A fluorescent probe and a fluorescent label for real-time non-destructive visualization monitoring of the freshness of meat products, and a preparation method and application thereof

Abstract

The present invention discloses a fluorescent probe and a fluorescent label for real-time non-destructive visualization monitoring of the freshness of meat food, and their preparation methods and applications. The structural formula of the fluorescent probe HBT-Bz is simple and easy to synthesize. Using the HBT fluorophore with ESIPT properties and AIE effect as the parent body and benzoxazole ester group as the recognition group for amine compounds, a fluorescence turn-on probe is designed and synthesized. The fluorescent probe HBT-Bz responds quickly and sensitively to amine compounds, with a detection limit as low as 5.1 ppm, and can be used to fabricate a solid fluorescence sensor for detecting volatile amine compounds. The synthetic route of the fluorescent probe involved in the present invention is simple, can recognize a variety of volatile amines, has a low detection limit, and the preparation process of the fluorescent label loaded with the fluorescent probe is simple. When in use, no pretreatment of the food is required. Placing the fluorescent label in the meat food packaging can realize real-time non-destructive visualization monitoring of the food freshness, and the results are accurate and reliable.

Description

Technical Field

[0001] The present invention belongs to the technical field of detection probes, and particularly relates to a fluorescence probe and a fluorescence label for real-time non-destructive visualization monitoring of the freshness of meat products, and a preparation method and application thereof. Background Art

[0002] Amines, especially low molecular weight volatile amines, are often regarded as key basic compounds and are widely used in fields such as dyes, pharmaceuticals, agriculture, and food processing, serving as raw materials, intermediates, and end products. However, many of these amines are toxic, corrosive, and dangerous, and may cause serious acute damage to the human body, such as damage to the eyes, skin, respiratory system, and nervous system. In addition, biogenic amines are typical substances in animals, plants, and foods, especially in spoiled foods such as meat, fish, seafood, wine, and cheese. Biogenic amines, nucleic acids, and functional proteins are essential for life, and they are all amine compounds or their complex derivatives. Meat products are an important source of protein and lipid nutrition for humans. During storage and transportation, meat products are prone to spoilage, and due to the growth of microorganisms, decarboxylation and deamination reactions of amino acids and proteins occur, resulting in the formation of biogenic amines and / or volatile amines. Abnormal increases in the concentrations of these biogenic amines and volatile amines may have toxic effects on human tissues and physiological systems. Excessive intake of biogenic amines may cause acute or delayed toxicity to the human skin, respiratory, nervous, urinary, and hematopoietic systems. Therefore, developing simple, selective, and sensitive methods for detecting volatile amines, especially methods that can be used for on-site real-time detection, is crucial for determining the freshness of meat products.

[0003] Although there are currently various traditional instrumental detection techniques for detecting volatile amines, such as gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography-mass spectrometry (HPLC-MS), capillary electrophoresis (CE), electrochemical sensors, enzyme methods, etc., these methods are expensive, time-consuming, labor-intensive, and require complex pretreatment of the samples to be detected. Therefore, they are not suitable for real-time and on-site monitoring of the freshness of meat products. As an emerging analytical method, fluorescence analysis can overcome the limitations of traditional detection methods. Fluorescence sensors are simple to prepare, easy to operate, highly specific and sensitive, have a fast response speed, a low detection limit, and can achieve real-time and on-site visualization of analyte monitoring, with advantages that cannot be matched by other detection methods.

[0004] In many existing studies, the fluorescence probes used for detecting volatile amine compounds are prone to aggregation-caused quenching (ACQ) phenomenon and need to be prepared in solution. In addition, the extraction of analytes requires the destruction of food samples, increasing the complexity of applications. In contrast to ACQ, organic dyes with aggregation-induced emission (AIE) phenomenon have high quantum yields and good photostability and do not need to be dispersed in solution, so they have potential in the sensing field. In recent years, AIE fluorescence sensors have attracted continuous attention in the field of gas detection due to their high sensitivity and multiple responsiveness. Therefore, it is necessary to develop portable solid-state fluorescence probes with AIE characteristics for convenient integration into portable devices for real-time visual detection of gaseous amines. Summary of the Invention

[0005] To solve the above technical problems, the object of the present invention is to provide a fluorescence probe for real-time non-destructive visual monitoring of the freshness of meat products, a preparation method of the fluorescence probe, a fluorescence label containing the fluorescence probe, a preparation method thereof and an application.

