A soybean phospholipid and its extraction method

Abstract

This invention discloses a soybean lecithin and its extraction method, belonging to the field of soybean lecithin technology. The extraction method uses fresh soybean oil by-products as raw material, which undergoes centrifugation, acetone degreasing, and ethanol extraction to obtain an ethanol extract. Finally, attapulgite-crosslinked chitosan microspheres are added to the ethanol extract to further remove impurity molecules, resulting in soybean lecithin with high stability and high soybean lecithin content. Utilizing the multi-porous structure and electrostatic interaction of the attapulgite-crosslinked chitosan microspheres, large impurity molecules, as well as polar inositol phospholipids and cephalins, which compete with soybean lecithin for solubility, are separated, thereby increasing the soybean lecithin content in the soybean lecithin. Furthermore, the attapulgite-crosslinked chitosan microspheres are grafted with tea polyphenols, which can scavenge free radicals through a hydrogen donation mechanism, blocking the phospholipid oxidation process and achieving both high stability and high antioxidant activity, thus improving the quality of the obtained soybean lecithin.

Description

Technical Field

[0001] This invention belongs to the field of soybean phospholipid technology, specifically relating to a soybean phospholipid and its extraction method. Background Technology

[0002] Soybean oil by-products, also known as soybean oil residue, are byproducts of hydration and degumming during the refining of soybean oil. Their main components include phospholipids, neutral oil, water, and other lipids, as well as small amounts of protein, sugars, pigments, and organic and inorganic impurities. Currently, the vast majority of soybean oil residues are not fully utilized, and soybean oil residues themselves are extremely prone to rancidity and foul odor, causing environmental pollution.

[0003] Soybean lecithin is one of the main components of soybean oil residue. It is a pure natural high-nutrient fortifier and a natural surfactant. It is widely used in many fields such as food, medicine, feed and cosmetics. It has high scientific research value and economic benefits. Extracting soybean lecithin from soybean oil residue is also one of the most effective methods for utilizing soybean oil residue.

[0004] However, extracting soybean phospholipids from soybean oil residue using traditional solvent extraction methods presents several challenges. These include solvent residue, cumbersome and complex separation steps between phospholipids and neutral oils / impurities, sensitivity to temperature and pressure parameters during extraction, low tolerance for errors, and poor product purity and quality stability. Furthermore, phospholipids are prone to oxidation during extraction, leading to increased peroxide values ​​and impacting product stability. Emerging extraction technologies, such as supercritical carbon dioxide extraction, face issues such as high equipment investment and the potential for high-viscosity phospholipids to clog the system, hindering continuous production.

[0005] Meanwhile, soybean lecithin, a core active ingredient in soybean lecithin, directly affects the functional value and application range of the obtained soybean lecithin. Soybean lecithin with high soybean lecithin content is of great significance in the fields of cardiovascular protection, targeted drugs, and functional foods. However, in the current process of extracting soybean lecithin from soybean oil residue, the separation is difficult due to the large polarity difference between soybean lecithin and impurity phospholipids such as inositol phospholipids in soybean lecithin, making it difficult to obtain soybean lecithin with high soybean lecithin content. Summary of the Invention

[0006] The purpose of this invention is to provide a soybean lecithin and its extraction method to solve the problems of poor quality stability and low soybean lecithin content of soybean lecithin extracted from soybean oil residue.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides a method for extracting soybean phospholipids, comprising the following process steps:

[0009] S101. Take fresh soybean oil by-products, centrifuge for 5-10 minutes, and leave the middle layer of oil residue;

[0010] S102. Mix the middle layer oil residue with acetone thoroughly, control the temperature at 40-50℃, stir for 0.5-1h, let it stand to separate into layers, remove the supernatant, collect the insoluble matter, and repeat the above operation 2-3 times.

[0011] S103. Filter the insoluble matter collected in step S2 to obtain crude phospholipids;

[0012] S104. Add crude phospholipids to 85-95% ethanol, adjust the temperature to 65-70℃, extract 3-4 times, and collect the ethanol extract by centrifugation.

[0013] S105. Add attapulgite composite cross-linked chitosan microspheres to the ethanol extract, stir and disperse for 3-4 hours, filter and recover the attapulgite composite cross-linked chitosan microspheres, and then evaporate the ethanol under reduced pressure to obtain soybean lecithin.

[0014] The cross-linked chitosan microspheres containing attapulgite are grafted with tea polyphenols.

[0015] Preferably, the amount of attapulgite composite cross-linked chitosan microspheres added is 5-10% of the mass of the ethanol extract.

