A method for preparing a raspberry tea extract

Abstract

The application provides a preparation method of a raspberry tea extract, which extracts effective components in raspberry tea through enzyme method and ultrasonic waves, has mild extraction conditions, is simple and convenient, reduces heat energy consumption, improves total flavonoid extraction efficiency and extraction rate, and finally uses MOF imprinting material to perform directional selection on dihydromyricetin, thereby improving the exclusive selectivity of dihydromyricetin separation, and the extraction efficiency is high, the purity is high, the performance is stable, and the MOF imprinting material can be repeatedly used.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plant extraction, in particular to a preparation method of raspberry tea extract. BACKGROUND

[0002] Raspberry tea is a kind of tea processed from the offspring of Ampelopsis aconitifolia Batal. At present, there are problems in the production of raspberry tea, such as inconvenience in drinking and processing, and low added value of products. The dried raspberry tea product processed from the stem and leaf of Ampelopsis aconitifolia Batal. is thin and winding, has a large volume, and has a high cost of packaging and transportation. If the original tea is directly drunk, it needs to be torn by hand during tea brewing, which is not only unhygienic but also difficult to control the proportion of tea soup, and it is not easy to obtain the best taste effect. When the original tea is packed in a small bag, the breakage rate of the original tea is high, the powder is much, and the material loss is as high as more than 20%. Moreover, the processing technology has low content, the product is single, the industrial chain is short, and the development of resource deep processing and industrial extension is restricted.

[0003] Traditional extraction methods of dihydromyricetin in raspberry tea include water extraction and alcohol extraction. However, the water extraction method has low extraction efficiency, requires high energy consumption and a large amount of time, and is not suitable for industrial production. The alcohol extraction method consumes a large amount of organic solvent, which needs to be recycled, and the extraction product contains residual organic solvent, which is difficult to control in the production process. Moreover, most of the extraction methods cannot accurately separate dihydromyricetin, and the purity of the extracted dihydromyricetin is low, usually containing a large amount of polysaccharides and polyphenols. SUMMARY

[0004] In order to solve the problems of low extraction efficiency, high energy consumption, and a large amount of time in the water extraction method, and the problems of a large amount of organic solvent consumption and the need for recycling in the alcohol extraction method, and the problem that most of the extraction methods cannot accurately separate dihydromyricetin, the present application provides a preparation method of raspberry tea extract, which has low energy consumption, short time, clean process, simple and efficient process, is easy to industrialize, can accurately separate dihydromyricetin, and improves the purity of dihydromyricetin.

[0005] To achieve the above-mentioned purposes, the technical solution adopted by the present application is as follows:

[0006] A preparation method of raspberry tea extract, comprising the following steps:

[0007] S01, picking fresh raspberry tea leaves, drying, crushing, and then placing them in a reaction container, adding ethanol for 10-15 min, adding a composite enzyme solution, and then ultrasonic extraction after enzyme hydrolysis is completed to obtain a filtrate. The synergistic extraction of enzyme hydrolysis and ultrasonic extraction can effectively improve the extraction efficiency and the total extraction rate. The extraction conditions are mild, simple and convenient, and the consumption of heat energy is reduced. The composite enzyme can simultaneously destroy the intercellular layer and cell wall between cells, and then destroy the inner cell layer, so that dihydromyricetin is easily extracted, and the extraction rate and purity are improved.

[0008] S02, the filtrate obtained in step S01 is added to the MOFs imprinting material, and the mixture is placed in a water bath constant temperature oscillator and oscillated at room temperature for 1 h, centrifuged at a stirring rate of 1000-3000 rpm for 5-15 min, and separated by filtration with a 0.45 μm microporous filter membrane to obtain the MOFs imprinting material adsorbed with the raspberry extract;

[0009] S03, the MOFs imprinting material adsorbed with the raspberry extract obtained in step S02 is added to a mixed solution of methanol and acetic acid, and ultrasonic-assisted centrifugation is performed at a rate of 3000 rpm for 10-15 min, and finally filtered with a 0.45 μm microporous filter membrane to obtain the filtrate containing the raspberry extract;

[0010] S04, the filtrate obtained in step S03 is repeated for 3-4 times of steps S02 and S03 to obtain the high-purity raspberry extract.

