Ternary composite intelligent preservative film as well as preparation method and application thereof

Abstract

The invention relates to a ternary composite intelligent preservative film as well as a preparation method and application thereof. The ternary composite intelligent preservative film comprises the following components: chitosan, zinc oxide nanofiber particles and lycium ruthenicum anthocyanin. The water vapor barrier property, the mechanical property and the oxidation resistance of the ternary composite intelligent preservative film prepared by adding ZnO NPs (at) YANF nanoparticles by using young fruit nanofibers extracted from young apples as a carrier for the first time are remarkably improved. The ternary composite intelligent preservative film has the advantages of high sensitivity to pH change and ammonia gas, obvious color change and high response speed, and is suitable for monitoring the freshness of food in real time. The YOLOv11 model is used for carrying out image recognition on the colors of the composite films of the shrimps with different freshness degrees, the accuracy rate reaches 98% or above, the method is suitable for practical application under different backgrounds, and an effective solution is provided for combination of intelligent packaging and artificial intelligence.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of comprehensive utilization of agricultural waste, and particularly relates to a ternary composite intelligent preservative film and a preparation method and application thereof. BACKGROUND

[0002] The rapid evolution of modern food consumption patterns has brought major challenges related to food safety and sustainability. Addressing these challenges requires advances in agricultural productivity, nutrition, and food packaging technologies. Traditional food packaging is mainly used for protection. However, the emergence of intelligent packaging technology can extend the shelf life, improve food safety, and improve quality. Intelligent packaging integrates sensors and indicators, such as biosensors, time-temperature indicators, and gas detectors, to monitor the freshness and quality of food in real time. Biosensors and chemical sensors have completely changed food quality control by monitoring microbial contamination, oxidation, and pH changes in packaged food in real time. By detecting volatile compounds and signs of spoilage, these sensors improve traceability and transparency throughout the supply chain. Intelligent packaging systems, especially those using pH-sensitive dyes and colorimetric sensors, have been shown to be effective in monitoring food freshness, such as ammonia and amines, which can indicate protein degradation. Deep learning combined with metal-organic framework hybrid matrix membranes has been used to measure chicken freshness in real time. By detecting amine gas through deep learning combined with a colorimetric sensor array, the freshness of frozen beef can be quickly and accurately evaluated.

[0003] The development of bio-based smart food packaging and anthocyanin-based pH indicator films have been tested to monitor the freshness of perishable foods such as meat and seafood, showing distinct color changes associated with spoilage. pH indicators play a crucial role in the food supply chain, revealing changes in food quality caused by microbial growth. Chemically synthesized dyes, such as bromocresol green, bromocresol violet, and bromophenol blue, offer advantages such as high stability, low cost, and pH-responsive color changes when integrated into packaging materials to indicate food freshness; however, their inherent toxicity poses health risks and jeopardizes food safety. Therefore, natural pigments are non-toxic, widely used, and environmentally friendly, making them an ideal choice for freshness indicators in smart packaging. Anthocyanin-based pH indicator films typically contain functional groups such as carboxyl, hydroxyl, and amino groups. When exposed to different pH levels, these functional groups ionize or protonate, causing changes in molecular conformation and intermolecular interactions, leading to membrane restructuring and subsequent color changes. For example, the anthocyanins commonly used in these films exist in different ionic forms depending on the pH value. Under acidic conditions, anthocyanins exist primarily as yellow cations, appearing red, while under alkaline conditions, they transform into quinone bases, turning purple or blue. Other natural pigments, such as betaine, curcumin, carotenoids, and chlorophyll, also exhibit pH sensitivity. These smart packaging materials not only provide consumers with visual cues of product freshness but also functionally respond to gas emissions. For example, increased ammonia production may lead to visible color changes indicating spoilage or may release antimicrobial agents to combat spoilage microorganisms. Therefore, pH-sensitive films containing natural pigments can better improve food quality and extend shelf life. Natural anthocyanins, as histamine-sensitive materials, exhibit excellent histamine colorimetric response characteristics due to their unique molecular structure (containing multiple phenolic hydroxyl groups and benzopyran cations). However, the inherent photothermal sensitivity of anthocyanins limits their practical application in smart packaging.

[0004] Chinese patent CN 117586564A discloses an anthocyanin-based smart food preservation film and its preparation method. The smart food preservation film is prepared using starch, polyvinyl alcohol, glycerol, anthocyanin slow-release particles, rosemary extract, and nanocrystalline cellulose. Among them, starch plays the role of the main film-forming agent and anthocyanin slow-release carrier. In order to achieve the purpose of slow-release anthocyanins, it is necessary to construct cross-linked porous starch particles using starch, including (1) using a mixed acid composed of citric acid and acetic anhydride to construct cross-linked starch driven by hydrogen bonding and hydrophobic interaction; (2) using octenyl succinic anhydride to modify cross-linked starch, and further increasing the local hydrophobicity of starch by grafting hydrophobic groups, so that the starch is driven by hydrophobic forces to form spheres in the aqueous dispersion; (3) using the hydrolysis of starch by α-amylase and saccharifying enzyme to create pores on the cross-linked starch spheres to form cross-linked porous starch particles. This patent utilizes starch to construct cross-linked porous starch particles to achieve the purpose of sustained release of anthocyanins. The disadvantage is that only a portion of the anthocyanins can come into contact with substances such as histamine in the atmosphere, resulting in poor response sensitivity and high usage costs.

[0005] On the other hand, apples are one of the most widely grown and consumed fruits in my country. During the period 2-3 weeks after pollination and flowering until the physiological fruit drop period, apples require fruit thinning, resulting in a large number of young apple fruits. In apple-producing areas, a significant amount of young apple fruit waste is generated each growing season, and this waste has not yet been effectively managed. Our team previously discovered that, compared to mature apples, the use of young apple fruit nanofibers cross-linked with chitosan to prepare a preservation film significantly improves the hydrophobicity, mechanical strength, and barrier properties of the chitosan film (see Chinese Patent 202411868647.6). Based on this preservation film, we are developing a ternary composite intelligent preservation film that can monitor food spoilage. This could greatly expand the application scenarios of young apple fruits as agricultural waste, deepen the industrial chain of agricultural product processing in apple-producing areas, and increase the profit margins of local farmers. Summary of the Invention

[0006] To address the above problems, this invention proposes a ternary composite intelligent food preservation film, its preparation method, and its application.

[0007] This invention proposes a ternary composite intelligent food preservation film, the components of which include chitosan, zinc oxide nanofiber particles, and black goji berry anthocyanins.

[0008] Furthermore, the zinc oxide nanofiber particles account for 2.5 wt% of the component mixture of the ternary composite smart food preservation film.

[0009] Furthermore, the black goji berry anthocyanins account for 0.4 wt% of the component mixture of the ternary composite smart preservation film.

