Preparation method and application of PVA-tannic acid-mesoporous silica entrapped cinnamon essential oil composite film

Abstract

The invention belongs to the technical field of antibacterial composite membranes, and provides a preparation method and application of a PVA-tannic acid-mesoporous silica entrapped cinnamon essential oil composite membrane, PVA, tannic acid and mesoporous silica entrapped cinnamon essential oil is adopted to prepare the composite membrane, more oxygen permeates due to the irregular structure of the composite membrane caused by the anthocyanin agglomeration phenomenon, and the antibacterial effect of the composite membrane is improved. The kale anthocyanin composite film with less agglomeration phenomenon has certain feasibility when being used as a food fresh-keeping packaging material. In the storage process, protein and fat in the pork can be decomposed by microorganisms to generate a large amount of volatile nitrogen-containing compounds, so that TVB-N of the pork is increased, the TVB-N values of a PVA / 20% TA / 5% cinnamon membrane group and a PVA / 20% TA / 5% cinnamon / kale membrane group are close to 15 mg / g in 3 days, and the pork becomes second-grade freshness after one day is delayed at the room temperature of 30 DEG C. And after 6 days, the control group reaches 25.0 mg / 100g and becomes deteriorated meat, and the other three groups only reach the deteriorated meat degree after 7 days, which proves that the treatment group has a good effect on the preservation of the pork.

Description

Technical Field

[0001] This invention belongs to the field of antibacterial composite membrane technology, specifically relating to a method for preparing a PVA-tannic acid-mesoporous silica-encapsulated cinnamon essential oil composite membrane. Background Technology

[0002] Meat often spoils due to microbial contamination, fat oxidation, and myoglobin discoloration. Currently, relatively mature preservation technologies on the market include low-temperature refrigeration, heat treatment, and preservative-based preservation. Research on combining film preservation and modified atmosphere packaging technologies is also progressing steadily. Song Shuxin et al. prepared a polylactic acid / poly(terephthalic acid-1,4-butanediol) blend film for spontaneous modified atmosphere packaging of Alashan Bactrian camel meat, and the results showed that this type of blend film can effectively extend the shelf life of meat samples. Yang HJ et al. prepared a lemongrass-oil-containing polylactic acid film for packaging pork sausages, which can effectively reduce the growth of Listeria monocytogenes and has good antibacterial activity. Zeng Liping et al. used a solvent casting method to prepare a polylactic acid nano-antibacterial composite film containing lemon essential oil, which can effectively preserve the quality of chilled pork and extend its shelf life. There is an urgent need in those skilled in the art to develop a method for preparing and applying a PVA-tannic acid-mesoporous silica-encapsulated cinnamon oil composite membrane to meet current usage requirements and market demands. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing a PVA-tannic acid-mesoporous silica-encapsulated cinnamon oil composite membrane and its application.

[0004] The technical solution adopted by this invention to solve its technical problem is as follows:

[0005] A method for preparing a PVA-tannic acid-mesoporous silica-coated cinnamon oil composite membrane includes the following steps: (1) Accurately weigh 1.5%~20% of the membrane dry weight of tannic acid and gradually dissolve it in 150 parts of a 5% PVA solution by mass, then weigh 30% of the membrane dry weight of glycerol and add it, stir at 70°C for 4 hours to fully dissolve it, and obtain a tannic acid-PVA solution; the membrane dry weight is the weight ratio of the PVA solution; (2) Add 3%~5% of the membrane dry weight of hollow mesoporous silica@cinnamon oil or add 3%~5% of the membrane dry weight of hollow mesoporous silica@cinnamon oil and anthocyanins to the tannic acid-PVA solution, the membrane dry weight is the weight ratio of the tannic acid-PVA solution; (3) After forming the membrane by solution casting, place it in an oven at 40°C for 12 hours to dry, and obtain the membrane.

[0006] Furthermore, the anthocyanins in step (2) are obtained from kale.

[0007] Furthermore, the anthocyanin solution is 20% of the total weight of the PVA-tannic acid-mesoporous silica-encapsulated cinnamon essential oil composite membrane solution.

[0008] Furthermore, the hollow mesoporous silica@cinnamon oil has an oil loading rate of 10%.

[0009] An application of a PVA-tannic acid-mesoporous silica-encapsulated cinnamon oil composite membrane for pork or chicken preservation.

[0010] The beneficial effects of this invention are as follows:

[0011] The anthocyanin aggregation phenomenon leads to an irregular composite film structure, resulting in greater oxygen permeation. Kale anthocyanin composite films with less aggregation have certain feasibility as food preservation packaging materials.

[0012] During storage, the proteins and fats in pork are decomposed by microorganisms, producing a large amount of volatile nitrogenous compounds, which leads to an increase in TVB-N. At 3 days, the TVB-N values ​​of the PVA / 20%TA / 5% cinnamon film group and the PVA / 20%TA / 5% cinnamon / kale film group were close to 15 mg / g, and at room temperature (30℃), the TVB-N level was delayed by one day to reach grade two freshness. At 6 days, the control group reached 25.0 mg / 100g, becoming spoiled meat, while the other three groups only reached spoiled meat level at 7 days. This demonstrates that the treatment groups had a good effect on preserving the freshness of pork. Attached Figure Description

[0013] Figure 1 These are infrared spectra of different composite films; Figure 2 These are XRD patterns of different composite membranes; Figure 3 These are graphs showing the stress variations of different composite films; Figure 4 The different composite membranes have different water solubility; Figure 5 The following are 6-hour solubility graphs of different composite membranes in water (pure PVA membrane is PVA-a, PVA / 20%TA composite membrane is PVA-b, PVA / 20%TA / carrier composite membrane is PVA-c, PVA / 20%TA / carrier / 3% cinnamon composite membrane is PVA-d, and PVA / 20%TA / carrier / 5% cinnamon composite membrane is PVA-e). Figure 6 These are the water vapor transmission coefficients of different thin films; Figure 7 The DPPH removal rates of different composite membranes; Figure 8 Oxygen permeability of different composite membranes; Figure 9 The carbon dioxide permeation rate of different composite membranes; Figure 10 The diameter (A) and inhibition zone (B) of Staphylococcus aureus 1d in different composite membranes. Figure 11 The diameter (A) and inhibition zone (B) of Escherichia coli in different composite membranes 1 day. Figure 12These are real photos of chicken meat from the control group and different treatment groups taken over 7 days at room temperature (20℃). Figure 13 This is a graph showing the pH changes of chicken meat stored at 20℃ for 7 days under different treatments; Figure 14 It represents the juice loss rate of chicken from different treatment groups during the storage period; Figure 15 These are chicken TVB-N samples processed in different groups during the storage period; Figure 16 Sensory changes of chicken in different treatment groups during storage: (a) odor rating chart, (b) color rating chart, and (c) appearance rating chart. Figure 17 Dilute 10 -6 Figure 18 shows the changes in total bacterial count of chicken meat preserved by different composite films at 20℃. Figure 19 (a) shows the color reaction of camellia in solutions of different pH values; (b) shows the absorbance of camellia in solutions of different pH values; (c) shows the comparison of pH and OD values ​​of camellia in solutions of different pH values. Figure 20 (a) shows the color reaction of kale in solutions of different pH values; (b) shows the absorbance of kale in solutions of different pH values; (c) shows the comparison of pH and OD values ​​of kale in solutions of different pH values. Figure 21 (a) shows the color reaction of mulberry in solutions of different pH values; (b) shows the absorbance of mulberry in solutions of different pH values; (c) shows the comparison of pH and OD values ​​of mulberry in solutions of different pH values. Figure 22 (a) shows the color reaction of purple cabbage in solutions with different pH values; (b) shows the absorbance of purple cabbage in solutions with different pH values; (c) shows the comparison of pH and OD values ​​of purple cabbage in solutions with different pH values. Figure 23 (a) shows the color reaction of onion in solutions of different pH values; (b) shows the absorbance of onion in solutions of different pH values; (c) shows the comparison of pH and OD values ​​of onion in solutions of different pH values. Figure 24 (a) shows the color reaction of onion in solutions of different pH values; (b) shows the absorbance of onion in solutions of different pH values; (c) shows the comparison of pH and OD values ​​of onion in solutions of different pH values. Figure 25 (a) shows the color reaction of Magnolia denudata in solutions with different pH values; (b) shows the absorbance of Magnolia denudata in solutions with different pH values; (c) shows the comparison of pH and OD values ​​of Magnolia denudata in solutions with different pH values. Figure 26 (a) shows the color reaction of radish flowers in solutions with different pH values; (b) shows the absorbance of radish flowers in solutions with different pH values; (c) shows the comparison of pH and OD values ​​of radish flowers in solutions with different pH values. Figure 27 These are infrared spectra of anthocyanin composite films from different plants; Figure 28 These are XRD diagrams of anthocyanin composite membranes from different plants; Figure 29 This is a graph showing the color changes of composite membranes containing different plant anthocyanins under acidic and alkaline conditions. Figure 30 This is a graph showing the changes in a* value of different plant anthocyanin composite membranes under alkaline (A) and acidic (B) conditions; Figure 31 This is a diagram showing the water solubility of composite membranes containing anthocyanins from different plants; Figure 32 These are dissolution graphs of different plant anthocyanin composite membranes in water over 6 hours. Figure 33 These are the water vapor transmission coefficients of different thin films; Figure 34 It refers to the stress variation of different thin films; Figure 35 The antioxidant properties of different composite films; Figure 36 Oxygen permeability (A) and carbon dioxide permeability (B) of different composite membranes. Figure 37 These are diagrams (A) and (B) showing the diameters of the inhibition zones of Staphylococcus aureus in different composite membranes. Figure 38 These are diagrams showing the diameters of the inhibition zones of E. coli using different composite membranes (A) and (B). Figure 39 Effects of different treatments on the appearance of pork stored at 20℃ for 10 days; Figure 40 It is the juice loss rate of pork in different treatment groups during the storage period; Figure 41 The effects of different composite films on the sensory properties of fresh pork; Figure 42 The effects of different composite films on the chewiness and elasticity of fresh pork; Figure 43 This is a graph showing the pH changes during storage using different composite membranes; Figure 44 This is a graph showing the changes in TVB-N during storage with different composite membranes; Figure 45 These are actual photos showing the color difference of the kale composite film. Figure 46 This is a graph showing the variation of the a* value of the kale composite film; Figure 47 These are real photos of the total bacterial count measured on pork in different treatment groups over 2 days. Figure 48 This is a graph showing the changes in total bacterial count in pork from different treatment groups. Detailed Implementation

