Water activity measuring device and water activity measuring method

Abstract

To provide a water activity measuring device capable of performing measurement of water activity under the same measuring environment on multiple identical samples at the same time or multiple non-identical samples at the same time without being affected by an error due to the individual difference of individual measuring environments.SOLUTION: A water activity measuring device includes: a plurality of storage means which store a sample to be measured and each of which has a temperature and humidity measuring element; support means for supporting the plurality of storage means; constant temperature means for storing the support means; and control means for calculating a water activity value from the humidity measured by the temperature and humidity measurement element. The support means supports each of the plurality of storage means in a state separated from the inner wall and the top surface of the constant temperature means.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a water activity measuring device and a water activity measuring method for measuring the water activity value of a sample such as food. [Background technology]

[0002] In recent years, it has become widely known that water activity is a useful index for the shelf life of foods. In order to use water activity as an index, it is essential to improve the accuracy of the measurement of water activity. To improve the accuracy of the measurement of water activity, the water activity of a sample is measured multiple times, the measured values ​​are averaged, and the error is minimized.

[0003] Here, an example of a conventional device for measuring water activity value is the device disclosed in Non-Patent Document 1. However, the device disclosed in Non-Patent Document 1 can only accommodate a single sample container, and can only measure the water activity value of a single sample per measurement.

[0004] Therefore, in order to increase the measurement accuracy of the water activity value (to minimize the error in the measurement value) in the device disclosed in Non-Patent Document 1, the sample must be measured multiple times as described above. However, performing multiple measurements in this manner takes a lot of time, and there is a problem (concern) that the measurement environment, such as the temperature and humidity around the measuring device, changes over time between the first and last measurements, resulting in errors in the measurement value.

[0005] In order to address such problems, an apparatus capable of simultaneously measuring multiple samples has been disclosed (Non-Patent Document 2). In the apparatus disclosed in Non-Patent Document 2, four sample containers are each connected to the main body of the apparatus by a cable, and four samples can be measured simultaneously. In addition, each of the four sample containers is provided with a constant temperature water bath structure (constant temperature means), and the inside of the sample container can be set to a predetermined temperature. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] DKSH Japan Co., Ltd. "Water Activity Measuring Device" manufactured by Novasina, Switzerland. Internet URL: https: / / novasina-dkshj.jimdofree.com / [Non-Patent Document 2] Rotronic HYGROLAB C1 High performance research equipment Internet〈https: / / www.rotronic.com / ja-jp / humidity-measurement-feuchtemessung-temperaturmessung / water-activity-wasseraktivitaet / benchtop-instruments / hygrolab.html〉 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the device disclosed in Non-Patent Document 2 is equipped with four sample containers, each of which is equipped with a thermostatic means, so there is no error in the measurement value over time due to changes in the measurement environment.However, even if the measurement environment (temperature environment) is set to be the same for all four sample containers, there is a problem that errors (variations) will occur in the measured water activity value due to individual differences in the thermostatic means.

[0008] An object of the present invention is to provide a water activity measuring device which makes it possible to measure the water activity value of multiple identical samples simultaneously or multiple non-identical samples simultaneously under the same measurement environment without being affected by errors due to individual differences in each measurement environment. [Means for solving the problem]

[0009] The water activity measuring device of the present invention comprises a plurality of storage means for storing samples to be measured, each of which has a temperature and humidity measuring element, a support means for supporting the plurality of storage means, a constant temperature means for housing the support means, and a control means for calculating a water activity value from the humidity measured by the temperature and humidity measuring element, and is characterized in that the support means supports each of the plurality of storage means in a state isolated from the inner walls and the top and bottom surfaces of the constant temperature means.

