Purple corn anthocyanin extraction method

Abstract

The invention relates to the technical field of anthocyanin extraction, in particular to a purple corn anthocyanin extraction method which comprises the following specific steps: taking purple corn stigma, spike stalks, straws and bracts as raw materials, and grinding the raw materials by using a grinding machine to obtain a mixed ground material; carrying out enzymolysis reaction on the mixed ground material and an enzyme solution, washing with deionized water, and filtering; mixing the mixed ground material after enzymolysis with an ethanol solution, then adding N-acylamino acid, and carrying out microwave extraction; after the extraction is completed, filtering, enabling the extract to pass through macroporous resin, and then enabling an ethanol solution to pass through the macroporous resin, so as to obtain anthocyanin eluent; concentrating the anthocyanin eluent by using a rotary evaporator to obtain an anthocyanin concentrated solution; and carrying out freeze drying to obtain the anthocyanin. The N-acylamino acid is added and can stabilize the molecular structure of the anthocyanin and reduce degradation through hydrogen bonds of the N-acylamino acid and anthocyanin molecules or other weak interaction, so that the integrity and quality of the extracted anthocyanin are improved.

Description

Technical Field

[0001] The invention relates to the technical field of anthocyanidin extraction, in particular to a method for extracting anthocyanidin from purple corn. Background Art

[0002] The greatest value of purple corn is anthocyanin, which is a water-soluble natural pigment belonging to the flavonoids of polyphenol compounds. It is the most effective antioxidant and the most powerful free radical scavenger discovered by humans today. It has extremely high nutritional value, health value and pharmacological effects. It can scavenge free radicals, anti-oxidation and anti-aging, anti-mutation and anti-tumor, improve vision, prevent and treat cardiovascular and cerebrovascular diseases, etc. It has huge market demand in the fields of food, cosmetics, medicine and health care.

[0003] Traditional anthocyanin extraction methods, such as solvent extraction, are relatively simple to operate, but the extraction process is time-consuming and often requires several hours or even longer soaking and stirring, resulting in low production efficiency. In addition, large amounts of solvent are used, and subsequent solvent recovery costs are high, which may also cause environmental pollution problems. At the same time, the anthocyanins extracted by conventional methods are usually of low purity and contain more impurities, which limits their application in high-end food, medicine and other fields. In view of this, we propose a method for extracting anthocyanins from purple corn. Summary of the invention

[0004] The object of the present invention is to provide a method for extracting anthocyanins from purple corn to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides a method for extracting anthocyanins from purple corn, comprising the following steps:

[0006] S1.1, using purple corn silk, cob, straw, and husk as raw materials, grinding with a grinder at a speed of 1000-2000 rpm for 10-15 min to obtain a mixed ground product; subjecting the mixed ground product to enzymatic hydrolysis with an enzyme solution, and after the reaction, washing with deionized water and filtering to obtain a mixed ground product after enzymatic hydrolysis;

[0007] The cell walls of purple corn silk, cobs, straw and bracts are mainly composed of cellulose, hemicellulose and pectin, which will hinder the dissolution of anthocyanins. Enzymatic hydrolysis can destroy the cell wall structure, making it easier for anthocyanins to be released from the cells and enter the extraction solvent more quickly, thereby shortening the time required for the entire extraction process. Enzymes can decompose impurities such as polysaccharides and proteins, which may be extracted together with anthocyanins when not treated, affecting the purity of anthocyanins. After removing these impurities through enzymatic hydrolysis, the obtained anthocyanins are of higher purity and more conducive to subsequent applications. In addition, by destroying the cell walls, enzymatic hydrolysis can also reduce the influence of other components in the cell on anthocyanins during storage, thereby extending the shelf life of anthocyanins and maintaining their biological activity and color stability.

