Method for separating and extracting tea polyphenol by membrane method

Abstract

The invention discloses a method for separating and extracting tea polyphenol by a membrane method. The method comprises the following steps: S1, taking crude tea leaves and deionized water; s2, extracting the crude tea leaves with deionized water; s3, merging the extracted leaching solutions, and filtering the merged leaching solutions by using a 150-mesh plate and frame filter; s4, reducing the temperature of the filtrate to 35 DEG C or below; s5, adding the filtrate into an ultrafiltration membrane system for filtering; s6, the ultrafiltration filtrate enters a nanofiltration membrane system to be separated, so that soluble salts are removed; s7, concentration treatment; and S8, drying treatment. According to the method for separating and extracting tea polyphenol through the membrane method, clarification, purification and concentration of tea juice are achieved, the defect of high-temperature concentration can be effectively avoided, the obtained product is excellent in fragrance, color and taste, the content of effective components of the product is obviously increased, solvent residues are avoided, and the water solubility is good; and in the application process, the phenomenon that polyphenols, water-soluble proteins and the like are complexed to form flocculent precipitates is avoided.

Description

Technical Field

[0001] The invention relates to the field of extraction of tea polyphenols, and in particular to a method for separating and extracting tea polyphenols using a membrane method. Background Art

[0002] Tea polyphenols is a general term for a class of polyphenol compounds in tea with important physiological functions. It is a complex of more than 30 phenolic substances in tea. Its main components are catechins and their derivatives, accounting for 60% to 80% of the total tea polyphenols. It has antioxidant, anti-aging, lipid-lowering, radiation protection and other effects. This property makes it widely used in many fields. In the food industry, tea polyphenols are used as antioxidants, preservatives and colorants, which can effectively prevent the oxidation of oils and meat foods, extend the ripening period of fruits and vegetables, and maintain the color and quality of food. In terms of daily necessities, tea polyphenols, as additives for cosmetics and daily chemical products, can be antibacterial, inhibit enzyme activity, and have sun protection and anti-wrinkle effects. The potential in the medical field is particularly significant. Tea polyphenols have multiple pharmacological effects such as lowering blood pressure, anti-coagulation, preventing and treating arteriosclerosis and diabetes. Its antiviral and antibacterial effects have also been widely recognized. It can inhibit a variety of pathogenic bacteria and has a protective effect on beneficial intestinal bacteria. It has broad application prospects.

[0003] At present, the extraction of tea polyphenols mainly includes solvent extraction, ion precipitation, resin adsorption, etc. The solvent extraction process is simple to operate, stable and reliable, but some impurities of similar nature will also be dissolved and extracted, such as caffeine, resulting in low purity. At the same time, the operation cycle is long, the amount of solvent used is large, and many organic solvents are toxic to the human body. The high temperature during the concentration process will accelerate the destruction of the effective ingredients. The ion precipitation process is also simpler and the cost is not high. Due to the specificity of the material structure, the precipitation selectivity is high and the purity is high, but in various filtering, transfer and other operations, tea polyphenols are easily lost, and the acidity and alkalinity of the solution are difficult to control. Improper use of alkali will destroy the structure of tea polyphenols, especially under alkaline conditions, tea polyphenols will be oxidized by oxidizing substances, which can easily reduce product quality. A series of physical and chemical processes may cause a large loss of tea polyphenols. The resin adsorption method is simple to operate, and the extraction principle is very simple and gentle, consuming very little energy. However, when applying the resin adsorption method, the quality and performance of the resin itself are very demanding. The cost of the resin is relatively high, and the lifespan is not long. After a period of time, a large number of new ones must be replaced, and the cost is too high, even far exceeding the benefits brought by the application of the resin adsorption method. Therefore, it is difficult to fully put it into use in actual enterprise production and is not suitable for mass production. Summary of the invention

[0004] The main purpose of the present invention is to provide a membrane separation and extraction method for tea polyphenols, which can effectively solve the problems in the background technology.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A membrane separation and extraction method for tea polyphenols comprises the following steps:

[0007] S1: Take crude tea leaves and add 15-20 times the amount of deionized water;