[0010] Furthermore, the preparation method of the zinc oxide nanofiber particles is as follows: a 1 wt% aqueous dispersion of nanofibers extracted from young apple fruit and a 0.2 mol / L ZnCl2 solution are mixed at a volume ratio of 2:1, stirred for 2 hours until homogeneous, and then... 2+ : OH - The molar ratio of NaOH to zinc oxide was 1:6, and 1 mol / L NaOH was added. The mixture was stirred for 2 hours. After the reaction was completed, the mixture was filtered and washed once with anhydrous ethanol and twice with deionized water. The washed complex was stored at 4°C for 12 hours to balance the moisture content. Deionized water was added to prepare a suspension with a mass fraction of 0.05 wt%. The suspension was uniformly dispersed using a high-speed homogenizer, filtered, and freeze-dried to obtain the zinc oxide nanofiber particles.

[0011] Furthermore, the method for extracting nanofibers from young apples is as follows: after crushing the young apples, they are added to a 1M sodium hydroxide solution at a weight ratio of 1:5-25 and soaked at room temperature for 10-30 hours for alkaline demethylation. The resulting fruit residue is then washed with water until neutral, and the neutral fruit residue is continuously processed several times using a high-pressure homogenizer. Water is added during the processing to obtain an aqueous dispersion of nanofibers with a diameter of less than 25 nanometers and a mass fraction of 1 wt%.

[0012] Furthermore, the crushed young apples are added to a sodium hydroxide solution at a weight ratio of 1:20 and soaked for 15 hours.

[0013] Furthermore, the young apples referred to are small apples that are removed within 2-3 weeks after pollination and flowering, up to the physiological fruit drop period.

[0014] This invention also provides a method for making a ternary composite smart food preservation film, comprising the following steps:

[0015] Chitosan powder was dissolved in a 1% acetic acid solution at a weight-to-volume ratio of 1:50. Glycerin equivalent to 30 wt% of the dry weight of chitosan was added, along with 2.5 wt% of the zinc oxide nanofiber particles and 0.4 wt% of the black goji berry anthocyanins. After mixing evenly, the mixture was poured into a polystyrene mold, with the height of the mixture not exceeding 2 cm. The mixture was allowed to stand for 24 hours to remove air bubbles, and then dried at 35°C for 12 hours to obtain the ternary composite intelligent food preservation film.

[0016] Furthermore, the thickness of the ternary composite smart food preservation film is 20±5μm.

[0017] The ternary composite intelligent preservation film provided by this invention is used for food preservation and monitoring whether food has spoiled.

[0018] The beneficial effects of this invention are as follows:

[0019] 1. For the first time, zinc oxide nanofiber particles (ZnO NPs@YANF) were synthesized using lignocellulose nanofibers (YANF) extracted from young apple fruits. These particles were then used as electrostatic crosslinking agents and anthocyanin stabilizers to enhance the histamine response properties of a black goji berry anthocyanin chitosan preservation film (C-BW). This invention utilizes young apple fruit nanofibers extracted as a carrier to successfully prepare ZnO NPs@YANF nanoparticles via biosynthesis. The addition of ZnO NPs@YANF nanoparticles significantly improved the water vapor barrier properties, mechanical properties, and antioxidant properties of the ternary composite smart preservation film. Specifically, tensile strength and elongation at break increased by 99.76% and 45.49%, respectively, antioxidant properties increased by 161.72%, and water vapor barrier properties decreased by 25.30%. This ternary composite smart preservation film exhibited good color stability after 21 days of storage at 4℃, with a ΔE value of only 5.66±0.44. This ternary composite smart preservation film exhibits high sensitivity to pH changes and ammonia levels, with noticeable color changes and a fast response speed, making it suitable for real-time monitoring of food freshness. Using the YOLOv11 model, image recognition of the composite film color for shrimp at different freshness levels was achieved with an accuracy rate exceeding 98%, making it suitable for practical applications under various backgrounds and providing an effective solution for combining smart packaging with artificial intelligence.

[0020] 2. In this invention, the nanofibers prepared from young apple fruit are rich in COO- pectin components, which can form a preservative film with chitosan rich in -NH4+ through electrostatic cross-linking, thereby overcoming the high water permeability of chitosan films. Simultaneously, zinc oxide nanofiber particles can stabilize the catechin groups of anthocyanins in black goji berry anthocyanins through coordination, reducing their oxidation / photodegradation rate. This allows for more thorough contact between anthocyanins and substances such as histamine in the atmosphere, resulting in more sensitive color development.

[0021] 3. In this invention, zinc oxide nanofiber particles have multiple functions, including acting as an electrostatic crosslinking agent to enhance the hydrophobicity of chitosan membranes and acting as an antibacterial active center to increase the antibacterial properties of chitosan membranes, thus significantly extending the shelf life of food. Attached Figure Description

[0022] Figure 1 These are comparative images of the appearance of the four composite films in Example 2;

[0023] Figure 2 Comparative microstructures of the four composite films in Example 2;

[0024] Figure 3 The following are FTIR curves of the infrared spectra of the four composite films in Example 2;

[0025] Figure 4The images show the X-ray diffraction patterns of the four composite films in Example 2. Figure 5 The water contact angles of the four composite membranes in Example 4; Figure 6 The water vapor permeability of the four composite membranes in Example 5; Figure 7 The tensile strength and elongation at break of the four composite films in Example 6 are shown. Figure 8 The DPPH free radical scavenging rate of the four composite membranes in Example 7; Figure 9 These are surface photographs of the C-ZnO NPs@YANF-BW membrane from Example 8 under different pH conditions. Figure 10 The ΔE values ​​of the C-BW membrane and C-ZnO NPs@YANF-BW membrane in Example 8 under different pH conditions; Figure 11 The color changes of BW solution under different pH conditions in Example 8; Figure 12 The sensitivity of the C-BW membrane and C-ZnO NPs@YANF-BW membrane in Example 9 to volatile nitrogen compounds; Figure 13 The duration of exposure and color change of the C-BW membrane and C-ZnO NPs@YANF-BW membrane in Example 9 to ammonia vapor; Figure 14 The appearance changes of shrimp packaged with different composite film groups in Example 10 during storage; Figure 15 This is Example 10, showing the pH changes of shrimp packaged with different composite film groups at 4°C. Figure 16 Example 10 shows the changes in total bacterial count of shrimp packaged with different composite film groups at 4°C; Figure 17 The changes in volatile basic nitrogen of shrimp packaged with different composite film groups at 4°C are shown in Example 10. Figure 18 The changes in lipid oxidation levels of shrimp packaged with different composite film groups at 4°C are shown in Example 10. Detailed Implementation

[0026] The present invention will be further described below with reference to the embodiments.

[0027] Experimental materials:

[0028] Young apples were supplied by GreenTech Food Co., Ltd. (Hebei, China). Chitosan (degree of deacetylation: 90%, molecular weight: approx. 91 kDa) was purchased from Lanji Technology Development Co., Ltd. (Shanghai, China). Black goji berries were sourced from Xinjiang Black Goji Berry Biotechnology Co., Ltd., and shrimp were purchased from CR Vanguard Supermarket in Chang'an District, Xi'an. Spectroscopic grade potassium bromide was purchased from Aladdin (Shanghai, China). Unless otherwise specified, all reagents mentioned were analytical grade, purchased from Aladdin (Shanghai, China) Co., Ltd., and distilled water was used throughout the process.

