A modified zein pickering emulsion, a preparation method thereof and application thereof in cold storage of sagu

Abstract

The application provides a modified Zein Pickering emulsion, a preparation method thereof and application of the Pickering emulsion in fresh-keeping of sandgrass at room temperature, and belongs to the technical field of food fresh-keeping. The preparation method comprises the following steps: Zein is added into an alkaline solution for amino treatment, and after high-temperature reaction, the solution is cooled and the pH value of the solution is adjusted. After removing impurities, the solid sample is obtained through freeze-drying; the obtained sample is added into water together with another natural extract for reaction, the solution is transferred after a period of time, and impurities are removed, and then the modified Zein polymer coating is obtained through freeze-drying; the modified Zein material is added into water together with cinnamyl aldehyde, and after emulsification by using an ultrasonic homogenizer, the target Pickering emulsion is obtained. The Pickering emulsion obtained by the application has the advantages of sustained drug release, high external tolerance, anti-freeze-thaw cycle, excellent sterilization performance and outstanding antioxidant performance, and can be applied to fresh-keeping of sandgrass at room temperature.

Description

Technical Field

[0001] This invention relates to the field of food preservation technology, and in particular to a modified zein Pickering emulsion, its preparation method, and its application in the room temperature preservation of jicama. Background Technology

[0002] Food security is a fundamental guarantee for social stability and economic development; however, traditional food preservation technologies still require further research and innovation. With increasing public health awareness, consumers are paying more attention to the quality of packaged food ingredients and nutrient retention. Traditional food storage strategies mainly rely on physical methods such as low-temperature refrigeration and controlled gas storage to inhibit pathogen growth and delay food spoilage. However, food spoilage stems not only from microbial activity but is also affected by various external stressors, including ultraviolet radiation, reactive oxygen species, temperature fluctuations, and humidity changes. While cold chain technology can effectively inhibit microorganisms, it is still insufficient to prevent oxidative nutrient degradation and flavor loss, ultimately leading to a decline in overall food quality.

[0003] Jicama ( Pachyrhizus erosus Jicama is a crisp and juicy legume vegetable, rich in starch and non-starch polysaccharides. Due to its excellent adaptability to both acidic and alkaline soils, it is widely cultivated in southern China. The nutritional value of jicama is mainly found in its pulp and juice, but these components are highly susceptible to external environmental factors. Traditional drying and preservation methods often lead to a decline in jicama quality, including enzymatic browning, loss of flavor, and reduced nutritional value. Therefore, there is an urgent need to develop innovative and efficient jicama preservation technologies to meet the growing demands of modern food safety.

[0004] With increasing emphasis on biosafety and environmental sustainability, natural preservatives have become a major research focus in food science and engineering. Cinnamaldehyde (CA), a plant essential oil extracted from cinnamon, exhibits higher antibacterial activity compared to other biocompounds such as chili oil, eugenol, and citric aldehyde. CA can disrupt the cell membranes of pathogenic microorganisms, thus effectively preserving fruits and other foods. However, its practical application in food packaging remains limited due to its photosensitivity, volatility, and poor biocompatibility. To avoid the deterioration and waste of essential oils, constructing nanocarrier delivery systems has been widely recognized as an effective strategy. Zuo et al. designed a tea tree oil picking emulsion that provides peanut plants with continuous protection for up to 21 days (J. Zuo, Y. Lin, J. Tian, ​​J. Cai, L. Hao, D. Liu, Q. Wang, G. Xiao, X. Zhou, H. Zhou, Tea tree oil Pickeringemulsions stabilized by sodium lignosulfonate-zein covalent conjugate for fungicide delivery and enhanced control efficacy against peanut sclerotiumblight, Chem. Eng. J. 513 (2025) 162876. DOI: 10.1016 / j.cej.2025.162876.). The advantage of the picking emulsion lies in solving the utilization problem of acetic acid (CA), but the development of CA-based drug delivery systems still requires higher precision and comprehensiveness. The microenvironment during food storage and transportation is complex and variable, therefore this passive drug release behavior cannot adapt to changes in the microenvironment in real time. Seeking innovative methods to construct sustained and stable drug release patterns in nanocarriers is key to improving their preservation efficacy.