[0010] The present invention is a method for measuring water activity in a water activity measuring device comprising a plurality of storage means for storing samples to be measured, each having a temperature and humidity measuring element, a support means for supporting the plurality of storage means, a constant temperature means for housing the support means, and a control means, and includes a storage step of storing a plurality of identical samples or a plurality of non-identical samples in each of the plurality of storage means, a joining step of joining the plurality of storage means in which the samples are stored to the support means, a storage step of housing the support means in the constant temperature means, a measurement step of measuring humidity in each of the plurality of storage means using the temperature and humidity measuring element, and a calculation step of calculating a water activity value from the humidity measured by the temperature and humidity measuring element, and is characterized in that the support means supports each of the plurality of storage means in a state isolated from the inner walls and the top and bottom of the constant temperature means. Effect of the Invention

[0011] According to the water activity measuring device of the present invention, it is possible to measure the water activity value of multiple identical samples or multiple non-identical samples simultaneously under the same measurement environment without being affected by errors due to individual differences in the individual measurement environments. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing a water activity measuring device. [Diagram 2] FIG. 1 is a schematic diagram of a sample containment vessel and connector. [Diagram 3] FIG. [Figure 4] FIG. 13 is a schematic diagram of a thermostatic means housing a panel plate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment does not limit the present invention, and not all of the combinations of features described in the present embodiment are necessarily essential to the solution of the present invention. In addition, various forms within the scope of the present invention that do not deviate from the gist of the present invention are also included in the present invention, and parts of the following embodiments can be appropriately combined.

[0014] 1 is a schematic diagram showing a water activity measuring apparatus. As shown in Fig. 1, the water activity measuring apparatus mainly includes a sample storage container 1, a panel plate 2, a thermostatic means 3, a calculator 4, a display device 5, and a communication cable 6.

[0015] In the water activity measuring device, the water activity value is calculated based on the temperature and humidity measured in an equilibrium state in the sample storage container 1. The temperature and humidity inside the sample storage container 1 are measured with the panel plate 2 supporting the sample storage container 1 housed in a thermostatic means 3.

[0016] Calculator 4 is a control means, and mainly controls temperature and humidity measuring device 14, heater 15, calculation control for calculating the average water activity value and the like from the measured temperature and humidity values, and display control on display device 5. Display device 5 displays the average water activity value and the like calculated by calculator 4, and, if necessary, displays a graph showing the elapsed measurement time and the relationship between the measurement time and the water activity value. Note that calculator 4 and display device 5 are preferably provided outside thermostatic means 3 so as not to affect the temperature inside thermostatic means 3.

[0017] The communication cable 6 is a wired cable such as a LAN (Local Area Network) cable, and the computer 4 communicates with the sample storage container 1 via the communication cable 6 (the panel board 2, the connector receptacle 21, and the connector 13). In this embodiment, an example of communication between the sample storage container 1 and the communication cable 6 using the communication cable 6 has been described (i.e., an example of wired communication has been described), but the communication here does not necessarily have to be wired and can also be wireless, such as via wireless LAN, as described later.

[0018] 2 is a diagram showing the sample storage container 1. As shown in FIG. 2, the sample storage container 1 is a storage unit, and includes a container upper part 11, a container lower part 12, a connector 13, a temperature and humidity measuring device 14, and a heater 15.

[0019] The sample storage container 1 of this embodiment has a structure in which the container upper part 11 and the container lower part 12 can be separated, and the inside of the container can be easily sealed by screwing the container upper part 11 and the container lower part 12 together. Furthermore, this screwing (sealing) is performed to such an extent that the container lower part 12 does not fall off the container upper part 11 due to gravity even when the connector 13 fixed to the container upper part 11 supports the entire sample storage container 1.

[0020] In this embodiment, the upper and lower container parts 11 and 12 are cylindrical in shape, but the shapes of the upper and lower container parts 11 and 12 are not limited to this, and for example, cubic box-shaped containers may be used. In addition, a screw structure is used as a structure for sealing the sample storage container 1, but the structure for sealing the sample storage container 1 is not limited to this, and for example, a structure for sealing with a hook, packing, magnet, etc. may be used.

[0021] In addition, as described above, in this embodiment, the upper container portion 11 and the lower container portion 12 are described as having a structure that can be separated for ease of handling. However, the upper container portion 11 and the lower container portion 12 do not necessarily have to have a structure that can be separated, and may have a structure (integral type) that cannot be separated, for example, by connecting them with a hinge or the like.

