A bifunctional fluorescent sensor, preparation method, food discoloration label and application thereof

Abstract

The application discloses a bifunctional fluorescent sensor and a preparation method, a food discoloration label and application. The bifunctional fluorescent sensor is 3-hydroxy-2-(4-(4-methylpiperazine-1-yl)phenyl)-4H-benzochromene, which is abbreviated as HMB, and a structural formula of the HMB is as follows: The bifunctional fluorescent sensor has a unique methylpiperazine structure, can simultaneously and rapidly detect acid and base release substances, and can evaluate the levels of organic amine, lactic acid and other release substances generated in a food spoilage process. The food discoloration label prepared based on the bifunctional fluorescent sensor emits green fluorescence in an acid environment and emits red fluorescence in an alkaline environment, can simultaneously detect acid and base metabolites generated in a food spoilage process, and is used for evaluating a food spoilage process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food engineering, and particularly relates to a dual-function fluorescent sensor, a preparation method, a food discoloration label and application. BACKGROUND

[0002] The freshness of food is of great importance to public health, and eating spoiled food can cause serious physiological diseases. With the increasing global circulation of food, food spoilage due to enzymatic reactions and microbial contamination during storage and transportation has become one of the most important problems in the food industry. During the spoilage of food, various volatile metabolites are released from the food, thereby changing the pH value around the food. According to the increase and decrease of the pH value, the metabolites can be divided into two categories, one of which involves the occurrence of glycolysis, which releases acidic compounds such as lactic acid, thereby reducing the pH value of the food. The other is the generation of volatile biogenic amines by bacteria metabolizing amino acids decarboxylation, thereby increasing the pH value of the food. Therefore, the change of the pH value is closely related to the freshness of the food.

[0003] In recent years, fluorescent sensors have attracted more and more attention due to their high sensitivity, non-invasive, real-time and on-site methods. In food analysis, the fluorescent sensor method has been widely used for the identification of food quality as a simple, low-cost, non-destructive and real-time detection method. So far, a variety of pH-responsive fluorescent sensors for monitoring the freshness of food have been reported. However, these sensors only detect the pH change of food in a single response mode, so their use is limited.

[0004] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0005] In view of the above deficiencies of the prior art, the purpose of the present application is to provide a dual-function fluorescent sensor, a preparation method, a food discoloration label and application, which aims to solve the problem that the existing sensor can only detect the pH change of food in a single response mode.

[0006] The optimal pH-responsive sensor should have a dual-response function mode to distinguish between acidic and basic releases, i.e. to simultaneously monitor the acidic and basic releases during the spoilage of food through two different fluorescent signals, so as to evaluate the level of acidic and basic releases generated during the spoilage of food.

[0007] Specifically, the technical solutions of the present application are as follows:

[0008] In a first aspect of the present application, a dual-function fluorescent sensor is provided, which is 3-hydroxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-4H-benzochromene, abbreviated as HMB, and the structural formula of the HMB is:

[0009] The bifunctional fluorescent sensor has a unique methylpiperazine structure, that is, has two pKa values, so that it can emit green fluorescence in a lower pH range and emit red fluorescence in a higher pH range, realizing synchronous tracking detection of acidic and basic releases.

[0010] In a second aspect, the application provides a preparation method of the bifunctional fluorescent sensor, comprising the following steps:

[0011] 1-(3-hydroxynaphthalen-2-yl)ethanone, 4-(4-methylpiperazin-1-yl)benzaldehyde and tetrahydro-pyrrole are dissolved in a polar solvent, and stirred for 14-20 hours to obtain a mixed solution;

[0012] An inorganic base and hydrogen peroxide are added to the mixed solution, and stirred for 12-18 hours, and then purified to obtain the bifunctional fluorescent sensor;

[0013] The above reaction route is as follows:

[0014]

[0015] Optionally, the molar ratio of the 1-(3-hydroxynaphthalen-2-yl)ethanone to the 4-(4-methylpiperazin-1-yl)benzaldehyde is 1:2-5, such as 1:2, 1:3, 1:4, 1:5, etc.

[0016] Optionally, the polar solvent is selected from one of methanol, ethanol and ethylene glycol.

