Double-layer preservative film and application of double-layer preservative film in quality guarantee of sauce braised meat products

Abstract

The invention provides a double-layer preservative film and application thereof in quality guarantee of sauce braised meat products, the preservative film is double-layer, the outer layer film is a hydrophobic layer, and the inner layer film is a hydrophilic layer; the hydrophobic layer is obtained by electrostatic spinning of zein, and the surface of the hydrophobic layer has a micro-nano structure; the hydrophilic layer is obtained by curtain coating of citric acid grafted soybean protein isolate, and the film contains lipidosome coating tea seed polyphenol and tea seed polypeptide. According to the invention, the double-layer preservative film is adopted, so that water can be directionally driven from the outer layer, water can directionally permeate into the hydrophilic layer from the hydrophobic layer, otherwise, the water cannot be directionally permeated into the hydrophilic layer, and in the process, the hydrophilic layer is kept wet, and the hydrophobic layer is kept dry; lipidosome in the hydrophilic layer can slowly release tea seed polypeptide and tea seed polyphenol, so that the effects of resisting oxidation, protecting color and resisting bacteria are achieved; the hydrophobic layer can slow down evaporation of moisture in the sauced meat and allows external moisture to be conveyed inwards, the effect of keeping moisture and tenderness of the sauced meat is achieved, and meanwhile, the dry hydrophobic layer can reduce growth of bacteria.

Description

Technical Field

[0001] The invention relates to the technical field of food preservation, and in particular to a double-layer fresh-keeping film and application thereof in preserving the quality of marinated meat products. Background Art

[0002] Braised meat products have a history of thousands of years in my country. They are easy to eat, bright in color, crispy and smooth in taste, and rich in flavor, and are deeply loved by the Chinese people. For a long time, the development of braised meat products in my country has been relatively slow. It was not until modern society that braised meat products came out of small family workshops and entered a new stage of industrialized and large-scale production. At present, the daily consumption of braised meat products in my country has reached about 15,000 tons. Small workshops and small-scale production are difficult to guarantee the demand for product quality and consumption. Therefore, it is necessary to improve and innovate the processing technology of traditional braised meat products, make the production process more scientific, and make the production equipment more modern, so as to further improve the product quality and meet the needs of consumers. The preservation and storage of braised meat products is also a major problem. There are preservatives added directly, but with the improvement of people's awareness of food safety, the addition of preservatives has also been questioned. The use of low-temperature freezing requires a lot of energy consumption. Therefore, providing a method that can be stored at room temperature and still maintain the quality of braised meat products is a problem that needs to be solved urgently. Summary of the invention

[0003] Technical problem to be solved: In view of the above-mentioned technical problems, the purpose of the present invention is to provide a double-layer cling film and its application in the preservation of marinated meat products. The double-layer cling film is adopted, the outer layer is a hydrophobic layer, and the inner layer is a hydrophilic layer, so as to realize directional water expulsion from the outer layer, and water can penetrate from the hydrophobic layer to the hydrophilic layer, but vice versa. In this process, the hydrophilic layer remains moist and the hydrophobic layer remains dry; the liposomes in the hydrophilic layer can slowly release tea seed polypeptides and tea seed polyphenols, so as to achieve antioxidant, color protection and antibacterial effects; the hydrophobic layer can slow down the evaporation of water in the marinated meat, and at the same time allow external water to be transported inward, so as to maintain the moisture and tenderness of the marinated meat. At the same time, the dry hydrophobic layer can reduce the growth of bacteria.

