A method for extracting polyphenols from agar industrial waste liquid using ionic liquid and its application

Abstract

The invention discloses a method for extracting polyphenols from agar industrial waste liquid using ionic liquid, comprising: removing impurities from agar industrial waste liquid, and adjusting the pH of the agar industrial waste liquid to 3-13 with HCL; mixing 1-butyl-3-methylimidazolium hexafluorophosphate with agar industrial waste liquid in a volume ratio of 1:0.25-1:4, vortexing for 1-2 minutes, performing primary extraction for 5-10 minutes, standing for stratification for 20-40 minutes, and obtaining an ionic liquid phase extraction layer; mixing the ionic liquid phase extraction layer with hot distilled water at 40°C-90°C in a volume ratio of 1:0.25-1:4, vortexing for 1-2 minutes, performing back extraction for 2-6 minutes, standing for stratification for 6-8 minutes, taking the hot distilled water phase, and obtaining total polyphenols. The method is safe, simple, easy to operate, and has high extraction efficiency. Total polyphenols can be extracted from agar industrial waste liquid, and green large-scale production of active ingredient recovery in agar industrial waste liquid is realized.

Description

Technical Field

[0001] The invention relates to the technical field of active substance extraction, and in particular to a method for extracting polyphenols from agar industrial waste liquid by utilizing ionic liquid and application thereof. Background Art

[0002] Agar, also known as agar gum, is a natural polysaccharide mainly extracted from red algae such as Gracilaria and Gelidium. It has gelling and thickening properties and is widely used in food, medicine, biology and other fields. Alkali extraction is currently a commonly used method in the industrial production of agar. The process of alkaline extraction of Gracilaria agar includes alkali treatment, cleaning of residual alkali, acidification, bleaching, boiling gel, filtration, gelling, pressing, drying and crushing. The waste alkali liquid produced by the agar industry puts great pressure on the environment. Among them, the protein, flavonoids and polyphenols rich in Gracilaria are dissolved in the alkali liquid during the alkali treatment process, and the waste alkali liquid produced by the alkali treatment process is often treated as wastewater, resulting in a waste of resources.

[0003] At present, the main methods for extracting polyphenols are solvent extraction, resin adsorption separation, supercritical fluid extraction, and ion precipitation. Among them, solvent extraction is the most common extraction method, and the extraction solvents are mainly water, ethanol, and methanol. The water extraction method has low extraction efficiency, and the extract has many impurities and is difficult to separate. The organic solvent extraction method uses highly volatile organic solvents in the separation process. These solvents are flammable and explosive, so there are great safety hazards in large-scale production. At the same time, the recovery of these volatile organic solvents also requires a lot of energy. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a method for extracting polyphenols from agar industrial waste liquid using ionic liquid. The method is safe, simple and easy to operate, has high extraction efficiency, can extract total polyphenols from agar industrial waste liquid, and realize green large-scale production of active ingredient recovery in agar industrial waste liquid.

[0005] In order to achieve the above object, an embodiment of the present invention provides a method for extracting polyphenols from agar industrial waste liquid using ionic liquid, which comprises the following steps:

[0006] The agar industrial waste liquid is treated to remove impurities, and then the pH of the agar industrial waste liquid is adjusted to 3-13 with HCL;

[0007] 1-butyl-3-methylimidazolium hexafluorophosphate and agar industrial waste liquid are mixed in a volume ratio of 1:0.25 to 1:4, vortexed for 1 to 2 minutes, subjected to primary extraction for 5 to 10 minutes, and allowed to stand for stratification for 20 to 40 minutes to obtain an ionic liquid phase extraction layer;

[0008] The ionic liquid phase extraction layer is mixed with hot distilled water at 40° C. to 90° C. in a volume ratio of 1:0.25 to 1:4, vortexed for 1 to 2 minutes, back-extracted for 2 to 6 minutes, allowed to stand for 6 to 8 minutes, and the hot distilled water phase is taken to obtain total polyphenols.

[0009] According to an embodiment of the present invention, a method for extracting polyphenols from agar industrial waste liquid by using ionic liquid is disclosed. The method uses agar industrial waste liquid as raw material, and adopts ionic liquid extraction method to extract total polyphenols from agar industrial waste liquid. The extraction process is simple and the extraction efficiency is high. The extraction rate of total polyphenols can be improved and the loss of raw materials can be reduced. The method can provide technical reserves for the extraction of total polyphenols from agar industrial waste liquid, and provide ideas and directions for recycling active substances in liquid raw materials and using them for deep processing. The method has certain application and promotion value.

