Low-temperature freezing vacuum drying nanometer processing method for extracting anthocyanin from purple corn

Abstract

The invention belongs to the technical field of extraction and purification of plant components, and relates to a low-temperature freezing vacuum drying nano processing method for extracting anthocyanin from purple corn, in particular to a method for extracting anthocyanin from corn kernels, cores, straws, roots and stigmas of purple corn. The processing method comprises the steps of pretreatment, concentration, hydroxyl radical treatment, quick freezing, nano crushing and the like. A hydroxyl radical treatment method is adopted, so that harmful substances such as pesticide residues can be efficiently, quickly and thoroughly removed; the effect of extracting the anthocyanin from corn kernels, roots, cores, stems and stigma of purple corn by adopting a low-temperature freezing vacuum drying technology is remarkable, the purification rate is high, and the anthocyanin containing 99% of biological activity is achieved. The nanoscale anthocyanin is processed by adopting jet mill equipment and can be conveniently absorbed by a human body and widely applied to various fields.

Description

Technical Field

[0001] This invention belongs to the field of plant component extraction and purification technology, and relates to a low-temperature freeze-drying nanoprocessing method for extracting anthocyanins from purple corn, specifically a method for extracting anthocyanins from the kernels, cobs, stalks, roots and silks of purple corn. Background Technology

[0002] Anthocyanins, also known as anthocyanin pigments, are a class of water-soluble natural pigments widely found in plants. With the improvement of people's living standards and the development of the "big health" concept, the demand for natural, healthy, and functional food ingredients is constantly increasing. Anthocyanins have excellent effects such as anti-cancer, anti-inflammatory, antibacterial, antioxidant, anti-aging, blood sugar lowering, and liver protection, and are often used in food coloring and medical care, demonstrating high application value. In recent years, they have gained increasing popularity among consumers, and the anthocyanin-related industry has also emerged. However, the raw materials for my country's current anthocyanin industry mainly come from fruits and vegetables such as blueberries, mulberries, purple cabbage, purple sweet potatoes, and various types of purple corn. These sources are low in yield, limited in number, and have a narrow planting area, resulting in high raw material costs and unstable costs that are difficult to control. In particular, there are significant differences in the purity of anthocyanin extraction processes, especially in the purification processes used in these species.

[0003] Purple corn is another natural variant of corn. After improvement and domestication, its plants contain more anthocyanins, have higher biomass, and possess unique nutritional value, thus giving it a high competitive edge in the market. According to the latest data, the Chinese anthocyanin market is continuously expanding and is currently experiencing a period of explosive demand growth. Future growth will depend on technological innovation and, as consumers' awareness of natural antioxidants and their health benefits increases, the anthocyanin market will continue to grow and expand into diversified application areas.

[0004] In recent years, the main extraction methods for anthocyanins from purple corn have been as follows: (1) Ultrasonic-assisted extraction: The cavitation effect of ultrasound is used to accelerate the contact and dissolution of anthocyanins in the solvent and improve the extraction efficiency. For example, some studies have used ultrasonic-assisted extraction of anthocyanins from purple corn and significantly improved the extraction rate of anthocyanins by optimizing the extraction parameters; (2) Microwave-assisted extraction: Microwaves can quickly heat the extraction system, shorten the extraction time, and reduce the degradation of anthocyanins. Compared with the traditional hot water extraction method, microwave-assisted extraction of anthocyanins from purple corn has the advantages of being fast, energy-saving, and efficient; (3) Aqueous two-phase extraction: By adding specific salts and organic solvents to the extract, a two-phase system is formed. The difference in the partition coefficient of anthocyanins in different phases is used to achieve efficient separation and enrichment; (4) Multi-stage extraction process: Multiple extractions are used to improve the extraction rate of anthocyanins. For example, ultrasonic-assisted extraction is performed first, and then the residue is extracted. (5) Application of membrane separation technology: Introduce membrane separation technologies such as ultrafiltration and nanofiltration during the extraction process to remove impurities and improve the purity of anthocyanins. For example, first remove macromolecular impurities through ultrafiltration membrane, and then further concentrate and purify anthocyanins using nanofiltration membrane. (6) Spray drying and microencapsulation: Spray dry the extracted anthocyanin concentrate to make powder, and add maltodextrin and other excipients for microencapsulation treatment to improve the stability and solubility of the product. (7) Enzyme-assisted extraction method: Add enzyme aids during the extraction process to improve the extraction rate of anthocyanins. For example, treat purple corn cob powder by enzyme-assisted extraction method, and then combine it with pulse electric field treatment to further improve the dissolution efficiency of anthocyanins.