[0029] Example 1: Preparation of four different components of food preservation film:

[0030] The steps are as follows:

[0031] 1.1 Preparation of YANF nanofibers from immature apple fruit:

[0032] Ten grams of dried young apple fruit were added to a 1M sodium hydroxide solution at a weight ratio of 1:20 and soaked at 25°C for 15 hours for alkaline demethylation. The resulting pomace was then washed with water until neutral and processed three times consecutively at 800 bar using a high-pressure homogenizer (JN-Mini Pro, Guangzhou Juneng Nanobiotechnology Co., Ltd., China). Water was added during the processing to obtain an aqueous dispersion of nanofibers with a diameter of less than 25 nanometers and a mass fraction of 1 wt%.

[0033] 1.2 Preparation of zinc oxide nanofiber particles (ZnO NPs@YANF):

[0034] The nanofiber aqueous dispersion extracted from young apple fruit was mixed with a 1 wt% ZnCl2 solution at a 2:1 volume ratio, and stirred for 2 hours until homogeneous. Then, according to the Zn... 2+ : OH - The molar ratio of 1:6 was 1 mol / L NaOH added, and the mixture was stirred for 2 h. After the reaction was completed, the mixture was filtered and washed once with anhydrous ethanol and twice with deionized water. The washed complex was stored at 4 °C for 12 h to balance the moisture content. Deionized water was added to prepare a suspension with a mass fraction of 0.05 wt%. The suspension was uniformly dispersed using a high-speed homogenizer, filtered, and freeze-dried to obtain the zinc oxide nanofiber particles (ZnO NPs@YANF).

[0035] 1.3 Preparation of chitosan / ZnO NPs@YANF / black goji berry anthocyanins ternary composite intelligent food preservation film:

[0036] A chitosan / ZnO NPs@YANF nanoparticles / black goji berry anthocyanins ternary composite smart preservation film (C-ZnO NPs@YANF-BW) was prepared by a casting method. 2g of chitosan powder was dissolved in 100mL of 1% acetic acid solution. Glycerin, equivalent to 30wt% of the dry weight of the chitosan, was added, along with 2.5wt% of the zinc oxide nanofiber particles (ZnO NPs@YANF) and 0.4wt% of black goji berry anthocyanins. After thorough mixing, the mixture was poured into a 9cm diameter polystyrene petri dish, with the height of the mixture not exceeding 2cm. The mixture was allowed to stand for 24 hours to remove air bubbles, and then dried at 35℃ for 12 hours to obtain the ternary composite smart preservation film. The ternary composite smart preservation film was stored in a desiccator with a saturated Mg(NO3)2 solution at a relative humidity of 53% for 48 hours before being used for further experiments.

[0037] 1.4 Using the method in 1.3, different composite preservation films (composite films) were prepared using different components as raw materials. Among them, the film without zinc oxide nanofiber particles (ZnO NPs@YANF) and black goji berry anthocyanins was a pure chitosan film, labeled CF; the film containing chitosan and black goji berry anthocyanins was a chitosan-black goji berry anthocyanin film, labeled C-BW; the film containing chitosan, apple young fruit nanofibers, and black goji berry anthocyanins was a chitosan-apple young fruit nanofiber-black goji berry anthocyanin film, labeled C-YANF-BW; and the film containing chitosan, zinc oxide nanofiber particles, and black goji berry anthocyanins was a chitosan-zinc oxide nanofiber particles-black goji berry anthocyanin film, labeled C-ZnO NPs@YANF-BW.

[0038] Example 2: Comparison of detection methods for characterizing four membrane structures:

[0039] 2.1 Measurement of color value and morphology:

[0040] The colors of four composite films were determined using a 3nh NS808 spectrophotometer, such as... Figure 1 As shown, the chitosan membrane CF is transparent. The addition of black goji berry anthocyanins in C-BW alters the apparent color of the chitosan membrane, giving it a unique bluish-green hue. C-YANF-BW and C-ZnO NPs@YANF-BW also exhibit a bluish-green hue due to the addition of black goji berry anthocyanins.

[0041] Table 1 shows the surface color data of CF, C-BW, C-YANF-BW, and C-ZnO NPs@YANF-BW. CF exhibits high surface brightness, with an L* value greater than 80. Upon addition of BW, the color changes significantly: brightness decreases significantly (L* value decreases significantly), while green and blue increase significantly (a* value decreases significantly, b* value increases significantly), resulting in a significantly increased total color difference (ΔE), and the composite film exhibits a bluish-green hue. In C-YANF-BW, due to the addition of YANF, red and yellow increase significantly (a* value increases significantly, b* value decreases significantly), and compared to C-BW, its color leans more towards brown, but remains predominantly blue. Compared to C-BW, the addition of ZnO NPs@YANF further significantly reduces brightness, significantly increases b* value, and significantly enhances the blue color of the composite film.

[0042]

[0043] The surface morphology of the four composite films prepared in Example 1 was observed using an environmental scanning electron microscope. Figure 2 The microstructure of the composite membrane was revealed. Compared to CF, C-BW exhibited serrated wrinkles in its cross-section, while C-YANF-BW showed both white spots and serrated wrinkles. Notably, the cross-section of C-ZnO NPs@YANF-BW displayed a denser amorphous structure. This dense structure not only significantly improved the mechanical and barrier properties of the composite membrane but also effectively delayed the diffusion of water vapor and air, thereby enhancing the membrane's stability and lifespan. Furthermore, the surface roughness of the C-ZnO NPs@YANF-BW membrane increased, likely due to the increased surface area after the addition of ZnO NPs@YANF. However, compared to C-YANF-BW, the C-ZnO NPs@YANF-BW membrane surface was denser, free of cracks or pores. This is mainly because black goji berry anthocyanins formed a more compact structure with chitosan and ZnO NPs@YANF through electrostatic interactions and hydrogen bonds. Meanwhile, ZnO NPs@YANF can be uniformly distributed in the chitosan matrix at low density, further optimizing the overall performance of the composite membrane. Further observation revealed that the surface of the C-ZnO NPs@YANF-BW composite membrane was dense and smooth, with no obvious phase separation. This indicates that black goji berry anthocyanins, chitosan, and ZnO NPs@YANF have good biocompatibility and interaction, forming a unified and stable whole.

[0044] 2.2 Infrared Measurement:

[0045] The four composite films described above were cut into 2cm × 2cm pieces and detected using Fourier transform infrared spectroscopy in total reflectance mode. The resolution was 4cm. -1 Between 4000 and 400 cm-1 The interaction between BW powder, ZnO NPs@YANF and chitosan in the composite film was analyzed in depth by scanning within the range.

