Preparation method of compound modified ginger residue dietary fiber

Abstract

This invention relates to the field of functional food technology, specifically to a method for preparing ginger residue dietary fiber through composite modification. This method solves the problems of limited technical effects from existing single-modification methods for dietary fiber, low soluble component content, and insufficient functional properties of ginger residue dietary fiber. The method includes the following steps: first, the ginger residue byproduct after supercritical CO2 extraction of ginger essential oil is dried to constant weight in a drying oven; then, the dried sample is pulverized and sieved to obtain ginger residue dietary fiber powder with uniform particle size. This invention, through strong shearing, cavitation, and instantaneous pressure release, disrupts the dense structure of the ginger residue cell walls, reduces crystallinity, and increases specific surface area, thereby improving water-holding capacity, oil-holding capacity, and swelling properties. This allows enzyme molecules to more fully contact the substrate, significantly improving the efficiency of subsequent enzymatic hydrolysis reactions. Therefore, the composite modification effect is significantly better than single treatment.

Description

Technical Field

[0001] This invention relates to the field of functional food technology, specifically to a method for preparing a composite modified dietary fiber from ginger residue. Background Technology

[0002] Ginger rhizomes are rich in nutrients, containing carbohydrates, protein, and a small amount of lipids, as well as minerals such as potassium and magnesium, and micronutrients such as vitamin C and B vitamins. In addition to these basic nutrients, its unique pungent flavor mainly comes from gingerols, shogaols, and related phenolic derivatives. These active substances have been proven to have various physiological functions, including antioxidant, anti-inflammatory, antibacterial, and lipid-regulating effects. During industrial processing, ginger is often used to extract ginger juice, ginger essential oil, or functional factors, resulting in a large amount of ginger residue as a byproduct. Ginger residue is high in dietary fiber, mainly composed of cellulose, hemicellulose, and pectin, along with a certain amount of polyphenols and volatile components. Therefore, structural regulation and functional modification of the dietary fiber in ginger residue can help improve its physicochemical and physiological activity properties.

[0003] Dietary fiber is recognized worldwide as one of the seven essential nutrients due to its various physiological functions, including promoting bowel movements and detoxification, preventing cardiovascular disease, and regulating blood sugar. Dietary fiber is divided into soluble dietary fiber (SDF) and insoluble dietary fiber (IDF), with SDF having superior physiological activity compared to IDF and being hailed as high-quality dietary fiber.

[0004] Existing dietary fibers are often treated using methods such as physical modification and enzymatic modification. Physical modification, such as ultrasonic treatment and high-pressure homogenization, mainly uses mechanical force to disrupt the fiber structure and increase the specific surface area. Enzymatic modification uses enzymes to selectively degrade polysaccharide molecular chains, promoting the conversion of IDF to SDF. However, single modification methods often have limited modification effects and incomplete functional enhancements. Therefore, they do not meet current needs. To address this, we propose a composite modification method for preparing ginger residue dietary fiber. Summary of the Invention

[0005] The purpose of this invention is to provide a composite modification preparation method for ginger residue dietary fiber, in order to solve the problems mentioned in the background art, such as the limited technical effect of existing dietary fiber through single modification, and the low content of soluble components and insufficient functional properties of ginger residue dietary fiber.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing composite modified ginger residue dietary fiber, comprising the following steps: S1: First, take the ginger residue byproduct after supercritical CO2 extraction of ginger essential oil, dry it in a drying oven to constant weight, then crush the dried sample and sieve it to obtain ginger residue dietary fiber powder with uniform particle size. S2: The ginger residue dietary fiber powder is mixed and dispersed with citric acid-sodium citrate buffer solution to obtain a mixed slurry. The mixed slurry is then subjected to high-pressure homogenization and the process is repeated n times. S3: Add a compound enzyme preparation to the slurry after high-pressure homogenization to carry out enzymatic hydrolysis. The compound enzyme preparation is composed of cellulase and xylanase. Enzymatic hydrolysis is carried out by constant temperature oscillation. S4: After the enzymatic hydrolysis reaction is completed, the enzyme is inactivated by high temperature. Then the product is dried in a drying oven to constant weight and pulverized through an 80-mesh sieve to obtain the modified ginger residue dietary fiber product.

[0007] Preferably, in step S1, the sieve used for sieving is 70-100 mesh, and the ginger residue dietary fiber powder is a byproduct obtained by supercritical CO2 extraction of fresh ginger after washing, slicing, and low-temperature drying, under conditions of 25-30 MPa and 40-45℃.

[0008] Preferably, in step S1, the drying oven is used for forced-air drying at 45°C until the moisture content of the raw material is below 8%. In step S4, the drying oven is used for forced-air drying at 50°C until the moisture content of the raw material is below 8%.

