Method for extracting and preparing tea pigment from tea leaves

Abstract

The invention relates to the technical field of tea leaf processing, in particular to a method for extracting and preparing tea pigment from tea leaves, which comprises the following steps: adding a tea leaf raw material into water, decocting and extracting to obtain a decoction, adjusting the pH value of the decoction with alkali, and concentrating in vacuum to obtain a concentrated solution; adding ethanol into the concentrated solution, performing reflux extraction after acid adjustment, and filtering to obtain reflux liquid; adding ethanol into the reflux liquid to increase the alcohol content, adjusting the pH value, and filtering and desalting after reflux to obtain a desalted liquid; the preparation method comprises the following steps: adjusting the pH value of a desalted solution by using alkali, standing and precipitating, removing supernate, stirring and heating precipitates for dealcoholization, adding purified water for dissolving to prepare a tea pigment solution, desalting the tea pigment solution through a sephadex chromatographic column, concentrating eluent into fluid extract, and drying to obtain the tea pigment, and the prepared tea pigment has the advantages of high extraction rate, good quality and low cost. And the tea pigment accords with and is superior to the tea pigment pharmacopeia standard.

Description

Technical Field

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

[0002] Tea pigments are a mixture of water-soluble pigments formed by the continuous oxidation and polymerization of polyphenolic compounds represented by catechins in tea leaves. The main components of tea pigments are theaflavins (TFs), thearubigins (TRs), and theabrownins (TBs). Tea pigments can be used in the fields of food and medicine. Tea pigment capsules have the effects of clearing the head and eyes, resolving phlegm and reducing fat, and are used for symptoms such as dizziness of the head and eyes, chest tightness and chest pain, hyperlipidemia, coronary heart disease, angina pectoris, and cerebral infarction caused by the intermingling of phlegm and stasis.

[0003] The production method of tea pigments disclosed in the prior invention patent CN1035660C applied by Jiangxi Green Industry (Group) Company takes tea leaves as raw materials and is prepared by decoction extraction, alkalization concentration, ethanol acidification reflux, and alkalization precipitation. The tea pigments prepared by this method are obtained from tea leaves, are natural and healthy, have high safety in use, good quality of tea pigments, and high market acceptance. However, it has been found in industrial applications that the technical solution of CN1035660C still has the following defects: the tea residues discarded during extraction contain more tea polyphenols that are not completely oxidized and tea pigments that are not extracted, resulting in waste of raw materials and low extraction rate. At the same time, the tea pigments prepared have a high salt content and strong corrosiveness to production equipment, especially high-temperature drying equipment. In view of this, this application aims to improve on the traditional method to obtain high-quality tea pigments while increasing the extraction rate of tea pigments and reducing the salt content. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose 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 salt content of tea pigments while ensuring the quality of tea pigments.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A method for extracting and preparing tea pigments from tea leaves provided by the present invention includes the following steps: S1. Add tea leaf raw materials to water for decoction extraction, and filter the decoction to obtain an extract; S2. Adjust the pH of the extract to 8 - 9 with an alkali, and perform vacuum concentration at 50°C - 75°C to obtain a concentrated solution, and the concentrated solution is 0.9 times - 1.1 times the weight of the tea leaf raw materials; S3. Add ethanol to the concentrated solution to make the alcohol content 40% v / v - 70% v / v, adjust the pH to 2 - 3, and perform reflux extraction for 0.5 h - 2 h, and filter to obtain a reflux solution; S4. Add ethanol to the reflux liquid until the alcohol content is 75% v / v - 85% v / v, adjust the pH to 3 - 4, reflux and extract for 0.5 h - 2 h, and filter to remove salts to obtain a desalted solution; S5. Adjust the pH of the desalted solution to 9 - 11 with an alkali, let it stand and precipitate for 4 h - 18 h, remove the supernatant, stir and heat up the precipitate to remove alcohol, then dissolve it in purified water to prepare a tea pigment solution. The tea pigment solution is desalted through a Sephadex gel chromatography column, eluted with purified water, and the eluate is concentrated to a fluid extract with a relative density of 1.05 - 1.12. The fluid extract is dried to obtain tea pigment.

