A controlled release antibacterial packaging film and a method for preparing the same

Abstract

The present application belongs to the technical field of active packaging film, and particularly relates to a controlled-release antibacterial packaging film and a preparation method thereof. The controlled-release antibacterial packaging film comprises the following components in parts by weight: 0.026-4.05 parts of composite nanoparticles, 0.52-10.51 parts of essential oil, 16.89-19.57 parts of plasticizer, 1.35-1.57 parts of auxiliary crosslinking agent, and 67.57-78.31 parts of film-forming base material. The composite nanoparticles are used to stably coat the essential oil droplets to form a stable coated dispersion system. The composite nanoparticles comprise zein and carboxylated cellulose nanowhiskers. The present application uses the method of stably coating essential oil with composite nanoparticles to prepare an essential oil emulsion, which is then added to a film to obtain an antibacterial active packaging film. The release rate of the essential oil is adjusted by adjusting the formula of the composite nanoparticles, so that the essential oil is slowly and continuously released, and the action time of the essential oil is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of active packaging film technology, specifically relating to a controlled-release antibacterial packaging film and its preparation method, and more particularly to a controlled-release antibacterial packaging film based on composite nanoparticle regulation and its preparation method. Background Technology

[0002] Compared to traditional packaging, active packaging technology can effectively extend the shelf life of food, making it a current research hotspot in food packaging both domestically and internationally, and one of the future development trends in packaging. Release-type antimicrobial active films are a type of active packaging. They involve incorporating antimicrobial active substances into a film substrate and then using film forming technology to create an antimicrobial film material. When applied to food packaging, these antimicrobial active substances are released onto the food surface or into the food during storage, exerting their antimicrobial effect and thus extending the shelf life. Related research indicates that an appropriate release rate can more effectively exert the antimicrobial effect of the antimicrobial active substances, prolonging their duration of action and improving the storage quality of the food.

[0003] Plant essential oils are widely available and possess broad-spectrum antibacterial and antioxidant activities, making them a viable alternative to traditional preservatives. However, due to their volatility and strong flavor, directly adding plant essential oils to food often negatively impacts its flavor and sensory characteristics. Incorporating essential oils into packaging films to create active films is one option. When applied to food packaging, the essential oils can be released into the packaging environment or onto the food surface to exert antibacterial effects, thus reducing the impact of essential oils on the food's flavor and sensory characteristics. Nevertheless, directly adding essential oils to the film results in significant losses due to their volatility, and the essential oils in the film tend to be released quickly during application, failing to provide a long-lasting, sustained-release effect. Currently, the main technologies for sustained / controlled-release of essential oils in active films include blending modification, microencapsulation, multilayer composite films, and adsorption using porous materials. Chinese patent CN106982825A discloses an antibacterial microcapsule and an antibacterial packaging film. The antibacterial microcapsule includes an essential oil core and a capsule wall covering the essential oil core. The capsule wall comprises nanocrystals and natural polymer materials. This patent utilizes microencapsulation technology to encapsulate essential oils, leveraging the reinforcing and barrier effects of nanocrystals on the natural polymer materials to improve the mechanical properties, controlled release capacity, and heat and moisture resistance of the capsule wall. However, the capsule powder prepared using microencapsulation technology has a relatively large particle size, which easily leads to agglomeration when added to the film, adversely affecting the film's performance and limiting the amount of essential oil that can be added to the film, thus affecting the film's antibacterial and antioxidant activities. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a controlled-release antibacterial packaging film based on composite nanoparticles and its preparation method.

[0005] In a first aspect, the present invention provides a controlled-release antibacterial packaging film comprising the following components in parts by weight: 0.026–4.05 parts composite nanoparticles, 0.52–10.51 parts essential oil, 16.89–19.57 parts plasticizer, 1.35–1.57 parts crosslinking agent, and 67.57–78.31 parts film-forming matrix material; wherein the composite nanoparticles coat essential oil droplets to form a stable coated dispersion system; the composite nanoparticles include zein and carboxylated cellulose nanocrystals.

