Preparation process of asparagus powder with high content of asparagus saponin

Abstract

The invention relates to the technical field of plant extracts, in particular to a preparation process of asparagus powder with high content of asparagus saponin. Comprising the following steps: S1, cutting fresh asparagus tender stems into segments, carrying out enzyme deactivation treatment, drying with hot air, and screening to obtain pretreated asparagus powder; s2, mixing the pretreated asparagus powder with a 70% ethanol solution, performing ultrasonic treatment, performing centrifugation, and taking supernate, so as to obtain an asparagus saponin crude extract; s3, washing the macroporous resin, filling the macroporous resin into a resin column, loading a sample of the asparagus saponin crude extract to the resin column, washing impurities with deionized water, eluting with ethanol, collecting the eluate, performing rotary evaporation on the eluate under reduced pressure, adding maltodextrin, performing spray drying, and sieving with a 100-mesh sieve after drying, thereby obtaining the asparagus powder with high asparagus saponin content. By optimizing the raw material combination and the preparation process, the requirements of asparagus saponin extraction can be better met, and the content of saponin in the asparagus powder is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of plant extracts, and particularly to a preparation process of asparagus powder with high content of asparagus saponins. Background Art

[0002] Asparagus is a vegetable rich in nutrients. It not only contains a variety of vitamins, minerals and dietary fibers, but also contains a variety of bioactive components, such as asparagus saponins, polysaccharides, flavonoids and polyphenols. In recent years, with the in-depth research on the active components of asparagus, asparagus saponins have received extensive attention due to their significant biological activities and medicinal values. Asparagus saponins have a variety of biological activities, including anti-tumor, immunomodulatory, lipid-lowering, and sleep-improving effects. Research shows that asparagus saponins have obvious inhibitory effects on the tumor growth of S180 and H22 tumor-bearing mice, and the tumor inhibition rates reach 39.53% and 34.81% respectively. In addition, asparagus saponins can also improve endocrine disorders and sleep quality by regulating the nervous, immune and endocrine systems, reducing the cortisol level, and increasing the normal secretion level of 5-hydroxytryptamine. At the same time, asparagus powder containing asparagus saponins, as a functional food raw material, has broad application prospects. It can be used to prepare solid beverages, health foods, pharmaceutical products, etc., to meet the needs of consumers for health and nutrition. At the same time, with the in-depth research on the biological activities of asparagus saponins, the application of asparagus powder in the field of tumor prevention and treatment will also be further expanded. There are various extraction methods for asparagus saponins, including heat reflux or water extraction methods, etc. Common extraction solvents include ethanol, etc. Through a preliminary separation column, deionized water and ethanol are used as eluents, and asparagus saponins can be obtained after vacuum drying.

[0003] In the prior art, in the process of preparing asparagus powder with high content of asparagus saponins, resins (such as ion exchange resins, etc.) are often used for the separation and purification of saponins. However, resins are prone to swelling or shrinking in solvents, resulting in column bed collapse or uneven flow rate, affecting the separation efficiency, and may cause resin particles to break and generate fine powder to block the chromatography column. In addition, the adsorption of saponins by resins may be accompanied by co-adsorption of impurities such as polysaccharides and pigments, requiring multiple elutions or gradient solvent adjustments, increasing the process complexity. At the same time, resin regeneration consumes a large amount of solvents, but the adsorption capacity may decrease after regeneration, and new resins need to be frequently replaced. Summary of the Invention

[0004] In order to solve the problems mentioned in the above background art, the present invention provides a preparation process of asparagus powder with high content of asparagus saponins.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: A preparation process of asparagus powder with high content of asparagus saponins, comprising the following steps: S1. Cut the fresh asparagus tender stems into sections, immediately perform steam enzyme inactivation treatment for 3 - 5 min, dry with hot air for 2 - 3 h until the water content is <5%, crush and pass through an 80 - mesh sieve to obtain pretreated asparagus powder; S2. Mix the asparagus powder with 70% (v / v) ethanol solution, perform ultrasonic extraction for 30 - 40 min, centrifuge for 15 - 20 min, take the supernatant to obtain the crude extract of asparagus saponins; S3. After rinsing the macroporous resin, load it into a resin column. Load the crude extract of asparagus saponins onto the resin column, first rinse the impurities with deionized water, then elute with ethanol, collect the eluate, perform rotary evaporation under reduced pressure on the eluate, add maltodextrin, spray - dry, and after drying, pass through a 100 - mesh sieve to obtain asparagus powder with high - content asparagus saponins.

