A fully biodegradable pectin-based food packaging film and a preparation method and application thereof

Abstract

This invention provides a fully biodegradable pectin-based food packaging film, its preparation method, and its application. The preparation method of the fully biodegradable pectin-based food packaging film includes: Step 1, adding pectin and vanillin to water and dissolving them to obtain a reaction solution; Step 2, adding a catalyst and a plasticizer to the reaction solution and stirring to obtain a film-forming solution; Step 3, shaping the film-forming solution into a film and drying it to obtain a vanillin crosslinked pectin film; Step 4, immersing the vanillin crosslinked pectin film in an aqueous solution containing glycerol and FeCl3, then removing and drying it to obtain the fully biodegradable pectin-based food packaging film. This food packaging film is completely biodegradable, reducing the dependence of food packaging films on non-renewable petroleum products and avoiding environmental pollution caused by incineration.

Description

Technical Field

[0001] This invention relates to a method for preparing a food packaging film, specifically to a fully biodegradable pectin-based food packaging film, its preparation method, and its applications. Background Technology

[0002] Food packaging films play a crucial role in food packaging, extending shelf life and preserving freshness. Currently, approximately 95% of packaging plastics on the market are non-biodegradable petroleum-derived products. Packaging plastics made from petroleum-based derivatives (such as polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyvinyl chloride (PVC)) are widely used due to their lightweight, water and oil resistance, simple production methods, low price, and suitability for large-scale industrial production. These plastic packaging materials are mostly single-use products, facing the challenge of difficult degradation and recycling. Incineration is one of the most common methods for disposing of these plastics; however, incineration releases toxic gases (such as dioxins), posing a serious challenge to human health and causing significant damage to the environment. Therefore, developing biomass-based biodegradable packaging films is of great significance for the sustainable development of the food packaging industry. Summary of the Invention

[0003] The purpose of this invention is to provide a fully biodegradable pectin-based food packaging film, its preparation method, and its application. This food packaging film is completely biodegradable, reducing the dependence of food packaging films on non-renewable petroleum products and avoiding environmental pollution caused by incineration.

[0004] This invention is achieved through the following technical solution:

[0005] A method for preparing a fully biodegradable pectin-based food packaging film, comprising:

[0006] Step 1: Add pectin and vanillin to water and dissolve them to obtain a reaction solution;

[0007] Step 2: Add the catalyst and plasticizer to the reaction solution and stir to obtain the film-forming solution;

[0008] Step 3: Set the film-forming solution into a film, dry it, and obtain a vanillin cross-linked pectin film;

[0009] Step 4: Soak the vanillin crosslinked pectin film in an aqueous solution containing glycerol and FeCl3, then remove and dry it to obtain a fully biodegradable pectin-based food packaging film.

[0010] Preferably, in step 1, the mass ratio of pectin to vanillin is (5~8):(1~2).

[0011] Preferably, in step 2, the catalyst is one or more of p-toluenesulfonic acid, pyridine p-toluenesulfonate, benzenesulfonic acid, and methanesulfonic acid.

[0012] Preferably, in step 2, the mass of the catalyst is 5% to 10% of the mass of pectin.

[0013] Preferably, in step 2, the plasticizer is one or more of glycerol, polyethylene glycol, sorbitol, and diethylene glycol.

[0014] Preferably, in step 2, the plasticizer is 20% to 40% of the pectin mass.

[0015] Preferably, in step 4, the mass concentration of glycerol in the aqueous solution of glycerol and FeCl3 is 20% to 40%.

[0016] Preferably, in step 4, the concentration of FeCl3 in the aqueous solution of glycerol and FeCl3 is 0.001 g / mL to 0.003 g / mL.

[0017] The fully biodegradable pectin-based food packaging film obtained by the preparation method described above.

