Food packaging film with freshness indication function as well as preparation method and application of food packaging film

Abstract

The invention discloses a food packaging film with a freshness indicating function as well as a preparation method and application thereof, and relates to the technical field of food packaging materials. According to the packaging film, the alizarin red, the lignin and the guar gum form a synergistic effect, so that the toughness of a network skeleton is remarkably improved, and the negative influence of the alizarin red on the tensile strength of the skeleton is reduced, so that the mechanical comprehensive performance of the food packaging film is favorably improved; moreover, the loading of alizarin red reduces the water vapor permeability of the food packaging film, and is beneficial to improving the barrier property of the packaging film; meanwhile, the alizarin red endows the packaging film with reversible color switching under stimulation of ammonia gas and acetic acid, and real-time monitoring of food freshness changes is achieved; the food packaging film has mechanical toughness and a proper water vapor barrier, is green and safe, has no potential toxic and side effects, can be completely biodegraded, has renewable raw materials, can significantly improve the problem of food waste caused by environmental uncertainty, and is suitable for large-scale popularization and application.

Description

Technical Field

[0001] This invention relates to the field of food packaging materials technology, mainly to the field of packaging film materials technology, and specifically to a food packaging film with freshness indication function, its preparation method and application. Background Technology

[0002] During food transportation and storage, the diverse environmental factors such as temperature fluctuations, humidity differences, and microbial cross-contamination make the path of quality degradation highly unpredictable, which has become a key reason for the waste of about one-third of the world's food. Traditional food packaging materials, such as polyethylene, polypropylene, or aluminum-plastic composite packaging materials, can effectively isolate contamination, but they are inert systems. They cannot capture in real time the alkaline TVB-N (trimethylamine, ammonia, etc.) released by protein-based foods due to spoilage or the acidic acetic acid volatilized from high-carbohydrate foods, nor can they actively intervene in the microenvironment within the packaging. This makes it easy to over-discard or misjudge hidden spoilage if relying solely on static shelf-life labels for identification. At the same time, petrochemical substrates also bring environmental problems such as difficulty in recycling and microplastic pollution.

[0003] Therefore, there is an urgent need to develop an indicator tag that uses natural biomass as a base material, requires no external power supply or complex reading equipment, and can quickly provide freshness signals with the naked eye. This tag can accurately reflect changes in headspace pH caused by spoilage metabolites such as TVB-N or acetic acid throughout the entire transportation, warehousing and retail chain, thereby providing timely freshness indications and significantly reducing misjudgments of freshness caused by environmental uncertainties such as temperature and humidity fluctuations and uncontrollable storage and transportation conditions.

[0004] Patent CN110606996A discloses a food packaging film using modified anthocyanins as an indicator of food freshness. This color-indicating food preservation film is prepared from benzoic acid-modified anthocyanins, low-methoxyl pectin, chitosan, glycerol, and acetic acid. Addressing the problem of natural anthocyanins being easily oxidized and decomposed in the natural environment, benzoic acid is grafted onto the natural anthocyanin molecules to enhance their stability. Using modified anthocyanins as a color indicator, low-methoxyl pectin, chitosan, and glycerol are mixed to prepare a color-indicating food preservation film. The color of this preservation film changes accordingly with changes in food freshness.

[0005] Patent CN118146546A discloses a method for preparing and applying an antibacterial and indicator film. This method uses a bacterial cellulose and pullulan polysaccharide membrane as the substrate for a bactericidal and preservative film. Bambusoide, anthocyanins, and alizarin are loaded onto the surface of the bacterial cellulose membrane and applied to photocatalytic antibacterial action. The combination of bacterial cellulose and polysaccharides gives the film substrate good mechanical properties. Different pigment complexes enable the film to exhibit sensitive pH color changes, and the addition of photosensitizers also induces high bactericidal efficiency.

[0006] Based on the foregoing, various preservation film technologies have been developed that use natural biomass as a substrate, require no external power supply or complex reading devices, and can quickly provide freshness signals with the naked eye. However, existing preservation films with natural biomass as a substrate that can quickly provide freshness signals with the naked eye suffer from poor mechanical properties due to unreasonable raw material formulations and preparation methods. In particular, the addition of color-indicating components greatly reduces the mechanical properties of the substrate. At the same time, existing preservation films of this type also have problems with unreasonable water vapor transmission rate and contact angle (hydrophobicity), resulting in poor preservation function and making them unsuitable for large-scale promotion and application. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of poor mechanical properties and preservation function of existing biomass preservation films, and to propose a food packaging film with freshness indication function, its preparation method and application.