[0008] S2: heating the crude tea leaves added with deionized water to 60-80°C and then soaking them for 40-60 minutes, and continuing the soaking for three times;

[0009] S3: combining the extracts extracted three times, filtering the extracts with a 150-mesh plate-and-frame filter to remove mechanical impurities contained in the extracts, thereby obtaining a filtrate;

[0010] S4: lowering the temperature of the filtrate after filtration in step S3 to below 35° C.;

[0011] S5: After cooling, the filtrate is added to the ultrafiltration membrane system for filtration until the protein macromolecules, colloids and suspended matter in the filtrate are removed;

[0012] S6: The ultrafiltration membrane permeate in the ultrafiltration membrane system and the ultrafiltration filtrate enter the nanofiltration membrane system for separation, thereby removing soluble salts;

[0013] S7: The nanofiltration membrane is concentrated by a filtrate membrane method, and a nanofiltration membrane with a molecular weight cutoff of 150-500Da is selected for concentration to obtain a concentrate, and the water produced by the nanofiltration membrane is returned to the extraction section for reuse;

[0014] S8: Drying the concentrated liquid to obtain finished tea polyphenols.

[0015] Preferably, in step S1, the crude tea leaves also include tea stems.

[0016] Preferably, in step S3, the mechanical impurities include but are not limited to particulate matter, residues and larger impurities.

[0017] Preferably, in step S5, the ultrafiltration membrane has a molecular weight cut-off of 30,000 Da to 100,000 Da.

[0018] Preferably, in step S6, the molecular weight cutoff of the nanofiltration membrane is 150Da-500Da.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The invention realizes the clarification, purification and concentration of tea juice, can effectively avoid the disadvantages of high-temperature concentration, the obtained product has excellent aroma, color and taste, the content of effective ingredients in the product is significantly increased, no solvent residue, good water solubility, and the application process will not produce polyphenols and water-soluble proteins to form flocculent precipitation;

[0021] The present invention uses a membrane method for concentration and separation, and the conditions are mild and phase-change-free, which effectively avoids the problems of insufficient tea aroma, high production cost, large solvent loss, and poor solubility. The membrane separation technology applied to tea polyphenol extraction also has the following advantages: high automation, simple operation, and easy cleaning. The membrane separation technology combined with the low-temperature extraction and separation technology can avoid the oxidation loss of active ingredients and improve the yield. The products produced by the membrane process not only have excellent color, aroma, and taste, but also have a production cost of 1 / 2-1 / 8 of that of the traditional method. There is no precipitation and turbidity in the tea beverages used. Less pollutants are discharged during the process, which reduces the pressure of wastewater discharge and reduces the investment in wastewater treatment. It has great technical and economic advantages.

[0022] This method has a high degree of automation, is easy to operate and clean, and the membrane separation technology combined with the low-temperature extraction and separation technology can avoid the oxidation loss of active ingredients and improve the yield. The production cost is greatly reduced, and the pollutant emissions during the process are small, which reduces the pressure of wastewater discharge and reduces the investment in wastewater treatment. It has great technical and economic advantages. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The present invention relates to a method for separating and extracting tea polyphenols using a membrane method, comprising the following steps:

[0025] S1: taking crude tea leaves and adding 15-20 times the amount of deionized water, the crude tea leaves also include tea stems;

[0026] S2: heating the crude tea leaves added with deionized water to 60-80°C and then soaking them for 40-60 minutes, and continuing the soaking for three times;

[0027] S3: combining the extracts extracted three times, filtering the extracts with a 150-mesh plate-and-frame filter to remove mechanical impurities contained in the extracts, thereby obtaining a filtrate, wherein the mechanical impurities include but are not limited to particulate matter, residues, and larger impurities;

[0028] S4: lowering the temperature of the filtrate after filtration in step S3 to below 35° C.;

[0029] S5: After cooling, the filtrate is added to the ultrafiltration membrane system for filtration until the protein macromolecules, colloids and suspended matter in the filtrate are removed, and the ultrafiltration membrane has a molecular weight cutoff of 30,000 Da to 100,000 Da;