[0005] Based on this, natural plant proteins have become ideal candidate materials for stabilizing and functionalizing Pickering emulsion interfaces. Tian et al. reported that zein-coated Pickering emulsion particles exhibit superior UV resistance compared to commercial emulsions (J. Tian, ​​J. Xie, L. Hao, H. Chen, X. Zhou, H. Zhou, Zein / sodium abietate complex stabilized pickering emulsion as a delivery system for controlled release of hydrophobic photosensitive pesticide, Ind. Crop. Prod. 212 (2024) 118347. DOI: 10.1016 / j.indcrop.2024.118347.). Despite these advances, simple Zein-based coatings still have some limitations, including acid and alkali resistance, interfacial adsorption, hydrophobic-hydrophilic balance, and thermal stability, thus requiring further modification and functionalization. Furthermore, considering the complexity and diversity of microbial communities in real-world environments, improving bacterial membrane permeability and bactericidal efficiency remains a key challenge in developing highly efficient antimicrobial nanoplatforms. Summary of the Invention

[0006] The purpose of this invention is to provide a modified zein Pickering emulsion, its preparation method, and its application in the preservation of jicama at room temperature, in order to solve the above-mentioned technical problems.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a modified zein Pickering emulsion, comprising the following steps: 1) Add zein to an alkaline solution to react. After the reaction is complete, adjust the reaction solution to neutral, add an amino polymer to react, and then dialyze and freeze-dry the reaction solution in sequence to obtain a solid sample powder. 2) The solid sample powder and natural extract were mixed in water and reacted. The reaction solution was then dialyzed and freeze-dried sequentially to obtain AZ-TS sample powder. 3) Disperse the AZ-TS sample powder in water, then add cinnamaldehyde, and emulsify under ultrasonication to obtain a modified zein Pickering emulsion, denoted as AZ-TS@CA.

[0008] Furthermore, in step 1), the alkaline solution is a sodium hydroxide solution; The mass fraction of the zein in the alkaline solution is 0.1-10%, and the mass fraction of the amino polymer in the alkaline solution is 1-20%.

[0009] Furthermore, the amino polymer includes one or more of ethylenediamine-terminated polyethyleneimine, polyethyleneimine, and poly(ethylene glycol)-block-polyethyleneimine.

[0010] Furthermore, in step 1), the reaction temperature of zein in the alkaline solution is 40~100℃, and the reaction time is 0.5~8h; after adding the amino polymer, the reaction temperature is 20~40℃, and the reaction time is 0.1~6h.

[0011] Furthermore, the natural extract contains one or more of tea saponins, astragalus polysaccharides, and resveratrol.

[0012] Furthermore, in step 2), the mass ratio of solid sample powder to natural extract is 1:0.1~3.0, the mass fraction of solid sample powder in the reaction solution is 0.1~10%, and the mass fraction of natural extract in the reaction solution is 0.1~10%.

[0013] Furthermore, in step 2), the reaction temperature is 20~40℃ and the reaction time is 0.5~8h.

[0014] Furthermore, in step 3), the mass fraction of the AZ-TS sample powder in water is 0.1-10%, and the volume fraction of cinnamaldehyde in water is 5-70%. The emulsification is carried out under the action of an ultrasonic homogenizer, with a homogenization speed of 10,000~15,000 rpm and a homogenization time of 5~20 min.

[0015] The present invention also provides a modified zein Pickering emulsion prepared by the above preparation method.

[0016] This invention also provides an application of modified zein Pickering emulsion in the room temperature preservation of jicama.

[0017] The beneficial effects of this invention are: 1. This invention proposes an encapsulation process for CA, which can effectively mitigate the volatility of CA and improve its preservation ability. All major synthetic raw materials are derived from natural plants, therefore the resulting AZ-TS@CA product is green, safe, and non-toxic.

[0018] 2. This invention proposes an amination treatment technology for Zein, which can directionally modify Zein under relatively mild conditions, making its molecular weight more flexible, hydrophilic and weavable, which is more conducive to its self-assembly, and finally forming a drug-loaded nanocarrier.

