Biological film coating agent, preparation method and application of biological film coating agent in preservation of poultry eggs

Abstract

The invention belongs to the technical field of preservation of agricultural products, and discloses a biological film coating agent, a preparation method and application of the biological film coating agent in preservation of poultry eggs. According to the biological film coating agent, the rice bran oil and the soluble soybean polysaccharide serve as film forming matrixes, the raw materials further comprise the walnut shell extract obtained through deep eutectic solvent extraction, the antioxidant, the preservative and the emulsifier, and the film coating agent has excellent film forming performance through the synergistic effect of all the raw material components; a compact protective film with relatively good mechanical strength can be formed, and the protective film has good antibacterial performance and oxidation resistance. The biological film coating agent is applied to preservation of poultry eggs, can effectively seal pores with the diameter of 1-10 microns on the surfaces of eggshells and prevent macromolecular bacteria from invading, but does not influence normal exchange of metabolic micromolecular substances such as carbon dioxide and oxygen between contents of the poultry eggs and the outside, so that the quality change of the poultry eggs in the storage period can be effectively delayed, and the shelf life of the poultry eggs is prolonged. The shelf life of the poultry eggs is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural product preservation, and particularly relates to a biological coating agent, a preparation method and application thereof in egg preservation. Background Art

[0002] Eggs are a common ingredient in our daily diet and are considered a high-quality nutritional food because they are rich in protein, fat, vitamins, minerals, and a variety of bioactive substances that are easily absorbed by the human body. However, the eggshells contain numerous micron-sized pores, which provide pathways for microbial invasion. This can lead to the egg's contents becoming easily spoiled during storage, reducing safety and seriously affecting its quality for both consumption and processing applications.

[0003] Preservation treatment of poultry eggs can delay changes in their quality during storage and extend the shelf life of poultry eggs. Currently, the commonly used preservation methods for poultry eggs include refrigeration preservation, controlled atmosphere preservation, radiation preservation and coating preservation. Among them, coating preservation is widely used in the poultry egg industry due to its advantages such as simple operation, low cost, and ability to enhance eggshell hardness and reduce the chance of eggshell damage due to collision. However, traditional poultry egg coating agents mostly use petroleum-based products such as mineral oil and paraffin as film-forming base materials. Although these products can extend the shelf life of eggs to 8 weeks or more under refrigerated conditions, due to potential food safety hazards and non-degradability, the market has gradually raised questions about their compliance and sustainability.

[0004] In recent years, biofilm coatings have become a research hotspot due to their wide availability, nutritional safety, and environmental friendliness. However, existing biofilm coatings typically use a single protein, lipid, or polysaccharide raw material as a film-forming matrix. Protein and polysaccharide raw materials are highly hydrophilic, and the protective film they form has poor water vapor barrier properties, which can easily cause water in the eggs to evaporate. In addition, while the raw materials themselves may have certain antibacterial properties, they rely on chemical inhibition and have a short bacteriostatic effect. Lipid raw materials, while highly hydrophobic, form a protective film with good water vapor barrier properties. However, on the one hand, the raw materials are highly fluid, making it difficult to form a uniform protective film on the surface of the egg, and the protective film that forms can seriously hinder the exchange of oxygen and carbon dioxide between the egg contents and the outside world. On the other hand, the raw materials themselves are generally not antibacterial, and the unsaturated fatty acids they are rich in are easily oxidized, causing the formed film to turn yellow and brittle. These shortcomings make it difficult for existing biofilm coatings to achieve long-term preservation effects in poultry eggs. Therefore, there is an urgent need to develop a biological coating agent with excellent film-forming properties and a protective film with good barrier properties and antibacterial properties, so as to break through the bottleneck of poultry egg preservation technology and enhance the competitiveness of the poultry egg industry.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] To address the above issues, the present invention aims to provide a biofilm coating agent, a preparation method, and its use in egg preservation. This biofilm coating agent exhibits excellent film-forming properties, and the resulting protective film possesses high barrier properties and excellent antibacterial properties. When used in egg preservation, it can effectively extend the shelf life of eggs at room temperature.