[0014] The present invention is illustrated below with specific embodiments, but these are not intended to limit the scope of the invention.

[0015] Example 1

[0016] 1.1 Composite membranes were prepared by solution casting.

[0017] Accurately weigh 75g of PVA and dissolve it in 1425mL of deionized water at room temperature. Stir at 50℃ for 2 hours to ensure complete dissolution, thus obtaining a 5% PVA solution. Based on the ratio of membrane dry weight to the weight of the 5% PVA solution, where membrane dry weight is the weight of pure PVA contained in the PVA solution (75:1500, 5%), accurately weigh 1.5%, 5%, 10%, 20%, and 25% of the membrane dry weight of tannic acid (TA) and gradually dissolve them in 150mL of PVA solution (the membrane dry weight in this solution is 150*5%=7.5%). Then, weigh 30% of the membrane dry weight of glycerol and add it. Stir at 70℃ for 4 hours to ensure complete dissolution, thus obtaining a tannic acid-PVA solution. The upper limit of tannic acid addition using this method was determined to be 20%. Cinnamon essential oil was loaded into hollow mesoporous silica, and its oil loading rate was measured. Then, 3% and 5% hollow mesoporous silica@cinnamon essential oil and 3% hollow mesoporous silica were added to the membrane dry weight, respectively. The dry weight of the membrane was the weight ratio of the tannic acid-PVA solution. The membranes were dried in an oven at 40°C for 12 hours. 15 ml of membrane solution was taken from each membrane to prepare five groups of films: PVA, PVA / 20%TA, PVA / 20%TA / carrier, PVA / 20%TA / 3% cinnamon, and PVA / 20%TA / 5% cinnamon.

[0018] The hollow mesoporous silica nanospheres have an average particle size of 230 nm and a BET surface area of ​​423.3 m². 2 / g, pore volume and average pore size are 0.456cm 3 / g and 3.95nm.

[0019] 100 mg of cinnamon essential oil was dissolved in 10 mL of dichloromethane using a solvent impregnation method. 100 mg of hollow mesoporous silica nanospheres were weighed and dispersed in the cinnamon essential oil dichloromethane solution with the aid of ultrasound. The mixture was then sealed and kept in the dark with shaking for 24 hours. After centrifugation, the precipitate was freeze-dried to obtain hollow mesoporous silica@cinnamon essential oil.

[0020] Infrared spectroscopy of the composite film: The FTIR spectrum of the thin film was measured using a Fourier transform infrared spectroscopy (FTIR) instrument. The film was analyzed in attenuated total reflectance (ATR) mode at a resolution of 4 cm⁻¹. −1 The number of scans was 64, and the scanning range was 4000cm. −1 ~400cm −1The conditions for acquiring the spectrum were as follows. X-ray diffraction (XRD) analysis of the composite film: equipped with a CuKα ray source, tube current of 15mA, tube voltage of 40kV, scanning speed of 10° / min, and scanning angle (2θ) of 10°~80°. Color difference of the composite film: the colorimetry of the composite film was measured using a precision colorimeter. Referring to the method of SUN et al., a CS-200 precision colorimeter was used to measure the colorimetry of the composite film. The color parameters involved were L (brightness), a (red / green), and b (yellow / blue), and the total color difference was calculated. The formula for ) is:

[0021] In the formula: , , L represents the color value of the white paper, while L, a, and b represent the color values ​​of the composite film.

[0022] Mechanical property analysis of the composite membrane: The composite membrane was cut into rectangular samples (20mm × 70mm), and its mechanical properties were evaluated using a microcomputer-controlled electronic universal testing machine. The initial distance of the clamps and the head speed were set to 45mm and 0.2mm / s, respectively, and the tensile strength and elongation at break of the samples were analyzed. The thickness of the membrane was measured at 5 random points using a thickness gauge, and the average value was calculated. Water solubility determination: The composite membrane was cut into square samples (20mm × 20mm) and dried in an oven at 102℃ for 24h to obtain its initial dry weight m1. Then, the sample was placed in 40mL of distilled water and soaked at room temperature for 24h. The undissolved film was removed and dried again under the same conditions, and its mass was recorded as m2. The water solubility (WS) of the film sample was calculated as shown in the formula: ;

[0023] Water vapor transmission rate determination: Cut the membrane into circular samples, take an appropriate amount of test container, add water to the marked volume, tighten the cap, and weigh accurately. Then place the container in a constant temperature and humidity chamber for 14 days. After removal, let it stand at room temperature for 45 minutes, weigh accurately, and calculate the percentage of water loss using the following formula: ×100%; W1 is the weight of the container and aqueous solution before the experiment; W0 is the weight of the empty container; W2 is the weight of the container and aqueous solution after the experiment.

[0024] Antioxidant performance testing: DPPH free radical scavenging rate determination: First, take 0.1g of each membrane and cut it into small pieces. Mix with 10mL of deionized water and sonicate for 5min. After standing at room temperature for 3h, centrifuge at 3000r / min for 10min. Take the supernatant after centrifugation as the test sample solution. Weigh 5.0mg of DPPH, dissolve it in an appropriate amount of anhydrous ethanol, sonicate in the dark for 10min, and then dilute to 100mL with anhydrous ethanol to prepare a 50.0μg / mL DPPH solution (prepare immediately before use). Take 2mL of the test sample solution into a stoppered graduated test tube, add 2mL of DPPH reagent, react in the dark for 30min, take the supernatant, and measure the absorbance value at a wavelength of 517nm. Record the value as A1. Replace 2mL of DPPH with 2mL of anhydrous ethanol and measure the absorbance value of the sample. Record the value as A2. Use deionized water as a blank control instead of the sample. Record the value as A0. Calculate the free radical scavenging rate using the formula:

[0025] Clearance rate (%) = A1 = Absorbance of 2 mL sample solution + 2 mL DPPH reagent; A2 = Absorbance of 2 mL sample solution + 2 mL anhydrous ethanol; A0 = Absorbance of 2 mL deionized water + 2 mL DPPH reagent.