[0010] In addition, the method for extracting polyphenols from agar industrial waste liquid using ionic liquid according to the above embodiment of the present invention may also have the following additional technical features:

[0011] Optionally, the pH of the agar industrial waste liquid is 3.

[0012] Optionally, the volume ratio of 1-butyl-3-methylimidazolium hexafluorophosphate to agar industrial waste liquid is 1:2.1.

[0013] Optionally, the volume ratio of the ionic liquid phase extraction layer to hot distilled water is 1:2.06.

[0014] Optionally, the temperature of the hot distilled water is 60°C.

[0015] Optionally, the time for the initial extraction is 6 minutes, and the standing and stratification time after the initial extraction is 20 minutes.

[0016] Optionally, the back extraction time is 3 minutes, and the standing and stratification time after the back extraction is 6 minutes.

[0017] In another aspect, the embodiments of the present invention further provide the use of the polyphenols obtained by the above method in the preparation of antioxidants.

[0018] The polyphenols extracted from agar industrial waste liquid have a scavenging rate of (67.19±0.24)% for DPPH free radicals and a scavenging rate of (92.23±0.22)% for ABTS free radicals. They have good antioxidant properties and can turn waste into treasure.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1The extraction process of total polyphenols from agar industrial waste liquid according to an embodiment of the present invention;

[0021] Figure 2 is a corresponding relationship diagram of pH value and polyphenol extraction rate according to an embodiment of the present invention;

[0022] Figure 3 is a corresponding relationship diagram between the solid-liquid ratio and the polyphenol extraction rate according to an embodiment of the present invention;

[0023] Figure 4 is a corresponding relationship diagram between temperature and polyphenol extraction rate according to an embodiment of the present invention;

[0024] Figure 5 is a corresponding relationship diagram between the distilled water extraction volume ratio and the polyphenol extraction rate according to an embodiment of the present invention;

[0025] Figure 6 The figure is a diagram showing the scavenging effect of total polyphenols in agar industrial wastewater on DPPH free radicals according to an embodiment of the present invention;

[0026] Figure 7 This is a diagram showing the scavenging effect of total polyphenols in agar industrial wastewater on ABTS free radicals according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is described below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combination step or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to limit the scope of the present invention. The change or adjustment of the relative relationship thereof shall also be regarded as the scope of the present invention without substantially changing the technical content.

[0028] In order to better understand the above technical scheme, the exemplary embodiments of the present invention are described in more detail below. Although exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0029] The test materials used in the present invention are all common commercial products and can be purchased in the market.

[0030] Among them, agar industrial wastewater is the waste alkali liquid discharged from the alkali treatment link in the agar production process obtained from the agar production plant.

[0031] Determination of total polyphenol content

[0032] (1) Method for determining polyphenol content by Folin phenol method

[0033] Preparation of reference solution: Accurately weigh 0.1000g of gallic acid reference substance, dilute to 100mL with distilled water to obtain 1000μg / mL gallic acid solution stock solution. After shaking well, accurately pipette 10mL of distilled water to dilute to 100mL to obtain 0.1mg / mL gallic acid standard solution.

[0034] (2) Drawing of standard curve: Accurately pipette 0.0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0 mL of gallic acid standard solution into 10 mL volumetric flasks, and dilute to the mark with distilled water. Prepare a series of standard solutions with mass concentrations of 0, 10, 20, 30, 40, 50, 100, 150, 200 μg / mL. Take 1 mL of standard solution into a 10 mL volumetric flask, add 1 mL of Folin phenol colorimetric reagent and 7.5% Na 2 CO 3 3mL of solution, mix well and dilute to 10mL with distilled water, and react for 2h in the dark. Take the sample of 0μg / mL as blank and measure the absorbance of different concentrations of gallic acid at 765nm. Each sample is measured three times in parallel. The gallic acid standard curve is drawn with the concentration of gallic acid standard solution as the horizontal axis and the absorbance as the vertical axis.

[0035] (3) Determination of total polyphenol content of samples: Take 200 μL of sample solution and measure the absorbance of the polyphenol sample at 765 nm according to the above method. The measurement is repeated three times in parallel to calculate the polyphenol content.