[0004] Technical solution: A double-layer cling film, wherein the cling film is double-layered, the outer layer is a hydrophobic layer, and the inner layer is a hydrophilic layer; the hydrophobic layer is obtained by electrostatic spinning of zein, and the surface has a micro-nano structure; The hydrophilic layer is obtained by casting citric acid grafted soybean protein isolate, and the membrane contains liposomes coated with tea seed polyphenols and tea seed polypeptides. Furthermore, the thickness of the hydrophilic layer is 5-8 μm, and the thickness of the hydrophobic layer is 3-5 μm. Furthermore, the preparation method of the liposome coated with tea seed polyphenols and tea seed polypeptides is as follows: Step 1: Dissolve 0.5 g of gelatin in 50 mL of water and heat to obtain a gelatin solution; Step 2: Dissolve 3 g of lecithin and 1 g of cholesterol in 100 mL of chloroform, add 50 mL of anhydrous ethanol solution containing 0.3 g of tea seed polyphenols, and perform rotary evaporation at 40-50°C to form a film; Step 3: Add 200 mL of phosphate buffer solution with a pH of 6.5-7.4, containing 0.5-0.8 g of tea seed polypeptide and 2 g of polysorbate 80 at a concentration of 0.01 mol / L, and shake at 60°C to mix well for full hydration; Step 4: Add gelatin solution and stir under ultrasonic wave for 1 h at 4°C to obtain a suspension; Step 5: Centrifugal drying to obtain liposomes coated with tea seed polyphenols and tea seed polypeptides. The preparation method of the double-layer cling film comprises the following steps: S1: Take 2 parts of soy protein isolate, add 30 parts of deionized water, adjust the pH to 7-8, heat to 90°C and stir to obtain a soy protein isolate solution; S2: Take 8-9 parts of citric acid and add 10-15 parts of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: cool to room temperature, add food-grade hydrochloric acid, adjust the pH to 4-5, centrifuge, and dry to obtain citric acid-grafted soy protein isolate; S4: Take 10 parts of citric acid grafted soy protein isolate, 6 parts of glycerol and 0.5-1 parts of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 150-200 parts of deionized water, and stir magnetically for 20 minutes; S5: adjust the pH to 8-9, heat to 70-80°C, keep warm for 30 minutes, cool to room temperature, degas for 10 minutes at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer; S7: dissolving 0.5 parts of zein in 3-5 parts of 80% acetic acid solution, adding nano zinc oxide, and stirring to obtain a spinning solution; S8: Using an electrospinning device to perform electrospinning, a hydrophilic layer is placed on a receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed. Furthermore, the mass ratio of zein to nano zinc oxide in S7 is (2-5):1. Furthermore, the electrospinning conditions are as follows: the spinning solution flow rate is 1.5-2.5 mL / h, the spinning temperature is 25° C., the spinning voltage is 18 kV, the air humidity is 50%, and the distance between the spinneret and the receiving plate is 15 cm. The application of the double-layer cling film in the preservation of marinated meat products is as follows: S1: The marinated meat product is sealed and packaged with a double layer of plastic wrap; S2: Sterilization; S3: Further packaging in conventional packaging bags and storage. Furthermore, the sterilization method adopts irradiation sterilization, and the irradiation dose is 3-4 kGy. Beneficial effects: 1. The present invention adopts a double-layer cling film, wherein the outer layer is a hydrophobic layer and the inner layer is a hydrophilic layer, so as to realize directional water expulsion from the outer layer. Water can directional penetrate from the hydrophobic layer to the hydrophilic layer, but vice versa. During this process, the hydrophilic layer remains moist and the hydrophobic layer remains dry. The liposomes in the hydrophilic layer can slowly release tea seed polypeptides and tea seed polyphenols to achieve antioxidant, color protection and antibacterial effects. The hydrophobic layer can slow down the evaporation of water in the marinated meat and allow external water to be transported inward, so as to maintain the moisture and tenderness of the marinated meat. Meanwhile, the dry hydrophobic layer can reduce the growth of bacteria. 2. The surface of the hydrophobic layer of the present invention has a micro-nano structure, which is composed of micron pores and nano zinc oxide. Zein itself has a certain hydrophobicity. After adding the micro-nano structure, the hydrophobicity is further improved, and the contact angle can reach 151.0°; at the same time, the nano zinc oxide in the micro-nano structure has good antibacterial properties and can improve the mechanical properties of the hydrophobic layer. 