[0016] Preferably, the mass-to-volume ratio of the intermediate oil residue to acetone is 1 g: (3-5) mL.

[0017] Preferably, the mass-to-volume ratio of crude phospholipid to ethanol is 1 g: (3-4) mL.

[0018] Preferably, the particle size of the attapulgite composite cross-linked chitosan microspheres is 10–30 μm.

[0019] By employing the above technical solution, mixing soybean oil residue with acetone first dissolves the oil and free fatty acids in the soybean oil residue, but does not dissolve soybean lecithin, thus achieving an oil removal effect. This effectively removes oil and other impurities from the soybean oil residue, improving the purity of the soybean lecithin. Then, the obtained crude lecithin is extracted with ethanol. Some major components of soybean lecithin, such as soybean lecithin, cephalin, and inositol phospholipids, can be effectively dissolved in the ethanol solution, further removing impurities and improving the purity and quality of the obtained soybean lecithin.

[0020] To improve the content of soybean lecithin in the extracted soybean lecithin, this invention adds attapulgite-based cross-linked chitosan microspheres to the ethanol extract. Specifically, soybean lecithin contains polar groups and is hydrophilic, resulting in high solubility in ethanol. However, soybean lecithin contains components such as inositol phospholipids, neutral lipids, and pigments, especially inositol phospholipids, which also contain hydrophilic groups. These components are difficult to separate from soybean lecithin using conventional solvent extraction. During the ethanol dissolution process, these polar substances compete with soybean lecithin for dissolution, indirectly affecting the content of soybean lecithin in the soybean lecithin. Therefore, this invention adds attapulgite-based cross-linked chitosan microspheres to improve this phenomenon, increase the solubility and retention rate of soybean lecithin, and selectively adsorb and remove impurity molecules such as inositol phospholipids and neutral lipids.

[0021] The attapulgite composite cross-linked chitosan microspheres of the present invention have amino and hydroxyl groups on the chitosan molecular chain that can preferentially adsorb negatively charged ions through electrostatic interactions. Including the composite attapulgite, the surface contains a large number of silanol groups and negative charges, which have a strong adsorption capacity for metal impurities and other impurities in soybean oil residue extract. The choline groups contained in soybean lecithin are polar groups, which will form electrostatic repulsion with the negatively charged regions, thereby reducing the specific adhesion of the attapulgite composite cross-linked chitosan microspheres to them, and helping soybean lecithin to be preferentially retained in ethanol solution, rather than being intercepted and adsorbed by the attapulgite composite cross-linked chitosan microspheres.

[0022] For inositol phospholipids, which also contain polar groups, the rod-shaped fibrous structure of attapulgite can form a microporous-mesoporous complex channel with chitosan microspheres. Since inositol phospholipids have large molecules and hydrophobic head groups, they mostly appear in the form of aggregates. When they pass through the chitosan microspheres cross-linked by attapulgite, they are intercepted. Soy lecithin, on the other hand, has a smaller molecular weight and can pass through the microporous structure smoothly into the ethanol solution. This reduces the competitive dissolution between inositol phospholipids and soybean lecithin, and increases the content of soybean lecithin in the ethanol extract.

[0023] Compared to other adsorbent materials, chitosan microspheres undergo cross-linking treatment, which enhances their strength and increases their specific surface area. Furthermore, they are incorporating attapulgite, which acts as a rigid carrier to reduce swelling and loss of chitosan during extraction, thereby improving the mechanical strength of the microspheres. Additionally, the polar groups in chitosan form a hydrogen bond network with the silanol groups in the attapulgite, significantly increasing the specific surface area and enhancing the adsorption capacity of the microspheres.

[0024] During the extraction process, soybean phospholipids are prone to oxidation due to metal ion impurities and free radical chain reactions, which greatly reduces their quality stability. To address this, tea polyphenols are grafted onto the attapulgite composite cross-linked chitosan microspheres of this invention. On the one hand, the metal ion impurities that act as catalysts are strongly adsorbed by the electrostatic adsorption of the attapulgite composite cross-linked chitosan microspheres, thereby reducing their impact on soybean phospholipids. On the other hand, the phenolic hydroxyl groups in tea polyphenols can directly scavenge free radicals through a hydrogen donation mechanism, blocking the phospholipid oxidation process. Selectively grafting them onto the surface of the attapulgite composite cross-linked chitosan microspheres can increase the exposure density of phenolic hydroxyl groups through the porous structure of the microspheres, thereby improving the antioxidant efficiency. It can also reduce the direct contact between the external environment and tea polyphenols during the extraction process, thereby delaying their own oxidative inactivation, increasing the effective antioxidant time of the microspheres, and enabling the reuse of the microspheres.

