Multicolor anti-counterfeiting food packaging film and preparation method thereof
By combining carbon dots with natural pigments and combining them with biomass base materials, multi-colored food packaging films are prepared, which solves the environmental pollution problems of existing petroleum-based plastic packaging films and chemical dyes, and achieves green, safe and well-being Food packaging materials with anti-counterfeiting function.
Patent Information
- Application Number
- CN202411796540.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-09
- Publication Date
- 2025-02-07
AI Technical Summary
The existing petroleum-based synthetic plastic packaging film is difficult to biodegrade, resulting in environmental pollution. At the same time, the use of chemical dyes also poses a threat to the environment, and lacks green, safe and anti-counterfeiting food packaging materials.
A multi-colored food packaging film is prepared by solution casting method by combining carbon dots with natural pigments, combined with biomass substrate materials such as carboxymethylcellulose and polyvinyl alcohol, and a multi-colored food packaging film is prepared, and the fluorescent characteristics of carbon dots are used to show an anti-counterfeiting pattern under ultraviolet light.
The preparation of a multi-color food packaging film based on a biomass substrate is realized, with green, safe and anti-counterfeiting functions, reducing the risk of environmental pollution, and providing low-cost food packaging solutions.
Smart Images
Figure CN119391021A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to an anti-counterfeit food packaging film composited with carbon dots and natural pigments and a preparation method thereof, belonging to the technical field of food packaging materials. Background Art
[0002] Carbon nanomaterials can be divided into zero-dimensional, one-dimensional and two-dimensional materials according to their dimensional characteristics. Among them, carbon dots, a new member of the zero-dimensional carbon-based fluorescent nanomaterial family, have attracted much attention due to their unique properties and broad application prospects. The size of carbon dots is usually less than 10 nm, and the morphology is spherical. Its fluorescence emission performance can be adjusted and controlled by parameters such as the size of nanoparticles, the degree of graphitization of carbon cores, the content of heteroatoms, and the degree of surface oxidation. Carbon dots have good photostability, high fluorescence quantum efficiency, large Stokes shift, and adjustable excitation emission. For example, under ultraviolet light, blue light or green light excitation, carbon dots can emit excitation-dependent or independent fluorescence. The multicolor fluorescence characteristics of carbon dots make it possible to apply them in anti-counterfeiting functions, especially in the food packaging film industry. The application of carbon dots is expected to provide a strong guarantee for the safety and authenticity of products. As a component of food commodities, food packaging plays a vital role in the production, storage and sales of food. However, the petroleum-based synthetic plastic packaging films currently widely used in the market will cause relatively serious pollution to the environment due to their difficult biodegradation characteristics. The development of bio-based food packaging films will be an important development direction in the packaging field. In addition, with the rapid development of the economy and the continuous improvement of people's living standards, among the dazzling array of commodities, foods with exquisite packaging and in line with consumer tastes can often stand out and quickly attract consumers' attention. The color effect of packaging design has a significant inductive effect on consumers. The use of color can not only enhance the visual recognition of commodities, but also make commodities more expressive and attractive, thereby arousing consumers' attention and purchasing interest. Also in view of the environmental problems that chemical dyes may cause, researchers in the field of food packaging are currently working on replacing chemical dyes with natural pigments. Natural pigments have good biocompatibility, rich color varieties, and certain antioxidant and antibacterial properties, showing great potential in the field of food packaging. These properties can be effectively transmitted and embedded in food packaging films through a series of advanced processing technologies, such as solvent extraction, microencapsulation or direct mixing. The specific combination process usually involves uniformly dispersing natural pigments in the polymer matrix of the packaging material, so as to achieve stable fixation and color expression of the pigment. For example, anthocyanins are widely studied because of their wide sources (25 different anthocyanins have been found in nature), wide pH response range and obvious color change, as well as antibacterial and antioxidant properties. Anthocyanin pH-responsive smart packaging films show significant color changes in the storage freshness detection of meat products, dairy products and aquatic products. In summary, in the process of reducing environmental pollution and reducing the cost of waste packaging disposal, it is particularly important to prepare a bio-based food packaging material. Combined with the fluorescent properties of carbon dots, the food packaging film is given the characteristics of fluorescent anti-counterfeiting. While ensuring the richness of food packaging colors, the preparation of a green, safe, anti-counterfeiting multi-color food packaging film will have broad application prospects. Summary of the invention
[0003] Purpose of the invention: The first object of the present invention is to provide a method for preparing a multi-color food packaging film based on a biomass substrate; The second purpose of the present invention is to utilize the fluorescent characteristics of carbon dots to composite carbon dots with multi-color food packaging film, to provide a new type of composite multi-color anti-counterfeiting food packaging film and to establish its anti-counterfeiting mode.