[0030] S6: The ultrafiltration membrane permeate in the ultrafiltration membrane system and the ultrafiltration filtrate enter the nanofiltration membrane system for separation to remove soluble salts. The molecular weight cutoff of the nanofiltration membrane is 150Da-500Da;

[0031] S7: The nanofiltration membrane is concentrated by a filtrate membrane method, and a nanofiltration membrane with a molecular weight cutoff of 150-500Da is selected for concentration to obtain a concentrate, and the water produced by the nanofiltration membrane is returned to the extraction section for reuse;

[0032] S8: Drying the concentrated liquid to obtain finished tea polyphenols. Specific embodiment one:

[0034] The finished tea polyphenols were filtered with a 150-mesh plate-and-frame filter and then cooled to 35°C. They were filtered with 30,000Da, 60,000Da, and 100,000Da ultrafiltration membranes at an operating pressure of 1.5 bar, respectively. The retention rates of the active ingredients by ultrafiltration membranes with different molecular weight cutoffs were tested. The following is a retention rate table:

[0035]

[0036]

[0037] It can be seen that the chemical composition of tea juice changes differently after passing through ultrafiltration membranes with different molecular weights: the content of macromolecular substances pectin and protein is significantly reduced. In the application process of tea polyphenols, protein is often the main substance causing the unstable state in the system. It can complex with tea polyphenols and other substances to cause smaller molecular substances to slowly condense into large particles and precipitate to make the tea beverage turbid. After passing through three ultrafiltration membranes with different molecular weights of 100,000Da, 60,000Da, and 30,000Da, the protein content dropped from 4.25% of the dry matter content of tea to 1.10%, 0.95%, and 0.64%, respectively. Pectin is also one of the reasons for the turbid precipitation of tea juice. , they can be basically removed after passing through three ultrafiltration membranes with different molecular weights; while the retention rates of active ingredients such as tea polyphenols, amino acids, and soluble sugars gradually decrease with the decrease of the molecular weight of the ultrafiltration membrane, especially the retention rates of 30000Da ultrafiltration membranes are very different from those of 60000Da and 100000Da ultrafiltration membranes. The retention rate of 30000Da ultrafiltration membrane is much lower than that of the other two ultrafiltration membranes, and a large amount of active ingredients are intercepted. The retention of active ingredients by 60000Da ultrafiltration membrane and 100000Da ultrafiltration membrane is not much different. Considering the membrane flux and retention rate comprehensively, 100000Da ultrafiltration membrane is preferred for filtration. Specific embodiment 2:

[0039] A membrane separation and extraction method for tea polyphenols comprises the following steps:

[0040] S1: Take crude tea leaves and add 15-20 times the amount of deionized water, the crude tea leaves also include tea stems, and the ratio of tea leaves to deionized water is 1:20;

[0041] S2: The crude tea leaves added with deionized water are heated to 70°C and then soaked for 60 minutes, and the operation is repeated twice and then soaked three times;

[0042] S3: combining the extracts extracted three times, filtering the extracts with a 150-mesh plate-and-frame filter to remove mechanical impurities contained in the extracts, thereby obtaining a filtrate, wherein the mechanical impurities include but are not limited to particulate matter, residues, and larger impurities;

[0043] S4: lowering the temperature of the filtrate after filtration in step S3 to below 35° C.;

[0044] S5: After cooling, the filtrate is added to the ultrafiltration membrane system for filtration until the protein macromolecules, colloids and suspended matter in the filtrate are removed. The ultrafiltration membrane has a molecular weight cutoff of 100,000 Da and a pressure of 0.15 MPa;

[0045] S6: The ultrafiltration membrane permeate in the ultrafiltration membrane system and the ultrafiltration filtrate enter the nanofiltration membrane system for separation to remove soluble salts. The molecular weight cutoff of the nanofiltration membrane is 300Da.