[0007] In order to achieve the above object, the first technical solution adopted by the present invention is: A biological film coating agent comprises the following raw materials in parts by weight: 100 parts of rice bran oil, 0.5-1 parts of water-soluble soybean polysaccharides, 0.1-0.3 parts of walnut shell extract, 0.04-0.175 parts of antioxidants, 0.2-0.3 parts of preservatives, 0.18-0.27 parts of emulsifiers, and 20-30 parts of water.

[0008] Preferably, the preparation method of the walnut shell extract is: adding walnut shell powder to a deep eutectic solvent, reacting at 45-50°C for 1.5-2 hours, filtering, decolorizing the filtrate, and vacuum concentrating the filtrate to 1 / 5-1 / 4 of the volume of the filtrate.

[0009] Preferably, the deep eutectic solvent is obtained by mixing betaine and lactic acid in a molar ratio of 1:1-1.5.

[0010] Preferably, the mass ratio of the walnut shell powder to the deep eutectic solvent is 1:10-15.

[0011] Preferably, the antioxidant comprises the following components in parts by weight: 0.005-0.01 parts of vitamin E, 0.01-0.03 parts of rosemary extract, 0.01-0.02 parts of ascorbyl palmitate, 0.005-0.01 parts of propyl gallate, and 0.01-0.015 parts of butylated hydroxyanisole.

[0012] Preferably, the preservative comprises the following components in parts by weight: 0.05-0.1 parts of sorbic acid and 0.15-0.2 parts of cinnamaldehyde.

[0013] Preferably, the emulsifier comprises the following components in parts by weight: 0.03-0.05 parts of modified soybean lecithin, 0.05-0.07 parts of glycerol, and 0.1-0.15 parts of sucrose fatty acid ester.

[0014] The second technical solution adopted in the present invention is: A method for preparing a biological coating agent comprises the following steps: dissolving water-soluble soybean polysaccharide in water to obtain an aqueous solution; Adding an antioxidant and a preservative to rice bran oil, stirring until dissolved, then adding an emulsifier and fully emulsifying to obtain an oil solution; The walnut shell extract is slowly added to the oil solution, mixed evenly, and then the aqueous solution is added, stirred at high speed and homogenized.

[0015] Preferably, the preparation method of the walnut shell extract is: adding walnut shell powder to a deep eutectic solvent, reacting at 45-50°C for 1.5-2 hours, filtering, decolorizing the filtrate, and vacuum concentrating the filtrate to 1 / 3-1 / 4 of the volume of the filtrate.

[0016] The third technical solution adopted in the present invention is: The use of the above-mentioned biological coating agent, or the biological coating agent prepared according to any of the above-mentioned preparation methods, in the preservation of poultry eggs.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The biological film-forming agent provided by the present invention uses rice bran oil and soluble soybean polysaccharides as film-forming matrices. The raw materials also include walnut shell extract obtained by extraction using a low eutectic solvent, as well as antioxidants, preservatives and emulsifiers. The synergistic effect of each component enables the film-forming agent to have excellent film-forming properties, can form a dense protective film with good mechanical strength, and has both good antibacterial and antioxidant properties.

[0018] 2. The present invention uses a low eutectic solvent to extract the active ingredients of walnut shells. The obtained walnut shell extract contains both hydrophilic active ingredients and hydrophobic active ingredients. When added to the biological coating agent, it can not only synergistically enhance the antibacterial and antioxidant properties of the coating agent with other antibacterial and antioxidant substances, but also enhance the mechanical properties and barrier properties of the film.

[0019] 3. All ingredients in the biological coating agent provided by this invention are biodegradable, environmentally friendly, and in line with the concept of green food packaging and preservation.

[0020] 4. In the preparation method provided by the present invention, the walnut shell extract is evenly mixed with the oil solution and then mixed with the aqueous solution. This not only effectively retains the activity of each component in the walnut shell extract and gives full play to the synergistic effect of each component with the antibacterial and antioxidant components in the oil solution, but also fully integrates the walnut shell extract with rice bran oil and soybean polysaccharides to obtain a uniform and stable coating agent.