[0011] Preferably, the preparation method of the MOFs imprinting material in step S02 comprises the following steps:

[0012] S11, 17 mg of dihydromyricetin is dissolved in a reaction container containing 3 mL of N,N-dimethylformamide solution, and 10 mg of methanol and 15 mL of acrylamide solution are added for pre-polymerization for 2-5 hours to obtain a pre-polymerized liquid;

[0013] S12, 4 parts of AIBME and 11 parts of EDGMA are added to the above pre-polymerized liquid, and 13 parts of rare earth-MOFs are further added, ultrasonic degassing is performed for 20-40 min, nitrogen is filled for 10-20 min, and the reaction is performed in a constant temperature water bath at a temperature of 60℃ for 24 h to obtain a semi-finished product;

[0014] S13, the above semi-finished product is eluted with a mixed solution of acetic acid and methanol in a volume ratio of 1:9, and then washed with a methanol solution, and the obtained solid is vacuum dried at 50-70℃ for 10-14 h, thereby obtaining a MOFs imprinting material using rare earth-MOFs as a molecular imprinting material, which has abundant and uniformly distributed tubular channels, exhibits good adsorption performance, and the tubular channels are beneficial to the adsorption of reactants and the desorption of products.

[0015] Preferably, the preparation method of the rare earth-MOFs in the step S12 comprises the following steps: adding cerium chloride, iminodiacetic acid and aluminum nitrate into deionized water in a proportion of 5.2:1:1.3, mixing, drying at 72 DEG C after stabilization, cooling and standby, and preparing the cerium aluminum MOFs material by using a hot melting method. The cerium aluminum MOFs material has good adsorption performance, high porosity and many active center sites, so that the adsorption efficiency is significantly improved, the stability of the organic-metal framework in water is improved, the chemical stability and thermal stability are enhanced, and the service life is increased.

[0016] Preferably, the raspberry tea fresh leaves picked in the step S01 are tender stems and leaves in April to May, and the crushing screen size is 60 meshes.

[0017] Preferably, 60-80% of ethanol is added for soaking in the step S01.

[0018] Preferably, after the addition of the composite enzyme solution in the step S01, enzymolysis is carried out at 40-50 DEG C for 40-50 min, and stirring is carried out once every 20 min.

[0019] Preferably, after the enzymolysis in the step S01, ultrasonic extraction is carried out at 50-60 DEG C for 40-50 min.

[0020] Preferably, methanol and acetic acid in a volume ratio of 9:1 are added in the step S03.

[0021] Preferably, the composite enzyme in the step S01 is pectinase, cellulase and amylase.

[0022] Preferably, the ratio of the pectinase, cellulase and amylase is 2:3:1.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] The preparation method of the raspberry tea extract provided in the present application extracts the effective components in the raspberry tea by enzyme method and ultrasonic wave, the extraction condition is mild, simple and convenient, the consumption of heat energy is reduced, the extraction efficiency and extraction rate of total flavonoids are improved, the specific selectivity of the separation of dihydromyricetin is improved by using the MOF imprinting material for directional selection, the extraction efficiency is high, the purity is high, the performance is stable, and the MOF imprinting material can be repeatedly used. DETAILED DESCRIPTION

[0025] The specific technical scheme of the present application is described below in combination with specific examples 1-3 and comparative examples 1-3:

[0026] (1) Preparation of rare earth-MOFs

[0027] CeCl3, iminodiacetic acid and Al(NO3)3 were added into deionized water in the ratio of 5.2:1:1.3, mixed uniformly, and after the solution was stable, placed in a drying oven at 72°C for drying, and after complete drying, cooled for standby use.

[0028] (2) Preparation of MOFs imprinted material

[0029] Dihydromyricetin 17 mg was dissolved in a reaction vessel containing 3 mL of N,N-dimethylformamide solution, 10 mg of methanol and 15 mL of acrylamide solution were added for pre-polymerization for 2-5 hours to obtain a pre-polymerization liquid; 4 parts of AIBME and 11 parts of EDGMA were added to the pre-polymerization liquid, and then 13 parts of rare earth-MOFs were added, ultrasonic degassing was performed for 20-40 min, nitrogen was filled for 10-20 min, and under the condition of a temperature of 60°C, constant temperature water bath reaction was performed for 24 h, elution was performed with a mixed solution of acetic acid and methanol in a volume ratio of 1:9, followed by cleaning with a methanol solution, and the obtained solid was vacuum dried at 50-70°C for 10-14 h to obtain the product.