[0019] 3. This invention proposes a functionalization strategy for Zein, which significantly improves the pathogenicity and freeze-thaw stability of the nanocarrier, laying a solid foundation for the long-term preservation of jicama using CA. Attached Figure Description

[0020] Figure 1 The images show the changes in appearance of Comparative Example 2 and Example 1 after three freeze-thaw cycles.

[0021] Figure 2 The graph shows the stability test results of Comparative Example 2 and Example 1 under solar radiation.

[0022] Figure 3 The graph shows the stability test results of Comparative Example 2 and Example 1 at 60 °C.

[0023] Figure 4 Representative images of the pathogens treated in Comparative Examples 2, 3 and 1 are shown.

[0024] Figure 5 To compare the effects of Example 2 and Example 1 on DPPH free radicals and ABTS, + Free radical scavenging rate curve.

[0025] Figure 6 The graph shows the changes in appearance and weight of jicama after treatment in Comparative Example 1 and Example 1. Detailed Implementation

[0026] This invention provides a method for preparing a modified zein Pickering emulsion, comprising the following steps: 1) Add zein to an alkaline solution to react. After the reaction is complete, adjust the reaction solution to neutral, add an amino polymer to react, and then dialyze and freeze-dry the reaction solution in sequence to obtain a solid sample powder. 2) The solid sample powder and natural extract were mixed in water and reacted. The reaction solution was then dialyzed and freeze-dried sequentially to obtain AZ-TS sample powder. 3) Disperse the AZ-TS sample powder in water, then add cinnamaldehyde, and emulsify under ultrasonication to obtain a modified zein Pickering emulsion, denoted as AZ-TS@CA.

[0027] In this invention, in step 1), the alkaline solution is a sodium hydroxide solution; The mass fraction of the zein in the alkaline solution is 0.1-10%, preferably 1-8%, and more preferably 2-7%; the mass fraction of the amino polymer in the alkaline solution is 1-20%, preferably 3-18%, and more preferably 5-16%.

[0028] In this invention, the amino polymer includes one or more of ethylenediamine-terminated polyethyleneimine, polyethyleneimine, and poly(ethylene glycol)-block-polyethyleneimine, preferably ethylenediamine-terminated polyethyleneimine.

[0029] In this invention, in step 1), the reaction temperature of zein in alkaline solution is 40~100℃, preferably 50~90℃, more preferably 60~80℃; the reaction time is 0.5~8h, preferably 1~7h, more preferably 2~6h; the reaction temperature after adding amino polymer is 20~40℃, preferably 25~35℃, more preferably 25~30℃; the reaction time is 0.1~6h, preferably 0.5~5h, more preferably 1~4h.

[0030] In this invention, the natural extract comprises one or more of tea saponin, astragalus polysaccharide and resveratrol, preferably tea saponin.

[0031] In this invention, in step 2), the mass ratio of solid sample powder to natural extract is 1:0.1~3.0, preferably 1:0.5~2.5, and more preferably 1:1~2; the mass fraction of solid sample powder in the reaction solution is 0.1~10%, preferably 1~9%, and more preferably 2~8%; the mass fraction of natural extract in the reaction solution is 0.1~10%, preferably 0.5~9%, and more preferably 1~8%.

[0032] In this invention, in step 2), the reaction temperature is 20~40℃, preferably 25~35℃, and more preferably 25~30℃; the reaction time is 0.5~8h, preferably 1~6h, and more preferably 2~5h.

[0033] In this invention, in step 3), the mass fraction of the AZ-TS sample powder in water is 0.1-10%, preferably 1-9%, more preferably 2-8%; the volume fraction of cinnamaldehyde in water is 5-70%, preferably 10-60%, more preferably 15-50%. The emulsification is carried out under the action of an ultrasonic homogenizer, with a homogenization speed of 10,000~15,000 rpm, preferably 12,000 rpm; and a homogenization time of 5~20 min, preferably 10 min.

[0034] The present invention also provides a modified zein Pickering emulsion prepared by the above preparation method.

