High-performance protein-based nano-emulsion food packaging film and preparation method thereof

Abstract

The invention provides a high-performance protein-based nano-emulsion food packaging film and a preparation method thereof, and the preparation method comprises the following steps: S1, adding glycerol into a collagen aqueous solution, and stirring to obtain an aqueous phase liquid; s2, adding an emulsifier into the essential oil aqueous solution, stirring, and performing high-pressure homogenization to obtain an oil-phase liquid; s3, adding the oil-phase liquid obtained in the step S2 into the water-phase liquid obtained in the step S1, and performing high-pressure homogenization to obtain nano-emulsion; and S4, pouring the nano-emulsion in the step S3 into a horizontally placed template groove, casting to form a film, and drying at room temperature to prepare the high-performance protein-based nano-emulsion food packaging film. The high-performance protein-based nano-emulsion food packaging film is easy to biodegrade, good in mechanical property, high in heat stability, strong in water blocking capacity and good in antibacterial and antioxidant effects, can effectively slow down spoilage of packaged food caused by microbiological contamination and oxidative decomposition of nutritional ingredients, has good fresh-keeping performance, can ensure food quality, and is suitable for popularization and application. The food shelf life is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and in particular relates to a high-performance protein-based nanoemulsion food packaging film and a preparation method thereof. Background Art

[0002] Petroleum-based packaging materials, represented by plastics, have caused tremendous pressure on the environment, aggravated the energy crisis, and triggered a series of severe economic problems due to their shortcomings such as non-degradability and difficulty in processing. Therefore, the demand for new biodegradable green and environmentally friendly packaging materials is imminent. Polymer packaging films made of natural polymer substances such as proteins, lipids and sugars can alleviate environmental pressure to a certain extent due to their advantages such as biodegradability, renewable raw materials and wide sources.

[0003] Packaging films based on proteins can be divided into animal protein films and plant protein films according to the source of the film-forming proteins. For example, collagen from animal sources exists in animal connective tissues and is the most abundant and widely distributed protein in mammals. In practical applications, collagen can be obtained in a more economical way from by-products of meat processing (such as skin, tendons, bones and cartilage of pigs, cattle, sheep, poultry, fish, shrimp and other seafood). Plant-based soy protein isolate is extracted from raw materials such as soybean meal. It is also widely available, rich in nutrients, and does not contain cholesterol. Protein films are easily biodegraded because their main component is protein, which reduces environmental pollution and improves the sensory and nutritional properties of food. At the same time, because protein films have good mechanical strength, they can be supplemented with small molecule film additives to enhance their barrier effect to ensure the quality of packaged food.

[0004] During the production, processing, transportation, storage and sales of food, it is inevitable that it will be affected by external factors such as physical, chemical or biological factors, resulting in deterioration of quality such as spoilage. Therefore, functional packaging materials that can effectively block and inhibit the above influences are an effective solution to ensure food quality and extend the shelf life of food. The two main reasons for food spoilage are food contamination and oxidative decomposition of nutrients, which have caused huge economic losses to the food industry. Pasteurization and the addition of preservatives are currently the two most common methods to prevent food spoilage. However, the pasteurization process consumes a lot of energy and will cause partial loss of food nutrients. Preservatives can inhibit the growth of microorganisms and the oxidation of nutrients to a certain extent, but they often have certain toxicity, causing potential food safety issues. Natural antibacterial agents and antioxidants, especially natural active ingredients extracted from pure natural plants, are safe and non-toxic. Their main ingredients can destroy microbial cell walls, cell membranes and membrane proteins, scavenge free radicals, and thus effectively inhibit bacteria and slow down the oxidative decomposition of nutrients such as unsaturated fatty acids in food. Essential oils are aromatic substances extracted from plants and have been identified as safe substances that can be added to food and medicine. Their main components are terpenes and phenolic compounds, which have excellent antibacterial properties and can resist bacteria, fungi, molds and viruses. Some of them also have strong antioxidant properties. Essential oils are hydrophobic and, when combined with hydrophilic film materials, can improve the mechanical properties of packaging films and enhance their water-barrier properties.

