Extraction method and application of peanut by-product

Abstract

The invention discloses an extraction method and application of peanut byproducts, and belongs to the technical field of comprehensive utilization of peanut byproducts. According to the method, peanut byproducts, namely the peanut shells and the peanut coats, are taken as raw materials, efficient extraction of the peanut shell cellulose and the peanut coat polyphenols is performed on the basis of a sodium hydroxide extraction method and an ultrasonic-ethanol extraction method respectively, and a premise and a guarantee are provided for efficient utilization of the peanut byproducts; then, the obtained peanut coat polyphenol is used for fruit and vegetable preservation, the obtained peanut coat cellulose and peanut coat polyphenol cooperate with carboxymethyl chitosan to prepare the cellulose / chitosan / polyphenol composite film for food preservation, and the composite film which is low in cost, green, natural, non-toxic, good in oxidation resistance, good in antibacterial performance and high in tensile strength is provided to meet actual requirements.

Description

Technical Field

[0001] This invention relates to a method for extracting peanut by-products and its application, particularly to a method for extracting peanut skin polyphenols and peanut shell cellulose from peanut by-products and its application, belonging to the field of comprehensive utilization technology of peanut by-products. Background Technology

[0002] Peanuts are a major oilseed and cash crop in my country, with a wide planting area and considerable yield. The processing of peanuts generates a large number of by-products, of which peanut skin and peanut shell are typical examples.

[0003] Peanut skins, a byproduct of peanut milk and other peanut processing, account for approximately 3%–3.6% of the peanut pod weight and are rich in various components. Among these, peanut skin polyphenols, with their antioxidant activity, have attracted considerable attention. These polyphenols can be used as antioxidant food additives and have broad application prospects in functional foods, health products, and other fields. Currently, there are many publicly available extraction technologies for peanut skin polyphenols, including organic solvent extraction, supercritical CO2 extraction, ultrasonic extraction, and microwave extraction. However, these technologies still have the following shortcomings: I. Organic solvent extraction has problems such as high impurity content, large solvent consumption, high cost, and high pollution. II. Supercritical CO2 extraction, although it yields high content and is pollution-free, requires large investment and is costly. Third, although ultrasonic and microwave extraction are energy-saving and efficient, they are difficult to apply on a large scale.

[0004] Therefore, finding a low-energy, low-cost, efficient, simple-to-operate, and environmentally friendly method for extracting high-content peanut skin polyphenols has become an urgent problem to be solved. Peanut shells, another major byproduct of peanut processing, are produced in huge quantities, reaching approximately 5 million tons annually. Their main components include 65.7%–79.3% crude cellulose. Utilizing peanut shells to prepare cellulose not only effectively utilizes inexpensive raw materials, replacing high-cost cotton and flax, and promoting the deep processing of agricultural byproducts, but also opens up new avenues for the comprehensive utilization of peanuts. Currently, cellulose preparation mostly employs acid hydrolysis, a method that suffers from problems such as consuming large amounts of acid and water, causing severe chemical pollution, and high costs. Finding a low-cost, efficient, and environmentally friendly method for extracting peanut cellulose has become an urgent problem to be solved. Although the prior art CN102488218A discloses a "method for extracting and preparing high-content peanut skin polyphenols from peanut skins", the peanut skins are extracted (leached) in pure water at low temperature, which is inefficient and has a low yield. In addition, the eluent fatty alcohol solution involved is an organic solvent, which is irritating to the skin and eyes, thus posing a certain safety threat to workers. CN105646788A discloses a "method for preparing a biodegradable nano dust suppressant from peanut shells", which provides a method for preparing cellulose by alkaline hydrolysis of peanut shells, but it involves a high concentration of sodium hydroxide solution.

[0005] Therefore, there is a need for an efficient method for extracting peanut byproducts, such as peanut skins and shells, that can transform them from waste into high-value-added products for subsequent applications. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of existing technologies by proposing a method for extracting peanut by-products and its application. In this technical solution, peanut shells and peanut skins—peanut by-products—are used as raw materials. High-efficiency extraction of peanut shell cellulose and peanut skin polyphenols is achieved using sodium hydroxide extraction and ultrasonic-ethanol extraction methods, respectively, providing a prerequisite for the efficient utilization of peanut by-products.

[0007] To achieve the above technical objectives, the following technical solution is proposed: The primary objective of this technical solution is to provide a method for extracting cellulose from peanut shells, comprising the following steps: X1 Pretreatment: Wash the peanut shells with deionized water, let them air dry, then crush them and pass them through a 60-mesh sieve to obtain peanut shell powder for later use. X2 Extraction: Based on the principle of 15-25L sodium hydroxide solution per 1kg of peanut shell powder (material-to-liquid ratio of 1:15-25 g / mL), add a 1.5-2.5% sodium hydroxide solution to the peanut shell powder; stir the reaction with a magnetic stirrer at a constant temperature water bath of 85-90℃ (speed of 25 r / min) for 3-5 hours, then filter until the alkali solution is removed to obtain the filter residue; Regarding the concentration of sodium hydroxide solution, if the concentration is too low (<1.5%), hemicellulose and lignin are not completely removed, resulting in low cellulose yield, low purity, many impurities, and poor performance. If the concentration of sodium hydroxide solution is moderate (1.5-2.5%), impurities are removed more thoroughly, resulting in higher yield, higher purity, and better performance. If the concentration of sodium hydroxide solution is too high (>2.5%), cellulose is degraded, leading to a decrease in yield, a decrease in the degree of polymerization of cellulose, and a decrease in mechanical properties. Regarding extraction temperature, if the temperature is too low (<85℃), the reaction rate is slow, impurities are not completely removed, and although the cellulose yield is high, the purity is low and the performance is poor; if the temperature is moderate (85~90℃), the reaction rate is faster, impurities are removed more thoroughly, the yield is higher, the cellulose purity is higher, and the performance is better; if the temperature is too high (>90℃), cellulose degradation is accelerated, the yield decreases, and the degree of polymerization of cellulose decreases, resulting in a decline in performance. Regarding extraction time, if the time is too short (<3h), impurities will not be completely removed, resulting in low cellulose yield, low purity, and poor performance; if the time is moderate (3-5h), impurities will be removed more thoroughly, resulting in higher yield, higher cellulose purity, and better performance; if the time is too long (>5h), cellulose will degrade, the degree of polymerization of cellulose will decrease, the yield will decrease, and the performance will decline. Therefore, a 1.5–2.5% sodium hydroxide solution is used, with a reaction time of 3–5 hours at 85–90°C. Precise control of the alkali treatment conditions ensures thorough removal of impurities while preventing cellulose degradation, ultimately guaranteeing cellulose yield and purity. During this process, temperature sensors and pH meters can be used to monitor the reaction conditions in real time, ensuring a stable reaction environment. X3 Bleaching: After the obtained filter residue is naturally dried, it is placed in a 1.5-2.0 w / v% NaClO2 solution (based on a material-to-liquid ratio of 1:15-25 g / mL) with 15-25 L of NaClO2 solution per 1 kg of filter residue. The pH is adjusted to 4.5-5.0 with glacial acetic acid. Then, the mixture is stirred with a magnetic stirrer in a constant temperature water bath at 75-85℃ for 5-6 hours. After filtration, the mixture is washed until the pH of the filtrate is neutral. After natural drying, peanut shell cellulose powder is obtained. Regarding the concentration of the bleaching agent NaClO2 solution, if the concentration is too low (<1.5%), lignin removal is incomplete, resulting in low cellulose yield, low purity, yellowish color, and poor performance; if the concentration is moderate (1.5-2.0%), lignin removal is more thorough, resulting in high cellulose purity, high yield, high whiteness, and good performance; if the concentration is too high (>2%), cellulose will be oxidized and degraded, leading to a decrease in yield, a decrease in the degree of polymerization of cellulose, and a decrease in mechanical properties. Regarding pH control, if the pH is too low (<4.5), NaClO2 decomposes too quickly, resulting in poor bleaching effect, low yield, oxidative damage to cellulose, and decreased performance. If the pH is moderate (4.5-5.0), the bleaching effect is optimal, the yield is high, the cellulose purity is high, and the performance is good. If the pH is too high (>5.0), the bleaching effect is poor, lignin residue remains, the yield is high but the purity is low, the cellulose purity is low, the color is yellowish, and the performance is poor. Regarding bleaching temperature (time), if it is less than 75℃, bleaching is incomplete, lignin remains, cellulose yield is high but purity is low, color is yellowish, and performance is poor; if the temperature is 75-85℃, the bleaching effect is good, cellulose yield is high, purity is high, whiteness is high, and performance is good; if the temperature is higher than 85℃, cellulose is oxidized and degraded, yield decreases, degree of polymerization of cellulose decreases, and mechanical properties decrease. Therefore, NaClO2 solution is used for bleaching, but the pH (4.5–5) and temperature (75–85℃) must be strictly controlled to ensure the yield, purity, and properties of peanut shell cellulose. For example, pH that is too high or too low will affect the bleaching effect and may even damage the cellulose. During this process, a pH meter can be used to monitor the process in real time and control the rate of addition of glacial acetic acid to avoid excessive pH fluctuations. Furthermore, residual alkali and bleach can affect the purity of cellulose, and the filtration process is time-consuming and inefficient. Therefore, multiple washing is employed: the filter cake is repeatedly washed with deionized water until the pH of the filtrate reaches neutral.