[0006] The above technical solution provided by this application reduces the amount of ethanol used in the subsequent alcohol extraction and salting - out processes by concentrating the extraction solution to approximately the weight of the tea raw materials. By adjusting the pH to 2 - 3 for extraction and purification at an alcohol content of 40% v / v - 70% v / v, it promotes the conversion of tea pigment and increases the tea pigment content. By adjusting the pH to 3 - 4 for extraction and purification at an alcohol content of 75% v / v - 85% v / v, it promotes the conversion of tea pigment to increase the tea pigment content and promotes the precipitation of salts. Finally, it is further desalted through a Sephadex gel chromatography column, and various process parameters are optimized, effectively improving the extraction yield of tea pigment, reducing the salt content rate of the tea pigment fluid extract, effectively alleviating the corrosion problem of drying equipment, and the finally prepared tea pigment has a low salt content. The prepared tea pigment product meets and is superior to the tea pigment pharmacopoeia standards in terms of caffeine, gallic acid, pH, and moisture, and the prepared tea pigment has high quality.

[0007] Furthermore, the decoction extraction in S1 includes the following steps: S11. Add the tea raw materials to 5 - 10 times the amount of water for the first decoction extraction, and filter the decoction to obtain extract I and residue I; S12. Add sodium carboxymethylcellulose to residue I, then add 2.5 - 7.5 times the weight of the tea raw materials in water, and adjust the pH to 8 - 9 for the second decoction extraction. Filter the decoction to obtain extract II and residue II; S13. Add sodium carboxymethylcellulose to residue II, then add 1.5 - 5 times the weight of the tea raw materials in water, and adjust the pH to 8 - 9 for the third decoction extraction. Filter the decoction to obtain extract III and residue III; S14. Combine extract I, extract II, and extract III to obtain an extract.

[0008] Traditional methods adopt a three - time water extraction process, which requires a relatively high proportion of water as the extraction solvent and has a low extraction rate. In this application, by optimizing the decoction process, after the first - time water extraction of tea residues, sodium carboxymethylcellulose is used and then secondary extraction is carried out under alkaline conditions. Sodium carboxymethylcellulose can form hydrogen bonds with tea pigments and their precursor substance tea polyphenols in tea residues under alkaline conditions to promote the dissolution of tea pigments / precursor substances and improve the extraction rate of caffeine. After the interaction between the combined sodium carboxymethylcellulose and tea polyphenols / tea pigments is destroyed under acidic conditions, tea polyphenols / tea pigments enter the solution, and sodium carboxymethylcellulose precipitates under the action of high - concentration alcohol to achieve separation, with almost no residue. Moreover, sodium carboxymethylcellulose is a common additive in food and medicine, and even trace residues are harmless to the human body.

[0009] Furthermore, in S12, the usage amount of sodium carboxymethylcellulose is 0.5% - 2% of the weight of tea raw materials; in S13, the usage amount of sodium carboxymethylcellulose is 2% - 5% of the weight of tea raw materials.

[0010] Furthermore, in S5, purified water is added to dissolve and prepare a tea pigment solution, and the mass ratio of tea pigment to purified water is 1:15 - 20. The tea pigment solution prepared with the above - mentioned ratio of tea pigment to purified water can be better used for subsequent column chromatography. If the tea pigment concentration is too high or too low, it will have an adverse impact on the column chromatography process, resulting in sample precipitation or low efficiency.

[0011] Furthermore, in S5, the drying is carried out by vacuum drying or spray drying. The inlet air temperature for spray drying is 260 - 330°C, and the outlet air temperature is 80°C - 130°C.

[0012] Furthermore, in S5, the filler used in the Sephadex gel chromatography column is Sephadex G - 15, and the height - to - diameter ratio of the Sephadex gel chromatography column is 5:1 - 10:1.

