Method for strengthening lignified bamboo shoot soluble dietary fiber by microwave-assisted compound enzyme

Abstract

The invention discloses a method for strengthening lignified bamboo shoot soluble dietary fibers by microwave-assisted compound enzyme, and belongs to the technical field of resource utilization. The method specifically comprises the following steps: firstly, preferentially attacking phenolic hydroxyl groups and methoxyl groups in lignin molecules by utilizing the specific oxidative degradation capability of laccase, destroying covalent cross-linking such as phenyl glycosidic bonds and gamma-ester bonds between LCC structures, and gradually disintegrating a three-dimensional network wrapping structure; on the basis, microwave assistance with proper power is introduced, on one hand, high-frequency vibration of water molecules is accelerated, and expansion of pores in the fibers and the substrate diffusion rate are promoted; on the other hand, the appropriate microwave intensity can adjust the enzyme molecule conformation, and more active catalytic sites are exposed, so that the efficiency of the enzyme is better exerted. The method disclosed by the invention not only greatly improves the yield of the soluble dietary fibers, but also improves the physicochemical and functional activities of the raw materials and the soluble dietary fibers.

Description

Technical Field

[0001] This invention relates to a method for microwave-assisted compound enzyme-enhanced soluble dietary fiber in lignified bamboo shoots, belonging to the field of resource utilization technology. Background Technology

[0002] Dietary fiber can be divided into soluble and insoluble dietary fiber based on its solubility. Soluble dietary fiber is a core functional component for maintaining human health due to its mechanisms of regulating gut microbiota, improving metabolic syndrome (such as obesity, diabetes, and cardiovascular disease), and reducing the risk of colorectal cancer. However, in natural dietary fiber, soluble dietary fiber typically accounts for only 5-15% of total dietary fiber, while insoluble dietary fiber (IDF) dominates, accounting for 75-90%. An excessively high proportion of insoluble dietary fiber not only negatively impacts the color, texture, and aftertaste of products but also limits the physiological functions and processing adaptability that dietary fiber itself should possess. Therefore, the imbalance in the ratio of the two has become a key bottleneck restricting the functional application of dietary fiber.

[0003] Bamboo shoots are highly seasonal, and some shoots, if not harvested in time, undergo natural aging, causing their bases to lignify and even rot immediately. Furthermore, bamboo shoots exhibit vigorous post-harvest physiological activity; even if left at room temperature for more than 48 hours after harvesting, lignin can rapidly synthesize, resulting in highly lignified bamboo shoots that lose their edible value and are discarded, leading to a serious waste of resources. As a typical source of dietary fiber, the degree of lignification in bamboo shoots directly affects the characteristics of their fiber components. Highly lignified bamboo shoots directly result in a higher proportion of insoluble dietary fiber and a more complex structure, making them difficult to degrade using conventional technologies.

[0004] Lignocellulose is a key component of the insoluble dietary fiber in highly lignified bamboo shoots. Its core structure consists of cellulose microfibrils as a rigid framework, hemicellulose as a filling and connecting matrix, and a three-dimensional network shell formed by lignin tightly cross-linking the former two through covalent bonds (such as phenyl glycosidic bonds and γ-ester bonds), forming a highly complex lignin-carbohydrate complex (LCC). This structure not only encapsulates potential soluble polysaccharides within the cell wall, hindering the natural release of soluble dietary fiber, but also, due to the hydrophobic shell and strong chemical stability of lignin, significantly inhibits the penetration and targeting of modifying agents / methods, especially by causing non-productive adsorption of enzyme molecules, thus inactivating enzymes. Therefore, by disrupting the three-dimensional network structure of lignin and breaking down the dense encapsulation of the LCC complex, it is hoped that high-purity soluble dietary fiber can be efficiently extracted from highly lignified bamboo shoots, transforming it from a difficult-to-use waste into a resource with both edible and industrial value.

[0005] Although research on dietary fiber extraction technology has gradually increased in recent years, for example: The literature (Wu Hongyi. Extraction and Characterization of Soluble Dietary Fiber from Bamboo Shoots and Its Application in Beverages [D]. Chongqing Three Gorges University, 2024.) discloses the extraction of soluble dietary fiber from bamboo shoots using ultrasound-microwave, ultrasound-enzyme, microwave-enzyme, and ultrasound-microwave-enzyme treatments. The ultrasound-microwave-enzyme treatment showed the best results, with a soluble dietary fiber yield of 11.12%. Patent CN117502658A (A method for extracting dietary fiber from bamboo shoot processing by-products) involves high-pressure homogenization, followed by enzymatic hydrolysis with type I complex enzymes, and finally enzymatic hydrolysis with type II complex enzymes; its highest yield of soluble dietary fiber is 24.3%.

[0006] However, these two published technologies mainly target tender bamboo shoots / shoot tips, which differ significantly from the dietary fiber composition of highly lignified bamboo shoots. Tender bamboo shoots have a loose fiber structure and extremely low lignocellulose content, making them easily damaged and degraded by conventional methods. The effectiveness of most existing technologies in treating lignified bamboo shoots is limited, indicating that LCC degradation remains the primary issue for the targeted conversion of soluble dietary fiber in lignified bamboo shoots. Furthermore, regarding the yield of soluble dietary fiber, neither technology specifies the soluble dietary fiber content of the original shoot tip, making it difficult to demonstrate an improvement in soluble dietary fiber yield. Moreover, the soluble dietary fiber yield is limited, only 11.12% and 24.3% respectively. Technically, the ultrasound / microwave methods used are physical pretreatments and do not effectively combine with enzymatic hydrolysis. In terms of functional activity, the cholesterol adsorption capacity of soluble dietary fiber is only 0.45 mg / g, indicating a weak potential for lowering blood lipids.

[0007] The aforementioned problems collectively restrict the efficient development and application of dietary fiber. Therefore, it is necessary to find an innovative technology to modify highly lignified bamboo shoots with low cost, high quality, and high soluble dietary fiber yield. Summary of the Invention

[0008] [Technical Issues] This invention aims to solve the core technical bottleneck in the field of highly lignified bamboo shoots / lignin-containing plant-derived dietary fiber modification, specifically including: How to efficiently disrupt the lignin-carbohydrate complex (LCC) structure of lignocellulose in the skeleton of insoluble dietary fiber and overcome its physicochemical barrier to soluble dietary fiber. How to improve the penetration efficiency of enzymatic hydrolysis reagents into the fiber interior based on the partial deconstruction of LCC structure, so as to achieve targeted degradation of cellulose and hemicellulose and a significant increase in soluble dietary fiber content; How to avoid side reactions such as polysaccharide conformation destruction caused by traditional methods such as strong acids / bases and high temperatures during the solubilization process, and preserve the natural functional activity of dietary fiber; And how to achieve soluble dietary fiber solubilization for highly lignified bamboo shoot raw materials.

