A method for obtaining citrus fiber from citrus peel

Abstract

This invention relates to the field of agricultural product processing technology, and in particular to a method for obtaining citrus fiber from citrus peel. The method includes the following steps: S1, raw material pretreatment; S2, ethanol decolorization treatment; S3, compound enzymatic extraction; S4, enzyme inactivation and centrifugation; S5, alcohol precipitation treatment; S6, fiber merging and drying; S7, high-pressure homogenization modification; S8, spray drying. This invention uses a compound enzyme preparation composed of cellulase and pectinase for synergistic enzymatic hydrolysis, which is not only mild but also effectively destroys the cell wall structure, promotes the full dissolution of soluble components such as pectin, and significantly improves the yield and purity of soluble dietary fiber. This lays the material basis for exerting its physiological functions such as lowering blood sugar and blood lipids. At the same time, combined with high-pressure homogenization modification, strong shear force is used to destroy the dense structure of the fiber, making the microstructure of the fiber loose and porous, which greatly enhances the water holding capacity and swelling properties of the product.

Description

Technical Field

[0001] This invention relates to the field of agricultural product processing technology, specifically a method for obtaining citrus fiber from citrus peel. Background Technology

[0002] Citrus fiber is a natural, high-quality dietary fiber extracted from citrus peels. It is mainly composed of water-soluble and insoluble dietary fibers and is also rich in bioactive components such as flavonoids and polyphenols. In the food industry, it plays a leading role in physical and chemical functions. Due to its strong water-holding capacity, oil-holding capacity, and swelling properties, it can effectively improve the texture and stability of food. It is often used as a thickener, water-retaining agent, and emulsifier in meat products, dairy products, and baked goods. Obtaining this fiber from citrus peels has dual value: on the one hand, it is a high-value utilization of citrus processing byproducts (peel pomace), which helps reduce resource waste and environmental pollution; on the other hand, the fiber derived from the peels not only performs the above-mentioned processing characteristics but has also been proven to have positive physiological effects such as lowering blood sugar, lowering blood lipids, regulating intestinal health, and anti-oxidation.

[0003] Currently, the main methods for extracting dietary fiber from citrus peels include heating, neutral washing, and single-enzyme methods. However, these existing technologies have significant limitations. While heating is simple to operate, high-temperature treatment can lead to excessive damage to the fiber structure, significantly reducing the product's water-holding capacity and swelling capacity, and resulting in a low total dietary fiber yield. Neutral washing primarily targets insoluble dietary fiber, yielding products with extremely low soluble dietary fiber content. Soluble dietary fiber is a key component for lowering blood sugar and lipids, severely limiting the product's functional properties and application range. Single-enzyme cellulase methods, while gentle, only partially hydrolyze cellulose, limiting the release of components like pectin and making it difficult to effectively dissociate cell wall polysaccharides, resulting in insufficient dissolution of soluble dietary fiber. The overall fiber yield and quality still have considerable room for improvement. Furthermore, all of the above methods lack subsequent modification treatments for the fiber products, resulting in dense fiber microstructures and poor hydration properties, making it difficult to meet the food industry's demand for functional ingredients with high water-holding capacity and high swelling capacity. Summary of the Invention

[0004] The purpose of this invention is to provide a method for obtaining citrus fiber from citrus peel, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for obtaining citrus fiber from citrus peel, the method comprising the following steps: S1. Raw material pretreatment: Fresh citrus peels are washed, cut, enzyme-inactivated, dried and pulverized to obtain citrus peel powder; S2, Ethanol decolorization treatment: The citrus peel powder obtained in step S1 is decolorized with edible ethanol. After centrifugation, the precipitate is collected and the ethanol is evaporated to obtain decolorized citrus peel powder. S3. Compound enzymatic hydrolysis extraction: Add the decolorized citrus peel powder obtained in step S2 to the buffer solution, and then add the compound enzyme preparation to carry out the enzymatic hydrolysis reaction; S4. Enzyme inactivation and centrifugation: After enzymatic hydrolysis, the enzyme is inactivated by heating, and the supernatant and precipitate are obtained by centrifugation. S5. Alcohol precipitation: Add ethanol to the supernatant obtained in step S4 to precipitate the precipitate by centrifugation. S6. Fiber merging and drying: Combine the precipitate obtained in step S4 with the precipitate obtained in step S5, wash and dry to obtain crude citrus fiber. S7. High-pressure homogenization modification: Disperse the crude citrus fiber obtained in step S6 in water and perform high-pressure homogenization treatment. S8. Spray drying: The fiber suspension obtained in step S7 is spray dried to obtain the modified citrus fiber product.