[0004] To achieve the above object, the present invention provides a technical solution: A method for preparing multi-color food packaging film based on biomass substrate The biomass substrate of the present invention is polyvinyl alcohol and carboxymethyl cellulose, the film forming method is a solution casting method, and the natural pigment is added by direct mixing during the film forming process. First, a mixture of carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) of different mass ratios is dissolved in deionized water, and the total solid content is 4.0-8.0 g / 100 mL solution. Then, 1.0-3.0 mL of glycerol is added as a plasticizer per 100 mL of film-forming solution, and natural pigments are introduced to achieve different color gradients (3.20-89.0 mg / 100 mL of film-forming solution per 100 mL). After stirring at an appropriate temperature for 30-60 min, the mixture is ultrasonically treated for about 20 min to obtain a colored composite film solution. Subsequently, 4.0-5.0 mL of the solution is poured into a glass culture dish with a diameter of ~40 mm to ensure sufficient coverage of the bottom surface of the culture dish. The solution is then cured in an oven preheated to 40-60 ° C for 6-10 h. After curing, the colored film is taken out and stored in a vacuum box for standby use.
[0005] The present invention discloses a polyvinyl alcohol which is a partially hydrolyzed type, has a hydrolysis degree of 73% to 99%, a polymerization degree of medium to high degree, and a viscosity of 19 to 67 (10 -3 Pa∙S) range (this viscosity value is measured at a concentration of 4%).
[0006] The natural pigments described in the present invention include, but are not limited to, one or more of amaranth red, peanut skin red, carmine, radish red, beet red, black bean red, black currant red, lac red, bilberry red, pepper red, red rice red, black bean red, sorghum red, indigo fruit red, natural beta-carotene, pepper orange, curcumin, gardenia yellow, citrus yellow, chrysanthemum yellow extract, safflower yellow, riboflavin, corn yellow, chlorophyll copper, indigo, brilliant blue, gardenia blue, anthocyanin, golden cherry brown, acorn shell brown, etc.
[0007] Preparation of a multi-color anti-counterfeiting food packaging film with composite carbon dots and establishment of anti-counterfeiting mode Preparation of composite anti-counterfeiting film: Fill the empty pen tube with a diameter of 0.5, 0.7 or 1.0 mm with carbon dot solution, or use a brush or brush to dip the carbon dot solution, and use writing tools to draw text or patterns on the surface of the multi-color food packaging film. After drawing, the surface of the film loaded with carbon dots is dried at room temperature for 2-4 hours to obtain a new type of composite carbon dot multi-color anti-counterfeiting food packaging film; Anti-counterfeiting mode establishment: Control the amount and concentration of carbon dots to ensure that the film with carbon dot pattern is invisible to the naked eye under sunlight. At the same time, due to the fluorescent emission of carbon dots, the pre-drawn pattern is clearly visible under a 365 nm ultraviolet light source. In addition, users can also use a household ultraviolet lamp to identify the pen, which can more conveniently realize the authenticity of food packaging film ( Figure 1 ).
[0008] The synthesis method of carbon dots (including carbon quantum dots, carbon nanodots, graphene quantum dots and carbonized polymer dots) in the present invention can adopt the methods disclosed in the prior art, such as carbonization method, water (solvent) thermal method and microwave method, and its raw materials are preferably natural products (flour, persimmon, green grass, wormwood, mulberry leaf, wolfberry, grape peel, watermelon peel, flour, silk, wool, milk, glucose and lignin, etc.), or chemical carbon sources (p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, hydroquinone, tartaric acid and urea, etc.). The present invention has no special restrictions on the preparation method of carbon dots, which can be prepared according to the technical scheme for preparing carbon dots well known to those skilled in the art.
