Method for extracting anthocyanin from mulberries

Abstract

The invention discloses a method for extracting anthocyanin from mulberries, and relates to the technical field of anthocyanin extraction. When anthocyanin is extracted, mulberries are used as raw materials, and the preparation method comprises the following steps: crushing the raw materials; ultrahigh pressure extraction: extracting anthocyanin under ultrahigh pressure; foam separation: taking the modified nanoparticles as a foaming agent and an adsorbent, and separating out anthocyanin in the extracting solution; and sterilizing: sterilizing in a high-voltage pulse electric field, and freeze-drying to obtain the anthocyanin. The anthocyanin prepared by the method has the advantages of high purity, high extraction rate and good biological activity.

Description

Technical Field

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

[0002] Mulberry belongs to the genus Morus in the Moraceae family. It is the mature fruit of the perennial woody plant mulberry tree and is rich in nutrients and functional ingredients. Many studies have shown that mulberry is rich in anthocyanins, which have physiological functions such as antioxidant, anti-cancer, lowering blood sugar, lowering blood lipids, and protecting cardiovascular and cerebrovascular vessels, and are beneficial to health.

[0003] Therefore, in order to make better use of this type of substance, it is very important to choose a suitable extraction method. Different extraction methods will directly affect its research and utilization. At present, ultrasonic method, microwave method, organic solvent method, enzyme-assisted method, etc. are the most commonly used methods for anthocyanin extraction. Solvent extraction takes a lot of time, but the yield is not high. When using the enzyme method, enzymes and anthocyanins are often difficult to separate. The structure of thermosensitive compounds such as anthocyanins is easily destroyed under the high temperature of microwaves. Compared with traditional extraction methods, new extraction methods such as ultra-high pressure extraction have simple processes, high efficiency, and less waste emissions, and have obvious advantages in industrialization. The principle of ultra-high pressure extraction technology is to use water and oil and other media to evenly apply 100-1000MPa pressure to the material for a certain period of time, destroy hydrogen bonds, hydrophobic bonds, ionic bonds, cell walls, etc., so that the effective ingredients in the cell can flow and dissolve to achieve the extraction effect.

[0004] After the first step of extraction, a crude extract containing a large amount of sugars, proteins and other polyphenols is obtained, which needs to be further separated and purified to obtain high-purity anthocyanins. At present, the main methods for purifying anthocyanins are macroporous resin column chromatography, membrane separation, high-speed countercurrent chromatography, etc. However, the above methods all have the problems of small preparation volume, low separation efficiency and difficulty in industrialization. Foam separation is based on the principle of adsorption of surfactants on the gas-liquid interface. The bubbles generated by the bubbling gas are used as the separation medium to adsorb and enrich the target components in the solution on the gas-liquid interface. By collecting the dried foam layer and defoaming treatment, the concentrated target components are finally obtained. Foam separation was originally used for the selection of minerals, dyes, and chemical raw materials. Because it has the characteristics of recovering and enriching low-concentration substances, mild operating conditions, high separation efficiency, low cost and good environmental compatibility, it has gradually begun to extend to the fields of biological separation and separation and concentration of natural active ingredients. Summary of the invention

[0005] The object of the present invention is to provide a method for extracting anthocyanins from mulberry to solve the problems existing in the prior art.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for extracting anthocyanins from mulberry, characterized in that it mainly comprises the following preparation steps: raw material crushing, ultra-high pressure extraction, foam separation, and sterilization;

[0008] The ultra-high pressure extraction is to extract anthocyanins from mulberries using ultra-high pressure assisted solvent in an ultra-high pressure device to obtain anthocyanin crude extract;

[0009] The foam separation is to use modified nanoparticles as foaming agents, foam stabilizers and adsorbents in a foam separation tower to enrich and separate anthocyanins in anthocyanin crude extract, and obtain anthocyanin enriched liquid after desorption;

[0010] The modified nanoparticles are prepared by treating the nanoparticles with an alkali solution and then modifying them with sebacic acid;

[0011] The sterilization is carried out in a high-voltage pulse electric field.