[0006] Furthermore, in step S1, the saponin content of the fresh asparagus tender stems is 0.8 - 1.2% (w / w), the section length is 3 - 5 mm, the enzyme inactivation treatment uses steam at 100 - 105 °C for enzyme inactivation, and the temperature of hot - air drying is 60 - 70 °C.

[0007] Furthermore, in step S2, the material - to - liquid ratio of the pretreated asparagus powder and 70% ethanol solution is 1:20 - 25 (g / mL), and the ultrasonic treatment conditions are: temperature 60 - 65 °C, power 200 - 300 W, frequency 30 - 40 kHz, and repeat the extraction 2 - 3 times.

[0008] Furthermore, the preparation of the macroporous resin in step S2 includes the following steps: A1. Dissolve lignosulfonate in deionized water, add sodium dodecyl sulfate and Tween 80, stir until a homogeneous solution is formed to obtain an aqueous phase. Mix pentafluorostyrene and hydroxypropyl acrylate, place in a water bath and stir for 20 - 30 min to obtain an oil phase; A2. Under nitrogen protection, slowly drop the oil phase into the aqueous phase, stir and dissolve, add azobisisobutyronitrile, emulsify for 15 - 25 min to obtain a microemulsion, transfer it to a reaction kettle, pass nitrogen to remove oxygen, raise the temperature and react for 12 - 18 h. After terminating the reaction, demulsify, centrifuge to collect the precipitate, wash to obtain white porous particles. Immerse the white porous particles in sulfuric acid solution, stir for 2 - 4 h, centrifuge to collect the precipitate, wash, and dry to obtain the macroporous resin.

[0009] Furthermore, in step S3, when rinsing, first rinse with 95% ethanol and then deionized water until there is no alcohol smell. The loading flow rate is 2 - 3 BV / h, the adsorption capacity is (1.2 - 1.5) g saponins / 100 g resin, the ethanol elution uses 70 - 80% (v / v) ethanol at a flow rate of (1.5 - 2) BV / h, and the elution end point is that the saponin concentration in the effluent is <0.1 mg / mL.

[0010] Further, the conditions for reduced-pressure rotary evaporation in step S3 are as follows: the temperature is 50 - 55°C, the vacuum degree is (-0.08) - (-0.09) MPa, and it is concentrated until the saponin concentration ≥ 15 mg / mL.

[0011] Further, maltodextrin is added at 2 - 3% of the mass of the solid matter in the concentrated solution in step S3, and the spray drying parameters are as follows: the inlet air temperature is 160 - 165°C, the outlet air temperature is 80 - 85°C, and the atomization pressure is 0.2 - 0.3 MPa.

[0012] Further, in step A1, the mass ratio of lignosulfonate, deionized water, sodium dodecyl sulfate, and Tween 80 is (4 - 5):(100 - 110):(1.0 - 1.5):(0.3 - 0.5), and the mass ratio of pentafluorostyrene and hydroxypropyl acrylate is (4.5 - 5.2):(2.3 - 2.8).

[0013] Further, in step A2, the mass ratio of the oil phase, the water phase, and azobisisobutyronitrile is 1:(5 - 10):(0.001 - 0.01), and the mass ratio of the white porous particles and the sulfuric acid solution is 1:(5 - 10), where the pH value of the sulfuric acid solution is 2.5 - 3.0.

[0014] Further, in step A1, the temperature of the water bath is 50 - 55°C, the stirring speed is 400 - 500 rpm, in step A2, the emulsification speed is 1000 - 2000 rpm, the temperature for heating up is 60 - 65°C, and the stirring speed is 100 - 200 rpm.

[0015] Advantages of the present invention: 1. In the technical solution of the present invention, through the gradient copolymerization of pentafluorostyrene and hydroxypropyl acrylate, a synergistic combination of rigid fluorinated chain segments and flexible hydrophilic chain segments is formed inside the resin. The high bond energy characteristic of the fluorinated chain segments endows the resin skeleton with strong mechanical support, while the hydrophilic chain segments restrict the swelling deformation through the hydrogen bond network, so that the swelling rate of the resin in the ethanol - water system is significantly reduced, effectively avoiding problems such as column bed collapse and uneven flow rate caused by swelling of traditional resins, and ensuring the stability of the chromatography column during the continuous separation process.