[0036] The total polyphenol extraction rate was calculated as follows:

[0037] S(%) = (N / W) x 100%, where N is the total polyphenol content in the distilled water phase, and W is the total polyphenol content in the agar industrial waste liquid.

[0038] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0039] Example 1

[0040] The agar industrial waste liquid was filtered and impurities were removed using an 80-mesh sieve to eliminate the interference of impurities such as sea sand, stones and crustaceans on the extraction process. The agar industrial waste liquid was centrifuged at 8000r / min for 10 minutes to remove the suspended matter in the solution, and then the pH of the agar industrial waste liquid was adjusted with 6mol / L HCL and stored in a cool and dry environment for later use. The pH value of the agar industrial waste liquid was set to 3, 5, 7, 9, 11 and 13.

[0041] The ionic liquid and the agar industrial waste liquid were mixed in a volume ratio of 1:1, vortexed for 2 minutes, subjected to primary extraction for 6 minutes, and allowed to stand for 20 minutes to separate into layers, thereby obtaining an ionic liquid phase extraction layer, which contained polyphenol compounds. The ionic liquid was 1-butyl-3-methylimidazolium hexafluorophosphate.

[0042] The ionic liquid phase extraction layer was mixed with hot distilled water at 60° C. in a volume ratio of 1:1, vortexed for 2 min, back-extracted for 3 min, allowed to stand for 6 min, and the hot distilled water phase was taken to obtain total polyphenols.

[0043] The results are as follows Figure 2 As shown, the total polyphenol extraction rate showed an overall downward trend, and reached the highest value at a pH of 3. Continuing to increase the pH value of agar industrial wastewater, the polyphenol extraction rate showed a downward trend, so the optimal pH value was 3.

[0044] Example 2

[0045] Use an 80-mesh sieve to filter and remove impurities from the agar industrial waste liquid to eliminate the interference of impurities such as sea sand, stones and crustaceans in the extraction process. Centrifuge the agar industrial waste liquid at 8000r / min for 10min to remove suspended matter in the solution, and then adjust the pH of the agar industrial waste liquid to 3 with 6mol / L HCL and store it in a cool and dry environment for future use.

[0046] The ionic liquid was mixed with agar industrial waste liquid, vortexed for 2 minutes, and subjected to primary extraction for 6 minutes. The ionic liquid phase extraction layer was obtained, and the ionic liquid phase extraction layer contained polyphenol compounds. The ionic liquid was 1-butyl-3-methylimidazolium hexafluorophosphate. The volume ratio of agar industrial waste liquid: ionic liquid was set to 6 treatments, namely 1:0.25, 1:0.5, 1:1, 1:2, 1:3 and 1:4.

[0047] The ionic liquid phase extraction layer was mixed with hot distilled water at 60° C. in a volume ratio of 1:1, vortexed for 2 min, back-extracted for 3 min, allowed to stand for 6 min, and the hot distilled water phase was taken to obtain total polyphenols.

[0048] The results are as follows Figure 3As shown in the figure, the total polyphenol extraction rate showed a trend of first increasing and then decreasing. When the volume ratio reached 1:2, the total polyphenol extraction rate reached the highest value. Continuing to increase the content of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, the polyphenol extraction rate showed a downward trend, so the optimal volume ratio was 1:2.

[0049] Example 3

[0050] Use an 80-mesh sieve to filter and remove impurities from the agar industrial waste liquid to eliminate the interference of impurities such as sea sand, stones and crustaceans in the extraction process. Centrifuge the agar industrial waste liquid at 8000r / min for 10min to remove suspended matter in the solution, and then adjust the pH of the agar industrial waste liquid to 3 with 6mol / L HCL and store it in a cool and dry environment for future use.

[0051] The ionic liquid and the agar industrial waste liquid were mixed in a volume ratio of 1:1, vortexed for 2 minutes, subjected to primary extraction for 6 minutes, and allowed to stand for 20 minutes to separate into layers, thereby obtaining an ionic liquid phase extraction layer, which contained polyphenol compounds. The ionic liquid was 1-butyl-3-methylimidazolium hexafluorophosphate.

[0052] The ionic liquid phase extraction layer was mixed with hot distilled water in a volume ratio of 1:1, vortexed for 2 minutes, back-extracted for 3 minutes, and allowed to stand for 6 minutes to separate, and the hot distilled water phase was taken to obtain total polyphenols. The temperature of the hot distilled water was set to 7 treatments: 25°C, 40°C, 50°C, 60°C, 70°C, 80°C, and 90°C.