[0009] [Technical Solution] To address the aforementioned problems, this invention provides a method for increasing the soluble dietary fiber content of highly lignified bamboo shoot raw materials through microwave-assisted complex enzyme treatment. Specifically, firstly, this invention utilizes the specific oxidative degradation ability of laccase to preferentially attack the phenolic hydroxyl and methoxy groups in lignin molecules, disrupting covalent cross-linking such as phenyl glycosidic bonds and γ-ester bonds between LCC structures, gradually disintegrating its three-dimensional network encapsulation structure. Furthermore, since cellulose and hemicellulose are the components with the highest content of insoluble dietary fiber in bamboo shoots, the addition of cellulase can directionally degrade cellulose, while its weak xylanase activity can also non-specifically degrade hemicellulose. Therefore, laccase can remove the hydrophobic shielding of lignin against external reagents, exposing the embedded cellulose and hemicellulose molecular chains, creating conditions for effective contact between cellulase and the substrate. Building upon this foundation, the introduction of microwave assistance with appropriate power accelerates the high-frequency vibration of water molecules, promoting the expansion of pores within the fiber and increasing substrate diffusion rates. Furthermore, appropriate microwave intensity adjusts the enzyme molecular conformation, exposing more active catalytic sites and thus maximizing enzyme efficiency. Simultaneously, it promotes the release of more embedded soluble dietary fiber (such as some hemicellulose and pectin). By employing a microwave-composite enzyme approach, through laccase pretreatment to break down the LCC barrier, cellulase for precise decomposition of polysaccharides, and microwave-assisted enhancement of mass transfer and catalysis, this invention not only significantly improves the yield of soluble dietary fiber but also enhances the physicochemical and functional activities of both the raw materials and the soluble dietary fiber.

[0010] The first objective of this invention is to provide a method for preparing bamboo shoot powder after microwave-enzyme combined treatment, comprising the following steps: The highly lignified bamboo shoot raw material powder was thoroughly mixed with phosphate buffer solution, laccase solution and cellulase solution were added, and the mixture was placed in a microwave. The enzymatic hydrolysis was carried out at a microwave power density of 5-7 W / g, 200-300 W, and 55℃ for 25-35 min, with an effective microwave working time of 4-6 min, to obtain a mixed solution of bamboo shoot powder treated by microwave-complex enzyme. The bamboo shoot powder mixture after microwave-enzyme combined treatment was freeze-dried to obtain the treated bamboo shoot powder.

[0011] In one embodiment of the present invention, microwave temperature-controlled enzymatic hydrolysis involves microwave-controlled enzymatic hydrolysis temperature, which is an intermittent operation. After the microwave operating temperature is set to 55 ℃, the microwave stops working when the temperature is raised to 57-58 ℃. The microwave restarts when the temperature naturally drops to 53-54 ℃, and this cycle continues.

[0012] In one embodiment of the present invention, the method for preparing highly lignified bamboo shoot raw material powder is as follows: After peeling, washing, slicing, blanching, cooling, hot air drying, pulverizing and sieving the highly lignified bamboo shoot raw material, a powder of highly lignified bamboo shoot raw material is obtained. Among them, highly lignified bamboo shoot raw materials include bamboo shoots that have not been harvested for a long time after sprouting and have aged naturally, bamboo shoots that have been left at room temperature for more than 48 hours and have lignified / rotten bases; the long time is more than 20 days. The slice thickness should be maintained at 2-3 mm; Blanching is rinsing in boiling water; the rinsing time is 10-15 minutes. Drying is done by hot air drying at 30-50℃ for 6-8 hours; The sieving process involves passing the material through a 40-mesh sieve.

[0013] In one embodiment of the present invention, the pH of the phosphate buffer solution is 5.0-5.5; it is prepared by dissolving dipotassium hydrogen phosphate and potassium dihydrogen phosphate in water.

[0014] In one embodiment of the present invention, the ratio of highly lignified bamboo shoot raw material powder to phosphate buffer is 1 g: (40-50) mL.

[0015] In one embodiment of the present invention, the mass-to-volume ratio of highly lignified bamboo shoot raw material powder to laccase solution is 1 g: 40~60 μL; the mass-to-volume ratio of highly lignified bamboo shoot raw material powder to cellulase solution is 1 g: 80~120 μL; and the volume ratio of laccase solution to cellulase solution is 1:2.

[0016] In one embodiment of the present invention, the laccase solution is obtained by dissolving laccase in the above-prepared phosphate buffer solution, with a concentration of 1% (w / v, g / 100mL); the cellulase solution is obtained by dissolving cellulase in the above-prepared phosphate buffer solution, with a concentration of 2% (w / v, g / 100mL).

[0017] In one embodiment of the present invention, the enzyme activity of laccase solution is 120 U / mL; the enzyme activity of cellulase is 1000 U / mL.

[0018] In one embodiment of the present invention, the drying is freeze drying, and the freeze drying time is 30-50 h.

[0019] The second objective of this invention is to prepare bamboo shoot powder treated with microwave and compound enzymes using the method described herein.

[0020] A third objective of this invention is to provide a method for extracting soluble dietary fiber from highly lignified bamboo shoot raw materials based on microwaves and complex enzymes, comprising the following steps: (1) Mix the highly lignified bamboo shoot raw material powder with phosphate buffer solution, add laccase solution and cellulase solution, and place it in a microwave oven. The microwave temperature is controlled at 5-7 W / g, 200-300 W, and 55-60℃ for 25-35 min. The effective working time of the microwave is 4-6 min, and a mixture of bamboo shoot powder treated with microwave and compound enzyme is obtained. (2) Adjust the pH of the mixture of bamboo shoot powder treated with microwave and compound enzyme, add heat-stable α-amylase, amyloglucosidase and papain for enzymatic hydrolysis to remove impurities, centrifuge to obtain supernatant; (3) The supernatant was precipitated with alcohol, filtered, and dried to obtain soluble dietary fiber.

[0021] In one embodiment of the present invention, the preparation method of the highly lignified bamboo shoot raw material powder in step (1) is as follows: After peeling, the highly lignified bamboo shoot raw material is washed, sliced, blanched, cooled, dried, crushed and sieved to obtain highly lignified bamboo shoot raw material powder. Among them, highly lignified bamboo shoot raw materials include bamboo shoots that have not been harvested for a long time after sprouting and have aged naturally, bamboo shoots that have been left at room temperature for more than 48 hours and have lignified / rotten bases; the long time is more than 20 days. The slice thickness should be maintained at 2-3 mm; Blanching is rinsing in boiling water; the rinsing time is 10-15 minutes. Drying is done by hot air drying at 30-50℃ for 6-8 hours; The sieving process involves passing the material through a 40-mesh sieve.

[0022] In one embodiment of the present invention, microwave temperature-controlled enzymatic hydrolysis in step (1) is an intermittent operation where the microwave controls the enzymatic hydrolysis temperature. After the microwave operating temperature is set to 55 ℃, the microwave stops working when the temperature is raised to 57-58 ℃. The microwave restarts when the temperature naturally drops to 53-54 ℃, and this cycle continues.

[0023] In one embodiment of the present invention, the pH of the phosphate buffer solution in step (1) is 5.0-5.5; it is prepared by dissolving disodium hydrogen phosphate and sodium dihydrogen phosphate in water.

[0024] In one embodiment of the present invention, the ratio of highly lignified bamboo shoot raw material powder to phosphate buffer in step (1) is 1 g: (40-50) mL.

[0025] In one embodiment of the present invention, in step (1), the mass-to-volume ratio of highly lignified bamboo shoot raw material powder to laccase solution is 1 g: 40~60 μL; the mass-to-volume ratio of highly lignified bamboo shoot raw material powder to cellulase solution is 1 g: 90~110 μL; and the volume ratio of laccase solution to cellulase solution is 1:2.

[0026] In one embodiment of the present invention, in step (1), the laccase solution is obtained by dissolving laccase in the above-prepared phosphate buffer solution, with a concentration of 1% (w / v, g / 100mL); the cellulase solution is obtained by dissolving cellulase in the above-prepared phosphate buffer solution, with a concentration of 2% (w / v, g / 100mL).

[0027] In one embodiment of the present invention, the enzyme activity of laccase in step (1) is 120 U / mL; the enzyme activity of cellulase is 1000 U / mL.

[0028] In one embodiment of the present invention, adjusting the pH in step (2) means adjusting the pH to 6-6.5.