[0022] The materials for the upper container portion 11 and the lower container portion 12 may be metal, resin, glass, or a combination of these. However, since the sample storage container 1 is kept at a constant temperature within the thermostatic means 3, it is preferable to use a material with high thermal conductivity, such as metal.

[0023] The connector 13 is a component that can be joined and separated from the panel plate 2, and is fixed to the sample storage container 1 to an extent that it can support the entire sample storage container 1 when the sample storage container 1 is joined to the panel plate 2.

[0024] In this embodiment, in order to improve workability during measurement by eliminating the need for connection cables, the connector 13 is used not only to support the entire sample storage container 1, but also to supply power to and transmit various commands to the temperature and humidity measuring device 14 and heater 15 that are connected via a printed circuit board or the like (for example, in accordance with standards such as USB (Universal Serial Bus)).

[0025] In this embodiment, the connector 13 is used to supply power to the sample storage container 1 and transmit various commands, but the communication does not necessarily have to be performed using the connector 13 and can be performed wirelessly such as wireless LAN (the sample storage container 1 can be powered by a built-in battery, so it can be wireless). In this embodiment, the connector 13 in the sample storage container 1 is fixed to the upper part 11 of the container as shown in Fig. 2, but it may be fixed to the lower part 12 of the container.

[0026] The temperature and humidity measuring device (temperature and humidity measuring element) 14 measures the temperature and humidity inside the sample storage container 1 sealed by the container upper part 11 and the container lower part 12. There are various types of temperature and humidity measuring devices, such as capacitance type, electrical resistance type, and mirror cooling type, but in this embodiment, a capacitance type humidity measuring device is used as the temperature and humidity measuring device 14.

[0027] In this embodiment, the temperature and humidity measuring device 14 is positioned adjacent to the connector 13 in order to reduce the effects of the sample on temperature and humidity and for ease of connection to the connector 13, but it does not necessarily have to be positioned adjacent to the connector 13 and may be structured to be installed, for example, in the lower part 12 of the container.

[0028] As described above, in this embodiment, a capacitance type thermo-hygrometer is used as the thermo-hygrometer, and therefore an offset change occurs due to the moisture absorption phenomenon of the wet-dry film. Here, it is preferable that the moisture-sensitive film contains a moderate amount of moisture, and if it is left in a high humidity environment for a long time and contains a large amount of moisture, or if it is left in a low humidity environment for a long time and is dry, an error will occur in the humidity measurement result. As a supplement, in water activity measurement, there are few opportunities for the thermo-hygrometer to dry out, but conversely, there are many opportunities for it to be left in a high humidity environment for a long time.

[0029] Therefore, in this embodiment, a heater 15 is provided to locally heat the temperature and humidity measuring instrument 14, thereby making it possible to easily bake (heat) the temperature and humidity measuring instrument 14. This baking makes it possible to recover the temperature and humidity measuring instrument 14 from the offset change (to adjust the temperature and humidity measuring instrument 14 from the offset change), thereby minimizing measurement errors of the water activity value.

[0030] Specifically, in this embodiment, when the calculator 4 detects that the sample storage container 1 is joined to the connector receptacle 21, it controls the heater 15 to start heating in order to recover from the offset change. In addition, after starting heating by the heater 15, the calculator 4 controls the heater 15 to stop heating according to the humidity measured by the temperature and humidity measuring device 14. More specifically, when it detects that the amount of change per unit time of the humidity measured by the temperature and humidity measuring device 14 is equal to or less than a predetermined threshold (for example, when it detects that the measured value for 10 seconds is within the range of ±0.02aw (±2% RH)), it controls the heater 15 to stop heating.

[0031] By controlling in this way, the temperature and humidity measuring instrument 14 is always maintained in an optimal state for measuring temperature and humidity, and the water activity value can be measured in a state where error is minimized. In this embodiment, when the measurement is completed, the calculator 4 controls the heater 15 to start heating the temperature and humidity measuring instrument 14, and the temperature and humidity measuring instrument 14 is restored from the offset change. By controlling in this way, the preparation time until the measurement of the next sample can be shortened. Even when an electrical resistance type temperature and humidity measuring instrument is used as the temperature and humidity measuring instrument, the problem of moisture absorption phenomenon of the dry and wet film occurs to a certain extent, and condensation may occur on the humidity measuring instrument, so that the effect of the baking operation can be expected.