[0025] Furthermore, compared to directly adding traditional antioxidants, such as vitamin C, which are more susceptible to degradation due to external pH and temperature, grafting tea polyphenols onto attapulgite-crosslinked chitosan microspheres can improve their stability and provide a certain sustained-release effect. It can also form hydrogen bonds or π-π stacking structures with the amino groups in chitosan and the silanol groups on the surface of attapulgite, thereby enhancing antioxidant activity. This achieves the dual functions of high stability and high antioxidant activity, thus avoiding the oxidation of soybean lecithin during extraction, reducing the peroxide value of soybean lecithin, and improving the quality of the obtained soybean lecithin.

[0026] Preferably, the pore size of the attapulgite composite cross-linked chitosan microspheres is 20–50 nm.

[0027] By adopting the above technical solution and adjusting the pore diameter of the attapulgite composite cross-linked chitosan microspheres, it is possible to better selectively adsorb impurity molecules and allow more soybean lecithin to dissolve in ethanol, thereby increasing the soybean lecithin content in the obtained soybean lecithin. Specifically:

[0028] Soy lecithin has a small molecular weight, with a molecular size much smaller than the micropore size. It can freely pass through the micropores of cross-linked chitosan microspheres and remain in the ethanol extract. In contrast, polar phospholipids like inositol phospholipids and cephalin, which are difficult to separate, have hydrophobic tails and exist as aggregates in the ethanol extract. These aggregates are intercepted by the micropores and then strongly adsorbed through electrostatic attraction, reducing the competitive dissolution of impurity phospholipids with soybean lecithin and increasing the soybean lecithin content. Pore size design allows for a better balance between adsorption capacity and mass transfer efficiency. On the one hand, it avoids the presence of small pores that could lead to the mis-adsorption of lecithin due to steric hindrance; on the other hand, larger pore sizes reduce fluid resistance, thereby accelerating the diffusion rate of molecules within the pores and shortening the time to reach equilibrium.

[0029] Furthermore, the composite structure of the attapulgite-crosslinked chitosan microspheres allows the microspheres to have multiple analytical structures. Through multiple separation mechanisms, impurity molecules can be better intercepted, thereby improving the purity of the obtained soybean lecithin.

[0030] Preferably, the raw materials for the attapulgite composite cross-linked chitosan microspheres include chitosan, purified attapulgite, and tea polyphenols in a mass ratio of 1:(0.15-0.2):(0.05-0.1).

[0031] Preferably, the attapulgite composite cross-linked chitosan microspheres are prepared according to the following steps:

[0032] S201. Add chitosan to a weak acid solution and stir to dissolve. Add a dispersant and mix evenly. Raise the temperature to 45-50°C. Add an emulsifier and emulsify for 10-15 minutes to obtain a pretreated solution.

[0033] S202. The purified attapulgite was dispersed in deionized water to obtain a suspension, which was added to the pretreatment solution and stirred at 60-70℃ for 3-4 hours. Then the pH of the mixed solution was adjusted to 9.5-10, a crosslinking agent was added, the temperature was raised to 70-75℃, and the reaction was stirred for 2-3 hours. Finally, the mixture was filtered, washed, and freeze-dried to obtain pretreated attapulgite composite crosslinked chitosan microspheres.

[0034] S203. Disperse pretreated attapulgite composite cross-linked chitosan microspheres in water, add a tea polyphenol solution with a mass fraction of 4-6%, and stir for 1-2 hours to obtain the product.

[0035] Preferably, the crosslinking agent is one or a combination of two of epichlorohydrin and glutaraldehyde; the mass ratio of the crosslinking agent to chitosan is (0.5-0.8):1.

[0036] Preferably, the weak acid solution includes either an acetic acid solution or a acetic acid solution with a mass fraction of 1 to 5%.

[0037] Preferably, the dispersant comprises one or a combination of two of liquid paraffin and ethyl benzoate.

[0038] Preferably, the emulsifier includes one or more of Span 80, magnesium stearate, and cetyltrimethylammonium bromide.

[0039] By adopting the above technical solution, the attapulgite-crosslinked chitosan microspheres of the present invention first pretreat the chitosan, mix it with purified attapulgite, and then gradually form a porous microsphere structure under the action of the crosslinking agent. Furthermore, attapulgite is composited between the molecular chain segments of chitosan, which can better improve the structural stability and mechanical properties of the chitosan microspheres. During the stirring process, the microspheres are not easy to collapse and swell, thereby changing the pore structure and losing the selective adsorption effect on impurity molecules.

