Preparation method and application of active intelligent packaging film based on curcumin and anthocyanin

Abstract

The invention provides a preparation method and application of an active intelligent packaging film based on curcumin and anthocyanin, and belongs to the technical field of food medicine and pharmaceutical materials. The active intelligent packaging film comprises the following raw materials: CZAC nanoparticles, carrageenan, water, glycerol and calcium chloride. The preparation method comprises the following steps: respectively preparing a curcumin-zein ethanol water solution and a chondroitin sulfate-anthocyanidin water solution which contain indicator factors, and obtaining the curcumin-zein-anthocyanidin-chondroitin sulfate quaternary mutually-embedded composite structure nano-particles by using an automatic injector and adopting an anti-solvent precipitation method, thereby obtaining the curcumin-zein-anthocyanidin-chondroitin sulfate quaternary mutually-embedded composite structure nano-particles. The quaternary mutually-inlaid composite structure nanoparticles have smaller and uniform particle sizes, the active intelligent packaging film based on the composite structure nanoparticles is high in stability and has the pH indication capability, the color of the film is obviously changed along with decay of fish meat, and decay and deterioration of the fish meat can be effectively delayed.

Description

Technical Field

[0001] The invention relates to the technical field of food medicine and pharmaceutical materials, and in particular to a preparation method and application of an active intelligent packaging film based on curcumin and anthocyanin. Background Art

[0002] In recent years, the preparation of a small amount of nanoparticles often uses a needle and a syringe for manual injection, draws a certain amount of solution and uses the anti-solvent precipitation method or pH-driven method to inject it into the organic solution, so that it is coated by the different solubility of the liquid to form nanoparticles. The above method can better and more clearly see the injection situation, and at the same time, due to the small preparation amount, it is impossible to use high-precision instruments for preparation, and there is no finished device on the market for this phenomenon.

[0003] For traditional manual production, different devices need to be assembled manually, and due to different needle scales or human errors, the particle sizes of the produced nanoparticles may be different. It is impossible to more accurately determine the amount of liquid added and the amount of injection, which can easily cause a certain degree of data deviation. Compared with automatic injection, manual injection requires holding the syringe until the liquid in the tube is injected. During the process, the nanoparticles will have different sizes due to human factors, and it is difficult to control the same speed manually. The automatic injector has greatly improved this, and it also relieves the pressure on the experimenter, allowing more things to be done at the same time and becoming more efficient.

[0004] Environmental pollution issues have also attracted public attention, and people are increasingly inclined to choose environmentally friendly products. Packaging materials made of natural materials are increasingly attracting public attention and prompting researchers to conduct research. Polysaccharides, as biological macromolecules, have the advantages of wide sources, environmental friendliness, low cost and good composition performance, and are widely used in the preparation of biofilms. Carrageenan, a linear polysaccharide extracted from red algae, contains many hydroxyl and sulfate groups, which enables it to effectively combine with bioactive compounds such as preservatives and indicators. Therefore, carrageenan has shown great potential in the development of multifunctional films such as extending the shelf life of food and showing the freshness of food.

[0005] In order to make biofilms more intelligent and accurate, substances such as curcumin (Cur), anthocyanin (ATH) are safe, non-toxic to the human body, edible, and have pH indication functions. They are natural active ingredients and are often added to biomass films. However, single natural pigments have certain limitations. Anthocyanins are unstable and easily affected by factors such as temperature, light, oxygen, and metal ions. When used as food packaging materials, oxygen is the main reason affecting its properties; curcumin has limitations in its color rendering range. There is no color change when the pH value is in the range of 1 to 7, and it cannot effectively cover the entire shelf life of fresh fish. At present, researchers have mixed anthocyanins, curcumin and other pigments and applied them to food packaging. The properties of the resulting films are often better than those of single pigments, but there are still problems such as insufficient stability and insufficient accuracy of indication. Summary of the invention

[0006] In view of the deficiencies of the above prior art, the present invention provides a method for preparing an active intelligent packaging film based on curcumin and anthocyanin and its application. The present invention uses zein with good biocompatibility and amphiphilicity to prepare a curcumin-zein solution, uses acidic mucopolysaccharide chondroitin sulfate (CS) to prepare anthocyanin-chondroitin sulfate solution, uses a syringe to prepare quaternary mutually embedded composite structure nanoparticles, then disperses the nanoparticles in a carrageenan matrix, and uses a blending casting technology to prepare a nanoparticle-filled "fresh-keeping-indicator" composite film.

[0007] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0008] In a first aspect, the present invention provides an active intelligent packaging film based on curcumin and anthocyanin, comprising the following raw materials: curcumin-zein-anthocyanin-chondroitin sulfate (CZAC) nanoparticles, carrageenan, water, glycerol, and calcium chloride;

[0009] The method for preparing the CZAC nanoparticles comprises the following steps: injecting a curcumin-zein ethanol aqueous solution into a chondroitin sulfate-anthocyanidin aqueous solution using a syringe, and removing the solvent to obtain CZAC quaternary interlocking composite structure nanoparticles.

