Preparation method for extracting caffeine

Abstract

The invention discloses a preparation method for extracting caffeine, relates to the technical field of natural product extraction, and aims to solve the problems of low efficiency, more impurities, solvent residues, environmental pollution and the like of a traditional extraction method. The method comprises the following steps: mixing tea leaf powder with purified water, adjusting the pH value, adding a compound enzyme preparation for enzymolysis, and carrying out inactivation, centrifugation and drying to obtain a pretreated raw material; mixing the composite extraction solvent with the pretreated raw material, performing ultrasonic extraction, and centrifuging to obtain a crude extract; adding petroleum ether into the crude extract to extract and remove impurities, and adding an anti-solvent into subnatant to separate out a caffeine crude product; and recrystallizing and purifying the crude product, and drying to obtain a caffeine finished product. Wherein the compound enzyme preparation contains enzyme and non-enzyme auxiliaries, and the compound extraction solvent is prepared by a specific process, so that the whole process is high in extraction efficiency, high in finished product purity and less in solvent residue, conforms to the green production concept, and has good large-scale application potential.

Description

Technical Field

[0001] This invention relates to the field of natural product extraction technology, specifically to a method for preparing caffeine extract. Background Technology

[0002] Caffeine, as an important natural active substance, is widely used in food, medicine, and beverage industries. Its main extraction raw materials are natural products such as tea leaves and coffee beans. Among these, tea leaves are the preferred raw material for caffeine extraction due to their abundant resources and low cost. Currently, the extraction technology of caffeine from tea leaves has been developed to a certain extent. Traditional methods mainly include water extraction and organic solvent extraction. Water extraction is widely used in small-scale production due to its simple operation and low cost, while organic solvent extraction uses solvents such as chloroform and petroleum ether to improve extraction efficiency and is often used in pilot-scale and early-stage industrial production.

[0003] However, existing extraction technologies have significant shortcomings. Traditional water extraction, while environmentally friendly, is inefficient. The dense cell wall structure of tea leaves makes it difficult for caffeine to dissolve fully, requiring extended extraction time and higher extraction temperatures to compensate. This not only increases energy consumption but also leads to the dissolution of large amounts of impurities such as tea polyphenols, making subsequent purification more difficult. While organic solvent extraction can improve extraction efficiency, the solvents used are often toxic and tend to remain in the product, affecting the safety of food-grade and pharmaceutical-grade caffeine. Furthermore, solvent recovery processes are complex, and wastewater discharge can cause environmental pollution, which is inconsistent with the concept of green production.

[0004] Furthermore, existing improvement technologies still have room for optimization. Some processes employ single enzymatic hydrolysis or ultrasound-assisted extraction. Single enzymatic hydrolysis lacks the synergistic effect of non-enzyme adjuvants, and enzyme activity is easily affected by the oxidation of polyphenols in tea leaves, resulting in limited cell wall damage. While ultrasound-assisted extraction can enhance mass transfer, its selectivity for caffeine is insufficient, and a large amount of impurities are still dissolved. Simultaneously, existing compound extraction solvent formulations have poor compatibility; some solvents are difficult to match with subsequent recrystallization processes, leading to low solvent recovery efficiency and high costs. Moreover, compound enzyme preparation systems lack a synergistic mechanism between enzymes and adjuvants, resulting in unstable enzymatic hydrolysis effects, which restricts the large-scale application of caffeine extraction processes and the improvement of product quality. Therefore, based on the limitations of the aforementioned technologies, there is an urgent need to develop a caffeine extraction preparation method. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for preparing caffeine extraction that effectively solves the problems of low extraction efficiency, high energy consumption and high leaching of impurities in traditional water extraction methods, as well as the problems of solvent toxicity residue, easy environmental pollution and difficulty in solvent recovery in organic solvent extraction methods.

[0006] The objective of this invention can be achieved through the following technical solutions: This invention provides a method for preparing caffeine extract, comprising the following preparation steps: S1: Mix tea powder with purified water, adjust the pH, add compound enzyme preparation for enzymatic hydrolysis, and obtain pretreated raw material after inactivation, centrifugation and drying. S2: The compound extraction solvent is mixed with the pretreated raw material and then extracted by ultrasonication, followed by centrifugation to obtain the crude extract; S3: Add petroleum ether to the crude extract to remove impurities, and add antisolvent to the lower layer to precipitate crude caffeine; S4: Crude caffeine is purified by recrystallization to obtain multi-stage recrystallized crystals, which are then dried to obtain the finished caffeine product.