[0053] The results are as follows Figure 4 As shown in the figure, when the extraction temperature is 40℃~60℃, the extraction amount of total phenol in agar industrial waste liquid gradually increases with the increase of extraction temperature. When the extraction temperature is 60℃, the extraction amount of total phenol in agar industrial waste liquid reaches the highest peak. As the temperature continues to increase, the extraction rate shows a downward trend, so the optimal extraction temperature is 60℃.

[0054] Example 4

[0055] Use an 80-mesh sieve to filter and remove impurities from the agar industrial waste liquid to eliminate the interference of impurities such as sea sand, stones and crustaceans in the extraction process. Centrifuge the agar industrial waste liquid at 8000r / min for 10min to remove suspended matter in the solution, and then adjust the pH of the agar industrial waste liquid to 3 with 6mol / L HCL and store it in a cool and dry environment for future use.

[0056] The ionic liquid and the agar industrial waste liquid were mixed in a volume ratio of 1:1, vortexed for 2 minutes, subjected to primary extraction for 6 minutes, and allowed to stand for 20 minutes to separate into layers, thereby obtaining an ionic liquid phase extraction layer, which contained polyphenol compounds. The ionic liquid was 1-butyl-3-methylimidazolium hexafluorophosphate.

[0057] The ionic liquid phase extraction layer was mixed with hot distilled water, vortexed for 2 minutes, back-extracted for 3 minutes, and allowed to stand for 6 minutes to separate into layers. The hot distilled water phase was taken to obtain total polyphenols. The volume ratio of the ionic liquid phase extraction layer to hot distilled water was set to 6 treatments of 1:0.25, 1:0.5, 1:1, 1:2, 1:3, and 1:4.

[0058] The results are as follows Figure 5 As shown in the figure, the total polyphenol extraction rate first increases and then decreases with the increase of the amount of distilled water added. The total polyphenol extraction rate reaches the highest value when the volume ratio reaches 1:2, which can effectively improve the extraction rate of total phenols in agar industrial waste liquid. In this process, the effective components inside and outside the material in the extract reach a balance. When the distilled water extraction volume ratio is 1:2, the total polyphenols in the agar industrial waste liquid have been fully extracted, so the distilled water extraction volume ratio is 1:2.

[0059] Example 5

[0060] According to the principle of response surface design, three single factors that significantly affect the total polyphenol extraction rate of agar industrial wastewater were selected on the basis of single factor experiments, namely, the solid-liquid ratio (volume ratio of ionic liquid to agar industrial wastewater), extraction temperature, and distilled water extraction volume ratio as independent variables, and the total polyphenol extraction rate as the response value. A three-factor three-level experiment was conducted, with a total of 17 experimental points and 5 central experimental points, to obtain the optimal extraction conditions and verify them. The response surface experimental factor levels are shown in Table 1, and the experimental design scheme and results are shown in Table 2.

[0061] Table 1 Factor levels of polyphenol response surface experiment

[0062]

[0063]

[0064] Table 2 Response surface experimental design and results

[0065]

[0066] Table 3 Analysis of variance of regression model

[0067]

[0068] * indicates significant P < 0.05; ** indicates extremely significant P < 0.01.

[0069] The response surface optimization software was used to perform variance analysis on the data, and the multivariate quadratic regression equation of polyphenol extraction rate was obtained by data fitting:

[0070] Y=52.51-1.6A+0.20B-1.08C-2.56AB-1.59AC-1.74BC-6.64A2-5.78B2-6.45C2

[0071] Wherein, the response value R is the extraction rate of total polyphenols in agar industrial wastewater, the variable parameter A is the solid-liquid ratio, the variable parameter B is the back-extraction distilled water temperature, and the variable parameter C is the distilled water back-extraction volume ratio.

[0072] The regression equation was subjected to variance analysis and significance test, and the results are shown in Table 3. 2 , calibration determination coefficient R Adj 2 , lack of fit term and other results to analyze the accuracy and credibility of the model. As shown in Table 3, the regression model P < 0.001, indicating that the regression model results are extremely significant; the lack of fit term P is 0.1096> 0.05, that is, the lack of fit term is not significant; the determination coefficient R 2 is 0.9623>0.8, indicating that the model can explain 96.23% of the response value variation; the correction determination coefficient R Adj 2 is 0.9138>0.8, which is consistent with R 2 The results are close, indicating that the model has a good fitting degree; in summary, the regression model has a high degree of fitting, small error, and high credibility, and can be used for the optimization of total polyphenol extraction from agar industrial wastewater.