[0029] In one embodiment of the present invention, in step (2), heat-stable α-amylase, amyloglucosidase, and papain are added for enzymatic hydrolysis to remove impurities. Specifically: First, add heat-stable α-amylase solution and hydrolyze in a water bath at 90-95 ℃ for 30-60 min, then cool; then add amyloglucosidase solution and hydrolyze in a water bath at 60-65 ℃ for 30-60 min, then cool; then add papain solution and hydrolyze in a water bath at 60-65 ℃ for 30-60 min. The mass-to-volume ratio of highly lignified bamboo shoot raw material powder to heat-stable α-amylase solution was 1 g: 40~60 μL. The mass-to-volume ratio of highly lignified bamboo shoot raw material powder to starch glucoside enzyme solution was 1 g: 90-110 μL. The mass-to-volume ratio of highly lignified bamboo shoot raw material powder to papain solution was 1 g: 90-110 μL; Cooling is achieved by cooling to 60°C; The heat-stable α-amylase solution is commercially available, with an enzyme activity of 14,000 U / mL; The amylase solution is commercially available, and its enzyme activity is 3260 U / mL; Papain solution was obtained by dissolving papain in the above-prepared phosphate buffer solution at a concentration of 2% (w / v, g / 100mL); the enzyme activity of papain was 16000 U / mL.

[0030] In one embodiment of the present invention, the centrifugation in step (2) is performed at room temperature (20-30℃) and 5000-10000 r / min for 5-15 min.

[0031] In one embodiment of the present invention, in step (3), alcohol precipitation is carried out by adding 3-5 times the volume of an aqueous ethanol solution with a volume fraction of 95%; the alcohol precipitation temperature is 3-5 °C and the time is 8-24 h.

[0032] The fourth objective of this invention is to prepare soluble dietary fiber using the method described in this invention.

[0033] The fifth objective of this invention is the application of the bamboo shoot powder or soluble dietary fiber treated with microwave and compound enzymes as described in this invention in the preparation of food or pharmaceuticals.

[0034] In one embodiment of the present invention, the food includes food additives (thickeners and stabilizers), dairy products, etc.

[0035] In one embodiment of the present invention, the pharmaceutical product includes drugs for preparing drug carriers, hypoglycemic drugs, cholesterol drugs, enteritis drugs, etc.

[0036] The sixth objective of this invention is to provide a method for improving the solubility, water-holding capacity, and oil-holding capacity of bamboo shoot powder, comprising the following steps: The highly lignified bamboo shoot raw material powder was thoroughly mixed with phosphate buffer solution, laccase solution and cellulase solution were added, and the mixture was placed in a microwave oven. The enzymatic hydrolysis was carried out at a microwave power density of 5-7 W / g, 200-300 W, and 55-60 ℃ for 25-35 min, with an effective microwave working time of 4-6 min, to obtain a mixture of bamboo shoot powder treated with microwave and compound enzyme. The mixture of microwave-treated and enzyme-treated bamboo shoot powder was dried to obtain microwave-treated and enzyme-treated bamboo shoot powder.

[0037] The seventh objective of this invention is to provide a method for enhancing the antioxidant, hypoglycemic, and hypolipidemic functional activities of soluble dietary fiber, comprising the following steps: (1) Mix the highly lignified bamboo shoot raw material powder with phosphate buffer solution, add laccase solution and cellulase solution, and place it in a microwave oven. The microwave temperature is controlled at 5-7 W / g, 200-300 W, 55-60 ℃ for 25-35 min, and the effective working time of the microwave is 4-6 min to obtain a mixture of bamboo shoot powder treated with microwave and compound enzyme. (2) Adjust the pH of the mixture of bamboo shoot powder treated with microwave and compound enzyme, add heat-stable α-amylase, amyloglucosidase and papain for enzymatic hydrolysis to remove impurities, centrifuge to obtain supernatant; (3) The supernatant was precipitated with alcohol, filtered, and dried to obtain soluble dietary fiber.

[0038] [Beneficial Effects] 1. This invention utilizes laccase to specifically degrade lignin, effectively disrupting the three-dimensional network structure of LCC, releasing its physical encapsulation of cellulose and hemicellulose, and releasing some soluble dietary fiber and soluble substances. Simultaneously, the degradation of lignin avoids non-productive adsorption of cellulase by lignin, thereby maximizing the activity of cellulase and degrading cellulose and hemicellulose in insoluble dietary fiber. Furthermore, the combined effect of microwaves in this invention not only reduces the amount of laccase and cellulase required but also shortens the time required for enzymatic hydrolysis, significantly reducing production costs.

[0039] 2. This invention significantly improves the proportion of soluble dietary fiber in bamboo shoot powder by microwave-assisted laccase-cellulase treatment. This method increases the soluble dietary fiber content in bamboo shoot powder from the original 9.8% to over 35%, and also improves the physicochemical properties of bamboo shoot powder, such as solubility, water-holding capacity, and oil-holding capacity, thus making the bamboo shoot powder more readily utilized.

[0040] 3. This invention achieves the efficient preparation and utilization of dietary fiber from bamboo shoots. Since the lipid-lowering and blood sugar-lowering functional activities of bamboo shoot powder are mainly provided by its soluble dietary fiber, this invention extracts the soluble dietary fiber from bamboo shoot powder by treating it with microwaves combined with laccase-cellulase. The results show that the antioxidant, blood sugar-lowering, and blood lipid-lowering functional activities of the treated soluble dietary fiber are greatly improved.

[0041] 4. The microwave-assisted laccase-cellulase treatment technology provided by this invention significantly improves the resource utilization efficiency of lignified bamboo shoots and bamboo shoot waste. Addressing the waste such as aged bamboo shoots and bamboo shoot shells generated in traditional bamboo shoot processing, this invention achieves the reconstruction of the lignocellulose structure through the synergistic effect of lignin-directed degradation and efficient cellulose dissociation, transforming previously unusable lignified tissue into high-value-added products. Attached Figure Description

[0042] Figure 1 This is a comparison chart of the physicochemical properties (solubility, water holding capacity, oil holding capacity) of bamboo shoot powder obtained in Example 1 and Comparative Examples 1-5.

[0043] Figure 2 The images show the FTIR spectra of soluble dietary fiber obtained in Examples 2, 6-7, and 10-12.

[0044] Figure 3 X-ray diffraction patterns of soluble dietary fiber obtained in Example 2, Comparative Examples 6-7, and Comparative Examples 10-12.

[0045] Figure 4 The DPPH scavenging rates of soluble dietary fiber obtained in Example 2, Comparative Examples 6-7, and Comparative Examples 10-12 are shown.

[0046] Figure 5 The ABTS clearance rate of soluble dietary fiber obtained in Example 2, Comparative Examples 6-7, and Comparative Examples 10-12 is shown.

[0047] Figure 6 This is a comparison chart of the lipid-lowering function of soluble dietary fiber obtained in Example 2, Comparative Examples 6-7, and Comparative Examples 10-12.

[0048] Figure 7 This is a comparison chart showing the lipid-lowering function of soluble dietary fiber obtained from Examples 2, 6-7, and 10-12 at pH=2 and pH=7. Detailed Implementation

[0049] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0050] Test method: 1. The soluble dietary fiber content of bamboo shoot powder was determined according to GB5009.88-2023; The yield of soluble dietary fiber was determined using formula (1): (1) In the formula: G1 is the weight of the extracted soluble dietary fiber, g; G2 is the weight of the bamboo shoot powder weighed, g.

[0051] 2. Solubility: Mix 0.5 g of bamboo shoot powder sample with 30 mL of deionized water. Dissolve the mixture by stirring in a 70 ℃ constant temperature water bath for 30 min, then centrifuge at 5000 r / min for 10 min. Freeze-dry the precipitate to obtain W2.

