A method for extracting and continuously modifying walnut polyphenols to prepare a fat-soluble antioxidant

Abstract

The application discloses a method for extracting and continuously modifying walnut polyphenols to prepare a fat-soluble antioxidant, and belongs to the technical field of oil deep processing. First, a mixture of walnut shells and divaricate witch hazel wood is dried and crushed, mixed with a eutectic solvent, stirred after heating, centrifugally separated, and the upper product is collected; then the upper product is treated by rotary evaporation, fatty acids are added, and after uniform heating and stirring, immobilized lipase is added for reaction, and after the reaction is completed, the reaction mixture is collected by centrifugation; finally, free fatty acids in the reaction mixture are separated and removed, and a fat-soluble antioxidant is obtained. The application can realize the extraction and continuous enzymatic modification of walnut polyphenols by regulating the water activity of the eutectic solvent, and the fat-soluble modified product of the walnut polyphenols has better antioxidant activity and safety compared with traditional chemical synthetic antioxidants, and has good industrial application prospect and social and economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of deep oil processing technology, specifically relating to a method for extracting walnut polyphenols and preparing fat-soluble antioxidants through continuous enzymatic modification. Background Technology

[0002] The deep processing of walnuts generates a large amount of walnut shells and septum. Currently, these are often discarded as waste, resulting in resource waste and environmental pollution. Walnut shells and septum contain abundant polyphenols, which have the effects of scavenging free radicals, reducing oxidative stress, and preventing macromolecular oxidation. They have become a research hotspot in the food and pharmaceutical fields. Therefore, fully developing and utilizing the polyphenols in walnut shells and septum can not only turn waste into treasure but also bring significant social and economic benefits.

[0003] Currently, the extraction of polyphenols from walnut husks, shells, and septa commonly employs organic solvents, water, and eutectic solvents. Compared to traditional organic solvents, eutectic solvents, with their naturally derived components, offer better stability, safety, and environmental friendliness, making them the preferred solvents for polyphenol extraction in recent years. However, the predominance of water-soluble polyphenols limits their application in lipid-soluble systems, thus restricting their antioxidant activity. Compared to traditional lipid-soluble antioxidants such as TBHQ and BHA, naturally derived polyphenols offer higher safety and antioxidant activity, but their lower lipid solubility limits their application in oils and lipid-soluble systems. Maintaining the antioxidant activity of natural polyphenols while improving their lipid solubility is one of the key bottlenecks in polyphenol modification. Summary of the Invention

[0004] To address the shortcomings of the existing technology, the present invention aims to provide a method for extracting walnut polyphenols and preparing a fat-soluble antioxidant through continuous enzymatic modification. This method enables the extraction and continuous enzymatic modification of walnut polyphenols, and the resulting fat-soluble modified walnut polyphenols exhibit better antioxidant activity and safety compared to traditional chemically synthesized antioxidants.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing a fat-soluble antioxidant by extracting walnut polyphenols and continuously enzymatically modifying them includes the following steps:

[0007] Step 1: After drying and pulverizing the mixture of walnut shells and septum, mix it with a eutectic solvent, heat and stir, centrifuge and collect the upper product;

[0008] Step 2: After rotary evaporation of the upper product obtained in Step 1, fatty acids are added, and the mixture is heated and stirred until homogeneous. Immobilized lipase is then added to carry out the reaction. After the reaction is completed, the reaction mixture is collected by centrifugation.

[0009] Step 3: Separate and remove the free fatty acids from the reaction mixture obtained in Step 2 to obtain a fat-soluble antioxidant.

[0010] Preferably, in step 1, vacuum drying is used to dry the walnut shells and septum, with a vacuum degree ≥0.095MPa, a drying temperature of 35~45℃, and a drying time of 4~6h; after drying, the walnut shells are crushed to below 30mm.

