CN114773421B - Novel process for extracting high-purity phytosterol by using bio-polar resin and continuous reflux liquid-solid extraction - Google Patents

Abstract

The present invention describes a new process for extracting phytosterols from deodorized distillate (DD oil) of vegetable oil. The process comprises the steps of firstly, esterifying methanol and free fatty acid under the catalysis of biological positive resin to generate fatty acid methyl ester, then catalyzing the DD oil by negative resin to enable the methanol and triglyceride in the DD oil to undergo transesterification, converting the triglyceride into the fatty acid methyl ester, and separating crude sterol from mother liquor (crude methyl ester) through freezing and fractionation after the completion. Finally, a multistage continuous reflux liquid-solid extraction method is utilized to separate out the high-purity phytosterol.

Description

Novel process for extracting high-purity phytosterol by using bio-polar resin and continuous reflux liquid-solid extraction

Technical Field

The present invention relates to a new process for extracting high-purity plant sterol by using biological polar resin, belonging to the field of separation of oil-and-fat compound and purification of trace functional component.

Background

The deodorized distillate (abbreviated as DD) obtained in refining vegetable oils and fats is an effective resource for extracting natural substances such as phytosterols. The sterol extracted from plant by DD oil is a mixture of several sterols, and the main components are beta-sitosterol, stigmasterol, campesterol and brassicasterol. It has high nutritive value and high physiological activity, and can inhibit the absorption of cholesterol in intestinal tract, promote the degradation and metabolism of cholesterol, inhibit the biochemical synthesis of cholesterol in liver, so that the sterol is suitable for treating high cholesterol, hyperlipemia, etc. The plant sterol also has good antioxidant property, and can be used as food additive (antioxidant and nutritional additive), or as raw material of animal growth agent, for promoting animal growth and improving animal health. The phytosterol is also used for preventing and treating coronary atherosclerosis heart diseases, and has obvious curative effects on ulcers, skin squamous cell carcinoma, cervical cancer and the like. Meanwhile, the product has wide application in the fields of medicine, cosmetics, paper processing, printing, spinning, food and the like. The health and planning committee 2010 3 bulletin of the people's republic of China identifies plant sterols as new resource foods for species range and requirements. In addition, sterols are widely used for fermenting and preparing medicines in production instead of diosgenin at present, and are a pharmaceutical raw material, and plant sterols are also important steroid medicines and raw materials for producing vitamin D3. Steroid drugs are a large variety of drugs with wide clinical application, are used for the treatment of rheumatism, cardiovascular diseases, lymphoblastic leukemia, tumors, bacterial encephalitis, skin diseases, endocrine dyscrasia, senile diseases and the like, and are one of the drug varieties with the largest treatment field and the largest market in parallel with antibiotics and the like. In asia, china and india are the major production countries for steroid ring drugs. Since nineties, the sales of steroid drugs in the international market has increased at a rate of 10-15% per year, keeping the potential for rapid development. With the expansion of the fermentation scale of steroid intermediates, the demand for sterols is increasing.

The traditional process for producing the phytosterol is that DD oil is subjected to methyl esterification reaction with methanol under the catalysis of concentrated sulfuric acid, and water and redundant methanol and concentrated sulfuric acid generated after the reaction are washed off. After vacuum dehydration, triglyceride is converted into fatty acid and glycerin under the catalysis of strong sodium hydroxide, and then the fatty acid and glycerin are processed by a fine process flow to obtain the phytosterol.

The invention discloses a method for extracting refined plant sterol from deodorized distillate, which is disclosed in patent No. CN201710324735.3, and comprises the steps of pre-treating a small amount of alkali liquor with low solubility to remove impurities, adding low-proportion methanol under the low-temperature condition, carrying out esterification reaction by a biological enzyme method, crystallizing mother liquor to obtain crude sterol, rinsing for multiple times, crystallizing again, and filtering to obtain refined sterol. The technological innovation of the method is characterized in that a saponification and esterification method is adopted firstly, and biological enzyme is adopted as a catalyst in the esterification process, and the method has the defects that the biological enzyme cannot be recycled and processed at high cost, the reaction time is long, and the production efficiency is low.