[0016] 2. In the technical solution of the present invention, lignosulfonate forms a through - hole multi - level pore structure during the high - temperature pyrolysis process, forming a rapid mass transfer channel, improving the dynamic adsorption rate, providing high - specific - surface - area adsorption sites, and realizing the synergistic improvement of mass transfer efficiency and selectivity. On the one hand, co - adsorption of macromolecular impurities such as polysaccharides is reduced through the size exclusion effect, and on the other hand, the diffusion path of saponin molecules is shortened, significantly reducing the column pressure and avoiding the problem of fine powder blockage, thereby improving the separation and purification efficiency.

[0017] 3. In the technical solution of the present invention, sulfuric acid treatment synchronously introduces sulfonic acid groups and carboxyl groups with controllable hydrolysis on the resin surface to form a double-regulated interface of charge and polarity. The sulfonic acid groups target and bind to the negatively charged region of the saponin glycosyl group through electrostatic interaction, while the fluorinated chain segments lock the saponin steroid nucleus structure through hydrophobic interaction, improving the selective adsorption of asparagus saponins and reducing the non-specific adsorption of impurities such as pigments and polysaccharides, thereby simplifying the subsequent elution steps and enabling the efficient recovery of high-purity products without gradient solvent adjustment. Detailed implementation mode

[0018] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the scope of protection of the present invention.

[0019] Unless otherwise specified, the raw materials used in the present invention are all conventional products purchased from the market.

[0020] Preparation example 1 The macroporous resin is prepared through the following steps: A1. Dissolve 40 g of lignosulfonate in 1000 g of deionized water, add 1 g of sodium dodecyl sulfate and 0.3 g of Tween 80, stir at a speed of 400 rpm until a homogeneous solution is formed to obtain an aqueous phase. Mix 4.5 g of pentafluorostyrene and 23 g of hydroxypropyl acrylate, place in a water bath at 50 °C and stir at a speed of 400 rpm for 20 min to obtain an oil phase; A2. Under nitrogen protection, slowly drop 10 g of the oil phase into 50 g of the aqueous phase, stir to dissolve, add 0.01 g of azobisisobutyronitrile, emulsify at a speed of 1000 rpm for 15 min to obtain a microemulsion, transfer it to a reaction kettle, pass nitrogen to remove oxygen, raise the temperature to 60 °C and react for 12 h. After terminating the reaction, demulsify, centrifuge to collect the precipitate, wash, and obtain white porous particles. Immerse 10 g of the white porous particles in 50 g of sulfuric acid solution with a pH value of 2.5, stir at a speed of 100 rpm for 2 h, centrifuge to collect the precipitate, wash, and dry to obtain the macroporous resin.

[0021] Preparation example 2 The macroporous resin is prepared through the following steps: A1. Dissolve 45 g of lignosulfonate in 1050 g of deionized water, add 1.3 g of sodium dodecyl sulfate and 0.4 g of Tween 80, stir at a speed of 450 rpm until a homogeneous solution is formed to obtain an aqueous phase. Mix 4.9 g of pentafluorostyrene and 25 g of hydroxypropyl acrylate, place in a water bath at 52 °C and stir at a speed of 450 rpm for 25 min to obtain an oil phase; A2. Under nitrogen protection, slowly add 10 g of the oil phase dropwise to 70 g of the water phase, stir to dissolve, add 0.08 g of azobisisobutyronitrile, emulsify at a speed of 1500 rpm for 20 min to obtain a microemulsion, transfer it to a reaction kettle, pass nitrogen to remove oxygen, raise the temperature to 62 °C and react for 16 h. After terminating the reaction, demulsify, centrifuge to collect the precipitate, wash it to obtain white porous particles. Immerse 10 g of the white porous particles in 70 g of sulfuric acid solution with a pH value of 2.7, stir at a speed of 150 rpm for 3 h, centrifuge to collect the precipitate, wash it, and dry it to obtain macroporous resin.