[0046] like Figure 3 As shown in the FTIR curves, in CF, characteristic peaks appear at 3000–3400 cm⁻¹ (-OH and -NH₂ stretching vibrations), 1633 cm⁻¹ (amide-IC=O stretching), 1540 cm⁻¹ (amide-II NH bending), and 1254 cm⁻¹ (amide-III C-N absorption band). The FTIR spectrum of BW powder shows characteristic absorption peaks at 1625 cm⁻¹ and 1027 cm⁻¹, corresponding to the C-C stretching vibration of aromatic compounds and the deformation vibration of phenolic hydroxyl groups (C-OH), respectively. When BW is added to CF, the amide II peak shifts from 1540 cm⁻¹ to 1545 cm⁻¹, mainly due to the formation of intramolecular hydrogen bonds between BW and -NH₂ in chitosan through hydrogen bonding. Simultaneously, the peaks at 3000–3400 cm⁻¹ (-OH and -NH₂ stretching vibrations) indicate a significant enhancement of hydrogen bonding. Upon further addition of ZnO NPs@YANF, the amide II peak shifted from 1540 cm⁻¹ to 1557 cm⁻¹, indicating that the hydrogen bonding between BW, ZnO NPs@YANF, and chitosan's -NH₂ groups was further enhanced. The characteristic absorption peak of BW gradually weakened and eventually disappeared in the composite film, without the appearance of any new characteristic peaks. This strongly demonstrates that physical entanglement and non-covalent interactions (hydrogen bonding, electrostatic interactions) are the main mechanisms of interaction between the reinforcing agents (BW, YANF, ZnO NPs@YANF) and chitosan, and are also key factors in the significant improvement of the composite film's performance.

[0047] 2.3 X-ray diffraction (XRD) analysis

[0048] The crystal structures of four composite films were tested using an X-ray diffraction instrument. The test conditions were: scanning range of 2θ = 10-35°, scanning speed of 5° / min, and voltage and current of the radiation tube of 40 kV and 100 mA.

[0049] like Figure 4As shown, the C-BW film exhibits a characteristic diffraction peak at 2θ = 21.18°, which may be due to the cross-linking structure formed between BW and chitosan through hydrogen bonding or electrostatic interactions. Further introduction of ZnO NPs@YANF significantly enhanced the intensity of this diffraction peak, resulting in a significant increase in the crystallinity of the C-ZnO NPs@YANF-BW film, with new characteristic peaks appearing at 2θ = 7.77°, 13.18°, and 20.87°. This enhancement is likely due to the ZnO NPs@YANF particles acting as nucleation sites, promoting the ordered arrangement of chitosan molecular chains, while the interactions between the two through hydrogen bonding or coordination bonds further enhance the crystallinity of chitosan. Furthermore, diffraction peaks observed at 2θ = 31.37°, 34.32°, and 36.32° confirm the successful loading of ZnONPs@YANF into the C-BW composite film.

[0050] Example 3: Determination of color stability of four composite films:

[0051] Intelligent composite food preservation film achieves visual monitoring of food freshness through changes in packaging color. The high color stability of intelligent composite food preservation film ensures the authenticity and accuracy of the detection.

[0052] To evaluate the color stability of the C-BW and C-ZnO NPs@YANF-BW composite films, they were stored at 4°C for 21 days, and the results are shown in Table 2. After 21 days of storage, C-ZnO NPs@YANF-BW exhibited the best color stability, with a ΔE value of only 5.66±0.44; C-BW showed the worst stability, with a ΔE value of 17.84±0.28. Therefore, C-ZnO NPs@YANF-BW demonstrates stable color and a relatively long indication shelf life.

[0053]

[0054] Example 4: Determination of the hydrophobicity of four composite membranes:

[0055] The water content, solubility, swelling degree, water contact angle and hydrophobicity of composite membranes are closely related.

[0056] Cut the composite membrane into 2cm × 2cm pieces, dry to constant weight (M1), place in a beaker containing 50mL of distilled water, seal with plastic wrap, and place at 25℃ for 24 hours. Remove the membrane, wipe off the surface moisture, and dry to constant weight (M2). The solubility of the membrane is calculated using the following formula: Composite membrane solubility = (M1 - M2) / M1 × 100%.

[0057] Cut the composite membrane into 2cm × 2cm pieces, weigh them (M1), place them in a beaker containing 50 mL of distilled water, seal with plastic wrap, and place at 25℃ for 24 hours. Remove the membrane, wipe off the surface moisture, and weigh it (M2). The swelling degree of the membrane is calculated using the following formula: Composite membrane swelling degree = (M2 - M1) / M1 × 100%.

[0058] In an indoor environment at 25°C, 2 μL of deionized water was dropped onto the composite membrane, and the water contact angle was measured using a contact angle meter.

[0059] Table 3 shows the film thickness and density of CF, C-BW, C-YANF-BW, and C-ZnO NPs@YANF-BW. The thickness (0.098±0.01 mm) and density (0.124±0.001 g•cm³) of CF and C-BW are also shown. -3 and 0.127±0.002g•cm -3 There was no significant difference. However, the thickness of the composite membrane increased significantly after the addition of YANF and ZnO NPs@YANF. This is because YANF and ZnO NPs@YANF reduce the porosity between chitosan molecules through electrostatic crosslinking and hydrogen bonding, making the chitosan molecules more tightly packed and the membrane structure more compact.

[0060] Table 3 also shows the water content, solubility, and swelling degree of CF, C-BW, C-YANF-BW, and C-ZnO NPs@YANF-BW. Membranes with stronger hydrophobicity exhibit lower solubility and swelling degree, which helps the composite membrane maintain strong physical integrity when preserving high-moisture foods. CF's relatively weak hydrophobicity limits its commercial application. C-ZnO NPs@YANF-BW has stronger hydrophobicity and is suitable for commercial applications.

[0061]

[0062] Figure 5 The water contact angles of four composite membranes are shown in Table 3. Figure 5It is evident that chitosan molecules contain a large number of hydrophilic groups (-OH and -NH2) and have a porous structure, readily binding with water molecules and exhibiting strong hydrophilicity. This results in high water content, solubility, and swelling degree of CF (29.29%, 29.05%, and 529.07%, respectively). For C-BW, the addition of BW significantly reduced the water content, solubility, and swelling degree of the composite membrane to 26.58%, 26.94%, and 104.07%, respectively, while increasing the water contact angle to 71.9°. This is mainly due to the electrostatic and hydrogen bonding interactions between BW and chitosan, which reduced the free volume within the membrane, enhanced the structural stability of the composite membrane, and reduced the space for water molecules to enter the membrane, consistent with X-ray diffraction results. Furthermore, the FTIR spectrum of BW showed a characteristic absorption peak at 1625 cm⁻¹, corresponding to the C / C stretching vibration of aromatic compounds. The addition of the hydrophobic aromatic ring of black goji berry anthocyanins reduces the hydrophilicity and increases the hydrophobicity of the membrane. Similarly, adding anthocyanins from red cabbage, black soybean seed coat, and saffron can also increase the contact angle and hydrophobicity of the composite membrane. After adding YANF to C-BW, due to strong electrostatic cross-linking, the membrane's water content, solubility, and swelling degree further decreased to 21.43%, 20.80%, and 64.08%, respectively, while the water contact angle increased to 81.3°. The -COO⁻ and -OH or -NH₂ groups of YANF enhance the network structure through electrostatic cross-linking and hydrogen bonding, thereby increasing the hydrophobicity of the composite membrane. Further addition of ZnO NPs@YANF to C-BW reduced the composite membrane's water content, solubility, and swelling degree, while increasing the water contact angle. This is mainly because the addition of ZnONPs@YANF creates a denser network structure in the composite membrane. Electrostatic and hydrogen bonding crosslinks with chitosan's -OH or -NH2 groups prevent the binding of hydrophilic groups and water molecules, increasing the membrane's hydrophobicity. Simultaneously, density has an inverse effect on the water absorption and swelling behavior of the porous structure. The composite membrane density increases with the addition of BW and ZnO NPs@YANF, thereby reducing the swelling ratio of the composite membrane. Furthermore, increased crystallinity also enhances the cohesiveness of the composite membrane, preventing water molecules from entering the membrane interior and further strengthening its hydrophobicity. Therefore, among the four composite membranes tested, C-ZnO NPs@YANF-BW exhibits the strongest hydrophobicity.

