Preparation method of konjac glucomannan with low moisture content

Abstract

The invention relates to the technical field of functional polysaccharide preparation, and discloses a preparation method of low-moisture-content konjac glucomannan, which comprises the following steps: 1) screening and pretreating a high-glucomannan konjac variety; 2) extracting; 3) modification treatment; according to the preparation method disclosed by the invention, the preparation of the high-stability konjac glucomannan of which the moisture content is less than or equal to 8% is realized through collaborative optimization of raw material screening, directional extraction, molecular modification and graded drying processes, the technical bottlenecks that the traditional konjac glucomannan is high in hygroscopicity and poor in storage stability are broken through, and the preparation method can be widely applied to the fields of food thickeners, medicine carriers and environment-friendly materials.

Description

Technical Field

[0001] This invention relates to the field of functional polysaccharide preparation technology, and in particular to a method for preparing konjac gum with low moisture content. Background Technology

[0002] Traditional konjac gum (mainly composed of glucomannan) contains a large number of hydrophilic groups, making it prone to moisture absorption and clumping (water activity Aw > 0.6). This leads to: a gel strength decrease of >30% during storage; the need to add anti-caking agents (such as silica) when used as a food additive; and uncontrolled drug release rate in pharmaceutical sustained-release carrier applications. Existing technologies include: single hot air drying, resulting in product moisture content ≥12%; acetic anhydride modification, but with excessive residual solvents; and mainstream freeze-drying processes, which are energy-intensive (>24h) and cause ice crystals to damage the colloidal network.

[0003] The core functional component of konjac gum is glucomannan (KGM), a natural high-molecular-weight polysaccharide. KGM's molecular structure contains numerous strongly hydrophilic groups such as hydroxyl (-OH), making it highly susceptible to absorbing moisture from the environment. This inherent strong hydrophilicity causes konjac gum powder to easily absorb moisture and clump together during storage or processing, especially when the relative humidity is high. Specifically, this manifests as: a significantly increased water activity (Aw): the water activity of the product after moisture absorption typically exceeds 0.6. Water activity is a key indicator of the free water content in a product; Aw > 0.6 signifies a significantly increased risk of microbial growth and many deteriorating reactions. Physical degradation: powder particles agglomerate to form hard lumps, resulting in extremely poor flowability and severely impacting subsequent metering, mixing, and processing operations.

[0004] Moisture absorption and clumping are not merely physical issues; they severely degrade the core functional property of konjac gum—gel strength—leading to significant application limitations: poor storage stability and drastically reduced gel performance. Moisture absorption causes plasticization of konjac gum molecules, increasing molecular chain mobility. Water penetrates the molecular network, disrupting existing intermolecular forces such as hydrogen bonds. The combined effect results in a sharp drop in gel strength of over 30% during storage (typically within weeks to months). This instability severely limits the product's shelf life and application reliability.

[0005] To overcome the hygroscopicity of konjac gum, existing technologies mainly employ physical drying or chemical modification methods, but both have significant shortcomings. Firstly, single hot air drying is the most commonly used primary drying method. Its main drawback is limited dehydration efficiency; the final product's moisture content is typically still 12% or higher. This moisture level is far above the safe threshold required to inhibit hygroscopic agglomeration and maintain long-term gel stability (generally considered to need to be reduced to 8% or even lower), thus failing to fundamentally solve the problems of hygroscopicity and gel degradation. The product remains hygroscopic, and its performance deteriorates significantly during storage.

[0006] Acetic anhydride chemical modification: Through acetylation, the hydrophilic hydroxyl groups on the KGM molecule are partially blocked, reducing its hygroscopicity. The main drawbacks include the risk of organic solvent residue. The modification process typically requires the use of organic solvents (such as pyridine, acetic acid, etc.) as reaction media or catalyst supports. Solvent residues that are difficult to completely remove (especially toxic solvents such as pyridine) can easily exceed safety limits, which is absolutely unacceptable for food and pharmaceutical applications. Process complexity and cost: Involving chemical reactions and purification steps, the process is complex and costly. It may also alter natural properties; chemical modification may partially change the natural structure and some functional properties of KGM.

