A method for recovering curcumin from turmeric by-products

Abstract

The present invention relates to the technical field of natural extracts, and in particular to a method for recovering curcumin from turmeric byproducts. The method of the present invention comprises: using turmeric byproducts as raw materials, dissolving turmeric byproducts in an organic solvent to obtain a mixed liquid, adjusting the pH of the mixed liquid to 8-11, and performing membrane separation to obtain a permeate, removing the organic solvent from the permeate to obtain a turmeric oil and curcumin mixed solution, and cooling and crystallizing the turmeric oil and curcumin mixed solution. The method of the present invention can obtain a low-solvent residual, high-content curcumin product, improve the safety of the product, and have a high recovery rate of curcumin, and also have the advantages of simple process, convenient operation, etc., and is easy to industrialize.

Description

Technical Field

[0001] The invention relates to the technical field of natural extracts, in particular to a method for recovering curcumin from turmeric byproducts. Background Art

[0002] Curcumin is a plant extract extracted from turmeric. As the main active ingredient of turmeric, it has antibacterial, anti-tumor, anti-inflammatory, choleretic, antioxidant, lipid-lowering, anti-atherosclerotic, liver damage reversal, and Alzheimer's disease prevention functions. It is a natural compound with multiple therapeutic effects and good application prospects.

[0003] In the traditional process, the method of separating curcumin from turmeric raw materials is usually to extract curcumin using an allowed solvent, and optionally include a further purification step, such as a crystallization step, which can achieve a maximum yield of about 60% of turmeric, that is, only about 60% of the curcumin originally present in the turmeric extract raw material is crystallized, and the remaining 40% of the curcumin is present in the by-product turmeric resin. At present, the market size of curcumin is about 2,500 tons, and a large amount of turmeric resin will be produced accordingly. However, turmeric resin has a strong odor and high viscosity, which makes it difficult to use. Most of the turmeric resin is discarded, and the curcumin in the turmeric resin cannot be used, resulting in a great waste of curcumin resources.

[0004] Patent application CN113773184A discloses a method for extracting curcuminoid compounds, wherein a product with a high content of bisdemethoxycurcumin is obtained by separating turmeric oil from turmeric resin and adding a solvent for crystallization. The process has a low recovery rate for the other two curcumin products in turmeric resin, namely, curcumin monomer and demethoxycurcumin, and an organic solvent is used in the crystallization process, resulting in a product with poor safety. Therefore, it is urgent to develop a method for efficiently recovering curcumin from turmeric byproducts. Summary of the invention

[0005] The invention provides a method for recovering curcumin from turmeric by-products.

[0006] The main substances in turmeric byproducts (turmeric resin) can be divided into three categories: (1) curcuminoids (a general term for diphenylheptenes contained in turmeric, i.e., total curcumin), mainly including curcumin and its dimer or polymer derivatives; (2) turmeric oils, the main components of which are low-polarity molecular compounds such as curcumone and curcumene; (3) resinoids, the main components of which are complex macromolecules such as resin esters or resin alcohols. Among them, the polarity of resinoids is very close to that of curcumin, so it is impossible to separate them from curcuminoids by conventional means such as solvent separation, which brings great difficulty to the recovery of curcumin in turmeric resin. Curcumin monomer, demethoxycurcumin and bisdemethoxycurcumin are the three most abundant compounds in curcuminoids. The existing methods for recovering curcumin from turmeric resin usually lose one or two of the above three curcuminoids, and it is impossible to recover the above three curcuminoids at the same time, and it is difficult to achieve a high yield and purity.

[0007] In the process of developing a method for recovering curcumin from turmeric by-products, the present invention finds that, after the turmeric by-products are first dissolved in an organic solvent and then the pH is adjusted to 8-11 for treatment, the separation efficiency of curcumin in the turmeric by-products and resinous substances is significantly improved, the turmeric oil and the curcumin can be better separated from the resinous substances through membrane separation, and the obtained mixture of turmeric oil and curcumin can be crystallized out of the turmeric oil through a specific crystallization method, thereby realizing the recovery of the curcumin.

