Extraction method of konjac glucomannan

Abstract

The present application relates to a method for extracting konjac glucomannan, and belongs to the technical field of natural high-molecular polysaccharide extraction. In view of the problems of low efficiency, limited purity and easy oxidative degradation in the extraction process of konjac glucomannan in the prior art, an improved extraction method is provided. The key points of the method are as follows: konjac powder is mixed with a special dissociation agent solution at a mass ratio of 1:10, and the reaction is carried out at 50 DEG C for 40 minutes, the dissociation agent is composed of epigallocatechin gallate with a concentration of 2g / L, sulfonated calix[6]arene with a concentration of 1g / L and water; after the reaction is completed, the pH of the system is adjusted to 4.5-5, and then the centrifugal separation, purification and drying steps are carried out, and finally the glucomannan is obtained. The method utilizes the synergistic effect of epigallocatechin gallate and sulfonated calix[6]arene, effectively destroys the structure of the raw material, removes impurities and inhibits oxidation, significantly improves the extraction efficiency and product purity of konjac glucomannan.

Description

Technical Field

[0001] This invention relates to the field of extraction technology. More specifically, this invention relates to a method for extracting konjac glucomannan. Background Technology

[0002] In the extraction of konjac glucomannan, conventional processing methods often fail to efficiently and completely release and extract the target component from the raw material. Specifically, glucomannan in konjac flour is tightly bound to cellulose, hemicellulose, and other substances, forming a dense physical barrier. Existing processes are not efficient at disrupting this barrier structure, resulting in insufficient glucomannan dissolution. Simultaneously, the processing easily triggers oxidation reactions in glucomannan, causing molecular chain breakage or degradation. These factors limit the extraction rate and purity of the final product. There is an urgent need for a glucomannan extraction method that can both strongly disrupt the physical barrier of the raw material to promote dissolution and simultaneously inhibit the oxidation process to protect the stability of the target component. Summary of the Invention

[0003] Another objective of this invention is to provide a method for extracting konjac glucomannan, which solves the problems that conventional processing methods in the extraction of konjac glucomannan in the prior art are not efficient at destroying the dense structure of the raw material and lack a mechanism to inhibit oxidative degradation, resulting in insufficient dissolution of the target component and easy breakage of molecular chains.

[0004] To address the issue that when mixing dissociation agents and raw materials in a single step, sulfonated cup[6] aromatics are prone to reduced cell wall destruction efficiency due to uneven local concentrations or insufficient contact with konjac flour.

[0005] This study aims to address the problem of incomplete release of glucomannan from the core region of untreated konjac flour due to the obstruction of its surface by gelatinous and hydrophobic components, which hinders the effective penetration of dissociation agents. Conventional pretreatment (such as warm water soaking) only partially softens the structure, has limited effect on breaking down stubborn barriers, and prolonged treatment can easily lead to thermal degradation. Targeted pretreatment methods are needed to activate the porosity of the raw material; however, over-treatment may damage the polysaccharide molecular chains. A balance must be struck between structural damage and component protection.

[0006] This addresses the issue that if the konjac colloid used in pretreatment has a single molecular weight, excessive penetration of low-molecular-weight colloids may damage the glucomannan backbone, while high-molecular-weight colloids may hinder the entry of the dissociation agent due to volume barriers. Conventional colloidal solutions, lacking molecular weight gradient regulation, cannot synergistically achieve deep penetration and surface protection, resulting in uneven swelling of the raw material after pretreatment and affecting subsequent dissociation efficiency.

[0007] This study addresses the issue of instantaneous high temperatures and cavitation effects generated during the pretreatment ultrasonic stage inducing free radical chain reactions that attack glucomannan molecular chains. Conventional antioxidants, due to their poor heat resistance or insufficient scavenging efficiency, lead to the accumulation of polysaccharide oxidative damage. A gradient antioxidant scheme adapted to the ultrasonic stage needs to be designed, but the dynamic changes in free radicals increase the difficulty of controlling the timing of protective agent addition.

