Detection method of food pigments based on fluorescence spectrometry

Abstract

The present invention discloses a method for detecting food pigments based on fluorescence spectrometry, which mainly includes the following steps: preparing a polymer nano-reverse micelle solution; placing the polymer nano-reverse micelle solution in a cuvette and scanning the fluorescence spectrum in a fluorescence spectrometer; dissolving the sample in water and slowly dropping it into the polymer nano-reverse micelle solution under stirring, followed by ultrasonic treatment, water removal, volume fixation, filtration to obtain a sample solution to be detected, placing it in a cuvette for mixing, scanning the fluorescence spectrum in a fluorescence spectrometer to obtain a fluorescence spectrogram, and analyzing and determining the pigment content in the food sample solution to be detected. The detection method of the present invention has a good detection effect on hydrophilic pigments in food, and has high sensitivity, good selectivity and low detection limit.

Description

Technical Field

[0001] The present invention relates to the technical field of food detection. More specifically, the present invention relates to a method for detecting food pigments based on fluorescence spectrometry. Background Art

[0002] Many natural foods have their own colors, which can stimulate people's appetite and increase the secretion of digestive juices, thus being beneficial to digestion and absorption and being important sensory indicators of food. However, natural foods are prone to fading or color change during processing and storage. In order to improve the color of foods, people often add edible pigments during the processing of foods to improve their sensory properties. Edible pigments are a type of pigment, that is, food additives that can be appropriately consumed by people and can change the original color of foods to a certain extent. The commonly used food pigments include two categories: natural pigments and synthetic pigments. Natural pigments come from natural substances, mainly extracted from plant tissues, and also include some pigments from animals and microorganisms. Synthetic pigments refer to organic pigments prepared by artificial chemical synthesis methods, mainly made from aniline dyes separated from coal tar. With the development of society and the improvement of people's living standards, more and more people have questioned whether the use of synthetic pigments in foods will harm human health. At the same time, a large number of research reports point out that almost all synthetic pigments cannot provide nutrients to the human body, and some synthetic pigments even harm human health. Therefore, it is necessary to explore a method for detecting food pigments to maximize the detection sensitivity. Summary of the Invention

[0003] An object of the present invention is to provide a method for detecting food pigments based on fluorescence spectrometry, which detects food pigments according to fluorescence spectrometry technology to improve the detection sensitivity.

[0004] To achieve these and other advantages in accordance with the present invention, in one aspect of the present invention, there is provided a method for detecting food pigments based on fluorescence spectrometry, which mainly includes the following steps:

[0005] Step 1: Prepare a polymer nano-reverse micelle solution, which is prepared by mixing a copolymer self-assembled reverse micelle with a solvent. The copolymer self-assembled reverse micelle is a nano-reverse micelle formed by the self-assembly of a styrene-methyl acrylate cinnamoyloxyethyl diblock copolymer in a solvent;

[0006] Step 2: Place the polymer nano-reverse micelle solution in a cuvette and scan the fluorescence spectrum in a fluorescence spectrometer;

[0007] Step 3: Dissolve the sample in water, and slowly add it dropwise to the polymer nano-reverse micelle solution under stirring. Then perform ultrasonic treatment, remove water, make up the volume, filter, and prepare the sample solution to be detected. Place it in a cuvette and mix, and scan the fluorescence spectrum in a fluorescence spectrometer to obtain a fluorescence spectrogram, and analyze and determine the pigment content in the sample solution to be detected.

[0008] Preferably, the specific preparation method of the polymer nano-reverse micelle solution in Step 1 is as follows:

[0009] Step a: Add styrene to a reactor, use anisole as a solvent, under the protection of an inert gas, add ethyl α-bromoisobutyrate as an initiator, add cuprous bromide as a catalyst, and then add N,N,N',N',N”-pentamethyldiethylenetriamine as a ligand. Heat up to 100 - 110 °C and stir for 3 - 8 h to prepare a polystyrene macroinitiator, where the molar ratio of styrene to ethyl α-bromoisobutyrate is (80 - 470):1, and the molar ratio of styrene to N,N,N',N',N”-pentamethyldiethylenetriamine is (30 - 167):1;

[0010] Step b: Add cinnamoyloxyethyl methacrylate to anisole as a solvent, under the protection of argon, add the polystyrene macroinitiator, add cuprous bromide as a catalyst, add N,N,N',N',N”-pentamethyldiethylenetriamine as a ligand. Heat up to 100 - 110 °C and stir for 3 - 8 h to obtain a styrene-cinnamoyloxyethyl methacrylate block copolymer, where the mass ratio of cinnamoyloxyethyl methacrylate to the polystyrene macroinitiator is 1:(1 - 4).

