Intelligent modified atmosphere packaging film with gas selectivity and pH / humidity double response as well as preparation method and application of intelligent modified atmosphere packaging film

Abstract

The invention discloses an intelligent modified atmosphere packaging film with gas selectivity and pH / humidity double response as well as a preparation method and application of the intelligent modified atmosphere packaging film. The preparation method comprises the following steps: mixing thymol emulsion and graphene oxide dispersion liquid, and stirring and reacting at room temperature in a dark place to prepare graphene oxide-thymol; the preparation method comprises the following steps: dissolving chitosan in an acetic acid aqueous solution, then adding graphene oxide-thymol and a plasticizer, and carrying out ultrasonic dispersion treatment to form a film-forming solution; and carrying out film forming treatment on the film forming solution by adopting a casting method to prepare the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity double response. The prepared intelligent modified atmosphere packaging film can be modified automatically, is uniform and stable in structure, high in encapsulation efficiency, close in coordination, good in antibacterial and antioxidant activity and excellent in mechanical property and gas barrier property, can realize selective adsorption of gas, controls release of thymol by responding to changes of the pH value and humidity in the environment, and has a good application prospect. The method has a good application prospect in the field of fruit and vegetable preservation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fruit and vegetable storage and preservation materials, and particularly relates to an intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response as well as a preparation method and application thereof. BACKGROUND

[0002] Postharvest fruits and vegetables are prone to oxidative browning and microbial spoilage, which is the core problem leading to quality deterioration and huge economic losses. To address this challenge, various technical means such as low-temperature storage, chitosan coating, melatonin regulation, and modified atmosphere preservation have emerged in the industry. Despite this, the existing technology still fails to achieve an ideal balance between effect stability, cost-effectiveness, and consumer safety. Some technologies are hindered in actual promotion due to large fluctuations in effect, safety hazards, or low consumer acceptance. In this context, the development of preservation technologies that are efficient, safe, and have good market prospects is not only the key to breaking through the bottleneck of industrial development but also has crucial significance in reducing postharvest losses and meeting consumers' demand for high-quality healthy food.

[0003] In recent years, modified atmosphere packaging has become a key postharvest preservation technology, and its strategic position has become increasingly prominent, but its effectiveness highly depends on the precise regulation of the internal gas environment of the packaging. An ideal modified atmosphere packaging material should have the ability of spontaneous modified atmosphere, that is, it should have differential selective permeation and adsorption performance for O2 and CO2 and other gases to dynamically balance the respiration of fruits and vegetables and automatically establish and maintain a suitable gas microenvironment. However, the gas selectivity regulation ability of existing conventional modified atmosphere packaging films (such as polyethylene, polypropylene, etc.) is generally insufficient, making it difficult to intelligently respond to the complex respiratory metabolism changes of postharvest fruits and vegetables, leading to excessively low O2 concentration or excessively high CO2 concentration in the packaging, which easily causes physiological damage such as anaerobic respiration or CO2 poisoning, thereby accelerating quality deterioration. At the same time, the existing modified atmosphere packaging has a single function and cannot achieve the synergy of intelligent controlled release and efficient spontaneous modified atmosphere function, resulting in unsatisfactory preservation effect. Therefore, it is urgent to develop an intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response. SUMMARY

[0004] The main purpose of the present application is to provide an intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response as well as a preparation method and application thereof to overcome the deficiencies of the prior art.

[0005] To achieve the aforementioned purposes, the technical solutions adopted by the present application include: The present application provides a preparation method of an intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response, which comprises: The graphene oxide, calcium chloride is dispersed in water to form a graphene oxide dispersion; the thymol, emulsifier and ethanol are mixed to form a thymol emulsion; then the thymol emulsion and the graphene oxide dispersion are mixed and stirred at room temperature to obtain graphene oxide-thymol; The chitosan is dissolved in an acetic acid aqueous solution, and then the graphene oxide-thymol and the plasticizer are ultrasonically dispersed to form a film-forming solution; The film-forming solution is formed by a casting method to obtain the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response.

[0006] The application further provides the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response prepared by the preparation method.

[0007] The application further provides application of the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response in fruit and vegetable storage and preservation.

[0008] The application further provides a fruit and vegetable preservation method, which comprises: sealing and packaging fruits or vegetables by using the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response and storing the fruits or vegetables. The environmental temperature of the storage is 20-25 DEG C, and the relative humidity is 70-80 %.

[0009] The application further provides a fruit and vegetable storage and preservation material, which comprises the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response.

[0010] Compared with the prior art, the application has the following beneficial effects: (1) The preparation method provided by the application has small energy consumption, mild conditions, simple operation and low cost, and the intelligent modified atmosphere packaging film prepared by the method has uniform and controllable structure and stable performance; (2) The intelligent modified atmosphere packaging film prepared by the application has self-induced modified atmosphere, high encapsulation rate, tight coordination, large specific surface area and pore volume and strong hydrophobicity; (3) The intelligent modified atmosphere packaging film prepared by the application has multifunctionality, good antibacterial and antioxidant activity, excellent mechanical performance and gas barrier performance, and can realize selective adsorption of gas; (4) The intelligent modified atmosphere packaging film prepared by the application can control the release of thymol by responding to the changes of pH and humidity in the environment, and can maximize the antioxidant and antibacterial effects. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only constitute some embodiments described in the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0012] Figures la-d SEM images and X-ray diffraction patterns of the graphite powder, graphene oxide and graphene oxide-thymol prepared in Example 1; Figure 2 AFM images, cross-sectional SEM images and water contact angle images of the chitosan film and chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5; Figure 3 Fourier infrared spectroscopy images of the chitosan film and chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5; Figures 4a-c Specific surface area, pore size and pore volume size images of the chitosan film and chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5; Figures 5a-g Thickness, mechanical properties and gas barrier properties images of the chitosan film and chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5; Figures 6a-g Antibacterial, antioxidant activity and hemolysis rate images of the chitosan film and chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5; Figure 7 Encapsulation efficiency images of the chitosan / graphene oxide-thymol composite film prepared in Examples 1-5; Figures 8a-d Adsorption free energy comparison images of the chitosan / graphene oxide-thymol composite film prepared in Example 1 for different gases (CO2 and O2); Figures 9a-b Humidity and pH responsive release performance images of the chitosan / graphene oxide-thymol composite film prepared in Example 1; Figures 10a-e Application images of the chitosan film and chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Example 1 for mango preservation. DETAILED DESCRIPTION

[0013] In view of the defects of the prior art, the present inventors have long studied and practiced to propose the technical solution of the present application. The present application is to first disperse graphite powder in concentrated sulfuric acid and place it in an ice bath for continuous stirring. After sufficient dispersion, potassium permanganate is added to the solution, and the oxidation of the graphite powder is carried out under stirring. After sufficient stirring, appropriate amount of distilled water is added to dilute the concentrated sulfuric acid, and appropriate amount of hydrogen peroxide is added to consume the excess potassium permanganate, and the stirring is continued to promote the dilution of the concentrated sulfuric acid and the consumption of the excess potassium permanganate. The crude product is obtained by centrifugation and discarding the supernatant, and then washed with distilled water, and then vacuum dried to obtain the graphene oxide product. Then the graphene oxide powder is dispersed in distilled water, appropriate amount of calcium chloride powder is added, and ultrasonic treatment is carried out at room temperature to promote uniform dispersion. Thymol is pre-dissolved in anhydrous ethanol, appropriate amount of Tween 80 is added, and ultrasonic emulsification is carried out. Then the thymol is slowly added dropwise to the graphene oxide dispersion, and the mixture is stirred at room temperature in the dark to fully mix. Then the crude product is obtained by centrifugation and discarding the supernatant, and then washed with anhydrous ethanol, and then vacuum dried to obtain the graphene oxide-thymol product. Then the chitosan powder is dissolved in an aqueous acetic acid solution, and then different proportions of graphene oxide-thymol powder are added to the chitosan solution, and appropriate amount of glycerol is added as a plasticizer. Ultrasonic treatment is carried out in an ice bath to promote uniform dispersion. After sufficient dispersion, the uniform film-forming solution is obtained by standing and degassing. Finally, the above-mentioned solution is cast into a film at room temperature by casting method, and after drying, the chitosan / graphene oxide-thymol composite film of different proportions is obtained (the aforementioned intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response).