[0063] Example 5: Measurement of water vapor permeability (WVP) of four composite membranes:

[0064] Cut the membrane into 6cm x 6cm squares and seal them in a special aluminum cup (inner diameter: 6cm, outer diameter: 9cm, exposed area: 28.27cm², depth: 1.3cm) containing dry, anhydrous CaCl₂. Place the cups in a desiccator containing distilled water at room temperature and weigh them every 2 hours. Calculate WVP using the following equation:

[0065] WVP=(Δm×d) / (A×t×P);

[0066] Wherein, WVP—water vapor permeability (gm) -1 s -1 Pa -1 );

[0067] Δm — Increase in mass of the test cup (g);

[0068] t — infiltration time (s);

[0069] A – Exposed area of ​​the membrane (m²) 2 );

[0070] d — membrane thickness (m);

[0071] P—The saturated vapor pressure of water at 25℃ (Pa).

[0072] In the food packaging industry, effectively reducing the rate at which water vapor migrates from the external atmosphere into the packaging is one of the key indicators for evaluating the performance of food packaging materials. Water vapor permeability (WVP), as an important parameter of edible films, directly affects the shelf life and quality stability of food. However, excessively high WVP can also hinder the application of edible films in food packaging. Figure 6 The WVP of CF, C-BW, C-YANF-BW, and C-ZnO NPs@YANF-BW were demonstrated. The WVP values ​​of the four composite films prepared in Example 1 ranged from 0.617 to 0.826 ng•m⁻¹s⁻¹Pa⁻¹, which is significantly higher than the WVP value of commercially available polyethylene (PE) (approximately 2.30 × 10⁻¹). 7The high WVP value is mainly attributed to the properties of chitosan. However, with the addition of BW, YANF, and ZnONPs@YANF, the WVP value decreased significantly. Compared with CF, the WVP of C-BW decreased by 10.17%. This decrease can be attributed to the following factors: First, the interaction between black goji berry anthocyanins and chitosan molecules, such as hydrogen bonds, increases the crystallinity of the membrane and makes the structure more compact, thereby enhancing the water vapor barrier performance; second, the addition of black goji berry anthocyanins makes the microstructure of the chitosan membrane more compact, effectively reducing the channels for water vapor permeation and further improving the barrier effect; in addition, black goji berry anthocyanins contain hydrophobic aromatic compound groups, which increase the hydrophobicity of the membrane and reduce the adsorption and permeation capacity of water vapor. When ZnONPs@YANF is introduced into the composite membrane, the WVP decreases by 25.30% compared with CF. ZnO NPs@YANF fills the pores of the chitosan membrane through electrostatic crosslinking and hydrogen bonding, not only reducing the channels for water vapor permeation and enhancing the membrane's density, but also increasing the path length for water vapor molecules to pass through the membrane, thus significantly improving its barrier properties. Simultaneously, ZnO NPs@YANF promotes the ordered arrangement of chitosan molecules, increasing the membrane's crystallinity, which further reduces water vapor permeation. Furthermore, ZnO NPs@YANF itself possesses a certain degree of hydrophobicity, and its addition enhances the membrane's hydrophobic properties, thereby reducing water vapor adsorption and permeation.

[0073] Example 6: Tensile property test of composite film:

[0074] Tensile strength and elongation at break are important indicators for evaluating the mechanical properties of membrane materials. Tensile strength reflects the tensile strength of the membrane material, while elongation at break reflects its ductility and flexibility. Following the national standard GB / T13022-1991, a universal testing machine was used to test the tensile properties of composite membranes. Test samples were cut into strips of 10 mm × 60 mm, with an initial distance of 50 mm between the clamps, and a tensile speed of 1 mm / s. Five samples were tested in each group of experiments.

[0075] Figure 7The tensile strength and elongation at break of CF, C-BW, C-YANF-BW, and C-ZnO NPs@YANF-BW were displayed. The study found that, compared with CF, the tensile strength of the C-BW composite film significantly increased from 12.52±0.25 MPa to 16.07±0.32 MPa after the addition of BW, while the elongation at break increased by 71.15%. This indicates that BW enhances the cross-linking between chitosan molecules through hydrogen bonding and electrostatic cross-linking, thereby improving the mechanical strength of the film. Simultaneously, the uniform dispersion of BW in the chitosan matrix makes the film structure more compact, further enhancing the tensile strength. Further analysis revealed that, after the addition of YANF, the tensile strength and elongation at break of C-YANF-BW significantly increased by 87.76% and 99.29%, respectively, compared to CF. This indicates that YANF and BW, as plasticizers, effectively improve the flexibility of the chitosan film. When ZnO NPs@YANF were added, compared with CF, the tensile strength and elongation at break increased by 99.76% and 45.49%, respectively, reaching 25.01±0.74 MPa and 23.38±0.89%. This is because of the -OH and -COO groups on the surface of ZnO NPs@YANF. - The addition of ZnO NPs@YANF enhances intermolecular crosslinking through electrostatic crosslinking and hydrogen bonding with the -NH2 group in chitosan molecules, resulting in a denser membrane structure and improved mechanical strength. Furthermore, the addition of ZnO NPs@YANF promotes the regular arrangement of chitosan molecular chains, increases membrane crystallinity, and further enhances tensile strength, consistent with XRD results. However, compared to C-BW, the elongation at break decreased by 16.79% after the addition of ZnO NPs@YANF. This may be because the addition of ZnO NPs@YANF enhances intermolecular crosslinking, restricting the movement of chitosan molecular chains, reducing the flexibility of the composite membrane, and making it more rigid. Consequently, it is less prone to significant deformation under stress, leading to a decrease in elongation at break.