[0011] Preferably, the ultrasonic treatment time in Step 3 is 0.5 - 1 h.

[0012] Preferably, the filtration in Step 3 is carried out by microfiltration membrane, and the pore size of the microfiltration membrane is 0.2 - 0.8 μm.

[0013] Preferably, the concentration of the sample dissolved in water in Step 3 is 0.1 - 5 mg / mL.

[0014] The present invention also provides the application of the method for detecting food pigments based on fluorescence spectrometry in the detection of hydrophilic pigments.

[0015] The present invention has at least the following beneficial effects: The present invention uses polymer nano-reverse micelles as carriers for capturing and embedding hydrophilic pigments, and applies them to fluorescence spectrometry detection, improving the detection ability, with high sensitivity, low detection limit, good reproducibility, and reliable results.

[0016] Other advantages, objects, and features of the present invention will be partially reflected in the following description and partially understood by those skilled in the art through the research and practice of the present invention. Detailed Embodiment

[0017] The following further elaborates on the present invention in conjunction with examples, enabling those skilled in the art to implement it with reference to the description in the specification.

[0018] It should be understood that terms such as "having", "comprising", and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0019] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials, unless otherwise specified, can all be obtained through commercial channels.

[0020] <Example 1>

[0021] Step 1: Add styrene into a reactor, use anisole as a solvent, under the protection of an inert gas, add ethyl α-bromoisobutyrate as an initiator, add cuprous bromide as a catalyst, and then add N,N,N',N',N”-pentamethyldiethylenetriamine as a ligand. Heat to 100 °C and stir for 8 h to obtain a polystyrene macroinitiator, where the molar ratio of styrene to ethyl α-bromoisobutyrate is 80:1, and the molar ratio of styrene to N,N,N',N',N”-pentamethyldiethylenetriamine is 30:1;

[0022] Step 2: Add cinnamoyloxyethyl methacrylate into anisole as a solvent, under the protection of argon, add the polystyrene macroinitiator, add cuprous bromide as a catalyst, add N,N,N',N',N”-pentamethyldiethylenetriamine as a ligand. Heat to 100 °C and stir for 8 h to obtain a styrene-cinnamoyloxyethyl methacrylate block copolymer, where the mass ratio of cinnamoyloxyethyl methacrylate to the polystyrene macroinitiator is 1:1.2;

[0023] Step 3: Prepare a polymer nano-reverse micelle solution, which is prepared by mixing a copolymer self-assembled reverse micelle and a solvent. The copolymer self-assembled reverse micelle is a nano-reverse micelle formed by the self-assembly of a styrene-cinnamoyloxyethyl methacrylate diblock copolymer in a solvent;

[0024] Step 4: Place the polymer nano-reverse micelle solution in a cuvette and scan the fluorescence spectrum in a fluorescence spectrometer;

[0025] Step 5: Dissolve tartrazine in water to make a solution with a concentration of 0.1 mg / mL. Under stirring conditions, slowly add it dropwise into the polymer nano-reverse micelle solution, sonicate for 0.5 h, remove water, make up the volume, filter through a microporous membrane with a pore size of 0.2 μm to obtain the sample solution to be detected. Place it in a cuvette and mix, then scan the fluorescence spectrum in a fluorescence spectrometer to obtain a fluorescence spectrogram, analyze and determine the pigment content in the sample solution to be detected. According to the degree of fluorescence quenching of the spectrum and combined with the standard curve of tartrazine, the concentration of tartrazine can be calculated.