[0007] Current mainstream freeze-drying utilizes low-temperature sublimation to remove moisture, theoretically preserving the material structure at low temperatures. Its main drawbacks are extremely high energy consumption and a very long cycle time. The entire freeze-drying process (pre-freezing, main drying, and desorption drying) is extremely time-consuming (usually exceeding 24 hours), and maintaining high vacuum and low temperatures requires enormous energy consumption, resulting in extremely high production costs and making large-scale industrial production impractical. Another drawback is ice crystal damage. Ice crystals formed during the pre-freezing stage can pierce and destroy the delicate colloidal network structure of konjac gum. This physical damage directly leads to a significant decrease in the gel strength of the final product, defeating the original purpose of using freeze-drying technology to protect product performance. Furthermore, its porous structure leads to secondary moisture absorption: freeze-dried products typically have a loose, porous structure, making them more prone to rapid moisture absorption during subsequent storage, requiring very strict packaging conditions.

[0008] In summary, existing technologies cannot economically, efficiently, and safely solve the problems of strong hygroscopicity and storage gel strength decay of konjac glucomannan, nor can they meet the stringent requirements for product purity, safety, and performance stability in high-end application fields such as food and medicine. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing konjac gum with low moisture content.

[0010] The solution of the present invention is: A method for preparing konjac gum with low moisture content includes the following steps: 1) Screening and pretreatment of high glucomannan konjac varieties: Select konjac tubers with glucomannan content ≥70%, and pretreat them after washing and slicing; 2) Extraction: The raw material extraction for pretreatment adopts one of the following methods: compound extraction, supercritical defatting and impurity removal, and extraction and purification. 3) Modification treatment: A modifier is added to the extract, the modifier accounting for 0.8-2.0% of the extract mass, and the mixture is reacted at 50-60°C for 4-12 hours to form hydrophobic modified konjac gum; 4) Drying, wherein the drying is performed using one of fluidized bed drying, freeze drying, and fractional dehydration drying, and a gel is obtained after drying; 5) Quality control: gel sampling, testing and qualification, yielding konjac gum with low moisture content.

[0011] The low moisture content range of the konjac gum is ≤12%.

[0012] As a preferred technical solution, S1, the screening and pretreatment of high glucomannan konjac varieties involves selecting konjac tubers with a glucomannan content ≥70%, washing and slicing them, and then using pulsed microwave pretreatment to break down the cell wall structure. This step completes the targeted screening of raw materials and establishes a correlation model between konjac variety, glucomannan content, and hygroscopicity. S2. Extraction and purification: The pretreated raw material is placed in a compound enzyme solution and enzymatically hydrolyzed at 45℃ for 2–4 hours. Then, it is transferred to a citric acid solution with pH 4.0 and extracted at 80℃ for 3–6 hours. After centrifugation, the supernatant is subjected to ultrafiltration through a 0.1μm ceramic membrane to remove impurities, obtaining a purified gel. This step completes the stepwise removal of impurities. The compound enzyme breaks down cell wall polysaccharides, thereby improving the purity of the colloidal gel (protein residue ≤0.8%). Membrane separation removes small molecule pigments / odor substances (molecular weight cutoff 10kDa). S3. Modification treatment: A modifier is added to the purified gel solution, the modifier accounting for 0.8-2.0% of the mass of the purified gel solution, and the reaction is carried out at 60°C for 4 hours to form hydrophobically modified konjac gum; this step completes the regulation of its molecular structure (see...). Figure 1 ); S4. Multi-stage dehydration and drying: The hydrophobic modified konjac gum is dehydrated with anhydrous ethanol gradient, then frozen at -40℃, and then dried in a vacuum stepwise manner to obtain a gel with a moisture content ≤8%. S5. Quality control: Gel sampling, determination of gel strength and water activity. Gel strength ≥ 800 g / cm², gel water activity ≤ 0.35, to obtain konjac gum with low moisture content.

[0013] As a preferred technical solution, the pulse microwave preprocessing in step S1 is performed with a power of 800W and a duration of 90s.

