Method for extracting pectin from citrus peels

Abstract

The invention discloses a method for extracting pectin from citrus peels, and relates to the field of pectin extraction, and the method comprises the following steps: S1, chopping the citrus peels, moistening the chopped citrus peels in a sodium chloride solution to make the moisture content at least reach 60%, taking out the chopped citrus peels, air-drying the chopped citrus peels until the surface moisture content is 10-20%, freezing the air-dried citrus peels at-40 to-50 DEG C, heating the air-dried citrus peels to 30-60 DEG C under a vacuum condition, and drying the air-dried citrus peels to obtain dried citrus peels; pre-treated citrus peels are obtained; s2, adding the pretreated citrus peels into an organic acid solution for electrifying treatment, and stirring and centrifuging at 50-60 DEG C after electrifying treatment to obtain a pectin extracting solution; s3, performing rotary evaporation on the pectin extracting solution at 45-65 DEG C for 0.5-2.0 hours, performing alcohol precipitation by using an ethanol solution of which the volume is 1-2 times that of the pectin extracting solution, washing and drying; according to the method, the citrus peels are pretreated, so that the citrus peels become loose and porous, subsequent acid leaching extraction of pectin is facilitated, and the pectin extraction rate is greatly increased.

Description

Technical Field

[0001] This invention relates to the field of pectin extraction, and more specifically to a method for extracting pectin from citrus peel. Background Technology

[0002] Solid waste (peel residue, seed residue, and fruit segments) accounts for 30% to 50% of the total waste generated during citrus processing. Citrus peels are rich in functional resources such as pectin and dietary fiber, making them excellent raw materials for producing pectin and other functional ingredients. Pectin is an acidic heteropolysaccharide widely used in food processing as a gelling agent, thickener, and stabilizer. Furthermore, as an active polysaccharide, pectin can regulate intestinal function and improve glucose metabolism, making it a fundamental ingredient in many pharmaceuticals and cosmetics.

[0003] Citrus peel is a high-quality raw material for extracting pectin, with a theoretical pectin content of approximately 30%. Currently, inorganic acid extraction is a commonly used method for pectin extraction, but its extraction conditions are quite stringent, which can cause excessive degradation of pectin molecules, accompanied by a decrease in pectin molecular weight and viscosity. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a method for extracting pectin from citrus peel.

[0005] The technical solution of the present invention is as follows: A method for extracting pectin from citrus peel includes the following steps: S1: Chop the citrus peel, first soak it in sodium chloride solution to make its moisture content at least 60%, then take it out and air dry it until the surface moisture content is 10-20%, put it in -40℃ to -50℃ to freeze it, and then dry it under vacuum conditions at 30-60℃ to obtain pre-treated citrus peel. S2: Add the pretreated citrus peel to an organic acid solution and electrolyze it. After electrolysis, stir at 50-60℃ and centrifuge to obtain pectin extract. S3: After rotary evaporating the pectin extract at 45-65℃ for 0.5-2.0h, precipitate it with 1-2 times its volume of ethanol solution, wash, and dry.

[0006] As a preferred embodiment of the present invention, in step S1, the sodium chloride solution is 0.1-3 wt%.

[0007] As a preferred embodiment of the present invention, in step S1, the air drying specifically refers to drying under cold air at 3-15°C.

[0008] As a preferred embodiment of the present invention, in step S2, the organic acid solution is acetic acid with a concentration of 20-30 wt%.

[0009] As a preferred embodiment of the present invention, in step S2, the power-on process specifically involves processing for 10-30 minutes at a current of 1-3mA.

[0010] As a preferred embodiment of the present invention, during the electrostatic treatment, a mixture of carbon dioxide and inert gas is first introduced, and then the volume ratio of carbon dioxide in the mixture is gradually adjusted, with the flow rate of the mixture being 1-3 L / min.

[0011] As a preferred embodiment of the present invention, the inert gas is nitrogen or argon or a mixture of nitrogen and argon in a volume ratio of 1-3:1-5.

