Preparation method of antioxidant compound beverage

Abstract

The invention discloses a preparation method of an antioxidant compound beverage, and belongs to the technical field of beverage processing. Comprising the following steps: raw material pretreatment; performing enzymolysis; filtering for the first time; performing alcoholic fermentation; performing acetic fermentation; filtering for the second time; performing blending; filtering for the third time; and sterilizing. The antioxidant compound fruit vinegar beverage which has unique sour and sweet taste, is clear and transparent, is rich in nutritional ingredients of various fruits and has an antioxidant effect is prepared by selecting various fruits through the processes of enzymolysis, fermentation, blending and the like. A three-stage filtering system is adopted, pulp residues, fruit seed fragments and the like in enzymatic hydrolysate can be effectively removed, impurities such as microorganisms and colloids in fermentation liquor can be effectively removed through second-time filtering, pigments, peculiar smells and small particles in the blended fruit vinegar beverage can be adsorbed through third-time filtering, the three-stage filtering is progressive layer by layer, and the effect is good. The impurities are treated more carefully and comprehensively, and the clarity and quality of the fruit vinegar can be better guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of beverage processing, and specifically relates to a method for preparing an antioxidant composite beverage. Background Art

[0002] Currently, most fruit vinegar beverages on the market are made from fermenting a single fruit, which presents numerous limitations. For example, single-fruit vinegar beverages only offer the nutritional benefits of a single fruit, failing to meet consumers' demand for diverse nutrition. Furthermore, because they are fermented from only one fruit, their flavor profile is relatively monotonous, lacking depth and richness. Furthermore, the filtration process in the current preparation of fruit vinegar beverages uses traditional filtration equipment and ordinary filter membranes, which also face severe challenges. Commonly used traditional filtration equipment, such as diatomaceous earth filters and plate and frame filters, has limited filtration accuracy and is unable to remove tiny impurities, colloids, and microorganisms from fruit vinegar. These residual substances not only affect the clarity and stability of fruit vinegar beverages, but may also cause safety issues such as excessive microorganisms. Ordinary filter membranes are even more disadvantageous when faced with the complex ingredients of fruit vinegar beverages. Substances such as organic acids, sugars, and proteins in fruit vinegar are easily adsorbed on the membrane surface, leading to serious membrane fouling, a rapid decrease in flux, and a significant reduction in the membrane's service life. At the same time, ordinary filter membranes do not have self-repair capabilities and cannot repair themselves when damaged, further affecting the quality and production efficiency of fruit vinegar beverages. Therefore, it is extremely important to develop a method for preparing an antioxidant composite fruit vinegar beverage that can integrate the nutritional and flavor advantages of multiple fruits and solve the technical difficulties in the filtration process. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing an antioxidant composite beverage to solve the problems of the prior art, such as single nutrition and flavor, low filtration accuracy and poor membrane performance in the filtration process.

[0004] The purpose of the present invention is achieved through the following technical solutions: A method for preparing an antioxidant composite beverage comprises the following steps: S1. Raw material pretreatment; the raw materials used include at least two different fruits; S2. Enzymatic hydrolysis; S3. First filtration: Filter using a micron-sized pore size mesh; S4. Alcoholic fermentation; S5. Acetic acid fermentation; S6. Second filtration: using a composite membrane, the composite membrane comprises the following materials: Modified polyvinylidene fluoride, modified tea polyphenols, tannic acid, modified nano-silica, and self-healing agent microcapsules; Modified polyvinylidene fluoride is obtained by grafting polyvinylidene fluoride with polyvinyl alcohol-lactic acid graft copolymer; Modified tea polyphenols are obtained by modifying tea polyphenols with a silane coupling agent; Modified nano-silica is obtained by modifying nano-silica with gum arabic; In the self-repairing agent microcapsules, the wall material is a composite wall material of sodium alginate-chitosan-sodium carboxymethyl cellulose. The monomer used in the self-repairing fluid is polycaprolactone monomer, and the initiator is a mixture of ammonium persulfate and sodium bisulfite; S7. Preparation; S8. Third filtration: filtration using activated carbon / diatomaceous earth composite material; S9. Sterilization.

[0005] As some possible implementation methods of the present application, the composite film includes the following components in parts by weight: 60-75 parts of modified polyvinylidene fluoride, 5-10 parts of modified tea polyphenols, 3-5 parts of tannic acid, 5-10 parts of modified nano-silica, and 10-20 parts of self-healing agent microcapsules; wherein, in the modified polyvinylidene fluoride, the mass ratio of polyvinyl alcohol-lactic acid graft copolymer to polyvinylidene fluoride is 1:(3-5); in the self-healing agent microcapsules, the mass ratio of sodium alginate, chitosan, and sodium carboxymethyl cellulose is 3:(2-3):(1-2).

[0006] As some possible implementation methods of the present application, the composite film includes the following components in parts by weight: 62-70 parts of modified polyvinylidene fluoride, 6-8 parts of modified tea polyphenols, 4.5 parts of tannic acid, 6-8 parts of modified nano-silica, and 12-16 parts of self-healing agent microcapsules.

