A microwave-assisted foam separation and enrichment device and a separation method thereof

Abstract

The present application belongs to the technical field of saponin extraction, and particularly relates to a microwave-assisted foam separation and enrichment device and a separation method thereof. The present application uses the separation and enrichment device to perform microwave-assisted water extraction combined with foam separation and enrichment. The method effectively promotes the leaching of saponin, and the extraction rate is close to that of the traditional ethanol leaching method, while the time is greatly shortened to less than 5 minutes, which is much lower than the time of the traditional hot reflux ethanol leaching and hot water extraction, and no organic solvent is needed. The extraction liquid obtained by microwave-assisted water extraction is directly used as the feed liquid for foam separation. The microwave heating not only accelerates the adsorption of saponin on the gas bubbles, but also reduces the solution viscosity and the interstitial liquid between the gas bubbles, thereby significantly improving the enrichment ratio. At the same time, the amphiphilic property of saponin and the intramolecular vibration under the action of microwave further enhance the adsorption of saponin on the gas bubbles, so that the enrichment ratio is as high as 1.6 or more, which is obviously better than the enrichment ratio of the traditional method combined with the foam separation and enrichment method.

Description

Technical Field

[0001] This invention belongs to the field of saponin extraction technology. More specifically, it relates to a microwave-coupled foam separation and enrichment device and its separation method. Background Technology

[0002] The outer shell of the soapberry plant is rich in chemical components, primarily triterpenoid saponins. These saponins possess multiple pharmacological effects, including antitumor, antibacterial, anti-inflammatory, antioxidant, hypoxia-resistant, myocardial ischemia-protective, and hemolytic properties. They can also be used in the daily chemical industry as detergents. However, despite their high content of triterpenoid saponins, the soapberry shell has not been mass-produced and commercialized due to factors such as insufficient technological research, raw material shortages, and high production costs.

[0003] Traditional saponin extraction methods mainly include reflux extraction, water extraction with alcohol precipitation, and ultrasonic extraction. While these methods can achieve saponin extraction to some extent, they have many drawbacks, such as low extraction efficiency, significant loss of active ingredients, high impurity content, and long extraction times. For example, reflux extraction requires prolonged heating, resulting in high energy consumption and potential degradation of active ingredients; water extraction with alcohol precipitation requires multiple washing and precipitation processes, making it cumbersome and yielding low results.

[0004] To overcome the limitations of traditional extraction methods, researchers have explored a series of innovative extraction technologies in recent years. Microwave-assisted extraction stands out for its high efficiency and speed. By using microwave heating, saponins can be extracted efficiently in a short time, significantly improving extraction efficiency and yield. For example, Chinese patent application CN108403741A discloses a microwave-assisted method for extracting ginsenosides, which changes the traditional production process by combining bio-fermentation and microwave-assisted ethanol extraction to significantly increase the content of ginsenosides extracted. However, this method also faces challenges such as the long time required for bio-fermentation (usually exceeding 35 hours) and the potential environmental and cost issues associated with using ethanol as an extraction solvent.

[0005] In summary, existing technologies still face numerous challenges in the extraction and application of saponins. Lagging technological research and development, tight raw material supply, and high production costs limit their commercialization process; while traditional extraction methods are inefficient and cumbersome, failing to meet practical needs. Therefore, there is an urgent need to develop more efficient, environmentally friendly, and low-cost extraction technologies for the commercial application of natural products such as saponins. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the existing traditional extraction methods, such as low efficiency and cumbersome operation, and to provide a microwave-coupled foam separation and enrichment device.

[0007] Another object of the present invention is to provide the application of the microwave-coated foam separation and enrichment device in the field of separation and purification.

[0008] Another object of the present invention is to provide a method for microwave-assisted water extraction combined with foam separation of saponins, the method using the microwave-assisted foam separation and enrichment device.

[0009] Another objective of this invention is to provide a method for separating saponins using microwave-assisted water extraction combined with foam extraction.