[0032] Fig. 3 is a diagram showing the panel plate 2. As shown in Fig. 3, a plurality of connector receptacles 21 are provided on the panel plate 2, and the panel plate 2 is provided with legs 22 at its lower part so that the panel plate 2 can stand on its own within the thermostatic means 3. In addition, the panel plate 2 is preferably made of a material that is not easily affected by the surrounding temperature, and here, a panel plate made of resin is used.

[0033] The connector receptacles 21 are mounted on the panel plate 2 so as to have sufficient strength to support the sample storage container 1 joined to the connector receptacle 21. Furthermore, the multiple connector receptacles 21 mounted on the panel plate 2 are arbitrarily mounted at positions isolated from one another so that, during measurement, a sample storage container 1 joined to one of the multiple connector receptacles 21 is not affected by sample storage containers 1 joined to other connector receptacles 21, allowing for rapid measurement.

[0034] 3 shows an example in which a plurality of connector receptacles 21 are regularly arranged so that the sample storage containers 1 can be arranged in an arbitrary isolated manner on the panel plate 2. In this way, the connector receptacle 21 (i.e., the panel plate 2) is joined to the connector 13 of the sample storage container 1, thereby serving as a medium between the sample storage container 1 and the computer 4, and enabling power supply to the sample storage container 1 and communication with the sample storage container 1.

[0035] The legs 22 are auxiliary means for supporting the panel plate 2. The legs 22 facilitate joining of the sample storage container 1 and enable the panel plate 2 to support itself within the thermostatic means 3. Note that the legs 22 do not necessarily have to be provided on the panel plate 2, and the panel plate 2 itself may be bent to support itself.

[0036] Fig. 4 is a diagram showing the thermostatic means 3. As shown in Fig. 4, the thermostatic means 3 includes a thermostatic container section 31, a door section 32, a temperature control section 33 with a sensor, and a power cable 34. As the thermostatic means 3, for example, a commercially available thermostatic bath or incubator can be used.

[0037] The thermostatic container section 31 houses the panel plate 2 on which one or more sample storage containers 1 are supported in the same measurement environment (same temperature environment). The panel plate 2 is housed in a position where the joined sample storage containers 1 are isolated from the inner wall and the top and bottom of the thermostatic means 3.

[0038] The door part 32 seals the opening of the thermostatic container part 31 so as to maintain a constant temperature inside the thermostatic container part 31. In this embodiment, as shown in Fig. 4, the door part 32 is located on the side surface of the thermostatic means 3, but it may be located in another position, such as on the top surface.

[0039] The sensor-equipped temperature adjustment unit 33 includes a temperature sensor, as well as a heater and a cooler. When the temperature sensor detects a temperature higher than the set temperature, the sensor-equipped temperature adjustment unit 33 operates to maintain the temperature inside the thermostatic means 3 at the set temperature by cooling with the cooler, and when the temperature sensor detects a temperature lower than the set temperature, the sensor-equipped temperature adjustment unit 33 operates to maintain the temperature inside the thermostatic means 3 at the set temperature by heating with the heater. The power cable 34 is a cable for supplying power to the sensor-equipped temperature adjustment unit 33.

[0040] Next, a method for measuring the water activity value (more specifically, a method for simultaneously measuring the water activity values ​​of a plurality of samples) will be described. First, a plurality of samples are stored in a plurality of sample storage containers 1, and the plurality of sample storage containers 1 storing the samples are each joined to the connector receptacle 21 of the panel plate 2, so that the sample storage containers 1 are supported by the panel plate 2. During this joining, each sample storage container 1 is joined so as to be isolated from the inner wall of the thermostatic means 3 and the other sample storage containers 1 in order to minimize errors in the measurement value.

[0041] Next, the panel plate 2 is stored in the thermostatic container section 31 and sealed with the door section 32. It is also possible to previously store the panel plate 2 in the thermostatic means 3 and then join the sample storage container 1. The measurement environment in the thermostatic means 3 is made uniform by the sensor-equipped temperature adjustment section 33 of the thermostatic means 3, and in the sample storage container 1, recovery from offset changes is achieved by heating with the heater 15.