[0076] Example 7: Determination of the antioxidant properties of the composite membrane:

[0077] Mix 0.5 mL of the component mixture (membrane solution) prepared in 1.3 of Example 1 with 4.5 mL of DPPH methanol solution (0.025 mg / mL), shake well, and let stand in the dark for 30 min (room temperature). Measure the absorbance of the mixture at 517 nm. The clearance rate is calculated using the following formula:

[0078] DPPH radical scavenging rate = 1 - (Ai - Aj) / A0;

[0079] Where: Ai—absorbance of the mixture of DPPH methanol solution and membrane solution;

[0080] Aj — Absorbance of the mixture of methanol solution and membrane solution;

[0081] A0 – Absorbance of DPPH methanol solution.

[0082] DPPH free radicals possess an unpaired electron and exhibit a strong absorption peak at 517 nm. When anthocyanins react with DPPH free radicals, they can donate hydrogen atoms to neutralize the DPPH free radicals, causing the color to change from deep purple to light yellow or colorless. Figure 8 As shown, the DPPH radical scavenging rate of the CF solution was 26.54±1.34%. When BW was added to CF, the antioxidant performance of the system was significantly improved (p<0.05), with the DPPH scavenging rates of C-BW and C-YANF-BW reaching 46.31±2.19% and 44.25±2.36%, respectively, with no significant difference between the two. This is mainly due to the phenolic hydroxyl groups in the BW molecule providing hydrogen atoms to directly scavenge free radicals, thus exhibiting strong antioxidant properties. Furthermore, when ZnONPs@YANF was added, the antioxidant performance of the composite membrane was significantly improved by 69.46±1.71%. This significant improvement can be attributed to the active sites on the surface of ZnO NPs, which can effectively capture DPPH free radicals, thereby inhibiting the oxidation reaction. In addition, Zn²⁺ itself has a certain reducing ability and can directly react with DPPH free radicals, further inhibiting the oxidation process. Meanwhile, YANF, due to its large specific surface area, can provide more active sites to react with free radicals. In summary, the free radical scavenging ability of the composite membrane is significantly enhanced through the synergistic effect of chitosan, ZnO NPs@YANF, and anthocyanins.

[0083] Example 8: pH response analysis of the composite membrane:

[0084] C-BW and C-ZnO NPs@YANF-BW membranes were cut into 2 cm × 2 cm pieces and immersed in a buffer solution with a pH range of 3-9 for 5 minutes. Color changes were recorded using a colorimeter, and the total color difference (ΔE) was calculated.

[0085] Surface images of C-ZnO NPs@YANF-BW membranes under different pH conditions (pH=3-9) are shown below. Figure 9 As shown. The ΔE values ​​of the C-BW membrane and the C-ZnO NPs@YANF-BW membrane (based on the color parameters of the composite membrane at pH=7) are as follows. Figure 10 As shown, the color of the composite membrane changes significantly under different pH conditions. The colors of both membranes change from pink at pH=3, purple at pH=4-5, to cyan and green at neutral and higher pH levels. The color changes of the C-BW and C-ZnO NPs@YANF-BW membranes with pH are consistent with the color changes of the BW solution.Figure 11 This is mainly related to the structure of BW: under low pH conditions, anthocyanins mainly exist in the form of red flavonoid cations, which are red; when the pH rises to neutral, the red flavonoid cations lose protons and are transformed into colorless methanol pseudobase (hemiacetal form), and the color gradually becomes lighter; when the pH rises further to alkaline, the colorless methanol pseudobase opens the ring to form a yellow chalcone structure, and the color turns yellow.

[0086] Table 4 shows the L*, a*, and b* color parameter values ​​in CIELab* mode and the ΔE values ​​for C-BW and C-ZnO NPs@YANF-BW. Brightness (L*) did not change significantly at different pH values. The highest a* values ​​were observed for both membranes at pH=3, while the highest b* values ​​were observed at pH=9. Notably, ΔE values ​​exceeding 5 were considered significant. The ΔE values ​​obtained in this study indicate a significant color change in both membranes. The ΔE values ​​increased with increasing pH. Under acidic conditions, the membranes exhibited a redder color, indicated by higher positive a* values. At alkaline pH values, the a* values ​​tended to be negative, indicating a greener color. Between pH values ​​of 3 and 9, the red color (a* value) of C-BW and C-ZnO NPs@YANF-BW decreased from 29.85±1.47 and 27.78±0.68 (pH=3) to -15.79±0.40 and -10.64±0.36 (pH=9), indicating an increase in greenness under alkaline conditions. The b* value (blue / yellow) shows that the blue color of the composite membrane increases with increasing pH until neutral, then the yellowness increases significantly under alkaline conditions.

[0087]

[0088] Example 9: Volatile nitrogen compound response test of composite membrane:

[0089] Ammonia is a typical volatile alkaline gas produced during the spoilage of aquatic products. The response of C-BW and C-ZnONPs@YANF-BW composite membranes to volatile nitrogen compounds was tested using ammonia vapor. The composite membranes were exposed to 15 mM ammonia vapor for 60 minutes, and color changes were observed at 0, 5, 10, 20, 30, and 60 minutes. The R, G, and B values ​​of the composite membranes were extracted using Photoshop, and the sensitivity (S) was calculated according to the following formula:

[0090] S=((R0-R1 )+(G0-G1 )+(B0-B1)) / (R0+G0+B0 );

[0091] Where: S—color sensitivity of the composite film;

[0092] R0, G0, B0 — Initial red, green, and blue values ​​of the composite membrane;

[0093] R1, G1, B1 — the final red, green, and blue values ​​of the composite membrane.

[0094] The results of the composite membrane's response sensitivity to volatile nitrogen compounds are shown in the figure. Figure 12 The sensitivity of the C-ZnO NPs@YANF-BW membrane is significantly higher than that of the C-BW membrane.

[0095] After the composite membranes were exposed to 15 mM ammonia vapor for 60 minutes, the C-BW and C-ZnO NPs@YANF-BW membranes changed from cyan to green and finally to yellow. Figure 13 The color change corresponds to the composite membrane being exposed to ammonia vapor for an increasingly longer period of time, during which the ammonia vapor hydrates and hydrolyzes into NH4⁺, resulting in increasingly stronger alkaline conditions.

[0096] Example 10: Study on the preservation effect and spoilage monitoring effect of composite membrane on shrimp:

[0097] Fresh shrimp were packaged in C-BW membrane and C-ZnO NPs@YANF-BW membrane respectively and placed in petri dishes in a refrigerator at 4°C. The analysis was performed regularly on days 0, 1, 3 and 5. A blank control group (CK) without any plastic wrap was also prepared.

[0098] 10.1 Changes in the appearance of shrimp:

[0099] Product appearance is the most direct factor influencing consumers' purchasing desires and consumption behavior. Figure 14 The changes in shrimp appearance during storage were observed. In the CK group (control group), the shrimp heads first showed signs of blackening with prolonged storage, and the degree of spoilage gradually worsened. By the third day of storage, the heads and tails of the shrimp in this group had turned noticeably red, and the entire shrimp body had turned black, accompanied by an abnormal odor. By the fifth day, the shrimp had completely lost their fresh appearance and showed severe spoilage. In contrast, the shrimp in the C-BW group only showed signs of gradual blackening of the shrimp heads during storage, without any other obvious signs of spoilage. The shrimp in the C-ZnO NPs@YANF-BW group showed only a slight darkening of the overall color, without significant spoilage characteristics such as blackening, reddening, or an off-odor, indicating better preservation of freshness.