[0008] To address the issue of impurities such as sugars and pigments in crude rosemary extract, direct use as a scavenging agent may interfere with glucomannan purification or introduce off-odors. Conventional purification methods (such as solvent extraction) result in high loss rates of active ingredients and cannot selectively enrich key antioxidant components (such as rosmarinic acid), leading to unstable free radical scavenging efficiency and affecting the protective effect of pretreatment.

[0009] Traditional hot air drying can cause the glucomannan surface to harden and form a crust, hindering internal moisture diffusion, prolonging drying time, and triggering Maillard reactions; while freeze-drying alone can damage the porous structure of polysaccharides due to ice crystal growth. Both can impair the gelation properties of the product, necessitating the development of a drying process that balances efficiency and structural integrity.

[0010] This addresses the problem that directly adjusting pH with acid can easily lead to localized over-acidity in the system (pH<4), inducing hydrolysis or uneven gelation of glucomannan; while conventional buffer solutions are difficult to precisely control the endpoint pH fluctuations with a single adjustment, resulting in incomplete precipitation of impurities or co-precipitation of target components, affecting separation purity.

[0011] This addresses the problem that if glucomannan and impurities are allowed to settle and cool directly before centrifugation, they can easily form aggregated particles, reducing the efficiency of centrifugation.

[0012] To achieve these objectives and other advantages according to the present invention, a method for extracting konjac glucomannan is provided, comprising the following steps:

[0013] Step 1: Mix konjac powder and dissociation agent solution at a mass ratio of 1:10 and react at 50°C for 40 minutes. The dissociation agent includes epigallocatechin gallate, sulfonated calix[6] aromatic hydrocarbon, and water. The concentration of epigallocatechin gallate in the dissociation agent is 2 g / L and the concentration of sulfonated calix[6] aromatic hydrocarbon is 1 g / L.

[0014] Step 2: After the reaction is complete, adjust the pH of the system to 4.5-5, centrifuge, purify, and dry to obtain glucomannan.

[0015] Preferably, in step one, water, epigallocatechin gallate and sulfonated calix[6] aromatic hydrocarbons are mixed in 60% of their total mass to obtain a premix;

[0016] The remaining 40% of the sulfonated cup[6] aromatics were premixed with konjac powder for 30 seconds to obtain a premix;

[0017] Add the premix to the premixed liquid and mix, then allow it to react at 50°C for 40 minutes.

[0018] Preferably, the konjac powder is pretreated before being mixed with the dissociation agent. The pretreatment method is as follows:

[0019] Konjac powder was mixed with an aqueous solution containing 1.5% w / w konjac polysaccharide colloid at a mass ratio of 1:6, and stirred for 45 minutes at 35°C and 50 rpm.

[0020] After stirring, the system was ultrasonically treated under nitrogen protection at an ultrasonic frequency of 28 kHz and a power density of 50 W / L. During the ultrasonic treatment, the temperature was increased from 35℃ to 50℃ at a heating rate of 1℃ / min and held at 50℃ for 10 minutes. Then, under nitrogen protection, the system was ultrasonically treated at an ultrasonic frequency of 40 kHz and a power density of 25 W / L at 50℃ for 5 minutes.

[0021] After the treatment is completed, the system is placed in an ice bath to cool down to 10°C, centrifuged to obtain pretreated konjac powder, and then the operation in step one is performed.

[0022] Preferably, in the konjac polysaccharide colloid, low molecular weight colloids with a molecular weight of 200-300 kDa account for 30% of the total colloid, and high molecular weight colloids with a molecular weight of 800-1000 kDa account for 70% of the total colloid.

[0023] Preferably, a trapping agent is added simultaneously during the ultrasonic treatment process. The trapping agent comprises rosemary extract and citric acid in a mass ratio of 1:0.5, and the amount of the trapping agent added is 1% of the mass of the konjac flour. The trapping agent is added in a gradient manner.