The invention discloses a method for extracting natural phytosterol from residual oil of vegetable oil deodorization distillate, which is disclosed in patent No. CN200910067652.6, wherein sterol ester and glyceride in the residual oil are converted into free sterols and fatty acid by catalytic decomposition, then the natural phytosterol is separated by cold precipitation and filtration, and a large amount of fatty acid contained in the filtrate can still be used for preparing a surfactant or biodiesel. The invention has the defect that the method is only limited to a method for extracting the phytosterol by taking the residual oil of the vegetable oil as a raw material.

The invention provides a method for extracting plant sterol from vegetable oil deodorization distillate, which mainly comprises the following steps of firstly, adding vegetable oil deodorization distillate, alcohol and solid super acid into a reaction kettle according to the mass ratio of 100:30:5, and stirring and reacting for 4 hours at 75 ℃; filtering after the reaction is finished, and taking filtrate; transferring the filtrate obtained in the step (II) into a cold separation tower, cooling, cold separation and crystallization with a gradient of 1 ℃/h, and preserving heat for 48h when the temperature is reduced to 10 ℃; performing filter pressing on the mixed solution obtained after cold separation and crystallization of the step, and obtaining a crude product of the phytosterol; and fifthly, dissolving the crude product of the plant sterol in the step (II) in an organic solvent with the weight being 5 times that of the crude product of the plant sterol, heating and dissolving fully, cooling and crystallizing by cooling with the gradient of 1 ℃/h, preserving the heat for 48 hours when the temperature is reduced to 10 ℃, and then filtering and drying to obtain the plant sterol.

The invention discloses a method for extracting plant sterol from biodiesel residue, which is disclosed in patent No. CN201310132738.9, wherein the method comprises the steps of firstly, adding biodiesel residue and sodium methoxide aqueous solution into a reaction kettle for alcoholysis reaction; adding fatty acid methyl ester and concentrated sulfuric acid into a reaction kettle after the alcoholysis reaction to carry out esterification reaction; thirdly, washing the materials after the esterification reaction to be neutral by hot water at 60-80 ℃, and filtering the materials while the materials are hot to obtain filtrate; fourth, four-stage molecular distillation is carried out on the filtrate; fifthly, mixing the third-stage distillation fraction and the fourth-stage distillation fraction of the four-stage molecular distillation, adding fatty acid methyl ester into the mixed fraction, heating until sterols are completely dissolved, then separating, and performing filter pressing to obtain crude sterols; and sixthly, washing the crude sterol with alcohol and drying to obtain refined phytosterol. The process adopts biodiesel residue as a raw material, and impurities in sterols are removed by using molecular distillation equipment to further ensure the purity of the sterols.

Patent No. CN201410670957.7, a method for extracting purified phytosterol from corn silk, relates to a method for extracting purified phytosterol from corn silk, which comprises the following steps of 1) adding 1g of crushed and dried corn silk into 2-6ml of saponification liquid, saponifying for 2-4h at 85+/-10 ℃, then adding absolute ethyl alcohol, ultrasonically extracting for 0.5-1h, centrifuging after ultrasonic extraction is finished, and taking supernatant for rotary evaporation to obtain a crude extract; the saponification liquid is potassium hydroxide ethanol solution with the concentration of 2-5 mol/L; 2) The invention relates to a method for extracting phytosterol by using corn silk as a raw material