[0008] To achieve the above-mentioned objective, this invention proposes a food packaging film with freshness indication function, which is prepared from the following raw materials in parts by weight: 10-100 parts of sodium lignosulfonate, 100-190 parts of cationic guar gum, 0.5-3 parts of alizarin red (sodium 1,2-dihydroxyanthraquinone-3-sulfonate, ARS) and 0.4-1.0 parts of polyethylene glycol.

[0009] This invention discloses a food packaging film with freshness indication function. With the plasticizing assistance of polyethylene glycol, alizarin red is loaded onto a network formed by a specific ratio of lignin and guar gum as its backbone. This not only creates a synergistic effect between alizarin red and lignin and guar gum (causing intermolecular hydrogen bond rearrangement), significantly improving the toughness of the network backbone, but also reduces the negative impact of alizarin red on the tensile strength of the backbone, thus improving the overall mechanical properties of the food packaging film. Furthermore, the loading of alizarin red can seal the gaps in the backbone network, thereby reducing the water vapor permeability of the food packaging film and improving its barrier properties. Simultaneously, alizarin red imparts a reversible color switch to the packaging film under the stimulation of ammonia and acetic acid, enabling real-time monitoring of freshness changes during the storage of high-protein foods. This invention's food packaging film combines mechanical toughness with a suitable water vapor barrier, is green and safe, has no potential toxic side effects, and is completely biodegradable. Its raw materials are renewable, and it can significantly improve the problem of food waste caused by environmental uncertainties, making it suitable for large-scale promotion and application.

[0010] Preferably, the average molecular weight of the polyethylene glycol is 300-500; more preferably, the average molecular weight is 400. The preferred polyethylene glycol molecular weight has better film-forming properties, and the resulting food packaging film has better overall performance in terms of tensile strength and elongation.

[0011] Preferably, the food packaging film is prepared from the following raw materials in parts by weight: 30-80 parts sodium lignosulfonate, 120-170 parts cationic guar gum, 1-2 parts alizarin red and 0.5 parts polyethylene glycol; the food packaging film prepared from the preferred raw materials has better overall performance.

[0012] To achieve the above-mentioned objectives, the present invention further proposes a method for preparing a food packaging film with a freshness indication function, comprising the following steps: (1) Dissolve the sodium lignosulfonate and cationic guar gum in 40-60 times their total weight of water, then add polyethylene glycol and stir to dissolve to obtain a mixed solution; (2) Add alizarin red to the mixed solution and stir at 40-60℃ for 0.5-2h to obtain the film-forming solution; (3) After casting the film-forming liquid into a film, it is dried to obtain a food packaging film with freshness indication function.

[0013] This invention discloses a method for preparing a food packaging film with freshness indication function. By specifically adjusting the process parameters in the preparation method, alizarin red can form a synergistic effect when loaded into the lignin and guar gum network skeleton. As a result, the packaging film loaded with alizarin red not only has excellent tensile strength and toughness, but also has a suitable water vapor barrier and real-time monitoring function for changes in food freshness. The preparation method of this invention is simple, environmentally friendly, cost-effective, and produces stable product performance, making it suitable for large-scale production of food packaging films with freshness indication function.

[0014] In step (1), preferably, the stirring and dissolving temperature is room temperature, the speed is 600~800 r / min, and the time is 30-60 min.

[0015] In step (2), preferably, the stirring speed of the stirring reaction is 600~800 r / min.

[0016] In step (3), preferably, the film-forming liquid is poured into a polytetrafluoroethylene plate to form a film; the film-forming speed is fast and the operation is convenient.

[0017] Preferably, the drying process is carried out at a temperature of 40-60°C for 12-24 hours; the preferred drying conditions have low energy consumption, fast drying speed, and will not affect the membrane performance.

[0018] To further achieve the above-mentioned objectives, this invention also proposes the application of a food packaging film with freshness indication function in smart food packaging materials, ammonia content monitoring materials, or environmental safety warning materials.

[0019] Preferably, the food packaging film is used for smart packaging of one or more types of aquatic products and meat.

[0020] The beneficial effects of the technical solution of this invention are as follows: 1. In the food packaging film of the present invention, alizarin red forms a synergistic effect with lignin and guar gum (causing intermolecular hydrogen bond rearrangement), which significantly improves the toughness of the network skeleton while reducing the negative impact of alizarin red on the tensile strength of the skeleton, thereby improving the overall mechanical properties of the food packaging film.