[0040] Then, the pretreated attapulgite composite cross-linked chitosan microspheres were mixed with a tea polyphenol solution, and the tea polyphenols were grafted onto the attapulgite composite cross-linked chitosan microspheres through hydrogen bonding.

[0041] The obtained attapulgite-crosslinked chitosan microspheres not only possess excellent mechanical strength and structural stability, providing effective protection for tea polyphenols, but also selectively adsorb impurity molecules in the ethanol extract through pore size regulation and electrostatic interaction, thereby increasing the content of soybean lecithin in the obtained soybean lecithin. Furthermore, the grafted tea polyphenols can synergistically prevent the easy oxidation of soybean lecithin during the extraction process by the attapulgite-crosslinked chitosan microspheres, thus reducing the peroxide value of soybean lecithin and improving the quality of the obtained soybean lecithin.

[0042] Preferably, in step S203, the tea polyphenol solution also contains 6-10% tannic acid by mass.

[0043] By employing the above technical solution, tea polyphenols are mainly bound to the hydroxyl or amino groups on the cross-linked chitosan microspheres of attapulgite composite via hydrogen bonds. However, the bond energy of hydrogen bonds is relatively low, and in polar solvents and during subsequent dynamic adsorption processes, tea polyphenols may detach due to solvent competition or mechanical shear forces. Furthermore, hydrogen bond-driven adsorption tends to occur in non-uniform media layers, leading to localized accumulation of tea polyphenols within the pores of the microspheres due to mass transfer. To mitigate this issue, tannic acid is added during the grafting process.

[0044] Tannic acid can serve as a bridge between tea polyphenols and attapulgite-crosslinked chitosan microspheres. The catechol groups in tannic acid can react with the amino groups in chitosan to form covalent bonds, and can also form a crosslinking network with the phenolic hydroxyl groups in tea polyphenols, thereby improving the binding force and uniform distribution of tea polyphenols grafted onto attapulgite-crosslinked chitosan microspheres.

[0045] Furthermore, tannic acid can synergistically enhance antioxidant properties with the phenolic hydroxyl groups in tea polyphenols, improve the absorption capacity of oxygen free radicals, and thus enhance the protective effect on soybean phospholipids, helping to form high-quality soybean phospholipids.

[0046] Secondly, the present invention provides a soybean lecithin, which is prepared according to the soybean lecithin extraction method described above.

[0047] The beneficial effects of this invention are:

[0048] 1. This invention uses fresh soybean oil by-products. High-quality soybean lecithin is extracted from these by-products. During the extraction process, attapulgite-crosslinked chitosan microspheres are added as an adsorbent. Utilizing their multi-porous structure and electrostatic interaction, they separate impurity macromolecules and polar compounds such as inositol phospholipids and cephalin, which compete with soybean lecithin for solubility. This results in soybean lecithin with high soybean lecithin content, improving the utilization value of soybean lecithin. Furthermore, the attapulgite-crosslinked chitosan microspheres have high mechanical strength. The attapulgite, acting as a rigid carrier, reduces the swelling and loss of chitosan during extraction. The polar groups in chitosan and the silanol groups in the attapulgite can also form a hydrogen bond network, significantly increasing the specific surface area and enhancing the adsorption capacity of the microspheres.

[0049] 2. The attapulgite composite cross-linked chitosan microspheres added in this invention are also grafted with tea polyphenols. Tea polyphenols can directly scavenge free radicals through a hydrogen donation mechanism, blocking the phospholipid oxidation process. Furthermore, the rigid porous structure of the attapulgite composite cross-linked chitosan microspheres can be used to improve the stability during the extraction and adsorption process, achieving the dual functions of high stability and high antioxidant activity, thereby improving the quality of the obtained soybean phospholipids. Detailed Implementation

[0050] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0051] Preparation Example

[0052] Preparation Example 1: A cross-linked chitosan microsphere with attapulgite composite was prepared according to the following method:

[0053] Add 10g of chitosan (90% degree of deacetylation) to a 1% acetic acid solution and stir to dissolve. Add 50mL of liquid paraffin and mix well. Raise the temperature to 50℃ and add 2 drops of Span 80 to emulsify for 10min to obtain the pretreated solution.