[0012] As an optimization, the preparation method of anthocyanidins mainly comprises the following steps:

[0013] (1) Raw material pulverization: adding air-dried mulberries into a high-speed pulverizer for pulverization, passing through an 80-100 mesh sieve, and vacuum drying at 45-55° C. for 8-10 hours to obtain mulberry powder;

[0014] (2) Ultrahigh pressure extraction: mulberry powder and extract were mixed evenly at a solid-liquid ratio of 1: (35-40) g / ml, pH adjusted to 5 at room temperature, soaked for 10-15 min, sealed and placed in an ultrahigh pressure device at a pressure of 250-300 MPa for 2-3 min, and after decompression, centrifuged at 5000-6000 rpm for 10-12 min to remove the precipitate, and concentrated by 50% to obtain anthocyanin crude extract;

[0015] (3) Foam separation: Add 400-500 mg / L of modified nanoparticles to the crude anthocyanin extract and mix evenly. Adjust the pH to 5, add to the foam separation tower, adjust the gas velocity to 300-350 ml / min, and blow air into the tower in the form of bubbles through a gas distributor. Perform foam separation at room temperature. Stop when there is no foam overflow. Add the defoaming liquid collected at the top of the tower to 10-12 times the volume of pure water. Stir at 25-30°C, 400-500 r / min for 4-5 h. Centrifuge at 5000-6000 rpm for 10-12 min. The precipitate is used to recover the modified nanoparticles. Concentrate the supernatant by 50% to obtain anthocyanin-enriched liquid.

[0016] (4) Sterilization: Place the anthocyanin-enriched liquid in a high-voltage pulse electric field at 5-10°C, with a field strength of 30-50 kV / cm and a pulse frequency of 200-400 Hz for 20-30 seconds, and then freeze-dry to obtain anthocyanins.

[0017] As an optimization, the extract in step (2) is a 55wt% to 65wt% ethanol aqueous solution.

[0018] As an optimization, the modified nanoparticles in step (3) are prepared by adding the nanoparticles to a 0.1 mol / L sodium hydroxide solution at a material-liquid ratio of 1:(20-30) g / ml, stirring at 300-400 r / min at room temperature for 2-3 h, centrifuging at 7000-8000 rpm for 10-12 min, removing the supernatant, washing with pure water for 3-4 times, vacuum drying at 50-60° C. for 8-10 h, then adding a 10 wt % N,N-dimethylformamide solution of sebacic acid at a material-liquid ratio of 1:(50-60) g / ml, reacting at 110-120° C., 400-500 r / min for 10-12 h, centrifuging at 8000-10000 rpm for 8-10 min, removing the supernatant, washing the precipitate with ethanol for 3-4 times, and vacuum drying at 50-60° C. for 16-18 h.

[0019] As an optimization, the liquid height in the foam separation tower in step (3) is controlled between one half and two thirds of the tower height.

[0020] As an optimization, the defoaming liquid collected at the top of the tower in step (3) is defoamed mechanically with a stirring speed of 400 to 500 r / min.

[0021] As an optimization, the air in step (3) needs to be moistened with pure water before use.

[0022] As an optimization, the nanoparticles are one of nano-titanium dioxide, nano-zinc oxide, nano-aluminum oxide, and nano-silicon dioxide.

[0023] As an optimization, the particle size of the nanoparticles is 20-100 nm.

[0024] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0025] When extracting anthocyanidins from mulberries, the present invention uses mulberries as raw materials, and the preparation method comprises: raw material crushing; ultra-high pressure extraction: extracting anthocyanidins under ultra-high pressure; foam separation: using modified nanoparticles as foaming agents and adsorbents to separate anthocyanidins from the extract; sterilization: sterilizing in a high-voltage pulse electric field and then freeze-drying to obtain anthocyanidins.

[0026] Firstly, the mulberries are crushed and then added to an ethanol extract for mixing, and then added to an ultra-high pressure device for ultra-high pressure extraction. During the ultra-high pressure extraction process, the pressure will first be increased to the set pressure within a few seconds. This stage will cause the pressure of the material to change instantaneously, destroying substances such as cell walls that block the dissolution of anthocyanins, so that anthocyanins and other effective substances in the cells can be fully in contact with the extraction solvent. Then the pressure remains unchanged. Under ultra-high pressure, the extract entering the cells reacts with anthocyanins and other effective substances, promoting the movement of chemical equilibrium, and anthocyanins and other effective substances are rapidly dissolved into the extract. After the pressure holding time is over, the pressure is released to normal pressure within 2 to 3 seconds. The pressure acts in the opposite direction instantly, and the impact brought about causes the extract entering the mulberry cells to bring out anthocyanins and other effective substances, and the extraction process is completed. During the entire extraction process, no heating or complex organic reagents are required, and the extraction process is rapid, efficient, and simple in process, which is convenient for industrial expansion.

