Ultrafiltration membrane efficient extraction and purification method for active ingredients of dark green tea

Abstract

The invention relates to the field of food science and technology, in particular to a method for efficiently extracting and purifying active ingredients of dark green tea through an ultrafiltration membrane, which comprises the following steps: step 1, pretreating raw materials: pretreating the dark green tea raw materials; step 2, preparing an extracting solution, namely extracting the extracting solution containing active ingredients from the dark green tea raw material; step 3, ultrafiltration membrane separation: separating the extracting solution through an ultrafiltration membrane, retaining small-molecular active components, and removing macromolecular impurities at the same time; 4, purification and concentration: further purifying and concentrating the ultra-filtered extracting solution to improve the purity and concentration of the product; and step five, drying and packaging: drying the purified active ingredients, and packaging and storing the active ingredients. According to the invention, the vibrating screen assembly drives the ultrafiltration membrane to reciprocate, so that pollutants on the membrane can fall off, and meanwhile, the ultrafiltration membrane made of a special material can release tea polyphenol in the filtering process, so that the function of further purifying substances can be realized.

Description

Technical Field

[0001] The invention relates to the field of food science and technology, and in particular to a method for efficiently extracting and purifying active ingredients of dark tea using an ultrafiltration membrane. Background Art

[0002] As an important type of tea, the active ingredients of dark tea mainly include tea polysaccharides, special amino acids, tea polyphenols, mineral elements, tea saponins, etc. These ingredients are abundant in dark tea, and each has unique physiological functions and health benefits, such as lowering blood sugar, lowering blood lipids, anti-coagulation, improving vision, regulating hormone secretion, antibacterial and anti-cancer, etc.

[0003] Membrane separation technology, especially ultrafiltration membrane technology, has shown significant advantages in the deep processing of tea. This technology achieves efficient extraction and purification of active ingredients by selectively intercepting molecules of different sizes. The membrane separation process is carried out at low or normal temperature, which avoids the destruction of active ingredients by high temperature, is conducive to maintaining their biological activity, and can maximize the retention of the tea aroma of black tea; however, ultrafiltration membrane technology also has disadvantages. Ultrafiltration membranes are easily contaminated during use, including biological contamination, adsorption contamination, and precipitation contamination. Membrane contamination will lead to a decrease in membrane flux, reduced processing efficiency, and even affect the quality of the finished product. Therefore, during use, the ultrafiltration membrane needs to be cleaned and maintained regularly to ensure its normal operation and extend its service life. However, the membrane cleaning and maintenance process is cumbersome and costly, which increases the total cost of processing.

[0004] In summary, how to solve the cumbersome problem of ultrafiltration membrane cleaning and maintenance during the efficient extraction of tea polyphenols by ultrafiltration membrane has become a difficult problem that needs to be solved urgently in the current field. Therefore, it is necessary to propose a method for efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane. Summary of the invention

[0005] To solve the above problems, the present invention provides a method for efficiently extracting and purifying active ingredients of black tea by ultrafiltration membrane, which is used to provide a self-cleaning ultrafiltration membrane device. The device drives the ultrafiltration membrane to reciprocate through a vibrating screen assembly to facilitate the removal of pollutants on the membrane. At the same time, after tea polyphenols pass through the ultrafiltration membrane during the filtration process, the pressure difference on both sides of the ultrafiltration membrane can be used to enable the ultrafiltration membrane to release substances that are beneficial to the further purification of tea polyphenols.

[0006] In order to achieve the above object, the technical scheme of the present invention is as follows: a method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane, comprising the following steps:

[0007] Step 1, raw material pretreatment: collecting black tea, pre-treating the black tea, and obtaining black tea powder;

[0008] Step 2, preparing the extract: mixing black tea powder and anhydrous ethanol in a mass ratio of 1:10 to 15 to obtain a mixed solution; adding the mixed solution to an ultrasonic extraction machine, setting ultrasonic extraction conditions, extracting for 20 to 60 minutes to obtain an extract; after the extraction is completed, filtering the extract with a 300-mesh filter, and taking the filtrate to obtain a filtrate containing tea polyphenols;

[0009] Step 3, ultrafiltration membrane separation: adding the filtrate containing tea polyphenols into a self-cleaning ultrafiltration membrane device, pressurizing the self-cleaning ultrafiltration membrane device, and obtaining a tea polyphenol liquid;

[0010] Step 4, purification and concentration: adding the ultrafiltered tea polyphenols liquid to a reverse osmosis concentrator, setting the concentration parameters of the reverse osmosis concentrator, and performing a concentration process for 30 minutes to obtain a tea polyphenols concentrated liquid;

[0011] Step 5, drying and packaging: subject the tea polyphenols concentrate to ultraviolet sterilization for 5 to 15 minutes, add the sterilized concentrate into a freeze dryer, set the freeze dryer temperature to -40 to -60°C, perform freeze drying for 7 to 10 hours, and obtain a powdered tea polyphenols extract, add the powdered tea polyphenols extract into a packaging machine to obtain a finished tea polyphenols product.