[0007] Furthermore, the mass ratio of the tea powder, purified water, and compound enzyme preparation is 1:5-8:0.01-0.04.

[0008] Furthermore, the preparation method of the compound enzyme preparation is as follows: Citric acid and chitosan were added to deionized water and stirred until dissolved. Vitamin C was added and stirred until homogeneous to obtain a non-enzyme premix. Cellulase and pectinase were added to the non-enzyme premix and stirred until homogeneous to obtain a compound enzyme preparation.

[0009] Further, the citric acid, chitosan, deionized water, vitamin C, cellulase and pectinase are, by weight, 0.1-0.2 parts of citric acid, 0.2-0.3 parts of chitosan, 50-60 parts of deionized water, 0.05-0.1 parts of vitamin C, 1-3 parts of cellulase and 1-2 parts of pectinase.

[0010] Furthermore, in S1, the enzymatic hydrolysis temperature is 40℃-50℃, and the time is 60min-120min; the inactivation temperature is 80℃-90℃, and the time is 10min-20min; the centrifugation speed is 7000rpm-9000rpm, and the time is 15min-25min; the drying temperature is 50℃-70℃, and the time is 1h-3h.

[0011] Furthermore, the preparation method of the composite extraction solvent is as follows: Choline chloride, D-sorbitol, betaine, glycerol, and L-proline were added to deionized water, and anhydrous ethanol was added. The mixture was stirred at 80℃-85℃ and 200rpm-300rpm for 30min-50min, followed by ultrasonic treatment at 100W-150W for 5min-8min to obtain the composite extraction solvent.

[0012] Further, the choline chloride, D-sorbitol, betaine, glycerol, L-proline, deionized water, and anhydrous ethanol, by weight, are as follows: choline chloride 55-65 parts, D-sorbitol 18-22 parts, betaine 9-12 parts, glycerol 4-6 parts, L-proline 2-3 parts, deionized water 55-70 parts, and anhydrous ethanol 8-24 parts.

[0013] Furthermore, in step S2, the mass ratio of the composite extraction solvent to the pretreated raw material is 25-35:10, the ultrasonic power is 200W-400W, the extraction temperature is 60℃-70℃, and the time is 15min-25min; the centrifugation speed is 7000rpm-9000rpm, and the time is 10min-20min.

[0014] Further, in step S3, the volume ratio of petroleum ether to crude extract is 1:1-2, the number of extractions is 2-4, and the extraction time for each extraction is 5-15 min; the volume ratio of antisolvent to lower layer is 1.5-2.5:1, the dropping rate is 0.5 mL / min-1.5 mL / min, the standing time is 6-10 h, and the antisolvent is deionized water.

[0015] Furthermore, the specific method for recrystallization purification in S4 is as follows: Primary recrystallization: Crude caffeine is added to a 70%-80% aqueous ethanol solution, stirred and dissolved at 75℃-80℃, filtered while hot, cooled to 5℃-10℃ after filtration, and vacuum filtered to obtain primary recrystallized crystals. Secondary recrystallization: Add the primary recrystallized crystals to a 40%-50% aqueous ethanol solution, stir and dissolve at 75℃-80℃, filter while hot, cool to 2℃-5℃ after filtration, and vacuum filter to obtain multi-stage recrystallized crystals.

[0016] Furthermore, both the primary and secondary recrystallization processes are carried out using food-grade qualitative filter paper as the filter medium during hot filtration, with the filter paper pore size controlled to be 1μm-3μm.

[0017] Furthermore, the drying in S4 is as follows: the multi-stage recrystallized crystals are dried at 50℃-70℃ for 3h-5h to obtain the finished caffeine product.

[0018] The beneficial effects of this invention are: 1. The caffeine extraction and preparation method of the present invention can effectively improve the caffeine extraction efficiency. By destroying the cell wall of tea leaves through the synergistic effect of enzymes and non-enzyme adjuvants in the compound enzyme preparation, and combined with the targeted dissolution ability of the compound extraction solvent, the problem of low efficiency and high energy consumption of traditional water extraction method is solved. At the same time, the defects of toxic solvent residue and environmental pollution in traditional organic solvent extraction method are avoided, which is in line with the concept of green production.