[0014] As a preferred technical solution, the complex enzyme solution in step S2 is a mixed solution of cellulase and pectinase, wherein the mass ratio of cellulase to pectinase is 1:2.

[0015] As a preferred technical solution, the konjac in step S1 is one or both of Amorphophallus konjac and Amorphophallus var. konjac.

[0016] As a preferred technical solution, the modifier in step S3 is one of octenyl succinic anhydride, stearyl chloride, and dodecyl glycidyl ether.

[0017] As a preferred technical solution, the modifier is dodecyl glycidyl ether, and the dodecyl glycidyl ether accounts for 1.5% of the mass of the purified adhesive solution.

[0018] As a preferred technical solution, in step S4, the anhydrous ethanol gradient dehydration is carried out by sequentially passing through 30% concentration ethanol, 50% pure ethanol, 70% concentration ethanol and 100% anhydrous ethanol.

[0019] As a preferred technical solution, the product is dehydrated and then frozen at -40°C for 4 hours to form the final product. This step reduces the moisture content to below 65%. As a preferred technical solution, the vacuum drying stage in step S4 is as follows: The frozen konjac gum was dried sequentially at 50°C for 2 hours, then at 60°C for 1 hour, and finally at 40°C for 4 hours. Through this step-drying process, its moisture content was reduced from 65% to 25%, and then further reduced from 25% to 8%, thus decreasing the moisture content in a stepwise manner.

[0020] As a preferred technical solution, the following steps are included: C1. Screening and pretreatment of high glucomannan konjac varieties: Konjac tubers with glucomannan content ≥70% were selected, washed, sliced ​​and pretreated. The pretreatment was carried out by pulsed microwave pretreatment to break down the cell wall structure. C2. The extraction is a purification method, which involves placing the pretreated raw material in a compound enzyme solution at 45°C for 2-4 hours for enzymatic hydrolysis, then transferring it to a citric acid solution at pH 4.0 for 3-6 hours for extraction at 80°C. After centrifugation, the supernatant is taken and ultrafiltered through a 0.1μm ceramic membrane to remove impurities, thereby obtaining a purified gel. C3. Modification treatment: Nano-silica is added to the purified adhesive solution, ultrasonically dispersed, and then allowed to stand for 12 hours for aging; the nano-silica accounts for 5-6% of the mass of the purified adhesive solution; the nano-silica particle size is 30 nm; the ultrasonic dispersion is performed with an ultrasonic power of 200 W and an ultrasonic time of 30 min; C4. Drying: The drying process uses a combination of microwave and vacuum drying. First, pre-freeze at -30℃, then intermittently process with microwave power of 400W. The intermittent process is 10s on and 20s off, for a total of 20min. C5. Quality control: Sampling and testing are conducted to ensure the konjac gum has a low moisture content.

[0021] As a preferred technical solution, the following steps are included: A1. Screening and pretreatment of high glucomannan konjac varieties: White konjac dried slices were pretreated by crushing them through an 80-mesh sieve to obtain crushed raw materials. A2. The extraction is a compound extraction. The pulverized raw material is treated with 0.5% oxalic acid solution at 60°C for 1-2 hours, and then extracted with sodium bicarbonate solution at pH 9.0 at 90°C for 2-4 hours to obtain the extract. A3. Modification treatment: Octenyl succinic anhydride was added to the extract and reacted at 50℃ for 6–12 h to obtain modified konjac gum; the octenyl succinic anhydride accounted for 0.8% of the extract mass; A4. Drying, fluidized bed drying, inlet air temperature 70℃, material temperature ≤45℃, to obtain the product; A5. Quality control: Product sampling, gel strength and water activity determination. Gel strength ≥ 800 g / cm², gel water activity ≤ 0.35, to obtain konjac gum with low moisture content.