3. The hydrophilic layer in the present invention is obtained by casting by grafting citric acid with soy protein isolate. The carboxyl group of citric acid reacts with the amino group in the soy protein isolate to form an amide bond or other types of chemical bonds, which are grafted onto the soy protein isolate to increase the number of carboxyl groups on the protein molecules, thereby improving the hydrophilicity of the soy protein isolate film and forming a good water retention effect on the marinated meat. 4. The soy protein isolate film of the present invention contains liposomes encapsulating tea seed polyphenols and tea seed polypeptides. The addition of gelatin to the liposomes can improve the stability of the liposomes and the encapsulation rate of tea seed polyphenols and tea seed polypeptides on the one hand; on the other hand, a temperature response is formed. During the storage of the marinated meat, if the temperature rises, the release of the tea seed polyphenols and tea seed polypeptides in the liposomes is accelerated, thereby regulating the preservation process. 5. The nano zinc oxide in the present invention is present in the outer hydrophobic layer and does not come into direct contact with the marinated meat, nor does it migrate. It is safer to use and is more favored by consumers. DETAILED DESCRIPTION The present invention proposes a double-layer cling film and its application in the preservation of marinated meat products. In order to make the purpose, technical scheme and effect of the present invention clearer and more specific, the present invention will be further described in detail with reference to the embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Example 1 The preparation method of liposomes coated with tea seed polyphenols and tea seed polypeptides is as follows: Step 1: Dissolve 0.5 g of gelatin in 50 mL of water and heat to obtain a gelatin solution; Step 2: Dissolve 3 g of lecithin and 1 g of cholesterol in 100 mL of chloroform, add 50 mL of anhydrous ethanol solution containing 0.3 g of tea seed polyphenols, and perform rotary evaporation at 40°C to form a film; Step 3: Add 200 mL of phosphate buffer solution with a pH of 7.2, containing 0.5 g of tea seed polypeptide and 2 g of polysorbate 80 at a concentration of 0.01 mol / L, and shake at 60°C to mix well for full hydration; Step 4: Add gelatin solution and stir under ultrasonic wave for 1 h at 4°C to obtain a suspension; Step 5: Centrifugal drying to obtain liposomes coated with tea seed polyphenols and tea seed polypeptides. Example 2 The preparation method of liposomes coated with tea seed polyphenols and tea seed polypeptides is as follows: Step 1: Dissolve 0.5 g of gelatin in 50 mL of water and heat to obtain a gelatin solution; Step 2: Dissolve 3 g of lecithin and 1 g of cholesterol in 100 mL of chloroform, add 50 mL of anhydrous ethanol solution containing 0.3 g of tea seed polyphenols, and perform rotary evaporation at 40°C to form a film; Step 3: Add 200 mL of phosphate buffer solution with a pH of 7.2, containing 0.8 g of tea seed polypeptide and 2 g of polysorbate 80 at a concentration of 0.01 mol / L, and shake at 60°C to mix well for full hydration; Step 4: Add gelatin solution and stir under ultrasonic wave for 1 h at 4°C to obtain a suspension; Step 5: Centrifugal drying to obtain liposomes coated with tea seed polyphenols and tea seed polypeptides. Comparative Example 1 The present invention is different from Example 2 in that gelatin is not added, specifically as follows: The preparation method of liposomes coated with tea seed polyphenols and tea seed polypeptides is as follows: Step 1: Dissolve 3 g of lecithin and 1 g of cholesterol in 100 mL of chloroform, add 50 mL of anhydrous ethanol solution containing 0.3 g of tea seed polyphenols, and perform rotary evaporation at 40°C to form a film; Step 3: Add 200 mL of phosphate buffer solution with a pH of 7.2, containing 0.8 g of tea seed polypeptide and 2 g of polysorbate 80 at a concentration of 0.01 mol / L, and shake at 60°C to mix well for full hydration; Step 4: ultrasonic stirring at 4°C for 1 h to obtain a suspension; Step 5: Centrifugal drying to obtain liposomes coated with tea seed polyphenols and tea seed polypeptides. Comparative Example 2 The difference between the present invention and Example 2 is that tea seed polypeptide is not added, and tea seed polyphenol is used instead, as follows: The preparation method of tea seed polyphenol-coated liposomes is as follows: Step 1: Dissolve 3 g of lecithin and 1 g of cholesterol in 100 mL of chloroform, add 50 mL of anhydrous ethanol solution containing 1.1 g of tea seed polyphenols, and perform rotary evaporation at 40°C to form a film; Step 3: Add 200 mL of phosphate buffer solution with a pH of 7.2 and a concentration of 0.01 mol / L containing 2 g of polysorbate 80, and shake at 60°C to mix well for full hydration; Step 4: ultrasonic stirring at 4°C for 1 h to obtain a suspension; Step 5: Centrifugal drying is performed to obtain liposomes coated with tea seed polyphenols. Comparative Example 3 The difference between the present invention and Example 2 is that tea seed polyphenols are not added, but tea seed polypeptides are used instead, as follows: The preparation method of tea seed polypeptide coated liposome is as follows: Step 1: Dissolve 3 g of lecithin and 1 g of cholesterol in 100 mL of chloroform, add 50 mL of anhydrous ethanol solution, and evaporate to form a film at 40 °C; Step 3: Add 200 mL of phosphate buffer solution with a pH of 7.2, containing 1.1 g of tea seed polypeptide and 2 g of polysorbate 80 at a concentration of 0.01 mol / L, and shake at 60°C to mix well for full hydration; Step 4: ultrasonic stirring at 4°C for 1 h to obtain a suspension; Step 5: Centrifugal drying to obtain liposomes coated with tea seed polypeptide. The encapsulation efficiency and average particle size of tea seed polyphenols and tea seed polypeptides of the above-mentioned embodiment and comparative example liposomes were measured respectively, and the results are shown in the following table: Table 1 Tea seed polyphenol encapsulation rate (%) Tea seed polypeptide encapsulation rate (%) Average particle size (nm) Example 1 77.6 74.5 82.8 Example 2 78.1 74.7 82.9 Comparative Example 1 74.5 71.2 71.4 Comparative Example 2 70.6 - 82.0 Comparative Example 3 - 69.3 80.2 The following examples all use the liposomes coated with tea seed polyphenols and tea seed polypeptides prepared in Example 2. Example 3 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 80g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.8g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Example 4 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.8g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Example 5 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.5g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Example 6 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 1.0g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Example 7 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.8g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 5 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Example 8 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.8g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 8 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Example 9 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.8g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.1 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Example 10 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.8g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.25 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Embodiment 11 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.8g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 1.5 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Example 12 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.8g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.5 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Embodiment 13 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.8g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 3 μm. Embodiment 14 A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.8g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 5 μm. Comparative Example 4 The difference between this comparative example and Example 4 is that citric acid is not used to graft the soy protein isolate, specifically as follows: A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 10g soy protein isolate, 6g glycerol and 0.8g liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g deionized water, and stir magnetically for 20min; S2: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S3: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S4: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S5: Electrospinning was performed using an electrospinning device. The electrospinning conditions were as follows: a spinning liquid flow rate of 2.0 mL / h, a spinning temperature of 25°C, a spinning voltage of 18 kV, an air humidity of 50%, a distance of 15 cm between the spinneret and the receiving plate, a hydrophilic layer was placed on the receiving plate, and after the hydrophobic layer was received, a double-layer plastic wrap was formed. The thickness of the hydrophobic layer was 4 μm. Comparative Example 5 The difference between this comparative example and Example 4 is that the liposomes prepared in Comparative Example 1 are as follows: A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10 g of citric acid-grafted soy protein isolate, 6 g of glycerol and 0.8 g of the liposome prepared in Comparative Example 1, add 180 g of deionized water, and stir magnetically for 20 min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Comparative Example 6 The difference between this comparative example and Example 4 is that the liposomes prepared in Comparative Example 2 are as follows: A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10 g of citric acid-grafted soy protein isolate, 6 g of glycerol and 0.8 g of the liposome prepared in Comparative Example 2, add 180 g of deionized water, and stir magnetically for 20 min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Comparative Example 7 The difference between this comparative example and Example 4 is that the liposomes prepared in Comparative Example 3 are as follows: A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10 g of citric acid-grafted soy protein isolate, 6 g of glycerol and 0.8 g of the liposome prepared in Comparative Example 3, add 180 g of deionized water, and stir magnetically for 20 min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Comparative Example 8 The difference between this comparative example and Example 4 is that nano zinc oxide is