[0021] 2. The alizarin red loaded in the food packaging film of the present invention can block the gaps in the skeleton network, thereby reducing the water vapor permeability of the food packaging film and improving the barrier properties of the packaging film.

[0022] 3. The alizarin red loaded in the food packaging film of the present invention can give the packaging film a reversible color switch under the stimulation of ammonia and acetic acid, which can realize real-time monitoring of the freshness changes of high-protein food during storage.

[0023] 4. The food packaging film of this invention has both mechanical toughness and a suitable water vapor barrier. It is green and safe, has no potential toxic side effects, and is completely biodegradable. Its raw materials are renewable, and it can significantly improve the problem of food waste caused by environmental uncertainty. It is suitable for large-scale promotion and application.

[0024] 5. The preparation method of the food packaging film of the present invention, by specifically adjusting the process parameters in the preparation method, enables alizarin red to form a synergistic effect with lignin and guar gum network skeleton, so that the prepared packaging film not only has excellent tensile strength and toughness, but also has a suitable water vapor barrier and real-time monitoring function for changes in food freshness.

[0025] 6. The preparation method of this invention is simple, environmentally friendly, cost-effective, and produces stable products, making it suitable for large-scale production of food packaging films with freshness indication function. Attached Figure Description

[0026] Figure 1 The images show the infrared spectra of the packaging films in Examples 1-6 and Comparative Example 1 of this invention.

[0027] Figure 2 The images show the XRD patterns of the packaging films in Examples 1-6 and Comparative Example 1 of this invention. Detailed Implementation

[0028] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the embodiments described herein.

[0029] Examples 1-6

[0030] A food packaging film with freshness indication function is prepared from the following raw materials in parts by weight: 30 parts sodium lignosulfonate, 170 parts cationic guar gum, 0.5 parts polyethylene glycol-400 and alizarin red; wherein the specific parts by weight of alizarin red are shown in Table 1. Table 1. Dosage of Alizarin Red in Examples 1-6

[0031] The specific preparation method is as follows: (1) Dissolve the sodium lignosulfonate and cationic guar gum in 10,000 parts (50 times the total weight of the two) of water, add polyethylene glycol, and stir to dissolve (at room temperature, at a speed of 700 r / min, for 60 min) to obtain a mixed solution. (2) Add alizarin red to the mixed solution, stir at 50°C (700 r / min) for 1 h to obtain the film-forming solution; (3) The film-forming liquid is poured into a polytetrafluoroethylene plate to form a film, and then dried (at a temperature of 40°C for 12 hours) to obtain a food packaging film with freshness indication function.

[0032] Examples 7-10

[0033] A food packaging film with freshness indication function is prepared from the following raw materials in parts by weight: 1.5 parts alizarin red, 0.5 parts polyethylene glycol-400, sodium lignosulfonate, and cationic guar gum; wherein the specific parts by weight of sodium lignosulfonate and cationic guar gum are shown in Table 2. Table 2. Dosage of Alizarin Red in Examples 7-10

[0034] The specific preparation method is as follows: (1) Dissolve the sodium lignosulfonate and cationic guar gum in 10,000 parts (50 times the total weight of the two) of water, add polyethylene glycol, and stir to dissolve (at room temperature, at a speed of 700 r / min, for 60 min) to obtain a mixed solution. (2) Add alizarin red to the mixed solution, stir at 50°C (700 r / min) for 1 h to obtain the film-forming solution; (3) The film-forming liquid is poured into a polytetrafluoroethylene plate to form a film, and then dried (at a temperature of 40°C for 12 hours) to obtain a food packaging film with freshness indication function.

[0035] Example 11

[0036] A food packaging film with freshness indication function is prepared from the following raw materials in parts by weight: 30 parts sodium lignosulfonate, 170 parts cationic guar gum, 1.5 parts alizarin red and 0.4 parts polyethylene glycol-300. The specific preparation method is as follows: (1) Dissolve the sodium lignosulfonate and cationic guar gum in 10,000 parts (60 times the total weight of the two) of water, add polyethylene glycol, and stir to dissolve (at room temperature, at a speed of 600 r / min, for 60 min) to obtain a mixed solution; (2) Add alizarin red to the mixed solution, stir at 60°C (speed 800 r / min) for 0.5 h to obtain the film-forming solution; (3) The film-forming liquid is poured into a polytetrafluoroethylene plate to form a film, and then dried (at a temperature of 60°C for 12 hours) to obtain a food packaging film with freshness indication function.