[0006] The technical solution of the present invention is realized as follows: A fluorescence probe for real-time non-destructive visual monitoring of the freshness of meat products, characterized in that the structural formula is

[0007]

[0008] In the present invention, the fluorescence probe uses the HBT fluorophore with excited state intramolecular proton transfer (ESIPT) property and AIE effect as the parent body. ESIPT is a unique fluorescence activation mechanism, which involves controlling fluorescence through intermolecular or intramolecular hydrogen bonds.

[0009] HBT is a typical ESIPT phosphor with large Stokes shift and good biocompatibility, which exhibits AIE characteristics by turning on the ESIPT process and restricting intramolecular motion (RIM). Utilizing the characteristics of "ESIPT+AIE", we introduced a benzoxazole group onto the hydroxyl group of HBT as an amine-responsive site and designed HBT-Bz as a portable sensor for real-time and on-site detection of amine vapors. The electron-withdrawing effect of the benzoxazole group disrupts the intramolecular hydrogen bond, effectively quenching the ESIPT process of HBT, resulting in weak fluorescence emission of the probe HBT-Bz itself. When HBT-Bz comes into contact with an amine, the amine undergoes an ester bond hydrolysis reaction through nucleophilic substitution, causing the benzoxazole group to cleave and releasing the phosphor HBT to produce strong fluorescence. HBT-Bz shows a response to amines in solution and solid state, presenting strong blue fluorescence under 365 nm ultraviolet light and also showing green fluorescence due to the AIE effect or the presence of a crystalline state. Specifically, the fluorescent probe in the present invention uses a benzoxazole group with strong electron-withdrawing properties to quench the fluorescence of HBT. After the fluorescent probe recognizes amine substances, the benzoxazole group undergoes an ammonolysis reaction with the amine, the ester bond is broken, the protecting group is removed, a hydroxyl group is released, and HBT with ESIPT properties is generated, thereby emitting blue fluorescence to achieve an "OFF-ON" recognition effect.

[0010] The second object of the present invention is achieved as follows: A preparation method of a fluorescent probe for real-time non-destructive visualization monitoring of the freshness of meat products, characterized in that the reaction formula is:

[0011]

[0012] It is prepared according to the following steps:

[0013] Step (1), preparing intermediate compound 2 (HBT): Dissolve compound 1 and 2-hydroxybenzaldehyde in ethanol, and then add hydrogen peroxide and hydrochloric acid to the mixture; Stir the reaction mixture at room temperature for 1-3 hours. After the reaction is completed, a large amount of gray precipitate is formed in the reaction solution. Filter and collect the precipitate, wash the filter cake with deionized water, and dry the solid under vacuum conditions to obtain compound 2. Further recrystallize the crude product in ethanol and dry it to obtain a white crystalline solid of HBT.

[0014] Step (2), preparing target compound 3 (HBT-Bz): Add compound 2 and potassium carbonate to anhydrous acetonitrile. Under a N2 atmosphere, stir and reflux the mixture at 80 °C until the reaction is complete. Cool the reaction mixture and add 2-chlorobenzoxazole; Stir and reflux the mixture at 80 °C again until the reaction is complete. When compound 2 is completely consumed, cool the reaction solution to room temperature; Filter out the insoluble solid, concentrate the solution under reduced pressure; Recrystallize the residue in methanol to obtain target compound 3, which is a white solid of HBT-Bz.

[0015] In the above scheme: the molar ratio of compound 1 to 2-hydroxybenzaldehyde is 1:1 - 1.2.

[0016] In the above scheme: the molar ratio of compound 3 to 2-chlorobenzoxazole is 1:1 - 1.6.

