Preparation method of phytosterol ester

Abstract

The invention discloses a preparation method of phytosterol ester, and belongs to the field of food. The preparation method comprises the following steps: mixing phytosterol, fatty acid, a deep eutectic solvent and lipase, reacting, and purifying to obtain the phytosterol ester. The method overcomes the influence of overhigh reaction temperature and long reaction time on the phytosterol ester in the chemical synthesis process, has the characteristics of low energy consumption and short preparation time, is simple in catalyst preparation, can be recycled and reused, is green and non-toxic, has very good industrial production benefits, and is suitable for industrial production. Therefore, the phytosterol ester is widely applied in the fields of food, medicine and health care products.

Description

Technical Field

[0001] The invention relates to a method for preparing phytosterol esters and belongs to the field of food. Background Art

[0002] Phytosterols have attracted extensive academic and industrial interest due to their advantages in lowering cholesterol, acting as antioxidants, and preventing or treating cancer. They are used in the food, pharmaceutical and other industries. However, phytosterols usually exist in crystalline or powdered form, have poor solubility in both aqueous and oil phases, and are easily decomposed by light, heat and oxidation. At the same time, phytosterols are prone to crystallization when added directly to food, which seriously affects the sensory quality and quality of the food and limits its actual food application. Studies have found that phytosterol esters generated by esterification of phytosterols and long-chain fatty acids have better fat solubility. Compared with phytosterols, their melting point and crystallization temperature are much lower, while their absorption and utilization rate is about 5 times higher than that of phytosterols, which can better inhibit the body's absorption of cholesterol and effectively reduce the oxidation rate of sterols.

[0003] Common methods for preparing phytosterol esters include enzymatic synthesis and chemical synthesis. The biocatalytic method has mild conditions and is green and environmentally friendly, but the stability and reusability of enzymes in traditional enzyme catalytic systems are poor, the cost is high, and the reaction time is long, which limits its large-scale industrial application. The chemical synthesis method has a fast reaction speed, but the esterification reaction catalyzed by traditional acidic catalysts often requires harsh reaction temperatures. During the high-temperature reaction process, it is easy to cause side reactions such as oxidation of unsaturated fatty acids and dehydration of phytosterols. At the same time, organic solvents are often required in the reaction. Adding the obtained product to food will cause food safety hazards.

[0004] In recent years, researchers have explored the use of deep eutectic solvents as new catalysts in esterification reaction systems. Deep eutectic solvents (DESs) refer to two-component or three-component eutectic mixtures composed of a certain molar ratio of hydrogen bond acceptors (such as quaternary ammonium salts) and hydrogen bond donors (such as compounds such as amides, carboxylic acids and polyols), and their freezing point is significantly lower than the melting point of the pure substances of each component. This solvent is designable, non-volatile, simple to prepare, low-cost, biodegradable, and recyclable. At present, in the prior art, "Optimization of the Synthesis Process of Stigmasterol Oleate Catalyzed by Deep Eutectic Solvents" explored the effect of using deep eutectic solvents to catalyze the synthesis of plant sterol esters, but its highest esterification rate was only 52.4%, and there is still a lot of room for improvement. In addition, there are no reports on the synthesis of deep eutectic solvents and enzymatic methods in plant sterol esters. Summary of the invention

[0005] Technical issues

[0006] At present, the common methods for preparing phytosterol esters include enzymatic synthesis and chemical synthesis, both of which have their own problems. Therefore, it is necessary to explore a method for preparing phytosterol esters with simple steps, short time, safe preparation and low cost to meet the needs of industrial development.

[0007] Technical content

[0008] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for the green synthesis of plant sterol esters in a non-aqueous phase system, aiming to solve the technical problems of long preparation time, harsh reaction conditions, solvent residues and potential safety hazards to food in the prior art.