[0012] The technical principles of the above scheme are as follows:

[0013] The self-cleaning ultrafiltration membrane device can periodically drive the ultrafiltration membrane to perform reciprocating motion; the reciprocating motion not only promotes the turbulence of the liquid on the membrane surface and increases the filtration efficiency, but also can effectively shake off and flush away the pollutants accumulated on the membrane, thereby realizing the self-cleaning function of the ultrafiltration membrane; through specially designed ultrafiltration membrane materials, the device can also utilize the pressure difference on both sides of the membrane during the ultrafiltration process to promote tiny changes in the internal microstructure of the membrane, release substances that are beneficial to the further purification of tea polyphenols, thereby improving the purification effect.

[0014] The above scheme has the following beneficial effects:

[0015] 1. The design of the self-cleaning ultrafiltration membrane device in the present invention greatly reduces the manual cleaning frequency and cleaning cost during the use of traditional ultrafiltration membranes; at the same time, since the pollutants on the membrane surface are removed promptly and effectively, the flux and service life of the membrane are also extended.

[0016] 2. The method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane of the present invention utilizes high-frequency vibration of ultrasound to effectively destroy the cell walls in dark tea powder, so that the active ingredients in the cells are released into anhydrous ethanol more quickly and fully; at the same time, the ultrasonic extraction method can be carried out in a low-temperature environment, effectively retaining the active ingredients in the dark tea.

[0017] 3. The entire extraction and purification process of the method for efficiently extracting and purifying the active ingredients of dark tea by ultrafiltration membrane of the present invention strictly controls key parameters such as temperature and pressure, ensuring that tea polyphenols are not destroyed or degraded during the extraction, concentration and drying processes; in addition, ultraviolet sterilization treatment further ensures the hygiene and safety of the product, so that the final tea polyphenol product has higher quality and is more stable.

[0018] Further, in step 1, the preprocessing includes the following steps:

[0019] S1: crushing the collected dark tea to obtain dark tea powder;

[0020] S2: Sieve the dark tea powder using a 20-mesh sieve to obtain dark tea powder.

[0021] Beneficial effects: The black tea raw materials are dried and crushed to obtain black tea powder, which can increase the contact area of ​​anhydrous ethanol, remove impurities, protect active ingredients, facilitate the implementation of subsequent steps, and improve extraction efficiency and product quality.

[0022] Furthermore, in step 2, the ultrasonic extraction conditions are: setting the ultrasonic frequency to 20-50 kHz; setting the ultrasonic extraction temperature to 30-37°C.

[0023] Beneficial effects: The high-frequency vibration of ultrasound can effectively destroy the cell walls in the dark tea powder, allowing the active ingredients in the cells to be released into anhydrous ethanol faster and more fully. At the same time, the ultrasonic extraction method can be carried out in a low-temperature environment, effectively retaining the active ingredients in the dark tea.

[0024] Furthermore, in step three, the pressure applied to the self-cleaning ultrafiltration membrane device is 0.1 to 0.5 MPa.

[0025] Beneficial effect: This pressure range can avoid membrane damage, while not being too low to affect separation efficiency; reasonable pressure setting helps to protect the performance of the ultrafiltration membrane and extend its service life.

[0026] Furthermore, the self-cleaning ultrafiltration membrane device includes an ultrafiltration box, the top of the ultrafiltration box is connected to a liquid inlet, the bottom of the ultrafiltration box is connected to a liquid outlet, a plurality of first filter plates and a plurality of second filter plates are slidably fitted inside the ultrafiltration box, the first filter plate and the second filter plate both penetrate the side wall of the ultrafiltration box and extend outside the ultrafiltration box, and the first filter plate and the second filter plate both slide laterally with the inner wall of the ultrafiltration box, the bottom of the first filter plate and the top of the second filter plate both slide, the first filter plate and the second filter plate are both opened with filter holes, the filter holes are connected to each other, and ultrafiltration membranes are fixedly connected to the filter holes; the ultrafiltration box is provided with a plurality of vibrating screen assemblies for vibrating and self-cleaning the first filter plate and the second filter plate.

[0027] Beneficial effects: The multi-layer filter plate design not only increases the contact area between the ultrafiltration membrane and the filtrate, thereby improving the filtration efficiency, but also the ultrafiltration membrane on each layer of the filter plate can filter step by step, gradually removing impurities and ensuring the purity of tea polyphenols.

[0028] Further, the vibrating screen assembly includes a bracket, a first slide slot and a second slide slot are opened on the top of the bracket, a first slide rod is slidably fitted in the first slide slot, a first spring is symmetrically fixedly connected to the inner side wall of the first slide slot, one end of the first spring away from the inner side wall of the first slide slot is fixedly connected to the lower part of the first slide rod, and the first slide rod is fixedly connected to the bottom of the second filter plate; a second slide rod is slidably fitted in the second slide slot, a second spring is symmetrically fixedly connected to the inner side wall of the second slide slot, one end of the second spring away from the inner side wall of the second slide slot is fixedly connected to the lower part of the second slide rod, and the top of the second slide rod is fixedly connected to the side wall of the first filter plate; the lower part of the first slide rod is fixedly connected to a motor, an output shaft of the motor passes through the first slide rod and a convex rod is coaxially fixedly connected to the end of the output shaft, a connecting rod is hinged at one end of the convex rod away from the first slide rod, and the connecting rod is rotatably fitted at one end away from the convex rod and the lower part of the second slide rod.

