How to clean the taste sensor

Abstract

To provide a cleaning liquid optimized for cleaning a taste sensor.SOLUTION: A cleaning liquid washes a taste sensor containing an amphiphilic substance. The sensor is washed by the cleaning liquid containing a water-soluble amphiphilic substance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for cleaning a taste sensor containing an amphiphilic substance. [Background technology]

[0002] An amphiphilic substance is a general term for molecules that have both a "hydrophilic group" that is compatible with water (aqueous phase) and a "lipophilic group" (hydrophobic group) that is compatible with oil (organic phase) within the same molecule. Examples include surfactants, biological molecules such as phospholipids, and amphiphilic polymers.

[0003] Taste sensors have been developed as sensors that use these amphipathic substances. Bitter and astringent substances are highly hydrophobic, and have the property of bonding strongly with the hydrophobic groups of amphipathic substances (hydrophobic bonding). Utilizing this hydrophobic bonding property, the inventors of the present application have developed taste sensors such as bitter and astringent sensors. Taste sensors are molecular membrane sensors whose membrane potential changes depending on the components in a sample solution when immersed in the solution, and can detect the bitterness or astringency of the components in the solution relatively by measuring the membrane potential.

[0004] During taste testing, bitter and astringent substances in the sample are strongly adsorbed to these sensors. To reuse the sensors during taste testing, it is necessary to wash away the bitter and astringent substances adsorbed to the sensor and return it to its original state. Such a washing solution must be optimized to wash away the bitter and astringent substances (adsorbed substances) adsorbed to the molecular membrane of the sensor.

[0005] As mentioned above, the inventors have developed a taste sensor using a molecular membrane made of lipids, which are amphiphilic substances, to conduct taste tests (gustatory tests), and this is disclosed in Patent Documents 1 to 4 and Non-Patent Document 1. Patent Document 1 discloses a "taste sensor and its manufacturing method," and describes the importance of lipids as taste sensors. Patent Document 2 also describes lipid membranes that are highly selective for bitterness and lipid membranes that are highly selective for astringency, and describes the compositions of these "lipid membranes." Patent Document 3 discloses "molecular membranes for taste testing," and presents the compositions of lipid membranes that are highly selective for sourness, saltiness, and umami. Furthermore, lipid membranes for the common sweetness of sucrose and fructose have been presented at academic conferences as "Highly sensitive sweetness sensor using lipid polymer membranes" in Non-Patent Document 1.

[0006] Patent Document 4 discloses an effective cleaning method for these lipid membranes. In this cleaning method, the cleaning solution is primarily composed of an organic solvent such as ethanol, an acid, an alkali, and a salt. A common detergent is a surfactant such as sodium lauryl sulfate, which is an amphiphilic substance. However, surfactants pose the risk of altering sensor properties or destroying the sensor for two reasons: first, they bind to the amphiphilic substance contained in the sensor; and second, they strip the amphiphilic substance contained in the sensor from the sensor. Therefore, Patent Document 4 proposes optimizing cleaning without using a surfactant, using an organic solvent such as ethanol, an acid, an alkali, and a salt. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 2578370 [Patent Document 2] Patent No. 4395236 [Patent Document 3] Patent No. 4520577 [Patent Document 4] Patent No. 4516879 [Non-patent literature]

[0008] [Non-Patent Document 1] "Highly sensitive sweetness sensor using lipid polymer membranes" Journal of the Japanese Society for Taste and Odor Studies 14(3), pp. 629-632 (2007) Summary of the Invention [Problem to be solved by the invention]

[0009] Bitter and astringent substances form strong hydrophobic bonds with the sensor, which makes cleaning the sensor time-consuming. The cleaning solution must meet the following two conditions:

[0010] Do not damage the sensor.

[0011] - Effectively remove hydrophobic substances (bitter substances, astringent substances, etc.) adsorbed on the sensor from the sensor.

[0012] Furthermore, the measurement process of a taste sensor consists of the time to measure the taste sample and the time to clean the sensor. Since the cleaning time accounts for two-thirds of the total time, shortening the cleaning time can significantly reduce the measurement time. Therefore, an effective cleaning solution that contributes to shortening the cleaning time of taste sensors is desired. [Means for solving the problem]

[0013] According to the embodiment, In a cleaning method for cleaning a taste sensor membrane that detects at least one taste substance selected from salty, sour, bitter, sweet, umami, and astringent tastes with a first cleaning liquid or a second cleaning liquid, the taste sensor membrane is composed of a lipid polymer membrane composed of a polymer material, a lipid, and a plasticizer; The lipid comprises a first amphiphilic substance composed of a group of lipid molecules having a hydrophobic region extending in a longitudinal direction of an atomic array and a hydrophilic region present in a portion of the longitudinally extending atomic array; The lipid-polymer membrane has a matrix surface that accommodates the lipid molecular group, A cleaning solution used in a taste sensor system in which a taste substance is detected based on a change in sensor membrane potential due to electrostatic and hydrophobic interactions acting between the taste sensor membrane and the taste substance, and the taste sensor membrane is then cleaned, In the cleaning of a taste sensor membrane in which the taste substance contains a negatively charged sensor responsive substance and the hydrophilic site of the first amphipathic substance that adsorbs the sensor responsive substance has a positive charge, the first cleaning solution is composed of a water-soluble second amphipathic substance that has a positive charge, In the cleaning of a taste sensor membrane in which the taste substance contains a positively charged sensor responsive substance and the hydrophilic site of the first amphipathic substance that adsorbs the sensor responsive substance has a negative charge, the second cleaning solution is composed of a water-soluble second amphipathic substance that has a negative charge, A method for cleaning a taste sensor is provided, characterized in that the taste sensor membrane is immersed in a test aqueous solution to which the taste substance has been added, and one of the first cleaning liquid and the second cleaning liquid is selected depending on the sensor membrane potential measured, and the taste sensor membrane is cleaned by immersing the taste sensor membrane in the selected first cleaning liquid or second cleaning liquid. .

