., but using a sensor 16 with a wider measurable range directly increases the cost required for manufacturing (assembling) the carbon dioxide measuring device 100. In this embodiment, the carbon dioxide measuring device 100 can adjust the ratio between the inner diameter of the probe 10 (the diameter of the first inlet 12) and the diameter of the second inlet 14 in advance based on the predicted carbon dioxide concentration generated from the object 40.

For example, if the carbon dioxide concentration generated from the target object 40 is expected to be high, the first inlet 12 can be made smaller, and if the carbon dioxide concentration is expected to be low, the first inlet 12 can be made larger. Predicting the carbon dioxide concentration generated from the target object 40 is easy when the target object is, for example, a culture solution of microorganisms or a fermentation solution obtained by fermenting a raw material.
Even when an inexpensive sensor 16 with a narrow and limited measurable range is used, the carbon dioxide measuring device 100 can perform measurements with sufficient accuracy and range by adjusting the probe 10.

The shape of the probe 10 in Figure 1 is such that the tip portion 10A is cylindrical with a fixed inner diameter, the central portion 10B is cylindrical with a larger inner diameter, and the rear end portion 10C is cylindrical with an inner diameter similar to that of the tip portion 10A, with multiple cylinders of different inner diameters joined and connected together. This is because the sensor 16 is housed inside the central portion 10B, and the inner diameter of the central portion 10B can be adjusted to accommodate the sensor 16 (and other sub-devices, such as a power supply and controller, if necessary).

On the other hand, as long as the sensor 16 can be accommodated, the inner diameter of the probe 10 may be constant. That is, the inner diameter may be the same from the tip portion 10A to the central portion 10B to the rear end portion 10C. Also, part or all of the probe may be tapered. Furthermore, the cross section does not need to be circular, but may be polygonal. In one embodiment, it is preferable that the inner diameter of the rear end portion 10C is smaller than that of the tip portion 10A.

The tip 10A of the probe 10 is provided with a first inlet 12 for introducing (sucking) a first gas FL1 and a second inlet 14 for introducing (sucking) a second gas FL2.
The first inlet 12 is provided as an open end of the probe 10. The first inlet 12 is used by being brought close to or in close contact with the surface 40A of the object 40. As will be described later, when the carbon dioxide measuring device 100 is in use, the suction unit 20 sucks in gas inside the probe 10, and a first gas FL1 mainly composed of gas generated from the object 40 (or consisting of gas generated from the object 40) is introduced from the first inlet 12 brought close to or in close contact with the surface of the object 40.

As is clear from the partially enlarged view of Figure 2, the first inlet 12 is configured as an open end at the tip 10A of the probe 10. However, the first inlet provided in the carbon dioxide measuring device is not limited to the above configuration. As long as it is located closer to the tip than the second inlet 14 (described below), it does not have to be located as an open end at the tip of the probe 10. For example, the tip of the probe 10 may be closed, and the first inlet 12 may be located on the side near the tip. The configuration of the first inlet 12 may be selected to suit the shape of the object 40 and to make it easy to approach or contact it.

On the other hand, when the object 40 is a liquid, particularly when the object 40 is contained in an open container 32, it is preferable that the tip of the probe 10 is open and that this open end is the first inlet 12, as this makes it easier to insert the probe 10 from vertically above the open container 32.

The tip 10A of the probe 10 is further provided with a second inlet 14. A second gas FL2 is introduced from the second inlet 14. The introduced second gas FL2 has a different composition from the first gas FL1, and although its composition is not particularly limited, it is preferable that the concentration of carbon dioxide contained therein is known, and it is even more preferable that the composition be known.

The second inlet 14 is provided closer to the central portion 10B than the first inlet 12. In other words, it is provided on the sensor 16 side. That is, from the tip side of the probe 10, the first inlet 12, the second inlet 14, and the sensor 16 are provided in this order. Specifically, the second inlet 14 is disposed on the side surface of the tip portion 10A of the probe 10.
By configuring in this manner, even when the first inlet 12 is brought close to or in contact with the object 40, the second inlet 14 can be placed further away from the object 40 than the first inlet 12 and/or can be prevented from coming into contact with the object 40.

