Packaging film as well as preparation method and application thereof

Abstract

The invention discloses a packaging film as well as a preparation method and application thereof, and belongs to the technical field of packaging. The preparation method comprises a carboxylated starch preparation step, a starch / polyhexamethylene guanidine / rutin preparation step and a degradable packaging film preparation step. The preparation method specifically comprises the following steps: by taking starch as a film-forming material, performing carboxylation treatment on the starch to prepare carboxylated starch; the preparation method comprises the following steps: performing cross-linking grafting reaction on carboxylated starch and polyhexamethylene guanidine to obtain starch / polyhexamethylene guanidine, reacting the starch / polyhexamethylene guanidine with rutin, and performing hydrogen bond connection to obtain starch / polyhexamethylene guanidine / rutin. The starch food packaging film is applied to food packaging, the problems that an existing starch food packaging film does not have antibacterial performance and is poor in oxidation resistance are solved, and the packaging film has excellent antibacterial and antioxidant functions.

Description

Technical Field

[0001] The present invention belongs to the technical field of packaging, and in particular relates to a packaging film, a preparation method and application thereof. Background Art

[0002] Bacterial contamination and oxidative deterioration are the main causes of food spoilage during storage in natural environments. Starch, a ubiquitous polysaccharide, offers excellent safety and film-forming properties, making it suitable for use in food packaging films. However, its lack of antibacterial properties and poor antioxidant capacity limit its practical application in the food packaging industry. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is to overcome the problem that the existing starch food packaging film has no antibacterial properties and poor antioxidant ability, and propose a packaging film with excellent antibacterial and antioxidant functions, its preparation method and application.

[0004] In order to solve the technical problem, the technical solution adopted by the present invention is:

[0005] On one hand, the present invention provides a method for preparing a packaging film, comprising the steps of preparing carboxylated starch, preparing starch / polyhexamethyleneguanidine / rutin, and preparing a degradable packaging film. The method specifically comprises: using starch as a film-forming material, performing a carboxylation treatment on the starch to prepare carboxylated starch; firstly performing a cross-linking grafting reaction on the carboxylated starch and polyhexamethyleneguanidine to obtain starch / polyhexamethyleneguanidine; then reacting the starch / polyhexamethyleneguanidine with rutin and connecting them through hydrogen bonds to obtain starch / polyhexamethyleneguanidine / rutin.

[0006] Preferably, the mass ratio of starch, polyhexamethyleneguanidine and rutin in the starch / polyhexamethyleneguanidine / rutin is selected from any value ratio of 1:0.05-0.1:0.1-0.2.

[0007] Preferably, the carboxylated starch preparation steps include: dissolving starch, standing at room temperature until completely hydrated, and adjusting the pH value to 8-10 to obtain a starch solution; dissolving succinic anhydride in anhydrous ethanol, pouring the solution into the starch solution, and then heating and stirring the mixed solution for reaction. After the reaction is completed, adjusting the pH value to 5-6, centrifuging and precipitating, washing and drying to obtain the carboxylated starch.

[0008] Preferably, the starch / polyhexamethyleneguanidine / rutin preparation steps include: dissolving the carboxylated starch in deionized water, adjusting the pH value to 4-6, adding a catalyst and polyhexamethyleneguanidine, stirring and reacting at room temperature to obtain the starch / polyhexamethyleneguanidine, then adding rutin and continuing to stir and react, washing and drying to prepare the starch / polyhexamethyleneguanidine / rutin.

[0009] Preferably, the catalyst is a mixture of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide in a mass ratio of 1:1.

[0010] Preferably, the preparation steps of the degradable packaging film include: adding the starch / polyhexamethyleneguanidine / rutin into deionized water, adding a plasticizer, stirring thoroughly, vacuum degassing, casting into a film, drying and peeling off to obtain the degradable packaging film.

