Soybean phospholipid and extraction method thereof

Abstract

The invention discloses soybean phospholipids and an extraction method thereof, and belongs to the technical field of soybean phospholipids, the extraction method of soybean phospholipids comprises the following steps: selecting fresh soybean oil leftovers as an extraction raw material, carrying out centrifugation, acetone deoiling and ethanol extraction to obtain an ethanol extraction liquid, finally adding attapulgite composite cross-linked chitosan microspheres into the ethanol extraction liquid, and carrying out centrifugation, acetone deoiling and ethanol extraction to obtain the soybean phospholipids. And further removing impurity molecules to obtain the soybean phospholipid with high stability and high soybean lecithin content. According to the present invention, by using the multiple pore structures and the electrostatic interaction of the attapulgite composite cross-linked chitosan microspheres, the impurity macromolecules and the polar inositol phospholipid, cephalin and other compounds having competitive dissolution with the soybean lecithin are separated so as to increase the soybean lecithin content in the soybean lecithin; moreover, tea polyphenol is also grafted on the attapulgite composite cross-linked chitosan microspheres, so that free radicals can be cleared through a hydrogen supply mechanism, the phospholipid oxidation process is blocked, the dual functions of high stability and high antioxidant activity are realized, and the quality of the obtained soybean phospholipid is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of soybean lecithin, and particularly relates to soybean lecithin and an extraction method thereof. Background Art

[0002] Soybean oil waste, also known as soybean oil foot, is a by-product of hydration degumming during the soybean oil refining process. Its main components are phospholipids, neutral oil, water and other lipids, in addition to a small amount of protein, sugar, pigment and organic and inorganic impurities. At present, most soybean oil foot has not been fully utilized, and the soybean oil foot itself is extremely easy to rancidity and stink, causing environmental pollution.

[0003] Soybean lecithin is one of the main components of soybean oil foot. It is a pure natural high-nutrition enhancer and also 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 foot is also one of the most effective methods to utilize soybean oil foot.

[0004] However, the traditional solvent method for extracting soybean lecithin from soybean oil foot is subject to problems such as residual solvent, cumbersome and complex separation steps for lecithin from neutral oils and impurities, sensitivity to temperature and pressure parameters during the extraction process, and low tolerance for errors. Furthermore, the resulting product has poor purity and quality stability. The lecithin is easily oxidized during the extraction process, resulting in an increase in the peroxide value, which affects product stability. Emerging extraction technologies, such as supercritical carbon dioxide extraction, also involve large equipment investments, and high-viscosity lecithin can easily clog the system, hindering continuous production.

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

[0006] The object of the present invention is to provide a soybean lecithin and an extraction method thereof, so as to solve the problems of poor quality stability and low soybean lecithin content of the soybean lecithin extracted from soybean oil residue.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

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

[0009] S101. Take fresh soybean oil scraps and centrifuge for 5-10 minutes, leaving the middle oil residue.

[0010] S102. The middle oil bottoms were thoroughly mixed with acetone, the temperature was controlled at 40-50°C, and the mixture was stirred for 0.5-1h. The mixture was allowed to stand for stratification, the supernatant was removed, the insoluble matter was collected, and the above operation was repeated 2-3 times.

[0011] S103. The insoluble matter collected in step S2 is filtered to obtain crude phospholipids;

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

[0013] S105. Adding attapulgite composite cross-linked chitosan microspheres to the ethanol extract, stirring and dispersing for 3 to 4 hours, filtering and recovering the attapulgite composite cross-linked chitosan microspheres, and then evaporating the ethanol under reduced pressure to obtain soybean lecithin;

[0014] Tea polyphenols are grafted onto the attapulgite composite cross-linked chitosan microspheres.

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

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

[0017] Preferably, the mass 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 to 30 μm.

[0019] By adopting the above technical solution, soybean oil residue is first mixed with acetone, which can dissolve the oil and free fatty acids in the soybean oil residue, but will not dissolve the soybean lecithin, thereby achieving a deoiling effect. The oil and other impurities in the soybean oil residue can be effectively removed first, thereby improving the purity of the soybean lecithin. The resulting crude lecithin is then subjected to ethanol extraction. Some major components of the soybean lecithin, such as soybean lecithin, cephalin, and inositol phospholipids, can be effectively dissolved in the ethanol solution, thereby further removing impurities in the soybean lecithin and improving the purity and quality of the obtained soybean lecithin.