[0010] The above-mentioned objective of this invention is achieved through the following technical solution:

[0011] This invention protects a microwave-coupled foam separation and enrichment device, comprising an air pump, a buffer device, a gas flow meter, a reaction vessel, a microwave device, a foam separation device, and a foam collector. The air pump, buffer device, gas flow meter, foam separation device, and foam collector are sequentially connected via gas pipelines. The foam separation device is directly connected to the microwave device through an opening. The microwave device contains a reaction vessel, and the inlet of the foam separation device is connected to the internal space of the reaction vessel.

[0012] This invention also protects the application of the microwave-coated foam separation and enrichment device in the field of separation and purification.

[0013] This invention also protects a method for microwave-assisted water extraction combined with foam separation of saponins, wherein the microwave-assisted foam separation and enrichment device is used to extract saponins.

[0014] When performing microwave-assisted water extraction of saponins, the foam separator and gas pipeline are removed. The saponin-containing raw water mixture (placed in the reaction vessel) is extracted using only the microwave device to obtain a crude saponin extract. When performing microwave-assisted foam separation for saponin enrichment, the air pump, buffer device, gas flow meter, microwave device, reaction vessel, foam separator, and foam collector are connected via gas pipelines. The air pump is turned on, and air is bubbled into the crude saponin extract in the reaction vessel. Surface-active saponins are adsorbed onto the bubbles, overflow from the foam separator tube, and are collected by the foam collector to obtain a saponin-enriched solution.

[0015] Furthermore, the microwave device is a microwave oven.

[0016] This invention also protects a method for separating saponins using microwave-assisted water extraction combined with foam extraction, comprising the following steps:

[0017] S1. Add the saponin-containing raw material to water, mix well, and perform microwave extraction under microwave conditions. After post-treatment, a crude saponin extract is obtained.

[0018] S2. The crude saponin extract obtained in step S1 is used as the original feed liquid for foam separation. Foam separation is carried out under microwave conditions to obtain a saponin-enriched liquid.

[0019] This invention employs a combination of microwave heating and water as a solvent for saponin extraction: microwave heating can rapidly shorten the extraction time and has high energy utilization efficiency; combined with water extraction, it avoids the use of organic solvents, thus avoiding the risks of explosion and environmental pollution caused by the use of organic solvents, and also avoids the presence of excessive non-polar impurities (such as flavonoids, polyphenols, pigments, etc.) in the extract.

[0020] The combined use of microwave heating and foam separation enrichment technology: heating can increase the adsorption rate of saponins on the bubble surface, while reducing the viscosity of the solution, thus reducing the amount of interstitial liquid carried by the bubbles and improving the enrichment ratio. In addition, saponins are amphiphilic polar molecules, and their intramolecular vibrations under microwave irradiation can further increase their adsorption rate on the bubble surface, further improving the enrichment ratio.

[0021] Furthermore, the enrichment ratio is used to assess the change in the relative content or concentration of a target component in a sample after extraction. Specifically, the enrichment ratio is the ratio between the content (or concentration) of the target component after extraction and its original content (or concentration) before the operation.

[0022] Preferably, in step S1, the microwave power of the microwave extraction is 500~2000 W, more preferably 600~1400 W, and most preferably 1000 W.

[0023] Preferably, in step S1, the microwave extraction time is ≤5 min, more preferably 0.5~2 min.

[0024] Preferably, in step S1, the mass ratio of the saponin-containing raw material to water is 1:(10~80) g / mL, more preferably (20~60) g / mL.

[0025] Preferably, in step S2, the microwave power for foam separation is 100~800 W, more preferably 200~600 W, and most preferably 300 W.

[0026] Preferably, in step S2, the gas flow rate for foam separation is 50~1000 mL / min, more preferably 200~600 mL / min, and most preferably 400 mL / min.