[0008] In the present invention, curcumin refers to curcuminoids (total curcumin), i.e., a general term for diphenylheptenes contained in turmeric, including curcumin monomer, demethoxycurcumin and bisdemethoxycurcumin.

[0009] Specifically, the present invention provides the following technical solutions:

[0010] The invention provides a method for recovering curcumin from turmeric by-products. The method comprises: taking the turmeric by-products as raw materials, dissolving the turmeric by-products in an organic solvent to obtain a mixed liquid, adjusting the pH of the mixed liquid to 8-11, and then performing membrane separation to obtain a permeate, removing the organic solvent from the permeate to obtain a mixed solution of turmeric oil and curcumin, and cooling and crystallizing the mixed solution of turmeric oil and curcumin.

[0011] In the above method, an alkaline substance is used to adjust the pH of the mixed liquid to 8-11.

[0012] Under the premise that the pH of the mixed liquid can be adjusted to 8-11, the present invention has no particular limitation on the type of alkaline substance, and commonly used alkalis in the art can be used, including sodium bicarbonate, sodium carbonate, sodium hydroxide, etc.

[0013] In the above method, after adjusting the pH, stirring treatment is performed for 1-4 hours. Under the condition of pH 8-11, the resinous substances in the turmeric by-products can be better separated from curcumin by stirring treatment.

[0014] In the above method, the membrane separation is performed using a nanofiltration membrane, and the molecular weight cutoff of the nanofiltration membrane is 500-2000Da. Within the above molecular weight cutoff range, the nanofiltration membrane can effectively intercept resin macromolecules and separate curcumin and turmeric oil.

[0015] Preferably, the nanofiltration membrane is an organic solvent-resistant nanofiltration membrane.

[0016] Preferably, the operating pressure during the nanofiltration membrane separation process is 1.0-2.5 MPa, and the temperature of the feed liquid is 0-30°C.

[0017] Before performing nanofiltration membrane separation, it is preferred to filter the feed liquid to remove solid insoluble matter.

[0018] In the above method, the cooling rate of the cooling crystallization is 20-50° C. / h, and the terminal temperature is -10 to 10° C. The present invention finds that for the mixed solution of curcumin and turmeric oil after the organic solvent is removed, the use of the faster cooling rate can make curcumin quickly reach supersaturation, and compared with the conventional cooling rate, the nucleation amount can be significantly increased under high supersaturation conditions, thereby effectively promoting the improvement of crystallization yield and improving the recovery rate of curcumin.

[0019] In the above method, after cooling to the end temperature, crystal growth is carried out at -10 to 10°C.

[0020] Preferably, the crystal growing time is 24-96 hours.

[0021] After crystal growth, the crystallized material is washed with a non-polar solvent and then separated into a solid-liquid product to obtain a crude curcumin product, and the crude curcumin product is dried to obtain curcumin crystals.

[0022] The non-polar solvent used for washing the crystallized material can be a commonly used crystal washing solvent.

[0023] Preferably, the non-polar solvent is one or more of n-hexane, petroleum ether, and vegetable oil extraction solvent.

[0024] Preferably, the mass volume ratio (g:mL) of the crystallization material to the non-polar solvent is 1:(2-5).

[0025] In the above method, the organic solvent used to dissolve the turmeric by-product is one or more selected from methanol, ethanol, acetone, ethyl acetate, methanol aqueous solution, and ethanol aqueous solution.

[0026] In some embodiments of the present invention, the organic solvent is ethyl acetate, acetone, methanol aqueous solution or ethanol aqueous solution.

[0027] Preferably, the mass percentage of the methanol aqueous solution and the ethanol aqueous solution is not less than 70%.

[0028] In some embodiments of the present invention, the mass percentage of the methanol aqueous solution and the ethanol aqueous solution is 70-90%.

[0029] Preferably, the mass volume ratio of the turmeric by-product to the organic solvent is g:mL 1:(3-35).