[0020] In order to increase the content of soybean lecithin in the extracted soybean lecithin, the present invention adds attapulgite composite cross-linked chitosan microspheres to the ethanol extract. Specifically, soybean lecithin contains polar groups and is hydrophilic, and has a high solubility in ethanol. However, components such as inositol phospholipids, neutral lipids, and pigments contained in soybean lecithin, especially inositol phospholipids, also contain hydrophilic groups. They are difficult to separate from soybean lecithin using general solvent extraction. During the ethanol dissolution process, these polar substances will compete with soybean lecithin for dissolution, thereby indirectly affecting the content of soybean lecithin in soybean lecithin. Therefore, the present invention adds attapulgite composite cross-linked chitosan microspheres to improve this phenomenon, improve the dissolution 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 groups and hydroxyl groups on the chitosan molecular chains that can preferentially adsorb negatively charged ions through electrostatic action. The composite attapulgite has a large number of silanol groups and negative charges on its surface, and has a strong adsorption capacity for metal impurities and other impurities in the soybean oil foot extract. The choline groups contained in soybean lecithin are polar groups and will form electrostatic repulsion with the negatively charged areas, thereby reducing the specific attachment of the attapulgite composite cross-linked chitosan microspheres to them, and helping the soybean lecithin to be preferentially retained in the 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-like fiber structure of attapulgite can form microporous-mesoporous composite channels with chitosan microspheres. Since inositol phospholipids have large molecules and also have hydrophobic head groups, they mostly appear in the form of aggregates and will be intercepted when passing through the composite cross-linked chitosan microspheres of attapulgite. Soy lecithin, on the other hand, has a smaller molecular weight and can smoothly pass through the microporous structure and enter the ethanol solution, thereby reducing the competitive dissolution between inositol phospholipids and soybean lecithin and increasing the content of soybean lecithin in the ethanol extract.

[0023] Compared with other adsorption materials, chitosan microspheres have undergone cross-linking treatment, which has improved their own strength and increased specific surface area. They are also compounded with attapulgite. Attached soil, as a rigid carrier, can reduce the swelling and loss of chitosan during the extraction process, thereby improving the mechanical strength of the microspheres. In addition, the polar groups in chitosan and the silanol groups contained in the attapulgite form a hydrogen bond network, which can greatly increase the specific surface area and enhance the adsorption capacity of the microspheres.

[0024] During the extraction process, soybean lecithin is prone to oxidation due to the metal ion impurities and free radical chain reactions it contains, which greatly reduces the quality stability of soybean lecithin. For this reason, tea polyphenols are also grafted onto the attapulgite composite cross-linked chitosan microspheres of the present invention. On the one hand, the metal ion impurities that play a catalytic role will be strongly adsorbed due to the electrostatic adsorption of the attapulgite composite cross-linked chitosan microspheres, thereby reducing their impact on soybean lecithin. On the other hand, the phenolic hydroxyl groups in tea polyphenols can directly scavenge free radicals through the hydrogen supply mechanism, blocking the phospholipid oxidation process. Selecting grafting on 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 the tea polyphenols during the extraction process, thereby delaying their own oxidative inactivation, increasing the effective antioxidant time of the microspheres, and realizing the reuse of the microspheres.

[0025] Compared with the direct addition of traditional antioxidants, such as vitamin C, which is greatly affected by external pH and temperature and is prone to degradation, tea polyphenols are grafted onto the composite cross-linked chitosan microspheres of attapulgite, which can improve their stability and have a certain sustained-release effect. They 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 improving the antioxidant activity. While achieving the dual functions of high stability and high antioxidant activity, it avoids the problem of easy oxidation of soybean lecithin during the extraction process, reduces the peroxide value of soybean lecithin, and improves the quality of the obtained soybean lecithin.

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

[0027] By adopting the above technical solution and regulating the pore diameter of the attapulgite composite cross-linked chitosan microspheres, the impurity molecules can be better selectively adsorbed, and more soybean lecithin can be dissolved in ethanol, thereby increasing the soybean lecithin content in the obtained soybean lecithin. Specifically:

[0028] Soy lecithin has a small molecular weight, far smaller than the micropore diameter. It can freely pass through the micropores of the attapulgite composite cross-linked chitosan microspheres and remain in the ethanol extract. However, similarly polar inositol phospholipids and cephalins, which are difficult to separate, affect their hydrophobic tails and aggregate in the ethanol extract, where they are intercepted by the micropores. They are then strongly adsorbed through electrostatic attraction, thus reducing competitive dissolution between impurity phospholipids and soy lecithin and increasing the soy lecithin content in soy lecithin. Aperture design can better balance adsorption capacity and mass transfer efficiency. On the one hand, it can prevent the misadsorption of lecithin due to steric hindrance caused by smaller pores. On the other hand, larger pores can reduce fluid resistance, thereby accelerating the diffusion rate of molecules within the pores and shortening the time to reach equilibrium.

