Preparation method of rapeseed oil decoloring membrane

Abstract

This invention relates to the food industry, specifically disclosing a method for preparing a rapeseed oil decolorizing membrane. The method includes: 1) Preparing the casting solution: Polyethersulfone powder, polyvinylpyrrolidone, distiller's grains, and SiO2 are added to N,N-dimethylacetamide and stirred until fully dissolved. The solution is then allowed to stand in an oven to remove bubbles, yielding the casting solution; 2) Coating the membrane: The prepared casting solution is poured onto a coating table, and the membrane is coated and then placed in air to allow the solvent to evaporate; 3) Forming the membrane: The membrane, after evaporation, is immediately immersed in distilled water. Once the membrane separates from the coating table, it is removed and soaked in distilled water for at least 24 hours. The membrane is then removed and air-dried. The composite polyethersulfone membrane prepared by this invention exhibits good ultrafiltration performance, requires no organic solvents, and can directly decolorize rapeseed oil without producing toxic or harmful substances. The method is convenient to operate and poses no environmental burden.

Description

Technical Field

[0001] This invention relates to the food industry, specifically to a method for preparing a rapeseed oil decolorizing film. Background Technology

[0002] There are many traditional methods for decolorizing oils, with activated clay adsorption being the most common in industry. This method utilizes the surface adsorption, ion exchange, and dispersion of porous materials to adsorb pigments within the oil. Common adsorbents include activated clay, silicates, bentonite, and activated carbon. However, this method has many drawbacks: high operating temperatures, high energy consumption, and the potential for generating toxic and harmful substances, causing oxidation and reducing tocopherol content, while retaining 30-70% of the tocopherols in the activated clay. Furthermore, the use of activated clay increases processing costs and creates environmental pressure. Ultrafiltration membrane decolorization technology, on the other hand, offers advantages such as mild operating conditions, low energy consumption, no generation of toxic and harmful substances, convenient operation, no oil waste, no environmental pressure, and being green, healthy, and energy-efficient. However, existing rapeseed oil decolorization membranes have low ultrafiltration performance, only suitable for decolorizing organic solvents and rapeseed oil blends, resulting in inedible decolorized rapeseed oil. Therefore, this invention prepares a composite polyethersulfone membrane suitable for directly decolorizing strong-aroma rapeseed oil. Summary of the Invention

[0003] In view of the deficiencies of the prior art, the purpose of this invention is to provide a method for preparing a rapeseed oil decolorizing film to solve the problems mentioned in the background art.

[0004] The present invention solves the technical problem by adopting the following technical solution:

[0005] This invention provides a method for preparing a rapeseed oil decolorizing film, comprising the following steps:

[0006] 1) Preparation of casting solution: Add polyethersulfone powder, polyvinylpyrrolidone, distiller's grains and SiO2 to N,N-dimethylacetamide, stir until fully dissolved, let stand in an oven to defoam, and obtain casting solution;

[0007] 2) Casting: Pour the prepared casting solution onto the coating table, and after casting, place it in the air to allow the solvent to evaporate.

[0008] 3): Film formation: Immediately immerse the film after it has been allowed to stand and evaporate into distilled water. Once the film separates from the coating table, remove the film and soak it in distilled water for more than 24 hours. Then remove the film and let it air dry.

[0009] As a further technical solution of the present invention, the mass ratio of the polyethersulfone powder, polyvinylpyrrolidone, distiller's grains and SiO2 is 18:8:1:1.

[0010] As a further technical solution of the present invention, in the step of preparing the casting solution, polyethersulfone powder, polyvinylpyrrolidone, distiller's grains and SiO2 are added to N,N-dimethylacetamide and stirred at room temperature to 40°C until the polyethersulfone powder is fully dissolved.

[0011] As a further technical solution of the present invention, in the step of preparing the casting solution, polyethersulfone powder, polyvinylpyrrolidone, distiller's grains and SiO2 are added to N,N-dimethylacetamide and stirred at 40°C until the polyethersulfone powder is fully dissolved.

[0012] As a further technical solution of the present invention, in the step of preparing the casting solution, the solution is left to stand in a 60°C oven for 60-90 minutes to defoam.