[0027] Secondly, the modified nanoparticles are used as foaming agents and adsorbents to separate anthocyanins from the extract. The modified nanoparticles treated with alkali solution and modified with sebacic acid have a contact angle of about 40° to 70°, and are both hydrophilic and hydrophobic, with excellent surface activity, and can be adsorbed on the gas-liquid interface to form stable foam. The alkali solution treatment increases the hydroxyl content on the surface of the nanoparticles, and then sebacic acid is grafted on the surface of the nanoparticles through an ester condensation reaction. After being modified with sebacic acid, the surface of the nanoparticles contains both the hydrophilicity of the carboxyl group and the hydrophobic long carbon chain. At the gas-liquid interface, the hydrophobic long carbon chain is exposed in the gas phase, and the hydrophilic carboxyl group retracts into the liquid phase along with the nanoparticle body, thereby forming a Stable bubbles. Under acidic conditions, the carboxyl group will carry a negative charge. At the same time, anthocyanins mainly exist in the form of positively charged chalcanal cations under this pH condition, which also contain a large number of hydroxyl, methoxy and other groups. The modified nanoparticles with negative charges and carboxyl groups can adsorb anthocyanins in the crude extract by electrostatic bonding, hydrogen bonding, and ester condensation, thereby separating and purifying the anthocyanins. The modified nanoparticles adsorbed with anthocyanins are collected by the foam collector on the top of the tower along with the foam and then defoamed by mechanical stirring to obtain a defoaming solution. The anthocyanins adsorbed on the modified nanoparticles are then desorbed with pure water. The desorbed modified nanoparticles can be reused after recovery, effectively reducing costs.

[0028] Finally, the anthocyanidin dissolved in the water is sterilized by a high-voltage pulse electric field. This process can effectively kill bacteria and ensure the storage stability of anthocyanidin. Anthocyanidin is obtained after freeze drying. The anthocyanidin extracted by the present invention has the advantages of high biological activity and good purity. At the same time, the extraction process is simple and the conditions are mild, which avoids the degradation of anthocyanidin and the loss of biological activity caused by long extraction time and bad conditions, and maximizes the utilization rate of anthocyanidin in mulberry. After the anthocyanidin is purified by foam separation, the remaining residual liquid can continue to extract other effective components, and there is no loss of other effective components due to the extraction of anthocyanidin. DETAILED DESCRIPTION

[0029] 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.

[0030] The information of some raw materials used in all the following examples and comparative examples is as follows:

[0031] Mulberry: The fresh fruit comes from Dechang County, Liangshan Yi Autonomous Prefecture, Sichuan Province. It is Dechang mulberry. The fresh mulberry fruit is air-dried through a natural air-drying process before extraction and then used.

[0032] Nanoparticles: Nano titanium dioxide with a particle size of 50-60 nm was purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.

[0033] The foam separation tower used in all the following examples and comparative examples has an inner diameter of 35 mm and a height of 1000 mm.

[0034] The preparation method of the modified nanoparticles used in all the following embodiments and comparative examples is as follows: nano-titanium dioxide is added to a 0.1 mol / L sodium hydroxide solution at a solid-liquid ratio of 1:25 g / ml, stirred at 300 r / min for 3 h at room temperature, centrifuged at 8000 rpm for 10 min, the supernatant is removed, washed with pure water 4 times, vacuum dried at 50°C for 10 h, and then added to a 10 wt% N,N-dimethylformamide solution of sebacic acid at a solid-liquid ratio of 1:55 g / ml, reacted at 110°C, 400 r / min for 12 h, centrifuged at 10000 rpm for 8 min, the supernatant is removed, the precipitate is washed with ethanol 4 times, and vacuum dried at 60°C for 16 h to obtain modified nanoparticles.

[0035] The extracting solution used in all the following examples and comparative examples is a 60 wt % ethanol aqueous solution.