[0021] 5. When the biological coating agent of the present invention is used in the preservation of poultry eggs, it can effectively seal the pores with a diameter of 1-10 μm on the eggshell surface to prevent the invasion of large molecular bacteria, but it does not affect the exchange of metabolic small molecules such as carbon dioxide and oxygen between the egg contents and the outside world. It also inhibits or kills bacteria that have invaded the eggshell surface, thereby effectively delaying the quality change of poultry eggs during storage and extending the shelf life of poultry eggs. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments.It should be understood that these descriptions are exemplary only, and are not intended to limit the scope of the present invention.In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.Unindicated specific conditions in the embodiment are carried out according to the conditions of normal conditions or manufacturer's advice.Reagents used or instruments that are not indicated by manufacturers are conventional products that can be purchased commercially.

[0023] Rice bran oil is a natural vegetable oil obtained by pressing or leaching rice bran, a byproduct of rice processing. Its triglycerides, oryzanol, phytosterols, and other ingredients spontaneously form a thin film. When applied to the surface of eggs, it fills the pores, reducing water evaporation and bacterial invasion. It also provides a certain antioxidant effect, preventing rancidity. Consequently, there have been reports of using rice bran oil as a coating for egg preservation. However, due to its high fluidity, rice bran oil alone tends to flow onto the egg surface, preventing it from forming a uniform film. Furthermore, it is unable to inhibit or kill bacteria that have already invaded the eggshell's pores, making it difficult to achieve effective antibacterial properties. The protective film it forms also hinders the exchange of oxygen and carbon dioxide between the egg's contents and the outside world, accelerating the egg's spoilage. In addition, although rice bran oil contains antioxidant ingredients, the unsaturated fatty acids it is rich in are easily affected by light and heat and become oxidative and rancid, causing the film to turn yellow and become brittle. The tensile strength and ductility of the film are also limited, and it is easy to crack after drying, which destroys the integrity of the film. The shelf life of poultry eggs is short, and it is difficult to maintain the quality of poultry eggs for a long time.

[0024] Based on the above problems, the first embodiment provided by the present invention is: A biological film coating agent comprises the following raw materials in parts by weight: 100 parts of rice bran oil, 0.5-1 parts of water-soluble soybean polysaccharides, 0.1-0.3 parts of walnut shell extract, 0.04-0.175 parts of antioxidants, 0.2-0.3 parts of preservatives, 0.18-0.27 parts of emulsifiers, and 20-30 parts of water.

[0025] The biological coating provided by the present invention uses rice bran oil as the core film-forming substance. The addition of water-soluble soybean polysaccharides and emulsifiers can improve the film-forming properties of the coating, allowing it to form a uniform, continuous protective film with certain toughness and strength on the surface of poultry eggs. This prevents bacterial invasion while not affecting the exchange of metabolic small molecules such as carbon dioxide and oxygen between the egg contents and the outside world, thereby achieving a more stable and effective preservation effect. Walnut shell extract is rich in antioxidant components and certain antibacterial substances. It synergizes with antioxidants and antibacterial agents to effectively prevent oxidative rancidity of the coating itself, while also inhibiting or killing bacteria that have invaded the pores of the eggshell, thereby effectively delaying the quality deterioration of the eggs and significantly extending the shelf life of the egg products.

[0026] In an embodiment of the present invention, a walnut shell extract is prepared by adding walnut shell powder to a deep eutectic solvent, reacting at 45-50°C for 1.5-2 hours, filtering, and decolorizing the filtrate and vacuum concentrating it to 1 / 5-1 / 4 of the filtrate volume. The applicant has discovered that the present invention uses a deep eutectic solvent to extract active ingredients from walnut shells. Compared to traditional solvents such as water and ethanol, the present invention not only extracts more active substances, resulting in a coating with better antibacterial and antioxidant properties, but also further improves the film-forming properties of the coating, resulting in a more excellent preservation effect.