[0024] During the 28 kHz ultrasonic phase, when the system temperature rises to 40°C, add 50% of the total amount of trapping agent;

[0025] Add the remaining 50% of the trapping agent when switching to the 40 kHz ultrasonic frequency.

[0026] Preferably, the method for preparing the rosemary extract is as follows:

[0027] Dried rosemary leaves were mixed with a 60% ethanol solution at a mass ratio of 1:15 and extracted twice by reflux for 1.5 hours each time. The extracts were combined, concentrated under reduced pressure, and freeze-dried to obtain the crude extract.

[0028] The crude extract was dissolved in 60% ethanol solution to a concentration of 100 mg / mL, and then loaded onto a macroporous resin chromatography column. The column was eluted with 3 column volumes of water and then with 6 column volumes of 60% ethanol solution. The ethanol eluent was collected, concentrated under reduced pressure, and dried to obtain rosemary extract.

[0029] Preferably, in step two, the drying process employs segmented variable-temperature microwave-freeze combined drying:

[0030] First stage: Drying to a moisture content of 15% under microwave power of 500W, vacuum degree of 50Pa, and temperature of 40℃.

[0031] Second stage: After cooling to -40℃, freeze-dry for 20 hours in a freeze dryer at -25℃ / 10Pa.

[0032] The third stage: the temperature is increased to 25℃ at a rate of 0.5℃ / min, and the product is dried until the moisture content is ≤5%.

[0033] Preferably, in step two, the pH adjustment employs a two-stage buffer system:

[0034] First, add 0.1 mol / L citrate buffer to pre-adjust the system to pH 5.5 ± 0.2;

[0035] Add 0.1 mol / L acetic acid solution dropwise at a flow rate of 0.5 mL / min until the pH reaches 4.5-5.0.

[0036] Preferably, in step two, the separation operation includes:

[0037] The pH-adjusted system was cooled to 5°C at a rate of 2°C / min. During the cooling process, the system was intermittently stirred at 400 rpm using a magnetic stirrer, with a 10-second pause after every 30 seconds of stirring. Stirring was stopped when the system temperature dropped to 5°C, and the system was aged at 5°C for 1 hour. During aging, the system was treated with ultrasound for 20 seconds every 5 minutes at a frequency of 40 kHz and a power density of 50 W / L. The system was then centrifuged at 10°C and 8000~12000 rpm for 20 minutes. The supernatant was collected, and the separation was completed.

[0038] Preferably, in step two, the purification method is as follows:

[0039] The supernatant obtained after separation was placed at 23~25℃ and added dropwise to a 75% ethanol solution with a mass fraction of 2 times the volume of the supernatant while stirring at 200 rpm. After the addition was complete, stirring was continued for 30 minutes, and then the mixture was allowed to stand for 30 minutes. The precipitate was collected and dried to obtain glucomannan.

[0040] The present invention has at least the following beneficial effects:

[0041] First, this invention uses sulfonated calix[6] aromatic hydrocarbon and epigallocatechin gallate (EGCG) as a dissociation agent, which can effectively destroy the raw material structure, remove impurities and inhibit oxidation, significantly improve the extraction efficiency and purity of konjac glucomannan, and solve the problem of the limitation of the single reagent.

[0042] Secondly, targeted pretreatment of konjac powder and the addition of scavenging agents (citric acid and specific rosemary extract) during ultrasonication can disrupt the raw material's encapsulation structure, scavenge free radicals, stabilize the system, reduce glucomannan loss and degradation, help preserve its molecular integrity, and enhance product functionality (such as gel strength).

[0043] Third, the use of a two-stage buffer system to adjust pH and separation operations including cooling, aging, and ultrasound assistance can precisely control the extraction environment, reduce the degradation of target components and interference from impurities, and further improve the extraction rate, purity, and product quality stability of glucomannan.