[0012] As a preferred embodiment of the present invention, the gradual increase of the volume percentage of carbon dioxide in the mixed gas is specifically as follows: The volume ratio of carbon dioxide to inert gas in the first stage is 1-3:1, and the introduction time is 3-5 minutes. The volume ratio of carbon dioxide to inert gas in the second stage is 3-5:1, and the introduction time is 4-10 minutes. The volume ratio of carbon dioxide to inert gas in the third stage is 2-4:1, and the introduction time is 3-10 minutes.

[0013] As a preferred embodiment of the present invention, in step S2, the centrifugation is performed at 6000-8000 rpm for 20-30 min.

[0014] The present invention also discloses the application of pectin obtained by any of the methods described above in acidic dairy beverages or jam products.

[0015] The beneficial effects of this invention are: This invention discloses a method for extracting pectin from citrus peel. The method involves pre-treating the citrus peel by first moistening it with salt water, then rinsing the surface. During air drying, the surface moisture evaporates more easily, while the salt water absorbed internally retains moisture, making it difficult for the moisture to evaporate. Even though the internal moisture content is higher than the surface moisture content, the increased volume after internal freezing enhances the cell wall freeze-swelling effect, thereby further improving the dissolution of active ingredients from the citrus peel. This also facilitates subsequent acid extraction of pectin. Furthermore, the use of an organic acid (acetic acid) for electrolysis ionizes the acetic acid, creating a microcurrent that further facilitates the extraction of H+. + The orderly flow in the solution increases the dissolution rate of protopectin; at the same time, the introduction of an inert gas containing carbon dioxide can effectively prevent pH instability in the solution and maintain pH stability, thereby affecting the extraction of pectin. Detailed Implementation

[0016] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0017] In the following examples, the citrus peel is orange peel.

[0018] Example 1

[0019] A method for extracting pectin from citrus peel includes the following steps: S1: Chop the citrus peel, first soak it in a 0.1wt% sodium chloride solution until its moisture content reaches 60%, then take it out and dry it with cold air at 10℃ until the surface moisture content is 15%, freeze it at -40℃, and then dry it at 45℃ under vacuum to obtain pretreated citrus peel; S2: The pretreated citrus peel was added to a 20wt% acetic acid solution and subjected to electrochemical treatment. Specifically, the electrochemical treatment was performed at a current of 1mA for 20min. After electrochemical treatment, the mixture was stirred at 55℃ and then centrifuged at 7000rpm for 30min to obtain pectin extract. During the energization process, a mixture of carbon dioxide and inert gas is first introduced, and then the volume ratio of carbon dioxide in the mixture is gradually adjusted. The flow rate of the mixture is 2 L / min.

[0020] The inert gas is nitrogen.

[0021] The gradual increase in the volume percentage of carbon dioxide in the gas mixture is specifically as follows: The volume ratio of carbon dioxide to inert gas in the first stage is 2:1, and the introduction time is 5 minutes. The volume ratio of carbon dioxide to inert gas in the second stage is 5:1, and the introduction time is 10 minutes. The volume ratio of carbon dioxide to inert gas in the third stage is 3:1, and the introduction time is 5 minutes.

[0022] S3: After rotary evaporating the pectin extract at 55℃ for 1 hour, precipitate it with 1.5 times its volume of ethanol solution, wash, and dry.

[0023] Example 2

[0024] A method for extracting pectin from citrus peel includes the following steps: S1: Chop the citrus peel, first soak it in a 0.1wt% sodium chloride solution until its moisture content reaches 60%, then take it out and dry it with cold air at 10℃ until the surface moisture content is 15%, freeze it at -40℃, and then dry it at 45℃ under vacuum to obtain pretreated citrus peel; S2: The pretreated citrus peel was added to a 25wt% acetic acid solution and subjected to electrochemical treatment. Specifically, the electrochemical treatment was performed at a current of 1mA for 20 minutes. After electrochemical treatment, the mixture was stirred at 55°C and then centrifuged at 7000rpm for 30 minutes to obtain pectin extract. During the energization process, a mixture of carbon dioxide and inert gas is first introduced, and then the volume ratio of carbon dioxide in the mixture is gradually adjusted. The flow rate of the mixture is 2 L / min.

