A chitosan-white oil-based nanometer antibacterial emulsion type egg coating preservative and a preparation method and application thereof

Abstract

The present application belongs to the field of agricultural product processing and preservation technology, and specifically relates to a chitosan-white oil-based nano bacteriostatic emulsion type egg film coating preservative as well as a preparation method and application thereof. The preservative is composed of water, chitosan, white oil, acetic acid, Tween 80, epsilon-polylysine hydrochloride and lauroyl arginine ethyl ester hydrochloride; wherein the mass fraction of chitosan is 0.3% to 0.75%, the mass fraction of white oil is 25% to 40%, the mass fraction of acetic acid is 1.2% to 1.5%, the addition amount of Tween 80 is 5% to 25% of the mass of white oil, the mass fraction of epsilon-polylysine hydrochloride is 0.2%, the mass fraction of lauroyl arginine ethyl ester hydrochloride is 0.2%, and the rest is water. The preservative has the outstanding advantages of safety and degradability, high bacteriostatic efficiency, stable film formation and adaptability to industrialization, and achieves the purpose of maintaining the freshness and nutritional quality of eggs.

Description

Technical Field

[0001] This invention belongs to the field of agricultural product processing and preservation technology, and relates to egg coating preservation technology, specifically a chitosan-white oil-based nano antibacterial emulsion type egg coating preservative, its preparation method and application. Background Technology

[0002] Eggshells have approximately 7,000 to 17,000 pores with a diameter of 0.01 to 0.03 mm. At room temperature, they are prone to spoilage due to moisture evaporation, CO2 escape, and invasion by pathogens, resulting in increased weight loss, decreased yolk index, and a drop in Haugh units. my country's total egg production is projected to exceed 32 million tons by 2025, but these eggs have a shelf life of only 7 to 10 days at room temperature, with an annual loss rate exceeding 10%. While a complete cold chain preservation system offers good results, it is energy-intensive and has limited coverage. Coating preservation, due to its low cost and ease of operation, has become the mainstream technology.

[0003] Preservative coatings are mainly divided into two categories: First, mineral oil-based coatings. These form a hydrophobic oil phase after film formation but lack antibacterial activity, only providing physical barrier properties. Furthermore, the weak intermolecular forces of long-chain alkanes result in highly fluid films that are prone to sagging and uneven thickness. They also suffer from surface greasiness and heavy metal residues in industrial-grade products. For example, CN201610007220.6 discloses "A Soybean Protein Composite Nanoparticle Egg Coating Preservative and Its Preparation Method," which uses soybean protein composite nanoparticles for coating, but the improvement in water resistance and antibacterial properties is limited. Second, single-component chitosan coatings. These form a hydrophilic continuous film through intermolecular hydrogen bonds. While the amino groups have some antibacterial properties, the large number of hydrophilic groups results in poor water resistance. The rigid polysaccharide chains make the film brittle and easily cracked, and it is only effective against Gram-positive bacteria. For example, CN202010685791.1 discloses "A Composite Chitosan Coating for Preserving Poultry Eggs, Its Preparation Method and Application," which uses a composite chitosan coating that suffers from problems such as the use of a single antibacterial material. Chitosan, as a natural, biodegradable polysaccharide with good film-forming properties and broad-spectrum antibacterial activity, has been widely studied for its use in egg coating preservation. White oil, as a coating agent permitted for use in the food industry, has a significant physical sealing effect and can effectively reduce the weight loss rate of eggs.

[0004] Existing technologies have attempted to directly mix chitosan and white oil to prepare composite coatings, aiming to combine the antibacterial advantages of chitosan with the highly efficient sealing properties of white oil. However, this method has significant drawbacks in practical applications. Because chitosan is typically soluble in acidic aqueous solutions and exhibits strong hydrophilicity, while white oil is hydrophobic, direct mixing of the two cannot form a thermodynamically stable, uniform dispersion system. Specifically: Poor coating uniformity: The mixture easily separates or forms discontinuous films, resulting in the inability to form a dense, uniform, and crack-free protective layer after coating the eggshell surface. Studies have shown that compared to using white oil alone, the direct chitosan / white oil mixture actually leads to a significantly higher egg weight loss rate, and its preservation effect is even inferior to the pure white oil treatment group. Mutual functional inhibition: The presence of the oil phase interferes with the orderly arrangement of chitosan molecular chains and the formation of hydrogen bonds, causing a decrease in the mechanical strength of the composite film and phase separation in the microstructure. This weakens the sealing effect of white oil and fails to fully utilize the antibacterial activity of chitosan, failing to achieve the technical objective of synergistic effect between the two. Insufficient storage stability: The prepared mixture rapidly separates into layers after standing, making it unsuitable for long-term storage or commercial application, thus limiting its practical value for promotion.