[0026] Composite membrane oxidation permeability testing: The membrane is first fixed to the mouth of a cup containing a deoxidizer and a sealing film. After weighing the initial weight of the cup, it is placed in a desiccator with a saturated barium chloride solution (RH 85%) for 48 hours. Oxygen permeability is calculated using the following formula: Oxygen Permeability (OP) In the formula, Δm is the increase in weight of the cup (g), t is time (h), and A is the area of ​​the cup's rim (cm²). 2 ).

[0027] Carbon Dioxide Permeability (CDP) Measurement of Composite Membrane: A concentrated sodium hydroxide solution is added to a cup, and the membrane is then fixed to the cup opening. After 48 hours, the weight difference of the cup is calculated. Carbon dioxide permeability is calculated using the following formula: Carbon Dioxide Permeability (CDP) Where Δm is the increase in weight of the cup (g), t is time (h), and A is the area of ​​the cup's rim (cm²). 2 ).

[0028] Determination of the antibacterial performance of the composite membrane: 1. Sterilization: Place the solid culture medium, filter paper, petri dishes, spreading rod, and tweezers into an autoclave for sterilization. 2. Before use, disinfect the surface of the laminar flow hood with alcohol, turn on the switch, and irradiate with a UV germicidal lamp for 20 minutes, then turn off the UV light and ventilate for 10 minutes. 3. In the laminar flow hood, take 4 ml of the prepared deionized water and 4 ml of each of the five membrane solutions into centrifuge tubes, and add an appropriate amount of sterilized filter paper. Soak the filter paper for 2 hours. 4. Pour plates in the laminar flow hood. After the plates have cooled, use a pipette to add 150 μL of bacterial solution to each plate. Spread the solution using a sterilized spreading rod. 5. Divide the spread culture medium into five groups. Use sterile tweezers to pick up the above membrane solutions and soak the filter paper until saturated. Drain off the excess solution on the tube wall and aseptically place it onto the corresponding test culture medium plate.

[0029] 1.2 Experimental Results and Analysis

[0030] 1.2.1 Infrared Spectrum

[0031] Figure 1 Infrared spectra of different composite films are shown, including the infrared spectrum of a pure PVA film at 3700 cm⁻¹. -1 The left and right sides represent the absorption peaks of the alcohol hydroxyl groups (hydrogen bond association) of PVA; 1800 cm⁻¹ -1 The peak at 1589 represents the characteristic peak of the C=O bond remaining in the polyvinyl alcohol production process from polyvinyl acetate. The composite membrane after the addition of tannic acid and TA shows a peak at 1589. -1 cm - A relatively obvious benzene ring absorption peak appears at approximately 1100 cm⁻¹, indicating successful recombination of TA and PVA. The main absorption peak of hollow mesoporous silica is located at approximately 1100 cm⁻¹. -1 and 1200-1250cm -1 The absorption peaks between 800 and 1000 cm⁻¹ are called silicon-oxygen bond absorption peaks. These peaks correspond to the vibrations between silicon and oxygen atoms in the silicon dioxide structure. Additionally, there are absorption peaks located between 800 and 1000 cm⁻¹. -1 The weaker absorption peaks within the range correspond to the silicon-oxygen vibrational mode. The added hollow mesoporous silica may not be shown in this figure due to its small amount.

[0032] 1.2.2 X-ray diffraction (XRD) analysis of the composite film

[0033] like Figure 2As shown, after adding TA and hollow mesoporous silica, the curves of each group are similar. The main characteristic peak of PVA diffraction is 2θ=19.6°. After the addition of TA, the diffraction peak shifts to the right. Compared with the image of the film with added nanoparticles, neither a new peak shift nor a peak shift was observed, indicating that the film is composed of two phases: polymer and nanoparticles. However, we observed that with the addition of TA and hollow mesoporous silica, the maximum intensity of the diffraction peak gradually increases, indicating that the diffraction intensity of the corresponding crystal planes becomes stronger.

[0034] 1.2.3 Color difference of composite film

[0035] Thin film samples: PVA, PVA / 20%TA, PVA / 20%TA / support, PVA / 20%TA / support / 3% cinnamon.

[0036] The color difference of different composite films with PVA / 20%TA / carrier / 5% cinnamon is shown in Table 1.

[0037] Table 1 Color difference of different composite films

[0038] Table 1 shows the effect of additives on the color of PVA film. * The value is brightness, a * Positive values ​​are red, negative values ​​are green; b * Positive values ​​are yellow, and negative values ​​are blue. ΔE * This represents color difference; the higher the value, the greater the color difference. Test results show that pure PVA film has the highest brightness and a whiter color. After adding TA, the film's ΔE... * b * The value increased significantly, the film turned yellow, L * The value does not change much, indicating that the brightness is not significantly affected. * A slight decrease in the value indicates a slight deepening of the green color of the film, since TA itself is yellow; this change is consistent with the color change caused by the addition of TA. After adding hollow mesoporous silica, the L value of the composite film... * value, a * value, b * Value, ΔE * The change was minimal, likely because hollow mesoporous silica is white, and its addition had a relatively small impact. Adding cinnamon oil resulted in a slight change in the composite membrane's b... * Value, ΔE * The color changed significantly and became more yellow, which may be due to the yellowish color of cinnamon essential oil.

[0039] 1.2.4 Mechanical property analysis of composite membrane

[0040] The mechanical properties of different composite films of PVA, PVA / 20%TA, PVA / 20%TA / carrier / 3% cinnamon, and PVA / 20%TA / carrier / 5% cinnamon are shown in Table 2.

[0041] Table 2 Mechanical properties of different composite films

[0042] The varying amounts of additives and film-forming conditions in each type of membrane result in differences in membrane thickness, which significantly impacts the membrane's physical properties and barrier properties. Table 2 shows that the addition of TA, hollow mesoporous silica, and cinnamon oil all increase film thickness. This may be because, with a fixed membrane solution weight, pure PVA membranes have a higher moisture content, while other composite membranes have lower moisture content; therefore, after drying the membrane solution, the composite membranes are thicker. Figure 3 Among them, the pure PVA film has the lowest maximum bearing capacity, while the PVA / 20%TA composite film has the highest tensile strength and elongation at break. After adding hollow mesoporous silica, the tensile strength and elongation at break of the composite film actually decreased. This may be because the hollow mesoporous silica enters between the PVA molecular chains, breaking the original tight structure of the PVA molecular chains and making the structure looser.

[0043] 1.2.5 Water solubility determination:

[0044] Water solubility is an important parameter for evaluating the water resistance of membrane materials, especially when the membrane is used for food packaging in a high-moisture environment. Figure 4 The water solubility of pure PVA film, PVA / 20%TA composite film, PVA / 20%TA / carrier composite film, PVA / 20%TA / carrier / 3% cinnamon composite film, and PVA / 20%TA / carrier / 5% cinnamon composite film in water at room temperature was shown. It can be seen that the pure PVA film has the highest water solubility, almost approaching 100%, making it difficult to apply in environments with high moisture content. Compared to the pure PVA film, the water solubility of the PVA / 20%TA composite film is significantly reduced. This may be because tannic acid (TA) is a natural polyphenol antibacterial small molecule; the numerous phenolic groups provide various interaction sites, including hydrogen bonds, ionic bonds, coordination bonds, and hydrophobic interactions, enabling it to bind with PVA and produce water resistance. For the composite film with hollow mesoporous silica encapsulated cinnamon essential oil, the water resistance further decreased. This may be because the added nanomaterials reduce the contact points between water and PVA, thereby preventing the dissolution of the PVA composite film. Figure 5In the above, we can observe more intuitively the solubility of several films in water over 6 hours: pure PVA film (PVA-a), PVA / 20%TA composite film (PVA-b), PVA / 20%TA / carrier composite film (PVA-c), PVA / 20%TA / carrier / 3% cinnamon composite film (PVA-d), and PVA / 20%TA / carrier / 5% cinnamon composite film (PVA-e). It can be seen that the pure PVA film has completely dissolved in water and cannot maintain its basic shape, while the composite films only swell slightly and can still maintain their shape.