[0025] The inert gas is nitrogen.

[0026] The gradual increase in the volume percentage of carbon dioxide in the gas mixture is specifically as follows: The volume ratio of carbon dioxide to inert gas in the first stage is 2:1, and the introduction time is 5 minutes. The volume ratio of carbon dioxide to inert gas in the second stage is 5:1, and the introduction time is 10 minutes. The volume ratio of carbon dioxide to inert gas in the third stage is 3:1, and the introduction time is 5 minutes.

[0027] S3: After rotary evaporating the pectin extract at 55℃ for 1 hour, precipitate it with 1.5 times its volume of ethanol solution, wash, and dry.

[0028] Example 3

[0029] A method for extracting pectin from citrus peel includes the following steps: S1: Chop the citrus peel, first soak it in a 0.1wt% sodium chloride solution until its moisture content reaches 60%, then take it out and dry it with cold air at 10℃ until the surface moisture content is 15%, freeze it at -40℃, and then dry it at 45℃ under vacuum to obtain pretreated citrus peel; S2: The pretreated citrus peel was added to a 30wt% acetic acid solution and subjected to electrochemical treatment. Specifically, the electrochemical treatment was performed at a current of 1mA for 20min. After electrochemical treatment, the mixture was stirred at 55℃ and then centrifuged at 7000rpm for 30min to obtain pectin extract. During the energization process, a mixture of carbon dioxide and inert gas is first introduced, and then the volume ratio of carbon dioxide in the mixture is gradually adjusted. The flow rate of the mixture is 2 L / min.

[0030] The inert gas is nitrogen.

[0031] The gradual increase in the volume percentage of carbon dioxide in the gas mixture is specifically as follows: The volume ratio of carbon dioxide to inert gas in the first stage is 2:1, and the introduction time is 5 minutes. The volume ratio of carbon dioxide to inert gas in the second stage is 5:1, and the introduction time is 10 minutes. The volume ratio of carbon dioxide to inert gas in the third stage is 3:1, and the introduction time is 5 minutes.

[0032] S3: After rotary evaporating the pectin extract at 55℃ for 1 hour, precipitate it with 1.5 times its volume of ethanol solution, wash, and dry.

[0033] Example 4

[0034] A method for extracting pectin from citrus peel includes the following steps: S1: Chop the citrus peel, first soak it in a 0.5wt% sodium chloride solution until its moisture content reaches 60%, then take it out and dry it with cold air at 10℃ until the surface moisture content is 15%, freeze it at -40℃, and then dry it at 45℃ under vacuum to obtain pretreated citrus peel; S2: The pretreated citrus peel was added to a 25wt% acetic acid solution and subjected to electrochemical treatment. Specifically, the electrochemical treatment was performed at a current of 1mA for 20 minutes. After electrochemical treatment, the mixture was stirred at 55°C and then centrifuged at 7000rpm for 30 minutes to obtain pectin extract. During the energization process, a mixture of carbon dioxide and inert gas is first introduced, and then the volume ratio of carbon dioxide in the mixture is gradually adjusted. The flow rate of the mixture is 2 L / min.

[0035] The inert gas is nitrogen.

[0036] The gradual increase in the volume percentage of carbon dioxide in the gas mixture is specifically as follows: The volume ratio of carbon dioxide to inert gas in the first stage is 3:1, and the introduction time is 5 minutes. The volume ratio of carbon dioxide to inert gas in the second stage is 5:1, and the introduction time is 10 minutes. The volume ratio of carbon dioxide to inert gas in the third stage is 2:1, and the introduction time is 5 minutes.

[0037] S3: After rotary evaporating the pectin extract at 55℃ for 1 hour, precipitate it with 1.5 times its volume of ethanol solution, wash, and dry.