[0006] The innovation of this invention lies in the fact that the controlled-release antibacterial packaging film contains a dispersion system of composite nanoparticles that stably coat essential oil droplets. The composite nanoparticles coating the plant essential oils are composed of zein and carboxylated cellulose nanofibers. Those skilled in the art know that plant essential oils have high chemical activity and poor stability, making the construction of emulsion systems technically challenging and complex. They are prone to reacting with emulsifying materials, leading to aggregation, precipitation, and demulsification. Zein is a major storage protein in corn, abundant in sources, and possesses good biocompatibility and bioadhesion. Its molecular structure contains abundant hydrophobic and hydrophilic structures, allowing it to self-assemble into zein colloidal particles. Current research on using zein to stabilize essential oil emulsions is extensive; however, emulsions stabilized by zein alone are usually unstable and require complexation with other substances to regulate the wettability of the zein particle surface. Nanocellulose uses cellulose, the most widely distributed and renewable biopolymer in nature, as its raw material. Nanocellulose not only possesses excellent biocompatibility and biodegradability, and is resistant to both high and low temperatures, but also exhibits strong hydrophilicity due to its large surface area and exposed hydroxyl groups. It also functions as an emulsifier and thickener. However, due to its abundant hydroxyl groups, nanocellulose is prone to aggregation. Modified carboxylated nanocellulose, with the introduction of a certain number of carboxyl functional groups on its surface, exhibits better solubility and biocompatibility, increasing its dispersibility. Furthermore, the strong negative charge of the carboxyl groups gives the surface a negative charge, enabling it to interact with positively charged zein. Due to the spherical structure of zein nanoparticles and the rod-like structure of cellulose nanoparticles, specific preparation processes can be used to composite them into nanoparticles with a "cocklebur"-like structure. On the one hand, the introduction of carboxylated cellulose nanoparticles increases the wettability of the zein nanoparticle surface, thereby increasing the stability of the emulsion. On the other hand, the "cocklebur"-like composite nanoparticles can form a certain interlocking effect between particles when stabilizing essential oil emulsions, further increasing the stability of the essential oil emulsion. Through amidation reactions, hydrophobic groups are introduced onto the surface of carboxylated cellulose nanoparticles or grafted onto zein as a matrix, resulting in a cross-linked state and synergistic effect.

[0007] Preferably, the essential oil is selected from one or more of the following: rose essential oil, jasmine essential oil, lemon essential oil, peppermint essential oil, rosemary essential oil, ylang-ylang essential oil, lavender essential oil, tea tree essential oil, crape myrtle essential oil, carnation essential oil, eucalyptus essential oil, pineapple essential oil, cactus essential oil, aloe vera essential oil, lemongrass essential oil, geranium essential oil, and clove essential oil.

[0008] Preferably, the plasticizer is selected from one or more of alcohols, polyethylene glycols, ethers, and glycerides, preferably alcohols, more preferably one or more of propylene glycol, glycerol, n-butanol, isobutanol, sec-butanol, isopropanol, n-hexanol, and ethanol, and more preferably glycerol.

[0009] Preferably, the film-forming matrix material is selected from sodium alginate or fish scale gelatin, preferably fish scale gelatin, which is selected from one or more of grass carp scale gelatin, black carp scale gelatin, silver carp scale gelatin and tilapia scale gelatin; the crosslinking agent is selected from one or more of calcium lactate, calcium chloride, magnesium chloride, propylene glycol, ethylenediaminetetrafluoroethylene, disodium acetate, new grass extract, calcium disodium acetate, disodium stannous citrate and transglutaminase, preferably transglutaminase.

[0010] Edible packaging films prepared using fish scale gelatin as a base material possess good air permeability and certain mechanical properties, and are being researched as a potential alternative to plastic films for food preservation. Utilizing fish scales to produce fish scale gelatin, which is then processed into easily biodegradable food preservation films, not only reduces environmental pollution but also provides high-value utilization of fish scales. Transglutaminase was used as a cross-linking agent to modify fish scale gelatin, thereby improving the film-forming properties and performance of the fish scale gelatin film.

[0011] Preferably, in the essential oil emulsion coated with composite nanoparticles, the mass ratio of the composite nanoparticles to the essential oil coated with the composite nanoparticles is 0.1 to 0.5; in the composite nanoparticles, the mass ratio of the carboxylated cellulose nanocrystals to the zein is (3:1) to (1:3).