[0008] S1.2, the mixed ground material after enzymatic hydrolysis was mixed with ethanol solution, stirred at 200-300 rpm for 15-30 min with a stirrer, and then N-acyl amino acid with a concentration of 3-5 mM was added, and the mixture was placed in a microwave reactor for extraction; after the extraction was completed, the mixture was filtered to obtain an extract containing anthocyanins;

[0009] During the microwave extraction process, the heat and electromagnetic field generated by microwaves may cause changes such as vibration and breakage of chemical bonds within anthocyanin molecules, while N-acyl amino acids can stabilize the molecular structure of anthocyanin through hydrogen bonds or other weak interactions with anthocyanin molecules, reduce degradation caused by microwave radiation, and thus improve the integrity and quality of anthocyanin after extraction; under the action of microwaves, N-acyl amino acids can interact with the membrane structure components of the raw material cells, increase the permeability of the cell membrane, and make anthocyanin more easily released from the inside of the cell into the extraction solvent, thereby improving the extraction efficiency; the microwave extraction process may produce some free radicals, which will have a negative impact on the quality of anthocyanin. Anthocyanin and N-acyl amino acids work together to remove these free radicals, thereby reducing the oxidative damage of anthocyanin to the free radicals.

[0010] Microwave extraction is a highly efficient extraction technology. Compared with traditional solvent extraction, microwave extraction can significantly shorten the extraction time. Under the action of the microwave field, polar molecules (such as water) in plant cells will quickly absorb microwave energy and generate a large amount of heat, causing the temperature inside the cells to rise sharply and the pressure to increase, thereby causing the cell wall to rupture. Anthocyanin molecular structure contains polar groups that can absorb microwave energy well, while other components in plant raw materials may have weaker absorption of microwave energy. This allows anthocyanins to be extracted from the raw materials first during microwave extraction, relatively reducing the dissolution of other impurities, which is beneficial to improving the purity of anthocyanins.

[0011] S1.3, slowly pass the extract containing anthocyanins through the activated macroporous resin so that the anthocyanins can fully contact and be adsorbed by the resin; rinse the resin with deionized water until the effluent is colorless; then pass a 70-95% ethanol solution through the macroporous resin at a flow rate of 1-2 mL / min to obtain anthocyanin eluate;

[0012] Anthocyanin molecules can enter the pores of the resin and be adsorbed, while some impurity molecules are not adsorbed or only adsorbed in small amounts due to their size, polarity, etc., which do not meet the adsorption conditions of the resin, and are thus separated from the anthocyanins through subsequent elution steps; compared with some traditional purification methods (such as chemical precipitation that may introduce new chemicals, or high-temperature distillation that may destroy the activity of anthocyanins), the macroporous resin purification process is relatively mild, and under appropriate operating conditions, the adsorption and elution process of anthocyanins by macroporous resin will not cause serious damage to the chemical structure and biological activity of anthocyanins.

[0013] S1.4. Concentrate the anthocyanin eluate using a rotary evaporator with a vacuum degree of 20-50 mmHg, a rotation speed of 80-150 rpm, a temperature of 30-40°C, and a concentration time of 4-6 h to obtain anthocyanin concentrate; then freeze-dry the anthocyanin concentrate to obtain anthocyanins.

[0014] Preferably, in S1.1, the enzyme solution is prepared by dissolving the hydrolase in a citric acid-phosphate buffer solution with a pH value of 4-6, and the concentration of the enzyme solution is 50-100 U / mL.

[0015] Preferably, the hydrolase is any one of hemicellulase or β-glucosidase.

[0016] Preferably, in S1.1, the enzymatic hydrolysis reaction is to react the mixed ground material with the enzyme solution at 37-50°C for 2-4 hours, and after the reaction is completed, leupeptin at a concentration of 1-10 μg / mL is added to terminate the enzymatic reaction.

[0017] Preferably, in S1.2, the concentration of the ethanol solution is 50-70%.

[0018] Preferably, in S1.2, the material-liquid ratio of the mixed ground material to the ethanol solution is 1:25-45 g / mL.