[0013] Furthermore, in S5, the flow rate of the tea pigment solution through the Sephadex gel chromatography column is 2bv / h - 4bv / h.

[0014] Furthermore, in S5, the flow rate of purified water for elution is 3bv / h - 6bv / h.

[0015] Furthermore, the acidic reagent used to adjust the pH is dilute hydrochloric acid with a concentration of 5% - 20%.

[0016] Furthermore, 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% - 30%.

[0017] In order to reduce solvent costs and resource waste, this application also includes the recovery of the generated ethanol waste liquid. The recovery process can be carried out using conventional recovery processes, such as distillation and rectification operations. The recovered ethanol can be reused for the extraction of tea pigments again, avoiding resource waste. The residue after extracting tea pigments in this application is rich in components such as polysaccharides and proteins, and can be used as feed raw materials after drying, improving the added value of products.

[0018] 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 by this application optimizes the decoction process. After the tea residue after the first water extraction is treated with sodium carboxymethylcellulose and then subjected to secondary extraction under alkaline conditions, the extraction rate of tea pigments is effectively improved. By performing alcohol extraction under different ethanol gradients and in combination with acidic conditions, while further increasing the extraction rate of tea pigments, salting out is carried out using the solubility difference of sodium chloride. Finally, further desalting is carried out through a Sephadex gel chromatography column, and various process parameters are optimized, 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 spray drying equipment. Finally, the prepared tea pigment has a low salt content, and the prepared tea pigment product is superior to the tea pigment pharmacopoeia standard in terms of caffeine, gallic acid, pH, and moisture. The prepared tea pigment has high quality. Brief Description of the Drawings

[0019] Figure 1 It is the process flow chart for extracting and preparing tea pigments from tea leaves in the embodiment of the present invention; Figure 2 It is the appearance of the tea pigment sample prepared in the embodiment. Detailed Embodiments

[0020] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0021] Unless otherwise specified, the methods are all conventional methods, and unless otherwise specified, the raw materials can all be obtained from public commercial channels. Figure 1 It is the process flow chart for extracting and preparing tea pigments from tea leaves in the embodiment of the present invention. The following further describes the solution of this application in conjunction with the embodiments and the drawings: Example 1 This example provides a method for extracting and preparing tea pigments from tea leaves, including the following steps: 1. Add 600 g of tea leaf raw materials (green tea) to 7.5 times the amount of purified water for the first decoction. After boiling, keep it slightly boiling for 1 h. The decoction liquid is filtered to obtain extract I and residue I.

[0022] 2. Add sodium carboxymethylcellulose accounting for 1% of the weight of the tea raw materials to the filter residue I, then add purified water with a weight 5 times that of the tea raw materials, and use 20% sodium hydroxide solution to adjust the pH to 9 for the second decoction extraction. Keep it slightly boiling for 1 h after boiling, and filter the decoction to obtain extract II and filter residue II.

[0023] 3. Add sodium carboxymethylcellulose accounting for 3% of the weight of the tea raw materials to the filter residue II, then add purified water with a weight 2.5 times that of the tea raw materials, and use 20% sodium hydroxide solution to adjust the pH to 9 for the third decoction extraction. Keep it slightly boiling for 1 h after boiling, and filter the decoction to obtain extract III and filter residue III.

[0024] 4. Combine extract I, extract II and extract III to obtain the decoction, adjust the pH of the decoction to 9, and concentrate it under vacuum at 60 °C until the concentrated solution is equal to the weight of the tea raw materials.

[0025] 5. Add ethanol to the concentrated solution until the alcohol content is 55% v / v, adjust the acidity to pH 2.5 with 10% dilute hydrochloric acid and reflux for 1 hour, cool to 45 °C and filter to obtain the reflux solution.

[0026] 6. Add ethanol to the reflux solution until the alcohol content is 80% v / v, adjust the pH to 3.5 with 10% dilute hydrochloric acid and reflux for 1 hour, cool to 45 °C and filter to remove salts to obtain the desalted solution.

