Preparation method of degradable composite food film based on antibacterial emulsion

Abstract

The invention provides a preparation method of a degradable composite food film based on a bacteriostatic emulsion and a food film, and belongs to the field of food packaging, and the preparation method comprises the following steps: preparing a bacteriostatic agent carvacrol oil-in-water system emulsion; adding glycerol into the biodegradable polymer and the biological polysaccharide, and fully and uniformly mixing; adding the bacteriostatic agent emulsion into the mixture; according to the polysaccharide / bacteriostatic agent emulsion composite food film and the preparation method thereof, a modern production process is adopted, the defect that a hydrophobic bacteriostatic agent needs to be dissolved in an organic solvent and then added into a polymer matrix is overcome, the influence of the organic solvent on food and human health and safety is reduced, and the polysaccharide / bacteriostatic agent emulsion composite food film is prepared. The produced food film is environment-friendly and non-toxic, can be completely biodegraded, is low in water absorption and water vapor permeability and strong in antibacterial performance, can effectively prevent food from being polluted and deteriorated, and provides a novel packaging material for the food industry.

Description

Technical Field

[0001] The invention belongs to the technical field of food packaging, and in particular relates to a method for preparing an environmentally friendly antibacterial emulsion composite food film. Background Art

[0002] Thanks to large-scale industrial production, petroleum-based plastics have high strength, low price, easy sealing, dust and moisture resistance, etc. They are widely used in various packaging. While bringing convenience to people, they also bring huge burdens to the natural environment. At the same time, due to its widespread use, small plastic fragments have accumulated in the living environment and food chain, posing a threat to human health. Therefore, it is urgent to develop green and environmentally friendly packaging materials, and natural and degradable active packaging provides a feasible solution to these problems. In addition, traditional food packaging simply encapsulates and stores food, bacteria are easy to reproduce and grow, and long-term storage will bring food safety hazards. Antibacterial packaging can kill or inhibit microorganisms on the surface of food during processing, storage, transportation and handling, and extend the shelf life and safety of food. Therefore, the use of natural and degradable polymer materials to replace non-degradable materials and add antibacterial agents to make them both antibacterial and degradable is the development trend of food packaging films in the future. Polycaprolactone (PCL) is a biodegradable polymer material with good processing performance, heat sealing performance, stiffness and toughness. It can improve the heat resistance and barrier properties of food films. Therefore, mixing PCL with bio-based polymers to form films has a complementary effect. Cellulose acetate (CA) is one of the cellulose derivatives. It can be used in the field of food packaging due to its excellent film-forming properties, high chemical and mechanical stability, high hydrophilicity, and stain resistance. Incorporating functional substances into the film matrix is ​​a feasible solution to food safety hazards. Carvacrol is a monoterpene organic compound that naturally exists in thyme essential oil. It has broad-spectrum antibacterial properties and strong antioxidant activity. It can also improve the thermal stability and hydrophobicity of food films, as well as improve light barrier properties. However, carvacrol is volatile and has poor water solubility, which limits its good integration with the hydrophilic polymer matrix.

[0003] At present, regarding the selection of raw materials for the preparation of antibacterial food films, some have not taken environmental degradation into consideration, while others have not provided encapsulation and protection for unstable antibacterial agents. For example, patent document number CN202310045903.0 discloses an antibacterial food packaging film and a preparation method thereof. The raw materials for the preparation include 5,5-dimethylhydantoin, N,N-dimethylaminochloropropane hydrochloride, etc. The antibacterial rate of the film can reach 99.99%, but the raw materials for the preparation are not biodegradable materials and are not easy to decompose in the natural environment; patent document number CN202011374017.5 uses chlorhexidine (CHX) and polydimethylsiloxane (PDMS) and other materials in the preparation of antibacterial food packaging film, which has good antibacterial effect, and its raw materials are also not environmentally degradable; patent CN202210810716.2 introduces a nanocellulose-based antibacterial and anti-oxidant hydrophobic film and its preparation method and application. The composite antibacterial agents tea polyphenols and clove essential oil are directly added into the film for cast film formation, which can easily cause the decomposition of the two in environments such as strong light, high cold and high heat. On the other hand, in the current field of degradable food film preparation, the antibacterial properties of food films are easily overlooked. For example, patent CN202410054323.2 discloses a high-strength degradable food packaging film material and its preparation method. The maximum tensile strength can reach about 56.68MPa and the mechanical properties are good, but the antibacterial properties have not been tested; Shanghai Jinghai Weixiang Biomaterials Co., Ltd. has prepared a tear-resistant, degradable polylactic acid food packaging film (patent number CN202110627876.9), which can significantly improve the tear strength of the polylactic acid packaging film, but it has also not been tested for antibacterial properties.