[0005] Therefore, how to overcome the compatibility problem between chitosan and white oil and prepare an egg coating preservative with high stability, uniform film formation, and synergistic effect of the two components is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative. The egg coating preservative prepared using this method, when used for egg preservation, leaves no heavy metal residue, is safe and biodegradable, and possesses both high barrier properties and synergistic antibacterial effects. Furthermore, the preparation process is simple and controllable; the spraying process does not increase production costs and can be directly adapted to existing industrial egg coating production lines, achieving the goal of maintaining egg freshness and nutritional quality.

[0007] To achieve the above-mentioned objectives, the specific technical solution of this invention is as follows: A chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative is characterized in that: the preservative is composed of water, chitosan, white oil, acetic acid, Tween 80, ε-polylysine hydrochloride, and lauroyl arginine ethyl ester hydrochloride; wherein, the mass fraction of chitosan is 0.3% to 0.75%, the mass fraction of white oil is 25% to 40%, the mass fraction of acetic acid is 1.2% to 1.5%, the amount of Tween 80 added is 5% to 25% of the mass of white oil, the mass fraction of ε-polylysine hydrochloride is 0.2%, the mass fraction of lauroyl arginine ethyl ester hydrochloride is 0.2%, and the remainder is water, with the total mass percentage being 100%.

[0008] In a preferred embodiment of this application, the chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative contains 0.75% chitosan, 25% white oil, 1.5% acetic acid, 15% Tween 80, 0.2% ε-polylysine hydrochloride, 0.2% lauroyl arginine ethyl ester hydrochloride, and the remainder is water, with a total mass percentage of 100%.

[0009] In a preferred embodiment of this application, the chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative contains 0.3% chitosan by mass, 40% white oil by volume, 1.2% acetic acid, 15% Tween 80 by mass of white oil, 0.2% ε-polylysine hydrochloride, 0.2% lauroyl arginine ethyl ester hydrochloride, and the remainder is water, with a total mass percentage of 100%.

[0010] As a preferred embodiment of this application, a method for preparing any of the above-described chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative includes the following steps: (1) Preparation of chitosan solution: The weighed chitosan is dissolved in an aqueous acetic acid solution and magnetically stirred in a constant temperature water bath until completely dissolved to obtain a chitosan solution, which is then used as a continuous phase and left to stand for later use. (2) Preparation of crude emulsion: Add white oil to the chitosan solution obtained in step (1), and then add Tween 80 as an emulsifier. Mix evenly to obtain crude emulsion. (3) Preparation of antibacterial emulsion: Add lauroyl arginine ethyl ester hydrochloride and ε-polylysine hydrochloride to the crude emulsion obtained in step (2), and mix gently and evenly; homogenize with a high-speed homogenizer; then place the homogenized emulsion in an ultrasonic cell pulverizer for emulsification, and obtain chitosan-white oil-based nano antibacterial emulsion type egg coating preservative.

[0011] As a preferred embodiment of this application, in step (1) of the preparation method, the mass fraction of the acetic acid aqueous solution is 2%; the temperature of the constant temperature water bath is 60°C.

[0012] As a preferred embodiment of this application, in step (3) of the preparation method, the high-speed homogenizer has a rotation speed of 8000 rpm and a homogenization time of 1 min; the ultrasonic cell disruptor has a power of 400 W and an emulsification time of 10 min.

[0013] This application also protects chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative prepared according to any of the methods described above.

[0014] This application also protects the application of the chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative or the chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative prepared according to the method in egg preservation.

[0015] As a preferred embodiment of this application, when applying the chitosan-white oil-based nano antibacterial emulsion type egg coating preservative, the prepared chitosan-white oil-based nano antibacterial emulsion type egg coating preservative is loaded into a spraying device, the nozzle pressure and egg feeding speed are adjusted, and the eggs are continuously sprayed. After a uniform thin coating film is formed on the surface, it is dried with hot air to form a film.