[0007] As some possible implementation methods of the present application, 0.1-0.3 wt% of nanocellulose is further added to the self-repairing liquid.

[0008] As some possible implementation methods of the present application, poly (N-isopropylacrylamide) is grafted onto the wall material of the self-healing agent microcapsule.

[0009] As some possible implementation methods of the present application, polyethylene glycol is grafted onto the surface of the modified nano-silica.

[0010] As some possible implementation methods of the present application, in the activated carbon / diatomaceous earth composite material, the mass ratio of activated carbon to diatomaceous earth is (30-50): (60-80).

[0011] As some possible implementation methods of the present application, in step S2, the enzymes added are cellulase and pectinase, and the added amounts are 0.05% - 0.15% of the mass of the fruit, respectively. The enzymolysis temperature is 40 - 50 ° C. and the enzymolysis time is 1 - 2 h.

[0012] As some possible implementation methods of the present application, in step S7, 0.02-0.1wt% of vitamin C and 0.002-0.02wt% of vitamin E are added.

[0013] As some possible implementation methods of the present application, in step S9, pulsed intense light sterilization technology is used for sterilization.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This method utilizes at least two fruits and, through enzymatic hydrolysis, fermentation, and blending processes, creates a composite fruit vinegar beverage that incorporates the nutrients of multiple fruits and creates a unique, rich, and layered flavor, breaking away from the monotonous taste and nutritional limitations of single fruit vinegar. Furthermore, through the synergistic effect of these steps, the composite fruit vinegar beverage is ensured to be clear, with a balanced sweetness and sourness, a smooth texture, and rich in functional properties, comprehensively enhancing the quality and health benefits of the fruit vinegar beverage.

[0015] 2. The present invention utilizes a three-stage filtration system. The first filtration, performed after enzymatic hydrolysis, promptly removes large particles of pulp residue and seed fragments, preventing these impurities from entering the fermentation process, reducing pressure on subsequent composite membrane filtration and increasing the service life of the composite membrane. A second filtration, performed after fermentation, effectively removes impurities such as microorganisms and colloids, targeting the complex composition and acidic environment of the fermented fruit vinegar beverage. A third filtration, performed after blending, further absorbs pigments, odors, and fine particles, improving clarity. These three stages of filtration are progressive, providing more detailed and comprehensive impurity treatment, thereby ensuring the clarity and quality of the fruit vinegar.

[0016] 3. This invention provides a composite membrane with high-efficiency filtration, antioxidant, antibacterial, and self-healing properties. Modified polyvinylidene fluoride improves hydrophilicity and reduces membrane fouling; modified tea polyphenols provide stable dispersion and exert antioxidant and antibacterial effects; tannic acid enhances component binding; modified nanosilica optimizes pore structure; and self-healing agent microcapsules enable membrane self-repair. This composite membrane precisely responds to the complex composition and acidic environment of fruit vinegar, effectively removing minute impurities, preserving nutrients, and extending membrane life, providing a solid foundation for the production of high-quality fruit vinegar beverages. DETAILED DESCRIPTION

[0017] A method for preparing an antioxidant composite beverage comprises the following steps: S1. Raw material pretreatment; the raw materials used include at least two different fruits; S2. Enzymatic hydrolysis; S3. First filtration: Filter using a micron-sized pore size mesh; S4. Alcoholic fermentation; S5. Acetic acid fermentation; S6. Second filtration: using a composite membrane, the composite membrane comprises the following materials: Modified polyvinylidene fluoride, modified tea polyphenols, tannic acid, modified nano-silica, and self-healing agent microcapsules; Modified polyvinylidene fluoride is obtained by grafting polyvinylidene fluoride with polyvinyl alcohol-lactic acid graft copolymer; Modified tea polyphenols are obtained by modifying tea polyphenols with a silane coupling agent; Modified nano-silica is obtained by modifying nano-silica with gum arabic; In the self-repairing agent microcapsules, the wall material is a composite wall material of sodium alginate-chitosan-sodium carboxymethyl cellulose. The monomer used in the self-repairing fluid is polycaprolactone monomer, and the initiator is a mixture of ammonium persulfate and sodium bisulfite; S7. Preparation; S8. Third filtration: filtration using activated carbon / diatomaceous earth composite material; S9. Sterilization.

[0018] In the method for preparing the antioxidant composite fruit vinegar beverage, the various steps are closely coordinated to ultimately produce a fruit vinegar beverage of excellent quality. In step S1, by selecting at least two different fruits, the beverage can be enriched with diverse flavors and nutritional value. In step S2, enzymatic hydrolysis decomposes fiber, pectin, and other substances in the fruit, releasing nutrients. In step S3, a micron-sized sieve (e.g., 50-100 microns) is used to intercept large particles of fruit pulp, seed fragments, and the like. In steps S4 and S5, yeast and acetic acid bacteria are introduced, respectively. The yeast converts the sugar in the juice into alcohol, and the acetic acid bacteria converts the alcohol into acetic acid. This two-stage fermentation imparts a unique flavor and composition to the fruit vinegar. In step S6, a composite membrane is used to remove microscopic impurities, microorganisms, and colloids (such as undecomposed pectin) from the fruit vinegar beverage. In step S7, the at least two different fruit vinegars are mixed in appropriate proportions, and sweeteners, acidity regulators, and antioxidants are added based on desired taste to impart a unique flavor and texture to the beverage. In step S8, the activated carbon / diatomaceous earth composite material performs deep filtration, adsorbing residual pigments, odorous substances, and fine particles, thereby improving the clarity and quality of the fruit vinegar. Finally, in step S9, sterilization is performed to kill microorganisms in the fruit vinegar beverage, ensuring its safety and shelf life.