[0027] 7. Adjust the pH of the desalted solution to 10.5 with 20% sodium hydroxide solution, let it stand for precipitation for 6 h, remove the supernatant, stir and heat up the precipitate to remove alcohol, then add purified water to dissolve and prepare an aqueous solution of tea pigment, and the ratio of tea pigment to purified water is 1:18.

[0028] 8. Swell Sephadex G-15 packing material with purified water and load it into a column (diameter 10 cm × height 50 cm). Load the tea pigment solution onto the Sephadex gel chromatography column, control the flow rate at 3 bv / h, elute with purified water at a flow rate of 5 bv / h, monitor the elution process in real time with ultraviolet light, and collect the tea pigment eluate.

[0029] 9. Vacuum-concentrate the tea pigment eluate at 60 °C to a flowing extract with a relative density of 1.08. Spray-dry the effluent, with an inlet air temperature of 300 °C and an outlet air temperature of 115 °C, and collect the dried product to obtain the tea pigment.

[0030] Example 2 This example provides a method for extracting and preparing tea pigment from tea, including the following steps: 1. Add 600 g of tea raw materials (black tea) to 7.5 times the amount of purified water for the first decoction. Keep it slightly boiling for 1 h after boiling, and filter the decoction to obtain extract I and filter residue I.

[0031] 2. Add sodium carboxymethylcellulose accounting for 0.5% of the weight of the tea raw materials to the filter residue I, then add purified water with a weight 5 times that of the tea raw materials, and adjust the pH to 8 with 20% sodium hydroxide solution for the second decoction extraction. Keep it slightly boiling for 1 h after boiling, and filter the decoction to obtain the extract II and the filter residue II.

[0032] 3. Add sodium carboxymethylcellulose accounting for 2% of the weight of the tea raw materials to the filter residue II, then add purified water with a weight 2.5 times that of the tea raw materials, and adjust the pH to 8 with 20% sodium hydroxide solution for the third decoction extraction. Keep it slightly boiling for 1 h after boiling, and filter the decoction to obtain the extract III and the filter residue III.

[0033] 4. Combine the extract I, extract II and extract III to obtain the decoction, adjust the pH of the decoction to 8, and concentrate it in vacuo at 60 °C until the concentrated solution is equal to the weight of the tea raw materials.

[0034] 5. Add ethanol to the concentrated solution until the alcohol content is 50% v / v, adjust the acidity to pH 2 with 10% dilute hydrochloric acid, reflux and extract for 1 h, cool to 45 °C and filter to obtain the reflux solution.

[0035] 6. Add ethanol to the reflux solution until the alcohol content is 75% v / v, adjust the pH to 3 with 10% dilute hydrochloric acid, reflux and extract for 1 h, cool to 45 °C and filter to remove salts to obtain the desalted solution.

[0036] 7. Adjust the pH of the desalted solution to 10.5 with 20% sodium hydroxide solution, let it stand and precipitate for 6 h, remove the supernatant, stir and heat up the precipitate to remove alcohol, then add purified water to dissolve it to prepare an aqueous solution of tea pigment, and the ratio of tea pigment to purified water is 1:18.

[0037] 8. Swell Sephadex G-15 packing material with purified water and then pack it into a column (diameter 10 cm × height 50 cm). Load the tea pigment solution onto the dextran gel chromatography column, control the flow rate at 3 bv / h, elute with purified water at a flow rate of 5 bv / h, monitor the elution process in real time with ultraviolet light, and collect the tea pigment eluate.

[0038] 9. Vacuum concentrate the tea pigment eluate at 60 °C to a fluid extract with a relative density of 1.08. Spray dry the effluent, with the inlet air temperature at 300 °C and the outlet air temperature at 115 °C, and collect the dried product to obtain the tea pigment.

[0039] Example 3 This example provides a method for extracting and preparing tea pigment from tea, including the following steps: 1. Add 600 g of tea raw materials (oolong tea) to 7.5 times the amount of purified water for the first decoction. Keep it slightly boiling for 1 h after boiling, and filter the decoction to obtain the extract I and the filter residue I.