In this specification, the terms tip portion 10A, central portion 10B, and rear end portion 10C represent longitudinal positions of the probe 10 and are defined according to the position where the sensor 16 is located. That is, the portion where the sensor 16 is located is defined as the central portion 10B, and with the central portion 10B as the reference, one side is defined as the tip portion 10A, and the other side is defined as the rear end portion 10C. Therefore, the second inlet 14 is located closer to the central portion 10B than the first inlet 12, and closer to the tip than the central portion 10B where the sensor 16 is housed.

From the second inlet 14 configured in this manner, a second gas FL2 having a different composition from the first gas FL1 can be introduced.
The second gas FL2 is introduced into the probe 10, and together with the first gas FL1, forms a mixed gas FL3, which is then drawn toward the sensor 16. By adjusting the positional relationship between the two inlets as described above, the second gas FL2 functions as a reference and/or a carrier.

The distance between the first inlet 12 and the second inlet 14 is not particularly limited, but it is preferable to provide the second inlet 14 near the first inlet 12, from the viewpoint of more efficiently transporting the first gas FL1 introduced into the probe 10 to the sensor 16 and, as a result, obtaining more real-time and/or more accurate measurement results.
Specifically, it is preferable that the second inlet 14 does not come into contact with at least the surface 40A of the object 40 during measurement, while being closer to the first inlet 12. In one embodiment, when the diameter of the first inlet 12 is 1, the lower end of the second inlet 14 is preferably positioned 1 to 20 from the (upper end of) the first inlet 12.

When the second inlet 14 is located near the first inlet 12, gas generated from the object 40 is more likely to be introduced into the second inlet 14. From the perspective of obtaining more accurate measurement results, in such cases, it is preferable to connect a conduit 18 to the second inlet 14 and introduce the second gas FL2 from a space further away from the object 40.

In FIG. 1, a conduit 18 is connected to the second inlet 14, and the other end of the conduit 18 is positioned outside the opening 30 of the open container 32. With this configuration, when the other end of the conduit 18 is opened, air is introduced as the second gas FL2 through this other end. The air drawn in from the separated space outside the opening 30 can be considered to have a composition similar to that of atmospheric air, and its carbon dioxide concentration is known (composition known) to be approximately 0.03 vol%. This enables more accurate measurements.

The diameter of the second inlet 14 is not particularly limited, but from the perspective of increasing the proportion of the first gas FL1 in the mixed gas FL3, it is preferably equal to or smaller than the diameter of the first inlet 12, and more preferably smaller than the diameter of the first inlet 12. For example, when the diameter of the first inlet 12 is 1, the diameter of the second inlet 14 is preferably 0.1 or greater and less than 1.

The suction unit 20 includes a flow meter and an air pump, and has the function of sucking gas from inside the probe 10 to generate a gas flow inside.
Specifically, the first gas FL1 and the second gas FL2 are sucked in from the first inlet 12 and the second inlet 14, respectively, and the mixed gas FL3 is directed toward the sensor 16, passes through the sensor 16 (mixed gas FL4 after passing through the sensor), and is then discharged outside the probe 10. The discharge amount at this time is preferably set to be equal to or greater than the maximum amount (speed) of gas generated from the object, and although there is no particular upper limit, it is preferably 10,000 mL or less per minute.

It should be noted that, instead of the suction unit 20, another type of airflow unit having a function of forming an airflow in the probe and circulating the mixed gas FL3 toward the sensor 16 can be used. Examples of such airflow units include a suction unit including an air ejector and a blower unit including a fan. Also, a discharge unit that forms an airflow by discharging a compressed second gas from a second inlet can be used.
Among these, the suction unit and the blower unit are preferred, and the suction unit is more preferred, as they enable more accurate measurements.

The gas flow rate from the suction unit 20 is not particularly limited, but may be adjusted appropriately depending on the measurable range (concentration range) of the sensor 16, etc. In one embodiment, the flow rate may be as described above if the carbon dioxide concentration in the first gas FL1 is 40,000 ppm or less and the amount of gas generated from the object is 80 mL/min or less.

The gas flow rate may be constant or may be varied. For example, assume that the target is sake mash. In this case, measurements are taken from the early stage of fermentation until a sufficient amount of ethanol (the designed amount) is produced. In other words, measurements are continued for a certain period of time, and changes in the carbon dioxide concentration are observed.
If the gas flow rate is constant throughout the entire measurement period, the concentration measurement results can be easily converted into the cumulative amount of carbon dioxide generated. In other words, if the flow rate is constant, the carbon dioxide generation rate can be calculated by multiplying it by the concentration, and by integrating this over the observation time, the cumulative amount of carbon dioxide generated can be obtained.