[0036] Embodiment 1:

[0037] A method for extracting anthocyanins from mulberry, the preparation method of the anthocyanins mainly comprising the following steps:

[0038] (1) Raw material pulverization: adding air-dried mulberries into a high-speed pulverizer for pulverization, passing through an 80-mesh sieve, and vacuum drying at 45° C. for 10 h to obtain mulberry powder;

[0039] (2) Ultrahigh pressure extraction: mulberry powder and extract were mixed evenly at a solid-liquid ratio of 1:35 g / ml, adjusted to pH 5 at room temperature, soaked for 15 min, sealed and placed in an ultrahigh pressure device at a pressure of 250 MPa for 3 min, and centrifuged at 5000 rpm for 12 min after pressure relief to remove the precipitate, and concentrated by 50% to obtain anthocyanin crude extract;

[0040] (3) Foam separation: Add 400 mg / L of modified nanoparticles to the crude anthocyanin extract and mix well. Adjust the pH to 5, add the mixture to the foam separation tower, adjust the gas velocity to 300 ml / min, and blow air into the tower in the form of bubbles through a gas distributor. Perform foam separation at room temperature. Stop when there is no foam overflow. Add the defoaming liquid collected at the top of the tower to 10 times the volume of pure water. Stir at 25°C, 400 r / min for 5 h, centrifuge at 5000 rpm for 12 min, and use the precipitate to recover the modified nanoparticles. Concentrate the supernatant by 50% to obtain anthocyanin-enriched liquid.

[0041] (4) Sterilization: The anthocyanin-enriched liquid was placed in a high-voltage pulse electric field at 5°C, with a field strength of 30 kV / cm and a pulse frequency of 400 Hz for 20 s, and anthocyanins were obtained after freeze-drying.

[0042] Embodiment 2:

[0043] A method for extracting anthocyanins from mulberry, the preparation method of the anthocyanins mainly comprising the following steps:

[0044] (1) Raw material pulverization: adding air-dried mulberries into a high-speed pulverizer for pulverization, passing through a 90-mesh sieve, and vacuum drying at 50° C. for 9 h to obtain mulberry powder;

[0045] (2) Ultrahigh pressure extraction: mulberry powder and extract were mixed evenly at a solid-liquid ratio of 1:38 g / ml, adjusted to pH 5 at room temperature, soaked for 12 min, sealed and placed in an ultrahigh pressure device at a pressure of 275 MPa for 2.5 min. After depressurization, centrifuged at 5500 rpm for 11 min to remove the precipitate, and concentrated by 50% to obtain anthocyanin crude extract;

[0046] (3) Foam separation: Add 450 mg / L of modified nanoparticles to the crude anthocyanin extract and mix well. Adjust the pH to 5 and add the mixture to the foam separation tower. Adjust the gas velocity to 325 ml / min. Bubble air into the tower through a gas distributor in the form of bubbles. Perform foam separation at room temperature. Stop when there is no foam overflow. Add the defoaming liquid collected at the top of the tower to 11 times the volume of pure water. Stir at 28°C, 450 r / min for 4.5 h. Centrifuge at 5500 rpm for 11 min. The precipitate is used to recover the modified nanoparticles. The supernatant is concentrated by 50% to obtain anthocyanin-enriched liquid.

[0047] (4) Sterilization: The anthocyanin-enriched liquid was placed in a high-voltage pulse electric field at 8°C, with a field strength of 40 kV / cm and a pulse frequency of 300 Hz for 25 s, and anthocyanins were obtained after freeze-drying.

[0048] Embodiment 3:

[0049] A method for extracting anthocyanins from mulberry, the preparation method of the anthocyanins mainly comprising the following steps:

[0050] (1) Raw material pulverization: adding air-dried mulberries into a high-speed pulverizer for pulverization, passing through a 100-mesh sieve, and vacuum drying at 55° C. for 8 h to obtain mulberry powder;

[0051] (2) Ultrahigh pressure extraction: mulberry powder and extract were mixed evenly at a solid-liquid ratio of 1:40 g / ml, adjusted to pH 5 at room temperature, soaked for 10 min, sealed and placed in an ultrahigh pressure device at a pressure of 300 MPa for 2 min, and after decompression, centrifuged at 6000 rpm for 10 min to remove the precipitate and concentrated by 50% to obtain anthocyanin crude extract;

[0052] (3) Foam separation: Add 500 mg / L of modified nanoparticles to the crude anthocyanin extract and mix well. Adjust the pH to 5, add the mixture to the foam separation tower, adjust the gas velocity to 350 ml / min, and blow air into the tower in the form of bubbles through a gas distributor. Perform foam separation at room temperature. Stop when there is no foam overflow. Add the defoaming liquid collected at the top of the tower to 12 times the volume of pure water. Stir at 30°C, 500 r / min for 4 h, centrifuge at 6000 rpm for 10 min, and use the precipitate to recover the modified nanoparticles. Concentrate the supernatant by 50% to obtain anthocyanin-enriched liquid.