[0016] In a preferred embodiment of this application, the nozzle pressure is 0.1–0.3 MPa and the egg delivery speed is 80%–100%. More preferably, the nozzle pressure for spray drying is 0.3 MPa and the egg delivery speed is 100%.

[0017] Compared with existing technologies, the beneficial effects of this invention are: (1) This invention provides a chitosan-white oil-based nano antibacterial emulsion type egg coating preservative and its preparation method. The coating agent prepared by this invention is simple to operate and can significantly improve the storage period of eggs under high temperature and high humidity conditions.

[0018] (2) This invention uses food-grade antibacterial agents as preservatives, which have the advantages of being safe, non-toxic, and highly efficient. They have significant antibacterial activity and can inhibit or kill pathogenic microorganisms, thereby extending the shelf life of eggs. Compared with traditional chemical preservatives, natural food-grade antibacterial agents are more environmentally friendly and can reduce the impact on the environment. At the same time, with the enhancement of health and environmental awareness, consumers are more inclined to choose products with natural ingredients, and natural food-grade antibacterial agents meet this demand. Natural food-grade antibacterial agents can be used as effective ingredients for egg coating preservation, and the optimal ratio combination of composite coating materials was obtained through single-factor experiments and orthogonal experiments. (3) This invention studied and explored the effects of chitosan concentration, white oil addition, Tween 80 addition, ultrasonic emulsification time, and ultrasonic emulsification power on the particle size and polydispersity coefficient of chitosan-white oil-based nano antibacterial emulsion through single-factor experiments, and then determined the optimal nano-emulsion preparation process through orthogonal experiments. The stability optimization study of the nanoemulsion prepared by the determined process was carried out. By adjusting the oil-water ratio and measuring the stratification of the emulsion after standing, the optimal stability formula was determined. (4) This invention explored the compounding effect of different natural antibacterial agents and studied the antibacterial effect of lauroyl arginine ethyl ester hydrochloride and ε-polylysine on the main foodborne pathogens on the surface of eggs. By measuring the minimum inhibitory concentration and the combined antibacterial index, and combining the effect of compound antibacterial agents on egg preservation, the optimal compounding ratio of antibacterial agents was determined. (5) This invention systematically studied the effect of industrial spraying process parameters on egg preservation. The two key parameters of nozzle pressure and egg delivery speed were examined. By measuring the weight loss rate, Haugh unit, yolk coefficient and other freshness indicators of eggs during storage, and combining the effect of composite coating on egg preservation, the optimal spraying process parameters were determined. (6) The raw materials used in this invention are all food grade, widely available and inexpensive. The preparation process is simple and does not require complex equipment. It can be directly connected to the existing egg washing and grading production line and has good prospects for industrial promotion. Attached Figure Description

[0019] Figure 1 A graph showing the change in weight loss rate of eggs during storage under different nozzle pressures; Figure 2 A graph showing the variation of Haugh units in eggs during storage under different nozzle pressures; Figure 3 A graph showing the change in yolk coefficient of eggs during storage under different nozzle pressures; Figure 4 A graph showing the change in yolk coefficient of eggs during storage under different egg delivery speeds; Figure 5 The graph shows the variation of Hough units in eggs during storage at different egg delivery speeds. Detailed Implementation

[0020] A method for preparing a chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative is as follows: (1) Preparation of chitosan solution: Weigh 0.5-1 g of chitosan and dissolve it in 100 mL of 2% acetic acid aqueous solution. Stir magnetically in a constant temperature water bath at 60℃ until completely dissolved to obtain a chitosan solution as a continuous phase. Let it stand for later use. (2) Preparation of crude emulsion: Add 5-25 g of white oil to 75-95 g of chitosan solution as an oil phase, and then add 5-25% of Tween 80 by mass of white oil as an emulsifier. Mix evenly to obtain a crude emulsion.

[0021] (3) Preparation of antibacterial emulsion: Lauroyl arginine ethyl ester hydrochloride and ε-polylysine hydrochloride were added to the above crude emulsion and mixed evenly by gentle stirring. The mixture was homogenized at 8000 rpm for 1 min using a high-speed homogenizer; the homogenized emulsion was then placed in an ultrasonic cell disruptor and emulsified at 300-700 W for 7.5-17.5 min to obtain chitosan-white oil-based nano antibacterial emulsion-type egg coating preservative.