[0009] The preparation method of the present invention adopts the following reaction catalytic system: a catalytic system combining a low eutectic solvent and an enzyme. The catalytic system solves the problems of solvent residue, by-product generation caused by high temperature and harmful catalyst in chemical synthesis, while overcoming the problem of low conversion rate of enzyme synthesis at low temperature, improving the stability and catalytic efficiency of the enzyme, reducing production costs and energy consumption, and being suitable for large-scale preparation and production.

[0010] The present invention provides a method for preparing phytosterol esters, which comprises the following steps:

[0011] The plant sterols, fatty acids, a low eutectic solvent and lipase are mixed, reacted and purified to obtain the plant sterol esters.

[0012] Furthermore, the fatty acid is a long-chain fatty acid.

[0013] Furthermore, the carbon chain in the long-chain fatty acid is C 15 ~C 20 .

[0014] Furthermore, the fatty acid includes one or more of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid.

[0015] Preferably, the fatty acids are oleic acid, linoleic acid and palmitic acid.

[0016] Most preferably, the fatty acid is palmitic acid.

[0017] Furthermore, the molar ratio of the phytosterols to the fatty acids is 1:1-10.

[0018] Furthermore, the molar ratio of the phytosterols to the fatty acids is 1:2-8.

[0019] Furthermore, the molar ratio of the phytosterols to the fatty acids is 1:2-6.

[0020] Furthermore, the deep eutectic solvent is a choline chloride-glycerol deep eutectic solvent; the molar ratio of choline chloride to glycerol is 1:1-3.

[0021] Specifically, the low eutectic solvent is a choline chloride-glycerol low eutectic solvent; the molar ratio of choline chloride to glycerol is 1:2.

[0022] Furthermore, the added amount of the low eutectic solvent is 5-10% of the mass of the phytosterols.

[0023] Preferably, the added amount of the low eutectic solvent is 7-9% of the mass of the phytosterols.

[0024] Specifically, optionally, the added amount of the low eutectic solvent is 8% of the mass of the phytosterols.

[0025] Furthermore, the lipase has an enzymatic activity of 5000 to 15000 U / g.

[0026] Furthermore, the lipase has an enzymatic activity of 8000 to 12000 U / g.

[0027] Furthermore, the added amount of the lipase is 0.05-0.5% of the mass of the phytosterols.

[0028] Furthermore, the added amount of the lipase is 0.1-0.3% of the mass of the phytosterols.

[0029] Furthermore, the reaction temperature is 50-80°C.

[0030] Preferably, the reaction temperature is 60-70°C.

[0031] Furthermore, the reaction time is 4 to 8 hours.

[0032] Preferably, the reaction time is 5 to 7 hours.

[0033] Furthermore, the purification is performed by column chromatography.

[0034] Furthermore, the column chromatography method is specifically as follows: using 200-300 mesh activated silica gel to pack the column, then pouring the reaction solution after the reaction into it, and then eluting with a mixed solvent of n-hexane and ethyl acetate in a volume ratio of 10 to 15:1, and collecting the eluate containing the target plant sterol esters, and then drying the eluate.

[0035] The present invention provides phytosterol esters obtained according to the above preparation method.

[0036] The phytosterol ester provided by the present invention is used in the fields of food, medicine preparation and health care products.

[0037] The present invention also provides a method for improving the esterification rate of phytosterol esters, the method comprising the following steps:

[0038] The plant sterols, fatty acids, a low eutectic solvent and lipase are mixed, reacted and purified to obtain the plant sterol esters.

[0039] Furthermore, the fatty acid includes one or more of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid.

[0040] Preferably, the fatty acids are oleic acid, linoleic acid and palmitic acid.

[0041] Most preferably, the fatty acid is palmitic acid.

[0042] Furthermore, the molar ratio of the phytosterols to the fatty acids is 1:2-8.

[0043] Furthermore, the molar ratio of the phytosterols to the fatty acids is 1:2-6.

[0044] Furthermore, the deep eutectic solvent is a choline chloride-glycerol deep eutectic solvent; the molar ratio of choline chloride to glycerol is 1:1-3.