The patent No. CN201911062053.5, a method for extracting plant sterol from cottonseed acidified oil, mainly comprises the steps of (1) pretreatment, namely filtering and impurity removing raw oil, dehydration, heating, mixing with phosphoric acid and water, passing through a reactor, and drying in a tower to obtain degummed oil; (2) Fatty acid distillation, namely heating and degassing the acidified oil, feeding the heated and degassed oil into a main distillation tower, and distilling the distilled oil in a residue distillation tower; (3) The distillation light phase esterification, namely mixing the molecular distillation light phase with methanol for esterification reaction, and mixing the molecular distillation light phase with methanol for secondary esterification reaction to obtain an esterified liquid with an acid value lower than 8; (4) Adding the esterified liquid into a cold separation kettle, performing primary cooling, deep cooling, growing crystals, and filtering to obtain a crude sterol filter cake; (5) Mixing and heating a crude sterol filter cake with ethanol, filtering impurities, performing primary cooling, sub-cooling, stopping stirring, growing crystals to obtain plant sterols, crushing, sieving to obtain finished sterols, wherein the process is characterized in that raw materials are purified to reduce impurities in sterols, the raw material purification is performed twice, firstly, the pretreatment is performed, secondly, the distillation is performed by a distillation tower, the process is cost-effective, the raw materials are refined, but inorganic K or Na particles remained after the subsequent secondary esterification reaction cannot be removed completely, theoretical analysis is performed, and the quality of the finished sterols is actually detected.

The invention relates to a method for producing plant sterol by fermenting plant grease deodorization distillate with microorganism, which is characterized in that the method uses the microorganism to ferment plant grease deodorization distillate, free fatty acid in the deodorization distillate is directly metabolized and utilized as nutrient substance of microorganism; because the phytosterol is insoluble in water, the phytosterol can be separated out after the filtrate is concentrated and then subjected to cold separation. The microbial fermentation method is only suitable for producing low-content 5-30% phytosterol, and has long processing time and difficult industrial production.

The invention discloses a method for producing a mixture of plant sterol and vitamin E, which is disclosed in patent No. CN200510020486.6, and comprises the steps of taking grease deodorization distillate as a raw material, preheating at the vacuum of 13-600 Pa and the temperature of 200-240 ℃, removing most of free fatty acid, further purifying at the vacuum of 1-100 Pa and the temperature of 120-200 ℃ to ensure that the acid value is less than 0.1, and decolorizing and refining a semi-finished product. The process can only be used for refining to obtain mixed concentrated solution containing 10-40% of sterol and 10-30% of vitamin E. Has far effect compared with the quality standard of the national sterol and the export purity of the sterol.

Patent number: CN201010104339.8 method for fully continuously extracting natural vitamin E and plant sterol invented by Tianke bioengineering (Tianjin) of Chinese food

Filtering and removing impurities by using leftover deodorizing distillate generated in the production process of vegetable oil as a raw material, and drying; (2) Fully mixing the material treated in the step (1) with low-carbon monohydric alcohol, heating and passing through a resin column; (3) decompressing and removing low-carbon monohydric alcohol and water; (4) Mixing the material obtained in the step (3) with low-carbon monohydric alcohol containing alkali, heating, continuously entering a reaction kettle, and converting neutral oil into fatty acid ester; (5) adding acid for neutralization; (6) washing with water to neutrality; (7) Crystallizing, filtering and separating to obtain solid crude phytosterol and liquid phase; the liquid phase is separated from fatty acid esters and natural vitamin E by molecular distillation. The process uses the treatment methods of strong acid neutralization, strong alkali transesterification and multiple water washing. Can produce more effective waste water and waste residue, and has a certain influence on the environment.

Patent number: CN 201410445798A plant sterol fatty acid ester and its catalytic synthesis method, the raw materials of the invention are plant sterol fatty acid ester and its catalytic synthesis method, the method includes steps of catalyst preparation, reactant dissolution, catalytic reaction, evaporation and distillation, etc., the total sterol content in the finished product of the invention is not less than 59%, the acid value is less than 1.0mgKOH/g, the peroxide value is not more than 5meq/kg, the color is not less than 15, and the red color is not less than 1.5. Such an index hardly reaches the standard of purity of 95 or more, which is a national standard.