[0037] Example 12

[0038] A food packaging film with freshness indication function is prepared from the following raw materials in parts by weight: 30 parts sodium lignosulfonate, 170 parts cationic guar gum, 1.5 parts alizarin red and 1.0 part polyethylene glycol-500. The specific preparation method is as follows: (1) Dissolve the sodium lignosulfonate and cationic guar gum in 10,000 parts (40 times the total weight of the two) of water, add polyethylene glycol, and stir to dissolve (at room temperature, at a speed of 800 r / min, for 30 min) to obtain a mixed solution; (2) Add alizarin red to the mixed solution, stir at 40°C (speed 600 r / min) for 2 h to obtain the film-forming solution; (3) The film-forming liquid is poured into a polytetrafluoroethylene plate to form a film, and then dried (at a temperature of 40°C for 24 hours) to obtain a food packaging film with freshness indication function.

[0039] Comparative Example 1

[0040] A food packaging film is prepared from the following raw materials in parts by weight: 30 parts sodium lignosulfonate, 170 parts cationic guar gum and 0.5 parts polyethylene glycol-400; The specific preparation method is as follows: (1) Dissolve the sodium lignosulfonate and cationic guar gum in 10,000 parts (50 times the total weight of the two) of water, add polyethylene glycol, and stir to dissolve (at room temperature, at a speed of 700 r / min, for 60 min) to obtain a mixed solution. (2) After stirring the mixed solution at 50°C (700 r / min) for 1 h, a film-forming solution is obtained; (3) The film-forming liquid is poured into a polytetrafluoroethylene plate to form a film, and then dried (at a temperature of 40°C for 12 hours) to obtain a food packaging film.

[0041] Comparative Example 2

[0042] A food packaging film was prepared using the same formulation and method as in Example 3, except that cationic guar gum was replaced with guar gum (guar gum was not subjected to cationization modification treatment).

[0043] Comparative Example 3

[0044] A food packaging film was prepared using the same formulation and method as in Example 3, except that sodium lignin sulfonate was replaced with alkaline lignin.

[0045] Comparative Example 4

[0046] A food packaging film was prepared using the same formula and method as in Example 3, except that the temperature of the stirring reaction in step (2) of the preparation process was changed to 70°C.

[0047] Comparative Example 5

[0048] A food packaging film was prepared using the same formula and method as in Example 3, except that the temperature of the stirring reaction in step (2) of the preparation process was changed to 30°C.

[0049] Comparative Example 6

[0050] A food packaging film was prepared using the same formula and method as in Example 3, except that the amount of alizarin red added was adjusted to 0.4 parts.

[0051] Comparative Example 7

[0052] A food packaging film was prepared using the same formulation and method as in Example 3, except that the amount of alizarin red added was adjusted to 3.5 parts.

[0053] Comparative Example 8

[0054] A food packaging film was prepared using the same formulation and method as in Example 7, except that the sodium lignosulfonate was 5 parts by weight and the cationic guar gum was 195 parts by weight.

[0055] Comparative Example 9

[0056] A food packaging film was prepared using the same formulation and method as in Example 7, except that the sodium lignosulfonate was 110 parts by weight and the cationic guar gum was 90 parts by weight.

[0057] Comparative Example 10

[0058] A food packaging film was prepared using the same formulation and method as in Example 3, except that polyethylene glycol was replaced with citric acid.

[0059] Comparative Example 11

[0060] A food packaging film was prepared using the same formulation and method as in Example 3, except that polyethylene glycol was replaced with glycerin.

[0061] Comparative Example 12

[0062] A food packaging film was prepared using the same formulation and method as in Example 3, except that polyethylene glycol was replaced with calcium chloride.

[0063] Experimental example: 1. The packaging films (0.05 mm thick) prepared in Examples 1-12 and Comparative Examples 1-12 were subjected to tensile strength (tested according to GB / T1040-2006), elongation at break (tested according to GB / T1040-2006), water vapor transmission rate (tested according to ASTM E 96), and contact angle (measured using a contact angle measuring instrument: the packaging film was cut into circular samples with a diameter of 2 cm, fixed on the measuring stage, and the water contact angle of the sample was measured by the seat drop method. The test liquid volume was 2 μL). The results are shown in Table 3.