[0030] Example 1:

[0031] S01, the tender stems and leaves of fresh raspberry tea in April and May were picked, dried, and when the water content of the tender stems and leaves was 6%, they were crushed, soaked in 60-80% ethanol for 10 min, and then a complex enzyme solution of pectinase, cellulase and amylase in a ratio of 2:3:1 was added, the pH was adjusted to 4, and enzyme hydrolysis was performed at 40°C for 40 min, with stirring every 20 min; after the enzyme hydrolysis was completed, ultrasonic extraction was performed at 50°C for 40 min to obtain a filtrate;

[0032] S02, the filtrate obtained in step S01 was added to MOFs imprinted material in a solid-liquid ratio of 5:12 g / mL, and placed in a water bath constant temperature oscillator for oscillation at room temperature for 1 h; centrifugation was performed at a stirring rate of 1000 rpm for 5 min, and then 0.45 μm microporous filter membrane was used for filtration and separation to obtain MOFs imprinted material adsorbed with raspberry tea extract;

[0033] S03, the MOFs imprinted material adsorbed with raspberry tea extract obtained in step S02 was added to a mixed solution of methanol and acetic acid in a volume ratio of 9:1, and ultrasonic assisted centrifugation was performed at a rate of 3000 rpm for 10 min; finally, 0.45 μm microporous filter membrane was used for filtration to obtain a filtrate containing raspberry tea extract;

[0034] S04, the filtrate obtained in step S03 was repeated for 3 times of steps S02 and S03 to obtain high-purity raspberry tea extract.

[0035] Example 2:

[0036] S01, pick the fresh raspberry tea stems and leaves in April and May, dry the stems and leaves until the water content is 6%, then crush the stems and leaves and put them in a reaction container, soak them in 70% ethanol for 13 minutes, then add a compound enzyme solution of pectinase, cellulase and amylase in a ratio of 2:3:1, adjust the pH to 4, and enzymatically hydrolyze at 45°C for 45 minutes, stirring every 20 minutes, then extract at 55°C using ultrasonic waves for 45 minutes to obtain a filtrate;

[0037] S02, add the filtrate obtained in step S01 to MOFs imprinting material at a solid-liquid ratio of 5:12 g / mL, and oscillate in a water bath constant temperature oscillator at room temperature for 1 hour, then centrifuge at a stirring rate of 2000 rpm for 13 minutes, and filter and separate using a 0.45 μm microporous filter membrane to obtain MOFs imprinting material adsorbed with raspberry tea extract;

[0038] S03, add the MOFs imprinting material adsorbed with raspberry tea extract obtained in step S02 to a mixed solution of methanol and acetic acid in a volume ratio of 9:1, and centrifuge at a rate of 3000 rpm for 13 minutes with the aid of ultrasonic waves, and finally filter using a 0.45 μm microporous filter membrane to obtain a filtrate containing raspberry tea extract;

[0039] S04, repeat steps S02 and S03 four times with the filtrate obtained in step S03 to obtain high-purity raspberry tea extract.

[0040] Example 3:

[0041] S01, pick the fresh raspberry tea stems and leaves in April and May, dry the stems and leaves until the water content is 6%, then crush the stems and leaves and put them in a reaction container, soak them in 60-80% ethanol for 15 minutes, adjust the pH to 4, add a compound enzyme solution of pectinase, cellulase and amylase in a ratio of 2:3:1, and enzymatically hydrolyze at 50°C for 50 minutes, stirring every 20 minutes, then extract at 60°C using ultrasonic waves for 50 minutes to obtain a filtrate;

[0042] S02, add the filtrate obtained in step S01 to MOFs imprinting material at a solid-liquid ratio of 5:12 g / mL, and oscillate in a water bath constant temperature oscillator at room temperature for 1 hour, then centrifuge at a stirring rate of 3000 rpm for 15 minutes, and filter and separate using a 0.45 μm microporous filter membrane to obtain MOFs imprinting material adsorbed with raspberry tea extract;

[0043] S03, add the MOFs imprinting material adsorbed with raspberry tea extract obtained in step S02 to a mixed solution of methanol and acetic acid in a volume ratio of 9:1, and centrifuge at a rate of 3000 rpm for 15 minutes with the aid of ultrasonic waves, and finally filter using a 0.45 μm microporous filter membrane to obtain a filtrate containing raspberry tea extract;

[0044] S04. Repeat steps S02 and S03 four times with the filtrate obtained in step S03 to obtain high-purity berry tea extract.