On the other hand, by changing the gas flow rate according to the amount of carbon dioxide generated from the object, it is possible to change and widen the actual measurable range (shifting the measurable range according to the amount generated and the passage of time) while using a sensor 16 that has a fixed measurable range.

The object 40 is contained in an open container 32, and the probe 10 is inserted from the opening 30 side, bringing the first inlet 12 close to or into contact with the surface 40A. By bringing the first inlet 12 into close contact with the surface 40A, more accurate measurement results are more likely to be obtained.

The first gas FL1 generated from the object 40 enters the probe 10 through the first inlet 12. At this time, the gas inside the probe 10 is sucked in by the suction unit 20. For example, when the suction unit 20 sucks in gas at a constant flow rate, even if the amount of gas generated from the object 40 is small and the amount of first gas FL1 is small, the second gas FL2 is sucked in accordingly, preventing the object 40 itself from entering the probe 10 through the open end of the first inlet 12. As a result, preventing the object 40 from being sucked in reduces clogging of the probe 10. When the object 40 is a suspension medium, the above configuration provides a greater clogging prevention effect.

On the other hand, the second inlet 14, which is located at a higher position (toward the central portion 10B) than the first inlet 12, can be positioned above the liquid level even when the first inlet 12 is in close contact with the surface 40A of the object 40, and therefore a second gas FL2 of a different composition can be introduced. A conduit 18 is connected to the second inlet 14, and the other end of the conduit 18 is adjusted to be located in a space separated from the open container 32, specifically, at a location away from the opening 30.
In this way, the proportion of the gas generated from the target object 40 in the second gas FL2 can be reduced.

In Figure 1, the object 40 is a liquid. A liquid refers to a substance or system that contains liquid and has fluidity. Specific examples include liquids (including mixtures of two or more components), suspensions, emulsions, gels, sols, and colloidal solutions. From the perspective of being able to monitor and adjust the fermentation/cultivation process by measuring the carbon dioxide concentration, the liquid is preferably a microbial culture solution or a fermentation solution obtained by fermenting raw materials.

Examples of microorganisms include fungi, bacteria, and microalgae. Examples of fungi include Aspergillus oryzae and yeast, which are used in brewing. Examples of bacteria include lactic acid bacteria, acetic acid bacteria, and Bacillus bacteria. Examples of microalgae include diatoms, blue-green algae, dinoflagellates, green algae, and red algae.

As long as the microbial culture solution contains the above-mentioned microorganism and liquid medium, it may also contain other components. Examples of other components include sugars, nitrogen sources, vitamins, inorganic salts, pH adjusters, and gelling agents. Microbial culture solutions also include, for example, yeast starter used in sake brewing.

The fermented liquid obtained by fermenting raw materials is not particularly limited, but examples include moromi (unrefined soybean mash) used in the production of sake, soy sauce, miso, etc., must used in wine production, etc., and wort used in beer production, etc.
In addition to the above, the fermentation liquid may be a fermentation liquid for producing amino acids, organic acids, vitamins, biofuels, etc.

Among these, microorganisms that perform alcohol (ethanol) fermentation are preferred. Examples of such microorganisms include yeasts such as Saccharomyces cerevisiae, Saccharomyces pastorianus, and Schizosaccharomyces pombe, and bacteria such as Zymomonas mobilis and Clostridium acetobutylicum.

Next, we will explain the flow of calculating the ethanol concentration in the object 40 and generating an alert using the carbon dioxide measuring device 100. Figure 3 is a flow diagram of calculating the ethanol concentration and generating an alert using the carbon dioxide measuring device 100.

First, in step S10, the concentration of carbon dioxide generated from the object 40 is measured. Specifically, the first inlet 12, which is the open end of the probe 10, is brought into contact with the surface 40A of the object 40, and the gas inside the probe 10 is sucked in by the suction unit 20.
As a result, a first gas FL1 containing carbon dioxide generated from the object 40 is sucked in through the first inlet 12, and a second gas FL2 consisting of air introduced through the conduit 18 is sucked in through the second inlet 14. Furthermore, when this mixed gas FL3 reaches the sensor 16 housed in the central portion 10B of the probe 10, the carbon dioxide is measured. The above process is carried out continuously, and the carbon dioxide concentration is measured in real time according to the data acquisition interval. At this time, the gas flow rate inside the probe 10 provided by the suction unit 20 (or a flow meter included therein) may also be recorded.