[0019] The present invention prepares an antioxidant composite fruit vinegar beverage which has a unique sweet and sour taste, is clear and transparent, has good stability, and is rich in various fruit nutrients and has antioxidant effects through the above nine steps.

[0020] Among them, composite membrane filtration is the core link of the present invention, which can effectively remove impurities such as tiny impurities, microorganisms and colloids. The functions of each component in the composite membrane are as follows: Modified polyvinylidene fluoride (PVDF): PVDF itself has good chemical stability and mechanical strength, but its hydrophilicity is poor, causing sugars, proteins, and other components in fruit vinegar beverages to easily adsorb on the membrane surface and cause contamination. Grafting a biodegradable polyvinyl alcohol-lactic acid graft copolymer significantly improves the hydrophilicity of the PVDF membrane, making it less likely for impurities in fruit vinegar beverages to adhere to the membrane. This reduces membrane fouling, improves filtration flux, and extends the membrane's service life.

[0021] Modified tea polyphenols: Tea polyphenols possess excellent antioxidant and antimicrobial properties, but they are difficult to disperse evenly in a polyvinylidene fluoride matrix and are prone to agglomeration, which reduces the contact area between the tea polyphenols and the fruit vinegar beverage, weakening its antioxidant and antimicrobial properties. Modified with a silane coupling agent, the dispersibility of the tea polyphenols in the polyvinylidene fluoride matrix is ​​significantly improved. The modified tea polyphenols can effectively inhibit the oxidation of vitamins, phenols, and other substances in the fruit vinegar beverage, better preserving the antioxidant properties and nutritional content of the fruit vinegar. Furthermore, the antimicrobial properties of the modified tea polyphenols can reduce the growth of microorganisms in the fruit vinegar beverage during filtration, reducing the pressure on the subsequent sterilization process.

[0022] Tannic acid: Under the complex composition and acidic environment of fruit vinegar beverages, the bonding between modified tea polyphenols and modified polyvinylidene fluoride will be affected over time, causing the modified tea polyphenols to precipitate from the membrane, reducing the antioxidant and antibacterial properties. Tannic acid molecules contain multiple phenolic hydroxyl groups. On the one hand, they can react with the hydroxyl groups in modified tea polyphenols and modified polyvinylidene fluoride to form stable hydrogen bonds and covalent bonds, strengthening the bonding between modified tea polyphenols and the membrane material, improving synergistic stability, and making it difficult for modified tea polyphenols to precipitate from the membrane in fruit vinegar beverages, allowing them to continue to exert their antioxidant and antibacterial effects. On the other hand, tannic acid itself is also a natural antioxidant and antibacterial agent, which can further enhance the antioxidant and antibacterial protection of the filter membrane for fruit vinegar beverages.

[0023] Modified Nanosilica: Nanosilica has a large specific surface area and excellent dispersibility. After modification with gum arabic, its dispersion stability is further enhanced. During the filtration process of fruit vinegar beverages, modified nanosilica can help evenly disperse modified tea polyphenols within the modified polyvinylidene fluoride matrix, preventing agglomeration and increasing the contact area between the modified tea polyphenols and the fruit vinegar beverage, thereby more effectively unleashing the antioxidant and antibacterial properties of the modified tea polyphenols. Furthermore, modified nanosilica can also improve the pore structure of the filter membrane to a certain extent, optimizing the filtration performance of the composite membrane.

[0024] Self-repairing agent microcapsules: When the filter membrane is mechanically damaged or chemically eroded, the microcapsules rupture and release the repair liquid, which undergoes a polymerization reaction under the action of the initiator system to fill the tiny holes or cracks in the filter membrane, thereby achieving self-repair of the filter membrane, extending the service life of the filter membrane, and ensuring the continuity and stability of the filtration process during the preparation of fruit vinegar beverages.

[0025] The wall material utilizes a ternary composite of sodium alginate, chitosan, and sodium carboxymethyl cellulose. All three are natural polymers with excellent biocompatibility and biodegradability. Sodium alginate and chitosan form a stable base structure through electrostatic interaction, while the addition of sodium carboxymethyl cellulose enhances the wall material's toughness, stability, and hydrophilicity. This allows the microcapsules to better maintain their structural integrity in the acidic environment of fruit vinegar and during filtration, reducing the risk of premature rupture and enabling more precise release of the self-healing fluid upon membrane damage. Polycaprolactone monomer (PCL) is also a biodegradable material that gradually degrades into small molecules both in the body and in the natural environment, ultimately being metabolized or decomposed. Initiated by an ammonium persulfate and sodium bisulfite initiation system, PCL rapidly and stably initiates polymerization in the weakly acidic environment of fruit vinegar beverages, resulting in faster repair and improved polymerization results.