[0009] Preferably, in step S2, the pH value of the citric acid-sodium citrate buffer solution is 4.5-5.5, and the ratio of the ginger residue dietary fiber powder to the citric acid-sodium citrate buffer solution is 1:20g / mL.

[0010] Preferably, in step S2, the pressure of the high-pressure homogenization treatment is 60 MPa, and the number of cycles n ≥ 3.

[0011] Preferably, in step S3, the cellulase has an enzyme activity ≥1.5×10⁻⁶. 4 U / g, the enzyme activity of the xylanase is ≥1.6×10⁻⁶. 5 U / g.

[0012] Preferably, in step S3, the oscillation speed of the enzymatic hydrolysis process is 150-200 r / min, the compound enzyme preparation is made of cellulase and xylanase in a mass ratio of 2:1, and the amount of compound enzyme preparation added is 0.4% of the mass of the slurry after high-pressure homogenization.

[0013] Preferably, in step S3, the isothermal oscillation temperature is 50°C and the enzymatic hydrolysis time is 120 min.

[0014] Preferably, in step S4, the temperature for high-temperature enzyme inactivation is 100°C, and the high-temperature enzyme inactivation time is 10 min.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes the synergistic effect of high-pressure homogenization and enzymatic hydrolysis to fully loosen the dietary fiber structure of ginger residue and form a porous network structure. Firstly, high-pressure homogenization, through strong shearing, cavitation, and instantaneous pressure release, disrupts the dense structure of the ginger residue cell walls, reducing crystallinity and increasing specific surface area. This improves water-holding capacity, oil-holding capacity, and swelling properties, allowing enzyme molecules to more fully contact the substrate and significantly increasing the efficiency of subsequent enzymatic hydrolysis. Secondly, enzymatic hydrolysis selectively breaks down polysaccharide molecular chains, promoting the conversion of insoluble dietary fiber into soluble dietary fiber and enhancing its physicochemical properties and physiological functions. Therefore, the combined modification effect is significantly superior to that of a single treatment. Attached Figure Description

[0016] Figure 1 This is a scanning electron microscope image of the unmodified ginger residue dietary fiber of this invention; Figure 2 This is a scanning electron microscope image of the ultrasonically crushed and modified ginger residue dietary fiber of the present invention; Figure 3 This is a scanning electron microscope image of the dietary fiber from the enzymatically modified ginger residue of the present invention. Figure 4 This is a scanning electron microscope image of the high-pressure homogenized modified ginger residue dietary fiber of the present invention; Figure 5 This is a scanning electron microscope image of the homogenized-enzymatically modified ginger residue dietary fiber of the present invention; Figure 6 The X-ray diffraction patterns of ginger residue dietary fiber before and after modification according to this invention are shown below. Figure 7 The images show the Fourier transform infrared spectra of dietary fiber from ginger residue before and after modification according to this invention. Figure 8 This is a graph showing the DPPH free radical scavenging rate of ginger residue dietary fiber in this invention. Figure 9 This is a graph showing the ABTS+ free radical scavenging rate of ginger residue dietary fiber in this invention. Figure 10 This is a graph showing the glucose adsorption capacity of ginger residue dietary fiber before and after modification according to the present invention. Figure 11 This is a graph showing the cholesterol adsorption capacity of ginger residue dietary fiber before and after modification according to the present invention. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0018] Please see Figures 1 to 11 The first embodiment of the present invention provides a method for preparing a composite modified ginger residue dietary fiber, comprising the following steps: S1: First, take the ginger residue byproduct after supercritical CO2 extraction of ginger essential oil, dry it in a drying oven to constant weight, then crush the dried sample and sieve it. The sieve screen is 70-100 mesh to obtain ginger residue dietary fiber powder with uniform particle size. S2: Ginger residue dietary fiber powder is mixed and dispersed with citric acid-sodium citrate buffer to obtain a mixed slurry. The mixed slurry is then subjected to high-pressure homogenization and the process is repeated n times. S3: Add a compound enzyme preparation to the slurry after high-pressure homogenization to carry out enzymatic hydrolysis. The compound enzyme preparation is composed of cellulase and xylanase. Enzymatic hydrolysis is carried out by constant temperature oscillation. S4: After the enzymatic hydrolysis reaction is completed, the enzyme is inactivated by high temperature. Then the product is dried in a drying oven to constant weight and pulverized through an 80-mesh sieve to obtain the modified ginger residue dietary fiber product.

[0019] In step S1, the ginger residue dietary fiber powder is a byproduct obtained by supercritical CO2 extraction of fresh ginger after washing, slicing, and drying at low temperature, under conditions of 25-30 MPa and 40-45℃.