[0014] Further, according to the embodiment, A method for cleaning a taste sensor that detects taste based on a change in membrane potential of a lipid membrane, using a cleaning solution, comprising: the cleaning liquid is an aqueous solution containing 0.05 to 0.2 mass % of a surfactant, a taste sensor having a positively charged lipid membrane is washed with a washing solution containing only a surfactant having a positive charge; For a taste sensor whose lipid membrane is negatively charged, a method for cleaning the taste sensor is provided, characterized in that the taste sensor is cleaned with a cleaning solution containing only a surfactant having a negative charge.

[0015] Furthermore, according to the embodiment, in the above embodiment A method for cleaning a taste sensor is provided, characterized in that the cleaned taste sensor membrane is immersed in a reference solution for a predetermined period of time to measure the sensor membrane potential, and the cleaning solution that brings the sensor membrane potential to a reference level is selected as the first cleaning solution or the second cleaning solution. .

[0016] Furthermore, according to the embodiment, in the above embodiment There is provided a cleaning method characterized in that the second amphiphilic substance contained in the cleaning solution has a positive charge, has a hydrophilic group such as a COOH group or a POOH group, and is acidic. According to the embodiment, in the above embodiment The method for cleaning a taste sensor according to claim 1 or 2 is provided, characterized in that the lipid molecular group contains at least one of a phosphate group, an amino group, an ammonium group, a hydroxyl group, and a carboxyl group, and a saturated hydrocarbon group. . [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram illustrating a taste sensor system equipped with a sensor membrane capable of evaluating taste, used to verify the examples. [Figure 2] (A) is a front view showing a schematic perspective of a part of the sensor probe in the taste sensor system shown in Figure 1, and (B) is a front view showing a schematic perspective of a part of the reference electrode probe in the taste sensor system shown in Figure 1. [Figure 3] FIG. 2 is a schematic diagram for explaining the composition and chemical structure of a sensor film used in the sensor system shown in FIG. [Figure 4] 2 is a flowchart showing the process of taste measurement in the taste sensor system shown in FIG. 1. [Figure 5] 2 is a schematic diagram showing the change in sensor output over time and the change in charge in a lipid-polymer membrane in taste measurements performed with the taste sensor system shown in FIG. 1. FIG. [Figure 6] 2 is a flowchart showing a cleaning solution evaluation process in the taste sensor system shown in FIG. 1 according to an embodiment. [Figure 7]2 is a graph showing response value characteristics over time from a sensor electrode and a reference electrode to a standard solution and a sample solution measured by the taste sensor system shown in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments will be described with reference to the drawings.

[0019] The cleaning solution according to the embodiment has been developed based on the findings of the following inventors.

[0020] When the charge of the first amphiphilic substance contained in the taste sensor (sensor membrane) and the charge of the second amphiphilic substance contained in the cleaning solution are made the same, they are electrically repelled, preventing the second amphiphilic substance in the cleaning solution from being adsorbed onto the sensor. This has led to the discovery that the sensor is not affected by the cleaning solution. Furthermore, it has been discovered that a cleaning effect can be obtained by the second amphiphilic substance.

[0021] As mentioned above, an amphiphilic substance is a general term for molecules that have both a "hydrophilic group" that is compatible with water (aqueous phase) and a "lipophilic group" (hydrophobic group) that is compatible with oil (organic phase) within a single molecule. Examples include surfactants, as well as biological molecules such as phospholipids and amphiphilic polymers.

[0022] Table 1 below shows the optimal relationship between the charge of the first and second amphiphiles contained in the sensor and the cleaning solution, and the charge of the sensor's responsive substance, which is a relationship that provides a cleaning effect without affecting the sensor characteristics.

[0023] [Table 1]

[0024] Note 1: Iso-α acids, which give beer its bitter taste, and tannic acids, which give red wine its astringency, etc. Note 2: Basic bitterness of pharmaceuticals such as quinine hydrochloride If the polarity of the electric charge of the bitter-astringent substance (sensor response substance) is opposite to that of the second amphiphilic substance contained in the cleaning solution, it will be electrically attracted to the second amphiphilic substance in the cleaning solution and form a hydrophobic bond with each other. This can be expected to have a cleaning effect in which the bitter-astringent substance (sensor response substance) adsorbed on the sensor is separated from the first amphiphilic substance of the sensor.