[0008] Online pH monitoring: Real-time monitoring of filtrate pH to ensure thorough washing.

[0009] The second objective of this technical solution is to provide a method for extracting peanut skin polyphenols, comprising the following steps: S1 Pretreatment: Dry the collected peanut skins to a moisture content of 3-8%; crush them and pass them through a 40-mesh sieve to obtain peanut skin powder for later use; The peanut variety used is red-skinned peanut. Controlling the peanut skin powder to pass through a 40-mesh sieve can improve subsequent extraction efficiency (smaller particle size means a larger specific surface area, faster solvent penetration, and higher polyphenol dissolution rate). S2 Extraction: Based on 20-30 L of ethanol solution per 1 kg of peanut skin powder (solid-liquid ratio of 1:20-30 g / mL), add a 50-60% ethanol solution to the peanut skin powder and sonicate at 20-28℃ for 20-30 min. Then, filter the solution, centrifuge the filtrate at 2800-3200 r / min for 20-30 min, collect the supernatant, and dilute to 1000 mL for later use. Among them, an ethanol solution with a concentration of 50-60% was selected. Based on the extraction efficiency and selectivity, this concentration of ethanol solution ensures the solubility of polyphenols and improves the extraction rate of peanut skin polyphenols. "Ultrasonic treatment at 20–28℃ for 20–30 minutes" enhances the extraction process. Ultrasound can disrupt cell walls, promote polyphenol release, shorten extraction time, and improve efficiency. Ultrasound, in conjunction with ethanol, ensures highly efficient extraction of peanut skin polyphenols. Centrifuge at 2800–3200 r / min for 20–30 min to achieve solid-liquid separation, effectively remove solid impurities, obtain a clear extract, and avoid difficulties in subsequent purification. The ratio of peanut skin powder to ethanol solution is 1:20-30, which ensures extraction efficiency while improving economy. If the ratio is too low, extraction will be incomplete; if the ratio is too high, solvent will be wasted. A balance needs to be struck between efficiency and cost. S3 Purification: The extract was evaporated under reduced pressure at 60-75℃ using a rotary evaporator to remove the ethanol solution and obtain a concentrated solution. The concentrated solution was then placed in a freeze dryer for pre-freezing and drying to obtain peanut skin polyphenol powder. The pre-freezing temperature was set to -20 to -18℃ for 10 to 14 hours; the drying temperature was maintained at -60 to -45℃ for 5 to 7 hours; ensuring complete removal of moisture and ethanol solution while maintaining the activity of peanut skin polyphenols. A rotary evaporator (concentration under reduced pressure at 60–75°C) was used to effectively remove the solvent. Evaporation under reduced pressure at 60–75°C avoids thermal degradation of polyphenols and maintains their activity. "Setting the pre-freezing temperature to -20 to -18℃ and pre-freezing for 10 to 14 hours" can maintain the structural stability of peanut skin polyphenols. Thorough pre-freezing can prevent ice crystals from damaging cell structure and protect polyphenol activity; "Maintain a drying temperature of -60 to -45°C for 5 to 7 hours." Low-temperature vacuum drying can be used to avoid polyphenol oxidative degradation and maintain high activity and stability. This means stabilizing the product while removing moisture. In this technical solution, since polyphenols are easily oxidized and degraded, and polyphenolic substances are sensitive to light, heat and oxygen and are easily deactivated, the following methods are used: ethanol solution combined with low temperature (20-28℃) ultrasonic extraction, low temperature (60-75℃) vacuum concentration, and ultra-low temperature (-60--45℃) vacuum drying.

[0010] Furthermore, if the concentration of the alkaline solvent is too high, impurities may be extracted; if the concentration of the alkaline solvent is too low, extraction will be incomplete. Therefore, an ethanol solution with a concentration of 50-60% is selected to ensure a balance between extraction efficiency and extraction selectivity.

[0011] Pre-freezing at -20 to -18°C for 10 to 14 hours ensures complete freezing of the polyphenols and avoids ice crystal damage during freeze-drying. Incomplete pre-freezing can lead to polyphenol structural collapse, affecting subsequent drying efficiency and indirectly impacting yield. Furthermore, incomplete pre-freezing can result in large ice crystals that damage cell structure and reduce polyphenol activity. The 10 to 14-hour pre-freezing time is crucial to prevent incomplete freezing and subsequent spraying during drying, which would also affect yield.

[0012] Dry at -60 to -45°C for 5 to 7 hours to avoid high-temperature degradation and ensure drying quality. Excessive drying temperature may lead to polyphenol degradation and decreased yield; excessively high temperature accelerates polyphenol oxidation and reduces activity. Insufficient drying time results in residual moisture, causing polyphenol hydrolysis or oxidation, affecting product stability and yield.

[0013] Ultimately, in the extraction of peanut skin polyphenols, it is crucial to avoid incomplete pre-freezing or excessively rapid drying, which could reduce polyphenol activity and damage the structure. Furthermore, residual alkaline solvent—ethanol solution—can affect product purity and safety. Therefore, vacuum rotary evaporation is used to thoroughly remove ethanol, followed by subsequent freeze-drying to further ensure no residue.