[0045] Comparative Example 1:

[0046] The tender stems and leaves of fresh berry tea were harvested in April and dried until the moisture content of the stems and leaves was 6%. After being crushed, they were placed in a reaction vessel and soaked in 60-80% ethanol for 15 minutes. Then, a complex enzyme solution of pectinase, cellulase and amylase in a ratio of 2:3:1 was added, the pH was adjusted to 4, and enzymatic hydrolysis was carried out at 50℃ for 50 minutes. After the enzymatic hydrolysis was completed, ultrasonic extraction was carried out at 60℃ for 50 minutes to obtain berry tea extract.

[0047] Comparative Example 2:

[0048] The tender stems and leaves of fresh berry tea were harvested in April and dried until the moisture content of the stems and leaves was 6%. Then, 60% ethanol was added, and the tea was first extracted using ultrasound at 60℃ for 50 minutes. After that, a complex enzyme solution of pectinase, cellulase and amylase in a ratio of 2:3:1 was added, the pH was adjusted to 4, and the tea was enzymatically hydrolyzed at 50℃ for 50 minutes, with stirring every 20 minutes. After the enzymatic hydrolysis was completed, the tea extract was obtained by filtration.

[0049] Comparative Example 3:

[0050] 1) Harvest the tender stems and leaves of fresh mulberry tea in April, dry them until the moisture content of the tender stems and leaves is 6%, add 60% ethanol, extract with ultrasound at 60℃ for 50 minutes, and filter to obtain the filtrate.

[0051] 2) The obtained filtrate was added to MOFs imprinted material at a material-to-liquid ratio of 5:12 g / mL, and the mixture was shaken in a water bath at room temperature for 1 hour. After centrifugation, the mixture was stirred at 3000 rpm for 15 minutes and then filtered through a 0.45 μm microporous membrane to obtain MOFs imprinted material adsorbed with berry tea extract. The MOFs imprinted material adsorbed with berry tea extract was added to a mixed solution of methanol and acetic acid at a volume ratio of 9:1, and centrifuged at 3000 rpm for 15 minutes with ultrasonic assistance. Finally, the mixture was filtered through a 0.45 μm microporous membrane to obtain a filtrate containing berry tea extract.

[0052] Repeat step 2 above 3 times to obtain the berry tea extract.

[0053] The extracts of berry tea prepared using the extraction method of this application in Examples 1-3 and Comparative Examples 1-3 were tested, and the results are shown in Table 1 below:

[0054] Table 1: Total extraction rate and dihydromyricetin content in Examples 1-3 and Comparative Examples 1-3

[0055] Test item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Total extraction rate (%) 66.12％ 68.56％ 69.13％ 42.75％ 38.56％ 56.61％ Dihydromyricetin content (%) 98.34％ 99.64％ 98.71％ 55.19％ 48.31％ 87.47％

[0056] As can be seen from Table 1, the preparation method of the berry tea extract provided by the application extracts the effective components in the berry tea by enzyme method and ultrasonic wave, the extraction condition is mild, simple and convenient, the consumption of heat energy is reduced, the extraction efficiency and extraction rate of total flavonoids are improved, the MOF imprint material is finally used for directional selection of dihydromyricetin, the exclusive selectivity of dihydromyricetin separation is improved, the extraction efficiency is high, the purity is high and the performance is stable, and the MOF imprint material can be repeatedly used for multiple times, the total extraction rate in Comparative Example 1 and the content of dihydromyricetin in the berry tea extract obtained are low, the extraction rate in Comparative Example 2 is lower than that in Comparative Example 1, the total extraction rate and the content of dihydromyricetin in the berry tea extract obtained in Comparative Example 3 are low, therefore, the preparation method of the berry tea extract provided by the application extracts the effective components in the berry tea by enzyme method and ultrasonic wave, the extraction condition is mild, simple and convenient, the consumption of heat energy is reduced, the extraction efficiency and extraction rate of total flavonoids are improved, the MOF imprint material is finally used for directional selection of dihydromyricetin, the exclusive selectivity of dihydromyricetin separation is improved, the extraction efficiency is high, the purity is high and the performance is stable, and the MOF imprint material can be repeatedly used for multiple times.