[0035] This invention innovatively proposes a green (water-soluble) and economical low-temperature hydrothermal synthesis method for encapsulating CA to construct a functionalized Zein-based antibacterial nanoparticle platform, and verifies its positive effects on eliminating jicama pathogens, providing antioxidant protection, and preserving juice. To slow down the volatilization time of CA and maximize its preservation contribution, this invention proposes preparing a Pickering emulsion to construct the nanocarrier. To improve the weavability and surface properties of the Zein polymer, it is first subjected to aminated treatment. Subsequently, the resulting aminated Zein (AZ) is further modified with tea saponin (TS) to improve its own framework stability and pathogen membrane recognition. CA is efficiently encapsulated in TS-modified AZ (AZ-TS) nanocarriers using a high-speed homogenization method, thereby obtaining AZ-TS@CA. Due to the good membrane recognition and membrane permeability of TS for bacteria and fungi, the obtained AZ-TS@CA is effective against Escherichia coli (E. coli). Escherichia coli , E. coli Staphylococcus aureus ( Staphylococcus aureus , S. aureus ) and Aspergillus niger ( Aspergillus niger , A. niger The AZ-TS@CA coating exhibits excellent bactericidal effects. Furthermore, the designed AZ-TS@CA demonstrates sustained and stable drug release behavior, maintaining the optimal bactericidal concentration range while extending the effective action time of the natural preservative. As a proof of concept, this invention systematically evaluated the preservation effect of AZ-TS@CA on jicama at different storage temperatures. The results show that the customized AZ-TS@CA coating has positive effects in pathogen elimination, antioxidant protection, and juice retention, enabling long-term preservation of jicama while maintaining its nutritional quality. Therefore, this invention proposes a novel, highly efficient, and environmentally friendly coating material design strategy, providing a promising method for advancing food preservation technology.

[0036] The preparation method of this invention is based on the following working principle: First, the encapsulation of CA. As a cinnamon oil extract, CA has flavoring, aroma-enhancing, preservative, and freshness-preserving effects on food products. Pickering emulsification is a process in which water-insoluble solid particles are adsorbed onto the water and oil phases through electrostatic repulsion. This effectively reduces the volatility and oxidative properties of CA, prevents its decomposition and deterioration under light and heat conditions, and extends its shelf life. Simultaneously, it provides a polymeric barrier on the outer layer of the carrier to control the slow release of CA, maintaining its long-term preservative and freshness-preserving effects.

[0037] Second, the amination treatment of Zein. Ordinary Zein can dissolve in 50-90% aqueous ethanol solution, but is insoluble in pure water and anhydrous ethanol. Amination treatment of Zein not only optimizes its molecular chain flexibility and improves protein emulsification properties, but also enhances its composability, making it easier to graft with other natural extracts.

[0038] Third, functional modification of Zein. Some natural extracts, such as TS, can effectively identify and disrupt the integrity of bacterial biofilms. Grafting TS with AZ can effectively improve the recognition efficiency and bactericidal activity of nanocarriers. At the same time, block copolymers prepared based on condensation reactions can improve the self-assembly degree of polymer chains to a certain extent, forming more stable and high-density nanocarriers, thereby exhibiting higher freeze-thaw stability and sustained drug release capability.

[0039] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0040] Example 1

[0041] 2 g of Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the AZ solid sample powder was obtained by vacuum freeze drying.

[0042] Weigh 1 g of AZ and 1 g of TS (tea saponin) and dissolve them in 50 mL of deionized water. The solution was then stirred and reacted at room temperature for 3 h. The resulting solution was dialyzed against deionized water to remove impurities. Finally, the AZ-TS solid sample powder was obtained by vacuum freeze drying.

[0043] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0044] Example 2

[0045] 0.2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the solid AZ sample powder was obtained by vacuum freeze drying.

[0046] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0047] AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). CA was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v) to construct a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at a speed of 12000 rpm for 10 min.

[0048] Example 3

[0049] 4 g of Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the AZ solid sample powder was obtained by vacuum freeze drying.

[0050] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0051] AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). CA was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v) to construct a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at a speed of 12000 rpm for 10 min.

[0052] Example 4

[0053] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 1 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the AZ solid sample powder was obtained by vacuum freeze drying.

[0054] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0055] AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). CA was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v) to construct a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at a speed of 12000 rpm for 10 min.

[0056] Example 5

[0057] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 10 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the AZ solid sample powder was obtained by vacuum freeze drying.

[0058] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0059] AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). CA was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v) to construct a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at a speed of 12000 rpm for 10 min.