[0019] Preferably, in S1.2, the power of the microwave reactor is 400-600 W, the temperature is maintained at 40-50° C., and the extraction time is 10-20 min.

[0020] Preferably, in S1.3, the speed at which the extract containing anthocyanins slowly passes through the macroporous resin is 1-2 mL / min.

[0021] Preferably, in S1.3, the macroporous resin is any one of AB-8 macroporous resin and D101 macroporous resin.

[0022] Preferably, in S1.4, the freeze drying temperature is -40 to -50°C and the drying time is 8 to 10 hours. Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. In the purple corn anthocyanin extraction method, hydrolase is added. Since hydrolase can destroy the cell wall structure, anthocyanins are more easily released from the cells and can enter the extraction solvent more quickly, thereby shortening the time required for the entire extraction process; in addition, the hydrolase can also remove some impurities, so that the obtained anthocyanins have a higher purity.

[0024] 2. In the purple corn anthocyanin extraction method, N-acyl amino acids are added. Since N-acyl amino acids can stabilize the molecular structure of anthocyanins through hydrogen bonds or other weak interactions with anthocyanin molecules, degradation caused by microwave radiation is reduced, thereby improving the integrity and quality of anthocyanins after extraction; free radicals generated during microwave extraction will affect the quality of anthocyanins, and N-acyl amino acids can scavenge these free radicals, thereby reducing the oxidative damage of free radicals to anthocyanins. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Macroporous resin activation: The resin was first washed with deionized water until the effluent was clear and transparent. After soaking in 95% ethanol for 24 h, the resin was treated alternately with 0.1 M HCl and 0.1 M NaOH. After each treatment, it was thoroughly washed with water to neutrality. Finally, the pH of the resin was balanced with citric acid-phosphate buffer.

[0027] The hydrolase is any one of hemicellulase and β-glucosidase, and the hydrolase is preferably β-glucosidase.

[0028] The macroporous resin is any one of AB-8 macroporous resin and D101 macroporous resin, and the macroporous resin is preferably AB-8 macroporous resin.

[0029] Embodiment 1: A method for extracting anthocyanins from purple corn, comprising the following steps:

[0030] S1.1. Grind purple corn silk, cob, straw and bracts as raw materials at 1500 rpm for 15 min using a grinder to obtain a mixed grind; dissolve β-glucosidase in a citric acid-phosphate buffer with a pH value of 5 to obtain a β-glucosidase solution with a concentration of 50 U / mL; subject the mixed grind to an enzymatic reaction with the β-glucosidase solution at 45°C for 3 h, add leupeptin with a concentration of 6 μg / mL to terminate the enzyme reaction after the reaction is completed, rinse with deionized water and filter to obtain a mixed grind after enzymatic reaction;

[0031] S1.2, the mixed grind after enzymatic hydrolysis was mixed with a 60% ethanol solution, the solid-liquid ratio of the mixed grind to the ethanol solution was 1:25 g / mL, and stirred at a speed of 300 rpm for 30 min with a stirrer, and then a 4 mM N-acyl amino acid was added, and the mixture was put into a microwave reactor for extraction at a power of 500 W and a temperature of 45°C. The extraction time was 15 min. After the extraction was completed, it was filtered to obtain an extract containing anthocyanins;

[0032] S1.3, slowly pass the extract containing anthocyanins through the activated AB-8 macroporous resin at a flow rate of 1 mL / min, so that the anthocyanins can fully contact and be adsorbed by the resin; rinse the resin with deionized water until the effluent is colorless; then pass a 90% ethanol solution through the AB-8 macroporous resin at a flow rate of 1 mL / min to obtain anthocyanin eluate;

[0033] S1.4. Concentrate the anthocyanin eluate using a rotary evaporator at a vacuum degree of 30 mmHg, a rotation speed of 120 rpm, a temperature of 40°C, and a concentration time of 6 h to obtain anthocyanin concentrate; then freeze-dry the anthocyanin concentrate at a drying temperature of -50°C and a drying time of 8 h to obtain anthocyanins.