[0025] Examples of the hydrophilic group portion of amphiphilic substances include those with a positive charge such as quaternary ammonium, alkylamine, and pyridine, and those with a negative charge such as carboxylic acid, sulfonic acid, sulfate, and phosphate. Hydrophobic groups of amphiphilic substances (first and second amphiphilic substances) include carbon chains and benzene rings. Highly hydrophobic amphiphilic substances are poorly soluble in water and are used as sensor materials (lipid membranes containing a first amphiphilic substance). Here, the lipidic substance of lipid 17B (lipidic substance containing a first amphiphilic substance) has a lipidic molecular group having a hydrophobic portion and a hydrophilic portion present in a portion of the atomic arrangement extending in the longitudinal direction, and the lipid membrane for the taste sensor is configured to have a matrix on its surface that can accommodate the lipidic molecular group. The lipid membrane for the taste sensor has a structure in which at least a portion of the lipid molecule group is accommodated within the lipid membrane matrix with its hydrophilic portions arranged on the surface, and is capable of detecting at least two tastes from among salty, sour, bitter, sweet, and umami. The lipid molecule group contains at least one of a phosphate group, an amino group, an ammonium group, a hydroxyl group, and a carboxyl group, and a saturated hydrocarbon group. Specific materials for this sensor have already been disclosed in Patent Documents 1 to 4 and Non-Patent Document 1.

[0026] On the other hand, if the second amphiphile is highly hydrophilic, it dissolves in water and is used as a cleaning agent (cleaning solution containing a second amphiphile). Negatively charged second amphiphiles are shown in Tables 2-1, 2-2, and 2-3 below, and positively charged second amphiphiles are shown in Tables 3-1 and 3-2. Some amphiphiles have both positive and negative hydrophilic groups. If the negative group is a carboxylic acid group or a phosphate group, the carboxylic acid group and the phosphate group do not dissociate under acidic conditions, resulting in an amphiphile (second amphiphile) that is only positively charged. An example of this is shown in Table 4. When using the second amphiphiles shown in Table 4 as cleaning solution materials, the pH of the cleaning solution is acidic and the second amphiphile is used as a positively charged substance.

[0027] [Table 2-1]

[0028] [Table 2-2]

[0029] [Table 2-3]

[0030] [Table 3-1]

[0031] [Table 3-2]

[0032] [Table 4]

[0033] [Taste sensor system] Prior to describing the examples, a taste sensor system used to verify the examples will be described.

[0034] <Taste detection process in taste sensor system> FIG. 1 shows a taste sensor system. In this taste sensor system, containers 10 are provided for individually storing a reference solution, a sample solution, a cleaning solution, etc., and a reference electrode probe 11 and one or more taste sensor probes 15 shown in FIG. 2 are supported by a vertically movable arm mechanism (not shown) so that they can be inserted and removed into the containers 10. This taste sensor system employs a CPA (Change of Membrane Potential Caused by Adsorption) measurement method. A sensor membrane (a lipid membrane containing a first amphiphilic substance) is provided to detect each taste quality, and a taste sensor probe 15 equipped with each sensor membrane is provided. The taste qualities are umami, sourness, saltiness, sweetness, astringency, and bitterness. Therefore, a taste sensor probe 15 equipped with a sensor membrane corresponding to each taste quality is provided.

[0035] As shown in FIG. 2(A), this taste sensor probe 15 has a sensor membrane (lipid membrane containing a first amphiphilic substance) 17 for detecting a corresponding taste quality fixed around a through-hole in a tube 16. The surface of the sensor membrane 17 is exposed to the interior of the container 11, and the opposite surface of the sensor membrane 17 is exposed to a conductive internal liquid contained in the tube 16. One example of this internal liquid is a 3.3M KCl saturated AgCl solution. A sensor electrode 19 is inserted into the tube 16, and its tip is immersed in the conductive internal liquid so as to face the sensor membrane 17. The electrode 19 is connected to a voltage detector 20 via a lead wire 19A.

[0036] 2(B), the reference electrode probe 11 is composed of a tubular glass tube 13 whose tip opening is sealed with a liquid-tight porous ceramic 18. The glass tube 13 is filled with a conductive internal liquid, similar to the sensor, and the reference electrode 12 is immersed in this conductive internal liquid. The reference electrode 12 is connected to a voltage detector 20 via a lead wire 12A.

[0037] In the measurement method of the embodiment, changes in membrane potential due to electrostatic / hydrophobic interactions acting between the sensor membrane and the taste substance are output as voltage signals. A voltage detector 20 detects the voltage between the reference electrode 12 and the sensor electrode 19 for the reference solution and the sample solution, and detects changes over time after the probes 12 and 15 are immersed in the reference solution and the sample solution. The detected voltage signals are converted into digital voltage signals by an A / D converter 22, and the digital voltage signals are sent to a computing device 23 and stored in memory 23A. The computing device 23 calculates the change over time between the sensor voltage Vr in the reference solution and the response voltage Vs in the sample solution as a response value (Vs-Vr) and stores it in memory 23A.

[0038] The memory 23A stores the response value (relative value: Vs-Vr) as data on the first taste response value, and the first taste response value (relative value: Vs-Vr) is compared with known data in the calculation device 23 to quantify the taste quality of the sample liquid, which is then output to the output device 24 for use in judging the taste, etc.

