Antibiotic-free egg and production process thereof

Abstract

The invention relates to an antibiotic-free egg and a production process thereof, and belongs to the technical field of laying hen breeding and functional feed processing, and the production process comprises the following steps: feeding laying hens in an egg producing period with basic ration containing functional modified microcapsules, and collecting produced eggs; the functional modified microcapsule is of a core-shell structure, a shell layer of the functional modified microcapsule is composed of an imine bond-containing polymer generated by cinnamyl aldehyde and carboxymethyl chitosan through a Schiff base reaction, and the core layer of the functional modified microcapsule is prepared by wrapping 80-100 parts of carboxymethyl chitosan, 20-40 parts of cinnamyl aldehyde, 2-5 parts of sodium selenite, 8-15 parts of ascorbic acid and 1-3 parts of an emulsifier which are generated through in-situ reduction. According to the invention, sodium selenite is converted into nano-selenium, and the nano-selenium is coated with microcapsules, so that the biotoxicity of selenium is effectively reduced.

Description

Technical Field

[0001] This invention relates to the fields of egg-laying hen breeding and functional feed processing, specifically to an antibiotic-free egg and its production process. Background Technology

[0002] With the development and construction of green farming and food safety projects, antibiotic-free production systems are gradually being established in typical egg-laying hen farming scenarios. However, in actual production, the failure response of antibiotic-free farming exhibits significantly complex characteristics. Traditional feeding analysis methods and disease prevention principles based on the direct addition of plant essential oils or inorganic selenium sources and physical mixing are difficult to adapt.

[0003] Due to the high volatility and irritant properties of natural active ingredients such as plant essential oils, significant losses of effective components and decreased palatability are easily observed during feed processing, storage, and consumption by laying hens. In the complex environment of the laying hen's digestive tract, active substances in existing technologies are often prematurely degraded or released by stomach acid before reaching the target intestines, leading to ineffective control of harmful bacteria and a high risk of pathogenic bacteria recurring. Simultaneously, traditional mineral supplementation methods suffer from unstable absorption efficiency and narrow biosafety thresholds, easily causing fluctuations in egg production and substandard egg quality. The increased risk of mis-activation or refusal to activate existing communication protection systems and the decreased stability of disease prevention systems under traditional farming models severely impact the stable operation of antibiotic-free laying hen farming systems.

[0004] The information disclosed in the background section above is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide antibiotic-free eggs and their production process to solve the problems mentioned in the background art.

[0006] The technical solution of the present invention includes feeding laying hens a basic diet containing functionalized modified microcapsules and collecting the produced eggs; the functionalized modified microcapsules have a core-shell structure, the shell layer of which is composed of a polymer containing imine bonds generated by the Schiff base reaction of cinnamaldehyde and carboxymethyl chitosan, and the core layer is encapsulated with 80-100 parts of carboxymethyl chitosan, 20-40 parts of cinnamaldehyde, 2-5 parts of sodium selenite, 8-15 parts of ascorbic acid and 1-3 parts of emulsifier, which are generated by in-situ reduction of nano-selenium.

[0007] Preferably, the preparation process of functionalized modified microcapsules includes a graft modification pretreatment of carboxymethyl chitosan, specifically the following steps:

[0008] Carboxymethyl chitosan was added to deionized water and placed in a constant-temperature magnetic stirrer. The stirring speed was set to 300-500 r / min, and the mixture was stirred for 30-60 min until it was completely swollen. The pH of the solution was adjusted to 4.5-5.5. Then, cinnamaldehyde was added, the temperature was raised to 50-60℃, and the reflux condenser was turned on. The reaction was carried out under constant-temperature reflux for 4-6 h in the dark. During the reaction, the aldehyde group of cinnamaldehyde and the amino group of carboxymethyl chitosan underwent a Schiff base condensation reaction, generating an amphiphilic polymer precursor solution containing imine bonds (-C=N-) through the Schiff base reaction.