[0027] In the preparation of the walnut shell extract, a deep eutectic solvent is prepared by mixing betaine and lactic acid in a molar ratio of 1:1-1.5, and the mass ratio of walnut shell powder to the deep eutectic solvent is 1:10-15. The filtrate is decolorized by adding 1%-2% of its mass to an adsorbent, stirring at 45-50°C for 15-20 minutes, and immediately filtering. The adsorbent is prepared by mixing activated carbon and diatomaceous earth in a mass ratio of 1:3-4 to prevent adsorption of the active ingredients. As can be appreciated, oxidation products such as quinones and lignin degradation products in the walnut shells can cause the extract to appear dark brown. Decolorization is intended to prevent the coating solution from darkening, which could lead to a darker surface and reduced quality when used for poultry eggs. After decolorization, the filtrate is vacuum-concentrated to reduce the effect of moisture in the extract on the film-forming properties of the coating agent. The vacuum concentration is performed at a pressure of -0.1 to -0.08 MPa and a temperature of 50-55°C. It should be noted that during the decolorization and concentration steps, the low eutectic solvent remaining in the filtrate can be removed at the same time without affecting the performance of the coating agent.

[0028] In an embodiment of the present invention, the antioxidant is a food-grade antioxidant that can be dissolved in rice bran oil. For example, the antioxidant includes the following components by weight: 0.005-0.01 parts of vitamin E, 0.01-0.03 parts of rosemary extract, 0.01-0.02 parts of ascorbyl palmitate, 0.005-0.01 parts of propyl gallate, and 0.01-0.015 parts of butylated hydroxyanisole.

[0029] Similarly, the preservative is a food-grade preservative with good solubility in rice bran oil. For example, the preservative includes the following components by weight: 0.05-0.1 parts of sorbic acid and 0.15-0.2 parts of cinnamaldehyde.

[0030] The emulsifier used in the embodiments of the present invention can be a common food-grade emulsifier and is not particularly limited in the present invention. For example, the emulsifier includes the following components by weight: 0.03-0.05 parts of modified soybean lecithin, 0.05-0.07 parts of glycerol, and 0.1-0.15 parts of sucrose fatty acid ester.

[0031] The second embodiment provided by the present invention is: A method for preparing a biological coating agent, characterized in that it comprises the following steps: dissolving water-soluble soybean polysaccharide in water to obtain an aqueous solution; Adding an antioxidant and a preservative to rice bran oil, stirring until dissolved, then adding an emulsifier and fully emulsifying to obtain an oil solution; The walnut shell extract is slowly added to the oil solution, mixed evenly, and then the aqueous solution is added, stirred at high speed and homogenized.

[0032] The key to the preparation method of the present invention lies in the time of adding the walnut shell extract. If the walnut shell extract is added during the aqueous solution preparation stage, the water-soluble soybean polysaccharide will first wrap the extract, making it difficult for the extract to fully fuse with the oil solution later, and the synergistic effect with the antibacterial and antioxidant components in the oil solution will be weakened; if the walnut shell extract is added during the oil solution preparation stage, the active ingredients are easily lost in large quantities during the high-temperature emulsification stage. The present invention first mixes the walnut shell extract with the oil solution, and the hydrophobic components in the extract can be quickly adsorbed to the surface of the rice bran oil droplets. After the aqueous solution is added, the soybean polysaccharide molecules will also be adsorbed on the surface of the rice bran oil liquid through hydrogen bonds, electrostatic effects, etc., and fully contact and fuse with the hydrophilic components in the extract. This not only effectively retains the activity of each component in the walnut shell extract and gives full play to the synergistic effect of each component with the antibacterial and antioxidant components in the oil solution, but also fully fuses the walnut shell extract with the rice bran oil and soybean polysaccharide to obtain a uniform and stable coating agent.

[0033] In one embodiment, the preparation method of the walnut shell extract is: adding walnut shell powder to a deep eutectic solvent, reacting at 45-50°C for 1.5-2 hours, filtering, decolorizing the filtrate, and vacuum concentrating the filtrate to 1 / 3-1 / 4 of the volume of the filtrate.