[0018] The application of the fully biodegradable pectin-based food packaging film in food preservation.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention discloses a method for preparing a biomass-based biodegradable food packaging film, using pectin as the base material. First, vanillin is grafted onto the pectin chain via an acid-catalyzed acetal reaction, and Fe is introduced into the pectin matrix. 3+ Ions form metal coordination bonds to prepare biomass-based biodegradable food packaging films containing multi-crosslinked networks. This method has the advantages of simple operation, mild reaction, and non-toxic and harmless degradation products to the environment.

[0021] The biomass-based biodegradable film prepared by this invention has good physical and mechanical properties, as well as excellent UV resistance and preservation properties. Therefore, it can be used as a food packaging film. Moreover, the film is completely degradable, which reduces the dependence of food packaging films on non-renewable petroleum products and is in line with the agricultural sustainable development strategy. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the mechanism of pectin-based films.

[0023] Figure 2 The swelling rate of the fully biodegradable pectin-based food packaging film prepared in this invention.

[0024] Figure 3The antioxidant properties of the fully biodegradable pectin-based food packaging film prepared in this invention.

[0025] Figure 4 The water vapor transmission rate of the fully biodegradable pectin-based food packaging film prepared in this invention.

[0026] Figure 5 The degradation diagram of the film in soil is prepared for Embodiment 5 of the present invention. Detailed Implementation

[0027] To further understand the present invention, the present invention will be described below with reference to embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0028] The method for preparing the fully biodegradable pectin-based food packaging film of the present invention includes:

[0029] Step 1: Add pectin and vanillin to water and stir continuously at 75 ℃~90 ℃ until all components are completely dissolved to obtain a reaction solution; the mass ratio of pectin to vanillin is (5~8):(0.1~0.3).

[0030] Step 2: Add 1% to 3% of the catalyst by weight of pectin to the reaction solution and stir. Then, add 20% to 40% of the plasticizer by weight of pectin and continue stirring at high speed to obtain the film-forming solution.

[0031] Step 3: Pour the film-forming solution into a polytetrafluoroethylene / glass mold, cool and set it at room temperature, and then dry it at 75℃~90℃ to obtain a vanillin crosslinked pectin film.

[0032] Step 4: The vanillin-crosslinked pectin film is immersed in a deionized aqueous solution containing 20%–40% plasticizer and 0.001 g / mL–0.003 g / mL FeCl3 for a period of time, and then dried at room temperature (during this period, the edges of the film are clamped to prevent wrinkling) to obtain Fe 3+ Cross-linked pectin-based food packaging film.

[0033] The catalyst is one or more selected from p-toluenesulfonic acid (PSTA), pyridine p-toluenesulfonate, benzenesulfonic acid, and methanesulfonic acid. The plasticizer is one or more selected from glycerol, polyethylene glycol, sorbitol, and diethylene glycol.

[0034] Vanillin contains two active functional groups that can be chemically modified (i.e., aldehyde and phenolic hydroxyl groups), and in Fe... 3+ In the presence of ions, the phenolic hydroxyl group has a stronger coordinating ability than the carboxyl group and can form strong metal coordination bonds. The mechanism of action is shown in the diagram below. Figure 1As shown. This invention utilizes an acid-catalyzed acetal reaction between the aldehyde group of vanillin and the hydroxyl group on the pectin chain to form covalent crosslinks, through Fe... 3+ Ions can further form metal coordination bonds between the carboxyl groups on the pectin chain and the phenolic hydroxyl groups of vanillin. These bonds, combined with the hydrogen bonds within the pectin molecular chain and those between the ions and the vanillin hydroxyl groups, collectively form a pectin-based multi-crosslinked network structure. This endows the film with excellent water resistance and mechanical properties, while reducing the air permeability and water vapor transmission rate of the pectin-based film. This helps regulate the oxygen and carbon dioxide concentrations in the fruit and vegetable storage environment, increasing the barrier to moisture penetration and thus achieving the purpose of preservation.