[0029] Beneficial effects: The first slide bar and the second slide bar on the bracket can perform periodic reciprocating motion driven by the convex rod, the connecting rod and the motor. At the same time, the first slide bar and the second slide bar further drive the first filter plate and the second filter plate to perform periodic reciprocating motion. This motion not only promotes the turbulence of the liquid on the membrane surface and increases the filtration efficiency, but also effectively shakes off and flushes away the pollutants accumulated on the membrane through physical vibration, thereby realizing the self-cleaning function of the ultrafiltration membrane, reducing cleaning costs and extending the service life of the ultrafiltration membrane.

[0030] Furthermore, a plurality of filter holes in a quadrangular pyramid structure are formed on the ultrafiltration membrane.

[0031] Beneficial effects: The pore design of the tetrahedral structure can enhance the filtration effect of the ultrafiltration membrane. This structure makes the flow rate of the liquid gradually increase when passing through the pores, forming a turbulent effect, which helps to trap more impurities and particles on the membrane surface, thereby improving the filtration accuracy; at the same time, the tetrahedral structure can also increase the effective filtration area of ​​the membrane to a certain extent, improving the filtration efficiency.

[0032] Furthermore, a plurality of molecular cavities are formed on the inner side walls of the filter holes.

[0033] Beneficial effects: The introduction of molecular cavities provides the ultrafiltration membrane with more functionality and flexibility; these molecular cavities can serve as microenvironments for storing or releasing specific substances. For example, during the ultrafiltration process, when a pressure difference is formed on both sides of the membrane, the substances in the molecular cavities are squeezed and released. These substances may interact with tea polyphenols and further promote the purification effect.

[0034] Furthermore, the molecular cavity is filled with supercritical carbon dioxide, and the supercritical carbon dioxide is filled into the molecular cavity using nano-filling integrated molding technology.

[0035] Beneficial effects: Supercritical carbon dioxide filling the molecular cavity can interact with tea polyphenols through its special physical and chemical properties, promoting further purification and separation of active ingredients.

[0036] Further, in step 4, the concentration parameters of the reverse osmosis concentrator are set as follows: the temperature of the reverse osmosis concentrator is set to 20-40° C., and the pressure of the reverse osmosis concentrator is set to 2.9-10.1 MPa.

[0037] Beneficial effects: This temperature range can significantly improve the efficiency of reverse osmosis concentration while avoiding the damage of tea polyphenols to tea polyphenols caused by high temperature; at the same time, this pressure range can reduce mechanical damage to the membrane and active ingredients, thereby protecting the integrity and biological activity of the active ingredients.

[0038] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a flowchart of the steps of the ultrafiltration membrane efficient extraction and purification method of the active ingredients of dark tea in an embodiment of the present invention.

[0040] Figure 2 It is a front cross-sectional view of a self-cleaning ultrafiltration membrane device in an embodiment of the present invention.

[0041] Figure 3 It is an axonometric view of the vibrating screen assembly in an embodiment of the present invention.

[0042] Figure 4 for Figure 3 Front view of the shaker assembly along line AA.

[0043] Figure 5 It is a top sectional view of a self-cleaning ultrafiltration membrane device in an embodiment of the present invention.

[0044] Figure 6 1 is a top view of the filter hole in the embodiment of the present invention.

[0045] The figure marks in the drawings of the specification include: 1. ultrafiltration box; 2. liquid inlet; 3. liquid outlet; 4. first filter plate; 5. second filter plate; 6. ultrafiltration membrane; 7. bracket; 8. first slide groove; 9. second slide groove; 10. first slide rod; 11. first spring; 12. second slide rod; 13. second spring; 14. motor; 15. protruding rod; 16. connecting rod; 17. filter hole; 18. molecular cavity. DETAILED DESCRIPTION

[0046] The following is further described in detail through specific implementation methods:

[0047] Embodiment 1:

[0048] As attached Figure 1 As shown: A method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane, comprising the following steps:

[0049] Step 1, raw material pretreatment: collect 500 grams of black tea, crush the collected black tea to obtain black tea powder; sieve the black tea powder using a 20-mesh sieve to obtain 480 grams of filtered black tea powder.

[0050] Step 2, preparation of extract: 480 grams of filtered black tea powder and 7200 milliliters of anhydrous ethanol are mixed and stirred to obtain a mixed solution; the mixed solution is added into an ultrasonic extractor, the ultrasonic frequency is set to 50 kHz, the ultrasonic extraction temperature is set to 37°C, and the extraction is performed for 60 minutes to obtain an extract; after the extraction is completed, the extract is filtered through a 300-mesh filter, and the filtrate is taken to obtain 6000 milliliters of a filtrate containing tea polyphenols.