[0017] Optionally, the step of adding an inorganic base and hydrogen peroxide to the mixed solution, stirring for 12-18 hours, and then purifying to obtain the bifunctional fluorescent sensor, specifically comprises:

[0018] In an ice water bath, an inorganic base and hydrogen peroxide are added to the mixed solution, and continuously stirred for 30-90 minutes (such as 30 minutes, 50 minutes, 70 minutes, 90 minutes, etc.), the ice water bath is removed and stirred at room temperature, and stirred at room temperature for 12-18 hours to obtain a post-reaction system;

[0019] The post-reaction system is adjusted to neutral with an acid, and then filtered, washed and recrystallized to obtain the bifunctional fluorescent sensor.

[0020] Optionally, the inorganic base is selected from one of potassium hydroxide and sodium hydroxide.

[0021] Optionally, the acid is selected from hydrochloric acid.

[0022] In a third aspect, the present application provides a food discoloration label, wherein the food discoloration label comprises a glass fiber paper and the bifunctional fluorescent sensor according to the present application combined on the glass fiber paper.

[0023] The food discoloration label based on the bifunctional fluorescent sensor according to the present application can be embedded in a transparent food packaging bag, thereby implementing non-destructive detection on the spoilage process of food.

[0024] In a fourth aspect, the present application provides a preparation method of the food discoloration label according to the present application, comprising the steps of:

[0025] dissolving the bifunctional fluorescent sensor in an organic solvent to obtain a bifunctional fluorescent sensor solution;

[0026] immersing a glass fiber paper in the bifunctional fluorescent sensor solution for 1-3 hours (such as 1 hour, 2 hours, 3 hours, etc.), and drying after taking out, to obtain the food discoloration label.

[0027] The food discoloration label based on the bifunctional fluorescent sensor can be embedded in a transparent food packaging bag, thereby implementing non-destructive detection on the spoilage process of food.

[0028] Optionally, the weight ratio of the bifunctional fluorescent sensor to the glass fiber paper is 1:10-1000, such as 1:10, 1:50, 1:100, 1:200, 1:300, 1:500, 1:700, 1:1000, etc.

[0029] Optionally, the concentration of the bifunctional fluorescent sensor solution is 0.01-1 mM, such as 0.01 mM, 0.05 mM, 0.1 mM, 0.5 mM, 1 mM, etc.

[0030] Optionally, the organic solvent is selected from one of dimethyl sulfoxide and ethanol.

[0031] Optionally, the volume of the organic solvent is 1-10 mL.

[0032] In a fifth aspect, the present application provides an application of the food discoloration label according to the present application in detecting acidic and alkaline release substances generated in the spoilage process of food.

[0033] In a sixth aspect, the present application provides an application of the food discoloration label according to the present application in evaluating the spoilage process of food.

[0034] The food discoloration label can be used for detecting acid release (such as lactic acid gas) and alkaline release (such as organic amine gas) generated in the food spoilage process, and the specific detection steps comprise: encapsulating the food discoloration label on the inner surface of a transparent food packaging film, irradiating with a handheld ultraviolet lamp, recording the fluorescence color with a mobile phone and reading the RGB value; when the R / G value is 1.2±0.1, it indicates that the food does not generate acid and alkaline release; when the R / G value is less than 1.1, it indicates that the food generates acid release; and when the R / G value is greater than 1.3, it indicates that the food generates alkaline release.

[0035] The RGB value refers to a color value, R is red, and G is green.

[0036] The food discoloration label can be used for detecting acid and alkaline release generated in the food spoilage process, the food discoloration label emits green fluorescence in an acidic environment and emits red fluorescence in an alkaline environment, and can simultaneously detect acid and alkaline metabolites generated in the food spoilage process.

[0037] The food discoloration label has the following beneficial effects:

[0038] (1) The bifunctional fluorescent sensor of the present application can simultaneously and rapidly detect acid and alkaline release by introducing methylpiperazine as a pH recognition group, so as to evaluate the level of organic amine, lactic acid and other release generated in the food spoilage process.

[0039] (2) The food discoloration label prepared from the bifunctional fluorescent sensor of the present application emits green fluorescence in an acidic environment and emits red fluorescence in an alkaline environment, and can simultaneously detect acid and alkaline metabolites generated in the food spoilage process, and is used for evaluating the spoilage process of food. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 It is a fluorescence spectrum diagram of HMB in the buffer solution with pH value from 4.0 to 12.0 in Example 2 of the present application.

[0041] Figure 2 It is a pH-dependent peak intensity diagram of HMB at 550 nm in Example 2 of the present application.