[0100] 10.2 pH changes in shrimp:

[0101] Add 25 mL of deionized water to 5 g of shrimp meat and homogenize. Measure the pH of the resulting liquid using a pH meter at 25°C.

[0102] Figure 15This study demonstrates the pH changes of shrimp packaged in three groups (control group, CK, chitosan-black goji berry anthocyanin membrane, C-BW, and chitosan / ZnO NPs@YANF / black goji berry anthocyanin membrane, C-ZnO NPs@YANF-BW) at 4°C. Shrimp and other aquatic products are considered inedible when the pH exceeds 7.7. The initial pH of the shrimp was 7.05 ± 0.03. During the 5-day storage period, the overall pH of the shrimp showed an upward trend. This is due to the deamination or decarboxylation of proteins in the shrimp under the action of enzymes and microorganisms, producing alkaline substances such as ammonia, trimethylamine, or histamine, leading to an increase in pH. During storage, the pH of the C-ZnO NPs@YANF group was significantly lower than that of the CF and CK groups (p < 0.05). This is mainly attributed to the inhibitory effect of ZnO NPs@YANF on microbial growth, limiting the production of alkaline compounds from protein decomposition by microorganisms, thereby delaying the spoilage and deterioration of the shrimp.

[0103] 10.3 Changes in total bacterial count (TVC) of shrimp:

[0104] Add 45 mL of sterile water to 5 g of shrimp meat, homogenize, and then dilute 10-fold with sterile water. Place 1 mL of the bacterial solution into a sterile petri dish (1 mL of sterile water was used as a control), incubate at 37°C for 24 hours, and count the colonies. The results are expressed as log CFU / g.

[0105] Seafood is prone to spoilage due to bacterial growth during storage. According to the TVC (Total Volatile Crude Oil) standard, Grade 1 fresh shrimp has a TVC ≤ 5.01 log CFU / g, and Grade 2 fresh shrimp has a TVC between 5.0 log CFU / g and 5.7 log CFU / g. When the TVC exceeds 6.0 log CFU / g, the shrimp is completely spoiled and should not be eaten. Figure 16The TVC changes of shrimp in each group at 4℃ are shown. The initial TVC of the shrimp was 3.62±0.06 log CFU / g. On day 1, the TVC of all three groups decreased slightly, possibly because the low temperature inhibited microbial growth. As time went on, bacteria grew and multiplied rapidly. On day 3, the TVC of the CK group reached 5.85±0.04 log CFU / g, indicating a significant decrease in shrimp freshness; the TVC of the CF group was 5.38±0.05 log CFU / g; and the TVC of the C-ZnO NPs@YANF-BW group was 4.51±0.08 log CFU / g. On day 5, the TVC of the CK group was 6.43±0.05 log CFU / g, and the shrimp was inedible; while the TVC of the C-ZnONPs@YANF-BW group was 5.58±0.03 log CFU / g, indicating that ZnO NPs@YANF effectively delayed the spoilage of the shrimp, extending the shelf life by 2 days. In summary, ZnO NPs@YANF has antibacterial properties, which helps maintain food freshness and extend the shelf life of shrimp, thus possessing good commercial value.

[0106] 10.4 Changes in volatile basic nitrogen (TVB-N) in shrimp:

[0107] Add 25 mL of deionized water to shrimp meat (5 g) and homogenize. After the homogenate has stood for 30 minutes, filter it. Titrate the filtrate with HCl and determine the volatile basic nitrogen (TVB-N).

[0108] Shrimp is rich in protein, but it is easily decomposed by microorganisms or enzymes during storage, producing volatile amine gases such as ammonia, dimethylamine, and trimethylamine, leading to an increase in TVB-N content. TVB-N value is one of the important indicators for assessing the degree of spoilage of aquatic products. According to the national standard GB 2733-2015 and related research, when the TVB-N content of shrimp is below 25 mg / 100g, the shrimp is in a secondary fresh state, of good quality, and suitable for consumption; when the TVB-N concentration is between 25-30 mg / 100g, it indicates that the shrimp has begun to rot, its freshness is declining, and it is recommended to consume it with caution or dispose of it as soon as possible; when the TVB-N content is above 30 mg / 100g, it indicates that the shrimp is completely rotten and should not be eaten. Figure 17The changes in TVB-N content in shrimp at 4℃ are shown. The initial TVB-N content was 6.83±0.06 mg / 100g, indicating good shrimp freshness. TVB-N content increased with storage time. In the early storage period (0-2 days), the increase in TVB-N content was slow due to the slow growth and reproduction rate of microorganisms. In the later storage period, microbial reproduction was rapid, and the TVB-N value of each treatment group increased at a faster rate, with the CK group showing the fastest increase. On day 3, the TVB-N value of the CK group reached 28.72±0.49 mg / 100g, indicating that the shrimp had begun to rot; while the TVB-N values ​​of the CF and C-ZnO NPs@YANF-BW groups were 22.82±0.46 mg / 100g and 14.71±0.45 mg / 100g, respectively, still at level two freshness. On day 5, the TVB-N values ​​of the CK and CF groups reached 45.01±0.67 mg / 100g and 34.49±0.31 mg / 100g, respectively, exceeding the edible standard; while the TVB-N value of the C-ZnO NPs@YANF-BW group remained below 30 mg / 100g, indicating that its shelf life was extended by 2 days. The results show that ZnO NPs@YANF in C-ZnO NPs@YANF-BW has a better inhibitory effect on bacterial growth and protein decomposition, effectively extending the shelf life of shrimp.

[0109] 10.5 Changes in the degree of lipid oxidation in shrimp (TBARS):

[0110] TBARS (Thiobarbituric Acid Reactive Material) is an important indicator for assessing the degree of lipid peroxidation and reflects changes in shrimp quality. Five grams of shrimp were chopped and added to 40 mL of trichloroacetic acid (5%) and 200 µL of 2,6-di-tert-butyl-p-cresol. The mixture was centrifuged at 4000 r / min and 4℃ for 15 minutes. Five mL of the supernatant was collected, and 1 mL of 0.01 M thiobarbituric acid was added. The mixture was heated in a boiling water bath for 40 minutes, cooled to room temperature, and the absorbance at 532 nm was measured. The malondialdehyde (MDAE) content was expressed as TBARS (mg MDAE / kg). A higher TBARS value indicates a higher degree of lipid oxidation. Figure 18The changes in TBARS content in shrimp at 4℃ were shown. The initial TBARS value was 0.24 ± 0.01 mg MDA / kg, and the TBARS values ​​of all groups increased with increasing storage time. During storage, the TBARS value of the CK group increased the fastest, indicating the fastest lipid oxidation rate. In contrast, the TBARS value of the C-ZnO NPs@YANF-BW group increased slowly. Starting from day 3, the TBARS value of the C-ZnO NPs@YANF-BW group (0.45 ± 0.03 mg MDA / kg) was significantly lower than that of the CK control group (1.03 ± 0.03 mg MDA / kg) and the CF group (0.76 ± 0.04 mg MDA / kg) (p < 0.05). This indicates that ZnO NPs@YANF in C-ZnO NPs@YANF-BW has a certain anti-lipid oxidation effect.