[0004] Although a lot of research has been done on food packaging films in the prior art, many bio-based polymers or antibacterial agents have been used in food-related packaging. Biopolymers, such as polysaccharides, proteins and lipids, are potential candidates for the development of food films due to their non-toxicity and biodegradability; similarly, adding antibacterial active ingredients to food films can extend the shelf life, which is conducive to the improvement of the antibacterial properties of food films. However, the food films currently produced have more or less poor mechanical properties, do not meet the requirements of green and environmentally friendly packaging materials, have poor water resistance, lack of antibacterial properties or antibacterial ingredients are easy to decompose, and still cannot meet actual needs. How to develop a degradable food packaging film with high antibacterial properties is an urgent problem to be solved. In view of the defects of the above-mentioned existing film preparation, the inventors have designed a degradable antibacterial emulsion composite food film, which has mild preparation conditions and simple methods. The resulting film is safe and reliable, has safe quality, good mechanical properties, is edible, easy to tear, and has good antibacterial effect. Summary of the invention

[0005] Technical problem to be solved: The purpose of the present invention is to provide a degradable emulsion composite food film based on polycaprolactone / cellulose acetate / carvacrol antibacterial emulsion and a preparation method thereof in order to address the problems in the prior art that food film materials cannot be naturally degraded, have poor antibacterial properties, and antibacterial agents are easily decomposed.

[0006] Technical solution:

[0007] A method for preparing a degradable composite food film based on an antibacterial emulsion comprises the following steps:

[0008] (1) Preparing carvacrol oil-in-water emulsion;

[0009] (2) Accurately weigh polycaprolactone and cellulose acetate into a beaker to ensure that the total mass of the two is constant, add an equal amount of glycerol and carvacrol emulsion, and mix them by stirring.

[0010] (3) All samples were hot-pressed into shape using a hot press, and then the pressure was released and peeled off to obtain a biodegradable antibacterial emulsion composite food film.

[0011] Preferably, the ingredients of the oil-in-water emulsion in step (1) are carvacrol, ultrapure water, emulsifier Tween 80, and co-emulsifier anhydrous ethanol;

[0012] Preferably, the preparation parameters of the emulsion in step (1) are high-speed disperser at 5000 r / min for 3 min, followed by ultrasonic treatment for 10 min;

[0013] Preferably, the carvacrol oil-in-water emulsion in step (1) is mixed in a ratio of 5 to 10 parts of water phase to 1 to 5 parts of oil phase, and the volume fraction of carvacrol is 12.5%;

[0014] Preferably, the mass ratio of polycaprolactone and cellulose acetate in step (2) is in the range of: (8-10): (0-2);

[0015] Preferably, after the glycerol described in step (2) is added, stirring is required for 30 minutes to ensure that it is fully mixed;

[0016] Preferably, the volume of the carvacrol emulsion in step (2) is 2 mL.

[0017] Preferably, the parameters of the hot press in step (3) are upper and lower mold temperature of 60°C, pressure of 20 MPa, and action time of 5 to 10 min.

[0018] Beneficial Effects

[0019] The food film of the present invention is composed of green materials / polysaccharides / antibacterial active substances, i.e., polycaprolactone-cellulose acetate-carvacrol, which is a further extension based on a biodegradable packaging film, has the advantages of being fully degradable, environmentally friendly and safe, and the packaging can inhibit the activity of microorganisms during use, ensure the nutritional flavor and food quality safety, and extend the shelf life of food. The antibacterial agent carvacrol is added in the form of an emulsion, and polycaprolactone is used as a carrier of carvacrol, which can play a protective and sustained-release role on the antibacterial agent to a certain extent, and significantly improves the antibacterial effect. At the same time, the preparation method of the food film is easy to carry out, the conditions are mild, the obtained film has stable properties, is smooth and compressive, has good mechanical properties, is safe and non-toxic, edible, easy to tear, and has a good antibacterial effect. Both the environmental protection is greatly improved and the quality of the product is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the emulsion particle size diagram of Example 1;