[0026] <Example 2>

[0027] Step 1: Add styrene into a reactor, use anisole as a solvent, under the protection of an inert gas, add ethyl α-bromoisobutyrate as an initiator, add cuprous bromide as a catalyst, and then add N,N,N',N',N”-pentamethyldiethylenetriamine as a ligand. Heat up to 110 °C and stir for 3 h to obtain a polystyrene macroinitiator, where the molar ratio of styrene to ethyl α-bromoisobutyrate is 470:1, and the molar ratio of styrene to N,N,N',N',N”-pentamethyldiethylenetriamine is 167:1;

[0028] Step 2: Add cinnamoyloxyethyl methacrylate into anisole as a solvent, under the protection of argon, add the polystyrene macroinitiator, add cuprous bromide as a catalyst, add N,N,N',N',N”-pentamethyldiethylenetriamine as a ligand. Heat up to 110 °C and stir for 3 h to obtain a block copolymer of styrene and cinnamoyloxyethyl methacrylate, where the mass ratio of cinnamoyloxyethyl methacrylate to the polystyrene macroinitiator is 1:4;

[0029] Step 3: Prepare a polymer nano-reverse micelle solution, which is prepared by mixing copolymer self-assembled reverse micelles and a solvent. The copolymer self-assembled reverse micelles are nano-reverse micelles formed by the self-assembly of styrene-cinnamoyloxyethyl methacrylate diblock copolymer in a solvent;

[0030] Step 4: Place the polymer nano-reverse micelle solution in a cuvette and scan the fluorescence spectrum in a fluorescence spectrometer;

[0031] Step 5: Dissolve sunset yellow in water to make a solution with a concentration of 5 mg / mL. Under stirring conditions, slowly add it dropwise into the polymer nano-reverse micelle solution, sonicate for 1 h, remove water, make up the volume, filter through a microporous membrane with a pore size of 0.8 μm to obtain the sample solution to be detected. Place it in a cuvette and mix, then scan the fluorescence spectrum in a fluorescence spectrometer to obtain a fluorescence spectrogram, analyze and determine the pigment content in the sample solution to be detected. According to the degree of fluorescence quenching of the spectrum and combined with the standard curve of sunset yellow, the concentration of sunset yellow can be calculated.

[0032] <Example 3>

[0033] Step 1: Add styrene into a reactor, use anisole as a solvent, under the protection of an inert gas, add ethyl α-bromoisobutyrate as an initiator, add cuprous bromide as a catalyst, and then add N,N,N',N',N”-pentamethyldiethylenetriamine as a ligand. Heat the temperature to 110 °C and stir for 5 h to obtain a polystyrene macroinitiator, where the molar ratio of styrene to ethyl α-bromoisobutyrate is 250:1, and the molar ratio of styrene to N,N,N',N',N”-pentamethyldiethylenetriamine is 100:1;

[0034] Step 2: Add cinnamoyloxyethyl methacrylate into anisole as a solvent, under the protection of argon, add the polystyrene macroinitiator, add cuprous bromide as a catalyst, add N,N,N',N',N”-pentamethyldiethylenetriamine as a ligand. Heat the temperature to 110 °C and stir for 5 h to obtain a styrene-cinnamoyloxyethyl methacrylate block copolymer, where the mass ratio of cinnamoyloxyethyl methacrylate to the polystyrene macroinitiator is 1:2;

[0035] Step 3: Prepare a polymer nano-reverse micelle solution, which is prepared by mixing a copolymer self-assembled reverse micelle and a solvent. The copolymer self-assembled reverse micelle is a nano-reverse micelle formed by the self-assembly of a styrene-cinnamoyloxyethyl methacrylate diblock copolymer in a solvent;

[0036] Step 4: Place the polymer nano-reverse micelle solution in a cuvette and scan the fluorescence spectrum in a fluorescence spectrometer;

[0037] Step 5: Dissolve tartrazine in water to make a concentration of 2 mg / mL, and slowly add it dropwise to the polymer nano-reverse micelle solution under stirring. Ultrasonic for 1 h, remove water, make up the volume, filter with a microporous membrane with a pore size of 0.5 μm to obtain a sample solution to be detected. Place it in a cuvette and mix, and scan the fluorescence spectrum in a fluorescence spectrometer to obtain a fluorescence spectrogram, analyze, and determine the pigment content in the sample solution to be detected. According to the degree of fluorescence quenching of the spectrum and combined with the standard curve of tartrazine pigment, the concentration of tartrazine pigment can be calculated.

[0038] <Comparative Example 1>

[0039] The steps are the same as those in Example 2, only replacing tartrazine with β-carotene. Since β-carotene is a hydrophobic pigment and cannot be captured by the polymer nano-reverse micelle, no fluorescence quenching phenomenon will occur, and it is not applicable to the detection method of food pigments based on fluorescence spectrometry described in the present invention.