[0057] The above only describes the preferred embodiments of the application and is not intended to limit the application. Any modification, equivalent replacement and improvement made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A method for preparing a berry tea extract, characterized in that, Includes the following steps: S01. Pick fresh tea leaves, dry them, crush them, put them in a reaction vessel, add ethanol and soak for 10-15 minutes, then add a compound enzyme solution. After the enzymatic hydrolysis is completed, extract with ultrasound to obtain the filtrate. S02. Add the filtrate obtained in step S01 to the MOFs imprinted material at a material-to-liquid ratio of 5:12 g / mL, place it in a water bath constant temperature shaker at room temperature and shake for 1 hour, centrifuge and stir at a stirring rate of 1000-3000 rpm for 5-15 minutes, filter and separate using a 0.45 μm microporous membrane to obtain the MOFs imprinted material adsorbed with berry tea extract. S03. Add the MOF imprinted material with adsorbed berry tea extract obtained in step S02 to a mixed solution of methanol and acetic acid, centrifuge at 3000 rpm for 10-15 min with ultrasonic assistance, and finally filter with a 0.45 μm microporous membrane to obtain a filtrate containing berry tea extract. S04. Repeat steps S02 and S03 3-4 times with the filtrate obtained in step S03 to obtain high-purity berry tea extract. The method for preparing the MOF imprinted material in step S02 includes the following steps: S11. Dissolve 17 mg of dihydromyricetin in a reaction vessel containing 3 mL of N,N-dimethylformamide solution, add 10 mg of methanol and 15 mL of acrylamide solution for prepolymerization for 2-5 hours to obtain a prepolymerized liquid. S12. Add 4 parts of AIBME and 11 parts of EDGMA to the above prepolymer liquid, then add 13 parts of rare earth-MOFs, degas by ultrasonication for 20-40 min, purge with nitrogen for 10-20 min, and react in a constant temperature water bath at 60℃ for 24 h to obtain a semi-finished product. S13. The above semi-finished product is eluted with a mixed solution of acetic acid and methanol in a volume ratio of 1:9, then washed with methanol solution, and the resulting solid is vacuum dried at 50-70℃ for 10-14 hours to obtain the product. The method for preparing rare earth-MOFs in step S12 includes the following steps: adding cerium chloride, iminodiacetic acid and aluminum nitrate to deionized water in a ratio of 5.2:1:1.3 and mixing. After stabilization, the mixture is dried at 72°C and cooled for later use.

2. The method for preparing the berry tea extract according to claim 1, characterized in that: The fresh tea leaves picked in step S01 are tender stems and leaves from April to May, and are pulverized to a mesh size of 60.

3. The method for preparing the berry tea extract according to claim 1, characterized in that: In step S01, 60-80% ethanol is added for soaking.

4. The method for preparing the berry tea extract according to claim 1, characterized in that: In step S01, after adding the compound enzyme solution, the enzyme is enzymatically hydrolyzed at 40-50℃ for 40-50 minutes, with stirring every 20 minutes.

5. The method for preparing the berry tea extract according to claim 1, characterized in that: In step S01, after enzymatic hydrolysis, the sample is extracted using ultrasound at 50-60℃ for 40-50 minutes.

6. The method for preparing the berry tea extract according to claim 1, characterized in that: In step S03, methanol and acetic acid are added in a volume ratio of 9:

1.

7. The method for preparing the berry tea extract according to claim 1, characterized in that: The complex enzyme in step S01 is pectinase, cellulase and amylase.

8. The method for preparing the berry tea extract according to claim 7, characterized in that: The ratio of pectinase, cellulase and amylase is 2:3:1.