[0052] The formula for calculating solubility is as follows (2): (2) Wherein, W1 is the weight (g) of the original bamboo shoot powder, and W2 is the weight (g) of the precipitate after centrifugation.

[0053] 3. Water Holding Capacity (WHC): Mix 0.2 g of bamboo shoot powder sample with 20 mL of distilled water at 37 ℃ for 1 h, and centrifuge the mixture at 5000 r / min for 15 min. Remove the supernatant and weigh the wet precipitate Ww.

[0054] The WHC of bamboo shoot powder is calculated by the following formula (3): (3) 4. Oil holding capacity (OHC): Mix 0.2 g of bamboo shoot powder sample with 20 mL of sunflower seed oil at room temperature for 12 h, and centrifuge the mixture at 5000 r / min for 20 min. Remove the supernatant and weigh the wet precipitate, which is recorded as W0.

[0055] The OHC of bamboo shoot powder is calculated by the following formula (4): (4) 5. Testing of cellulose, hemicellulose, and lignin content: Neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) were determined using Van Soest's detergent fiber analysis method.

[0056] Accurately weigh 1g of sample into a cylindrical beaker, add 100mL of neutral detergent, a few drops of decahydronaphthalene, and 0.5g of anhydrous sodium sulfite. Place the beaker on a condenser on an electric furnace and boil for 10 minutes, maintaining a gentle boil for 60 minutes. After boiling, remove the beaker and pour the solution into a pre-weighed glass crucible mounted on a suction flask for filtration. Transfer all residue from the beaker to the crucible and rinse with boiling water until the filtrate is neutral. Place the residue in a 105℃ oven for 2 hours, then cool in a desiccator for 30 minutes and weigh until constant weight is achieved. The residue is NDF.

[0057] Place NDF in a cylindrical beaker, add 100 mL of acidic detergent and a few drops of decahydronaphthalene, and filter while hot using a glass crucible of known weight. Rinse the glass crucible and residue repeatedly with boiling water until the filtrate is neutral. Place the glass crucible in an oven at 105°C for 2 hours, then cool it in a desiccator for 30 minutes and weigh it until a constant weight is reached. The residue is ADF.

[0058] Add a 72% sulfuric acid aqueous solution to ADF, digest at 20°C for 3 hours, filter, and rinse until neutral. The dissolved portion during digestion is cellulose, while the undissolved residue consists of acid-washed lignin and acid-insoluble ash. The content of ADL and acid-insoluble ash can be obtained by drying and calcining the residue.

[0059] The formulas for calculating cellulose content, hemicellulose content, and acid-washed lignin content are as follows: Cellulose content (%) = ADF (%) - Residue after sulfuric acid treatment (%) (5) Hemicellulose content (%) = NDF (%) - ADF (%) (6) Acid-washed lignin content (ADL) = Residue after sulfuric acid treatment (%) - Ash content (%) (7) 6. Fourier transform infrared spectroscopy test: The dried sample was mixed with KBr at a ratio of 2:100 (w / w) and ground thoroughly, then compressed into a transparent sheet for spectral analysis.

[0060] The infrared spectra of soluble dietary fiber were obtained using an IS50 FTIR spectrometer (Thermo Fisher Scientific, USA). The spectral scanning range was 400–4000 cm⁻¹. -1 The resolution is 1 cm. -1 .

[0061] 7. X-ray diffraction pattern testing: The crystal structure of soluble dietary fiber was examined using a Bruker D8 ADVANCE X-ray diffractometer (Germany). Instrument settings included a voltage of 40 kV and an incident current of 40 mA. Scans were performed at a rate of 5° / min between 10° and 80°. Peak areas were analyzed and the crystallinity of the samples was determined using an Origin 2024.

[0062] 8. DPPH free radical scavenging ability test: Prepare soluble dietary fiber solutions with concentration gradients of 0.5 mg / mL, 1.0 mg / mL, 1.5 mg / mL, 2 mg / mL, and 2.5 mg / mL. Mix 1 mL of the soluble dietary fiber solution with 3 mL of 0.15 mmol / L DPPH working solution, and denote this mixture as sample mixture A. s Mix 1 mL of distilled water with 3 mL of 0.15 mmol / L DPPH working solution, and denote this mixture as blank mixture A. b 1 mL of soluble dietary fiber was mixed with 3 mL of anhydrous ethanol and labeled as control mixture A. c The three substances were reacted at room temperature in the dark for 30 min, and the absorbance was measured at 517 nm after zeroing with anhydrous ethanol.

[0063] The DPPH free radical scavenging capacity of different soluble dietary fibers is calculated using the following formula: (8) 9. ABTS free radical scavenging ability: Prepare soluble dietary fiber solutions with concentration gradients of 0.5 mg / mL, 1.0 mg / mL, 1.5 mg / mL, 2 mg / mL, and 2.5 mg / mL. Add 200 mg of ABTS and 34.4 mg of potassium persulfate to 50 mL of distilled water, mix thoroughly, and react at room temperature in the dark for 18 h. Then, dilute to an appropriate concentration (OD734 = 0.70 ± 0.02) to prepare the working solution. Mix 0.4 mL of the soluble dietary fiber solution thoroughly with 3.6 mL of the ABTS working solution; this mixture is designated as sample mixture A. s Mix 0.4 mL of distilled water with 3.6 mL of ABTS working solution thoroughly to form A. b The two were reacted at room temperature in the dark for 5 min, and the absorbance of the blank mixture was measured at 734 nm after zeroing.

[0064] The ABTS free radical scavenging capacity of different soluble dietary fibers is calculated using the following formula: (9) 10. Bile salt adsorption capacity test: 0.1 g of soluble dietary fiber, 10 mL of 0.15 mol / L NaCl solution (pH=7.0), and 40 mg of sodium cholate were mixed thoroughly. The mixture was then reacted in a 37°C water bath for 3 h, followed by centrifugation at 8000 r / min for 10 min. 1 mL of the supernatant was collected, and 6 mL of 45% (v / v) sulfuric acid solution and 1 mL of 0.3% (v / v) furfural solution were added and mixed thoroughly. The mixture was then reacted in a 65°C water bath for 30 min, cooled to room temperature, and the absorbance was measured at 620 nm.

[0065] The SCAC of different soluble dietary fibers is calculated using the following formula: (10) Where N1 is the cholesterol content (mg) in the blank solution, N2 is the cholesterol content (mg) in the supernatant after adsorption, and M is the mass (g) of soluble dietary fiber.

[0066] 11. Cholesterol adsorption capacity: Whisk fresh egg yolks thoroughly with 9 times the volume of deionized water to form an emulsion. Then, mix 0.1 g of soluble dietary fiber with 10 mL of the emulsion. Adjust the pH of the emulsion to 7 with 0.1 mol / L NaOH (adjust the pH to 2 with 0.1 mol / L HCl) and react in a water bath at 37°C for 2 h. Then, centrifuge the mixture at 10000 r / min for 10 min, and collect 0.04 mL of the supernatant. Determine the cholesterol content at 550 nm using the phthalaldehyde method.

[0067] (11) Where N1 is the cholesterol content (mg) in the blank solution, N2 is the cholesterol content (mg) in the supernatant after adsorption, and M is the mass (g) of soluble dietary fiber.

[0068] Raw materials used in the examples: Highly lignified bamboo shoots: bamboo shoots that have naturally aged 25 days after sprouting without being harvested. The activity of the heat-stable α-amylase solution was 14000 U / mL; The enzyme activity of the amyloglucosidase solution was 3260 U / mL; The enzyme activity of papain is 16000 U / mL; The enzyme activity of laccase is 120 U / mL; The cellulase activity is 1000 U / mL; The pH of the phosphate buffer solution is 5.0; it is prepared by dissolving dipotassium hydrogen phosphate and potassium dihydrogen phosphate in water.