[0021] Figure 2 The surface images (1) and scanning electron microscope images (2: surface image, 3: cross-sectional image) of the composite food films of Examples 2-5 and Comparative Examples 1 and 2;

[0022] Figure 3 The Fourier transform infrared spectra of Examples 2-5 and Comparative Examples 1 and 2 are shown;

[0023] Figure 4 Thermal characteristic test diagrams of Examples 2-5 and Comparative Examples 1 and 2; (a) crystallization diagram, (b) melting diagram;

[0024] Figure 5 is a graph showing the changes in degradation rates within 72 D of Examples 2-5 and Comparative Examples 1 and 2;

[0025] Figure 6 The scanning electron microscope images of Examples 2-5 and Comparative Examples 1 and 2 after degradation for 72 D are shown;

[0026] Figure 7 The figures are the inhibitory effects of Examples 2-5 and Comparative Examples 1 and 2 on Escherichia coli (a) and Staphylococcus aureus (b);

[0027] Figure 8 The graph shows the inhibition rates of Examples 2-5 and Comparative Examples 1 and 2 against Escherichia coli and Staphylococcus aureus. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention and the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the following examples, polycaprolactone, cellulose acetate, medium chain triglyceride, Tween 80, anhydrous ethanol and carvacrol were purchased from Aladdin Reagent Co., Ltd.

[0030] Example 1

[0031] The preparation of carvacrol emulsion, firstly, 3-8 parts of carvacrol and 1-3 parts of anhydrous ethanol were mixed as the oil phase, 5% Tween 80 was added as the water phase, and the mixture was mixed in a ratio of 5-10 parts of the water phase and 1-5 parts of the oil phase, and the mixture was treated at a high speed of 5000 r / min for 3 min using a high-speed disperser, and then the pre-emulsion was further treated in ultrasound for 10 min to obtain a more uniformly dispersed emulsion. During this process, the volume fraction of carvacrol was maintained at 12.5%.

[0032] The particle size of the emulsion of Example 1 was measured. The parameters were set as temperature 25°C, refractive index 1.522, equilibrium time 120 s, and dynamic light scattering (DLS) was used to measure the particle size distribution of the sample. The measurement results are shown in Figure 1 As shown. Figure 1 It can be seen that when the addition amount of carvacrol is 12.5%, the carvacrol emulsion is uniformly milky white, with basically no particle adhesion and aggregation, and no precipitation, indicating that the emulsion is relatively stable. The average particle size of the emulsion is mainly distributed in two types, of which the main proportion of 70% is 94.94 nm, and the remaining 30% is 499 nm.

[0033] Example 2

[0034] A PCL / CA / CE emulsion composite food film, the raw materials of which include: polycaprolactone (PCL), cellulose acetate (CA), glycerol and carvacrol emulsion (CE). The preparation method of the composite food film includes the following steps:

[0035] Accurately weigh 8.0 g of polycaprolactone powder in a beaker, and then add 2.0 g of cellulose acetate powder to prepare a constant total content of 10.0 g. Add an appropriate amount of glycerol and stir with a glass rod for 30 min to mix it thoroughly, then add 2 mL of carvacrol emulsion to mix and obtain the sample. Set the upper and lower mold temperatures of the hot press to 60 ° C, spread all the sample powders evenly on the film, apply pressure until it reaches 20 MPa, maintain this temperature and pressure for 5-10 min, and then cool it down. Remove the pressure and take out the film. After peeling off the composite film, store it in a sealed bag at room temperature. The PCL / CA / CE composite food film is recorded as P80-CA20-CE.

[0036] Example 3

[0037] A degradable composite food film based on an antibacterial emulsion is prepared by the following method:

[0038] 9.0 g of polycaprolactone powder was accurately weighed in a beaker, and 1.0 g of cellulose acetate powder was added to prepare a total content of 10.0 g, and 2 mL of carvacrol emulsion was added before film pressing to obtain a sample. Other details were the same as in Example 2, and the PCL / CA / CE composite food film was recorded as P90-CA10-CE.