[0022] Preparation Example 3 The macroporous resin is prepared by the following steps: A1. Dissolve 50 g of lignosulfonate in 1100 g of deionized water, add 1.5 g of sodium dodecyl sulfate and 0.5 g of Tween 80, stir at a speed of 500 rpm until a homogeneous solution is formed to obtain an aqueous phase. Mix 5.2 g of pentafluorostyrene and 28 g of hydroxypropyl acrylate, place it in a water bath at 55 °C and stir at a speed of 500 rpm for 30 min to obtain an oil phase; A2. Under nitrogen protection, slowly add 10 g of the oil phase dropwise to 100 g of the water phase, stir to dissolve, add 0.1 g of azobisisobutyronitrile, emulsify at a speed of 2000 rpm for 25 min to obtain a microemulsion, transfer it to a reaction kettle, pass nitrogen to remove oxygen, raise the temperature to 65 °C and react for 18 h. After terminating the reaction, demulsify, centrifuge to collect the precipitate, wash it to obtain white porous particles. Immerse 10 g of the white porous particles in 100 g of sulfuric acid solution with a pH value of 3.0, stir at a speed of 200 rpm for 4 h, centrifuge to collect the precipitate, wash it, and dry it to obtain macroporous resin.

[0023] Example 1 A preparation process of asparagus powder with a high content of asparagus saponins includes the following steps: S1. Cut the fresh asparagus tender stems into sections of 3 mm, immediately carry out enzyme inactivation treatment with 100 °C steam for 3 min, dry with 60 °C hot air for 2 h, and pulverize and pass through an 80-mesh sieve to obtain pretreated asparagus powder; S2. Mix 10 g of asparagus powder with 20 mL of 70% (v / v) ethanol solution, carry out ultrasonic extraction at 60 °C for 30 min, the power of ultrasonic treatment is 200 W and the frequency is 30 kHz, centrifuge at a speed of 3000 rpm for 15 min, take the supernatant to obtain a crude extract of asparagus saponins; S3. The macroporous resin prepared in Preparation Example 1 was rinsed successively with 95% ethanol and deionized water until the alcohol smell disappeared, then loaded into a resin column. The crude extract of asparagus saponins was loaded onto the resin column at a loading flow rate of 2 BV / h, with an adsorption capacity of 1.2 g saponins / 100 g resin. First, impurities were rinsed with deionized water, and then eluted with ethanol. 70% (v / v) ethanol was used for elution at a flow rate of 1.5 BV / h. The elution end point was that the saponin concentration in the effluent was 0.05 mg / mL. The eluate was collected and rotary evaporated under reduced pressure at 50 °C and a vacuum degree of -0.09 MPa until the saponin concentration reached 15 mg / mL. Maltodextrin was added at 2% of the solid mass of the concentrated solution, and then spray-dried. The inlet air temperature was 160 °C, the outlet air temperature was 80 °C, and the atomization pressure was 0.2 MPa. After drying, it was sieved through a 100-mesh sieve to obtain asparagus powder with a high content of asparagus saponins.

[0024] Example 2 A preparation process for asparagus powder with a high content of asparagus saponins, comprising the following steps: S1. Cut fresh asparagus tender stems into sections of 4 mm, immediately treat them with steam at 102 °C for enzyme inactivation for 4 min, dry them with hot air at 65 °C for 2.5 h, pulverize and sieve through an 80-mesh sieve to obtain pretreated asparagus powder; S2. Mix 10 g of asparagus powder with 22 mL of 70% (v / v) ethanol solution, ultrasonically extract at 62 °C for 35 min. The power of the ultrasonic treatment is 250 W and the frequency is 35 kHz. Centrifuge at a speed of 3500 rpm for 18 min, take the supernatant to obtain the crude extract of asparagus saponins; S3. The macroporous resin prepared in Preparation Example 2 was rinsed successively with 95% ethanol and deionized water until the alcohol smell disappeared, then loaded into a resin column. The crude extract of asparagus saponins was loaded onto the resin column at a loading flow rate of 2.5 BV / h, with an adsorption capacity of 1.4 g saponins / 100 g resin. First, impurities were rinsed with deionized water, and then eluted with ethanol. 75% (v / v) ethanol was used for elution at a flow rate of 1.7 BV / h. The elution end point was that the saponin concentration in the effluent was 0.05 mg / mL. The eluate was collected and rotary evaporated under reduced pressure at 52 °C and a vacuum degree of -0.08 MPa until the saponin concentration reached 16 mg / mL. Maltodextrin was added at 2.5% of the solid mass of the concentrated solution, and then spray-dried. The inlet air temperature was 162 °C, the outlet air temperature was 82 °C, and the atomization pressure was 0.2 MPa. After drying, it was sieved through a 100-mesh sieve to obtain asparagus powder with a high content of asparagus saponins.