[0042] Figure 3 It is a pH-dependent peak intensity diagram of HMB at 609 nm in Example 2 of the present application.

[0043] Figure 4 It is a red-green color ratio (R / G) of the food discoloration label in different pH in Example 3 of the present application.

[0044] Figure 5The food discoloration label was used to detect the freshness of cheese placed at room temperature (a) and in the refrigerator (b) in Example 3 of the present application. (c) R / G value of the paper-based device placed under different storage conditions.

[0045] Figure 6 The food discoloration label was used to detect the freshness of shrimp placed at room temperature (a) and in the refrigerator (b) in Example 3 of the present application. (c) R / G value of the paper-based device placed under different storage conditions. DETAILED DESCRIPTION

[0046] The present application provides a bifunctional fluorescent sensor and a preparation method, a food discoloration label and an application. In order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0047] Example 1

[0048] 1-(3-hydroxynaphthalen-2-yl)ethanone (0.93 g), 4-(4-methylpiperazin-1-yl)benzaldehyde (0.82 g) and 200 μL tetrahydro-pyrrole were stirred in 100 mL ethanol at room temperature for 18 h to obtain a mixed solution, then an aqueous potassium hydroxide solution (1 g / mL) and 30% hydrogen peroxide aqueous solution were added, and stirred for 16 h. After the reaction was completed, the system was neutralized with hydrochloric acid (1 M) to make it more neutral. The solution was filtered and recrystallized with ethanol / dichloromethane to obtain the bifunctional fluorescent sensor 3-hydroxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-4H-chromen, abbreviated as HMB, with a yield of 38%.

[0049] Product structure characterization data:

[0050] 1 H NMR (500 MHz, CDCl3): 8.82 (s, 1H), 8.27 (d, J = 9.1 Hz, 2H), 8.05 (d, J = 8.4 Hz, 1H), 8.02 (s, 1H), 7.92 (d, J = 8.4 Hz, 1H), 7.59 (t, J = 7.6 Hz, 1H), 7.50 (t, J = 7.6 Hz, 1H), 7.07-6.99 (m, 2H), 6.92 (s, 1H).

[0051] 13C NMR (126 MHz, CDC13): 173.49, 151.99, 151.36, 146.60, 136.05, 135.58, 129.77, 129.39, 129.31, 128.45, 127.08, 126.07, 125.59, 121.04, 120.14, 114.33, 113.91, 54.67, 47.45, 46.00. HRMS: m / z calcd for C 24 H 22 N2O3 + [M+H] + :387.16304,found:387.17160.

[0052] Example 2

[0053] The HMB prepared in Example 1 was added to the Tris-HCl buffer at different pH values to test the effect of different pH values on the bifunctional fluorescent sensor.

[0054] The HMB was dissolved in dimethyl sulfoxide to prepare an HMB solution, and the same concentration of HMB solution was added to the Tris-HCl buffer at different pH values to obtain the test solution. The fluorescence spectrum of the test solution was tested, as shown in Figure 1 , the fluorescence intensity at 550 nm gradually decreased with the increase of pH value, and when the pH value reached 7.9, it was almost completely quenched. Subsequently, with the further increase of pH value, the emission peak red-shifted, and the emission wavelength was 609 nm. The maximum fluorescence intensity was fitted with pH to obtain two pKa values (see Figure 2 and Figure 3 ). Importantly, one of the two pKa values is in the acidic region, and the other is in the basic region, which indicates that the bifunctional fluorescent sensor can produce a fluorescence response to the acidic and basic changes in the environment.

[0055] Example 3

[0056] Preparation steps of food discoloration label: take glass fiber paper as the substrate material, dissolve 38 mg of HMB prepared in Example 1 in dimethyl sulfoxide to prepare a 0.1 mM solution, soak the glass fiber paper in the solution, take it out with tweezers after 2 h and place it on a glass sheet, dry it in an 80 °C oven for 30 min, and cut it into a rectangular shape according to the experimental needs to obtain the food discoloration label loaded with HMB. As shown in Figure 4 , the red-green color ratio (R / G) of the food discoloration label is related to pH, and the R / G value gradually increases with the increase of pH.