[0022] As a preferred technical solution, the following steps are included: B1. Screening and pretreatment of high glucomannan konjac varieties: Konjac tubers with glucomannan content ≥70% were selected, washed, sliced ​​and pretreated. The pretreatment was carried out by pulsed microwave pretreatment to break down the cell wall structure. B2. Extraction: The pretreated raw material is degreased and impurities removed by supercritical CO2-assisted degreasing at a pressure of 25 MPa and a temperature of 50 °C to obtain the extract; the impurity removal is carried out by ultrafiltration of the supernatant after centrifugation through a 0.1 μm ceramic membrane. B3. Modification treatment: Stearoyl chloride is added to the extract. After the reaction is complete, the residual reagent is removed by dialysis to obtain modified konjac gum; the stearoyl chloride accounts for 2% of the mass of the extract; B4. Drying, freeze drying. Freeze drying is performed using programmed temperature control and step-by-step heating, with each stage lasting 2-4 hours, to obtain the product. B5. Quality control: The product is tested for heavy metals <10ppm and total bacterial count ≤100CFU / g to obtain konjac gum with low moisture content.

[0023] As a preferred technical solution, the step temperature rise in step B4 is a step temperature rise from -45℃ to 20℃, with each stage lasting 2 hours, for a total of 4 stages: Stage 1: -45℃ to -30℃ (2 hours), Stage 2: -30℃ to -10℃ (2 hours), Stage 3: -10℃ to 0℃ (2 hours), and Stage 4: 0℃ to 20℃ (2 hours).

[0024] As a preferred technical solution, the step temperature rise in step B4 is a step temperature rise from -80℃ to 45℃, with each stage lasting 4 hours, and consists of 5 extremes: -80℃ to -50℃ (4 hours), deep freezing to fix the microporous structure; -50℃ to -25℃ (4 hours), free water sublimation; -25℃ to 0℃ (4 hours), controlled temperature to prevent collapse; 0℃ to 25℃ (4 hours), hydrophobic chain self-assembly; 25℃ to 45℃ (4 hours), thermal desorption and removal of residual reagents.

[0025] The present invention also discloses a method for preparing low-moisture konjac gum. The low-moisture konjac gum prepared by the method has a moisture content increase of ≤1.2% after being placed at 25°C and 65% relative humidity for 30 days.

[0026] This invention also discloses the application of low-moisture konjac gum in food thickeners, pharmaceutical carriers, and environmentally friendly materials.

[0027] Advantages of this invention: 1. Moisture control: final product moisture content ≤8% (national standard requirement ≤12%), and moisture increase ≤1.2% in 30-day accelerated testing.

[0028] 2. Performance improvement: Gel strength reaches 850±30g / cm² (40% higher than unmodified); oil absorption rate is 6.8g / g (suitable for oil stain treatment).

[0029] 3. Cost advantage: drying time is shortened to 7 hours (traditional freeze drying > 24 hours), and energy consumption is reduced by 62%.

[0030] 4. Application expansion: Food industry: lipid substitute gel without added anti-caking agents; Pharmaceutical industry: gastric pH-responsive sustained-release capsules.

[0031] 5. Environmentally friendly materials: biodegradable oil-absorbing sponge (oil absorption ratio ≥8). Attached Figure Description

[0032] Figure 1 This is a comparison diagram of the molecular structure regulation of konjac gum before and after the modification in this invention; Figure 2 This is a comparison chart of the moisture content of konjac gum before and after modification in Example 1 of the present invention; Figure 3 This is a comparison diagram of moisture removal in the step drying process before and after modification in Example 1 of the present invention; Figure 4 This is a comparative diagram showing the application of low-moisture konjac gum in yogurt according to Example 1 of the present invention. Detailed Implementation

[0033] To overcome the above deficiencies, the present invention provides a method for preparing konjac gum with low moisture content to solve the problems in the background art.