[0040] 2. Add sodium carboxymethylcellulose accounting for 0.5% of the weight of the tea raw materials to the filter residue I, then add purified water with a weight 5 times that of the tea raw materials, and adjust the pH to 8 with 20% sodium hydroxide solution for the second decoction extraction. Keep it slightly boiling for 1 h after boiling, and filter the decoction to obtain extract II and filter residue II.

[0041] 3. Add sodium carboxymethylcellulose accounting for 2% of the weight of the tea raw materials to the filter residue II, then add purified water with a weight 2.5 times that of the tea raw materials, and adjust the pH to 9 with 20% sodium hydroxide solution for the third decoction extraction. Keep it slightly boiling for 1 h after boiling, and filter the decoction to obtain extract III and filter residue III.

[0042] 4. Combine extract I, extract II and extract III to obtain the decoction, adjust the pH of the decoction to 9, and concentrate it in vacuo at 60 °C until the concentrated solution reaches the weight of the tea raw materials.

[0043] 5. Add ethanol to the concentrated solution until the alcohol content is 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 solution.

[0044] 6. Add ethanol to the reflux solution until the alcohol content is 85% v / v, adjust the pH to 3.5 with 10% dilute hydrochloric acid, reflux and extract for 1 hour, cool to 45 °C and filter to remove salts to obtain the desalted solution.

[0045] 7. Adjust the pH of the desalted solution to 10.5 with 20% sodium hydroxide solution, let it stand and precipitate for 6 h, remove the supernatant, stir and heat up the precipitate to remove alcohol, then add purified water to dissolve it to prepare an aqueous solution of tea pigment, and the ratio of tea pigment to purified water is 1:18.

[0046] 8. Swell Sephadex G-15 packing material with purified water and then pack it into a column (diameter 10 cm × height 50 cm). Load the tea pigment solution onto the Sephadex gel chromatography column, control the flow rate at 3 bv / h, elute with purified water at a flow rate of 5 bv / h, monitor the elution process in real time with ultraviolet light, and collect the tea pigment eluate.

[0047] 9. Vacuum-concentrate the tea pigment eluate at 60 °C to a flow extract with a relative density of 1.08, spray-dry the effluent, with the inlet air temperature at 300 °C and the outlet air temperature at 115 °C, and collect the dried product to obtain the tea pigment.

[0048] Comparative Example 1 According to the method of Example 1, the difference is that the decoction methods in Steps 1 to 3 are as follows: 1. Add 600 g of tea raw materials (green tea) to 7.5 times the amount of purified water for the first decoction, keep it slightly boiling for 1 h after boiling, and filter the decoction to obtain extract I and filter residue I.

[0049] 2. Add purified water with a weight 5 times that of the tea raw materials to the filter residue I for the second decoction. Keep it slightly boiling for 1 h after boiling. Filter the decoction to obtain extract II and filter residue II.

[0050] 3. Add purified water with a weight 2.5 times that of the tea raw materials to the filter residue II for the second decoction. Keep it slightly boiling for 1 h after boiling. Filter the decoction to obtain extract III and filter residue III.

[0051] Comparative Example 2 According to the method of Example 1, the difference is that the decoction methods in Steps 1 to 3 are as follows: 1. Add 600 g of tea raw materials (green tea) to 7.5 times the amount of purified water for the first decoction. Keep it slightly boiling for 1 h after boiling. Filter the decoction to obtain extract I and filter residue I.

[0052] 2. Add sodium carboxymethylcellulose with a weight 1% of the tea raw materials to the filter residue I, then add purified water with a weight 5 times that of the tea raw materials, and adjust the pH to 10 with 20% sodium hydroxide solution for the second decoction extraction. Keep it slightly boiling for 1 h after boiling. Filter the decoction to obtain extract II and filter residue II.

[0053] 3. Add sodium carboxymethylcellulose with a weight 3% of the tea raw materials to the filter residue II, then add purified water with a weight 2.5 times that of the tea raw materials, and adjust the pH to 10 with 20% sodium hydroxide solution for the third decoction extraction. Keep it slightly boiling for 1 h after boiling. Filter the decoction to obtain extract III and filter residue III.

