A method for extracting and preparing tea pigment from tea leaves

Abstract

The invention relates to the technical field of tea processing, and in particular to a method for extracting and preparing tea pigment from tea leaves. The method comprises the following steps: adding tea raw materials into water for decoction extraction to obtain a decoction liquid; adjusting the pH of the decoction liquid with alkali, and vacuum concentrating the decoction liquid to obtain a concentrated liquid; adding ethanol to the concentrated liquid, adjusting the acidity, performing reflux extraction, and filtering to obtain a reflux liquid; adding ethanol to the reflux liquid to increase the alcohol content and adjust the pH, and filtering and desalting the reflux liquid after reflux to obtain a desalted liquid; adjusting the pH of the desalted liquid with alkali, allowing it to settle, removing the supernatant, stirring the precipitate, heating it, and dealcoholizing it, and then adding purified water to dissolve it to obtain a tea pigment solution; desalting the tea pigment solution by passing it through a dextran gel chromatography column, and concentrating the eluate into a fluid extract, which is then dried to obtain the tea pigment. The prepared tea pigment has a high extraction rate and good quality, and meets and exceeds the pharmacopoeial standards for tea pigments.

Description

Technical Field

[0001] The present invention relates to the technical field of tea processing, and in particular to a method for extracting and preparing tea pigment from tea leaves. Background Art

[0002] Tea pigments are a mixture of water-soluble pigments formed through the continuous oxidation and polymerization of polyphenolic compounds in tea leaves, particularly catechins. The main components of tea pigments are theaflavins (TFs), thearubigins (TRs), and theabrownins (TBs). Tea pigments can be used in both food and pharmaceutical applications. Tea pigment capsules have the effects of clearing the head, resolving phlegm, and reducing fat. They are used to treat dizziness, chest tightness, and pain caused by phlegm and blood stasis, hyperlipidemia, coronary heart disease, angina pectoris, and cerebral infarction.

[0003] The tea pigment production method disclosed in patent CN1035660C, previously filed by Jiangxi Green Industry (Group) Co., Ltd., uses tea leaves as raw material and is prepared through a process of decoction extraction, alkaline concentration, ethanol acidification and reflux, and alkaline precipitation. The tea pigment produced by this method is extracted from tea leaves and is natural, healthy, safe, high-quality, and highly market-acceptable. However, during industrial application, this method was found to have the following drawbacks: the discarded tea residues from extraction contain a high amount of incompletely oxidized tea polyphenols and unextracted tea pigments, resulting in a waste of raw materials and a low extraction rate. Furthermore, the tea pigment produced has a high salt content and is highly corrosive to production equipment, especially high-temperature drying equipment. In light of these issues, the present application aims to improve upon this traditional method, thereby increasing the tea pigment extraction rate, reducing the salt content, and obtaining high-quality tea pigments. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for extracting and preparing tea pigments from tea leaves, which can improve the extraction rate of tea pigments and reduce the tea pigment salt content while ensuring the quality of tea pigments.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for extracting and preparing tea pigment from tea leaves, comprising the following steps:

[0007] S1, adding tea raw materials to water for decoction extraction, and filtering the decoction to obtain an extract;

[0008] S2, adjusting the pH of the extract to 8-9 with alkali, and concentrating in vacuo at 50-75°C to obtain a concentrated solution, wherein the concentrated solution is 0.9-1.1 times the weight of the tea raw material;

[0009] S3. Add ethanol to the concentrated solution until the alcohol content is 40% v / v to 70% v / v, adjust the pH to 2 to 3, perform reflux extraction for 0.5 h to 2 h, and filter to obtain the reflux solution;

[0010] S4. Add ethanol to the reflux solution until the alcohol content is 75% v / v to 85% v / v, adjust the pH to 3 to 4, reflux and extract for 0.5 h to 2 h, filter and remove salt to obtain a desalted solution;

[0011] S5. Adjust the pH of the desalted solution to 9-11 with alkali, let it settle for 4-18 hours, remove the supernatant, stir and heat the precipitate to dealcoholize, and then add purified water to dissolve it to prepare a tea pigment solution. Desalt the tea pigment solution through a dextran gel chromatography column, elute with purified water, and concentrate the eluate to a fluid extract with a relative density of 1.05-1.12. The fluid extract is dried to obtain the tea pigment.