[0053] (4) Sterilization: The anthocyanin-enriched liquid was placed in a high-voltage pulse electric field at 10°C, with a field strength of 50 kV / cm and a pulse frequency of 200 Hz for 30 s, and anthocyanins were obtained after freeze-drying.

[0054] Comparative Example 1:

[0055] The difference between the method for extracting anthocyanins from mulberry in Comparative Example 1 and Example 2 is the difference in step (2), which is modified as follows: Extraction: mulberry powder and extract are mixed evenly at a solid-liquid ratio of 1:38 g / ml, adjusted to pH 5 at room temperature, soaked for 12 hours, ultrasonically treated at 35° C., 150 W for 60 minutes, centrifuged at 5500 rpm for 11 minutes, the precipitate is removed, and concentrated by 50% to obtain anthocyanin crude extract. The remaining steps are the same as in Example 2.

[0056] Comparative Example 2:

[0057] The difference between the method for extracting anthocyanins from mulberry in Comparative Example 2 and Example 2 lies in the difference in step (3), which is modified as follows: Foam separation: 450 mg / L of nano-titanium dioxide is added to the crude anthocyanin extract and mixed evenly, the pH is adjusted to 5, and the mixture is added to the foam separation tower, the gas velocity is adjusted to 325 ml / min, and air is bubbled into the tower through a gas distributor in the form of bubbles, and foam separation is performed at room temperature. When no foam overflows, the foam separation is stopped, and the defoaming liquid collected at the top of the tower is added to 11 times the volume of pure water, stirred at 28° C. and 450 r / min for 4.5 h, centrifuged at 5500 rpm for 11 min, and the precipitate is used to recover the modified nanoparticles, and the supernatant is concentrated by 50% to obtain anthocyanin enriched liquid. The remaining steps are the same as in Example 2.

[0058] Comparative Example 3:

[0059] The difference between the method for extracting anthocyanins from mulberry in Comparative Example 3 and Example 2 lies in the difference in step (3), which is modified as follows: Foam separation: 50 μg / L of lauryl betaine is added to the crude anthocyanin extract and mixed evenly, the pH is adjusted to 5, and the mixture is added to the foam separation tower, the gas velocity is adjusted to 325 ml / min, and air is bubbled into the tower through a gas distributor in the form of bubbles, and foam separation is performed at room temperature. When no foam overflows, the foam separation is stopped, and the defoaming liquid collected at the top of the tower is added to 2 times the volume of pure water, stirred at 28° C. and 450 r / min for 4.5 h, and concentrated by 50% to obtain anthocyanin enriched liquid. The remaining steps are the same as those in Example 2.

[0060] Test Example 1:

[0061] Anthocyanin extraction rate test: Take the crude anthocyanin extract prepared in step (2) and measure it with an ultraviolet spectrophotometer at a wavelength of 535 nm. The concentration of anthocyanins in the crude anthocyanin extract is calculated using the standard curve. The extraction rate of anthocyanins is calculated based on the mass of mulberry powder in mg / g. Each group is tested 5 times and the average value is recorded.

[0062] The results are shown in Table 1.

[0063] Table 1

[0064] Extraction rate Extraction rate Example 1 9.845mg / g Comparative Example 1 6.548mg / g Example 2 9.987mg / g Comparative Example 2 9.983mg / g Example 3 9.832mg / g Comparative Example 3 9.979mg / g

[0065] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1, it can be found that the anthocyanins prepared by the present invention have a high extraction rate.

[0066] By comparing the data in the table, it can be seen that the ultra-high pressure extraction method effectively improves the extraction rate of anthocyanins in mulberry. The traditional ultrasonic-assisted solvent extraction method not only has a long process time but also has poor extraction efficiency. The ultra-high pressure extraction method, with its unique technical principles, not only greatly shortens the extraction time, but also effectively improves the extraction rate of anthocyanins and effectively improves the utilization rate of mulberry.