[0011] Preferably, in the carboxylated starch preparation step, the starch is dissolved, allowed to stand at room temperature until it is completely hydrated, and the pH value is adjusted to 8-10 with a sodium hydroxide solution to obtain a starch solution.

[0012] Preferably, in the starch / polyhexamethyleneguanidine / rutin preparation step, the carboxylated starch is dissolved in deionized water, and the pH value of the solution is adjusted to 4-6 with hydrochloric acid.

[0013] Another aspect of the present invention provides a packaging film, which is prepared by the packaging film preparation method described in any of the above technical solutions. The packaging film uses starch as a film-forming material, and the starch is carboxylated to obtain the carboxylated starch. The carboxylated starch is grafted with the polyhexamethylene guanidine, and then the rutin is compounded through hydrogen bonding. Finally, the packaging film is prepared through a film-forming reaction.

[0014] The present invention also provides application of the packaging film described in the above technical solution in food packaging.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention provides a method for preparing a packaging film. Starch is used as a film-forming material. Through covalent grafting of polyhexamethylene guanidine and rutin, the packaging film is endowed with excellent antibacterial and antioxidant functions. The starch-based degradable packaging film material is used for food preservation, which can greatly extend the storage time of food. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a diagram showing the antibacterial effect of the experimental group in Example 1 of the present invention;

[0018] Figure 2 This is a diagram showing the antibacterial effect of the blank control group in Example 1 of the present invention. DETAILED DESCRIPTION

[0019] The following is a detailed and complete description of the technical solutions in the specific embodiments of the present invention. Obviously, the described embodiments are only some specific implementation methods of the overall technical solution of the present invention, and are not all implementation methods. Based on the overall concept of the present invention, all other embodiments obtained by ordinary skill in the art are within the scope of protection of the present invention.

[0020] In one aspect, the present invention provides a method for preparing a packaging film, comprising steps of preparing carboxylated starch, preparing starch / polyhexamethyleneguanidine / rutin, and preparing a degradable packaging film. Specifically, the method comprises: using starch as a film-forming material, carboxylating the starch to prepare carboxylated starch; crosslinking and grafting the carboxylated starch with polyhexamethyleneguanidine to produce starch / polyhexamethyleneguanidine; and then reacting the starch / polyhexamethyleneguanidine with rutin via hydrogen bonding to produce starch / polyhexamethyleneguanidine / rutin. Starch is a ubiquitous polysaccharide with excellent safety and film-forming properties, making it suitable for making food packaging films. However, its lack of antibacterial properties and poor antioxidant capacity limit its practical application in the food packaging field. Polyhexamethyleneguanidine is a cationic polymer that can destroy bacterial cell structures and kill bacteria through electrostatic interactions. Rutin is a natural flavonoid glycoside containing a large number of keto and phenolic hydroxyl groups, which can effectively scavenge free radicals. The preparation method of the packaging film provided by the present invention uses starch as the film-forming material and endows the packaging film with excellent antibacterial and antioxidant functions through covalent grafting of polyhexamethylene guanidine and rutin. The film is green and environmentally friendly, conforms to the development trend of low-carbon materials, and has high application prospects.

[0021] To overcome the poor compatibility between starch and polyhexamethyleneguanidine, the present invention first carboxylates the starch. This carboxylation process ensures that polyhexamethyleneguanidine can be covalently grafted onto the starch / polyhexamethyleneguanidine, resulting in a starch / polyhexamethyleneguanidine composition with enhanced compatibility. After the starch is carboxylated, polyhexamethyleneguanidine is first grafted onto the starch and then hydrogen-bonded with rutin, thereby preventing the destruction of rutin's phenolic hydroxyl groups and reducing its antioxidant properties. It should be noted that the present invention carboxylates the starch and then grafts polyhexamethyleneguanidine onto the starch and hydrogen-bonds the starch / polyhexamethyleneguanidine composition. First, as a natural polysaccharide, starch's molecular chains are tightly packed due to intermolecular interactions, resulting in poor mechanical properties. When made into packaging film material, starch is prone to brittle fracture, resulting in film breakage. The grafting of polyhexamethyleneguanidine cross-links the starch molecular chains, increasing tensile strength while slightly decreasing elongation at break. Rutin and starch / polyhexamethyleneguanidine molecules are hydrogen-bonded, maintaining essentially unchanged tensile strength while significantly improving elongation at break. This is because rutin acts as a plasticizer, increasing the distance between starch / polyhexamethyleneguanidine molecules and weakening the intermolecular forces, significantly improving the toughness of the film. Overall, starch / polyhexamethyleneguanidine / rutin has better mechanical properties.