[0005] Emulsification utilizes the amphiphilicity of the emulsifier to make it possible for the incompatible aqueous phase and milk phase to emulsify and form a relatively stable emulsion. Emulsions can be divided into coarse emulsions, microemulsions and nanoemulsions according to the size of the dispersed droplets. Among them, nanoemulsions with a particle diameter of 1-100nm have higher dispersibility and stronger stability. When the particle size of the material is reduced to the nanometer level, its surface energy increases, and it has a stronger adsorption capacity and reactivity. It can more effectively contact bacteria and destroy its cell structure, thus having an antibacterial effect. There are two methods of nanoemulsification technology: low-energy method (including: phase change temperature method, phase change component method and spontaneous emulsification method) and high-energy method (including: high-pressure homogenization method, ultrasonic homogenization method and high-pressure microfluid homogenization method). The high-pressure homogenization method uses the high hydraulic pressure generated by the piston pump to repeatedly break up the droplets into smaller droplets with a diameter that meets the range of nanoemulsions. It is a common and effective method for preparing nanoemulsions in industry. The new food packaging film developed by combining hydrophobic functional ingredients with hydrophilic film-forming matrix using nanoemulsification technology can not only improve the physical and chemical properties of the film, but also give the film antibacterial and antioxidant functions, thereby extending the shelf life of packaged food. Therefore, nanoemulsification technology plays an important role in the development of new food packaging materials. Invention content

[0006] In view of this, the invention aims to propose a high-performance protein-based nanoemulsion food packaging film and a preparation method thereof to solve at least one technical problem in the background technology. The high-performance protein-based nanoemulsion food packaging film of the present invention is made of protein (animal collagen or plant soy protein isolate) as a matrix, and natural plant antibacterial agents and antioxidants (thyme essential oil and cinnamon essential oil) are uniformly dispersed in it as nano-scale particles using nano-emulsification technology.

[0007] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0008] A method for preparing a high-performance protein-based nanoemulsion food packaging film comprises the following steps:

[0009] S1: Add glycerol to the collagen aqueous solution and stir to obtain an aqueous phase;

[0010] S2: adding an emulsifier to the essential oil aqueous solution and stirring, and obtaining an oil phase liquid after high pressure homogenization;

[0011] S3: the oil phase liquid obtained in step S2 is added to the water phase liquid in step S1, and a nanoemulsion is obtained after high pressure homogenization;

[0012] S4: the nanoemulsion in step S3 is poured into a horizontally placed template groove, cast into a film, and dried at room temperature to prepare a high-performance protein-based nanoemulsion food packaging film.

[0013] Further, the concentration of the collagen aqueous solution in step S1 is 2%-8%;

[0014] And / or, the aqueous solution in the collagen aqueous solution in step S1 is deionized water;

[0015] And / or, in step S1, the weight of glycerol is 38-42% of the weight of collagen.

[0016] Furthermore, the protein in step S1 includes one or both of animal-derived protein and plant-derived protein;

[0017] And / or, the animal-derived protein includes one or more of collagen, gelatin, whey protein, casein, fish protein isolate, and keratin,

[0018] And / or, the plant-based protein includes one or more of soy protein isolate, zein, wheat protein, sorghum protein, rice bran protein, and peanut protein.

[0019] Further, the essential oil in step S2 includes one or more of thyme essential oil, cinnamon essential oil, clove essential oil, peppermint essential oil, basil essential oil, oregano essential oil, rosemary essential oil, tea tree essential oil, ginger essential oil, garlic essential oil, bergamot essential oil, sunflower essential oil, citronella essential oil, lemongrass essential oil, and chamomile essential oil.

[0020] Further, the concentration of the essential oil in step S2 is 1%-4%;

[0021] and / or, the weight of the emulsifier is 25% by weight of the thyme essential oil;

[0022] And / or, the emulsifier is one or both of Tween-20 and Tween-80.

[0023] Furthermore, the pressure of the high-pressure homogenization in step S2 is 10-30 MPa, the time is 5-10 min, and the high-pressure homogenization process is carried out using a high-speed dispersing homogenizer.

[0024] Furthermore, the pressure of the high-pressure homogenization in step S3 is 10-30 MPa, the time is 10-20 min, and the high-pressure homogenization process is carried out using a high-speed dispersing homogenizer.

[0025] Furthermore, in step S4, the nanoemulsion is poured into a horizontally placed template groove, cast into a film, and after drying at room temperature for 20-24 hours, it is taken out to form a film.

[0026] A method for preparing a high-performance protein-based nanoemulsion food packaging film is disclosed. The high-performance protein-based nanoemulsion food packaging film has a thickness of 0.082 mm to 0.134 mm and an average particle size of 49.35 to 57.41 nm.

[0027] Furthermore, the high-performance protein-based nanoemulsion food packaging film has a polydispersity index of <0.3, a tensile strength of 12.65-17.64 MPa, an elongation at break of 15.89%-32.78%, and a water vapor permeability coefficient of 0.64×10 -11 gm -1 s -1 Pa~2.77×10 -11 gm -1 s -1 .