[0045] 1.2.6 Measurement of water vapor transmission rate

[0046] Water vapor transmission rate (WVP) refers to the total amount of water vapor that permeates through a sample per unit area per unit time, with the transmission direction perpendicular to a specific surface of the sample. The water vapor transmission rate (WVP) of thin films is an important indicator for food packaging materials, often influenced by the film's hydrophobic and hydrophilic components and its structural density. Hydrophilic films have higher WVP values ​​but lower resistance to water vapor. Figure 6 As shown, the WVP value of pure PVA film is relatively high among all films, because PVA film is a hydrophilic film. Adding tannic acid (TA) to the PVA film significantly reduces the WVP value of the composite film, indicating that TA improves the water vapor barrier properties of the PVA film. This may be because the addition of TA introduces water resistance, leading to a decrease in the hydrophilicity of the composite film, which is consistent with the results of the water solubility experiment in section 1.5. The addition of hollow mesoporous silica and cinnamon oil resulted in a slight decrease in the WVP value of the composite film, unlike the significant decrease after the addition of TA. Furthermore, according to the mechanical property results in experiment 1.4, the thickness of the composite film increased after the addition of hollow mesoporous silica and cinnamon oil. Therefore, the increase in the WVP value of the composite film after the addition of hollow mesoporous silica and cinnamon oil may be due to the thicker composite film extending the diffusion path of gas molecules within the film, while the hollow mesoporous silica, as a nanomaterial, partially fills the gaps in the composite film.

[0047] 1.2.7 Antioxidant properties

[0048] Experimental results of DPPH removal rates of different composite membranes are as follows: Figure 7 As shown, the pure PVA film exhibits a DPPH scavenging rate of 5.79%, indicating almost no antioxidant activity. However, the addition of 20% TA significantly improves the DPPH scavenging rate to 83.12%, demonstrating a marked increase in the antioxidant activity of the composite film. This is likely due to the abundance of ortho-hydroxyl groups in tannins, from which hydrogen is released, reducing Fe... 3+It exhibits strong antioxidant capacity by scavenging free radicals (ROS, DPPH, OH·, HO2·, NO·) and blocking their chain reactions and inhibiting lipid peroxidation. Simultaneously, it can be seen that the DPPH scavenging rate of the composite membrane with different amounts of cinnamon essential oil increases slightly, further enhancing the free radical scavenging ability of the composite membrane. This also proves that the cinnamon essential oil embedded in the hollow mesoporous silica in the composite membrane is still playing a role.

[0049] 1.2.8 Oxygen and carbon dioxide permeability of composite membrane

[0050] Oxygen permeating into packaging materials can cause rancidity and other oxidation reactions, leading to food quality loss. Therefore, most food packaging materials are required to have high oxygen barrier properties. Figure 8 As shown, the pure PVA film exhibits the highest oxygen permeability. With the gradual addition of TA, hollow mesoporous silica, and different concentrations of cinnamon oil embedded in hollow mesoporous silica, the oxygen permeability of the composite membrane shows a gradual decreasing trend. Combined with mechanical property experiments, this may be due to the increasing thickness of the composite membrane, as thickness is one of the main factors affecting membrane oxygen permeability. Simultaneously, both TA and cinnamon oil demonstrated good antioxidant properties in the previous antioxidant tests, and these factors may also have played a role in the decrease in oxygen permeability.

[0051] Carbon dioxide can be used as a protective gas to help extend the shelf life of food while reducing the oxidative effects of oxygen. By controlling the concentration of carbon dioxide in packaging, spoilage and oxidation of food can be slowed down, thereby extending its shelf life. Figure 9 In all tests, the carbon dioxide permeability of the membranes was within 0.2 × 10⁻¹⁵ cm⁻¹. 3 ·cm / cm 2 Within the range of ·s·Pa, this indicates that the added substance does not have much impact on the carbon dioxide permeability of PVA material.

[0052] 1.2.9 Determination of antibacterial properties of composite membrane:

[0053] like Figure 10 , Figure 11The images show the diameter of the inhibition zones against Staphylococcus aureus and Escherichia coli in different composite films, along with actual photographic images. The size of the inhibition zones in each composite film is clearly visible. Pure PVA film has no antibacterial properties. After adding TA (tazobium phosphate), the composite films produced inhibition zones against both Staphylococcus aureus and Escherichia coli. Comparing the diameter of the inhibition zones reveals that the composite film with directly added cinnamon oil has inhibition zones similar to those of the composite film with only TA added, regardless of whether it's Staphylococcus aureus or Escherichia coli. The composite film with hollow mesoporous silica-encapsulated cinnamon oil generally has larger inhibition zones. This indicates that the hollow mesoporous silica-encapsulated cinnamon oil composite film effectively preserves the cinnamon oil, delaying its volatility. The spherical structure of the hollow mesoporous silica allows for effective storage of the cinnamon oil within, thus improving the long-lasting antibacterial performance of the composite film and contributing to the long-term antibacterial effect on fruit and vegetable preservation, extending their shelf life. The images also compare the inhibition zones against the two pathogenic bacteria. At the same time, it can be clearly seen that the inhibitory zone of the composite membrane against Staphylococcus aureus is generally larger, which may be due to the stronger antibacterial activity of TA against Staphylococcus aureus.

[0054] 1.2.10 Changes in the appearance of chicken during storage:

[0055] Figure 12 These are real-life photos of chicken meat from the control group and different treatment groups taken over 7 days at 20℃. The control group consisted of unwrapped fresh chicken. The treatment groups were wrapped with PVA film, PVA / 20%TA, PVA / 20%TA / carrier, PVA / 20%TA / 3% cinnamon, and PVA / 20%TA / 5% cinnamon, respectively. The images show that all treatment groups remained white on day 1, while the control group turned reddish on day 3. Other treatment groups showed little change, indicating that the treatments did indeed have a certain effect on preserving the chicken. On day 5, all treatment groups' chicken meat turned yellow and exhibited varying degrees of dryness, likely due to moisture evaporation and fat oxidation, indicating visible spoilage on day 5. On day 7, the control group's chicken meat turned brownish-red, while the yellow color of the other treatment groups deepened, likely due to further fat oxidation.

[0056] 1.2.11 Changes in pH value of chicken during storage

[0057] Figure 13 This graph shows the pH changes of chicken meat under different treatments after 7 days of storage at 20°C. During storage, pH changes are closely related to the freshness and quality of the meat. The evaluation criteria for chicken pH are: Grade 1 fresh meat should have a pH below 6.2, Grade 2 fresh meat should have a pH of 6.3-6.6, and spoiled meat should have a pH above 6.7. Figure 13It was found that the initial pH of all chicken samples was below 5.6, meeting the standard for Grade 1 fresh meat. The pH of the chicken samples in the control group and PVA group increased significantly with prolonged storage time, exceeding the pH threshold after 2 days and becoming spoiled meat, significantly higher than other treatment groups with added TA. This is consistent with the trends in total bacterial count and TVB-N; the increase in pH is mainly due to the massive proliferation of microorganisms causing protein decomposition into alkaline substances such as amines. Although the pH of the chicken samples in the TA-treated groups increased, it did not exceed 6.7 during the 8-day storage period, indicating that TA can effectively delay the increase in chicken pH. The pH of the treatment group with added cinnamon oil did not differ significantly from the pH of the TA-only group, which may mean that the addition of cinnamon had little effect on delaying the increase in chicken pH.

[0058] 1.2.12 Chicken juice loss rate during storage

[0059] Figure 14 This represents the juice loss rate of chicken from different treatment groups during storage. Figure 14 The results show that the juice loss rate of both the treatment and control groups increased with prolonged storage time, while the increase was faster in the blank group. At day 2, there was no significant difference in juice loss rate among the groups. After day 2, the juice loss rate of the blank group increased rapidly, widening the gap with the other groups. This may be because the chicken in the blank group was directly exposed to the environment, resulting in faster moisture evaporation, while in the other treatment groups, some moisture was blocked by the composite membranes, preventing loss.

[0060] 1.2.13 Volatile basic nitrogen (TVB-N) of chicken during storage

[0061] Figure 15 This refers to the TVB-N content of chicken meat from different treatment groups during storage. TVB-N, an important indicator of meat freshness, is a general term for volatile nitrogenous substances (such as dimethylamine, trimethylamine, and ammonia) produced after protein oxidative degradation. GB / 2707–2016, "National Food Safety Standard for Fresh (Frozen) Livestock and Poultry Products," stipulates that the TVB-N content of fresh poultry products must not exceed 15 mg / 100g. Figure 15It was found that the TVB-N content in all chicken samples increased with prolonged storage time, but the increase varied significantly among different treatment groups. The initial TVB-N values ​​in all treatment groups did not exceed 10 mg / 100g. At day 1, the control group and the PVA group increased to nearly 20 mg / 100g, exceeding national safety standards. At day 3, the TVB-N levels in the PVA / 20%TA, PVA / 20%TA / carrier, PVA / 20%TA / 3% cinnamon, and PVA / 20%TA / 5% cinnamon groups increased to 19.98 mg / 100g, 18.12 mg / 100g, 18.24 mg / 100g, and 16.40 mg / 100g, respectively. At this point, all treatment groups exceeded the upper limit stipulated in the national standard GB / 2707–2016. Furthermore, the TVB-N content in the control group reached as high as 56.66 mg / 100g at day 7. The above trends are largely consistent with the total bacterial count results, indicating that the increase in TVB-N content is due to the rapid proliferation of spoilage microorganisms, which leads to the accelerated oxidative decomposition of proteins into alkaline nitrogenous substances such as amines and amine derivatives. These results suggest that TA and the cinnamon oil-coated composite film can effectively inhibit the increase of TVB-N content in chicken by suppressing the activity of spoilage microorganisms and thus inhibiting the oxidative degradation of proteins.