[0045] Specifically, the low eutectic solvent is a choline chloride-glycerol low eutectic solvent; the molar ratio of choline chloride to glycerol is 1:2.

[0046] Preferably, the added amount of the low eutectic solvent is 7-9% of the mass of the phytosterols.

[0047] Specifically, optionally, the added amount of the low eutectic solvent is 8% of the mass of the phytosterols.

[0048] Furthermore, the lipase has an enzymatic activity of 8000 to 12000 U / g.

[0049] Furthermore, the added amount of the lipase is 0.1-0.3% of the mass of the phytosterols.

[0050] Furthermore, the reaction temperature is 50-80°C.

[0051] Preferably, the reaction temperature is 60-70°C.

[0052] Furthermore, the reaction time is 4 to 8 hours.

[0053] Preferably, the reaction time is 5 to 7 hours.

[0054] Furthermore, the purification is performed by column chromatography.

[0055] Furthermore, the column chromatography method is specifically as follows: using 200-300 mesh activated silica gel to pack the column, then pouring the reaction solution after the reaction into it, and then eluting with a mixed solvent of n-hexane and ethyl acetate in a volume ratio of 10 to 15:1, and collecting the eluate containing the target plant sterol esters, and then drying the eluate.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] 1) The preparation method of the present invention not only has the characteristics of high esterification rate of plant sterols and high product purity, but also has the advantages of simple process, green environmental protection, reduced emissions and reduced energy consumption, etc., has a good prospect for industrial promotion, and can make plant sterol esters more widely used in the fields of food, medicine and health care products.

[0058] 2) The present invention adopts a catalytic system obtained by combining a low eutectic solvent and a lipase, which solves the problems of high temperature causing the product color to darken, accumulation of by-products and low temperature causing prolonged reaction time, poor catalytic effect, and increased economic cost in the preparation of plant sterol esters. A more efficient preparation method is constructed under milder conditions, and the improvement of the esterification rate of plant sterols achieves the effect of 1+1>2. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 HPLC chromatogram of the oleic acid sterol ester product in Example 1.

[0060] Figure 2 The HPLC chromatogram of the linoleic acid sterol ester product in Example 2.

[0061] Figure 3 It is the HPLC chromatogram of the oleic acid sterol ester product in Comparative Example 3.

[0062] Figure 4 It is the HPLC chromatogram of the oleic acid sterol ester product in Comparative Example 4.

[0063] Figure 5 It is the HPLC chromatogram of the oleic acid sterol ester product in Comparative Example 5. DETAILED DESCRIPTION

[0064] In order to better illustrate the above-mentioned purpose and features of the present invention, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0065] Source of raw materials: Phytosterols (70% β-sitosterol, 16.7% stigmasterol, 13.3% campesterol) were purchased from Shaanxi Jinkangtai Biotechnology Co., Ltd.; oleic acid, linoleic acid, α-linolenic acid, and palmitic acid were purchased from Aladdin Reagent (Shanghai) Co., Ltd.; Novozym 435 immobilized lipase was purchased from Wuxi Upco Biotechnology Co., Ltd., with an enzyme activity of 10,000 U / g.

[0066] Method for determining esterification rate: Use high performance liquid chromatography (HPLC) to perform esterification rate analysis and determination, prepare plant sterol standard solutions with different concentration gradients, and draw a standard curve based on the peak area and the concentration of the standard solution after high performance liquid chromatography determination. Calculate the concentration of plant sterols contained in the reaction solution based on the peak area of ​​the measured crude product mixture, and then calculate the esterification rate according to the following formula.

[0067] Esterification rate (%) = (the content of phytosterols in the system before the reaction - the content of phytosterols in the system after the reaction) / the content of phytosterols in the system before the reaction × 100%

[0068] HPLC conditions: normal silica gel column; mobile phase: n-hexane / isopropanol: 99 / 1 (v / v); column temperature: 30°C; flow rate: 1 mL / min; injection volume: 20 μL.