In the patent No. CN201010253358.7, plant sterol and fatty acid are added into a three-neck flask with a reflux condensing device, a catalyst and a water-carrying agent are added, nitrogen is introduced as a protective gas, and the mixture is reacted at 80-120 ℃ for 8-72 hours to synthesize the high-purity plant sterol ester (the purity is more than 90%). The process is a process for synthesizing sterol ester from sterol.

The research on the various processes shows that: the method has various characteristics, and has obvious advantages from the aspects of raw material source, processing environment friendliness, catalyst cost, production efficiency and product quality analysis and extraction of the phytosterol by using the bio-polar resin.

Disclosure of Invention

The invention provides a novel process for extracting phytosterol by using a biological polar resin by taking deodorized distillate (DD oil) in a vegetable oil refining process as a raw material.

The vegetable oil is mainly deodorized distillate (DD oil) of rice bran oil, corn germ oil, peanut oil, sunflower seed oil and soybean oil, and the process comprises the steps of mixing raw material DD oil with low alcohol by using bio-polar resin as a catalyst, respectively passing through a solidified bed which is respectively made of strong acid bio-polar resin and strong polarity reducing resin twice, respectively carrying out esterification and transesterification on the mixed oil and the low alcohol under the action of proper temperature and flow rate, and simultaneously converting a small amount of plant sterol ester in the raw material into free sterol. And then separating the esterification mother liquor obtained by the reaction by cold separation, and continuously refining the high-purity phytosterol by utilizing a multistage reflux solid-liquid extraction device. The specific process comprises the following steps:

1. esterification reaction: adding 12-20 times of low-carbon alcohol with the mole number of free fatty acid into deodorized distillate (DD oil) of vegetable oil, wherein the low-carbon alcohol is methanol or ethanol, and reacting for 2-4 hours at a reflux temperature of 40-55 ℃ by using a solidified bed based on trong cation exchange resin C-25S strong cation exchange resin; the fatty acid in the raw oil and low alcohol are subjected to esterification reaction to generate fatty acid methyl ester, and the acid value in the finished (DD oil) is smaller than 3.0mgKOH/g and is qualified;

2. vacuum desolventizing and drying: after the step (1), the raw oil is subjected to vacuum desolventizing and dewatering, the vacuum degree is 20-80 mbar, the temperature is 80-100 ℃, and the water content is less than 0.005, which is qualified:

3. transesterification: supplementing 12-20 times of mole number of methanol or ethanol solution to the qualified raw oil produced in the step (2) after the steps (1) and (2) are carried out, stirring uniformly, then, feeding the raw oil into a curing bed based on strong alkaline anion exchange resin with the model Ambersep900OH, adjusting the PH value of the raw oil to 7-7.5 by using a trace amount of methanol alkali before the raw oil is carried out, carrying out transesterification reaction on triglyceride and low alcohol in the raw oil for 3-5 hours at a reflux temperature of 40-45 ℃, generating fatty acid methyl ester, measuring the sterol ester content <0.003 in the raw oil after the step (3) is completed, proving that the sterol ester in the (DD) is converted into free sterol, improving the yield and yield of total sterol, and then, repeating the step (2) to remove redundant methanol, wherein the treated raw oil is collectively called qualified;

4. freezing and separating: transferring the qualified mother liquor treated in the steps (1), 2) and (3) into a special cold separation kettle, cooling at a cooling rate of 1 ℃ per hour under the condition of 5-10 revolutions per minute from the temperature of 40-45 ℃, and starting solid sterol precipitation when the temperature of the qualified mother liquor is reduced to 25-30 ℃, wherein the stirring speed is reduced to 3-6 revolutions per minute, and the cooling rate of 0.5-0.8 ℃ per hour is required to be continuously cooled. When the temperature is reduced to 2-4 ℃, all solid sterols are folded out, and the solid plant matters are crude sterols with low content:

5. multistage reflux liquid-solid extraction: freezing and separating the crude sterols with low content in the step (3), and treating the crude sterols by using a multi-stage countercurrent liquid-solid extraction special device; dissolving the extraction liquid phase solvent into n-hexane, petroleum or ethanol; the solid phase is low in crude sterol, and the mass (g) of the solid phase is as follows: liquid phase solvent volume (ml): solid-liquid ratio=1:15-25;

6. solid phase desolventizing: removing the solvent from the extraction solid phase in the step (4) through reduced pressure distillation, and obtaining a concentrated phytosterol product, wherein the drying weight loss is less than 0.003;

7. recovering liquid residual phase: and (3) carrying out cold precipitation (time is 20-24 hours) on the raffinate phase obtained in the step (4) under a certain condition at (-20 to minus 10 ℃), and separating steroid. And recycling the raffinate in a decompression recycling tower to obtain qualified liquid phase solvent, wherein the water content of the qualified liquid phase solvent is less than 0.002.

Drawings

Fig. 1: the invention adopts a process route pattern.

DD oil, strong alcohol resin esterification, strong alkaline lipid esterification cold separation, cold separation of crude sterol, countercurrent continuous extraction of sterol, desolventizing and drying, and 95 sterols

Detailed Description

Example 1

The soybean oil is deodorized by 300g of dehydrated and deslagged soybean oil, the acid value is 180, and the total plant sterol is 9.5%. Wherein 1.5% of sterol ester; 8% of free sterols; 4% of brassicasterol, 24% of campesterol, 25% of stigmasterol and 47% of B-sitosterol.

The operation steps are as follows:

(1) 300g of pure raw material was added to a flask with a condenser, 6000ml of methanol was added, the mixture was stirred and heated to 45℃and a column of a solidified bed resin based on a strong cation exchange resin of trong cation exchange resin C-25S was added by titration in a separating bottle. Detecting acid value of the resin column effluent, wherein the acid value is less than 3.0mgKOH/g and is qualified mother liquor; when the effluent is unqualified, titrating the effluent to an upper port of a resin column by using a liquid separating bottle until the effluent at the lower part is completely qualified;

(2) After the completion, transferring the sample into a batch distillation device, desolventizing and dehydrating by using a 2X-4A vacuum pump, wherein the vacuum degree is 60mbar, the temperature is 100 ℃, and the water content is less than 0.005 after 1 hour: at this time, the pH was 6, the total sterol content was 9.4%, and the mixture was weighed to give 315g of a methyl ester sample, and the oil yield was 315/300=105%.

(3) Adding methyl esterification sample into a flask with a condenser, adding 6000ml of methanol, stirring and heating to 45 ℃, adjusting the PH to 7-7.5 by using a trace amount of sodium methoxide, and then titrating into an upper mouth of a solidified bed resin column based on Ambersep900OH strong-base anion exchange resin by using a liquid-separating bottle. The sampling at the lower port of the resin column was completed to determine sterol ester=0.2% in the mother liquor, and ph=7.5 was determined.

(4) After the completion, transferring the sample into a batch distillation device, desolventizing and dehydrating by using a 2X-4A vacuum pump, wherein the vacuum degree is 60mbar, the temperature is 100 ℃, and the drying loss is less than 0.005 percent after 1 hour: at this time, the pH value was measured to be 7, the total sterol content in the mother liquor was measured to be 9.4%, and 295g of a methyl secondary esterified sample was obtained by weighing, and the oil yield was 295/300=98.3%.