[0022] In a preferred embodiment, the mass ratio of starch, polyhexamethyleneguanidine, and rutin in the starch / polyhexamethyleneguanidine / rutin is selected from any point value ratio of 1:0.05-0.1:0.1-0.2. This technical solution defines the mass ratio of starch, polyhexamethyleneguanidine, and rutin in starch / polyhexamethyleneguanidine / rutin. It is understandable that the mass ratio of starch, polyhexamethyleneguanidine, and rutin in starch / polyhexamethyleneguanidine / rutin can also be any point value ratio of 1:0.06:0.1, 1:0.06:0.2, 1:0.07:0.1, 1:0.07:0.2, 1:0.08:0.1, 1:0.08:0.2, 1:0.09:0.1, and 1:0.09:0.2.

[0023] In a preferred embodiment, the carboxylated starch preparation step comprises: dissolving starch, allowing it to stand at room temperature until it is completely hydrated, and adjusting the pH value to 8-10 to obtain a starch solution; dissolving succinic anhydride in anhydrous ethanol, pouring it into the starch solution, and then heating and stirring the mixed solution to react. After the reaction is completed, adjusting the pH value to 5-6, centrifuging and precipitating, washing and drying to obtain the carboxylated starch. In the carboxylated starch preparation step, the starch is dissolved, allowed to stand at room temperature until it is completely hydrated, and the pH value is adjusted to 8-10 with sodium hydroxide solution to obtain the starch solution.

[0024] In a preferred embodiment, the starch / polyhexamethyleneguanidine / rutin preparation step comprises: dissolving the carboxylated starch in deionized water, adjusting the pH to 4-6, adding a catalyst and polyhexamethyleneguanidine, stirring and reacting at room temperature to obtain the starch / polyhexamethyleneguanidine, then adding rutin and continuing to stir and react, washing and drying to obtain the starch / polyhexamethyleneguanidine / rutin. In a preferred embodiment, the catalyst is a mixture of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide in a mass ratio of 1:1. In the starch / polyhexamethyleneguanidine / rutin preparation step, the carboxylated starch is dissolved in deionized water, and the pH of the solution is adjusted to 4-6 with hydrochloric acid.

[0025] In a preferred embodiment, the degradable packaging film preparation step includes: adding the starch / polyhexamethyleneguanidine / rutin to deionized water, adding a plasticizer, stirring thoroughly, vacuum degassing, casting into a film, drying, and peeling off to obtain the degradable packaging film. In a preferred embodiment, the plasticizer is glycerol.

[0026] Another aspect of the present invention provides a packaging film, which is prepared by the packaging film preparation method described in any of the above technical solutions. The packaging film uses starch as a film-forming material, and the starch is carboxylated to obtain the carboxylated starch. The carboxylated starch is grafted with the polyhexamethylene guanidine, and then the rutin is compounded through hydrogen bonding. Finally, the packaging film is prepared through a film-forming reaction.

[0027] The present invention also provides an application of the packaging film described in the above technical solution in food packaging. The starch-based degradable packaging film material is used to keep food fresh, which can greatly extend the storage time of food.

[0028] In order to more clearly and in detail introduce the packaging film provided by the embodiments of the present invention, its preparation method and application, the following description will be made in conjunction with specific embodiments.