[0029] Moreover, the composite structure of attapulgite-cross-linked chitosan microspheres can make the microspheres have multiple analytical structures, which can better intercept impurity molecules through multiple separation mechanisms and improve the purity of the obtained soybean lecithin.

[0030] Preferably, the raw materials of 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. Chitosan was added to the weak acid solution and stirred to dissolve, a dispersant was added and mixed evenly, and the temperature was raised to 45 to 50 ° C. An emulsifier was added and emulsified for 10 to 15 minutes to obtain a pre-treated solution;

[0033] S202. The purified attapulgite was dispersed in deionized water to obtain a suspension, which was added to the pretreated solution and stirred at 60-70°C for 3-4 hours. The pH of the mixed solution was then adjusted to 9.5-10, a crosslinking agent was added, the temperature was raised to 70-75°C, and the reaction was stirred for 2-3 hours. Finally, the pretreated attapulgite composite cross-linked chitosan microspheres were obtained by filtration, washing, and freeze-drying.

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

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

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

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

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

[0039] By adopting the above technical solution, the attapulgite composite cross-linked chitosan microspheres of the present invention are prepared by pre-treating chitosan and then mixing it with purified attapulgite. Under the action of a cross-linking agent, a multi-porous microsphere structure is gradually formed. In addition, attapulgite is compounded between the molecular 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 prone to collapse and swelling, thereby changing the pore structure and losing the selective adsorption effect on impurity molecules.

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

[0041] The obtained attapulgite composite cross-linked chitosan microspheres not only have excellent mechanical strength and structural stability, providing effective protection for tea polyphenols, but can also selectively adsorb impurity molecules in the ethanol extract through pore size regulation and electrostatic action, thereby increasing the content of soybean lecithin in the obtained soybean lecithin. In addition, the grafted tea polyphenols can cooperate with the attapulgite composite cross-linked chitosan microspheres to effectively avoid the problem of easy oxidation of soybean lecithin during the extraction process, thereby 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 further contains tannic acid with a mass fraction of 6 to 10%.

[0043] By adopting the above technical solution, tea polyphenols primarily bind to the hydroxyl or amino groups on the attapulgite composite cross-linked chitosan microspheres through hydrogen bonds. However, hydrogen bonds have low bond energies, and in polar solvents and subsequent dynamic adsorption processes, tea polyphenols can fall off due to solvent competition or mechanical shear forces. Furthermore, hydrogen-bond-driven adsorption tends to favor non-uniform dielectric layers, leading to localized accumulation of tea polyphenols within the pores of the microspheres due to mass transfer. To address this issue, tannic acid is added during the grafting process.

[0044] Tannic acid can serve as a bridge between tea polyphenols and attapulgite composite cross-linked 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 cross-linked network with the phenolic hydroxyl groups in tea polyphenols, thereby improving the binding force and uniform distribution of tea polyphenols grafted on the attapulgite composite cross-linked chitosan microspheres.

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

[0046] In a second aspect, the present invention provides a soybean lecithin prepared according to the above-described soybean lecithin extraction method.

[0047] Beneficial effects of the present invention:

[0048] 1. The present invention selects fresh soybean oil waste. High-quality soybean lecithin is extracted from it, and attapulgite composite cross-linked chitosan microspheres are added as an adsorbent during the extraction process. The multi-pore structure and electrostatic effect of the composite cross-linked chitosan microspheres are utilized to separate impurity macromolecules and polar inositol phospholipids and cephalins, which are competitively dissolved with soybean lecithin. Thus, soybean lecithin with high soybean lecithin content is obtained, thereby improving the use value of soybean lecithin. In addition, the composite cross-linked chitosan microspheres of attapulgite have high mechanical strength. Attachment as a rigid carrier can reduce the swelling and loss of chitosan during the extraction process. The polar groups in chitosan can also form a hydrogen bond network with the silanol groups contained in the attapulgite, greatly increasing the specific surface area and improving the adsorption capacity of the microspheres.