[0011] Preferably, in step 1, the eutectic solvent is choline chloride-urea, betaine-urea, choline chloride-xylitol, or choline chloride-glucose-water; in choline chloride-urea, the molar ratio of choline chloride to urea is 1:(1-2); in betaine-urea, the molar ratio of betaine to urea is 1:(1-2); in choline chloride-xylitol, the molar ratio of choline chloride to xylitol is 1:(1-2); in choline chloride-glucose-water, the molar ratio of choline chloride, glucose, and water is (2.5-1):1:(2.5-10).

[0012] More preferably, the water activity Aw of the eutectic solvent is 0.3 to 0.7.

[0013] Preferably, in step 1, the mass ratio of the eutectic solvent to the mixture of walnut shell and septum is 10 to 20:1.

[0014] Preferably, in step 1, the heating temperature is 50-70℃; the stirring speed is 300-500 rpm; the stirring time is 1-2 hours; and the centrifugation speed after stirring is 12000-15000 rpm, and the time is 5-10 minutes.

[0015] Preferably, in step 2, the rotary evaporation process is carried out until the water activity Aw of the eutectic solvent drops below 0.2; the heating temperature is 50–70°C.

[0016] Preferably, in step 2, the added fatty acid is palmitic acid or oleic acid, and the amount added is 0.5 to 1 times the mass of the mixture of walnut shell and septum.

[0017] Preferably, in step 2, the added immobilized lipase is Novozym 435 or Lipozyme 435, and the amount added is 5% to 10% of the fatty acid mass; the stirring speed is 300 to 500 rpm, and the reaction time is 6 to 12 h.

[0018] Preferably, in step 3, a solid-phase extraction column is used to separate and remove fatty acids from the reaction mixture to obtain a fat-soluble antioxidant.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] This invention discloses a method for extracting walnut polyphenols and preparing a fat-soluble antioxidant via continuous enzymatic modification. The method uses a eutectic solvent as both the extraction and reaction medium. By controlling the water activity of the eutectic solvent, the extraction and continuous enzymatic modification of walnut polyphenols can be achieved. Furthermore, by controlling the enzymatic reaction conditions, the fat solubility, antioxidant activity, and yield of the modified product of walnut polyphenols can be controlled. Compared to traditional methods for extracting and modifying polyphenols, this invention uses a eutectic solvent as both the extraction and reaction medium. On the one hand, the extraction effect of the eutectic solvent on walnut polyphenols can be controlled by adjusting the water activity; on the other hand, the degree of esterification of walnut polyphenols can be controlled by adjusting the water activity of the eutectic solvent. This invention achieves the extraction and continuous enzymatic modification of walnut polyphenols by controlling the water activity of the eutectic solvent and the enzymatic reaction conditions. Moreover, the fat-soluble modified walnut polyphenols exhibit better antioxidant activity and safety compared to traditional chemically synthesized antioxidants. This invention enables the extraction and continuous enzymatic modification of walnut polyphenols, allowing for the continuous extraction and modification of polyphenolic substances. The modified products exhibit higher safety and antioxidant activity, demonstrating not only promising prospects for industrial application but also significant social and economic benefits.

[0021] Furthermore, the type, component ratio, and water activity of the eutectic solvent can not only ensure a good extraction effect of walnut polyphenols, but also a good esterification effect of walnut polyphenols.

[0022] Furthermore, the drying conditions and degree of grinding of walnut shells and septum, as well as the mass ratio of eutectic solvent to walnut shell and septum powder, extraction temperature, rotation speed, and time, can ensure that walnut polyphenols are fully extracted.

[0023] Furthermore, the fatty acids used are palmitic acid or oleic acid, which can effectively promote the esterification of walnut polyphenols.

[0024] Furthermore, the immobilized lipase used is Novozym 435 or Lipozyme 435, and the amount added is 5% to 10% of the total substrate mass. This not only ensures the efficient esterification of walnut polyphenols, but also ensures the economy of the reaction. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the technical process of the present invention. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for illustrative purposes only and not for limiting the scope of the invention. Unless otherwise stated, all percentages are by weight.

