Method for extracting effective components of white tea

Abstract

The invention relates to the related technical field of white tea component extraction, and discloses a white tea effective component extraction method, which comprises a raw material pretreatment device, a multi-stage countercurrent extraction unit and a dynamic circulation separation module. A stable concentration gradient field is formed through the synergistic effect of a spiral flow guide pipe and a vibration screening plate in the multi-stage countercurrent extraction unit, the purpose of improving the transfer rate of effective components is achieved, and the extraction efficiency is improved by combining a rotatable filter screen of the dynamic circulation separation module with ultrasonic-assisted extraction. The oxidation loss rate of heat-sensitive components in the separation stage is reduced, the cascade design of the membrane refining assembly and the resin adsorption tower realizes a dual purification mechanism of molecular weight interception and polar adsorption, the purity of polyphenol substances in a final product is improved, and the negative pressure crushing environment of the raw material pretreatment device is matched with microwave pretreatment to improve the purification effect of the polyphenol substances. The dissipation amount of volatile organic compounds is greatly reduced, and meanwhile, the dust explosion risk is eliminated.

Description

Technical Field

[0001] The present invention relates to the technical field related to the extraction of white tea components, and in particular to a method for extracting effective components of white tea. Background Art

[0002] The extraction of effective components of white tea is a product extracted from white tea and contains rich substances such as tea polyphenols and flavonoids. Its main components include tea catechins (flavanols), phenolic acids, flavonols, condensed phenolic acids, etc., among which catechin compounds account for 65% - 80% of the total amount of tea polyphenols. As an antioxidant, tea polyphenols can be applied to meat product processing, oil storage, baking food, dairy product beverage formulation, etc.; as a preservative, it can slow down the biochemical activities of fruits and vegetables after picking and delay their ripening period; it can prevent the fading of natural pigments (such as carotene, chlorophyll, vitamin B2, carmine, etc.) due to photooxidation; white tea extracts have pharmacological activities such as treating measles, improving eyesight, anti-cancer, anti-tumor, anti-mutation, antibacterial, antioxidant, anti-radiation, reducing blood sugar, protecting the liver, eliminating fatigue, losing weight, and regulating immune function.

[0003] In the extraction process of most existing extraction processes for effective components of white tea, high-temperature extraction may cause the oxidation loss of heat-sensitive components such as tea polyphenols, resulting in the problem of failure in extracting effective components. Moreover, it is difficult to completely remove the residual organic solvents during the extraction process, leading to poor purity of the effective components and inability to be used subsequently. And the multi-step separation and purification process in the extraction process is cumbersome and the product yield is low. To solve such problems, a method for extracting effective components of white tea is proposed. Summary of the Invention

[0004] The present invention provides a method for extracting effective components of white tea, which solves the problems in the above background art.

[0005] The present invention solves its technical problems by adopting the following technical solutions:

[0006] A method for extracting effective components of white tea includes a raw material pretreatment device, a multi-stage countercurrent extraction unit, a dynamic circulation separation module, a membrane refining component, and a vacuum concentration unit;

[0007] The outlet of the raw material pretreatment device is connected to the feed bin of the multi-stage countercurrent extraction unit through an airtight conveyor belt. The bottom of the feed bin is provided with a vibrating screening plate, and its surface is distributed with staggered diversion protrusions;

[0008] The multi-stage countercurrent extraction unit includes at least three series-connected extraction tanks, and adjacent extraction tanks are connected through a spiral diversion pipe, and the outer wall of the spiral diversion pipe is coated with a constant temperature jacket;

[0009] The dynamic circulation separation module includes a primary centrifugal separator, an ultrasonic-assisted extraction chamber, and a resin adsorption tower. A rotatable filter screen is provided in the ultrasonic-assisted extraction chamber, and the pore density of the filter screen changes in a gradient along the axial direction.

[0010] The input end of the membrane refining component is connected to the output end of the dynamic circulation separation module through a high-pressure pump, and its output end is divided into two paths and connected to a vacuum concentration unit and a solvent recovery pipeline respectively.