[0014] The technical solution of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0015] Specifically, as one aspect of the technical solution of the present application, the preparation method of an intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response comprises: dispersing graphene oxide and calcium chloride in water to form a graphene oxide dispersion; mixing thymol, emulsifier and ethanol for emulsification treatment to form a thymol emulsion; then mixing the thymol emulsion and the graphene oxide dispersion and stirring at room temperature in the dark to prepare graphene oxide-thymol; dissolving chitosan in an aqueous acetic acid solution, then adding graphene oxide-thymol and a plasticizer for ultrasonic dispersion treatment to form a film-forming solution; and using casting method to carry out film-forming treatment on the film-forming solution to prepare the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response.

[0016] In some preferred embodiments, the preparation method specifically comprises: dispersing graphene oxide in water, then adding calcium chloride and performing ultrasonic dispersion treatment at room temperature to form a graphene oxide dispersion; wherein the mass-volume ratio of graphene oxide to water is 1 g: 500 mL ~ 1 g: 2000 mL; the mass-volume ratio of calcium chloride to water is 1 g: 50 mL ~ 1 g: 200 mL; and the ultrasonic dispersion treatment is performed for 0.5 ~ 1 h.

[0017] In some preferred embodiments, the preparation method specifically comprises: dissolving thymol in ethanol, then adding an emulsifier and performing ultrasonic emulsification treatment to form a thymol emulsion; wherein the mass-volume ratio of thymol to ethanol is 1 g: 10 mL ~ 1 g: 20 mL; the mass ratio of thymol to emulsifier is 2:1 ~ 1:1; the emulsifier comprises any one or a combination of multiple of Tween 80, Tween 20, Tween 60, sucrose ester, and monoglyceride; and the ultrasonic emulsification treatment is performed for 10 ~ 15 min.

[0018] In some preferred embodiments, the preparation method specifically comprises: slowly adding the thymol emulsion to the graphene oxide dispersion and stirring and reacting at room temperature in the dark for 2 ~ 4 h, then performing centrifugation, washing, and vacuum drying treatment to obtain graphene oxide-thymol; wherein the mass ratio of graphene oxide to thymol is 0.5 ~ 1:0.2 ~ 1; The centrifugation treatment is performed at a speed of 8000 ~ 10000 rpm, a temperature of 20 ~ 30℃, and for a time of 10 ~ 15 min; The washing treatment comprises washing the centrifuged product with anhydrous ethanol 2 ~ 3 times; The vacuum drying treatment is performed at a temperature of 60 ~ 80℃ for a time of 12 ~ 24 h.

[0019] In some preferred embodiments, the preparation method specifically comprises: dissolving chitosan in an aqueous acetic acid solution, then adding graphene oxide-thymol and a plasticizer and performing ultrasonic dispersion treatment under ice bath conditions, followed by standing and degassing to form a film-forming solution; performing film-forming treatment on the film-forming solution at room temperature using a casting method, followed by drying treatment to obtain an intelligent modified atmosphere packaging film having gas selectivity and pH / humidity dual response.

[0020] Further, the mass ratio of chitosan to graphene oxide-thymol is 100:1 ~ 5.

[0021] Further, the mass-volume ratio of chitosan to aqueous acetic acid solution is 1 g: 50 mL ~ 1 g: 200 mL.

[0022] Further, the mass / volume ratio of the plasticizer to the film-forming solution is 1-2 g: 100 mL.

[0023] Further, the volume concentration of the aqueous acetic acid solution is 1-2%.

[0024] Further, the ultrasonic dispersion treatment is performed for 1-3 h.

[0025] Further, the standing and degassing is performed at a temperature of 20-30°C for 12-24 h.

[0026] Further, the drying treatment is performed at a temperature of 40-50°C for 12-16 h.

[0027] In some more specific embodiments, the method for preparing the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response comprises: (1) dispersing graphite powder in concentrated sulfuric acid and stirring continuously in an ice bath, adding potassium permanganate to the solution after the graphite powder is dispersed sufficiently, oxidizing the graphite powder under stirring, adding distilled water to dilute the concentrated sulfuric acid after sufficient stirring, adding appropriate amount of hydrogen peroxide to consume the excess potassium permanganate, and continuing to stir to promote the dilution of the concentrated sulfuric acid and the consumption of the excess potassium permanganate, obtaining the crude product by centrifugation and discarding the supernatant, washing with distilled water, and vacuum drying to obtain the graphene oxide product; (2) dispersing graphene oxide powder in distilled water, adding appropriate amount of calcium chloride powder, and treating with ultrasonic waves at room temperature to promote uniform dispersion, dissolving thymol in anhydrous ethanol, adding appropriate amount of Tween 80, and ultrasonic emulsifying, then slowly adding thymol to the graphene oxide dispersion, stirring at room temperature in the dark to mix thoroughly, then obtaining the crude product by centrifugation and discarding the supernatant, washing with anhydrous ethanol, and vacuum drying to obtain the graphene oxide-thymol product; (3) dissolving chitosan powder in an aqueous acetic acid solution, then adding graphene oxide-thymol powder in different proportions to the chitosan solution, adding appropriate amount of glycerol as a plasticizer, treating with ultrasonic waves under ice bath to promote uniform dispersion, standing and degassing to obtain a uniform film-forming solution after sufficient dispersion, and finally casting the solution into a film by casting method at room temperature, and drying to obtain chitosan / graphene oxide-thymol composite films in different proportions, i.e. the aforementioned graphene oxide-thymol intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response.

[0028] As preferred, in the step (1), the graphite powder is dispersed in concentrated sulfuric acid, and is placed in an ice bath for continuous stirring, the mass of the graphite powder is 1-2 g, the volume of the concentrated sulfuric acid is 20-30 mL, the mass-volume ratio (g / mL) of the graphite powder to the concentrated sulfuric acid is 1:10-1:30, the stirring speed is 200-400 rpm, the temperature is 0-5℃, and the time length is 0.5-1 h.

[0029] As preferred, in the step (1), after the sufficient dispersion, potassium permanganate is added to the solution, and the oxidation of the graphite powder is carried out under stirring, the mass of the potassium permanganate is 3-4 g, the stirring speed is 400-600 rpm, the temperature is 0-5℃, and the time length is 3-5 h.

[0030] As preferred, in the step (1), after the sufficient stirring, an appropriate amount of distilled water is added to dilute the concentrated sulfuric acid, and an appropriate amount of hydrogen peroxide is added to consume the excess potassium permanganate, and the stirring is continued to promote the dilution of the concentrated sulfuric acid and the consumption of the excess potassium permanganate, the volume of the distilled water is 100-200 mL, the volume of the hydrogen peroxide is 5-10 mL, the stirring speed is 600-800 rpm, the temperature is 0-5℃, and the time length is 1-2 h.