[0019] 2. This invention can significantly improve the quality of finished caffeine products. By combining petroleum ether extraction for impurity removal with recrystallization, impurities such as tea polyphenols in the extraction process can be gradually removed, reducing solvent residue and ensuring that the purity of the finished product meets the application requirements of the food and pharmaceutical fields. At the same time, by precisely controlling the drying conditions, the moisture content of the finished product can be effectively controlled, ensuring product stability.

[0020] 3. The process of this invention has good stability and potential for large-scale application. The parameters of each step are clear and highly operable. The formulation design of the compound enzyme preparation and the compound extraction solvent realizes the synergistic optimization of the enzymatic hydrolysis and extraction process, avoiding the problem of unstable effect of a single process or a single reagent. The overall process flow is coherent and compatible with conventional production equipment, which is convenient for industrial scale-up production. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The choline chloride used in the following examples is food-grade choline chloride, purchased from Shandong Aicai Biotechnology Co., Ltd.

[0023] The cellulase was an acidic cellulase, purchased from Xiasheng (Beijing) Biotechnology Development Co., Ltd.

[0024] Pectinase was purchased from Sichuan Huatang Jurui Biotechnology Co., Ltd.

[0025] Example 1 A method for preparing caffeine extraction includes the following preparation steps: S1: Take 0.1 parts of citric acid and 0.2 parts of chitosan and add them to 50 parts of deionized water and stir to dissolve. Then add 0.05 parts of vitamin C and stir evenly to obtain a non-enzyme premix. Add 1 part of acidic cellulase and 1 part of pectinase to the premix and stir evenly to obtain a compound enzyme preparation. Take 10 parts of tea powder and add 50 parts of purified water and mix evenly. After adjusting the pH to 4.5, add 0.1 parts of the compound enzyme preparation for enzymatic hydrolysis. The enzymatic hydrolysis temperature is controlled at 40℃ and the enzymatic hydrolysis time is 60min. After the enzymatic hydrolysis is completed, heat to 80℃ for 10min to inactivate the enzyme. Then centrifuge at 7000rpm for 15min, collect the precipitate and dry it in a 50℃ environment for 1h to obtain the pretreated raw material.

[0026] S2: Take 55 parts of choline chloride, 18 parts of D-sorbitol, 9 parts of betaine, 4 parts of glycerol, and 2 parts of L-proline and add them to 55 parts of deionized water. Then add 8 parts of anhydrous ethanol and stir at 80℃ and 200rpm for 30min. Then, sonicate at 100W for 5min to obtain a composite extraction solvent. Take 25 parts of the composite extraction solvent and mix it with 10 parts of the pretreated raw material. Perform ultrasonic extraction at 200W power, 60℃, and 15min. After extraction, centrifuge at 7000rpm for 10min and collect the centrifuged liquid as the crude extract.

[0027] S3: Add petroleum ether to the crude extract at a volume ratio of 1:1, extract twice for 5 min each time, discard the petroleum ether layer and collect the lower layer; add deionized water as the antisolvent to the lower layer at a volume ratio of 1.5:1 and a dropping rate of 0.5 mL / min, let stand for 6 h to precipitate crude caffeine.

[0028] S4: Take crude caffeine and add 70% ethanol aqueous solution (1 part crude caffeine corresponds to 4 parts ethanol aqueous solution). Stir and dissolve at 75°C, then filter while hot using food-grade qualitative filter paper with a pore size of 1μm. After filtration, cool to 5°C and vacuum filter to obtain primary recrystallized crystals. Take the primary recrystallized crystals and add 40% ethanol aqueous solution (1 part primary recrystallized crystal corresponds to 3 parts ethanol aqueous solution). Stir and dissolve at 75°C, then filter while hot using food-grade qualitative filter paper with a pore size of 1μm. After filtration, cool to 2°C and vacuum filter to obtain multi-stage recrystallized crystals. Dry the multi-stage recrystallized crystals at 50°C for 3 hours to obtain the finished caffeine product.