[0009] Preferably, the molding process of functionalized modified microcapsules includes in-situ reduction and self-assembly steps, specifically:

[0010] Sodium selenite was added to the amphiphilic polymer precursor solution, and stirring was continued for 15-20 min to ensure uniform dispersion of the selenium source. Then, ascorbic acid was prepared into an aqueous solution and slowly added dropwise to the reaction system at a flow rate of 2-5 mL / min using a peristaltic pump.

[0011] During the dropwise addition process, the system undergoes an in-situ reduction reaction to generate nano-selenium. Simultaneously, the hydrophobic effect induces the polymer chain segments to encapsulate the nano-selenium for self-assembly. After the dropwise addition is complete, the reaction solution is transferred into an ultrasonic disperser, the frequency is set to 40-60 kHz, and ultrasonic treatment is performed for 20-30 min to obtain a core-shell structured nanosphere dispersion.

[0012] Preferably, the nanosphere dispersion needs to undergo drying and solidification treatment, and the specific steps are as follows:

[0013] The nanosphere dispersion was fed into a centrifugal spray dryer, with the inlet air temperature set at 160-180℃, the outlet air temperature at 70-90℃, and the feed rate at 500-800 mL / h. After atomization drying, powdered functionalized modified microcapsules were obtained.

[0014] The functionalized modified microcapsules maintain a relatively stable structure in a simulated gastric fluid environment at pH 2.5–3.5, and undergo responsive cleavage and release cinnamaldehyde and nano-selenium in a simulated intestinal fluid environment at pH 6.0–7.0.

[0015] Preferably, the amount of functionalized modified microcapsules added to the basal diet is 200-500 g / t, and it needs to be premixed step by step before feeding, with the coefficient of variation of mixing uniformity CV ≤ 5%.

[0016] Specifically, the microcapsules are first mixed with 10 times their weight of corn flour, then expanded to 100 times, and finally added to the complete basic diet in proportion.

[0017] Preferably, the molar ratio of ascorbic acid to sodium selenite is controlled at 2.5:1 to ensure that selenite ions are completely reduced to red elemental nano-selenium.

[0018] Preferably, the emulsifier is selected from at least one of polyoxyethylene sorbitan monooleate or sorbitan monooleate, to assist in the dispersion of cinnamaldehyde in the aqueous phase.

[0019] An antibiotic-free egg production process produces antibiotic-free eggs with undetectable antibiotic residues and a whole egg selenium content of 0.3–0.5 mg / kg, with nano-selenium particles deposited in the yolk.

[0020] This invention provides an improved antibiotic-free egg and its production process, which, compared with the prior art, has the following improvements and advantages:

[0021] 1. By converting sodium selenite into nano-selenium and encapsulating it in microcapsules, the biotoxicity of selenium was effectively reduced. In contrast, Comparative Example 3, which directly added inorganic selenium, not only showed large fluctuations in selenium content, but also had some samples approaching the safety limit, and even exhibited negative growth in egg production. This method significantly improved bioavailability through speciation conversion.

[0022] 2. The scheme demonstrates that different functional emphases can be achieved by adjusting process parameters. For example, Example 3 uses a lower reaction temperature, which preserves the integrity of the carboxymethyl chitosan molecular chains, thereby enhancing the electrostatic interaction between the microcapsules and intestinal mucosal mucosa mucoproteins and improving bioadhesion performance;

[0023] 3. By introducing a compound emulsifier, the interfacial tension between oil and water is reduced, resulting in microcapsules with a regular spherical shape, which is superior to conventional processes and ensures the stability of addition in large-scale production. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0025] Example 1

[0026] This invention provides a process for producing antibiotic-free eggs. The process includes feeding laying hens a basal diet containing functionalized modified microcapsules and collecting the produced eggs. In this embodiment, the raw material components of the functionalized modified microcapsules are selected as follows (fixed values): 80 parts by weight of carboxymethyl chitosan (92% deacetylation, 85% carboxylation, purchased from Sinopharm Chemical Reagent Co., Ltd.); 20 parts by weight of cinnamaldehyde (99% purity, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.); 2 parts by weight of sodium selenite (purchased from Tianjin Kemei Chemical Reagent Co., Ltd.); 8 parts by weight of ascorbic acid (purchased from Xilong Scientific Co., Ltd.); 1 part by weight of polyoxyethylene sorbitan monooleate (Tween-80) emulsifier (purchased from Guangdong Guanghua Technology Co., Ltd.); and 1000 parts by weight of deionized water.