not used, and the details are as follows: A method for preparing a double-layer fresh-keeping film comprises the following steps: S1: Take 20 g of soy protein isolate, add 300 g of deionized water, adjust the pH to 8, heat to 90° C. and stir to obtain a soy protein isolate solution; S2: Take 90g of citric acid and add 130g of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: Cooling to room temperature, adding food-grade hydrochloric acid, adjusting the pH to 4.5, centrifuging, and drying to obtain citric acid-grafted soy protein isolate; S4: Take 10g of citric acid grafted soy protein isolate, 6g of glycerol and 0.8g of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 180g of deionized water, and stir magnetically for 20min; S5: adjust the pH to 8.5, heat to 70°C, keep warm for 30 min, cool to room temperature, degas for 10 min at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer with a thickness of 7 μm; S7: dissolving 0.5 g of zein in 5 g of 80% acetic acid solution, adding 0.2 g of nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Electrospinning is performed using an electrospinning device. The electrospinning conditions are as follows: the spinning solution flow rate is 2.0 mL / h, the spinning temperature is 25°C, the spinning voltage is 18 kV, the air humidity is 50%, the distance between the spinneret and the receiving plate is 15 cm, a hydrophilic layer is placed on the receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed, and the thickness of the hydrophobic layer is 4 μm. Determine the static contact angle and sliding angle of the hydrophobic layer; The mechanical properties of the double-layer cling film were measured, including tensile strength and elongation at break. The tensile strength and elongation at break of the double-layer cling film samples were measured using a texture analyzer. The tensile rate was 15 mm / min, and three parallel experiments were performed on each sample. The results are shown in Table 2: Table 2 Note: “-” means not tested The antibacterial properties of the double-layer cling film prepared in Example 4 and the comparative example were determined. Referring to QB / T 2591-2003 "Test Methods and Antibacterial Effects of Antibacterial Plastics" and "Technical Specifications for Disinfection", the prepared double-layer cling film was cultured after being exposed to a certain amount of bacterial suspension for a period of time, and the colony count was performed according to GB 4789.2-2022 "Determination of Total Colony Count in Food Hygiene Microbiological Examination", thereby determining the antibacterial properties of the double-layer cling film. The results are shown in Table 3: Table 3 Embodiment 15 The application of double-layer plastic wrap in the preservation of marinated meat products is as follows: S1: Sealing and packaging the marinated meat product with the double-layer plastic wrap prepared in Example 4; S2: irradiation sterilization, irradiation dose is 3.5kGy; S3: Further packaging in conventional packaging bags and storage. Comparative Example 9 The difference between this comparative example and Example 15 is that the double-layer cling film prepared in Comparative Example 4 is used. Comparative Example 10 The difference between this comparative example and Example 15 is that the double-layer cling film prepared in Comparative Example 5 is used. Comparative Example 11 The difference between this comparative example and Example 15 is that the double-layer cling film prepared in Comparative Example 6 is used. Comparative Example 12 The difference between this comparative example and Example 15 is that the double-layer cling film prepared in Comparative Example 7 is used. Comparative Example 13 The difference between this comparative example and Example 15 is that the double-layer cling film prepared in Comparative Example 8 is used. Total colony count: Determined according to the plate count method in the national standard GB / T4789.2-2022, with 3 plates for each dilution gradient. Volatile basic nitrogen: Using the principle of semi-micro nitrogen determination, a fully automatic Kjeldahl nitrogen analyzer was used to determine the volatile basic nitrogen of marinated meat products. Sensory evaluation: A scoring panel consisting of 10 faculty and students from the college conducted the sensory evaluation. The evaluation criteria are shown in Table 4. Table 4 Sensory scoring standards for marinated meat products After the marinated meat products were stored at room temperature (24-26°C) for 20 days, the total colony count, volatile basic nitrogen and sensory evaluation were performed. The results are shown in Table 5 below: Table 5 It can be seen from Table 5 that the total colony counts of Examples 13 to 15 are all relatively low, which fully complies with the provisions of the Hygienic Standard for Cooked Meat Products (GB2726-2016), that the total bacterial count of marinated meat is ≤4.9lg (CFU / g). At the same time, after Example 15 and Comparative Example 10 were stored at high temperature (37-38° C.) for 20 days, the total bacterial count, volatile basic nitrogen and sensory evaluation were performed. The results are shown in Table 6: Table 6

