Preparation method and application of oat beta-glucan prebiotic

Abstract

The present invention discloses a preparation method and application of oat beta-glucan prebiotics, and belongs to the technical field of polysaccharide extraction. The preparation method comprises the following steps: oat bran is ground to obtain bran powder; the bran powder, deionized water and hydrophobic aldehyde ionic liquid are mixed and stirred to form an extraction system, protonic acid is added to the extraction system and mixed and stirred to form a reaction solution, and the reaction solution is ultrasonically impregnated for 1h to 2h in an environment of ultrasonic power 400W to 500W and ultrasonic temperature 30°C to 40°C to obtain an organic hydrophobic layer; the organic hydrophobic layer is treated with inorganic acid acid to obtain oat beta-glucan prebiotics. The extraction system constructed by the present invention combines the extraction method of acid catalysis and ultrasonic leaching to achieve the purpose of increasing the yield of oat beta-glucan.

Description

Technical Field

[0001] The invention belongs to the technical field of polysaccharide extraction, and particularly relates to a preparation method of oat beta-glucan prebiotic and application thereof. Background Art

[0002] Oats are a crop rich in a variety of bioactive substances, and are superior to many other grains in terms of nutritional value. Oats are usually eaten as grains and can provide important nutrients such as protein, unsaturated fatty acids, soluble dietary fiber, vitamins and minerals. Oats synthesize a wide variety of secondary metabolites during the maturation process, which makes oats contain a large number of bioactive substances. Oat β-glucan has significant bioactive functions and nutritional properties. As the main soluble dietary fiber in oats, oat β-glucan has received widespread attention. Studies have shown that oat β-glucan can have a positive effect on major health diseases or chronic diseases such as cardiovascular disease, type I diabetes, cancer, Alzheimer's disease, hypertension, obesity, allergies and autism by interacting with microbial flora. Oat β-glucan has good water solubility, viscosity and gel properties, and is widely used in food. Oat β-glucan is mainly distributed in the cell walls of aleurone, subaleurone and endosperm tissues. Its structure is composed of pyranose glucose units connected by β-(1→3) and β-(1→4) glycosidic bonds. The dry weight of β-glucan in oat bran is about 4%, which is composed of 70% β-(1→4) and 30% β-(1→3) glycosidic bond-linked glucose groups. The basic unit in the polymer chain is composed of trimers and tetramers.

[0003] Patent CN101798357B discloses a method for extracting oat β-glucan, which first removes impurities such as protein by weak alkali and weak acid treatment, then uses α-amylase for enzymatic hydrolysis to obtain an aqueous solution containing oat β-glucan, and then filters through a macromolecular ultrafiltration membrane to obtain an oat β-glucan aqueous solution. Patent CN109400750A discloses a method for preparing oat β-glucan, which first enzymatically hydrolyzes oat bran, then uses ethanol's high solubility to other low molecular weight organic compounds and impurities and low solubility to polysaccharides to separate oat β-glucan by using the difference in solubility, and then removes water by drying to obtain oat β-glucan. Patent CN114805630B discloses an oat β-glucan and a preparation method and application thereof. The invention releases the active substances in oats through pretreatment with a wall-breaking enzyme, and then mixes the oat β-glucan and soluble proteoglycans through water extraction and ethanol extraction to prepare oat β-glucan with a certain concentration of soluble proteoglycans.

[0004] According to the invention content of the above patent, if oat β-glucan is directly precipitated by ethanol without other post-treatment, although the process is simple, the yield is low, only about 12%.

[0005] Therefore, an oat β-glucan extraction system is designed to avoid the use of costly ultrafiltration membranes, thereby improving the yield of oat β-glucan, which has practical application value. Summary of the invention

[0006] According to the deficiencies of the prior art, the present invention constructs a hydrophobic aldehyde-formyl ionic liquid with an aldehyde functional group, and then achieves a mechanical cell wall breaking effect through the ultrasonic cavitation effect, thereby releasing the oat β-glucan in the oat. During the ultrasonic cell wall breaking process, the added hydrophobic aldehyde-formyl ionic liquid can condense with the hydroxyl group on the surface of the oat β-glucan through the aldehyde group to form an acetal structure, thereby extracting the oat β-glucan, and then hydrolyzing and releasing the oat β-glucan, so as to solve the problems raised in the background technology. Specifically, the technical solution of the present invention includes the following contents:

[0007] A method for preparing oat β-glucan prebiotics, the preparation method comprising the following steps:

[0008] Oat bran is ground to obtain bran powder;

[0009] The bran powder, deionized water and hydrophobic aldehyde-containing ionic liquid are mixed and stirred to form an extraction system, the bran powder, deionized water and hydrophobic aldehyde-containing ionic liquid are mixed and stirred to form an extraction system, protonic acid is added to the extraction system and mixed and stirred to form a reaction liquid, and the reaction liquid is ultrasonically immersed for 1 hour to 2 hours in an environment with an ultrasonic power of 400W to 500W and an ultrasonic temperature of 30°C to 40°C to obtain an organic hydrophobic layer;

[0010] The organic hydrophobic layer is acidified with an equal volume of inorganic acid to obtain oat beta-glucan prebiotics.

[0011] Furthermore, the preparation method of the hydrophobic formaldehyde ionic liquid comprises the following steps:

[0012] The nitrogen-containing imidazole compound and the aldehyde halide are mixed and dissolved in a solvent and then heated under reflux to obtain a mixture, and the mixture is subjected to rotary evaporation to obtain the hydrophobic aldehyde-containing ionic liquid.

[0013] Furthermore, the nitrogen-containing imidazole compound includes N-methylimidazole, 2-methylimidazole or 4-methylimidazole.

[0014] Furthermore, the aldehyde halide comprises chloroacetaldehyde.

[0015] Furthermore, the molar ratio of the nitrogen-containing imidazole compound to the aldehyde halide is 1:1-3.

[0016] Furthermore, the solvent includes acetone.

[0017] Furthermore, the heating reflux conditions include a heating temperature of 60° C. to 70° C. and a reflux time of 5 h to 8 h.

[0018] Furthermore, the structure of the hydrophobic aldehyde-containing ionic liquid includes but is not limited to the following structure:

[0019]

[0020] Furthermore, the weight ratio of the bran powder: deionized water: hydrophobic aldehyde-containing ionic liquid is 1:30-40:30-40.

[0021] Furthermore, the protonic acid includes methanesulfonic acid, benzenesulfonic acid or p-toluenesulfonic acid, and the protonic acid has a strong ability to provide proton hydrogen ions.

[0022] Furthermore, the weight ratio of the extraction system: the protonic acid is 1:0.1-0.2.

[0023] Furthermore, the inorganic acid includes hydrochloric acid or concentrated sulfuric acid.

[0024] Furthermore, the conditions of the inorganic acid acidification treatment include a reaction temperature of 40° C. to 50° C. and a reaction time of 10 min to 20 min.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention creatively synthesizes a hydrophobic aldehyde-containing ionic liquid having an aldehyde group as a reactive functional group. Oat β-glucan is a water-soluble dietary fiber that can be released and dissolved in water after being broken by ultrasonic cavitation effect. The proton-donating effect of proton acid is used to make the oxygen atom on the aldehyde group of the hydrophobic aldehyde-containing ionic liquid form an oxonium ion, thereby promoting the generation of a carbon cation on the aldehyde group. The hydroxyl group on the oat β-glucan reacts with the carbon cation to dehydrate and form an acetal structure, thereby removing the water-soluble oat β-glucan from the water. Separation is achieved by extraction into a hydrophobic formaldehyde ionic liquid. The acetal structure is a covalent bond with a reversible effect. Further treatment in an acidic environment can rehydrolyze and restore the original hydroxyl and aldehyde structures, thereby achieving separation from the hydrophobic formaldehyde ionic liquid. Compared with reducing the polarity of the solution by ethanol to polymerize and precipitate oat β-polysaccharide through hydrogen bonding, the covalent binding force of the acetal structure is significantly stronger than the hydrogen bonding. Therefore, the yield of oat β-glucan can be increased without purification by ultrafiltration membrane.

[0027] (2) It was unexpectedly found that the hydrophobic aldehyde-containing ionic liquid constructed by the present invention can still obtain a high yield of oat β-glucan after being recycled and reused for extraction, indicating that the hydrophobic aldehyde-containing ionic liquid of the present invention has a good economic advantage of being reusable.

[0028] (3) The extraction system constructed by the present invention needs to be acid-catalyzed to form acetal covalent bonds, and acid catalysis will affect the biological activity of the wall-breaking enzyme. Therefore, the extraction of oat β-glucan is achieved by combining the cavitation effect of ultrasound with the specificity characteristic. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be clearly and completely described below through the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0030] Unless otherwise specified, the raw materials and reagents used in the present invention are commercially available or can be prepared by known methods.