[0039] Example 4

[0040] A degradable composite food film based on an antibacterial emulsion is prepared by the following method:

[0041] 9.5 g of polycaprolactone powder was accurately weighed into a beaker, and 0.5 g of cellulose acetate powder was added to prepare a total content of 10.0 g. 2 mL of carvacrol emulsion was added before film pressing to obtain a sample. Other details were the same as in Example 2, and the PCL / CA / CE composite food film was recorded as P95-CA5-CE.

[0042] Example 5

[0043] A degradable composite food film based on an antibacterial emulsion is prepared by the following method:

[0044] 9.8 g of polycaprolactone powder was accurately weighed into a beaker, and 0.2 g of cellulose acetate powder was added to prepare a total content of 10.0 g. 2 mL of carvacrol emulsion was added before film pressing to obtain a sample. Other details were the same as in Example 2, and the PCL / CA / CE composite food film was recorded as P98-CA2-CE.

[0045] Comparative Example 1

[0046] The difference between Comparative Example 1 and Example 2 is that no cellulose acetate (CA) and carvacrol emulsion are added during film formation, and the rest is the same as Example 2, denoted as PCL100.

[0047] Comparative Example 2

[0048] Comparative Example 2 differs from Example 2 in that cellulose acetate (CA) is not added during film formation, and the rest is the same as Example 2, and is denoted as PCL100-CE.

[0049] Test Example 1

[0050] The surface morphology and cross-sectional morphology of Examples 2-5 and Comparative Examples 1 and 2 were observed at 5 kV using a field emission electron scanning microscope (NanoSEM-450, FEI Company, USA). The surface morphology of the composite film was observed at a magnification of 1000 times after the 3× 3 mm square sample was sprayed with gold; the cross-sectional morphology of the composite film was observed at a magnification of 3500 times after the 5× 30 mm sample was embrittled by liquid nitrogen (-80°C) and bonded to a 30× 30 mm silicon wafer, which was perpendicular to the stage and sprayed with gold.

[0051] Figure 2 The present invention provides the apparent images and SEM photos (surface image, cross-sectional image) of the cross sections of the food films obtained in Examples 2-5 and Comparative Examples 1 and 2; wherein A is Comparative Example 1, B is Comparative Example 2, C is Example 2, D is Example 3, E is Example 4, and F is Example 5.

[0052] Depend on Figure 2 It can be seen that:

[0053] The surface of the PCL film of Comparative Example 1 is smooth and flat, showing an opaque milky white color and a small amount of white granular matter, but for its cross section, there is a fracture surface and a layered structure, reflecting its high toughness;

[0054] In Examples 2-5, due to the addition of carvacrol emulsion, the surface image in its microstructure shows a dense and uniform structure, and its protrusions and insoluble particles are reduced. This may be because the carvacrol emulsion is liquid, which increases the binding sites between PCL and cellulose acetate, promotes the fluidity between the substances, and makes its surface smoother.

[0055] Test Example 2

[0056] The structural interactions between the molecules of Examples 2-5 and Comparative Examples 1 and 2 were analyzed and observed using an FTIR spectrometer (Nicolet iS10, Thermo Fisher Scientific, USA) in attenuated total reflection mode. With air as the measurement background, the samples were scanned and tested in the transmission mode of 4000-400 cm-1 with a resolution of 4 cm-1.

[0057] Figure 3The following are Fourier transform infrared spectra of the food films obtained in Examples 2-5 and Comparative Examples 1 and 2.

[0058] Depend on Figure 3 It can be seen that:

[0059] In Example 2-5, due to the addition of carvacrol emulsion, the characteristic peak generated at 2364 cm-1 indicates that the emulsion can be integrated into the PCL / CA film, and the three substances have a chemical reaction. The stretching vibration absorption peak corresponding to the OH bond is about 3368 cm-1. After adding CE, it can be clearly observed that the peak at the OH bond becomes flatter, which is due to the cross-linking reaction of strengthening the hydrogen bond between carvacrol and PCL / CA; the symmetric and asymmetric stretching vibration modes shown at 2956 and 2881 cm-1 are respectively attributed to the CH bond in the CH3 group; in addition, the C=O bond (amide I band) and CO vibration absorption peaks at 1727 cm-1 and 1192 cm-1 respectively correspond to the absorption peaks. With the increase of CA content, the peaks at these two places show a decreasing trend, which also shows that PCL and CA are only physically mixed.