[0012] According to the present invention, the controlled-release antibacterial packaging film provided by the present invention contains essential oil stably coated by composite nanoparticles. The composite nanoparticles are composed of zein and carboxylated cellulose nanofibers. By adjusting the ratio between zein and carboxylated cellulose nanofibers, composite nanoparticles with different structural morphologies are prepared. The release rate of essential oil in the film is controlled by utilizing the differences in the stable coating of essential oil by composite nanoparticles with different structural morphologies.

[0013] Secondly, the present invention also provides a method for preparing the controlled-release antibacterial packaging film as described above, comprising the following steps:

[0014] Step (1), preparation of composite nanoparticles: mix the ethanol solution of zein with the aqueous dispersion of carboxylated cellulose nanocrystals to obtain a mixture; then remove the ethanol and some water from the mixture under vacuum conditions, pre-freeze at a certain temperature and then freeze-dry under vacuum to obtain composite nanoparticles.

[0015] Step (2), preparation of essential oil emulsion: The composite nanoparticles obtained in step (1) are dispersed in distilled water to obtain a composite nanoparticle dispersion. The essential oil and the composite nanoparticle dispersion are then mixed evenly and homogenized to obtain an essential oil emulsion in which the composite nanoparticles coat the essential oil droplets.

[0016] Step (3), preparation of film: dissolve film-forming matrix material, plasticizer and crosslinking agent in distilled water, and then slowly add essential oil emulsion obtained in step (2) to the mixed solution to obtain film solution; spread the prepared film solution on a platform by solution casting method and dry it at a certain temperature to obtain the controlled release antibacterial packaging film.

[0017] Preferably, in step (1), a high-pressure micro-injection pump is used to inject the zein ethanol solution dropwise into the carboxylated cellulose nanofiber aqueous dispersion that is stirred at high speed, and finally a mixture is obtained.

[0018] Preferably, in step (1), the pre-freezing temperature is -100℃ to -60℃, the pre-freezing time is 1 to 24 hours, and the vacuum freeze-drying time is 60 to 84 hours; in step (2), an ultrasonic cell disruptor is used for homogenization, and the working parameters of the ultrasonic cell disruptor are: working time 10 minutes, power 250W, and interval 10 seconds; in step (3), the drying temperature after the membrane solution is spread out is 30-50℃, and the drying time is 5-15 hours.

[0019] Preferably, in step (2), the concentration of the composite nanoparticle dispersion is 1-2%, and the concentration of the essential oil in the essential oil emulsion containing the composite nanoparticles coated with essential oil droplets is 5-20%.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention uses a method of stabilizing essential oils with composite nanoparticles to prepare an essential oil emulsion, which is then added to a film to obtain an antibacterial active packaging film. The release rate of the essential oil is controlled by adjusting the composite nanoparticle formula, so as to achieve the purpose of slow and continuous release of the essential oil and prolong its effect time. Attached Figure Description

[0022] Figure 1 and Figure 2The curves show the release amount of rosemary essential oil from the films prepared in the embodiments and comparative examples of the present invention into the food simulation liquid (10% ethanol solution) over time. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to specific embodiments; however, the scope of protection of the present invention is not limited to these embodiments. All changes or equivalent substitutions that do not depart from the concept of the present invention are included within the scope of protection of the present invention.

[0024] Example 1: (Carboxylated cellulose nanocrystals: Zead protein = 3:1)

[0025] (1) Preparation of composite nanoparticles:

[0026] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. Using a high-pressure micro-injection pump, 1 part by weight of the zein-ethanol solution was dropwise added to 3 parts by weight of the carboxylated cellulose nanofiber aqueous dispersion. The injection pump pressure was 0.5 MPa, and the injection flow rate was 0.1 mL / min. During the addition process, the carboxylated cellulose nanofiber aqueous dispersion was stirred at a high speed of 2000 rpm to obtain the final mixture. Then, under vacuum conditions, a rotary evaporator was used to remove ethanol and some water from the mixture. After pre-freezing at -80℃ for 12 hours, the mixture was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0027] (2) Preparation of essential oil emulsion:

[0028] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 1% and 10%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0029] (3) Thin film preparation:

[0030] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 4.5g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0031] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0032] Example 2: (Carboxylated cellulose nanocrystals: Zead protein = 1:1)

[0033] (1) Preparation of composite nanoparticles:

[0034] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. Using a high-pressure micro-injection pump, 2 parts by weight of the zein-ethanol solution were dropwise added to 2 parts by weight of the carboxylated cellulose nanofiber aqueous dispersion. The injection pump pressure was 0.5 MPa, and the injection flow rate was 0.1 mL / min. During the addition process, the carboxylated cellulose nanofiber aqueous dispersion was stirred at a high speed of 2000 rpm to obtain the final mixture. Then, under vacuum conditions, a rotary evaporator was used to remove ethanol and some water from the mixture. After pre-freezing at -80℃ for 12 hours, the mixture was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0035] (2) Preparation of essential oil emulsion:

[0036] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 1% and 10%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0037] (3) Thin film preparation:

[0038] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 4.5g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0039] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0040] Example 3: (Carboxylated cellulose nanocrystals: Zead protein = 1:3)

[0041] (1) Preparation of composite nanoparticles:

[0042] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. Using a high-pressure micro-injection pump, 3 parts by weight of the zein-ethanol solution were dropwise added to 1 part by weight of the carboxylated cellulose nanofiber aqueous dispersion. The injection pump pressure was 0.5 MPa, and the injection flow rate was 0.1 mL / min. During the addition process, the carboxylated cellulose nanofiber aqueous dispersion was stirred at a high speed of 2000 rpm to obtain the final mixture. Then, under vacuum conditions, a rotary evaporator was used to remove ethanol and some water from the mixture. After pre-freezing at -80℃ for 12 hours, the mixture was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0043] (2) Preparation of essential oil emulsion:

[0044] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 1% and 10%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0045] (3) Thin film preparation:

[0046] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 4.5g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0047] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0048] Example 4: (Carboxylated cellulose nanocrystals: Zea prolysin = 1:1)

[0049] (1) Preparation of composite nanoparticles:

[0050] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. Using a high-pressure micro-injection pump, 2 parts by weight of the zein-ethanol solution were dropwise added to 2 parts by weight of the carboxylated cellulose nanofiber aqueous dispersion. The injection pump pressure was 0.5 MPa, and the injection flow rate was 0.1 mL / min. During the addition process, the carboxylated cellulose nanofiber aqueous dispersion was stirred at a high speed of 2000 rpm to obtain the final mixture. Then, under vacuum conditions, a rotary evaporator was used to remove ethanol and some water from the mixture. After pre-freezing at -80℃ for 12 hours, the mixture was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0051] (2) Preparation of essential oil emulsion:

[0052] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 1% and 20%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0053] (3) Thin film preparation:

[0054] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 2.25g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain fish scale gelatin solution.

[0055] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0056] Example 5: (Carboxylated cellulose nanocrystals: Zead protein = 1:1)

[0057] (1) Preparation of composite nanoparticles:

[0058] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. Using a high-pressure micro-injection pump, 2 parts by weight of the zein-ethanol solution were dropwise added to 2 parts by weight of the carboxylated cellulose nanofiber aqueous dispersion. The injection pump pressure was 0.5 MPa, and the injection flow rate was 0.1 mL / min. During the addition process, the carboxylated cellulose nanofiber aqueous dispersion was stirred at a high speed of 2000 rpm to obtain the final mixture. Then, under vacuum conditions, a rotary evaporator was used to remove ethanol and some water from the mixture. After pre-freezing at -80℃ for 12 hours, the mixture was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0059] (2) Preparation of essential oil emulsion:

[0060] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 2% and 5%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0061] (3) Thin film preparation:

[0062] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 9g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0063] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0064] Example 6: (Carboxylated cellulose nanocrystals: Zead protein = 3:1)

[0065] (1) Preparation of composite nanoparticles:

[0066] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. Using a high-pressure micro-injection pump, 1 part by weight of the zein-ethanol solution was dropwise added to 3 parts by weight of the carboxylated cellulose nanofiber aqueous dispersion. The injection pump pressure was 0.5 MPa, and the injection flow rate was 0.1 mL / min. During the addition process, the carboxylated cellulose nanofiber aqueous dispersion was stirred at a high speed of 2000 rpm to obtain the final mixture. Then, under vacuum conditions, a rotary evaporator was used to remove ethanol and some water from the mixture. After pre-freezing at -80℃ for 12 hours, the mixture was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0067] (2) Preparation of essential oil emulsion:

[0068] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 1% and 20%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0069] (3) Thin film preparation:

[0070] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 0.1g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0071] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0072] Example 7: (Carboxylated cellulose nanocrystals: Zea prolysin = 1:1)