[0049] 2. Tea polyphenols are also grafted onto the attapulgite composite cross-linked chitosan microspheres added in the present invention. Tea polyphenols can directly scavenge free radicals through a hydrogen supply mechanism, blocking the phospholipid oxidation process. The rigid porous structure of the attapulgite composite cross-linked chitosan microspheres can also be utilized to improve the stability during the extraction and adsorption process, achieving the dual functions of high stability and high antioxidant activity, and improving the quality of the obtained soybean lecithin. DETAILED DESCRIPTION

[0050] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0051] Preparation Example

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

[0053] 10 g of chitosan (90% deacetylation) was added to a 1% acetic acid solution and stirred to dissolve. 50 mL of liquid paraffin was added and mixed evenly. The temperature was raised to 50° C. 2 drops of Span 80 were added and emulsified for 10 minutes to obtain a pretreatment solution.

[0054] 2 g of purified attapulgite (average particle size of 200 mesh) was dispersed in 100 mL of deionized water to obtain a suspension, which was added to the pretreated solution and stirred at 60° C. for 3 h. The pH of the mixed solution was then adjusted to 10, 7 g of epichlorohydrin was added, the temperature was raised to 70° C., and the mixture was stirred for 2 h. 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% mass fraction of tea polyphenol solution (wherein the added amount of tea polyphenol is 0.8g), stir and react for 1h, wherein the obtained attapulgite composite cross-linked chitosan microspheres have an average particle size of 15μm and a pore size of 20-50nm.

[0056] Preparation Example 2, a composite cross-linked chitosan microsphere of attapulgite, is different from Preparation Example 1 only in that the added amount of purified attapulgite is 1.5 g; the added amount of tea polyphenols is 0.5 g.

[0057] Preparation Example 3, a composite cross-linked chitosan microsphere made of attapulgite, is different from Preparation Example 1 only in that the added amount of tea polyphenols is 1 g.

[0058] Preparation Example 4, a composite cross-linked chitosan microsphere of attapulgite, is different from Preparation Example 1 only in that the added amount of purified attapulgite is 1 g.

[0059] Preparation Example 5, a composite cross-linked chitosan microsphere of attapulgite, is different from Preparation Example 1 only in that the added amount of purified attapulgite is 3 g.

[0060] Preparation Example 6, a composite cross-linked chitosan microsphere made of attapulgite, is different from Preparation Example 1 only in that the amount of tea polyphenols added is 0.2 g.

[0061] Preparation Example 7, a composite cross-linked chitosan microsphere made of attapulgite, is different from Preparation Example 1 only in that the amount of tea polyphenols added is 1.5 g.

[0062] Preparation Example 8, a composite cross-linked chitosan microsphere made of attapulgite, is different from Preparation Example 1 only in that the 5% by mass tea polyphenol solution also contains 8% by mass tannic acid.

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

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

[0065] 10 g of pretreated cross-linked chitosan microspheres were dispersed in 250 mL of water, and a 5% by mass tea polyphenol solution (the amount of tea polyphenol added was 0.8 g) was added, and the mixture was stirred for reaction for 1 h.

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

[0067] 10 g of chitosan (90% deacetylation) was added to a 1% acetic acid solution and stirred to dissolve. 50 mL of liquid paraffin was added and mixed evenly. The temperature was raised to 50° C. 2 drops of Span 80 were added and emulsified for 10 minutes to obtain a pretreatment solution.

[0068] 2 g of purified attapulgite (average particle size of 200 mesh) was dispersed in 100 mL of deionized water to obtain a suspension, which was added to the pretreatment solution and stirred at 60 ° C for 3 h. Then, the pH value of the mixed solution was adjusted to 10, 7 g of epichlorohydrin was added, the temperature was increased to 70 ° C, and the reaction was stirred for 2 h. Finally, the attapulgite composite cross-linked chitosan microspheres were obtained by filtration, washing and freeze-drying.

[0069] Example

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

[0071] S101. Take fresh soybean oil scraps and centrifuge for 10 minutes, leaving the middle oil residue;

[0072] S102. Thoroughly mix the middle oil bottoms with acetone at a mass volume ratio of 1 g to 4 mL at 50°C. Stir for 0.5 h, allow to stand, remove the supernatant, collect the insoluble matter, and repeat this process three times.

[0073] S103. The insoluble matter collected in step S2 is filtered to obtain crude phospholipids;

[0074] S104. Crude phospholipids were added to 90% ethanol at a mass volume ratio of 1 g of crude phospholipids to 90% ethanol of 1 mL. The temperature was adjusted to 70°C, and the mixture was extracted four times. The ethanol extract was collected by centrifugation.