[0062] 1.2.14 The effect of composite film on the sensory evaluation of chicken during storage

[0063] Figure 16 The sensory changes of chicken samples from different treatment groups during storage are shown in (a) odor rating chart, (b) color rating chart, and (c) appearance rating chart. Sensory evaluation is the most commonly used method for consumers to judge meat products and is also an important indicator in professional meat inspection. The changes in sensory scores (appearance, color, and odor) of chicken samples from different treatment groups over 7 days are shown in the figure. Figure 16 As shown in the figure, the initial sensory scores of all samples were above 8 points, indicating that the chicken samples on day 0 had high freshness. With prolonged storage, the sensory scores of all groups decreased, especially the control group and the PVA group. Among the three sets of scores, all showed a downward trend, with the most significant decrease in odor scores. At day 2, the odor scores of the control group and the PVA group were significantly lower, showing a large gap compared to the treatment groups. At day 5, the differences between the treatment groups were not significant, indicating that all treated chicken samples had spoiled. These results demonstrate that the TA film and cinnamon oil composite film can effectively maintain the appearance, color, and odor of chicken samples up to day 3.

[0064] 1.2.15 Changes in total bacterial count in chicken meat during storage

[0065] Figure 17 It is diluted 10 -6 Images of bacterial counts in each treatment group at different multiplication rates were taken. Figure 18This graph shows the changes in total bacterial count of chicken preserved using different composite films at 20℃. Total bacterial count is an important indicator for evaluating meat quality and shelf life, reflecting the degree of microbial contamination. GB / 16869–2005, the National Food Safety Standard for Fresh and Frozen Poultry Products, stipulates that the total bacterial count in fresh poultry products must not exceed 1×10⁶ CFU / g. Grade 1 fresh meat should have a total bacterial count below 1×10⁴ CFU / g, Grade 2 fresh meat should have a total bacterial count between 1×10⁴ and 1×10⁶ CFU / g, and spoiled meat should have a total bacterial count greater than 1×10⁶ CFU / g. Figure 18 It can be seen that the total number of colonies in all samples at day 0 was less than 4 log₂. 10 The CFU / g level met the Grade 1 fresh meat standard. The total bacterial count of all chicken samples increased with prolonged storage time. The total bacterial count in the control group and the PVA treatment group was higher than other treatment groups during storage. This is partly due to the packaging's ability to isolate some microorganisms from the external environment, and partly due to the antibacterial effects of TA and cinnamon oil. Specifically, the chicken samples in the control group and the PVA group were close to spoiled meat on day 1 of storage, with total bacterial counts reaching 6.17 and 5.66 log₂O₅, respectively. 10 CFU / g, reaching as high as 9.26 and 8.56 log on day 3. 10 The CFU / g concentration increased rapidly thereafter. Chicken samples treated with TA and cinnamon oil films only became spoiled on day 3 of storage. At day 7, the chicken samples with a 5% cinnamon oil film had the lowest total bacterial count, indicating that TA and cinnamon oil films can inhibit the growth of microorganisms on the surface of chicken, thereby extending its shelf life. These results show that the PVA / 20%TA / 5% cinnamon treatment group has a better antibacterial effect than other treatment groups, and the antibacterial effect increases with increasing cinnamon oil loading concentration.

[0066] Example 2

[0067] Preparation and performance study of PVA-tannic acid-anthocyanin-hollow mesoporous microsphere cinnamon essential oil composite membrane (antioxidant and pH colorimetric properties)

[0068] 2.1.1 Selection of common plant anthocyanins

[0069] Common plants and flowers were harvested, and anthocyanins were extracted by weight using 95% ethanol at a ratio of 1:1. 1 ml of anthocyanin was added to 3 ml of pH 2-10 solution to observe the color change reaction, and then a full-spectrum analysis was performed using an enzyme-linked immunosorbent assay (ELISA) reader.

[0070] 2.1.2 Preparation of composite membranes

[0071] Five plant anthocyanins most sensitive to acids and alkalis were selected, and 3 mL of each was added to a PVA / 20%TA / 5% cinnamon membrane solution. The anthocyanin solution was prepared using ethanol as the solvent, with a mass ratio of anthocyanins to ethanol of 1:100. The cinnamon essential oil content in each unit of hollow mesoporous silica@cinnamon essential oil material was 10% of the total weight. The anthocyanin solution comprised 20% of the total weight of the PVA-tannic acid-mesoporous silica-coated cinnamon essential oil composite membrane solution, and 3 g of anthocyanin solution was added to 15 g of the PVA-tannic acid-mesoporous silica-coated cinnamon essential oil composite membrane solution.

[0072] 2.1.3 Infrared spectrum, same as in Example 1.

[0073] 2.1.4 X-ray diffraction (XRD) analysis of the composite film, same as in Example 1.

[0074] 2.1.5 Color difference of composite film, same as in Example 1.

[0075] 2.1.6 Acid-base sensitivity of composite membrane

[0076] Five plant anthocyanin composite films were placed in a container, and 1 ml of acetic acid and ethanol were added to each. After standing for 1 hour, the color change of the composite films was observed and photographed.

[0077] 2.1.7 The mechanical properties of the composite membrane are the same as in Example 1.

[0078] 2.1.8 The air permeability of the composite membrane is the same as in Example 1.

[0079] 2.1.9 The antioxidant properties of the composite membrane are the same as in Example 1.

[0080] 2.1.10 The antibacterial properties of the composite membrane are the same as in Example 1.

[0081] 2.2 Results Analysis

[0082] 2.2.1 Selection of common plant anthocyanins

[0083] Figure 19 (a) shows the color reaction of camellia in solutions of different pH values; (b) shows the absorbance of camellia in solutions of different pH values; (c) shows the comparison of pH and OD values ​​of camellia in solutions of different pH values. Figure 20 (a) shows the color reaction of kale in solutions of different pH values; (b) shows the absorbance of kale in solutions of different pH values; (c) shows the comparison of pH and OD values ​​of kale in solutions of different pH values. Figure 21 (a) shows the color reaction of mulberry in solutions of different pH values; (b) shows the absorbance of mulberry in solutions of different pH values; (c) shows the comparison of pH and OD values ​​of mulberry in solutions of different pH values. Figure 22(a) shows the color reaction of purple cabbage in solutions with different pH values; (b) shows the absorbance of purple cabbage in solutions with different pH values; (c) shows the comparison of pH and OD values ​​of purple cabbage in solutions with different pH values. Figure 23 (a) shows the color reaction of onion in solutions of different pH values; (b) shows the absorbance of onion in solutions of different pH values; (c) shows the comparison of pH and OD values ​​of onion in solutions of different pH values. Figure 24 (a) shows the color reaction of onion in solutions of different pH values; (b) shows the absorbance of onion in solutions of different pH values; (c) shows the comparison of pH and OD values ​​of onion in solutions of different pH values. Figure 25 (a) shows the color reaction of Magnolia denudata in solutions with different pH values; (b) shows the absorbance of Magnolia denudata in solutions with different pH values; (c) shows the comparison of pH and OD values ​​of Magnolia denudata in solutions with different pH values. Figure 26 (a) shows the color reaction of radish flowers in solutions with different pH values; (b) shows the absorbance of radish flowers in solutions with different pH values; (c) shows a comparison of pH and OD values ​​of radish flowers in solutions with different pH values.

[0084] The above are some common plant anthocyanin acid-base solution change graphs and absorbance values. By comparing the colors and absorbance value dispersion of several plant anthocyanin acid-base solutions, kale, radish flower, onion, black rice, and purple cabbage were selected and added to the membrane solution.

