Moringa oleifera leaf polyphenol composite membrane as well as preparation method and application thereof

Abstract

The invention discloses a horseradish tree leaf polyphenol composite membrane, a preparation method and application thereof. The moringa oleifera leaf polyphenol composite film comprises 0.5-10% of a moringa oleifera leaf polyphenol extract. By adding the moringa oleifera leaf polyphenol extract, the mechanical performance, water resistance, oxidation resistance and antibacterial performance of the pure polysaccharide-based composite film are enhanced, and the obtained moringa oleifera leaf polyphenol composite film has wide application prospects in the fields of food preservation and the like.

Description

Technical Field

[0001] This invention relates to the field of active food packaging, specifically to a Moringa leaf polyphenol composite film, its preparation method, and its application. Background Technology

[0002] In recent years, with increasing environmental awareness and concerns about food quality, safety, freshness, and health, safe, non-toxic, and biodegradable food packaging materials have received growing attention. Molecular gum (MOLE) is a rich polysaccharide composed of L-arabinose, D-glucose, D-lythose, D-mannose, D-xylose, and D-galactose, with a molecular weight of approximately 1.42 × 10⁻⁶. 5 With a concentration of g / mol, it exhibits good biocompatibility, film-forming properties, and emulsifying properties. As a natural polymer, it has a low environmental impact, high cost-effectiveness, and strong sustainability, making it promising for the development of biodegradable films. The linear backbone of *Aureobasidium* gum is a network structure formed by the branching and entanglement of molecular chains. However, when *Aureobasidium* gum is used alone as a film-forming raw material, the resulting film exhibits poor mechanical properties and is sensitive to humidity. To improve these shortcomings, other high-molecular polymers (such as proteins, polysaccharides, starch, and cellulose) are often added to enhance the performance of single-film materials. For example, pullulan, a colorless, tasteless, water-soluble extracellular polysaccharide produced by *Aureobasidium pullulan*, not only possesses properties similar to synthetic materials but also offers advantages such as food safety, biodegradability, and good gas barrier properties. Combined with *Aureobasidium* gum, it can improve the mechanical properties and oxygen barrier properties of the film.

[0003] Moringa leaf polyphenols are polyphenolic compounds extracted from Moringa leaves, containing a variety of small molecules. Due to their excellent antioxidant, antibacterial, and hydrophobic properties, they are used as active ingredients in drug carriers and packaging. However, there are no reports on using Moringa leaf polyphenols to strengthen Artemisia argyi / pullulan polysaccharide composite films.

[0004] There is an urgent need for a low-cost membrane material that also has good barrier properties, antioxidant and antibacterial effects, and physical strength. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies: pure polysaccharide membranes have poor mechanical properties and insignificant antibacterial effects. This invention provides a Moringa leaf polyphenol composite membrane, which features low cost, good barrier properties, strong antioxidant and antibacterial effects, and high physical strength.

[0006] Another objective of this invention is to provide a method for preparing a Moringa leaf polyphenol composite membrane.

[0007] Another objective of this invention is to provide an application of Moringa leaf polyphenol composite film in food packaging.

[0008] To achieve the purpose of this invention, this invention provides a Moringa leaf polyphenol composite film containing 0.5-10% by weight of Moringa leaf polyphenol extract.

[0009] The weight content of the Moringa leaf polyphenol extract refers to the ratio of the mass of the Moringa leaf polyphenol extract to the total weight of the composite film, which is 0.5-10%, preferably 3-8%, and more preferably 3-6%.

[0010] The polyphenol content of the Moringa leaf polyphenol extract is 20-25%.

[0011] The Moringa leaf polyphenol extract of this invention is prepared by an ultrasound-assisted aqueous two-phase extraction method, and the specific preparation process is as follows:

[0012] 1) Crush the Moringa leaf sample, add the Moringa leaf powder to an ethanol and ammonium sulfate two-phase system, and extract using an ultrasonic cleaner. The main parameters are set as follows: material-to-liquid ratio 1:9~1:12 g / ml, ethanol concentration 55~60%, ammonium sulfate concentration 0.1~0.3g / ml, ultrasonic time 20~50min, and ultrasonic temperature controlled at 55~65℃;

[0013] 2) After ultrasonic treatment, the powder was purified by D101 macroporous adsorption resin and finally dried to obtain a brownish-yellow powder. The drying process was carried out by freeze drying at -40~-50℃ for 36~48h.