[0010] The present invention uses mixed pigments curcumin and anthocyanin as indicator factors, utilizes the interaction between protein-polysaccharide-polyphenol, and uses a syringe to automatically prepare curcumin-zein-anthocyanin-chondroitin sulfate quaternary interlocking composite structure nanoparticles by downstream flow; the composite structure nanoparticles have a small and uniformly distributed particle size (average particle size of 90 nm), which is conducive to improving its water solubility and stability. The composite structure nanoparticles are evenly dispersed in the carrageenan base film, and the small and uniform particle size promotes its uniform dispersion in the carrageenan base film. The composite structure interlocked in the nanoparticles interacts with the carrageenan containing numerous hydroxyl groups and sulfate groups, further enhancing the stability of the composite film.

[0011] Preferably, the mass ratio of the carrageenan to the CZAC nanoparticles is (0.6-0.8): (0.2-0.4).

[0012] More preferably, the mass ratio of the carrageenan to the CZAC nanoparticles is 0.6:0.4.

[0013] Preferably, the mass ratio of carrageenan to glycerol is (2.5-4):1.

[0014] Preferably, the mass ratio of carrageenan to calcium chloride is (100-160):3.

[0015] Preferably, the volume ratio of the curcumin-zein solution to the chondroitin sulfate-anthocyanidin solution is 20:60.

[0016] Preferably, the preparation method of the curcumin-zein ethanol aqueous solution is as follows: dissolving curcumin and zein in an ethanol aqueous solution, and stirring for 6 to 10 hours in a dark environment to obtain the curcumin-zein ethanol aqueous solution.

[0017] Preferably, the mass ratio of curcumin to zein is 4:100.

[0018] Preferably, the dosage ratio of curcumin to ethanol aqueous solution is 6:10 (w / v, mg / mL).

[0019] Preferably, the ethanol aqueous solution contains 80% ethanol (v / v).

[0020] Preferably, the chondroitin sulfate-anthocyanidin aqueous solution is prepared as follows: stir chondroitin sulfate in water in the dark for 30 minutes to fully dissolve, and then add anthocyanidin to obtain the chondroitin sulfate-anthocyanidin aqueous solution.

[0021] Preferably, the mass ratio of chondroitin sulfate to anthocyanin is 16:50.

[0022] Preferably, the dosage ratio of the chondroitin sulfate to water is 8:10 (w / v, mg / mL).

[0023] Preferably, the syringe is assembled as follows:

[0024] (1) Prepare an injection needle with a caliber of 0.55 x 20 mm to 0.7 x 25 mm, a hose that matches the injection needle (with a universal interface on the hose head), and a syringe of the required capacity (without a needle);

[0025] (2) Assemble the needle to the end of the hose, connect the universal connector of the hose to the end of the syringe, assemble to form an automatic syringe, fix the syringe on the stand so that it is above the container, and start the operation; if the syringe has a piston inside, it needs to be removed before assembly to prevent negative pressure from preventing the solution from flowing down.

[0026] In a second aspect, the present invention provides a method for preparing the active smart packaging film based on curcumin and anthocyanin, comprising: uniformly dispersing the composite structure nanoparticles into a carrageenan-based film to obtain the active smart packaging film based on curcumin and anthocyanin.

[0027] Preferably, the method for preparing the active intelligent packaging film based on curcumin and anthocyanin comprises the following steps:

[0028] S1, mix carrageenan and water at 80°C, add glycerin, and cool the solution to 50°C to obtain a carrageenan base film liquid;

[0029] S2, mixing the carrageenan base film liquid, CZAC nanoparticles, and calcium chloride solution uniformly to obtain a CZAC nanoparticle-carrageenan composite solution;

[0030] S3, placing the CZAC nanoparticle-carrageenan composite solution in a mold, drying it into a film, and obtaining an active intelligent packaging film based on curcumin and anthocyanin.

[0031] Preferably, the concentration of carrageenan in the carrageenan base film liquid is 15 mg / mL.

[0032] Preferably, the concentration of carrageenan in the CZAC nanoparticle-carrageenan composite solution is 5-9 mg / mL.

[0033] Preferably, the concentration of the calcium chloride solution is 5.25 mg / mL.

[0034] Preferably, the drying temperature is 40° C. and the drying time is 72 h.

[0035] In a third aspect, the present invention provides application of the active smart packaging film or the active smart packaging film prepared by the method in food packaging.

[0036] Compared with the prior art, the present invention is beneficial in that:

[0037] 1. The active intelligent packaging film based on curcumin and anthocyanin provided by the present invention has the ability of pH indication. As the fish meat spoils, the color of the film changes accordingly, and it can effectively delay the spoilage of the fish meat.