[0039] As will be explained later, when measuring high-intensity sweeteners, after a response value (relative value: Vs-Vr) is detected as the first taste, probes 12 and 15 are immersed in a reference solution and washed with the reference solution. Then, the voltage Vr' between reference electrode 12 and sensor electrode 19 relative to the reference solution is detected, and the differential voltage (CPA value: Vr'-Vr) is calculated as the aftertaste response value and stored in memory 23A. Then, probes 12 and 15 are washed and used again for taste testing.

[0040] The taste sensor membrane (lipid membrane containing a first amphipathic substance) 17 is composed of a lipid-polymer membrane as shown in Fig. 3. As the outline structure of the sensor membrane 17 according to the embodiment is shown in Fig. 3, the membrane is composed of PVC (polyvinyl chloride) 17A as a polymer material, lipid (lipid containing a first amphipathic substance) 17B that adjusts the flexibility and hydrophobicity of the membrane, and plasticizer 17C that adjusts the charge and hydrophobicity of the membrane.

[0041] Here, the lipidic substance of lipid 17B (a lipidic substance containing a first amphipathic substance) has a molecular structure with a hydrophobic region extending longitudinally in an atomic arrangement and a hydrophilic region at or near one end of the hydrophobic region. That is, the lipidic substance has a lipidic molecular group having a hydrophobic region and a hydrophilic region present in a portion of the longitudinally extending atomic arrangement, and the lipid membrane for the taste sensor is configured to have a matrix on its surface that can accommodate the lipidic molecular group. The lipid membrane for the taste sensor has a structure in which at least a portion of the lipidic molecular group is accommodated within the lipid membrane matrix with the hydrophilic regions arranged on the surface, and is capable of detecting at least two tastes selected from salty, sour, bitter, sweet, and umami. Furthermore, the lipidic molecular group contains at least one of a phosphate group, an amino group, an ammonium group, a hydroxyl group, and a carboxyl group, as well as a saturated hydrocarbon group.

[0042] In the examples, bitter sensor C00 is described as the first sensor, and this first sensor has the composition shown in Table 5 below. Similarly, bitter sensor BT0 is described as the second sensor, and this first sensor has the composition shown in Table 5 below.

[0043] [Table 5]

[0044] The lipid 17B and plasticizer 17C are fixed and supported by PVC (polyvinyl chloride) 17A. When this sensor membrane 17 is exposed to a taste solution (aqueous solution) 28 containing a taste substance, electrostatic and hydrophobic interactions occur between the lipid-polymer membrane 17B and the taste substance in the sample aqueous solution (sample liquid) 28 containing the taste substance, changing the membrane potential of the sensor membrane 17. More specifically, in the salty taste sensor membrane 17, for example, a negative membrane potential is generated by the negative charges 34 of the negatively charged lipid and ion excluder. When Na ions are present in the sample aqueous solution, they are taken up by the sodium ionophore 30 in the membrane, and the positive charges 36 of Na change the membrane potential in the positive direction. In the high-intensity sweetener sensor membrane 17, a positive membrane potential is generated by the positively charged lipid. When a negatively charged high-intensity sweetener is present in the sample liquid, it is adsorbed to the sensor membrane, changing the membrane potential in the negative direction. This change in the membrane potential of the sensor membrane 17 is detected by the sensor electrode 19, and the difference between the potential of the sensor electrode 19 and the potential of the reference electrode 12 is output as a voltage signal.

[0045] Taste measurement using the sensor membrane 17 in the sensor system shown in FIG. 1 is specifically performed according to the procedure shown in FIG. 4, resulting in the sensor output (voltage change) shown in FIG. 5(A). The sensor output (voltage change) shown in FIG. 5(A) corresponds to the action of negative charges on the sensor membrane 17 in the reference solution 30 and the aqueous solution to be measured (so-called sample solution 28) in FIGS. 5(B), 5(C), 5(D), and 5(E). In FIGS. 5(C) to 5(E), rectangles represent negative charges 34 of bitter or astringent substances (hydrophobic substances), and circles represent negative charges 36 of sour, salty, or umami substances (hydrophilic substances). Arrows indicate the movement of these negative charges toward or away from the sensor membrane 17. These changes in the membrane potential of the sensor membrane 17 are detected by the sensor electrode 19, and the difference in potential with the reference electrode 12 is output as a voltage signal, as shown in FIG. 4.

[0046] Taste measurement in the sensor system shown in Fig. 1 is specifically performed according to the procedure shown in Fig. 4. When starting taste measurement, a reference solution is first prepared, and a test solution (so-called sample solution 28) to which a predetermined additive has been added as the target of taste measurement is also prepared. The reference solution, the test solution (so-called sample solution 28), and a cleaning solution (cleaning solution containing a second amphiphilic substance) are each stored in different containers 10, and preparations for measurement are completed. Thereafter, the reference electrode probe 11 and the taste sensor probe 15 are immersed in the reference solution, and a reference voltage Vr between the reference electrode 12 and the sensor electrode 19 is measured and stored in memory 23A (S1). An example of a reference solution 30 prepared for taste measurement is a solution in which 30 mM KCI is added with 0.3 mM tartaric acid (30 mM KCI + 0.3 mM tartaric acid), and an example of a test solution (so-called sample solution 28) prepared for taste measurement is quinine hydrochloride, iso-α acid, etc., as will be explained later.