[0026] In summary, the composite membrane of the present invention is an innovative material that combines multiple excellent properties, including high-efficiency filtration, antioxidant properties, antibacterial properties, and self-repair. Designed specifically for the complex composition and acidic environment of fruit vinegar beverages, it performs stably during the filtration process, effectively removing impurities while preserving the nutritional content and flavor of the fruit vinegar. It also reduces membrane fouling and loss, lowering production costs and providing a reliable guarantee for the high-quality preparation of antioxidant composite fruit vinegar beverages.

[0027] In order to further improve the filtration performance of the composite membrane, as some possible implementation methods of the present application, the amount of each component in the composite membrane is further limited, that is, the composite membrane includes the following components in parts by weight: 60-75 parts of modified polyvinylidene fluoride, 5-10 parts of modified tea polyphenols, 3-5 parts of tannic acid, 5-10 parts of modified nano-silica, and 10-20 parts of self-healing agent microcapsules.

[0028] Wherein, in the modified polyvinylidene fluoride, the mass ratio of polyvinyl alcohol-lactic acid graft copolymer to polyvinylidene fluoride is 1:(3-5).

[0029] In the self-healing agent microcapsules, the mass ratio of sodium alginate, chitosan and sodium carboxymethyl cellulose is 3:(2-3):(1-2).

[0030] In order to further improve the filtration performance of the composite membrane, as some possible implementation methods of the present application, the amount of each component in the composite membrane is further limited, that is, the composite membrane includes the following components in parts by weight: 62-70 parts of modified polyvinylidene fluoride, 6-8 parts of modified tea polyphenols, 4.5 parts of tannic acid, 6-8 parts of modified nano-silica, and 12-16 parts of self-healing agent microcapsules.

[0031] When the self-repairing liquid repairs the composite membrane, the strength of the repaired structure formed by the simple polymerization of polycaprolactone monomers may be insufficient, and it is easy to be damaged again during the continuous filtration process. Based on this, as some possible implementation methods of this application, the components of the self-repairing liquid are further limited, that is, 0.1-0.3wt% of nanocellulose is also added to the self-repairing liquid. After adding nanocellulose, its high specific surface area and mechanical strength can be used to enhance the structural strength of the repaired composite membrane, so that the composite membrane can restore the filtration performance faster after repair and extend its service life.

[0032] During the production of fruit vinegar beverages, the ambient temperature and pH of the beverage may fluctuate, causing the self-healing agent microcapsules to rupture prematurely or incompletely, rendering them ineffective when the composite membrane is actually damaged. Based on this, as some possible implementations of this application, poly (N-isopropylacrylamide) is grafted onto the wall material of the self-healing agent microcapsules. Poly (N-isopropylacrylamide) is temperature-sensitive. After grafting, the microcapsule wall material becomes dual-responsive to temperature and pH, enabling more precise release of the self-healing fluid when the membrane is damaged and the environmental conditions meet the requirements, thereby improving the accuracy and effectiveness of the self-healing process.

[0033] During the filtration process of fruit vinegar beverages, especially after multiple filtration cycles or long filtration periods, the nano-silica modified with gum arabic may be affected by the components in the fruit vinegar beverage (such as organic acids, sugars, etc.), resulting in a decrease in dispersion stability and agglomeration. Based on this, as some possible implementation methods of the present application, polyethylene glycol is grafted onto the surface of the modified nano-silica. Polyethylene glycol has good hydrophilicity and dispersibility and can form a protective film on the surface of the modified nano-silica to prevent the agglomeration of the modified nano-silica, maintain its dispersion stability, ensure that the modified nano-silica continues to assist in the dispersion of tea polyphenols, and optimize the pore structure of the composite membrane.

[0034] To further enhance the filtration performance of the activated carbon / diatomaceous earth composite material, some possible implementations of this application further limit the dosage of each component in the activated carbon / diatomaceous earth composite material. Specifically, the weight ratio of activated carbon to diatomaceous earth in the activated carbon / diatomaceous earth composite material is (30-50):(60-80). The activated carbon particle size is 50-100 mesh. This particle size offers a large specific surface area and a rich pore structure, effectively adsorbing residual pigments, odorous substances, and some small particles in the fruit vinegar beverage. The diatomaceous earth particle size is 5-30 microns. This particle size effectively intercepts small impurities and, when used in conjunction with the activated carbon, provides a fine filtration effect, resulting in a clearer and more transparent fruit vinegar beverage.

[0035] Due to the complex structure of fruit cell walls, if the cell walls cannot be fully destroyed, the juice yield is low and the nutrient dissolution is insufficient, seriously affecting the yield and quality of the fruit vinegar beverage. Based on this, as some possible implementation methods of this application, the enzymatic hydrolysis parameters are further limited. That is, in step S2, the enzymes added are cellulase and pectinase, and the addition amount is 0.05%-0.15% of the fruit mass, respectively. The enzymatic hydrolysis temperature is 40-50°C, and the enzymatic hydrolysis time is 1-2 hours. By rationally determining the enzymatic hydrolysis parameters, the present invention can efficiently destroy the fruit cell structure, improve the juice yield and nutrient dissolution rate, and ensure the quality and flavor of the fruit vinegar beverage.