[0038] 2. The present invention prepares two solutions containing indicator factors respectively, and obtains curcumin-zein-anthocyanidin-chondroitin sulfate quaternary interlocking composite structure nanoparticles by an automatic syringe and an anti-solvent precipitation method. The quaternary interlocking composite structure nanoparticles of the present invention have a smaller and uniform particle size, and thus have better water solubility and stability; the above characteristics are conducive to the uniform dispersion of the composite structure nanoparticles in the carrageenan base film, further improving the stability and quality of the active intelligent packaging film.

[0039] 3. The active intelligent packaging film of the present invention is easy to use and has a simple preparation method. The raw materials of the film are all green, natural, environmentally friendly, and biodegradable materials and will not cause any pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A diagram of a device for preparing nanoparticles by an automatic syringe according to the present invention;

[0041] Figure 2 The test results of the color change rate of the films 0.4CZAC-CAR and 0.4AC-CAR;

[0042] Figure 3 The scanning electron microscope images of the surface and cross section of the thin films 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR, and CAR; wherein, Figure 3 A and 3B are surface scanning electron micrographs of 0.2CZAC-CAR; Figure 3 C, 3D is a cross-sectional scanning electron micrograph of 0.2CZAC-CAR; Figure 3 E, 3F are surface scanning electron micrographs of 0.3CZAC-CAR; Figure 3 G, 3H are cross-sectional scanning electron micrographs of 0.3CZAC-CAR; Figure 3 I, 3J are surface scanning electron microscopy images of 0.4CZAC-CAR; Figure 3 K, 3L are cross-sectional scanning electron micrographs of 0.4CZAC-CAR;

[0043] Figure 4 It is a comparison chart of transmittance and opacity of the films 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR, and CAR;

[0044] Figure 5 This is a comparison chart of thermal stability of films 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR, and CAR;

[0045] Figure 6 The pH color development test results of the films 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR and CAR;

[0046] Figure 7 The hydrophobicity comparison diagram of the films 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR, and CAR;

[0047] Figure 8 The following is a comparison chart of the changes in the color of the mandarin fish meat labeled with 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR, and CAR films during the storage period and the color changes of the films; Figure 8 a is the film color at different times; Figure 8 b is the actual picture of the film; Figure 8 c is the color change rate;

[0048] Fig. 9 The following is a comparison of the changes in the color of the film 0.4CZAC-CAR and CAR labeled mandarin fish meat during storage and the film; Fig. 9 a is the TVB-N value change curve; Fig. 9 b is the color change rate; Fig. 9 c is a real picture of mandarin fish meat. DETAILED DESCRIPTION

[0049] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] The present invention provides an active intelligent packaging film based on curcumin and anthocyanin, comprising the following raw materials: carrageenan, water, glycerin, calcium chloride, curcumin-zein-anthocyanin-chondroitin sulfate (CZAC) nanoparticles;

[0051] The method for preparing the CZAC nanoparticles comprises the following steps: using a syringe to inject a curcumin-zein ethanol aqueous solution into a chondroitin sulfate-anthocyanidin aqueous solution to obtain CZAC quaternary interlocking composite structure nanoparticles.

[0052] In some examples, the mass ratio of the carrageenan to the CZAC nanoparticles is (0.6-0.8): (0.2-0.4).

[0053] In some examples, the mass ratio of carrageenan to glycerol is (2.5~4):1.

[0054] In some examples, the mass ratio of carrageenan to calcium chloride is (100~160):3.

[0055] In the following specific examples, the preparation method of the curcumin-zein ethanol aqueous solution is as follows: 78 mg of curcumin and 1950 mg of zein are weighed and dissolved in 130.0 mL of ethanol aqueous solution (80%, v / v), and stirred with a magnetic stirrer at 300 rpm / min in the dark for 6 hours to obtain the curcumin-zein ethanol aqueous solution for standby use.

[0056] In the following specific examples, the preparation method of the chondroitin sulfate-anthocyanidin aqueous solution is as follows: weigh 296 mg of chondroitin sulfate in 370.0 mL of distilled water, put it into a 35°C water bath with magnetic stirring, stir in the dark at 300 rpm / min for 30 minutes to fully dissolve, and then add 925 mg of anthocyanidin to obtain a chondroitin sulfate-anthocyanidin aqueous solution for use.

[0057] In the following specific embodiments, the syringe is a syringe that can be automatically injected, and the preparation method of the syringe is as follows:

[0058] (1) Prepare a 0.6 x 25 mm injection needle and a 2 cm long hose at the curved interface. Assemble the needle to the hose head and set aside.

[0059] (2) Assemble the needle tube part to the head of the 20 mL syringe through the connecting port (remove the piston first), fix the syringe on the iron frame column, and fix the height of the syringe to about 6.5~7 cm from the mouth of the beaker for use. Figure 1 shown.