[0005] In recent years, it has been reported that Northeast Forestry University has used purple corn cobs as raw materials and various membrane separation technologies to extract anthocyanin powder with an average purity of 66% and a maximum purity of 77%. According to foreign reports, supercritical fluid extraction (SFE) utilizes the strong penetrating power and high solubility of supercritical fluids (such as carbon dioxide) to extract and separate monomers such as anthocyanins with a purity of up to 97.82%.

[0006] Therefore, a new extraction technology is needed to make the method of extracting anthocyanins from purple corn simple, efficient, without adding any reagents, and with higher anthocyanin bioactivity. Summary of the Invention

[0007] In view of the aforementioned technical problems, the purpose of this invention is to provide a low-temperature freeze-drying nanoprocessing method for extracting anthocyanins from purple corn. This method is simple, efficient, and yields high extraction rates and anthocyanin purity without containing any harmful substances.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] A low-temperature freeze-vacuum drying nanoprocessing method for extracting anthocyanins from purple corn includes the following steps: Step 1, Pre-treatment: First, the cobs, stalks and roots of purple corn are coarsely crushed separately, and then soaked and washed in a dynamic circulating filter water tank. The corn kernels and silks are not soaked and washed. After washing, the materials are sent to a vacuum drying equipment (processing 5 tons per hour) for drying, and then sent to a crushing equipment for fine crushing to obtain raw materials that meet the standard requirements for extraction and concentration. Step 2: Put the above raw materials into the reaction vessel of the extraction and concentration unit, mix the raw materials with water to make a slurry, and vacuum concentrate it under a certain temperature and negative pressure to obtain concentrated anthocyanin stock solution. Step 3: Remove macromolecular impurities from the above concentrated anthocyanin stock solution by ultrafiltration membrane, then further concentrate and purify it by nanofiltration membrane, and then treat the concentrated and purified anthocyanin stock solution with hydroxyl radicals. Step 4: The anthocyanin stock solution treated with hydroxyl radicals in Step 3 is transported to the freeze-drying chamber for quick freezing at a set time and controlled temperature to form an ice-like material. Then, it is transported to the freezer and vacuumed to lower the temperature of the material and form another ice-like material. The ice-like material is then vacuum-evacuated to sublimate into a gaseous state, followed by vacuum exhaust. Simultaneously, a defrosting operation is performed during vacuum exhaust. After exiting the freezer, 99% bioactive anthocyanin, i.e., anthocyanin freeze-dried powder, is obtained. Step 5: Process the anthocyanin freeze-dried powder using an airflow pulverizer to achieve nano-sized anthocyanins.

[0010] Furthermore, in step 1, the corn stalks and roots are soaked in purified water at a ratio of 1:3 (T / L) for 15 minutes in a pool (a dynamic circulating filtration water pool); the corn cobs are soaked for 5 minutes to remove contaminants from the surface of the materials; the corn kernels and corn silks do not need to be soaked or washed.

[0011] Furthermore, in step 1, the temperature of the coarsely crushed material is controlled at 70℃ in the drying kettle, and the vacuum degree is controlled at a negative pressure of 0.07 MPa. The moisture content of the dried material is about 10%.