[0006] Preferably, in step S1, the enzyme inactivation process involves pre-boiling the peel in boiling water for 3-5 minutes, drying it at 45-55°C, and then pulverizing it and passing it through a 60-80 mesh sieve.

[0007] Preferably, in step S2, the ethanol decolorization treatment uses an ethanol volume fraction of 85%-95%, a liquid-to-solid ratio of 15-25 mL / 1g, a decolorization temperature of 35-45℃, and a treatment time of 40-60 min per treatment, with 2-3 treatments.

[0008] Preferably, in step S3, the compound enzyme preparation is a mixture of cellulase and pectinase in a mass ratio of 2-4:1, and the total amount of enzyme added is 0.5%-1.5% of the mass of the citrus peel powder.

[0009] Preferably, in step S3, the buffer solution is a citrate-sodium citrate buffer solution with a pH of 4.5-5.5, a material-to-liquid ratio of 1:20-1:40 (g / mL), an enzymatic hydrolysis temperature of 45-60℃, and an enzymatic hydrolysis time of 2-4 h.

[0010] Preferably, in step S4, the enzyme inactivation conditions are: heating to 90-100℃ and holding for 5-10 minutes, centrifuging at 4000-6000 r / min, and centrifuging for 10-15 minutes.

[0011] Preferably, in step S5, the amount of ethanol added is such that the final volume fraction of ethanol reaches 70%-80%, the alcohol precipitation temperature is 4℃, the alcohol precipitation time is 10-14h, the centrifugation speed is 5000-8000r / min, and the centrifugation time is 10-15min.

[0012] Preferably, in step S6, the drying is vacuum freeze drying, with a temperature of -50 to -60°C, a vacuum degree of 10-20 Pa, and a drying time of 24-36 hours.

[0013] Preferably, in step S7, the mass fraction of the crude citrus fiber dispersed in water is 2%-5%, the high-pressure homogenization pressure is 40-60 MPa, and the number of cycles is 2-4.

[0014] Preferably, in step S8, the inlet air temperature of the spray dryer is 160-180℃, the outlet air temperature is 80-90℃, and the feed flow rate is 5-10mL / min.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a composite enzyme preparation composed of cellulase and pectinase for synergistic enzymatic hydrolysis. This approach not only provides mild conditions but also effectively disrupts cell wall structures, promoting the full dissolution of soluble components such as pectin. This significantly improves the yield and purity of soluble dietary fiber, laying a material foundation for its physiological functions such as lowering blood sugar and blood lipids. Simultaneously, high-pressure homogenization modification utilizes strong shear force to disrupt the dense fiber structure, making the fiber microstructure loose and porous. This greatly enhances the product's water retention and swelling properties, effectively solving the industry pain point of poor fiber hydration performance obtained by traditional methods. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments thereof. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] A method for obtaining citrus fiber from citrus peel, the method comprising the following steps: S1. Raw material pretreatment: Fresh citrus peels are washed, cut, enzyme-inactivated, dried and pulverized to obtain citrus peel powder. The specific process of enzyme inactivation is to pre-boil the peels in boiling water for 3-5 minutes, dry them at 45-55℃, and then pass them through a 60-80 mesh sieve. S2. Ethanol decolorization treatment: The citrus peel powder obtained in step S1 is decolorized with edible ethanol. After centrifugation, the precipitate is collected and the ethanol is evaporated to obtain decolorized citrus peel powder. The volume fraction of ethanol used in the ethanol decolorization treatment is 85%-95%, the liquid-solid ratio is 15-25mL / 1g, the decolorization temperature is 35-45℃, the treatment time is 40-60min each time, and the treatment is repeated 2-3 times. S3. Compound Enzymatic Extraction: The decolorized citrus peel powder obtained in step S2 is added to a buffer solution, and then a compound enzyme preparation is added for enzymatic hydrolysis. The compound enzyme preparation is a mixture of cellulase and pectinase with a mass ratio of (2-4):1. The total amount of enzyme added is 0.5%-1.5% of the mass of the citrus peel powder. The buffer solution is a citrate-sodium citrate buffer solution with a pH of 4.5-5.5. The material-liquid ratio is 1:20-1:40 (g / mL). The enzymatic hydrolysis temperature is 45-60℃, and the enzymatic hydrolysis time is 2-4h. S4. Enzyme inactivation and centrifugation: After enzymatic hydrolysis, heat to inactivate the enzyme, and centrifuge to obtain the supernatant and precipitate. The conditions for enzyme inactivation are to heat to 90-100℃ and hold for 5-10 min, centrifuge at 4000-6000 r / min, and centrifuge for 10-15 min. S5. Alcohol precipitation: Add ethanol to the supernatant obtained in step S4 to precipitate the precipitate by centrifugation. The amount of ethanol added is such that the final volume fraction of ethanol reaches 70%-80%. The alcohol precipitation temperature is 4℃, the alcohol precipitation time is 10-14h, the centrifugation speed is 5000-8000r / min, and the centrifugation time is 10-15min. S6. Fiber merging and drying: The precipitate obtained in step S4 and step S5 are merged, washed and dried to obtain crude citrus fiber. The drying is carried out by vacuum freeze drying at a temperature of -50 to -60°C, a vacuum degree of 10-20 Pa, and a drying time of 24-36 h. S7. High-pressure homogenization modification: Disperse the crude citrus fiber obtained in step S6 in water and perform high-pressure homogenization treatment. The mass fraction of the crude citrus fiber dispersed in water is 2%-5%, the high-pressure homogenization pressure is 40-60MPa, and the number of cycles is 2-4. S8. Spray drying: The fiber suspension obtained in step S7 is spray dried to obtain the modified citrus fiber product. The inlet air temperature of the spray dryer is 160-180℃, the outlet air temperature is 80-90℃, and the feed flow rate is 5-10mL / min.