[0044] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0046] <Example 1>

[0047] The extraction method of konjac glucomannan includes the following steps:

[0048] Step 1: Mix konjac powder and dissociation agent solution at a mass ratio of 1:10 and react at 50°C for 40 minutes. The dissociation agent includes epigallocatechin gallate, sulfonated calix[6] aromatic hydrocarbon, and water. The concentration of epigallocatechin gallate in the dissociation agent is 2 g / L and the concentration of sulfonated calix[6] aromatic hydrocarbon is 1 g / L.

[0049] Step 2: After the reaction is complete, adjust the pH of the system to 4.5-5, centrifuge, purify, and dry to obtain glucomannan;

[0050] Centrifugation, purification into alcohol precipitation, and drying temperature were all performed using conventional techniques.

[0051] <Example 2>

[0052] The extraction method of konjac glucomannan includes the following steps:

[0053] Step 1: Mix konjac powder and dissociation agent solution at a mass ratio of 1:10 and react at 50°C for 40 minutes. The dissociation agent includes epigallocatechin gallate, sulfonated calix[6] aromatic hydrocarbon, and water. The concentration of epigallocatechin gallate in the dissociation agent is 2 g / L and the concentration of sulfonated calix[6] aromatic hydrocarbon is 1 g / L.

[0054] Step 2: After the reaction is complete, adjust the pH of the system to 4.5-5, centrifuge, purify, and dry to obtain glucomannan.

[0055] In step one, water, epigallocatechin gallate and sulfonated calix[6] aromatic hydrocarbons totaling 60% by mass are mixed to obtain a premix;

[0056] The remaining 40% of the sulfonated cup[6] aromatics were premixed with konjac powder for 30 seconds to obtain a premix;

[0057] Add the premix to the premixed liquid and mix, then allow it to react at 50°C for 40 minutes.

[0058] Before mixing konjac powder with the dissociation agent, it is pretreated. The pretreatment method is as follows:

[0059] Konjac powder was mixed with an aqueous solution containing 1.5% w / w konjac polysaccharide colloid at a mass ratio of 1:6, and stirred for 45 minutes at 35°C and 50 rpm.

[0060] After stirring, the system was ultrasonically treated under nitrogen protection at an ultrasonic frequency of 28 kHz and a power density of 50 W / L. During the ultrasonic treatment, the temperature was increased from 35℃ to 50℃ at a heating rate of 1℃ / min and held at 50℃ for 10 minutes. Then, under nitrogen protection, the system was ultrasonically treated at an ultrasonic frequency of 40 kHz and a power density of 25 W / L at 50℃ for 5 minutes.

[0061] After the treatment is completed, the system is placed in an ice bath to cool down to 10°C, centrifuged to obtain pretreated konjac powder, and then the operation in step one is performed.

[0062] In konjac polysaccharide colloids, low molecular weight colloids with a molecular weight of 200-300 kDa account for 30% of the total colloids, while high molecular weight colloids with a molecular weight of 800-1000 kDa account for 70% of the total colloids.

[0063] A trapping agent is added simultaneously during the ultrasonic treatment process. The trapping agent comprises rosemary extract and citric acid in a mass ratio of 1:0.5. The amount of the trapping agent added is 1% of the mass of the konjac flour, and the trapping agent is added in a gradient manner.

[0064] During the 28 kHz ultrasonic phase, when the system temperature rises to 40°C, add 50% of the total amount of trapping agent;

[0065] Add the remaining 50% of the trapping agent when switching to the 40 kHz ultrasonic frequency.

[0066] The preparation method of the rosemary extract is as follows:

[0067] Dried rosemary leaves were mixed with a 60% ethanol solution at a mass ratio of 1:15 and extracted twice by reflux for 1.5 hours each time. The extracts were combined, concentrated under reduced pressure, and freeze-dried to obtain the crude extract.