[0040] <Determination of pigment content>

[0041] The detection results of Example 1, Example 2, and Example 3 are shown in Table 1:

[0042] It can be seen from the detection results that the detection results of Example 1, Example 2, and Example 3 for water-soluble lemon yellow pigment and sunset yellow pigment have small deviations, and the detection results are stable, indicating that the detection method described in the present invention is effective for hydrophilic pigments, has high selectivity, and low detection limit.

[0043] Table 1

[0044]

[0045] <Selectivity effect determination>

[0046] Adopt the steps described in Example 3, and additionally add interfering substances that may exist in the food matrix, including glycine, aspartic acid, sucrose, and glucose, to the sample solution to be detected, so that their concentrations in the sample to be detected are 0.5 mg / mL respectively. Record the fluorescence intensities before and after the addition. The measurement results show that when interfering substances are added to the solution to be detected, there is no obvious change in fluorescence intensity, indicating that the detection method of food pigments based on fluorescence spectroscopy described in the present invention has good anti-interference ability and good selectivity for hydrophilic pigments.

[0047] The number of devices and the processing scale described here are used to simplify the description of the present invention. The application, modification, and variation of the present invention are obvious to those skilled in the art.

[0048] Although the embodiments of the present invention have been disclosed as above, it is not limited to the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the examples shown and described here.

Claims

1. A detection method for food pigments based on fluorescence spectrometry, characterized in that, It mainly includes the following steps: Step 1: Prepare a polymer nano-reverse micelle solution, which is obtained by mixing copolymer self-assembled reverse micelles with a solvent. The copolymer self-assembled reverse micelles are nano-reverse micelles formed by the self-assembly of styrene-methyl acrylate cinnamoyloxyethyl diblock copolymer in a solvent; Step 2: Place the polymer nano-reverse micelle solution in a cuvette and scan the fluorescence spectrum in a fluorescence spectrometer; Step 3: Dissolve the sample in water, and slowly add it dropwise to the polymer nano-reverse micelle solution under stirring, then perform ultrasonic treatment, remove water, make up the volume, filter to obtain a sample solution to be detected, place it in a cuvette for mixing, scan the fluorescence spectrum in a fluorescence spectrometer to obtain a fluorescence spectrogram, and analyze and determine the pigment content in the sample solution to be detected; The specific preparation method of the polymer nano-reverse micelle solution in Step 1 is as follows: Step a: Add styrene to a reactor, use anisole as a solvent, under the protection of an inert gas, add ethyl α-bromoisobutyrate as an initiator, add cuprous bromide as a catalyst, and then add N,N,N',N',N''-pentamethyldiethylenetriamine as a ligand, heat up to 100-110 °C and stir for 3-8 h to obtain a polystyrene macroinitiator, where the molar ratio of styrene to ethyl α-bromoisobutyrate is (80-470):1, and the molar ratio of styrene to N,N,N',N',N''-pentamethyldiethylenetriamine is (30-167):1; Step b: Add methyl acrylate cinnamoyloxyethyl to anisole as a solvent, under the protection of argon, add the polystyrene macroinitiator, add cuprous bromide as a catalyst, add N,N,N',N',N''-pentamethyldiethylenetriamine as a ligand, heat up to 100-110 °C and stir for 3-8 h to obtain a styrene-methyl acrylate cinnamoyloxyethyl block copolymer, where the mass ratio of methyl acrylate cinnamoyloxyethyl to the polystyrene macroinitiator is 1:(1-4).

2. The detection method of food pigments based on fluorescence spectrometry according to claim 1, characterized in that, The ultrasonic time in Step 3 is 0.5-1 h.

3. The detection method of food pigments based on fluorescence spectrometry according to claim 1, wherein, In Step 3, microfiltration membrane filtration is used for filtration, and the pore size of the microfiltration membrane is 0.2-0.8 μm.

4. The detection method of food pigments based on fluorescence spectrometry according to claim 1, characterized in that, The concentration of the sample dissolved in water in Step 3 is 0.1-5 mg / mL.

5. Application of the method for detecting food pigments based on fluorescence spectrometry according to claim 1 in the detection of hydrophilic pigments.

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