[0034] Embodiment 2: A method for extracting anthocyanins from purple corn, comprising the following steps:

[0035] S1.1. Use purple corn silk, cob, straw and bract as raw materials, grind with a grinder at a speed of 1500 rpm for 15 minutes to obtain a mixed grind; dissolve β-glucosidase in a citric acid-phosphate buffer with a pH value of 5 to obtain a β-glucosidase solution with a concentration of 50 U / mL; subject the mixed grind to an enzymatic hydrolysis reaction with the β-glucosidase solution at 45°C for 3 hours, add leupeptin with a concentration of 6 μg / mL to terminate the enzyme reaction after the reaction is completed, rinse with deionized water and filter to obtain a mixed grind after enzymatic hydrolysis;

[0036] S1.2, the mixed grind after enzymatic hydrolysis was mixed with a 60% ethanol solution, the solid-liquid ratio of the mixed grind to the ethanol solution was 1:30 g / mL, and stirred at a speed of 300 rpm for 30 min with a stirrer, and then N-acyl amino acid with a concentration of 4 mM was added, and the mixture was put into a microwave reactor for extraction at a power of 500 W and a temperature maintained at 45°C. The extraction time was 15 min. After the extraction was completed, it was filtered to obtain an extract containing anthocyanins;

[0037] S1.3, slowly pass the extract containing anthocyanins through the activated AB-8 macroporous resin at a flow rate of 1 mL / min, so that the anthocyanins can fully contact and be adsorbed by the resin; rinse the resin with deionized water until the effluent is colorless; then pass a 90% ethanol solution through the AB-8 macroporous resin at a flow rate of 1 mL / min to obtain anthocyanin eluate;

[0038] S1.4. Concentrate the anthocyanin eluate using a rotary evaporator at a vacuum degree of 30 mmHg, a rotation speed of 120 rpm, a temperature of 40°C, and a concentration time of 6 h to obtain anthocyanin concentrate; then freeze-dry the anthocyanin concentrate at a drying temperature of -50°C and a drying time of 8 h to obtain anthocyanins.

[0039] Embodiment 3: A method for extracting anthocyanins from purple corn, comprising the following steps:

[0040] S1.1. Use purple corn silk, cob, straw and bract as raw materials, grind with a grinder at a speed of 1500 rpm for 15 minutes to obtain a mixed grind; dissolve β-glucosidase in a citric acid-phosphate buffer with a pH value of 5 to obtain a β-glucosidase solution with a concentration of 50 U / mL; subject the mixed grind to an enzymatic hydrolysis reaction with the β-glucosidase solution at 45°C for 3 hours, add leupeptin with a concentration of 6 μg / mL to terminate the enzyme reaction after the reaction is completed, rinse with deionized water and filter to obtain a mixed grind after enzymatic hydrolysis;

[0041] S1.2, the mixed grind after enzymatic hydrolysis was mixed with a 60% ethanol solution, the solid-liquid ratio of the mixed grind to the ethanol solution was 1:45 g / mL, and stirred at a speed of 300 rpm for 30 min with a stirrer, and then N-acyl amino acid with a concentration of 4 mM was added, and the mixture was put into a microwave reactor for extraction at a power of 500 W and a temperature maintained at 45°C. The extraction time was 15 min. After the extraction was completed, it was filtered to obtain an extract containing anthocyanins;

[0042] S1.3, slowly pass the extract containing anthocyanins through the activated AB-8 macroporous resin at a flow rate of 1 mL / min, so that the anthocyanins can fully contact and be adsorbed by the resin; rinse the resin with deionized water until the effluent is colorless; then pass a 90% ethanol solution through the AB-8 macroporous resin at a flow rate of 1 mL / min to obtain anthocyanin eluate;

[0043] S1.4. Concentrate the anthocyanin eluate using a rotary evaporator at a vacuum degree of 30 mmHg, a rotation speed of 120 rpm, a temperature of 40°C, and a concentration time of 6 h to obtain anthocyanin concentrate; then freeze-dry the anthocyanin concentrate at a drying temperature of -50°C and a drying time of 8 h to obtain anthocyanins.