[0027] Furthermore, the saponin-containing raw material includes soapberry shells and / or soapberry thorns.

[0028] Furthermore, the pretreatment includes washing, drying, pulverizing, and sieving.

[0029] Specifically, the pretreatment involves washing the saponin-containing raw material, drying it at 50-120°C (preferably 105°C), grinding it into powder, passing it through a 50-20 mesh sieve (preferably 100 mesh), and then sealing and storing it under dry conditions.

[0030] Furthermore, as a preferred embodiment, steps S1 and S2 are performed using the microwave-coupled foam separation and enrichment device.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention employs a microwave-assisted water extraction combined with foam separation enrichment method, effectively promoting the leaching of saponins. The extraction rate is close to that of traditional ethanol extraction, while the extraction time is significantly reduced to less than 5 minutes, far lower than the time required for traditional hot reflux ethanol extraction and hot water extraction, and no organic solvents are needed. The extract obtained from microwave-assisted water extraction is directly used as the feed liquid for foam separation. Microwave heating not only accelerates the adsorption of saponins on bubbles but also reduces solution viscosity, decreases interstitial liquid, and significantly improves the enrichment ratio. Simultaneously, the amphiphilic nature of saponins and the intramolecular vibrations under microwave irradiation further enhance their adsorption on bubbles, resulting in an enrichment ratio of 1.6 or higher, significantly superior to the enrichment ratio achieved by combining traditional methods with foam separation enrichment. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a microwave-coupled foam separation and enrichment device. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0035] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0036] Soapberry (the soapberry pods required for the experiment were collected from the Qianzhi Mingguang Soapberry Rice Processing Base in Maochang Town, Zhijin County, Bijie City, Guizhou Province)

[0037] Preparation of soapberry shell powder: After washing the soapberry shells, dry them in an oven at 105 ℃. After drying, grind them into powder using a pulverizer. After passing through a 100-mesh sieve, obtain soapberry shell powder. Store it in a sealed bag in a desiccator for later use.

[0038] Example 1: Extraction of saponins from saponins using microwave-assisted water extraction

[0039] The process of confirming the optimal extraction conditions for saponins from saponins using microwave-assisted water extraction is as follows:

[0040] (1) Process and evaluation indicators

[0041] Weigh out the powdered soapberry shells, add deionized water and stir until homogeneous. Microwave for a certain time, let stand for 30 min, and then filter to obtain an aqueous extract of soapberry shells. Concentrate the aqueous extract by rotary evaporation, add anhydrous ethanol, shake well, let stand for 1 h, and filter into a round-bottom flask. This step removes proteins and sugars insoluble in ethanol from the aqueous extract of soapberry shells, obtaining a preliminarily purified crude extract of soapberry shell surfactants. Concentrate the crude extract of soapberry shell surfactants under reduced pressure and dry it in an oven at 105 °C until the quality is stable. Calculate the yield of the surfactant extract from soapberry shells (since the surfactants extracted from soapberry shells are mainly saponins, but pure saponins cannot be obtained directly during the extraction process, this invention indirectly represents the efficiency of this extraction process by calculating the yield of the surfactant extract to reflect the saponin yield). The yield calculation of the surfactant extract is shown in formula (1).

[0042] (1)

[0043] (2) Single-factor experiment

[0044] Using W1 as the evaluation index, the effects of four factors—raw material particle size, microwave power, microwave time, and liquid-to-material ratio—on W1 were investigated. Each reaction was performed in triplicate.

[0045] (3) Response surface methodology

[0046] Microwave time (A), microwave power (B), and liquid-to-material ratio (C) were used as experimental factors, and W1 was used as the response value. The Box-Behnken design response surface experiment was conducted using Design-Expert 8.0.6.