[0060] Example 1

[0061] An active intelligent packaging film based on curcumin and anthocyanin, comprising the following raw materials: 2240.0 mg of carrageenan, 290.0 mL of distilled water, 640.0 mg of glycerol, 48.0 mg of calcium chloride, and 960.0 mg of CZAC nanoparticles;

[0062] Prepare as follows:

[0063] (1) Preparation of CZAC nanoparticles: Curcumin-zein ethanol aqueous solution was placed in an automatic syringe, and the anti-solvent was placed in a chondroitin sulfate-anthocyanidin aqueous solution, and stirred for 20 min. The solvent was removed to obtain CZAC nanoparticles. The volume ratio of the curcumin-zein solution to the chondroitin sulfate-anthocyanidin solution was 20:60.

[0064] (2) Preparation of carrageenan base film liquid: Weigh 2240.0 mg of carrageenan, add 170.67 mL of distilled water, and stir evenly in a water bath (80 °C, 300 rpm / min) to form a 15 mg / mL carrageenan solution. Then add 640.0 mg of glycerol as a plasticizer to the carrageenan solution, and cool the solution to 50 °C to obtain the carrageenan base film liquid for later use.

[0065] (3) Prepare 5.25 mg / mL calcium chloride solution: weigh 52.5 mg of calcium chloride, add 10 mL of distilled water, stir evenly to obtain 5.25 mg / mL calcium chloride solution for later use.

[0066] (4) Preparation of CZAC nanoparticle-carrageenan composite solution: The carrageenan base film liquid of step (2), the CZAC nanoparticles of step (1) and the calcium chloride solution of step (3) were mixed, wherein the dry mass of the CZAC nanoparticles was 960.0 mg and the calcium chloride solution was 9.14 mL, and water was added to a total volume of 290.0 mL to obtain a CZAC nanoparticle-carrageenan composite solution.

[0067] (5) The CZAC nanoparticle-carrageenan composite solution was poured into a non-stick coating mold with a side length of 28 cm by the solution casting method and dried in a constant temperature incubator (40 °C, 72 h) to form a film. The film was named 0.3CZAC-CAR and stored in a desiccator at room temperature until the performance indicators of the composite film were measured.

[0068] Example 2

[0069] An active intelligent packaging film based on curcumin and anthocyanin, comprising the following raw materials: 2560.0 mg of carrageenan, 290.0 mL of distilled water, 640.0 mg of glycerol, 48.0 mg of calcium chloride, and 640.0 mg of CZAC nanoparticles;

[0070] Prepare as follows:

[0071] (1) Preparation of CZAC nanoparticles: Curcumin-zein ethanol aqueous solution was placed in an automatic syringe, and the anti-solvent was placed in a chondroitin sulfate-anthocyanidin aqueous solution, and stirred for 20 min. The solvent was removed to obtain CZAC nanoparticles. The volume ratio of the curcumin-zein solution to the chondroitin sulfate-anthocyanidin solution was 20:60.

[0072] (2) Preparation of carrageenan base film liquid: Weigh 2560.0 mg of carrageenan, add 149.33 mL of distilled water, and stir evenly in a water bath (80 °C, 300 rpm / min) to form a 15 mg / mL carrageenan solution. Then add 640.0 mg of glycerol as a plasticizer to the carrageenan solution, and cool the solution to 50 °C to obtain the carrageenan base film liquid for later use.

[0073] (3) Prepare 5.25 mg / mL calcium chloride solution: weigh 52.5 mg of calcium chloride, add 10 mL of distilled water, stir evenly to obtain 5.25 mg / mL calcium chloride solution for later use.

[0074] (4) Preparation of CZAC nanoparticle-carrageenan composite solution: The carrageenan base film liquid of step (2), the CZAC nanoparticles of step (1) and the calcium chloride solution of step (3) were mixed, wherein the dry mass of the CZAC nanoparticles was 640.0 mg and the calcium chloride solution was 9.14 mL, and water was added to a total volume of 290.0 mL to obtain a CZAC nanoparticle-carrageenan composite solution.

[0075] (5) The CZAC nanoparticle-carrageenan composite solution was poured into a non-stick coating mold with a side length of 28 cm by the solution casting method and dried in a constant temperature incubator (40 °C, 72 h) to form a film. The film was named 0.2CZAC-CAR and stored in a desiccator at room temperature until the performance indicators of the composite film were measured.

[0076] Example 3

[0077] An active intelligent packaging film based on curcumin and anthocyanin, comprising the following raw materials: 1920.0 mg of carrageenan, 290.0 mL of distilled water, 640.0 mg of glycerol, 48.0 mg of calcium chloride, and 1280.0 mg of CZAC nanoparticles;

[0078] Prepare as follows:

[0079] (1) Preparation of CZAC nanoparticles: Curcumin-zein ethanol aqueous solution was placed in an automatic syringe, and the anti-solvent was placed in a chondroitin sulfate-anthocyanidin aqueous solution, and stirred for 20 min. The solvent was removed to obtain CZAC nanoparticles. The volume ratio of the curcumin-zein solution to the chondroitin sulfate-anthocyanidin solution was 20:60.