[0014] The third aspect of this technical solution is that it provides: using the above-mentioned peanut shell cellulose to prepare a cellulose / chitosan composite membrane. The method for preparing the cellulose / chitosan composite membrane includes: Add a 0.5-1.5% glycerol solution to peanut shell cellulose powder and stir in a constant temperature water bath at 55-65°C until the powder is completely dissolved to prepare a 1-2% cellulose solution. Let it stand until all bubbles are removed to obtain the cellulose solution for later use. Glycerol is a polar solvent that can form hydrogen bonds with the hydroxyl groups in cellulose molecules, disrupting the hydrogen bond network between cellulose molecules and thus promoting dissolution. In addition, glycerol has a certain plasticizing effect, improving the flexibility and extensibility of the membrane. Besides glycerol, ionic liquids such as 1-butyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium acetate can also be used, which have strong cellulose-dissolving capabilities but are more expensive. Alkali / urea systems, such as NaOH / urea aqueous solutions (used at low temperatures), can also be used; these are environmentally friendly but require stringent dissolution conditions. Using a glycerol solution with a mass fraction of 0.5%–1.5% ensures good dissolution quality and composite membrane performance. If the glycerol solution mass fraction is less than 0.5%, the dissolving ability is insufficient, the cellulose cannot swell sufficiently, and the solution is uneven. If the glycerol solution mass fraction is greater than 1.5%, the viscosity increases, stirring becomes difficult, and excessive residual solvent affects the performance of the composite membrane. Stirring in a constant-temperature water bath at 55–65°C accelerates molecular motion during the dissolution of peanut shell cellulose powder, promotes solvent penetration and hydrogen bond breaking, and avoids thermal degradation of cellulose at high temperatures (>80°C). 55–65°C is the optimal condition for balancing dissolution efficiency and stability. If the temperature is below 55°C, the dissolution rate is slow and incomplete dissolution occurs, resulting in an uneven film. If the temperature is above 65°C, glycerol volatilization or localized degradation of cellulose may occur, affecting the film strength. A cellulose solution with a mass fraction of 1–2% is prepared to meet the requirements for film casting. If the concentration is too low (<1%), the solution viscosity is low, the mechanical properties are poor, and the film is prone to cracking after formation; if the concentration is too high (>2%), the viscosity is too high, the casting is uneven, the film is too thick, the drying time is long, and bubbles or brittleness may occur. A cellulose solution with a mass fraction of 1–2% can form a dense network structure, balancing the flexibility and strength of the composite film. Add pure water (e.g., ultrapure water) to carboxymethyl chitosan powder and stir in a constant temperature water bath at 55-65°C until the powder is completely dissolved to prepare a carboxymethyl chitosan solution with a mass fraction of 0.5-1.5%. Let it stand until all bubbles are removed to obtain a carboxymethyl chitosan solution for later use. In this process, carboxymethyl chitosan is stirred in a constant-temperature water bath at 55–65°C to ensure a high dissolution rate while avoiding damage to the membrane's mechanical properties. For example, below 55°C, the dissolution rate is slow, the dissolution time is long, and the efficiency is low; above 65°C, carboxymethyl chitosan will degrade, reducing its molecular weight and decreasing the membrane's mechanical properties. A carboxymethyl chitosan solution with a mass fraction of 0.5–1.5% was prepared to meet the requirements for film casting. If the concentration is too low (<0.5%), the solution viscosity is low, resulting in poor mechanical properties and easy cracking after film formation; if the concentration is too high (>1.5%), the viscosity is too high, leading to uneven casting, excessively thick films, long drying times, and potential bubble formation or brittleness. A carboxymethyl chitosan solution with a mass fraction of 0.5–1.5% can form a dense network structure, balancing the flexibility and strength of the composite film. The cellulose solution and carboxymethyl chitosan solution were mixed at a mass ratio of 1:2 to 2:1 and stirred evenly with a power stirrer to prepare a blend solution. The mixture was allowed to stand until completely defoamed, poured onto a clean and flat glass plate, cast evenly, and placed in an oven to dry at 55 to 65°C to obtain a composite film. In this process, the mass ratio of cellulose solution to carboxymethyl chitosan solution is 1:2 to 2:1 to ensure that the resulting composite membrane has good properties, such as antibacterial properties, flexibility, and mechanical strength. Drying the film at 55–65°C allows for rapid solvent evaporation while preventing excessive solvent evaporation that could lead to a skin formation on the film surface (affecting internal solvent diffusion). Below 55°C, the drying time is prolonged, and residual solvent may cause the film structure to become loose or sticky. Above 60°C, due to the high temperature, the solvent on the film surface evaporates rapidly to form a dense layer, but the internal solvent is difficult to escape, which can lead to film cracking or bubbles.

[0015] The fourth objective of this technical solution is to provide a method for preparing an antioxidant cellulose / chitosan / polyphenol composite membrane by using the aforementioned peanut shell cellulose and peanut skin polyphenols. The method for preparing the antioxidant cellulose / chitosan / polyphenol composite membrane includes: Add a 0.5-1.5% glycerol solution to peanut shell cellulose powder and stir in a constant temperature water bath at 55-65°C until the powder is completely dissolved to prepare a 1-2% cellulose solution. Let it stand until all bubbles are removed to obtain the cellulose solution for later use. Add pure water to carboxymethyl chitosan powder and stir in a constant temperature water bath at 55-65°C until the powder is completely dissolved to prepare a carboxymethyl chitosan solution with a mass fraction of 0.5-1.5%; let stand until completely degassed to obtain a carboxymethyl chitosan solution for later use. Add a 40-50% ethanol solution to peanut skin polyphenol powder and stir in a constant temperature water bath at 20-25°C until the powder is completely dissolved to prepare a 10-20% polyphenol solution. Let it stand until all bubbles are removed to obtain the polyphenol solution for later use. A cellulose solution, carboxymethyl chitosan solution, and polyphenol solution were mixed at a mass ratio of 14–16:14–16:1 and stirred evenly using a power stirrer to prepare a blend solution. The mixture was allowed to stand until completely defoamed, poured onto a clean and flat glass plate, cast evenly, and placed in an oven to dry at 55–65°C to obtain an antioxidant cellulose / chitosan / polyphenol composite film.

[0016] For cellulose / chitosan / polyphenol composite membranes, cellulose provides the membrane's skeletal structure, enhancing its mechanical strength; carboxymethyl chitosan imparts good film-forming properties, antibacterial activity, and a certain degree of flexibility; and polyphenols provide antioxidant, antibacterial, and preservative functions. Furthermore, by limiting the mass ratio of the three components (14–16:14–16:1), the performance of the cellulose / chitosan / polyphenol composite membrane is ensured to avoid damage to the membrane structure. The film is dried at 55–65°C to control the solvent evaporation rate while ensuring the film's density and surface smoothness. Temperatures below 55°C result in solvent residue and decreased film performance; temperatures above 65°C lead to polyphenol degradation and brittle film formation.

[0017] In this technical solution, cellulose, carboxymethyl chitosan, and polyphenols work synergistically to form a film. By limiting specific conditions, problems such as poor compatibility, uneven film formation, and unstable function are avoided. Ultimately, a composite film with stable performance and diverse functions is obtained. For example, drying the film at 55-65℃ can prevent polyphenol degradation, control the compactness of the film structure, and maintain the functional activity of polyphenols, thereby improving the performance of the film.