[0028] Protein molecules can form stable colloids in aqueous solution by relying on the hydration film and double electric layer on their surface, while the internal structure of protein molecules is maintained stable by the disulfide bonds, hydrogen bonds, ionic bonds, hydrophobic interactions and van der Waals forces in the molecules. When the internal interactions are destroyed after certain treatments, the disulfide bonds in the molecules are broken, and the sulfhydryl and hydrophobic groups in the molecules are exposed, the spatial conformation of the protein will be stretched, and the interaction between adjacent proteins will be enhanced to form a stable network matrix structure and a protein film with certain barrier functions. Protein edible films are easy to be biodegraded because their main component is protein, which reduces environmental pollution and improves the sensory and nutritional properties of food. At the same time, because protein films have good mechanical strength, they can be supplemented with small molecule film additives to enhance their barrier effect and reduce their permeability to substances such as oxygen, water vapor, light and oil to ensure the quality of the packaged food.

[0029] Thyme essential oil has health functions such as promoting digestion, has a broad spectrum of antibacterial properties, can resist bacteria, fungi, molds and viruses, and is considered to be one of the most antibacterial natural antibacterial agents. The main components of thyme essential oil are volatile terpenes and phenolic substances, including: thymol, carvacrol, cinnamaldehyde, terpinene, linalool, thymol, linalool, eugenol, pinene, etc. The main antibacterial active ingredients of thyme essential oil are thymol and carvacrol. Its antibacterial mechanism is that lipophilic components can destroy bacterial cell membranes and membrane proteins, increase the permeability of bacterial cell membranes, and cause bacteria to die due to leakage of cell contents. Thyme essential oil also has certain antioxidant properties. Its active ingredients such as phenolic compounds can act as donors for free radical transfer hydrogen, converting them into low-activity substances, thereby removing free radicals and reducing the deterioration and loss of packaged food caused by oxidation.

[0030] The main components of cinnamon essential oil are: cinnamaldehyde, phellandrene, eugenol, caryophyllene, linalool, pinolene, geraniol, cinnamyl alcohol, etc. The polyphenols in cinnamon essential oil have the effect of scavenging free radicals and slowing down the oxidation of substances in the body. Cinnamon essential oil has a certain scavenging effect on diphenyl pyrohydrazyl (DPPH·), superoxide anion radicals (O2-·) and hydroxyl radicals (OH·). Cinnamaldehyde in cinnamon essential oil can increase the content of enzymatic and non-enzymatic antioxidants, thereby playing an antioxidant role. In addition, cinnamon essential oil also has a good inhibitory effect on common bacteria and even fungi in food. Because it can be used as a natural antioxidant and has antibacterial effects, cinnamon essential oil has been used in the preservation of fruits and vegetables.

[0031] Tween-80, also known as polysorbate-80, is a non-ionic surfactant and emulsifier with a chemical formula of C 24 H 44O6(C2H4O)n, which is colloidal at low temperature, has good emulsification, dispersion, wetting and stabilization effects and has been widely used in food, medicine, cosmetics and other fields. In the preparation process of emulsion, Tween-80 can reduce the interfacial tension of each component in the mixed system, and form a relatively strong film on the surface of the droplets, or form a double electric layer on the surface of the dispersed droplets, preventing the droplets from aggregating with each other, forming a homogeneous dispersion system, and enhancing the stability of the emulsion.

[0032] Glycerol, also known as propylene glycol, is a simple polyol compound with the chemical formula C3H8O3. It is a colorless, odorless, sweet viscous liquid, non-toxic, with certain antibacterial and antiviral properties. It can be miscible with water and alcohols, amines, and phenols in any proportion, and is hygroscopic. It has been widely used in food, medicine, cosmetics and other fields. In the preparation process of protein-based membranes, glycerol can combine with protein molecules to play the role of plasticizer, increase the hardness of the final film, and improve the mechanical properties of the membrane.

[0033] Compared with the prior art, the high-performance protein-based nanoemulsion food packaging film and the preparation method thereof created by the present invention have the following advantages:

[0034] The high-performance protein-based nanoemulsion food packaging film of the present invention is easily biodegradable, has good mechanical properties, high thermal stability, strong water barrier ability, good antibacterial and antioxidant effects, can effectively slow down the spoilage and deterioration of packaged food caused by bacterial contamination and oxidative decomposition of nutrients, has good fresh-keeping performance, can ensure food quality, and extend the shelf life of food, solving the problems of existing food packaging films that pollute the environment and easily cause the spoilage of packaged food. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0036] Figure 1 Schematic diagram of the release of volatile basic nitrogen from pork packaged with the protein-based nanoemulsified film during refrigeration according to the embodiments of the present invention (1 is unpackaged, 2 is comparative example packaging, and 3-9 are embodiments 1-6 respectively). DETAILED DESCRIPTION

[0037] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0038] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0039] Embodiment 1:

[0040] Preparation of high-performance animal protein-based nanoemulsion food packaging films:

[0041] (1) Preparation of aqueous phase liquid: Weigh 0.4000 g of collagen powder, dissolve it in 10 ml of deionized water, stir it with a magnetic stirrer, let it stand for 2 hours to swell, then add 0.1600 g of glycerol, stir it with a magnetic stirrer to prepare an aqueous phase liquid.