[0012] The above-mentioned technical solution provided in the present application reduces the amount of ethanol used in the subsequent alcohol extraction and salting-out processes by concentrating the extract to approximately the weight of the tea raw material, and promotes the conversion of tea pigments and increases the tea pigment content by adjusting the pH to 2-3 when the alcohol content is 40% v / v-70% v / v. It also promotes the conversion of tea pigments and increases the tea pigment content and promotes the precipitation of salts when the alcohol content is 75% v / v-85% v / v and the pH is adjusted to 3-4 when the alcohol content is 75% v / v-85% v / v. Finally, it further desalts through a dextran gel chromatography column, and optimizes various process parameters, effectively improving the extraction yield of tea pigments and reducing the salt content of the tea pigment fluid extract, effectively alleviating the corrosion problem of the drying equipment, and the tea pigment salt content of the final prepared tea pigment is low. The caffeine, gallic acid, pH and moisture content of the prepared tea pigment product meet and exceed the pharmacopoeial standards for tea pigments, and the prepared tea pigments are of high quality.

[0013] Furthermore, the decoction extraction in S1 includes the following steps:

[0014] S11, adding 5 to 10 times the amount of water to the tea raw material for a first decoction extraction, and filtering the decoction to obtain an extract I and a filter residue I;

[0015] S12, adding sodium carboxymethyl cellulose to the filter residue I, and then adding water 2.5 to 7.5 times the weight of the tea raw material, and adjusting the pH to 8 to 9 for a second decoction extraction, and filtering the decoction to obtain an extract II and a filter residue II;

[0016] S13, adding sodium carboxymethyl cellulose to the filter residue II, and then adding 1.5 to 5 times the weight of water of the tea raw material, and adjusting the pH to 8 to 9 for a third decoction extraction, and filtering the decoction to obtain the extract III and the filter residue III;

[0017] S14, combining the extract I, the extract II and the extract III to obtain an extract.

[0018] The traditional method uses a three-step water extraction process, which requires a high proportion of water as the extraction solvent and has a low extraction rate. This application optimizes the decoction process and uses sodium carboxymethyl cellulose on the tea residue after the first water extraction and then performs a secondary extraction under alkaline conditions. Under alkaline conditions, sodium carboxymethyl cellulose can form hydrogen bonds with tea pigments and their precursors, tea polyphenols, in the tea residue to promote the dissolution of tea pigments / precursors and increase the extraction rate of caffeine. After the interaction between the combined sodium carboxymethyl cellulose and tea polyphenols / tea pigments is destroyed under acidic conditions, the tea polyphenols / tea pigments enter the solution, and the sodium carboxymethyl cellulose precipitates under the action of high concentrations of alcohol to achieve separation, leaving almost no residue. Sodium carboxymethyl cellulose is a common additive in food and medicine, and even trace amounts of residue are harmless to the human body.

[0019] Furthermore, the amount of sodium carboxymethyl cellulose used in S12 is 0.5% to 2% by weight of the tea raw material; the amount of sodium carboxymethyl cellulose used in S13 is 2% to 5% by weight of the tea raw material.

[0020] Furthermore, in S5, purified water is added to dissolve the tea pigment to prepare a tea pigment solution, with the mass ratio of tea pigment to purified water being 1:15-20. The tea pigment solution prepared using this ratio of tea pigment to purified water is well suited for subsequent chromatography column chromatography. Excessively high or low tea pigment concentrations can adversely affect the column chromatography process, causing sample precipitation or lowering efficiency.

[0021] Furthermore, in S5, the drying is performed by vacuum drying or spray drying, and the inlet air temperature of the spray drying is 260-330°C, and the outlet air temperature is 80-130°C.

[0022] Furthermore, the filler used in the dextran gel chromatography column in S5 is Sephadex G-15, and the height-to-diameter ratio of the dextran gel chromatography column is 5:1 to 10:1.

[0023] Furthermore, the flow rate of the tea pigment solution in S5 passing through the dextran gel chromatography column is 2 bv / h to 4 bv / h.