[0027] In the preparation process, the framework was first constructed and grafted: 80 parts of carboxymethyl chitosan were dissolved in deionized water and stirred for 40 minutes until completely swollen. The pH was adjusted to 5.0, and 20 parts of cinnamaldehyde were added. The mixture was then refluxed at 55°C in the dark for 5 hours. This step utilizes chemical grafting to induce a Schiff base condensation reaction between the aldehyde group of cinnamaldehyde and the amino group of carboxymethyl chitosan, forming an imine bond. The introduction of this chemical bond is not a simple physical mixing, but rather endows the material with a crucial pH-responsive switching function, making it stable in acidic environments and breaking in neutral environments. This solves the technical problem of cinnamaldehyde's easy volatilization and premature release in feed processing and the acidic environment of chicken stomachs.

[0028] Subsequently, in-situ composite and self-assembly were performed: 2 parts of sodium selenite were added to the amphiphilic polymer precursor solution after the above reaction, and after stirring and dispersion, ascorbic acid aqueous solution was added dropwise at a flow rate of 3 mL / min, with the molar ratio of ascorbic acid to sodium selenite controlled at 2.5:1. During this process, an in-situ reduction reaction occurred to generate selenium nanoparticles. Driven by hydrophobic interactions, polymer segments self-assembled with selenium nanoparticles as the core and cinnamaldehyde-chitosan as the shell. After ultrasonic treatment at 50 kHz for 25 min, a core-shell structured nanosphere dispersion was formed. This simultaneous in-situ reduction and self-assembly not only effectively reduced the biotoxicity of selenium using the polymer shell, but also synergistically scavenged intestinal free radicals using the high surface activity of selenium nanoparticles, demonstrating a synergistic effect of structure and function.

[0029] The average particle size of the functionalized modified microcapsules, as determined by a laser particle size analyzer, was 150–300 nm, exhibiting a uniform spherical distribution.

[0030] Transmission electron microscopy revealed that the microcapsules contained high electron density particles with a diameter of 20-50 nm, and EDS energy dispersive spectroscopy confirmed that the particles were elemental selenium.

[0031] Finally, drying and application were carried out: the dispersion was processed into powder using a centrifugal spray dryer with an inlet air temperature of 170°C and an outlet air temperature of 80°C. The obtained functionalized modified microcapsules were added to the basal diet at a ratio of 300 g / t. After stepwise premixing, the coefficient of variation of mixing uniformity was measured. The microcapsules were then fed to laying hens. Since the carboxymethyl chitosan was not completely destroyed by gastric acid, the functionalized modified microcapsules entered the intestines. At pH 6.5, the Schiff base bonds cleaved in response, releasing cinnamaldehyde. At the same time, the chitosan backbone was anchored to the intestinal mucosa through electrostatic interaction, prolonging the retention time of the active ingredients and achieving targeted sterilization and nutrient deposition.

[0032] Example 2

[0033] This embodiment relates to a production process for antibiotic-free eggs, aiming to verify the process stability under high loading. In this embodiment, except for the adjustment of raw material dosage and some process parameters, the remaining steps are carried out as in Example 1. The raw material composition of the functionalized modified microcapsules is adjusted as follows: 100 parts by weight of carboxymethyl chitosan, degree of deacetylation 95%, degree of carboxylation 88%, purchased from Sinopharm Chemical Reagent Co., Ltd.; 40 parts by weight of cinnamaldehyde, purity 98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; 5 parts by weight of sodium selenite; 15 parts by weight of ascorbic acid; 3 parts by weight of emulsifier sorbitan monooleate (Span-80), purchased from Yuanye Biotechnology; and 1500 parts by weight of deionized water.