[0018] The beneficial technical effects of adopting this technical solution are as follows: In this invention, peanut shells, a by-product of peanut production, are used as raw materials to efficiently extract cellulose from peanut shells; peanut skins, another by-product of peanut production, are used as raw materials to efficiently extract and maintain the activity of peanut skin polyphenols; and, while retaining the characteristics of peanut shell cellulose and peanut skin polyphenols, they are used to prepare composite membranes, thereby realizing the rational utilization of peanut by-products and ultimately industrializing and resource-based utilizing peanut by-products. Furthermore, a composite membrane that is low-cost, green, natural, non-toxic, has good antioxidant properties (high ABTS and DPPH removal capacity), good antibacterial properties (significant antibacterial effect against Escherichia coli and Staphylococcus aureus), and high tensile strength is provided to meet practical needs. Attached Figure Description

[0019] Figure 1 This is a photograph of the peanut shell cellulose involved in this invention. Figure 2 Here is a photograph of the peanut skin polyphenols involved in this invention; Figure 3 This is an overlay spectrum of the total ion chromatogram of the positive ion mode QC sample in the determination of peanut skin polyphenol content involved in this invention (where the horizontal axis represents the retention time of each chromatographic peak and the vertical axis represents the peak intensity value). Figure 4 This is an overlay spectrum of the total ion chromatogram of the negative ion mode QC sample in the determination of peanut skin polyphenol content involved in this invention (where the horizontal axis represents the retention time of each chromatographic peak and the vertical axis represents the peak intensity value). Figure 5 The PCA analysis diagram of the overall positive ion mode sample in the determination of peanut skin polyphenol content involved in this invention is shown (where PC[1] represents principal component 1, PC[2] represents principal component 2, and the degree of aggregation of QC samples reflects the repeatability of the experiment; the denser the aggregation, the better the repeatability of the experiment). Figure 6 The PCA analysis diagram of the overall sample of negative ion mode in the determination of peanut skin polyphenol content involved in this invention is shown (where PC[1] represents principal component 1, PC[2] represents principal component 2, and the degree of aggregation of QC samples reflects the repeatability of the experiment; the denser the aggregation, the better the repeatability of the experiment). Figure 7 This is a correlation spectrum of QC samples in the positive ion model for the determination of peanut skin polyphenol content involved in this invention (wherein, the QC sample correlation coefficient scatter plot, the numbers represent the correlation between QC samples, the larger the correlation coefficient, the higher the sample similarity and the better the experimental repeatability). Figure 8This is a correlation spectrum of negative ion model QC samples in the determination of peanut skin polyphenol content involved in this invention (wherein, the QC sample correlation coefficient scatter plot, the numbers represent the correlation between QC samples, the larger the correlation coefficient, the higher the sample similarity and the better the experimental repeatability). Figure 9 The Hotellings T2 plot of the overall positive ion mode sample in the determination of peanut skin polyphenol content involved in this invention; Figure 10 The Hotellings T2 plot of the overall sample in the negative ion mode for the determination of peanut skin polyphenol content involved in this invention; Figure 11 This is the MCC chart of the positive ion mode QC sample in the determination of peanut skin polyphenol content involved in this invention (where the horizontal axis represents each QC sample, the vertical axis reflects the standard deviation, the yellow line defines plus or minus 2 standard deviations, and the red line defines plus or minus 3 standard deviations). Figure 12 This is the MCC chart of negative ion mode QC samples in the determination of peanut skin polyphenol content involved in this invention (where the horizontal axis represents each QC sample, the vertical axis reflects the standard deviation, the yellow line defines plus or minus 2 standard deviations, and the red line defines plus or minus 3 standard deviations). Figure 13 The relative standard deviation of the positive ion mode QC sample in the determination of peanut skin polyphenol content involved in this invention; Figure 14 This represents the relative standard deviation of the negative ion mode QC sample in the determination of peanut skin polyphenol content involved in this invention. Figure 15 The percentage of metabolites identified by SuperClass in the determination of peanut skin polyphenol content involved in this invention in each chemical category (wherein, different colored blocks represent different chemical category entries, the percentage represents the percentage of the number of metabolites in that chemical category entry out of the total number of identified metabolites, and metabolites without a chemical category are defined as undefined). Figure 16 This refers to the percentage of metabolites identified in each chemical category during the determination of peanut skin polyphenol content in this invention (where different colored blocks represent different chemical category entries, the percentage represents the percentage of metabolites in that chemical category entry out of all identified metabolites, and metabolites without a chemical category are defined as undefined). Figure 17 This is a diagram showing the state of Staphylococcus aureus in the determination of the antibacterial properties of peanut skin polyphenols involved in this invention. Figure 18 This is a diagram showing the state of Escherichia coli in the determination of the antibacterial properties of peanut skin polyphenols involved in this invention. Figure 19 This is a bar chart of Staphylococcus aureus colony counts in the determination of the antibacterial properties of peanut skin polyphenols involved in this invention. Figure 20 This is a bar chart of Escherichia coli colony counts in the determination of the antibacterial properties of peanut skin polyphenols involved in this invention. Figure 21 This is a line graph showing the Staphylococcus aureus colony count in the determination of the antibacterial properties of peanut skin polyphenols involved in this invention. Figure 22 This is a line graph showing the Escherichia coli colony count in the determination of the antibacterial properties of peanut skin polyphenols involved in this invention. Figure 23 This refers to the DPPH free radical scavenging ability in the determination of the antioxidant properties of peanut skin polyphenols involved in this invention; Figure 24 This refers to the ABTS free radical scavenging ability in the determination of the antioxidant properties of peanut skin polyphenols involved in this invention; Figure 25 The images shown are of the composite membranes involved in this invention (where a represents a cellulose / chitosan composite membrane with a mass ratio of cellulose to chitosan of 1:1; bd both represent cellulose / chitosan / polyphenol composite membranes with mass ratios of cellulose to chitosan of 2:1, 1:1, and 1:2, respectively). Figure 26 The following is a comparison diagram of the composite membranes involved in this invention (A represents cellulose / imidazolium / polyphenol composite membrane; B represents nanofiber / chitosan / polyphenol composite membrane; C represents cellulose / chitosan / polyphenol composite membrane, wherein the mass ratio of cellulose, chitosan and polyphenol is 22:22:1). Figure 27 This is a graph showing the inhibition of Escherichia coli by the corresponding membrane involved in Example 9; Figure 28 This is a graph showing the inhibition of Staphylococcus aureus by the corresponding membrane involved in Example 9; Figure 29 This is a diagram showing the state of the corresponding membrane inhibiting Escherichia coli, as described in Example 9. Figure 30 This is a diagram showing the state of Staphylococcus aureus inhibition by the corresponding membrane involved in Example 9; Figure 31 The preservation results of the cellulose / chitosan / polyphenol composite film solution involved in Example 10 are shown in Figure 10 (1, 2, and 3 are blank paper bags, and 4, 5, and 6 are polyphenol film paper bags). Figure 32 The preservation results of the cellulose / chitosan / polyphenol composite film solution involved in Example 10 are shown in Figure 2 (1, 2, and 3 are blank paper bags, and 4, 5, and 6 are polyphenol film paper bags). Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Peanut skins and shells, as byproducts of peanut processing, have an annual output of several million tons, but most are used as fuel, feed, or considered waste, failing to fully realize their potential value. Therefore, this invention extracts polyphenols and cellulose from peanut skins and shells, respectively. Peanut skin polyphenols possess significant antibacterial and antioxidant capabilities, while peanut shell cellulose exhibits film-forming ability. Thus, using peanut skin and shell extracts to prepare preservation materials—preservative films (especially suitable for fruit preservation)—not only improves the utilization rate of peanut skins and shells and reduces resource waste, but also transforms them from waste into high-value-added products. Furthermore, currently permitted preservatives for fruits and vegetables are all food-grade additives or low-toxicity pesticides; therefore, a safer and more effective fruit preservation method is needed to meet market demand.