[0009] The beneficial effects of the present invention are: (1) A method for preparing a biomass-based multicolor food packaging film is provided, in which carboxymethyl cellulose and polyvinyl alcohol are used as base materials to replace petroleum-based plastics such as polyethylene, low-density polyethylene, polystyrene, polycarbonate, polyethylene terephthalate (PET), and polypropylene; (2) In multi-color food packaging films, natural pigments replace chemical dyes, which are low-cost and environmentally safe. Different types and concentrations of natural pigments can give food packaging films rich colors; (3) A multi-color anti-counterfeiting food packaging film with composite carbon dots is provided, and a simple and feasible anti-counterfeiting mode is established. Carbon dots are widely available and have good optical properties. Combined with the multi-color food packaging film with biological substrate, a green and low-cost food anti-counterfeiting packaging material is provided to ensure food safety. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 Images of the anti-counterfeiting composite food packaging film under natural light (a) and ultraviolet light (b).
[0011] Figure 2 The breaking growth rate (EB, %) of carboxymethyl cellulose (CMC)-polyvinyl alcohol (PVA) biomass substrate films.
[0012] Figure 3 XRD spectrum of carboxymethyl cellulose (CMC)-polyvinyl alcohol (PVA) biomass substrate film.
[0013] Figure 4 Anthocyanin film with white carbon dot anti-counterfeiting pattern.
[0014] Figure 5 Color change of anthocyanin film (carbon dots / anthocyanin, CMC-PVA substrate) at different pH values (a), and white carbon dots anti-counterfeiting pattern visible under 365 nm UV light (b). DETAILED DESCRIPTION
[0015] In order to further illustrate the present invention, the carbon dot composite multicolor food packaging film material provided by the present invention is described in detail below with reference to the examples.
[0016] Example 1: A mixture of carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) in a mass ratio of 1:3 was dissolved in deionized water, and the total solid content was 4.0 g / 100 mL solution. Then, 1.0 mL of glycerol was added as a plasticizer to every 100 mL of film-forming solution, and anthocyanins (15.7~84.5 mg / 100 mL film-forming solution) were introduced. After stirring at an appropriate temperature for 30 min, the mixture was ultrasonically treated for about 20 min to obtain an anthocyanin composite film solution. Subsequently, 4.5 mL of the film-forming solution was poured into a glass culture dish with a diameter of ~40 mm, ensuring that the bottom of the culture dish was fully covered. The solution was then cured in an oven preheated to 40 °C for 6 h. After curing, the anthocyanin film was taken out and stored in a vacuum box for later use. The mechanical properties of the CMC-PVA film prepared by the above method were further tested, and its tensile strength could reach 8.81 MPa and its elongation at break could reach 91.72% ( Figure 2 ). The XRD spectrum shows that the CMC-PVA film shows a characteristic diffraction peak at a 2θ value of about 21.5°, corresponding to the (200) diffraction plane in the cellulose I crystal structure; the XRD absorption peak of the single PVA film is at 19.6°, attributed to the (101) crystal plane, which does not appear in the composite film spectrum. The above results indicate that the CMC in the base material composed of PVA and CMC is a semi-crystalline structure, and PVA forms a CMC / PVA co-assembled film in an amorphous state ( Figure 3 ).
[0017] Weigh 0.10 g of tartaric acid and 0.10 g of o-phenylenediamine, slowly add them to 8.0 mL of ethanol solvent, and after ultrasonic dispersion, immediately put them into an 18 mL polytetrafluoroethylene reactor and react at 180 °C for 12 h. The prepared product is filtered through a 0.22 µm microporous filter membrane, and the filtrate is dialyzed in an ethanol system for 24 h (dialysis bag MW1000). After changing ethanol 2 to 5 times, a carbon dot solution is obtained. The carbon dot solution is injected into an empty neutral pen tube to draw a figure. After drawing the figure, the anti-counterfeiting anthocyanin packaging film with composite carbon dots is dried at room temperature for 2 h to obtain an anthocyanin composite carbon dot anti-counterfeiting film, which can be seen as a clear cartoon image under ultraviolet light ( Figure 4 ).