[0020] In step S1, the drying oven is used for forced-air drying at 45°C until the moisture content of the raw material is below 8%. In step S4, the drying oven is used for forced air drying at 50°C until the moisture content of the raw material is below 8%.

[0021] In step S2, the pH value of the citric acid-sodium citrate buffer solution is 4.5-5.5, and the ratio of ginger residue dietary fiber powder to citric acid-sodium citrate buffer solution is 1:20g / mL.

[0022] In step S2, the pressure of the high-pressure homogenization process is 60 MPa, and the number of cycles n ≥ 3.

[0023] In step S3, the cellulase activity is ≥1.5×10⁻⁶. 4 U / g, xylanase enzyme activity ≥1.6×10 5 U / g.

[0024] In step S3, the oscillation speed during the enzymatic hydrolysis process is 150-200 r / min. The compound enzyme preparation is made of cellulase and xylanase at a mass ratio of 2:1. The amount of compound enzyme preparation added is 0.4% of the mass of the slurry after high-pressure homogenization.

[0025] In step S3, the isothermal oscillation temperature is 50℃, and the enzymatic hydrolysis time is 120 min.

[0026] In step S4, the temperature for high-temperature enzyme inactivation is 100℃, and the high-temperature enzyme inactivation time is 10 minutes.

[0027] The above method can be used to prepare a composite modified ginger residue dietary fiber, denoted as DF-HE; The modification effect of the composite modified ginger residue dietary fiber was demonstrated by an additional four comparative groups.

[0028] Comparative Example 1: Take the same ginger residue raw material powder as in the first embodiment, without any modification treatment, and only in step S1 of the first embodiment, dry it to constant weight in a drying oven at 50°C and then pulverize it through an 80-mesh sieve. This powder serves as the unmodified control group sample and is denoted as DF-C.

[0029] Comparative Example 2: Raw material pretreatment: Same as step S1 in the first embodiment.

[0030] Ultrasonic modification treatment: Weigh 100g of ginger residue powder, add deionized water at a material-to-liquid ratio of 1:10, mix well, and place in an ultrasonic cell disruptor. Treat for 30 minutes at 20kHz and 900W power.

[0031] After the treatment, the sample was dried at 50°C to constant weight, pulverized and passed through an 80-mesh sieve to obtain the ultrasonically modified control group sample, denoted as DF-U.

[0032] Comparative Example 3: Raw material pretreatment: Same as step S1 in the first embodiment.

[0033] Enzymatic hydrolysis modification: Weigh 100g of ginger residue powder and add citric acid-sodium citrate buffer at a material-to-liquid ratio of 1:10. Add the same amount of compound enzyme preparation as in Example 1, and hydrolyze at 50℃ for 120min.

[0034] After the treatment is completed, the same as step S4 of the first embodiment is followed to obtain a single enzymatically modified control group sample, denoted as DF-E.

[0035] Comparative Example 4: Raw material pretreatment: Same as step S1 in the first embodiment.

[0036] High-pressure homogenization modification treatment: Weigh 100g of ginger residue powder, add deionized water at a material-to-liquid ratio of 1:20, and homogenize and circulate 3 times under a pressure of 60MPa.

[0037] After the treatment, the sample was dried at 50°C to constant weight, pulverized and passed through an 80-mesh sieve to obtain a single high-pressure homogenized modified control group sample, denoted as DF-H.

[0038] I. Effect Verification Experiment: The basic components and functional properties of the control group samples prepared in the first embodiment and comparative examples 1-4 were determined as follows: 1.1 Analysis of water-holding or oil-holding capacity: Accurately weigh 0.20 g of each sample dried to constant weight and place it in a 15 mL centrifuge tube. Quickly add 10 mL of distilled water or vegetable oil, stir thoroughly, seal with food-grade plastic wrap, and place at room temperature for 12 h. Then, centrifuge at 4000 r / min for 30 min at room temperature. Quickly decant the supernatant. After absorbing any remaining water or oil with filter paper, record the wet mass of the sample and calculate the water-holding capacity and oil-holding capacity using the following formulas: in, The sum of the mass of the sample after absorbing water or oil and the mass of the centrifuge tube is expressed in grams. The mass of the centrifuge tube is expressed in grams. The mass of the constant mass sample is expressed in grams.