[0060] Example 6

[0061] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of polyethyleneimine was added, and the reaction continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the solid AZ sample powder was obtained by vacuum freeze drying.

[0062] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0063] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0064] Example 7

[0065] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of poly(ethylene glycol)-block-polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the AZ solid sample powder was obtained by vacuum freeze drying.

[0066] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0067] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0068] Example 8

[0069] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 40 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the AZ solid sample powder was obtained by vacuum freeze drying.

[0070] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0071] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0072] Example 9

[0073] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 90 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the AZ solid sample powder was obtained by vacuum freeze drying.

[0074] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0075] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0076] Example 10

[0077] (Add 2 g Zein to 100 mL of 0.5 mol / L NaOH solution. Heat the zein solution to 80 °C and maintain for 0.5 h with magnetic stirring. After cooling to room temperature, adjust the pH of the solution to neutral. Then, add 6 g of ethylenediamine-terminated polyethyleneimine and continue the reaction for 1 h. Transfer the resulting solution to a dialysis bag and dialyze it in deionized water for 12 h to remove excess impurities. Finally, obtain AZ solid sample powder by vacuum freeze drying.)

[0078] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0079] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0080] Example 11

[0081] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 8 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the AZ solid sample powder was obtained by vacuum freeze drying.

[0082] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0083] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0084] Example 12

[0085] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 0.1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the AZ solid sample powder was obtained by vacuum freeze drying.

[0086] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0087] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0088] Example 13

[0089] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 6 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the solid AZ sample powder was obtained by vacuum freeze drying.

[0090] Weigh 1 g of AZ and 1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 hours. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0091] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0092] Example 14

[0093] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the solid AZ sample powder was obtained by vacuum freeze drying.

[0094] Weigh 1 g of AZ and 0.1 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 h. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0095] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0096] Example 15

[0097] (Add 2 g Zein to 100 mL of 0.5 mol / L NaOH solution. Heat the zein solution to 80 °C and maintain for 4 h with magnetic stirring. After cooling to room temperature, adjust the pH of the solution to neutral. Then, add 6 g of ethylenediamine-terminated polyethyleneimine and continue the reaction for 1 h. Transfer the resulting solution to a dialysis bag and dialyze it in deionized water for 12 h to remove excess impurities. Finally, obtain AZ solid sample powder by vacuum freeze drying.)

[0098] Weigh 1 g of AZ and 3 g of TS and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 h. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain the AZ-TS solid sample powder by vacuum freeze drying.

[0099] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0100] Example 16

[0101] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the solid AZ sample powder was obtained by vacuum freeze drying.

[0102] Weigh 1 g of AZ and 1 g of Astragalus polysaccharide and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 h. Dialyze the resulting solution in deionized water to remove impurities. Finally, obtain AZ-TS solid sample powder by vacuum freeze drying.

[0103] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0104] Example 17

[0105] 2 g Zein was added to 100 mL of 0.5 mol / L NaOH solution. The zein solution was heated to 80 °C and maintained for 4 h with magnetic stirring. After cooling to room temperature, the pH of the solution was adjusted to neutral. Subsequently, 6 g of ethylenediamine-terminated polyethyleneimine was added, and the reaction was continued for 1 h. The resulting solution was transferred to a dialysis bag and dialyzed against deionized water for 12 h to remove excess impurities. Finally, the solid AZ sample powder was obtained by vacuum freeze drying.

[0106] Weigh 1 g of AZ and 1 g of resveratrol and dissolve them in 50 mL of deionized water. Then, stir the solution at room temperature for 3 h. Dialyze the resulting solution into deionized water to remove impurities. Finally, obtain AZ-TS solid sample powder by vacuum freeze drying.

[0107] The AZ-TS solid sample powder was dispersed in water to obtain a DZ-TS dispersion (2% w / v). Cinnamaldehyde (CA) was selected as the lipid phase and emulsified with the DZ-TS dispersion (2% w / v). The volume fraction of CA in the dispersion was 30% (v / v), constructing a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at 12000 rpm for 10 min.

[0108] Comparative Example 1

[0109] Zein was dispersed in water to obtain a Zein dispersion (2% w / v). CA was selected as the lipid phase and emulsified with the Zein dispersion (2% w / v) to construct a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at a speed of 12,000 rpm for 10 min.