[0073] (1) Preparation of composite nanoparticles:

[0074] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. Using a high-pressure micro-injection pump, 2 parts by weight of the zein-ethanol solution were dropwise added to 2 parts by weight of the carboxylated cellulose nanofiber aqueous dispersion. The injection pump pressure was 0.5 MPa, and the injection flow rate was 0.1 mL / min. During the addition process, the carboxylated cellulose nanofiber aqueous dispersion was stirred at a high speed of 2000 rpm to obtain the final mixture. Then, under vacuum conditions, a rotary evaporator was used to remove ethanol and some water from the mixture. After pre-freezing at -80℃ for 12 hours, the mixture was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0075] (2) Preparation of essential oil emulsion:

[0076] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 1% and 20%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0077] (3) Thin film preparation:

[0078] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 0.1g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0079] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0080] Example 8: (Carboxylated cellulose nanocrystals: Zead protein = 1:3)

[0081] (1) Preparation of composite nanoparticles:

[0082] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. Using a high-pressure micro-injection pump, 3 parts by weight of the zein-ethanol solution were dropwise added to 1 part by weight of the carboxylated cellulose nanofiber aqueous dispersion. The injection pump pressure was 0.5 MPa, and the injection flow rate was 0.1 mL / min. During the addition process, the carboxylated cellulose nanofiber aqueous dispersion was stirred at a high speed of 2000 rpm to obtain the final mixture. Then, under vacuum conditions, a rotary evaporator was used to remove ethanol and some water from the mixture. After pre-freezing at -80℃ for 12 hours, the mixture was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0083] (2) Preparation of essential oil emulsion:

[0084] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 2% and 5%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0085] (3) Thin film preparation:

[0086] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 0.4g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0087] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0088] Comparative Example 1: (without composite nanoparticles)

[0089] (1) Preparation of essential oil emulsion:

[0090] A certain mass of rosemary essential oil and Tween 80 were added to a certain mass of distilled water, and the mixture was homogenized using an ultrasonic cell disruptor to obtain an essential oil emulsion, in which the mass fraction of rosemary essential oil was 10%. The operating parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0091] (2) Thin film preparation:

[0092] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 4.5g of the essential oil emulsion prepared in step (1) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0093] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0094] Comparative Example 2: (without composite nanoparticles)

[0095] (1) Preparation of essential oil emulsion:

[0096] A certain mass of rosemary essential oil and Tween 80 were added to a certain mass of distilled water, and the mixture was homogenized using an ultrasonic cell disruptor to obtain an essential oil emulsion, in which the mass fraction of rosemary essential oil was 10%. The operating parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0097] (2) Thin film preparation:

[0098] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 0.2g of the essential oil emulsion prepared in step (1) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain fish scale gelatin solution.

[0099] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0100] Comparative Example 3: (Carboxylated cellulose nanocrystals: Zeadin = 7:1)

[0101] (1) Preparation of composite nanoparticles:

[0102] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. Using a high-pressure micro-injection pump, 0.5 parts by weight of the zein-ethanol solution was dropwise added to 3.5 parts by weight of the carboxylated cellulose nanofiber aqueous dispersion. The injection pump pressure was 0.5 MPa, and the injection flow rate was 0.1 mL / min. During the addition process, the carboxylated cellulose nanofiber aqueous dispersion was stirred at a high speed of 2000 rpm to obtain the final mixture. Then, under vacuum conditions, a rotary evaporator was used to remove ethanol and some water from the mixture. After pre-freezing at -80℃ for 12 hours, the mixture was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0103] (2) Preparation of essential oil emulsion:

[0104] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 1% and 10%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0105] (3) Thin film preparation:

[0106] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 4.5g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0107] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0108] Comparative Example 4: (Carboxylated cellulose nanocrystals: Zead protein = 1:7)

[0109] (1) Preparation of composite nanoparticles:

[0110] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. Using a high-pressure micro-injection pump, 3.5 parts by weight of the zein-ethanol solution was dropwise added to 0.5 parts by weight of the carboxylated cellulose nanofiber aqueous dispersion. The injection pump pressure was 0.5 MPa, and the injection flow rate was 0.1 mL / min. During the addition process, the carboxylated cellulose nanofiber aqueous dispersion was stirred at a high speed of 2000 rpm to obtain the final mixture. Then, under vacuum conditions, a rotary evaporator was used to remove ethanol and some water from the mixture. After pre-freezing at -80℃ for 12 hours, the mixture was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0111] (2) Preparation of essential oil emulsion:

[0112] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 1% and 20%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0113] (3) Thin film preparation:

[0114] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 2.25g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain fish scale gelatin solution.