[0012] Furthermore, in step 1, the fineness of the material is 100-300 mesh.

[0013] Furthermore, in step 2, the mass-to-volume ratio of the raw material to the purified water is 1:5 (T / L).

[0014] Furthermore, in step 2, the temperature in the extraction and concentration reactor is controlled at 50°C, and the vacuum degree is controlled at a negative pressure of 0.06 MPa.

[0015] Furthermore, in step 3, the hydroxyl radical treatment is performed by dynamically cleaning the concentrated and purified anthocyanin stock solution with an ozone aqueous solution at a concentration of 1.5 mg / L for 25 minutes, thereby removing harmful substances to the point that there are no pesticide residues or other harmful substances.

[0016] Furthermore, in step 4, the quick-freezing time is 2.5 hours, and the anthocyanin stock solution is removed from the storage when the temperature reaches -35℃.

[0017] Furthermore, in step 5, the air jet mill is processed into a QD40E tower-shoe type air jet mill, which can achieve an anthocyanin effect of 28 nanometers.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0019] 1. The production process and route for extracting anthocyanin species raw materials in this invention are scientific, effective, and save water and electricity while reducing production costs.

[0020] 2. This invention relates to a process in which pesticide residues and other harmful substances in the kernels, roots, cobs, stems, and silks of purple corn are efficiently and rapidly degraded using a hydroxyl radical treatment method. This method achieves a high degradation rate in a short time; for example, the degradation rate of permethrin is 98.53% within 40 minutes, and most pesticides are completely degraded within one minute at room temperature. Currently, there are no reports in domestic or international media regarding processes for extracting anthocyanins from fruits, vegetables, and purple corn that demonstrate the thorough removal of pesticide residues and other harmful substances from the extract.

[0021] 3. This invention utilizes low-temperature freeze-drying technology to extract anthocyanins from the kernels, roots, cobs, stems, and silks of purple corn, achieving a high extraction rate and a concentration of 99% bioactive anthocyanins.

[0022] 4. This invention uses QD40E tower-type airflow pulverization technology to process lyophilized anthocyanin powder containing 99% bioactive properties through the principle of rotating airflow collision, achieving an anthocyanin effect of 28 nanometers, which can be applied in various fields. Detailed Implementation

[0023] To make the technical means, innovative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0024] Example 1.

[0025] A low-temperature freeze-drying nanoprocessing method for extracting anthocyanins from purple corn includes the following steps: Step 1: First, coarsely crush the cobs, stalks, and roots of the purple corn separately, then soak and wash them separately in a dynamic circulating filtered water tank. Corn kernels and silks do not require soaking. Soak the materials separately: corn stalks and roots in a 1:3 water tank for 15 minutes (using a water circulating filter); corn cobs for 5 minutes. After soaking and washing, the materials are sent to a vacuum drying autoclave (processing 5 tons per hour). The temperature is controlled at 70℃ and the negative pressure at 0.07Mpa for vacuum drying (the moisture content of the dried material is controlled at 10%). After drying, fine crushing is performed. Corn kernels and silks, which do not require drying, are finely crushed to a fineness of 100-300 mesh. The materials are then transferred to a raw material storage tank for later use. Step 2: The above raw materials are fed into the extraction reactor respectively. The mass-volume ratio of the raw materials to the pure water is 1:5 (T / L). The materials and water are mixed to form a slurry. The extraction slurry is placed in a vacuum concentration device and concentrated under vacuum at a temperature of 50℃ and a negative pressure of 0.06MPa. In step 3, large molecular impurities are removed using ultrafiltration, followed by further concentration and purification using nanofiltration. The concentrated anthocyanin solution is then subjected to hydroxyl radical treatment using a dynamic ozone-water solution cleaning method at an ozone concentration of 1.5 mg / L for 25 minutes, achieving a solution free of pesticide residues and other harmful substances. Step 4: The quick-freezing time is 2.5 hours. When the material temperature reaches -35℃, a vacuum operation is performed to lower the material temperature and form an ice-like material. Then, water is sublimated into a gaseous state under vacuum. During the vacuum degassing, a defrosting operation is performed simultaneously. After being removed from the chamber, 99% bioactive anthocyanins are extracted. Step 5: The extracted freeze-dried anthocyanin powder containing 99% biological activity is crushed using the principle of rotating airflow collision technology, that is, using QD40E type tower shoe airflow pulverization technology to achieve 28-nanometer anthocyanin effect.