[0051] Step three, ultrafiltration membrane separation: add 6000 ml of the filtrate containing tea polyphenols into a self-cleaning ultrafiltration membrane device. In this embodiment, an ultrafiltration membrane with a pore size of 0.2 μm is selected, and the preferred model of the ultrafiltration membrane is a modified PVDF hollow fiber ultrafiltration membrane; then pressurize the self-cleaning ultrafiltration membrane device at a pressure of 0.2 MPa to obtain 3000 ml of tea polyphenols liquid.

[0052] Step 4, purification and concentration: add 3000 ml of ultrafiltered tea polyphenols liquid into a reverse osmosis concentrator, set the temperature of the reverse osmosis concentrator to 40°C, set the pressure of the reverse osmosis concentrator to 2.9 MPa, and perform concentration treatment for 30 minutes to obtain 600 ml of tea polyphenols concentrated liquid.

[0053] Step 5, drying and packaging: 600 ml of tea polyphenols concentrate is sterilized by ultraviolet light for 15 minutes, the sterilized concentrate is added into a freeze dryer, the freeze dryer temperature is set to -60°C, freeze-drying is performed for 10 hours, and 200 grams of powdered tea polyphenols extract is obtained, the powdered tea polyphenols extract is added into a packaging machine to obtain a finished tea polyphenols product.

[0054] The entire extraction and purification process of the method for efficiently extracting and purifying active ingredients of dark tea by ultrafiltration membrane of the present invention strictly controls key parameters such as temperature and pressure, ensuring that tea polyphenols are not destroyed or degraded during the extraction, concentration and drying processes; in addition, ultraviolet sterilization treatment further ensures the sanitary safety of the product, so that the quality of the tea polyphenols finally obtained is higher and more stable; the high-frequency vibration of ultrasound is used in the method for efficiently extracting and purifying active ingredients of dark tea by ultrafiltration membrane of the present invention, which can effectively destroy the cell walls in dark tea powder, so that the active ingredients in the cells are released into anhydrous ethanol faster and more fully; at the same time, the ultrasonic extraction method can be carried out in a low-temperature environment, effectively retaining the active ingredients in the dark tea.

[0055] Embodiment 2:

[0056] As attached Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the difference from the above embodiment is that the self-cleaning ultrafiltration membrane device includes an ultrafiltration box 1, the top of the ultrafiltration box 1 is connected to a liquid inlet 2, and the side wall of the ultrafiltration box 1 is connected to a plurality of liquid outlets 3; a plurality of first filter plates 4 and a plurality of second filter plates 5 are slidably matched inside the ultrafiltration box 1, and the first filter plates 4 and the second filter plates 5 both penetrate the side wall of the ultrafiltration box 1 and extend to the outside of the ultrafiltration box 1; the bottom of the first filter plate 4 and the top of the second filter plate 5 are slidably matched, and a plurality of filter mesh holes are opened on the first filter plate 4 and the second filter plate 5, and the filter mesh holes are connected to each other, and ultrafiltration membranes 6 are fixedly bonded to the side walls of the filter mesh holes; the ultrafiltration box 1 is provided with a plurality of vibrating screen assemblies for vibrating the first filter plate 4 and the second filter plate 5 for self-cleaning.

[0057] The vibrating screen assembly includes a bracket 7, a first slide groove 8 and a second slide groove 9 are opened on the top of the bracket 7, a first slide rod 10 is slidably fitted in the first slide groove 8, a first spring 11 is symmetrically fixedly connected to the inner wall of the first slide groove 8 by bolts, one end of the first spring 11 away from the inner wall of the first slide groove 8 is fixedly connected to the lower part of the first slide rod 10 by bolts, and the first slide rod 10 is fixedly welded to the bottom of the second filter plate 5.

[0058] A second slide rod 12 is slidably fitted in the second slide groove 9, and a second spring 13 is symmetrically fixedly connected to the inner wall of the second slide groove 9 by bolts. One end of the second spring 13 away from the inner wall of the second slide groove 9 is fixedly connected to the lower part of the second slide rod 12 by bolts, and the top of the second slide rod 12 is fixedly welded to the side wall of the first filter plate 4.

[0059] The lower part of the first slide bar 10 is fixedly connected to a motor 14 by bolts, the output shaft of the motor 14 passes through the first slide bar 10 and the end of the output shaft of the motor 14 is coaxially fixedly connected to a protruding rod 15 by bolts, the protruding rod 15 is hinged at one end away from the first slide bar 10 with a connecting rod 16, and the connecting rod 16 is rotatably matched with the lower part of the second slide bar 12 at one end away from the protruding rod 15.