[0054] 2g of purified attapulgite (average particle size of 200 mesh) was dispersed in 100mL of deionized water to obtain a suspension, which was added to the pretreatment solution and stirred at 60℃ for 3h. Then the pH of the mixed solution was adjusted to 10, 7g of epichlorohydrin was added, the temperature was raised to 70℃, and the reaction was stirred for 2h. Finally, the pretreated attapulgite composite cross-linked chitosan microspheres were obtained by filtration, washing and freeze drying.

[0055] Take 10g of pretreated attapulgite composite cross-linked chitosan microspheres and disperse them in 250mL of water. Add 5% (w / w) of tea polyphenol solution (0.8g of tea polyphenols) and stir for 1h to obtain the product. The average particle size of the obtained attapulgite composite cross-linked chitosan microspheres is 15μm and the pore size is 20-50nm.

[0056] Preparation Example 2: A cross-linked chitosan microsphere with attapulgite as the composite material, which differs from Preparation Example 1 only in that the amount of purified attapulgite added is 1.5g and the amount of tea polyphenols added is 0.5g.

[0057] Preparation Example 3: A cross-linked chitosan microsphere with attapulgite as the base material, which differs from Preparation Example 1 only in that the amount of tea polyphenols added is 1g.

[0058] Preparation Example 4: A cross-linked chitosan microsphere with attapulgite as the composite material, which differs from Preparation Example 1 only in that the amount of purified attapulgite added is 1g.

[0059] Preparation Example 5: A cross-linked chitosan microsphere with attapulgite as the composite material, which differs from Preparation Example 1 only in that the amount of purified attapulgite added is 3g.

[0060] Preparation Example 6: A cross-linked chitosan microsphere with attapulgite as the base material, differing from Preparation Example 1 only in that the amount of tea polyphenols added is 0.2g.

[0061] Preparation Example 7: A cross-linked chitosan microsphere with attapulgite as the base material, differing from Preparation Example 1 only in that the amount of tea polyphenols added is 1.5g.

[0062] Preparation Example 8: A cross-linked chitosan microsphere with attapulgite as the base material, differing from Preparation Example 1 only in that the 5% (w / w) tea polyphenol solution also contains 8% (w / w) tannic acid.

[0063] Preparation Example 9: A cross-linked chitosan microsphere was prepared according to the following method:

[0064] 10g of chitosan (90% degree of deacetylation) was added to a 1% acetic acid solution and stirred to dissolve. 50mL of liquid paraffin was added and mixed evenly. The temperature was raised to 50℃, 2 drops of Span 80 were added and emulsified for 10min. The pH of the mixed solution was adjusted to 10. 7g of epichlorohydrin was added, the temperature was raised to 70℃, and the reaction was stirred for 2h. Finally, the pretreated cross-linked chitosan microspheres were obtained by filtration, washing and freeze-drying.

[0065] Take 10g of pretreated cross-linked chitosan microspheres and disperse them in 250mL of water. Add a 5% (w / w) tea polyphenol solution (0.8g of tea polyphenols) and stir for 1 hour to obtain the final product.

[0066] Preparation Example 10: A cross-linked chitosan microsphere with attapulgite composite was prepared according to the following method:

[0067] Add 10g of chitosan (90% degree of deacetylation) to a 1% acetic acid solution and stir to dissolve. Add 50mL of liquid paraffin and mix well. Raise the temperature to 50℃ and add 2 drops of Span 80 to emulsify for 10min to obtain the pretreated solution.

[0068] 2g of purified attapulgite (average particle size of 200 mesh) was dispersed in 100mL of deionized water to obtain a suspension, which was added to the pretreatment solution and stirred at 60℃ for 3h. Then the pH of the mixed solution was adjusted to 10, 7g of epichlorohydrin was added, the temperature was raised to 70℃, and the reaction was stirred for 2h. Finally, the mixture was filtered, washed and freeze-dried to obtain attapulgite composite cross-linked chitosan microspheres.

[0069] Example

[0070] Example 1: A soybean lecithin, obtained by extraction according to the following steps:

[0071] S101. Take fresh soybean oil by-products, centrifuge for 10 minutes, and leave the middle layer of oil residue;

[0072] S102. Mix the middle layer oil residue with acetone thoroughly, wherein the mass-volume ratio of the middle layer oil residue to acetone is 1g:4mL, control the temperature at 50℃, stir for 0.5h, let stand for separation, remove the supernatant, collect the insoluble matter, and repeat the above operation 3 times.