[0054] Comparative Example 3 This comparative example provides a method for extracting and preparing tea pigments from tea, including the following steps: 1. Add 600 g of tea raw materials (green tea) to 7.5 times the amount of purified water for the first decoction. Keep it slightly boiling for 1 h after boiling. Filter the decoction to obtain extract I and filter residue I.

[0055] 2. Add sodium carboxymethylcellulose with a weight 1% of the tea raw materials to the filter residue I, then add purified water with a weight 5 times that of the tea raw materials, and adjust the pH to 9 with 20% sodium hydroxide solution for the second decoction extraction. Keep it slightly boiling for 1 h after boiling. Filter the decoction to obtain extract II and filter residue II.

[0056] 3. Add sodium carboxymethylcellulose with a weight 3% of the tea raw materials to the filter residue II, then add purified water with a weight 2.5 times that of the tea raw materials, and adjust the pH to 9 with 20% sodium hydroxide solution for the third decoction extraction. Keep it slightly boiling for 1 h after boiling. Filter the decoction to obtain extract III and filter residue III.

[0057] 4. Combine Extract I, Extract II, and Extract III to obtain a decoction, adjust the pH of the decoction to 9, and concentrate it under vacuum at 60 °C until the concentrated solution weighs the same as the tea raw material.

[0058] 5. Add ethanol to the concentrated solution to a content of 55% v / v, adjust the acidity to pH 2.5 with 10% dilute hydrochloric acid, reflux for 1 hour, cool to 45 °C, and filter to obtain a reflux solution.

[0059] 6. Adjust the pH of the reflux solution to 10.5 with 20% sodium hydroxide solution, let it stand and precipitate for 6 h, remove the supernatant, stir and heat the precipitate to remove alcohol, then dissolve it in purified water to prepare a fluid extract with a relative density of 1.08. The effluent is spray-dried, with an inlet air temperature of 300 °C and an outlet air temperature of 115 °C. Collect the dried product to obtain tea pigment.

[0060] Comparative Example 4 According to the method of Example 1, the difference is that the desalting process in step 6 is not involved, and the reflux solution obtained in step 5 is directly fed into step 7 for alkali adjustment.

[0061] Comparative Example 5 According to the method of Example 1, the difference is that the method in step 6 is as follows: Add ethanol to the reflux solution to a content of 80% v / v, reflux for 1 hour, cool to 45 °C, and filter to remove salt to obtain a desalted solution. Comparative Example 6 According to the method of Example 1, the difference is that the method in step 6 is as follows: Add ethanol to the reflux solution to a content of 90% v / v, adjust the pH to 3.5 with 10% dilute hydrochloric acid, reflux for 1 hour, cool to 45 °C, and filter to remove salt to obtain a desalted solution.

[0062] Comparative Example 7 According to the method of Example 1, the difference is that the method in step 8 is as follows: Swell Sephadex G-15 packing material with purified water and load it into a column (diameter 10 cm × height 50 cm). Load the tea pigment solution onto the Sephadex gel chromatography column, control the flow rate at 3 bv / h, elute with purified water at a flow rate of 8 bv / h, monitor the elution process in real time with ultraviolet light, and collect the tea pigment eluate.

[0063] Comparative Example 8 According to the method of Example 1, the difference is that the method in step 8 is as follows: Swell Sephadex G-25 packing material with purified water and load it into a column (diameter 10 cm × height 50 cm). Load the tea pigment solution onto the Sephadex gel chromatography column, control the flow rate at 3 bv / h, elute with purified water at a flow rate of 5 bv / h, monitor the elution process in real time with ultraviolet light, and collect the tea pigment eluate.