[0067] Test Example 2:

[0068] Separation efficiency determination: The recovery rate R and enrichment ratio E of the foam separation in step (3) are used to evaluate the separation efficiency of the foam separation process, where R = (C 1 ×V 1 ) / (C 0 ×V 0 )×100%, E=C 1 / C 0 , V 1 is the volume of defoaming solution, V 0 is the volume of the crude anthocyanin extract, C 1 is the concentration of anthocyanins in the defoaming solution, C 0 is the concentration of anthocyanins in the crude anthocyanin extract, and the concentration is measured according to the method in Test Example 1.

[0069] The results are shown in Table 2.

[0070] Table 2

[0071] Recovery rate Enrichment ratio Example 1 96.42％ 39.48 Example 2 97.25％ 40.17 Example 3 96.68％ 38.98 Comparative Example 1 96.84％ 39.82 Comparative Example 2 5.47％ 0.22 Comparative Example 3 62.83％ 3.28

[0072] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 2, it can be found that the separation process for preparing anthocyanidins of the present invention has good separation efficiency.

[0073] Comparison of the data in the table shows that the modification of the nanoparticles fully improves their surface activity, and their recovery rate and enrichment ratio are greater than those of the unmodified nanoparticles. At the same time, the separation effect of the modified nanoparticles is also greater than that of the traditional surfactant lauryl betaine, which effectively improves the separation efficiency of the foam separation process, improves the purity of the anthocyanins obtained, and reduces the loss of biological activity.

[0074] Test Example 3:

[0075] Anthocyanin bioactivity assay: The free radical scavenging rate of the prepared anthocyanin was tested to evaluate its bioactivity. The prepared anthocyanin was dissolved in pure water to prepare a 100 mg / L anthocyanin sample. The specific test method is as follows:

[0076] DPPH method: dissolve 1,1-diphenyl-2-picrylhydrazyl in ethanol to prepare a 0.1mmol / L 1,1-diphenyl-2-picrylhydrazyl ethanol solution, mix the anthocyanin sample and the 0.1mmol / L 1,1-diphenyl-2-picrylhydrazyl ethanol solution in a volume ratio of 1:9, let it stand in the dark at room temperature for 30 minutes, and use a UV spectrophotometer to measure the absorbance at 517nm. The control group is added with ethanol as a replacement for the anthocyanin sample. Each sample is made in triplicate, and the free radical scavenging rate is calculated.

[0077] ABTS method: 7mmol / L 2,2-azino-bis(3-ethyl-benzothiazole-6-sulfonic acid) diammonium salt aqueous solution was mixed with 2.45mmol / L potassium persulfate aqueous solution in a volume ratio of 1:1, and allowed to stand in the dark at room temperature for 12h to obtain ABTS free radical solution; it was diluted with anhydrous ethanol to stabilize its absorbance at 734nm at 0.7±0.02; 20μL anthocyanin sample was reacted with 4mL ABTS free radical solution for 60min, and the absorbance was measured at 734nm. The control group was treated with ethanol as an anthocyanin sample. Three parallels were made for each sample, and the free radical scavenging rate was calculated.

[0078] Superoxide anion free radical scavenging: 1 ml of anthocyanin sample was mixed with 4.5 ml of tris(hydroxymethyl)aminomethane hydrochloride buffer solution with a pH value of 8.2, and then 0.4 ml of 3 mmol / L pyrogallic acid was added. The mixed solution was protected from light for 30 minutes, and the absorbance of each group was measured at 320 nm. The control group was added with ethanol as a replacement for the anthocyanin sample. Three parallels were made for each sample, and the free radical scavenging rate was calculated.

[0079] The results are shown in Table 3.

[0080] Table 3

[0081]

[0082] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 3, it can be found that the anthocyanidins prepared by the present invention have good biological activity.

[0083] By comparing the data in the table, it is shown that the high extraction efficiency and short extraction time of the ultrahigh pressure extraction method fully retain the biological activity of anthocyanins, while the use of traditional ultrasonic assisted solvent extraction method causes some anthocyanins to denature and lose their antioxidant activity due to long extraction time; at the same time, the foam separation method also effectively separates and removes other impurities to ensure the purity of anthocyanins, and high-purity anthocyanins have better biological activity. At the same time, the modified nanoparticles are selective in the adsorption of anthocyanins, and higher purity anthocyanins can be obtained compared with lauryl betaine. In addition, lauryl betaine is difficult to separate and difficult to recycle, while the modified nanoparticles are simple to desorb and separate, and are easier to recycle.