[0111] 10.6 Image Preprocessing and Model Architecture

[0112] An LED supplemental light was placed directly above the shrimp, and images of the C-ZnO NPs@YANF membrane experimental material were captured using a USB camera (1080P). Three images were taken daily, stored for 0-8 days, totaling 27 images (categorized as fresh, semi-fresh, and spoiled based on shrimp freshness), and saved in TIFF format. After capturing the images, basic image processing was performed: the original images were rotated to simulate angle issues in practical applications; the exposure of the images was increased and decreased to simulate the lighting conditions in practical applications, resulting in 2160 images. Labeling was performed manually using Labelimg to ensure accuracy, and corresponding TXT files were generated. Finally, the dataset was divided into training and validation sets in a 7:3 ratio.

[0113]

[0114] The training set was fed into the YOLOv11 model, and the relevant parameters were set for training. During the training process, the accuracy continuously increased, while the training loss and validation loss function curves continuously decreased, indicating that the model was continuously optimized during training and can be used for classifying different freshness levels. To further verify the model's performance, the accuracy of freshness recognition under different backgrounds (indoor lighting, natural sunlight, and dusk) was investigated. As shown in Table 6, the accuracy of the YOLOv11 model in recognizing freshness under different backgrounds was higher than 98%, demonstrating that the YOLOv11 model has the ability to accurately identify the freshness of shrimp under different backgrounds.

[0115]

[0116] In summary, this study successfully developed a highly sensitive smart composite membrane based on chitosan (CS) / ZnO NPs@YANF / black goji berry anthocyanins (BW), which enhanced the histamine response performance of the black goji berry anthocyanin chitosan preservation film. The main conclusions are as follows:

[0117] (1) Improved performance of composite membranes: By adding BW and ZnO NPs@YANF, the water vapor barrier properties, mechanical properties, and antioxidant properties of the composite membranes were significantly improved. Specifically, the tensile strength and elongation at break of the C-ZnO NPs@YANF-BW membrane increased by 99.76% and 45.49%, respectively, the antioxidant properties increased by 161.72%, and the water vapor barrier properties decreased by 25.30%.

[0118] (2) Improved color stability and pH response performance: The C-ZnO NPs@YANF-BW membrane showed good color stability after 21 days of storage at 4 ℃, with a ΔE value of only 5.66±0.44. This membrane is highly sensitive to pH changes and ammonia, with obvious color changes and fast response speed, making it suitable for real-time monitoring of food freshness.

[0119] (3) Preservation effect of shrimp: After the shrimp packaged with C-ZnO NPs@YANF-BW film were stored at 4 ℃ for 5 days, the pH value, TVB-N content, TBARS value and total bacterial count (TVC) were significantly lower than those of the control group, and the shelf life was extended by 2 days, indicating that the film has a good preservation effect.

[0120] (4) Image recognition model application: The YOLOv11 model is used to perform image recognition of the composite film color of shrimp with different freshness, with an accuracy rate of over 98%. It is suitable for practical applications under different backgrounds and provides an effective solution for the combination of intelligent packaging and artificial intelligence.

[0121] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0122] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A ternary composite intelligent food preservation film, characterized in that, The components of the ternary composite smart food preservation film include chitosan, zinc oxide nanofiber particles, and black goji berry anthocyanins.

2. The ternary composite intelligent food preservation film according to claim 1, characterized in that, The zinc oxide nanofiber particles account for 2.5 wt% of the component mixture of the ternary composite smart food preservation film.

3. The ternary composite intelligent food preservation film according to claim 1, characterized in that, The black goji berry anthocyanin accounts for 0.4 wt% of the component mixture of the ternary composite smart preservation film.

4. The ternary composite intelligent food preservation film according to claim 1, characterized in that, The zinc oxide nanofiber particles are prepared as follows: a 1 wt% aqueous dispersion of nanofibers extracted from young apple fruit and a 0.2 mol / L ZnCl2 solution are mixed at a volume ratio of 2:1, stirred for 2 hours until homogeneous, and then... 2+ : OH - The molar ratio of NaOH to zinc oxide was 1:6, and 1 mol / L NaOH was added. The mixture was stirred for 2 hours. After the reaction was completed, the mixture was filtered and washed once with anhydrous ethanol and twice with deionized water. The washed complex was stored at 4°C for 12 hours to balance the moisture content. Deionized water was added to prepare a suspension with a mass fraction of 0.05 wt%. The suspension was uniformly dispersed using a high-speed homogenizer, filtered, and freeze-dried to obtain the zinc oxide nanofiber particles.

5. The ternary composite intelligent food preservation film according to claim 4, characterized in that, The method for extracting nanofibers from young apples is as follows: after crushing the young apples, they are added to a 1M sodium hydroxide solution at a weight ratio of 1:5-25 and soaked at room temperature for 10-30 hours for alkaline demethylation. The resulting fruit residue is then washed with water until neutral, and the neutral fruit residue is continuously processed several times using a high-pressure homogenizer. Water is added during the processing to obtain an aqueous dispersion of nanofibers with a diameter of less than 25 nanometers and a mass fraction of 1 wt%.

6. The ternary composite intelligent food preservation film according to claim 5, characterized in that, The crushed young apples were added to a sodium hydroxide solution at a weight ratio of 1:20 and soaked for 15 hours.

7. The ternary composite intelligent food preservation film according to any one of claims 4 to 5, characterized in that, The young apples referred to are small apples that are picked within 2-3 weeks after pollination and before the physiological fruit drop period.

8. A method for producing a ternary composite intelligent food preservation film, characterized in that, Includes the following steps: Chitosan powder was dissolved in a 1% acetic acid solution at a weight-to-volume ratio of 1:

50. Glycerin equivalent to 30 wt% of the dry weight of chitosan was added, followed by zinc oxide nanofiber particles as described in claim 2 (2.5 wt% of the component mixture) and black goji berry anthocyanins as described in claim 3 (0.4 wt% of the component mixture). After mixing evenly, the component mixture was poured into a polystyrene mold, with the height of the component mixture not exceeding 2 cm. The mixture was allowed to stand for 24 hours to remove air bubbles, and then dried at 35°C for 12 hours to obtain the ternary composite intelligent food preservation film.

9. The method for using the ternary composite intelligent food preservation film according to claim 8, characterized in that, The thickness of the ternary composite smart food preservation film is 20±5μm.

10. The application of the ternary composite intelligent food preservation film according to claim 1 in food preservation and monitoring whether food has deteriorated.

Images