[0080] (2) Preparation of carrageenan base film liquid: Weigh 1920.0 mg of carrageenan, add 149.33 mL of distilled water, and stir evenly in a water bath (80 °C, 300 rpm / min) to form a 15 mg / mL carrageenan solution. Then add 640.0 mg of glycerol as a plasticizer to the carrageenan solution, and cool the solution to 50 °C to obtain the carrageenan base film liquid for later use.

[0081] (3) Prepare 5.25 mg / mL calcium chloride solution: weigh 52.5 mg of calcium chloride, add 10 mL of distilled water, stir evenly to obtain 5.25 mg / mL calcium chloride solution for later use.

[0082] (4) Preparation of CZAC nanoparticle-carrageenan composite solution: The carrageenan base film liquid of step (2), the CZAC nanoparticles of step (1) and the calcium chloride solution of step (3) were mixed, wherein the dry mass of the CZAC nanoparticles was 1280.0 mg and the calcium chloride solution was 9.14 mL, and water was added to a total volume of 290.0 mL to obtain a CZAC nanoparticle-carrageenan composite solution.

[0083] (5) The CZAC nanoparticle-carrageenan composite solution was poured into a non-stick coating mold with a side length of 28 cm by the solution casting method and dried in a constant temperature incubator (40 °C, 72 h) to form a film. The film was named 0.4CZAC-CAR and stored in a desiccator at room temperature until the performance indicators of the composite film were measured.

[0084] Comparative Example 1

[0085] A packaging film, comprising the following raw materials: 3200.0 mg of carrageenan, 290.0 mL of distilled water, 640.0 mg of glycerol, and 48.0 mg of calcium chloride;

[0086] Prepare as follows:

[0087] (1) Preparation of carrageenan base film liquid: Weigh 3200.0 mg of carrageenan, add 170.67 mL of distilled water, and stir evenly in a water bath (80 °C, 300 rpm / min) to form a 15 mg / mL carrageenan solution. Then, add 640.0 mg of glycerol as a plasticizer to the carrageenan solution, and cool the solution to 50 °C to obtain the carrageenan base film liquid for later use.

[0088] (2) Prepare 5.25 mg / mL calcium chloride solution: weigh 52.5 mg of calcium chloride, add 10 mL of distilled water, stir evenly to obtain 5.25 mg / mL calcium chloride solution for later use.

[0089] (3) Preparation of carrageenan film-forming solution: Mix the carrageenan base film solution of step (1) and the calcium chloride solution of step (2), wherein the calcium chloride solution is 9.14 mL, and add water to a total volume of 290.0 mL to obtain a carrageenan film-forming solution.

[0090] (4) The carrageenan film-forming liquid was poured into a non-stick coating mold with a side length of 28 cm by the solution casting method and dried in a constant temperature incubator (40 °C, 72 h) to form a film. The film was named CAR and stored in a desiccator at room temperature until the performance indicators of the composite film were measured.

[0091] Comparative Example 2

[0092] An active intelligent packaging film based on curcumin and anthocyanin is prepared according to the following method:

[0093] (1) Preparation of carrageenan base film liquid: Weigh 3200.0 mg of carrageenan, add 170.67 mL of distilled water, and stir evenly in a water bath (80 °C, 300 rpm / min) to form a 15 mg / mL carrageenan solution. Then, add 640.0 mg of glycerol as a plasticizer to the carrageenan solution, and cool the solution to 50 °C to obtain the carrageenan base film liquid for later use.

[0094] (2) Prepare 5.25 mg / mL calcium chloride solution: weigh 52.5 mg of calcium chloride, add 10 mL of distilled water, stir evenly to obtain 5.25 mg / mL calcium chloride solution for later use.

[0095] (3) Preparation of carrageenan film-forming solution: Under magnetic stirring, a curcumin anthocyanin solution (5.0 mg / mL) (the amounts of curcumin and anthocyanin are the same as those in Example 3) is injected into the carrageenan base film solution of step (1) using a syringe, followed by adding 9.14 mL of the calcium chloride solution of step (2) and adding water to a total volume of 290.0 mL to obtain a carrageenan film-forming solution.

[0096] (4) The carrageenan film-forming liquid was poured into a 28 cm x 28 cm non-stick coating mold using the solution casting method and dried in a constant temperature incubator (40 °C, 72 h) to form a film. The film was named 0.4AC-CAR and stored in a desiccator at room temperature until the performance indicators of the composite film were measured.

[0097] Performance Testing

[0098] The chromaticity, opacity, thickness, transmittance, pH color rendering, water contact angle, mechanical properties and thermal properties of the films obtained in Examples 1 to 3 and Comparative Example 1 were tested.