[0017] The third object of the present invention is achieved as follows: a fluorescent label, characterized in that: it includes the fluorescent probe for real-time non-destructive visualization monitoring of the freshness of meat products, and the fluorescent probe is attached to a solid support.

[0018] In the above scheme: the solid support is at least one of filter paper, cotton, non-woven fabric, fabric, or electrospun fiber.

[0019] In the above scheme: the solid support is immersed in a solution of the fluorescent probe, taken out and dried to obtain.

[0020] In the above scheme: the solution of the fluorescent probe is a dichloromethane solution of the fluorescent probe.

[0021] An application of the fluorescent label in the freshness monitoring of meat products.

[0022] During use: the fluorescent label loaded with the fluorescent probe HBT-Bz is placed in a sealed container, in which there is a meat product sample. As the degree of spoilage of the meat product increases, the fluorescent label undergoes a specific reaction through the fluorescent probe HBT-Bz with the volatile biogenic amines generated during the spoilage process of the meat, and the fluorescence of the fluorescent label is turned on, and the emitted blue fluorescence is within the visible light range. The content of volatile biogenic amines is judged according to the visual optical characteristics, so as to monitor the freshness of the meat product.

[0023] The present invention can be used for the spoilage monitoring of chicken breast, pork and fish. As the degree of spoilage of the meat sample increases, the fluorescence of the fluorescent label loaded with the fluorescent probe HBT-Bz gradually changes from colorless to blue, and is used for the freshness monitoring of meat. Specifically, under sealed conditions at -18°C (frozen), 4°C (refrigerated) and 25°C (room temperature), as the degree of spoilage of the meat sample increases, under ultraviolet light irradiation, the fluorescence of the fluorescent label loaded with the fluorescent probe HBT-Bz gradually changes from colorless to blue; when the fluorescent label has no fluorescence, it indicates that the meat is fresh, and when the indicator label has blue fluorescence, it indicates that the meat begins to go bad, and as the blue fluorescence intensifies, it indicates an increase in the degree of spoilage of the meat.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The fluorescent probe HBT-Bz has a simple structure and is easy to synthesize. Using the HBT fluorophore with ESIPT properties and AIE effect as the parent body and benzoxazole ester group as the recognition group for amine compounds, a fluorescence-turn-on probe is designed and synthesized. The fluorescent probe HBT-Bz responds quickly and sensitively to amine compounds, with a detection limit as low as 5.1 ppm, and can be used to fabricate a solid fluorescence sensor for detecting volatile amine compounds.

[0026] 2) The excitation light of the fluorophore HBT is in the ultraviolet wavelength range, and a 365 nm handheld ultraviolet lamp can be used as the excitation light source. Its emission light is blue and in the visible light range. When an amine compound interacts with the fluorescent probe HBT-Bz, the fluorophore HBT is released, and the emitted fluorescence can be recognized by the naked eye. Therefore, when using the fluorescent probe HBT-Bz to detect volatile amine compounds, no complex detection equipment is required.

[0027] 3) The fluorescent probe HBT-Bz interacts with volatile amine compounds under mild reaction conditions and can proceed smoothly at room temperature. It can be used to detect the volatile amine substances generated during the spoilage of meat products stored under normal conditions.

[0028] 4) The preparation of the fluorescent label loaded with the fluorescent probe HBT-Bz is simple and convenient. When the fluorescent label is placed in meat packaging, as the degree of meat spoilage increases, the fluorescence of the label turns on, changing from colorless to blue. The fluorescent label can visually monitor the freshness of meat products in real time and without damage. Description of the Drawings

[0029] Figure 1 1H NMR spectrum of intermediate compound 2 (HBT), where the abscissa is the chemical shift and the ordinate is the signal intensity. 1 H NMR spectrum of intermediate compound 2 (HBT), where the abscissa is the chemical shift and the ordinate is the signal intensity.