There are no particular restrictions on the interval at which data is acquired, but one example is every 1 to 60 seconds. The data actually obtained depends on the measurement method used by the sensor 16, but is generally expressed as vol%.

Next, in step S11, the obtained concentration data is averaged at a predetermined time interval. For example, data is aggregated at a time interval longer than the sampling interval (the data acquisition interval). Aggregating the data (reducing the amount of data) makes calculations easier. The time interval for aggregating the data is not particularly limited, and may be selected appropriately depending on the processing speed of the controller, the type of object 40, etc. In one embodiment, the time interval is preferably about 5 to 50 times the sampling interval.
This step is not essential and can be omitted depending on the purpose, the processing speed of the controller, etc. In other words, the measurement values themselves may be used to perform the calculation in the next step without aggregating the data.

Specific examples of controllers include a microcontroller unit (MCU), a programmable logic controller (PLC), a programmable automation controller (PAC), and a personal computer (PC). The controller may also be implemented using a field-programmable gate array (FPGA). It is preferable that the controller is typically a computer including a memory and a processor.

Next, in step S12, the carbon dioxide generation rate (mL/min) is calculated from the gas flow rate inside the probe 10 generated by the suction unit 20. Specifically, the average carbon dioxide concentration calculated in step S11 (or the measured value itself) is multiplied by the flow rate (mL/min) at the time of measurement. If the gas flow rate inside the probe (near the central portion 10B) generated by the suction unit 20 is constant, this constant value is multiplied. On the other hand, if the gas flow rate caused by the suction unit 20 changes, the gas flow rate recorded along with the measured value is used in the calculation.

If the second gas FL2 contains carbon dioxide, the generation rate may be corrected to reduce the contribution of the carbon dioxide concentration contained in the second gas FL2, for example, by using the ratio of the opening diameters of the first inlet 12 and the second inlet 14. On the other hand, if the carbon dioxide content in the second gas FL2 is negligibly small compared to the carbon dioxide content in the first gas FL1, no correction may be necessary. For example, if the second gas FL2 is air, nitrogen gas, or another inert gas, no correction may be necessary.

Next, in step S13, the cumulative amount of carbon dioxide emitted from the object (mL) is calculated. Specifically, the time integral of the emission rate is calculated. In one specific example, this is calculated as the product of the emission rate (mL/min) calculated in step S12 and the time interval used in step S11 (or the sampling interval if data aggregation is not being performed).

Next, in step S14, the cumulative amount of carbon dioxide generated is converted into the ethanol concentration in the target object. The conversion is performed based on the correlation (generation mechanism) between the production of carbon dioxide and ethanol in the target object. For example, in ethanol fermentation by yeast, it is known that two molecules of ethanol and two molecules of carbon dioxide are produced from one molecule of glucose. Based on this relationship, the cumulative amount of carbon dioxide generated is converted into the cumulative amount of ethanol generated, and the ethanol concentration is calculated based on the total volume of the target object 40.

Next, in step S15, the obtained ethanol concentration is compared with a predetermined alert condition. If this condition is met (step S15: YES), an alert is generated (step S16). The alert condition is not particularly limited, but may be, for example, a target ethanol concentration. In other words, by issuing an alert that the ethanol concentration has reached the target value, the operator can recognize that fermentation has ended normally. On the other hand, an alert may also be generated when a predetermined concentration has not been reached in relation to the observation time. In this way, it is easier to detect poor fermentation.
On the other hand, if the alert condition is not met (step S15: NO), the measurement flow ends. Note that even if the flow ends, measurement may be performed if a preset condition is met (for example, within a predetermined time), and the operations of steps S10 to S16 may be repeated each time.

In the above flow, the ethanol concentration is calculated from the carbon dioxide concentration, and an alert is generated based on the ethanol concentration, but this is not limited to the above.
In addition to the ethanol concentration, other substrates and/or metabolic substances in the fermentation process may also be calculated.
For example, in the case of the above-mentioned alcoholic fermentation, the amount of glucose consumed may be calculated from the cumulative amount of carbon dioxide produced, or the glucose concentration in the target object 40 may be calculated by giving an initial glucose concentration in advance.
In addition to the above, if the mechanism of change (metabolism) involving the generation of carbon dioxide in the object 40 is clear, the amount of change in the components contributing to it and the concentration in the object 40 may be calculated.