[0014] Furthermore, the composite membrane of the present invention also contains Artemisia argyi gum and pullulan polysaccharide.

[0015] Both the *Artemisia argyi* gum and pullulan polysaccharide were selected from food-grade polysaccharides. The *Artemisia argyi* gum is a heteropolysaccharide with a molecular weight of 1.42 × 10⁻⁶. 5 ~3.46×10 5 Da, pullulan has a molecular weight of 1×10⁻⁶. 6 ~ 2×10 6 Da.

[0016] The weight ratio of Moringa leaf polyphenol extract, Artemisia gum, and pullulan polysaccharide is 1~10:50~60:30~50.

[0017] Furthermore, the composite film also contains plasticizers and crosslinking agents.

[0018] The plasticizer is glycerol, sorbitol, xylitol, polyethylene glycol, glucose, or sucrose.

[0019] The cross-linking agent is anhydrous calcium chloride, tyrosinase, or transglutaminase.

[0020] Further, the composite film (also known as Moringa leaf polyphenol-Artemisia gum / pullulan composite preservation film) comprises 1.00-1.50 parts of Artemisia gum, 0.60-1.50 parts of pullulan, 0.30-0.45 parts of plasticizer, 0.01-0.02 parts of crosslinking agent, and 0.02-0.18 parts of Moringa leaf polyphenol extract; preferably, the composite film comprises 1.00-1.20 parts of Artemisia gum, 0.60-1.00 parts of pullulan, 0.30-0.45 parts of plasticizer, 0.01-0.02 parts of crosslinking agent, and 0.02-0.18 parts of Moringa leaf polyphenol extract.

[0021] This invention also provides a method for preparing a Moringa leaf polyphenol extract composite film, comprising: first preparing a sand wormwood gum solution and a pullulan polysaccharide solution respectively, mixing them in a certain proportion, adding a plasticizer and a crosslinking agent, then dissolving the Moringa leaf polyphenol extract, and then fusing it with the above solution to obtain the final film-forming liquid, and after drying, obtaining a composite film with meat preservation properties, namely Moringa leaf polyphenol-sand wormwood gum / pullulan polysaccharide composite preservation film.

[0022] Specifically, the method for preparing the composite membrane includes the following steps:

[0023] 1) Prepare polysaccharide solutions by mixing Artemisia argyi gum and pullulan polysaccharide separately with deionized water, and then prepare polysaccharide-based film solution by mixing the two polysaccharide solutions in a certain proportion;

[0024] 2) Add the plasticizer and crosslinking agent to step 1) respectively, and stir well;

[0025] 3) Then add Moringa leaf polyphenol extract to the solution obtained in step 2), stir well, and obtain the final film solution;

[0026] 4) Finally, pour the final film solution into the mold and dry it to form a film.

[0027] The concentration ratio of Artemisia argyi gum to pullulan polysaccharide is 1:1.

[0028] When preparing the membrane solution, the stirring temperature is 50~60℃ and the stirring speed is 300~500r / min.

[0029] The final film solution is dried at 50-60℃ for 8-16 hours.

[0030] This invention also provides an application of Moringa leaf polyphenol composite film in food packaging films, particularly for the preservation and antibacterial properties of meat products.

[0031] The Moringa leaf polyphenol composite membrane of the present invention enhances the mechanical properties, water resistance, antioxidant and antibacterial properties of the pure polysaccharide-based composite membrane by adding Moringa leaf polyphenol extract, and has the following beneficial effects:

[0032] 1. In addition to adding Moringa leaf polyphenol extract, this invention also selectively adds a crosslinking agent (anhydrous calcium chloride), which makes the resulting preservation film have high strength and mechanical properties, good elasticity and easy stretching, and is not easy to break, thus overcoming the problem of poor mechanical properties of pure polysaccharide film itself.

[0033] 2. The mechanical properties, water resistance, antioxidant and antibacterial properties of the pure polysaccharide-based composite film were enhanced by adding Moringa leaf polyphenol extract. The resulting Moringa leaf polyphenol composite film has broad application prospects in food preservation and other fields.

[0034] 3. In the composite membrane of this invention, Artemisia argyi gum and pullulan polysaccharide are selected as film-forming matrices, and Moringa leaf polyphenol extract provides active ingredients for meat preservation, which can inhibit the growth and reproduction of microorganisms on the surface of meat and slow down the oxidation rate of meat fat, thereby extending the shelf life of food.