[0035] The process of preparing films from unmodified pectin

[0036] Place 5g of pectin and 110ml of water in a three-necked flask and stir continuously at 85°C until all components are completely dissolved. Then, add 20% glycerol and continue stirring at high speed for 2 minutes. Pour the film-forming solution into a polytetrafluoroethylene / glass mold, cool and set at room temperature, and then dry at 85°C to obtain an unmodified pectin film.

[0037] Implementation Case 1

[0038] 5g pectin, 0.1g vanillin, and 110ml water were placed in a three-necked flask and stirred continuously at 85℃ until all components were completely dissolved. Then, 1% p-toluenesulfonic acid was added to the reaction solution and stirred for 4 hours. Subsequently, 20% glycerol was added and stirring was continued at high speed for 2 minutes. The film-forming solution was poured into a polytetrafluoroethylene / glass mold, cooled and set at room temperature, and then dried at 85℃ to obtain a vanillin-crosslinked pectin film. Finally, the film was immersed in a deionized aqueous solution containing 20% ​​glycerol and 0.001 g / mL FeCl3 for 10 minutes and dried at room temperature for 12 hours (during which time the edges of the film were clamped to prevent wrinkling) to obtain Fe... 3+ Cross-linked pectin-based film.

[0039] Implementation Case 2

[0040] 6 g pectin, 0.2 g vanillin, and 110 mL water were placed in a three-necked flask and stirred continuously at 75 ℃~90 ℃ until all components were completely dissolved. Then, 3% p-toluenesulfonic acid was added to the reaction solution and stirred for 4 h. Subsequently, 30% glycerol was added and stirring was continued at high speed for 2 min. The film-forming solution was poured into a polytetrafluoroethylene / glass mold, cooled and shaped at room temperature, and then dried at 85 ℃ to obtain a vanillin crosslinked pectin film. Finally, the above film was immersed in a deionized water solution containing 40% glycerol and 0.0015 g / mL FeCl3 for 10 min and dried at room temperature for 12 h (during which time the edges of the film were clamped to prevent wrinkling) to obtain Fe 3+ Cross-linked pectin-based film.

[0041] Implementation Case 3

[0042] 5g pectin, 0.1g vanillin, and 110mL water were placed in a three-necked flask and stirred continuously at 85℃ until all components were completely dissolved. Then, 1% p-toluenesulfonic acid was added to the reaction solution and stirred for 4 hours. Subsequently, 40% glycerol was added and stirring was continued at high speed for 2 minutes. The film-forming solution was poured into a polytetrafluoroethylene / glass mold, cooled and set at room temperature, and then dried at 85℃ to obtain a vanillin-crosslinked pectin film. Finally, the film was immersed in a deionized aqueous solution containing 20% ​​glycerol and 0.002 g / mL FeCl3 for 10 minutes and dried at room temperature for 12 hours (during which time the edges of the film were clamped to prevent wrinkling) to obtain Fe... 3+ Cross-linked pectin-based film.

[0043] Implementation Case 4

[0044] 8 g pectin, 0.3 g vanillin, and 110 mL water were placed in a three-necked flask and stirred continuously at 85 °C until all components were completely dissolved. Then, 3% p-toluenesulfonic acid was added to the reaction solution and stirred for 4 h. Subsequently, 30% glycerol was added and stirring was continued at high speed for 2 min. The film-forming solution was poured into a polytetrafluoroethylene / glass mold, cooled and set at room temperature, and then dried at 85 °C to obtain a vanillin-crosslinked pectin film. Finally, the film was immersed in a deionized aqueous solution containing 30% glycerol and 0.0025 g / mL FeCl3 for 10 min and dried at room temperature for 12 h (during which time the edges of the film were clamped to prevent wrinkling) to obtain Fe... 3+ Cross-linked pectin-based film.

