An on-line freshness monitor for aquatic products based on QCM sensing principle

Abstract

This utility model discloses an online monitoring instrument for the freshness of aquatic products based on the QCM sensing principle, including a housing, a QCM sensing system, and a gas introduction system. The housing contains a detection pool for holding the gas to be tested. The QCM sensing system includes a detachable QCM detection chip installed within the detection pool. The gas introduction system includes a dustproof net, an air inlet grid inside the dustproof net, and a gas turbulence channel. By setting up a detection pool within the housing to hold the gas to be tested, and placing the QCM detection chip within the detection pool to sense the mass change caused by gas adsorption and generate a frequency signal, real-time online monitoring of the freshness of aquatic products is achieved. By setting up a dustproof net and establishing a serpentine gas turbulence channel between the inlet of the detection pool and the dustproof net, the incoming airflow is buffered and turbulence is generated, thereby effectively improving the detection accuracy. This utility model belongs to the field of aquatic product freshness monitoring.

Description

Technical Field

[0001] This utility model belongs to the field of aquatic product freshness monitoring, and more specifically relates to an online aquatic product freshness monitoring instrument based on the QCM sensing principle. Background Technology

[0002] In the fresh food sector, especially for livestock and poultry meat and aquatic products, freshness directly determines the safety, nutritional value, and market acceptance of the products. These foods have a natural tendency to spoil, especially aquatic products, which are high in protein and have fragile muscle tissue. In a special inspection of aquatic products by market regulators in 2023, the failure rate of freshness indicators reached 22.1%. Due to the lack of rapid and effective freshness testing methods, about 18% of the catch fails to meet standards each year due to quality degradation during transportation and storage, resulting in significant economic losses.

[0003] Traditional sensory evaluation methods rely excessively on the subjective feelings of testers, such as smell, sight, and taste. Different testers have vastly different standards for judging the smell, appearance, and taste of food, resulting in poor repeatability of test results and making it difficult to form unified and accurate conclusions.

[0004] Physicochemical analysis methods are highly dependent on laboratories, lack timeliness, and have high operational barriers. Methods such as high-performance liquid chromatography (HPLC) and the Kjeldahl method require complex sample pretreatment and specialized equipment. For instance, the national standard (GB 5009.228-2016 National Food Safety Standard - Determination of Volatile Basic Nitrogen in Food) uses the Kjeldahl method. This method involves complex and cumbersome pretreatment, and the result interpretation relies heavily on indicator color changes, introducing significant subjective factors. Furthermore, it can only be performed in a laboratory, often taking hours or even days from sampling to obtaining results, exhibiting significant limitations in timeliness and convenience, and failing to address the issue of real-time online monitoring during cold chain transportation. In addition, the testing process requires the use of various hazardous chemical reagents such as boric acid and hydrochloric acid, posing safety risks not only during transportation and storage but also, if the waste liquid is not properly treated, leading to pH imbalances in water bodies and impacting the living environment of aquatic organisms.

[0005] Therefore, there is an urgent need for a device that can address the problem of poor timeliness in current physicochemical analysis methods for the freshness of aquatic products and enable real-time online monitoring during cold chain transportation. Utility Model Content

[0006] The main purpose of this invention is to provide an online monitoring instrument for the freshness of aquatic products based on the QCM sensing principle. It is not only simple to operate, easy to carry, and has a fast response speed, but also has low environmental requirements, high sensitivity, and can provide continuous monitoring.

[0007] To achieve the above objectives, the technical solution of this utility model is as follows:

[0008] An online freshness monitoring instrument for aquatic products based on the QCM sensing principle includes a housing, a QCM sensing system, and a gas introduction system connected to the detection pool. The housing contains a detection pool for holding the gas to be tested, and the side walls of the detection pool are respectively equipped with constant temperature heating elements. The QCM sensing system includes a detachable QCM detection chip disposed in the detection pool, a chip base disposed below the QCM detection chip, and conductive elements disposed on both sides of the QCM detection chip. The QCM detection chip is used to sense the mass change caused by gas adsorption and generate a frequency signal. The gas introduction system includes a dustproof net, an air inlet grid disposed inside the dustproof net, and a gas turbulence channel disposed between the inlet of the detection pool and the dustproof net. The gas turbulence channel is a serpentine channel, and the output end of the gas turbulence channel is connected to the detection pool.