[0039] 1.2 Analysis and determination of swelling force: Accurately weigh 0.25g of each dried sample to constant mass and place it in a 10mL graduated cylinder. Read and record the volume of the sample after natural accumulation. Then, add distilled water to the 5mL mark at room temperature, seal with food wrap, and let stand at room temperature for 18 hours. Read and record the volume of the sample after water absorption and expansion, and calculate the swelling force using the following formula: in, The volume measured after the sample absorbs water and swells is in mL; The volume of a constant-mass sample determined by natural stacking, in mL; The mass of the constant mass sample is expressed in grams.

[0040] 1.3 Analysis and determination of cation exchange capacity: Accurately weigh 1.00 g of each sample dried to constant weight and place it in a clean 250 mL Erlenmeyer flask. Add 50 mL of 1 mol / L HCl solution, stir thoroughly, seal with food-grade plastic wrap, and place at room temperature for 24 h to allow the sample to be completely acidified. Then filter and wash the sample thoroughly with distilled water until the filtrate is free of Cl⁻. Transfer the filter residue to an Erlenmeyer flask containing 150 mL of 5 g / 100 mL NaCl solution, and magnetically stir at 300 r / min for 30 min. Then add 2 drops of phenolphthalein indicator and titrate with 0.05 mol / L NaOH solution to the endpoint while shaking. At the same time, perform a blank test with distilled water and calculate the cation exchange capacity using the following formula: in, The volume of NaOH solution used for titrating the blank sample, in mL; The volume of NaOH solution used for titrating the sample, in mL; The mass of the constant mass sample is expressed in grams. The concentration of the NaOH solution used in the titration is given in mol / L.

[0041] 1.4 Analysis and determination of glucose adsorption capacity: Weigh 2.50 g of each dried sample into a 250 mL beaker, add 150 mL of 85% (volume fraction) ethanol solution, incubate in a water bath for 15 min (80℃), then filter. Wash the filter residue three times and dry it to constant weight using hot air at 60℃. Accurately weigh 0.50 g of the dried sample to constant weight into a 50 mL centrifuge tube, add 30 mL of 100 mmol / L glucose solution, stir thoroughly, and then place in a 37℃ constant temperature shaking water bath for 2, 4, 6, 8, 10, 12, 14, 16, and 18 h. Then, quickly remove the tube and centrifuge at 12000 r / min for 20 min. Collect the supernatant and dilute to 100 mL. Take 2 mL of the supernatant after dilution, and plot a glucose standard curve using the anthrone-sulfuric acid colorimetric method with glucose standard: y = 0.12689x - 0.38189 (R² = 0.9971). Measure the glucose concentration in the supernatant at a wavelength of 540 nm and calculate the glucose adsorption capacity using the following formula: in, The concentration of glucose in the glucose solution before adsorption is expressed in mmol / L. The concentration of glucose in the supernatant after adsorption is expressed in mmol / L. The volume of the glucose solution is in liters (L), and in this experiment it is 0.1 L. The mass of the constant mass sample is expressed in grams.

[0042] 1.5 Analysis and determination of cholesterol adsorption capacity: Take several fresh eggs and quickly separate the yolks. Add distilled water at a volume ratio of 1:9 and stir thoroughly to form an egg yolk emulsion. Accurately weigh 0.50 g of each sample dried to constant weight and place it in a clean 250 mL Erlenmeyer flask. Add 30 mL of egg yolk emulsion and stir thoroughly. Then, phosphate buffer solutions of 0.1 mol / L HCl and 0.1 mol / L NaOH at pH 2 (simulating the stomach environment) and pH 7 (simulating the small intestine environment) were used respectively. After incubation at 37°C with shaking for 2, 4, 6, 8, 10, 12, 14, 16, and 24 hours, the mixture was quickly removed and centrifuged at 4000 rpm for 20 minutes. 1 mL of the supernatant was collected, and a cholesterol standard curve was plotted using the phthalaldehyde method with cholesterol standards: y = 0.0085x - 0.0036 (R² = 0.9921). The cholesterol concentration p1 in the supernatant and the cholesterol concentration p2 in the egg yolk emulsion before adsorption were measured at 550 nm. The cholesterol adsorption capacity was calculated using the following formula: in, The concentration of cholesterol in the egg yolk emulsion before adsorption is expressed in mg / mL. The mass concentration of cholesterol in the supernatant after adsorption is expressed in mg / mL. The mass of the constant mass sample is expressed in grams.

[0043] After all the above experiments were completed, the experimental data were processed using Origin 8.0 and Statistic software. The measurement results were expressed as "mean ± standard error". The data are expressed as mean ± standard deviation (±s), with standard error used as the error bar in the figure. SPSS 22.0 software was used for statistical analysis of the experimental data. P < 0.05 was considered statistically significant, and P < 0.01 was considered highly statistically significant.