[0060] Test Example 3

[0061] Thermal properties of Examples 2-5 and Comparative Examples 1 and 2 were measured. Differential scanning calorimetry (Q2000, Waters, USA) was used to analyze the crystallization and melting processes of the food film under N2 atmosphere. The sample was heated from 20°C to 240°C at a rate of 20°C / min, kept for 5 min, and then cooled to 20°C at the same rate to eliminate the historical program, and the crystallization curve and melting curve were obtained. The crystallization temperature (Tc), melting temperature (Tm), crystallization enthalpy value (ΔHc) and melting enthalpy value (ΔHm) were calculated by software.

[0062] Figure 4 The crystallization diagram (a) and melting diagram (b) of the food films obtained in Examples 2-5 and Comparative Examples 1 and 2 are shown in Table 1. The thermal characteristic parameters of the food films obtained in Examples 2-5 and Comparative Examples 1 and 2 are shown in Table 1. The experimental data are expressed as mean ± standard deviation. The experiment was repeated 3 times. Different letters in the same column indicate significant differences (P<0.05).

[0063] Table 1 Thermal properties of PCL / CA and PCL / CA / CE food films

[0064]

[0065] Depend on Figure 4 From Table 1, we can conclude that:

[0066] All examples and comparative examples have significant crystallization peaks and melting peaks, and the sizes and positions are similar. Only one crystallization peak indicates that the compatibility between the substances is good, forming a stable and uniform continuous phase. At the same time, the melting peak of the sample is presented in the form of continuous peaks, and the temperature is roughly around 50°C.

[0067] In Comparative Examples 1 and 2, the addition of CE reduces Tc, indicating that CE can cause the molecules of the composite food film to begin to form an ordered crystal structure at a lower temperature;

[0068] In Examples 2-5, the addition of CA did not have a significant effect on its crystallization temperature, but caused the ΔHc and ΔHm values ​​to decrease to varying degrees, indicating that the addition of cellulose acetate reduced the difficulty of the crystallization and melting process of the composite food film, which means that less energy is required to achieve phase change during processing, which helps to maintain the structural integrity of the film during heat treatment. At the same time, the reduced ΔHc and ΔHm values ​​may mean that the film is less sensitive to temperature changes during food storage and transportation, thereby reducing the risk of degradation of film performance due to temperature fluctuations.

[0069] Test Example 4

[0070] The degradation of food films was characterized under natural conditions. Degradability tests were performed on Examples 2-5 and Comparative Examples 1 and 2. The samples were cut into 20 × 20 mm squares, dried in an oven at 60°C to constant weight, marked and buried in the soil, recorded as W0. The samples were taken out every other week, the soil on the surface was wiped clean, weighed and recorded as W1. The weight loss rate was calculated as follows:

[0071] Weight loss (%) = (W0-W1) / W0 × 100%

[0072] Figure 5 The degradation rates of the food films obtained in Examples 2-5 and Comparative Examples 1 and 2. Figure 6 The scanning electron microscope images of the food films prepared in Examples 2-5 and Comparative Examples 1 and 2 after degradation for 72 days, wherein A is Comparative Example 1, B is Comparative Example 2, C is Example 5, D is Example 4, E is Example 3, and F is Example 2.

[0073] Depend on Figure 5 , Figure 6 It can be concluded that:

[0074] Comparative Example 1 contains only one material, PCL. Due to the regularity and crystallinity of its structure, the intermolecular force is strong, and the microorganisms face certain difficulties in attaching to the membrane surface and decomposing the molecular chains, which hinders the degradation process to a certain extent, resulting in the slowest degradation rate;

[0075] In Examples 2-5 and Comparative Example 2, as the CA ratio increases, the degradation rate gradually increases. Example 2 has the best degradation effect, which can reach 45.51%. This is mainly because the addition of cellulose acetate destroys the regularity and crystallinity of the polycaprolactone molecular chain. The presence of carvacrol also makes the molecular structure of the composite film looser, weakens the intermolecular force, and reduces the orderliness of the overall structure, which makes it easier for the degradation medium to contact the interior of the film, providing more sites and channels for the degradation reaction, thereby facilitating the degradation process.