[0013] As a further technical solution of the present invention, in the film scraping step, the film is placed in the air after scraping to allow the solvent to evaporate for 5 to 10 seconds.

[0014] As a further technical solution of the present invention, in the film forming step, after the film is separated from the coating table, the film is taken out and completely immersed in distilled water for more than 24 hours, and the water is changed every 12 hours to fully remove the residual solvent. The film is then taken out and dried to obtain the composite polyethersulfone film.

[0015] Compared with the prior art, the present invention has the following beneficial effects: the composite polyethersulfone membrane prepared by the present invention has good ultrafiltration performance, does not require the addition of organic solvents, can directly decolorize rapeseed oil, does not produce toxic and harmful substances, is easy to operate, and has no environmental pressure. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a method for preparing a rapeseed oil decolorizing film according to an embodiment of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] The distillers' grains used in the examples were barley distillers' grains, all of which were dried and ground into powder after deacidification and deproteinization treatment; polyethersulfone powder (6020P) was purchased from Zhongheng New Materials; N,N-dimethylacetamide was purchased from Tianjin Damao; N-methylpyrrolidone was purchased from Tianjin Damao; and silica was purchased from Tianjin Zhiyuan Chemical Reagent Co., Ltd.

[0019] Example 1.

[0020] Please see Figure 1 Weigh 50g of N,N-dimethylacetamide solution into an Erlenmeyer flask and heat it in a water bath at 40℃. Add 18% (w / w) of dried polyethersulfone powder, 8% (w / w) of polyvinylpyrrolidone powder, 1% (w / w) of distiller's grains, and 1% (w / w) of SiO2 to the N,N-dimethylacetamide solution. Stir with a glass rod at 40℃ until the polyethersulfone powder is completely dissolved. Place the solution in a 60℃ constant temperature oven and let it stand for 60-90 minutes to remove bubbles. Then, take out the casting solution for later use. Adjust the height of the doctor blade of the adjustable film-forming device to 35 micrometers to control the thickness of the film. Pour an appropriate amount of film-forming solution evenly onto a rectangular drying coating table, which can be a glass plate. Use the doctor blade of the film-forming device to slowly and evenly form a film. Let it stand for 5-10 seconds to evaporate, then immediately immerse it in distilled water. Once the film separates from the coating table, remove the film and completely immerse it in distilled water for at least 24 hours, changing the water every 12 hours to thoroughly remove any residual solvent. Remove the film and let it air dry to obtain the composite polyethersulfone film.

[0021] Example 2.

[0022] Weigh 50g of N,N-dimethylacetamide solution into an Erlenmeyer flask and heat it in a water bath at 35℃. Add 18% by mass of dry polyethersulfone powder, 8% by mass of polyethylene glycol, 1% by mass of distiller's grains, and 1% by mass of SiO2 to the N,N-dimethylacetamide. Stir with a glass rod at 35℃ for 90min until the polyethersulfone powder is fully dissolved. Place the solution in a 70℃ constant temperature oven and let it stand for 60min-90min to remove bubbles. Then, take out the casting solution for later use. Adjust the height of the doctor blade of the adjustable film-forming device to 35 micrometers to control the thickness of the film. Pour an appropriate amount of film-forming solution evenly onto the rectangular drying coating table. Use the doctor blade of the film-forming device to slowly and evenly form a film. Let it stand for 30 seconds to evaporate, then immediately immerse it in distilled water. Once the film separates from the coating table, remove the film and completely immerse it in distilled water for more than 24 hours, changing the water every 12 hours to thoroughly remove any residual solvent. Remove the film and let it air dry to obtain the composite polyethersulfone film.

[0023] Example 3.