Claims

1. A double-layer cling film, characterized in that: The cling film is double-layered, the outer film is a hydrophobic layer, and the inner film is a hydrophilic layer; the hydrophobic layer is obtained by electrostatic spinning of zein, and the surface has a micro-nano structure; The hydrophilic layer is obtained by casting citric acid grafted soybean protein isolate, and the membrane contains liposomes coated with tea seed polyphenols and tea seed polypeptides.

2. A double-layer cling film according to claim 1, characterized in that: The thickness of the hydrophilic layer is 5-8 μm, and the thickness of the hydrophobic layer is 3-5 μm.

3. A double-layer cling film according to claim 1, characterized in that: The hydrophobic layer has micropores with a pore diameter of 0.1-0.8 μm.

4. A double-layer cling film according to claim 1, characterized in that: The preparation method of the liposome coated with tea seed polyphenols and tea seed polypeptides is as follows: Step 1: Dissolve 0.5 g of gelatin in 50 mL of water and heat to obtain a gelatin solution; Step 2: Dissolve 3 g of lecithin and 1 g of cholesterol in 100 mL of chloroform, add 50 mL of anhydrous ethanol solution containing 0.3 g of tea seed polyphenols, and perform rotary evaporation at 40-50°C to form a film; Step 3: Add 200 mL of phosphate buffer solution with a pH of 6.5-7.4, containing 0.5-0.8 g of tea seed polypeptide and 2 g of polysorbate 80 at a concentration of 0.01 mol / L, and shake at 60°C to mix well for full hydration; Step 4: Add gelatin solution and stir under ultrasonic wave for 1 h at 4°C to obtain a suspension; Step 5: Centrifugal drying to obtain liposomes coated with tea seed polyphenols and tea seed polypeptides.

5. The method for preparing a double-layer cling film according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: Take 2 parts of soy protein isolate, add 30 parts of deionized water, adjust the pH to 7-8, heat to 90°C and stir to obtain a soy protein isolate solution; S2: Take 8-9 parts of citric acid and add 10-15 parts of deionized water to obtain a citric acid solution; S3: cool the soy protein isolate solution to 60°C, add citric acid solution dropwise at a rate of 1 drop / s, and stir to react for 1-2 hours after the addition is complete; S3: cool to room temperature, add food-grade hydrochloric acid, adjust the pH to 4-5, centrifuge, and dry to obtain citric acid-grafted soy protein isolate; S4: Take 10 parts of citric acid grafted soy protein isolate, 6 parts of glycerol and 0.5-1 parts of liposomes coated with tea seed polyphenols and tea seed polypeptides, add 150-200 parts of deionized water, and stir magnetically for 20 minutes; S5: adjust the pH to 8-9, heat to 70-80°C, keep warm for 30 minutes, cool to room temperature, degas for 10 minutes at a vacuum degree of 0.1 MPa to obtain a hydrophilic layer membrane liquid; S6: casting the hydrophilic layer film liquid into a film, and drying it at a temperature of 50° C. to obtain a hydrophilic layer; S7: dissolving 0.5 parts of zein in 3-5 parts of 80% acetic acid solution, adding nano zinc oxide, and stirring evenly to obtain a spinning solution; S8: Using an electrospinning device to perform electrospinning, a hydrophilic layer is placed on a receiving plate, and after the hydrophobic layer is received, a double-layer plastic wrap is formed.

6. The method for preparing a double-layer cling film according to claim 5, characterized in that: The mass ratio of zein to nano zinc oxide in the S7 is (2-5):

1.

7. The method for preparing a double-layer cling film according to claim 5, characterized in that: The particle size of the nano zinc oxide in S7 is 15-35 nm.

8. The method for preparing a double-layer cling film according to claim 5, characterized in that: The electrospinning conditions are as follows: the spinning solution flow rate is 1.5-2.5 mL / h, the spinning temperature is 25° C., the spinning voltage is 18 kV, the air humidity is 50%, and the distance between the spinneret and the receiving plate is 15 cm.

9. Application of a double-layer cling film according to any one of claims 1 to 4 in the preservation of marinated meat products, characterized in that: The application method is as follows: S1: The marinated meat products are sealed and packaged with a double layer of plastic wrap; S2: Sterilization; S3: Further packaging in conventional packaging bags and storage.

10. Application of a double-layer cling film according to claim 9 in the preservation of marinated meat products, characterized in that: The sterilization method adopts irradiation sterilization, and the irradiation dose is 3-4 kGy.

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