[0069] Example 1

[0070] Phytosterols and oleic acid (the molar ratio of phytosterols to oleic acid is 1:3.5) are added to a reaction vessel and mixed under ultrasonic conditions for 15 minutes, 8% of choline chloride-glycerol low eutectic solvent (the molar ratio of choline chloride to glycerol is 1:2) relative to the mass of phytosterols and 0.1% of lipase relative to the mass of phytosterols are added, and the reaction temperature is controlled at 60°C for esterification reaction for 5 hours.

[0071] After the reaction is completed, a crude phytosterol ester product is obtained, which is filtered and separated and purified by silica gel column chromatography to obtain a phytosterol ester product. The silica gel column chromatography conditions are as follows: the adsorbent is 200-300 mesh silica gel, the eluent is n-hexane / ethyl acetate (15:1, v:v), the sample amount is 200 mg / mL, the column filling height is 20 cm, the flow rate is 1.5 mL / min, the chromatography eluate is collected, and the generation of the target product is detected by thin layer chromatography using an oleic acid sterol ester standard sample as a control, and finally the collected target product is rotary evaporated.

[0072] Example 2

[0073] Phytosterols and linoleic acid (the molar ratio of phytosterols to linoleic acid is 1:3.5) are added to a reaction vessel and mixed under ultrasonic conditions for 15 minutes, 8% of choline chloride-glycerol low eutectic solvent (the molar ratio of choline chloride to glycerol is 1:2) relative to the mass of phytosterols and 0.1% of lipase relative to the mass of phytosterols are added, and the reaction temperature is controlled at 60°C for esterification reaction for 5 hours.

[0074] After the reaction is completed, a crude phytosterol ester product is obtained, which is filtered and separated and purified by silica gel column chromatography to obtain a phytosterol ester product. The silica gel column chromatography conditions are as follows: the adsorbent is 200-300 mesh silica gel, the eluent is n-hexane / ethyl acetate (15:1, v:v), the sample amount is 200 mg / mL, the column filling height is 20 cm, the flow rate is 1.5 mL / min, the chromatography eluate is collected, and the generation of the target product is detected by thin layer chromatography using a linoleic acid sterol ester standard sample as a control, and finally the collected target product is rotary evaporated.

[0075] Example 3

[0076] Phytosterols and α-linolenic acid (the molar ratio of phytosterols to α-linolenic acid is 1:3.5) are added to a reaction vessel and mixed under ultrasonic conditions for 15 minutes, 8% of choline chloride-glycerol low eutectic solvent (the molar ratio of choline chloride to glycerol is 1:2) relative to the mass of phytosterols and 0.1% of lipase relative to the mass of phytosterols are added, and the reaction temperature is controlled at 60°C for esterification reaction for 5 hours.

[0077] After the reaction is completed, a crude phytosterol ester product is obtained, which is filtered and separated and purified by silica gel column chromatography to obtain a phytosterol ester product. The silica gel column chromatography conditions are as follows: the adsorbent is 200-300 mesh silica gel, the eluent is n-hexane / ethyl acetate (15:1, v:v), the loading amount is 200 mg / mL, the column filling height is 20 cm, the flow rate is 1.5 mL / min, the chromatography eluate is collected, and the generation of the target product is detected by thin layer chromatography using an α-linolenic acid sterol ester standard sample as a control, and finally the collected target product is rotary evaporated.

[0078] Example 4

[0079] Phytosterols and palmitic acid (the molar ratio of phytosterols to palmitic acid is 1:3.5) are added to a reaction vessel and mixed under ultrasonic conditions for 15 minutes, 8% of choline chloride-glycerol low eutectic solvent (the molar ratio of choline chloride to glycerol is 1:2) relative to the mass of phytosterols and 0.1% of lipase relative to the mass of phytosterols are added, and the reaction temperature is controlled at 60°C for esterification reaction for 5 hours.