[0018] This embodiment provides a method for obtaining citrus fiber from citrus peel, including the following steps: Example Steps (1) Raw material pretreatment: Take 5 kg of fresh sweet orange peel, remove the moldy parts, wash and cut into 1.5 cm strips. Boil the peel in boiling water for 4 minutes, rinse with cold water 3 times, drain and dry in a 50℃ forced-air drying oven for 24 hours until constant weight, pulverize and pass through an 80 mesh sieve to obtain citrus peel powder, and seal and store. Example Step (2): Ethanol decolorization treatment: Weigh 200g of citrus peel powder, add 4L of 95% edible ethanol, stir and decolorize in a 40℃ water bath for 50min, centrifuge at 3000r / min for 10min and collect the precipitate. Repeat the above operation 3 times to fully evaporate the ethanol from the precipitate and obtain decolorized citrus peel powder; Example Step (3): Compound enzymatic hydrolysis extraction: Take 20g of decolorized citrus peel powder, add 600mL of citrate-sodium citrate buffer solution with pH 5.0 at a material-liquid ratio of 1:30, add 0.2g of compound enzyme preparation (cellulase to pectinase mass ratio 3:1, total enzyme amount 1.0%), and enzymatically hydrolyze in a constant temperature water bath shaker at 52℃ for 3.2h; Example Step (4): Enzyme inactivation and centrifugation: After enzymatic hydrolysis, rapidly heat to 95℃ and maintain for 8 minutes to inactivate the enzyme. After cooling, centrifuge at 5000 r / min for 15 minutes to separate the supernatant and precipitate. Wash the precipitate twice with distilled water for later use. Example Step (5): Alcohol precipitation: Add anhydrous ethanol to the supernatant to a final volume fraction of 75%, let stand at 4°C for 12 hours for alcohol precipitation, and centrifuge at 8000 r / min for 10 minutes to collect the precipitate. Example Step (6), fiber merging and drying: The precipitates from step (4) and step (5) are merged, washed twice with distilled water, and dried in a vacuum freeze dryer (cold trap temperature -55℃, vacuum degree 15Pa, drying time 30h) to obtain crude citrus fiber; Example Step (7): High pressure homogenization modification: Take 5g of crude citrus fiber, disperse it in 95mL of distilled water to prepare a 5% suspension, and use a high pressure homogenizer to circulate it 3 times under a pressure of 50MPa. Example Step (8): Spray drying: The homogenized suspension is spray dried with an inlet air temperature of 170°C, an outlet air temperature of 85°C, and a feed flow rate of 8 mL / min. The collected powder is the modified citrus fiber product.