[0030] Figure 2 13C NMR spectrum of intermediate compound 2 (HBT), where the abscissa is the chemical shift and the ordinate is the signal intensity. 13 13C NMR spectrum of intermediate compound 2 (HBT), where the abscissa is the chemical shift and the ordinate is the signal intensity.

[0031] Figure 3 1H NMR spectrum of target compound 3 (HBT-Bz), where the abscissa is the chemical shift and the ordinate is the signal intensity. 1 1H NMR spectrum of target compound 3 (HBT-Bz), where the abscissa is the chemical shift and the ordinate is the signal intensity.

[0032] Figure 4 13C NMR spectrum of target compound 3 (HBT-Bz), where the abscissa is the chemical shift and the ordinate is the signal intensity. 13 13C NMR spectrum of target compound 3 (HBT-Bz), where the abscissa is the chemical shift and the ordinate is the signal intensity.

[0033] Figure 5 High-resolution mass spectrometry (HRMS) spectrum of target compound 3 (HBT-Bz).

[0034] Figure 6 It is a fluorescence response result diagram of a fluorescent label to different types of amines and various analytes. In the figure: (A)(B) are the fluorescence response results of the fluorescent label to propylamine vapor at different concentration gradients; (C)(D) are the changes in the fluorescence response intensity of the fluorescent label to propylamine vapor over time; (E)(F) are the fluorescence response of the fluorescent label to the vapors of various common volatile amine compounds and their interferents. Compound abbreviations: PA (propylamine), EA (ethylamine), EDA (ethylenediamine), BA (n-butylamine), CHA (cyclohexylamine), HAH (hydrazine hydrate), CAD (cadaverine), DMA (aqueous dimethylamine), DEA (diethylamine), AN (aniline), AA (ammonia water), TEA (triethylamine), PY (pyridine), H2S (hydrogen sulfide), SO2 (sulfur dioxide), HCl (hydrogen chloride).

[0035] Figure 7 It is a measurement result diagram of the freshness of food at different times by a fluorescent label at different temperatures (-18°C, 4°C, 25°C). In the figure: (A) Measurement results of the fluorescence color change of chicken breast samples under 365 nm ultraviolet light at three temperatures; (B) Measurement results of the fluorescence color change of pork samples under 365 nm ultraviolet light at three temperatures; (C) Measurement results of the fluorescence color change of fish samples under 365 nm ultraviolet light at three temperatures. Detailed implementation manners

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] Example 1:

[0038] A fluorescent probe for real-time non-destructive visual monitoring of the freshness of meat food, with the structural formula

[0039]

[0040] The synthesis route is as follows:

[0041]

[0042] 1. Prepare intermediate compound 2 (HBT):

[0043] Compound 1 (1.88 g, 15 mmol), 2-hydroxybenzaldehyde (1.83 g, 15 mmol) were dissolved in ethanol (30 mL), then 30% hydrogen peroxide (10 mL) and 37% hydrochloric acid (4.5 mL) were added. The reaction mixture was stirred at room temperature for 1.5 h. After completion of the reaction (monitored by thin layer chromatography), a large amount of grey precipitate formed in the reaction solution. Then, the precipitate was collected by suction filtration, washed with deionized water (3×5 mL), and dried under vacuum to obtain the crude product. The crude product was further recrystallized and dried in ethanol to obtain Compound 2 as a white crystalline solid (2.59 g, yield 76%).

[0044] of HBT 1 The 1H NMR spectrum and 13 13C NMR spectrum are as Figure 1-2 follows.

[0045] 1 1H NMR (600 MHz, Chloroform-d) δ: 12.41 (s, 1H), 7.89 (dt, J = 8.2, 0.8 Hz, 1H), 7.79 (ddd, J = 8.0, 1.2, 0.6 Hz, 1H), 7.59 (dd, J = 7.8, 1.6 Hz, 1H), 7.40 (ddd, J = 8.3, 7.2, 1.2 Hz, 1H), 7.30 (dddd, J = 12.7, 8.6, 7.2, 1.4 Hz, 2H), 7.02 (dd, J = 8.3, 1.1 Hz, 1H), 6.86 (ddd, J = 7.8, 7.2, 1.2 Hz, 1H).