[0047] (4) Test results

[0048] Response surface methodology analysis revealed the optimal extraction conditions as follows: microwave duration 33 s, microwave power 1000 W, and liquid-to-solid ratio 35:1 (mL / g). Under these conditions, the predicted W1 value was 63.91%. Due to limitations of the microwave device, the microwave duration was adjusted to 30 s. Three parallel experiments were conducted based on the adjusted optimal extraction conditions, yielding a W1 value of 60.40%, with a relative error of 3.51% compared to the model prediction, indicating that the optimized conditions are reliable.

[0049] Example 2 Microwave-assisted water extraction combined with foam separation to enrich saponins

[0050] (1) Design of microwave-coupled foam separation and enrichment device

[0051] According to microwave-coupled foam separation and enrichment devices, such as Figure 1As shown, when microwave-assisted water extraction combined with foam separation to enrich saponins, the air pump 1, buffer device 3, airflow meter 4, reaction vessel 5, microwave device (in this embodiment, the microwave device is a microwave oven) 6, foam separation device 7 (including inlet 9), and foam collector 8 are connected via gas pipeline 2. The microwave oven serves as the heating device for foam separation. The foam separation device is directly connected to the microwave oven 6 through the top opening of the microwave oven; the reaction vessel 5 is placed inside the microwave oven 6, and the inlet 9 of the foam separation device 7 is connected to the internal space of the reaction vessel 5.

[0052] (2) Quantitative analysis of saponins and testing of enrichment ratio

[0053] The crude extract of saponin shell surfactant obtained by the optimal process adjusted in Example 1 was used as the original feed liquid for foam separation by using the perchloric acid-vanillin-glacial acetic acid color development method.

[0054] Place the reaction vessel in a microwave oven, turn on the gas pump, adjust the gas flow meter to change the gas flow rate, and turn on the microwave to its rated power. Gas is introduced from the lower end of the foam separation tube, and bubbles are generated as it passes through the glass orifice plate. Due to the surface activity of saponins, saponins are enriched around the foam, making the bubbles stable. Bubbles are continuously generated and move upward, forming a foam layer on the upper layer of the liquid, and are finally collected by the foam collector. The foam separation and enrichment method uses the enrichment ratio as the evaluation index, and its calculation is shown in formula (2).

[0055] (2)

[0056] In the formula: E —Enrichment ratio; C f —Concentration of saponins in the feed solution, mg / mL; C o —Concentration of saponins in the foam layer, mg / mL.

[0057] (3) Orthogonal experiment

[0058] Based on the results of single-factor experiments, experimental factors with no significant differences were eliminated. Using gas flow rate (L) and microwave power (M) as independent variables and E as response values, a Box-Behnken design-response surface methodology was conducted using Design-Expert 8, and the experimental results were analyzed.

[0059] (4) Test results

[0060] Response surface methodology analysis revealed the optimal extraction conditions for foam separation and enrichment of saponins from saponins to be: a gas flow rate of 400 mL / min and a microwave power of 300 W. Under these optimal conditions, the enrichment ratio was 1.832.

[0061] Example 3 Microwave-assisted water extraction combined with foam separation to enrich saponins

[0062] Powdered soapberry shells were added to deionized water and stirred until a liquid-to-solid ratio of 20:1 (mL / g) was formed. The mixture was heated under microwave power of 600 W for 120 s, allowed to stand for 30 min, and then filtered to obtain an aqueous extract of soapberry shells. The yield of the surface-active extract was determined to be 59.48%.

[0063] Microwave-coupled foam enrichment and separation was performed according to the method in Example 2. The aqueous extract of the soapberry shells obtained above was placed in a microwave reactor. The gas pump was turned on, and the gas flow rate was adjusted to 200 mL / min. The microwave oven was turned on and its power was set to 200 W. Gas was introduced from the lower end of the foam separation tube, and bubbles were generated after passing through the glass plate. Due to the surface activity of soapberry saponins, the soapberry saponins were enriched around the foam, making the bubbles stable. Bubbles were continuously generated and moved upward, forming a foam layer on the upper layer of the liquid. Finally, the foam was collected by the foam collector, and the enrichment ratio was determined to be (1.623) by the perchloric acid-vanillin-glacial acetic acid colorimetric method.