[0018] Embodiment 2: Anthocyanin anti-counterfeiting film was prepared according to the method in Example 1 to examine whether the color-changing property of anthocyanin was transmitted to the film material. Specifically, a purple anthocyanin film was placed in a 0.1 mol∙L -1 HAc solution and 0.1 mol∙L -1 The color change was observed above the ammonia solution. The experimental results showed that the anthocyanin composite film showed characteristic pH sensitivity in both acid and alkaline solutions. The film turned red in acidic solutions and blue in alkaline solutions. It should be noted that the anti-counterfeiting performance is not affected by the pH value. The prefabricated triangular anti-counterfeiting pattern information can be clearly presented under different pH conditions ( Figure 5 ).
[0019] Embodiment 3: A mixture of carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) in a mass ratio of 1:3 was dissolved in deionized water with a total solid content of 4.0 g / 100 mL of solution. Then, 1.0 mL of glycerol was added as a plasticizer per 100 mL of the film-forming solution, and 0.3-1.9 mL of gardenia yellow and gardenia blue (both at a concentration of 20 g / L) in a volume ratio of 1:1 were introduced. After stirring at an appropriate temperature for 30 min, the mixture was ultrasonically treated for about 20 min to obtain a green composite film solution. Subsequently, 5.0 mL of the solution was poured into a glass Petri dish with a diameter of ~40 mm, ensuring that the bottom of the Petri dish was fully covered. The solution was then cured in an oven preheated to 40 °C for 6 h. After curing, the green food packaging film was taken out and stored in a vacuum box for later use.
[0020] Embodiment 4: A mixture of carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) in a mass ratio of 1:3 was dissolved in deionized water with a total solid content of 4.0 g / 100 mL of solution. Then, 1.0 mL of glycerol was added as a plasticizer to every 100 mL of the film-forming solution, and 0.1 to 0.6 mL of gardenia blue and amaranth (both 30 g / L) were mixed in a volume ratio of 6:1. After stirring for 30 min at an appropriate temperature, the mixture was ultrasonically treated for about 20 min to obtain a purple composite film solution. Subsequently, 5.0 mL of the solution was poured into a glass Petri dish with a diameter of ~40 mm, ensuring that the bottom of the Petri dish was fully covered. The solution was then cured in an oven preheated to 40 °C for 6 h. After curing, the purple food packaging film was taken out and stored in a vacuum box for later use.
[0021] Embodiment 5: A mixture of carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) in a mass ratio of 1:3 was dissolved in deionized water with a total solid content of 4.0 g / 100 mL of solution. Then, 1.0 mL of glycerol was added as a plasticizer per 100 mL of the film-forming solution, and 0.1-1.15 mL of gardenia yellow and amaranth (both 30 g / L) in a volume ratio of 20:1 were introduced. After stirring for 30 min at an appropriate temperature, the mixture was ultrasonically treated for about 20 min to obtain an orange composite film solution. Subsequently, 5.0 mL of the solution was poured into a glass Petri dish with a diameter of ~40 mm, ensuring sufficient coverage of the bottom surface of the Petri dish. The solution was then cured in an oven preheated to 40 °C for 6 h. After curing, the orange food packaging film was taken out and stored in a vacuum box for later use.
[0022] Embodiment 6: A mixture of carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) in a mass ratio of 1:3 was dissolved in deionized water with a total solid content of 4.0 g / 100 mL solution. Then, 1.0 mL of glycerol was added as a plasticizer per 100 mL of film-forming solution, and amaranth (2.15~30 mg / 100 mL of film-forming solution) was introduced. After stirring at an appropriate temperature for 30 min, the mixture was ultrasonically treated for about 20 min to obtain a red composite film solution. Subsequently, 4.5 mL of the solution was poured into a glass Petri dish with a diameter of ~40 mm, ensuring sufficient coverage of the bottom surface of the Petri dish. The solution was then cured in an oven preheated to 40 °C for 6 h. After curing, the red film was taken out and stored in a vacuum box for later use.