[0036] In order to further improve the antioxidant properties of the fruit vinegar beverage, as some possible implementation methods of the present application, in step S7, 0.02-0.1wt% of vitamin C and 0.002-0.02wt% of vitamin E are added.

[0037] To further reduce the loss of nutrients in the fruit vinegar beverage, as some possible implementations of the present application, pulsed intense light sterilization technology is used for sterilization in step S7. Pulsed intense light sterilization technology has a short action time, generates little heat, and can effectively kill microorganisms without destroying the nutrients and flavor of the fruit vinegar beverage.

[0038] Next, the preparation method of the antioxidant compound fruit vinegar beverage is described in detail.

[0039] Example 1 S1. Select apples and grapes, ensuring they are fresh, pest-free, and ripe. Perform all of the following steps on each fruit: After washing the fruit, peel and core it, beat the pulp into pulp, and then add purified water three times the mass of the fruit pulp.

[0040] Among them, for apples, after being beaten into pulp, 0.008% of the mass of the fruit pulp of vitamin C is immediately added to inhibit the browning of the apples.

[0041] S2. Add 0.08% cellulase (activity 10,000 U / g) and 0.08% pectinase (activity 15,000 U / g) based on the weight of the fruit pomace to the product obtained in step S1. Incubate the mixture at 45°C for 2 h, then raise the temperature to 65°C and maintain for 10 min. S3. The product after enzymatic hydrolysis in step S2 is filtered through a sieve with a pore size of 80 microns to obtain juice.

[0042] S4. Add 20wt% white sugar and 0.15wt% activated yeast to the juice and ferment in a sealed container at 25-30℃ for 5-7 days.

[0043] S5. Add 0.8 wt% of the activated acetic acid bacteria of the fermentation product in step S4 and perform acetic acid fermentation at 30-35°C for 7-10 days to obtain a fruit vinegar beverage.

[0044] S6. Filter the fruit vinegar beverage through a composite membrane.

[0045] S7. Mix the two fruit vinegar beverages obtained after filtration in S6 in a 1:1 mass ratio. Add an appropriate amount of white sugar, honey, or a sweetener to the mixed fruit vinegar to adjust the sweetness. Add citric acid or malic acid to adjust the acidity. The resulting composite fruit vinegar beverage has a sugar content of 8-12°Bx and a total acidity of 0.8%-1.2% (calculated as acetic acid, by mass fraction). Additionally, add 0.05% by weight of vitamin C and 0.005% by weight of vitamin E.

[0046] S8. Filter the prepared fruit vinegar beverage through the activated carbon / diatomaceous earth composite material.

[0047] The activated carbon / diatomite composite material is made by mixing diatomite and activated carbon in a mass ratio of 2:3. When used, the activated carbon / diatomite composite material is mixed at a mass ratio of 1.3 g / cm 3 The filling density is 100%, and the flow rate of the fruit vinegar liquid is 1m / s.

[0048] S9. Pulsed intense light sterilization technology is used for sterilization to obtain an antioxidant compound fruit vinegar beverage.

[0049] The preparation method of the composite film is as follows: S61. Preparation of raw materials.

[0050] A. The preparation method of modified polyvinylidene fluoride is as follows: A1. First, add 50g of PVA to 800mL of deionized water and stir to dissolve at 85°C. Once completely dissolved, add 80g of lactic acid and 1.5g of potassium persulfate. Raise the temperature to 70°C and continue stirring for 4 hours. After the reaction is complete, cool the solution to room temperature and dialyze it in deionized water for 3 days using a dialysis bag. Then, freeze-dry it to obtain a PVA-lactic acid graft copolymer.

[0051] A2. Dissolve 150g of polyvinylidene fluoride in 800mL of N,N-dimethylacetamide (DMAc). Then add 50g of PVA-lactic acid graft copolymer and stir at 55°C until thoroughly mixed. Next, add 1g of KH-570. Under nitrogen, raise the temperature to 80°C and allow to react for 7 hours. After the reaction, slowly pour the solution into 3000mL of deionized water to precipitate the modified polyvinylidene fluoride. Filter, wash, and vacuum dry at 60°C to constant weight to obtain the modified polyvinylidene fluoride. B. The preparation method of modified tea polyphenols is as follows: 100g tea polyphenols are dissolved in 1800mL anhydrous ethanol, followed by the addition of 3g silane coupling agent KH550 and 1g glacial acetic acid, and the mixture is stirred at 55°C for 5h. After the reaction is completed, the solution is evaporated on a rotary evaporator to remove the ethanol to obtain modified tea polyphenols. C. The preparation method of modified nano-silica is as follows: C1. Add 100g of nano-silica to 4000mL of deionized water and ultrasonically disperse for 45 minutes to obtain a nano-silica suspension. Dissolve 12g of gum arabic in 200mL of deionized water to obtain a gum arabic solution.