[0064] Example 4 Microwave-assisted water extraction combined with foam separation to enrich saponins

[0065] Weigh out powdered soapberry shells and add them to deionized water. Stir until a liquid-to-solid ratio of 60:1 (mL / g) is formed. Heat the solution in a microwave at 1400 W for 30 seconds, let it stand for 30 minutes, and then filter to obtain an aqueous extract of soapberry shells. The yield of the surface-active extract was determined to be 58.60%.

[0066] Following the method in Example 2, microwave-coated foam enrichment and separation was performed. The obtained aqueous extract of soapberry shells was placed in a microwave reactor. The gas pump was turned on, and the gas flow rate was adjusted to 600 mL / min. The microwave oven was turned on at a power of 600 W. Gas was introduced from the lower end of the foam separation tube, generating bubbles as it passed through the glass orifice plate. Due to the surface activity of soapberry saponins, the saponins accumulated around the bubbles, stabilizing them. Bubbles were continuously generated and moved upward, forming a foam layer on the upper layer of the liquid. Finally, the foam was collected by a foam collector, and the enrichment ratio was determined to be (1.767) using the perchloric acid-vanillin-glacial acetic acid colorimetric method.

[0067] Comparative Example 1: Extraction of saponins from saponins using conventional hot reflux ethanol extraction method

[0068] The process of confirming the optimal extraction conditions for extracting saponins from saponins using the traditional hot reflux ethanol extraction method is as follows:

[0069] (1) Process and evaluation indicators

[0070] Weigh 100-mesh soapberry powder and add different volumes and concentrations of ethanol solution, stirring until homogeneous. Reflux at a specific reflux extraction temperature for a certain time, then filter under reduced pressure to obtain a crude extract of surfactants from soapberry shells. Evaporate the crude extract under reduced pressure and then dry it in an oven at 105 ℃ until the quality stabilizes. Calculate the yield of the surfactant extract from soapberry shells. The yield calculation is given by formula (1).

[0071] Formula: W1 represents the yield of the surface active extract from the soapberry shell. m m1 is the weight of the soapberry shell powder, in g. m2 is the weight of the round-bottom flask dried at 105℃, in g. m3 is the total weight of the surfactant solids obtained by drying at 105℃ and the round-bottom flask, in g.

[0072] (2) Single-factor experiment

[0073] Using W1 as the evaluation index, the effects of four factors—ethanol concentration, reflux extraction temperature, liquid-to-solid ratio, and reflux time—on W1 were investigated. Each reaction was performed in triplicate.

[0074] (3) Response surface methodology

[0075] Based on the results of the single-factor experiments, experimental factors with no significant differences were eliminated. Response surface methodology was then conducted with ethanol concentration (E), liquid-to-solid ratio (F), and reflux time (G) as independent variables and W1 as the response value. The Box-Behnken design-response surface methodology was implemented using Design-Expert 8.

[0076] (4) Test results

[0077] Response surface methodology analysis revealed the optimal extraction conditions for the traditional hot reflux ethanol extraction method as follows: reflux time 60 min, liquid-to-solid ratio 35:1 (mL / g), and ethanol concentration 60%. Under these conditions, the W1 value predicted using Design-Expert 8.0 was 64.13%.

[0078] After adjusting the optimal extraction process conditions according to the actual situation, three parallel experiments were conducted. The actual W1 was measured to be 63.59%, with a relative deviation of 0.8% from the model prediction, indicating that the optimized process conditions are relatively reliable.