[0069] The laccase solution was obtained by dissolving laccase in the phosphate buffer solution prepared above, with a concentration of 1% (w / v, g / 100mL). The cellulase solution was obtained by dissolving cellulase in the phosphate buffer solution prepared above, with a concentration of 2% (w / v, g / 100mL). Papain solution is obtained by dissolving papain in the above-prepared phosphate buffer solution at a concentration of 2% (w / v, g / 100mL).

[0070] Example 1 A method for preparing bamboo shoot powder after microwave-enzyme combined treatment includes the following steps: (1) After peeling the highly lignified bamboo shoots, rinse the surface residue with running water and cut them into uniform thin slices with a thickness of 2-3 mm; then boil them in boiling water for 10 min, cool them and place them in an oven at 40℃ for 8 h; after drying, crush them with a multi-functional pulverizer and pass the powder through a 40-mesh sieve to obtain highly lignified bamboo shoot raw material powder. (2) Mix 1 g of highly lignified bamboo shoot raw material powder with 50 mL of phosphate buffer (pH=5) thoroughly, add 50 μL of laccase solution and 100 μL of cellulase solution, and place in a microwave at 250 W and 55 °C for 30 min (the effective working time of the microwave is 5 min) to obtain a mixture of bamboo shoot powder treated with microwave and compound enzyme. (3) The mixture of microwave-treated and compound enzyme-treated bamboo shoot powder was freeze-dried for 48 h to obtain microwave-treated and compound enzyme-treated bamboo shoot powder.

[0071] Comparative Example 1: Untreated bamboo shoot powder The highly lignified bamboo shoot raw material powder prepared in step (1) of Example 1 was directly used.

[0072] Compare with Example 2 (microwave only) Omit the laccase solution and cellulase solution in step (2) of Example 1, and keep everything else the same as in Example 1 to obtain bamboo shoot powder.

[0073] Control Example 3: Enzymatic hydrolysis only Microwave treatment in step (2) of Example 1 was omitted. After adding the compound enzyme, the mixture was heated in a water bath at 55°C for 30 min for enzymatic hydrolysis. Everything else was the same as in Example 1 to obtain bamboo shoot powder.

[0074] Comparative Example 4: Microwave-assisted laccase (cellulase omitted) Omit the cellulase in step (2) of Example 1, and keep everything else the same as in Example 1 to obtain bamboo shoot powder.

[0075] Comparative Example 5: Microwave-assisted cellulase (laccase omitted) Omit the laccase in step (2) of Example 1, and keep everything else the same as in Example 1 to obtain bamboo shoot powder.

[0076] The powders obtained in Example 1 and Comparative Examples 1-5 were subjected to performance tests, and the test results are as follows: The solubility of bamboo shoot powder is a core indicator for evaluating its digestibility and absorption performance. Higher solubility indicates a higher degree of exposure of hydrophilic groups (such as hydroxyl and carboxyl groups) in the powder, more complete molecular chain breakage of insoluble dietary fiber, and easier decomposition and utilization by intestinal enzymes. Bamboo shoot powder has good water-holding and oil-holding capacity, which can effectively improve the texture and taste of products. Therefore, the physicochemical properties of bamboo shoot powder are not only related to processing quality, but also closely related to its functional activities (such as the ability to lower blood sugar and blood lipids). Figure 1 This is a comparison graph showing the physicochemical properties (solubility, water-holding capacity, oil-holding capacity) of the bamboo shoot powders obtained in Example 1 and Comparative Examples 1-5. From... Figure 1 It can be seen that: (1) The solubility of untreated bamboo shoot powder in Control Example 1 was only 21.37%, which directly reflects the high proportion of insoluble dietary fiber, affecting its solubility and digestibility. The solubility of bamboo shoot powder in Control Example 2 was 38.84%; the solubility of bamboo shoot powder in Control Example 3 was 46.94%; the solubility of bamboo shoot powder in Control Example 4 was 42.12%; and the solubility of bamboo shoot powder in Control Example 5 was 40.65%.

[0077] The bamboo shoot powder in Example 1 showed the highest solubility and the most significant improvement, which confirms that laccase and cellulase, with the assistance of microwaves, can better exert their enzymatic hydrolysis efficiency, thereby effectively degrading macromolecules such as cellulose in the bamboo shoot powder and increasing the solubility of the bamboo shoot powder to 59.42%.

[0078] (2) The water-holding capacity of the untreated bamboo shoot powder in Control Example 1 was only 7.97 g / g; after microwave treatment, the water-holding capacity of Control Example 2 increased to 10.71 g / g. Further enzymatic synergistic treatment or compound enzyme treatment significantly improved the water-holding capacity of the bamboo shoot powder, with Control Example 3 having a water-holding capacity of 12.22 g / g and Example 1 having a water-holding capacity of 15.26 g / g. Comparing the data from Control Example 3 and Example 1, it can be found that the synergistic effect of microwaves can effectively improve the enzymatic hydrolysis efficiency: the combined action of laccase and cellulase can specifically degrade hydrophobic macromolecules in the bamboo shoot powder, making the powder porosity and honeycomb structure characteristics more pronounced. The water-holding capacity of Control Example 4 was 11.15 g / g; the water-holding capacity of Control Example 5 was 11.76 g / g.

[0079] (3) The bamboo shoot powder obtained in Example 1 has good oil holding capacity (9.88 g / g), which can effectively adsorb oil, delay gastric emptying, slow down the rate of fat digestion and absorption, and help regulate postprandial blood lipid levels. The oil holding capacity of Control Example 1 is 4.75 g / g; the oil holding capacity of Control Example 2 is 6.06 g / g; the oil holding capacity of Control Example 3 is 7.66 g / g; the oil holding capacity of Control Example 4 is 7.09 g / g; and the oil holding capacity of Control Example 5 is 7.14 g / g.

[0080] Table 1. Effects of different treatment methods on typical components of insoluble dietary fiber in bamboo shoots.

[0081] Note: Different lowercase superscript letters for the same indicator indicate significant differences between data. p <0.05).

[0082] Table 1 shows the test results of the main components of lignocellulose (cellulose, hemicellulose, and lignin), a typical insoluble dietary fiber in bamboo shoot powders of Example 1 and Comparative Examples 1-5. The natural three-dimensional network structure of lignocellulose (cellulose crystalline regions, lignin encapsulation) is the main barrier to enzymatic hydrolysis. As can be seen from Table 1, microwave-assisted laccase-cellulase treatment increases the proportion of amorphous cellulose regions by disrupting the hydrogen bond network and lignin-carbohydrate complex (LCC), making it easier for enzyme molecules to contact the substrate, and significantly reducing the content of cellulose and hemicellulose. Furthermore, since cellulose molecules are rich in hydroxyl groups, they can efficiently absorb water by binding with water molecules through hydrogen bonds; therefore, this treatment may indirectly improve the water-holding capacity of the powder by reducing the cellulose content.