[0034] In a specific embodiment, the emulsification temperature is 50-60° C.; the homogenization pressure is 25-35 MPa, and the homogenization time is 20-30 min.

[0035] The third embodiment provided by the present invention is: The use of the above-mentioned biological coating agent, or the biological coating agent prepared according to the above-mentioned preparation method, in the preservation of poultry eggs.

[0036] The biological coating agent can be applied to the surface of poultry eggs by conventional methods such as spraying and soaking. It can form a uniform protective film on the surface of poultry eggs, preventing bacterial invasion without affecting the exchange of metabolic small molecules such as carbon dioxide and oxygen between the contents of the poultry eggs and the outside world. It can also inhibit or kill bacteria that have invaded the pores of the eggshell, thereby effectively delaying the quality changes of poultry eggs during storage and extending the shelf life of poultry eggs.

[0037] To further illustrate the technical solution of the present invention, examples for implementing the present invention and corresponding comparative examples will be disclosed below to demonstrate the relevant technical effects of the present invention.

[0038] The raw materials used in the embodiments of the present invention are all purchased from the market.

[0039] Example 1 Preparation of biological coating agent Raw material formula (by weight): 100 parts of rice bran oil, 0.5 parts of water-soluble soybean polysaccharides, 0.1 parts of walnut shell extract, 0.04 parts of antioxidant, 0.2 parts of preservative, 0.18 parts of emulsifier, 20 parts of water; Wherein: the antioxidant is specifically 0.005 parts of vitamin E, 0.01 parts of rosemary extract, 0.01 parts of ascorbyl palmitate, 0.005 parts of propyl gallate, and 0.01 parts of butylated hydroxyanisole; The preservatives specifically include 0.05 parts of sorbic acid and 0.15 parts of cinnamaldehyde; The emulsifier is specifically 0.03 parts of modified soybean lecithin, 0.05 parts of glycerol, and 0.1 parts of sucrose fatty acid ester; The preparation method of walnut shell extract is as follows: Walnut shell powder was added to a low eutectic solvent (the molar ratio of betaine to lactic acid was 1:1) with a mass 10 times that of the walnut shell powder, reacted at 45 °C for 1.5 h, and then filtered. 1% of the mass of the adsorbent (the mass ratio of activated carbon to diatomaceous earth was 1:3) was added to the filtrate, stirred at 45 °C for 20 min, and then immediately filtered to remove the adsorbent. The walnut shell extract was then concentrated in vacuo to 1 / 4 of the volume of the filtrate at a vacuum degree of -0.1 MPa and a temperature of 50 °C to obtain the walnut shell extract.

[0040] Preparation of biofilm: dissolving water-soluble soybean polysaccharide in water to obtain an aqueous solution; The antioxidant and preservative are added to rice bran oil, stirred until dissolved, and then an emulsifier is added and fully emulsified at 60°C to obtain an oil solution; The walnut shell extract was slowly added to the oil solution, mixed evenly, and then the aqueous solution was added. After high-speed stirring, the mixture was homogenized under a pressure of 35 MPa for 30 minutes to obtain the biofilm coating agent.

[0041] Example 2 Preparation of biological coating agent Raw material formula (by weight): 60 parts of rice bran oil, 0.8 parts of water-soluble soybean polysaccharides, 0.2 parts of walnut shell extract, 0.059 parts of antioxidant, 0.25 parts of preservative, 0.22 parts of emulsifier, 25 parts of water; The antioxidant is specifically 0.008 parts of vitamin E, 0.02 parts of rosemary extract, 0.01 parts of ascorbyl palmitate, 0.008 parts of propyl gallate, and 0.013 parts of butylated hydroxyanisole; The preservatives specifically include 0.07 parts of sorbic acid and 0.18 parts of cinnamaldehyde; The emulsifier is specifically 0.04 parts of modified soybean lecithin, 0.06 parts of glycerol, and 0.12 parts of sucrose fatty acid ester; The preparation method of walnut shell extract is as follows: Walnut shell powder was added to a low eutectic solvent (the molar ratio of betaine to lactic acid was 1:1.2) with a mass 12 times that of the walnut shell powder, reacted at 50 °C for 2 h, and then filtered. 1.5% of the mass of the adsorbent (the mass ratio of activated carbon to diatomaceous earth was 1:3.5) was added to the filtrate, stirred at 48 °C for 18 min, and then immediately filtered to remove the adsorbent. The walnut shell extract was then concentrated in vacuo to 1 / 5 of the volume of the filtrate at a vacuum degree of -0.1 MPa and a temperature of 50 °C to obtain the walnut shell extract.