[0011] Preferably, the raw material pretreatment device includes a negative-pressure crushing bin and a microwave pretreatment unit. A double-shaft staggered crushing knife group is provided in the negative-pressure crushing bin, and the rotation directions of the crushing knife groups are opposite and the rotational speed difference is 15-20%.

[0012] Preferably, the spiral angle of the spiral guide pipe is 25°-30°, and the solvent inlet of each extraction tank is located at 2 / 3 of the tank height.

[0013] Preferably, the rotatable filter screen is driven by a driving motor to perform periodic forward and reverse alternating movements, and the forward and reverse time ratio is 1:1.5-2.

[0014] A method for extracting active ingredients from white tea includes the following steps:

[0015] S1: After the white tea raw materials are subjected to cell wall crushing by a pretreatment device, they are transported to a multi-stage countercurrent extraction unit;

[0016] S2: Circulating extraction is carried out at a gradient temperature in the multi-stage countercurrent extraction unit, and the flow direction of the extraction liquid is opposite to the movement direction of the raw materials; S3: The extraction liquid is subjected to solid-liquid separation and enrichment of active ingredients by a dynamic circulation separation module;

[0017] S4: The enriched liquid enters the vacuum concentration unit for drying after being fractionally purified by a membrane refining component.

[0018] Preferably, the gradient temperature in S2 is set as follows: the first-stage extraction temperature is 45-50°C, the second stage is 55-60°C, the third stage is 65-70°C, and the temperature deviation is controlled within ±1.5°C.

[0019] Preferably, the enrichment of active ingredients in S3 includes: sequentially passing the separated liquid phase through macroporous adsorption resin and ion exchange resin, and the adsorption-desorption cycle times are 2-3 times.

[0020] Preferably, the pretreatment includes: carrying out crushing treatment in a negative-pressure environment with a relative humidity ≤30%, and the particle size distribution of the crushed raw materials satisfies D90≤150μm.

[0021] The advantages and positive effects of the present invention are as follows: Through the synergistic effect of the spiral guide pipe and the vibrating sieve plate in the multi-stage countercurrent extraction unit, a stable concentration gradient field is formed, achieving the purpose of increasing the transfer rate of active ingredients. And through the combination of the rotatable filter screen of the dynamic circulation separation module and ultrasonic-assisted extraction, the oxidation loss rate of heat-sensitive components in the separation stage is reduced. The cascaded design of the membrane refining module and the resin adsorption tower realizes a dual purification mechanism of molecular weight retention and polar adsorption, improving the purity of polyphenols in the final product. The negative-pressure crushing environment of the raw material pretreatment device combined with microwave pretreatment greatly reduces the emission of volatile organic compounds and eliminates the risk of dust explosion at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below with reference to the drawings and embodiments.

[0023] Figure 1 is a schematic process diagram of the present invention.

[0024] The reference signs in the drawings are described separately as follows:

[0025] 1. Raw material pretreatment device; 11. Negative-pressure crushing bin; 111. Crushing knife group; 12. Microwave pretreatment unit; 13. Airtight conveyor belt;

[0026] 2. Multi-stage countercurrent extraction unit; 21. Feed bin; 211. Vibrating sieve plate; 212. Flow guide protrusion; 22. Multi-stage extraction tank; 23. Spiral guide pipe; 231. Constant temperature jacket;

[0027] 3. Dynamic circulation separation module; 31. Primary centrifuge; 32. Ultrasonic-assisted extraction chamber; 321. Rotatable filter screen; 322. Driving motor; 33. Resin adsorption tower; 34. Output end; 35. High-pressure pump;

[0028] 4. Membrane refining module; 41. Input end; 42. Solvent recovery pipeline;

[0029] 5. Vacuum concentration unit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention will now be described in further detail with reference to the drawings. These drawings are all simplified schematic diagrams, only illustrating the basic structure of the present invention in a schematic manner, and therefore only showing the components related to the present invention.