[0027] like Figure 1 The present invention is a technical flow chart. By regulating the water activity, the extraction effect of eutectic solvent on walnut polyphenols can be controlled on the one hand, and the degree of esterification of walnut polyphenols by eutectic solvent can be controlled on the other hand, thereby controlling the fat solubility, antioxidant activity and yield of walnut polyphenol fatty acid esters.

[0028] Example 1

[0029] 100g of walnut shell and septum powder (dried at 0.095MPa and 35℃ for 6h, then pulverized to below 30mm) was added to a 2L extraction flask. Then, 1000g of a eutectic solvent composed of choline chloride and urea (molar ratio of choline chloride to urea was 1:2) was added. The water activity of the eutectic solvent was 0.3. The mixture was heated to 50℃ and stirred at 500rpm for 2h, followed by centrifugation at 15000rpm for 5min. The eutectic solvent was collected. The recovered eutectic solvent was subjected to rotary evaporation until the water activity (Aw) decreased to 0.1. Then, 100g of palmitic acid was added to the eutectic solvent, heated to 60℃ and stirred until homogeneous. Finally, 10g of Novozym was added. The reaction mixture was heated to 435°C and reacted at 500 rpm for 6 hours. After the reaction was completed, the reaction mixture was collected. Two volumes of chloroform-methanol (2:1, volume ratio) were added to the reaction mixture, followed by 0.5 volumes of deionized water. After shaking and extraction, the organic and aqueous phases were separated. 4.02 g of walnut polyphenol fat-soluble modifier was obtained after removing the organic solvent from the organic phase. Accelerated oxidation experiments showed that the oxidation induction time of the walnut polyphenol fat-soluble modifier group was 2.30 times and 2.95 times that of the TBHQ group, respectively, and the walnut polyphenol group, respectively.

[0030] Example 2

[0031] 100g of walnut shell and septum powder (dried at 0.096MPa and 45℃ for 4h, then pulverized to below 30mm) was added to a 2L extraction flask. Then, 2000g of a eutectic solvent composed of choline chloride and urea (molar ratio of choline chloride to urea 1:1) was added. The water activity of the eutectic solvent was 0.7. The mixture was heated to 70℃ and stirred at 300rpm for 1h, followed by centrifugation at 12000rpm for 10min. The eutectic solvent was collected. The recovered eutectic solvent was subjected to rotary evaporation until the water activity (Aw) decreased to 0.08. Then, 100g of oleic acid was added to the eutectic solvent, heated to 70℃, and stirred until homogeneous. Finally, 10g of Lipozyme was added. The reaction mixture was heated to 435°C and reacted at 300 rpm for 6 hours. After the reaction was completed, the reaction mixture was collected. Three volumes of chloroform-methanol (2:1, volume ratio) were added to the reaction mixture, followed by one volume of deionized water. After shaking and extraction, the organic and aqueous phases were separated. 4.54 g of walnut polyphenol fat-soluble modifier was obtained after removing the organic solvent from the organic phase. Accelerated oxidation experiments showed that the oxidation induction time of the walnut polyphenol fat-soluble modifier group was 2.41 times and 3.09 times that of the TBHQ group, respectively, and the walnut polyphenol group, respectively.