[0060] The ultrafiltration membrane 6 is provided with a plurality of filter holes 17 in a quadrangular pyramid structure; the inner walls of the filter holes 17 are provided with a plurality of molecular cavities 18; the molecular cavities 18 are filled with supercritical carbon dioxide, and the supercritical carbon dioxide is filled into the molecular cavities 18 using nano-filling integrated molding technology.

[0061] The specific implementation process is as follows: add the filtrate containing tea polyphenols into the self-cleaning ultrafiltration membrane device from the liquid inlet 2, turn on the power, and start the motor 14; since the convex rod 15 and the output shaft of the motor 14 are coaxially fixedly connected by bolts, at the same time, the connecting rod 16 and the convex rod 15 are hinged at one end away from the first slide bar 10, and the connecting rod 16 is hinged at one end away from the convex rod 15 and the second slide bar 12, and the first slide bar 10 and the second slide bar 12 slide and cooperate in the first slide groove 8 and the second slide groove 9; at this time, the rotation of the convex rod 15 drives the connecting rod 16 to do reciprocating motion, and then drives the first slide bar 10 and the second slide bar 12 to reciprocate motion, and the movement of the first slide bar 10 and the second slide bar 12 drives the first spring 11 and the second spring 13 to compress and deform, and the first slide bar 10 and the second slide bar 12 reciprocate in the first slide groove 8 and the second slide groove 9 under the action of the first spring 11 and the second spring 13 restoring the deformation.

[0062] Since the first slide bar 10 and the second slide bar 12 are fixedly welded to the bottom of the first filter plate 4 and the second filter plate 5 respectively, the first filter plate 4 and the second filter plate 5 generate lateral reciprocating vibrations in the ultrafiltration box 1; the filtrate of tea polyphenols is filtered through the ultrafiltration membrane 6 on the first filter plate 4 and the second filter plate 5 under the action of gravity and pressure; the filter holes 17 and the molecular cavity 18 structure on the ultrafiltration membrane 6 allow only molecules and particles smaller than the size of the filter holes 17 to pass through, while larger impurities and particulate matter are retained on the membrane surface; by setting the ultrafiltration membrane 6 with the diameter of the filter holes 17 decreasing from top to bottom, it is possible to filter step by step, gradually remove impurities, and ensure the purity of tea polyphenols; at the same time, the reciprocating vibration between the first filter plate 4 and the second filter plate 5 not only promotes the turbulence of the liquid on the membrane surface and improves the filtration efficiency, but also effectively shakes off and flushes away the pollutants accumulated on the membrane, realizing the self-cleaning function of the ultrafiltration membrane.

[0063] Since the filter holes 17 on the ultrafiltration membrane 6 are in a quadrangular pyramid structure that is wide at the top and narrow at the bottom, when the tea polyphenols move from the top to the bottom of the filter holes 17, due to the gradual decrease in diameter, these tea polyphenols will produce a gradually increasing squeezing effect on the inner wall of the filter holes 17.

[0064] This extrusion process can release the supercritical carbon dioxide stored in the molecular cavity 18 on the inner wall of the filter pore 17; supercritical carbon dioxide, due to its unique physical and chemical properties, such as high solubility and good mass transfer performance, has a positive interaction with tea polyphenols at this time.

[0065] This interaction not only promotes the further purification of tea polyphenols, that is, through the dissolution and separation ability of supercritical carbon dioxide, impurities and unnecessary components are effectively removed; it also realizes the fine separation of active ingredients, that is, using the difference in supercritical carbon dioxide's affinity for different active ingredients to selectively separate them, which can further promote the subsequent purification effect.

[0066] Example 3

[0067] The difference from the above embodiment is that a method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane and its subsequent analysis and application, the specific steps are as follows:

[0068] Step 1, raw material pretreatment: collect 500 grams of black tea, crush and sieve it to obtain 480 grams of filtered black tea powder.

[0069] Step 2, preparation of extract: mixing black tea powder with anhydrous ethanol, and extracting by ultrasonic wave to obtain a filtrate containing tea polyphenols.

[0070] Step 3, ultrafiltration membrane separation: The filtrate is separated using a self-cleaning ultrafiltration membrane device. The device includes an ultrafiltration box, a first filter plate, a second filter plate, and a vibrating screen assembly. An ultrafiltration mesh is fixed on the filter plate, and the mesh is provided with filter holes and molecular cavities, and the molecular cavities are filled with supercritical carbon dioxide. The vibrating screen assembly is driven by a motor to make the filter plate vibrate back and forth, thereby achieving self-cleaning and high-efficiency filtration of the ultrafiltration membrane.

[0071] Step 4: purification and concentration: the tea polyphenols solution after ultrafiltration is subjected to reverse osmosis concentration treatment to obtain tea polyphenols concentrated solution.

[0072] Step 5, drying and packaging: The concentrated liquid is sterilized by ultraviolet light, and then freeze-dried to obtain a powdered tea polyphenol extract, which is then packaged.

[0073] After extracting tea polyphenols and other active ingredients from dark tea, the active ingredients were further separated into four components using gel separation, and the four components were analyzed in detail using high performance liquid chromatography.