[0031] The following further details the embodiments of the present invention with reference to the drawings:

[0032] Refer to Figure 1As shown, the extraction of the active ingredients of white tea is a product extracted from white tea, containing rich substances such as tea polyphenols and flavonoids. Its main components include catechins (flavanols), phenolic acids, flavonols, condensed phenolic acids, etc., among which catechin compounds account for 65% - 80% of the total amount of tea polyphenols. Tea polyphenols can be used as antioxidants in aspects such as meat product processing, oil storage, baking food, and dairy product beverage formulation; as a preservative, it can slow down the biochemical activities of fruits and vegetables after picking and delay their ripening period; it can prevent natural pigments (such as carotene, chlorophyll, vitamin B2, and carmine, etc.) from fading due to photooxidation; the extract of white tea has pharmacological activities such as treating measles, improving eyesight, anti-cancer, anti-tumor, anti-mutation, antibacterial, antioxidant, anti-radiation, reducing blood sugar, protecting the liver, eliminating fatigue, losing weight, and regulating immune function. In the existing extraction processes of most of the active ingredients of white tea, high-temperature extraction during the extraction process may cause oxidative loss of heat-sensitive components such as tea polyphenols, resulting in the problem of failure to extract active ingredients. Moreover, there will be residual organic solvents in the extraction process that are difficult to completely remove, resulting in poor purity of the active ingredients and inability to be used subsequently. And the multi-step separation and purification process in the extraction process is cumbersome, and the product yield is low. To solve such problems, a white tea active ingredient extraction system is proposed, including a raw material pretreatment device 1, a multi-stage countercurrent extraction unit 2, a dynamic circulation separation module 3, a membrane refining component 4, and a vacuum concentration unit 5;

[0033] The outlet of the raw material pretreatment device 1 is connected to the feed bin 21 of the multi-stage countercurrent extraction unit 2 through an airtight conveyor belt 13. The bottom of the feed bin 21 is provided with a vibrating sieve plate 211, and diversion protrusions 212 are arranged in a staggered manner on its surface;

[0034] The multi-stage countercurrent extraction unit 2 includes at least three series-connected extraction tanks, and adjacent extraction tanks are connected through a spiral diversion pipe 23. The outer wall of the spiral diversion pipe 23 is coated with a constant temperature jacket 231;

[0035] The dynamic circulation separation module 3 includes a primary centrifuge 31, an ultrasonic-assisted extraction chamber 32, and a resin adsorption tower 33. A rotatable filter screen 321 is arranged in the ultrasonic-assisted extraction chamber 32, and the pore density thereof changes in a gradient along the axial direction;

[0036] The input end 41 of the membrane refining component 4 is connected to the output end 34 of the dynamic circulation separation module 3 through a high-pressure pump 35, and its output end 34 is divided into two paths and connected to a vacuum concentration unit 5 and a solvent recovery pipeline 42 respectively; through the synergistic effect of the spiral diversion tube 23 and the vibrating sieve plate 211 in the multi-stage countercurrent extraction unit 2, a stable concentration gradient field is formed, achieving the purpose of increasing the transfer rate of active ingredients. And through the combination of the rotatable filter screen 321 of the dynamic circulation separation module 3 and ultrasonic-assisted extraction, the oxidation loss rate of heat-sensitive components in the separation stage is reduced. The cascade design of the membrane refining component 4 and the resin adsorption tower 33 realizes a dual purification mechanism of molecular weight retention and polar adsorption, improving the purity of polyphenols in the final product. The negative-pressure crushing environment of the raw material pretreatment device 1 combined with microwave pretreatment greatly reduces the emission of volatile organic compounds and eliminates the risk of dust explosion at the same time.