[0022] The preferred addition amount of chitosan in step (1) is 0.75%, the preferred addition amount of white oil in step (2) is 25%, and the preferred addition amount of Tween 80 is 15% of the mass of white oil; the optimal ultrasonic parameters in step (3) are: power 400W, ultrasonic time 10min; the preferred addition amount of antibacterial agent is: ε-polylysine 0.2% (mass fraction), lauroyl arginine ethyl ester hydrochloride 0.2% (mass fraction); the optimal spraying parameters in step (4) are: nozzle pressure 0.3MPa, egg delivery speed 100%.

[0023] The application method of this chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative is as follows: The prepared chitosan-white oil-based nano antibacterial emulsion egg coating preservative was loaded into a spraying equipment (Guangdong Guangxing Gonghe Machinery Co., Ltd. - automatic egg grading machine). The nozzle pressure was adjusted to 0.1-0.3 MPa and the egg feeding speed to 80%-100%. The eggs were continuously sprayed. After a uniform thin coating was formed on the surface, it was dried with hot air to form a film.

[0024] The coating agent prepared according to the preparation method described in steps (1) to (3) has the following advantages: (1) The basic nanoemulsion formulation optimized by orthogonal experiments is 0.75% chitosan, 25% white oil, and Tween 80 accounting for 15% of the white oil mass. The average particle size of the nanoemulsion with this formulation is 187.59±8.34 nm, and the polydispersity index (PDI) is 0.109±0.031. (2) The optimal coating agent formulation after further stability optimization is 0.5% chitosan, 40% white oil, 15% Tween 80 by mass of white oil, 0.2% ε-polylysine hydrochloride, and 0.2% lauroyl arginine ethyl ester hydrochloride. The nanoemulsion of this formulation only separated into a small amount of aqueous phase after standing for 2 days, which significantly reduced the separation height of the emulsion compared with other groups. (3) The FIC index of graded inhibition of Escherichia coli, Salmonella and Staphylococcus aureus is 0.25, which shows a significant synergistic antibacterial effect.

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] In this invention, some conventional operating equipment, devices and components have been omitted or only briefly described.

[0029] Unless otherwise specified in the examples, the conditions shall be performed according to the standard conditions or the conditions recommended by the manufacturer.

[0030] In this application, any percentage not marked indicates its weight percentage content.

[0031] The coating agent prepared by the preparation method described in steps (1) to (3) was tested at a temperature of 35°C and a relative humidity of 70%. The measured indicators included weight loss rate, yolk coefficient, and Haugh unit.

[0032] The testing methods used in this application are as follows: (1) PDI determination and determination of minimum inhibitory concentration (MIC) and combined inhibitory index (FIC) of antibacterial agent. The particle size and polydispersity coefficient of nanoemulsion were determined by nanolaser particle size analyzer; the minimum inhibitory concentration of antibacterial agent was determined by double dilution method for lauroyl arginine ethyl ester hydrochloride and ε-polylysine hydrochloride against Escherichia coli, Salmonella and Staphylococcus aureus respectively; the combined inhibitory effect was evaluated by graded inhibition concentration index method, and the calculation formula is: FIC = MIC(compound) / MIC(A) + MIC(compound) / MIC(B) where: MIC(compound) represents the minimum inhibitory concentration of compound antibacterial agent; MIC(A) represents the minimum inhibitory concentration of antimicrobial agent A; MIC(B) represents the minimum inhibitory concentration of antimicrobial agent B.

[0033] When FIC≤0.5, it is a synergistic effect; when 0.5<FIC≤4, it is an additive effect; and when FIC>4, it is an antagonistic effect. (2) The weight loss rate of eggs was determined by gravimetric method. The weight of eggs before and after storage was accurately determined by an electronic balance with an accuracy of 0.0001g: W%=(m1-m2) / m1×100% Where: m1— weight of the egg before storage, g; m2— weight of the egg after storage, g. (3) Determination of Hough units for eggs First, weigh the egg precisely on an electronic balance, then break it horizontally along the equator and pour the contents onto a horizontally placed glass plate. While keeping the yolk and thick albumen intact, avoid the chalaza and measure the height of the thick albumen at three different positions 10 mm away from the yolk. Take the average value as the height of the thick albumen: HU=100×lg (H-1.7w^0.37+7.57) Where: HU— Hough units; H— height of thick albumen, mm; w— weight of the egg, g. (4) Determination of egg yolk index: Crack the egg horizontally along the equator onto a horizontally placed glass plate. Measure the height of the yolk with vernier calipers, and then measure the diameter of the yolk with vernier calipers (take the average of the widths at three different locations). Calculate the yolk index using the following formula: YI = h / d Where: YI—yolk index; h—yolk height, mm; d—yolk diameter, mm. Example 1 (Based on the specific implementation method, the basic formula is optimized by orthogonal optimization) A method for preparing a chitosan-white oil-based nano-antibacterial emulsion type egg coating preservative includes the following steps: (1) Preparation of chitosan solution: Dissolve chitosan in 100 mL of 2% acetic acid aqueous solution and stir at 60°C until completely dissolved.