[0064] Table 3 Performance test results of packaging films in Examples 1-12 and Comparative Examples 1-12

[0065] 2. The packaging films prepared in Examples 1-12 and Comparative Examples 1-12 were tested for their indicator function: The packaging films were exposed to ammonia (0.08 mol / L) and acetic acid (0.8 mol / L) at room temperature (25°C) for 30 min, respectively, and the color change of the indicator films was observed. The results are shown in Table 4.

[0066] Table 4. Test results of the indicating function of the packaging films in Examples 1-12 and Comparative Examples 1-12

[0067] 3. Shrimp Freshness Monitoring Experiment: Fresh shrimp were placed in sealed plastic boxes. The packaging films prepared in Comparative Example 1 and Example 3 were placed next to the shrimp, with no direct contact between the indicator film and the shrimp. The shrimp samples were stored in a 28°C incubator for 24 hours. Changes in shrimp freshness and the corresponding color changes of the indicator film were observed and recorded periodically. The results are shown in Table 5.

[0068] Table 5 Results of Shrimp Freshness Monitoring Experiment

[0069] 4. The structures of the packaging film prepared in Comparative Example 1 (labeled as CLA-0) and the packaging films prepared in Examples 1-6 (labeled as CLA-1, CLA-2, CLA-3, CLA-4, CLA-5, and CLA-6, respectively) were determined using an infrared spectrometer. The results are shown in the figure. Figure 1 As shown. By Figure 1 It can be seen that the spectral profiles and characteristic wavenumbers of the seven films are almost identical, indicating that the introduction of alizarin red did not change the basic framework of the matrix. (1140 cm⁻¹) -1 Belongs to sulfonic acid group stretching, 1600 and 1520 cm -1 Corresponding to aromatic ring C=C and skeletal vibrations, 3330 and 2940 cm⁻¹ -1 The peaks reflect the vibrations of OH and CH, respectively. The stretching peak of the hydroxyl group shifts slightly to a higher wavenumber, while the bending peak shifts slightly to a lower wavenumber, suggesting intermolecular hydrogen bond rearrangement.

[0070] 5. The packaging films prepared in Comparative Example 1 and Examples 1-6 were tested using XRD, and the results are as follows: Figure 2 As shown. Figure 2 The results indicate that all samples exhibit a broad, diffuse peak at 2θ≈20°, maintaining an amorphous structure, and that there are no significant differences in peak position and intensity, confirming that alizarin red is uniformly dispersed in the blend film and has not formed an independent crystalline phase.

[0071] The above description is merely a specific embodiment of the present invention and the technical principles used, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A food packaging film with freshness indication function, characterized in that, It is prepared from the following raw materials in parts by weight: 10-100 parts sodium lignosulfonate, 100-190 parts cationic guar gum, 0.5-3 parts alizarin red and 0.4-1.0 parts polyethylene glycol.

2. The food packaging film according to claim 1, characterized in that, The average molecular weight of the polyethylene glycol is 300-500.

3. The food packaging film according to claim 1, characterized in that, The food packaging film is prepared from the following raw materials in parts by weight: 30-80 parts sodium lignosulfonate, 120-170 parts cationic guar gum, 1-2 parts alizarin red and 0.5 parts polyethylene glycol.

4. A method for preparing the food packaging film according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Dissolve the sodium lignosulfonate and cationic guar gum in 40-60 times their total weight of water, then add polyethylene glycol and stir to dissolve to obtain a mixed solution; (2) Add alizarin red to the mixed solution and stir at 40-60℃ for 0.5-2h to obtain the film-forming solution; (3) After casting the film-forming liquid into a film, it is dried to obtain a food packaging film with freshness indication function.

5. The method for preparing the food packaging film according to claim 4, characterized in that, In step (1), the stirring and dissolving temperature is room temperature, the speed is 600~800 r / min, and the time is 30-60 min.

6. The method for preparing the food packaging film according to claim 4, characterized in that, In step (2), preferably, the stirring speed of the stirring reaction is 600~800 r / min.

7. The method for preparing the food packaging film according to claim 4, characterized in that, In step (3), the film-forming liquid is poured onto the polytetrafluoroethylene plate to form a film.

8. The method for preparing the food packaging film according to claim 4, characterized in that, In step (3), the drying process is carried out at a temperature of 40-60°C for 12-24 hours.

9. The application of the food packaging film according to any one of claims 1-3 in smart food packaging materials, ammonia content monitoring materials, or environmental safety warning materials.

10. The application of the food packaging film according to claim 9, characterized in that, The food packaging film is used for smart packaging of one or more types of aquatic products and meat.

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