[0030] In the above method, the organic solvent is removed by evaporation, and the evaporation rate is 100-400L / (m 2 h).

[0031] After the above-mentioned permeate is evaporated to remove the organic solvent, curcumin can form a relatively uniform mixed solution with turmeric oil, which is conducive to the crystallization of curcumin. Within the above-mentioned evaporation rate range, it can ensure convenient operation conditions, and will not cause crystal precipitation and encapsulation of residual solution during the evaporation process due to the evaporation rate being too low, resulting in an increase in residual crystal solution.

[0032] In the present invention, the turmeric by-product is a low-content turmeric resin obtained by extracting and separating curcumin from turmeric as a raw material.

[0033] Preferably, the content of curcumin in the turmeric by-product is 10-25%.

[0034] The beneficial effects of the present invention include at least: the method of the present invention significantly improves the separation efficiency of macromolecular substances such as resin and curcumin in turmeric resin by dissolving turmeric byproducts in an organic solvent and adjusting the pH of the system to 8-11, and the macromolecular substances in turmeric resin can be efficiently separated and removed by membrane separation to obtain a solution of turmeric oil and curcumin, and the ratio of the three curcumin monomers in the raw material is retained; further, turmeric oil is used as a crystallizing agent, so that curcumin is crystallized in turmeric oil, and a low solvent residue and high content curcumin product can be obtained, which improves the safety of the product; at the same time, by utilizing the property that curcumin is insoluble in turmeric oil, the curcumin product obtained by crystallization maintains the ratio of the three curcumin monomers in the turmeric byproduct, and significantly improves the recovery rate of curcumin. In addition, the method of the present invention also has the advantages of simple process, convenient operation, etc., and is easy to industrialize. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0036] The curcumin content in the following examples was determined according to the detection method of "United States Pharmacopoeia USP39-Curcumin".

[0037] Example 1

[0038] This embodiment provides a method for recovering curcumin from turmeric byproducts, the steps of which are as follows:

[0039] (1) 500 g of turmeric byproduct (curcumin content 16.3%) was dissolved in 10 L of ethyl acetate, a certain amount of sodium hydroxide was added to adjust the pH to 11, and then the mixture was stirred and decomposed for 4 h, solid insoluble matter was filtered to remove, and the feed liquid was put into an organic solvent-resistant nanofiltration membrane device with a molecular weight cutoff of 800 Da to separate curcumin. The separation process ensured that the operating pressure during the organic solvent-resistant nanofiltration membrane treatment was 2.0 MPa, the feed liquid temperature was 10° C., and the permeate was collected. The permeate was evaporated at an evaporation rate of 300 L / (m 2 h) concentrating to remove the organic solvent under the conditions to obtain 321.5 g of a mixed solution of curcumin and turmeric oil;

[0040] (2) cooling the mixed solution of curcumin and turmeric oil obtained in step (1) to -10°C at a cooling rate of 40°C / h, and growing the crystals for 96 hours;

[0041] (3) The crystallized liquid was washed with 964.5 mL of n-hexane, filtered, and dried to obtain 68.7 g of curcumin.

[0042] After testing, the content of curcumin prepared by the above method was 97.8%, the residual solution was less than 50ppm, and the recovery rate of curcumin was 82.44%.

[0043] Example 2

[0044] This embodiment provides a method for recovering curcumin from turmeric byproducts, the steps of which are as follows:

[0045] (1) 2000 g of turmeric byproduct (curcumin content 13.5%) was dissolved in 6 L of acetone, a certain amount of sodium carbonate was added to adjust the pH to 9, and then the mixture was stirred and decomposed for 1 h, solid insoluble matter was filtered to remove, and the feed liquid was put into an organic solvent-resistant nanofiltration membrane device with a molecular weight cutoff of 2000 Da to separate curcumin. The separation process ensured that the operating pressure during the organic solvent-resistant nanofiltration membrane treatment was 1.0 MPa, the feed liquid temperature was 0° C., and the permeate was collected. The permeate was evaporated at an evaporation rate of 400 L / (m 2 h) concentrating to remove the organic solvent under the conditions to obtain 1237.4 g of a mixed solution of curcumin and turmeric oil;

[0046] (2) cooling the mixed solution of curcumin and turmeric oil obtained in step (1) to 10° C. at a cooling rate of 20° C. / h, and growing the crystals for 24 hours;

[0047] (3) The crystallized liquid was washed with 2474.8 mL of petroleum ether, filtered, and dried to obtain 68.7 g of curcumin.