[0080] After the reaction is completed, a crude phytosterol ester product is obtained, which is filtered and separated and purified by silica gel column chromatography to obtain a phytosterol ester product. The silica gel column chromatography conditions are as follows: the adsorbent is 200-300 mesh silica gel, the eluent is n-hexane / ethyl acetate (15:1, v:v), the sample amount is 200 mg / mL, the column filling height is 20 cm, the flow rate is 1.5 mL / min, the chromatography eluate is collected, and the generation of the target product is detected by thin layer chromatography using a palmitic acid sterol ester standard sample as a control, and finally the collected target product is rotary evaporated.

[0081] The reaction conditions and esterification rate results of Examples 1 to 4 are shown in Table 1.

[0082] Table 1

[0083] Example 1 Example 2 Example 3 Example 4 Sterols Phytosterols Phytosterols Phytosterols Phytosterols fatty acid Oleic acid Linoleic acid α-linolenic acid Palmitic acid Alkyd molar ratio 1:3.5 1:3.5 1:3.5 1:3.5 DES dosage 8％ 8％ 8％ 8％ Lipase dosage 0.1％ 0.1％ 0.1％ 0.1％ Reaction temperature 60℃ 60℃ 60℃ 60℃ Reaction time 5h 5h 5h 5h Esterification rate 93.34％ 92.67％ 90.65％ 95.99％

[0084] As can be seen from Table 1, the esterification efficiency of the phytosterol esters synthesized by the combination of deep eutectic solvent and enzyme is high and the reaction conditions are mild, which solves the problem of high reaction temperature leading to dark product color and accumulation of by-products in general chemical synthesis. At the same time, it shows that this method has a certain wide applicability.

[0085] Comparative Example 1

[0086] Phytosterols and oleic acid (the molar ratio of phytosterols to oleic acid is 1:3.5) are added to a reaction vessel and mixed under ultrasonic conditions for 15 minutes, and choline chloride-glycerol low eutectic solvent (the molar ratio of choline chloride to glycerol is 1:2) with an amount of 8% relative to the mass of phytosterols is added, and the esterification reaction is carried out at a reaction temperature of 120°C for 5 hours.

[0087] After the reaction is completed, a crude phytosterol ester product is obtained, which is filtered and separated and purified by silica gel column chromatography to obtain a phytosterol ester product. The silica gel column chromatography conditions are as follows: the adsorbent is 200-300 mesh silica gel, the eluent is n-hexane / ethyl acetate (15:1, v:v), the sample amount is 200 mg / mL, the column filling height is 20 cm, the flow rate is 1.5 mL / min, the chromatography eluate is collected, and the generation of the target product is detected by thin layer chromatography using an oleic acid sterol ester standard sample as a control, and finally the collected target product is rotary evaporated.

[0088] Comparative Example 2

[0089] Phytosterols and oleic acid (the molar ratio of phytosterols to oleic acid is 1:3.5) were added into a reaction vessel and mixed under ultrasonic conditions for 15 minutes, 0.1% lipase relative to the mass of phytosterols was added, and the esterification reaction was carried out at a temperature of 60°C for 36 hours.

[0090] After the reaction is completed, a crude phytosterol ester product is obtained, which is filtered and separated and purified by silica gel column chromatography to obtain a phytosterol ester product. The silica gel column conditions are as follows: the adsorbent is 200-300 mesh silica gel, the eluent is n-hexane / ethyl acetate (15:1, v:v), the sample amount is 200 mg / mL, the column filling height is 20 cm, the flow rate is 1.5 mL / min, the chromatography eluate is collected, and the generation of the target product is detected by thin layer chromatography using an oleic acid sterol ester standard sample as a control, and finally the collected target product is rotary evaporated.

[0091] Comparative Example 3

[0092] Phytosterols and oleic acid (the molar ratio of phytosterols to oleic acid is 1:3.5) are added to a reaction vessel and mixed under ultrasonic conditions for 15 minutes, and choline chloride-glycerol low eutectic solvent (the molar ratio of choline chloride to glycerol is 1:2) is added at 8% of the mass of phytosterols, and the esterification reaction is carried out at a reaction temperature of 60°C for 5 hours.