[0046] 13 13C NMR (151 MHz, Chloroform-d) δ: 169.38, 157.95, 151.80, 132.77, 132.59, 128.42, 126.70, 125.55, 122.17, 121.51, 119.52, 117.88, 116.78.

[0047] 2. Preparation of the target compound 3 (HBT-Bz):

[0048] Compound 2 (227.28 mg, 1.25 mmol) and potassium carbonate (276.42 mg, 2.5 mmol) were added to anhydrous acetonitrile (10 mL). Under a N2 atmosphere, the mixture was stirred and refluxed at 80 °C for 4 hours. Then, the reaction mixture was cooled and 2-chlorobenzoxazole (297.92 mg, 1.94 mmol) was added. The mixture was stirred at 80 °C for another 4 hours. When 2-hydroxybenzaldehyde was completely consumed (monitored by thin layer chromatography), the solution was cooled to room temperature. The insoluble solid was filtered off, and then the solution was concentrated using a rotary evaporator under reduced pressure. The resulting residue was recrystallized from methanol to give Compound 3, the final probe HBT-Bz as a white solid (220 mg, yield 51%).

[0049] For HBT-Bz 1 the 1H NMR spectrum, 13 13C NMR spectrum and HRMS spectrum are as Figure 3-5 shown.

[0050] 1 1H NMR (600 MHz, Chloroform-d) δ: 8.41 (dd, J = 7.9, 1.7 Hz, 1H), 7.95 (dt, J = 8.5, 0.9 Hz, 1H), 7.80 (dt, J = 8.0, 0.9 Hz, 1H), 7.60–7.49 (m, 2H), 7.47–7.33 (m, 4H), 7.29 (ddd, J = 8.1, 7.1, 1.2 Hz, 1H), 7.22–7.10 (m, 2H).

[0051] 13 13C NMR (151 MHz, Chloroform-d) δ: 160.74, 160.46, 151.62, 149.03, 147.75, 139.60, 134.58, 130.89, 129.57, 126.12, 125.28, 124.58, 124.38, 123.59, 122.58, 122.40, 121.05, 120.36, 117.93, 109.00.

[0052] HRMS (ESI, m / z): [M+H] + calcd for C 20 H 13 N2O2S: 345.0698, found: 5.0695.

[0053] Preparation of the probe in Example 2:

[0054] 1. Preparation of the intermediate compound 2 (HBT):

[0055] Compound 1 (1.88 g, 15 mmol) and 2-hydroxybenzaldehyde (2.20 g, 18 mmol) were dissolved in ethanol (30 mL), and then 30% hydrogen peroxide (10 mL) and 37% hydrochloric acid (4.5 mL) were added. The reaction mixture was stirred at room temperature for 1.5 h. After the reaction was completed (monitored by thin-layer chromatography), a large amount of gray precipitate formed in the reaction solution. Then, the precipitate was collected by suction filtration, washed with deionized water (3×5 mL), and dried under vacuum to obtain the crude product. The crude product was further recrystallized and dried in ethanol to obtain Compound 2 as a white crystalline solid (2.62 g, yield 77%).

[0056] 2. Preparation of the target compound 3 (HBT-Bz):

[0057] Compound 2 (227.28 mg, 1.25 mmol) and potassium carbonate (276.42 mg, 2.5 mmol) were added to anhydrous acetonitrile (10 mL). Under a N2 atmosphere, the mixture was stirred and refluxed at 80 °C for 4 h. Then, the reaction mixture was cooled, and 2-chlorobenzoxazole (191.95 mg, 1.25 mmol) was added. The mixture was stirred at 80 °C for another 4 h. When 2-hydroxybenzaldehyde was completely consumed (monitored by thin-layer chromatography), the solution was cooled to room temperature. The insoluble solid was filtered off, and then the solution was concentrated using a rotary evaporator under reduced pressure. The resulting residue was recrystallized in methanol to obtain Compound 3 as the final probe HBT-Bz as a white solid (207 mg, yield 48%).