[0084] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for extracting anthocyanins from mulberry, characterized in that: The main preparation steps include: raw material crushing, ultra-high pressure extraction, foam separation, and sterilization; The ultra-high pressure extraction is to extract anthocyanins from mulberries using ultra-high pressure assisted solvent in an ultra-high pressure device to obtain anthocyanin crude extract; The foam separation is to use modified nanoparticles as foaming agents, foam stabilizers and adsorbents in a foam separation tower to enrich and separate anthocyanins in anthocyanin crude extract, and obtain anthocyanin enriched liquid after desorption; The modified nanoparticles are prepared by treating the nanoparticles with an alkali solution and then modifying them with sebacic acid; The sterilization is carried out in a high-voltage pulse electric field.

2. The method for extracting anthocyanins from mulberry according to claim 1, characterized in that: The preparation method of anthocyanidins mainly comprises the following steps: (1) Raw material pulverization: adding air-dried mulberries into a high-speed pulverizer for pulverization, passing through an 80-100 mesh sieve, and vacuum drying at 45-55° C. for 8-10 hours to obtain mulberry powder; (2) Ultrahigh pressure extraction: mulberry powder and extract were mixed evenly at a solid-liquid ratio of 1: (35-40) g / ml, pH adjusted to 5 at room temperature, soaked for 10-15 min, sealed and placed in an ultrahigh pressure device at a pressure of 250-300 MPa for 2-3 min, and after decompression, centrifuged at 5000-6000 rpm for 10-12 min to remove the precipitate, and concentrated by 50% to obtain anthocyanin crude extract; (3) Foam separation: Add 400-500 mg / L of modified nanoparticles to the crude anthocyanin extract and mix evenly. Adjust the pH to 5, add to the foam separation tower, adjust the gas velocity to 300-350 ml / min, and blow air into the tower in the form of bubbles through a gas distributor. Perform foam separation at room temperature. Stop when there is no foam overflow. Add the defoaming liquid collected at the top of the tower to 10-12 times the volume of pure water. Stir at 25-30°C, 400-500 r / min for 4-5 h. Centrifuge at 5000-6000 rpm for 10-12 min. The precipitate is used to recover the modified nanoparticles. Concentrate the supernatant by 50% to obtain anthocyanin-enriched liquid. (4) Sterilization: Place the anthocyanin-enriched liquid in a high-voltage pulse electric field at 5-10°C, with a field strength of 30-50 kV / cm and a pulse frequency of 200-400 Hz for 20-30 seconds, and then freeze-dry to obtain anthocyanins.

3. A method for extracting anthocyanins from mulberry according to claim 2, characterized in that: The extract in step (2) is a 55wt% to 65wt% ethanol aqueous solution.

4. The method for extracting anthocyanins from mulberry according to claim 2, characterized in that: The modified nanoparticles in step (3) are prepared by adding the nanoparticles to a 0.1 mol / L sodium hydroxide solution at a material-liquid ratio of 1:(20-30) g / ml, stirring at 300-400 r / min at room temperature for 2-3 hours, centrifuging at 7000-8000 rpm for 10-12 minutes, removing the supernatant, washing with pure water for 3-4 times, vacuum drying at 50-60° C. for 8-10 hours, then adding the nanoparticles to a 10 wt % N,N-dimethylformamide solution of sebacic acid at a material-liquid ratio of 1:(50-60) g / ml, reacting at 110-120° C. and 400-500 r / min for 10-12 hours, centrifuging at 8000-10000 rpm for 8-10 minutes, removing the supernatant, washing the precipitate with ethanol for 3-4 times, and vacuum drying at 50-60° C. for 16-18 hours.

5. The method for extracting anthocyanins from mulberry according to claim 2, characterized in that: The liquid height in the foam separation tower in step (3) is controlled between one half and two thirds of the tower height.

6. The method for extracting anthocyanins from mulberry according to claim 2, characterized in that: The defoaming liquid collected at the top of the tower in step (3) is defoamed mechanically at a stirring speed of 400 to 500 r / min.

7. The method for extracting anthocyanins from mulberry according to claim 2, characterized in that: The air in step (3) needs to be moistened with pure water before use.

8. The method for extracting anthocyanins from mulberry according to claim 4, characterized in that: The nanoparticles are one of nano titanium dioxide, nano zinc oxide, nano aluminum oxide and nano silicon dioxide.

9. The method for extracting anthocyanins from mulberry according to claim 4, characterized in that: The particle size of the nanoparticles is 20-100 nm.

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