[0034] The preparation parameters for this functionalized modified microcapsule were set as follows: carboxymethyl chitosan dissolution time 60 min, pH adjusted to 4.5, reaction temperature 60℃, and reflux reaction for 4 h. Under these conditions, the higher reaction temperature and shorter reaction time facilitated the rapid formation of Schiff base bonds in the high-concentration system, locking in a high content of cinnamaldehyde. In the in-situ reduction stage, the ascorbic acid dropping rate was adjusted to 5 mL / min, and ultrasonic treatment at a frequency of 60 kHz for 20 min was performed to ensure that the high concentration of selenium source could be evenly dispersed and completely encapsulated. In the drying step, the inlet air temperature was increased to 180℃, and the feed rate was 800 mL / h.

[0035] The high-concentration functionalized modified microcapsules were added to the diet at a relatively low dosage of 200 g / t. Despite the reduced dosage, the increased loading of cinnamaldehyde and nano-selenium within the microcapsules, along with the dense core-shell structure prepared using the aforementioned process, effectively prevented the oxidative degradation of the high-concentration essential oil. In laying hens, the functionalized modified microcapsules exhibited strong intestinal release capability. The high-concentration local release effectively inhibited drug-resistant bacteria, while the high content of nano-selenium significantly improved selenium deposition efficiency in eggs through efficient transport via the intestinal mucosa, validating the flexibility and effectiveness of this process in adjusting drug loading.

[0036] Example 3

[0037] This embodiment relates to a production process for antibiotic-free eggs, focusing on the protection of the bioactivity of the materials under mild reaction conditions. In this embodiment, the raw material components for the functionalized modified microcapsules are: 90 parts by weight of carboxymethyl chitosan, 30 parts by weight of cinnamaldehyde, 3.5 parts by weight of sodium selenite, 11.5 parts by weight of ascorbic acid, 2 parts by weight of polyoxyethylene sorbitan monooleate (Tween-80) emulsifier, and 1250 parts by weight of deionized water. The source of the raw materials used is the same as in Example 1.

[0038] During the preparation process, the dissolution and stirring time was 45 min, the system pH was adjusted to 5.5, the reaction temperature was lowered to 50℃, and the reaction time was extended to 6 h. While the mild temperature conditions slowed down the formation rate of Schiff bases, they effectively reduced the heat loss of cinnamaldehyde during the reaction process and improved the utilization rate of raw materials. In the self-assembly stage, the molar ratio of ascorbic acid to sodium selenite was set at 3:1, the flow rate was 2 mL / min, and the ultrasonic treatment was performed at a frequency of 40 kHz for 30 min. The slow reduction and assembly process facilitated the formation of more uniformly sized and more perfectly crystalline nano-selenium cores, reducing structural defects.

[0039] During drying, the inlet air temperature was set at 160℃, the outlet air temperature at 70℃, and the feed rate at 500mL / h. The resulting functionalized modified microcapsules were added at a ratio of 500g / t. Experiments showed that the functionalized modified microcapsules produced by this mild process exhibited excellent bioadhesion in the intestine. This was attributed to the fact that the low-temperature reaction preserved the integrity of the carboxymethyl chitosan molecular chains, preventing thermal degradation and thus maintaining more effective amino and carboxyl groups for electrostatic interaction with intestinal mucosal mucins. This further confirms the regulatory role of process parameters on bioadhesion performance.

[0040] Example 4

[0041] This embodiment relates to a production process for antibiotic-free eggs, focusing on verifying the effect of the ratio of ascorbic acid to selenium source on product performance. In this embodiment, the raw material components of the functionalized modified microcapsules include 4 parts by weight of sodium selenite and 16 parts by weight of ascorbic acid, with a molar ratio of approximately 4:1, which is close to the upper limit of the preferred range in the technical solution. The remaining components and raw material sources are consistent with those in Example 1.