[0042] (2) Preparation of oil phase liquid: Weigh 0.2000 g of thyme essential oil, dissolve it in 10 ml of deionized water, mix it with magnetic stirring, add 0.0500 g of Tween-80, use a high-speed dispersing homogenizer, homogenize for 10 min at a pressure of 25 MPa to prepare an oil phase liquid.

[0043] (3) Preparation of nanoemulsion film-forming liquid: The oil phase liquid of step (2) is slowly dripped into the water phase liquid of step (1), and homogenized for 20 min at a pressure of 25 MPa using a high-speed dispersing homogenizer. The particle size analysis shows that the droplet diameter is distributed in the range of 1-100 nm, thereby obtaining a nanoemulsion film-forming liquid.

[0044] (4) Film casting: The nanoemulsion prepared in step (3) is poured into a horizontally placed template tank and cast into a film. After drying at room temperature for 24 hours, the film is peeled off and removed.

[0045] The high-performance collagen-based nanoemulsion food packaging film containing thyme essential oil of the present invention is obtained through the above steps and material proportions.

[0046] Embodiment 2:

[0047] Preparation of high-performance animal protein-based nanoemulsion food packaging films:

[0048] (1) Preparation of aqueous phase liquid: Weigh 0.4000 g of collagen powder, dissolve it in 10 ml of deionized water, stir it with a magnetic stirrer, let it stand for 2 hours to swell, then add 0.1600 g of glycerol, stir it with a magnetic stirrer to prepare an aqueous phase liquid.

[0049] (2) Preparation of oil phase liquid: Weigh 0.2000 g of cinnamon essential oil, dissolve it in 10 ml of deionized water, mix it with magnetic stirring, add 0.0500 g of Tween-80, use a high-speed dispersing homogenizer, homogenize for 10 min at a pressure of 25 MPa to prepare an oil phase liquid.

[0050] (3) Preparation of nanoemulsion film-forming liquid: The oil phase liquid of step (2) is slowly dripped into the water phase liquid of step (1), and homogenized for 20 min at a pressure of 25 MPa using a high-speed dispersing homogenizer. The particle size analysis shows that the droplet diameter is distributed in the range of 1-100 nm, thereby obtaining a nanoemulsion film-forming liquid.

[0051] (4) Film casting: The nanoemulsion prepared in step (3) is poured into a horizontally placed template tank and cast into a film. After drying at room temperature for 24 hours, the film is peeled off and removed.

[0052] The high-performance collagen-based nanoemulsion food packaging film containing cinnamon essential oil of the present invention is obtained through the above steps and material proportions.

[0053] Embodiment 3:

[0054] Preparation of high-performance animal protein-based nanoemulsion food packaging films:

[0055] (1) Preparation of aqueous phase liquid: Weigh 0.4000 g of collagen powder, dissolve it in 10 ml of deionized water, stir it with a magnetic stirrer, let it stand for 2 hours to swell, then add 0.1600 g of glycerol, stir it with a magnetic stirrer to prepare an aqueous phase liquid.

[0056] (2) Preparation of oil phase liquid: Weigh 0.1000 g of thyme essential oil and 0.1000 g of cinnamon essential oil, dissolve in 10 ml of deionized water, mix with magnetic stirring, add 0.0500 g of Tween-80, use a high-speed dispersing homogenizer, homogenize at a pressure of 25 MPa for 10 min to prepare an oil phase liquid.

[0057] (3) Preparation of nanoemulsion film-forming liquid: The oil phase liquid of step (2) is slowly dripped into the water phase liquid of step (1), and homogenized for 20 min at a pressure of 25 MPa using a high-speed dispersing homogenizer. The particle size analysis shows that the droplet diameter is distributed in the range of 1-100 nm, thereby obtaining a nanoemulsion film-forming liquid.

[0058] (4) Film casting: The nanoemulsion prepared in step (3) is poured into a horizontally placed template tank and cast into a film. After drying at room temperature for 24 hours, the film is peeled off and removed.

[0059] The high-performance collagen-based nanoemulsion food packaging film containing thyme essential oil and cinnamon essential oil of the present invention is obtained through the above steps and material proportions.