[0031] As preferred, in the step (1), the crude product is obtained by centrifugation and discarding the supernatant, and is washed with distilled water, and then is vacuum dried to obtain the graphene oxide product, the centrifugation conditions are: the speed is 10000-12000 rpm, the temperature is 20-30℃, and the time length is 10-15 min, the washing with distilled water is performed for 2-3 times, the vacuum drying temperature is 80-90℃, and the time length is 24-36 h.

[0032] As preferred, in the step (2), the graphene oxide powder is dispersed in distilled water, an appropriate amount of calcium chloride powder is added, and ultrasonic treatment is performed at room temperature to promote the uniform dispersion, the mass of the graphene oxide powder is 0.5-1 g, the volume of the distilled water is 500-1000 mL, the mass-volume ratio (g / mL) of the graphene oxide to the distilled water is 1:500-1:2000, the mass of the calcium chloride powder is 5-10 g, the mass-volume ratio (g / mL) of the calcium chloride to the distilled water is 1:50-1:200, and the ultrasonic treatment time length is 0.5-1 h.

[0033] As preferred, in the step (2), the thymol is pre-dissolved in anhydrous ethanol, an appropriate amount of Tween 80 is added, and ultrasonic emulsification is performed, the mass-volume ratio (g / mL) of the thymol to the anhydrous ethanol is 1:10-1:20, the mass ratio (g / g) of the thymol to the Tween 80 is 2:1-1:1, and the ultrasonic emulsification time length is 10-15 min.

[0034] Preferably, in step (2), the thymol is slowly added dropwise into the graphene oxide dispersion solution, and the solution is fully mixed under stirring at room temperature in the dark. The amount of thymol added is 0.2-1 g, and the stirring time in the dark is 2-4 h.

[0035] Preferably, in step (2), the crude product is obtained by centrifugation and discarding the supernatant, and then washed with anhydrous ethanol, and the graphene oxide-thymol product is obtained by vacuum drying. The centrifugation conditions are as follows: the rotation speed is 8000-10000 rpm, the temperature is 20-30℃, and the time is 10-15 min. The anhydrous ethanol is washed for 2-3 times. The vacuum drying temperature is 60-80℃, and the time is 12-24 h.

[0036] Preferably, in step (3), the chitosan powder is dissolved in an aqueous acetic acid solution, and then different proportions of graphene oxide-thymol powder are added into the chitosan solution, and an appropriate amount of glycerol is added as a plasticizer. The solution is ultrasonically treated under ice bath to promote uniform dispersion. The mass of chitosan is 1-2 g. The concentration of the aqueous acetic acid solution is 1-2% (v / v), and the volume is 100-200 mL. The mass-volume ratio (g / mL) of chitosan to the aqueous acetic acid solution is 1:50-1:200. The ultrasonic treatment time is 1-3 h. The amount of graphene oxide-thymol added is 1%, 2%, 3%, 4%, or 5% of the dry weight of chitosan (for example, when the amount of chitosan added is 2 g, the amount of graphene oxide-thymol added is 0.02 g, 0.04 g, 0.06 g, 0.08 g, or 0.10 g). The mass-volume ratio (g / mL) of the amount of glycerol added to the total volume of the solution in the system is 1%-2%. The ultrasonic treatment time is 1-3 h.

[0037] Preferably, in step (3), after sufficient dispersion, the solution is left to stand and degassed to obtain a uniform film-forming solution. Finally, the solution is cast into a film by casting method at room temperature, and the film is dried to obtain chitosan / graphene oxide-thymol composite films with different proportions. The temperature for standing and degassing is 20-30℃, and the time is 12-24 h. The drying temperature is 40-50℃, and the time is 12-16 h.

[0038] Another aspect of the embodiment of the present application also provides the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response prepared by the preparation method.

[0039] Another aspect of the embodiment of the present application also provides the application of the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response in fruit and vegetable storage and preservation.

[0040] Another aspect of the embodiment of the present application also provides a fruit and vegetable preservation method, which comprises: sealing and packaging fruits or vegetables by using the aforementioned intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response and storing them. wherein the storage environment temperature is 20-25 ℃ and the relative humidity is 70-80 %.

[0041] Another aspect of the embodiment of the present application also provides a fruit and vegetable storage preservation material, which comprises: the aforementioned intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response.

[0042] The technical solutions of the present application will be further described in detail below in combination with several preferred embodiments and the accompanying drawings. The present embodiment is implemented on the premise of the technical solutions of the present application, and gives detailed implementation modes and specific operation processes, but the protection scope of the present application is not limited to the following embodiments.

[0043] The experimental materials used in the following examples are commercially available from conventional biochemical reagent companies, unless otherwise specified.

[0044] Example 1 The present embodiment gives a preparation method of an intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response, which specifically comprises the following steps: (1) Disperse 1 g of graphite powder in 25 mL of concentrated sulfuric acid, and place it in an ice bath and continuously stir at a speed of 200 rpm for 0.5 h. After sufficient dispersion, add 3 g of potassium permanganate to the solution, and stir in an ice bath at a speed of 400 rpm for 3 h to oxidize the graphite powder. After sufficient stirring, add 150 mL of distilled water to dilute the concentrated sulfuric acid, and then add 5 mL of hydrogen peroxide to consume the excess potassium permanganate, and continue to stir in an ice bath at a speed of 600 rpm for 1 h to promote the dilution of the concentrated sulfuric acid and the consumption of the excess potassium permanganate. Obtain the crude product by centrifugation (10000 rpm, 25℃, 10 min) and discarding the supernatant, and wash it with distilled water for 2 times, and then vacuum dry it at 90℃ for 24 h to obtain the graphene oxide product.

[0045] (2) 0.5 g of graphene oxide powder was dispersed in 500 mL of distilled water, 5 g of calcium chloride powder was added, and ultrasonic treatment was performed at room temperature for 1 h to promote uniform dispersion. 5 g of thymol was pre-dissolved in 100 mL of anhydrous ethanol, 5 g of Tween 80 was added, and ultrasonic emulsification was performed for 10 min. Then, thymol (0.8 g, i.e., 16 mL of thymol ethanol solution was added) dissolved in ethanol was slowly added to the graphene oxide dispersion, and it was allowed to mix thoroughly by stirring at room temperature for 2 h in the dark. Then, the crude product was obtained by centrifugation (8000 rpm, 25°C, 10 min) and discarding the supernatant, and washed twice with anhydrous ethanol, and then dried at 60°C under vacuum for 12 h to obtain a graphene oxide-thymol product.

[0046] (3) 2 g of chitosan powder was dissolved in 100 mL of 1% acetic acid aqueous solution, and ultrasonic treatment was performed for 2 h to promote complete dissolution, and then the above graphene oxide-thymol powder (0.06 g, 3% of the dry weight of chitosan) was added to the chitosan solution, and 1.5 g of glycerol was added as a plasticizer, and ultrasonic treatment was performed for 1 h in an ice bath to promote uniform dispersion. After sufficient dispersion, a uniform film-forming solution was obtained by degassing at room temperature for 12 h. Finally, the above solution was cast into a film by a casting method at room temperature, and a chitosan / graphene oxide-thymol composite film was obtained after drying at 45°C for 12 h.