[0115] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0116] Comparative Example 5: (Carboxylated cellulose nanocrystals: Zead protein = 3:1)

[0117] (1) Preparation of composite nanoparticles:

[0118] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. While magnetically stirring, 1 part by weight of the zein-ethanol solution was added dropwise to 3 parts by weight of the carboxylated cellulose nanofiber aqueous dispersion using a syringe to obtain the final mixture. Then, under vacuum conditions, the mixture was removed by rotary evaporation to remove ethanol and some water. After pre-freezing at -80℃ for 12 hours, it was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0119] (2) Preparation of essential oil emulsion:

[0120] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 1% and 10%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0121] (3) Thin film preparation:

[0122] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 4.5g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0123] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0124] Comparative Example 6: (Carboxylated cellulose nanocrystals: Zea prolysin = 1:1)

[0125] (1) Preparation of composite nanoparticles:

[0126] The composite nanoparticles consist of zein and carboxylated cellulose nanocrystals. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanocrystals was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. While magnetically stirring, 2 parts by weight of the zein-ethanol solution were added dropwise to 2 parts by weight of the carboxylated cellulose nanocrystal aqueous dispersion using a syringe to obtain the final mixture. Then, under vacuum conditions, the mixture was removed by rotary evaporation to remove ethanol and some water. After pre-freezing at -80℃ for 12 hours, it was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0127] (2) Preparation of essential oil emulsion:

[0128] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 1% and 10%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0129] (3) Thin film preparation:

[0130] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 4.5g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0131] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0132] Comparative Example 7: (Carboxylated cellulose nanocrystals: Zead protein = 1:3)

[0133] (1) Preparation of composite nanoparticles:

[0134] The composite nanoparticles consist of zein and carboxylated cellulose nanofibers. 1.0 g of zein was added to 100 mL of 80% ethanol aqueous solution and magnetically stirred for 3 hours to mix thoroughly. 1.0 g of carboxylated cellulose nanofibers was added to 100 mL of distilled water and magnetically stirred for 3 hours to mix thoroughly. While magnetically stirring, 3 parts by weight of the zein-ethanol solution were added dropwise to 1 part by weight of the carboxylated cellulose nanofiber aqueous dispersion using a syringe to obtain the final mixture. Then, under vacuum conditions, a rotary evaporator was used to remove ethanol and some water from the mixture. After pre-freezing at -80℃ for 12 hours, the mixture was then freeze-dried under vacuum for 72 hours to obtain the composite nanoparticles.

[0135] (2) Preparation of essential oil emulsion:

[0136] The composite nanoparticles obtained in step (1) were dispersed in distilled water using an ultrasonic cell disruptor, and then a certain mass of rosemary essential oil was added. The mixture was then homogenized using an ultrasonic cell disruptor to finally obtain an essential oil emulsion stably encapsulated with composite nanoparticles. The mass fractions of composite nanoparticles and rosemary essential oil were 1% and 10%, respectively. The working parameters of the ultrasonic cell disruptor were: working time 10 min, power 250 W, and interval 10 s.

[0137] (3) Thin film preparation:

[0138] Add 3g of fish scale gelatin, 0.75g of glycerol and 0.06g of transglutaminase to 100mL of distilled water, heat and stir at 40℃ for 3h to dissolve the fish scale gelatin and mix evenly. After ultrasonic defoaming, slowly add 4.5g of the essential oil emulsion prepared in step (2) to the mixed solution, heat and stir slowly at 40℃ for 1h to mix evenly, and obtain the fish scale gelatin solution.

[0139] The prepared fish scale gelatin solution was spread evenly on a glass plate placed on a heating table by solution casting and dried at 40°C for 10 hours to obtain the controlled-release antibacterial packaging film.