[0034] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments. Example 1:

[0035] Five kilograms of Amorphophallus konjac tubers were collected, washed with high-pressure water jet, and sliced ​​(3 mm thick). The slices were then treated with pulsed microwaves (800 W / 90 s). An enzymatic hydrolysate (0.5% cellulase + 1.0% pectinase) was added, and the mixture was shaken at 45°C for 2 hours. Extraction was then performed with citric acid solution (pH 4.0) at 80°C for 6 hours. After ultrafiltration, the purified gel was mixed with 1.5% dodecyl glycidyl ether and reacted at 60°C for 4 hours. The gel was then dehydrated using an ethanol gradient and dried under vacuum in stages to obtain the final product. Tests showed a moisture content of 7.2%, a gel strength of 865 g / cm², and a moisture gain of 2.0% after 30 days of storage.

[0036] Table 1. Comparison of Konjac Gum Product Performance Between Traditional Process and Example 1 Performance indicators Traditional crafts Embodiment 1 of the present invention Improvement range Moisture content (%) 12.3±0.5 7.2±0.3 -41.5% gel strength (g / cm²) 610±25 865±30 +41.8% 30-day moisture gain (%) 15.7±1.2 1.0±0.2 -93.6% Drug release error (%) 32.5±3.1 8.7±1.5 -73.2% The traditional process involves the following methods: 1. Raw material processing: Take 5 kg of the same variety of flower konjac tubers, wash them manually and slice them (3 mm thick). 2. Drying: Dry with hot air at 50℃ until the moisture content is ≤15%; 3. Grinding: After coarse grinding, pass through an 80-mesh sieve to obtain konjac coarse powder; 4. Alkali extraction and purification: Add NaOH solution with pH 9.0 at a material-to-liquid ratio of 1:10, and extract by stirring at 70℃ for 3 hours; 5. Centrifugation to remove impurities: Centrifuge at 4000 r / min for 20 min and collect the supernatant; 6. Ethanol precipitation: Add 3 times the volume of 95% ethanol to the supernatant and let it stand for 12 hours to precipitate; 7. Dehydration and drying: The precipitate is dehydrated twice with anhydrous ethanol, dried at 50°C with forced air until constant weight, and then pulverized to obtain the finished product. Example 2:

[0037] 10 kg of Amorphophallus konjac tubers were collected, washed with high-pressure water jet, and sliced ​​(6 mm thick). The slices were then treated with pulsed microwaves (800 W / 90 s). An enzymatic hydrolysate (0.5% cellulase + 1.0% pectinase) was added, and the mixture was shaken at 45°C for 4 hours. Extraction was then performed with citric acid solution (pH 4.0) at 80°C for 3 hours. After ultrafiltration, the purified gel was mixed with 1.5% dodecyl glycidyl ether and reacted at 60°C for 4 hours. The gel was then dehydrated using an ethanol gradient and subjected to stepwise vacuum drying to obtain the final product. Tests showed: moisture content 7.2%, gel strength 865 g / cm², and moisture gain of 1.0% after 30 days of storage.

[0038] Example 3: Dried white konjac slices (8% moisture content) were used and pulverized through an 80-mesh sieve. Compound extraction: first, treatment with 0.5% oxalic acid solution at 60℃ for 1 hour, followed by extraction with pH 9.0 sodium bicarbonate solution at 90℃ for 2 hours. In the modification stage, 0.8% octenyl succinic anhydride was added, and the reaction was carried out at 50℃ for 6 hours. Fluidized bed drying was used (inlet air temperature 70℃, material temperature ≤45℃), resulting in a finished product with a moisture content of 6.5% and a gel strength of 810 g / cm².

[0039] Example 4: Dried white konjac slices (16% moisture content) were used and pulverized through an 80-mesh sieve. Compound extraction: first, treatment with 0.5% oxalic acid solution at 60℃ for 2 hours, followed by extraction with pH 9.0 sodium bicarbonate solution at 90℃ for 4 hours. In the modification stage, 0.8% octenyl succinic anhydride was added, and the reaction was carried out at 50℃ for 12 hours. Fluidized bed drying was used (inlet air temperature 70℃, material temperature ≤45℃), resulting in a finished product with a moisture content of 6.5% and a gel strength of 920 g / cm². Example 5:

[0040] In Example 1, 5% nano-silica (30nm particle size) was added to the purified gum solution, ultrasonically dispersed (200W / 30min), and then allowed to stand for 12 hours for aging. Drying was performed using a microwave-vacuum combined process: pre-freezing at -30℃, followed by intermittent microwave treatment at 400W power (10s on / 20s off, 20min total), resulting in a final moisture content of 5.9%. The resulting dried product showed significantly improved anti-caking properties and exhibited no adhesion after 90 days of standing. During the drying process, the nano-silica migrated to the surface of the konjac gum, forming a physical barrier layer that effectively reduced moisture penetration and molecular chain adhesion. Simultaneously, the ultra-low moisture content (≤5.9%) further inhibited the tendency to agglomerate. Example 6:

[0041] In Example 1, 6% nano-silica (30nm particle size) was added to the purified gum solution, ultrasonically dispersed (200W / 30min), and then allowed to stand for 24h. Drying was performed using a combined microwave and vacuum process: pre-freezing at -80℃, followed by intermittent microwave treatment at 400W (10s on / 20s off, 20min total), resulting in a final moisture content of 5.9%. The resulting dried product showed significantly improved anti-caking properties and remained unclumped after 120 days of standing. The nano-silica migrated to the surface of the konjac gum during drying, forming a physical barrier layer that effectively reduced moisture penetration and molecular chain adhesion. Simultaneously, the ultra-low moisture content (≤5.9%) further inhibited the tendency to clump. Example 7:

[0042] The preparation method was the same as in Example 1, except that supercritical CO2-assisted degreasing and impurity removal was used in the extraction stage (pressure 25 MPa, temperature 50℃). Stearoyl chloride (addition amount 2.0%) was replaced with a modifier, and residual reagents were removed by dialysis after the reaction. Drying was performed by lyophilization using a programmed temperature control: a stepwise temperature increase from -45℃ to 20℃ (each step lasting 2 hours). Specifically, the stepwise temperature increase was divided into the following stages: Stage 1: -45℃ to -30℃ (2 hours), Stage 2: -30℃ to -10℃ (2 hours), Stage 3: -10℃ to 0℃ (2 hours), and Stage 4: 0℃ to 20℃ (2 hours). The finished product met the United States Pharmacopeia (USP) standards: heavy metals <10 ppm, total bacterial count ≤100 CFU / g. Sustained-release test: the ibuprofen-loaded capsules showed a release rate of <15% in simulated gastric fluid over 2 hours. Example 8:

[0043] The preparation method was the same as in Example 1, except that supercritical CO2 was used for degreasing and impurity removal during the extraction stage (pressure 25 MPa, temperature 50 °C). The modifier was replaced with stearoyl chloride (addition amount 2.0%), and residual reagents were removed by dialysis after the reaction. Drying was performed by lyophilization, and the lyophilization was carried out with programmed temperature control: stepwise heating from -80 °C to 45 °C (each stage 4 h). Specifically, the stepwise heating stages were: 80 °C to -50 °C (4 h), deep freezing to fix the microporous structure; -50 °C to -25 °C (4 h), sublimation of free water; -25 °C to 0 °C (4 h), controlled rate to prevent collapse; 0 °C to 25 °C (4 h), self-assembly of hydrophobic chains; 25 °C to 45 °C (4 h), thermal desorption and removal of residual reagents. Example 9:

[0044] The low-moisture konjac gum product obtained in Example 1 was compounded with sodium alginate at a ratio of 3:1 (dry weight), and 1% CaCO3 pore-forming agent was added. The mixed colloid was injected into a mold and frozen at -20°C. After thawing, it was immersed in a 2% calcium chloride solution for cross-linking for 1 hour, and then dried with supercritical CO2 (31°C / 7.4MPa) to obtain a porous sponge. The obtained porous sponge had the following characteristics: oil absorption ratio: 12.3 g / g (diesel); biodegradability: 62% weight loss after 30 days of soil burial. Example 10:

[0045] The low-moisture konjac gum product obtained in Example 1 was compounded with sodium alginate at a ratio of 6:1 (dry weight), and 2% CaCO3 was added as a pore-forming agent. The mixed colloid was injected into a mold and frozen at -80°C. After thawing, it was immersed in a 4% calcium chloride solution for cross-linking for 2 hours, and finally dried by supercritical CO2 (critical temperature 31°C, pressure 7.4 MPa). The resulting porous sponge had the following characteristics: oil absorption ratio: 24.6 g / g (diesel); biodegradability: 68% weight loss after 30 days of soil burial.