[0057] Detection of real food samples using food discoloration label:

[0058] Two portions of cheese were placed in petri dishes, and the food discoloration label was attached to the inside top of the petri dishes. One portion of cheese was placed in room temperature at 25°C, and the other portion of cheese was placed in a refrigerator at 4°C. As shown in (a), (b), and (c), the cheese sample stored at room temperature showed a significant change in fluorescent color after 24 hours of storage, with the R / G value decreasing from 1.2 to 1.0, indicating that acidic release was produced in the internal environment of the food. The sample stored in the refrigerator did not show a significant change in 24 hours. Figure 5

[0059] Real food samples were detected using the food discoloration label.

[0060] Two portions of fresh shrimp samples were placed in petri dishes, and the food discoloration label was attached to the inside top of the petri dishes. One portion of fresh shrimp sample was placed in room temperature at 25°C, and the other portion of fresh shrimp sample was placed in a refrigerator at 4°C. As shown in (a), (b), and (c), the fresh shrimp sample stored at room temperature showed a significant change in fluorescent color after 24 hours of storage, with the R / G value increasing from 1.2 to 1.6, indicating that basic release (such as organic amine) was produced in the internal environment of the food. The sample stored in the refrigerator did not show a significant change in 24 hours. Figure 6

[0061] It should be understood that the application of the present application is not limited to the above examples, and can be improved or changed by those of ordinary skill in the art according to the above description, and all such improvements and changes shall fall within the scope of the appended claims of the present application.​​

Claims

1. A bifunctional fluorescent sensor, characterized in that, The bifunctional fluorescent sensor is 3-hydroxy-2-(4-(4-methylpiperazin-1-yl)phenyl)-4H-benzochromene, abbreviated as HMB, and the structural formula of HMB is:

2. A method for preparing a bifunctional fluorescent sensor as claimed in claim 1, characterized by, The method comprises the steps of: 1-(3-hydroxynaphthalen-2-yl)ethanone, 4-(4-methylpiperazin-1-yl)benzaldehyde and tetrahydro-pyrrole are dissolved in a polar solvent to obtain a mixed solution by stirring for 14-20 hours; An inorganic base and hydrogen peroxide are added to the mixed solution, and after stirring for 12-18 hours, the bifunctional fluorescent sensor is obtained by purification treatment.

3. The method for preparing a bifunctional fluorescent sensor according to claim 2, wherein, The molar ratio of the 1-(3-hydroxynaphthalen-2-yl)ethanone to the 4-(4-methylpiperazin-1-yl)benzaldehyde is 1:2-1:5; The polar solvent is selected from one of methanol, ethanol and ethylene glycol.

4. The method for preparing a bifunctional fluorescent sensor according to claim 2, wherein The step of adding an inorganic base and hydrogen peroxide to the mixed solution, stirring for 12-18 hours, and then purifying to obtain the bifunctional fluorescent sensor, specifically comprises: An inorganic base and hydrogen peroxide are added to the mixed solution in an ice water bath, and stirring is continued for 30-90 minutes, the ice water bath is removed and stirring is carried out at room temperature, and stirring is carried out at room temperature for 12-18 hours to obtain a post-reaction system; The post-reaction system is adjusted to neutral with an acid, and the bifunctional fluorescent sensor is obtained by suction filtration, washing and recrystallization.

5. The method for preparing a bifunctional fluorescent sensor according to claim 4, wherein, The inorganic base is selected from one of potassium hydroxide and sodium hydroxide; The acid is selected from hydrochloric acid.

6. A food discoloration label characterized by The food discoloration label comprises glass fiber paper and the bifunctional fluorescent sensor as claimed in claim 1 combined on the glass fiber paper.

7. A method of preparing a food color change label according to claim 6, characterized in that, The method comprises the steps of: The bifunctional fluorescent sensor is dissolved in an organic solvent to obtain a bifunctional fluorescent sensor solution; The glass fiber paper is soaked in the bifunctional fluorescent sensor solution for 1-3 hours, and then taken out and dried to obtain the food discoloration label.

8. The method of claim 7, wherein the food color-changing label is prepared by the steps of: The weight ratio of the bifunctional fluorescent sensor to the glass fiber paper is 1:10-1000; The organic solvent is selected from one of dimethyl sulfoxide and ethanol.

9. The food discoloration label of claim 6 in the application of detecting acidic and alkaline releases generated in the process of food spoilage.

10. The food discoloration label of claim 6 in the application of evaluating the process of food spoilage and deterioration.

Images