[0035] 4. This invention utilizes the antioxidant, antibacterial, and hydrophobic properties of polyphenols. The resulting food preservation film not only has antioxidant and antibacterial effects, but also effectively blocks water vapor, thus providing a better preservation effect.

[0036] 5. The preparation method of the composite membrane of the present invention is simple and the raw material cost is low. Attached Figure Description

[0037] Figure 1 This is a comparison diagram of the antibacterial experiment results of the embodiments and comparative examples of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] The following reagent was obtained from: Artemisia argyi gum, Jiangsu Kelunduo Food Ingredients Co., Ltd., with a molecular weight of 1.42 × 10⁻⁶. 5 ~3.46×10 5 Da;

[0040] Pullulan, Jiangsu Ruikanglai Technology Co., Ltd., has a molecular weight of 1×10⁻⁶. 6 ~ 2×10 6 Da;

[0041] Glycerin, Shandong Keyuan Biochemical Co., Ltd.;

[0042] Anhydrous calcium chloride, Shanghai Maclean Biochemical Technology Co., Ltd.

[0043] Example 1

[0044] This example is used to prepare Moringa leaf polyphenol extract.

[0045] Moringa leaf polyphenol extract was prepared using an ultrasound-assisted aqueous two-phase extraction method. The specific preparation process is as follows:

[0046] 1) After pulverizing the Moringa leaf sample and passing it through an 80-mesh sieve, an appropriate amount of Moringa leaf powder was placed in a 50ml centrifuge tube. An ethanol and ammonium sulfate two-phase system was added, and extraction was performed in an ultrasonic cleaner. The main parameters were set as follows: material-to-liquid ratio 1:10 g / ml, ethanol concentration 55%, ammonium sulfate concentration 0.2g / ml, ultrasonic time 30min, and ultrasonic temperature controlled at 60℃.

[0047] 2) After ultrasonic treatment, the powder was purified by D101 macroporous adsorption resin and then freeze-dried at -50℃ for 48 hours in a vacuum freeze dryer to obtain a brownish-yellow powder.

[0048] The absorbance of the sample was measured at 765 nm, and the polyphenol content was calculated to be 23.14%.

[0049] Moringa leaf polyphenol extract was identified by liquid chromatography-mass spectrometry (LC-MS). Key parameters were summarized as follows: Mobile phase composition: A binary mobile phase was used, with phase A being an aqueous solution containing 0.1% formic acid and phase B being an acetonitrile solution containing 0.1% formic acid. Gradient elution program: At 0 minutes, phase A comprised 95% and phase B 5%; at 12 minutes, phase A comprised 5% and phase B 95%; at 12.9 minutes, phase A was maintained at 5% and phase B at 95%; at 13 minutes, phase A recovered to 95% and phase B decreased to 5%; at 15 minutes, phase A was maintained at 95% and phase B at 5%. Flow rate: 0.4 mL / min; Column temperature: 40°C; Injection volume: 10 μL.

[0050] Analysis revealed the presence of: chlorogenic acid, caffeic acid, rosmarinic acid, phenethyl caffeate, ethyl caffeate, methyl rosmarinic acid, isoflavone A, forsythoside I, isorhortioside, verbascoside, akebia phenylethanol glycoside B, epigallocatechin, epigallocatechin gallate, gallocatechin, dihydroresveratrol, resveratrol, phloretin, isopsoralen dihydroflavonoids, psoralen B, kavalpinx B, stigmosiderin, norsyringone, rhodopsin, isozymidine, ash extract, paeoniflorin, difuric acid, azelaic acid, ethyl p-methoxycinnamate, methyl 4-hydroxycinnamate, methyl ferulic acid, isoflavonic acid, coniferaldehyde, 4-methoxysalicylic acid, 5- Acetyl salicylic acid, paeonol, lansodium succinate, methyl ophiopogon dihydroisoflavones A, tetrahydrocurcumin, 8-shogaol, 6-shogaol, tripterygium oleracea, and other polyphenols.