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

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

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

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

[0079] Example 5, a soybean lecithin, is different from Example 1 only in that the attapulgite composite cross-linked chitosan microspheres prepared in Preparation Example 1 are replaced by an equal amount of the attapulgite composite cross-linked chitosan microspheres prepared in Preparation Example 3.

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

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

[0082] Example 8, a soybean lecithin, is different from Example 1 only in that the attapulgite composite cross-linked chitosan microspheres prepared in Preparation Example 1 are replaced by an equal amount of the attapulgite composite cross-linked chitosan microspheres prepared in Preparation Example 6.

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

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

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

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

[0087] Comparative Example

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

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

[0090] Comparative Example 3, a soybean lecithin, differs from Example 1 only in that the attapulgite composite cross-linked chitosan microspheres prepared in Preparation Example 1 are replaced by an equal amount of a mixture of attapulgite composite cross-linked chitosan microspheres and tea polyphenols prepared in Preparation Example 10 (wherein the amount of tea polyphenols added is 8% of the mass of the attapulgite composite cross-linked 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 scraps and centrifuge for 10 minutes, leaving the middle oil residue;

[0093] S102. Thoroughly mix the middle oil bottoms with acetone at a mass volume ratio of 1 g to 4 mL at 50°C. Stir for 0.5 h, allow to stand, remove the supernatant, collect the insoluble matter, and repeat this process three times.

[0094] S103. The insoluble matter collected in step S2 is filtered to obtain crude phospholipids;

[0095] S104. Crude phospholipids were added to 90% ethanol at a mass volume ratio of 1 g of crude phospholipids to 90% ethanol of 1 mL. The temperature was adjusted to 70°C, and the mixture was extracted four times. The ethanol extract was collected by centrifugation.

[0096] S105. The obtained ethanol extract is subjected to reduced pressure rotary evaporation to dry the ethanol to obtain 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 Preparation Example 1.

[0098] Performance testing

[0099] 1. Soybean lecithin content test: The soybean lecithin content per gram of 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 and Fats", the peroxide value of the soybean lecithin obtained in the examples and comparative examples was tested after constant temperature storage at 50°C for 20 days.

[0101] The above test results are shown in Table 1:

[0102] Table 1 Performance test results

[0103]

[0104] According to Table 1, in combination with Example 1, Example 6, Example 7 and Comparative Example 1, it can be seen that the content of soybean lecithin in the soybean lecithin of Example 6, Example 7 and Comparative Example 1 is significantly reduced compared to Example 1. The reason is that the difference between Example 6, Example 7 and Comparative Example 1 compared to Example 1 is only that the attapulgite content in the attapulgite composite cross-linked chitosan microspheres is adjusted. In Example 6, the composite amount of attapulgite is reduced, which directly affects the multiple pore structure of the microspheres. The decrease in the attapulgite content will lead to a decrease in the density of negatively charged areas in the microspheres, a decrease in the adsorption capacity of metal ion impurities in the system, and a decrease in electrostatic effects, thereby resulting in a decrease in the adsorption effect of the microspheres on impurity molecules. There is a competitive dissolution relationship between impurity molecules and soybean lecithin, which will lead to a decrease in the content of soybean lecithin in the obtained soybean lecithin, and a decrease in the effect of improving the structural stability and mechanical strength of the microspheres. In Comparative Example 1, there is no composite attapulgite, and the performance degradation is more obvious. In Example 7, the composite content of attapulgite is increased, which will cause the pores inside the microspheres to be filled, the internal steric hindrance increases, and the impurity adsorption efficiency decreases.

[0105] Combining 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 the soybean lecithin in Examples 8, 9, and Comparative Example 2 decreased compared to Example 1. The reason for this is that 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 polyphenol added was reduced, and accordingly, the effect of tea polyphenol on the antioxidant activity of soybean lecithin decreased, making soybean lecithin easily oxidized, resulting in an increase in the peroxide value and a decrease in stability. In Comparative Example 2, the attapulgite composite cross-linked chitosan microspheres were not grafted with tea polyphenols, and the performance degradation was more obvious. In Example 9, the increased tea polyphenol content occupied the pores of the microspheres, forming a barrier that hindered the dispersion of soybean lecithin, thereby resulting in a decrease in the content of soybean lecithin.