[0073] S103. Filter the insoluble matter collected in step S2 to obtain crude phospholipids;

[0074] S104. Add crude phospholipid to 90% ethanol, wherein the mass-to-volume ratio of crude phospholipid to 90% ethanol is 1 g: 3 mL, adjust the temperature to 70℃, extract 4 times, and collect the ethanol extract by centrifugation.

[0075] S105. Add the attapulgite-crosslinked chitosan microspheres prepared in Preparation Example 1 to the ethanol extract, wherein the amount of attapulgite-crosslinked chitosan microspheres added is 8% of the mass of the ethanol extract, stir and disperse for 3 hours, filter and recover the attapulgite-crosslinked chitosan microspheres, and then evaporate the ethanol under reduced pressure to obtain soybean lecithin.

[0076] Example 2, a soybean lecithin, differs from Example 1 only in that the mass-to-volume ratio of the middle layer oil residue to acetone is 1g:3mL; the mass-to-volume ratio of crude lecithin to 90% ethanol is 1g:4mL; and the amount of attapulgite composite cross-linked chitosan microspheres added is 10% of the mass of the ethanol extract.

[0077] Example 3, a soybean lecithin, differs from Example 1 only in that the mass-to-volume ratio of the middle layer oil residue to acetone is 1 g: 5 mL; the amount of attapulgite composite cross-linked chitosan microspheres prepared in Example 1 added is 5% of the mass of the ethanol extract.

[0078] Example 4, a soybean lecithin, differs from Example 1 only in that an equal amount of attapulgite composite cross-linked chitosan microspheres prepared in Example 2 are used instead of the attapulgite composite cross-linked chitosan microspheres prepared in Example 1.

[0079] Example 5, a soybean lecithin, differs from Example 1 only in that an equal amount of attapulgite composite cross-linked chitosan microspheres prepared in Example 3 are used instead of the attapulgite composite cross-linked chitosan microspheres prepared in Example 1.

[0080] Example 6, a soybean lecithin, differs from Example 1 only in that an equal amount of attapulgite composite cross-linked chitosan microspheres prepared in Example 4 are used instead of the attapulgite composite cross-linked chitosan microspheres prepared in Example 1.

[0081] Example 7, a soybean lecithin, differs from Example 1 only in that an equal amount of attapulgite composite cross-linked chitosan microspheres prepared in Example 5 are used instead of the attapulgite composite cross-linked chitosan microspheres prepared in Example 1.

[0082] Example 8, a soybean lecithin, differs from Example 1 only in that an equal amount of attapulgite composite cross-linked chitosan microspheres prepared in Example 6 are used instead of the attapulgite composite cross-linked chitosan microspheres prepared in Example 1.

[0083] Example 9, a soybean lecithin, differs from Example 1 only in that an equal amount of attapulgite composite cross-linked chitosan microspheres prepared in Example 7 are used instead of the attapulgite composite cross-linked chitosan microspheres prepared in Example 1.

[0084] Example 10, a soybean lecithin, differs from Example 1 only in that the amount of attapulgite composite cross-linked chitosan microspheres prepared in Example 1 added is 2% of the mass of the ethanol extract.

[0085] Example 11, a soybean lecithin, differs from Example 1 only in that the amount of attapulgite composite cross-linked chitosan microspheres prepared in Example 1 added is 15% of the mass of the ethanol extract.

[0086] Example 12, a soybean lecithin, differs from Example 1 only in that an equal amount of attapulgite composite cross-linked chitosan microspheres prepared in Preparation Example 8 are used instead of the attapulgite composite cross-linked chitosan microspheres prepared in Preparation Example 1.

[0087] Comparative Example

[0088] Comparative Example 1, a soybean lecithin, differs from Example 1 only in that an equal amount of cross-linked chitosan microspheres prepared in Preparation Example 9 are used instead of the attapulgite composite cross-linked chitosan microspheres prepared in Preparation Example 1.

[0089] Comparative Example 2, a soybean lecithin, differs from Example 1 only in that an equal amount of attapulgite composite cross-linked chitosan microspheres prepared in Preparation Example 10 are used instead of the attapulgite composite cross-linked chitosan microspheres prepared in Preparation Example 1.

[0090] Comparative Example 3, a soybean lecithin, differs from Example 1 only in that an equal amount of a mixture of attapulgite-crosslinked chitosan microspheres prepared in Preparation Example 10 and tea polyphenols (wherein the amount of tea polyphenols added is 8% of the mass of the attapulgite-crosslinked chitosan microspheres prepared in Preparation Example 10) is used instead of the attapulgite-crosslinked chitosan microspheres prepared in Preparation Example 10.