[0052] C2. Slowly add the gum arabic solution to the nanosilica suspension while stirring. Continue stirring for 2.5 hours. After the reaction is complete, centrifuge, wash, and vacuum dry at 65°C to constant weight to obtain modified nanosilica. D. The preparation method of self-healing agent microcapsules is as follows: D1. Dissolve 30g of sodium alginate in 3000mL of deionized water to prepare a sodium alginate solution; dissolve 25g of chitosan in 1250mL of 2% acetic acid solution to prepare a chitosan solution; and dissolve 15g of sodium carboxymethylcellulose in 1500mL of deionized water to prepare a CMC solution. Mix the three solutions and stir thoroughly to obtain a ternary composite wall material solution. First, 100g of polycaprolactone monomer and 0.2g of nanocellulose were added to 500mL of dichloromethane and dispersed evenly by ultrasonication. Then, 1g of ammonium persulfate and 2g of sodium bisulfite were added and stirred to dissolve to obtain a self-healing liquid. D2. Slowly add the self-healing liquid dropwise to the ternary composite wall material solution under stirring. After the addition is complete, continue stirring for 38 minutes. Then, add 100 mL of a 0.8% calcium chloride solution and stir for 1.5 hours. After the reaction is complete, centrifuge, wash, and dry at room temperature to obtain self-healing agent microcapsules.

[0053] S62. Composite membrane preparation: S621. Dissolve 70 parts by mass of modified polyvinylidene fluoride in N,N-dimethylacetamide (DMAc), then add 10 parts by mass of modified tea polyphenols, 4.5 parts by mass of tannic acid, 7 parts by mass of modified nano-silica, and 15 parts by mass of self-healing agent microcapsules in that order. Stir and mix thoroughly at 65°C to form a casting solution. S622. Apply the casting solution evenly to a clean glass plate, using a doctor blade to control the film thickness to 100 microns. Slowly immerse the glass plate coated with the casting solution in deionized water to initiate a phase inversion process. During this phase inversion, DMAc gradually diffuses into the water, while the polymer solidifies to form a film. S623. The composite membrane peeled from the glass plate was soaked in deionized water for 40 h. The membrane was then air-dried at room temperature and finally vacuum-dried at 70°C to constant weight to obtain a composite membrane.

[0054] Example 2 Compared with Example 1, the amount of each component in the composite film was adjusted. After adjustment, the amount of each component was as follows: 65 parts of modified polyvinylidene fluoride, 8 parts of modified tea polyphenols, 4.5 parts of tannic acid, 6 parts of modified nano-silica, and 13 parts of self-healing agent microcapsules.

[0055] The remaining parameters and steps are the same as in Example 1.

[0056] Example 3 Based on Example 1, poly (N-isopropylacrylamide) was grafted onto the wall material of the self-healing agent microcapsule to obtain PNIPAM-grafted self-healing agent microcapsules. The specific preparation method of the PNIPAM-grafted self-healing agent microcapsules is as follows: D1. Same as Example 1; D2. While stirring at 400 rpm, the self-healing liquid was slowly dripped into the wall material solution. After complete addition, stirring was continued for 38 minutes. Then, 15g of N-isopropylacrylamide (NIPAM) monomer and 0.3g of N,N'-methylenebisacrylamide were added to the emulsion and dissolved by stirring. The temperature was then raised to 60°C and nitrogen was introduced for 30 minutes to deoxygenate. 0.5g of potassium persulfate initiator was then added, and the reaction was allowed to proceed under nitrogen for 4 hours. After completion of the reaction, the mixture was cooled to room temperature. 100mL of 0.8% calcium chloride solution was then slowly added, and the reaction was continued at 300 rpm for 1.5 hours. The mixture was centrifuged, washed, and dried under vacuum at room temperature to constant weight to obtain PNIPAM-grafted self-healing agent microcapsules.

[0057] In this embodiment, the amount of the PNIPAM-grafted self-healing agent microcapsules used is the same as the amount of the self-healing agent microcapsules used in Example 1.

[0058] The remaining parameters and steps are the same as in Example 1.

[0059] Example 4 Based on Example 3, polyethylene glycol was grafted onto the surface of the modified nano-silica to obtain PEG-grafted modified nano-silica. The specific preparation method of the PEG-grafted modified nano-silica is as follows: C1. Same as Example 1; C2. As in Example 1, to obtain gum arabic modified nano-silica; C3. Add 12 g of PEG-3000 to 200 mL of ethanol and stir to dissolve. Then add 2.5 g of MPTMS and 0.8 g of acetic acid. Reflux at 65°C for 2 h to obtain an activated PEG-3000 solution.

[0060] 100 g of gum arabic modified nano-silica was added to 500 mL of deionized water and ultrasonically dispersed for 30 min to form a suspension.

[0061] Activated PEG-3000 solution was slowly added to the suspension, and the reaction was carried out at 55°C with stirring (300 r / min) for 4.5 h. After the reaction, the suspension was centrifuged, washed, and vacuum-dried at 60°C to constant weight to obtain PEG-grafted modified nano-silica.

[0062] In this embodiment, the amount of PEG-grafted modified nano-silica used is the same as the amount of modified nano-silica used in Example 1.

[0063] The remaining parameters and steps are the same as in Example 1.