[0022] The following example illustrates this.

[0023] In the following embodiments, the detection / measuring instruments involved include: Rotary evaporator (RE-52AA, Shanghai Yarong Biochemical Instrument Factory) Analytical balance (Secura 224-1CN, Sartorius) Freeze dryer (SCIENTZ-10N, Ningbo Xinzhi Biotechnology Co., Ltd.) Crusher (MG-100Wiltal) Multifunctional microplate reader (Agilent BioTek SH1M2) Ultrasonic machine (Xinzhi Biotechnology) Constant temperature drying oven (DHG-9070A, Shanghai Yiheng Scientific Instruments Co., Ltd.) Water-jacketed constant temperature incubator (Shanghai Jinghong Experimental Equipment Co., Ltd.) Benchtop centrifuge (H1750R, Hunan Xiangyi Laboratory Instrument Development Co., Ltd.) Constant temperature shaking culture incubator (HZ-9210K, Taicang Hualida Experimental Equipment Co., Ltd.).

[0024] In the following embodiments, the samples, strains, and reagents involved include: Peanut skin, peanut shell, Staphylococcus aureus ( Staphylococci aureus ), Escherichia coli ( Escherichia coli Anhydrous ethanol, DPPH reagent, ABTS reagent, ascorbic acid, potassium persulfate, sodium hydroxide, glycerol, hydroxymethyl chitosan, and glacial acetic acid.

[0025] Example 1 This embodiment provides a method for extracting cellulose from peanut shells, comprising the following steps: X1 Pretreatment: Wash the peanut shells with deionized water, let them air dry, then crush them and pass them through a 60-mesh sieve to obtain peanut shell powder for later use. X2 Extraction: Add a 2% sodium hydroxide solution to peanut shell powder at a material-to-liquid ratio of 1:20 (g / mL); stir the mixture with a magnetic stirrer in a constant temperature water bath at 90℃ for 4 hours, then filter until the alkaline solution is removed. X3 bleaching: After naturally drying the obtained filter residue, it was placed in 1.7 w / v% NaClO2 at a material-to-liquid ratio of 1:20 (g / mL), and the pH was adjusted to 4.50 with glacial acetic acid. Then, the mixture was stirred with a magnetic stirrer in a constant temperature water bath at 80℃ for 4 hours. After filtration, the mixture was washed until the pH of the filtrate was neutral. After natural drying, peanut shell cellulose powder was obtained (e.g., ...). Figure 1 (As shown).

[0026] Example 2 This embodiment provides a method for extracting peanut skin polyphenols, comprising the following steps: S1 Pretreatment: Dry the collected peanut skins to a moisture content of 3-8%; crush them and pass them through a 40-mesh sieve to obtain peanut skin powder for later use; Among them, the peanut variety is red-skinned peanut; S2 Extraction: Based on 25L of ethanol solution per 1kg of peanut skin powder (solid-liquid ratio of 1:25 g / mL), add 55% ethanol solution to the peanut skin powder and sonicate at 25℃ for 30min; then filter, centrifuge the filtrate at 3000r / min for 30min, take the supernatant, and make up to 1000mL for later use; S3 Purification: The extract was evaporated under reduced pressure at 65°C using a rotary evaporator to remove the ethanol solution, yielding a concentrated solution. This concentrated solution was then placed in a freeze dryer for pre-freezing and drying to obtain high-purity peanut skin polyphenol powder (e.g., ...). Figure 2 (as shown) The pre-freezing temperature was set to -20℃ for 12 hours; the temperature was maintained at -60℃ for 6 hours to ensure complete removal of moisture and ethanol solution while maintaining the activity of peanut skin polyphenols.

[0027] Example 3 Based on Examples 1-2, this example uses the peanut shell cellulose described above to prepare a cellulose / chitosan composite membrane.

[0028] The method for preparing the cellulose / chitosan composite membrane includes: Add a 1% (w / w) glycerol solution to peanut shell cellulose powder and stir in a constant temperature water bath at 60°C until the powder is completely dissolved to prepare a 1.5% (w / w) cellulose solution; let stand until completely degassed to obtain the cellulose solution for later use. Add pure water to carboxymethyl chitosan powder and stir in a constant temperature water bath at 55-65°C until the powder is completely dissolved to prepare a 1% carboxymethyl chitosan solution; let stand until completely degassed to obtain a carboxymethyl chitosan solution for later use. Cellulose solution and carboxymethyl chitosan solution were mixed at a mass ratio of 1:2, 1:1, and 2:1, and stirred evenly with a power stirrer to prepare a blend solution. The mixture was allowed to stand until completely degassed, poured onto a clean and flat glass plate, cast evenly, placed in an oven, and dried at 60°C to form a film, thus obtaining a cellulose / chitosan composite film. Among them, when the mass ratio of cellulose to carboxymethyl chitosan is 1:1, the cellulose / chitosan composite membrane involved is as follows: Figure 25 As shown.

[0029] Example 4 Based on Examples 1-2, this example uses the aforementioned peanut shell cellulose to prepare an antioxidant cellulose / chitosan / polyphenol composite membrane. The method for preparing the antioxidant cellulose / chitosan / polyphenol composite membrane includes: Add a 1% (w / w) glycerol solution to peanut shell cellulose powder and stir in a constant temperature water bath at 60°C until the powder is completely dissolved to prepare a 1.5% (w / w) cellulose solution; let stand until completely degassed to obtain the cellulose solution for later use. Add pure water to carboxymethyl chitosan powder and stir in a constant temperature water bath at 55-65°C until the powder is completely dissolved to prepare a 1% carboxymethyl chitosan solution; let stand until completely degassed to obtain a carboxymethyl chitosan solution for later use. Add a 45% ethanol solution to peanut skin polyphenol powder and stir in a constant temperature water bath at 25°C until the powder is completely dissolved to prepare a 15% polyphenol solution. Let it stand until all bubbles are removed to obtain the polyphenol solution for later use. Using cellulose, carboxymethyl chitosan, and polyphenols in a mass ratio of 30:15:1, the cellulose solution, carboxymethyl chitosan solution, and polyphenol solution were mixed and stirred evenly using a power stirrer to prepare a blend solution. After standing until completely degassed, the mixture was poured onto a clean, flat glass plate, cast evenly, and then placed in an oven to dry at 60°C to obtain an antioxidant cellulose / chitosan / polyphenol composite film (e.g., ...). Figure 25 (As shown).

[0030] Similarly, using the above method, oxidized cellulose / chitosan / polyphenol composite membranes (e.g., cellulose, carboxymethyl chitosan, and polyphenols in a mass ratio of 22:22:1) were prepared. Figure 25 (as shown) Using the above method, oxidized cellulose / chitosan / polyphenol composite membranes (e.g., cellulose, carboxymethyl chitosan, and polyphenols in a mass ratio of 15:30:1) were prepared. Figure 25 (As shown).

[0031] Example 5 Based on Example 2, this example describes the determination of polyphenol content in peanut skin extract, specifically including: I. Comparison of Total Ion Chromatograms (TIC) of QC Samples The total ion chromatogram (TIC) of the QC samples was compared by spectral overlap, such as... Figure 3-4 As shown in the figure. The experimental results show that the response intensity and retention time of each chromatographic peak basically overlap, indicating that the variation caused by instrument error is small throughout the experiment.