(5) Transferring the secondary esterification mother liquor into a beaker, sealing a mouth with a plastic mould, putting the beaker into a temperature-controllable refrigerator, cooling at a cooling rate of 1 ℃ per hour from 40-45 ℃, and keeping standing for 24 hours when the temperature of the qualified mother liquor is reduced to 2-4 ℃ to completely separate out solid-phase sterols;

(6) Vacuum-filtering twice by adding 2X-4A vacuum pump to obtain 45g crude sterol, 248g mother liquor, and measuring 45g crude sterol content to 59.8%; the total sterol content in the mother liquor was 0.1%. The crude sterol yield was 94.42%;

(7) Transferring 45g of the crude sterol obtained in the above to a multistage reflux liquid-solid extraction device, and slowly adding 900g of ethanol extract with the content of 99.8%; discharging a mixture of ethanol and solid sterol from a lower outlet of the multistage countercurrent liquid-solid extraction device after extraction is completed, and then performing desolventizing and drying treatment on the mixture to finish drying weight loss less than 0.002; 27g of refined sterol is obtained by weighing, the total content is 98%, wherein: 4% of brassicasterol, 24% of campesterol, 25% of stigmasterol and 47% of B-sitosterol. Total sterol yield was 27×98%/9.5% ×300= 92.85%; the content purification is 3 percent higher than the traditional process, and the yield is 9 percent higher than the traditional process; and the percentage of the grouping is unchanged.

Example 2

300g of dehydrated and deslagged corn deodorization distillate DD oil, 190% of acid value and 5.5% of plant total sterol. Wherein the sterol ester is 0.7%; 4.8% of free sterols; 0% of brassicasterol, 30% of campesterol, 10% of stigmasterol and 60% of B-sitosterol.

The operation steps are as follows:

(1) 300g of pure raw material was added to a flask with a condenser, 6000ml of methanol was added, the mixture was heated to 45℃with stirring, and the mixture was titrated with a separating bottle and then added to a cation resin column. Detecting acid value of the resin column effluent, wherein the acid value is less than=1.5.0 mg KOH/g;

(2) After the completion, the sample is transferred, distilled, desolventized and dehydrated, and the moisture content is measured to be 0.003: measuring the pH value to be 6, measuring the total sterol content to be 50%, and weighing to obtain 310g of monomethyl esterified sample, wherein the oil yield is=103%;

(3) Putting the grease into a flask with a condenser tube, adding 6000ml of methanol, stirring and heating to 45 ℃, dripping 4-point sodium methoxide by a burette, and measuring PH=7.5; then the upper opening of the negative solidification bed is titrated by a liquid separating bottle. The sampling at the lower port of the resin column was completed to determine sterol ester=0.1% in the mother liquor, and ph=7.5 was determined.

(4) When vacuum desolventizing and dewatering was completed, the loss on drying was measured after 1 hour to be = 0.003: the pH value is 7, the total sterol content in the mother liquor is 5.4%, 290g of a methyl secondary esterification sample is obtained by weighing, and the oil yield is=96.6%.

(5) Transferring the secondary esterification mother liquor into a beaker, sealing a mouth with a plastic mould, putting the beaker into a temperature-controllable refrigerator, cooling at a cooling rate of 1 ℃ per hour from 40-45 ℃, and keeping standing for 24 hours when the temperature of the qualified mother liquor is reduced to 2 ℃ to completely separate out solid-phase sterols;

(6) Vacuum filtering twice with Buchner funnel to obtain 33g of crude sterol, 255g of mother liquor, and measuring the crude sterol content to be 47.8%; the total sterol content in the mother liquor was 0.15%. Calculate crude first sterol yield 95.98%;

(7) Transferring 33g of the crude sterol obtained in the above to a multistage reflux liquid-solid extraction device, slowly adding 700g of ethanol with the content of 99.8%; desolventizing and drying after extraction is completed, and measuring drying weight loss=0.002; weighing to obtain 15g of refined sterol, wherein the total content is 97%, and the method comprises the following steps: 0% of brassicasterol, 30% of campesterol, 10% of stigmasterol and 60% of B-sitosterol. Total sterol yield = 89.44%; the content purification is 3.5 percent higher than the traditional process, and the yield is 7 percent higher than the traditional process.