[0085] 2.2.1 Infrared Spectroscopic Analysis

[0086] Figure 27 These are infrared spectra of anthocyanin composite films from different plants. Figure 27 Infrared spectra of anthocyanin complex films from different plants were shown, with only the 3700 cm⁻¹ region observed. -1 The left and right sides represent the absorption peaks of the alcohol hydroxyl groups (hydrogen bond association) of PVA; 1800 cm⁻¹ -1 The peak at 1589 cm⁻¹ represents the characteristic peak of the C=O bond remaining in the polyvinyl alcohol production process from polyvinyl acetate. No new peaks appeared after the addition of plant anthocyanins. The composite membrane after the addition of tannic acid and TA showed a peak at 1589 cm⁻¹. -1 A noticeable increase in the height of the benzene ring absorption peak was observed, shifting to 1523. -1 In addition, 500cm -1 -1000cm -1 Miscellaneous peaks appeared at that point.

[0087] 2.2.2 X-ray diffraction (XRD) analysis of the composite film

[0088] Figure 28 These are XRD diagrams of anthocyanin complex membranes from different plants, such as... Figure 28 As shown, the diffraction characteristic peaks of several plant anthocyanin composite films did not change significantly.

[0089] 2.2.3 Color difference of composite film

[0090] Table 3 shows the color difference of composite films containing different plant anthocyanins.

[0091] Table 3 Color difference of composite films containing different plant anthocyanins

[0092] Table 3 lists the color difference values ​​(L) of composite films with different plant anthocyanins added. * (Brightness), a * (Green / Red), b * (Blue / Yellow) and ΔE * Color parameters such as (total color difference) are important. The color of the membrane has a significant impact on food quality and consumer acceptance. Table 3-1 shows photographs of the membrane samples, revealing that the composite membrane a with added black rice pigment... * The value is the highest, and the composite membrane's appearance is pink, significantly different from other composite membranes that tend to be greenish. From b * In terms of values, the kale composite film had the highest value, reaching 38.11, indicating that the kale composite film is more yellow and more suitable as a food packaging film than green and pink.

[0093] 2.2.4 Acid-base sensitivity

[0094] Figure 29 Color changes of composite membranes containing different plant anthocyanins under acidic and alkaline conditions; Figure 30 Different plant anthocyanin composite membranes under alkaline (A) and acidic (B) conditions a * Value variation graph;

[0095] This experiment measured the color response of the membrane under acidic and alkaline gas conditions. Figure 29 As shown, under acidic gas conditions, the colors of several plant anthocyanin composite films all changed to varying degrees towards red and yellow. The kale and black rice anthocyanin composite films were the darkest, appearing deep red, while the other plant anthocyanin composite films appeared yellow. Figure 30 (B) From this perspective, all composite membranes, after being exposed to acetic acid gas, showed a... * The values ​​all increased, while the anthocyanin complex membranes of kale and black rice showed an increase. * The increase in value was most significant, but the black rice anthocyanin composite membrane under normal conditions showed the most significant increase in a. * The values ​​are also very high, so kale anthocyanins are most sensitive to acidic gases. Under alkaline gas conditions, the color of the anthocyanin complex membranes of several plants all show varying degrees of greening. Figure 30 (A) Looking at the anthocyanin complex membranes of kale, radish flowers, onions, and purple cabbage... *The values ​​are all negative, which also indicates that the color of the anthocyanin composite film from several plants has turned green.

[0096] Based on the appearance of the membrane, the color of the resulting membrane differed somewhat from the color change of the anthocyanin solution itself when different plant anthocyanins were added to the composite membrane solution. The results showed that the kale anthocyanin composite membrane exhibited good sensitivity under both acidic and alkaline gas conditions.

[0097] 2.2.5 Water solubility determination

[0098] Figure 31 Water solubility of composite membranes containing different plant anthocyanins; Figure 32 Solubility diagrams of different plant anthocyanin composite membranes in water over 6 hours; for example Figure 31 As shown, the water solubility of composite membranes with different plant anthocyanins added is lower than that of the composite membrane without anthocyanins in the previous chapter. This may be because the hydroxyl groups in anthocyanins form hydrogen bonds with the hydrophilic groups in the membrane matrix, thereby reducing the ability of the hydrophilic groups in the membrane to absorb water. Among them, the onion anthocyanin composite membrane has the lowest water solubility at 41.58%. This may be because the extracted onion anthocyanins contain some onion oil, the main component of which is sulfur-containing compounds. Although these compounds are present in small amounts, they constitute the unique flavor and physiological efficacy components of onions. These oily substances hinder the direct contact between the onion anthocyanin composite membrane and water. The water solubility of other plant anthocyanin composite membranes also remained between 40% and 50%, exhibiting good water resistance.

[0099] from Figure 32 As can be seen, all plant anthocyanin composite films maintained their original structure after being soaked in water for 6 hours, with only slight swelling, which also proves that the plant anthocyanin composite films also have high water resistance.

[0100] 2.2.6 Measurement of water vapor transmission rate

[0101] Figure 33 Different thin film water vapor transmission coefficients; by Figure 33 It can be seen that, compared with the results of the water vapor transmission rate measurement experiment in 2.6, the water vapor transmission coefficients of all plant anthocyanin composite membranes are lower than those of pure PVA films, but higher than those of PVA / 20%TA / carrier / 5% cinnamon composite membranes. This may be because the addition of more anthocyanins causes aggregation, which disrupts the dense molecular structure of the membrane, resulting in uneven dispersion of anthocyanins in the film-forming matrix and making the membrane surface more porous, thus increasing the water vapor transmission coefficient. Wu Fuqi (2021) and Luches et al. (2018) also found similar phenomena in their studies. At the same time, during the membrane liquid drying process, the membrane liquid can also be observed to have an automatic tumbling phenomenon, followed by agglomeration, which also indirectly confirms the aggregation phenomenon of anthocyanins.

[0102] 2.2.7 Mechanical property analysis of composite membrane

[0103] Table 4 Mechanical Properties of Different Composite Membranes

[0104] Figure 34 This is a graph showing the stress variation of different films. Mechanical properties are an important indicator for evaluating the application value of films. Food packaging with good mechanical properties can protect food from physical pressure and environmental conditions. The film thickness, tensile strength, and elongation at break are shown in Table 4. Table 4 shows that there is no significant difference in film thickness, indicating that the addition of anthocyanins has little effect on film thickness. Except for the kale anthocyanin composite film, which has a tensile strength of 11.85 MPa, the tensile strength of other composite films is between 4-5 MPa. Compared with the tensile strength of the PVA / 20%TA / 5% cinnamon composite film, the strength is slightly lower. This may be because anthocyanin aggregation occurred in the anthocyanin composite films other than the kale film, leading to an uneven composite film structure and overall dispersion, resulting in poor mechanical properties. Figure 34 It is also evident that the kale anthocyanin composite membrane exhibits the highest breaking force, while the breaking forces of the other composite membranes are not significantly different. This indicates that anthocyanins do have some influence on the mechanical properties of the composite membrane.

[0105] 2.2.8 Antioxidant properties

[0106] Figure 35 These are the antioxidant properties of different composite films. Food is easily oxidized, leading to quality degradation. Therefore, films containing natural colorants with strong antioxidant capabilities can be a viable method to protect food from oxidation. For example... Figure 35 As shown, compared to the DPPH scavenging rate of 84.93% for the PVA / 20%TA / carrier / 5% cinnamon composite membrane, all plant anthocyanin composite membranes exhibited improved antioxidant properties. The onion anthocyanin composite membrane had the lowest DPPH scavenging rate at 88.16%, while the highest was 95.17% for the purple cabbage membrane. This demonstrates that the addition of anthocyanins improved the antioxidant properties of the membranes. The antioxidant properties of the membranes can be attributed to the phenolic hydroxyl groups contained in anthocyanins, which act as effective reducing agents by forming phenoxy groups to eliminate free radicals. This also indirectly confirms the good compatibility between different plant anthocyanins and the composite membranes.