[0042] Preparation of biofilm: dissolving water-soluble soybean polysaccharide in water to obtain an aqueous solution; The antioxidant and preservative are added to rice bran oil, stirred until dissolved, and then an emulsifier is added and fully emulsified at 50°C to obtain an oil solution; The walnut shell extract was slowly added to the oil solution, mixed evenly, and then the aqueous solution was added. After high-speed stirring, the mixture was homogenized under a pressure of 30 MPa for 20 min to obtain the biofilm coating agent.

[0043] Example 3 Preparation of biological coating agent Raw material formula (by weight): 50 parts of rice bran oil, 1 part of water-soluble soybean polysaccharide, 0.3 parts of walnut shell extract, 0.085 parts of antioxidant, 0.3 parts of preservative, 0.27 parts of emulsifier, 30 parts of water; The antioxidant is specifically 0.01 part of vitamin E, 0.03 part of rosemary extract, 0.02 part of ascorbyl palmitate, 0.01 part of propyl gallate, and 0.015 part of butylated hydroxyanisole; The preservatives specifically include 0.1 parts of sorbic acid and 0.2 parts of cinnamaldehyde; The emulsifier is specifically 0.05 parts of modified soybean lecithin, 0.07 parts of glycerol, and 0.15 parts of sucrose fatty acid ester; The preparation method of walnut shell extract is as follows: Walnut shell powder was added to a low eutectic solvent (the molar ratio of betaine to lactic acid was 1:1.5) with a mass 15 times that of the walnut shell powder, reacted at 48 °C for 1.8 h, and then filtered. 2% of its mass of adsorbent (the mass ratio of activated carbon to diatomaceous earth was 1:4) was added to the filtrate, stirred at 50 °C for 15 min, and then immediately filtered to remove the adsorbent. Subsequently, the filtrate was vacuum concentrated to 1 / 4 of the volume of the filtrate under vacuum conditions of -0.08 MPa and 55 °C to obtain a walnut shell extract.

[0044] Preparation of biofilm: dissolving water-soluble soybean polysaccharide in water to obtain an aqueous solution; Adding antioxidants and preservatives to rice bran oil, stirring until dissolved, adding emulsifier, and fully emulsifying at 55°C to obtain an oil solution; The walnut shell extract was slowly added to the oil solution, mixed evenly, and then the aqueous solution was added. After high-speed stirring, the mixture was homogenized under a pressure of 25 MPa for 25 minutes to obtain the biofilm coating agent.

[0045] Comparative Example 1 The preparation method is the same as that of Example 1, except that the walnut shell extract, emulsifier, water-soluble soybean polysaccharide and water are not added.

[0046] Comparative Example 2 The preparation method is the same as that of Example 1, except that no emulsifier, water-soluble soybean polysaccharide and water are added.

[0047] Comparative Example 3 The preparation method is the same as that of Example 1, except that the walnut shell extract is not added.

[0048] Comparative Example 4 The preparation method is the same as that of Example 1, except that, during the preparation of the walnut shell extract, the deep eutectic solvent is replaced with an equal amount of water.

[0049] Comparative Example 5 The preparation method is the same as that of Example 1, except that, during the preparation of the walnut shell extract, the deep eutectic solvent is replaced with an equal amount of 60% ethanol solution.

[0050] Comparative Example 6 The preparation method is the same as that of Example 1, except that the vacuum concentration process is omitted during the preparation of the walnut shell extract.