[0025] Example 3 A preparation process for asparagus powder with a high content of asparagus saponins, comprising the following steps: S1. Cut fresh asparagus tender stems into sections of 5 mm, immediately treat them with steam at 105 °C for enzyme inactivation for 5 min, dry them with hot air at 70 °C for 3 h, pulverize and sieve through an 80-mesh sieve to obtain pretreated asparagus powder; S2. Mix 10 g of asparagus powder with 25 mL of 70% (v / v) ethanol solution, perform ultrasonic treatment for extraction at 65 °C for 40 min. The power of ultrasonic treatment is 300 W and the frequency is 40 kHz. Centrifuge at a speed of 4000 rpm for 20 min, take the supernatant to obtain the crude extract of asparagus saponins; S3. Wash the macroporous resin prepared in Preparation Example 3 successively with 95% ethanol and deionized water until there is no alcohol smell, load it into a resin column, load the crude extract of asparagus saponins onto the resin column, with a loading flow rate of 3 BV / h and an adsorption capacity of 1.5 g saponins / 100 g resin. First, wash the impurities with deionized water, and then elute with ethanol. Use 80% (v / v) ethanol for elution at a flow rate of 2 BV / h. The elution end point is that the saponin concentration in the effluent is 0.08 mg / mL. Collect the eluate, and perform rotary evaporation under reduced pressure on the eluate at 55 °C and a vacuum degree of -0.08 MPa until the saponin concentration is 17 mg / mL. Add maltodextrin according to 3% of the solid content of the concentrated solution, perform spray drying, with an inlet air temperature of 165 °C, an outlet air temperature of 85 °C, and an atomization pressure of 0.3 MPa. After drying, sieve through a 100-mesh sieve to obtain asparagus powder with a high content of asparagus saponins.

[0026] Comparative Example 1 The difference between this comparative example and Preparation Example 1 is that pentafluorostyrene is not added, and the remaining steps are the same as those in Preparation Example 1.

[0027] Comparative Example 2 The difference between this comparative example and Preparation Example 2 is that hydroxypropyl acrylate is not added, and the remaining steps are the same as those in Preparation Example 2.

[0028] Comparative Example 3 The difference between this comparative example and Preparation Example 3 is that lignosulfonate is not added, and the remaining steps are the same as those in Preparation Example 3.

[0029] Comparative Example 4 The difference between this comparative example and Example 1 is that the resin prepared in Comparative Example 1 is used instead of the resin prepared in Preparation Example 1, and the remaining steps are the same as those in Example 1.

[0030] Comparative Example 5 The difference between this comparative example and Example 2 is that the resin prepared in Comparative Example 2 is used instead of the resin prepared in Preparation Example 1, and the remaining steps are the same as those in Example 2.

[0031] Comparative Example 6 The difference between this comparative example and Example 3 is that the resin prepared in Comparative Example 3 is used instead of the resin prepared in Preparation Example 1, and the remaining steps are the same as those in Example 3.

[0032] Comparative Example 7 The difference between this comparative example and Example 3 is that a commercially available AB-8 resin is used instead of the resin prepared in Preparation Example 3, and the remaining steps are the same as those in Example 3.