[0029] Example 1

[0030] A method for preparing a starch-based degradable packaging film comprises the following steps:

[0031] (1) Preparation of carboxylated starch

[0032] Weigh 1.0g of starch and dissolve it in 500mL of deionized water, and let it stand at room temperature for 18h until it is completely hydrated. Adjust the pH value of the starch solution to 8-10 with 2mol / L sodium hydroxide solution. Dissolve 0.6g of succinic anhydride in 100mL of anhydrous ethanol and pour it into the starch solution. Then stir the mixed solution at 40-60℃ for 12h, and set the stirring speed to 800rpm. After the reaction is completed, adjust the pH to 5-6. Finally, the reacted solution is centrifuged and precipitated, and the precipitate is washed three times with anhydrous ethanol, and the precipitate is dried at 60℃ for 24h to obtain carboxylated starch.

[0033] (2) Preparation of starch / polyhexamethyleneguanidine / rutin

[0034] The carboxylated starch prepared above was dissolved in 500 mL of deionized water, and the pH of the solution was adjusted to 4-6 with hydrochloric acid. 0.05 g of the catalyst and 0.05 g of polyhexamethylene guanidine were added, and the mixture was stirred at room temperature for 4 hours at 800 rpm. Then, 0.1 g of rutin was added, and the mixture was stirred for another 6 hours. The mixture was washed several times with deionized water and dried at 60°C for 18 hours to prepare a starch / polyhexamethylene guanidine / rutin mixture.

[0035] (3) Preparation of degradable packaging film

[0036] Starch / polyhexamethyleneguanidine / rutin was added to 300 mL of deionized water, and a plasticizer with a weight percentage of 10% was added. After stirring for 30 minutes, the mixture was vacuum degassed for 1 hour, and then poured onto a flat plate to form a film. The flat plate was then placed in a drying oven to dry, and finally peeled off from the flat plate to obtain a degradable packaging film.

[0037] Example 2

[0038] A method for preparing a starch-based degradable packaging film comprises the following steps:

[0039] (1) Preparation of carboxylated starch

[0040] Weigh 1.0g of starch and dissolve it in 500mL of deionized water, and let it stand at room temperature for 18h until it is completely hydrated. Adjust the pH value of the starch solution to 8-10 with 2mol / L sodium hydroxide solution. Dissolve 0.6g of succinic anhydride in 100mL of anhydrous ethanol and pour it into the starch solution. Then stir the mixed solution at 40-60℃ for 12h, and set the stirring speed to 800rpm. After the reaction is completed, adjust the pH to 5-6. Finally, the reacted solution is centrifuged and precipitated, and the precipitate is washed three times with anhydrous ethanol, and the precipitate is dried at 60℃ for 24h to obtain carboxylated starch.

[0041] (2) Preparation of starch / polyhexamethyleneguanidine / rutin

[0042] The carboxylated starch prepared above was dissolved in 500 mL of deionized water, and the pH of the solution was adjusted to 4-6 with hydrochloric acid. 0.1 g of the catalyst and 0.1 g of polyhexamethylene guanidine were added, and the mixture was stirred at room temperature for 4 hours at 800 rpm. Then, 0.2 g of rutin was added, and the mixture was stirred for another 6 hours. The mixture was washed several times with deionized water and dried at 60°C for 18 hours to prepare a starch / polyhexamethylene guanidine / rutin mixture.

[0043] (3) Preparation of degradable packaging film

[0044] Starch / polyhexamethyleneguanidine / rutin was added to 300 mL of deionized water, stirred for 30 minutes, and then 10% by weight of a plasticizer was added. The mixture was vacuum degassed for 1 hour, then poured onto a flat plate to form a film. The flat plate was then placed in a drying oven and dried at 30°C for 24 hours. Finally, the film was peeled off from the flat plate to obtain a degradable packaging film.