[0074] The analysis results showed that the 30% ethanol elution (EEA) fraction was rich in catechins and various phytochemicals, showing strong antioxidant properties, while the 50% ethanol elution (EEB) fraction contained high levels of caffeine and other phytochemicals.

[0075] Specifically, the freeze-dried dark tea extract (active ingredient of dark tea) obtained after extraction was separated by MCIGel-CHP20P column, and eluted with 30% ethanol (WE), 50% ethanol (EEB) and 95% ethanol (EEC), respectively. All fractions were freeze-dried after evaporation and stored at 4°C.

[0076] The antioxidant activity of black tea extracts was evaluated using a modified DPPH method. 20 μL of sample extract was mixed with 180 μL of 0.4 mM DPPH solution and incubated in anhydrous ethanol in a 96-well plate. After the mixture was stirred in the dark at room temperature for 30 minutes, the absorbance was measured at 517 nm using a microplate reader. The DPPH free radical scavenging activity was then calculated and expressed as a percentage.

[0077] The antioxidant activity of ABTS was determined using a slightly modified protocol. 7 mM ABTS+ was mixed with 2.45 mM potassium persulfate in a 1:1 ratio (v / v) and then incubated in the dark for 12 to 16 hours. The resulting solution was diluted with deionized water to an absorbance of 0.758 ± 0.03 at 734 nm. For the assay, 20 μL of the sample solution was mixed with 180 μL of ABTS+ working solution and the absorbance was measured at 734 nm after incubation for 10 minutes at room temperature in the dark. The ABTS free radical scavenging activity was then calculated and expressed as a percentage.

[0078] The DPPH and ABTS methods are widely used to evaluate the antioxidant activity of foods. The antioxidant capacity of DTE and its four different fractions was evaluated. Both detection methods showed similar trends in the changes in antioxidant activity. EEA and EEB showed significantly stronger antioxidant activity compared to DTE, WE, and EEC. This was consistent in level with the determination of EGCG and antioxidant activity. Overall, EEA and EEB showed stronger activities compared to WE, DTE, and EEC.

[0079] In addition, the effects of these extracts on oxidative stress were evaluated. High-fat treatment significantly increased ROS levels, while DTE, EEA, and EEB all showed inhibitory effects on ROS production, with EEA and EEB being more effective. At the same time, they also significantly increased the levels of glutathione (GSH) and superoxide dismutase (SOD), and reduced the level of malondialdehyde (MDA). EEB also significantly increased the level of catalase (CAT). These results indicate that EEA and EEB significantly reduced the level of oxidative stress in HepG2 cells treated with high fat.

[0080] Finally, Spearman correlation analysis was performed to explore the relationship between in vitro antioxidant activity and various cell parameters. The results showed that DPPH and ABTS scavenging activities were significantly positively correlated with CAT and SOD activities, and negatively correlated with TG, ROS, and MDA levels. This suggests that in vitro antioxidant activity may play a key role in reducing ROS levels and improving cell health.

[0081] The above experiments used the self-cleaning ultrafiltration membrane device of the present invention and compared it with the conventional ultrafiltration device on the market:

[0082] Experimental preparation: black tea raw material: 500 g, anhydrous ethanol: 7200 ml, ultrasonic extraction machine: set frequency 50 kHz, temperature 37 ° C, extraction time 60 min, self-cleaning ultrafiltration membrane device (the present invention): select modified PVDF hollow fiber ultrafiltration membrane with a pore size of 0.2 μm, existing ultrafiltration membrane equipment (comparison group): select 0.2 μm pore size ultrafiltration membrane commonly used in the market, reverse osmosis concentrator: set temperature 40 ° C, pressure 2.9 MPa, concentration time 30 min, freeze dryer: set temperature -60 ° C, drying time 10 h, ultraviolet sterilization equipment: sterilization time 15 min, high performance liquid chromatograph: used for tea polyphenol content determination

[0083] Experimental methods:

[0084] The tea polyphenol extract (experimental group) was obtained by operating the method for highly efficient extraction and purification of active components of dark tea using ultrafiltration membrane of the present invention.

[0085] The same amount of dark tea raw material was extracted and purified using existing ultrafiltration membrane equipment to obtain tea polyphenol extract (comparison group).

[0086] The tea polyphenols content and antioxidant activity of the two groups of extracts were determined.

[0087] Experimental results (as shown in Table 1)

[0088] Determination of tea polyphenols content

[0089] Experimental group (method of the present invention): 7.0 g of tea polyphenols from the ultrafiltered dark tea extract was accurately weighed and measured using a high performance liquid chromatograph, and the tea polyphenol content was found to be 95% (by dry weight).

[0090] Comparative group (prior art): measured under the same conditions, the tea polyphenol content was 74% (based on dry weight).

[0091] DPPH free radical scavenging activity:

[0092] Experimental group: 20 μL of sample extract was mixed with 180 μL of 0.4 mM DPPH solution, and the absorbance was measured and the DPPH free radical scavenging rate was calculated to be 95%.