[0110] Comparative Example 2

[0111] The AZ solid sample powder prepared in Example 1 was dispersed in water to obtain an AZ dispersion (2% w / v). CA was selected as the lipid phase and emulsified with the AZ dispersion (2% w / v) to construct a water-in-oil (O / W) emulsion. The emulsification process was carried out using an ultrasonic homogenizer at a speed of 12,000 rpm for 10 min.

[0112] Comparative Example 3

[0113] Tween 80 was dispersed in water to obtain a Tween 80 dispersion (2% w / v). CA was selected as the lipid phase and emulsified with the Tween 80 dispersion (2% w / v) to construct a water-in-oil (O / W) emulsion. The emulsification process was performed using an ultrasonic homogenizer at a speed of 12,000 rpm for 10 min.

[0114] Test conditions and methods

[0115] Freeze-thaw cycle stability test:

[0116] Prepare 20 mL sample solutions and add them to glass sample vials. Store the vials at -20°C for 24 h, then thaw naturally. The experiment was conducted under controlled conditions, with a total of three freeze-thaw cycles. Record the appearance of the samples and their associated emulsion parameters. Record the CA content of the samples in real time using a UV spectrophotometer (UV-2550, Shimadzu, Japan). CA concentration can be monitored by its characteristic absorption wavelength (λmax = 290 nm). Briefly, centrifuge 500 μL of sample solution at 10000 rpm for 10 min. Afterward, separate and determine the supernatant. Quantify the CA content using a standard curve (A = 0.09176C + 0.95931, R² = 0.999).

[0117] Light and thermal stability test: Prepare a 1 mL sample solution and dilute it to 10 mL. Then, place the resulting solution in a photoreactor (365 nm) or an oven (60 °C) to study the release rate of CA. During the experiment, 100 μL of sample solution was taken and analyzed using a UV spectrophotometer.

[0118] DPPH and ABTs + Determination of free radical scavenging rate:

[0119] Weigh 3 mg of DPPH and add it to 100 mL of methanol. Then, take 100 μL of DPPH solution and 100 μL of sample solution and mix them in a 96-well plate. After the mixture is incubated in the dark for 2 h, the absorbance is measured using a microplate reader (517 nm). The DPPH scavenging rate is calculated using formula (1), where... A s The absorbance is the result of mixing the sample solution with the DPPH solution. A c The absorbance is the result of mixing the sample solution with methanol. A b The absorbance is the result of mixing deionized water and DPPH solution.

[0120] (1)

[0121] 38.4 mg APTs and 13.4 mg potassium persulfate were dissolved separately in 10 mL of deionized water. The two solutions were mixed with magnetic stirring (300 rpm) and reacted in the dark for 12 h. Subsequently, 1 mL of the reaction solution was taken and diluted to 20 mL with PBS buffer. Then, 100 μL of APTs was added... + The solution was mixed with 100 μL of sample solution and reacted in a 96-well plate. The absorbance of the resulting solution at 734 nm was analyzed, and ABTs were calculated using formula (2). + Clearance capabilities, among which A s For sample solution and ABTs + Absorbance after solution mixing A c The absorbance is the result of mixing the sample solution with PBS buffer. A b For deionized water and ABTs + Absorbance after the solution is mixed.

[0122] (2)

[0123] In vitro antibacterial test: The antibacterial ability of the samples was tested using the agar diffusion method. E. coli , S. aureus and A. niger It is the original pathogen.

[0124] First, 100 μL of bacterial suspension (Escherichia coli and Staphylococcus aureus: 1 × 10^6 CFU / mL) was inoculated onto LB medium and covered with LB medium. A 12 mm diameter well was punched in the medium using a puncher. Then, 10 μL of sample solution was diluted to 100 μL with sterile water and added to the well. After incubation at 37°C for 24 h, the size of the inhibition zone was recorded.

[0125] In summary, prepare a 100 μL sample solution and dilute it to 2.0 mL with sterile water. Inside a laminar flow hood, add 2 mL of sterile water to a petri dish covered with *Aspergillus niger*. After gentle rinsing, collect the resulting spore suspension and dilute it to 20 mL. Then, spread 100 μL of the diluted spore suspension onto PDA medium. Use a punch to create a 12 mm diameter hole in the medium. Add 100 μL of the test sample to each hole and incubate at 37 °C for 24 h. Finally, measure the diameter of the inhibition zone using the cross-sectional method.