[0060] Embodiment 4:

[0061] Preparation of high-performance animal protein-based nanoemulsion food packaging films:

[0062] (1) Preparation of aqueous phase liquid: Weigh 0.4000 g of soy protein isolate powder, dissolve it in 10 ml of deionized water, stir it with a magnetic stirrer, let it stand for 2 hours to swell, then add 0.1600 g of glycerol, stir it with a magnetic stirrer to prepare an aqueous phase liquid.

[0063] (2) Preparation of oil phase liquid: Weigh 0.2000 g of thyme essential oil, dissolve it in 10 ml of deionized water, mix it with magnetic stirring, add 0.0500 g of Tween-80, use a high-speed dispersing homogenizer, homogenize for 10 min at a pressure of 25 MPa to prepare an oil phase liquid.

[0064] (3) Preparation of nanoemulsion film-forming liquid: The oil phase liquid of step (2) is slowly dripped into the water phase liquid of step (1), and homogenized for 20 min at a pressure of 25 MPa using a high-speed dispersing homogenizer. The particle size analysis shows that the droplet diameter is distributed in the range of 1-100 nm, thereby obtaining a nanoemulsion film-forming liquid.

[0065] (4) Film casting: The nanoemulsion prepared in step (3) is poured into a horizontally placed template tank and cast into a film. After drying at room temperature for 24 hours, the film is peeled off and removed.

[0066] The high-performance soybean protein isolate-based nanoemulsion food packaging film containing thyme essential oil of the present invention is obtained through the above steps and material proportions.

[0067] Embodiment 5:

[0068] Preparation of high-performance animal protein-based nanoemulsion food packaging films:

[0069] (1) Preparation of aqueous phase liquid: Weigh 0.4000 g of soy protein isolate powder, dissolve it in 10 ml of deionized water, stir it with a magnetic stirrer, let it stand for 2 hours to swell, then add 0.1600 g of glycerol, stir it with a magnetic stirrer to prepare an aqueous phase liquid.

[0070] (2) Preparation of oil phase liquid: Weigh 0.2000 g of cinnamon essential oil, dissolve it in 10 ml of deionized water, mix it with magnetic stirring, add 0.0500 g of Tween-80, use a high-speed dispersing homogenizer, homogenize for 10 min at a pressure of 25 MPa to prepare an oil phase liquid.

[0071] (3) Preparation of nanoemulsion film-forming liquid: The oil phase liquid of step (2) is slowly dripped into the water phase liquid of step (1), and homogenized for 20 min at a pressure of 25 MPa using a high-speed dispersing homogenizer. The particle size analysis shows that the droplet diameter is distributed in the range of 1-100 nm, thereby obtaining a nanoemulsion film-forming liquid.

[0072] (4) Film casting: The nanoemulsion prepared in step (3) is poured into a horizontally placed template tank and cast into a film. After drying at room temperature for 24 hours, the film is peeled off and removed.

[0073] The high-performance soybean protein isolate-based nanoemulsion food packaging film containing cinnamon essential oil of the present invention is obtained through the above steps and material proportions.

[0074] Embodiment 6:

[0075] Preparation of high-performance animal protein-based nanoemulsion food packaging films:

[0076] (1) Preparation of aqueous phase liquid: Weigh 0.4000 g of soy protein isolate powder, dissolve it in 10 ml of deionized water, stir it with a magnetic stirrer, let it stand for 2 hours to swell, then add 0.1600 g of glycerol, stir it with a magnetic stirrer to prepare an aqueous phase liquid.

[0077] (2) Preparation of oil phase liquid: Weigh 0.1000 g of thyme essential oil and 0.1000 g of cinnamon essential oil, dissolve in 10 ml of deionized water, mix with magnetic stirring, add 0.0500 g of Tween-80, use a high-speed dispersing homogenizer, homogenize at a pressure of 25 MPa for 10 min to prepare an oil phase liquid.

[0078] (3) Preparation of nanoemulsion film-forming liquid: The oil phase liquid of step (2) is slowly dripped into the water phase liquid of step (1), and homogenized for 20 min at a pressure of 25 MPa using a high-speed dispersing homogenizer. The particle size analysis shows that the droplet diameter is distributed in the range of 1-100 nm, thereby obtaining a nanoemulsion film-forming liquid.

[0079] (4) Film casting: The nanoemulsion prepared in step (3) is poured into a horizontally placed template tank and cast into a film. After drying at room temperature for 24 hours, the film is peeled off and removed.