[0091] Comparative Example 4: A soybean lecithin was extracted according to the following steps:

[0092] S101. Take fresh soybean oil by-products, centrifuge for 10 minutes, and leave the middle layer of oil residue;

[0093] S102. Mix the middle layer oil residue with acetone thoroughly, wherein the mass-volume ratio of the middle layer oil residue to acetone is 1g:4mL, control the temperature at 50℃, stir for 0.5h, let stand for separation, remove the supernatant, collect the insoluble matter, and repeat the above operation 3 times.

[0094] S103. Filter the insoluble matter collected in step S2 to obtain crude phospholipids;

[0095] S104. Add crude phospholipid to 90% ethanol, wherein the mass-to-volume ratio of crude phospholipid to 90% ethanol is 1 g: 3 mL, adjust the temperature to 70℃, extract 4 times, and collect the ethanol extract by centrifugation.

[0096] S105. The obtained ethanol extract was evaporated under reduced pressure to dry the ethanol, yielding soybean lecithin.

[0097] Comparative Example 5, a soybean lecithin, differs from Example 1 only in that an equal amount of starch microspheres (average particle size of 500 nm, pore size of 30-50 nm) are used to replace the attapulgite composite cross-linked chitosan microspheres prepared in Example 1.

[0098] Performance testing

[0099] 1. Soybean lecithin content test: The content of soybean lecithin per gram in the soybean lecithin obtained in the examples and comparative examples was tested by ultraviolet-visible spectrophotometry.

[0100] 2. Stability test: According to the relevant records in GB / T 5538-2005 "Determination of Peroxide Value of Animal and Vegetable Oils", the peroxide value of soybean lecithin obtained in the test examples and comparative examples was tested after being stored at 50℃ for 20 days.

[0101] The results of the above experiments are shown in Table 1:

[0102] Table 1 Performance Test Results

[0103]

[0104] According to Table 1, and in conjunction with Examples 1, 6, 7, and Comparative Example 1, it can be seen that the content of soybean lecithin in the soybean lecithin of Examples 6, 7, and Comparative Example 1 is significantly lower than that of Example 1. This is because the only difference between Examples 6, 7, and Comparative Example 1 and Example 1 is the adjustment of the attapulgite content in the attapulgite-composite cross-linked chitosan microspheres. Example 6 reduces the amount of attapulgite composite, which directly affects the multi-pore structure of the microspheres. Furthermore, the decrease in attapulgite content leads to a decrease in the density of negatively charged regions in the microspheres, a decrease in the adsorption capacity for metal ion impurities in the system, and a decrease in electrostatic interaction. This results in a decrease in the adsorption effect of the microspheres on impurity molecules. The competitive dissolution relationship between impurity molecules and soybean lecithin leads to a decrease in the soybean lecithin content in the resulting soybean lecithin, and a decrease in the improvement effect on the structural stability and mechanical strength of the microspheres. In Comparative Example 1, which does not have composite attapulgite, the performance degradation is even more pronounced. In Example 7, the increased attapulgite composite content leads to the filling of the internal pores of the microspheres, increasing the internal steric hindrance and resulting in a decrease in impurity adsorption efficiency.

[0105] Based on Examples 1, 8, 9, and Comparative Example 2, it can be seen that the peroxide values ​​of Examples 8, 9, and Comparative Example 2 increased compared to Example 1, indicating that the stability of soybean lecithin in Examples 8, 9, and Comparative Example 2 decreased compared to Example 1. This is because the only difference between Examples 8, 9, and Comparative Example 2 and Example 1 is the adjustment of the tea polyphenol content grafted onto the attapulgite composite cross-linked chitosan microspheres. In Example 8, the amount of tea polyphenols added was reduced, consequently decreasing the antioxidant activity of tea polyphenols on soybean lecithin. Soybean lecithin is easily oxidized, leading to an increase in peroxide value and decreased stability. In Comparative Example 2, the attapulgite composite cross-linked chitosan microspheres were not grafted with tea polyphenols, resulting in a more significant performance decline. In Example 9, the increased tea polyphenol content occupies the pores of the microspheres, forming a barrier that hinders the dispersion of soybean lecithin, thus leading to a decrease in soybean lecithin content.

[0106] Combining Examples 1 and 12, it can be seen that the performance of Example 12 is improved compared to Example 1. The reason is that tannic acid was added to the attapulgite composite cross-linked chitosan microspheres used in Example 12 during the grafting of tea polyphenols. The addition of tannic acid can enhance the binding force of tea polyphenols on the microspheres, prevent tea polyphenols from detaching and affecting the purity of soybean lecithin, and can also synergistically enhance the antioxidant activity of tea polyphenols, resulting in higher quality soybean lecithin.