[0126] Food preservation survey: Some cowpeas were purchased from a local supermarket and thoroughly washed. A 5 mL sample suspension was then prepared and diluted to 500 mL with deionized water. The resulting solution was transferred to a spray bottle and sprayed evenly onto the food surface. All treated food was stored in a cool, well-ventilated place. The weight and spoilage of the cowpeas were monitored daily during the experiment.

[0127] Results Analysis

[0128] The introduction of TS not only optimizes the bactericidal properties of the carrier but also further enhances the intermolecular interactions between protein chains, thereby forming a denser and more stable molecular protective layer on the surface of the nanocarrier. To investigate the storage stability and resistance to external interference of the designed AZ-TS@CA carrier, freeze-thaw cycle stability tests were conducted on Comparative Example 2 and Example 1. Figure 1 As shown, the Pickering emulsion prepared in Comparative Example 2 exhibited significant phase separation after three consecutive freeze-thaw cycles. Furthermore, the degree of oil droplet leakage in Comparative Example 2 increased with increasing CA content. In contrast, the delivery platforms prepared in Example 1 maintained a uniformly dispersed state, and no significant oil droplets were observed. To further clarify the results, the UV resistance and heat-resistant properties of the samples were further analyzed. Figure 2As shown, after 3 hours of UV irradiation, the CA loss rate of the emulsion obtained in Comparative Example 2 reached 89.22%. In contrast, the CA loss rate of the emulsion in Example 1 was significantly reduced to 36.70%, indicating that it has higher photostability. The poor stability of the samples obtained in the comparative examples is due to the susceptibility of the amino functional groups introduced after the amination process to photo-oxidative degradation. However, the AZ polypeptide backbone itself has good thermal stability, therefore the nanocarriers obtained in Comparative Example 2 and Example 1 both exhibit strong resistance to thermal interference. Figure 3 ).

[0129] The excellent antibacterial properties of CA-containing Pickering emulsions are crucial for their application in food preservation. To evaluate the antibacterial effect of the AZ-TS@CA nanoplatform, [the following was selected]. E. coli , S. aureus and A. niger As representative pathogenic microorganisms, Comparative Example 2 and Comparative Example 3 were also prepared as controls to further verify the applicability of the designed nanocarrier to CA encapsulation. Figure 4 Representative bactericidal images of different samples obtained using the agar diffusion method are shown. Clearly, the inhibition zone formed in Comparative Example 3 is smaller than that of the designed inhibition zones in Comparative Example 2 and Example 1, indicating that the designed AZ and its derived nanocarriers have superior performance. Specifically, the inhibition zone diameters of the culture treated with Comparative Example 2 against *Escherichia coli*, *Staphylococcus aureus*, and *Aspergillus niger* were 34.73 ± 0.51 mm, 34.83 ± 1.53 mm, and 40.32 ± 0.38 mm, respectively. In contrast, Example 1 exhibited higher antibacterial and antifungal properties, with inhibition zone diameters reaching 42.32 ± 1.20 mm, 38.29 ± 0.82 mm, and 44.08 ± 1.92 mm, respectively.

[0130] To evaluate whether the nanoplatform can maintain the antioxidant activity of CA, this invention also conducted DPPH and ABTS tests. + Free radical scavenging experiments. For example... Figure 5 As shown, there is a significant positive correlation between emulsion concentration and free radical scavenging efficiency. When the emulsion concentration is 10 μL / mL, Comparative Example 2 shows a significant positive correlation between DPPH and ABTS. + The free radical scavenging efficiencies reached 67.47 ± 0.46% and 77.59 ± 0.36%, respectively. Due to the higher encapsulation efficiency of CA, Example 1 exhibited superior antioxidant properties. Specifically, the Pickering emulsion prepared in Example 1 showed better antioxidant performance against DPPH and ABTS. + The free radical scavenging efficiencies reached 105.87 ± 2.95% and 81.62 ± 4.21%, respectively. These results indicate that Example 1 effectively preserved the antioxidant function of CA.