[0038] Example 5

[0039] A method for extracting pectin from citrus peel includes the following steps: S1: Chop the citrus peel, first soak it in a 1wt% sodium chloride solution until its moisture content reaches 60%, then take it out and dry it with cold air at 10℃ until the surface moisture content is 15%, freeze it at -40℃, and then dry it at 45℃ under vacuum to obtain pretreated citrus peel. S2: The pretreated citrus peel was added to a 25wt% acetic acid solution and subjected to electrochemical treatment. Specifically, the electrochemical treatment was performed at a current of 1mA for 25 minutes. After electrochemical treatment, the mixture was stirred at 55°C and then centrifuged at 7000rpm for 30 minutes to obtain pectin extract. During the energization process, a mixture of carbon dioxide and inert gas is first introduced, and then the volume ratio of carbon dioxide in the mixture is gradually adjusted. The flow rate of the mixture is 2 L / min.

[0040] The inert gas is nitrogen.

[0041] The gradual increase in the volume percentage of carbon dioxide in the gas mixture is specifically as follows: The volume ratio of carbon dioxide to inert gas in the first stage is 1:1, and the introduction time is 5 minutes. The volume ratio of carbon dioxide to inert gas in the second stage is 4:1, and the introduction time is 10 minutes. The volume ratio of carbon dioxide to inert gas in the third stage is 2:1, and the introduction time is 10 minutes.

[0042] S3: After rotary evaporating the pectin extract at 55℃ for 1 hour, precipitate it with 1.5 times its volume of ethanol solution, wash, and dry.

[0043] Comparative Example 1 Unlike Example 2, in step S1, water was used directly for soaking without adding sodium chloride, and the rest remained unchanged.

[0044] S1 specifically involves: chopping citrus peel, first soaking it in concentrated water to achieve a moisture content of 60%, then removing it and drying it with cold air at 10°C until the surface moisture content reaches 15%, freezing it at -40°C, and then drying it under vacuum conditions at 45°C to obtain pre-treated citrus peel. Comparative Example 2 Unlike Example 2, in step S1, there was no cold air drying process; the product was directly frozen after being moistened, and the rest remained unchanged.

[0045] S1 specifically involves: chopping citrus peel, first soaking it in a 0.1wt% sodium chloride solution until its moisture content reaches 60%, then taking it out and freezing it at -40℃, and drying it under vacuum conditions at 45℃ to obtain pretreated citrus peel.

[0046] Comparative Example 3 Unlike Example 2, no electrostatic treatment was applied; the sample was directly immersed in acetic acid solution, and nothing else changed.

[0047] S2 specifically involves: adding pretreated citrus peel to a 25wt% acetic acid solution for immersion; stirring at 55°C during immersion, followed by centrifugation at 7000rpm for 30min to obtain pectin extract; During impregnation, a mixture of carbon dioxide and inert gas is first introduced, and then the volume ratio of carbon dioxide in the mixture is gradually adjusted. The flow rate of the mixture is 2 L / min.

[0048] The inert gas is nitrogen.

[0049] The gradual increase in the volume percentage of carbon dioxide in the gas mixture is specifically as follows: The volume ratio of carbon dioxide to inert gas in the first stage is 2:1, and the introduction time is 5 minutes. The volume ratio of carbon dioxide to inert gas in the second stage is 5:1, and the introduction time is 10 minutes. The volume ratio of carbon dioxide to inert gas in the third stage is 3:1, and the introduction time is 5 minutes.

[0050] Comparative Example 4 Unlike Example 2, carbon dioxide was directly introduced without mixing with inert gases, and everything else remained unchanged.

[0051] Specifically, during the electrostatic treatment, dioxide is directly introduced at a flow rate of 2 L / min.

[0052] Comparative Example 5 Unlike Example 2, the concentration of carbon dioxide was not adjusted; instead, a volume ratio of 2:1 for carbon dioxide and an inert gas was used directly, with the rest remaining unchanged.

[0053] Specifically, during the electrostatic treatment, a mixture of carbon dioxide and inert gas with a volume ratio of 2:1 is introduced, and the flow rate of the mixture is 2 L / min.