[0009] According to a first aspect of the present invention, a control system is also included, the control system comprising a PCB board electrically connected to the power supply system and the QCM sensing system respectively, and a Bluetooth communication system integrated within the PCB board.

[0010] According to a first aspect of the present invention, the QCM detection chip includes a piezoelectric wafer, metal electrode layers respectively disposed on the upper and lower surfaces of the piezoelectric wafer, and a sensitive layer coated on the surface of the upper metal electrode layer. The sensitive layer is made of a polydopamine film material that has a specific adsorption effect on volatile basic nitrogen.

[0011] According to a first aspect of the present invention, the piezoelectric wafer is a piezoelectric quartz wafer.

[0012] According to a first aspect of the present invention, the fundamental frequency of the piezoelectric wafer is 9MHz.

[0013] According to a first aspect of the present invention, the diameter of the piezoelectric wafer is 13.4 mm to 14.0 mm.

[0014] According to a first aspect of the present invention, the metal electrode layer is a gold component.

[0015] According to a first aspect of the present invention, the housing includes a front plate of the sensing system, a back plate of the sensing system, and a top plate of the sensing system, which are respectively disposed on the outside of the QCM sensing system.

[0016] According to a first aspect of the present invention, a sensor system protective frame is further sleeved on the outside of the QCM sensing system, and a sealing gasket is provided inside the sensor system protective frame.

[0017] According to a first aspect of the present invention, the bottom surface of the detection pool is provided with a slot for fixing the QCM detection chip and a contact for transmitting detection signals that can be connected to the QCM detection chip.

[0018] One of the above-described technical solutions of this utility model has at least one of the following advantages or beneficial effects:

[0019] This invention achieves real-time online monitoring of the freshness of aquatic products by setting a detection pool inside the shell to contain the gas to be tested, and placing a QCM detection chip inside the detection pool to sense the mass change caused by gas adsorption and generate a frequency signal.

[0020] By setting up a dustproof screen to filter dust particles in the air, the gas entering the detection cell is kept clean, preventing dust particles from adhering to the surface of the QCM detection chip and interfering with its frequency signal. A serpentine gas turbulence channel is set between the inlet of the detection cell and the dustproof screen to buffer the incoming airflow and generate a turbulence effect, making the gas more evenly distributed in the detection cell, thereby effectively improving the detection accuracy. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0022] Appendix Figure 1 This is an exploded view of one embodiment of the present invention;

[0023] Appendix Figure 2 This is a cross-sectional view of a QCM detection chip according to an embodiment of the present invention;

[0024] Appendix Figure 3 This is an overall external view of one embodiment of the present utility model;

[0025] Appendix Figure 4 This is an external view of a QCM sensing system according to an embodiment of the present invention. Detailed Implementation

[0026] The embodiments of this utility model are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0027] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0028] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first" or "second" is used in the description, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" and "second" may explicitly or implicitly include one or more features.

[0030] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, it can be a fixed connection or a movable connection, a detachable connection or a non-detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection or a connection that can communicate with each other; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two elements, an indirect connection, or an interaction between two elements.

[0031] The following disclosure provides many different implementation methods or examples for different solutions to implement this utility model.

[0032] See attached document Figure 1 To be continued Figure 4 As shown, an online freshness monitoring instrument for aquatic products based on the QCM sensing principle includes a power supply system, a housing 1, a QCM sensing system 2, a gas introduction system 3 connected to the detection pool, and a control system. The QCM (quartz crystal microbalance) is a mass-sensitive sensor that measures the resonant frequency to reflect the mass change caused by adsorption in the sensitive layer. It has high detection accuracy and can achieve nanogram or even picogram-level mass detection. At the same time, it has high time resolution and can achieve long-term in-situ online monitoring.

[0033] In one embodiment of this utility model, the housing 1 includes a front plate 11, a back plate 12, and a top plate 13 of the sensing system, which are respectively disposed on the outside of the QCM sensing system 2. The housing 1 is provided with a detection cell for containing the gas to be tested. The side walls of the detection cell are respectively provided with constant temperature heating elements to stabilize the overall working temperature and reduce the impact of ambient temperature fluctuations on the accuracy of QCM frequency detection.