[0033] Take 0.1 g of asparagus powder from Examples 1-3 and Comparative Examples 4-7, dissolve it in 10 mL of 70% ethanol, perform ultrasonic extraction for 30 min, centrifuge to obtain the supernatant, filter through a 0.22 μm filter membrane and then inject the sample into HPLC, record the peak area of saponins, and calculate the saponin content through the standard curve. Determine the initial saponin concentration of the crude extract in step S2 above, denoted as , determine the saponin concentration of the effluent after loading, denoted as , collect the eluate, determine the saponin concentration, denoted as . The elution end point is saponin concentration < 0.1 mg / mL, repeat 3 times. Calculate the adsorption rate and elution rate, adsorption rate , elution rate . The results are shown in Table 1: Table 1. Test results of Examples 1-3 and Comparative Examples 4-7

[0034] As can be seen from Table 1, the saponin content in the asparagus powder prepared in Examples 1-3 is relatively high, and the adsorption rate and elution rate are also relatively ideal. While the saponin content in Comparative Examples 4-7 is significantly lower than that in the examples, and the adsorption rate and elution rate are also significantly reduced.

[0035] Pentafluorostyrene is a monomer containing fluorine atoms. During the preparation of macroporous resin, its participation in the polymerization reaction can introduce fluorine atoms. Fluorine atoms have characteristics such as high electronegativity and small atomic radius, which make the resin molecular chain have special polarity and spatial structure, and may be beneficial to the formation of stronger interaction forces between the resin and asparagus saponin molecules, such as hydrogen bonds, van der Waals forces, etc., thereby improving the adsorption ability of the resin to asparagus saponins. In Comparative Example 4, without adding pentafluorostyrene, the structure and properties of the resin change, the adsorption sites for asparagus saponins decrease, and the adsorption force weakens, resulting in a significant decrease in the adsorption rate, and further reducing the saponin content in the final asparagus powder.

[0036] Hydroxypropyl acrylate contains polar groups such as hydroxyl groups, which can interact with the polar part of asparagus saponin molecules and enhance the adsorption selectivity of the resin for saponins. At the same time, the addition of hydroxypropyl acrylate can adjust the pore structure and specific surface area of the resin, providing more adsorption space for saponin molecules. In Comparative Example 5, without adding hydroxypropyl acrylate, the polarity and pore structure of the resin change, the adsorption ability for saponins decreases, and the elution rate is also affected, ultimately resulting in a decrease in the saponin content in the asparagus powder.

[0037] In Example 3, a self-prepared macroporous resin was used, while in Comparative Example 7, a commercially available AB-8 resin was used. The adsorption rate and elution rate decreased, possibly because the self-prepared macroporous resin formed a structure and pore size distribution more suitable for adsorbing asparagus saponins through a specific monomer combination and preparation process, enabling it to bind more effectively with saponin molecules and achieve elution. Although the commercially available AB-8 resin is also a commonly used adsorption resin, its structure and properties may not fully match the characteristics of asparagus saponins, resulting in relatively poor adsorption and elution effects. Eventually, the saponin content in the asparagus powder is also lower than that in Example 3.

[0038] In summary, the addition of each raw material when preparing the macroporous resin in the Preparation Example has an important impact on the structure and properties of the resin, thereby affecting its adsorption and elution effects on asparagus saponins, and ultimately determining the saponin content in the asparagus powder. The macroporous resin in the Preparation Example can better meet the requirements of asparagus saponin extraction and increase the saponin content in the asparagus powder by optimizing the raw material combination and preparation process.

[0039] In the description of the specification, the descriptions referring to terms such as "Preparation Example", "Example", "each Example", etc. mean that the specific features, structures, materials or characteristics described in connection with that Example or Preparation Example are included in at least one Example or Preparation Example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same Example or Preparation Example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more Examples or Preparation Examples.

[0040] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered by the protection scope of the present invention.