[0051] Example 2

[0052] This embodiment is used to prepare a Moringa leaf polyphenol composite membrane, which contains Moringa leaf polyphenols-Artemisia gum / pullulan polysaccharide. The preparation of the composite membrane includes the following steps:

[0053] 1) Preparation of membrane solution: Dissolve 1.5g of Artemisia argyi gum and 1.2g of pullulan polysaccharide in 100ml of deionized water respectively. Add 0.038g of anhydrous calcium chloride and 1.05g of glycerol and stir well. Then add Moringa leaf polyphenol extract (taken from Example 1, polyphenol content is 23.14%), which accounts for 0.5% of the total membrane components and stir for 30min to obtain the membrane solution.

[0054] 2) Membrane preparation: The stirred membrane solution was degassed and defoamed by ultrasonication. 45 ml of the membrane solution was poured into a glass dish with a diameter of 90 mm and placed at 52 °C for 14 h to dry and prepare the membrane.

[0055] Example 3

[0056] This embodiment is used to prepare a Moringa leaf polyphenol composite membrane, which contains Moringa leaf polyphenols-Artemisia gum / pullulan polysaccharide. The preparation of the composite membrane includes the following steps:

[0057] 1) Preparation of membrane solution: Dissolve 1g of Artemisia argyi gum and 0.6g of pullulan polysaccharide in 100ml of deionized water respectively. Add 0.016g of anhydrous calcium chloride and 0.5g of glycerol and stir evenly. Then add Moringa leaf polyphenol extract (polyphenol content of 22.34%), which accounts for 1% of the total membrane components, and stir for 30min to obtain the membrane solution.

[0058] 2) Membrane preparation: The stirred membrane solution was degassed and defoamed by ultrasonication. 45 ml of the membrane solution was poured into a glass dish with a diameter of 90 mm and placed at 60 °C for 10 h to prepare the membrane.

[0059] Example 4

[0060] This embodiment is used to prepare a Moringa leaf polyphenol composite membrane, which contains Moringa leaf polyphenols-Artemisia gum / pullulan polysaccharide. The preparation of the composite membrane includes the following steps:

[0061] 1) Preparation of membrane solution: Dissolve 1.1g of Artemisia argyi gum and 0.8g of pullulan polysaccharide in 100ml of deionized water respectively. Add 0.032g of anhydrous calcium chloride and 0.6g of glycerol and stir evenly. Then add Moringa leaf polyphenol extract (polyphenol content of 24.06%), which accounts for 3% of the total membrane components, and stir for 30min to obtain the membrane solution.

[0062] 2) Membrane preparation: The stirred membrane solution was degassed and defoamed by ultrasonication. 45 ml of the membrane solution was poured into a glass dish with a diameter of 90 mm and placed at 55 °C for 15 h to prepare the membrane.

[0063] Example 5

[0064] This embodiment is used to prepare a Moringa leaf polyphenol composite membrane, which contains Moringa leaf polyphenols-Artemisia gum / pullulan polysaccharide. The preparation of the composite membrane includes the following steps:

[0065] 1) Preparation of membrane solution: Dissolve 1.2g of Artemisia argyi gum and 1g of pullulan polysaccharide in 100ml of deionized water respectively. Add 0.04g of anhydrous calcium chloride and 0.7g of glycerol and stir evenly. Then add Moringa leaf polyphenol extract (polyphenol content of 23.14%), which accounts for 5% of the total membrane components, and stir for 30min to obtain the membrane solution.

[0066] 2) Membrane preparation: The stirred membrane solution was degassed and defoamed by ultrasonication. 45 ml of the membrane solution was poured into a glass dish with a diameter of 90 mm and placed at 60 °C for 10 h to prepare the membrane.

[0067] Example 6

[0068] This embodiment is used to prepare a Moringa leaf polyphenol composite membrane, which contains Moringa leaf polyphenols-Artemisia gum / pullulan polysaccharide. The preparation of the composite membrane includes the following steps:

[0069] 1) Preparation of membrane solution: Dissolve 1.3g of Artemisia argyi gum and 1g of pullulan polysaccharide in 100ml of deionized water respectively. Add 0.045g of anhydrous calcium chloride and 1.0g of glycerol and stir evenly. Then add Moringa leaf polyphenol extract (polyphenol content of 23.14%), which accounts for 7% of the total membrane components, and stir for 30min to obtain the membrane solution.

[0070] 2) Membrane preparation: The stirred membrane solution was degassed and defoamed by ultrasonication. 45 ml of the membrane solution was poured into a glass dish with a diameter of 90 mm and placed at 60 °C for 11 h to prepare the membrane.