[0068] The crude extract was dissolved in 60% ethanol solution to a concentration of 100 mg / mL, and then loaded onto a macroporous resin AB-8 chromatography column. The column was eluted with 3 column volumes of water and then with 6 column volumes of 60% ethanol solution. The ethanol eluent was collected, concentrated under reduced pressure, and dried to obtain rosemary extract (the obtained rosemary extract contained ≥20% rosmarinic acid and ≥15% rosmarinic acid).

[0069] In step two, the drying process employs a segmented variable-temperature microwave-freeze combined drying method:

[0070] First stage: Drying to a moisture content of 15% under microwave power of 500W, vacuum degree of 50Pa, and temperature of 40℃.

[0071] Second stage: After cooling to -40℃, freeze-dry for 20 hours in a freeze dryer at -25℃ / 10Pa.

[0072] The third stage: the temperature is increased to 25℃ at a rate of 0.5℃ / min, and the product is dried until the moisture content is ≤5%.

[0073] In step two, pH adjustment employs a two-stage buffer system:

[0074] First, add 0.1 mol / L citrate buffer to pre-adjust the system to pH 5.5 ± 0.2;

[0075] Add 0.1 mol / L acetic acid solution dropwise at a flow rate of 0.5 mL / min until the pH reaches 4.5-5.0.

[0076] In step two, the separation operation includes:

[0077] The pH-adjusted system was cooled to 5°C at a rate of 2°C / min. During the cooling process, the system was intermittently stirred at 400 rpm using a magnetic stirrer, with a 10-second pause after every 30 seconds of stirring. Stirring was stopped when the system temperature dropped to 5°C, and the system was aged at 5°C for 1 hour. During aging, the system was treated with ultrasound for 20 seconds every 5 minutes at a frequency of 40 kHz and a power density of 50 W / L. The system was then centrifuged at 10°C and 8000~12000 rpm for 20 minutes. The supernatant was collected, and the separation was completed.

[0078] In step two, the purification method is as follows:

[0079] The supernatant obtained after separation was placed at 23~25℃ and added dropwise to a 75% ethanol solution with a mass fraction of 2 times the volume of the supernatant while stirring at 200 rpm. After the addition was complete, stirring was continued for 30 minutes, and then the mixture was allowed to stand for 30 minutes. The precipitate was collected and dried to obtain glucomannan.

[0080] <Example 3>

[0081] Konjac glucomannan was extracted using the method in Example 2, except that the konjac powder was not pretreated in this example.

[0082] <Example 4>

[0083] Konjac glucomannan was extracted using the method of Example 2, except that no capturing agent was added during the processing of konjac powder in this example.

[0084] <Example 5>

[0085] Konjac glucomannan was extracted using the method of Example 2, except that the drying method in step two of this example was to dry at 40°C for 24 hours.

[0086] <Example 6>

[0087] Konjac glucomannan was extracted using the method in Example 2, except that the pH adjustment method in step two of this example was to add 0.1 mol / L acetic acid solution dropwise until the pH was 4.5-5.0.

[0088] <Example 7>

[0089] Konjac glucomannan was extracted using the method of Example 2, except that in step two of this example, after pH adjustment, the mixture was directly centrifuged at 10°C and 8000~12000 rpm for 20 minutes, and the supernatant was collected.

[0090] <Comparative Example 1>

[0091] Konjac glucomannan was extracted using the method of Example 2, except that the dissociation agent included sulfonated calix[6] aromatic hydrocarbon and water, and the concentration of sulfonated calix[6] aromatic hydrocarbon was 3 g / L.

[0092] <Comparative Example 2>

[0093] Konjac glucomannan was extracted using the method of Example 2, except that the dissociation agent included epigallocatechin gallate and water, and the concentration of epigallocatechin gallate (EGCG) was 3 g / L.

[0094] <Comparative Example 3>

[0095] Konjac glucomannan was extracted using the method described in Example 2, except that: dried rosemary leaves were mixed with a 60% ethanol solution at a mass ratio of 1:15, and refluxed twice for 1.5 hours each time. The extracts were combined, concentrated under reduced pressure, and freeze-dried to obtain the rosemary extract.