[0047] This reference voltage Vr is compared with the previously measured reference voltage to confirm whether it is within the reference range. If the difference between the previously measured reference voltage Vr and the currently measured reference voltage Vr is within a predetermined value, the process proceeds to step S2. If the difference between the previously measured reference voltage Vr and the currently measured reference voltage Vr is not within the predetermined value, step S1 is executed again to measure the reference solution again. When measuring the reference solution for the first time, step S1 is repeated a predetermined number of times, and the averaged values ​​are determined to determine the reference value Vr, which is then stored in memory 23A (S1). Here, since the reference solution 30 does not contain any charge of the object to be measured, the potential of the sensor membrane 17 is maintained constant, and a baseline voltage is output from the reference electrode 12 and the sensor electrode 19. Next, the reference electrode probe 11 and the taste sensor probe 15 are immersed in the solution to be measured (sample solution), and the sample voltage Vs between the reference electrode 12 and the sensor electrode 19 is measured and stored in memory 23A (S2).

[0048] This measurement produces a sensor output as shown in Figure 5. As shown in Figure 5(B), the negative charges 34 of bitter or astringent substances (hydrophobic substances) and the negative charges 36 of sour, salty, or umami substances (hydrophilic substances) are moved so that they are adsorbed to the high-intensity sweetener sensor membrane 17, which is at a positive potential. As shown in Figure 5(A), the potential of the sensor membrane 17 decreases significantly from time t1, and a sample voltage Vs is output between the reference electrode 12 and the sensor electrode 19. The sample voltage Vs is compared with a reference voltage Vr, and the difference voltage between the sample voltage Vs and the reference voltage Vr is calculated as a sample response value (relative value: ΔV = Vs - Vr) (S3). Here, the response value (relative value: ΔV=Vs−Vr) corresponds to the first taste at high sweetness.

[0049] Thereafter, the reference electrode probe 11 and the taste sensor probe 15 are immersed in the reference solution 30 again, and the sensor membrane 17 is washed with the reference solution 30 .

[0050] As the sensor membrane 17 is washed with the reference solution 30 from time t2, the negative charges 36 of the sour, salty, or umami substances (hydrophilic substances) are moved (dispersed) into the reference solution 30 so as to be separated from the sensor membrane 17, as shown in FIG. 5(D). Therefore, the potential of the sensor membrane 17 is slightly increased to a potential where only the negative charges 34 of the bitter or astringent substances (hydrophobic substances) remain. The output voltage between the reference electrode 12 and the sensor electrode 19 is changed to a sensor output Vr' corresponding to the potential where only an aftertaste remains. This reference value voltage Vr' is measured and stored in memory 23A (S4).

[0051] Thereafter, the differential voltage between the reference voltage Vr' and the reference voltage Vr (CPA value: ΔV'=Vr'-Vr) is calculated by the calculation device 23 as the aftertaste response value (CPA value) for the measured solution (sample solution) 28, and is stored in the memory 23A (S5).

[0052] At time t3, the reference electrode probe 11 and the taste sensor probe 15 are placed in another container 10. In cleaning solution It is then soaked and washed (S6).

[0053] When the sensor membrane 17 is washed with the cleaning solution, the negative charges 34 of the bitter or astringent substances (hydrophobic substances) are separated from the sensor membrane 17. In cleaning solution Therefore, the potential of the sensor membrane 17 is changed so as to rise over time to the baseline reference voltage Vr. Thereafter, steps S1 to S4 are repeated as necessary.

[0054] When measuring the aftertaste, the reference electrode probe 11 and the taste sensor probe 15 are again immersed in the reference solution, and the reference voltage Vr' between the reference electrode 12 and the sensor electrode 19 is measured and stored in the memory 23A (S4). By measuring the potential in the reference solution again, the aftertaste response value (CPA) for the sample is also calculated by the arithmetic unit 23 as (ΔVr'=Vr'-Vr) (S5).

[0055] After step S3 or step S5, a cleaning step shown in step S6 is carried out. In this cleaning step, the reference electrode probe 11 and the taste sensor probe 15 are immersed in a cleaning solution (cleaning solution containing a second amphiphilic substance) prepared in another container 10, and the reference electrode probe 11 and the taste sensor probe 15 are washed with the cleaning solution, and steps S1 to S3 or S1 to S5 are repeated again. In these steps, when the repetition of steps S1 to S4 reaches a predetermined number of times, for example, five times, the average value [ΔVaver=(ΔV1+ΔV2+ΔV3+ΔV4+ΔV5) / 5] of the response value of the differential voltage (ΔV=Vs-Vr) and / or the average value [Δ'raver=(ΔVr'1+ΔVr'2+ΔVr'3+ΔVr'4+ΔVr'5) / 5] of the CPA value (ΔVr'=Vr'-Vr) are calculated. The taste measurement of the aqueous solution to be measured (so-called sample solution 28) is completed through the processes of steps S1 to S6, and if there is a new aqueous solution to be measured (so-called sample solution 28), the processes of steps S1 to S6 are performed again. If there is no new aqueous solution to be measured (so-called sample solution 28), the process ends after the process of step S6. In the above-mentioned process, the level of a known taste value can be determined from the average value ΔVaver of the response values ​​of the differential voltage.