[0079] Comparative Example 2: Extraction of saponins from saponins by hydrothermal extraction

[0080] The process of confirming the optimal extraction conditions for saponins from saponins using the hydrothermal extraction method is as follows:

[0081] (1) Process and evaluation indicators

[0082] Weigh 100-mesh soapberry powder and add different volumes of deionized water. Extract at a certain temperature for a certain time, and filter under reduced pressure to obtain a crude extract of surfactants from soapberry shells. Concentrate the aqueous extract by rotary evaporation, add anhydrous ethanol, shake well, and let stand for 1 h. Filter into a round-bottom flask. This step removes proteins and sugars insoluble in ethanol from the aqueous extract of soapberry shells, obtaining a preliminarily purified crude extract of surfactants from soapberry shells. Evaporate the crude extract of surfactants from soapberry shells under reduced pressure and dry in an oven at 105 °C until the quality is stable. Calculate the yield of the surfactant extract from soapberry shells. The yield calculation of the surfactant extract is given by formula (1).

[0083] (2) Single-factor experiment

[0084] Using W1 as the evaluation index, the effects of three factors—water extraction temperature, water extraction liquid-to-solid ratio, and water extraction time—on W1 were investigated. Each reaction was performed in triplicate.

[0085] (3) Response surface methodology

[0086] Based on the results of the single-factor experiments, experimental factors with no significant differences were eliminated. Response surface methodology was then conducted with water extraction temperature (H), water extraction liquid-to-material ratio (I), and water extraction time (J) as independent variables and W1 as the response value. Box-Behnken design-response surface methodology was used for this experiment.

[0087] (4) Test results

[0088] Response surface methodology analysis revealed the optimal extraction conditions for saponins from saponins via hydrothermal extraction: extraction time 80 min, extraction temperature 70 °C, and liquid-to-solid ratio 30:1 (mL / g). Under these conditions, Design-Expert 8.0 predicted a W1 value of 58.24%.

[0089] After adjusting the optimal extraction process conditions according to the actual situation, three parallel experiments were conducted. The actual W1 was measured to be 56.35%, with a relative deviation of 1.89% from the model prediction, indicating that the optimized process conditions are relatively reliable.

[0090] Comparative Example 3: Microwave-assisted ethanol extraction of saponins from saponins.

[0091] The process of confirming the optimal extraction conditions for saponins from saponins using microwave-assisted ethanol extraction is as follows:

[0092] (1) Process and evaluation indicators

[0093] Weigh out powdered soapberry shells and add different volumes and concentrations of ethanol solution, stirring until homogeneous. Microwave for a certain period of time. Concentrate the crude extract of surface-active substances from soapberry shells under reduced pressure and dry in an oven at 105 °C until the quality is stable. Calculate the yield of the surface-active extract from soapberry shells. The yield of the surface-active extract is calculated using formula (1).

[0094] (2) Single-factor experiment

[0095] Using W1 as the evaluation index, the effects of four factors—ethanol concentration, microwave power, microwave time, and liquid-to-solid ratio—on W1 were investigated. Each reaction was performed in triplicate.

[0096] (3) Response surface methodology

[0097] Microwave time (A), microwave power (B), liquid-to-solid ratio (C), and ethanol concentration (D) were used as experimental factors, and W1 was used as the response value. A Box-Behnken design response surface experiment was conducted using Design-Expert 8.0.6.

[0098] (4) Test results

[0099] Response surface methodology analysis revealed the optimal extraction conditions as follows: microwave duration 57 s, microwave power 800 W, liquid-to-solid ratio 35:1 (mL / g), and ethanol concentration 60%. Under these conditions, the predicted W1 value was 65.74%. Due to limitations of the microwave device, the microwave duration was adjusted to 60 s. Three parallel experiments were conducted based on the adjusted optimal extraction conditions, yielding a W1 value of 64.44%, with a relative error of 1.30% compared to the model prediction, indicating that the optimized conditions are reliable.