[0019] The total dietary fiber content of the citrus fiber obtained in this example was determined to be 84.6%, of which the soluble dietary fiber content was 28.3%, the ratio of soluble dietary fiber to insoluble dietary fiber was 0.33, the water holding capacity was 12.8 g / g, and the swelling capacity was 9.2 mL / g.

[0020] Example 2: This embodiment is basically the same as Example 1, except that in step (3), the amount of compound enzyme preparation added is 0.8% (the mass ratio of cellulase to pectinase is 2:1), the enzymatic hydrolysis temperature is 50℃, and the enzymatic hydrolysis time is 3.0h. The total dietary fiber content of the obtained citrus fiber is 81.2%, the soluble dietary fiber content is 24.7%, the water holding capacity is 11.5g / g, and the swelling capacity is 8.3mL / g.

[0021] Example 3: This embodiment is basically the same as that of embodiment 1, except that the high pressure homogenization pressure in step (7) is 40MPa, and the cycle treatment is repeated twice. The total dietary fiber content of the obtained citrus fiber is 82.9%, the soluble dietary fiber content is 26.8%, the water holding capacity is 11.2g / g, and the swelling capacity is 8.6mL / g.

[0022] Comparative Example 1 (Heating Extraction): Take 20g of citrus peel powder, add distilled water at a water-to-powder ratio of 40:1, heat at 110℃ for 30min, centrifuge, precipitate the supernatant with alcohol, combine the precipitates and dry. The obtained fiber has a total dietary fiber content of 76.1%, a soluble dietary fiber content of 20.6%, a water-holding capacity of 7.3g / g, and a swelling capacity of 4.5mL / g.

[0023] Comparative Example 2 (Extraction using neutral washing method): Take 20g of decolorized citrus peel powder, add distilled water at a material-to-water ratio of 1:30, extract at 70℃ for 90min, centrifuge to separate the precipitate, and dry to obtain insoluble dietary fiber. The obtained fiber is mainly insoluble dietary fiber with low soluble dietary fiber content. The total dietary fiber content is 72.5%, the water-holding capacity is 5.1g / g, and the swelling capacity is 3.4mL / g.

[0024] Comparative Example 3 (Single Cellulose Enzyme Extraction): Take 20g of citrus peel powder, add pH 4.6 buffer solution at a material-to-liquid ratio of 1:20, add 0.1U / g cellulase, and enzymatically hydrolyze at 37℃ for 4h. Subsequent treatment is the same as in Example 1. The obtained fiber has a total dietary fiber content of 78.3%, a soluble dietary fiber content of 18.5%, a water holding capacity of 8.9g / g, and a swelling capacity of 6.1mL / g.

[0025] Experimental data: Table 1. Effects of different extraction methods on the yield and composition of citrus fiber Table 2. Comparison of physicochemical properties of citrus fibers obtained by different methods Table 3. Changes in water-holding capacity of citrus fibers under different pH and temperature conditions As shown in Table 1, the total dietary fiber content of the citrus fiber obtained in Example 1 reached 84.6%, and the soluble dietary fiber content reached 28.3%, significantly higher than that of Comparative Examples 1-3 (p<0.05). This indicates that the compound enzymatic hydrolysis combined with high-pressure homogenization modification process of the present invention can effectively improve the yield of dietary fiber and promote the conversion of some insoluble dietary fiber into soluble dietary fiber. As shown in Table 2, the water-holding capacity (12.8 g / g) and swelling capacity (9.2 mL / g) of the fiber in Example 1 were significantly better than those of the comparative examples (p<0.05). Benefiting from the moderate degradation of the fiber structure by compound enzymatic hydrolysis and high-pressure homogenization, the microstructure of the fiber becomes more loose and porous, increasing the binding sites with water. As shown in Table 3, the citrus fiber obtained by this invention exhibits good water-holding stability under different pH and temperature conditions. In particular, the water-holding capacity is significantly improved under slightly acidic (pH 3.0) and higher temperature (80℃) conditions. This is consistent with the characteristics of insoluble dietary fiber reported by Hao Ruijuan et al. However, the water-holding capacity of the fiber of this invention is better than that of the comparative example under all conditions, indicating that it has a wider range of application adaptability.