[0080] The high-performance soybean protein isolate-based nanoemulsion food packaging film containing thyme essential oil and cinnamon essential oil of the present invention is obtained through the above steps and material proportions.

[0081] Comparative Example 1:

[0082] Preparation of comparative packaging film:

[0083] (1) Preparation of aqueous phase liquid: Weigh 0.4000 g of collagen powder, dissolve it in 10 ml of deionized water, stir it with a magnetic stirrer, let it stand for 2 hours to swell, then add 0.1600 g of glycerol, stir it with a magnetic stirrer to prepare an aqueous phase liquid.

[0084] (2) Preparation of oil phase liquid: Weigh 0.0500 g of Tween-80, dissolve it in 10 ml of deionized water, and use a high-speed dispersing homogenizer at a pressure of 25 MPa for 10 min to prepare an oil phase liquid.

[0085] (3) Preparation of nanoemulsion: The oil phase liquid of step (2) is slowly dripped into the water phase liquid of step (1), and homogenized for 20 minutes at a pressure of 25 MPa using a high-speed dispersing homogenizer to prepare a membrane liquid.

[0086] (4) Film casting: The nanoemulsion prepared in step (3) is poured into a horizontally placed template tank and cast into a film. After drying at room temperature for 24 hours, the film is peeled off and removed.

[0087] Through the above steps and material ratios, a comparative example of an animal protein-based nanoemulsion packaging film without essential oil components is obtained.

[0088] Comparative Example 2:

[0089] Preparation of comparative packaging film:

[0090] (1) Preparation of aqueous phase liquid: Weigh 0.4000 g of soy protein isolate powder, dissolve it in 10 ml of deionized water, stir it with a magnetic stirrer, let it stand for 2 hours to swell, then add 0.1600 g of glycerol, stir it with a magnetic stirrer to prepare an aqueous phase liquid.

[0091] (2) Preparation of oil phase liquid: Weigh 0.0500 g of Tween-80, dissolve it in 10 ml of deionized water, and use a high-speed dispersing homogenizer at a pressure of 25 MPa for 10 min to prepare an oil phase liquid.

[0092] (3) Preparation of nanoemulsion: The oil phase liquid of step (2) is slowly dripped into the water phase liquid of step (1), and homogenized for 20 minutes at a pressure of 25 MPa using a high-speed dispersing homogenizer to prepare a membrane liquid.

[0093] (4) Film casting: The nanoemulsion prepared in step (3) is poured into a horizontally placed template tank and cast into a film. After drying at room temperature for 24 hours, the film is peeled off and removed.

[0094] Through the above steps and material ratios, a comparative example of a plant protein-based nanoemulsion packaging film without essential oil components was obtained.

[0095] By carrying out corresponding tests on the above-mentioned Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Comparative Example 1 and Comparative Example 2, it is shown that the present invention has excellent performance in physical properties, antibacterial properties, antioxidant properties and freshness preservation properties.

[0096] Test items include:

[0097] (1) Physical properties test of high-performance protein-based nanoemulsion food packaging film.

[0098] The mechanical properties of the films, including tensile strength and elongation at break, were measured using a texture analyzer.

[0099] The water barrier properties of the membranes were determined by the pseudo-cup method.

[0100] The thermal stability of the membrane was analyzed using a thermogravimetric analyzer.

[0101] The physical properties of the embodiments and comparative examples are shown in Table 1:

[0102] Table 1 Physical properties comparison table of embodiments and comparative examples

[0103]

[0104] The physical properties of the embodiments of the present invention are better than those of the comparative examples.

[0105] (2) Antibacterial test of high-performance protein-based nanoemulsion food packaging film

[0106] Prepare a membrane sample with a diameter of 25 mm

[0107] Common food spoilage bacteria and pathogenic bacteria were selected, including Gram-positive bacteria: Bacillus subtilis, Staphylococcus aureas; Gram-negative bacteria: Escherichia coli, Salmonella, from Tianjin University of Science and Technology as the biological strain preservation management center, and cultured in LB medium to the logarithmic growth phase. The above-mentioned film samples and control films (both with a diameter of 25±5mm) were placed in a culture dish and cultured at 37°C for 24 hours, and the size of the inhibition zone was observed and recorded. The antibacterial effects of the embodiments and comparative examples are shown in Table 2:

[0108] Table 2 Antibacterial effect comparison table of the embodiments and comparative examples From the comparison of the diameters of the inhibition zones, it can be seen that the antibacterial effects of the embodiments are better than those of the comparative examples. The antibacterial effect of the protein-based emulsion film with thyme essential oil added is slightly better than that of the cinnamon essential oil film. The protein-based emulsion film with mixed essential oil added has the best antibacterial effect, especially for Gram-positive bacteria.