[0042] In the preparation of this functionalized modified microcapsule, excess ascorbic acid not only acts as a reducing agent to completely reduce selenite ions to red elemental selenium nanoparticles, but also exists as an antioxidant in the microcapsule system. In the grafting modification step, the reaction was carried out at pH 5.2 and 58℃ for 5 hours. In the self-assembly step, the rapid addition of ascorbic acid promoted the explosive nucleation of nano-selenium, forming small-sized nano-cores, which were then tightly encapsulated by the amphiphilic polymer precursor.

[0043] This functionalized modified microcapsule was added to the diet at a rate of 400 g / t. Due to its smaller particle size and ascorbic acid protection, the nano-selenium exhibited higher transmembrane absorption efficiency after release in the intestine. Simultaneously, the additional antioxidants synergistically enhanced the nano-selenium, contributing to the repair of intestinal inflammation in laying hens and improving the villus height / crypt depth ratio. The values ​​had a positive impact, indicating that this process can enhance the repair function of the intestinal health of laying hens through component fine-tuning.

[0044] Example 5

[0045] This embodiment relates to a production process for antibiotic-free eggs, verifying the pelleting effect under different emulsifier systems. In this embodiment, the functionalized modified microcapsules are a compound of emulsifiers sorbitan monooleate (Span-80) and polyoxyethylene sorbitan monooleate (Tween-80) in a mass ratio of 1:1, totaling 2 parts by weight. The remaining raw materials are: 85 parts by weight of carboxymethyl chitosan, 25 parts by weight of cinnamaldehyde, 3 parts by weight of sodium selenite, 10 parts by weight of ascorbic acid, and 1100 parts by weight of water, with the same source as in the previous embodiment.

[0046] During preparation, a compound emulsifier was added before the grafting reaction to assist in the pre-dispersion of cinnamaldehyde in the aqueous phase. Reaction conditions: pH 4.8, 52℃, 5.5 h. The use of the compound emulsifier reduced the oil-water interfacial tension, making it easier for the generated amphiphilic polymer precursor to form a regular spherical structure during subsequent self-assembly. Spray drying parameters: inlet air 175℃, outlet air 85℃.

[0047] The addition amount during the feeding stage was 350 g / t. Results showed that the functionalized modified microcapsules exhibited good flowability and dispersibility, and the coefficient of variation during feed premixing was [not specified]. Within the digestive tract of laying hens, the regular spherical structure provides a stable specific surface area, resulting in a more stable pH-responsive release kinetics, avoiding burst release effects, and ensuring continuous antibacterial concentration coverage throughout the small intestine, thus improving the application stability of the product from a process perspective.

[0048] Comparative Example 1

[0049] This comparative example uses a physical mixing method instead of a chemical grafting process. Unlike Example 1, a heating reflux reaction was not performed. Instead, carboxymethyl chitosan was dissolved and directly mixed with cinnamaldehyde and nano-selenium in a pre-prepared mixture, which was then spray-dried to prepare microcapsules.

[0050] Due to the lack of chemical anchoring via Schiff base bonds, cinnamaldehyde exists only in a physically encapsulated form. Experiments showed that this physical mixture exhibited a cinnamaldehyde release rate exceeding 60% in simulated gastric juice at pH 3.0, indicating that physical encapsulation is ineffective against the acidic gastric environment, leading to premature loss of the active ingredient. After feeding, the number of Salmonella bacteria in the cecum of laying hens did not decrease significantly, indicating a failure to maintain an effective bactericidal concentration in the posterior intestinal tract. This further demonstrates the crucial role of Schiff base bond construction in achieving gastric protection and intestinal release in this invention.

[0051] Comparative Example 2

[0052] This comparative example prepared single-celled selenium nanocapsules free of cinnamaldehyde. Cinnamaldehyde was removed from the raw materials, and the remaining process steps were the same as in Example 1.