[0044] II. Results and Analysis: 2.1 Basic Component Analysis of Modified Ginger Residue: The basic components of ginger residue after different modification treatments were determined using national standard methods, and the results are shown in Table 1.

[0045] The differences in moisture content among the treatment groups were small, indicating that the modification process had a limited impact on the overall moisture content of the samples. Overall, the treatment methods did not significantly affect the total dietary fiber (TDF) content, but the soluble dietary fiber (SDF) content was significantly increased (P<0.05), while the insoluble dietary fiber (IDF) showed a decreasing trend, indicating that some IDF underwent structural depolymerization and was converted into SDF during the treatment process.

[0046] This change may stem from physical treatment that disrupts the dense structure of the cell wall, exposing fibrous components, while enzymatic hydrolysis further breaks down the polysaccharide chain structure, promoting the conversion of insoluble components into soluble components.

[0047] Compared to single treatment methods, the combined treatment of high-pressure homogenization and enzymatic hydrolysis showed a more significant improvement in SDF (storage density). This indicates a synergistic effect between physical disruption and enzymatic hydrolysis.

[0048] This result is consistent with the subsequent trend of structural changes and improved functional properties.

[0049] Table 1. Basic components of ginger residue

[0050] Note: Different lowercase letters in the same column's header indicate significant differences (P<0.05), the same applies below.

[0051] 2.2 Observation of surface microstructure: Figures 1 to 5 The microstructure changes of dietary fiber in ginger residue under different treatments are shown under a 2000x scanning electron microscope.

[0052] refer to Figure 1 The untreated sample has a relatively dense overall structure and a relatively flat surface with only a few natural cracks and pores, indicating that the fibers are still tightly wrapped by the cell wall structure, and some areas may have residual protein or starch and other non-fiber components attached to them. refer to Figure 2 After ultrasonic treatment, cracks and local pores appeared on the surface of the particles, and the overall structure tended to be loose, indicating that the ultrasonic cavitation effect destroyed part of the cell structure, causing the internal fibers to be gradually exposed. refer to Figure 3 Enzymatic hydrolysis further increases surface roughness and the number of pores, accompanied by particle erosion and peeling, indicating that the enzyme preparation degrades non-fibrous components in the cell wall, releasing the fibrous skeleton. refer to Figure 4 After high-pressure homogenization, the particles are significantly broken, the structure is refined and more porous, and the fiber bundles are gradually dispersed. refer to Figure 5After the combined treatment, the particle structure was basically disintegrated, forming a loose and porous network structure with the highest degree of fiber exposure, indicating that physical crushing and enzymatic hydrolysis have a synergistic strengthening effect.

[0053] The aforementioned structural changes provide a structural basis for improving the water-holding capacity, oil-holding capacity, and swelling properties of the modified ginger residue dietary fiber.

[0054] 2.3 X-ray diffraction scan results: refer to Figure 6 XRD results showed that although different treatment methods had some impact on the crystal structure of the samples, the positions of the main diffraction peaks were basically consistent, indicating that the treatment process did not change the crystal form of dietary fiber, and the overall polysaccharide backbone remained stable. All samples showed obvious diffraction peaks in the range of approximately 15°–25° at 2θ, which is the characteristic diffraction region of cellulose type I structure, indicating that the samples still retain a certain degree of cellulose microcrystalline structure. Meanwhile, broad diffuse peaks appeared in the high diffraction angle region, indicating that the samples are still predominantly amorphous.

[0055] Compared with the control group, the diffraction peak intensity decreased and the peak shape broadened after ultrasonic, enzymatic hydrolysis and high pressure homogenization treatment, indicating that the treatment process disturbed the original ordered structure, some microcrystalline regions were destroyed, and the proportion of amorphous regions increased. This phenomenon is usually related to the loosening of cell wall structure and fiber bundle dissociation caused by mechanical shearing, cavitation effect or enzymatic hydrolysis.

[0056] Further comparison revealed that the diffraction peaks of the sample treated with high-pressure homogenization combined with enzymatic hydrolysis (DF-HE) decreased most significantly, indicating that the combined treatment most thoroughly disrupted the crystalline regions, resulting in a more pronounced amorphous structure. This change helps to break down the dense cell wall structure and release internal polysaccharide components, thereby improving the accessibility, water absorption, and functional activity of dietary fiber. Overall, all treatment methods reduced sample crystallinity and promoted amorphous structure, with the combined treatment showing the most significant effect. Reduced crystallinity is usually accompanied by increased pore size and specific surface area, which facilitates the entry of water and active substances into the fiber interior, thus promoting enhanced functional properties.