[0044] Embodiment 4: A method for extracting anthocyanins from purple corn, comprising the following steps:

[0045] S1.1. Use purple corn silk, cob, straw and bract as raw materials, grind with a grinder at a speed of 1500 rpm for 15 min to obtain a mixed grind; dissolve β-glucosidase in a citric acid-phosphate buffer with a pH value of 5 to obtain a β-glucosidase solution with a concentration of 70 U / mL; subject the mixed grind to an enzymatic hydrolysis reaction with the β-glucosidase solution at 45°C for 3 h, add leupeptin with a concentration of 6 μg / mL to terminate the enzyme reaction after the reaction is completed, rinse with deionized water and filter to obtain a mixed grind after enzymatic hydrolysis;

[0046] S1.2, the mixed grind after enzymatic hydrolysis was mixed with a 60% ethanol solution, the solid-liquid ratio of the mixed grind to the ethanol solution was 1:30 g / mL, and stirred at a speed of 300 rpm for 30 min with a stirrer, and then N-acyl amino acid with a concentration of 4 mM was added, and the mixture was put into a microwave reactor for extraction at a power of 500 W and a temperature maintained at 45°C. The extraction time was 15 min. After the extraction was completed, it was filtered to obtain an extract containing anthocyanins;

[0047] S1.3, slowly pass the extract containing anthocyanins through the activated AB-8 macroporous resin at a flow rate of 1 mL / min, so that the anthocyanins can fully contact and be adsorbed by the resin; rinse the resin with deionized water until the effluent is colorless; then pass a 90% ethanol solution through the AB-8 macroporous resin at a flow rate of 1 mL / min to obtain anthocyanin eluate;

[0048] S1.4. Concentrate the anthocyanin eluate using a rotary evaporator at a vacuum degree of 30 mmHg, a rotation speed of 120 rpm, a temperature of 40°C, and a concentration time of 6 h to obtain anthocyanin concentrate; then freeze-dry the anthocyanin concentrate at a drying temperature of -50°C and a drying time of 8 h to obtain anthocyanins.

[0049] Comparative Example 1

[0050] The method of Example 4 was used to remove the hydrolase.

[0051] Comparative Example 2

[0052] The method of Example 4 was used to remove the N-acyl amino acid.

[0053] Comparative Example 3

[0054] The method of Example 4 was adopted without using a microwave-assisted extraction process.

[0055] Comparative Example 4

[0056] The method of Example 4 was adopted without using a macroporous resin purification process.

[0057] The present invention provides a method for extracting purple corn anthocyanidins by adding hydrolase and N-acylamino acid and adopting microwave-assisted extraction process, wherein the performance index test items and test standards of purple corn anthocyanidins are as follows:

[0058] The purity and extraction rate of anthocyanins were measured by high performance liquid chromatography in accordance with GB / T 22244-2008. The higher purity and extraction rate indicated that the extraction of anthocyanins from purple corn silk, cobs, straw, and bracts as raw materials not only had a high content but also a reliable analysis method, and was suitable for applications with high quality requirements.