[0099] 1. Color change rate determination

[0100] Film samples 0.4CZAC-CAR and 0.4AC-CAR with a size of 4.0 cm x 4.0 cm were taken and exposed to the same light (30 W / m 2 ), and lasted for 72 h. During this period, the color of the composite film was measured using a colorimeter, L (light and dark), a (red and green), b (yellow and blue), and the color change rate of the composite film was calculated as follows:

[0101]

[0102] In the formula, L i 、a i 、b i is the initial color parameter of the composite film, L c 、a c 、b c It is the color measurement of the composite film after being exposed to light.

[0103] Test results such as Figure 2 As shown. Figure 2 A shows that in 0.4CZAC-CAR, curcumin and anthocyanins are evenly dispersed. In 0.4AC-CAR, curcumin and anthocyanins are obviously unevenly distributed and aggregated, which may be due to the different polarities of curcumin and anthocyanins, making them difficult to dissolve. The above results show that CZAC nanoparticles effectively promote the uniformity of curcumin and anthocyanins after mixing. Figure 2 As shown in Figure B, after 3 days of illumination, the color change rate of 0.4AC-CAR was 69.19%, which was much higher than the color change rate of 0.4CZAC-CAR (15.85%), indicating that the nano-encapsulation technology of the present invention can improve the stability of the mixed pigment.

[0104] 2. Morphological determination

[0105] The surfaces and interfaces of the thin film samples 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR, and CAR were scanned using a scanning electron microscope. The surface scanning electron microscope images (×1000) and cross-sectional scanning electron microscope images (×1000) obtained at an accelerating voltage of 5 kV are shown in Figure 2. Figure 2As shown, Figure 3 A and 3B are surface scanning electron micrographs of 0.2CZAC-CAR; Figure 3 C, 3D is a cross-sectional scanning electron micrograph of 0.2CZAC-CAR; Figure 3 E, 3F are surface scanning electron micrographs of 0.3CZAC-CAR; Figure 3 G and 3H are cross-sectional scanning electron micrographs of 0.3CZAC-CAR; 3I and 3J are surface scanning electron micrographs of 0.4CZAC-CAR; Figure 3 K and 3L are cross-sectional scanning electron micrographs of 0.4CZAC-CAR. All samples were gold-sprayed before observation.

[0106] from Figure 3 It can be seen that some slight protrusions were observed in the CZAC-loaded composite film, but there was no obvious sign of nanoparticle aggregation on the film surface, indicating that the CZAC nanoparticles were uniformly dispersed in the carrageenan matrix and that the CZAC nanoparticles and carrageenan had good compatibility and miscibility.

[0107] 3. Thickness and color measurement

[0108] (1) Thickness measurement

[0109] The thickness of the film samples 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR, and CAR were measured by a screw micrometer with an accuracy of 0.001 mm. Three points were randomly selected to measure the film thickness.

[0110] (2) Chroma measurement

[0111] The color of the film samples 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR, and CAR was characterized using a colorimeter. The L (light and dark), a (red and green), b (yellow and blue), and ΔE (total color difference) values ​​were used to characterize the surface color, and a white standard plate was used as a background reference for instrument calibration. The total color difference (ΔE) of the film was calculated as follows:

[0112]

[0113] In the formula, , and value( =94.41, = -1.21 and = -1.58) is the color parameter of the standard plate, and L 0 ，a0 and b 0 The values ​​are the color parameters of the films. Each sample was repeated three times.

[0114] The thickness and color results of the films are shown in Table 1.

[0115] Table 1: Opacity, colorimetric parameters (L, a and b) and color difference (ΔE) of the films

[0116]

[0117] As shown in Table 1, under natural light conditions, the film CAR appears colorless and transparent; as the amount of CZAC nanoparticles added to carrageenan increases from 20% (the proportion of CZAC nanoparticles in the total mass of CZAC nanoparticles and carrageenan) to 40% (the proportion of CZAC nanoparticles in the total mass of CZAC nanoparticles and carrageenan), the color of the film gradually changes from green-brown to reddish-brown, which is mainly due to the presence of curcumin and anthocyanins in CZAC nanoparticles. The L value reflects the brightness of the composite film. As the proportion of CZAC nanoparticles increases, the L value of the composite film decreases from 33.47 (0.2CZAC-CAR) to 22.80 (0.4CZAC-CAR), indicating that the increase in the proportion of CZAC nanoparticles helps to enhance the film's UV resistance.

[0118] 4. Transmittance and opacity measurement

[0119] (1) The UV-visible spectra of the film samples 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR and CAR (3 cm x 1 cm) were measured using a UV-visible spectrophotometer in the wavelength range of 200-800 nm.

[0120] (2) Opacity measurement

[0121] The opacity of the film samples 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR, and CAR was measured using a UV-visible spectrophotometer. The absorbance of the film (8 mm x 30 mm) was measured at 600 nm. The opacity of the film was calculated as follows:

[0122]

[0123] In the formula, A 600 The absorbance of the film at 600 nm, x is the thickness of the film (mm). Each sample was repeated three times.