[0073] The optimal extraction conditions predicted by response surface software are solid-liquid ratio of 1:2.12, extraction temperature of 60.30℃, distilled water back extraction volume ratio of 1:2.06, and total polyphenol extraction rate of 52.58%. According to actual operation, the optimal conditions are adjusted to solid-liquid ratio of 1:2.1, extraction temperature of 60℃ and distilled water back extraction volume ratio of 1:2. The actual extraction rate of total polyphenols in agar industrial waste liquid measured by Folin phenol method is 51.78%, and the relative deviation is 1.55% compared with the predicted value, indicating that the optimal extraction process obtained by response surface analysis has a relatively high credibility.

[0074] Example 6

[0075] Use an 80-mesh sieve to filter and remove impurities from the agar industrial waste liquid to eliminate the interference of impurities such as sea sand, stones and crustaceans in the extraction process. Centrifuge the agar industrial waste liquid at 8000r / min for 10min to remove suspended matter in the solution, and then adjust the pH of the agar industrial waste liquid to 3 with 6mol / L HCL and store it in a cool and dry environment for future use.

[0076] The ionic liquid and agar industrial waste liquid were mixed in a volume ratio of 1:2.1, vortexed for 2 minutes, subjected to primary extraction for 6 minutes, and allowed to stand for 20 minutes to separate into layers, thereby obtaining an ionic liquid phase extraction layer, which contained polyphenol compounds. The ionic liquid was 1-butyl-3-methylimidazolium hexafluorophosphate.

[0077] The ionic liquid phase extraction layer was mixed with 60°C hot distilled water in a volume ratio of 1:2.06, vortexed for 2 minutes, back-extracted for 3 minutes, allowed to stand for 6 minutes, and the hot distilled water phase was taken and vacuum freeze-dried for 72 hours to obtain a crude polyphenol powder.

[0078] Determination of the antioxidant activity of the above crude polyphenol powder:

[0079] Determination of DPPH free radical scavenging ability: Weigh 3.9 mg of DPPH and dissolve it in 100 mL of anhydrous ethanol to prepare a 0.1 mmol / L DPPH ethanol solution, seal it in a brown bottle and place it in a refrigerator at 4°C. Take 1.0 mL of the sample solution and 1.0 mL of 0.1 mmol / L DPPH ethanol solution in a 5 mL centrifuge tube, react at room temperature in the dark for 30 minutes, and measure the absorbance A at a wavelength of 517 nm. 1 , the absorbance value measured by replacing the sample solution with ultrapure water is A 0 , calculate the DPPH free radical scavenging rate of the sample, and the calculation formula for the ability to scavenging DPPH free radicals is as follows:

[0080]

[0081] Where: A 0 A is the absorbance value obtained by the reaction of ultrapure water and DPPH ethanol solution. 1 It is the absorbance value measured by the reaction between the sample and DPPH ethanol solution;

[0082] DPPH free radicals carry odd electron ions, which are stable in ethanol solutions and have a maximum absorption peak at 517nm. When DPPH reacts with proton-donating polymers, the number of DPPH free radicals decreases and the absorption peak at 517nm also weakens.

[0083] The results are as follows Figure 6 As shown in the results, the total polyphenols in agar industrial wastewater have a certain scavenging ability for DPPH free radicals, which increases with the increase of concentration and is dose-dependent. In the mass concentration range of 1-6 mg / mL, the scavenging ability of polyphenol samples for DPPH free radicals increases with the increase of sample concentration. When the mass concentration is 6 mg / mL, the scavenging rate for DPPH free radicals is (67.19±0.24)%, and the half inhibition concentration (IC 50This indicates that the polyphenol sample has a strong ability to reduce the concentration of DPPH free radicals and block the lipid peroxidation chain reaction.