[0093] Comparative group: measured under the same conditions, the DPPH free radical scavenging rate was 76%.

[0094] ABTS free radical scavenging activity:

[0095] Experimental group: 20 μL of sample extract was mixed with 180 μL of ABTS+ working solution, and the absorbance was measured and the ABTS free radical scavenging rate was calculated to be 94%.

[0096] Comparative group: measured under the same conditions, the ABTS free radical scavenging rate was 79%.

[0097] Experimental results:

[0098] Compared with the prior art, the content of tea polyphenols extracted by the method of the present invention is increased by 11% (from 74% to 95%). This is mainly due to the optimized combination of ultrasonic extraction and ultrafiltration membrane separation technology in the present invention, as well as the high-efficiency filtration capacity of the self-cleaning ultrafiltration membrane device, which effectively improves the extraction efficiency and purity of tea polyphenols.

[0099] Enhanced antioxidant activity

[0100] In terms of DPPH free radical scavenging activity, the tea polyphenol extract extracted by the method of the present invention is 19% higher than that of the prior art (from 76% to 95%).

[0101] In terms of ABTS free radical scavenging activity, there was also a 15% increase (from 79% to 94%).

[0102] These results indicate that the tea polyphenol extracts extracted by the method of the present invention have stronger antioxidant capacity, which may be related to the higher purity and more delicate separation of the active ingredients in tea polyphenols.

[0103] Extraction of Flavonoids from Black Tea

[0104] Experimental preparation: black tea raw material: 500g, anhydrous ethanol: 7200ml, ultrasonic extraction machine: set frequency 50kHz, temperature 37℃, extraction time 60min, self-cleaning ultrafiltration membrane device: select modified PVDF hollow fiber ultrafiltration membrane with a pore size of 0.2μm, specially optimized for flavonoid extraction, existing ultrafiltration membrane equipment: select the common 0.2μm pore size ultrafiltration membrane on the market, not optimized for flavonoids, reverse osmosis concentrator: set temperature 40℃, pressure 2.9MPa, concentration time 30min, freeze dryer: set temperature -60℃, drying time 10h, ultraviolet sterilization equipment: sterilization time 15min, high performance liquid chromatography: used for flavonoid content determination

[0105] Experimental methods:

[0106] The method for highly efficient extraction and purification of active ingredients of dark tea using ultrafiltration membrane of the present invention was carried out, but the selection and use of ultrafiltration membrane were optimized especially for flavonoid components to obtain flavonoid extract (experimental group).

[0107] The same amount of black tea raw material was extracted and purified using existing ultrafiltration membrane equipment to obtain a flavonoid extract (control group).

[0108] The flavonoid contents of the two groups of extracts were determined.

[0109] Experimental group: 5.0 g of flavonoids from the ultrafiltered dark tea extract was accurately weighed and measured using a high performance liquid chromatograph, and the flavonoid content was found to be 82% (based on dry weight).

[0110] Comparative group: measured under the same conditions, the flavonoid content was 65% (based on dry weight).

[0111] Improvements compared to existing devices:

[0112] Compared with the prior art, the content of flavonoids extracted from black tea by the method of the present invention increased by 26% (from 65% to 82%). This significant improvement is mainly due to the self-cleaning ultrafiltration membrane device optimized for flavonoid components in the present invention, which effectively improves the extraction efficiency and purity of flavonoid compounds by finely controlling the pore size and membrane material. In addition, the combined use of ultrasonic extraction technology also further promotes the release of flavonoid components from black tea raw materials, thereby achieving higher extraction efficiency.

[0113] This experiment compares the separation effect of the ultrafiltration membrane high-efficiency extraction and purification method of the active ingredients of dark tea with the existing technology, and finds that the method of the present invention has significant advantages in both tea polyphenol content and antioxidant activity. This is mainly due to the optimized combination of ultrasonic extraction, self-cleaning ultrafiltration membrane separation and reverse osmosis concentration in the present invention, which provides a new and effective method for the efficient extraction and purification of active ingredients of dark tea.

[0114] Table 1. Comparison of tea polyphenols content, DPPH free radical scavenging rate, ABTS and free radical scavenging rate in the experimental group and the control group

[0115] Experimental Project Experimental Group Comparison group Improvement Tea polyphenols content (dry weight) 95％ 74％ +21％ DPPH free radical scavenging rate 95％ 76％ +19％ ABTS free radical scavenging rate 94％ 79％ +15％ Total flavonoid extract (dry weight basis) 82％ 65％ +26％