[0083] Example 2 A method for extracting soluble dietary fiber from highly lignified bamboo shoots based on microwave-complex enzyme combination includes the following steps: (1) After peeling the highly lignified bamboo shoots, rinse the surface residue with running water and cut them into uniform thin slices with a thickness of 2-3 mm; then boil them in boiling water for 10 min, cool them and place them in an oven at 40℃ for 8 h; after drying, crush them with a multi-functional pulverizer and pass the powder through a 40-mesh sieve to obtain highly lignified bamboo shoot raw material powder. (2) Mix 1g of highly lignified bamboo shoot raw material powder with 50 mL of phosphate buffer (pH=5) thoroughly, add 50 μL of laccase solution and 100 μL of cellulase solution, and place in a microwave oven. Perform microwave enzymatic hydrolysis at 250 W and 55℃ for 30 min (the effective working time of the microwave is 5 min) with a microwave power density of 5 W / g to obtain a mixture of bamboo shoot powder treated with microwave and compound enzyme. (3) Adjust the pH of the mixture of bamboo shoot powder treated with microwave and compound enzyme to 6.0±0.2, add 50 μL of heat-stable α-amylase solution, and incubate in a water bath at 95±2℃ for 30 min; then cool to 60℃, add 100 μL of amyloglucosidase solution, and incubate in a water bath at 60±2℃ for 30 min; then cool to 60℃, add 100 μL of papain solution, and incubate in a water bath at 60±2℃ for 30 min; remove impurities such as starch and protein, centrifuge at 8000 r / min at room temperature for 10 min, and separate to obtain the supernatant; (4) Add 4 times the volume of 95% (v / v) ethanol aqueous solution to the supernatant and let it stand at 4 ℃ for 10 h to precipitate. After precipitation, filter the precipitate using a Buchner funnel and dry the precipitate in an oven at 30±5℃ for 1 h to obtain soluble dietary fiber.

[0084] Comparative Example 6: Untreated bamboo shoot powder The highly lignified bamboo shoot powder was not subjected to the microwave complex enzyme treatment in step (2) of Example 2, but was directly subjected to subsequent treatments such as step (3), while the rest remained the same as in Example 2, to obtain soluble dietary fiber.

[0085] Control Example 7: Microwave only (complex enzyme omitted) Omit the laccase solution and cellulase solution in step (2) of Example 2, and keep everything else the same as in Example 2 to obtain soluble dietary fiber.

[0086] Comparative Example 8: Microwave only, with controlled microwave temperature (complex enzyme omitted). Omit the laccase and cellulase solution in step (2) of Example 2, and microwave at 30°C for 30 min with a power of 5 W / g (where the effective working time of the microwave is 5 min), and keep the rest the same as in Example 2 to obtain soluble dietary fiber.

[0087] Comparative Example 9: Microwave only, with control of microwave power (complex enzyme omitted). Omit the laccase and cellulase solution in step (2) of Example 2, adjust the microwave power density in step (2) of Example 2 to 7 W / g, and keep everything else the same as in Example 2 to obtain soluble dietary fiber.

[0088] Comparative Example 10: Enzymatic hydrolysis only (microwave treatment omitted) Omit the microwave step (2) in Example 2, and after adding the enzyme, perform enzymatic hydrolysis in a water bath at 55°C for 30 min. Keep everything else the same as in Example 2 to obtain soluble dietary fiber.

[0089] Comparative Example 11: Microwave-assisted laccase (cellulase omitted) Omit the cellulase in step (2) of Example 2, and keep everything else the same as in Example 2 to obtain soluble dietary fiber.

[0090] Comparative Example 12: Microwave-assisted cellulase (laccase omitted) Omit the laccase in step (2) of Example 2, and keep everything else the same as in Example 2 to obtain soluble dietary fiber.

[0091] Comparative Example 13: Microwave-assisted xylanase and cellulase (with xylanase replaced by laccase in the complex enzyme). In step (2) of Example 2, laccase was changed to xylanase, while the rest remained the same as in Example 2, to obtain soluble dietary fiber.

[0092] The xylanase solution used in this control example had an activity of 3000 U / mL. The xylanase solution was obtained by dissolving xylanase in the phosphate buffer solution prepared above, with a concentration of 1% (w / v, g / 100mL).

[0093] Compare with Example 14: Investigation of the effects of probe-type ultrasound (with a change in physical field processing method) Replace the microwave complex enzyme in step (2) of Example 2 with probe-only ultrasonic treatment, using 300 W and 30℃, with a total duration of 10 min, working parameters of 2 s on and 2 s off, and an effective working time of 5 min. Other parameters are the same as in Example 2 to obtain soluble dietary fiber.

[0094] Compare with Example 15: Probe-based ultrasound combined with microwave (two physical methods used in combination) The microwave complex enzyme in step (2) of Example 2 is replaced with ultrasound-assisted microwave treatment, specifically: First, place it in a probe-type ultrasonic instrument and sonicate at 300 W and 30℃ for a total duration of 10 min. Set the working parameters to 2 s on and 2 s off, with an effective working time of 5 min. After removing it, place it in a microwave oven at 5 W / g and 30℃ for 5 min (effective working time of 5 min). Other parameters are consistent with those in Example 2 to obtain soluble dietary fiber.

[0095] Comparative Example 16: Probe-based ultrasound synergistic effect on laccase and cellulase (physical field pretreatment - synergistic complex enzyme) In step (2) of Example 2, the microwave complex enzyme is replaced with an ultrasonic pretreatment synergistic complex enzyme, as follows: First, the bamboo shoot powder was pretreated by ultrasound at 250 W and 30℃ for a total duration of 10 min. The working parameters were set to 2 s on and 2 s off, with an effective working time of 5 min. Then, 50 μL of laccase solution and 100 μL of cellulase solution were added, and the mixture was enzymatically hydrolyzed in a water bath at 55℃ for 30 min. Other parameters were kept the same as in Example 2 to obtain soluble dietary fiber.

[0096] Comparative Example 17: Probe-based ultrasound-microwave synergistic laccase and cellulase (physical field combined with pretreatment for synergistic complex enzyme) In step (2) of Example 2, the microwave complex enzyme is replaced with a synergistic complex enzyme combining ultrasound and microwave pretreatment, as follows: Place the bamboo shoot powder in a probe-type ultrasonic chamber and sonicate it at 250 W and 30℃ for a total duration of 10 min. Set the working parameters to 2s on and 2s off, with an effective working time of 5 min. Then place it in a microwave chamber and microwave it at 250 W and 55℃ for 30 min to pretreat the bamboo shoot powder. Finally, add 50 μL of laccase solution and 100 μL of cellulase solution and enzymatically hydrolyze it in a 55℃ water bath for 30 min. Everything else remained the same as in Example 2, resulting in soluble dietary fiber.

[0097] Comparative Example 18: Water bath ultrasound-assisted laccase and cellulase digestion (with replacement of physical field-assisted complex enzymatic hydrolysis) In step (2) of Example 2, the microwave-assisted complex enzyme treatment is replaced with water bath ultrasound-assisted complex enzyme treatment, as follows: Place the mixture in a water bath ultrasonic bath, add 50 μL of laccase solution and 100 μL of cellulase solution, and sonicate continuously at 120 W and 55℃ for 30 min (control the reaction temperature in the water bath and perform continuous ultrasonic treatment). Everything else remained the same as in Example 2, resulting in soluble dietary fiber.

[0098] The obtained soluble dietary fiber was subjected to performance testing, and the test results are as follows: (1) Soluble dietary fiber yield test: Table 2. Effects of different treatment methods on the yield of soluble dietary fiber

[0099] (2) Infrared spectral analysis: Figure 2 The images show the FTIR spectra of soluble dietary fiber obtained in Examples 2, 6-7, and 10-12. Figure 2 It can be seen that all soluble dietary fibers have OH groups at 3408 -1 The broad absorption peaks caused by nearby stretching vibrations mainly originate from pectin (galacturonic acid) and soluble hemicellulose (galactose and mannose). The absorption peaks induced by Example 2 and Control Example 10 are stronger, followed by Control Example 11. This is attributed to the degradation of cellulose and hemicellulose by microwaves, laccase, and cellulase through the disruption of hydrogen bonds, forming new amorphous cellulose and soluble sugars, exposing more functional groups with free hydroxyl groups. Simultaneously, this result also indicates that the soluble carbohydrate content increased more significantly after treatment in Example 2 and Control Example 10.