[0024] Furthermore, the flow rate of the purified water for elution in S5 is 3 bv / h to 6 bv / h.

[0025] Furthermore, the acidic reagent used to adjust the pH is dilute hydrochloric acid with a concentration of 5% to 20%.

[0026] Furthermore, the alkaline agent used to adjust the pH is selected from at least one of sodium hydroxide, sodium carbonate, and sodium bicarbonate, and the concentration of the alkaline agent is 10% to 30%.

[0027] To reduce solvent costs and resource waste, this application also includes recycling the ethanol waste liquid produced. This recycling process can be processed using conventional recovery processes, such as distillation and rectification. The recovered ethanol can be reused for tea pigment extraction, thus avoiding resource waste. The residue after tea pigment extraction in this application is rich in polysaccharides, proteins, and other components. After drying, it can be used as a feed ingredient, increasing the added value of the product.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: the method for extracting and preparing tea pigments from tea leaves provided in the present application optimizes the decoction process, uses sodium carboxymethyl cellulose on the tea residue after the first water extraction and then performs a secondary extraction under alkaline conditions to effectively improve the extraction rate of tea pigments, adopts alcohol extraction under different ethanol gradients and cooperates with acidic conditions to further improve the extraction rate of tea pigments while utilizing the solubility difference of sodium chloride to precipitate salts, and finally further desalts by using a dextran gel chromatography column, and optimizes various process parameters at the same time, effectively improving the extraction yield of tea pigments, reducing the salt content of the tea pigment fluid extract, and effectively alleviating the corrosion problem of the spray drying equipment. The tea pigments finally prepared have a low salt content, and the caffeine, gallic acid, pH and moisture of the prepared tea pigment product are better than the pharmacopoeia standards for tea pigments, and the prepared tea pigments are of high quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a process flow chart for extracting and preparing tea pigment from tea leaves according to an embodiment of the present invention;

[0030] Figure 2 This is the appearance of the tea pigment sample prepared in the example. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. The embodiments described 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 making creative efforts are within the scope of protection of the present invention.

[0032] Unless otherwise specified, the methods are conventional methods, and the raw materials can be obtained from public commercial channels unless otherwise specified. Figure 1 This is a process flow chart for extracting tea pigments from tea leaves according to an embodiment of the present invention. The following is a further explanation of the scheme of the present application in conjunction with the examples and drawings:

[0033] Example 1

[0034] This embodiment provides a method for extracting and preparing tea pigment from tea leaves, comprising the following steps:

[0035] 1. Add 600 g of tea leaves (green tea) to 7.5 times the volume of purified water for the first decoction. After boiling, keep the water slightly boiling for 1 hour. Filter the decoction to obtain extract I and residue I.

[0036] 2. To the filter residue I, 1% sodium carboxymethyl cellulose by weight of the tea raw material was added, and then 5 times the weight of purified water of the tea raw material was added. The pH was adjusted to 9 with 20% sodium hydroxide solution for a second decoction extraction. After boiling, the mixture was kept at a slight boil for 1 hour. The decoction was filtered to obtain the extract II and the filter residue II.

[0037] 3. Add sodium carboxymethyl cellulose (3% by weight of the tea raw material) to the residue II, then add purified water (2.5 times the weight of the tea raw material), adjust the pH to 9 with 20% sodium hydroxide solution, and perform a third decoction extraction. After boiling, maintain a slight boil for 1 hour. Filter the decoction to obtain extract III and residue III.

[0038] 4. Combine extracts I, II, and III to obtain a decoction, adjust the pH of the decoction to 9, and vacuum concentrate at 60°C until the concentrate is the weight of the tea raw material.

[0039] 5. Add ethanol to the concentrate to an alcohol content of 55% v / v, adjust the acidity to pH 2.5 with 10% dilute hydrochloric acid, reflux and extract for 1 hour, cool to 45°C, and filter to obtain the reflux liquid.

[0040] 6. Add ethanol to the reflux liquid to make the alcohol content 80% v / v, adjust the pH to 3.5 with 10% dilute hydrochloric acid, reflux and extract for 1 hour, cool to 45℃, filter and remove salt to obtain desalted liquid.