[0124] The transmittance and opacity of the film are as follows Figure 4 As shown, with an opacity of 1.14 A mm - Compared with the film CAR of ¹, the opacity of the composite film containing 0.2CZAC nanoparticles is significantly improved, reaching 24.54 A mm - ¹, with the increase of CZAC nanoparticles addition, the opacity of the film 0.4CZAC-CAR further increased to 41.25 A mm - ¹. The significant increase in opacity is due to the CZAC nanoparticles being evenly dispersed in the film matrix, which enhances light scattering and absorption within the film. With the addition of CZAC nanoparticles, the transmittance of the composite film is significantly reduced, especially in the UV range of 200-400 nm, where the transmittance drops to almost zero. The main reason for this effect is that the curcumin and anthocyanin in the CZAC nanoparticles have strong UV absorption properties, and these natural pigments effectively improve the UV blocking ability of the composite film by enhancing its UV blocking properties and opacity.

[0125] 5. Thermal stability determination

[0126] The thermal stability of the film samples 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR and CAR was analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) using a Q600 SDT instrument by adding 5.0 mg of the packaging film into a crucible. The temperature scanning range was 30~600 ℃, the heating rate was 10 ℃ / min and the nitrogen flow rate was 50 mL / min.

[0127] The thermal stability results of the films are shown in Figure 5 As shown. Figure 5 It can be seen that at 600 °C, the total weight loss of pure carrageenan film (CAR) is 67.81%. In contrast, the weight loss of the composite film (0.4CZAC-CAR) with the addition of CZAC nanoparticles is significantly reduced (p < 0.05) to only 62.83%, indicating that the thermal stability of the film is significantly enhanced due to the addition of nanoparticles.

[0128] 6. pH colorimetric determination

[0129] The pH colorimetric properties of the films 0.2CZAC-CAR, 0.3CZAC-CAR, 0.4CZAC-CAR, and CAR were measured by immersing the films (40 mm x 40 mm) in different buffer solutions (pH 2-12) at room temperature for 10 min. The color changes of the composite films were recorded using a colorimeter. Three replicates were performed for each sample.

[0130] The pH color development results of the film are as follows Figure 6 As shown. Figure 6 It can be seen that the film shows obvious color changes under different pH values. Specifically, under acidic conditions (pH 2.0-4.0), the composite film is red; under neutral to weakly alkaline conditions (pH 5.0-10.0), it turns into dark brown; under strongly alkaline conditions (pH 11.0-12.0), it turns into light brown. In addition, as the amount of CZAC nanoparticles added increases, the color change becomes more obvious.

[0131] 7. Determination of water contact angle

[0132] The water contact angle (WCA) of the composite films was measured using a contact angle meter (JY-PHA, China Unitech Co., Ltd.) to obtain the average contact angle on both sides of the droplet. Each type of composite film was measured three times at different positions.

[0133] The water contact angle results are as follows Figure 7 The results show that the contact angle of water with the film CAR is 70.37 o ) compared with the composite film with 20% CZAC nanoparticles (0.2CZAC-CAR has a water contact angle of 62.60 o ) showed weak hydrophobicity, while the composite films 0.3CZAC-CAR and 0.4CZAC-CAR with an addition amount exceeding 20% ​​(water contact angles were 75.83 o , 77.00 o The above results show that 0.3CZAC-CAR and 0.4CZAC-CAR have strong hydrophobicity.

[0134] Application Testing

[0135] In this application test, the inventors explored the effect of carrageenan-based composite film loaded with curcumin-zein-anthocyanin-chondroitin sulfate nanoparticles on the quality index of mandarin fish during cold storage, as well as the changes in the film's color index during cold storage, and systematically evaluated the preservation indicator effect of the film on mandarin fish. The specific implementation steps are as follows:

[0136] The experimental group was made by gluing the particle-filled composite film (0.2 CZAC-CAR, 0.3 CZAC-CAR, 0.4 CZAC-CAR) (4 cm x 4 cm) to the inside of a culture dish containing mandarin fish pieces (5 cm x 3 cm), while the control group was made by gluing the pure carrageenan film (CAR) (4 cm x 4 cm) to the inside of an empty culture dish. The non-film control group included a culture dish without any film and mandarin fish pieces (5 cm x 3 cm).

[0137] The fish pieces rinsed with distilled water and wiped dry were placed in each culture dish respectively. All samples were stored at room temperature for 24 hours. The indicators at 0, 6, 12, and 24 hours were measured respectively. The total volatile basic nitrogen (TVB-N) and film color of mandarin fish were measured. The volatile basic nitrogen measurement method was determined according to the GB 5009228-2016 method. The test results are as follows: Figure 8 , Fig. 9 shown.