[0029] Example 2 A method for preparing caffeine extraction includes the following preparation steps: S1: Dissolve 0.15 parts citric acid and 0.25 parts chitosan in 55 parts deionized water by stirring. Add 0.075 parts vitamin C and stir until homogeneous to obtain a non-enzyme premix. Add 2 parts acidic cellulase and 1.5 parts pectinase to the premix and stir until homogeneous to obtain a compound enzyme preparation. Take 10 parts tea powder, add 65 parts purified water and mix until homogeneous. Adjust the pH to 5.0, then add 0.25 parts of the compound enzyme preparation for enzymatic hydrolysis. Control the hydrolysis temperature at 45℃ and the hydrolysis time at 90 min. After hydrolysis, heat to 85℃ for 15 min to inactivate the enzyme, then centrifuge at 8000 rpm for 20 min. Collect the precipitate and dry it at 60℃ for 2 h to obtain the pretreated raw material.

[0030] S2: Take 60 parts of choline chloride, 20 parts of D-sorbitol, 10.5 parts of betaine, 5 parts of glycerol, and 2.5 parts of L-proline and add them to 62.5 parts of deionized water, then add 16 parts of anhydrous ethanol. Stir at 82℃ and 250rpm for 40min, then sonicate at 125W for 6.5min to obtain a composite extraction solvent. Take 30 parts of the composite extraction solvent and mix it with 10 parts of the pretreated raw material, and perform ultrasonic extraction at 300W, 65℃, and 20min. After extraction, centrifuge at 8000rpm for 15min and collect the centrifuged liquid as the crude extract.

[0031] S3: Add petroleum ether to the crude extract at a volume ratio of 1:1.5, extract 3 times, each extraction time is 10 min, discard the petroleum ether layer and collect the lower layer; add deionized water as the antisolvent to the lower layer at a volume ratio of 2:1, drop rate is 1 mL / min, let stand for 8 h, and crude caffeine will precipitate.

[0032] S4: Take crude caffeine and add 75% ethanol aqueous solution (1 part crude caffeine corresponds to 5 parts ethanol aqueous solution). Stir and dissolve at 80℃, then filter while hot using food-grade qualitative filter paper with a pore size of 2μm. After filtration, cool to 8℃ and vacuum filter to obtain primary recrystallized crystals. Take the primary recrystallized crystals and add 45% ethanol aqueous solution (1 part primary recrystallized crystal corresponds to 4 parts ethanol aqueous solution). Stir and dissolve at 80℃, then filter while hot using food-grade qualitative filter paper with a pore size of 2μm. After filtration, cool to 3.5℃ and vacuum filter to obtain multi-stage recrystallized crystals. Dry the multi-stage recrystallized crystals at 60℃ for 4 hours to obtain the finished caffeine product.

[0033] Example 3 A method for preparing caffeine extraction includes the following preparation steps: S1: Take 0.2 parts of citric acid and 0.3 parts of chitosan and add them to 60 parts of deionized water and stir to dissolve. Then add 0.1 parts of vitamin C and stir evenly to obtain a non-enzyme premix. Add 3 parts of acidic cellulase and 2 parts of pectinase to the premix and stir evenly to obtain a compound enzyme preparation. Take 10 parts of tea powder and add 80 parts of purified water and mix evenly. After adjusting the pH to 5.5, add 0.4 parts of the compound enzyme preparation for enzymatic hydrolysis. The enzymatic hydrolysis temperature is controlled at 50℃ and the enzymatic hydrolysis time is 120 min. After the enzymatic hydrolysis is completed, heat to 90℃ for 20 min to inactivate the enzyme. Then centrifuge at 9000 rpm for 25 min, collect the precipitate and dry it in a 70℃ environment for 3 h to obtain the pretreated raw material.

[0034] S2: Take 65 parts of choline chloride, 22 parts of D-sorbitol, 12 parts of betaine, 6 parts of glycerol, and 3 parts of L-proline and add them to 70 parts of deionized water, then add 24 parts of anhydrous ethanol. Stir at 85℃ and 300rpm for 50min, then sonicate at 150W for 8min to obtain a composite extraction solvent. Take 35 parts of the composite extraction solvent and mix it with 10 parts of the pretreated raw material, and perform ultrasonic extraction. The ultrasonic extraction power is 400W, the extraction temperature is 70℃, and the extraction time is 25min. After extraction, centrifuge at 9000rpm for 20min and collect the centrifuged liquid as the crude extract.