[0076] The SEM image shows that due to the increase in the CA ratio, the holes, particles and filamentous substances on the surface of the composite membrane are significantly increased, further proving the improvement of the degradation performance; compared with the embodiment, the surface of the PCL composite membrane of Comparative Example 1 is still relatively smooth after degradation, with protruding granular substances but not in large quantities, indicating that even in some environments that are not conducive to degradation, ingredients such as carvacrol and cellulose acetate can promote the degradation reaction to a certain extent and reduce the negative impact of environmental factors on the degradation rate.

[0077] Test Example 5

[0078] The antibacterial performance of Examples 2-5 and Comparative Examples 1 and 2 was measured, using Escherichia coli and Staphylococcus aureus as test bacteria. First, Escherichia coli and Staphylococcus aureus were activated and diluted to obtain Escherichia coli and Staphylococcus aureus suspensions, and then the antibacterial effect of the composite film was evaluated.

[0079] Figure 7 The antibacterial effect of the food films prepared in Examples 2-5 and Comparative Examples 1 and 2, wherein A is the original bacterial solution (Figure a is Escherichia coli, Figure b is Staphylococcus aureus), B is Comparative Example 1, C is Comparative Example 2, D is Example 5, E is Example 4, F is Example 3, and G is Example 2. Figure 8 The antibacterial efficiency of the food films prepared in Examples 2-5 and Comparative Examples 1 and 2.

[0080] Depend on Figure 7 , Figure 8 It can be seen that:

[0081] The antibacterial rates of comparative example 1 were only 5.67% (a) and 14.55% (b), indicating that its antibacterial effects on Escherichia coli and Staphylococcus aureus were weak;

[0082] In Comparative Example 2 and Examples 2-5, the antibacterial efficiency of the composite food film after adding CE is generally higher than 80% (a), among which Example 4 has an inhibition rate of up to 90.34% (a) on Escherichia coli, which is 16 times stronger than that of Comparative Example 1; Example 3 has an inhibition rate of up to 81.99% on Staphylococcus aureus, which is 6 times stronger than that of Comparative Example 1, showing the significant antibacterial efficiency of carvacrol emulsion. The antibacterial mechanism of carvacrol is attributed to its effect on the surface structure and function of bacterial cell membranes, specifically destroying the structure of cell membranes, hindering proton motive force and electron flow, and increasing the level of intracellular ROS; at the same time, the emulsion form of carvacrol enables the continuous release of carvacrol molecules, ensuring their continuous destruction of the cell plasma membrane.

Claims

1. A method for preparing a degradable composite food film based on an antibacterial emulsion, characterized in that: The steps include: (1) Preparing carvacrol oil-in-water emulsion; (2) Weighing polycaprolactone and cellulose acetate to ensure that the total mass of the two is constant, and then adding glycerol and carvacrol emulsion to mix well; (3) Pressing the film with a hot press, releasing the pressure and peeling it off to obtain a biodegradable material / modified polysaccharide / antibacterial agent emulsion composite food film.

2. The method for preparing the degradable antibacterial emulsion composite food film according to claim 1, characterized in that: The ingredients of the water-in-oil emulsion in step (1) are carvacrol, ultrapure water, emulsifier Tween 80, and co-emulsifier anhydrous ethanol.

3. The method for preparing the degradable antibacterial emulsion composite food film according to claim 1, characterized in that: The preparation parameters of the emulsion in step (1) are high-speed disperser at 5000 r / min for 3 min, followed by ultrasonic treatment for 10 min.

4. The method for preparing the degradable antibacterial emulsion composite food film according to claim 1, characterized in that: The carvacrol oil-in-water emulsion is mixed in a ratio of 5 to 10 parts of water phase and 1 to 5 parts of oil phase, and the volume fraction of carvacrol is 12.5%.

5. The method for preparing the degradable antibacterial emulsion composite food film according to claim 1, characterized in that: The mass ratio of polycaprolactone and cellulose acetate in step (2) is in the range of (8-10): (0-2).

6. The method for preparing the degradable antibacterial emulsion composite food film according to claim 1, characterized in that: After the glycerol described in step (2) is added, it needs to be stirred for 30 minutes to ensure that it is fully mixed.

7. The method for preparing the degradable antibacterial emulsion composite food film according to claim 1, characterized in that: The volume of the carvacrol emulsion was 2 mL.

8. The method for preparing the degradable antibacterial emulsion composite food film according to claim 1, characterized in that: The parameters of the hot press described in step (3) are upper and lower mold temperature 60°C, pressure 20 MPa, and action time 5 to 10 min.

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