[0071] Example 7

[0072] This embodiment is used to prepare a Moringa leaf polyphenol composite membrane, which contains Moringa leaf polyphenols-Artemisia gum / pullulan polysaccharide. The preparation of the composite membrane includes the following steps:

[0073] 1) Preparation of membrane solution: Dissolve 1.4g of Artemisia argyi gum and 1.4g of pullulan polysaccharide in 100ml of deionized water respectively. Add 0.05g of anhydrous calcium chloride and 1.1g of glycerol and stir evenly. Then add Moringa leaf polyphenol extract (polyphenol content of 23.14%), which accounts for 9% of the total membrane components, and stir for 30min to obtain the membrane solution.

[0074] 2) Membrane preparation: The stirred membrane solution was degassed and defoamed by ultrasonication. 45 ml of the membrane solution was poured into a glass dish with a diameter of 90 mm and placed at 53 °C for 14 h to dry and prepare the membrane.

[0075] Example 8

[0076] Similar to Example 5, except that the crosslinking agent used is transglutaminase. The preparation of this composite membrane includes the following steps:

[0077] 1) Preparation of membrane solution: Dissolve 1.2 g of Artemisia argyi gum and 1 g of pullulan polysaccharide in 100 ml of deionized water respectively. Add 0.038 g of transglutaminase and 0.7 g of glycerol and stir well. Then add Moringa leaf polyphenol extract, which accounts for 7% of the total membrane components. Stir for 30 min to obtain the membrane solution.

[0078] 2) Membrane preparation: The stirred membrane solution was degassed and defoamed by ultrasonication. 40 ml of the membrane solution was poured into a glass dish with a diameter of 90 mm and placed at 56 ℃ for 9.5 h to prepare the membrane.

[0079] Example 9

[0080] Similar to Example 5, except that the plasticizer used is polyethylene glycol, and the preparation of the composite film includes the following steps:

[0081] 1) Preparation of membrane solution: Dissolve 1.2g of Artemisia argyi gum and 1g of pullulan polysaccharide in 100ml of deionized water respectively. Add 0.04g of anhydrous calcium chloride and 0.75g of polyethylene glycol and stir well. Then add Moringa leaf polyphenol extract, which accounts for 7% of the total membrane components. Stir for 30min to obtain the membrane solution.

[0082] 2) Membrane preparation: The stirred membrane solution was degassed and defoamed by ultrasonication. 45 ml of the membrane solution was poured into a glass dish with a diameter of 90 mm and placed at 60 °C for 12 h to prepare the membrane.

[0083] Comparative Example 1

[0084] The film-forming solution was prepared according to the method of Example 2, except that Moringa leaf polyphenol extract and calcium chloride were not added as a crosslinking agent. The preparation process of the composite membrane in this comparative example is as follows:

[0085] 1) Preparation of membrane solution: Dissolve 1g of Artemisia argyi gum and 1g of pullulan polysaccharide in 100ml of deionized water respectively, add 0.9g of glycerol and stir well for 30min to obtain membrane solution.

[0086] 2) Membrane preparation: The stirred membrane solution was degassed and defoamed by ultrasonication. 45 ml of the membrane solution was poured into a glass dish with a diameter of 90 mm and placed at 60 °C for 15 h to prepare the membrane.

[0087] Comparative Example 2

[0088] The film-forming solution was prepared according to the method of Comparative Example 1, except that the mixing method was different; Comparative Example 2 used a miscibility method. The composite membrane preparation process of this comparative example is as follows:

[0089] 1) Preparation of membrane solution: Take 1g of Artemisia argyi gum and 1g of pullulan polysaccharide, mix them and dissolve them in 200ml of deionized water, add 0.8g of glycerol and stir well for 30min to obtain the membrane solution.

[0090] 2) Membrane preparation: The stirred membrane solution was degassed and defoamed by ultrasonication. 45 ml of the membrane solution was poured into a glass dish with a diameter of 90 mm and placed at 40 °C for 12 h to prepare the membrane.

[0091] Comparative Example 3

[0092] The film-forming solution was prepared according to the method of Example 2, except that Moringa leaf polyphenol extract was not added, and the amount of glycerol added was 20% of the substrate mass, which is relatively low. The preparation process of the composite membrane in this comparative example is as follows:

[0093] 1) Preparation of membrane solution: Dissolve 1g of Artemisia argyi gum and 1g of pullulan polysaccharide in 100ml of deionized water, add 0.038g of anhydrous calcium chloride and 0.4g of glycerol and stir well for 30min to obtain membrane solution.