[0037] It should be noted that the raw material pretreatment device 1 includes a negative-pressure crushing bin 11 and a microwave pretreatment unit 12. A double-shaft staggered crushing knife group 111 is provided in the negative-pressure crushing bin 11. The rotation directions of the crushing knife groups 111 are opposite and the rotational speed difference is 15% - 20%; the negative-pressure crushing bin 11 is connected to the microwave pretreatment unit 12 through an air lock valve, and the crushed raw material enters the microwave cavity under nitrogen protection; the blades of the double-shaft staggered crushing knife group 111 adopt a serrated edge design, and the edge spacing decreases by 20% - 25% from the feed end to the discharge end.

[0038] Furthermore, in the structural layout of the multi-stage countercurrent extraction unit 2, the three-stage extraction tanks are arranged in a Z shape, and the offset angle between the center line of the first-stage tank body and the center line of the second-stage tank body is 15° - 20°;

[0039] The flow direction of the circulating medium in the constant-temperature jacket 231 of the spiral diversion tube 23 is opposite to the material flow direction, forming reverse heat exchange;

[0040] Multiple layers of umbrella-shaped distributors are arranged in the extraction tank, and the aperture of the distributors increases by 10% - 15% from the upper layer to the lower layer.

[0041] It should also be noted that in the operation logic of the dynamic separation module, the solid phase outlet of the primary centrifuge 31 is connected to the ultrasonic-assisted extraction chamber 32 through a screw conveyor;

[0042] The forward and reverse rotation periods of the rotatable filter screen 321 are synchronously adjusted with the pulse frequency of the ultrasonic generator;

[0043] The resin adsorption tower 33 adopts a series - parallel switchable pipeline design to adapt to the enrichment requirements of different polar components.

[0044] Additionally, the specific method for the processing stage of the above entire process flow is as follows:

[0045] S1: Feed the white tea raw materials through a pretreatment device for cell wall disruption and then transport them to the multi-stage countercurrent extraction unit 2;

[0046] S2: In the multi-stage countercurrent extraction unit 2, perform cyclic extraction at gradient temperatures, with the flow direction of the extraction liquid opposite to the movement direction of the raw materials;

[0047] S3: The extraction liquid undergoes solid-liquid separation and enrichment of active ingredients through the dynamic circulation separation module 3;

[0048] S4: The enriched liquid is fractionally purified through the membrane refining component 4 and then enters the vacuum concentration unit 5 for drying.

[0049] Raw material pretreatment stage: Balance the white tea leaves in an environment with a relative humidity ≤ 25% for 24 hours and then enter the negative pressure crushing bin 11; Continuously introduce food-grade carbon dioxide during the crushing process to displace air and inhibit the activity of oxidase;

[0050] Gradient extraction stage: Solvent countercurrent path: pure water → ethanol solution → supercritical carbon dioxide fluid (selected according to the polarity of the target component);

[0051] Extraction liquid circulation method: The overflow liquid from the third-stage extraction tank returns to the second-stage tank as a secondary extraction solvent;

[0052] Dynamic separation enhancement stage: After the solid-liquid mixture is initially separated by the rotatable filter 321, the liquid phase is processed in two paths:

[0053] The main path directly enters the resin adsorption tower 33;

[0054] The branch path returns to the ultrasonic-assisted extraction chamber 32 for secondary extraction of the residue;

[0055] Coupled refining stage: The membrane refining component 4 includes an ultrafiltration membrane and a nanofiltration membrane arranged in parallel, and the flow path is switched through an electric three-way valve; The concentrated liquid is preliminarily concentrated by the scraper evaporator of the vacuum concentration unit 5 and then enters the spray drying tower.

[0056] It should be noted that for environmental protection treatment integration: A tail gas absorption tower is configured at the end of the system to condense and recover volatile components, and the condensate returns to the solvent recovery pipeline 42;

[0057] Moreover, for extended compatibility: The extraction tank is connected by a quick-release clamp and can be quickly replaced with a pressurized extraction container to meet different raw material requirements;

[0058] Furthermore, for quality control nodes: An on-line particle size analyzer is set before the spray drying tower to provide real-time feedback for adjusting the atomization pressure.