[0138] from Figure 8 It can be seen that after 24 h of storage, the color change rates of the films 0.2 CZAC-CAR, 0.3 CZAC-CAR, and 0.4 CZAC-CAR were 22.78%±4.14%, 36.53%±2.01%, and 56.30%±5.33%, respectively. The results show that the higher the content of CZAC nanoparticles, the better the color indication effect of the composite film; after 24 h of storage of fish meat, the color of the film 0.4CZAC-CAR obviously changed from reddish brown to dark brown. This result shows that the film can be used to detect the freshness of fish meat. Fig. 9 It can be seen that the TVB-N value of the fish meat after storage for 24 h in the film 0.4CZAC-CAR is 13.68±0.39 mg / 100 g, which is still within the fresh limit value. In addition, the TVB-N value of the film 0.4CZAC-CAR did not increase within 0-6 h, and the fish meat was still fresh, indicating that its antiseptic effect on fish meat is particularly obvious. This result proves that the film 0.4CZAC-CAR can delay the corruption of mandarin fish. In summary, the carrageenan-based composite film loaded with CZAC nanoparticles can delay the corruption of food, improve the antiseptic and fresh-keeping effect of food, and change color during the food corruption process to achieve the effect of indicating the freshness of food.

[0139] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, the technical solution of the present invention can be modified and changed in many simple ways, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. An active intelligent packaging film based on curcumin and anthocyanin, characterized in that: The following raw materials are included: carrageenan, water, glycerin, calcium chloride, CZAC nanoparticles; The method for preparing the CZAC nanoparticles comprises the following steps: injecting a curcumin-zein ethanol aqueous solution into a chondroitin sulfate-anthocyanidin aqueous solution using a syringe, and removing the solvent to obtain the CZAC nanoparticles.

2. The active intelligent packaging film based on curcumin and anthocyanin according to claim 1, characterized in that: The mass ratio of the carrageenan to the CZAC nanoparticles is (0.6-0.8): (0.2-0.4).

3. The active intelligent packaging film based on curcumin and anthocyanin according to claim 2, characterized in that: The mass ratio of the carrageenan to the CZAC nanoparticles is 0.6:0.

4.

4. The active intelligent packaging film based on curcumin and anthocyanin according to claim 1, characterized in that: The volume ratio of the curcumin-zein solution to the chondroitin sulfate-anthocyanidin solution is 20:

60.

5. The active intelligent packaging film based on curcumin and anthocyanin according to claim 1, characterized in that: The preparation method of the curcumin-zein ethanol aqueous solution is as follows: dissolving curcumin and zein in an ethanol aqueous solution, stirring for 6 to 10 hours in a dark environment, and obtaining the curcumin-zein ethanol aqueous solution; the mass ratio of the curcumin to the zein is 4:100; and the dosage ratio of the curcumin to the ethanol aqueous solution is 6:10 (w / v, mg / mL).

6. The active intelligent packaging film based on curcumin and anthocyanin according to claim 1, characterized in that: The preparation method of the chondroitin sulfate-anthocyanidin aqueous solution is as follows: stir chondroitin sulfate in water in the dark for 30 minutes to fully dissolve it, and then add anthocyanidin to obtain a chondroitin sulfate-anthocyanidin aqueous solution; the mass ratio of chondroitin sulfate to anthocyanidin is 16:50; the dosage ratio of chondroitin sulfate to water is 8:10 (w / v, mg / mL).

7. The active intelligent packaging film based on curcumin and anthocyanin according to claim 1, characterized in that: The assembly method of the syringe is as follows: (1) Prepare an injection needle with a caliber of 0.55 x 20 mm to 0.7 x 25 mm, a hose that matches the injection needle, and a syringe without a needle; (2) Assemble the needle to the tail of the hose, connect the universal interface of the hose to the tail of the syringe, assemble to form an automatic syringe, fix the syringe on the stand so that it is above the container, and then start the operation.

8. A method for preparing an active intelligent packaging film based on curcumin and anthocyanin, characterized in that: include: The CZAC nanoparticles are uniformly dispersed in a carrageenan-based film to obtain an active smart packaging film based on curcumin and anthocyanin.

9. The method for preparing an active intelligent packaging film based on curcumin and anthocyanin according to claim 8, characterized in that: The following steps are involved: S1, mixing carrageenan and water at 80°C, adding glycerin, and mixing to obtain a carrageenan base film liquid; S2, mixing the carrageenan base film liquid, CZAC nanoparticles, and calcium chloride solution uniformly to obtain a CZAC nanoparticle-carrageenan composite solution; S3, placing the CZAC nanoparticle-carrageenan composite solution in a mold, drying it into a film, and obtaining an active intelligent packaging film based on curcumin and anthocyanin.

10. Use of the active intelligent packaging film according to any one of claims 1 to 7 or the active intelligent packaging film prepared by the method according to any one of claims 8 to 9 in food packaging.

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