[0042] Thereafter, the temperature and humidity measuring device 14 continues to measure the water activity value, and the calculator 4 controls the heater 15 to stop heating according to the measured humidity (more specifically, when it detects that the amount of change (difference) in the humidity measured by the temperature and humidity measuring device 14 per unit time has fallen below a predetermined threshold value), and further controls the heater 15 to calculate the water activity value from the result measured in the equilibrium state (for example, the measured value for one minute is within the range of ±0.002aw (±0.2% RH)).

[0043] When the calculator 4 calculates the water activity value, it controls the display device 5 to display the calculated water activity value, and controls the temperature and humidity measuring instrument 14, which has completed the measurement, to start baking (heating) again.

[0044] As described above, according to the water activity measuring device of this embodiment, since no constant temperature means is provided for each sample storage container, there is no influence due to individual differences between the sample storage containers, and there is no need to supply high voltage power for the purpose of constant temperature (i.e., there is no need to provide a power line for the purpose of supplying high voltage power to each sample storage container). Furthermore, the water activity value can be measured simultaneously for multiple identical samples or multiple non-identical samples under the same measurement environment.

[0045] In the above description, the positions of the multiple connector receivers installed on the panel plate are fixed, but the positions of the connector receivers on the panel plate may be made movable so that the sample storage container can be supported at any position.

[0046] Specifically, a panel plate may be provided with a plurality of screw holes into which a connector receiver can be screwed, and an arbitrary screw hole may be selected from the screw holes, and the connector receiver may be screwed into the arbitrary position to fix the sample storage container. Also, on the premise that each sample storage container is equipped with a wireless communication function and a battery, the sample storage containers may be fixed to the panel plate using a magnet or the like. [Explanation of symbols]

[0047] 1: Sample storage container 2: Panel board 3: Constant temperature means 4: Calculator 5:Display device 6: Communication cable

Claims

1. a plurality of storage means for storing samples to be measured, each of which has a temperature and humidity measuring element and a heater for heating the temperature and humidity measuring element; a support means for supporting the plurality of storage means; a thermostatic means for housing the support means; A control means for calculating a water activity value from the humidity measured by the temperature and humidity measuring element; Equipped with The water activity measuring device is characterized in that the support means supports each of the multiple storage means in a state where it is isolated from the inner walls and the top and bottom of the thermostatic means, and in a state where the multiple storage means are isolated from each other so that heating by the heater in one of the multiple storage means does not affect measurements in the other storage means.

2. When the containment means is joined to the support means, 2. The water activity measuring device according to claim 1, wherein the control means controls the housing means joined to the support means so as to start heating the temperature and humidity measuring element by the heater.

3. 3. The water activity measuring device according to claim 2, wherein the control means controls the heater to stop heating the temperature and humidity measuring element in accordance with the humidity measured by the temperature and humidity measuring element.

4. A method for measuring water activity in a water activity measuring device comprising: a plurality of storage means for storing samples to be measured, each of the storage means having a temperature and humidity measuring element and a heater for heating the temperature and humidity measuring element; a support means for supporting the plurality of storage means; a thermostatic means for housing the support means; and a control means, storing a plurality of identical samples or a plurality of non-identical samples in each of said plurality of storage means; a bonding step of bonding a plurality of storage means, in which the samples are stored, to the support means; a first control step of controlling the heater to heat the temperature and humidity measuring element when the temperature and humidity measuring element is joined to the supporting means; a housing step of housing the support means in the thermostatic means; a measuring step of measuring humidity by the temperature and humidity measuring element in each of the plurality of storage means; a second control step of controlling the temperature and humidity measuring device to stop heating when a change in humidity per unit time measured by the temperature and humidity measuring element becomes equal to or less than a predetermined threshold value; a calculation step of calculating a water activity value from the humidity measured by the temperature and humidity measuring element; Including, A method for measuring water activity, characterized in that the support means supports each of the plurality of storage means in a state isolated from an inner wall and top and bottom surfaces of the thermostatic means.

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