[0041] 7. Adjust the pH of the desalted liquid to 10.5 with 20% sodium hydroxide solution, let it stand for 6 hours, remove the supernatant, stir the precipitate and heat it to dealcoholize it, then add purified water to dissolve it to prepare a tea pigment aqueous solution, with the ratio of tea pigment to purified water being 1:18.

[0042] 8. Sephadex G-15 filler was swelled with purified water and then packed into a column (10 cm in diameter × 50 cm in height). The tea pigment solution was applied to the dextran gel chromatography column at a controlled flow rate of 3 bv / h. Purified water was used for elution at a flow rate of 5 bv / h. The elution process was monitored in real time by ultraviolet light, and the tea pigment eluate was collected.

[0043] 9. The tea pigment eluate was vacuum concentrated at 60°C to form a fluid extract with a relative density of 1.08. The effluent was spray-dried with an inlet air temperature of 300°C and an outlet air temperature of 115°C. The dried product was collected to obtain the tea pigment.

[0044] Example 2

[0045] This embodiment provides a method for extracting and preparing tea pigment from tea leaves, comprising the following steps:

[0046] 1. Add 600 g of tea raw material (black tea) to 7.5 times the volume of purified water for the first decoction. After boiling, keep it slightly boiling for 1 hour. Filter the decoction to obtain extract I and residue I.

[0047] 2. To the filter residue I, 0.5% sodium carboxymethyl cellulose by weight of the tea raw material was added, and then 5 times the weight of the tea raw material was added with purified water. The pH was adjusted to 8 with 20% sodium hydroxide solution for a second decoction extraction. After boiling, the mixture was kept at a slight boil for 1 hour. The decoction was filtered to obtain the extract II and the filter residue II.

[0048] 3. Add sodium carboxymethyl cellulose (2% by weight of the tea raw material) to the residue II, then add purified water (2.5 times the weight of the tea raw material), adjust the pH to 8 with 20% sodium hydroxide solution, and perform a third decoction extraction. After boiling, keep it at a slight boil for 1 hour. Filter the decoction to obtain extract III and residue III.

[0049] 4. Combine extracts I, II, and III to obtain a decoction, adjust the pH of the decoction to 8, and vacuum concentrate at 60°C until the concentrate is the weight of the tea raw material.

[0050] 5. Add ethanol to the concentrate to make the alcohol content 50% v / v, adjust the acidity to pH 2 with 10% dilute hydrochloric acid, reflux and extract for 1 hour, cool to 45°C, and filter to obtain the reflux liquid.

[0051] 6. Add ethanol to the reflux liquid until the alcohol content is 75% v / v, adjust the pH to 3 with 10% dilute hydrochloric acid, reflux and extract for 1 hour, cool to 45°C, filter and desalinate to obtain desalted liquid.

[0052] 7. Adjust the pH of the desalted liquid to 10.5 with 20% sodium hydroxide solution, let it stand for 6 hours, remove the supernatant, stir the precipitate and heat it to dealcoholize it, then add purified water to dissolve it to prepare a tea pigment aqueous solution, with the ratio of tea pigment to purified water being 1:18.

[0053] 8. Sephadex G-15 filler was swelled with purified water and then packed into a column (10 cm in diameter × 50 cm in height). The tea pigment solution was applied to the dextran gel chromatography column at a controlled flow rate of 3 bv / h. Purified water was used for elution at a flow rate of 5 bv / h. The elution process was monitored in real time by ultraviolet light, and the tea pigment eluate was collected.

[0054] 9. The tea pigment eluate was vacuum concentrated at 60°C to form a fluid extract with a relative density of 1.08. The effluent was spray-dried with an inlet air temperature of 300°C and an outlet air temperature of 115°C. The dried product was collected to obtain the tea pigment.

[0055] Example 3

[0056] This embodiment provides a method for extracting and preparing tea pigment from tea leaves, comprising the following steps:

[0057] 1. Add 600 g of tea material (oolong tea) to 7.5 times the volume of purified water for the first decoction. After boiling, keep it slightly boiling for 1 hour. Filter the decoction to obtain extract I and filter residue I.