[0059] According to the above standards, the data obtained are shown in Table 1:

[0060] Table 1 Purity and extraction rate of anthocyanins in Examples 1-4 and Comparative Examples 1-4

[0061] Implementation / Comparative Example purity% Extraction rate % Example 1 65.5 81.9 Example 2 67.6 83.1 Example 3 68.9 83.7 Example 4 70.2 84.8 Comparative Example 1 35.1 36.3 Comparative Example 2 38.4 37.9 Comparative Example 3 34.9 35.2 Comparative Example 4 39.8 40.1

[0062] It can be seen from Table 1 that the anthocyanins in Examples 1-4 showed significantly high purity and high extraction rate; Taking Example 4 as the optimal example, combined with Comparative Example 1, it can be seen that in the purple corn anthocyanin extraction method, when the hydrolase is removed, the purity and extraction rate of anthocyanins are significantly reduced;

[0063] When the cell structure of purple corn silk, cobs, straw, and bracts is intact, anthocyanins are wrapped inside the cells, and hydrolases (such as hemicellulase, β-glucosidase, etc.) can act on the components of the cell wall, making the structure of the cell wall loose or even broken, thereby creating a channel for anthocyanins to be released from the cell into the extraction solvent. When the hydrolase is removed, the cell wall remains intact, and it is difficult for anthocyanins to diffuse out of the cell, resulting in a significant reduction in the extraction rate. In addition to destroying the cell wall, hydrolases may also participate in the decomposition of some complex components combined with anthocyanins. In purple corn, anthocyanins may be combined with sugars, proteins and other components. Hydrolases can decompose these components so that anthocyanins can be extracted in a purer form, thereby improving the purity of anthocyanins.

[0064] Comparing Example 3 with Comparative Example 2, it can be seen that in the purple corn anthocyanin extraction method, when the N-acylamino acid is removed, the purity and extraction rate of anthocyanin are significantly reduced;

[0065] Anthocyanins themselves are chemically unstable and are easily degraded by factors such as light, heat, oxygen, and changes in their own chemical structure during the extraction process. N-acyl amino acids can form complexes with anthocyanins, and this complex structure can provide certain protection for anthocyanins; N-acyl amino acids can make anthocyanins easier to dissolve from purple corn raw materials by changing the properties of the solvent or the interaction between anthocyanins, thereby increasing the extraction rate; N-acyl amino acids may help to separate anthocyanins from other impurities to a certain extent. It may selectively bind to anthocyanins or change the interaction between anthocyanins and impurities, so that anthocyanins can be more effectively separated from impurity components (such as sugars, proteins, etc.) during extraction and subsequent purification.

[0066] Further comparing Example 3 with Comparative Example 3, it can be seen that in the purple corn anthocyanin extraction method, the microwave-assisted extraction process is not used, and the purity and extraction rate of anthocyanin are significantly reduced;

[0067] Microwave-assisted extraction can make the polar molecules in the cells move and rub rapidly under the action of the microwave electromagnetic field, thereby generating heat, causing the temperature inside the cells to rise rapidly, resulting in more complete rupture of the cell walls. When microwave assistance is not used, it is difficult to fully rupture the cell walls by relying solely on conventional solvent soaking, stirring, etc., and anthocyanins are wrapped in the cells and difficult to dissolve in large quantities, resulting in a lower extraction rate. Conventional extraction methods usually require a long period of heating to promote the dissolution of anthocyanins. For example, solvent extraction may require soaking at a certain temperature for several hours or even longer. Long-term heating will place anthocyanins in a relatively high temperature environment, which can easily lead to changes in their chemical structure, such as glycosidic bond breakage, hydroxyl oxidation, etc., thereby degrading anthocyanins and reducing their purity and extraction rate.

[0068] Combining the best example 3 with the comparative example 4, it can be seen that in the purple corn anthocyanin extraction method, the purity and extraction rate of anthocyanin are significantly reduced without using a macroporous resin purification process;

[0069] Macroporous resin has a suitable pore size and specific surface area, and can selectively adsorb anthocyanins, while leaving macromolecular impurities in the solution, thereby achieving effective separation. When macroporous resin is not used for purification, these macromolecular impurities cannot be effectively removed, resulting in a high impurity content in the anthocyanin product and reduced purity; in addition to macromolecular impurities, some small molecular impurities such as inorganic salts and organic acids will also affect the purity and stability of anthocyanins. Macroporous resin can remove some small molecular impurities and improve the purity of anthocyanins through physical adsorption and chemical adsorption; anthocyanin itself is an unstable compound. In the extracted solution, there are some factors that can trigger oxidation reactions, such as dissolved oxygen, metal ions, etc. Macroporous resin can adsorb some metal ions and other oxidizing promoters, thereby reducing their oxidation effect on anthocyanins, improving the stability of anthocyanins, and thus improving the extraction rate.