[0026] Table 1. Timetable for different species / water purification, cleaning and soaking.

[0027] According to Table 1: (1) it shows that when the ratio of species to cleaned and soaked to purified water is controlled at 1:1 or 1:2, the soaking effect cannot be fully met due to insufficient ratio, and the impurities on the surface of the species cannot be removed within a certain time, affecting the extraction quality; when the ratio of species to purified water is controlled at 1:3, the standard is met, and the species cleaning and soaking can be fully met, and the impurities on the surface of the species can be removed within a certain time; when it is greater than 1:3, at 1:4 or 1:5, although the species cleaning and soaking can be met, it causes waste of water resources and waste of other production links and increases production costs.

[0028] (2) This indicates that when the washing and soaking time of corn stalks and roots is controlled within 5 to 10 minutes, the soaking effect cannot be achieved, and the impurities on the surface of the species cannot be removed within a certain time, which affects the extraction quality. When the washing and soaking time of corn stalks and roots is 15 minutes and the washing and soaking time of corn cobs is 5 minutes, it is most suitable to meet the standard requirements. When the washing and soaking time of corn stalks and roots exceeds 15 minutes and the washing and soaking time of corn cobs exceeds 5 minutes, anthocyanins can be easily released from the cells of corn stalks, roots and cobs, which affects the extraction capacity and reduces the yield.

[0029] Table 2. Different control temperatures, negative pressures, and crushing fineness.

[0030] According to Table 2, in step 1, (1) when the material is coarsely crushed, cleaned, soaked and then transported to the vacuum drying equipment, the drying effect is poor when the temperature is controlled at 50℃ and 60℃ respectively. The material has a water content of about 25%, which does not meet the standard. To meet the standard, the drying time must be extended, which will cause energy waste and increase production costs. The most suitable temperature is 70℃. When the temperature is controlled at 80℃, the material is close to the coking state. When the material is close to 90℃, it is in the coking state, which will cause material waste and increase production costs. (2) when the coarsely crushed material is cleaned, soaked and then transported to the vacuum drying equipment, the drying effect is not ideal when the vacuum negative pressure of the vacuum drying kettle is 0.06Mpa and the temperature is 70℃, and the drying time is long. The effect is suitable when the vacuum negative pressure is 0.07Mpa. Although the vacuum time is shortened when the vacuum negative pressure is 0.08Mpa, the material is close to the coking state. The results show that the vacuum drying effect is good when the temperature is controlled at 70℃ and the negative pressure is 0.07Mpa. That is, saving energy, saving time, and reducing production costs; (3) When the fine crushed material has a mesh size of more than 300 mesh, the cell components are excessively crushed, resulting in a large amount of enzymes and impurities in the cells being dissolved. These impurities will react with anthocyanins, reducing the purity and stability of anthocyanins. Excessive crushing leads to increased costs and impurity dissolution problems; When the crushed mesh size is below 100 mesh, the cell wall is not broken enough, and anthocyanins cannot be fully released from the cells; When the extraction effect is balanced at 100~300 mesh, the mass transfer resistance of anthocyanins is reduced, allowing anthocyanins to be efficiently dissolved in a shorter time and more easily released from the cells. While ensuring extraction efficiency, it avoids increased costs and impurity dissolution problems caused by excessive crushing. This degree of crushing is suitable for large-scale industrial production, which can effectively extract anthocyanins and control production costs.