[0056] In step S1, if the measurement value is outside the predetermined range even after repeated measurements of the reference liquid, it is determined that the cleaning of the taste sensor probe 15 is insufficient, and the reference electrode probe 11 and the taste sensor probe 15 are immersed in a cleaning liquid (cleaning liquid containing a second amphiphilic substance) prepared in the container 10, and the reference electrode probe 11 and the taste sensor probe 15 are cleaned again with the cleaning liquid. In addition, in the measurement of the reference liquid in step S1, if it is determined that the sensor film of the taste sensor probe 15 is not restored even by cleaning, the taste sensor probe 15 is subject to replacement and is replaced with a new taste sensor probe 15.

[0057] <Verification of cleaning in taste sensor system> In the taste sensor system shown in FIG. 1, the verification of cleaning of the reference electrode probe 11 and the taste sensor probe 15 involves preparing the taste sensor probe 15 to be verified (a sensor probe having a lipid membrane containing a first amphipathic substance) and a reference solution. In addition, a test solution (so-called sample solution 28) containing a predetermined additive as the target of taste measurement and a cleaning solution (cleaning solution containing a second amphipathic substance) to be verified are also prepared. The reference electrode probe 11 and the taste sensor probe 15 are immersed in the reference solution, and the reference voltage Vr between the reference electrode 12 and the sensor electrode 19 is measured and stored in the memory 23A (S11). As already explained, during the period R1 during which the reference electrode 12 and the sensor electrode 19 are immersed in the reference solution as shown in FIG. 7, the sensor output from the sensor is maintained at the reference value (relative value 0%). Thereafter, the reference electrode probe 11 and the taste sensor probe 15 are immersed in the test solution (so-called sample solution 28), and the sensor output from the sensor is detected. Since the adsorbable substance in the sample is adsorbed to the lipid membrane (lipid membrane containing the first amphiphilic substance) of the sensor probe 15, the sensor outputs a sensor signal whose output level gradually increases toward a relative value of 100% as shown in period R2. Thereafter, the reference electrode probe 11 and the taste sensor probe 15 are immersed in a cleaning solution (cleaning solution containing the second amphiphilic substance) to clean the lipid membrane (lipid membrane containing the first amphiphilic substance) of the taste sensor probe 15. During this cleaning period R3, the adsorbable substance escapes from the lipid membrane (lipid membrane containing the first amphiphilic substance) of the sensor probe 15 into the cleaning solution (cleaning solution containing the second amphiphilic substance) along with positive or negative charges, thereby cleaning the lipid membrane (lipid membrane containing the first amphiphilic substance). During this cleaning process period R3, the output from the sensor gradually attenuates from a relative value of 100%. After cleaning, the reference electrode probe 11 and the taste sensor probe 15 are again immersed in the reference solution for period R4, and the output signal is measured. When the lipid membrane (lipid membrane containing the first amphiphilic substance) is ideally washed with a cleaning solution (cleaning solution containing the second amphiphilic substance), the sensor output will be a signal level corresponding to a residual value of 0% (relative value) with no adsorbed substance, but the sensor will output a signal at a level dependent on the proportion of remaining adsorbed substance.As the period R4 of immersion in the reference solution elapses, the signal level output from the sensor reaches a verification level at which it no longer decreases. This verification level corresponds to the residual value without adsorbed substances; the higher this level, the greater the residual rate of adsorbed substances, and the lower this level, the smaller the residual rate of adsorbed substances. This verification process verifies the optimality of the sensor material (lipid membrane containing the first amphiphile) and cleaning agent (cleaning solution containing the second amphiphile). The verification results for the optimal sensor material (lipid membrane containing the first amphiphile) and cleaning agent (cleaning solution containing the second amphiphile) for the following examples are described along with comparative examples.

[0058] [Example] The first sensor in the embodiment is bitter sensor C00, which detects acidic bitter substances (negatively charged), such as iso-α acids, contained in beer. This sensor is positively charged. The second sensor in the embodiment is bitter sensor BT0, which detects basic bitter substances (positively charged), such as quinine hydrochloride, contained in pharmaceuticals. This sensor is negatively charged. Measurements were performed using the system shown in Figure 1. The membrane potential was detected when bitter or astringent substances adsorbed onto the sensor. The measurement procedure involves measuring a reference solution in place of human saliva, which is used as the zero point. The potential change in the sensor when the sample is measured is then used as the output. After measuring the sample, the sensor is cleaned by inserting it into and removing it from a cleaning solution. As explained with reference to Figure 7, if there is adsorption, the sensor does not return to the original zero point of the reference solution. The cleaning effect can be evaluated by the extent to which it returns. Furthermore, if the sample is replaced with only the non-adsorbent reference solution, the zero point position changes, allowing the deterioration of the sensor due to the cleaning solution to be evaluated.