[0034] (2) Preparation of crude emulsion: Add white oil and Tween 80 to the chitosan solution prepared in step (1) and mix evenly to obtain crude emulsion.

[0035] (3) High-speed homogenization: The crude emulsion obtained in step (2) is homogenized for 1 min at 8000 rpm using a high-speed homogenizer.

[0036] (4) Ultrasonic emulsification: The homogenized emulsion in step (3) is placed in an ultrasonic cell disruptor and ultrasonically treated with 400 W power for 10 min to obtain chitosan-white oil nano-based emulsion.

[0037] (5) Antibacterial agent compounding: Add ε-polylysine hydrochloride to the nano-based emulsion obtained in step (4) to make the final concentration 0.2%, add lauroyl arginine ethyl ester hydrochloride to make the final concentration 0.2%, and gently stir to mix evenly to obtain chitosan-white oil-based nano antibacterial emulsion type egg coating preservative.

[0038] Table 1 Orthogonal Level Table

[0039] Orthogonal Experiment Optimization Analysis The nanoemulsion preparation process described in steps (1) to (4) was further optimized through orthogonal experiments. The effects of chitosan addition, white oil addition, Tween 80 addition, ultrasonic emulsification time, and ultrasonic emulsification power on the nanoemulsion particle size and PDI were investigated through single-factor experiments. Based on this, using chitosan addition (A), white oil addition (B), Tween 80 addition (C), and error (D) as evaluation factors, the L9(3) method was applied. 4 Orthogonal experiments were conducted to optimize and determine the optimal formulation. Particle size was used as the primary indicator, and PDI as a secondary indicator for evaluation. The results of the orthogonal experiments are shown in the table below.

[0040] Table 2 Orthogonal Results Table

[0041] Particle size was used as the primary indicator, and PDI as a secondary indicator. The k-value indicates that the combination with the lowest particle size is A2B3C2D2, which corresponds to 0.75% chitosan, 25% white oil, and 15% Tween 80 by mass of white oil. Validation experiments showed that the emulsion particle size was 187.59±8.34 nm, and the PDI was 0.109±0.031. The range R-value indicates that the order of influence of each factor on particle size is B>A>C>D, with white oil having the greatest impact, followed by chitosan, and finally Tween 80.

[0042] The antibacterial agent compounding analysis was performed, and the antibacterial agent compounding described in step (5) was systematically validated. The minimum inhibitory concentrations (MICs) of lauroyl arginine ethyl ester hydrochloride and ε-polylysine hydrochloride against Escherichia coli, Salmonella, and Staphylococcus aureus were determined by the agar dilution method. The results are shown in the table below. Table 3 MIC values ​​of antibacterial agents and FIC values ​​of compounded agents.

[0043] In the evaluation of the combined antibacterial effect, the two antibacterial agents were combined at 1 / 8, 1 / 4, and 1 / 2 times their respective MICs. The FIC values ​​for the combined use of lauroyl arginine ethyl ester hydrochloride and ε-polylysine hydrochloride against *Escherichia coli*, *Salmonella*, and *Staphylococcus aureus* were all determined to be 0.25. Since FIC = 0.25 < 0.5, this indicates a significant synergistic effect between the two antibacterial agents; that is, at the same antibacterial efficacy, the concentration of the combined antibacterial agent is much lower than that of the individual antibacterial agents. Example 2 (Optimal Stability Formulation) A method for preparing a chitosan-white oil-based nano antibacterial emulsion type egg coating preservative includes the following steps: (1) Chitosan solution preparation: Dissolve 0.5 g of chitosan in 100 mL of acetic acid aqueous solution with a volume fraction of 2%, stir magnetically in a constant temperature water bath at 60℃ until completely dissolved, and let stand for later use.

[0044] (2) Preparation of crude emulsion: Take 60 g of chitosan solution, add 40 g of white oil and 3.75 g of Tween 80, mix evenly to obtain crude emulsion.