[0064] Comparative Example 1 On the basis of Example 1, the mixture was directly blended after fermentation without composite membrane filtration.

[0065] The remaining parameters and steps are the same as in Example 1.

[0066] Comparative Example 2 On the basis of Example 1, the composite membrane was replaced with a PVDF membrane.

[0067] The remaining parameters and steps are the same as in Example 1.

[0068] Comparative Example 3 Based on Example 1, the components of the composite membrane were adjusted as follows: 70 parts by mass of polyvinylidene fluoride, 10 parts by mass of tea polyphenols, 4.5 parts by mass of tannic acid, 7 parts by mass of nano-silica and 15 parts by mass of self-repairing agent microcapsules.

[0069] The remaining parameters and steps are the same as in Example 1.

[0070] Comparative Example 4 Based on Example 1, no self-repairing agent microcapsules were added to the composite membrane.

[0071] The remaining parameters and steps are the same as in Example 1.

[0072] Experimental example (1) Quality testing of fruit vinegar beverages.

[0073] 1. Clarity and taste test of fruit vinegar beverage.

[0074] Test Method: The transmittance of the fruit vinegar beverage was measured using a UV-Vis spectrophotometer at a wavelength of 660 nm. The results are shown in Table 1.

[0075] Table 1: From Table 1 we can see that: In Examples 1-4, a three-stage filtration system (screen + composite membrane + activated carbon / diatomaceous earth) is used to effectively remove impurities such as pulp residue, colloids, and microorganisms, resulting in high light transmittance and a smooth taste.

[0076] Comparative Example 1 was not filtered through a composite membrane, and large particles of impurities remained in the fermentation broth. The subsequent activated carbon / diatomaceous earth had limited ability to remove impurities and proteins, resulting in low light transmittance and a grainy taste.

[0077] 2. Antioxidant activity test of fruit vinegar beverage.

[0078] ① DPPH free radical scavenging rate: Take 1 mL of fruit vinegar beverage, add 4 mL of 0.1 mmol / L DPPH ethanol solution, shake well and react in the dark for 30 min, and measure the absorbance at 517 nm. ②ABTS free radical scavenging rate: Mix ABTS solution with potassium persulfate solution, incubate in the dark for 12-16 hours, and dilute with ethanol to an absorbance of 0.7 ± 0.02 at 734 nm. Add 4 mL of ABTS working solution to 1 mL of fruit vinegar beverage and allow to react for 6 minutes. Measure the absorbance at 734 nm. Table 2: As shown in Table 2, the fruit vinegar beverages in Examples 1-4 all have excellent antioxidant properties.

[0079] (2) Composite membrane performance test (taking apple cider vinegar beverage as an example).

[0080] 1. Filtration flux and retention rate test.

[0081] Filtration flux: The volume of fruit vinegar beverage passing through a unit area membrane per unit time at a pressure of 0.1 MPa, with the unit being L / (m²・h). Retention rate: The content of macromolecules such as protein and pectin in the fruit vinegar beverage before and after composite membrane filtration was measured, and the retention rate was calculated. In the control group, the fermented fruit vinegar beverage was not filtered through the composite membrane but directly through the activated carbon / diatomaceous earth composite material, using the same filtration method as in Example 1. The test results are shown in Table 3.

[0082] Table 3: From Table 3 we can see that: In Example 1, the synergistic effect of the components in the composite membrane can effectively increase the retention rate of protein and pectin, thereby improving the taste of the fruit vinegar beverage.

[0083] In Example 3, the temperature responsiveness of the PNIPAM grafted microcapsules optimized the membrane pore structure, and the flux and the retention rate of protein and pectin were further improved.

[0084] In Example 4, PEG grafted modified nano-silica reduced the membrane surface energy, forming a "hydration repulsion effect", and the flux and retention rate reached the highest level.

[0085] In Comparative Example 2, the common PVDF membrane is highly hydrophobic, and protein adsorption causes flux attenuation and a significant decrease in the retention rate.

[0086] In Comparative Example 3, the unmodified nano-silica was severely agglomerated, the membrane pores were blocked, and the flux and retention rate were reduced.

[0087] In Comparative Example 4, the lack of self-repairing agent caused the flux and retention rate to decrease slightly after membrane fouling.

[0088] In the control group, the retention rate of activated carbon / diatomaceous earth composite material for protein and pectin was significantly lower than that of the composite membrane.

[0089] 2. Self-healing performance.

[0090] Membrane damage simulation: Use a needle (needle diameter 0.1-0.5 mm) to create tiny holes on the membrane surface. Evaluation of repair effect: The damaged membrane was placed at 37°C for 24-48 hours, and the filtration flux recovery rate before and after repair was measured. The test results are shown in Table 4.

[0091] Table 4: From Table 4 we can see that: In Example 1, the self-repairing agent microcapsules physically fill and repair the membrane pores, thereby giving the composite membrane an excellent flux recovery rate.

[0092] In Example 3, the PNIPAM grafted microcapsules shrink at 37°C to release the repair agent, and the polymerization reaction fills the damage, thereby improving the recovery rate.

[0093] In Example 4, PEG grafting and the repair agent polymer form an interpenetrating network, which enhances the bonding strength of the repair layer and achieves the highest recovery rate.