[0140] Release performance experiment:

[0141] Using a 10% ethanol solution as a food simulant (simulating aqueous food), a certain amount of film sample was immersed in the food simulant. Through release (migration) experiments, the amount of active substance (rosemary essential oil) released from the film into the food simulant was periodically measured. Figure 1 This diagram illustrates the change over time in the release amount of rosemary essential oil from the controlled-release antibacterial packaging films prepared in Examples 1-3, 6-8, Comparative Example 1, and Comparative Example 2 of this invention into the food simulation liquid. Figure 2The graph shows the change in the amount of rosemary essential oil released into the food simulant liquid from the films prepared in Examples 3 to 5 and Comparative Examples 1 to 7 over time. The vertical axis represents the amount of rosemary essential oil released from the film into the food simulant liquid (μg / mL).

[0142] Depend on Figure 1 It can be seen that the release amount of rosemary essential oil in the six films corresponding to Examples 1-3 and Examples 6-8 gradually increased with time. Firstly, comparing the films of Examples 1, 2, and 3, the rate at which the release reached equilibrium was as follows: Example 1 (approximately 70 h) > Example 3 (approximately 130 h) > Example 2 (approximately 160 h). This shows that the release rate of rosemary essential oil in the film changes with the ratio of zein to carboxylated cellulose nanofibers in the composite nanoparticles. The main reason is that the structural morphology of the composite nanoparticles changes with the ratio of zein to carboxylated cellulose nanofibers, thus affecting the stable encapsulation effect of the composite nanoparticles on the essential oil, and consequently regulating the release rate of rosemary essential oil. This indicates that the release rate of essential oil in the film can be controlled by utilizing the difference in the stable encapsulation of essential oil by the composite nanoparticles. Furthermore, compared to Comparative Example 1, the release rate of rosemary essential oil in the films of Examples 1, 2, and 3 was significantly slower, indicating that the stable encapsulation of the essential oil by the composite nanoparticles delayed its release. Similar results were observed in the films of Examples 6, 7, and 8, and their comparison with Comparative Example 2; the only difference between these examples and the films of Examples 1, 2, and 3 was the amount of composite nanoparticles used to stabilize the essential oil emulsion.

[0143] Comparing the films prepared in Examples 2, 4, and 5, the main difference lies in the varying ratio of composite nanoparticles to essential oils during the preparation of the essential oil emulsion. Figure 2 It can be seen that there is no significant difference in the release patterns of the three thin-film rosemary essential oils in Examples 2, 4, and 5, indicating that the ratio of composite nanoparticles to essential oils during the preparation of essential oil emulsions has virtually no effect on the release of essential oils.

[0144] The films prepared in Comparative Examples 3 and 4 had a mass ratio of carboxylated cellulose nanocrystals to zein in their composite nanoparticles that was not within the range of (3:1) to (1:3). Figure 2 It can be seen that the release pattern of rosemary essential oil in the films of Comparative Examples 3 and 4 is not significantly different from that of Comparative Example 1, nor does it delay the release of essential oil like the films of Examples 1, 2, and 3. This indicates that the mass ratio of carboxylated cellulose nanocrystals and zein in the composite nanoparticles exceeds the range of (3:1) to (1:3), and the composite nanoparticles in the film have basically no effect on the release of essential oil and cannot regulate the release rate of essential oil.

[0145] The films prepared in Comparative Examples 5, 6, and 7 had the same formulation as those in Examples 1, 2, and 3, respectively. However, the preparation of their composite nanoparticles differed from that in Examples 1-3 and 6-8, as the high-pressure jetting and high-speed stirring method was not used. Figure 2 It can be seen that there is no significant difference in the release pattern of rosemary essential oil among the three films in Comparative Examples 5, 6, and 7. Unlike the films in Examples 1, 2, and 3, the release rate of rosemary essential oil does not change with the ratio of zein and carboxylated cellulose nanofibers in the composite nanoparticles. This indicates that the composite nanoparticle preparation process (high-pressure injection + high-speed stirring addition) plays an important role in regulating the release rate of essential oil in the film.