[0034] In one embodiment of this utility model, the QCM sensing system 2 includes a detachable QCM detection chip 21 disposed in a detection pool, a wafer base 22 disposed below the QCM detection chip 21, and conductive members 23 disposed on both sides of the QCM detection chip 21. (See attached drawing for details.) Figure 2 The conductive element 23 is a contact wire. The outer side of the QCM sensing system 2 is fitted with a sensing system protective frame 14. The sensing system protective frame 14 is equipped with a sealing gasket 15. The front panel 11, back panel 12, top panel 13, and sensing system protective frame 14 of the sensing system are all made of acrylic material. The sealing gasket 15 makes the monitoring instrument airtight.

[0035] In one embodiment of this utility model, the QCM detection chip 21 includes a piezoelectric wafer 211, metal electrode layers 212 respectively disposed on the upper and lower surfaces of the piezoelectric wafer 211, and a sensitive layer coated on the surface of the upper metal electrode layer 212. The sensitive layer is made of polydopamine film material that has a specific adsorption effect on volatile basic nitrogen. The sensitive layer is coated on the metal electrode layer 212 on the upper surface of the piezoelectric wafer 211 by electrochemical polymerization. The metal electrode layer 212 is a gold component, and the piezoelectric wafer 211 is a piezoelectric quartz wafer with AT cut.

[0036] In one embodiment of this utility model, the QCM detection chip 21 is composed of a piezoelectric wafer 211 sandwiched between a pair of metal electrode layers 212. By applying an AC voltage and transmitting it through the conductor 23, i.e., the contact wire, the QCM detection chip 21 can be excited to oscillate at a unique resonant frequency. The resonant frequency depends on the total mass of the QCM detection chip 21 and the sensitive layer adhered to its surface. When the adsorption of gas on the sensitive layer causes a change in mass, the resonant frequency changes, the QCM sensing system 2 collects the signal, and the wafer base 22 is used to fix the QCM detection chip 21 and stabilize it in the detection pool.

[0037] In one embodiment of this utility model, the preparation steps of the QCM sensing system 2 include: Step 1: Pretreatment of the QCM detection chip 21, the piezoelectric chip 211 is ultrasonically cleaned in piranha solution (concentrated sulfuric acid: hydrogen peroxide = 3:7 (v / v)) for 30 seconds, rinsed with deionized water, and then dried with nitrogen; then ultrasonically cleaned with anhydrous ethanol for 1 minute, rinsed with deionized water, dried with nitrogen, and finally placed in a vacuum drying oven at 50°C for 1 hour for later use;

[0038] Step 2: Prepare a phosphate buffer solution containing dopamine with a pH of 7.0, wherein the phosphate buffer solution is used as the electrolyte and dopamine is used as the monomer solution;

[0039] Step 3: Electrochemical polymerization is carried out on the piezoelectric wafer 211 using cyclic voltammetry via a three-electrode system to synthesize a polydopamine film with specific adsorption of volatile basic nitrogen (TVB-N). After polymerization, the surface phosphate residue is gently rinsed with deionized water and dried with nitrogen gas to prepare the QCM detection chip 21 for the freshness of aquatic products.

[0040] Step 4: Install the QCM detection chip 21 obtained in step 3 into the slot of the detection pool.

[0041] When the QCM sensing system 2 prepared by the above steps is placed together with spoiled aquatic products, and the sensitive layer on the piezoelectric chip 211 adsorbs volatile basic nitrogen, the Bluetooth communication system can wirelessly output the real-time detected and collected changes in the resonant frequency of the QCM sensing system 2 through the mobile terminal, thereby realizing real-time online monitoring of the freshness of aquatic products.

[0042] In one embodiment of this utility model, the gas introduction system 3 includes a dustproof net 31, an air inlet grid 33 disposed inside the dustproof net 31, and a gas turbulence channel disposed between the inlet of the detection pool and the dustproof net 31. The output end of the gas turbulence channel is connected to the detection pool, and the gas turbulence channel is a serpentine channel. The air inlet grid 33 and the dustproof net 31 are disposed at the gas inlet to filter dust particles in the air, ensuring that the gas entering the detection pool is clean and preventing dust particles from adsorbing onto the surface of the QCM detection chip 21 and interfering with its frequency signal. The gas turbulence channel is set as a serpentine channel and connected between the gas inlet and the detection pool, which can buffer the incoming airflow and generate a turbulence effect, making the gas more evenly distributed in the detection pool and improving the detection accuracy.