[0094] In Comparative Example 4, due to the lack of self-repairing agent, the membrane cannot repair itself after being damaged, and the recovery rate is significantly lower than that of Example 1.

[0095] 3. Anti-pollution performance.

[0096] The fruit vinegar beverage was filtered continuously for 20 hours. The filtration flux was measured every hour and the flux decay rate was calculated. The test results are shown in Table 5.

[0097] Table 5: From Table 5 we can see that: In Example 1, the components in the composite film act synergistically to effectively reduce the attenuation rate.

[0098] In Example 3, the temperature responsiveness of PNIPAM stripped away some of the contaminants, further reducing the attenuation rate.

[0099] In Example 4, the PEG-grafted hydrophilic layer produces a "hydration repulsion effect" that hinders the adsorption of pollutants and results in the lowest attenuation rate.

[0100] In Comparative Example 2, the hydrophobicity of the ordinary PVDF membrane resulted in rapid protein adsorption and an increased attenuation rate.

[0101] In Comparative Example 3, the unmodified tannic acid had weak binding ability with protein and its anti-pollution ability decreased.

[0102] In Comparative Example 4, the self-repairing agent microcapsules are missing and the attenuation rate is increased.

[0103] In summary, Examples 1-4 are significantly superior to the comparative examples in terms of beverage clarity, antioxidant properties and composite membrane performance through the synergistic effect of the three-stage filtration system, composite membrane modification components and self-repairing technology.

Claims

1. A method for preparing an antioxidant compound beverage, characterized in that: The steps include: S1. Raw material pretreatment; the raw materials used include at least two different fruits; S2. Enzymatic hydrolysis; S3. First filtration: Filter using a micron-sized pore size mesh; S4. Alcoholic fermentation; S5. Acetic acid fermentation; S6. Second filtration: using a composite membrane, the composite membrane comprises the following materials: Modified polyvinylidene fluoride, modified tea polyphenols, tannic acid, modified nano-silica, and self-healing agent microcapsules; Modified polyvinylidene fluoride is obtained by grafting polyvinylidene fluoride with polyvinyl alcohol-lactic acid graft copolymer; Modified tea polyphenols are obtained by modifying tea polyphenols with a silane coupling agent; Modified nano-silica is obtained by modifying nano-silica with gum arabic; In the self-repairing agent microcapsules, the wall material is a composite wall material of sodium alginate-chitosan-sodium carboxymethyl cellulose. The monomer used in the self-repairing fluid is polycaprolactone monomer, and the initiator is a mixture of ammonium persulfate and sodium bisulfite; S7. Preparation; S8. Third filtration: filtration using activated carbon / diatomaceous earth composite material; S9. Sterilization.

2. The method for preparing an antioxidant compound beverage according to claim 1, characterized in that: The composite film comprises the following components in parts by weight: 60-75 parts of modified polyvinylidene fluoride, 5-10 parts of modified tea polyphenols, 3-5 parts of tannic acid, 5-10 parts of modified nano-silica, and 10-20 parts of self-healing agent microcapsules; wherein, in the modified polyvinylidene fluoride, the mass ratio of polyvinyl alcohol-lactic acid graft copolymer to polyvinylidene fluoride is 1:(3-5); in the self-healing agent microcapsules, the mass ratio of sodium alginate, chitosan, and sodium carboxymethyl cellulose is 3:(2-3):(1-2).

3. The method for preparing an antioxidant composite beverage according to claim 2, characterized in that: The composite film comprises the following components in parts by weight: 62-70 parts of modified polyvinylidene fluoride, 6-8 parts of modified tea polyphenols, 4.5 parts of tannic acid, 6-8 parts of modified nano-silica, and 12-16 parts of self-healing agent microcapsules.

4. The method for preparing an antioxidant compound beverage according to claim 1, characterized in that: 0.1-0.3 wt% of nanocellulose is also added to the self-repairing liquid.

5. The method for preparing an antioxidant compound beverage according to claim 1, characterized in that: Poly (N-isopropylacrylamide) was grafted onto the wall material of the self-healing agent microcapsule.

6. The method for preparing an antioxidant compound beverage according to claim 1, characterized in that: Polyethylene glycol was grafted onto the surface of modified nano-silica.

7. The method for preparing an antioxidant compound beverage according to claim 1, characterized in that: In the activated carbon / diatomaceous earth composite material, the mass ratio of activated carbon to diatomaceous earth is (30-50):(60-80).

8. The method for preparing an antioxidant compound beverage according to claim 1, characterized in that: In step S2, the enzymes added are cellulase and pectinase, and the added amounts are 0.05%-0.15% of the fruit mass, respectively. The enzymatic hydrolysis temperature is 40-50°C, and the enzymatic hydrolysis time is 1-2 h.

9. The method for preparing an antioxidant compound beverage according to claim 1, characterized in that: In step S7, 0.02-0.1 wt% of vitamin C and 0.002-0.02 wt% of vitamin E are added.

10. The method for preparing an antioxidant compound beverage according to claim 1, characterized in that: In step S9, pulsed intense light sterilization technology is used for sterilization.

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