[0100] In 1652 -1 The broad peaks detected were related to C=O double bonds, a characteristic of benzodiazepines in polyphenols, indicating that lignin was degraded by laccase and partially converted into smaller phenolic compounds. Furthermore, the data showed that the peak width increased significantly after microwave treatment compared to the original soluble dietary fiber, indicating that microwaves have a significant effect on the release of phenolic compounds from soluble dietary fiber. Laccase, by attacking the phenolic phenylpropane units in lignin and their connected β-O-4 ether bonds, initiated an oxidative free radical reaction, leading to ether bond breakage and further promoting the release of phenolic compounds. Therefore, Example 2 showed the highest peak intensity, followed by Control Example 11 and Control Example 10, demonstrating that these treatment methods enhanced the antioxidant capacity of soluble dietary fiber.

[0101] (3) X-ray diffraction pattern test: Figure 3X-ray diffraction patterns of soluble dietary fiber obtained in Example 2, Comparative Examples 6-7, and Comparative Examples 10-12. Figure 3 It can be seen that all six soluble dietary fibers exhibit relatively obvious characteristic crystal peaks at approximately 23.81° and 30.65°. Among them, Control Example 6 shows the most prominent diffraction peak at 23.81°, with some secondary diffraction peaks between 30.65° and 46.39°. This indicates that the soluble dietary fiber crystal region of bamboo shoots contains amorphous or cellulose type I crystals or amorphous structures. After treatment with five methods, it was observed that the diffraction peaks at approximately 23.81° of the soluble dietary fibers treated by all five methods decreased significantly. The treatments in Example 2 and Control Example 11 showed the most significant damage to the cellulose crystal structure, followed by Control Example 10. This indicates that laccase and microwaves played a significant role in the degradation of lignin and the destruction of the rigid structure of LCC, thus enabling microwave / cellulase to act on the interior of cellulose molecules. Furthermore, the crystallinity data revealed that Example 2 and Control Example 11 showed the most significant decreases in crystallinity, at 18.56% and 18.88%, respectively. This indicates that both treatment methods effectively disrupt the cellulose and hemicellulose crystal structures in the cell wall, thereby reducing the crystallinity of soluble dietary fiber. This reduction in soluble dietary fiber crystallinity not only increases the number of exposed sites on its surface, significantly improving its water-holding and oil-holding capacities, but also enhances the overall solubility of DF (diethyltoluene).

[0102] (3) Antioxidant capacity determination Figure 4 The DPPH scavenging rates of soluble dietary fiber obtained in Example 2, Comparative Examples 6-7, and Comparative Examples 10-12; Figure 5 The ABTS clearance rate of soluble dietary fiber obtained in Examples 2, 6-7, and 10-12 is shown. Figure 4 and Figure 5 It can be seen that the antioxidant capacity of soluble dietary fiber was improved after treatment by all five methods, and the increase was with the increase of soluble dietary fiber concentration, indicating that the DPPH and ABTS scavenging capacity is positively correlated with the concentration of soluble dietary fiber. Furthermore, the DPPH and ABTS scavenging capacities of these six soluble dietary fibers were almost identical. The antioxidant capacity of the obtained soluble dietary fibers was in the following order: Example 2 > Control Example 11 > Control Example 10 > Control Example 12 > Control Example 7 > Control Example 6. At a concentration of 2.5 mg / mL, Example 2 showed the highest DPPH and ABTS scavenging rates, at 59.68 ± 0.21% and 58.16 ± 0.98%, respectively.

[0103] The differences in antioxidant capacity among the five treated soluble dietary fiber samples are primarily due to the different types of enzymes used. In Examples 2, 11, and 10, laccase degrades lignin to generate phenolic acids such as ferulic acid and vanillic acid. The phenolic hydroxyl groups in these substances directly enhance their antioxidant capacity. Secondly, the synergistic microwave treatment disrupts the structure of bamboo shoot cell walls, increasing the accessibility of enzymes and substrates and promoting the release of some antioxidant molecules, thereby further improving the antioxidant capacity of soluble dietary fiber. In contrast, the treatment in Example 12 failed to effectively degrade lignin, potentially resulting in the inclusion of some antioxidant-inert lignin fragments within the soluble dietary fiber, thus leading to a lower antioxidant capacity.

[0104] (4) Assay for lipid-lowering function In vitro SCAC is a key parameter for evaluating the lipid-lowering potential of dietary fiber. Essentially, soluble dietary fiber reduces intestinal reabsorption of bile salts (such as sodium cholate) through physical / chemical interactions (hydrogen bonds, van der Waals forces, electrostatic interactions, etc.), thereby decreasing the conversion of cholesterol to bile salts and achieving lipid regulation.

[0105] Figure 6 This is a comparison chart of the lipid-lowering function of soluble dietary fiber obtained in Example 2, Control Examples 6-7, and Control Examples 10-12. From... Figure 6 It can be seen that the SCAC of the soluble dietary fiber obtained from the six treatments (Comparative Examples 6, 7, 10, 11, 12, and Example 2) were 7.43 mg / g, 8.70 mg / g, 19.05 mg / g, 17.13 mg / g, 12.53 mg / g, and 21.6 mg / g, respectively. The soluble dietary fiber obtained from Example 2 exhibited the best SCAC, indicating its potential lipid-lowering activity. Cholesterol adsorption in the human body mainly occurs in the gastric environment and intestines. Therefore, the CAC of six soluble dietary fibers was measured at pH=2 and pH=7, respectively. Figure 7 This is a comparison chart showing the lipid-lowering function of soluble dietary fiber obtained in Example 2, Control Examples 6-7, and Control Examples 10-12 at pH=2 and pH=7. Figure 7 It can be seen that the CAC of each soluble dietary fiber in a neutral environment (pH=7) is greater than its adsorption capacity in an acidic environment. This is mainly attributed to the fact that in an acidic environment, dietary fiber and cholesterol carry a positive charge, and due to the repulsion of like charges and H+... + Competition for adsorption sites leads to a lower CAC (cholesterol-dependent cholesterol) in soluble dietary fiber. Therefore, the CAC of soluble dietary fiber is significantly lower in acidic environments than in neutral environments, but the magnitude trends are similar for all types of soluble dietary fiber. This also indicates that the gut, in a neutral environment, is the primary site for cholesterol adsorption by dietary fiber.

[0106] At pH 7, the CAC of all five treated methods was higher than that of control example 6. This is likely because the treated soluble dietary fiber has a looser surface structure, increased porosity, and is more likely to form gels and mucosal layers, thus enhancing CAC. Example 2 exhibited the best CAC at 21.35 mg / g. This indicates that microwave-assisted complex enzyme treatment exposed more active groups that interact with cholesterol.