[0035] S3: Add petroleum ether to the crude extract at a volume ratio of 1:2, extract 4 times, each extraction time is 15 min, discard the petroleum ether layer and collect the lower layer; add deionized water as the antisolvent to the lower layer at a volume ratio of 2.5:1, drop rate is 1.5 mL / min, let stand for 10 h, and crude caffeine will precipitate.

[0036] S4: Take crude caffeine and add 80% ethanol aqueous solution (1 part crude caffeine corresponds to 6 parts ethanol aqueous solution). Stir and dissolve at 80℃, then filter while hot using food-grade qualitative filter paper with a pore size of 3μm. After filtration, cool to 10℃ and vacuum filter to obtain primary recrystallized crystals. Take the primary recrystallized crystals and add 50% ethanol aqueous solution (1 part primary recrystallized crystal corresponds to 5 parts ethanol aqueous solution). Stir and dissolve at 80℃, then filter while hot using food-grade qualitative filter paper with a pore size of 3μm. After filtration, cool to 5℃ and vacuum filter to obtain multi-stage recrystallized crystals. Dry the multi-stage recrystallized crystals at 70℃ for 5 hours to obtain the finished caffeine product.

[0037] Comparative Example 1 Compared with Example 1, this comparative example replaces "choline chloride in the compound extraction solvent" with an equal mass of "sodium chloride". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, the caffeine product is obtained.

[0038] Comparative Example 2 Compared with Example 1, this comparative example replaces "acidic cellulase and pectinase in the compound enzyme preparation" with an equal mass of "single acidic cellulase". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, the caffeine product is obtained.

[0039] Comparative Example 3 Compared with Example 1, the comparative example replaced D-sorbitol in the compound extraction solvent with an equal mass of sucrose. All other steps and parameters were the same, and will not be repeated in this comparative example. Finally, the caffeine product was obtained.

[0040] Comparative Example 4 Compared with Example 1, this comparative example replaces "chitosan in the compound enzyme preparation" with an equal mass of "starch". All other steps and parameters are the same, and will not be repeated here. The final product is caffeine.

[0041] Comparative Example 5 Compared with Example 1, the concentrations of the ethanol aqueous solution used for the first-stage recrystallization and the second-stage recrystallization in S4 were replaced. Specifically, the ethanol aqueous solution used for the first-stage recrystallization was 40% ethanol aqueous solution, and the ethanol aqueous solution used for the second-stage recrystallization was 70% ethanol aqueous solution. All other steps and parameters were the same, and will not be repeated in this comparative example. Finally, the caffeine product was obtained.

[0042] The caffeine products prepared in Examples 1-3 and Comparative Examples 1-5 were tested, and the results are recorded in Table 1.

[0043] Caffeine extraction rate determination: Caffeine purity determination: Methods: HPLC external standard method was used, referring to GB 5009.139-2014 "Determination of Caffeine in Food"; Standard curve preparation: Prepare caffeine standard solutions of 50, 100, 200, 400, and 800 μg / mL, inject the samples, determine the peak area, and plot the standard curve (R²≥0.999). Sample determination: Take 0.1g of caffeine product, dissolve it in methanol and make up to 100mL, filter and determine by HPLC, and calculate the purity according to the standard curve.

[0044] Determination of tea polyphenol residue Methods: Folin-Ciocalteu colorimetric method, referring to GB / T 8313-2023 "Determination of tea polyphenols and catechins in tea"; Steps: Take 0.5g of the finished product, dissolve it in 50mL of 70% ethanol, take 1mL of the sample solution, add 1mL of Folin reagent and 2mL of 20% sodium carbonate solution, and make up to 10mL. Measure the absorbance at 765nm and calculate the residual amount through the gallic acid standard curve.

[0045] Determination of residual amounts of petroleum ether and anhydrous ethanol solvents Methods: Gas chromatography (GC), referring to GB 5009.262-2016 "Determination of Solvent Residues in Food"; Instruments and conditions: Agilent 7890AGC instrument, HP-5 capillary column (30m×0.32mm×0.25μm); column temperature program: initial 40℃, hold for 3 min, increase to 150℃ at 5℃ / min, hold for 2 min; detector FID, temperature 250℃, injection port temperature 200℃, carrier gas nitrogen (flow rate 1.0mL / min).