[0057] 2.4 Fourier transform infrared spectroscopy results: refer to Figure 7 The FTIR spectrum of the dietary fiber sample is at approximately 3300 cm⁻¹. -1 It exhibits a broad OH stretching vibration absorption peak at 1200-1000 cm⁻¹. -1 The presence of COC vibrational absorption peaks in the region indicates that both untreated and treated samples retained the polysaccharide backbone structure of cellulose and hemicellulose, demonstrating that different treatment methods did not destroy the basic structural characteristics of dietary fiber.

[0058] Enzymatic hydrolysis disrupts cell wall structure and promotes the release of polysaccharide components. Simultaneously, high-pressure homogenization further weakens the dense fiber structure through strong shearing and impact, increasing the exposure of polysaccharide chains. Furthermore, after high-pressure homogenization and enzymatic hydrolysis, the exposure of hydroxyl groups increases, and the glycosidic bond structure undergoes certain changes, thereby improving the accessibility of functional groups.

[0059] 2.5 Physicochemical Properties Analysis of Dietary Fiber: As shown in Table 2, different modification treatments significantly improved the water-holding capacity, oil-holding capacity, water absorption and swelling capacity, and cation exchange capacity of ginger residue dietary fiber. Among them, high-pressure homogenization combined with enzymatic hydrolysis showed the best overall effect. After treatment with DF-U, DF-E, DF-H, and DF-HE, the water-holding capacity was 1.31, 1.25, 1.31, and 1.38 times that of the DF-C group, respectively; the oil-holding capacity increased to 1.41–1.60 times; the water absorption and swelling capacity increased to 1.36–1.73 times; and the cation exchange capacity increased to 1.09–1.31 times, indicating that the modification treatment significantly enhanced the functional properties of the fiber. This change mainly stems from the destruction of the dense fiber structure during the modification process, forming more pores and wrinkles, increasing the specific surface area, and further exposing the hydrophilic and lipophilic groups, thereby enhancing the binding capacity of water and oil. Meanwhile, enzymatic hydrolysis and high-pressure homogenization degrade some macromolecular polysaccharides, transforming the structure from dense to loose, promoting water penetration into the fiber interior and enhancing swelling capacity. The increased cation exchange capacity is mainly related to the increased exposure of charged groups; in this experiment, the DF-H group showed slightly higher capacity than the DF-HE group, possibly due to the degradation of some acidic groups during enzymatic hydrolysis. Overall, the results of this experiment are consistent with the modification patterns of dietary fibers from various plant sources, indicating that modification treatment can effectively improve the functional properties of ginger residue dietary fiber.

[0060] Table 2 Physicochemical properties of dietary fiber

[0061] Note: Different lowercase letters in the same column's header indicate significant differences (P<0.05), the same applies below.

[0062] 2.6 Analysis of the antioxidant activity of dietary fiber: like Figure 8As shown, different modification treatments can improve the DPPH free radical scavenging ability of ginger residue dietary fiber, and the scavenging rate shows a significant dose-dependent relationship with increasing sample concentration. Within the concentration range of 0.625–10 mg / mL, the free radical scavenging ability of each treatment group gradually increased. At the highest concentration of 10 mg / mL, the DPPH free radical scavenging rate of the control group (DF-C) was approximately 65%, while the DF-U, DF-E, DF-H, and DF-HE treatments increased to approximately 68%, 82%, 80%, and 79%, respectively, representing increases of approximately 3%, 17%, 15%, and 14% compared to the DF-C group. The DF-E treatment group showed the best performance, indicating that enzymatic hydrolysis treatment has a significant advantage in enhancing antioxidant capacity.

[0063] This enhancement may be related to the enzymatic hydrolysis process breaking down the fiber structure and promoting the release of bound phenolic substances, making the antioxidant active components more likely to react with free radicals, thereby enhancing their scavenging ability.

[0064] refer to Figure 9 The ABTS radical scavenging results also showed a concentration-dependent increasing trend. At a concentration of 10 mg / mL, the scavenging rate of the DF-C group was approximately 65%, while the scavenging rates of DF-U, DF-E, DF-H, and DF-HE treatments increased to approximately 75%, 73%, 80%, and 80%, respectively, representing increases of approximately 10%, 8%, 15%, and 15% compared to the control group. Among these, the DF-H and DF-HE treatments showed the most significant effects, with scavenging abilities approaching those of the positive control VC group. The enhanced ABTS radical scavenging ability is mainly related to the refinement of the fiber structure and the formation of pore structures during the modification process. This facilitates the release of antioxidant active substances and the exposure of active groups, thereby enhancing the radical scavenging ability.