[0032] II. Principal Component Analysis (PCA) of the Population Sample All peaks extracted from experimental and QC samples were subjected to PCA analysis, see [link to PCA analysis]. Figure 5-6 As shown in the figure. The experimental results show that the QC samples are tightly aggregated together under both positive and negative ion modes, indicating good reproducibility of the experiment.

[0033] III. QC Sample Correlation Perform Pearson correlation analysis on the QC samples (generally, a correlation coefficient greater than 0.9 indicates a good correlation). Figure 7-8 As shown in the figure. The experimental results show that the correlation coefficients among the QC samples are all above 0.90, indicating that the experiment has good repeatability.

[0034] IV. Hotelling's T2 Test for the Overall Sample Hotelling's T2 test uses multivariate modeling to test samples, defining 95% or 99% confidence intervals, and can be used to diagnose outliers. The results of Hotelling's T2 test are shown below. Figure 9-10The results showed that all QC samples were within the 99% confidence interval, indicating good reproducibility of the experiment. V. Multivariate Control of QC Samples A multivariate control chart (MCC) is a multivariate statistical model based on ion peaks detected in QC samples. It is a quality management tool used to monitor and determine the stability of instrument status. Each point in the MCC represents a QC sample, and the X-axis represents the order in which all QC samples were tested. Due to fluctuations in instrument status, the points on the chart will show ups and downs; generally, a range of plus or minus 3 standard deviations is considered normal. The MCC for the QC samples in this project is shown below. Figure 11-12 The experimental results show that the fluctuations in the QC samples are all within plus or minus 3 standard deviations, reflecting that the instrument fluctuations are within the normal range, and the data can be used for subsequent analysis.

[0035] VI. Relative Standard Deviation (RSD) of QC Samples A smaller relative standard deviation (RSD) of ion peak abundance in QC samples indicates better instrument stability and is an important indicator of data quality. In this experiment, the number of peaks with RSD ≤ 30% accounted for more than 80% of the total number of peaks in the QC samples. Figure 13-14 This indicates that the instrument analysis system has good stability and the data can be used for subsequent analysis.

[0036] VII. Statistical Classification of Metabolites by Chemical Category All identified metabolites (including those identified by both positive and negative ions) were classified and statistically analyzed according to their chemical taxonomy information. The proportion of each type of metabolite was as follows: Figure 15-16 As shown. Example 6 Based on Example 2, this example measures the antibacterial properties of polyphenols in peanut skin extract, specifically including: I. Bacterial activation and scale-up culture: Frozen Staphylococcus aureus and Escherichia coli were inoculated into NB medium and cultured overnight (16 hours). II. Dilution of bacterial strains The expanded culture was diluted with NB medium to achieve OD... 600 = Between 0.16 and 0.18; III. Diluting the Drug The polyphenols involved in Staphylococcus aureus were diluted to different concentrations: 8 g / L, 4 g / L, 2 g / L, 1 g / L, 0.5 g / L, 0.25 g / L, 0.125 g / L, and 0.0625 g / L; The polyphenols involved in Escherichia coli were diluted to different concentrations: 5 g / L, 2.5 g / L, 1.25 g / L, 0.625 g / L, 0.3125 g / L, 0.51625 g / L, 0.07813 g / L, and 0.01953 g / L. IV. Joint Training The diluted polyphenols were co-cultured with Escherichia coli and Staphylococcus aureus at 37°C for 3 h. 5. Add drop by drop After co-culturing the system, a certain amount of liquid for each concentration was taken and added dropwise to the culture medium. After culturing at 37°C for 16 hours, colony counting was performed. The results are as follows Figure 17-22 Therefore, we can conclude that: 1. The antibacterial effect of peanut skin polyphenols is positively correlated with concentration. The inhibitory effect of peanut skin polyphenols on Staphylococcus aureus and Escherichia coli increased with increasing concentration. An 8 g / L polyphenol solution completely inhibited the growth of Staphylococcus aureus, with no colony growth observed; a 5 g / L polyphenol solution showed a significant inhibitory effect on Escherichia coli, while low concentrations of 0.07813 g / L and 0.01953 g / L polyphenol solutions showed no significant inhibitory effect. like Figure 17 , 19 As shown, when the polyphenol solution concentration is ≥0.5 g / L, the number of Staphylococcus aureus colonies is significantly reduced, and when the polyphenol solution concentration is less than 0.5 g / L, the number of Staphylococcus aureus colonies is close to that of the control group. like Figure 18 , 20 As shown, when the polyphenol solution concentration is ≥2.5 g / L, the antibacterial effect on Escherichia coli is significant; low concentration polyphenol solutions (such as 0.07813 g / L) may be ineffective.

[0037] 2. Differences in susceptibility among bacterial strains The antibacterial effect of Staphylococcus aureus was significant at polyphenol concentrations (≥0.5 g / L), while the antibacterial effect of Escherichia coli was significant at concentrations (≥2.5 g / L), indicating that Staphylococcus aureus is more sensitive to peanut skin polyphenols. 3. Determination of MIC (Minimum Inhibitory Concentration) The MIC for Staphylococcus aureus is between 1 and 2 g / L (the lowest concentration to completely inhibit growth), while the MIC for Escherichia coli may be between 5 and 6 g / L.

[0038] Among them, peanut skin polyphenols can exert their effects by damaging bacterial cell membranes, inhibiting enzyme activity, or interfering with metabolic pathways. Staphylococcus aureus, as a Gram-positive bacterium, has a thick cell wall mainly composed of peptidoglycan, which is easily destroyed by polyphenols. Escherichia coli, as a Gram-negative bacterium, has an outer membrane composed of lipopolysaccharide on the outer layer of its cell wall, which has a more complex structure and a stronger barrier effect, making it more difficult for polyphenols to penetrate.

[0039] Peanut skin polyphenols exhibit concentration-dependent antibacterial activity against both Staphylococcus aureus and Escherichia coli, with a more significant inhibitory effect against Staphylococcus aureus (effective at lower concentrations). Therefore, peanut skin polyphenols can be considered as a candidate natural preservative or antibacterial agent, particularly in the food and pharmaceutical fields.

[0040] Example 7 Based on Example 2, this example measures the antioxidant properties of polyphenols in peanut skin extract, specifically including: I. Scavenging effect of peanut skin polyphenols on DPPH free radicals Preparation of DPPH free radical working solution: Accurately weigh 1g of DPPH powder, dissolve it in anhydrous ethanol, and bring the volume to 1L to obtain a DPPH free radical stock solution with a concentration of 1 g / L. Store the stock solution at 4℃ for later use. Take 2mL of the DPPH free radical stock solution and add 18mL of anhydrous ethanol to prepare a 100 mg / L DPPH free radical working solution. Determination of DPPH free radical scavenging rate: An appropriate amount of peanut skin extract-polyphenol was taken and successively diluted with anhydrous ethanol to prepare sample solutions with concentrations (g / L) of 0.5, 0.1, 0.02, 0.004, 0.0008, and 0.00016, respectively. The polyphenol sample solutions of different concentrations were mixed with 100 mg / L DPPH free radical working solution at a volume ratio of 1:1, and incubated at 37℃ for 0.5 h. The absorbance at 517 nm was measured, with 6 replicates for each concentration. Ascorbic acid of equal concentration was used as a positive control. The results are as follows: Figure 23 As shown. Calculate the DPPH free radical scavenging rate using the following formula: DPPH free radical scavenging rate = (1 - (A1 - A2) / A0) × 100% In the formula: A1 is the absorbance of the sample solution + DPPH free radical working solution; A2 is the absorbance of the sample solution + anhydrous ethanol; A0 is the absorbance of anhydrous ethanol + DPPH free radical working solution.