Claims

1. A low-temperature freeze-vacuum drying nanoprocessing method for extracting anthocyanins from purple corn, characterized in that, Includes the following steps: Step 1, Pre-treatment: First, the cobs, stalks and roots of purple corn are coarsely crushed separately, and then soaked and washed in a dynamic circulating filter water tank. Corn kernels and silks are not soaked and washed. After washing, the materials are sent to a vacuum drying equipment for drying, and then sent to a crushing equipment for fine crushing to obtain raw materials that meet the standard requirements for extraction and concentration. Step 2: Put the above raw materials into the reaction vessel of the extraction and concentration unit, mix the raw materials with water to make a slurry, and vacuum concentrate it under a certain temperature and negative pressure to obtain concentrated anthocyanin stock solution. Step 3: Remove macromolecular impurities from the above concentrated anthocyanin stock solution by ultrafiltration membrane, then further concentrate and purify it by nanofiltration membrane, and then treat the concentrated and purified anthocyanin stock solution with hydroxyl radicals. Step 4: The anthocyanin stock solution treated with hydroxyl radicals in Step 3 is transported to the freeze-drying chamber for quick freezing at a set time and controlled temperature to form an ice-like material. Then, it is transported to the freezer and vacuumed to lower the temperature of the material and form another ice-like material. The ice-like material is then vacuum-evacuated to sublimate into a gaseous state, followed by vacuum exhaust. Simultaneously, a defrosting operation is performed during vacuum exhaust. After exiting the freezer, 99% bioactive anthocyanin, i.e., anthocyanin freeze-dried powder, is obtained. Step 5: Process the anthocyanin freeze-dried powder using an air jet mill to obtain nano-sized anthocyanins.

2. The low-temperature freeze-drying nanoprocessing method for extracting anthocyanins from purple corn according to claim 1, characterized in that, In step 1, the corn stalks and roots are soaked in a pool at a ratio of 1:3 (T / L) with purified water for 15 minutes; the corn cobs are soaked for 5 minutes to remove contaminants from the surface of the materials.

3. The low-temperature freeze-drying nanoprocessing method for extracting anthocyanins from purple corn according to claim 1, characterized in that, In step 1, the temperature of the coarsely crushed material is controlled at 70°C in the drying kettle, the vacuum degree is controlled at negative pressure at 0.07 MPa, and the moisture content of the dried material is 10%.

4. The low-temperature freeze-drying nanoprocessing method for extracting anthocyanins from purple corn according to claim 1, characterized in that, In step 1, the fineness of the material is 100-300 mesh.

5. The low-temperature freeze-drying nanoprocessing method for extracting anthocyanins from purple corn according to claim 1, characterized in that, In step 2, the mass-to-volume ratio of the raw material to the purified water is 1:5 (T / L).

6. The low-temperature freeze-drying nanoprocessing method for extracting anthocyanins from purple corn according to claim 1, characterized in that, In step 2, the temperature in the extraction and concentration reactor is controlled at 50°C, and the vacuum degree is controlled at a negative pressure of 0.06 MPa.

7. The low-temperature freeze-drying nanoprocessing method for extracting anthocyanins from purple corn according to claim 1, characterized in that, In step 3, the hydroxyl radical treatment is performed by dynamically cleaning the concentrated and purified anthocyanin stock solution with an ozone aqueous solution at a concentration of 1.5 mg / L for 25 minutes.

8. The low-temperature freeze-drying nanoprocessing method for extracting anthocyanins from purple corn according to claim 1, characterized in that, In step 4, the quick-freezing time is 2.5 hours, and the anthocyanin stock solution is removed from the storage when the temperature reaches -35℃.

9. The low-temperature freeze-drying nanoprocessing method for extracting anthocyanins from purple corn according to claim 1, characterized in that, In step 5, the air jet mill is processed into a QD40E tower-shoe type air jet mill, and anthocyanins can reach 28 nanometers.

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