[0048] After testing, the content of curcumin prepared by the above method was 95.4%, the residual solvent was less than 50ppm, and the recovery rate of curcumin was 63.18%.

[0049] Example 3

[0050] This embodiment provides a method for recovering curcumin from turmeric byproducts, the steps of which are as follows:

[0051] (1) 1000 g of turmeric byproduct (curcumin content 19.6%) was dissolved in 10 L of 70% ethanol by mass, a certain amount of sodium bicarbonate was added to adjust the pH to 8, and then the mixture was stirred and decomposed for 2 h, solid insoluble matter was removed by filtration, and the feed liquid was put into an organic solvent-resistant nanofiltration membrane device with a molecular weight cutoff of 500 Da for curcumin separation. The separation process ensured that the operating pressure during the organic solvent-resistant nanofiltration membrane treatment was 1.5 MPa, the feed liquid temperature was 30°C, and the permeate was collected. The permeate was evaporated at an evaporation rate of 100 L / (m 2 h) concentrating to remove the organic solvent under the conditions to obtain 653.8 g of a mixed solution of curcumin and turmeric oil;

[0052] (2) cooling the mixed solution of curcumin and turmeric oil obtained in step (1) to 0° C. at a cooling rate of 50° C. / h, and growing the crystals for 48 hours;

[0053] (3) The crystallized liquid was washed with 3269 mL of petroleum ether, filtered, and dried to obtain 147.1 g of curcumin.

[0054] After testing, the content of curcumin prepared by the above method is 97.3%, the residual solution is less than 50ppm; and the recovery rate of curcumin is 73.02%.

[0055] Example 4

[0056] This embodiment provides a method for recovering curcumin from turmeric byproducts, the steps of which are as follows:

[0057] (1) 300 g of turmeric byproduct (curcumin content 21.7%) was dissolved in 10 L of 85% methanol by mass, a certain amount of sodium carbonate was added to adjust the pH to 10, and then the mixture was stirred and decomposed for 3 h, solid insoluble matter was removed by filtration, and the feed liquid was put into an organic solvent-resistant nanofiltration membrane device with a molecular weight cutoff of 700 Da for curcumin separation. The separation process ensured that the operating pressure during the organic solvent-resistant nanofiltration membrane treatment was 2.5 MPa, the feed liquid temperature was 20°C, and the permeate was collected. The permeate was evaporated at an evaporation rate of 200 L / (m 2 h) concentrating to remove the organic solvent under the conditions to obtain 203.6 g of a mixed solution of curcumin and turmeric oil;

[0058] (2) cooling the mixed solution of curcumin and turmeric oil to -5°C at a cooling rate of 30°C / h and growing the crystals for 72 hours;

[0059] (3) The crystallized liquid was washed with 814.4 mL of petroleum ether, filtered, and dried to obtain 51.2 g of curcumin.

[0060] After testing, the content of curcumin prepared by the above method is 96.4%, the residual solution is less than 50ppm; and the recovery rate of curcumin is 75.82%.

[0061] Example 5

[0062] This embodiment provides a method for recovering curcumin from turmeric by-products, which differs from Embodiment 1 only in that in step (2), the cooling rate is 10° C. / h.

[0063] After testing, the content of curcumin prepared by the above method was 96.80%, the residual solution was less than 50ppm, and the recovery rate of curcumin was 43.94%.