[0023] 0.20 g of lignin was placed in 15 mL of deionized water and magnetically stirred for 5 min to ensure uniform mixing. Subsequently, the above reactants were transferred to a 50 mL hydrothermal reactor and reacted at 200 °C for 10 h. After the reaction was completed, the mixture was cooled to room temperature. The sample was centrifuged at 8000 r / min for 15 min. After centrifugation, only the upper clear liquid was retained. Subsequently, the upper clear liquid was filtered using a filter membrane with a pore size of 0.22 μm, transferred to a dialysis bag with a molecular weight cutoff of 1000 Da, and dialyzed in deionized water for 24 h. The inner solution was taken to obtain a lignin blue carbon dot solution (365 nm wavelength excitation, emission peak at ~440 nm). The lignin carbon dot solution was injected into the pen tube of a neutral pen to draw a graph. After drawing the graph, the amaranth red packaging film of the composite carbon dots was dried at room temperature for 2 h to obtain a red anti-counterfeiting packaging film of the composite carbon dots.
[0024] The above embodiments are only used to help understand the method and core idea of the present invention. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications may be made to the present invention, and these improvements and modifications should also be within the scope of protection of the claims of the present invention.
Claims
1. A method for preparing a multi-color food packaging film material based on a biomass substrate, characterized in that: The biomass substrate is polyvinyl alcohol and carboxymethyl cellulose, the film-forming method is solution casting, and natural pigments are added by direct mixing during the film-forming process. First, a mixture of carboxymethyl cellulose and polyvinyl alcohol with different mass ratios was dissolved in deionized water, and the total solid content was 4.0 ~ 8.0 g / 100 mL solution. Then 1.0 ~ 3.0 mL of glycerol was added as a plasticizer per 100 mL of film-forming solution, and natural pigments (single or a combination of multiple pigments) were introduced to achieve different color gradients (3.20 ~ 89.0 mg / 100 mL of film-forming solution). After stirring at an appropriate temperature for 30 ~ 60 min, the mixture was ultrasonically treated for about 20 min to obtain a colored composite film solution. Subsequently, 4.0 ~ 5.0 mL of the solution was poured into a glass Petri dish with a diameter of ~ 40 mm, ensuring sufficient coverage of the bottom surface of the Petri dish. The solution was then cured in an oven preheated to 40 ~ 60 °C for 6 ~ 10 h. After curing, the colored film was taken out and stored in a vacuum box for later use.
2. The material according to claim 1, characterized in that: The polyvinyl alcohol is a partially hydrolyzed type, with a hydrolysis degree of 73% to 99%, a polymerization degree of medium to high degree, and a viscosity of 19 to 67 (10 -3 Pa∙S) range (this viscosity value is measured at a concentration of 4%).
3. The material according to claim 1, characterized in that: The pigment is a natural pigment, including but not limited to one or more of amaranth red, peanut skin red, carmine, radish red, beet red, black bean red, black currant red, lac red, bilberry red, pepper red, red rice red, black bean red, sorghum red, indigo red, natural beta-carotene, pepper orange, curcumin, gardenia yellow, citrus yellow, chrysanthemum yellow extract, safflower yellow, riboflavin, corn yellow, chlorophyll copper, indigo, brilliant blue, gardenia blue, anthocyanin, golden cherry brown, acorn shell brown, etc.
4. Preparation of a multi-color anti-counterfeiting food packaging film with composite carbon dots and establishment of an anti-counterfeiting mode, characterized in that: The composite anti-counterfeiting film is prepared by filling an empty pen tube with a diameter of 0.5, 0.7 or 1.0 mm with a carbon dot solution, or by dipping a brush or brush into the carbon dot solution and drawing text or patterns on the surface of the multi-color food packaging film with the help of a writing tool. After drawing, the surface of the film loaded with carbon dots is dried at room temperature for 2 to 4 hours to obtain a new type of composite carbon dot multi-color anti-counterfeiting food packaging film; The anti-counterfeiting mode is established by controlling the amount and concentration of carbon dots to ensure that the film with the carbon dot pattern is invisible to the naked eye under sunlight. At the same time, due to the fluorescent emission of carbon dots, the pre-drawn pattern is clearly visible under a 365 nm ultraviolet light source. In addition, users can also use a household ultraviolet light identification pen to more conveniently identify the authenticity of food packaging film.
5. The method for preparing the anti-counterfeit food packaging film and establishing the anti-counterfeit mode according to claim 4, characterized in that: The carbon dots are one or more of carbon quantum dots, carbon nanodots, graphene quantum dots and carbonized polymer dots.