[0045] (3) Preparation of antibacterial emulsion: Lauroyl arginine ethyl ester hydrochloride and ε-polylysine hydrochloride were added to the above crude emulsion and mixed evenly by gentle stirring. The mixture was homogenized at 8000 rpm for 1 min using a high-speed homogenizer; the homogenized emulsion was then placed in an ultrasonic cell disruptor and emulsified at 400 W for 10 min to obtain chitosan-white oil nanomatrix antibacterial emulsion.

[0046] (4) Spraying and drying: The prepared chitosan-white oil nano-matrix antibacterial emulsion is loaded into the spraying equipment, the nozzle pressure is adjusted to 0.3 MPa and the egg feeding speed is 100%, and the eggs are continuously sprayed. After a uniform thin film is formed on the surface, it is dried with hot air.

[0047] The emulsion prepared in this embodiment only separated into a small amount of aqueous phase after standing for 2 days, which significantly reduced the separation height of the emulsion compared with other groups, and showed the best storage stability.

[0048] Preservation test: a) The effect of nozzle pressure on preservation effect Weight loss rate: As shown in Figure 1, the weight loss rate of all groups showed an increasing trend. There was no significant difference between the white oil and the emulsion with a nozzle pressure of 0.3 at any time point. This indicates that the white oil and the emulsion with a nozzle pressure of 0.3 have comparable abilities to inhibit the weight loss rate of eggs. Half units: As shown in Figure 2, all groups showed a decreasing trend in Half units. In each interval, the blank group showed significant differences from other groups, indicating that the spraying effect was effective. Significant differences were found between white oil and the 0.3 pressure at each time point, indicating that the emulsion at 0.3 pressure was better than white oil at inhibiting the decrease in Half units. Egg yolk coefficient: As shown in Figure 3, the egg yolk coefficient showed a decreasing trend in all groups. Before day 14, the control group showed significant differences from other groups; on day 12, the nozzle pressure of 0.3 showed a significant difference from other groups, but at other time points, excluding the control group, there were no significant differences among the groups. This indicates that the white oil and the emulsions at nozzle pressures of 0.1, 0.2, and 0.3 have comparable ability to inhibit the egg yolk coefficient.

[0049] Summary: Spraying emulsion and white oil can slow down the decreasing trend in Haugh units and yolk coefficient. Spraying white oil and emulsion at 0.3 MPa have comparable ability to suppress weight loss. Regarding the suppression of yolk coefficient, the data for the spraying group are comparable. In suppressing the decrease in Haugh units, a pressure of 0.3 MPa is the most significant, superior to the white oil group. Therefore, a nozzle pressure of 0.3 MPa is preferred. (b) Effect of egg delivery speed on preservation effect Egg yolk coefficient: As shown in Figure 4, the egg yolk coefficient showed a decreasing trend in all groups. Before day 14, there were significant differences between the control group and other groups; on day 12, there were significant differences between the sprayed emulsion and other groups, but at other time points, excluding the control group, there were no significant differences among the groups. For the white oil group, the emulsions at 100% and 80% egg delivery speeds had similar abilities to inhibit the egg yolk coefficient, with the sprayed emulsion being slightly better than the white oil group. Hough units: As shown in Figure 5, all groups showed a decreasing trend in Hough units. Significant differences were observed between the blank group and other groups at each time point, indicating that the spraying effect was effective. Significant differences were found between the white oil group and the 100% egg delivery speed group at certain time points, but no significant differences were observed at other time points; this indicates that the 100% egg delivery speed was better than the white oil group at inhibiting the decrease in Hough units.

[0050] Summary: Both the spray emulsion and the white oil slowed the decline in Haugh units and yolk coefficient. The spray emulsion was slightly better than the white oil group in suppressing the yolk coefficient. In suppressing the Haugh unit, a 100% egg delivery speed was better than the white oil in suppressing the decline in Haugh units. Therefore, a 100% egg delivery speed is preferred. Preservation effect comparison. Eggs coated in Example 2, compared with uncoated eggs and eggs coated with white oil, were stored for 14 days at 35°C and 70% relative humidity, and various indicators were measured: (1) Weight loss rate: There was no significant difference between the coated group and the white oil group in this invention; both were significantly lower than the uncoated blank group. (2) Hough units: The coating group of the present invention is significantly higher than that of the white oil group, and the white oil group is significantly higher than that of the uncoated blank group; (3) Egg yolk coefficient: The coating group of the present invention is slightly better than the pure white oil group, and both are significantly higher than the uncoated blank group; (4) Antibacterial effect: The FIC value of the coating group of the present invention against Escherichia coli, Salmonella and Staphylococcus aureus is 0.25, which shows a significant synergistic antibacterial effect.