[0096] <Experimental Data>

[0097] 1. Extraction rate and purity

[0098] The extraction rate, glucomannan content, and protein residue of glucomannan in Examples 2, 3, 4, 6, 7, Comparative Example 1, and Comparative Example 2 were calculated, and the results are shown in Table 1.

[0099] Extraction rate (%) = final dry glucomannan mass (g) / total mass of glucomannan in raw konjac flour (g) × 100%;

[0100] Table 1 shows the extraction rate and purity.

[0101] Extraction rate (%) Glucomannan content (%) Protein residue (%) Example 1 73.0 73.4 2.9 Example 2 93.9 97.3 0.8 Example 3 77.2 85.3 2.0 Example 4 84.1 89.1 1.7 Example 6 88.6 91.2 1.4 Example 7 83.7 83.6 2.1 Comparative Example 1 54.4 62.8 3.4 Comparative Example 2 60.5 65.2 3.2 Comparative Example 3 92.2 93.4 1.2

[0102] Comparative analysis of the data from Example 1, Comparative Example 1, and Comparative Example 2 in Table 1 shows that sulfonated calix[6] aromatics disrupt the cellulose / starch encapsulation network by inserting into the raw material structure, opening the release channel of glucomannan; while EGCG can at this time pre-react with proteins and metal ions (such as Fe) in the raw material. 3+ Cu 2+These ions catalyze the oxidation of glucomannan and combine to form a precipitate, reducing the interference of impurities on subsequent steps. If EGCG is lacking, impurities will preferentially occupy the cavity of the sulfonated cup [6], reducing its ability to target and encapsulate glucomannan. If the sulfonated cup [6] is lacking, EGCG cannot penetrate into the raw material and can only remove surface impurities, failing to solve the core problem of "release obstruction". The aromatic hydrocarbons of the sulfonated cup [6] continuously encapsulate the released glucomannan, enhancing its water solubility through hydrophilic groups, and avoiding reprecipitation due to hydrogen bond aggregation between glucomannan molecules. At the same time, EGCG captures free radicals (such as hydroxyl radicals ·OH) in the extraction system through phenolic hydroxyl groups, preventing the glycosidic bonds of glucomannan from being oxidized and broken.

[0103] Comparative analysis of Examples 2, 3, 4, and 3 shows that the pretreatment of konjac flour in this invention effectively breaks down the physical and chemical barriers to glucomannan dissolution. It not only destroys the cell walls composed of cellulose and hemicellulose, as well as the encapsulation structures formed by starch and protein, creating channels for the extraction reagent to penetrate, but also removes interfering impurities in advance, reducing competitive adsorption of glucomannan while protecting the integrity of the glucomannan molecules. In Example 2, the scavenging agent added during ultrasonic treatment (citric acid and rosemary extract extracted by the method of this application) significantly improved the extraction efficiency and glucomannan stability through synergistic effects. Rosemary extract can efficiently remove free radicals generated by cavitation during ultrasonic treatment, preventing the degradation of glucomannan's glycosidic bonds due to oxidative breakage; citric acid, by adjusting the pH of the system's microenvironment, enhances the water solubility and stability of the active ingredients in rosemary extract, making its antioxidant effect more lasting, while inhibiting the damage to the glucomannan structure caused by localized high temperatures induced by ultrasonication.

[0104] Comparative analysis of Examples 2 and 6 shows that this application uses a two-stage buffer system to adjust the pH. First, the pH is pre-adjusted to 5.5±0.2 with citrate buffer, and then acetic acid is slowly added dropwise to the target range. This can accurately maintain the stability of the pH of the system and avoid local over-acidity / over-alkalinity leading to glucomannan degradation. At the same time, it reduces the dissolution of impurities such as starch and protein. In contrast, Example 6 directly adds acetic acid, which easily causes drastic pH fluctuations, resulting in the loss of the target component and increased interference from impurities.