[0059] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention is not limited to the embodiments described in the specific embodiments. Any other embodiments derived by those skilled in the art based on the technical solutions of the present invention also fall within the scope of protection of the present invention.

Claims

1. An extraction system for the effective components of white tea, characterized in that: It includes a raw material pretreatment device (1), a multi-stage countercurrent extraction unit (2), a dynamic circulation separation module (3), a membrane refining component (4), and a vacuum concentration unit (5); The outlet of the raw material pretreatment device (1) is connected to the feed bin (21) of the multi-stage countercurrent extraction unit (2) through an airtight conveyor belt (13). A vibrating screening plate (211) is provided at the bottom of the feed bin (21), and diversion protrusions (212) arranged in a staggered manner are distributed on its surface; The multi-stage countercurrent extraction unit (2) includes at least three series-connected extraction tanks, and adjacent extraction tanks are connected through a spiral diversion pipe (23). A constant temperature jacket (231) is coated on the outer wall of the spiral diversion pipe (23); The dynamic circulation separation module (3) includes a primary centrifuge (31), an ultrasonic-assisted extraction chamber (32), and a resin adsorption tower (33). A rotatable filter screen (321) is provided in the ultrasonic-assisted extraction chamber (32), and the pore density thereof changes in a gradient along the axial direction; The input end (41) of the membrane refining component (4) is connected to the output end (34) of the dynamic circulation separation module (3) through a high-pressure pump (35), and its output end (34) is divided into two paths and is respectively connected to the vacuum concentration unit (5) and a solvent recovery pipeline (42).

2. The extraction system for the effective components of white tea according to claim 1, wherein: The raw material pretreatment device (1) includes a negative pressure crushing bin (11) and a microwave pretreatment unit (12). A double-axis staggered crushing knife group (111) is provided in the negative pressure crushing bin (11), and the rotation directions of the crushing knife groups (111) are opposite and the rotational speed difference is 15% - 20%.

3. The extraction system for the effective components of white tea according to claim 1, wherein: The spiral angle of the spiral diversion pipe (23) is 25° - 30°, and the solvent inlet of each extraction tank is located at 2 / 3 of the tank height.

4. The extraction system for the effective components of white tea according to claim 1, wherein: The rotatable filter screen (321) is driven by a driving motor (322) to perform periodic forward and reverse alternating movements, and the forward and reverse time ratio is 1:1.5 - 2.

5. A method for extracting effective components of white tea based on the system according to any one of claims 1 to 4, characterized in that: It includes the following steps: S1: The white tea raw material is subjected to cell wall crushing by the pretreatment device and then conveyed to the multi-stage countercurrent extraction unit (2); S2: In the multi-stage countercurrent extraction unit (2), gradient temperature is used for cyclic extraction, and the flow direction of the extraction liquid is opposite to the movement direction of the raw material; S3: The extraction liquid is subjected to solid-liquid separation and enrichment of active ingredients by the dynamic circulation separation module (3); S4: The enriched liquid enters the vacuum concentration unit (5) for drying after being fractionally purified by the membrane refining component (4).

6. The extraction method of effective components of white tea according to claim 5, characterized in that: The gradient temperature set in S2 is: The first-stage extraction temperature is 45 - 50°C, the second stage is 55 - 60°C, the third stage is 65 - 70°C, and the temperature deviation is controlled within ±1.5°C.

7. The extraction method of effective components of white tea according to claim 5, characterized in that: The enrichment of the active ingredients in S3 includes: passing the separated liquid phase through macroporous adsorption resin and ion exchange resin in sequence, and the adsorption-desorption cycle times are 2 - 3 times.

8. A method for extracting effective components of white tea according to claim 5, characterized in that: The pretreatment includes: performing crushing treatment in a negative pressure environment with a relative humidity ≤ 30%, and the particle size distribution of the crushed raw material satisfies D90 ≤ 150μm.

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