[0084] ABTS free radical scavenging ability determination: prepare 7mmol / L ABTS, 2.4mmol / L K 2 S 2 O 8 and 0.2 mol / L NaH 2 PO 4 -Na 2 HPO 4 (pH = 7.0). Mix the prepared ABTS solution with the prepared K 2 S 2 O 8 The solutions were mixed in equal proportions, and after mixing evenly, placed in a dark place at room temperature and away from light for 12-16 hours to prepare ABTS·+ stock solution. When using the ABTS·+ stock solution, dilute it with the prepared phosphate buffer until its absorbance at a wavelength of 734nm is 0.7±0.02. 0.1mL of sample solutions of different mass concentrations and 1mL of the prepared ABTS·+ working solution were added to the test tube in sequence, mixed evenly, and placed in a water bath at 37℃ for 1 hour. Detected at a wavelength of 734nm, the absorbance was A 1 . Distilled water was used instead of the sample to measure the absorbance value A 0 , calculate the free radical scavenging rate of the sample. The calculation formula for the ability of total polyphenols in agar industrial wastewater to scavenge ABTS free radicals is as follows:

[0085]

[0086] In the formula, A 1 is the absorbance value of the sample group; A 0 is the absorbance value of the blank group.

[0087] ABTS is a free radical initiator, which is oxidized by potassium persulfate to generate stable blue-green free radicals (ABTS+). ABTS free radicals can easily obtain electrons or protons from ABTS and have strong absorption at 734nm. If the added test sample has the ability to scavenge ABTS+, the color will fade.

[0088] The results are as follows Figure 7 As shown in the figure, the total polyphenols in agar industrial wastewater have a significant effect on scavenging ABTS free radicals, and the scavenging activity of ABTS free radicals shows a trend of increasing with the increase of concentration. In the mass concentration range of 0.5-10 mg / mL, the scavenging rate of polyphenol samples on ABTS free radicals shows an obvious dose relationship with the mass concentration. When the mass concentration is 8 mg / mL, the scavenging rate of ABTS free radicals is (92.23±0.22)%, and the half inhibition concentration (IC 50value) was about 2.1 mg / mL, and the polyphenol sample had a strong scavenging effect on ABTS free radicals.

[0089] In summary, according to the embodiments of the present invention, on the basis of single factor experiments, the Box-Behnken response surface analysis method is used to design the experimental scheme, with the solid-liquid ratio, extraction temperature, and distilled water extraction ratio as experimental factors, and the total polyphenol extraction rate of agar industrial waste liquid as the response value, a regression model is established, the effectiveness of the regression model and the influence of each single factor are analyzed, and each factor in the total polyphenol extraction of agar industrial waste liquid is optimized to obtain the optimized process conditions for total polyphenol extraction. There is a good fit between the measured value and the theoretical value of the model, which is suitable for the total polyphenol extraction of agar industrial waste liquid. The present application uses agar industrial waste liquid as a raw material to process polyphenols, and the obtained total polyphenols of agar industrial waste liquid have strong activity and good antioxidant effect, and have a scavenging effect on DPPH free radicals and ABTS free radicals. The preparation method is fast and efficient with a high yield, which is conducive to subsequent purification, structural analysis and activity identification work, and provides a reference for its subsequent application in the fields of comprehensive development and utilization of seaweed glue making and high value utilization of agar industrial waste liquid.

[0090] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily being directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0091] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for extracting polyphenols from agar industrial waste liquid using ionic liquid, characterized in that: The following steps are involved: The agar industrial waste liquid is treated to remove impurities, and then the pH of the agar industrial waste liquid is adjusted to 3 with HCl; 1-butyl-3-methylimidazolium hexafluorophosphate and agar industrial waste liquid are mixed in a volume ratio of 1:2.1, vortexed for 1 to 2 minutes, subjected to primary extraction for 5 to 10 minutes, and allowed to stand for stratification for 20 to 40 minutes to obtain an ionic liquid phase extraction layer; The ionic liquid phase extraction layer was mixed with hot distilled water at 60° C. in a volume ratio of 1:0.25 to 1:4, vortexed for 1 to 2 minutes, back-extracted for 2 to 6 minutes, allowed to stand for 6 to 8 minutes, and the hot distilled water phase was taken to obtain total polyphenols.

2. The method according to claim 1, characterized in that The initial extraction time was 6 minutes, and the standing and stratification time after the initial extraction was 20 minutes.

3. The method according to claim 1, characterized in that The back extraction time was 3 minutes, and the standing stratification time after back extraction was 6 minutes.

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