[0058] Example 3

[0059] Preparation of the fluorescent label:

[0060] Whatman G4 filter paper was cut into strips (dimensions: 0.8 cm×1.5 cm, dimensions: 1.5 cm×2.0 cm). The fluorescent probe HBT-Bz was dissolved in dichloromethane to prepare a dichloromethane solution of HBT-Bz (0.1 mM). The filter paper strips were immersed in the dichloromethane solution of HBT-Bz for 10 min, taken out and left to dry naturally in a fume hood to obtain the fluorescent label loaded with the fluorescent probe HBT-Bz.

[0061] Of course, the solid support can also be at least one of filter paper, cotton, non-woven fabric, fabric, or electrospun fiber. Filter paper was selected in this example.

[0062] The fluorescent label was attached to the inside of the container lid. Different types of amine compounds were added to a 70 mL glass container, and the container was placed in a thermostat at 40 °C. After 1 min, the fluorescent label was taken out, and under a handheld 365 nm ultraviolet lamp, a fluorescent photo was taken with a smartphone, and then the fluorescence emission intensity of the fluorescent label was recorded with a fluorescence spectrophotometer.

[0063] Figure 6 It is a fluorescence response result graph of the fluorescence label to different kinds of amines and various analytes. In the graph: (A)(B) are the fluorescence response results of the fluorescence label to propylamine vapor with different concentration gradients; (C)(D) are the changes in the fluorescence response intensity of the fluorescence label to propylamine vapor over time; (E)(F) are the fluorescence response situations of the fluorescence label to various common volatile amine compounds and other interfering substance vapors. Compound abbreviations: PA (propylamine), EA (ethylamine), EDA (ethylenediamine), BA (n-butylamine), CHA (cyclohexylamine), HAH (hydrazine hydrate), CAD (cadaverine), DMA (aqueous dimethylamine solution), DEA (diethylamine), AN (aniline), AA (ammonia water), TEA (triethylamine), PY (pyridine), H2S (hydrogen sulfide), SO2 (sulfur dioxide), HCl (hydrogen chloride).

[0064] Figure 6 (A) and (B) are the fluorescence change situations of the fluorescence label in the presence of propylamine vapor with different concentration gradients. It can be seen that as the concentration of propylamine continuously increases, the fluorescence color of the fluorescence label under the handheld 365 nm fluorescent lamp gradually changes from non-fluorescent to blue fluorescence, and the fluorescence intensity I 465 / I0 has an obvious linear relationship with the concentration of propylamine.

[0065] Figure 6 (C) and (D) are the changes in the fluorescence response intensity of the fluorescence label to propylamine vapor over time. The specific operation is: 13 fluorescence labels are successively placed into 200 ppm propylamine vapor and taken out after 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120 seconds. The fluorescence intensity of the fluorescence label at 465 nm increases with the prolonging of the contact time with propylamine vapor, and the growth rate significantly slows down after 60 seconds.

[0066] Figure 6 (E) and (F) are the fluorescence response situations of the fluorescence label to the vapors of various common volatile amine compounds and other interfering substances. It can be seen that the fluorescence label shows an obvious colorless to blue fluorescence transition for some volatile amines, and there is no obvious fluorescence change for other various analytes. Therefore, this fluorescence label has good recognition ability and practical applicability to a variety of volatile amine compounds under a 365 nm ultraviolet lamp.

[0067] Put the fluorescent label loaded with the fluorescent probe HBT-Bz into a sealed container containing meat food samples. As the degree of spoilage of the meat food increases, the fluorescent label undergoes a specific reaction with the volatile biogenic amines generated during the spoilage process of the meat through the fluorescent probe HBT-Bz, and the fluorescence of the fluorescent label is turned on, emitting blue fluorescence within the visible light range. The content of volatile biogenic amines is judged based on the visual optical characteristics, thereby monitoring the freshness of the meat food.