[0065] Furthermore, high-pressure homogenization reduces fiber particle size and increases specific surface area through intense shearing and cavitation, thereby further enhancing antioxidant capacity. Overall, all modification treatments can improve the antioxidant activity of ginger residue dietary fiber to varying degrees, with enzymatic hydrolysis and high-pressure homogenization showing the most significant effects. These experimental results are consistent with the modification patterns of dietary fibers from various plant sources, indicating that appropriate modification can help enhance the application potential of ginger residue dietary fiber in functional foods.

[0066] 2.7 Analysis of glucose adsorption capacity: like Figure 10As shown, the adsorption capacity of dietary fiber from ginger residue treated with different modifications for glucose was significantly improved (P<0.05), and gradually increased with the extension of adsorption time, reaching adsorption equilibrium at around 12 h. At adsorption equilibrium, the adsorption capacity of glucose by DF-U, DF-E, DF-H, and DF-HE increased from (8.37±0.18) mmol / g in the unmodified sample DF-C to (11.34±0.24) mmol / g, (11.06±0.13) mmol / g, (12.08±0.16) mmol / g, and (13.89±0.22) mmol / g, respectively, which were 1.35, 1.32, 1.44, and 1.66 times that of DF-C, respectively. Among them, the extrusion-enzymatic hydrolysis composite modification (DF-HE) showed the best effect. This may be because the modification treatment disrupts the dense structure of dietary fiber, converting some insoluble dietary fiber (IDF) into soluble dietary fiber (SDF). SDF has high viscosity and hydration capacity, and can retain glucose molecules through encapsulation and binding, thereby improving its adsorption capacity. This result is consistent with the trend of a significant increase in SDF content after modification.

[0067] 2.8 Analysis of cholesterol adsorption capacity: refer to Figure 11 Under pH conditions of 2 (simulating the gastric environment) and 7 (simulating the small intestinal environment), the adsorption capacity of unmodified ginger residue dietary fiber (DF-C) and different modified samples (DF-U, DF-E, DF-H, DF-HE) for cholesterol gradually increased with the extension of adsorption time, and tended to reach adsorption equilibrium at about 12 h, indicating that the adsorption of cholesterol by dietary fiber is a dynamic process that gradually reaches saturation. Under the same pH conditions, the cholesterol adsorption capacity of each modified sample was significantly higher than that of the unmodified sample (P<0.05). Meanwhile, the overall adsorption capacity of all samples was higher at pH 7 than at pH 2, indicating that a neutral or weakly alkaline environment is more conducive to the binding of dietary fiber and cholesterol molecules.

[0068] This may be because changes in pH affect the solubility of cholesterol and the surface charge properties of dietary fiber, thus altering its adsorption efficiency. Among different treatment methods, the extrusion-enzymatic hydrolysis composite modified sample (DF-HE) exhibited the best cholesterol adsorption capacity. At adsorption equilibrium, its adsorption capacity at pH=7 was approximately 2.70–2.75 mg / (mL·g), significantly higher than DF-H (approximately 2.55 mg / (mL·g)), DF-E (approximately 2.45 mg / (mL·g)), and DF-U (approximately 2.40 mg / (mL·g)), while the unmodified sample DF-C had the lowest, at only approximately 2.05 mg / (mL·g). A similar trend was observed at pH=2, with DF-HE exhibiting the highest adsorption capacity (approximately 2.20 mg / (mL·g)) and DF-C the lowest (approximately 1.85 mg / (mL·g)).

[0069] This difference is likely closely related to the structural changes in dietary fiber after modification. On the one hand, extrusion and enzymatic hydrolysis can disrupt the dense structure of dietary fiber, converting some insoluble dietary fiber (IDF) into soluble dietary fiber (SDF), increasing the number of polar groups, and thus enhancing its interaction with cholesterol molecules. On the other hand, modification also creates more pores and wrinkles on the surface of the dietary fiber, increasing the specific surface area and providing more adsorption sites, thereby improving the physical adsorption capacity of cholesterol. Therefore, the combined modification treatment, through the synergistic effect of structural reconstruction and exposure of active groups, enables ginger residue dietary fiber to exhibit superior cholesterol adsorption performance.

[0070] III. Conclusion: The above experiments analyzed the effects of ultrasonic disruption, enzymatic hydrolysis, high-pressure homogenization, and a combined homogenization-enzymatic hydrolysis treatment on the structure and functional properties of ginger residue dietary fiber. The results showed that each modification method could improve the fiber structure to varying degrees, converting some insoluble dietary fiber into soluble dietary fiber, thereby increasing the SDF content.

[0071] Scanning electron microscopy showed that the modified sample changed from its original dense and flat structure to a loose, porous and wrinkled structure, with a significant increase in specific surface area. Meanwhile, XRD and FTIR results further indicated that although the treatment did not change the basic polysaccharide skeleton of dietary fiber, it destroyed some crystalline regions, increased the degree of amorphization of the structure, thereby improving the binding capacity of water and oil and the degree of exposure of active groups.