[0146] 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 controlled-release antibacterial packaging film, characterized in that, The composition comprises the following components in parts by weight: 0.026–4.05 parts composite nanoparticles, 0.52–10.51 parts essential oil, 16.89–19.57 parts plasticizer, 1.35–1.57 parts crosslinking agent, and 67.57–78.31 parts film-forming matrix material; wherein, The composite nanoparticles encapsulate essential oil droplets to form a stable, dispersed system. The composite nanoparticles include zein and carboxylated cellulose nanofibers. The essential oil is selected from one or more of the following: rose essential oil, jasmine essential oil, lemon essential oil, peppermint essential oil, rosemary essential oil, ylang-ylang essential oil, lavender essential oil, tea tree essential oil, crape myrtle essential oil, carnation essential oil, eucalyptus essential oil, pineapple essential oil, cactus essential oil, aloe vera essential oil, lemongrass essential oil, geranium essential oil, and clove essential oil. The plasticizer is selected from one or more of propylene glycol, glycerol, n-butanol, isobutanol, sec-butanol, isopropanol, n-hexanol, and ethanol; The film-forming matrix material is selected from sodium alginate or fish scale gelatin; The fish scale gelatin is selected from one or more of grass carp fish scale gelatin, black carp fish scale gelatin, silver carp fish scale gelatin and tilapia fish scale gelatin; The crosslinking agent is selected from one or more of calcium lactate, calcium chloride, magnesium chloride, propylene glycol, disodium acetate, herbal extract, calcium disodium acetate, disodium stannous citrate, and transglutaminase. In the essential oil emulsion coated with composite nanoparticles, the mass ratio of the composite nanoparticles to the essential oil coated with the composite nanoparticles is 0.1~0.5:1; In the composite nanoparticles, the mass ratio of the carboxylated cellulose nanocrystals to the zein is 3:1 to 1:3; The preparation process of the composite nanoparticles includes: mixing an ethanol solution of zein with an aqueous dispersion of carboxylated cellulose nanocrystals to obtain a mixture; then removing ethanol and some water from the mixture under vacuum conditions, pre-freezing at a certain temperature, and then freeze-drying under vacuum to obtain composite nanoparticles; wherein, a high-pressure micro-injection pump is used to dropwise inject the ethanol solution of zein into the high-speed stirred aqueous dispersion of carboxylated cellulose nanocrystals to obtain the mixture.

2. The controlled-release antibacterial packaging film according to claim 1, characterized in that, The plasticizer is glycerol.

3. The controlled-release antibacterial packaging film according to claim 1, characterized in that, The film-forming matrix material is fish scale gelatin; The cross-linking agent is transglutaminase.

4. The method for preparing the controlled-release antibacterial packaging film according to any one of claims 1 to 3, characterized in that, Includes the following steps: Step (1), preparation of composite nanoparticles: The ethanol solution of zein is mixed with the aqueous dispersion of carboxylated cellulose nanofibers to obtain a mixture; then, under vacuum conditions, the ethanol and some water in the mixture are removed, and after pre-freezing at a certain temperature, the mixture is freeze-dried under vacuum to obtain composite nanoparticles; wherein, the ethanol solution of zein is added dropwise to the aqueous dispersion of carboxylated cellulose nanofibers stirred at high speed using a high-pressure micro-injection pump to obtain the mixture; Step (2), Preparation of essential oil emulsion: The composite nanoparticles obtained in step (1) are dispersed in distilled water to obtain a composite nanoparticle dispersion. The essential oil, emulsifier and composite nanoparticle dispersion are then mixed evenly and homogenized to obtain an essential oil emulsion in which the composite nanoparticles coat the essential oil droplets. Step (3), preparation of film: dissolve film-forming matrix material, co-emulsifier and film-forming agent in distilled water, and then slowly add essential oil emulsion obtained in step (2) to the mixed solution to obtain film solution; spread the prepared film solution on the platform by solution casting method and dry it at a certain temperature to obtain controlled release antibacterial packaging film.

5. The preparation method according to claim 4, characterized in that, In step (1), the pre-freezing temperature is -100 ~ -60°C, the pre-freezing time is 1 ~ 24h, and the vacuum freeze-drying time is 60 ~ 84h; In step (2), an ultrasonic cell disruptor is used for homogenization. The working parameters of the ultrasonic cell disruptor are: working time 10 min, power 250 W, and interval 10 s. In step (3), the temperature for drying the membrane solution after it is spread out is 30-50°C, and the drying time is 5-15h.

6. The preparation method according to claim 4, characterized in that, In step (2), the mass concentration of the composite nanoparticle dispersion is 1-2%, and the mass concentration of the essential oil in the essential oil emulsion with essential oil droplets coated by the composite nanoparticles is 5-20%.

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