[0043] In one embodiment of this utility model, the control system includes a PCB board 41 electrically connected to the power supply system and the QCM sensing system 2, and a Bluetooth communication system integrated inside the PCB board 41, which facilitates the realization of functions such as wireless data transmission. Thus, the frequency signal can be displayed in real time through a wireless monitoring process on a mobile terminal to form a complete Internet of Things solution.

[0044] In one embodiment of this utility model, the bottom surface of the detection pool is provided with a slot for fixing the QCM detection chip 21 and a contact point that can be connected to the QCM detection chip 21. The slot is used to fix the wafer base 22 of the QCM detection chip 21, and the contact point is used to transmit detection signals, thereby realizing a plug-in installation structure for the QCM detection chip 21, which is convenient for replacement and maintenance. All components are integrated and encapsulated inside an acrylic plate. The acrylic body has dimensions of 100mm×100mm×90mm. This monitoring instrument belongs to a miniature structure instrument.

[0045] In one embodiment of this invention, the fundamental frequency of the piezoelectric crystal 211 is set to 9MHz, and the diameter of the piezoelectric crystal 211 is set to 13.4mm-14.0mm, thereby achieving high sensitivity and fast response. By using an AT-cut piezoelectric crystal 211 with a fundamental frequency of 9MHz, combined with the specific adsorption of the polydopamine sensitive layer, it is sensitive to minute changes in volatile basic nitrogen, and the electrochemical polymerization process makes the film uniform and stable, significantly improving the detection efficiency.

[0046] In one embodiment of this invention, the sensitive layer is a polydopamine film, which is electrochemically polymerized onto the surface of the metal electrode layer 212 of the QCM detection chip 21 using cyclic voltammetry. Because the polydopamine molecule contains a large number of active groups such as catechol, amino (-NH2), and imino (-NH-), these groups can achieve broad adsorption capacity through hydrogen bonding, electrostatic interactions, etc. Furthermore, this dopamine can form a micro / nanoporous structure during polymerization, providing a large specific surface area and enhancing the physical adsorption of molecules or particles. The specific preparation process includes the following steps:

[0047] Step 1: Before starting polymerization, the QCM detection chip 21 is cleaned. The piezoelectric chip 211 is ultrasonically cleaned in piranha solution (concentrated sulfuric acid: hydrogen peroxide = 3:7 (v / v)) for 30 seconds, rinsed with deionized water, and then dried with nitrogen. Then it is ultrasonically cleaned with anhydrous ethanol for 1 minute, rinsed with deionized water, dried with nitrogen, and finally placed in a 50°C vacuum drying oven to dry for 1 hour for later use.

[0048] Step 2: Prepare a phosphate buffer solution containing dopamine with a pH of 7.0. The phosphate buffer solution is used as the electrolyte and has a concentration of 0.1 mol / L. The dopamine solution is a monomer solution with a concentration of 5 mmol / L. Note that the dopamine solution is easily oxidized. After preparation, nitrogen gas should be continuously purged to remove oxygen. Prepare and use immediately.

[0049] Step 3: Electrochemical polymerization was performed on the piezoelectric wafer 211 using cyclic voltammetry with a three-electrode system. The working electrode was the gold electrode of the QCM detection chip 21, the reference electrode was a saturated calomel electrode, and the counter electrode was a platinum electrode. The electrolyte was a 0.1 mol / L phosphate buffer solution with pH 7.0 containing 5 mmol / L dopamine. The polymerization potential was -0.5 to 0.5 V, the scan rate was 50 mV / s, and the number of scan cycles was 15. A polydopamine film with specific adsorption of volatile basic nitrogen was synthesized. After polymerization, the surface phosphate residue was gently rinsed with deionized water and dried with nitrogen to obtain the QCM detection chip 21 for the freshness of aquatic products.

[0050] The above preparation process only requires electrochemical polymerization and cleaning steps, without the need for expensive equipment, and the sensitive layer material (dopamine) is green and environmentally friendly, which can significantly reduce the cost of use and maintenance.