[0059] The conventional cleaning solution used for the first sensor C00 was 30% ethanol, 100 mM MHCl, and the conventional cleaning solution used for the second sensor BT0 was 30% ethanol, 100 mM HCl. The first sensor C00 measured 0.1% iso-α-acid, and the second sensor BT0 measured 1 mM quinine hydrochloride, and then washed with the conventional cleaning solution for 90 seconds. It was found that the sensor output did not return to zero by approximately 10% with the conventional cleaning solution. When 0.2% lauryl dimethylaminoacetic acid (a representative example from Tables 2-1, 2-2, and 2-3) was added to the first sensor C00, and 0.05% sodium lauryl sulfate (a representative example from Tables 2-1, 2-2, and 2-3) was added to the second sensor BT0, the rate of return to zero was reduced by 3 to 10 times compared to the conventional cleaning solution, demonstrating sufficient cleaning effectiveness. Furthermore, it was found that the membrane potential of these sensors remained constant after immersion in each cleaning solution, and that there was no effect on the sensors. The structure of sodium lauryl sulfate is shown in Chemical Formula 1(a), and the structure of lauryldimethylamino acid is shown in Chemical Formula 1(b). Chemical Formula 1

[0060] TIFF0007752347000009.tif40130

[0061] Conventional wisdom has suggested that sensors made from lipid amphipathic substances would be destroyed by cleaning agents containing water-soluble amphipathic substances. In this embodiment, the charges of the sensor and the amphipathic substance contained in the cleaning agent are aligned, causing them to repel each other and minimizing damage to the sensor. Furthermore, substances that adsorb bitter or astringent to the sensor have an opposite charge to the sensor, which is also opposite to the charge of the amphipathic substance contained in the cleaning solution. This allows the adsorbent and the amphipathic substance in the cleaning solution to electrically attract each other and easily form hydrophobic bonds. This facilitates adsorption between the adsorbent and the amphipathic substance in the cleaning solution, while the amphipathic substance in the cleaning solution is water-soluble. As a result, the bitter or astringent substances adsorbed to the membrane are easily removed.

[0062] The present invention is not limited to cleaning solutions containing lauryl dimethylamino acetic acid and sodium lauryl sulfate, which are amphiphilic substances according to the examples, but can also be applied to cleaning solutions containing water-soluble, negatively charged amphiphilic substances shown in Tables 2-1, 2-2, and 2-3, water-soluble, positively charged amphiphilic substances shown in Tables 3-1 and 3-2, and water-soluble, positively and negatively charged amphiphilic substances in acidic conditions shown in Table 4.

[0063] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims. Furthermore, the scope of the present invention also includes cases in which each component of the claims is expressed separately, as a combination of multiple components, or as a combination of these components. Furthermore, multiple embodiments may be combined, and examples composed of such combinations are also within the scope of the invention. The following is a summary of the scope of the claims originally proposed in this application. (1) A cleaning solution for cleaning a taste sensor membrane that detects at least one taste substance selected from salty, sour, bitter, sweet, umami, and astringent tastes, the taste sensor membrane comprises a lipid containing a first amphipathic substance composed of a lipid molecule group having a hydrophobic region in which an atomic arrangement extends in the longitudinal direction and a hydrophilic region present in a portion of the atomic arrangement extending in the longitudinal direction, and is composed of a lipid polymer membrane having a matrix surface that accommodates the lipid molecule group; and the taste sensor membrane comprises a sensor that detects the taste substance based on a change in the sensor membrane potential due to electrostatic and hydrophobic interactions acting between the taste sensor membrane and the taste substance; In a cleaning solution for cleaning a taste sensor membrane in which the taste substance contains a negatively charged sensor responsive substance and the hydrophilic site of the first amphipathic substance that adsorbs the sensor responsive substance has a positive charge, the cleaning solution is composed of a water-soluble second amphipathic substance that has a positive charge, In a cleaning solution for cleaning a taste sensor membrane in which the taste substance contains a positively charged sensor response substance and the hydrophilic portion of the first amphipathic substance that adsorbs this sensor response substance has a negative charge, the cleaning solution is characterized by being composed of a water-soluble second amphipathic substance that has a negative charge. (2) A cleaning solution according to (1), characterized in that the second amphiphilic substance contained in the cleaning solution has a positive charge, has a hydrophilic group such as a COOH group or a POOH group, and is acidic. (3) The cleaning solution according to (1), wherein the lipid-polymer membrane is composed of a polymer membrane, a lipid containing the first amphiphilic substance, and a plasticizer. (4) The cleaning solution of (1), wherein the lipid molecule group contains at least one of a phosphate group, an amino group, an ammonium group, a hydroxyl group, and a carboxyl group, and a saturated hydrocarbon group. (5) In a cleaning method for cleaning a taste sensor membrane that detects at least one taste substance selected from salty, sour, bitter, sweet, umami, and astringent tastes with a first cleaning liquid or a second cleaning liquid, The taste sensor membrane comprises a lipid containing a first amphipathic substance composed of a lipid molecule group having a hydrophobic region in which an atomic arrangement extends in the longitudinal direction and a hydrophilic region present in a portion of the atomic arrangement extending in the longitudinal direction, and the sensor membrane has a matrix surface that accommodates the lipid molecule group, and the sensor membrane comprises a molecular membrane sensor that detects the taste substance based on a change in sensor membrane potential due to electrostatic and hydrophobic interactions acting between the sensor membrane and the taste substance, In the cleaning of a taste sensor membrane in which the taste substance contains a negatively charged sensor responsive substance and the hydrophilic site of the first amphipathic substance that adsorbs the sensor responsive substance has a positive charge, the first cleaning solution is composed of a water-soluble second amphipathic substance that has a positive charge, In the cleaning of a taste sensor membrane in which the taste substance contains a positively charged sensor responsive substance and the hydrophilic site of the first amphipathic substance that adsorbs the sensor responsive substance has a negative charge, the second cleaning solution is composed of a water-soluble second amphipathic substance that has a negative charge, A cleaning method characterized in that the taste sensor membrane is immersed in a test aqueous solution to which the taste substance has been added, and one of the first cleaning liquid and the second cleaning liquid is selected depending on the measured sensor membrane potential, and the taste sensor membrane is cleaned by immersing the taste sensor membrane in the selected first cleaning liquid or second cleaning liquid. (6) A cleaning method according to (5), characterized in that the cleaned taste sensor membrane is immersed in a reference solution for a predetermined period of time to measure the sensor membrane potential, and the cleaning solution that brings the sensor membrane potential to a reference level is selected as the first cleaning solution or the second cleaning solution. (7) The cleaning method according to (5), wherein the second amphiphilic substance contained in the cleaning solution has a positive charge, has a hydrophilic group such as a COOH group or a POOH group, and is acidic. (8) The cleaning method according to (5), wherein the lipid-polymer membrane is composed of a polymer membrane, a lipid containing the first amphiphilic substance, and a plasticizer. (9) The cleaning method according to (5), wherein the lipid molecule group contains at least one of a phosphate group, an amino group, an ammonium group, a hydroxyl group, and a carboxyl group, and a saturated hydrocarbon group. (10) A method for cleaning a taste sensor that detects taste based on a change in membrane potential of a lipid membrane, using a cleaning solution, comprising: the cleaning solution is an aqueous solution containing 0.05 to 0.2 mass % of a surfactant, and for a taste sensor whose lipid membrane is positively charged, cleaning is performed with a cleaning solution containing only a surfactant having a positive charge; For a taste sensor in which the lipid membrane is negatively charged, the taste sensor is washed with a washing solution containing only a negatively charged surfactant. How to clean the taste sensor. [Explanation of symbols]