[0032] Example 3

[0033] 100g of walnut shell and septum powder (dried at 0.095MPa and 40℃ for 5h, then pulverized to below 30mm) was added to a 2L extraction flask. Then, 1500g of a eutectic solvent composed of betaine and urea (molar ratio of betaine to urea 1:2) was added. The water activity of the eutectic solvent was 0.6. The mixture was heated to 60℃ and stirred at 400rpm for 1.5h, followed by centrifugation at 12000rpm for 10min. The eutectic solvent was collected. The recovered eutectic solvent was subjected to rotary evaporation until the water activity (Aw) decreased to 0.04. Then, 50g of oleic acid was added to the eutectic solvent, heated to 50℃, and stirred until homogeneous. Finally, 5g of Lipozyme was added. The reaction mixture was heated to 435°C and reacted at 500 rpm for 12 hours. After the reaction was completed, the reaction mixture was collected. 2.5 times the volume of chloroform-methanol (2:1, volume ratio) was added to the reaction mixture, followed by 0.8 times the volume of deionized water. After shaking and extraction, the organic and aqueous phases were separated. 4.02 g of walnut polyphenol fat-soluble modifier was obtained after removing the organic solvent from the organic phase. Accelerated oxidation experiments showed that the oxidation induction time of the walnut polyphenol fat-soluble modifier group was 2.24 times and 2.87 times that of the TBHQ group, respectively, and the walnut polyphenol group, respectively.

[0034] Example 4

[0035] 100g of walnut shell and septum powder (dried at 0.096MPa and 35℃ for 6h, then pulverized to below 30mm) was added to a 2L extraction flask. Then, 2000g of a eutectic solvent composed of betaine and urea (molar ratio of betaine to urea 1:1) was added. The water activity of the eutectic solvent was 0.7. The mixture was heated to 65℃ and stirred at 450rpm for 1h, followed by centrifugation at 15000rpm for 5min. The eutectic solvent was collected. The recovered eutectic solvent was subjected to rotary evaporation until the water activity (Aw) decreased to 0.12. Then, 80g of palmitic acid was added to the eutectic solvent, heated to 60℃ and stirred until homogeneous. Finally, 8g of palmitic acid was added... Novozym435 was reacted at 400 rpm for 8 hours. After the reaction, the reaction mixture was collected. Three volumes of chloroform-methanol (2:1, volume ratio) were added to the reaction mixture, followed by 0.6 volumes of deionized water. After shaking and extraction, the organic and aqueous phases were separated. 4.18 g of walnut polyphenol fat-soluble modifier was obtained after removing the organic solvent from the organic phase. Accelerated oxidation experiments showed that the oxidation induction time of the walnut polyphenol fat-soluble modifier group was 2.39 times and 3.06 times that of the TBHQ group, respectively, and the walnut polyphenol group, respectively.

[0036] Example 5

[0037] 100g of walnut shell and septum powder (dried at 0.096MPa and 45℃ for 4h, then pulverized to below 30mm) was added to a 2L extraction flask. Then, 1200g of a eutectic solvent composed of choline chloride and xylitol (molar ratio of choline chloride to xylitol 1:1) was added. The water activity of the eutectic solvent was 0.55. The mixture was heated to 60℃ and stirred at 350rpm for 2h, followed by centrifugation at 15000rpm for 5min. The eutectic solvent was collected. The recovered eutectic solvent was subjected to rotary evaporation until the water activity (Aw) decreased to 0.06. Then, 100g of palmitic acid was added to the eutectic solvent, heated to 55℃ and stirred until homogeneous. Finally, 5g of Novozym was added. The reaction mixture was heated to 435°C and reacted at 450 rpm for 12 hours. After the reaction was complete, the reaction mixture was collected. 2.8 times the volume of chloroform-methanol (2:1, volume ratio) was added to the reaction mixture, followed by 0.9 times the volume of deionized water. After shaking and extraction, the organic and aqueous phases were separated. 4.07 g of walnut polyphenol fat-soluble modifier was obtained after removing the organic solvent from the organic phase. Accelerated oxidation experiments showed that the oxidation induction time of the walnut polyphenol fat-soluble modifier group was 2.50 times and 3.21 times that of the TBHQ group, respectively, and the walnut polyphenol group, respectively.