[0047] (4) In a fruit orchard in Anhui Province, China, fresh mangoes were carefully selected to ensure that the selected fruits were similar in shape, size, color, and ripeness, and had no obvious visual defects and diseases. After picking, the fruits were quickly transported to the laboratory for further processing. In the laboratory, the fruits were first thoroughly washed with distilled water and naturally dried. Then a square "micro window" with a length and width of 5 x 5 cm was cut on the lid of a plastic box of uniform size and specification, and the composite film in Comparative Example 1 and Example 1 was adhered to the "micro window" to form a sealed environment, and the plastic box without cutting the "micro window" was used as a control group. Then the fruits were divided into 3 groups and placed in the three types of plastic boxes for sealed storage. Each group had 20 boxes, and each box contained 3 mangoes. After treatment, the boxes were placed in an incubator at 25°C and 75% relative humidity for storage. Samples were collected periodically on days 0, 2, 4, 6, and 8, and various parameters such as browning index, flesh firmness, weight loss, rot rate, total soluble solids content, and microbial indicators were measured, and optical photographs were taken. Each group had three replicates, and all operations were performed at room temperature.

[0048] Figures la-d SEM images and X-ray diffraction patterns of the graphite powder, graphene oxide, and graphene oxide-thymol prepared in Example 1 are shown in FIGS. 1 to 3, respectively. Figure la The SEM image of the graphite powder is shown in FIG. 1, Figure lbSEM image of graphene oxide, Figure lc SEM image of graphene oxide-thymol, Figure Id XRD patterns of the three. As shown in Figures la-d graphene powder sample exhibited irregular clusters stacked by compact layered structures. After oxidation, the obtained graphene oxide showed disordered stacked sheet structures with a significantly increased surface wrinkling. After loading thymol, the graphene oxide-thymol composite was transformed into a structure with continuous sheet distribution, compactness and more uniform order. In terms of crystal structure, the XRD pattern results were consistent with the morphology evolution. Graphite powder had a sharp and high-intensity diffraction peak near 26.5 degrees, which indicated that it had a highly ordered crystal structure. After oxidation, the characteristic peak completely disappeared, and a broadened diffraction peak appeared in the range of 10 to 12 degrees, confirming that the oxidation process successfully destroyed the original crystal form of graphite and generated amorphous layered graphene oxide with disordered stacking. Further, after loading thymol, the diffraction peak of graphene oxide-thymol composite in the range of 10 to 12 degrees disappeared, and a new broadened characteristic peak appeared near 20 degrees. This phenomenon indicated that thymol molecules had successfully intervened between the graphene oxide sheets, destroying the original stacking order, thus confirming the successful loading of thymol from the structural level.

[0049] Figure 2 Surface atomic force microscope images, cross-sectional scanning electron microscope images and water contact angles of the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. As shown in Figure 2As shown, in terms of three-dimensional surface morphology, the pure chitosan film of Comparative Example 1 has a relatively smooth and uniform surface. In stark contrast, the composite films of Examples 1-5 all exhibit irregular three-dimensional protrusion structures, with sheet-like or wrinkled graphene oxide features emerging from the originally uniform chitosan substrate. At lower composite addition levels, the number of sheet-like structures on the film surface gradually increases with the increase of graphene oxide-thymol content. Among them, the film of Example 1 has the most uniform sheet distribution and the most regular protrusion structure. However, when the addition level increases to a higher level, the graphene oxide sheets show obvious stacking and aggregation, forming larger and more irregular protrusions, resulting in a decrease in film surface continuity and the generation of more grooves and pores. At the same time, cross-sectional morphology analysis further confirms the above trend. The cross-section of the film of Comparative Example 1 also shows a smooth and uniform characteristic. With the increase of composite addition, the cross-sectional morphology of the films of Examples 1-5 shows a synergistic change pattern, with Example 1 consistently exhibiting the best dispersion uniformity and morphological structure. Furthermore, water contact angle tests showed that the pure chitosan film in Comparative Example 1 exhibited the highest hydrophilicity. With the introduction and increasing amount of the graphene oxide-thymol composite, the hydrophobic properties of the films in Examples 1-5 showed an increasing trend. This phenomenon demonstrates that the introduction of this composite effectively improves the hydrophobicity of the film, laying a solid foundation for its excellent water vapor barrier performance.

[0050] Figure 3 Fourier transform infrared spectra of the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Figure 3 As shown, in the infrared spectrum, compared to the pure chitosan film of Comparative Example 1, all composite films of Examples 1-5 show an infrared spectrum of 1516 cm⁻¹. -1 With 1755 cm -1 Two new characteristic absorption peaks appeared at 3413 cm⁻¹, which are attributed to the benzene ring skeletal vibration of thymol and the stretching vibration of the carboxyl group of graphene oxide, respectively. Meanwhile, a peak was observed at 3413 cm⁻¹. -1 The hydroxyl stretching vibration peaks in the vicinity exhibit a significant narrowing trend in the composite film. These spectral changes, including the appearance of new characteristic peaks and the alteration of existing absorption peak shapes, collectively constitute clear evidence that the graphene oxide-thymol composite has been successfully introduced into the film substrate. These phenomena further reveal significant intermolecular interactions among chitosan, graphene oxide, and thymol, primarily characterized by hydrogen bonding and π-π stacking.

[0051] Figures 4a-c The graph shows the specific surface area, pore size, and pore volume of the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Figure 4aThe graph shows the specific surface area of ​​the chitosan film and the chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5. Figure 4b The graph shows the pore size of the chitosan film and the chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5. Figure 4c The diagram shows the pore volume of the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Figures 4a-c As shown, regarding specific surface area and pore volume, with the increase of the graphene oxide-thymol composite addition, the specific surface area and pore volume of all composite films exhibit a trend of first increasing and then decreasing, reaching their maximum values ​​in Example 1. In contrast, the average pore size of the composite films shows a continuous upward trend with increasing addition. At lower addition levels, the pore size growth is relatively gradual; however, when the addition level is further increased to a higher level, the pore size increases sharply, which may be attributed to the stacking and aggregation of graphene oxide sheets. The above results collectively indicate that the composite addition amount corresponding to Example 1 is the key balance point for achieving the optimal pore structure. Under this condition, the film maintains a moderate pore size while constructing the richest pore network, thus obtaining excellent specific surface area and pore volume characteristics.

[0052] Figures 5a-g The graphs show the thickness, mechanical properties, and gas barrier properties of the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Figure 5a The thickness diagrams show the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Figure 5b The tensile strength diagrams are for the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Figure 5c The graph shows the elongation at break of the chitosan film and the chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5. Figure 5d The graph shows the water vapor transmission rate of the chitosan film and the chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5. Figure 5e The graph shows the carbon dioxide transmittance of the chitosan film and the chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5. Figure 5f The graph shows the oxygen permeability of the chitosan film and the chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5. Figure 5g Gas selectivity (CO2 / O2) plots of the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Figures 5a-cAs shown, regarding thickness and mechanical properties, with the increase of the amount of graphene oxide-thymol composite added, the thickness and tensile strength of all composite films showed a continuous upward trend, with Example 1 exhibiting a relatively moderate thickness and a high tensile strength value. Meanwhile, the elongation at break of the composite film gradually decreased with increasing addition, but Example 1 still maintained a high elongation at break under these conditions. Furthermore, as... Figures 5d-g As shown, regarding gas barrier performance, the water vapor, oxygen, and carbon dioxide permeability of the composite film all exhibited a pattern of first decreasing and then increasing with the amount added, reaching their lowest values ​​in Example 1. Notably, the decrease in water vapor and oxygen permeability was significantly greater than that of carbon dioxide, indicating that the film of Example 1, while possessing excellent overall barrier performance, also exhibits a high selective permeability to carbon dioxide. Further gas selectivity (CO2 / O2) calculations and analyses showed that the film of Example 1 performed significantly better than other groups in this aspect, fully demonstrating its outstanding application potential in the field of selective modified atmosphere packaging materials.