[0024] Weigh 50g of N,N-dimethylacetamide solution into an Erlenmeyer flask. Add 18% (w / w) of dry polyethersulfone powder, 8% (w / w) of polyvinylpyrrolidone powder, 1% (w / w) of carbonized distiller's grains, and 1% (w / w) of SiO2 to the N,N-dimethylacetamide. Stir at room temperature for 6 hours until the polyethersulfone powder is completely dissolved. Finally, let it stand at room temperature overnight to remove bubbles, ready for membrane preparation. Adjust the height of the doctor blade of the adjustable membrane maker to 35 micrometers to control the membrane thickness. Pour an appropriate amount of membrane preparation solution evenly onto a rectangular dry coating table. Use the doctor blade of the membrane maker to slowly and evenly scrape the membrane into a film. Let it stand for 30 seconds to evaporate, then immediately immerse it in distilled water. Once the membrane separates from the coating table, remove the membrane and completely immerse it in distilled water. Change the water every 6 hours, for a total of at least 8 times, to thoroughly remove residual solvent. After removing the membrane, let it air dry to obtain the composite polyethersulfone membrane.

[0025] Precautions

[0026] The barley lees used in the experiment need to be fully deacidified and deproteinized before being ground to a smaller particle size (100-200 mesh). If the lees particle size is too large, it will affect film formation.

[0027] The polyethersulfone powder used in the experiment needs to be placed in a 60℃ oven for more than 24 hours before use to keep the polyethersulfone powder dry;

[0028] The conical flasks, glass rods, doctor blades, coating tables, and other instruments used in the preparation of casting solutions and coating processes must be kept clean and dry.

[0029] The container for placing the casting solution should be a glass container with a small opening, such as an Erlenmeyer flask, to prevent the solvent from evaporating during prolonged stirring and standing, which would affect the fluidity of the casting solution and thus the smoothness of the film surface.

[0030] The film scraping speed needs to be uniform and slow, but the scraping time needs to be controlled. At the same time, the film should be scraped in one go to avoid repeated scraping, which will affect the evaporation time.

[0031] During film formation, the film needs to be completely immersed in distilled water and removed only after it has completely separated from the coating table.

[0032] The test data is shown in Table 1 below:

[0033] Table 1

[0034]

[0035]

[0036] The composite polyethersulfone membrane with added distiller's grains has better porosity, higher ultrapure water flux, larger porosity and average pore size, and a higher decolorization rate than other polyethersulfone membranes, with a decolorization rate as high as 45.04%.

[0037] No organic solvents such as n-hexane need to be added; rapeseed oil can be decolorized directly without producing toxic or harmful substances. The operation is convenient and poses no environmental burden.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0039] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a rapeseed oil decolorizing film, characterized in that, Includes the following steps: 1) Preparation of casting solution: Polyethersulfone powder, polyvinylpyrrolidone, distiller's grains and SiO2 are added to N,N-dimethylacetamide and stirred until fully dissolved. The mixture is then allowed to stand in an oven to remove bubbles, thus obtaining the casting solution. The mass ratio of polyethersulfone powder, polyvinylpyrrolidone, distiller's grains and SiO2 is 18:8:1:

1. In the step of preparing the casting solution, the mixture is allowed to stand in an oven at 60°C for 60-90 minutes to remove bubbles. 2) Casting: Take the prepared casting solution and pour it onto the coating table. After casting, place it in the air to allow the solvent to evaporate for 5-10 seconds. 3) Film formation: Immediately immerse the membrane after it has been allowed to stand and evaporate into distilled water. Once the membrane separates from the coating table, remove it and soak it in distilled water for more than 24 hours. Then remove the membrane and let it air dry.

2. The method for preparing a rapeseed oil decolorizing film according to claim 1, characterized in that, In the step of preparing the casting solution, polyethersulfone powder, polyvinylpyrrolidone, distillers' grains and SiO2 are added to N,N-dimethylacetamide and stirred at room temperature to 40°C until the polyethersulfone powder is fully dissolved.

3. The method for preparing a rapeseed oil decolorizing film according to claim 1, characterized in that, In the step of preparing the casting solution, polyethersulfone powder, polyvinylpyrrolidone, distillers' grains and SiO2 are added to N,N-dimethylacetamide and stirred at 40°C until the polyethersulfone powder is fully dissolved.

4. The method for preparing a rapeseed oil decolorizing film according to claim 1, characterized in that, In the film-forming step, after the film is separated from the coating table, the film is taken out and completely immersed in distilled water for more than 24 hours, with the water changed every 12 hours to fully remove the residual solvent. The film is then taken out and dried to obtain the composite polyethersulfone film.

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