[0072] Physicochemical property analysis showed that the water-holding capacity, oil-holding capacity, swelling capacity, and cation exchange capacity of all treatment groups were significantly improved, with the composite treatment showing the most significant improvement, exhibiting increased water-holding capacity, oil-holding capacity, and swelling capacity compared to the control group. Antioxidant experiments indicated that different modification methods could enhance free radical scavenging ability, suggesting that structural fragmentation facilitates the release of antioxidant active components.

[0073] In terms of functional adsorption characteristics, all treatments can improve the adsorption capacity of glucose and cholesterol. High-pressure homogenization treatment has a slight advantage in glucose adsorption, while the composite treatment shows a more balanced performance in terms of overall adsorption stability and comprehensive functional improvement.

[0074] Considering the overall improvement in structure and the performance of various functional indicators, high-pressure homogenization combined with enzymatic hydrolysis modification (DF-HE) was the best treatment method in this experiment.

[0075] Therefore, this preparation method, through the synergistic effect of mechanical crushing and enzymatic hydrolysis, fully loosens the fiber structure and forms a porous network structure, thus exhibiting advantages in water retention, oil retention, swelling performance and functional adsorption.

[0076] 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 its spirit or essential characteristics. 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, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing composite modified ginger residue dietary fiber, characterized in that, Includes the following steps: S1: First, take the ginger residue byproduct after supercritical CO2 extraction of ginger essential oil, dry it in a drying oven to constant weight, then crush the dried sample and sieve it to obtain ginger residue dietary fiber powder with uniform particle size. S2: The ginger residue dietary fiber powder is mixed and dispersed with citric acid-sodium citrate buffer solution to obtain a mixed slurry. The mixed slurry is then subjected to high-pressure homogenization and the process is repeated n times. S3: Add a compound enzyme preparation to the slurry after high-pressure homogenization to carry out enzymatic hydrolysis. The compound enzyme preparation is composed of cellulase and xylanase. Enzymatic hydrolysis is carried out by constant temperature oscillation. S4: After the enzymatic hydrolysis reaction is completed, the enzyme is inactivated by high temperature. Then the product is dried in a drying oven to constant weight and pulverized through an 80-mesh sieve to obtain the modified ginger residue dietary fiber product.

2. The method for preparing composite modified ginger residue dietary fiber according to claim 1, characterized in that, In step S1, the sieve used for sieving is 70-100 mesh, and the ginger residue dietary fiber powder is a byproduct obtained by supercritical CO2 extraction of fresh ginger after washing, slicing, and low-temperature drying, under conditions of 25-30 MPa and 40-45℃.

3. The method for preparing composite modified ginger residue dietary fiber according to claim 1, characterized in that, In step S1, the drying oven is used for forced-air drying at 45°C until the moisture content of the raw material is below 8%. In step S4, the drying oven is used for forced-air drying at 50°C until the moisture content of the raw material is below 8%.

4. The method for preparing composite modified ginger residue dietary fiber according to claim 1, characterized in that, In step S2, the pH value of the citric acid-sodium citrate buffer solution is 4.5-5.5, and the ratio of ginger residue dietary fiber powder to citric acid-sodium citrate buffer solution is 1:20g / mL.

5. The method for preparing composite modified ginger residue dietary fiber according to claim 1, characterized in that, In step S2, the pressure of the high-pressure homogenization process is 60 MPa, and the number of cycles n ≥ 3.

6. The method for preparing composite modified ginger residue dietary fiber according to claim 1, characterized in that, In step S3, the cellulase activity is ≥1.5×10⁻⁶. 4 U / g, the enzyme activity of the xylanase is ≥1.6×10⁻⁶. 5 U / g.

7. The method for preparing composite modified ginger residue dietary fiber according to claim 1, characterized in that, In step S3, the oscillation speed of the enzymatic hydrolysis process is 150-200 r / min, the compound enzyme preparation is made of cellulase and xylanase in a mass ratio of 2:1, and the amount of compound enzyme preparation added is 0.4% of the mass of the slurry after high-pressure homogenization.

8. The method for preparing composite modified ginger residue dietary fiber according to claim 1, characterized in that, In step S3, the isothermal oscillation temperature is 50°C, and the enzymatic hydrolysis time is 120 min.

9. The method for preparing composite modified ginger residue dietary fiber according to claim 1, characterized in that, In step S4, the temperature for high-temperature enzyme inactivation is 100°C, and the high-temperature enzyme inactivation time is 10 min.

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