[0045] Comparative Example 1

[0046] A method for preparing a starch-based degradable packaging film comprises the following steps:

[0047] (1) Preparation of carboxylated starch

[0048] Weigh 1.0g of starch and dissolve it in 500mL of deionized water, and let it stand at room temperature for 18h until it is completely hydrated. Adjust the pH value of the starch solution to 8-10 with 2mol / L sodium hydroxide solution. Dissolve 0.6g of succinic anhydride in 100mL of anhydrous ethanol and pour it into the starch solution. Then stir the mixed solution at 40-60℃ for 12h, and set the stirring speed to 800rpm. After the reaction is completed, adjust the pH to 5-6. Finally, the reacted solution is centrifuged and precipitated, and the precipitate is washed three times with anhydrous ethanol, and the precipitate is dried at 60℃ for 24h to obtain carboxylated starch.

[0049] (2) Preparation of starch / polyhexamethyleneguanidine

[0050] The carboxylated starch prepared above was dissolved in 500 mL of deionized water. The pH of the solution was adjusted to 4-6 with hydrochloric acid. 0.05 g of the catalyst and 0.05 g of polyhexamethyleneguanidine were added. The mixture was stirred at room temperature for 4 h at 800 rpm. The mixture was washed several times with deionized water and dried at 60°C for 18 h to prepare a starch / polyhexamethyleneguanidine solution.

[0051] (3) Preparation of degradable packaging film

[0052] Starch / polyhexamethylene guanidine was added to 300 mL of deionized water, stirred for 30 minutes, and then 10% by weight of a plasticizer was added. The mixture was vacuum degassed for 1 hour, then poured onto a flat plate to form a film. The flat plate was then placed in a drying oven to dry, and finally peeled off from the flat plate to obtain a degradable packaging film.

[0053] Comparative Example 2

[0054] A method for preparing a starch-based degradable packaging film comprises the following steps:

[0055] (1) Preparation of starch / rutin

[0056] 1 g of starch was dissolved in 500 mL of deionized water, 0.1 g of rutin was added, and the mixture was stirred for reaction for 6 h. The mixture was washed with deionized water several times and dried at 60° C. for 18 h to prepare starch / polyhexamethyleneguanidine / rutin.

[0057] (2) Preparation of degradable packaging film

[0058] Starch / rutin was added to 300 mL of deionized water, and 10% by weight of a plasticizer was added. After stirring for 30 minutes, vacuum degassing was performed for 1 hour, and then the mixture was poured onto a flat plate to form a film. The flat plate was then placed in a drying oven to dry, and finally peeled off from the flat plate to obtain a degradable packaging film.

[0059] Comparative Example 3

[0060] A method for preparing a starch-based degradable packaging film comprises the following steps:

[0061] 1g of starch was dissolved in 300mL of deionized water, 10% by weight of plasticizer was added, and after stirring for 30min, vacuum degassing was performed for 1h. Then, it was poured onto a flat plate to form a film. The flat plate was placed in a drying oven to dry, and finally peeled off from the flat plate to obtain a degradable packaging film.

[0062] Performance Testing

[0063] (1) Antibacterial performance test

[0064] The antibacterial properties of Examples 1-2 and Comparative Examples 1-3 were tested according to the national standard GB / T 37206-2018. The inoculated bacteria were Escherichia coli. A group of blank samples without any sample was set as a control group. The results are as follows: Figure 1 、 2 The number of surviving bacteria in the test group and the control group was counted, and the inhibition rate was calculated.

[0065] (2) Antioxidant performance test

[0066] The degradable packaging films prepared in Examples 1-2 and Comparative Examples 1-3 were cut into 1 x 1 cm samples and placed in a 0.05 mM DPPH ethanol solution. The samples were incubated in the dark for 30 minutes, and the absorbance at 517 nm was measured using a spectrophotometer, denoted as A1. A control group containing no added substances in a 0.05 mM DPPH ethanol solution was also incubated in the dark for 30 minutes, and the absorbance at 517 nm was measured using a spectrophotometer, denoted as A0. The results are shown in Table 1.