[0131] Oxidation-induced spoilage and microbial invasion are the main causes of food spoilage. Collagen oxyphylla (CA) has been proven to have excellent antioxidant and antibacterial properties. Therefore, this invention involves impregnating jicama samples in a Pickering emulsion to construct a protective barrier on the food surface. As a proof of concept, a theory-guided food preservation experiment was conducted (…). Figure 6 The effect of DZ-TS@CA-based Pickering emulsion on the 12-day preservation performance of jicama was evaluated. Clearly, no visible mold was observed in either the Comparative Example 1 treatment group or the Example 1 treatment group after 12 days of storage. Although free CA could inhibit microbial growth to some extent, it failed to effectively prevent nutrient loss from the jicama. The weight loss curves showed that only the Example 1 group had a low weight loss rate (11.08%), while the Comparative Example 1 group had a high weight loss rate of 27.41%. This demonstrates that the construction of a functional Zein-based Pickering emulsion can effectively improve the long-term preservation ability of CA, providing a reasonable strategy for designing natural, efficient, and sustainable preservation systems.

[0132] As shown in the above embodiments, this invention provides a modified zein Pickering emulsion, its preparation method, and its application in the room-temperature preservation of jicama. The nanocarrier prepared by this invention not only exhibits good stability during freeze-thaw cycles and continuous and stable CA release performance in its respective microenvironment, but also possesses highly efficient bactericidal and fungal-killing properties, making it suitable for the room-temperature preservation and anti-corrosion storage of jicama. The structural stability and biological performance of a nanodelivery system are determined by its core drug and outer shell material components. This invention believes that customizing a suitable outer shell material can significantly improve its stability and bacterial recognition performance, thereby enhancing the food preservation efficacy of the nanocarrier.

[0133] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified zein Pickering emulsion, characterized in that, Includes the following steps: 1) Add zein to an alkaline solution to react. After the reaction is complete, adjust the reaction solution to neutral, add an amino polymer to react, and then dialyze and freeze-dry the reaction solution in sequence to obtain a solid sample powder. 2) The solid sample powder and natural extract were mixed in water and reacted. The reaction solution was then dialyzed and freeze-dried sequentially to obtain AZ-TS sample powder. 3) Disperse the AZ-TS sample powder in water, then add cinnamaldehyde, and emulsify under ultrasonication to obtain a modified zein Pickering emulsion, denoted as AZ-TS@CA.

2. The preparation method according to claim 1, characterized in that, In step 1), the alkaline solution is a sodium hydroxide solution; The mass fraction of the zein in the alkaline solution is 0.1-10%, and the mass fraction of the amino polymer in the alkaline solution is 1-20%.

3. The preparation method according to claim 1 or 2, characterized in that, The amino polymer includes one or more of ethylenediamine-terminated polyethyleneimine, polyethyleneimine, and poly(ethylene glycol)-block-polyethyleneimine.

4. The preparation method according to claim 3, characterized in that, In step 1), the reaction temperature of zein in alkaline solution is 40~100℃ and the reaction time is 0.5~8h; after adding the amino polymer, the reaction temperature is 20~40℃ and the reaction time is 0.1~6h.

5. The preparation method according to claim 1, 2, or 4, characterized in that, The natural extract contains one or more of tea saponins, astragalus polysaccharides, and resveratrol.

6. The preparation method according to claim 5, characterized in that, In step 2), the mass ratio of solid sample powder to natural extract is 1:0.1~3.0, the mass fraction of solid sample powder in the reaction solution is 0.1~10%, and the mass fraction of natural extract in the reaction solution is 0.1~10%.

7. The preparation method according to claim 1 or 6, characterized in that, In step 2), the reaction temperature is 20~40℃ and the reaction time is 0.5~8h.

8. The preparation method according to claim 7, characterized in that, In step 3), the mass fraction of AZ-TS sample powder in water is 0.1-10%, and the volume fraction of cinnamaldehyde in water is 5-70%. The emulsification is carried out under the action of an ultrasonic homogenizer, with a homogenization speed of 10,000~15,000 rpm and a homogenization time of 5~20 min.

9. The modified zein Pickering emulsion prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the modified zein Pickering emulsion according to claim 9 in the room temperature preservation of jicama.

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