[0064] Test Example The prepared tea pigment samples of the examples and comparative examples were measured. The contents of theabrownin, thearubigins and theaflavins were determined by spectrophotometry, the NaCl content was determined by potentiometric titration, the contents of caffeine and gallic acid were determined by HPLC, the moisture content was determined by oven drying to constant weight, and the pH was determined by a pH meter. The total yield of the preparation of tea pigments in the examples and comparative examples was statistically analyzed. The crude extraction rate of tea pigments = the weight of the tea pigment sample obtained by spray drying / the amount of tea leaves input × 100%, and the net extraction rate of tea pigments = the weight of the tea pigment sample obtained by spray drying × (the content of theabrownin + the content of thearubigins + the content of theaflavins) / the amount of tea leaves input × 100%. The results are shown in Table 1 below: Table 1: Results of the determination of tea pigments

[0065] Continued Table 1: Results of the determination of tea pigments

[0066] Combined with Example 1 and Comparative Example 1, in steps 2 and 3 of Comparative Example 1 during decoction extraction, sodium carboxymethylcellulose and sodium hydroxide were not added to adjust the pH. As a result, the crude extraction rate and net extraction rate of the obtained tea pigments decreased, and the total content of tea pigments decreased, and the caffeine content did not meet the pharmacopoeia standard.

[0067] Combined with Example 1 and Comparative Example 2, in steps 2 and 3 of Comparative Example 2 during decoction extraction, sodium hydroxide was added to adjust the pH to 10. As a result, the net extraction rate of the obtained tea pigments decreased, and the total content of tea pigments decreased, and the caffeine content did not meet the pharmacopoeia standard.

[0068] Combined with Example 1 and Comparative Example 3, the desalting process of steps 6 and 8 was not involved in Comparative Example 3. The NaCl content in the obtained sample reached 15.77%. The crude extraction rate of tea pigments was relatively high, but the actual net extraction rate was not high, and the total content of tea pigments decreased.

[0069] Combined with Example 1 and Comparative Example 4, the desalting process of step 6 was not involved in Comparative Example 4. The NaCl content in the obtained sample reached 6.24%, indicating that the desalting effect was not good only by column chromatography.

[0070] Combined with Example 1 and Comparative Example 5, during the desalting process of step 6 in Comparative Example 5, acid was not added to adjust the pH. As a result, the NaCl content in the obtained sample increased, and the crude extraction rate and net extraction rate of tea pigments decreased significantly.

[0071] Combined with Example 1 and Comparative Example 6, during the desalting process of step 6 in Comparative Example 6, the ethanol concentration used was 90%. The crude extraction rate and net extraction rate also decreased significantly, and the gallic acid content did not meet the pharmacopoeia standard; Combined with Example 1 and Comparative Example 7, in step 8 of Comparative Example 7 during the elution process, a relatively fast elution rate was used, and the desalting effect was not good, and the gallic acid content did not meet the pharmacopoeia standard; Combined with Example 1 and Comparative Example 8, the filler used in Step 8 of Comparative Example 8 was G-25, and the desalination effect was not good.

[0072] The raw materials applicable to the tea pigment extraction method provided in this application include green tea, black tea, and oolong tea. Green tea is preferably used as the raw material. From the perspective of appearance characteristics, the tea pigment prepared in Example 1 is a brownish powder, with a fragrant smell, salty and astringent taste. The appearance of the tea pigment product prepared in Example 1 is as Figure 2 shown.

[0073] In summary, for the method for extracting and preparing tea pigment from tea provided in this application, by optimizing the decocting process, after using sodium carboxymethylcellulose on the tea residue after the first water extraction and then performing secondary extraction under alkaline conditions, the extraction rate of tea pigment is effectively improved. By performing alcohol extraction under different ethanol gradients and in combination with acidic conditions, while further increasing the extraction rate of tea pigment, salting out is carried out by utilizing the solubility difference of sodium chloride. Finally, further desalination is carried out through a dextran chromatography column, and at the same time, various process parameters are optimized, effectively improving the extraction yield of tea pigment and reducing the salt content of the tea pigment fluid extract, effectively alleviating the corrosion problem of the spray drying equipment. The finally prepared tea pigment has a low salt content, and the prepared tea pigment product is superior to the tea pigment pharmacopoeia standard in terms of caffeine, gallic acid, pH, and moisture. The quality of the prepared tea pigment is relatively high.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them; although this application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that it is still possible to modify the specific implementation manners of this application or perform equivalent replacements for some technical features, and they should all be covered within the scope of the technical solutions claimed in this application.