[0053] After feeding the single-component capsule, although the selenium content in the eggs increased, the number of pathogenic bacteria in the intestines of the laying hens was not effectively controlled, resulting in mild diarrhea in some laying hens and a smaller increase in egg production rate than in Example 1. This indicates that immune-enhancing selenium alone cannot completely replace the bactericidal effect of antibiotics. The synergistic effect of cinnamaldehyde (bactericidal) and nano-selenium (immune / repair) in this invention is a necessary condition for achieving antibiotic-free production and improving production performance.

[0054] Comparative Example 3

[0055] This comparative example uses ordinary sodium selenite added directly without microencapsulation. An equal amount of selenium-rich sodium selenite and an equal amount of free cinnamaldehyde are added directly to the basal diet.

[0056] The results showed that the feed intake of laying hens decreased due to the irritant and volatile nature of free cinnamaldehyde. Meanwhile, ordinary inorganic selenium had low absorption rate and a narrow toxicity threshold, resulting in significant fluctuations in selenium content in eggs, with some samples approaching safety limits. In contrast, the functionalized modified microcapsules in Example 1, through sustained release and speciation, significantly improved the safety and deposition efficiency of selenium, demonstrating the advantages of the present invention's configuration in enhancing bioavailability and safety.

[0057] Application effect test

[0058] To further verify the practical effect of the antibiotic-free egg production process of this invention, the products prepared in Examples 1-5 and Comparative Examples 1-3 were applied to 300-day-old Lohmann pink-shelled laying hens for a 60-day feeding trial. The test indicators included: cecal Salmonella count, egg selenium content (mg / kg), feed conversion ratio, and antibiotic residues. The test results are shown in the table below:

[0059] Group Salmonella cecum (Log10 CFU / g) Selenium content in eggs (mg / kg) Egg ratio Egg production rate increased (%) antibiotic residue Example 1 3.2±0.1 0.42±0.02 2.05 +4.8 Not detected Example 2 3.1±0.2 0.48±0.03 2.04 +5.1 Not detected Example 3 3.3±0.1 0.40±0.02 2.06 +4.5 Not detected Example 4 3.2±0.1 0.45±0.02 2.03 +4.9 Not detected Example 5 3.2±0.2 0.41±0.02 2.05 +4.6 Not detected Comparative Example 1 5.8±0.3 0.35±0.04 2.18 +1.2 Not detected Comparative Example 2 6.1±0.2 0.38±0.03 2.20 +0.8 Not detected Comparative Example 3 5.5±0.4 0.25±0.08 2.25 -1.5 Not detected Blank control 6.5±0.3 0.15±0.01 2.28 - -

[0060] As can be seen from the table above, the functionalized modified microcapsules produced using the processes of Examples 1-5 of this invention have a significant effect on reducing the number of Salmonella, reducing it by about 3 logarithmic orders, and keeping the selenium content of eggs stable within the selenium-enriched safe range of 0.3-0.5 mg / kg, with a significant improvement in the feed conversion ratio.

[0061] The core inventiveness of this invention lies in the pH responsiveness provided by the cinnamaldehyde-chitosan Schiff base bond, the synergistic effect of gastric and intestinal release and in-situ reduction of nano-selenium;

[0062] Comparative analysis shows that the overall performance of the example group is significantly better than that of the comparative example. Data from Comparative Example 1 demonstrates that chemical grafting and Schiff bases are crucial for ensuring cinnamaldehyde reaches the intestines to exert its bactericidal effect; Comparative Example 2 demonstrates that the lack of bactericidal components cannot effectively improve the intestinal flora; Comparative Example 3 shows that simple physical mixing cannot solve the problems of raw material volatilization, low absorption rate, and poor palatability. In summary, this invention, through a specific process, organically integrates cinnamaldehyde and nano-selenium into a pH-responsive chitosan backbone, utilizing their synergistic effect and intelligent release characteristics to successfully achieve antibiotic-free aquaculture and produce high-quality selenium-enriched eggs.