[0064] Comparative Example 1

[0065] This comparative example provides a method for recovering curcumin from turmeric byproducts, which differs from Example 1 only in that: in step (1), the nanofiltration membrane separation step is removed, and the stirred decomposed liquid is directly evaporated at an evaporation rate of 300 L / (m 2 h) to remove the organic solvent.

[0066] The results show that the curcumin product cannot be crystallized using the method of this comparative example.

[0067] Comparative Example 2

[0068] This comparative example provides a method for recovering curcumin from turmeric byproducts, which differs from Example 1 only in that: in step (1), a certain amount of sodium hydroxide is added to adjust the pH to 12 and then stirred for decomposition for 4 hours.

[0069] After testing, the content of curcumin prepared by the method of this comparative example was 90.60%, the residual solution was less than 50 ppm, and the recovery rate of curcumin was 24.65%.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recovering curcumin from turmeric by-products, characterized in that, The method comprises: using turmeric byproduct as raw material, dissolving the turmeric byproduct in an organic solvent to obtain a mixed liquid, adjusting the pH of the mixed liquid to 8-11 and then performing membrane separation to obtain a permeate, removing the organic solvent from the permeate to obtain a mixed solution of turmeric oil and curcumin, and cooling and crystallizing the mixed solution of turmeric oil and curcumin; The organic solvent is one or more selected from methanol, ethanol, acetone, ethyl acetate, methanol aqueous solution, and ethanol aqueous solution; The membrane separation is performed using a nanofiltration membrane, and the molecular weight cutoff of the nanofiltration membrane is 500-2000Da; The cooling rate of the cooling crystallization is 20-50°C / h; The content of curcumin in the turmeric by-product is 10-25%.

2. The method for recovering curcumin from turmeric byproducts according to claim 1, characterized in that: The pH of the mixed liquid is adjusted to 8-11 using an alkaline substance.

3. The method for recovering curcumin from turmeric byproducts according to claim 1, characterized in that: After adjusting the pH, the mixture was stirred for 1-4 h.

4. The method for recovering curcumin from turmeric byproducts according to any one of claims 1 to 3, characterized in that: The terminal temperature of the cooling crystallization is -10~10°C.

5. The method for recovering curcumin from turmeric byproducts according to claim 4, characterized in that: After cooling to the end temperature, crystal growth is carried out at -10~10℃.

6. The method for recovering curcumin from turmeric byproducts according to claim 5, characterized in that: The crystal growing time is 24-96 h.

7. The method for recovering curcumin from turmeric byproducts according to any one of claims 1 to 3, 5 and 6, characterized in that: The mass percentage of methanol aqueous solution and ethanol aqueous solution shall not be less than 70%.

8. The method for recovering curcumin from turmeric byproducts according to any one of claims 1 to 3, 5 and 6, characterized in that: The mass volume ratio of the turmeric byproduct to the organic solvent is g:mL 1:(3-35).

9. The method for recovering curcumin from turmeric byproducts according to any one of claims 1 to 3, 5 and 6, characterized in that: The organic solvent is removed by evaporation, and the evaporation rate is 100-400L / (m 2 ·h).

10. The method for recovering curcumin from turmeric byproducts according to any one of claims 1 to 3, 5 and 6, characterized in that: The turmeric by-product is a low-content turmeric resin obtained by extracting and separating curcumin from turmeric as a raw material.

11. The method for recovering curcumin from turmeric byproducts according to claim 4, characterized in that: The turmeric by-product is a low-content turmeric resin obtained by extracting and separating curcumin from turmeric as a raw material.

12. The method for recovering curcumin from turmeric byproducts according to claim 7, characterized in that: The turmeric by-product is a low-content turmeric resin obtained by extracting and separating curcumin from turmeric as a raw material.

13. The method for recovering curcumin from turmeric byproducts according to claim 8, characterized in that: The turmeric by-product is a low-content turmeric resin obtained by extracting and separating curcumin from turmeric as a raw material.

14. The method for recovering curcumin from turmeric byproducts according to claim 9, characterized in that: The turmeric by-product is a low-content turmeric resin obtained by extracting and separating curcumin from turmeric as a raw material.