[0051] Comparative Example 7 The preparation method is the same as that of Example 1, except that, in the preparation stage of the biological coating agent, the walnut shell extract and the water-soluble soybean polysaccharide solution are added into water.

[0052] Comparative Example 8 The preparation method is the same as that of Example 1, except that, in the preparation stage of the biofilm coating agent, the walnut shell extract is added to the rice bran oil together with the antioxidant and the preservative.

[0053] Experimental Example 1 The biofilm coatings obtained in the above examples and comparative examples were tested for performance, including average particle size, viscosity, and surface tension. The average particle size was measured using a particle size analyzer. The smaller the particle size, the denser the protective film formed, and the stronger the barrier against bacterial invasion and water evaporation from the egg. Viscosity and surface tension play a decisive role in the exchange of metabolic small molecules such as oxygen and carbon dioxide between the egg contents and the outside world. Viscosity was measured using a digital viscometer. If the coating viscosity is too high (>200 mPa·s), the film formed on the egg surface is too thick, hindering the exchange of metabolic small molecules between the egg contents and the outside world. On the other hand, if the coating viscosity is too low (<80 mPa·s), the film formed is too thin. While this allows for material exchange, it reduces the inhibitory effect on bacterial invasion and water evaporation from the egg. Furthermore, films that are too thick or too thin are prone to rupture. Surface tension was measured using an automatic surface tension meter. When the surface tension of the coating agent is less than that of the egg (approximately 45 mN / m), the coating agent can spread spontaneously on the egg surface, forming a complete protective film. However, if the surface tension is too low (less than 35 mN / m), it will over-occlude the eggshell pores, hindering the exchange of metabolic small molecules between the egg contents and the outside world. The coating agent of the present invention, with a viscosity of 80-120 mPa·s and a surface tension of 35-40 mN / m, can form a complete, appropriately thick protective film on the egg surface. This protective film not only has good strength and elasticity, is resistant to rupture, effectively prevents bacterial invasion and water evaporation from the egg contents, but also ensures normal exchange of metabolic small molecules between the egg contents and the outside world. The performance test results of each group of biological coating agents are shown in Table 1.

[0054] Table 1 Performance test results of each group of biological coating agents .

[0055] According to the performance test results in Table 1, it can be seen that the biological coating agent prepared by the process of the present invention has the smallest average particle size, a viscosity in the range of 80-120 mPa·s, and a surface tension in the range of 35-40 mN / m, and can form a protective film with excellent performance on the surface of poultry eggs.

[0056] Experimental Example 2 The antioxidant and antibacterial properties of the biofilm coatings obtained in the above examples and comparative examples were measured. The specific indicators and measurement methods are as follows: DPPH free radical scavenging ability and ABTS free radical scavenging ability: measured using kits; Antibacterial activity: Sterilized solid culture medium was poured into Petri dishes and placed horizontally to solidify completely. 0.1 mL of Escherichia coli and Staphylococcus aureus culture solutions were then evenly added to each dish. Sterilized filter paper pieces with a diameter of approximately 1 cm were placed in different groups of biofilm coating agents and soaked for 2 minutes. The sterilized filter paper pieces were then placed on the Petri dishes in a herringbone pattern. Sterile saline was used as the control group. The Petri dishes were placed in a constant temperature incubator and incubated at 37°C for 24 hours. The diameters of the inhibition zones were measured using the cross-hatch method, and the average of three measurements was taken.

[0057] The results of the antioxidant and antibacterial properties of the biofilms in each group are shown in Table 2.

[0058] Table 2 Antioxidant and antibacterial properties of each group of biofilms .

[0059] According to the results in Table 2, it can be seen that the biofilm coating prepared according to the process of the present invention has better antioxidant and antibacterial properties than the comparative examples.