[0046] The examples were used in performance testing, and the test results are shown in Table 2 below. Table 2: Example Performance conditions Moisture (%) gel strength (g / cm²) Application scenarios and verification results 1 Hydrophobic chemical modification 7.2 865 Thickening agent for yogurt increases product viscosity by 76%. 3 Alternating acid-base extraction 6.5 810 Vegetarian meat adhesive, improving product water retention by 40%. 5 Nanocomposite 5.9 780 Powdered health supplement, product flowability index 92 7 Supercritical purification 4.8 830 Gastric retention tablets have a sustained-release time of up to 8 hours. 9 Bio-based sponge molding 8.1 - Marine oil spill recovery, product reuse ≥ 5 times The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing konjac gum with low moisture content, characterized in that, Includes the following steps: 1) Screening and pretreatment of high glucomannan konjac varieties: Select konjac tubers with glucomannan content ≥70%, and pretreat them after washing and slicing; 2) Extraction: The raw material extraction for pretreatment adopts one of the following methods: compound extraction, supercritical defatting and impurity removal, and extraction and purification. 3) Modification treatment: A modifier is added to the extract, wherein the modifier accounts for 0.8 to 5.0% of the mass of the extract, to form hydrophobically modified konjac gum; 4) Drying, wherein the drying is performed by one of the following methods: fluidized bed drying, freeze drying, staged dehydration drying and microwave vacuum combined drying, and a gel is obtained after drying; 5) Quality control: gel sampling, testing and qualification, yielding konjac gum with low moisture content.

2. The method for preparing low-moisture konjac gum as described in claim 1, characterized in that, Includes the following steps: S1. Screening and pretreatment of high glucomannan konjac varieties: Konjac tubers with glucomannan content ≥70% were selected, washed, sliced ​​and pretreated. The pretreatment was carried out by pulsed microwave pretreatment to break down the cell wall structure. S2. The extraction is a purification method. The extraction and purification method is to place the pretreated raw material in a compound enzyme solution and hydrolyze it at 45°C for 2-4 hours, then transfer it to a citric acid solution with pH 4.0 and extract it at 80°C for 3-6 hours. After centrifugation, the supernatant is taken and ultrafiltered through a 0.1μm ceramic membrane to remove impurities, and a purified gel is obtained. S3. Modification treatment: Dodecyl glycidyl ether is added to the purified gel solution, wherein the dodecyl glycidyl ether accounts for 1.5% of the mass of the purified gel solution, and the reaction is carried out at 60°C for 4 hours to form hydrophobically modified konjac gum. S4. Graded dehydration and drying: The hydrophobic modified konjac gum is dehydrated with anhydrous ethanol in a gradient, then frozen at -40℃, and then dried in a vacuum stepwise manner to obtain a gel with a moisture content ≤8%. S5. Quality control: Gel sampling, determination of gel strength and water activity. Gel strength ≥ 800 g / cm², gel water activity ≤ 0.35, to obtain konjac gum with low moisture content.

3. The method for preparing low-moisture konjac gum as described in claim 2, characterized in that: In step S1, the pulsed microwave pretreatment is performed at a power of 800W for 90s; the konjac is Amorphophallus konjac; in step S2, the compound enzyme solution is a mixed solution of cellulase and pectinase, with a mass ratio of cellulase to pectinase of 1:

2.

4. The method for preparing low-moisture konjac gum as described in claim 2, characterized in that: In step S4, the anhydrous ethanol gradient dehydration involves sequentially passing the ethanol through 30% concentration ethanol, 50% pure ethanol, 70% concentration ethanol, and 100% anhydrous ethanol.