[0109] (3) Antioxidant test of high-performance protein-based nanoemulsion food packaging film

[0110] The in vitro antioxidant activity of the membrane was determined by the scavenging ability of DPPH free radicals. -1 2 mL of methanol solution was vortexed for 1 min to mix evenly. After dark treatment for 30 min, the absorbance at a wavelength of 517 nm was measured using a UV-visible spectrophotometer. The DPPH free radical scavenging rate of the film sample was calculated according to the following formula. The antioxidant effects of the embodiments and comparative examples are shown in Table 3:

[0111]

[0112] Parameters in the formula: A DPPH : absorbance of DPPH methanol solution at 517nm;

[0113] A S : The absorbance of the mixture of film-forming solution and DPPH methanol at 517nm.

[0114] Table 3 Comparison of the antioxidant effects of the embodiments and comparative examples

[0115] Membrane samples Free radical scavenging rate Membrane samples Free radical scavenging rate Comparative Example 1 5.13％ Comparative Example 1 5.06％ Example 1 33.45％ Example 1 31.76％ Example 2 42.37％ Example 2 40.98％ Example 3 43.26％ Example 3 41.90％

[0116] From the comparison of free radical scavenging rates, it can be seen that the antioxidant effects of the embodiments are better than those of the comparative examples, the antioxidant effect of the protein-based emulsion membrane with cinnamon essential oil added is slightly better than that of the cinnamon essential oil membrane, and the antioxidant effect of the protein-based emulsion membrane with mixed essential oil added is the best.

[0117] (4) Application test of high-performance protein-based nanoemulsion food packaging film for packaging fresh cold meat

[0118] ① Determination of the total number of colonies in fresh meat packaged with high-performance protein-based nanoemulsion food packaging film

[0119] According to the method in GB 4789.2-2022 "National Food Safety Standard Food Microbiological Examination Colony Count Determination", the total colony count (TVC) of unpackaged, comparative example packaged and example packaged cold fresh meat (10g fresh pork stored at 4°C) was measured after 0, 1, 3, 5 and 10 days, as shown in Table 4:

[0120] Table 5 Total colony count of pork packaged with protein-based nanoemulsion film during refrigeration (unit: lg (CFU / g))

[0121]

[0122] As shown in Table 5, the total number of colonies of pork in different packaging states gradually increases with the extension of time during the cold storage process. The total number of colonies of the unpackaged pork sample increases most significantly. The antibacterial effects of the embodiments are better than those of the comparative examples, especially the emulsified film with thyme essential oil and mixed essential oil has a more effective inhibitory effect on the total number of colonies of fresh cold meat.

[0123] ② Determination of peroxide value of fresh meat packaged in high-performance protein-based nanoemulsion food packaging film

[0124] According to GB 5009.227-2023 "Determination of Peroxide Value in Foods - National Food Safety Standard", the peroxide value (POV) of unpackaged, comparative example packaged and example packaged chilled fresh meat was measured after 0, 1, 3, 5 and 10 days, as shown in Table 6:

[0125] Table 6 Peroxide value of pork packaged in protein-based nanoemulsion film during refrigeration (unit: meq / Kg)

[0126]

[0127]

[0128] As shown in Table 6, during the cold storage process, the peroxide value of pork in different packaging states gradually increases with the extension of storage time. Among them, the increase in the peroxide value of the unpackaged pork sample is the most significant. The antioxidant effects of the embodiments are better than those of the comparative examples, especially the emulsion film with cinnamon essential oil and mixed essential oil has a more effective inhibitory effect on the oxidation of fresh cold meat.

[0129] ③ Determination of freshness of fresh meat packaged in high-performance protein-based nanoemulsion food packaging film

[0130] According to GB 5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food", the quality of the film-packaged chilled meat samples was tested by semi-micro distillation. The release of volatile basic nitrogen (TVB-N) was measured after 0, 1, 3, 5, and 10 days for the unpackaged, comparative example packaged, and example packaged chilled meats. Figure 1 As shown:

[0131] Depend on Figure 1 It can be seen that during the cold storage process, as time goes by, the amount of volatile basic nitrogen released by pork in different packaging states during the spoilage process gradually increases. Among them, the release of volatile basic nitrogen in the unpackaged pork sample is the largest, followed by the sample of the comparative packaging film. The release amounts of the embodiments are significantly lower than those of the comparative examples, and the release amount of volatile basic nitrogen in the film sample mixed with two essential oils is the least. The results show that the protein-based nanoemulsion film with added essential oils of the present invention has obvious antibacterial and antioxidant functions, especially the addition of essential oils with antibacterial and antioxidant functions to the protein-based emulsion film has the best preservation effect on meat, which can ensure the quality of meat and extend the shelf life of the packaged food.