[0046] Moisture content determination Method: Karl Fischer volumetric method, referring to GB 5009.3-2016 "Determination of Moisture in Food"; Instrument: Mettler DL38 Karl Fischer moisture analyzer, titrant is Karl Fischer reagent (for moisture determination), weigh 1g of sample for determination.

[0047] Table 1: Test Results of Caffeine Products According to the data in Table 1, the caffeine products prepared in Examples 1-3 have comprehensive advantages such as excellent extraction efficiency, high purity, low impurity residue, low solvent residue, and good moisture content control. The overall quality is stable and significantly better than the comparative products, which can fully meet the stringent requirements of the food and pharmaceutical fields for high-purity caffeine.

[0048] A comparison of Example 1 and Comparative Example 1 shows that the selection of choline chloride components in the compound extraction solvent plays a crucial role in the overall extraction process. In Comparative Example 1, replacing choline chloride with common salts resulted in the loss of its synergistic effect as a key hydrogen bond acceptor with other components in the solvent system. This prevented the effective enhancement of targeted dissolution and separation of caffeine, leading to a significant decrease in extraction efficiency and product purity, while simultaneously increasing impurities and solvent residues. This fully demonstrates the core value of choline chloride in the compound extraction solvent.

[0049] A comparison of Example 1 and Comparative Example 2 shows that the synergistic effect of cellulase and pectinase in the compound enzyme preparation system is indispensable. Comparative Example 1, which uses a single cellulase instead of the compound enzyme preparation, can only specifically decompose the cellulose components in the cell wall and cannot effectively destroy the cross-linking structure of pectin and cellulose. This results in a limited cell wall damage rate in tea leaves and insufficient caffeine dissolution, which not only reduces extraction efficiency but also increases the residual amount of impurities such as tea polyphenols. This highlights the technological advantages of the compound enzyme preparation system over the single enzymatic hydrolysis method.

[0050] A comparison of Example 1 and Comparative Example 3 shows that the selection of D-sorbitol in the composite extraction solvent is crucial for improving solvent performance. In Comparative Example 3, replacing D-sorbitol with ordinary sucrose disrupted the balance between hydrogen bond donors and acceptors in the solvent system, reducing the solvent's ability to dissolve caffeine and its compatibility with subsequent processes. This resulted in decreased extraction efficiency and product purity, and increased impurities and solvent residues, verifying the synergistic effect of D-sorbitol in the composite extraction solvent.

[0051] A comparison of Example 1 and Comparative Example 4 shows that the role of chitosan as an adjuvant in the compound enzyme preparation significantly affects the enzymatic hydrolysis effect. In Comparative Example 4, replacing chitosan with starch resulted in the loss of chitosan's function of disrupting the cross-linked structure of tea cell walls and increasing the contact area between the enzyme and the substrate. This led to a decrease in the enzymatic hydrolysis efficiency of the compound enzyme preparation, insufficient disruption of tea cell walls, hindered caffeine dissolution, and an increase in residual impurities. This fully demonstrates the important auxiliary value of chitosan in the compound enzyme preparation system.

[0052] A comparison of Example 1 and Comparative Example 5 shows that the concentration gradient design of "first-stage high-concentration ethanol aqueous solution and second-stage low-concentration ethanol aqueous solution" in the recrystallization process is key to achieving efficient impurity removal and improving the quality of the finished product. The core of the gradient logic of the original process is that the first-stage high-concentration ethanol can fully dissolve the crude caffeine and simultaneously separate low-polarity impurities; the second-stage low-concentration ethanol can specifically dissolve the residual polar impurities, achieving deep purification. The two steps form a gradual impurity separation mechanism. Therefore, the ethanol concentrations in the two stages of recrystallization cannot be replaced. Once replaced, the synergistic effect of impurity separation in the original process will be destroyed, leading to a decrease in purification effect and failing to meet the quality requirements of high purity and low impurities in the finished product.