In addition to ethanol concentration, the conditions for generating an alert may also be carbon dioxide concentration or other values calculated from this concentration. Examples of other values include substrates, other metabolic substances, cumulative carbon dioxide concentration, and changes in carbon dioxide concentration.

All of the above processes are carried out under the control of a controller. The controller is a computer having a processor, memory, etc. The controller controls each part of the carbon dioxide measuring device 100, acquires data from the sensor 16, suction unit 20, etc., and executes the processing for each of the above steps based on pre-stored settings (e.g., the area of the first inlet 12 and second inlet 14, etc.). Note that the controller's memory has pre-stored programs for executing the above processes.

Next, we will explain the results of an experiment that examined the correlation between the carbon dioxide concentration measured using a carbon dioxide measuring device and the ethanol concentration in the target object.

(Probe preparation)
Figure 4 shows an image of the probe of the carbon dioxide measuring device used in the experiment. The probe 10 was constructed by connecting multiple polyvinyl chloride pipes of different diameters. The tip 10A of the probe 10 was a pipe with an inner diameter of 40 mm, and the inner diameter of the first inlet 12 was also 40 mm. The tip 10A of the probe 10 was also provided with a second inlet 14, which had a diameter of 13 mm. A conduit 18 of approximately the same inner diameter was connected to the second inlet 14, and a joint 18A for attaching a flexible tube was provided at the tip of the second inlet 14.
The length from the lower end of the probe 10 to the lower end of the second inlet 14 was approximately 415 mm.

The sensor 16 was housed in the central portion 10B of the probe 10. An infrared absorption type SCD30 manufactured by Sensirion was used as the sensor 16. The central portion 10B had an inner diameter of 51 mm.
The rear end 10C is made of a pipe having a smaller inner diameter than the front end 10A and the central portion 10B, and a joint 20B for connecting the suction unit 20 is provided at the tip of the pipe.
The probe was approximately 950 mm from tip to tail.

(Preparation of the object)
The target liquid was prepared as follows: First, 2 kg of pregelatinized rice, 1 kg of dried koji, and 5 L of purified water were placed in an open tank and heated at 56°C for 8 hours. After allowing to cool and fermenting at 25°C for 2 days, 300 mL of sake yeast was added and fermented to prepare a liquid.

(Measurement of carbon dioxide concentration, measurement of alcohol concentration)
The tip of the probe was inserted into the object by about 5 cm and fixed perpendicular to the liquid surface using a support stand.
The carbon dioxide concentration was measured at a measurement interval of 30 seconds and a gas flow rate of 2 L/min. The carbon dioxide concentration at 30-second intervals was averaged over 10 minutes, and the average value was multiplied by the gas flow rate to calculate the amount of carbon dioxide generated (ml/min). The cumulative value of carbon dioxide was calculated by multiplying the generated amount by the time (10 minutes) and integrating the result.

The alcohol concentration of the liquid was measured in accordance with the analytical method prescribed by the National Tax Agency. First, the liquid to be measured was filtered to obtain a filtrate. The alcohol concentration of the filtrate was then measured using an alcoholizer (Anton Paar).

(result)
Figure 5 shows the experimental results. The horizontal axis represents elapsed time (h), and the first vertical axis (left) represents the _CO2 generation rate (mL/min) measured by the carbon dioxide measurement device and the alcohol concentration (%) measured by the sampling method (National Tax Agency designated analysis method). The second vertical axis (right) represents the cumulative value of the _CO2 generation rate (mL). Figure 6 shows the correlation between the alcohol concentration measurement results using the sampling method (National Tax Agency designated analysis method) and the cumulative value of the _CO2 generation rate measured by the carbon dioxide measurement device.

The above results showed a very high correlation between the cumulative carbon dioxide values measured using the carbon dioxide measuring device and the alcohol concentration of the liquid (correlation coefficient: 0.99). This confirmed the effectiveness of the carbon dioxide measuring device and measurement method. Furthermore, a regression line between the two could be obtained, allowing the alcohol concentration to be estimated from the cumulative carbon dioxide values.