[0105] Comparative analysis of Examples 2 and 7 shows that the separation operation in Example 7, through the synergistic effect of cooling, intermittent stirring, aging, and ultrasonic treatment, is significantly superior to the direct centrifugation in Example 7. First, the system is cooled to 5°C and intermittently stirred to reduce glucomannan loss and ensure system homogeneity. Ultrasonic treatment during aging (40kHz, 50W / L) breaks down or agglomerates fine impurity particles, enhancing their sedimentation ability, reducing adsorption of glucomannan, and improving the purity of the supernatant. These ultrasonic parameters only affect small molecule impurities; because glucomannan has a large molecular weight and a stable structure at low temperatures, it does not affect its sedimentation characteristics during subsequent centrifugation, thus avoiding the loss of the target component.

[0106] 2. Gel strength

[0107] The strength of the gels made from the glucomannan prepared in Examples 1, 2, 3, and 5 was tested. The gel strength was tested as follows: dried glucomannan powder was dissolved in water at a mass concentration of 2%, and the mixture was heated, stirred, and cooled to form a uniform gel. The gel was poured into a standard mold, avoiding air bubbles, and allowed to stand and equilibrate to 25℃±1℃ to obtain the gel. The strength of the gel was then tested, and the results are shown in Table 2.

[0108] Table 2 shows the gel strength.

[0109] <![CDATA[Gel strength (g / cm 2 )]]> Example 1 233 Example 2 354 Example 5 317 Example 3 281

[0110] As shown in Table 2, the glucomannan gel prepared in Example 2 has the highest strength. This is related to the fact that the pretreatment in its process more fully disrupts the raw material structure, the scavenger reduces oxidative degradation, and the stepwise dissociation and optimized post-treatment (such as segmented drying) retain more intact macromolecular glucomannan, resulting in stronger intermolecular crosslinking ability. In Example 3, due to the lack of pretreatment, the glucomannan in the raw material is not fully released and there may be more impurities interfering, resulting in a lower gel strength than in Example 2. Example 1 has the simplest process, lacking pretreatment and subsequent optimization steps, resulting in slightly poorer glucomannan structural integrity and purity, and the lowest gel strength. In Example 5, a single drying at 40℃ for 24 hours is used. Long-term constant temperature drying may cause some glucomannan molecules to undergo slight degradation or change in aggregation state due to local overheating, weakening the intermolecular crosslinking ability, and ultimately making the gel strength slightly lower than that of Example 2.

[0111] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for extracting konjac glucomannan, characterized in that, Includes the following steps: Step 1: Mix konjac powder and dissociation agent solution at a mass ratio of 1:10 and react at 50°C for 40 minutes. The dissociation agent includes epigallocatechin gallate, sulfonated calix[6] aromatic hydrocarbon, and water. The concentration of epigallocatechin gallate in the dissociation agent is 2 g / L and the concentration of sulfonated calix[6] aromatic hydrocarbon is 1 g / L. Step 2: After the reaction is complete, adjust the pH of the system to 4.5-5, centrifuge, purify, and dry to obtain glucomannan; In step one, water, epigallocatechin gallate and sulfonated calix[6] aromatic hydrocarbons totaling 60% by mass are mixed to obtain a premix; The remaining 40% of the sulfonated cup[6] aromatics were premixed with konjac powder for 30 seconds to obtain a premix; Add the premix to the premixed liquid and mix, then allow it to react at 50°C for 40 minutes; Before mixing konjac powder with the dissociation agent, it is pretreated. The pretreatment method is as follows: Konjac powder was mixed with an aqueous solution containing 1.5% w / w konjac polysaccharide colloid at a mass ratio of 1:6, and stirred for 45 minutes at 35°C and 50 rpm. After stirring, the system was ultrasonically treated under nitrogen protection at an ultrasonic frequency of 28 kHz and a power density of 50 W / L. During the ultrasonic treatment, the temperature was increased from 35℃ to 50℃ at a heating rate of 1℃ / min and held at 50℃ for 10 minutes. Then, under nitrogen protection, the system was ultrasonically treated at an ultrasonic frequency of 40 kHz and a power density of 25 W / L at 50℃ for 5 minutes. After the treatment is completed, the system is placed in an ice bath to cool down to 10°C, centrifuged to obtain pretreated konjac powder, and then the operation in step one is performed. In konjac polysaccharide colloids, low molecular weight colloids with a molecular weight of 200-300 kDa account for 30% of the total colloids, while high molecular weight colloids with a molecular weight of 800-1000 kDa account for 70% of the total colloids.