[0045] Implementation Case 5

[0046] 8 g of pectin, 0.2 g of vanillin, and 110 mL of water were placed in a three-necked flask and stirred continuously at 75 ℃~90 ℃ until all components were completely dissolved. Then, 2% p-toluenesulfonic acid was added to the reaction solution and stirred for 4 h. Subsequently, 20% glycerol was added and stirring was continued at high speed for 2 min. The film-forming solution was poured into a polytetrafluoroethylene / glass mold, cooled and set at room temperature, and then dried at 85 ℃ to obtain a vanillin-crosslinked pectin film. Finally, the film was immersed in a deionized aqueous solution containing 20% ​​glycerol and 0.003 g / mL FeCl3 for 10 min and dried at room temperature for 12 h (during which time the edges of the film were clamped to prevent wrinkling) to obtain Fe... 3+ Cross-linked pectin-based film.

[0047] The mechanical properties of the fully biodegradable pectin-based food packaging film prepared according to ASTM (American Society for Testing and Materials) standard method D882-09 (2009) were tested. The test results are summarized in Table 1.

[0048] Table 1. Comparison of physical properties of fully biodegradable pectin-based food packaging films

[0049]

[0050] As shown in Table 1, compared with unmodified pectin, the fully biodegradable pectin-based food packaging film prepared in this invention exhibits significantly improved tensile stress. This superior mechanical strength is attributed to the high content of pectin, vanillin, and Fe. 3+ The increased density of metal coordination interactions between ions leads to an increase in the crosslinking density of the plastic film. This demonstrates that the fully biodegradable pectin-based food packaging film of this invention possesses high strength.

[0051] The swelling rate of the fully biodegradable pectin-based food packaging film prepared according to this invention was tested. A 2 × 2 cm sample strip was weighed... m 0. Immerse the sample in deionized water for 5 hours, carefully wipe off any residual water from the sample surface, and weigh it. m 1. Remove undissolved residue from the water, air dry (40 ℃, 1 h), and weigh out the contents. m 2. The swelling ratio is calculated using formula (1). The test result is the average of three experimental tests. The test results are then summarized to obtain... Figure 2 result.

[0052] (1)

[0053] from Figure 2The results show that the films in Examples 1-5 exhibit superior water resistance compared to the unmodified pectin film. This is due to the interaction between pectin, vanillin, and Fe. 3+ Stronger metal-coordination interactions form between ions, thereby enabling PT-V / Fe 3+ The swelling ratio of the plastic film decreases. And when Fe... 3+ As the ion concentration increases, the degree of cross-linking between pectin chains increases; therefore, the film in Example 5 exhibits the best water resistance. This fully demonstrates that the fully biodegradable, high-strength pectin-based food packaging film prepared by this invention possesses excellent water resistance and can meet the practical application requirements of food packaging films.

[0054] The fully biodegradable pectin-based food packaging film prepared according to this invention was subjected to ultraviolet (UV) testing. The UV-Vis spectra of the sample films were recorded using UV-Vis-NIR spectrophotometry (Cary 5000) with a wavenumber of 200-800 nm.

[0055] from Figure 3 The results show that the unmodified pectin film has poor UV resistance. After modification, due to the phenolic hydroxyl groups and Fe in vanillin... 3+ The strong ultraviolet absorption properties of ions allow the prepared thin film to effectively block the most harmful UVC radiation (200). 280 nm) and part of UVB (280 nm) 320 nm) and UVA (320 nm) The ultraviolet light intensity (400 nm) helps prevent UV-induced discoloration, nutrient loss, and spoilage in food. Therefore, the fully biodegradable pectin-based food packaging film prepared in this invention can be used as a food packaging material to extend the shelf life of food.

[0056] The water vapor transmission rate (WVTR) of the fully biodegradable pectin-based food packaging film prepared according to this invention was tested. The WVTR of the pectin-based film was tested according to the method specified in ASTM E96-16, using a water vapor transmission rate meter (C360H, Labthink, China) at a test temperature of 38°C and a RH of 90%. The test results were summarized to obtain... Figure 4 result.

[0057] The water vapor transmission coefficient (WVP) is determined by the following formula:

[0058]

[0059] In the formula,

[0060] d —Thickness of the film;

[0061] ΔP — represents the water vapor pressure difference.