[0053] Figures 6a-g The graph shows the antibacterial, antioxidant, and hemolytic activities of the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Figure 6a The images show colony counts of the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Figure 6b The graph shows the Staphylococcus aureus inhibition rate of the chitosan film and the chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5. Figure 6c The graph shows the Escherichia coli inhibition rate of the chitosan film and the chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5. Figure 6d The graph shows the botrytis cinerea inhibition rate of the chitosan film and the chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Examples 1-5. Figure 6e The graph shows the DPPH radical scavenging rates of the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Figure 6f The graph shows the ABTS radical scavenging rates of the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Figure 6g The hemolysis rate graphs are shown for the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Examples 1-5. Antibacterial properties are a key indicator for food packaging materials. For example... Figures 6a-dAs shown, the antibacterial performance test shows that the chitosan / graphene oxide-thymol composite film exhibits significant broad-spectrum inhibition effect on Staphylococcus aureus, Escherichia coli and Botrytis cinerea, and the antibacterial rates of Example 1 and Example 4 are more than 99%, which can almost achieve complete inhibition, and the antibacterial performance is far superior to that of the pure chitosan film of Comparative Example 1. Meanwhile, in terms of antioxidant activity, as shown in Figures 6e-f As shown, the films of Example 1 and Example 4 exhibit excellent free radical scavenging ability, and the DPPH (1,1-diphenyl-2-trinitrobenzene hydrazine radical) free radical scavenging rates are 88.38% and 86.72% respectively, and the ABTS (2,2'-azobis (3-ethylbenzothiazoline-6-sulfonic acid)) free radical scavenging rates are 87.26% and 85.23% respectively, both of which are significantly higher than that of Comparative Example 1. In addition, the biocompatibility evaluation results show that, as shown in Figure 6g As shown, the hemolysis rates of all the tested films are between 0.16% and 0.75%, which is far below the biological safety threshold of 5%, fully proving that the material has excellent blood compatibility, and providing a reliable safety basis for its practical application in the field of food packaging.

[0054] Figure 7 The encapsulation efficiency of the chitosan / graphene oxide-thymol composite film prepared in Examples 1-5. As shown in Figure 7 The encapsulation efficiencies of the films in Examples 1-5 are 85.40%, 92.02%, 89.59%, 73.36% and 58.57% respectively, and overall show a gradual downward trend with the increase of the addition amount of graphene oxide-thymol composite. At a lower addition amount stage, the encapsulation efficiency decreases relatively gently; while when the addition amount increases to a higher level, the encapsulation efficiency decreases significantly. It is worth noting that although at a higher addition amount level, Example 1 still achieves a high retention of active composite components, and the encapsulation efficiency can still be maintained at an excellent level of about 85.40%.

[0055] Figures 8a-d The adsorption free energy comparison chart of the key graphene oxide-thymol composite in the chitosan / graphene oxide-thymol composite film prepared in Example 1 for different gases (CO2 and O2), wherein, Figure 8a The adsorption free energy comparison chart of the key graphene oxide-thymol composite in the chitosan / graphene oxide-thymol composite film prepared in Example 1 for different gases (CO2 and O2), Figure 8b The adsorption distance comparison chart of the key graphene oxide-thymol composite in the chitosan / graphene oxide-thymol composite film prepared in Example 1 for different gases (CO2 and O2), Figure 8cThis is a model diagram of CO2 adsorption by the key graphene oxide-thymol complex in the chitosan / graphene oxide-thymol composite film prepared in Example 1. Figure 8d This is a model diagram of the adsorption of O2 by the key graphene oxide-thymol composite in the chitosan / graphene oxide-thymol composite film prepared in Example 1. Figures 8a-d As shown, in the gas adsorption free energy test, the composite film in Example 1 exhibited a higher adsorption free energy and a closer adsorption distance for O2, indicating a stronger interaction force between it and O2, resulting in relatively weaker O2 permeability in the film. This finding confirms, from the perspective of gas adsorption mechanism, that the film possesses higher selective permeability for CO2, providing a key theoretical basis for its application in the field of selective modified atmosphere packaging.

[0056] Figures 9a-b The graph shows the humidity and pH response release performance of the chitosan / graphene oxide-thymol composite film prepared in Example 1. Figure 9a This is a pH-responsive release performance graph of the chitosan / graphene oxide-thymol composite film prepared in Example 1. Figure 9b This is a humidity-responsive release performance diagram of the chitosan / graphene oxide-thymol composite film prepared in Example 1. Figures 9a-b As shown, the film in Example 1 exhibits excellent dual-response release characteristics based on pH and humidity, highly matching the slightly acidic environment (pH 5-6) and high humidity conditions (>85% RH) of post-harvest fruit storage. Experimental results show that when the ambient humidity increases from 30% to 90%, the cumulative release of thymol from the film in Example 1 significantly increases from 19.51% to 87.80% within 48 hours. This phenomenon can be attributed to the hydrophilic swelling effect of the graphene oxide-thymol complex under high humidity conditions. Simultaneously, the film also exhibits significant acid-promoted release behavior, with a thymol release of 2.72 mg at pH 5.0, more than nine times the release at neutral conditions (0.29 mg). This process mainly stems from the polymer network expansion caused by the protonation of amino groups in chitosan molecules, and the breaking of non-covalent interactions between graphene oxide and thymol molecules. This intelligent release mechanism achieves dual regulation: high humidity ensures basic release, while a slightly acidic environment triggers accelerated release, which not only prolongs the effect of active ingredients but also avoids premature depletion, providing a precise and controllable active substance delivery system for fruit preservation.

[0057] Figures 10a-e The figures show the application of the chitosan film and chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Example 1 in mango preservation. Figure 10aThe images show the changes in the appearance of mangoes when the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Example 1 were used for mango preservation. Figure 10b The image shows the red-green value of mangoes when comparing the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Example 1 for mango preservation. Figure 10c The image shows the mango firmness of the chitosan film and chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Example 1 when used for mango preservation. Figure 10d The image shows the weight loss of mangoes when the chitosan films and chitosan / graphene oxide-thymol composite films prepared in Comparative Example 1 and Example 1 are used for mango preservation. Figure 10e The image shows the mango rot rate when the chitosan film and chitosan / graphene oxide-thymol composite film prepared in Comparative Example 1 and Example 1 are used for mango preservation. Figures 10a-e As shown, the composite film exhibits significant effects in mango preservation. The results indicate that, compared to the films in the control group and Comparative Example 1, the film in Example 1 effectively maintains the quality indicators of mangoes during storage: maintaining lower [specific parameters / specific parameters]. The film exhibits enhanced color vibrancy, slows down firmness decline (inhibits cell wall component degradation), reduces weight loss (reduces transpiration and respiration), and significantly inhibits mango spoilage (inhibits microbial growth). This comprehensive preservation effect stems from the film's unique multifunctional synergistic mechanism. Its excellent gas selective adsorption capacity creates a suitable spontaneous modified atmosphere environment; its high barrier properties effectively delay quality deterioration; its sustained antibacterial and antioxidant activity inhibits microbial invasion and oxidation reactions; and its intelligent humidity and pH-responsive release characteristics enable precise controlled release of active ingredients. The synergistic effect of these properties collectively demonstrates the practical application value of this composite film as a new generation of multifunctional modified atmosphere packaging material.