[0058] 2. To the filter residue I, 0.5% sodium carboxymethyl cellulose by weight of the tea raw material was added, and then 5 times the weight of the tea raw material was added with purified water. The pH was adjusted to 8 with 20% sodium hydroxide solution for a second decoction extraction. After boiling, the mixture was kept at a slight boil for 1 hour. The decoction was filtered to obtain the extract II and the filter residue II.

[0059] 3. Add sodium carboxymethyl cellulose (2% by weight of the tea raw material) to the residue II, then add purified water (2.5 times the weight of the tea raw material), adjust the pH to 9 with 20% sodium hydroxide solution, and perform a third decoction extraction. After boiling, maintain a slight boil for 1 hour. Filter the decoction to obtain extract III and residue III.

[0060] 4. Combine extracts I, II, and III to obtain a decoction, adjust the pH of the decoction to 9, and vacuum concentrate at 60°C until the concentrate is the weight of the tea raw material.

[0061] 5. Add ethanol to the concentrate to an alcohol content of 60% v / v, adjust the acidity to pH 2.5 with 10% dilute hydrochloric acid, reflux and extract for 1 hour, cool to 45°C, and filter to obtain the reflux liquid.

[0062] 6. Add ethanol to the reflux liquid to make the alcohol content 85% v / v, adjust the pH to 3.5 with 10% dilute hydrochloric acid, reflux and extract for 1 hour, cool to 45℃, filter and remove salt to obtain desalted liquid.

[0063] 7. Adjust the pH of the desalted liquid to 10.5 with 20% sodium hydroxide solution, let it stand for 6 hours, remove the supernatant, stir the precipitate and heat it to dealcoholize it, then add purified water to dissolve it to prepare a tea pigment aqueous solution, with the ratio of tea pigment to purified water being 1:18.

[0064] 8. Sephadex G-15 filler was swelled with purified water and then packed into a column (10 cm in diameter × 50 cm in height). The tea pigment solution was applied to the dextran gel chromatography column at a controlled flow rate of 3 bv / h. Purified water was used for elution at a flow rate of 5 bv / h. The elution process was monitored in real time by ultraviolet light, and the tea pigment eluate was collected.

[0065] 9. The tea pigment eluate was vacuum concentrated at 60°C to form a fluid extract with a relative density of 1.08. The effluent was spray-dried with an inlet air temperature of 300°C and an outlet air temperature of 115°C. The dried product was collected to obtain the tea pigment.

[0066] Comparative Example 1

[0067] The method of Example 1 is the same, except that the decoction methods of steps 1 to 3 are as follows:

[0068] 1. Add 600 g of tea leaves (green tea) to 7.5 times the volume of purified water for the first decoction. After boiling, keep the water slightly boiling for 1 hour. Filter the decoction to obtain extract I and residue I.

[0069] 2. Add 5 times the weight of purified water of the tea raw material to the filter residue I for a second decoction. After boiling, keep it at a slight boil for 1 hour. Filter the decoction to obtain the extract II and the filter residue II.

[0070] 3. Add 2.5 times the weight of purified water of the tea raw material to the residue II for a second decoction. After boiling, keep it slightly boiling for 1 hour. Filter the decoction to obtain the extract III and the residue III.

[0071] Comparative Example 2

[0072] The method of Example 1 is the same, except that the decoction methods of steps 1 to 3 are as follows:

[0073] 1. Add 600 g of tea leaves (green tea) to 7.5 times the volume of purified water for the first decoction. After boiling, keep the water slightly boiling for 1 hour. Filter the decoction to obtain extract I and residue I.

[0074] 2. To the residue I, 1% sodium carboxymethyl cellulose by weight of the tea raw material was added, and then 5 times the weight of purified water of the tea raw material was added. The pH was adjusted to 10 with 20% sodium hydroxide solution for a second decoction extraction. After boiling, the mixture was kept at a slight boil for 1 hour. The decoction was filtered to obtain the extract II and the residue II.