[0100] Comparative Example 4: Enrichment of saponins using conventional hot reflux ethanol extraction combined with foam separation

[0101] (1) Quantitative analysis of saponins and testing of enrichment ratio

[0102] Following the method described in Example 2, the crude extract of saponin shell surfactant obtained from the optimal process adjusted in Comparative Example 1 was used as the initial feed liquid for foam separation via a perchloric acid-vanillin-glacial acetic acid colorimetric method. In this case, the microwave oven ⑥ was replaced with a water bath heating pot.

[0103] The reaction vessel was placed in a water bath at different temperatures for heating. The gas pump was turned on, and the gas flow meter was adjusted to change the gas flow rate. Gas was introduced from the lower end of the foam separation tube, and bubbles were generated after passing through the glass orifice plate. Due to the surface activity of saponins, saponins were enriched around the bubbles, making them stable. Bubbles were continuously generated and moved upward, forming a foam layer on the upper layer of the liquid, and were finally collected by the foam collector. However, due to the defoaming effect of ethanol, the adsorption performance of saponins on the bubble surface was reduced, and the foaming rate slowed down. The surface foam separation and enrichment method of saponins uses the enrichment ratio as the evaluation index, and its calculation is shown in formula (2).

[0104] (2) Orthogonal experiment and its results

[0105] Using water bath temperature (K) and gas flow rate (L) as the experimental factors, the optimal conditions were determined through orthogonal experiments to be a temperature of 65 °C and a gas flow rate of 300 mL / min. The enrichment ratio under these optimal conditions was 1.136.

[0106] Comparative Example 5: Hydrothermal extraction combined with foam separation for enrichment of saponins from saponins.

[0107] (1) Quantitative analysis of saponins and testing of enrichment ratio

[0108] According to the method described in Example 2, the crude extract of saponin shell surfactant obtained by the optimal process after adjustment in Comparative Example 2 was used as the original feed liquid for foam separation by using the perchloric acid-vanillin-glacial acetic acid color development method.

[0109] The reaction vessel was placed in a water bath at different temperatures for heating. The gas pump was turned on, and the gas flow meter was adjusted to change the gas flow rate. Gas was introduced from the lower end of the foam separation tube, and bubbles were generated after passing through the glass orifice plate. Due to the surface activity of saponins, the saponins were enriched around the bubbles, making the bubbles stable. Bubbles were continuously generated and moved upward, forming a foam layer on the upper layer of the liquid, and finally collected by the foam collector. The foam separation and enrichment method uses the enrichment ratio as the evaluation index, and its calculation is shown in formula (2).

[0110] (2) Orthogonal experiment and its results

[0111] Using water bath temperature (K) and gas flow rate (L) as the experimental factors, the optimal conditions were determined through orthogonal experiments to be a temperature of 70 °C and a gas flow rate of 300 mL / min. The enrichment ratio under these optimal conditions was 1.358.

[0112] Comparative Example 6: Microwave-assisted ethanol extraction coupled with foam separation for enrichment of saponins

[0113] (1) Quantitative analysis of saponins and testing of enrichment ratio

[0114] Following the method described in Example 2, the crude extract of saponin shell surfactant obtained by the optimal process adjusted in Comparative Example 3 was used as the original feed liquid for foam separation by using the perchloric acid-vanillin-glacial acetic acid color development method.

[0115] Place the reaction vessel in a microwave oven, turn on the gas pump, adjust the gas flow meter to change the gas flow rate, and turn on the microwave to its rated power. Gas is introduced from the lower end of the foam separation tube, and bubbles are generated as it passes through the glass orifice plate. Due to the surface activity of saponins, saponins are enriched around the foam, making the bubbles stable. Bubbles are continuously generated and move upward, forming a foam layer on the upper layer of the liquid, and are finally collected by the foam collector. The foam separation and enrichment method uses the enrichment ratio as the evaluation index, and its calculation is shown in formula (2).

[0116] (2) Orthogonal experiment

[0117] Based on the results of single-factor experiments, experimental factors with no significant differences were eliminated. Using gas flow rate (L) and microwave power (M) as independent variables and E as response values, a Box-Behnken design-response surface methodology was conducted using Design-Expert 8, and the experimental results were analyzed.