5. The method for preparing low-moisture konjac gum as described in claim 2, characterized in that, The vacuum drying stage in step S4 is as follows: The frozen konjac gum was dried sequentially at 50°C for 2 hours, then at 60°C for 1 hour, and finally at 40°C for 4 hours.

6. The method for preparing low-moisture konjac gum as described in claim 1, characterized in that, Includes the following steps: C1. Screening and pretreatment of high glucomannan konjac varieties: Konjac tubers with glucomannan content ≥70% were selected, washed, sliced ​​and pretreated. The pretreatment was carried out by pulsed microwave pretreatment to break down the cell wall structure. C2. The extraction is a purification method, which involves placing the pretreated raw material in a compound enzyme solution at 45°C for 2-4 hours for enzymatic hydrolysis, then transferring it to a citric acid solution at pH 4.0 for 3-6 hours for extraction at 80°C. After centrifugation, the supernatant is taken and ultrafiltered through a 0.1μm ceramic membrane to remove impurities, thereby obtaining a purified gel. C3. Modification treatment: Nano-silica is added to the purified adhesive solution, ultrasonically dispersed, and then allowed to stand for 12 hours for aging; the nano-silica accounts for 5-6% of the mass of the purified adhesive solution; the nano-silica particle size is 30 nm; the ultrasonic dispersion is performed with an ultrasonic power of 200 W and an ultrasonic time of 30 min; C4. Drying: The drying process uses a combination of microwave and vacuum drying. First, pre-freeze at -30℃, then intermittently process with microwave power of 400W. The intermittent process is 10s on and 20s off, for a total of 20min. C5. Quality control: Sampling and testing are conducted to ensure the konjac gum has a low moisture content.

7. The method for preparing low-moisture konjac gum as described in claim 1, characterized in that, Includes the following steps: A1. Screening and pretreatment of high glucomannan konjac varieties: White konjac dried slices were pretreated by crushing them through an 80-mesh sieve to obtain crushed raw materials. A2. The extraction is a compound extraction. The pulverized raw material is treated with 0.5% oxalic acid solution at 60°C for 1-2 hours, and then extracted with sodium bicarbonate solution at pH 9.0 at 90°C for 2-4 hours to obtain the extract. A3. Modification treatment: Octenyl succinic anhydride is added to the extract and reacted at 50℃ for 6-12 hours to obtain modified konjac gum. Octenyl succinic anhydride accounts for 0.8% of the extract mass; A4. Drying, fluidized bed drying, inlet air temperature 70℃, material temperature ≤45℃, to obtain the product; A5. Quality control: Product sampling, gel strength and water activity determination. Gel strength ≥ 800 g / cm², gel water activity ≤ 0.35, to obtain konjac gum with low moisture content.

8. The method for preparing low-moisture konjac gum as described in claim 1, characterized in that, Includes the following steps: B1. Screening and pretreatment of high glucomannan konjac varieties: Konjac tubers with glucomannan content ≥70% were selected, washed, sliced ​​and pretreated. The pretreatment was carried out by pulsed microwave pretreatment to break down the cell wall structure. B2. Extraction: The pretreated raw materials are degreased and impurities removed by supercritical CO2 assisted degreasing at a pressure of 25 MPa and a temperature of 50 °C to obtain the extract. B3. Modification treatment: Stearoyl chloride is added to the extract. After the reaction is complete, the residual reagent is removed by dialysis to obtain modified konjac gum; the stearoyl chloride accounts for 2% of the mass of the extract; B4. Drying, freeze drying. Freeze drying is performed using programmed temperature control and step-by-step heating, with each stage lasting 2-4 hours, to obtain the product. B5. Quality control: The product is tested for heavy metals <10ppm and total bacterial count ≤100CFU / g to obtain konjac gum with low moisture content.

9. A low-moisture konjac gum prepared by the method for preparing low-moisture konjac gum according to any one of claims 1 to 8, characterized in that: The moisture content of low-moisture konjac gum increased by ≤1.2% after being placed at 25℃ and 65% relative humidity for 30 days.

10. The application of the low-moisture konjac gum as described in claim 9 in food thickeners, pharmaceutical carriers, and environmentally friendly materials.

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