[0041] It can be seen that: ① The scavenging rate of DPPH free radicals by peanut skin polyphenols increases significantly with increasing polyphenol concentration: at low concentrations (0.00016-0.02 g / L), the scavenging rate increases slowly; when the concentration of peanut skin polyphenols is ≥0.02 g / L, the scavenging rate increases sharply, and at 0.5 g / L, the scavenging rate is ≥90%; ② Comparison with ascorbic acid: At the same concentration, the scavenging rate of peanut skin polyphenols on DPPH free radicals is close to that of ascorbic acid (positive control) on DPPH free radicals, and the difference is further reduced at high concentrations of peanut skin polyphenols; Peanut skin polyphenols exhibit a high scavenging rate of DPPH free radicals, approaching the effect of anti-ascorbic acid, indicating that peanut skin polyphenols possess excellent antioxidant capabilities.

[0042] II. Scavenging effect of peanut skin polyphenols on ABTS free radicals Preparation of ABTS radical working solution: Mix 7 mmol / L ABTS radical solution and 4.9 mmol / L K2S2O8 solution at a volume ratio of 1:1, react in the dark for 16 h to obtain the ABTS radical stock solution, and store at 4℃ for later use. Take an appropriate amount of the ABTS radical stock solution and dilute it with anhydrous ethanol until its absorbance at 734 nm is 0.70 ± 0.02, which is the ABTS radical working solution. Determination of ABTS free radical scavenging rate: An appropriate amount of peanut skin extract-polyphenol was taken and successively diluted with anhydrous ethanol to prepare sample solutions with concentrations (g / L) of 0.5, 0.1, 0.02, 0.004, 0.0008, and 0.00016. The polyphenol sample solutions of different concentrations were mixed with ABTS free radical working solution at a volume ratio of 1:1 and reacted at room temperature for 6 min. The absorbance at 734 nm was measured, with 6 replicates for each concentration. Ascorbic acid of equal concentration was used as a positive control. The results are as follows: Figure 24 As shown. The ABTS radical scavenging rate is calculated using the following formula: ABTS radical scavenging rate = (1 - (A1 - A2) / A0) × 100% In the formula: A1 is the absorbance of the sample solution + ABTS free radical working solution; A2 is the absorbance of the sample solution + anhydrous ethanol; A0 is the absorbance of anhydrous ethanol + ABTS free radical working solution.

[0043] It can be seen that: ① The scavenging rate of peanut skin polyphenols against ABTS free radicals increases significantly with increasing polyphenol concentration: at low concentrations (0.00016-0.02 g / L), the scavenging rate increases slowly; when the concentration of peanut skin polyphenols is ≥0.02 g / L, the scavenging rate increases sharply, and at 0.5 g / L, the scavenging rate is ≥90%; ② Comparison with ascorbic acid: At the same concentration, the scavenging rate of peanut skin polyphenols against ABTS free radicals is close to that of ascorbic acid (positive control) against ABTS free radicals, and the difference is further reduced at high concentrations of peanut skin polyphenols; Peanut skin polyphenols exhibit a high scavenging rate against ABTS free radicals, approaching the effect of anti-ascorbic acid, indicating that peanut skin polyphenols possess excellent antioxidant capabilities.

[0044] Example 8 Based on Example 4, the cellulose / chitosan / polyphenol composite membrane, cellulose / imidazolium / polyphenol composite membrane, and nanofiber / chitosan / polyphenol composite membrane prepared in Example 4 were compared (e.g.) Figure 26 (As shown). Specifically includes: I. Preparation of Cellulose / Imidazole / Polyphenol Composite Membranes Add a 45% ethanol solution to peanut skin polyphenol powder and stir in a constant temperature water bath at 25°C until the powder is completely dissolved to prepare a 15% polyphenol solution. Let it stand until all bubbles are removed to obtain the polyphenol solution for later use. Imidazole chloride ionic liquid was mixed with cellulose powder and heated to dissolve the cellulose in the imidazole chloride ionic liquid. Then, polyphenol solution was added to obtain a mixed solution. The mixture was stirred evenly with a power stirrer and then allowed to stand until all bubbles were removed. The mixture was poured onto a clean and flat glass plate (fixed in a horizontal position). The mixed solution was poured down one end of the glass plate and coated into a wet film using a film scraper. The glass plate coated with the wet film was placed in a container filled with deionized water. The container was gently shaken to allow the deionized water to flow and cause the imidazole chloride ionic liquid to precipitate and elute from the wet film. After repeating the elution process 3 times, the glass plate coated with the wet film was removed and placed in a constant temperature drying oven to dry, thus obtaining a cellulose / imidazole / polyphenol composite membrane.

[0045] II. Preparation of Nanofiber / Chitosan / Polyphenol Composite Films Add a 1% (w / w) glycerol solution to the nanocellulose and stir in a constant temperature water bath at 60°C until the powder is completely dissolved to prepare a 1.5% (w / w) nanocellulose solution; let stand until completely degassed to obtain the nanocellulose solution for later use. Add ultrapure water to carboxymethyl chitosan powder and stir in a constant temperature water bath at 60°C until the powder is completely dissolved to prepare a 1% carboxymethyl chitosan solution; let stand until completely degassed to obtain a carboxymethyl chitosan solution for later use. Add a 45% ethanol solution to peanut skin polyphenol powder and stir in a constant temperature water bath at 25°C until the powder is completely dissolved to prepare a 15% polyphenol solution. Let it stand until all bubbles are removed to obtain the polyphenol solution for later use. The nanocellulose solution, carboxymethyl chitosan solution, and polyphenol solution were mixed in a mass ratio of 15:15:1 and stirred evenly with a power stirrer to prepare a blend solution. The mixture was allowed to stand until completely degassed, poured onto a clean and flat glass plate, cast evenly, and placed in an oven to dry at 60°C to obtain a nanocellulose / chitosan / polyphenol composite film.

[0046] III. The obtained cellulose / chitosan / polyphenol composite membranes, cellulose / imidazolium / polyphenol composite membranes, and nanofiber / chitosan / polyphenol composite membranes were compared, and the results are shown in Table 1 below. Figure 26 As shown.

[0047] Table 1

[0048] It can be known that: Nanofiber / chitosan / polyphenol composite films exhibit the best performance in terms of mechanical strength, density, and functionality, making them suitable for high-end food packaging and medical materials. However, nanofiber materials are expensive to manufacture. Cellulose / chitosan / polyphenol composite membranes have good air permeability and antibacterial properties, making them suitable for the preservation of fruits and vegetables, and they have low production costs. Cellulose / imidazolium / polyphenol composite films have lower performance and are only suitable for general food packaging applications. In addition, the introduction of polyphenols significantly improves the antioxidant and antibacterial properties of the membrane, showing promising application prospects.