[0118] (3) Test results

[0119] Response surface methodology analysis revealed the optimal extraction conditions for microwave-assisted ethanol extraction combined with foam separation of saponins: a gas flow rate of 450 mL / min and a microwave power of 400 W. Under these optimal conditions, the enrichment ratio was 1.223.

[0120] Based on the results of the examples and comparative examples, it can be seen that the present invention utilizes a microwave-assisted water extraction combined with foam separation and enrichment method to extract saponins. In the microwave-assisted water heating stage, the yield of the obtained surface-active extract (mainly saponins) is 57% or higher, which is close to that of the traditional methods (comparative examples 1-3). The enrichment ratio of saponins obtained in the foam separation and enrichment stage reaches 1.6 or higher, with a maximum of 1.832. In contrast, the enrichment ratios of the traditional hot reflux ethanol extraction method (comparative example 4), hydrothermal extraction method (comparative example 5), and microwave-assisted ethanol extraction method (comparative example 6) combined with the foam separation and enrichment method are 1.136, 1.358, and 1.223, respectively, which are relatively low.

[0121] As can be seen from the above results, this invention utilizes a microwave-assisted water extraction combined with foam separation and enrichment method to microwave-assisted water heating of pulverized soap pods, which efficiently promotes the leaching of soap pod saponins. The extraction rate of its surface-active components (mainly saponins) is close to that of the traditional ethanol extraction method, while its extraction time (<1 min) is much shorter than that required by the traditional hot reflux ethanol extraction method (60 min) and hot water extraction method (80 min). This method avoids the use of organic solvents and further combines foam separation and enrichment methods. The extract obtained by microwave-assisted water extraction is used as the original feed liquid for foam separation. Microwave heating can increase the adsorption rate of saponins on the bubble surface and reduce the viscosity of the solution, thereby reducing the amount of interstitial liquid carried by the bubbles and improving the enrichment ratio. In addition, saponins are amphiphilic polar molecules, and they undergo intramolecular vibration under microwave action, which can further increase their adsorption rate on the bubble surface and further improve the enrichment ratio. The enrichment ratio can reach 1.6 or higher, which is significantly higher than the enrichment ratios of traditional hot reflux ethanol extraction (Comparative Example 4, enrichment ratio of 1.136), hydrothermal extraction (Comparative Example 5, enrichment ratio of 1.358), and microwave-assisted ethanol extraction (Comparative Example 6, enrichment ratio of 1.223) combined with foam separation and enrichment methods.

[0122] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for separating saponins by microwave-assisted water extraction combined with foam separation, characterized in that, Includes the following steps: S1. Add the saponin-containing raw material to water, mix well, and perform microwave extraction under microwave conditions. After post-treatment, a crude saponin extract is obtained. S2. The crude saponin extract obtained in step S1 is used as the original feed liquid for foam separation. Foam separation is carried out under microwave conditions to obtain saponin enrichment liquid. In step S1, the microwave power of the microwave extraction is 500~2000 W; the microwave extraction time is ≤5 min. In step S2, the microwave power for foam separation is 100~800 W; the gas flow rate for foam separation is 50~1000 mL / min. Steps S1 and S2 are performed using a microwave-coupled foam separation and enrichment device. The microwave-coupled foam separation and enrichment device includes an air pump (1), a buffer device (3), a gas flow meter (4), a reaction vessel (5), a microwave device (6), a foam separation device (7), and a foam collector (8). The air pump (1), buffer device (3), gas flow meter (4), foam separation device (7), and foam collector (8) are connected in sequence through a gas pipeline (2). The foam separation device (7) is directly connected to the microwave device (6) through an opening. The microwave device (6) is equipped with a reaction vessel (5), and the feed inlet (9) of the foam separation device (7) is connected to the internal space of the reaction vessel (5).

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