[0054] The samples from the above embodiments and comparative examples were tested, and the test results are shown in Table 1.

[0055] Pectin extraction rate (%) = pectin mass / citrus peel mass × 100%.

[0056] Table 1 Performance test results of the examples and comparative examples

[0057] As shown in Table 1, the performance of the embodiments is superior to that of the comparative examples. The main reasons may be as follows: The embodiments pre-treat the citrus peel by first soaking it in salt water and then rinsing the surface. During air drying, the surface moisture evaporates more easily, while the salt water inside has a certain water-retaining capacity and is difficult to evaporate. Even though the internal water content is higher, the surface water content is lower. The increased volume after freezing inside enhances the cell wall freeze-swelling effect, thereby further improving the dissolution of active ingredients in the citrus peel. It is also more conducive to the subsequent acid extraction of pectin. Furthermore, the use of organic acid (acetic acid) for electrolysis causes the acetic acid to ionize, resulting in a microcurrent, which makes it easier for H+ to be extracted. + The orderly flow in the solution increases the dissolution rate of protopectin; at the same time, the introduction of an inert gas containing carbon dioxide can effectively prevent pH instability in the solution and maintain pH stability, thereby affecting the extraction of pectin.

[0058] Meanwhile, the pectin obtained in Example 2 was applied to fermented acidic dairy beverages and jams, and its quality remained stable.

[0059] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of the present invention.

Claims

1. A method for extracting pectin from citrus peel, characterized in that, Includes the following steps: S1: Chop the citrus peel, first soak it in sodium chloride solution, then rinse the surface with pure water to make its moisture content reach at least 60%, then take it out and air dry it until the surface moisture content is 10-20%, put it in -40℃ to -50℃ to freeze it, and then dry it under vacuum conditions at 30-60℃ to obtain pre-treated citrus peel. S2: Add the pretreated citrus peel to an organic acid solution and electrolyze it. After electrolysis, stir at 50-60℃ and centrifuge to obtain pectin extract. S3: After rotary evaporating the pectin extract at 45-65℃ for 0.5-2.0h, precipitate it with 1-2 times its volume of ethanol solution, wash, and dry.

2. The method for extracting pectin from citrus peel according to claim 1, characterized in that, In step S1, the sodium chloride solution is 0.1-3 wt%.

3. The method for extracting pectin from citrus peel according to claim 1, characterized in that, In step S1, the air drying specifically refers to drying under cold air at 3-15℃.

4. The method for extracting pectin from citrus peel according to claim 1, characterized in that, In step S2, the organic acid solution is acetic acid with a concentration of 20-30 wt%.

5. The method for extracting pectin from citrus peel according to claim 1, characterized in that, In step S2, the power-on process specifically involves processing for 10-30 minutes at a current of 1-3mA.

6. The method for extracting pectin from citrus peel according to claim 1, characterized in that, During the electrostatic treatment, a mixture of carbon dioxide and inert gas is first introduced, and then the volume ratio of carbon dioxide in the mixture is gradually adjusted. The flow rate of the mixture is 1-3 L / min.

7. The method for extracting pectin from citrus peel according to claim 6, characterized in that, The inert gas is nitrogen, argon, or a mixture of nitrogen and argon in a volume ratio of 1-3:1-5.

8. A method for extracting pectin from citrus peel according to claim 6, characterized in that, The gradual increase in the volume percentage of carbon dioxide in the gas mixture is specifically as follows: The volume ratio of carbon dioxide to inert gas in the first stage is 1-3:1, and the introduction time is 3-5 minutes. The volume ratio of carbon dioxide to inert gas in the second stage is 3-5:1, and the introduction time is 4-10 minutes. The volume ratio of carbon dioxide to inert gas in the third stage is 2-4:1, and the introduction time is 3-10 minutes.

9. The method for extracting pectin from citrus peel according to claim 1, characterized in that, In step S2, the centrifugation is performed at 6000-8000 rpm for 20-30 minutes.

10. The use of pectin obtained by the method of any one of claims 1-9 in acidic dairy beverages or jam products.

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