Claims

1. A preparation process of asparagus powder with a high content of asparagus saponins, characterized in that, It includes the following steps: S1. Cut the fresh asparagus tender stems into sections, perform enzyme inactivation treatment for 1 - 2 min, dry with hot air for 2 - 3 h, pulverize and pass through an 80 - mesh sieve to obtain pretreated asparagus powder; S2. Mix the pretreated asparagus powder with 70% ethanol solution, perform ultrasonic treatment for 30 - 40 min, centrifuge for 15 - 20 min, take the supernatant to obtain the crude extract of asparagus saponins; S3. After rinsing the macroporous resin, load it into a resin column. Load the crude extract of asparagus saponins onto the resin column. First, rinse the impurities with deionized water, then elute with ethanol, collect the eluate, perform rotary evaporation under reduced pressure on the eluate, add maltodextrin, perform spray drying, and after drying, pass through a 100 - mesh sieve to obtain asparagus powder with high - content asparagus saponins; Among them, the macroporous resin in step S2 is prepared by the following steps: A1. Dissolve lignosulfonate in deionized water, add sodium dodecyl sulfate and Tween 80, stir until a homogeneous solution is formed to obtain an aqueous phase. Mix pentafluorostyrene and hydroxypropyl acrylate, place it in a water bath and stir for 20 - 30 min to obtain an oil phase; A2. Under nitrogen protection, slowly drop the oil phase into the aqueous phase, stir and dissolve, add azobisisobutyronitrile, emulsify for 15 - 25 min to obtain a microemulsion. Transfer it to a reaction kettle, pass nitrogen to remove oxygen, raise the temperature and react for 12 - 18 h. After terminating the reaction, demulsify, centrifuge to collect the precipitate, wash to obtain white porous particles. Immerse the white porous particles in sulfuric acid solution, stir for 2 - 4 h, centrifuge to collect the precipitate, wash and dry to obtain the macroporous resin.

2. The preparation process of asparagus powder with high content of asparagus saponins according to claim 1, characterized in that, In step S1, the length of the cut fresh asparagus tender stems is 3 - 5 mm, the enzyme inactivation treatment uses microwave enzyme inactivation treatment with a power of 700 - 800 W, and the temperature of hot - air drying is 60 - 70 °C.

3. The preparation process of asparagus powder with high content of asparagus saponins according to claim 1, characterized in that, In step S2, the material - liquid ratio of the pretreated asparagus powder to 70% ethanol solution is 1:20 - 25 (g / mL), and the ultrasonic treatment conditions are: temperature 60 - 65 °C, power 200 - 300 W, frequency 30 - 40 kHz, and repeat extraction 2 - 3 times.

4. The preparation process of asparagus powder with high content of asparagus saponins according to claim 1, characterized in that, In step S3, when rinsing, rinse successively with 95% ethanol and deionized water until there is no alcohol smell. The loading flow rate is 2 - 3 BV / h, the adsorption capacity is (1.2 - 1.5) g saponins / 100 g resin, the elution is carried out with 70 - 80% (v / v) ethanol at a flow rate of (1.5 - 2) BV / h, and the elution end point is that the saponin concentration in the effluent is < 0.1 mg / mL.

5. The preparation process of asparagus powder with high content of asparagus saponins according to claim 1, characterized in that, In step S3, the conditions for rotary evaporation under reduced pressure are: temperature 50 - 55 °C, vacuum degree (-0.08) - (-0.09) MPa, and concentrate until the saponin concentration ≥ 15 mg / mL.

6. The preparation process of asparagus powder with high content of asparagus saponins according to claim 1, characterized in that, In step S3, maltodextrin is added at 2 - 3% of the mass of the solids in the concentrated solution, and the spray - drying parameters are: inlet air temperature 160 - 165 °C, outlet air temperature 80 - 85 °C, and atomization pressure 0.2 - 0.3 MPa.

7. The preparation process of asparagus powder with high content of asparagus saponins according to claim 1, characterized in that, In step A1, the mass ratio of lignosulfonate, deionized water, sodium dodecyl sulfate and Tween 80 is (4 - 5):(100 - 110):(1.0 - 1.5):(0.3 - 0.5), and the mass ratio of pentafluorostyrene and hydroxypropyl acrylate is (4.5 - 5.2):(2.3 - 2.8).

8. The preparation process of asparagus powder with high content of asparagus saponins according to claim 1, characterized in that, In step A2, the mass ratio of the oil phase, the water phase and azobisisobutyronitrile is 1:(5 - 10):(0.001 - 0.01), and the mass ratio of the white porous particles and the sulfuric acid solution is 1:(5 - 10), where the pH value of the sulfuric acid solution is 2.5 - 3.

0.

9. The preparation process of asparagus powder with high content of asparagus saponins according to claim 1, characterized in that, In step A1, the temperature of the water bath is 50 - 55 °C, and the stirring speed is 400 - 500 rpm. In step A2, the emulsification speed is 1000 - 2000 rpm, the temperature for heating up is 60 - 65 °C, and the stirring speed is 100 - 200 rpm.

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