[0053] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing caffeine extraction, characterized in that, The preparation steps include the following: S1: Mix tea powder with purified water, adjust the pH, add compound enzyme preparation for enzymatic hydrolysis, and obtain pretreated raw material after inactivation, centrifugation and drying. S2: The compound extraction solvent is mixed with the pretreated raw material and then extracted by ultrasonication, followed by centrifugation to obtain the crude extract; S3: Add petroleum ether to the crude extract to remove impurities, and add antisolvent to the lower layer to precipitate crude caffeine; S4: Crude caffeine is purified by recrystallization to obtain multi-stage recrystallized crystals, which are then dried to obtain the finished caffeine product.

2. The method for preparing caffeine extraction according to claim 1, characterized in that, The mass ratio of the tea powder, purified water, and compound enzyme preparation is 1:5-8:0.01-0.

04.

3. The method for preparing caffeine extraction according to claim 2, characterized in that, The preparation method of the compound enzyme preparation is as follows: Citric acid and chitosan were added to deionized water and stirred until dissolved. Vitamin C was added and stirred until homogeneous to obtain a non-enzyme premix. Cellulase and pectinase were added to the non-enzyme premix and stirred until homogeneous to obtain a compound enzyme preparation.

4. The method for preparing caffeine extraction according to claim 3, characterized in that, The citric acid, chitosan, deionized water, vitamin C, cellulase, and pectinase are present in the following weight proportions: citric acid 0.1-0.2 parts, chitosan 0.2-0.3 parts, deionized water 50-60 parts, vitamin C 0.05-0.1 parts, cellulase 1-3 parts, and pectinase 1-2 parts.

5. The method for preparing caffeine extraction according to claim 1, characterized in that, In S1, the enzymatic hydrolysis temperature is 40℃-50℃, and the time is 60min-120min; the inactivation temperature is 80℃-90℃, and the time is 10min-20min; the centrifugation speed is 7000rpm-9000rpm, and the time is 15min-25min; the drying temperature is 50℃-70℃, and the time is 1h-3h.

6. The method for preparing caffeine extraction according to claim 1, characterized in that, The preparation method of the composite extraction solvent is as follows: Choline chloride, D-sorbitol, betaine, glycerol, and L-proline were added to deionized water, and anhydrous ethanol was added. The mixture was stirred at 80℃-85℃ and 200rpm-300rpm for 30min-50min, followed by ultrasonic treatment at 100W-150W for 5min-8min to obtain the composite extraction solvent.

7. The method for preparing caffeine extraction according to claim 6, characterized in that, The choline chloride, D-sorbitol, betaine, glycerol, L-proline, deionized water, and anhydrous ethanol, by weight, are as follows: choline chloride 55-65 parts, D-sorbitol 18-22 parts, betaine 9-12 parts, glycerol 4-6 parts, L-proline 2-3 parts, deionized water 55-70 parts, and anhydrous ethanol 8-24 parts.

8. The method for preparing caffeine extraction according to claim 1, characterized in that, In step S2, the mass ratio of the compound extraction solvent to the pretreated raw material is 25-35:10, the ultrasonic power is 200W-400W, the extraction temperature is 60℃-70℃, and the time is 15min-25min; the centrifugation speed is 7000rpm-9000rpm, and the time is 10min-20min.

9. The method for preparing caffeine extraction according to claim 1, characterized in that, In step S3, the volume ratio of petroleum ether to crude extract is 1:1-2, the number of extractions is 2-4, and the extraction time for each extraction is 5-15 min; the volume ratio of antisolvent to lower layer is 1.5-2.5:1, the dropping rate is 0.5 mL / min-1.5 mL / min, and the standing time is 6-10 h; the antisolvent is deionized water.

10. The method for preparing caffeine extraction according to claim 1, characterized in that, The specific method for recrystallization purification in S4 is as follows: Primary recrystallization: Crude caffeine is added to a 70%-80% aqueous ethanol solution, stirred and dissolved at 75℃-80℃, filtered while hot, cooled to 5℃-10℃ after filtration, and vacuum filtered to obtain primary recrystallized crystals. Secondary recrystallization: Add the primary recrystallized crystals to a 40%-50% aqueous ethanol solution, stir and dissolve at 75℃-80℃, filter while hot, cool to 2℃-5℃ after filtration, and vacuum filter to obtain multi-stage recrystallized crystals.

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