[0070] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for extracting anthocyanins from purple corn, characterized in that: The following steps are involved: S1.1, using purple corn silk, cob, straw, and husk as raw materials, grinding with a grinder at a speed of 1000-2000 rpm for 10-15 min to obtain a mixed ground product; subjecting the mixed ground product to enzymatic hydrolysis with an enzyme solution, and after the reaction, washing with deionized water and filtering to obtain a mixed ground product after enzymatic hydrolysis; S1.2, the mixed ground material after enzymatic hydrolysis was mixed with ethanol solution, stirred at 200-300 rpm for 15-30 min with a stirrer, and then N-acyl amino acid with a concentration of 3-5 mM was added, and the mixture was placed in a microwave reactor for extraction; after the extraction was completed, the mixture was filtered to obtain an extract containing anthocyanins; S1.3, slowly pass the extract containing anthocyanins through the activated macroporous resin so that the anthocyanins can fully contact and be adsorbed by the resin; rinse the resin with deionized water until the effluent is colorless; then pass a 70-95% ethanol solution through the macroporous resin at a flow rate of 1-2 mL / min to obtain anthocyanin eluate; S1.

4. Concentrate the anthocyanin eluate using a rotary evaporator with a vacuum degree of 20-50 mmHg, a rotation speed of 80-150 rpm, a temperature of 30-40°C, and a concentration time of 4-6 h to obtain anthocyanin concentrate; then freeze-dry the anthocyanin concentrate to obtain anthocyanins.

2. The method for extracting anthocyanins from purple corn according to claim 1, characterized in that: In the above S1.1, the enzyme solution is prepared by dissolving the hydrolase in a citric acid-phosphate buffer solution with a pH value of 4-6, and the concentration of the enzyme solution is 50-100 U / mL.

3. The method for extracting anthocyanins from purple corn according to claim 2, characterized in that: The hydrolase is any one of hemicellulase or β-glucosidase.

4. The method for extracting anthocyanins from purple corn according to claim 1, characterized in that: In S1.1, the enzymatic hydrolysis reaction is to react the mixed ground material with the enzyme solution at 37-50° C. for 2-4 hours, and after the reaction is completed, leupeptin with a concentration of 1-10 μg / mL is added to terminate the enzyme reaction.

5. The method for extracting anthocyanins from purple corn according to claim 1, characterized in that: In the S1.2, the concentration of the ethanol solution is 50-70%.

6. The method for extracting anthocyanins from purple corn according to claim 1, characterized in that: In the S1.2, the material-liquid ratio of the mixed ground material to the ethanol solution is 1:25-45 g / mL.

7. The method for extracting anthocyanins from purple corn according to claim 1, characterized in that: In S1.2, the power of the microwave reactor is 400-600 W, the temperature is maintained at 40-50° C., and the extraction time is 10-20 min.

8. The method for extracting anthocyanins from purple corn according to claim 1, characterized in that: In S1.3, the extraction solution containing anthocyanins slowly passes through the macroporous resin at a speed of 1-2 mL / min.

9. The method for extracting anthocyanins from purple corn according to claim 1, characterized in that: In the above S1.3, the macroporous resin is any one of AB-8 macroporous resin and D101 macroporous resin.

10. The method for extracting anthocyanins from purple corn according to claim 1, characterized in that: In S1.4, the freeze-drying temperature is -40 to -50°C, and the drying time is 8 to 10 hours.