[0038] Example 6

[0039] 100g of walnut shell and septum powder (dried at 0.097MPa and 35℃ for 6h, then pulverized to below 30mm) was added to a 2L extraction flask. Then, 1800g of a eutectic solvent composed of choline chloride and xylitol (molar ratio of choline chloride to xylitol 1:2) was added. The water activity of the eutectic solvent was 0.68. The mixture was heated to 65℃ and stirred at 450rpm for 2h, followed by centrifugation at 15000rpm for 5min. The eutectic solvent was collected. The recovered eutectic solvent was subjected to rotary evaporation until the water activity (Aw) decreased to 0.09. Then, 75g of oleic acid was added to the eutectic solvent, heated to 65℃, and stirred until homogeneous. Finally, 7.5g of Novozym was added. The reaction mixture was heated to 435°C and reacted at 500 rpm for 12 hours. After the reaction was complete, the reaction mixture was collected. 2.3 times the volume of chloroform-methanol (2:1, volume ratio) was added to the reaction mixture, followed by 0.8 times the volume of deionized water. After shaking and extraction, the organic and aqueous phases were separated. 4.48 g of walnut polyphenol fat-soluble modifier was obtained after removing the organic solvent from the organic phase. Accelerated oxidation experiments showed that the oxidation induction time of the walnut polyphenol fat-soluble modifier group was 2.34 times and 3.00 times that of the TBHQ group, respectively, and the walnut polyphenol group, respectively.

[0040] Example 7

[0041] 100g of walnut shell and septum powder (dried at 0.095MPa and 40℃ for 5h, then pulverized to below 30mm) was added to a 2L extraction flask. Then, 2000g of a eutectic solvent consisting of choline chloride, glucose, and water (molar ratio of choline chloride to glucose and water was 2.5:1:10) was added. The water activity of the eutectic solvent was 0.7. The mixture was heated to 60℃ and stirred at 500rpm for 2h, followed by centrifugation at 15000rpm for 5min. The eutectic solvent was collected. The recovered eutectic solvent was subjected to rotary evaporation until the water activity (Aw) decreased to 0.06. Then, 100g of oleic acid was added to the eutectic solvent, heated to 60℃, and stirred until homogeneous. Finally, 10g of Novozym was added. The reaction mixture was heated to 435°C and reacted at 500 rpm for 6 hours. After the reaction was completed, the reaction mixture was collected. Two volumes of chloroform-methanol (2:1, volume ratio) were added to the reaction mixture, followed by 0.5 volumes of deionized water. After shaking and extraction, the organic and aqueous phases were separated. 4.26 g of walnut polyphenol fat-soluble modifier was obtained after removing the organic solvent from the organic phase. Accelerated oxidation experiments showed that the oxidation induction time of the walnut polyphenol fat-soluble modifier group was 2.67 times and 3.42 times that of the TBHQ group, respectively, and the walnut polyphenol group, respectively.

[0042] Example 8

[0043] 100g of walnut shell and septum powder (dried at 0.098MPa and 45℃ for 4h, then pulverized to below 30mm) were added to a 2L extraction flask. Then, 1500g of a eutectic solvent consisting of choline chloride, glucose, and water (molar ratio of choline chloride to glucose and water was 1:1:2.5) was added. The water activity of the eutectic solvent was 0.3. The mixture was heated to 70℃ and stirred at 400rpm for 2h, followed by centrifugation at 15000rpm for 5min. The eutectic solvent was collected. The recovered eutectic solvent was subjected to rotary evaporation until the water activity (Aw) decreased to 0.05. Then, 100g of palmitic acid was added to the eutectic solvent, heated to 65℃, and stirred until homogeneous. Finally, 10g of Lipozyme was added. The reaction mixture was heated to 435°C and reacted at 500 rpm for 6 hours. After the reaction was completed, the reaction mixture was collected. Three volumes of chloroform-methanol (2:1, volume ratio) were added to the reaction mixture, followed by one volume of deionized water. After shaking and extraction, the organic and aqueous phases were separated. 4.65 g of walnut polyphenol fat-soluble modifier was obtained after removing the organic solvent from the organic phase. Accelerated oxidation experiments showed that the oxidation induction time of the walnut polyphenol fat-soluble modifier group was 2.16 times and 2.77 times that of the TBHQ group, respectively, and the walnut polyphenol group, respectively.