[0051] This detector integrates the power supply system, PCB control, gas introduction, constant temperature heating, and Bluetooth communication modules into a compact 100mm×100mm×90mm acrylic body through a highly integrated and miniaturized design. Its small size makes it portable and suitable for rapid on-site testing and mobile scenarios. By combining the QCM detection chip 21 with a sensitive layer specifically for volatile basic nitrogen (TVB-N), it can detect the release of TVB-N from spoiled aquatic products in real time and transmit data wirelessly via Bluetooth, enabling continuous dynamic monitoring and overcoming the lag of traditional laboratory testing. Furthermore, the constant temperature heating element effectively suppresses the impact of ambient temperature fluctuations on detection accuracy. The serpentine gas turbulence channel and dustproof mesh 31 design ensure uniform gas distribution and filter particulate interference, maintaining high reliability even in complex environments. It employs a 9MHz baseband AT-cut quartz piezoelectric crystal 211, combined with the specific adsorption of a polydopamine sensitive layer, providing sensitive response to minute changes in TVB-N. The electrochemical polymerization process ensures a uniform and stable thin film, significantly improving detection efficiency. The QCM detection chip 21 features a pluggable structure for easy replacement.

[0052] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An on-line freshness monitor for aquatic products based on the QCM sensing principle, characterized in that, include: The housing (1) is provided with a detection cell for containing the gas to be tested, and the side walls of the detection cell are respectively provided with constant temperature heating elements; QCM sensing system (2), the QCM sensing system (2) includes a detachable QCM detection chip (21) disposed in the detection pool, a wafer base (22) disposed below the QCM detection chip (21), and conductive elements (23) disposed on both sides of the QCM detection chip (21). The QCM detection chip (21) is used to sense the mass change caused by gas adsorption and generate a frequency signal. A gas introduction system (3) connected to the detection pool includes a dustproof net (31), an air inlet grid (33) provided inside the dustproof net (31), and a gas turbulence channel provided between the entrance of the detection pool and the dustproof net (31). The gas turbulence channel is a serpentine channel, and the output end of the gas turbulence channel is connected to the detection pool.

2. The online freshness monitor for aquatic products based on the QCM sensing principle according to claim 1, characterized in that: It also includes a control system, which includes a PCB board (41) electrically connected to the power supply system and the QCM sensing system (2) respectively, and a Bluetooth communication system integrated inside the PCB board (41).

3. The online freshness monitor for aquatic products based on the QCM sensing principle according to claim 2, characterized in that: The QCM detection chip (21) includes a piezoelectric wafer (211), metal electrode layers (212) respectively disposed on the upper and lower surfaces of the piezoelectric wafer (211), and a sensitive layer coated on the surface of the upper metal electrode layer (212). The sensitive layer is made of polydopamine film material that has a specific adsorption effect on volatile basic nitrogen.

4. The online freshness monitoring instrument for aquatic products based on the QCM sensing principle according to claim 3, characterized in that: The piezoelectric wafer (211) is a piezoelectric quartz wafer.

5. The online freshness monitoring instrument for aquatic products based on the QCM sensing principle according to claim 4, characterized in that: The fundamental frequency of the piezoelectric chip (211) is 9MHz.

6. The online freshness monitoring instrument for aquatic products based on the QCM sensing principle according to claim 5, characterized in that: The diameter of the piezoelectric wafer (211) is 13.4 mm to 14.0 mm.

7. The online freshness monitoring instrument for aquatic products based on the QCM sensing principle according to claim 3, characterized in that: The metal electrode layer (212) is a gold component.

8. The online freshness monitoring instrument for aquatic products based on the QCM sensing principle according to claim 1, characterized in that: The housing (1) includes a front panel (11), a back panel (12), and a top panel (13) of the sensing system, which are respectively disposed on the outside of the QCM sensing system (2).

9. The online freshness monitoring instrument for aquatic products based on the QCM sensing principle according to claim 8, characterized in that: The QCM sensing system (2) is also fitted with a sensing system protective frame (14), and a sealing gasket (15) is provided inside the sensing system protective frame (14).

10. The online freshness monitoring instrument for aquatic products based on the QCM sensing principle according to claim 1, characterized in that: The bottom surface of the detection pool is provided with a slot for fixing the QCM detection chip (21) and a contact for transmitting detection signals that can be connected to the QCM detection chip (21).

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