[0064] 10...container, 11...reference electrode probe, 12...reference electrode, 13...glass tube, 15...taste sensor probe, 16...tube, 17...sensor membrane, 17A...PVC (polyvinyl chloride), 17B...lipid, 17C...plasticizer, 18...porous ceramic, 19...sensor electrode, 12A, 19A...lead wire, 20...voltage detector, 22...A / D converter, 23...arithmetic unit, 23A...memory, 24...output unit, 28...aqueous solution, 30...Na ionophore

Claims

1. A cleaning method for cleaning a taste sensor membrane that detects at least one taste substance selected from salty, sour, bitter, sweet, umami, and astringent tastes with a first cleaning solution or a second cleaning solution, the taste sensor membrane is composed of a lipid polymer membrane composed of a polymer material, a lipid, and a plasticizer; The lipid includes a first amphiphilic substance composed of a group of lipid molecules having a hydrophobic region extending in a longitudinal direction of an atomic array and a hydrophilic region present in a portion of the longitudinally extending atomic array, The lipid-polymer membrane has a matrix surface that accommodates the lipid molecular group, A cleaning solution used in a taste sensor system in which a taste substance is detected based on a change in sensor membrane potential due to electrostatic and hydrophobic interactions acting between the taste sensor membrane and the taste substance, and the taste sensor membrane is then cleaned, In the cleaning of a taste sensor membrane in which the taste substance contains a negatively charged sensor responsive substance and the hydrophilic site of the first amphipathic substance that adsorbs the sensor responsive substance has a positive charge, the first cleaning solution is composed of a water-soluble second amphipathic substance that has a positive charge, In the cleaning of a taste sensor membrane in which the taste substance contains a positively charged sensor responsive substance and the hydrophilic site of the first amphipathic substance that adsorbs the sensor responsive substance has a negative charge, the second cleaning solution is composed of a water-soluble second amphipathic substance that has a negative charge, A method for cleaning a taste sensor, characterized in that the taste sensor membrane is immersed in a test aqueous solution to which the taste substance has been added, and one of the first cleaning liquid and the second cleaning liquid is selected depending on the measured sensor membrane potential, and the taste sensor membrane is cleaned by immersing the taste sensor membrane in the selected first cleaning liquid or second cleaning liquid.

2. A method for cleaning a taste sensor that detects taste based on changes in membrane potential of a lipid membrane, using a cleaning solution, comprising: the cleaning liquid is an aqueous solution containing 0.05 to 0.2 mass % of a surfactant; a taste sensor having a positively charged lipid membrane is washed with a washing solution containing only a surfactant having a positive charge; A method for cleaning a taste sensor, characterized in that a taste sensor whose lipid membrane is negatively charged is cleaned with a cleaning solution containing only a surfactant having a negative charge.

3. A method for cleaning a taste sensor as described in claim 1 or claim 2, characterized in that the taste sensor membrane after cleaning is immersed in a reference liquid for a predetermined period of time to measure the sensor membrane potential, and the cleaning liquid that brings the sensor membrane potential to a reference level is selected as the first cleaning liquid or the second cleaning liquid.

4. A method for cleaning a taste sensor according to claim 1 or claim 2, characterized in that the second amphiphilic substance contained in the cleaning solution has a positive charge, has a hydrophilic group such as a COOH group or a POOH group, and is acidic.

5. A method for cleaning a taste sensor as described in claim 1 or claim 2, characterized in that the lipid molecular group contains at least one of a phosphate group, an amino group, an ammonium group, a hydroxyl group, and a carboxyl group, and a saturated hydrocarbon group.

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