Claims

1. A method for extracting and preparing tea pigment from tea leaves, characterized in that, It includes the following steps: S1. Add tea raw materials to water for decoction extraction, and filter the decoction to obtain the extract; S2. Adjust the pH of the extract to 8 - 9 with an alkali, and conduct vacuum concentration at 50°C - 75°C to obtain the concentrated solution, and the concentrated solution is 0.9 - 1.1 times the weight of the tea raw materials; S3. Add ethanol to the concentrated solution until the alcohol content is 40% v / v - 70% v / v, adjust the pH to 2 - 3, and conduct reflux extraction for 0.5 h - 2 h, then filter to obtain the reflux solution; S4. Add ethanol to the reflux solution until the alcohol content is 75% v / v - 85% v / v, adjust the pH to 3 - 4, conduct reflux extraction for 0.5 h - 2 h, and filter to remove salts to obtain the desalted solution; S5. Adjust the pH of the desalted solution to 9 - 11 with an alkali, let it stand for precipitation for 4 h - 18 h, remove the supernatant, stir and heat up the precipitate to remove alcohol, then dissolve it in purified water to prepare a tea pigment solution. The tea pigment solution is desalted through a Sephadex G - 15 gel chromatography column, eluted with purified water, and the eluate is concentrated to a flow extract with a relative density of 1.05 - 1.12, and the flow extract is dried to obtain the tea pigment.

2. The method for extracting and preparing tea pigment from tea leaves according to claim 1, characterized in that, The decoction extraction in S1 includes the following steps: S11. Add tea raw materials to 5 - 10 times the amount of water for the first decoction extraction, and filter the decoction to obtain extract I and residue I; S12. Add sodium carboxymethylcellulose to residue I, then add 2.5 - 7.5 times the weight of the tea raw materials of water, and adjust the pH to 8 - 9 for the second decoction extraction, and filter the decoction to obtain extract II and residue II; S13. Add sodium carboxymethylcellulose to residue II, then add 1.5 - 5 times the weight of the tea raw materials of water, and adjust the pH to 8 - 9 for the third decoction extraction, and filter the decoction to obtain extract III and residue III; S14. Combine extract I, extract II and extract III to obtain the extract.

3. A method for extracting and preparing tea pigment from tea leaves according to claim 2, characterized in that, The usage amount of sodium carboxymethylcellulose in S12 is 0.5% - 2% of the weight of the tea raw materials; the usage amount of sodium carboxymethylcellulose in S13 is 2% - 5% of the weight of the tea raw materials.

4. A method for extracting and preparing tea pigment from tea leaves according to claim 1, characterized in that, In S5, when preparing the tea pigment solution by dissolving it in purified water, the mass ratio of the tea pigment to the purified water is 1:15 - 20.

5. A method for extracting and preparing tea pigment from tea leaves according to claim 1, characterized in that, In S5, the drying is carried out by vacuum drying or spray drying. The inlet air temperature for the spray drying is 260 - 330°C, and the outlet air temperature is 80°C - 130°C.

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

1.

7. A method for extracting and preparing tea pigment from tea leaves according to claim 1, characterized in that, The flow rate of the tea pigment solution through the Sephadex G - 15 gel chromatography column in S5 is 2 bv / h - 4 bv / h.

8. A method for extracting and preparing tea pigment from tea leaves according to claim 1, characterized in that, The flow rate of the purified water for elution in S5 is 3 bv / h - 6 bv / h.

9. A method for extracting and preparing tea pigment from tea leaves according to claim 1, characterized in that, The acidic reagent used to adjust the pH is dilute hydrochloric acid with a concentration of 5% - 20%.

10. A 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% - 30%.

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