[0107] Combining Example 1 and Comparative Example 3, it can be seen that the performance of Comparative Example 3 is lower than that of Example 1. The reason is that the difference between Comparative Example 3 and Example 1 is that the tea polyphenols are directly mixed with the attapulgite composite cross-linked chitosan microspheres instead of being grafted onto the surface of the attapulgite composite cross-linked chitosan microspheres. This causes the tea polyphenols to dissolve rapidly in the ethanol extract, resulting in a rapid loss of antioxidant activity. Moreover, direct mixing easily leads to uneven distribution and is also prone to forming hydrogen bonds with the polar groups of soybean lecithin, resulting in a decrease in the content of soybean lecithin in soybean lecithin and affecting the purity and quality of soybean lecithin.

[0108] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0109] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for extracting soybean lecithin, characterized in that, The process includes the following steps: S101. Take fresh soybean oil by-products, centrifuge for 5-10 minutes, and leave the middle layer of oil residue; S102. Mix the middle layer oil residue with acetone thoroughly, control the temperature at 40-50℃, stir for 0.5-1h, let it stand to separate into layers, remove the supernatant, collect the insoluble matter, and repeat the above operation 2-3 times. S103. Filter the insoluble matter collected in step S2 to obtain crude phospholipids; S104. Add crude phospholipids to 85-95% ethanol, adjust the temperature to 65-70℃, extract 3-4 times, and collect the ethanol extract by centrifugation. S105. Add attapulgite composite cross-linked chitosan microspheres to the ethanol extract, stir and disperse for 3-4 hours, filter and recover the attapulgite composite cross-linked chitosan microspheres, and then evaporate the ethanol under reduced pressure to obtain soybean lecithin. Tea polyphenols are grafted onto the cross-linked chitosan microspheres of the attapulgite composite. The raw materials for the attapulgite composite cross-linked chitosan microspheres include chitosan, purified attapulgite, and tea polyphenols in a mass ratio of 1:(0.15-0.2):(0.05-0.1). The attapulgite composite cross-linked chitosan microspheres were prepared according to the following steps: S201. Add chitosan to a weak acid solution and stir to dissolve. Add a dispersant and mix evenly. Raise the temperature to 45-50°C. Add an emulsifier and emulsify for 10-15 minutes to obtain a pretreated solution. S202. The purified attapulgite was dispersed in deionized water to obtain a suspension, which was added to the pretreatment solution and stirred at 60-70℃ for 3-4 hours. Then the pH of the mixed solution was adjusted to 9.5-10, a crosslinking agent was added, the temperature was raised to 70-75℃, and the reaction was stirred for 2-3 hours. Finally, the mixture was filtered, washed, and freeze-dried to obtain pretreated attapulgite composite crosslinked chitosan microspheres. S203. Disperse pretreated attapulgite composite cross-linked chitosan microspheres in water, add a tea polyphenol solution with a mass fraction of 4-6%, and stir for 1-2 hours to obtain the product; The crosslinking agent is one or a combination of two of epichlorohydrin and glutaraldehyde; The dispersant includes one or a combination of two of liquid paraffin and ethyl benzoate; The emulsifier includes one or more of Span 80, magnesium stearate, and cetyltrimethylammonium bromide.

2. The method for extracting soybean phospholipids according to claim 1, characterized in that, The pore size of the attapulgite composite cross-linked chitosan microspheres is 20–50 nm.

3. The method for extracting soybean phospholipids according to claim 1, characterized in that, The amount of the attapulgite composite cross-linked chitosan microspheres added is 5-10% of the mass of the ethanol extract.

4. The method for extracting soybean phospholipids according to claim 1, characterized in that, In step S203, the tea polyphenol solution also contains 6-10% tannic acid by mass.

5. The method for extracting soybean phospholipids according to claim 1, characterized in that, The crosslinking agent is one or a combination of two of epichlorohydrin and glutaraldehyde; the mass ratio of the crosslinking agent to chitosan is (0.5-0.8):

1.

6. The method for extracting soybean phospholipids according to claim 1, characterized in that, The mass-to-volume ratio of the intermediate oil residue to acetone is 1 g: (3-5) mL.

7. The method for extracting soybean phospholipids according to claim 1, characterized in that, The mass-to-volume ratio of the crude phospholipid to ethanol is 1 g: (3-4) mL.

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