[0044] Example 9

[0045] 100g of walnut shell and septum powder (dried at 0.095MPa and 35℃ for 6h, then pulverized to below 30mm) was added to a 2L extraction flask. Then, 1600g of a eutectic solvent consisting of choline chloride, glucose, and water (molar ratio of choline chloride to glucose and water was 2.5:1:2.5) was added. The water activity of the eutectic solvent was 0.5. The mixture was heated to 60℃ and stirred at 300rpm for 2h, followed by centrifugation at 12000rpm for 10min. The eutectic solvent was collected. The recovered eutectic solvent was subjected to rotary evaporation until the water activity (Aw) decreased to 0.03. Then, 90g of palmitic acid was added to the eutectic solvent, heated to 60℃, and stirred until homogeneous. Finally, 9g of palmitic acid was added... Lipozyme 435 was reacted at 500 rpm for 12 h. After the reaction, the reaction mixture was collected. 2.5 times the volume of chloroform-methanol (2:1, volume ratio) was added to the reaction mixture, followed by 0.75 times the volume of deionized water. After shaking extraction, the organic and aqueous phases were separated. 4.36 g of walnut polyphenol fat-soluble modifier was obtained after removing the organic solvent from the organic phase. Accelerated oxidation experiments showed that the oxidation induction time of the walnut polyphenol fat-soluble modifier group was 2.28 times and 2.92 times that of the TBHQ group, respectively, and the walnut polyphenol group, respectively, when the same mass of TBHQ, walnut polyphenol, and walnut polyphenol fat-soluble modifier were added to walnut oil.

[0046] Example 10

[0047] 100g of walnut shell and septum powder (dried at 0.096MPa and 45℃ for 4h, then pulverized to below 30mm) was added to a 2L extraction flask. Then, 1600g of a eutectic solvent consisting of choline chloride, glucose, and water (molar ratio of choline chloride to glucose and water was 2:1:8) was added. The water activity of the eutectic solvent was 0.7. The mixture was heated to 60℃ and stirred at 500rpm for 1.5h, followed by centrifugation at 15000rpm for 5min. The eutectic solvent was collected. The recovered eutectic solvent was subjected to rotary evaporation until the water activity (Aw) decreased to 0.05. Then, 60g of oleic acid was added to the eutectic solvent, heated to 60℃, and stirred until homogeneous. Finally, 6g of Novozym was added. The reaction mixture was heated to 435°C and reacted at 500 rpm for 12 hours. After the reaction was complete, the reaction mixture was collected. Two volumes of chloroform-methanol (2:1, volume ratio) were added to the reaction mixture, followed by 0.6 volumes of deionized water. After shaking and extraction, the organic and aqueous phases were separated. 4.71 g of walnut polyphenol fat-soluble modifier was obtained after removing the organic solvent from the organic phase. Accelerated oxidation experiments showed that the oxidation induction time of the walnut polyphenol fat-soluble modifier group was 2.62 times and 3.36 times that of the TBHQ group, respectively, and the walnut polyphenol group, respectively.

[0048] The table below shows the extraction and reaction systems, fatty acid types, yields of fat-soluble modified products, and oxidative induction times compared to the control group for each example:

[0049]

[0050]

[0051] The above description is only a part of the embodiments of the present invention. Although some terms are used in the present invention, the possibility of using other terms is not excluded. The use of these terms is merely for the convenience of describing and explaining the essence of the present invention, and interpreting them as any kind of additional limitation would contradict the spirit of the present invention. The above description is only to further illustrate the content of the present invention through embodiments to facilitate easier understanding, but it does not mean that the embodiments of the present invention are limited to this. Any technical extension or re-creation based on the present invention is protected by the present invention.