2. The method for extracting konjac glucomannan as described in claim 1, characterized in that, A trapping agent is added simultaneously during the ultrasonic treatment process. The trapping agent comprises rosemary extract and citric acid in a mass ratio of 1:0.

5. The amount of the trapping agent added is 1% of the mass of the konjac flour, and the trapping agent is added in a gradient manner. During the 28 kHz ultrasonic phase, when the system temperature rises to 40°C, add 50% of the total amount of trapping agent; Add the remaining 50% of the trapping agent when switching to the 40 kHz ultrasonic frequency; The preparation method of the rosemary extract is as follows: Dried rosemary leaves were mixed with a 60% ethanol solution at a mass ratio of 1:15 and extracted twice by reflux for 1.5 hours each time. The extracts were combined, concentrated under reduced pressure, and freeze-dried to obtain the crude extract. The crude extract was dissolved in 60% ethanol solution to a concentration of 100 mg / mL, and then loaded onto a macroporous resin chromatography column. The column was eluted with 3 column volumes of water and then with 6 column volumes of 60% ethanol solution. The ethanol eluent was collected, concentrated under reduced pressure, and dried to obtain rosemary extract.

3. The method for extracting konjac glucomannan as described in claim 1, characterized in that, In step two, the drying process employs a segmented variable-temperature microwave-freeze combined drying method: First stage: Drying to a moisture content of 15% under microwave power of 500W, vacuum degree of 50Pa, and temperature of 40℃; Second stage: After cooling to -40℃, freeze-dry for 20 hours in a freeze dryer at -25℃ / 10Pa. The third stage: the temperature is increased to 25℃ at a rate of 0.5℃ / min, and the product is dried until the moisture content is ≤5%.

4. The method for extracting konjac glucomannan as described in claim 1, characterized in that, In step two, pH adjustment employs a two-stage buffer system: First, add 0.1 mol / L citrate buffer to pre-adjust the system to pH 5.5 ± 0.2; Add 0.1 mol / L acetic acid solution dropwise at a flow rate of 0.5 mL / min until the pH reaches 4.5-5.

0.

5. The method for extracting konjac glucomannan as described in claim 1, characterized in that, In step two, the separation operation includes: The pH-adjusted system was cooled to 5°C at a rate of 2°C / min. During the cooling process, the system was intermittently stirred at 400 rpm using a magnetic stirrer, with a 10-second pause after every 30 seconds of stirring. Stirring was stopped when the system temperature dropped to 5°C, and the system was aged at 5°C for 1 hour. During aging, the system was treated with ultrasound for 20 seconds every 5 minutes at a frequency of 40 kHz and a power density of 50 W / L. The system was then centrifuged at 10°C and 8000~12000 rpm for 20 minutes. The supernatant was collected, and the separation was completed.

6. The method for extracting konjac glucomannan as described in claim 1, characterized in that, In step two, the purification method is as follows: The supernatant obtained after separation was placed at 23~25℃ and added dropwise to a 75% ethanol solution with a mass fraction of 2 times the volume of the supernatant while stirring at 200 rpm. After the addition was complete, stirring was continued for 30 minutes, and then the mixture was allowed to stand for 30 minutes. The precipitate was collected and dried to obtain glucomannan.