[0094] 2) Membrane preparation: The stirred membrane solution was degassed and defoamed by ultrasonication. 45 ml of the membrane solution was poured into a glass dish with a diameter of 90 mm and placed at 60 °C for 10 h to prepare the membrane.

[0095] Experimental Example 1

[0096] This experimental example is used to test the mechanical properties of different composite membranes.

[0097] The mechanical property testing method for this experiment is as follows: Composite food preservation film samples from Examples 2-9 and the comparative example were cut to 1cm × 10cm. Testing was conducted under the conditions of an extensometer gauge length (L0) of 2.5cm, a displacement speed of 50mm / min, and a constant load of 50N. After the samples broke, the corresponding tensile strength and elongation at break of the sample film were calculated, as shown in Table 1.

[0098] Table 1

[0099]

[0100] As shown in Examples 2-7, the tensile strength of the membrane significantly increased (P<0.05) from 7.94 MPa to 12.37 MPa with the increase of Moringa leaf polyphenol extract. This is due to the formation of hydrogen bonds between the polysaccharides and phenolic substances, which enhances the intermolecular bonding. Simultaneously, it also affected the elongation at break of the membrane; with increasing Moringa leaf polyphenol extract content, the elongation at break first increased and then decreased. This is because the polar molecules in the phenolic substances insert into the polysaccharide molecular chains, weakening the hydrogen bonds and thus increasing the flexibility of the polysaccharide chains. However, with increasing concentration, the extract interferes with the normal interactions between the polysaccharide molecular chains, leading to a decrease in elongation at break. Examples 7-9 show that changing the crosslinking agent and plasticizer does not significantly affect the preparation of the film. Compared with the control group, the tensile strength of the composite membrane was significantly higher with the addition of Moringa leaf polyphenol extract.

[0101] Experiment Example 2

[0102] This experimental example is used to detect the water content of different composite membranes.

[0103] The method for detecting moisture content in this experiment is as follows: The composite plastic wrap from Examples 2-9 and Comparative Examples 1-3 were cut into 2cm × 2cm samples, with an initial weight recorded as W0. Each sample was placed in a 50ml EP tube, and then 25ml of deionized water was added to the 50ml EP tube. The samples were soaked overnight (approximately 12 hours). After drying in an oven at 105℃ for 4 hours, the samples were weighed and recorded as W1.

[0104] The formula for calculating moisture content is: Moisture content WS=(W0-W1) / W0×100%.

[0105] The calculation results are shown in Table 2.

[0106] Table 2

[0107]

[0108] As shown in Table 2, the water content of Comparative Examples 1-3 was significantly higher. This is because the numerous hydroxyl groups in Artemisia argyi gum, pullulan polysaccharide, and plasticizers (such as glycerol) interact with water molecules, making the control membranes highly soluble in water. In contrast, the addition of Moringa leaf polyphenol extract significantly reduced the water content of the membranes in this invention, with higher amounts resulting in lower water content. This is because the aggregation of polyphenols on the membrane surface partially inhibits the solubility of the membrane in water.

[0109] Experimental Example 3

[0110] This experimental example is used to detect the water vapor transmission rate of different composite membranes.

[0111] The detection method for water vapor transmission rate in this experiment is as follows: Place 25 ml of deionized water in a 50 ml centrifuge tube. Cut the plastic wrap from Examples 2-9 and Comparative Examples 1-3 into 5 cm × 5 cm sample molds, cover the mouth of the centrifuge tube with the sample molds, and secure the portion below the mouth of the sample mold with adhesive tape. Weigh the initial amount and record it as W0. Then place the tube in a glass desiccator with a relative humidity of 50%, and weigh it every 3 hours until 24 hours.

[0112] The formula for calculating water vapor transmission rate (WVP) is: WVP(g·m -1 ·s -1 ·Pa -1 ) = (Δm × d) / (t × S × ΔP), where Δm is the weight gain in the centrifuge tube (g), d is the membrane thickness (m), t is the time taken for the centrifuge tube to gain weight (s), and S is the area of ​​the centrifuge tube sealed by the membrane (m²). 2 ), where ΔP(3167Pa) is the partial vapor pressure between pure water and dry atmosphere.