[0067] DPPH free radical scavenging rate (%) = (A0-A1) / A0×100%

[0068] Table 1 Antioxidant performance test results

[0069] project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Antibacterial rate (%) 93.0 98.5 89.1 47.8 No antibacterial effect DPPH free radical scavenging rate (%) 64.4 72.7 1.3 63.5 7.8

[0070] It can be seen from the experimental data that the degradable packaging film prepared by the present invention has a high antibacterial rate and DPPH free radical scavenging rate, can effectively kill bacteria and prevent food from oxidative deterioration, and can provide excellent food preservation effect.

Claims

1. A method for preparing a packaging film, characterized in that: include: The carboxylated starch preparation step comprises: using starch as a film-forming material and subjecting the starch to a carboxylation treatment to prepare the carboxylated starch; a starch / polyhexamethyleneguanidine / rutin preparation step, wherein the carboxylated starch is first subjected to a cross-linking grafting reaction with polyhexamethyleneguanidine to obtain starch / polyhexamethyleneguanidine, and then the starch / polyhexamethyleneguanidine is reacted with rutin and connected via hydrogen bonds to obtain starch / polyhexamethyleneguanidine / rutin; as well as Steps for preparing degradable packaging film.

2. The method for preparing the packaging film according to claim 1, wherein: The mass ratio of starch, polyhexamethyleneguanidine and rutin in the starch / polyhexamethyleneguanidine / rutin is selected from any value ratio between 1:0.05-0.1 and 0.1-0.

2.

3. The method for preparing the packaging film according to claim 1, wherein: The carboxylated starch preparation steps include: dissolving starch, standing at room temperature until completely hydrated, and adjusting the pH value to 8-10 to obtain a starch solution; dissolving succinic anhydride in anhydrous ethanol, pouring the solution into the starch solution, and then heating and stirring the mixed solution for reaction. After the reaction is completed, adjusting the pH value to 5-6, centrifuging and precipitating, washing and drying to obtain the carboxylated starch.

4. The method for preparing a packaging film according to claim 1, wherein: The starch / polyhexamethyleneguanidine / rutin preparation steps include: dissolving the carboxylated starch in deionized water, adjusting the pH value to 4-6, adding a catalyst and polyhexamethyleneguanidine, stirring and reacting at room temperature to obtain the starch / polyhexamethyleneguanidine, then adding rutin and continuing to stir and react, washing and drying to prepare the starch / polyhexamethyleneguanidine / rutin.

5. The method for preparing the packaging film according to claim 4, wherein: The catalyst is a mixture of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide in a mass ratio of 1:

1.

6. The method for preparing a packaging film according to claim 1, wherein: The preparation steps of the degradable packaging film include: adding the starch / polyhexamethyleneguanidine / rutin into deionized water, adding a plasticizer, fully stirring, vacuum degassing, casting into a film, drying and peeling off to obtain the degradable packaging film.

7. The method for preparing the packaging film according to claim 3, wherein: In the carboxylated starch preparation step, starch is dissolved, allowed to stand at room temperature until fully hydrated, and the pH value is adjusted to 8-10 with sodium hydroxide solution to obtain a starch solution.

8. The method for preparing a packaging film according to claim 4, wherein: In the starch / polyhexamethyleneguanidine / rutin preparation step, the carboxylated starch is dissolved in deionized water, and the pH value of the solution is adjusted to 4-6 with hydrochloric acid.

9. A packaging film, characterized in that: The packaging film is prepared by the method for preparing a packaging film according to any one of claims 1 to 8, wherein starch is used as a film-forming material, the starch is carboxylated to obtain the carboxylated starch, the carboxylated starch is grafted with the polyhexamethylene guanidine, and then the rutin is compounded through hydrogen bonding, and finally the packaging film is prepared through a film-forming reaction.

10. Use of the packaging film according to claim 9 in food packaging.

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