[0075] 3. Add sodium carboxymethyl cellulose (3% by weight of the tea raw material) to the residue II, then add purified water (2.5 times the weight of the tea raw material), adjust the pH to 10 with 20% sodium hydroxide solution, and perform a third decoction extraction. After boiling, keep it at a slight boil for 1 hour. Filter the decoction to obtain extract III and residue III.

[0076] Comparative Example 3

[0077] This comparative example provides a method for extracting and preparing tea pigment from tea leaves, comprising the following steps:

[0078] 1. Add 600 g of tea leaves (green tea) to 7.5 times the volume of purified water for the first decoction. After boiling, keep the water slightly boiling for 1 hour. Filter the decoction to obtain extract I and residue I.

[0079] 2. To the filter residue I, 1% sodium carboxymethyl cellulose by weight of the tea raw material was added, and then 5 times the weight of purified water of the tea raw material was added. The pH was adjusted to 9 with 20% sodium hydroxide solution for a second decoction extraction. After boiling, the mixture was kept at a slight boil for 1 hour. The decoction was filtered to obtain the extract II and the filter residue II.

[0080] 3. Add sodium carboxymethyl cellulose (3% by weight of the tea raw material) to the residue II, then add purified water (2.5 times the weight of the tea raw material), adjust the pH to 9 with 20% sodium hydroxide solution, and perform a third decoction extraction. After boiling, maintain a slight boil for 1 hour. Filter the decoction to obtain extract III and residue III.

[0081] 4. Combine extracts I, II, and III to obtain a decoction, adjust the pH of the decoction to 9, and vacuum concentrate at 60°C until the concentrate is the weight of the tea raw material.

[0082] 5. Add ethanol to the concentrate to an alcohol content of 55% v / v, adjust the acidity to pH 2.5 with 10% dilute hydrochloric acid, reflux and extract for 1 hour, cool to 45°C, and filter to obtain the reflux liquid.

[0083] 6. The pH of the reflux liquid was adjusted to 10.5 with 20% sodium hydroxide solution, and the mixture was allowed to settle for 6 hours. The supernatant was removed, and the precipitate was stirred and heated to dealcoholize. Purified water was added to dissolve the precipitate to prepare a fluid extract with a relative density of 1.08. The effluent was spray-dried at an inlet air temperature of 300°C and an outlet air temperature of 115°C. The dried product was collected to obtain the tea pigment.

[0084] Comparative Example 4

[0085] The method of Example 1 is different in that the desalting process in step 6 is not involved, and the reflux liquid obtained in step 5 is directly fed into step 7 for alkali adjustment.

[0086] Comparative Example 5

[0087] The method of Example 1 is followed, except that, in step 6, ethanol is added to the reflux solution until the alcohol content is 80% v / v, reflux extraction is performed for 1 hour, and the solution is cooled to 45° C. and filtered to remove salt to obtain a desalted solution;

[0088] Comparative Example 6

[0089] The method of Example 1 is followed, except that, in step 6, ethanol is added to the reflux solution to obtain an alcohol content of 90% v / v, the pH is adjusted to 3.5 with 10% dilute hydrochloric acid, and reflux extraction is performed for 1 hour, and the solution is cooled to 45° C. and filtered to remove salt to obtain a desalted solution.

[0090] Comparative Example 7

[0091] The method of Example 1 was followed, except that in step 8, the Sephadex G-15 filler was swollen with purified water and then loaded onto a column (10 cm diameter × 50 cm height). The tea pigment solution was applied to the dextran gel chromatography column at a controlled flow rate of 3 bv / h. Purified water was used for elution at a flow rate of 8 bv / h. The elution process was monitored in real time by ultraviolet light, and the tea pigment eluate was collected.

[0092] Comparative Example 8

[0093] The method of Example 1 was followed, except that in step 8, the Sephadex G-25 filler was swollen with purified water and then loaded onto a column (10 cm diameter × 50 cm height). The tea pigment solution was applied to the dextran gel chromatography column at a controlled flow rate of 3 bv / h. Purified water was used for elution at a flow rate of 5 bv / h. The elution process was monitored in real time by ultraviolet light, and the tea pigment eluate was collected.