[0113] The calculation results are shown in Table 3.

[0114] Table 3

[0115]

[0116] As shown in Table 3, the water vapor transmission rate (WVP) of the film is a key parameter for controlling the humidity around the packaged product. To protect the product from microbial contamination and extend its lifespan, the WVP of the film should be as low as possible. The water vapor transmission rate of the Moringa leaf polyphenol-Artemisia gum / pullulan polysaccharide composite preservation film of Examples 2-9 of this invention is significantly lower than that of the comparative example.

[0117] Experiment Example 4

[0118] This experimental example is used to detect the oxygen permeability of different composite membranes.

[0119] The method for detecting oxygen permeability in this experiment is as follows: Accurately measure 3 mL of linoleic acid and add it to the test cup. Completely seal the mouth of the test cup with a composite membrane and secure it with a rubber band. After weighing, place all cups in the same environment (25℃, RH 75%) for 8 days, weighing them every 24 hours. The calculation formula is as follows: OP = In the formula: OP, oxygen permeability, g·mm / (m 2 ·d); Δm, change in mass of the test cup, g; D, thickness of the composite membrane, mm; t, time, d; S, area of ​​the test cup opening, m² 2 .

[0120] The calculation results are shown in Table 4.

[0121] Table 4

[0122]

[0123] As shown in Table 4, the oxygen permeability (OP) of the film is a key parameter for controlling the oxygen level around the packaged product. To protect the product from microbial contamination and extend its lifespan, the film's OP should be kept as low as possible. The oxygen permeability of the Moringa leaf polyphenol-Artemisia gum / pullulan polysaccharide composite preservation film of Examples 2-9 of this invention is significantly lower than that of the comparative example.

[0124] Experimental Example 5

[0125] This experimental example is used to test the antioxidant properties of different composite membranes.

[0126] The method for detecting the antioxidant performance in this experiment is as follows: Dissolve 50 mg of the composite membrane sample in 10 mL of 75% ethanol, homogenize the mixture using a homogenizer, and let it stand for 30 min. Take 2 mL of the supernatant, then add 2 mL of 0.1 mM DPPH solution, and let it stand at room temperature in the dark for 45 min. Measure the absorbance at 517 nm. A control was measured using 75% ethanol instead of the sample solution in the same manner.

[0127] Calculate the DPPH free radical scavenging rate using the following formula.

[0128] DPPH = In the formula: DPPH, the free radical scavenging rate of the membrane, %; A1, the absorbance value of the control solution; A2, the absorbance value of the membrane solution to be tested.

[0129] Prepare the ABTS solution by mixing 0.3 mL of the film sample solution and 75% ethanol with 3 mL of ABTS solution, respectively, and incubating at room temperature in the dark for 10 min. Measure the absorbance at 734 nm.

[0130] The ABTS free radical scavenging rate is calculated using the following formula.

[0131] ABTS = In the formula: ABTS, the free radical scavenging rate of the membrane, %; A1, the absorbance value of the control solution; A2, the absorbance value of the membrane solution to be tested.

[0132] The results are shown in Table 5.

[0133] Table 5

[0134]

[0135] As shown in Table 5, the antioxidant activity of the film was evaluated using DPPH and ABTS free radical scavenging tests. Table 5 shows that the film without added active substances exhibited scavenging rates of 6.20% and 8.13% for DPPH and ABTS free radicals, respectively, indicating limited antioxidant activity. In Examples 8-9, the antioxidant capacity did not change significantly despite variations in the crosslinking agent and plasticizer. In Examples 2-9, the addition of different concentrations of Moringa leaf polyphenol extract resulted in a continuous increase in the DPPH and ABTS scavenging rates of the composite film with increasing extract concentration. This indicates that the scavenging efficiency of the Moringa leaf polyphenol extract-Artemisia gum / pullulose composite preservation film against DPPH and ABTS free radicals is related to the extract concentration, and the scavenging efficiency increases with increasing Moringa leaf polyphenol extract concentration. In summary, the addition of Moringa leaf polyphenol extract significantly enhances the antioxidant activity of the composite film.

[0136] Experimental Example 6

[0137] This experimental example is used to test the antibacterial properties of different composite films.