The embodiment (1-2) can be obtained, the bio-polar resin is adopted as a solid catalytic bed for catalytic reaction, the quality is stable and reliable, the conversion rate is high, the reflux liquid-solid extraction process is adopted in the purification and refining process of the crude sterol, the purification effect is good, the efficiency and the practical cost are low, the whole set of process flow can realize complete continuous industrial production, and compared with the traditional process, the invention has obvious advantages.

Claims (1)

1. The process for extracting the phytosterol by using the bio-polar resin is characterized by comprising the following steps of:

step 1 esterification reaction: adding low-carbon alcohol with the mole number of 12-20 times of free fatty acid into the deodorized distillate after pretreatment dehydration and deslagging, wherein the low-carbon alcohol is methanol or ethanol, and reacting for 2-4 hours at the reflux temperature of 40-55 ℃ by using a curing bed with the model trong cation exchange resin C-25S strong cation exchange resin as a base; the fatty acid in the raw oil and low alcohol are subjected to esterification reaction to generate fatty acid methyl ester or fatty acid ethyl ester, and the acid value in the deodorized distillate is measured to be less than 3.0mgKOH/g after the esterification reaction is finished to be qualified;

step 2, vacuum desolventizing and drying: after the step 1, the raw oil is subjected to vacuum desolventizing and dewatering, the vacuum degree is 20-80 mbar, the temperature is 80-100 ℃, and the water content is measured to be less than 0.005;

step 3 transesterification: supplementing the qualified raw oil produced in the step 2 with a methanol or ethanol solution with the molar number of 12-20 times after the steps 1 and 2 are carried out, stirring uniformly, then, feeding the raw oil into a curing bed based on strong alkaline anion exchange resin with the model Ambersep900OH, adjusting the PH value of the raw oil to 7-7.5 by using trace sodium methoxide before the raw oil is carried out, reacting for 3-5 hours under the reflux temperature condition of 40-45 ℃, carrying out transesterification reaction on triglyceride and low alcohol in the raw oil to generate fatty acid methyl ester or fatty acid ethyl ester, and simultaneously, converting sterol ester in the deodorized distillate into free sterol under the action of sodium methoxide, thereby improving the yield and the yield of total sterols; step 3, measuring the sterol ester content of the raw oil to be less than 0.003, and repeating step 2 to remove redundant methanol, wherein the treated raw oil is commonly called as qualified mother liquor;

step 4, freezing and separating: transferring the qualified mother liquor treated in the steps 1, 2 and 3 into a special cold separation kettle, cooling at a cooling rate of 1 ℃ per hour under the condition of stirring speed of 5-10 revolutions per minute from 40-45 ℃, and starting solid sterol precipitation when the temperature of the qualified mother liquor is reduced to 25-30 ℃, wherein the stirring speed is reduced to 3-6 revolutions per minute, and the cooling rate of 0.5-0.6 ℃ per hour is reduced to continue cooling; when the temperature is reduced to 2-4 ℃, all solid sterols are folded out, and crude phytosterol with low content is obtained;

step 5 multistage continuous reflux liquid-solid extraction: freezing and separating the crude sterols with low content in the step 4, and treating the crude sterols by using a multi-stage reflux liquid-solid extraction device; dissolving the extraction liquid phase solvent into n-hexane, petroleum or ethanol; the solid phase is crude sterol with low content, and the mass (g) of the solid phase is 1:10-20 compared with the volume (ml) of the liquid phase solvent;

step 6, solid phase desolventizing: removing redundant solvent from the extraction solid phase in the step 5 by reduced pressure distillation, and determining that the drying loss is less than 0.003 to be qualified, thereby obtaining a concentrated phytosterol product;

and 7, recovering a liquid residual phase: and (3) separating the phytosterol from the raffinate in the step (5) by liquid phase cold separation, and recovering the phytosterol by a decompression recovery tower to obtain a qualified liquid phase solvent, wherein the water content of the qualified liquid phase solvent is less than 0.002.