[0107] 2.2.9 Oxygen and carbon dioxide permeability of composite membrane

[0108] Figure 36 The oxygen permeability (A) and carbon dioxide permeability (B) of different composite membranes; Figure 36It is evident that the air permeability of different plant anthocyanin composite films varies, indicating that the addition of anthocyanins can also affect the air permeability of PVA / 20%TA / carrier / 5% cinnamon composite films. Air permeability plays a crucial role in food packaging for preservation. Experiments show that the kale anthocyanin composite film has the lowest oxygen permeability, even slightly lower than the PVA / 20%TA / carrier / 5% cinnamon composite film, while other plant anthocyanin composite films show a slight increase. Combined with mechanical property test results, this may still be due to anthocyanin aggregation leading to an uneven composite film structure, resulting in greater oxygen permeability. Therefore, kale anthocyanin composite films, which exhibit less aggregation, have a certain feasibility as food preservation packaging materials.

[0109] 2.2.10 Determination of antibacterial properties of composite membrane

[0110] Figure 37 Diagrams showing the diameters of the inhibition zones of Staphylococcus aureus on different composite membranes (A) and (B). Figure 38 These are diagrams of the diameter of the inhibition zone of E. coli in different composite membranes (A) and (B). Figure 37 (B) and 38(B) are actual photographs of the inhibition zones of different plant anthocyanin composite membranes against Staphylococcus aureus and Escherichia coli. Figure 37 (A) and (A) represent the diameters of the inhibition zones of different plant anthocyanin composite membranes against Staphylococcus aureus and Escherichia coli. The figures clearly show a comparison of the size of the inhibition zones of the various composite membranes. It is evident that all the plant anthocyanin composite membranes exhibited high antibacterial activity. The onion anthocyanin composite membrane showed the highest inhibition zones against Staphylococcus aureus and Escherichia coli, while the inhibition zones of the other plant anthocyanin composite membranes were not significantly different. This may be due to the strong antibacterial effect of onion oil present in onion anthocyanins. Compared to the PVA / 20%TA / 5% cinnamon composite membrane, the size of the inhibition zones of the plant anthocyanin composite membranes decreased to varying degrees. This may be because anthocyanins hinder the direct contact between the antibacterial components and the pathogens.

[0111] Example 3

[0112] Study on the Preservation Effect of PVA-Tanolic Acid-Anthocyanin-Hollow Mesoporous Microspheres@Cinnamon Oil Composite Membrane on Pork

[0113] 3.1.1 Methods for preserving pork

[0114] Cut 10g of fresh pork evenly and place it in a beaker. Cover the mouth of the beaker with a composite film and seal the edges with tape. Since the kale group performed well in the test in Chapter 3, the following groups were set up: no treatment control group, PVA group, PVA / 20%TA / carrier / 5% cinnamon group, and PVA / 20%TA / carrier / 5% cinnamon / kale group.

[0115] 3.1.2 Changes in appearance during storage

[0116] 3.1.3 Juice Loss Rate Determination

[0117] The method of Xu Ping et al. was used to determine the juice loss rate of pork slices. The total mass of each sample was weighed sequentially (m1); all the juice from the plastic wrap was poured out, and the remaining juice on the surface of the meat and the film was absorbed, and the total mass of the plastic wrap and meat was measured (m2); the plastic wrap was weighed separately (m3).

[0118] Juice loss rate is calculated as shown in formula (1).

[0119] Juice loss rate = (m1-m2) / (m1-m3)×100%(1)

[0120] 3.1.4 Sensory evaluation

[0121] Six evaluators were selected to conduct sensory evaluations of the experimental pork samples. Specific requirements were explained to each evaluator before the evaluation, and they were assigned scores according to the sensory scoring criteria (see Table 5). The total score was 10 points. Evaluators would comprehensively assess the samples based on four aspects: appearance, color, odor, and texture. The comprehensive evaluation results were then statistically analyzed.

[0122] 3.1.5 pH value determination

[0123] First, weigh 10g of pork, then add 90mL of distilled water, homogenize with a high-speed discrete homogenizer (10000r / min) for 2min, let stand for 40min, and finally measure with a pH meter.

[0124] 3.1.6 Determination of Volatile Basic Nitrogen Value (TVB-N)

[0125] The determination of volatile basic nitrogen values ​​was performed using an automatic Kjeldahl nitrogen analyzer. The pork was chopped and mixed thoroughly. 10g of the sample was weighed, accurate to 0.001g. 75mL of water was added to the distillation tube, and the mixture was shaken thoroughly to ensure the sample was evenly dispersed in the solution. The sample was then soaked for 30 minutes. The instrument was operated according to the instructions. A blank value was first obtained, and then the sample was analyzed.

[0126] 3.1.7 Color difference (same as Example 1)

[0127] 3.1.8 Determination of total bacterial count

[0128] The bacterial count of pork at different shelf-life times was determined in accordance with the standard GB4789—2016 National Food Safety Standard for Microbiological Examination of Food: Determination of Total Colony Count.

[0129] 3.2 Analysis of Experimental Results

[0130] 3.2.1 Changes in the appearance of pork during storage

[0131] Figure 39 Effects of different treatments on the appearance of pork stored at 20℃ for 10 days

[0132] Using unwrapped fresh pork as the control group, the treatment groups were wrapped with PVA film, PVA / 20%TA / 5% cinnamon film, and PVA / 20%TA / 5% cinnamon / kale film, respectively. Figure 39 This is a photographic record of pork from the control group and different treatment groups taken at room temperature (20℃) over 10 days.

[0133] As shown in the figure, the control group deteriorated on day 2, with the lean meat turning dark brown and drying out. By day 6, the lean meat had turned black. The PVA film turned dark brown on day 4 and also black on day 6. Pork wrapped in PVA / 20%TA / 5% cinnamon film, PVA / 20%TA / 5% cinnamon film, and PVA / 20%TA / 5% cinnamon / kale film still had some liquid residue on the surface on day 8, and the lean meat had not turned black, indicating that the treated groups had a significant pork preservation effect.

[0134] 3.2.2 Juice Loss Rate Determination

[0135] Juice loss rate of pork in different treatment groups during storage: Figure 40 As shown. Figure 40 Juice loss rate of pork from different treatment groups during storage; from Figure 40 As can be seen, the juice loss rate of both the treatment and control groups increased with prolonged storage time. On the second day, there was no significant difference in juice loss rate among the sample groups. After the second day, the juice loss rate of the control group increased rapidly, widening the gap with the other three groups. On the tenth day, the treatment group still maintained a significant difference from the control group.

[0136] exist Figure 39 In the PVA group, no liquid residue remained on the surface of the pork on the tenth day. Figure 20 The difference in juice loss rate between the middle group and the other two treatment groups is not significant. This may be due to the hydrophilicity of the PVA film. The strong water absorption of the PVA film causes water in the meat to migrate into the film, resulting in less liquid on the surface of the pork compared to the other two treatment groups. Since the water vapor permeability of the three treatment groups is similar, the juice loss rate of the three treatment groups is also similar.

[0137] 3.2.3 Sensory evaluation

[0138] Sensory evaluation is one of the routine methods for assessing the freshness of pork. This sensory evaluation includes odor,

[0139] Changes in color and appearance. The effects of different treatment groups (blank control group, PVA film, PVA / 20%TA / 5% cinnamon film, PVA / 20%TA / 5% cinnamon / kale film) on the sensory properties of pork are as follows: Figure 41 As shown, the odor scores of the control group, PVA membrane group, PVA / 20%TA / 5% cinnamon membrane group, and PVA / 20%TA / 5% cinnamon / kale membrane group decreased with increasing storage time. The odor scores of the blank sample group and the PVA group showed significant differences from the other two groups after 2 days of storage, producing a distinct odor, which approached unacceptable levels by day 4. On day 8, the PVA / 20%TA / 5% cinnamon membrane group and the PVA / 20%TA / 5% cinnamon / kale membrane group only produced a slight odor. By day 10, all treatment groups produced unacceptable odors. The putrid, sour odor of meat is often caused by fat oxidation and microbial growth. Oxidation products of meat and meat products, such as peroxides, low-molecular-weight fatty acids, aldehydes, and ketones, all produce unpleasant odors. The tannins and cinnamon essential oil in the membrane have excellent antioxidant and antibacterial properties, and the unique aroma of cinnamon essential oil can also neutralize the putrid, sour odor of meat.

[0140] Color scores also decreased with increasing storage time. The control group and its color scores were significantly lower than the other groups, and the pork turned black on the 6th day after storage, reaching an unacceptable level. After the 2nd day of storage, the color scores of the PVA / 20%TA / 5% cinnamon film group and the PVA / 20%TA / 5% cinnamon / kale film group were significantly higher than the other two groups. This indicates that the addition of cinnamon and tannins is beneficial to maintaining the color of fresh pork during preservation.