[0094] Test example

[0095] The tea pigment samples prepared in the Examples and Comparative Examples were assayed. The theabrownin, thearubigins, and theaflavins contents were determined spectrophotometrically, the NaCl content was determined by potentiometric titration, the caffeine and gallic acid contents were determined by HPLC, the moisture content was determined by oven constant weight, and the pH was determined using an acidometer. The total yield of the tea pigments prepared in the Examples and Comparative Examples was calculated as follows: crude tea pigment extraction yield = spray-dried tea pigment sample weight / tea leaf feed amount × 100%, and net tea pigment extraction yield = spray-dried tea pigment sample weight × (theabrownin content + tea red content + theaflavins content) / tea leaf feed amount × 100%. The results are shown in Table 1 below:

[0096] Table 1: Tea pigment determination results

[0097]

[0098] Table 1: Tea pigment determination results

[0099]

[0100] In combination with Example 1 and Comparative Example 1, in step 2 and step 3 of Comparative Example 1, sodium carboxymethyl cellulose and sodium hydroxide were not added to adjust the pH during the decoction extraction, the crude extraction rate and net extraction rate of the obtained tea pigment were reduced, the total content of tea pigment was reduced, and the caffeine content did not meet the pharmacopoeia standard.

[0101] In combination with Example 1 and Comparative Example 2, in step 2 and step 3 of Comparative Example 2, sodium hydroxide was added during the decoction extraction to adjust the pH to 10, the net extraction rate of the obtained tea pigment was reduced, the total content of the tea pigment was reduced, and the caffeine content did not meet the pharmacopoeia standard.

[0102] Combining Example 1 and Comparative Example 3, Comparative Example 3 does not involve the desalination process of Step 6 and Step 8. The sodium chloride content in the obtained sample reaches 15.77%, the crude extraction rate of tea pigments is high, the actual net extraction rate is not high, and the total content of tea pigments is reduced.

[0103] Combining Example 1 and Comparative Example 4, Comparative Example 4 does not involve the desalting process in step 6, and the sodium chloride content in the obtained sample reaches 6.24%, indicating that the desalting effect of column chromatography alone is not good.

[0104] In combination with Example 1 and Comparative Example 5, in the desalination process in step 6 of Comparative Example 5, no acid was added to adjust the pH, the sodium chloride content in the obtained sample increased, and the crude extraction rate and net extraction rate of tea pigment decreased significantly.

[0105] In combination with Example 1 and Comparative Example 6, in the desalination process in step 6 of Comparative Example 6, the ethanol concentration used was 90%, and the crude extraction rate and the net extraction rate also decreased significantly, and the gallic acid content did not meet the pharmacopoeia standard;

[0106] In combination with Example 1 and Comparative Example 7, in step 8 of Comparative Example 7, a faster elution rate was used during the elution process, resulting in poor desalination effect and the gallic acid content failing to meet the pharmacopoeia standard;

[0107] In combination with Example 1 and Comparative Example 8, the filler used in step 8 of Comparative Example 8 is G-25, and the desalination effect is not good.

[0108] The raw materials applicable to the tea pigment extraction method provided in this application include green tea, black tea and oolong tea, with green tea being the preferred raw material. From the appearance properties, the tea pigment prepared in Example 1 is a brown powder with a fragrant smell and a salty and astringent taste. The appearance of the tea pigment product prepared in Example 1 is as follows: Figure 2 shown.

[0109] In summary, the method for extracting and preparing tea pigments from tea leaves provided in the present application optimizes the decoction process, uses sodium carboxymethyl cellulose on the tea residue after the first water extraction and then performs a secondary extraction under alkaline conditions to effectively improve the tea pigment extraction rate, adopts alcohol extraction under different ethanol gradients and cooperates with acidic conditions to further improve the tea pigment extraction rate while utilizing the solubility difference of sodium chloride to precipitate salt, and finally uses a dextran chromatography column for further desalination. At the same time, various process parameters are optimized, which effectively improves the extraction yield of tea pigments and reduces the salt content of tea pigment fluid extract, effectively reduces the corrosion problem of spray drying equipment, and finally the prepared tea pigment has a low salt content. The caffeine, gallic acid, pH and moisture of the prepared tea pigment product are better than the pharmacopoeia standards for tea pigments, and the prepared tea pigments are of high quality.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them. Although the present application has been described in detail with reference to preferred embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present application can still be modified or some technical features can be replaced by equivalents, which should all be included in the scope of the technical solutions requested for protection in this application.