[0046] S7: The nanofiltration membrane is concentrated by a filtrate membrane method, and a nanofiltration membrane with a molecular weight cutoff of 200Da is used for concentration. The concentrate is concentrated until the volume is reduced by 75%-80% to obtain a concentrate. The water produced by the nanofiltration membrane is returned to the extraction section for reuse;

[0047] S8: spray drying the concentrated solution to obtain a finished tea polyphenol product;

[0048] S9: Test the active ingredients of tea polyphenols products. The following is the test table:

[0049] Test items content% Tea polyphenols% 83.6％ Catechin% 57.2％ Caffeine% 2.1％ Total ash % 1.2％ Moisture% 0.8％

[0050] After testing, the tea polyphenols prepared by this method meet the standard requirements of TP80 in GB / T31740.2-2015.

[0051] The invention realizes the clarification, purification and concentration of tea juice, can effectively avoid the disadvantages of high-temperature concentration, the obtained product has excellent aroma, color and taste, the content of effective ingredients in the product is significantly increased, no solvent residue, good water solubility, and the application process will not produce polyphenols and water-soluble proteins to form flocculent precipitation;

[0052] The present invention uses a membrane method for concentration and separation, and the conditions are mild and phase-change-free, which effectively avoids the problems of insufficient tea aroma, high production cost, large solvent loss, and poor solubility. The membrane separation technology applied to tea polyphenol extraction also has the following advantages: high automation, simple operation, and easy cleaning. The membrane separation technology combined with the low-temperature extraction and separation technology can avoid the oxidation loss of active ingredients and improve the yield. The products produced by the membrane process not only have excellent color, aroma, and taste, but also have a production cost of 1 / 2-1 / 8 of that of the traditional method. There is no precipitation and turbidity in the tea beverages used. Less pollutants are discharged during the process, which reduces the pressure of wastewater discharge and reduces the investment in wastewater treatment. It has great technical and economic advantages.

[0053] This method has a high degree of automation, is easy to operate and clean, and the membrane separation technology combined with the low-temperature extraction and separation technology can avoid the oxidation loss of active ingredients and improve the yield. The production cost is greatly reduced, and the pollutant emissions during the process are small, which reduces the pressure of wastewater discharge and reduces the investment in wastewater treatment. It has great technical and economic advantages.

[0054] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A membrane separation and extraction method for tea polyphenols, characterized in that: The steps include: S1: Take crude tea leaves and add 15-20 times the amount of deionized water; S2: heating the crude tea leaves added with deionized water to 60-80°C and then soaking them for 40-60 minutes, and continuing the soaking for three times; S3: combining the extracts extracted three times, filtering the extracts with a 150-mesh plate-and-frame filter to remove mechanical impurities contained in the extracts, thereby obtaining a filtrate; S4: lowering the temperature of the filtrate after filtration in step S3 to below 35° C.; S5: After cooling, the filtrate is added to the ultrafiltration membrane system for filtration until the protein macromolecules, colloids and suspended matter in the filtrate are removed; S6: The ultrafiltration membrane permeate in the ultrafiltration membrane system and the ultrafiltration filtrate enter the nanofiltration membrane system for separation, thereby removing soluble salts; S7: The nanofiltration membrane is concentrated by a filtrate membrane method, and a nanofiltration membrane with a molecular weight cutoff of 150-500Da is selected for concentration to obtain a concentrate, and the water produced by the nanofiltration membrane is returned to the extraction section for reuse; S8: Drying the concentrated liquid to obtain finished tea polyphenols.

2. The method for separating and extracting tea polyphenols by membrane method according to claim 1, characterized in that: In step S1, the crude tea leaves also include tea stems.

3. The method for separating and extracting tea polyphenols by membrane method according to claim 1, characterized in that: In step S3, mechanical impurities include but are not limited to particulate matter, residues and larger impurities.

4. The method for separating and extracting tea polyphenols by membrane method according to claim 1, characterized in that: In step S5, the ultrafiltration membrane has a molecular weight cut-off of 30,000 Da to 100,000 Da.

5. The method for separating and extracting tea polyphenols by membrane method according to claim 1, characterized in that: In step S6, the molecular weight cutoff of the nanofiltration membrane is 150Da-500Da.

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