[0058] Comparative Example 1: (1) Dissolve 2g of chitosan powder in 100mL of 1% acetic acid aqueous solution and sonicate for 2h to promote complete dissolution. Then add 1.5g of glycerol as a plasticizer and sonicate in an ice bath for 1h to promote uniform dispersion. After sufficient dispersion, allow to stand at room temperature for 12h to degas and obtain a uniform film-forming solution. Finally, cast the above solution into a film at room temperature by casting and dry at 45℃ for 12h to obtain the chitosan film in Comparative Example 1.

[0059] Comparative Example 2: (1) 1 g of graphite powder was dispersed in 25 mL of concentrated sulfuric acid and placed in an ice bath with continuous stirring at a speed of 200 rpm for 0.5 h. After being well dispersed, 3 g of potassium permanganate was added to the solution, and ice bath stirring was performed at a speed of 400 rpm for 3 h to oxidize the graphite powder. After sufficient stirring, 150 mL of distilled water was added to dilute the concentrated sulfuric acid, 5 mL of hydrogen peroxide was added to consume the excess potassium permanganate, and ice bath stirring was continued at a speed of 600 rpm for 1 h to facilitate the dilution of the concentrated sulfuric acid and the consumption of the excess potassium permanganate. The crude product was obtained by centrifugation (10000 rpm, 25°C, 10 min) and discarding the supernatant, and was washed twice with distilled water and vacuum dried at 90°C for 24 h to obtain the graphene oxide product.

[0060] (2) 2 g of chitosan powder was dissolved in 100 mL of 1% acetic acid aqueous solution, and ultrasonic treatment was performed for 2 h to facilitate complete dissolution. Then, the above graphene oxide powder (0.06 g, 3% of the dry weight of chitosan) was added to the chitosan solution, and 1.5 g of glycerol was added as a plasticizer, and ultrasonic treatment was performed for 1 h under ice bath to facilitate uniform dispersion. After being well dispersed, the solution was degassed at room temperature for 12 h to obtain a uniform film-forming solution. Finally, the above solution was cast into a film by the casting method at room temperature, and dried at 45°C for 12 h to obtain a chitosan / graphene oxide composite film.

[0061] Comparative Example 3: (1) 2 g of chitosan powder was dissolved in 100 mL of 1% acetic acid aqueous solution, and ultrasonic treatment was performed for 2 h to facilitate complete dissolution. 5 g of thymol was pre-dissolved in 100 mL of anhydrous ethanol, 5 g of Tween 80 was added, and ultrasonic emulsification was performed for 10 min. Then, the thymol (0.8 g, i.e. 16 mL of thymol ethanol solution) dissolved in ethanol was slowly added to the chitosan solution, and 1.5 g of glycerol was added as a plasticizer, and the mixture was stirred at room temperature in the dark for 2 h to facilitate mixing. After being well mixed, the solution was degassed at room temperature for 12 h to obtain a uniform film-forming solution. Finally, the above solution was cast into a film by the casting method at room temperature, and dried at 45°C for 12 h to obtain a chitosan / thymol composite film in Comparative Example 3.

[0062] Comparative Example 4: (1) 1 g of graphite powder was dispersed in 25 mL of concentrated sulfuric acid and placed in an ice bath with continuous stirring at a speed of 200 rpm for 0.5 h. After sufficient dispersion, 3 g of potassium permanganate was added to the solution, and ice bath stirring was continued at a speed of 400 rpm for 3 h to perform the oxidation of the graphite powder. After sufficient stirring, 150 mL of distilled water was added to dilute the concentrated sulfuric acid, 5 mL of hydrogen peroxide was added to consume the excess potassium permanganate, and ice bath stirring was continued at a speed of 600 rpm for 1 h to facilitate the dilution of the concentrated sulfuric acid and the consumption of the excess potassium permanganate. The crude product was obtained by centrifugation (10000 rpm, 25°C, 10 min) and discarding the supernatant, washed twice with distilled water, and vacuum dried at 90°C for 24 h to obtain the graphene oxide product.

[0063] (2) 5 g of graphene oxide powder was dispersed in 500 mL of distilled water, 5 g of calcium chloride powder was added, and ultrasonic treatment was performed at room temperature for 1 h to facilitate uniform dispersion. 5 g of thymol was pre-dissolved in 100 mL of anhydrous ethanol, 5 g of Tween 80 was added, and ultrasonic emulsification was performed for 10 min. Then, the thymol (0.8 g, i.e., 16 mL of thymol ethanol solution) dissolved in ethanol was slowly added to the graphene oxide dispersion, and stirring was performed at room temperature for 2 h to allow sufficient mixing. Then, the crude product was obtained by centrifugation (8000 rpm, 25°C, 10 min) and discarding the supernatant, washed twice with anhydrous ethanol, and vacuum dried at 60°C for 12 h to obtain the graphene oxide-thymol product.

[0064] (3) 2 g of chitosan powder was dissolved in 100 mL of 1% acetic acid aqueous solution, and ultrasonic treatment was performed for 2 h to facilitate complete dissolution. Then, the above graphene oxide-thymol powder (0.06 g, 3% of the dry weight of chitosan) was added to the chitosan solution, and 1.5 g of glycerol was added as a plasticizer, and ultrasonic treatment was performed for 1 h in an ice bath to facilitate uniform dispersion. After sufficient dispersion, the solution was degassed at room temperature for 12 h to obtain a uniform film-forming solution. Finally, the above solution was cast into a film by the casting method at room temperature, and a chitosan / graphene oxide-thymol composite film in Comparative Example 4 was obtained after drying at 45°C for 12 h.

[0065] Comparative Example 5: (1) 1 g of graphite powder was dispersed in 25 mL of concentrated sulfuric acid and placed in an ice bath with continuous stirring at 200 rpm for 0.5 h. After being well dispersed, 3 g of potassium permanganate was added to the solution, and ice bath stirring was continued at 400 rpm for 3 h to perform the oxidation of the graphite powder. After sufficient stirring, 150 mL of distilled water was added to dilute the concentrated sulfuric acid, 5 mL of hydrogen peroxide was added to consume the excess potassium permanganate, and ice bath stirring was continued at 600 rpm for 1 h to facilitate the dilution of the concentrated sulfuric acid and the consumption of the excess potassium permanganate. The crude product was obtained by centrifugation (10000 rpm, 25°C, 10 min) and discarding the supernatant, washed twice with distilled water, and vacuum dried at 90°C for 24 h to obtain the graphene oxide product.

[0066] (2) 0.05 g of graphene oxide powder was dispersed in 500 mL of distilled water, 5 g of calcium chloride powder was added, and ultrasonic treatment was performed at room temperature for 1 h to facilitate uniform dispersion. 5 g of thymol was pre-dissolved in 100 mL of anhydrous ethanol, 5 g of Tween 80 was added, and ultrasonic emulsification was performed for 10 min. Then, the thymol (0.8 g, i.e. 16 mL of thymol ethanol solution) dissolved in ethanol was slowly added to the graphene oxide dispersion, and stirring was performed at room temperature for 2 h to allow sufficient mixing. Then, the crude product was obtained by centrifugation (8000 rpm, 25°C, 10 min) and discarding the supernatant, washed twice with anhydrous ethanol, and vacuum dried at 60°C for 12 h to obtain the graphene oxide-thymol product.

[0067] (3) 2 g of chitosan powder was dissolved in 100 mL of 1% acetic acid aqueous solution, and ultrasonic treatment was performed for 2 h to facilitate complete dissolution. Then, the above graphene oxide-thymol powder (0.06 g, 3% of the dry weight of chitosan) was added to the chitosan solution, and 1.5 g of glycerol was added as a plasticizer, and ultrasonic treatment was performed for 1 h in an ice bath to facilitate uniform dispersion. After sufficient dispersion, the solution was degassed at room temperature for 12 h to obtain a uniform film-forming solution. Finally, the above solution was cast into a film by the casting method at room temperature, and a chitosan / graphene oxide-thymol composite film in Comparative Example 5 was obtained after drying at 45°C for 12 h.