[0026] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for obtaining citrus fiber from citrus peel, characterized in that, The method includes the following steps: S1. Raw material pretreatment: Fresh citrus peels are washed, cut, enzyme-inactivated, dried and pulverized to obtain citrus peel powder; S2, Ethanol decolorization treatment: The citrus peel powder obtained in step S1 is decolorized with edible ethanol. After centrifugation, the precipitate is collected and the ethanol is evaporated to obtain decolorized citrus peel powder. S3. Compound enzymatic hydrolysis extraction: Add the decolorized citrus peel powder obtained in step S2 to the buffer solution, and then add the compound enzyme preparation to carry out the enzymatic hydrolysis reaction; S4. Enzyme inactivation and centrifugation: After enzymatic hydrolysis, the enzyme is inactivated by heating, and the supernatant and precipitate are obtained by centrifugation. S5. Alcohol precipitation: Add ethanol to the supernatant obtained in step S4 to precipitate the precipitate by centrifugation. S6. Fiber merging and drying: Combine the precipitate obtained in step S4 with the precipitate obtained in step S5, wash and dry to obtain crude citrus fiber. S7. High-pressure homogenization modification: Disperse the crude citrus fiber obtained in step S6 in water and perform high-pressure homogenization treatment. S8. Spray drying: The fiber suspension obtained in step S7 is spray dried to obtain the modified citrus fiber product.

2. The method for obtaining citrus fiber from citrus peel according to claim 1, characterized in that: In step S1, the specific process of enzyme inactivation treatment is to pre-boil the peel in boiling water for 3-5 minutes, dry it at a temperature of 45-55℃, and then pulverize it and pass it through a 60-80 mesh sieve.

3. The method for obtaining citrus fiber from citrus peel according to claim 1, characterized in that: In step S2, the ethanol decolorization treatment uses an ethanol volume fraction of 85%-95%, a liquid-to-solid ratio of 15-25 mL / 1g, a decolorization temperature of 35-45℃, and a treatment time of 40-60 min each time, with 2-3 treatments.

4. The method for obtaining citrus fiber from citrus peel according to claim 1, characterized in that: In step S3, the compound enzyme preparation is a mixture of cellulase and pectinase in a mass ratio of 2-4:1, and the total amount of enzyme added is 0.5%-1.5% of the mass of citrus peel powder.

5. A method for obtaining citrus fiber from citrus peel according to claim 1, characterized in that: In step S3, the buffer solution is a citrate-sodium citrate buffer solution with a pH of 4.5-5.5, a material-to-liquid ratio of 1:20-1:40 (g / mL), an enzymatic hydrolysis temperature of 45-60℃, and an enzymatic hydrolysis time of 2-4 h.

6. A method for obtaining citrus fiber from citrus peel according to claim 1, characterized in that: In step S4, the enzyme inactivation conditions are: heating to 90-100℃ and holding for 5-10 minutes, centrifuging at 4000-6000 r / min, and centrifuging for 10-15 minutes.

7. The method for obtaining citrus fiber from citrus peel according to claim 1, characterized in that: In step S5, the amount of ethanol added is such that the final volume fraction of ethanol reaches 70%-80%, the alcohol precipitation temperature is 4℃, the alcohol precipitation time is 10-14h, the centrifugation speed is 5000-8000r / min, and the centrifugation time is 10-15min.

8. A method for obtaining citrus fiber from citrus peel according to claim 1, characterized in that: In step S6, the drying is vacuum freeze drying, with a temperature of -50 to -60°C, a vacuum degree of 10-20 Pa, and a drying time of 24-36 hours.

9. A method for obtaining citrus fiber from citrus peel according to claim 1, characterized in that: In step S7, the crude citrus fiber is dispersed in water at a mass fraction of 2%-5%, the high-pressure homogenization pressure is 40-60 MPa, and the number of cycles is 2-4.

10. A method for obtaining citrus fiber from citrus peel according to claim 1, characterized in that: In step S8, the inlet air temperature of the spray dryer is 160-180℃, the outlet air temperature is 80-90℃, and the feed flow rate is 5-10mL / min.

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