[0106] Combining Example 1 and Example 12, it can be seen that the various properties of Example 12 are improved compared with Example 1. The reason is that tannic acid is added to the attapulgite composite cross-linked chitosan microspheres used in Example 12 during the process of grafting tea polyphenols. The addition of tannic acid can enhance the binding force of tea polyphenols on the microspheres, prevent the detachment of tea polyphenols from affecting the purity of soybean lecithin, and can also synergize with tea polyphenols to enhance the antioxidant activity, thereby obtaining higher quality soybean lecithin.

[0107] Combining Example 1 and Comparative Example 3, it can be seen that the various properties of Comparative Example 3 are lower than those of Example 1. The reason is that the difference between Comparative Example 3 and Example 1 is that tea polyphenols are directly mixed with the attapulgite composite cross-linked chitosan microspheres instead of being grafted on the surface of the attapulgite composite cross-linked chitosan microspheres, which will cause the tea polyphenols to dissolve rapidly in the ethanol extract, resulting in a rapid loss of antioxidant activity, and direct mixing can easily lead to uneven distribution, and it is also easy to form hydrogen bonds with the polar groups of soybean lecithin, resulting in a decrease in the content of soybean lecithin in soybean lecithin, affecting the purity and quality of soybean lecithin.

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

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

Claims

1. A method for extracting soybean lecithin, characterized in that: The process steps include: S101. Take fresh soybean oil scraps and centrifuge for 5-10 minutes, leaving the middle oil residue. S102. The middle oil bottoms were thoroughly mixed with acetone, the temperature was controlled at 40-50°C, and the mixture was stirred for 0.5-1h. The mixture was allowed to stand for stratification, the supernatant was removed, the insoluble matter was collected, and the above operation was repeated 2-3 times. S103. The insoluble matter collected in step S2 is filtered to obtain crude phospholipids; S104. Add crude phospholipids to 85-95% ethanol, adjust the temperature to 65-70°C, extract 3-4 times, and collect the ethanol extract by centrifugation; S105. Adding attapulgite composite cross-linked chitosan microspheres to the ethanol extract, stirring and dispersing for 3 to 4 hours, filtering and recovering the attapulgite composite cross-linked chitosan microspheres, and then evaporating the ethanol under reduced pressure to obtain soybean lecithin; Tea polyphenols are grafted onto the attapulgite composite cross-linked chitosan microspheres.

2. The method for extracting soybean lecithin according to claim 1, wherein The pore size of the attapulgite composite cross-linked chitosan microspheres is 20-50 nm.

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

4. The method for extracting soybean lecithin according to claim 1, wherein The raw materials of 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).

5. The method for extracting soybean lecithin according to claim 4, wherein The attapulgite composite cross-linked chitosan microspheres are prepared according to the following steps: S201. Chitosan was added to the weak acid solution and stirred to dissolve, a dispersant was added and mixed uniformly, and the temperature was raised to 45 to 50 ° C. An emulsifier was added and emulsified for 10 to 15 minutes to obtain a pre-treated solution; S202. The purified attapulgite was dispersed in deionized water to obtain a suspension, which was added to the pretreated solution and stirred at 60-70°C for 3-4 hours. The pH of the mixed solution was then adjusted to 9.5-10, a crosslinking agent was added, the temperature was raised to 70-75°C, and the reaction was stirred for 2-3 hours. Finally, the pretreated attapulgite composite cross-linked chitosan microspheres were obtained by filtration, washing, and freeze-drying. S203. Disperse the pretreated attapulgite composite cross-linked chitosan microspheres in water, add 4-6% by mass of tea polyphenol solution, and stir to react for 1-2 hours.

6. The method for extracting soybean lecithin according to claim 5, wherein In the step S203, the tea polyphenol solution further contains tannic acid with a mass fraction of 6 to 10%.

7. The method for extracting soybean lecithin according to claim 5, wherein The cross-linking agent is one or a combination of epichlorohydrin and glutaraldehyde; the mass ratio of the cross-linking agent to chitosan is (0.5-0.8):

1.

8. The method for extracting soybean lecithin according to claim 1, wherein The mass volume ratio of the middle layer oil bottoms to acetone is 1 g: (3-5) mL.

9. The method for extracting soybean lecithin according to claim 1, wherein The mass volume ratio of the crude phospholipid to ethanol is 1 g: (3-4) mL.

10. A soybean lecithin, characterized in that The soybean lecithin is prepared according to the extraction method of any one of claims 1 to 9.

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