[0107] Example 3 A method for extracting soluble dietary fiber from highly lignified bamboo shoot raw materials based on microwave and complex enzymes includes the following steps: (1) After peeling the highly lignified bamboo shoots, rinse the surface residue with running water and cut them into uniform thin slices with a thickness of 2-3 mm; then boil them in boiling water for 10 min, cool them and place them in an oven at 40℃ for 8 h; after drying, crush them with a multi-functional pulverizer and pass the powder through a 40-mesh sieve to obtain highly lignified bamboo shoot raw material powder. (2) Mix 1g of highly lignified bamboo shoot raw material powder with 40 mL of phosphate buffer (pH=5) thoroughly, add 50 μL of laccase solution and 100 μL of cellulase solution, and place in a microwave oven. Microwave heating and enzymatic hydrolysis at 280 W and 60℃ for 30 min (the effective working time of the microwave is 5 min) at a microwave power density of 7 W / g, to obtain a mixture of bamboo shoot powder treated with microwave and compound enzyme. (4) Adjust the pH of the mixture of bamboo shoot powder treated with microwave and compound enzyme to 6.0±0.2, add 50 μL of heat-stable α-amylase solution, and incubate in a water bath at 95±2℃ for 30 min; then cool to 60℃, add 100 μL of amyloglucosidase solution, and incubate in a water bath at 60±2℃ for 30 min; then cool to 60℃, add 100 μL of papain solution, and incubate in a water bath at 60±2℃ for 30 min; remove impurities such as starch and protein, and centrifuge at 8000 r / min at room temperature for 10 min to separate the supernatant. (5) Add 4 times the volume of 95% (v / v) ethanol aqueous solution to the supernatant and let it stand at 4℃ for 10 h to precipitate. After precipitation, filter the precipitate using a Buchner funnel and dry the precipitate in an oven at 30±5℃ for 2 h to obtain soluble dietary fiber.

[0108] The obtained soluble dietary fiber was subjected to performance testing, and the test results are as follows: The yield of soluble dietary fiber was 34.39%.

[0109] Example 4 A method for extracting soluble dietary fiber from highly lignified bamboo shoot raw materials based on microwave and complex enzymes includes the following steps: (1) After peeling the highly lignified bamboo shoots, rinse the surface residue with running water and cut them into uniform thin slices with a thickness of 2-3 mm; then boil them in boiling water for 10 min, cool them and place them in an oven at 40℃ for 8 h; after drying, crush them with a multi-functional pulverizer and pass the powder through a 40-mesh sieve to obtain highly lignified bamboo shoot raw material powder. (2) Mix 1g of highly lignified bamboo shoot raw material powder with 60 mL of phosphate buffer (pH=5) thoroughly, add 50 μL of laccase solution and 100 μL of cellulase solution, and place in a microwave oven. Microwave heating at 300 W and 55℃ for 30 min (the effective working time of the microwave is 5 min) to obtain a mixture of bamboo shoot powder treated with microwave and compound enzyme. (4) Adjust the pH of the mixture of bamboo shoot powder treated with microwave and compound enzyme to 6.0±0.2, add 50 μL of heat-stable α-amylase solution, and incubate in a water bath at 95±2℃ for 30 min; then cool to 60℃, add 100 μL of amyloglucosidase solution, and incubate in a water bath at 60±2℃ for 30 min; then cool to 60℃, add 100 μL of papain solution, and incubate in a water bath at 60±2℃ for 30 min; remove impurities such as starch and protein, and centrifuge at 8000 r / min at room temperature for 10 min to separate the supernatant. (5) Add 4 times the volume of 95% (v / v) ethanol aqueous solution to the supernatant and let it stand at 4℃ for 10 h to precipitate. After precipitation, filter the precipitate using a Buchner funnel and dry the precipitate in an oven at 30±5℃ for 2 h to obtain soluble dietary fiber.

[0110] The obtained soluble dietary fiber was subjected to performance testing, and the test results are as follows: The yield of soluble dietary fiber was 36.13%.

[0111] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing bamboo shoot powder after microwave and complex enzyme treatment, characterized in that, Includes the following steps: The highly lignified bamboo shoot raw material powder was thoroughly mixed with phosphate buffer solution, laccase solution and cellulase solution were added, and the mixture was placed in a microwave oven. The enzymatic hydrolysis was carried out at a microwave power density of 5-7 W / g, 200-300 W, and 55-60 ℃ for 25-35 min, with an effective microwave working time of 4-6 min, to obtain a mixture of bamboo shoot powder treated with microwave and compound enzyme. The mixture of microwave-treated and enzyme-treated bamboo shoot powder was dried to obtain microwave-treated and enzyme-treated bamboo shoot powder.

2. The bamboo shoot powder prepared by the method of claim 1 after microwave and complex enzyme treatment.

3. A method for extracting soluble dietary fiber from highly lignified bamboo shoot raw materials based on microwave and compound enzymes, characterized in that, Includes the following steps: (1) Mix the highly lignified bamboo shoot raw material powder with phosphate buffer solution, add laccase solution and cellulase solution, and place it in a microwave oven. The microwave temperature is controlled at 5-7 W / g, 200-300 W, 55-60 ℃ for 25-35 min, and the effective working time of the microwave is 4-6 min to obtain a mixture of bamboo shoot powder treated with microwave and compound enzyme. (2) Adjust the pH of the mixture of bamboo shoot powder treated with microwave and compound enzyme, add heat-stable α-amylase, amyloglucosidase and papain for enzymatic hydrolysis to remove impurities, centrifuge to obtain supernatant; (3) The supernatant was precipitated with alcohol, filtered, and dried to obtain soluble dietary fiber.

4. The method according to claim 3, characterized in that, In step (1), the mass-to-volume ratio of highly lignified bamboo shoot raw material powder to laccase solution is 1 g: 40~60 μL; the mass-to-volume ratio of highly lignified bamboo shoot raw material powder to cellulase solution is 1 g: 90~110 μL; and the volume ratio of laccase solution to cellulase solution is 1:

2.

5. The method according to claim 3, characterized in that, In step (2), heat-stable α-amylase, amyloglucosidase, and papain are added for enzymatic hydrolysis to remove impurities. Specifically: First, add heat-stable α-amylase solution and hydrolyze in a water bath at 90-95 ℃ for 30-60 min, then cool. Next, add amyloglucosidase solution and hydrolyze in a water bath at 60-65 ℃ for 30-60 min, then cool. Finally, add papain solution and hydrolyze in a water bath at 60-65 ℃ for 30-60 min.

6. The method according to claim 3, characterized in that, In step (3), alcohol precipitation is carried out by adding 3-5 times the volume of a 95% ethanol aqueous solution; the alcohol precipitation temperature is 3-5 ℃ and the time is 8-24 h.

7. Soluble dietary fiber prepared by the method according to any one of claims 3-6.

8. The use of the bamboo shoot powder treated with microwave and compound enzyme as described in claim 2 or the soluble dietary fiber as described in claim 7 in the preparation of food or pharmaceuticals.

9. A method for improving the solubility, water-holding capacity, and oil-holding capacity of bamboo shoot powder, characterized in that, Includes the following steps: The highly lignified bamboo shoot raw material powder was thoroughly mixed with phosphate buffer solution, laccase solution and cellulase solution were added, and the mixture was placed in a microwave oven. The enzymatic hydrolysis was carried out at a microwave power density of 5-7 W / g, 200-300 W, and 55-60 ℃ for 25-35 min, with an effective microwave working time of 4-6 min, to obtain a mixture of bamboo shoot powder treated with microwave and compound enzyme. The mixture of microwave-treated and enzyme-treated bamboo shoot powder was dried to obtain microwave-treated and enzyme-treated bamboo shoot powder.

10. A method for enhancing the antioxidant, hypoglycemic, and hypolipidemic functional activities of soluble dietary fiber, characterized in that, Includes the following steps: (1) Mix the highly lignified bamboo shoot raw material powder with phosphate buffer solution, add laccase solution and cellulase solution, and place it in a microwave oven. The microwave temperature is controlled at 5-7 W / g, 200-300 W, 55-60 ℃ for 25-35 min, and the effective working time of the microwave is 4-6 min to obtain a mixture of bamboo shoot powder treated with microwave and compound enzyme. (2) Adjust the pH of the mixture of bamboo shoot powder treated with microwave and compound enzyme, add heat-stable α-amylase, amyloglucosidase and papain for enzymatic hydrolysis to remove impurities, centrifuge to obtain supernatant; (3) The supernatant was precipitated with alcohol, filtered, and dried to obtain soluble dietary fiber.

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