[0141] Appearance scoring showed that the appearance score of all samples gradually decreased with prolonged storage time. Furthermore, in...

[0142] After 4 days of storage, there were significant differences in appearance scores among different samples. The PVA / 20%TA / 5% cinnamon film group and the PVA / 20%TA / 5% cinnamon / kale film group also showed some large differences, indicating that the addition of kale anthocyanins also had a protective effect on the appearance of fresh pork.

[0143] 3.2.4 Determination of texture

[0144] Figure 42 This study investigates the effects of different composite membranes on the chewiness and elasticity of fresh pork. The textural properties of pork samples are correlated with numerous intrinsic factors, such as muscle fat content, fiber density, and collagen content. As storage time increases, the internal composition of pork samples...

[0145] The texture of pork samples will gradually soften under the action of microorganisms, affecting the texture of the pork samples. Figure 42This study investigates the effects of different film treatments on the chewiness and elasticity of pork samples during storage. The figure shows that the chewiness of pork samples increases with prolonged storage time. Increased chewiness indicates that more effort is required to chew the pork for swallowing. The control group and the pure PVA group have larger color blocks in the chewiness graph compared to the other two treatment groups. The elasticity of meat is related to its moisture content and protein content. As storage time increases, the moisture content of pork decreases, and protein decomposes, leading to a decrease in elasticity. The distribution of color blocks in the figure clearly shows that the control group without any treatment and the pure PVA group have higher elasticity, indicating the ability of the treatment groups to protect the moisture and protein in the pork.

[0146] 3.2.5 pH value determination

[0147] Figure 43 This is a graph showing pH changes during storage with different composite membranes. pH is an important indicator of meat freshness; an increase in pH is caused by the decomposition of proteins and amino acids (ammonia compounds) in raw meat by microorganisms. The pH of fresh meat is generally around 5.6. Reference standards for pH are: Grade 1 freshness: pH 5.8 to 6.2; Grade 2 freshness: pH 6.3 to 6.6; spoiled meat: pH above 6.7. The pH changes of pork under different treatments during storage (0-10 days) are shown in the graph. Figure 43 The pH of pork showed an increasing trend with storage time. The most rapid increase in pH was observed in all treatment groups during storage periods of 0-2 days, followed by a slower and more gradual increase. As shown in the graph, at 2 days of storage, the pH of the control group and the PVA group exceeded 7.0, reaching spoilage levels. The PVA / 20%TA / 5% cinnamon film group and the PVA / 20%TA / 5% cinnamon / kale film group reached spoilage levels at 4 days. The slower increase in pork pH after the second day is likely because during the initial storage period, the active respiration of the meat's tissue cells during maturation and preservation led to glycogenolysis and ATP decomposition, producing acidic substances such as lactic acid and phosphoric acid, thus slowing the pH increase. As storage time increases, the endogenous proteases in the meat and the protein-degrading enzymes secreted by microorganisms degrade muscle proteins into polypeptides and amino acids, releasing alkaline gases, causing the pH value of the meat to continue to rise. This also provides an alkaline gas environment for the acid-base discoloration of the composite membrane.

[0148] 3.2.6 Determination of Volatile Basic Nitrogen Value (TVB-N)

[0149] Figure 44This is a graph showing the changes in TVB-N during storage with different composite films. During storage, the proteins and fats in pork are decomposed by microorganisms, producing a large amount of volatile nitrogenous compounds, which leads to an increase in the TVB-N of the pork. Therefore, TVB-N can be used as an indicator of pork freshness. According to the TVB-N standard in GB2707-2016, pork can be divided into three grades: Grade 1 freshness is specified as ≤15.0mg / 100g; Grade 2 freshness is ≤25.0mg / 100g; and spoiled meat is >25mg / 100g. Figure 44 As shown, at 2 days, the TVB-N values ​​of the control group and the pure PVA group were already higher than 15 mg / g, indicating that the meat was no longer fresh. At 3 days, the TVB-N values ​​of the PVA / 20%TA / 5% cinnamon film group and the PVA / 20%TA / 5% cinnamon / kale film group were close to 15 mg / g, and at room temperature of 30℃, the TVB-N value was delayed by one day to reach the second-grade freshness level. At 6 days, the control group reached 25.0 mg / 100g, becoming spoiled meat, while the other three groups only reached the spoiled meat level at 7 days. This demonstrates that the treatment groups have a good effect on the preservation of pork.

[0150] 3.2.7 Color difference of composite film

[0151] Figure 45 These are actual photos showing the color difference of the kale composite film. Figure 46 It is a kale composite film a * Value change graph

[0152] Figure 45 The color change of the kale composite film during pork storage was demonstrated. The film gradually turned green, changing from a slightly yellowish color at 2d to a yellowish-green at 10d. Anthocyanins undergo color changes under acidic or alkaline conditions. Combined with pH measurements at 4.5, the pH of the pork shifted to alkaline during the later stages of storage. Under the action of decomposing enzymes, the pork gradually produced alkaline gases, which caused the anthocyanins in the kale composite film to change color. (The colorimeter shows a...) * Positive values ​​are red, and negative values ​​are green, such as... Figure 46 As shown, the kale composite film has a * The value gradually decreased, reaching a negative value at 8 days, and officially turning green. This proves that kale anthocyanins are effective in determining freshness in composite membranes.

[0153] 3.2.8 Determination of total bacterial count

[0154] Figure 47 Real photos of total bacterial count measurements on pork treated with different groups after 2 days; Figure 48 Graph showing changes in total bacterial count in pork under different treatment groups; microorganisms are the main cause of spoilage in chilled pork, therefore, the total bacterial count is an important indicator of the degree of meat spoilage. The standard references GB4789.2-2010, exceeding 6 log...10 CFU / g indicates spoiled meat. (From...) Figure 48 It can be seen that the total number of colonies in all treatment groups showed an increasing trend. In the control group, the total number of colonies exceeded 6 log₂S / day at 2 days. 10 The concentration of CFU / g indicated spoilage. Other treatment groups reached spoilage levels between 3 and 4 days. This is consistent with the experimental results of other groups in this chapter. The control group and the pure PVA group reached spoilage levels on the second day, while the PVA / 20%TA / 5% cinnamon film group and the PVA / 20%TA / 5% cinnamon / kale film group spoiled between 3 and 4 days, delaying spoilage by one to two days.

Claims

1. A method for preparing a PVA-tannic acid-mesoporous silica-coated cinnamon oil composite membrane, characterized in that, The steps include: (1) Accurately weigh 1.5% to 20% of the dry weight of the membrane into 150 parts of 5% PVA solution, then weigh 30% of the dry weight of the membrane into glycerol, stir at 70°C for 4 hours to fully dissolve it, and obtain tannic acid-PVA solution, wherein the dry weight of the membrane is the proportion of the solution weight; (2) Add 3% to 5% of the dry weight of the membrane into the tannic acid-PVA solution, which is hollow mesoporous silica@cinnamon essential oil or 3% to 5% of the dry weight of the membrane into the membrane, which is hollow mesoporous silica@cinnamon essential oil and anthocyanins, wherein the dry weight of the membrane is the proportion of the solution weight; (3) After forming the membrane by solution casting, place it in an oven at 40°C for 12 hours to dry, and obtain the solution.

2. The method for preparing a PVA-tannic acid-mesoporous silica-coated cinnamon oil composite membrane according to claim 1, characterized in that, The anthocyanins in step (2) are obtained from kale.

3. The method for preparing a PVA-tannic acid-mesoporous silica-coated cinnamon oil composite membrane according to claim 1, characterized in that, In step (2), the anthocyanin solution is 20% of the total weight of the PVA-tannic acid-mesoporous silica-coated cinnamon oil composite membrane solution. 3g of anthocyanin solution is added to 15g of PVA-tannic acid-mesoporous silica-coated cinnamon oil composite membrane solution.

4. The method for preparing a PVA-tannic acid-mesoporous silica-coated cinnamon oil composite membrane according to claim 1, characterized in that, The cinnamon oil content in each unit of hollow mesoporous silica@cinnamon oil material is 10% of the total weight.

5. The application of the PVA-tannic acid-mesoporous silica-coated cinnamon oil composite membrane as described in claims 1-4, characterized in that, Used for preserving pork or chicken.

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