100 Carbon dioxide measuring device 10: Probe, 12: First inlet, 14: Second inlet, 16: Sensor, 18: Conduit, 20: Suction unit, 40: Object

Claims (16)

A carbon dioxide measuring device that measures the concentration of carbon dioxide generated from an object by bringing an end of a cylindrical probe close to or in contact with the object,
a first inlet for introducing a first gas into the probe and a second inlet for introducing a second gas into the probe, the first inlet and the second inlet being disposed at the end portions, respectively;
a sensor that is accommodated in the probe at a midpoint in the longitudinal direction and that measures the concentration;
an airflow unit that circulates a mixed gas of the first gas and the second gas in a direction from the end toward the sensor,
The carbon dioxide measuring device, wherein the second inlet is disposed closer to the sensor than the first inlet. The carbon dioxide measuring device of claim 1, wherein the airflow unit is positioned closer to the opposite end of the probe than the first inlet. The carbon dioxide measuring device of claim 1, wherein the object is a liquid, the first inlet is in close contact with or inserted into the liquid surface of the object, and the first gas generated from the object is introduced through the first inlet, and the second gas of known composition is introduced through the second inlet. The carbon dioxide measuring device of claim 1, wherein the first inlet is an open end of the probe and the second inlet is located on a side of the probe. The carbon dioxide measuring device of claim 1, wherein a conduit for introducing the second gas is connected to the second inlet. The carbon dioxide measuring device of claim 1, wherein the second gas is air. The carbon dioxide measuring device of claim 5, wherein the object is a liquid contained in an open container, and the second gas is taken in by the conduit from a space separated from the opening of the open container. The carbon dioxide measuring device of claim 7, wherein the object is a microbial culture medium or a fermentation medium obtained by fermenting a raw material. The carbon dioxide measuring device of claim 1, wherein the first inlet is larger than the second inlet. Equipped with a controller,
The carbon dioxide measuring device according to any one of claims 1 to 9, wherein the controller generates an alert when the concentration or a calculation result based on the concentration satisfies an alert condition. The carbon dioxide measuring device of claim 10, wherein the calculation result includes an integrated amount of carbon dioxide calculated based on the concentration measured over a predetermined period of time and the gas flow rate due to the circulation during the period, or a concentration of a predetermined substance in the object calculated from the integrated amount. Equipped with a controller,
The carbon dioxide measuring device according to any one of claims 1 to 9, wherein the controller calculates the concentration of a predetermined substance in the object based on a predetermined conversion formula from the concentration measured over a predetermined period of time and an integrated amount of carbon dioxide calculated from the gas flow rate due to the circulation during the period . The carbon dioxide measuring device of claim 12, wherein the target substance is a microbial culture medium or a fermentation medium obtained by fermenting a raw material, and the specified substance is ethanol. An ethanol concentration measurement device that measures the concentration of carbon dioxide generated from a target object, which is a culture medium for a microorganism or a fermented liquid obtained by fermenting a raw material, by bringing an end of a cylindrical probe into close contact with or inserting the end of the cylindrical probe into the liquid surface of the target object, and calculates the concentration of ethanol in the target object based on the measured concentration of carbon dioxide ,
a first inlet for introducing a first gas into the probe and a second inlet for introducing a second gas into the probe, the first inlet and the second inlet being disposed at the end portions, respectively;
a sensor that is housed in the probe at a midpoint in the longitudinal direction and that measures the concentration of carbon dioxide ;
an airflow unit that circulates a mixed gas of the first gas and the second gas in a direction from the end toward the sensor;
a controller;
the second inlet is disposed closer to the sensor than the first inlet,
The controller calculates the concentration of ethanol in the object based on a predetermined conversion formula from the concentration of carbon dioxide measured over a predetermined period of time and an integrated amount of carbon dioxide calculated from the gas flow rate due to the distribution over the period of time. A method for measuring carbon dioxide concentration, comprising measuring the concentration of carbon dioxide generated from the object using the carbon dioxide measuring device described in claim 1. Measuring the concentration of carbon dioxide generated from the object using the carbon dioxide measuring device according to claim 1;
calculating, based on a predetermined conversion formula, the concentration of ethanol contained in the target object, which is a culture solution of a microorganism or a fermentation solution obtained by fermenting a raw material, from the concentration measured over a predetermined period of time and an integrated amount of carbon dioxide calculated from the gas flow rate due to the distribution during the period.