[0068] Comparative Example 6: The method was the same as in Example 1, except that the graphene oxide-thymol powder (0.006 g, 0.3% of the dry weight of chitosan) was used.

[0069] Comparative Example 7: The method was the same as in Example 1, except that the graphene oxide-thymol powder (0.3 g, 15% of the dry weight of chitosan) was used.

[0070] The films prepared in Example 1 and Comparative Examples 1-7 were tested, and the performance is shown in Table 1.

[0071] Table 1

[0072]

[0073] Example 2: (1) 1 g of graphite powder was dispersed in 25 mL of concentrated sulfuric acid and placed in an ice bath with continuous stirring at a speed of 200 rpm for 0.5 h. After sufficient dispersion, 3 g of potassium permanganate was added to the solution, and ice bath stirring was continued at a speed of 400 rpm for 3 h to perform the oxidation of the graphite powder. After sufficient stirring, 150 mL of distilled water was added to dilute the concentrated sulfuric acid, 5 mL of hydrogen peroxide was added to consume the excess potassium permanganate, and ice bath stirring was continued at a speed of 600 rpm for 1 h to facilitate the dilution of the concentrated sulfuric acid and the consumption of the excess potassium permanganate. The crude product was obtained by centrifugation (10000 rpm, 25°C, 10 min) and discarding the supernatant, washed twice with distilled water, and vacuum dried at 90°C for 24 h to obtain the graphene oxide product.

[0074] (2) 0.5 g of graphene oxide powder was dispersed in 500 mL of distilled water, 5 g of calcium chloride powder was added, and ultrasonic treatment was performed at room temperature for 1 h to facilitate uniform dispersion. 5 g of thymol was pre-dissolved in 100 mL of anhydrous ethanol, 5 g of Tween 80 was added, and ultrasonic emulsification was performed for 10 min. Then, the thymol (0.8 g, i.e. 16 mL of thymol ethanol solution) dissolved in ethanol was slowly added to the graphene oxide dispersion, and stirring was performed at room temperature in the dark for 2 h to allow sufficient mixing. Then, the crude product was obtained by centrifugation (8000 rpm, 25°C, 10 min) and discarding the supernatant, washed twice with anhydrous ethanol, and vacuum dried at 60°C for 12 h to obtain the graphene oxide-thymol product.

[0075] (3) 2 g of chitosan powder was dissolved in 100 mL of 1% acetic acid aqueous solution, and ultrasonic treatment was performed for 2 h to facilitate complete dissolution. Then, the above graphene oxide-thymol powder (0.02 g, 1% of the dry weight of chitosan) was added to the chitosan solution, and 1.5 g of glycerol was added as a plasticizer, and ultrasonic treatment was performed for 1 h in an ice bath to facilitate uniform dispersion. After sufficient dispersion, the solution was degassed at room temperature for 12 h to obtain a uniform film-forming solution. Finally, the above solution was cast into a film at room temperature by the casting method, and dried at 45°C for 12 h to obtain a chitosan / graphene oxide-thymol composite film.

[0076] Example 3: (1) 1 g of graphite powder was dispersed in 25 mL of concentrated sulfuric acid and placed in an ice bath with continuous stirring at 200 rpm for 0.5 h. After sufficient dispersion, 3 g of potassium permanganate was added to the solution, and ice bath stirring was continued at 400 rpm for 3 h to perform the oxidation of the graphite powder. After sufficient stirring, 150 mL of distilled water was added to dilute the concentrated sulfuric acid, 5 mL of hydrogen peroxide was added to consume the excess potassium permanganate, and ice bath stirring was continued at 600 rpm for 1 h to facilitate the dilution of the concentrated sulfuric acid and the consumption of the excess potassium permanganate. The crude product was obtained by centrifugation (10,000 rpm, 25°C, 10 min) and discarding the supernatant, washed twice with distilled water, and vacuum dried at 90°C for 24 h to obtain the graphene oxide product.

[0077] (2) 0.5 g of graphene oxide powder was dispersed in 500 mL of distilled water, 5 g of calcium chloride powder was added, and ultrasonic treatment was performed at room temperature for 1 h to facilitate uniform dispersion. 5 g of thymol was pre-dissolved in 100 mL of anhydrous ethanol, 5 g of Tween 80 was added, and ultrasonic emulsification was performed for 10 min. Then, the thymol (0.8 g, i.e., 16 mL of thymol ethanol solution was added) dissolved in ethanol was slowly added to the graphene oxide dispersion, and stirring was performed at room temperature for 2 h to allow sufficient mixing. Then, the crude product was obtained by centrifugation (8,000 rpm, 25°C, 10 min) and discarding the supernatant, washed twice with anhydrous ethanol, and vacuum dried at 60°C for 12 h to obtain the graphene oxide-thymol product.

[0078] (3) 2 g of chitosan powder was dissolved in 100 mL of 1% acetic acid aqueous solution, and ultrasonic treatment was performed for 2 h to facilitate complete dissolution. Then, the above graphene oxide-thymol powder (0.04 g, 2% of the dry weight of chitosan) was added to the chitosan solution, and 1.5 g of glycerol was added as a plasticizer, and ultrasonic treatment was performed for 1 h in an ice bath to facilitate uniform dispersion. After sufficient dispersion, the solution was left to stand at room temperature for 12 h to obtain a uniform film-forming solution. Finally, the above solution was cast into a film at room temperature by the casting method, and dried at 45°C for 12 h to obtain a chitosan / graphene oxide-thymol composite film.

[0079] Example 4: (1) 1 g of graphite powder was dispersed in 25 mL of concentrated sulfuric acid and placed in an ice bath with continuous stirring at 200 rpm for 0.5 h. After sufficient dispersion, 3 g of potassium permanganate was added to the solution, and ice bath stirring was continued at 400 rpm for 3 h to perform the oxidation of the graphite powder. After sufficient stirring, 150 mL of distilled water was added to dilute the concentrated sulfuric acid, 5 mL of hydrogen peroxide was added to consume the excess potassium permanganate, and ice bath stirring was continued at 600 rpm for 1 h to facilitate the dilution of the concentrated sulfuric acid and the consumption of the excess potassium permanganate. The crude product was obtained by centrifugation (10,000 rpm, 25°C, 10 min) and discarding the supernatant, washed twice with distilled water, and vacuum dried at 90°C for 24 h to obtain the graphene oxide product.

[0080] (2) 0.5 g of graphene oxide powder was dispersed in 500 mL of distilled water, 5 g of calcium chloride powder was added, and ultrasonic treatment was performed at room temperature for 1 h to facilitate uniform dispersion. 5 g of thymol was pre-dissolved in 100 mL of anhydrous ethanol, 5 g of Tween 80 was added, and ultrasonic emulsification was performed for 10 min. Then, the thymol (0.8 g, i.e., 16 mL of thymol ethanol solution was added) dissolved in ethanol was slowly added to the graphene oxide dispersion, and stirring was performed at room temperature for 2 h to allow sufficient mixing. Then, the crude product was obtained by centrifugation (8,000 rpm, 25°C, 10 min) and discarding the supernatant, washed twice with anhydrous ethanol, and vacuum dried at 60°C for 12 h to obtain the graphene oxide-thymol product.