[0132] In order to better solve the existing technical problems and expand the application scope of the existing technology, the present invention provides a biodegradable antibacterial and antioxidant food packaging film. The matrix of the film adopts protein, which is easy to be biodegraded, cheap and easy to obtain, highly renewable, and has good biocompatibility. Nano-emulsification technology is used, combined with natural plant-derived antibacterial agents and antioxidants, safe and harmless thyme essential oil and cinnamon essential oil with health-care effects on the body, which can effectively inhibit common food spoilage bacteria, slow down the oxidative decomposition of nutrients in food, ensure food quality, and extend the shelf life of food.

[0133] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high-performance protein-based nanoemulsion food packaging film, characterized in that: The steps include: S1: Add glycerol to the collagen aqueous solution and stir to obtain an aqueous phase; S2: adding an emulsifier to the essential oil aqueous solution and stirring, and obtaining an oil phase liquid after high pressure homogenization; S3: the oil phase liquid obtained in step S2 is added to the water phase liquid in step S1, and a nanoemulsion is obtained after high pressure homogenization; S4: the nanoemulsion in step S3 is poured into a horizontally placed template groove, cast into a film, and dried at room temperature to prepare a high-performance protein-based nanoemulsion food packaging film.

2. The method for preparing a high-performance protein-based nanoemulsion food packaging film according to claim 1, characterized in that: The concentration of the collagen aqueous solution in step S1 is 2%-8%; And / or, the aqueous solution in the collagen aqueous solution in step S1 is deionized water; And / or, in step S1, the weight of glycerol is 38-42% of the weight of collagen.

3. The method for preparing a high-performance protein-based nanoemulsion food packaging film according to claim 1, characterized in that: The protein in step S1 includes one or both of animal-derived protein and plant-derived protein; And / or, the animal-derived protein includes one or more of collagen, gelatin, whey protein, casein, fish protein isolate, and keratin, And / or, the plant-based protein includes one or more of soy protein isolate, zein, wheat protein, sorghum protein, rice bran protein, and peanut protein.

4. The method for preparing a high-performance protein-based nanoemulsion food packaging film according to claim 1, characterized in that: The essential oil in step S2 includes one or more of thyme essential oil, cinnamon essential oil, clove essential oil, peppermint essential oil, basil essential oil, oregano essential oil, rosemary essential oil, tea tree essential oil, ginger essential oil, garlic essential oil, bergamot essential oil, sunflower essential oil, citronella essential oil, lemongrass essential oil, and chamomile essential oil.

5. The method for preparing a high-performance protein-based nanoemulsion food packaging film according to claim 1, characterized in that: The concentration of the essential oil in step S2 is 1%-4%; and / or, the weight of the emulsifier is 25% by weight of the thyme essential oil; And / or, the emulsifier is one or both of Tween-20 and Tween-80.

6. The method for preparing a high-performance protein-based nanoemulsion food packaging film according to claim 1, characterized in that: The pressure of the high-pressure homogenization in step S2 is 10-30 MPa, the time is 5-10 min, and the high-pressure homogenization process is carried out using a high-speed dispersing homogenizer.

7. The method for preparing a high-performance protein-based nanoemulsion food packaging film according to claim 1, characterized in that: The pressure of the high-pressure homogenization in step S3 is 10-30 MPa, the time is 10-20 min, and the high-pressure homogenization process is carried out using a high-speed dispersing homogenizer.

8. The method for preparing a high-performance protein-based nanoemulsion food packaging film according to claim 1, characterized in that: In step S4, the nanoemulsion is poured into a horizontally placed template groove, cast into a film, and after drying at room temperature for 20-24 hours, the film is taken out to form a film.

9. The high-performance protein-based nanoemulsion food packaging film prepared by the method for preparing a high-performance protein-based nanoemulsion food packaging film according to any one of claims 1 to 8, characterized in that: The thickness of the high-performance protein-based nanoemulsion food packaging film is 0.082 mm to 0.134 mm, and the average particle size is 49.35 to 57.41 nm.

10. A high-performance protein-based nanoemulsion food packaging film according to claim 9, characterized in that: The average particle size of the nanoemulsion of the high-performance protein-based nanoemulsion food packaging film is 49.35-57.41nm, the polydispersity index is <0.3, the tensile strength is 12.65-17.64Mpa, the elongation at break is 15.89%-32.78%, and the water vapor permeability coefficient is 0.64×10 - 11 gm -1 s -1 Pa~2.77×10 -11 gm -1 s -1 .

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