[0138] The antibacterial performance testing method in this experiment was as follows: *Escherichia coli* and *Staphylococcus aureus* were used as test bacteria. The activated bacterial solution (10...) 5 ~10 6 Pour the CFU / mL solution into petri dishes, then place them into LB agar plates and shake well. After solidification, punch a hole in the center using a 6 mm punch. Add 100 μL of the membrane solution to the hole using a pipette. Incubate the plates at 37°C for 24 h in a constant temperature and humidity incubator. Measure the diameter of the inhibition zone of the membrane. Results are as follows: Figure 1 As shown.

[0139] Antimicrobial activity is a key performance characteristic of food packaging. With increasing polyphenol concentration, the diameters of the inhibition zones against *Escherichia coli* (Gram-negative bacteria) and *Staphylococcus aureus* (Gram-positive bacteria) increased from 5.00 mm to 18.07 mm and from 7.00 mm to 21.46 mm, respectively. Therefore, as... Figure 1 As shown, the addition of Moringa leaf polyphenol extract significantly enhanced the antibacterial activity of the composite membrane. Furthermore, at the same concentration, it exhibited greater inhibitory activity against Staphylococcus aureus than against Escherichia coli.

[0140] Experimental Example 7

[0141] This invention uses the composite food preservation film prepared in Examples 2-9 and ordinary commercially available preservation films to conduct preservation packaging tests on pork. The results were measured per 225cm³. 2 300 g of beef was packaged in plastic wrap at a test temperature of 4℃. The state inside the plastic wrap was recorded at different time periods. The test results are listed in Table 6.

[0142] Table 6

[0143]

[0144] As can be seen from the results in the table above, the plastic wrap produced according to the method provided by this invention has a better preservation effect on meat and extends the shelf life of chilled beef.

[0145] This invention addresses the poor mechanical properties and low toughness of polysaccharide-based membranes by incorporating Moringa leaf polyphenols into a composite membrane. Instead of complex modification of the polysaccharide, it utilizes Moringa leaf polyphenol extract as an active ingredient and crosslinking agent to improve the mechanical properties of the polysaccharide-based membrane. Simultaneously, the hydrophobicity, antioxidant properties, and antibacterial properties of the film are enhanced. The resulting Moringa leaf polyphenol-Artemisia gum / pullulan polysaccharide composite membrane shows broad application prospects in food preservation and other fields.

[0146] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A Moringa leaf polyphenol composite film, characterized in that, It contains 0.5-10% by weight of Moringa leaf polyphenol extract.

2. The Moringa leaf polyphenol composite membrane according to claim 1, characterized in that, The polyphenol content of the Moringa leaf polyphenol extract is 20-25%.

3. The Moringa leaf polyphenol composite membrane according to claim 1 or 2, characterized in that, The Moringa leaf polyphenol extract was prepared by ultrasound-assisted aqueous two-phase extraction.

4. The Moringa leaf polyphenol composite membrane according to claim 1, characterized in that, It also contains Artemisia argyi gum and pullulan polysaccharide.

5. The Moringa leaf polyphenol composite membrane according to claim 4, characterized in that, The weight ratio of Moringa leaf polyphenol extract, Artemisia gum, and pullulan polysaccharide is 1~10:50~60:30~50.

6. The Moringa leaf polyphenol composite membrane according to claim 5, characterized in that, It also contains plasticizers and crosslinking agents.

7. The Moringa leaf polyphenol composite membrane according to claim 6, characterized in that, The plasticizer is glycerol, sorbitol, xylitol, polyethylene glycol, glucose, or sucrose; the crosslinking agent is anhydrous calcium chloride, tyrosinase, or transglutaminase.

8. The Moringa leaf polyphenol composite membrane according to claim 7, characterized in that, The composite membrane comprises 1.00-1.50 parts of Artemisia argyi gum, 0.60-1.50 parts of pullulan polysaccharide, 0.30-0.45 parts of plasticizer, 0.01-0.02 parts of crosslinking agent, and 0.02-0.18 parts of Moringa leaf polyphenol extract.

9. The method for preparing the Moringa leaf polyphenol composite film according to any one of claims 1-8, characterized in that, The process includes the following steps: First, prepare Artemisia argyi gum solution and pullulan polysaccharide solution separately, mix them in proportion, add plasticizer and crosslinking agent, then dissolve Moringa leaf polyphenol extract, and then fuse it with the above solution to obtain the final film-forming liquid, which is then dried.

10. The application of the Moringa leaf polyphenol composite film according to any one of claims 1-8 in the preparation of food packaging films.

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