[0051] In summary, the chitosan-white oil nanocomposite emulsion film preservative prepared by this invention has both excellent physical barrier properties and synergistic antibacterial properties. Its good preservation effect on eggs can effectively extend the shelf life, and it is suitable for the continuous spraying requirements of industrial production lines, showing good application prospects.

[0052] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

[0053] This background section is provided to generally present the context of the invention. The work of the currently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither expressly nor impliedly acknowledged as prior art to the invention.

Claims

1. A chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative, characterized in that: This preservative is composed of water, chitosan, white oil, acetic acid, Tween 80, ε-polylysine hydrochloride, and lauroyl arginine ethyl ester hydrochloride. The chitosan comprises 0.3%–0.75% by mass, the white oil comprises 25%–40% by mass, the acetic acid comprises 1.2%–1.5% by mass, the Tween 80 comprises 5%–25% by mass of the white oil, the ε-polylysine hydrochloride comprises 0.2% by mass, the lauroyl arginine ethyl ester hydrochloride comprises 0.2% by mass, and the remainder is water, with a total mass percentage of 100%.

2. The chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative according to claim 1, characterized in that: The chitosan has a mass fraction of 0.75%, the white oil has a mass fraction of 25%, the acetic acid has a mass fraction of 1.5%, the Tween 80 has a mass fraction of 15% of the white oil, the ε-polylysine hydrochloride has a mass fraction of 0.2%, the lauroyl arginine ethyl ester hydrochloride has a mass fraction of 0.2%, and the remainder is water, with a total mass percentage of 100%.

3. The chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative according to claim 1, characterized in that: The chitosan content is 0.3% by mass, the white oil content is 40% by volume, the acetic acid content is 1.2%, the Tween 80 content is 15% of the white oil content, the ε-polylysine hydrochloride content is 0.2% by mass, the lauroyl arginine ethyl ester hydrochloride content is 0.2% by mass, and the remainder is water, with a total mass percentage of 100%.

4. A method for preparing a chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Preparation of chitosan solution: The weighed chitosan is dissolved in an aqueous acetic acid solution and magnetically stirred in a constant temperature water bath until completely dissolved to obtain a chitosan solution, which is then used as a continuous phase and left to stand for later use. (2) Preparation of crude emulsion: Add white oil as oil phase to the chitosan solution obtained in step (1), and then add Tween 80 as emulsifier. Mix evenly to obtain crude emulsion. (3) Preparation of antibacterial emulsion: Add lauroyl arginine ethyl ester hydrochloride and ε-polylysine hydrochloride to the crude emulsion obtained in step (2), and mix gently and evenly; homogenize with a high-speed homogenizer; then place the homogenized emulsion in an ultrasonic cell disruptor for emulsification, and obtain chitosan-white oil-based nano antibacterial emulsion type egg coating preservative.

5. The preparation method according to claim 4, characterized in that: In step (1), the mass fraction of the acetic acid aqueous solution is 2%; the temperature of the constant temperature water bath is 60℃.

6. The preparation method according to claim 4, characterized in that: In step (3), the high-speed homogenizer rotates at 8000 rpm and the homogenization time is 1 min; the ultrasonic cell disruptor has a power of 400W and an emulsification time of 10 min.

7. Chitosan-white oil-based nano-antibacterial emulsion-type egg coating preservative prepared according to the method described in claim 5 or 6.

8. The application of a chitosan-white oil-based nano-antibacterial emulsion type egg coating preservative as described in any one of claims 1 to 3, or a chitosan-white oil-based nano-antibacterial emulsion type egg coating preservative prepared by any one of claims 4 to 6, in egg preservation.

9. The application according to claim 8, characterized in that: The prepared chitosan-white oil-based nano antibacterial emulsion egg coating preservative was loaded into a spraying device. The nozzle pressure and egg feeding speed were adjusted to continuously spray the eggs. After a uniform thin coating was formed on the surface, it was dried with hot air to form a film.

10. The application according to claim 8, characterized in that: The nozzle pressure is 0.1–0.3 MPa, and the egg delivery speed is 80%–100%.

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