[0068] Application of the fluorescent label loaded with the fluorescent probe HBT-Bz in the spoilage monitoring of chicken breast, pork, and fish. As the degree of spoilage of the meat samples increases, the fluorescence of the fluorescent label loaded with the fluorescent probe HBT-Bz gradually changes from colorless to blue, which is used for monitoring the freshness of the meat. Specifically, under sealed conditions at -18°C (frozen), 4°C (refrigerated), and 25°C (room temperature), they were stored for 0, 4, 8, 12, 16, 20, 24, 36, 48, and 72 hours respectively, and a smartphone (HUWEIP60) was used to record the fluorescence images of these fluorescent labels under a 365 nm ultraviolet lamp.

[0069] As Figure 7 As shown in (A), (B), and (C), at different temperatures, as the storage time prolongs, the degree of spoilage of the meat samples also increases. Under the irradiation of a 365 nm ultraviolet lamp, the fluorescence of the fluorescent label loaded with the fluorescent probe HBT-Bz gradually changes from colorless to blue; when the fluorescent label has no fluorescence, it indicates that the meat is fresh, and when the indicator label has blue fluorescence, it indicates that the meat starts to go bad, and as the blue fluorescence intensifies, it indicates an increase in the degree of spoilage of the meat.

[0070] The results show that the fluorescent label exhibits good practical applicability and can achieve real-time non-destructive visual detection of the freshness of meat food.

[0071] The present invention is not limited to the above embodiments. Those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A fluorescence probe for real-time non-destructive visualization monitoring of the freshness of meat food, characterized in that: The structural formula is 2. A method for preparing a fluorescence probe for real-time non-destructive visualization monitoring of the freshness of meat products according to claim 1, characterized in that, The reaction formula is as follows: It is prepared according to the following steps: Step (1), preparing intermediate compound 2: Dissolve compound 1 and 2-hydroxybenzaldehyde in ethanol, and then add hydrogen peroxide and hydrochloric acid to the mixture; Stir the reaction mixture at room temperature for 1 - 3 hours. After the reaction is completed, a gray precipitate is formed in the reaction solution. Filter and collect the precipitate, wash the filter cake with deionized water, and dry the solid under vacuum conditions to obtain compound 2. Further recrystallize the crude product in ethanol and dry it to obtain the white crystalline solid of compound 2; Step (2), preparing target compound 3: Add compound 2 and potassium carbonate to anhydrous acetonitrile. Under a nitrogen atmosphere, stir and reflux the mixture at 80 °C until the reaction is complete. Cool the reaction mixture and add 2-chlorobenzoxazole; Stir and reflux the mixture at 80 °C again until the reaction is complete. When compound 2 is completely consumed, cool the reaction solution to room temperature; Filter out the insoluble solid and concentrate the solution under reduced pressure; Recrystallize the residue in methanol to obtain target compound 3.

3. The preparation method of the fluorescence probe for real-time non-destructive visualization monitoring of the freshness of meat food according to claim 2, characterized in that, The molar ratio of compound 1 to 2-hydroxybenzaldehyde is 1:1 - 1.

2.

4. The preparation method of the fluorescence probe for real-time non-destructive visualization monitoring of the freshness of meat food according to claim 3, characterized in that, The molar ratio of compound 3 to 2-chlorobenzoxazole is 1:1 - 1.

6.

5. A fluorescent label, characterized in that: It includes the fluorescence probe for real-time non-destructive visualization monitoring of the freshness of meat food described in claim 1, and the fluorescence probe is attached to a solid support.

6. The fluorescent label according to claim 5, wherein: The solid support is at least one of filter paper, cotton, non-woven fabric, fabric, or electrospun fiber.

7. The fluorescent label according to claim 6, wherein It is prepared by the following operations: Immerse the solid support in the solution of the fluorescence probe, take it out and dry it to obtain.

8. The fluorescent label according to claim 7, wherein The solution of the fluorescence probe is the dichloromethane solution of the fluorescence probe.

9. Use of the fluorescence label described in claim 5 in the monitoring of the freshness of meat food.

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