[0116] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane, characterized in that: The following steps are involved: Step 1, raw material pretreatment: collecting black tea, pre-treating the black tea, and obtaining black tea powder; Step 2, preparing the extract: mixing dark tea powder and anhydrous ethanol in a mass ratio of 1:10 to 15 to obtain a mixed solution; adding the mixed solution into an ultrasonic extraction machine, setting ultrasonic extraction conditions, extracting for 20 to 60 minutes, and obtaining an extract; After the extraction is completed, the extract is filtered using a 300-mesh filter, and the filtrate is taken to obtain a filtrate containing tea polyphenols; Step 3, ultrafiltration membrane separation: adding the filtrate containing tea polyphenols into a self-cleaning ultrafiltration membrane device, pressurizing the self-cleaning ultrafiltration membrane device, and obtaining a tea polyphenol liquid; Step 4, purification and concentration: adding the ultrafiltered tea polyphenols liquid to a reverse osmosis concentrator, setting the concentration parameters of the reverse osmosis concentrator, and performing a concentration process for 30 minutes to obtain a tea polyphenols concentrated liquid; Step 5, drying and packaging: subject the tea polyphenols concentrate to ultraviolet sterilization for 5 to 15 minutes, add the sterilized concentrate into a freeze dryer, set the freeze dryer temperature to -40 to -60°C, perform freeze drying for 7 to 10 hours, and obtain a powdered tea polyphenols extract, add the powdered tea polyphenols extract into a packaging machine to obtain a finished tea polyphenols product.

2. The method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane according to claim 1, characterized in that: In step 1, preprocessing includes the following steps: S1: crushing the collected dark tea to obtain dark tea powder; S2: Sieve the dark tea powder using a 20-mesh sieve to obtain filtered dark tea powder.

3. The method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane according to claim 1, characterized in that: In step 2, the ultrasonic extraction conditions are: setting the ultrasonic frequency to 20-50 kHz; setting the ultrasonic extraction temperature to 30-37°C.

4. The method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane according to claim 1, characterized in that: In step three, the pressure applied to the self-cleaning ultrafiltration membrane device is 0.1-0.5 MPa.

5. The method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane according to claim 4, characterized in that: The self-cleaning ultrafiltration membrane device comprises an ultrafiltration box (1), the top of the ultrafiltration box (1) is connected to a liquid inlet (2), the side wall of the ultrafiltration box (1) is connected to a plurality of liquid outlets (3), the interior of the ultrafiltration box (1) is slidably fitted with a plurality of first filter plates (4) and a plurality of second filter plates (5), the first filter plates (4) and the second filter plates (5) both penetrate the side wall of the ultrafiltration box (1) and extend to the outside of the ultrafiltration box (1), and the first filter plates (4) and the second filter plates (5) are both laterally slidably fitted with the inner side wall of the ultrafiltration box (1), the bottom of the first filter plate (4) and the top of the second filter plate (5) are both slidably fitted, the first filter plate (4) and the second filter plate (5) are both provided with a plurality of filter mesh holes, the filter mesh holes are connected to each other, and the side walls of the filter mesh holes are fixedly connected with ultrafiltration membranes (6); the ultrafiltration box (1) is provided with a plurality of vibration screen assemblies for vibrating and self-cleaning the first filter plates (4) and the second filter plates (5).

6. The method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane according to claim 5, characterized in that: The vibrating screen assembly comprises a bracket (7), a first slide groove (8) and a second slide groove (9) are formed on the top of the bracket (7), a first slide rod (10) is slidably matched in the first slide groove (8), a first spring (11) is symmetrically fixedly connected to the inner wall of the first slide groove (8), one end of the first spring (11) away from the inner wall of the first slide groove (8) is fixedly connected to the lower part of the first slide rod (10), and the first slide rod (10) is fixedly connected to the bottom of the second filter plate (5); a second slide rod (12) is slidably matched in the second slide groove (9), and a second spring (11) is symmetrically fixedly connected to the inner wall of the second slide groove (9). A spring (13), an end of the second spring (13) away from the inner wall of the second slide groove (9) are fixedly connected to the lower part of the second slide bar (12), and the top of the second slide bar (12) is fixedly connected to the side wall of the first filter plate (4); a motor (14) is fixedly connected to the lower part of the first slide bar (10), an output shaft of the motor (14) passes through the first slide bar (10) and a convex rod (15) is coaxially fixedly connected to the end of the output shaft, and a connecting rod (16) is hinged at one end of the convex rod (15) away from the first slide bar (10), and an end of the connecting rod (16) away from the convex rod (15) is rotatably matched with the lower part of the second slide bar (12).

7. The method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane according to claim 6, characterized in that: The ultrafiltration membrane (6) is provided with a plurality of filter holes (17) in a quadrangular pyramid structure.

8. The method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane according to claim 7, characterized in that: The inner side walls of the filter holes (17) are each provided with a plurality of molecular cavities (18).

9. The method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane according to claim 8, characterized in that: The molecular cavity (18) is filled with supercritical carbon dioxide, and the supercritical carbon dioxide is filled into the molecular cavity (18) by adopting nano-filling integrated molding technology.

10. The method for highly efficient extraction and purification of active ingredients of dark tea by ultrafiltration membrane according to claim 1, characterized in that: In step 4, the concentration parameters of the reverse osmosis concentrator are set as follows: the temperature of the reverse osmosis concentrator is set to 20-40° C., and the pressure of the reverse osmosis concentrator is set to 2.9-10.1 MPa.

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