[0060] Experimental Example 3 The biofilm coating agents obtained in the above examples and comparative examples were sprayed onto the surface of cleaned eggs to a thickness of 1.0-1.5 μm. After film formation, the eggs were placed in plastic egg trays and stored in a constant temperature and humidity chamber at 25±1°C and 60±5% RH for 30 days. The eggs were then taken out for index measurement. The specific indexes and measurement methods are as follows: (1) Weight loss rate: Measure the initial weight m0 and final weight m1 of the egg, and calculate the weight loss rate according to the following formula: ; (2) Haugh value: Use an albumen height meter to measure the egg. First, weigh the egg M. Then, crack the egg on a platform and use the albumen height meter to measure the height H of the thick albumen 1 cm away from the yolk. Measure three times, take the average value, and then calculate the Haugh value according to the following formula: ; (3) Yolk Index: Crack the egg and pour it onto a glass platform. Use a vernier caliper to accurately measure the yolk height and yolk diameter. Calculate the yolk index based on the following: Yolk index = yolk height / yolk diameter (4) Egg white pH value: measured using a pH meter.

[0061] The results of the index measurements of eggs in different treatment groups during storage are shown in Table 3. Uncoated eggs were used as blank controls.

[0062] Table 3 Index measurement results of eggs in different treatment groups after 30 days of storage .

[0063] According to the results in Table 3, it can be seen that the biological coating agent prepared according to the process of the present invention is used in egg preservation, which can effectively delay the quality change process of eggs during storage, thereby extending the shelf life of eggs.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A biological coating agent, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of rice bran oil, 0.5-1 parts of water-soluble soybean polysaccharide, 0.1-0.3 parts of walnut shell extract, 0.04-0.175 parts of antioxidant, 0.2-0.3 parts of preservative, 0.18-0.27 parts of emulsifier and 20-30 parts of water.

2. The biofilm coating agent according to claim 1, wherein The preparation method of the walnut shell extract comprises: adding walnut shell powder to a low eutectic solvent, reacting at 45-50° C. for 1.5-2 hours, filtering, decolorizing the filtrate, and vacuum concentrating the filtrate to 1 / 5-1 / 4 of the volume of the filtrate.

3. The biofilm coating agent according to claim 2, characterized in that The deep eutectic solvent is obtained by mixing betaine and lactic acid in a molar ratio of 1:1-1.

5.

4. The biofilm coating agent according to claim 2, characterized in that The mass ratio of the walnut shell powder to the deep eutectic solvent is 1:10-15.

5. The biofilm coating agent according to claim 1, characterized in that The antioxidant comprises the following components in parts by weight: 0.005-0.01 parts of vitamin E, 0.01-0.03 parts of rosemary extract, 0.01-0.02 parts of ascorbyl palmitate, 0.005-0.01 parts of propyl gallate, and 0.01-0.015 parts of butylated hydroxyanisole.

6. The biofilm coating agent according to claim 1, characterized in that The preservative comprises the following components by weight: 0.05-0.1 part of sorbic acid and 0.15-0.2 part of cinnamaldehyde.

7. The biofilm coating agent according to claim 1, characterized in that The emulsifier comprises the following components by weight: 0.03-0.05 parts of modified soybean lecithin, 0.05-0.07 parts of glycerol, and 0.1-0.15 parts of sucrose fatty acid ester.

8. A method for preparing a biological coating agent, characterized in that: The following steps are involved: dissolving water-soluble soybean polysaccharide in water to obtain an aqueous solution; Adding an antioxidant and a preservative to rice bran oil, stirring until dissolved, then adding an emulsifier and fully emulsifying to obtain an oil solution; The walnut shell extract is slowly added to the oil solution, mixed evenly, and then the aqueous solution is added, stirred at high speed and homogenized.

9. The preparation method according to claim 8, wherein The preparation method of the walnut shell extract comprises: adding walnut shell powder to a low eutectic solvent, reacting at 45-50° C. for 1.5-2 hours, filtering, decolorizing the filtrate, and vacuum concentrating the filtrate to 1 / 4-1 / 5 of the volume of the filtrate.

10. Use of the biological coating agent according to any one of claims 1 to 7, or the biological coating agent prepared by the preparation method according to any one of claims 8 to 9, in preserving poultry eggs.