[0063] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A production process for antibiotic-free eggs, characterized in that, The invention includes feeding laying hens a basal diet containing functionalized modified microcapsules and collecting the produced eggs. The functionalized modified microcapsules have a core-shell structure. The shell layer is composed of a polymer containing imine bonds generated by the Schiff base reaction of cinnamaldehyde and carboxymethyl chitosan. The core layer is encapsulated with 80-100 parts of carboxymethyl chitosan, 20-40 parts of cinnamaldehyde, 2-5 parts of sodium selenite, 8-15 parts of ascorbic acid, and 1-3 parts of emulsifier, all of which are nano-selenium generated in situ.

2. The production process for antibiotic-free eggs according to claim 1, characterized in that, The preparation process of functionalized modified microcapsules includes a pretreatment of carboxymethyl chitosan by graft modification, specifically the following steps: Carboxymethyl chitosan was added to deionized water and placed in a constant-temperature magnetic stirrer. The stirring speed was set to 300-500 r / min, and the mixture was stirred for 30-60 min until it was completely swollen. The pH of the solution was adjusted to 4.5-5.

5. Then, cinnamaldehyde was added, the temperature was raised to 50-60℃, and the reflux condenser was turned on. The reaction was carried out under constant-temperature reflux for 4-6 h in the dark. During the reaction, the aldehyde group of cinnamaldehyde and the amino group of carboxymethyl chitosan underwent a Schiff base condensation reaction, generating an amphiphilic polymer precursor solution containing imine bonds (-C=N-) through the Schiff base reaction.

3. The production process for antibiotic-free eggs according to claim 2, characterized in that, The molding process of functionalized modified microcapsules includes in-situ reduction and self-assembly steps, specifically: Sodium selenite was added to the amphiphilic polymer precursor solution, and stirring was continued for 15-20 min to ensure uniform dispersion of the selenium source. Subsequently, ascorbic acid was prepared into an aqueous solution and slowly added dropwise to the reaction system at a flow rate of 2-5 mL / min using a peristaltic pump. During the dropwise addition process, the system undergoes an in-situ reduction reaction to generate nano-selenium. Simultaneously, the hydrophobic interaction induces the polymer chain segments to encapsulate the nano-selenium for self-assembly. After the dropwise addition is complete, the reaction solution is transferred into an ultrasonic disperser, the frequency is set to 40–60 kHz, and ultrasonic treatment is performed for 20–30 min to obtain a core-shell structured nanosphere dispersion.

4. The production process for antibiotic-free eggs according to claim 3, characterized in that, The nanosphere dispersion needs to undergo drying and solidification treatment. The specific steps are as follows: The nanosphere dispersion was fed into a centrifugal spray dryer, with the inlet air temperature set at 160-180℃, the outlet air temperature at 70-90℃, and the feed rate at 500-800 mL / h. After atomization drying, powdered functionalized modified microcapsules were obtained. The functionalized modified microcapsules maintain a relatively stable structure in a simulated gastric fluid environment at pH 2.5–3.5, and undergo responsive cleavage and release cinnamaldehyde and nano-selenium in a simulated intestinal fluid environment at pH 6.0–7.

0.

5. The production process for antibiotic-free eggs according to claim 1, characterized in that, The amount of functionalized modified microcapsules added to the basal diet is 200-500 g / t, and it needs to be premixed step by step before feeding, with the coefficient of variation (CV) of the mixing uniformity ≤ 5%.

6. The production process for antibiotic-free eggs according to claim 1, characterized in that, The molar ratio of ascorbic acid to sodium selenite is controlled at 2.5:1 to ensure that selenite ions are completely reduced to red elemental nano-selenium.

7. The production process for antibiotic-free eggs according to claim 1, characterized in that, The emulsifier is selected from at least one of polyoxyethylene sorbitan monooleate or sorbitan monooleate, and is used to assist the dispersion of cinnamaldehyde in the aqueous phase.

8. An antibiotic-free egg produced by the antibiotic-free egg production process according to any one of claims 1 to 7, characterized in that, Antibiotic residues were not detected in the eggs, and the selenium content of the whole eggs was 0.3-0.5 mg / kg, with nano-selenium particles deposited in the yolks.