Claims

1. A method for extracting and preparing tea pigment from tea leaves, characterized in that: The following steps are involved: S1, adding tea raw materials to water for decoction extraction, and filtering the decoction to obtain an extract; S2, adjusting the pH of the extract to 8-9 with alkali, and concentrating in vacuo at 50-75°C to obtain a concentrate, wherein the concentrate is 0.9-1.1 times the weight of the tea raw material; S3. Add ethanol to the concentrated solution until the alcohol content is 40% v / v to 70% v / v, adjust the pH to 2 to 3, perform reflux extraction for 0.5 h to 2 h, and filter to obtain the reflux solution; S4. Add ethanol to the reflux solution until the alcohol content is 75% v / v to 85% v / v, adjust the pH to 3 to 4, reflux and extract for 0.5 h to 2 h, filter and remove salt to obtain a desalted solution; S5. Adjust the pH of the desalted solution to 9-11 with alkali, let it settle for 4-18 hours, remove the supernatant, stir and heat the precipitate to dealcoholize, and then add purified water to dissolve it to prepare a tea pigment solution. Desalt the tea pigment solution through a dextran gel chromatography column, elute with purified water, and concentrate the eluate to a fluid extract with a relative density of 1.05-1.

12. The fluid extract is dried to obtain the tea pigment. The decoction extraction in S1 includes the following steps: S11, adding 5 to 10 times the amount of water to the tea raw material for a first decoction extraction, and filtering the decoction to obtain an extract I and a filter residue I; S12, adding sodium carboxymethyl cellulose to the filter residue I, and then adding water 2.5 to 7.5 times the weight of the tea raw material, and adjusting the pH to 8 to 9 for a second decoction extraction, and filtering the decoction to obtain an extract II and a filter residue II; S13, adding sodium carboxymethyl cellulose to the filter residue II, and then adding 1.5 to 5 times the weight of water of the tea raw material, and adjusting the pH to 8 to 9 for a third decoction extraction, and filtering the decoction to obtain the extract III and the filter residue III; S14, combining the extract I, the extract II and the extract III to obtain an extract.

2. The method for extracting tea pigment from tea leaves according to claim 1, wherein: The amount of sodium carboxymethyl cellulose used in S12 is 0.5% to 2% by weight of the tea raw material; the amount of sodium carboxymethyl cellulose used in S13 is 2% to 5% by weight of the tea raw material.

3. The method for extracting tea pigment from tea leaves according to claim 1, wherein: In S5, purified water is added to dissolve the tea pigment to prepare a tea pigment solution, and the mass ratio of the tea pigment to the purified water is 1:15-20.

4. The method for extracting tea pigment from tea leaves according to claim 1, wherein: In S5, the drying is performed by vacuum drying or spray drying, and the air inlet temperature used in the spray drying is 260-330°C, and the air outlet temperature is 80-130°C.

5. The method for extracting tea pigment from tea leaves according to claim 1, wherein: The filler used in the dextran gel chromatography column in S5 is Sephadex G-15, and the height-to-diameter ratio of the dextran gel chromatography column is 5:1 to 10:

1.

6. The method for extracting tea pigment from tea leaves according to claim 1, wherein: The flow rate of the tea pigment solution in S5 passing through the dextran gel chromatography column is 2 bv / h to 4 bv / h.

7. The method for extracting tea pigment from tea leaves according to claim 1, characterized in that: The flow rate of purified water for elution in S5 is 3 bv / h to 6 bv / h.

8. The method for extracting tea pigment from tea leaves according to claim 1, wherein: The acidic reagent used to adjust the pH is dilute hydrochloric acid with a concentration of 5% to 20%.

9. The method for extracting and preparing tea pigment from tea leaves according to claim 1, characterized in that: The alkaline reagent used to adjust the pH is selected from at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate, and the concentration of the alkaline reagent is 10% to 30%.

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