[0049] Example 9 Based on Examples 3-4, this example tests the antibacterial properties of the obtained cellulose / chitosan composite membrane and cellulose / chitosan / polyphenol composite membrane. Specifically, this includes: 1. Bacterial activation and expansion culture: Frozen Staphylococcus aureus and Escherichia coli were inoculated into NB medium and cultured overnight (16 hours). 2. Dilution: Dilute the expanded culture strain with NB medium to adjust the OD... 600 = Between 0.16 and 0.18; 3. Co-culture: The prepared membrane material (concentration of 10 g / L, mass of 0.5 g) was co-cultured with Escherichia coli and Staphylococcus aureus at 37°C. 200 μL was taken every 1 hour to measure the absorbance value and record the data. 4. Drop addition: After co-culturing for 6 hours, the liquid (bacterial suspensions of different membrane materials) is taken and dropped onto the culture medium. After culturing at 37°C for 16 hours, colony counting is performed. Through co-culture experiments of cellulose / chitosan composite membranes (chitosan membranes), cellulose / chitosan / polyphenol composite membranes (polyphenol membranes), and Escherichia coli and Staphylococcus aureus, combined with absorbance (OD) analysis, the results were analyzed. 600 Based on dynamic monitoring and colony counting results, we can conclude that: I. OD 600 Dynamic changes like Figure 27-28As shown, during the 6-hour co-culture process, the OD600 value of the blank control group (containing only bacterial culture) without any membrane added continuously increased, indicating rapid bacterial growth; the OD600 value of the cellulose / chitosan composite membrane group... 600 Slow growth indicates a certain antibacterial effect; OD of the cellulose / chitosan / polyphenol composite membrane group 600 It grows more slowly and has a better antibacterial effect than cellulose / chitosan composite membrane; II. Colony Count ( Figures 29-30 ): The blank control group had the highest number of colonies, indicating active bacterial growth; the cellulose / chitosan composite membrane group had a reduced number of colonies, showing a certain antibacterial ability; the cellulose / chitosan / polyphenol composite membrane group had the lowest number of colonies and the highest antibacterial rate, indicating that the cellulose / chitosan / polyphenol composite membrane has the strongest antibacterial performance. Chitosan inhibits bacterial growth by disrupting bacterial cell membrane structure; polyphenols interfere with bacterial metabolism through oxidative stress and enzyme activity inhibition; in the cellulose / chitosan / polyphenol composite membrane, chitosan and polyphenols work synergistically to enhance the antibacterial effect, while cellulose provides good mechanical support and stability.

[0050] Example 10 Based on Example 4, the preservation performance of the blended solution (cellulose / chitosan / polyphenol composite film solution) prepared in Example 4 was tested. Specifically, this included: The prepared cellulose / chitosan / polyphenol composite film solution (concentration of 10 g / L) was sprayed onto paper bags to make cellulose / chitosan / polyphenol composite film paper bags, and then allowed to dry; a blank paper bag was used as a control experiment, and strawberries were placed in the two types of paper bags to observe the state of the strawberries. The results are as follows Figures 31-32 As shown, the fruit in the paper bag sprayed with the cellulose / chitosan / polyphenol composite film solution did not develop mold, while the fruit in the blank paper bag did. Therefore, it can be concluded that the polyphenols in peanut skins can be used for fruit preservation.

Claims

1. A method for extracting cellulose from peanut shells, characterized in that, Includes the following steps: X1 Pre-treatment: Clean the collected peanut shells, dry them, crush them, and pass them through a 60-mesh sieve to obtain peanut shell powder for later use. X2 Extraction: Add a 1.5-2.5% sodium hydroxide solution to peanut shell powder; stir the mixture with a magnetic stirrer in a constant temperature water bath at 85-90℃ for 3-5 hours, then filter to obtain the residue. X3 bleaching: After drying the obtained filter residue, add it to a NaClO2 solution with a concentration of 1.5-2.0 w / v% and adjust the pH to 4.5-5.0; then, stir the reaction with a magnetic stirrer in a constant temperature water bath at 75-85℃ for 5-6 hours, filter, and wash until the pH of the filtrate is neutral; after drying, peanut shell cellulose powder is obtained.

2. The method for extracting cellulose from peanut shells according to claim 1, characterized in that, In step X2, a sodium hydroxide solution with a concentration of 1.5-2.5% is added to the peanut shell powder, and the ratio of peanut shell powder to sodium hydroxide is 1:15-25.

3. The method for extracting cellulose from peanut shells according to claim 2, characterized in that, In step X3, the ratio of the dried filter residue to the NaClO2 solution is 1:15-25.

4. The method for extracting cellulose from peanut shells according to claim 3, characterized in that, In step X3, glacial acetic acid is used to adjust the pH.

5. A method for extracting peanut skin polyphenols, characterized in that, Includes the following steps: S1 Pretreatment: Crush the collected peanut skins and pass them through a 40-mesh sieve to obtain peanut skin powder for later use; S2 extraction: Add a 50-60% ethanol solution to the peanut skin powder; sonicate at 20-28℃ for 20-30 min; then filter, centrifuge, and collect the centrifuged liquid for later use; S3 Purification: The centrifuged liquid was evaporated under reduced pressure at 60-75°C using a rotary evaporator to obtain a concentrated liquid; the concentrated liquid was then placed in a freeze dryer for pre-freezing and drying to obtain peanut skin polyphenol powder. The pre-freezing temperature was set to -20 to -18℃, and the pre-freezing time was 10 to 14 hours. The temperature was maintained at -60 to -45℃, and the drying time was 5 to 7 hours.

6. The method for extracting peanut skin polyphenols according to claim 5, characterized in that, In step S1, the moisture content of the peanut skin is 3-8%.

7. The method for extracting peanut skin polyphenols according to claim 6, characterized in that, In step S2, an ethanol solution with a concentration of 50-60% is added to the peanut skin powder, and the ratio of peanut skin powder to ethanol solution is 1:20-30.

8. The method for extracting peanut skin polyphenols according to claim 7, characterized in that, In step S2, the filtrate produced by filtration is centrifuged at 2800-3200 r / min for 20-30 min.

9. Peanut shell cellulose prepared by the extraction method according to any one of claims 1-4, and / or peanut skin polyphenol prepared by the extraction method according to any one of claims 5-8, are used in cellulose / chitosan / polyphenol composite films for food preservation.

10. The application according to claim 9, characterized in that, The preparation method of the cellulose / chitosan / polyphenol composite membrane includes the following steps: Add a 0.5-1.5% glycerol solution to peanut shell cellulose powder and stir in a constant temperature water bath at 55-65°C until the powder is completely dissolved to prepare a 1-2% cellulose solution. Let it stand until all bubbles are removed to obtain the cellulose solution for later use. Add pure water to carboxymethyl chitosan powder and stir in a constant temperature water bath at 55-65°C until the powder is completely dissolved to prepare a carboxymethyl chitosan solution with a mass fraction of 0.5-1.5%; let stand until completely degassed to obtain a carboxymethyl chitosan solution for later use. Add a 40-50% ethanol solution to peanut skin polyphenol powder and stir in a constant temperature water bath at 20-25°C until the powder is completely dissolved to prepare a 10-20% polyphenol solution. Let it stand until all bubbles are removed to obtain the polyphenol solution for later use. A cellulose solution, carboxymethyl chitosan solution, and polyphenol solution were mixed at a mass ratio of 14–16:14–16:1 and stirred evenly using a power stirrer to prepare a blend solution. The mixture was allowed to stand until completely defoamed, poured onto a clean and flat glass plate, cast evenly, and placed in an oven to dry at 55–65°C to obtain an antioxidant cellulose / chitosan / polyphenol composite film.

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