[0062] from Figure 4 The results show that the fully biodegradable high-strength pectin-based food packaging film prepared in this invention has excellent water vapor barrier properties, which are superior to those of unmodified pectin. To test the food preservation ability of the prepared plastic film, non-target products, cherry tomatoes, were respectively packaged in polyethylene (PE) preservation film and the film of Example 5, and then sealed for storage. The results are as follows... Figure 4 As shown, unprotected cherry tomatoes wilted and even dried out after 10 days of storage due to water loss from the peel. Cherry tomatoes stored with PE plastic wrap were noticeably soft and rotten, with mold spots on the surface. However, the cherry tomatoes stored in the film of Example 5 remained fresh. Their excellent preservation performance is due to the continuous respiration of the fruit within the film of Example 5, which lowers the O2 concentration and increases the CO2 concentration, further inhibiting the physiological metabolism of the fruit and thus maintaining better sensory quality. Therefore, the fully biodegradable high-strength pectin-based food packaging film prepared in this invention can better inhibit oxidation reactions and food microbial spoilage, achieving the effects of extending shelf life and preserving and stabilizing fresh food.

[0063] The biodegradability of the fully biodegradable pectin-based food packaging film prepared according to this invention was tested. Film samples were cut into 2×2 cm pieces. 2 The sample was placed in a weighing bottle containing natural soil. The bottle was then placed in a culture chamber (temperature 28±2℃, RH 50±5%) for periodic incubation. The degradation of the film was observed and recorded. Figure 5 As shown, implementation case 5 can be completely degraded in 7 weeks.

[0064] The results above show that the fully biodegradable pectin-based food packaging film prepared by this invention has excellent mechanical properties and its freshness preservation is comparable to that of commercially available PE food preservation film. The fully biodegradable high-strength food packaging film prepared by this invention also has the advantage of being fully biodegradable, which is of great significance for environmental protection.

[0065] It is understood that those skilled in the art can make equivalent substitutions or modifications to the technical solution and inventive concept of the present invention, and all such substitutions or modifications should fall within the protection scope of the appended claims.

Claims

1. A process for the preparation of a fully biodegradable pectin-based food packaging film, characterized in that, The application relates to a preparation method of a full-biodegradable pectin-based food packaging film. Step 1: pectin and vanillin are added into water to be dissolved to obtain a reaction solution; the mass ratio of the pectin to the vanillin is (5-8):(0.1-0.3); Step 2: a catalyst and a plasticizer are added into the reaction solution to be stirred to obtain a film-forming solution; the catalyst is one or more of p-toluenesulfonic acid, pyridine p-toluenesulfonate, benzene sulfonic acid and methyl sulfonic acid; the mass of the catalyst is 5%-10% of the mass of the pectin; Step 3: the film-forming solution is shaped into a film and dried to obtain a vanillin cross-linked pectin film; Step 4: the vanillin cross-linked pectin film is soaked in a glycerol and FeCl3-containing aqueous solution, then taken out and dried to obtain the full-biodegradable pectin-based food packaging film; in the glycerol and FeCl3-containing aqueous solution, the concentration of the FeCl3 is 0.001 g / mL-0.003 g / mL.

2. The process for the preparation of a fully biodegradable pectin-based food packaging film according to claim 1, characterized in that, In step 2, the plasticizer is one or more of glycerol, polyethylene glycol and sorbitol.

3. The process for the preparation of fully biodegradable pectin-based food packaging films according to claim 1, characterized in that, In step 2, the mass of the plasticizer is 20%-40% of the mass of the pectin.

4. The process for the preparation of fully biodegradable pectin-based food packaging films according to claim 1, characterized in that, In step 4, in the glycerol and FeCl3-containing aqueous solution, the mass concentration of the glycerol is 20%-40%.

5. The full-biodegradable pectin-based food packaging film obtained by the preparation method in any one of claims 1-4.

6. Application of the full-biodegradable pectin-based food packaging film in claim 5 in food preservation.

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