Claims

1. A method for extracting walnut polyphenols and preparing a fat-soluble antioxidant via continuous enzymatic modification, characterized in that, Includes the following steps: Step 1: After drying and pulverizing the mixture of walnut shells and septum, mix it with a eutectic solvent, heat and stir, centrifuge and separate, and collect the eutectic solvent containing walnut polyphenols as the upper product. Step 2: Using the eutectic solvent containing walnut polyphenols collected in Step 1 as the reaction medium, rotary evaporate it to reduce its water activity. Then fatty acids are added to it, and after heating and stirring evenly, immobilized lipase is added to carry out the reaction. After the reaction is completed, the reaction mixture is collected by centrifugation. Step 3: Separate and remove free fatty acids from the reaction mixture obtained in Step 2 to obtain a fat-soluble antioxidant; In step 1, the water activity Aw of the eutectic solvent is 0.3 to 0.7; in step 2, the rotary evaporation process is carried out until the water activity Aw of the eutectic solvent drops below 0.

2.

2. The method for extracting walnut polyphenols and preparing fat-soluble antioxidants by continuous enzymatic modification according to claim 1, characterized in that, In step 1, vacuum drying is used to dry the walnut shells and septum, with a vacuum degree ≥0.095MPa, a drying temperature of 35~45℃, and a drying time of 4~6h; after drying, the walnut shells and septum are crushed to below 30mm.

3. The method for extracting walnut polyphenols and preparing fat-soluble antioxidants by continuous enzymatic modification according to claim 1, characterized in that, In step 1, the eutectic solvent is choline chloride. Urea, betaine Urea, choline chloride Xylitol or choline chloride glucose Water; choline chloride In urea, the molar ratio of choline chloride to urea is 1:(1-2); betaine In urea, the molar ratio of betaine to urea is 1:(1-2); choline chloride In xylitol, the molar ratio of choline chloride to xylitol is 1:(1-2); choline chloride glucose In water, the molar ratio of choline chloride, glucose, and water is (2.5–1):1:(2.5–10).

4. The method for extracting walnut polyphenols and preparing fat-soluble antioxidants by continuous enzymatic modification according to claim 1, characterized in that, In step 1, the mass ratio of the eutectic solvent to the mixture of walnut shells and septum is 10–20:

1.

5. The method for extracting walnut polyphenols and preparing a fat-soluble antioxidant by continuous enzymatic modification according to claim 1, characterized in that, In step 1, the heating temperature is 50-70℃; the stirring speed is 300-500 rpm; the stirring time is 1-2 hours; after stirring, the centrifugation speed is 12000-15000 rpm; and the time is 5-10 minutes.

6. The method for extracting walnut polyphenols and preparing fat-soluble antioxidants by continuous enzymatic modification according to claim 1, characterized in that, In step 2, the heating temperature is 50–70°C.

7. The method for extracting walnut polyphenols and preparing a fat-soluble antioxidant by continuous enzymatic modification according to claim 1, characterized in that, In step 2, the added fatty acid is palmitic acid or oleic acid, and the amount added is 0.5 to 1 times the mass of the mixture of walnut shells and septum.

8. The method for extracting walnut polyphenols and preparing a fat-soluble antioxidant by continuous enzymatic modification according to claim 1, characterized in that, In step 2, the added immobilized lipase is Novozym 435 or Lipozyme 435, and the amount added is 5% to 10% of the fatty acid mass; the stirring speed is 300 to 500 rpm, and the reaction time is 6 to 12 hours.

9. The method for extracting walnut polyphenols and preparing a fat-soluble antioxidant by continuous enzymatic modification according to claim 1, characterized in that, In step 3, a solid-phase extraction column is used to separate and remove fatty acids from the reaction mixture to obtain a fat-soluble antioxidant.

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