[0093] After the reaction is completed, a crude phytosterol ester product is obtained, which is filtered and separated and purified by silica gel column chromatography to obtain a phytosterol ester product. The silica gel column conditions are as follows: the adsorbent is 200-300 mesh silica gel, the eluent is n-hexane / ethyl acetate (15:1, v:v), the sample amount is 200 mg / mL, the column filling height is 20 cm, the flow rate is 1.5 mL / min, the chromatography eluate is collected, and the generation of the target product is detected by thin layer chromatography using an oleic acid sterol ester standard sample as a control, and finally the collected target product is rotary evaporated.

[0094] Comparative Example 4

[0095] Phytosterols and oleic acid (the molar ratio of phytosterols to oleic acid is 1:3.5) were added into a reaction vessel and mixed under ultrasonic conditions for 15 minutes, 0.1% lipase relative to the mass of phytosterols was added, and the esterification reaction was carried out at a temperature of 60°C for 5 hours.

[0096] After the reaction is completed, a crude phytosterol ester product is obtained, which is filtered and separated and purified by silica gel column chromatography to obtain a phytosterol ester product. The silica gel column conditions are as follows: the adsorbent is 200-300 mesh silica gel, the eluent is n-hexane / ethyl acetate (15:1, v:v), the sample amount is 200 mg / mL, the column filling height is 20 cm, the flow rate is 1.5 mL / min, the chromatography eluate is collected, and the generation of the target product is detected by thin layer chromatography using an oleic acid sterol ester standard sample as a control, and finally the collected target product is rotary evaporated.

[0097] Comparative Example 5

[0098] Add phytosterol and oleic acid (the molar ratio of phytosterol to oleic acid is 1:3.5) into the reaction vessel and mix under ultrasonic conditions for 15 minutes. Control the reaction temperature to 60°C for esterification for 5 hours. After the reaction, a crude phytosterol ester product is obtained. After filtration, the phytosterol ester product is separated and purified by silica gel column chromatography. The silica gel column conditions are as follows: the adsorbent is 200-300 mesh silica gel, the eluent is n-hexane / ethyl acetate (15:1, v:v), the sample amount is 200 mg / mL, the column height is 20 cm, and the flow rate is 1.5 mL / min. The chromatographic eluent is collected, and the formation of the target product is detected by thin layer chromatography using the oleic acid sterol ester standard as a control. Finally, the collected target product is rotary evaporated.

[0099] The reaction conditions and esterification rate results of Comparative Examples 1 to 5 are shown in Table 2.

[0100] Table 2

[0101]

[0102]

[0103] As can be seen from Table 2, the temperature required for the synthesis of plant sterol esters using a single low eutectic solvent is relatively high, and at least 120 degrees Celsius is required to achieve an esterification rate of more than 80%; the reaction time required for the synthesis of plant sterol esters using enzyme catalysis is relatively long, and at least 36 hours of reaction time is required to achieve a relatively ideal esterification rate; the esterification rates of both are not as high as the esterification rate of the synthesis of plant sterol esters using the combination of low eutectic solvent and enzyme catalysis, and the catalytic effect is not good.

[0104] It can be seen from Comparative Examples 3-5 that under the same low temperature and low reaction time, the synergistic catalytic effect of low eutectic solvent-enzyme is stronger than the sum of the effects of using enzyme catalyst alone and low eutectic solvent catalysis alone. Compared with Comparative Example 5, Comparative Example 3 only uses low eutectic solvent catalysis, and the esterification rate is increased by 35.51%; Comparative Example 4 uses lipase catalysis more than Comparative Example 5, and the esterification rate is increased by 16.1%; Example 1 combines low eutectic solvent and lipase catalysis, and the esterification rate is increased by 54.22% compared with Comparative Example 5, and 54.22%>35.51%+16.1%. Therefore, the combination of low eutectic solvent catalysis and lipase catalysis in the present invention has an effect of 1+1>2, and the technical effect after the combination is superior to the sum of the effects of each technical feature.