[0081] (3) 2 g of chitosan powder was dissolved in 100 mL of 1% acetic acid aqueous solution, and ultrasonic treatment was performed for 2 h to facilitate complete dissolution. Then, the above graphene oxide-thymol powder (0.08 g, 4% of the dry weight of chitosan) was added to the chitosan solution, and 1.5 g of glycerol was added as a plasticizer, and ultrasonic treatment was performed for 1 h in an ice bath to facilitate uniform dispersion. After sufficient dispersion, the solution was degassed at room temperature for 12 h to obtain a uniform film-forming solution. Finally, the above solution was cast into a film by the casting method at room temperature, and dried at 45°C for 12 h to obtain a chitosan / graphene oxide-thymol composite film.

[0082] Example 5: (1) 1 g of graphite powder was dispersed in 25 mL of concentrated sulfuric acid, and it was placed in an ice bath and stirred at a speed of 200 rpm for 0.5 h. After being fully dispersed, 3 g of potassium permanganate was added to the solution, and it was stirred in an ice bath at a speed of 400 rpm for 3 h to oxidize the graphite powder. After being fully stirred, 150 mL of distilled water was added to dilute the concentrated sulfuric acid, 5 mL of hydrogen peroxide was added to consume the excess potassium permanganate, and it was continuously stirred in an ice bath at a speed of 600 rpm for 1 h to facilitate the dilution of the concentrated sulfuric acid and the consumption of the excess potassium permanganate. The crude product was obtained by centrifugation (10000 rpm, 25°C, 10 min) and discarding the supernatant, and it was washed twice with distilled water, and then vacuum dried at 90°C for 24 h to obtain the graphene oxide product.

[0083] (2) 0.5 g of graphene oxide powder was dispersed in 500 mL of distilled water, 5 g of calcium chloride powder was added, and it was ultrasonically treated at room temperature for 1 h to facilitate uniform dispersion. 5 g of thymol was pre-dissolved in 100 mL of anhydrous ethanol, 5 g of Tween 80 was added, and it was ultrasonically emulsified for 10 min. Then, the thymol (0.8 g, i.e. 16 mL of thymol ethanol solution) dissolved in ethanol was slowly added to the graphene oxide dispersion, and it was fully mixed by stirring at room temperature for 2 h in the dark. Then, the crude product was obtained by centrifugation (8000 rpm, 25°C, 10 min) and discarding the supernatant, and it was washed twice with anhydrous ethanol, and then vacuum dried at 60°C for 12 h to obtain the graphene oxide-thymol product.

[0084] (3) 2 g of chitosan powder was dissolved in 100 mL of 1% acetic acid aqueous solution, and it was ultrasonically treated for 2 h to facilitate complete dissolution, then the above graphene oxide-thymol powder (0.1 g, accounting for 5% of the dry weight of chitosan) was added to the chitosan solution, and 1.5 g of glycerol was added as a plasticizer, and it was ultrasonically treated in an ice bath for 1 h to facilitate uniform dispersion. After being fully dispersed, it was left to stand at room temperature for 12 h to obtain a uniform film-forming solution. Finally, the above solution was cast into a film by the casting method at room temperature, and it was dried at 45°C for 12 h to obtain a chitosan / graphene oxide-thymol composite film.

[0085] In addition, the inventors of the present case also carried out tests with other raw materials, process operations, process conditions described in the specification, and all obtained relatively ideal results.

[0086] It should be understood that the technical solutions of the present application are not limited to the specific implementation cases described above, and any technical modification made according to the technical solutions of the present application without departing from the purpose of the present application and the scope protected by the claims falls within the protection scope of the present application.

Claims

1. A method for preparing an intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response, characterized in that, The application relates to a graphene oxide-thymol film and a preparation method thereof. The graphene oxide is dispersed in water, then calcium chloride is added and ultrasonic dispersion treatment is carried out at room temperature to form a graphene oxide dispersion liquid. The chitosan is dissolved in an acetic acid aqueous solution, then the graphene oxide-thymol and a plasticizer are added and ultrasonic dispersion treatment is carried out under ice bath conditions, and then standing degassing is carried out to form a film-forming solution. The film-forming solution is subjected to film-forming treatment by using a casting method at room temperature, and then drying treatment is carried out to obtain the intelligent gas packaging film with gas selectivity and pH / humidity dual response.

2. The production method according to claim 1, characterized by, The graphene oxide is dispersed in water, then calcium chloride is added and ultrasonic dispersion treatment is carried out at room temperature to form a graphene oxide dispersion liquid. The mass-volume ratio of the graphene oxide to water is 1g:500mL-1g:2000mL; the mass-volume ratio of the calcium chloride to water is 1g:50mL-1g:200mL; and the ultrasonic dispersion treatment is carried out for 0.5-1h. The thymol is dissolved in ethanol, then an emulsifier is added and ultrasonic emulsification treatment is carried out to form a thymol emulsion.

3. The production method according to claim 1, characterized by, The mass-volume ratio of the thymol to ethanol is 1g:10mL-1g:20mL; the mass ratio of the thymol to the emulsifier is 2:1-1:1; the emulsifier comprises any one or a combination of multiple kinds of Tween 80, Tween 20, Tween 60, sucrose ester and monoglyceride; and the ultrasonic emulsification treatment is carried out for 10-15min. The thymol emulsion is slowly added to the graphene oxide dispersion liquid, and then stirring reaction is carried out at room temperature in the dark for 2-4h, and then centrifugal treatment, washing treatment and vacuum drying treatment are carried out to obtain the graphene oxide-thymol. The mass ratio of the graphene oxide to the thymol is 0.5-1:0.2-1; 4. The production method according to claim 1, characterized by, The centrifugal treatment is carried out at a rotating speed of 8000-10000rpm and a temperature of 20-30 DEG C for 10-15min; The washing treatment comprises washing the centrifuged product with anhydrous ethanol for 2-3 times; The vacuum drying treatment is carried out at a temperature of 60-80 DEG C for 12-24h. The chitosan is dissolved in an acetic acid aqueous solution, then the graphene oxide-thymol and a plasticizer are added and ultrasonic dispersion treatment is carried out under ice bath conditions, and then standing degassing is carried out to form a film-forming solution. The film-forming solution is subjected to film-forming treatment by using a casting method at room temperature, and then drying treatment is carried out to obtain the intelligent gas packaging film with gas selectivity and pH / humidity dual response. The mass ratio of the chitosan to the graphene oxide-thymol is 100:1-5; 5. The preparation method according to claim 1, characterized in that, And / or, the mass-volume ratio of the chitosan to the acetic acid aqueous solution is 1g:50mL-1g:200mL; And / or, the mass-volume ratio of the plasticizer to the film-forming solution is 1-2g:100mL; And / or, the volume concentration of the acetic acid aqueous solution is 1-2%; 6. The method of claim 5, wherein: And / or, the ultrasonic dispersion treatment is carried out for 1-3h; And / or, the standing degassing is carried out at a temperature of 20-30 DEG C for 12-24h; ​ ​ ​ ​ And / or, the temperature of the drying treatment is 40-50℃, and the time is 12-16h. 7.The intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response, which is prepared by the preparation method of any one of claims 1-6. 8.The application of the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response in claim 7 in fruit and vegetable storage and preservation.

9. A method for preserving fruits and vegetables, characterized by, Comprising: sealing and packaging fruits or vegetables by using the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response in claim 7, and storing them; wherein, the environmental temperature of the storage is 20-25℃, and the relative humidity is 70-80 %.

10. A fruit and vegetable storage and preservation material, characterized by comprising: Comprising: the intelligent modified atmosphere packaging film with gas selectivity and pH / humidity dual response in claim 7.

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