[0105] Comparative Example 6

[0106] Referring to Example 1, only the reaction conditions were changed, and the other steps remained unchanged. The esterification rate of oleic acid sterol ester was measured, and the results are shown in Table 3.

[0107] Table 3

[0108] Example 1 Test 1 Test 2 Test 3 Test 4 Sterols Phytosterols Phytosterols Phytosterols Phytosterols Phytosterols fatty acid Oleic acid Oleic acid Oleic acid Oleic acid Oleic acid Alkyd molar ratio 1:3.5 1:2 1:3.5 1:3.5 1:3.5 DES dosage 8％ 8％ 4％ 8％ 8％ Lipase dosage 0.1％ 0.1％ 0.1％ 0.1％ 0.1％ Reaction temperature 60℃ 60℃ 60℃ 30℃ 60℃ Reaction time 5h 5h 5h 5h 2h Esterification rate 93.34％ 74.63％ 72.98％ 73.55％ 76.85％

[0109] As can be seen from Table 3, when the acid-alcohol molar ratio is too low, the amount of catalyst used is too little, the reaction temperature is low or the reaction time is short, the esterification rate of plant sterol ester is low. The reason may be that when the acid-alcohol molar ratio is too low, the reaction cannot be promoted in the forward direction; when the amount of catalyst used is small, the specific system of the present invention cannot be effectively formed, and thus the esterification reaction cannot be effectively catalyzed; when the reaction temperature is low or the reaction time is short, the rapid coupling of molecules in the reaction system cannot be promoted, and sterol esters cannot be effectively catalyzed.

[0110] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing phytosterol esters, characterized in that: The preparation method comprises the following steps: The phytosterols, fatty acids, a low eutectic solvent and lipase are mixed, reacted and purified to obtain phytosterol esters; The low eutectic solvent is a choline chloride-glycerol low eutectic solvent, wherein the molar ratio of choline chloride to glycerol is 1:1-3; the addition amount of the low eutectic solvent is 5-10% of the mass of the phytosterols; The enzyme activity of the lipase is 5000-15000 U / g; the added amount of the lipase is 0.05-0.5% of the mass of the phytosterol.

2. The preparation method according to claim 1, characterized in that: The fatty acids are long-chain fatty acids.

3. The preparation method according to claims 1 to 2, characterized in that: The fatty acid includes one or more of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid.

4. The preparation method according to claims 1 to 3, characterized in that: The molar ratio of the phytosterol to the fatty acid is 1:1-10.

5. The preparation method according to claims 1 to 4, characterized in that: The reaction temperature is 50-80° C.; the reaction time is 4-8 hours.

6. The preparation method according to claims 1 to 5, characterized in that: The purification is performed by column chromatography.

7. A plant sterol ester, characterized in that The phytosterol ester is prepared according to the preparation method described in any one of claims 1 to 6.

8. A method for increasing the esterification rate of phytosterol esters, characterized in that: The method comprises the following steps: The plant sterols, fatty acids, a low eutectic solvent and lipase are mixed, reacted and purified to obtain the plant sterol esters. The phytosterols, fatty acids, a low eutectic solvent and lipase are mixed, reacted and purified to obtain phytosterol esters; The low eutectic solvent is a choline chloride-glycerol low eutectic solvent, wherein the molar ratio of choline chloride to glycerol is 1:1-3; the addition amount of the low eutectic solvent is 5-10% of the mass of the phytosterols; The enzyme activity of the lipase is 5000-15000 U / g; the added amount of the lipase is 0.05-0.5% of the mass of the phytosterol.

9. The method according to claim 8, characterized in that The fatty acid includes one or more of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid.

10. The method according to claims 8 to 9, characterized in that The molar ratio of the phytosterol to the fatty acid is 1:1-10; the reaction temperature is 50-80° C.; and the reaction time is 4-8 hours.

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