[0031] Preparation Example 1:

[0032] The preparation method of the hydrophobic formaldehyde ionic liquid specifically comprises the following steps:

[0033] 0.1 mol of N-methylimidazole was weighed and placed in a three-necked flask, and then 50 mL of acetone solution was added to the three-necked flask, stirred evenly, and placed in a water bath, and then heated to 60° C. At this temperature, 0.1 mol of chloroacetaldehyde was added to the three-necked flask containing N-methylimidazole through a constant pressure dropping funnel and dripped within 1 minute. After the dripping was completed, the timing of heating and reflux reaction for 5 hours was started. After the reaction was completed, the solvent acetone was removed in a rotary evaporator at 50° C. to obtain a hydrophobic formaldehyde ionic liquid.

[0034] Preparation Example 2:

[0035] The preparation method of the hydrophobic formaldehyde ionic liquid specifically comprises the following steps:

[0036] 0.1 mol of N-methylimidazole was weighed and placed in a three-necked flask, and then 50 mL of acetone solution was added to the three-necked flask, stirred evenly, and placed in a water bath, and then heated to 62° C. At this temperature, 0.2 mol of chloroacetaldehyde was added to the three-necked flask containing N-methylimidazole through a constant pressure dropping funnel and dripped within 1 minute. After the dripping was completed, the timing was started and the heating reflux reaction was carried out for 5 hours. After the reaction was completed, the solvent acetone was removed in a rotary evaporator at 50° C. to obtain a hydrophobic formaldehyde ionic liquid.

[0037] Preparation Example 3:

[0038] The preparation method of the hydrophobic formaldehyde ionic liquid specifically comprises the following steps:

[0039] 0.1 mol of 2-methylimidazole was weighed and placed in a three-necked flask, and then 50 mL of acetone solution was added to the three-necked flask, stirred evenly, and placed in a water bath, and then heated to 64°C. At this temperature, 0.2 mol of chloroacetaldehyde was added to the three-necked flask containing N-methylimidazole through a constant pressure dropping funnel and dripped within 1 minute. After the dripping was completed, the timing of heating reflux reaction for 6 hours was started. After the reaction was completed, the solvent acetone was removed in a rotary evaporator at 50°C to obtain a hydrophobic formaldehyde ionic liquid.

[0040] Preparation Example 4:

[0041] The preparation method of the hydrophobic formaldehyde ionic liquid specifically comprises the following steps:

[0042] 0.1 mol of 2-methylimidazole was weighed and placed in a three-necked flask, and then 50 mL of acetone solution was added to the three-necked flask, stirred evenly, and placed in a water bath, and then heated to 66° C. At this temperature, 0.3 mol of chloroacetaldehyde was added to the three-necked flask containing N-methylimidazole through a constant pressure dropping funnel and dripped within 1 minute. After the dripping was completed, the timing of heating reflux reaction for 7 hours was started. After the reaction was completed, the solvent acetone was removed in a rotary evaporator at 50° C. to obtain a hydrophobic formaldehyde ionic liquid.

[0043] Preparation Example 5:

[0044] The preparation method of the hydrophobic formaldehyde ionic liquid specifically comprises the following steps:

[0045] 0.1 mol of 4-methylimidazole was weighed and placed in a three-necked flask, and then 50 mL of acetone solution was added to the three-necked flask, stirred evenly, and placed in a water bath, and then heated to 70°C. At this temperature, 0.3 mol of chloroacetaldehyde was added to the three-necked flask containing N-methylimidazole through a constant pressure dropping funnel and dripped within 1 minute. After the dripping was completed, the timing of heating and reflux reaction for 8 hours was started. After the reaction was completed, the solvent acetone was removed in a rotary evaporator at 50°C to obtain a hydrophobic formaldehyde ionic liquid.

[0046] Embodiment 1:

[0047] A method for preparing oat beta-glucan prebiotics, specifically comprising the following steps:

[0048] The oats were ground into bran powder by a grinder, 10 parts by weight of bran powder was added with 300 parts by weight of deionized water and stirred to form a suspended mucus, 300 parts by weight of the hydrophobic formaldehyde ionic liquid of Preparation Example 1 was mixed and stirred with the suspended mucus to form an extraction system, the extraction system was placed in an ultrasonic cleaning machine, and 61 parts by weight of methanesulfonic acid were added to the extraction system for mixing and stirring, and then the ultrasonic power was set to 400 W and the ultrasonic temperature was set to 30°C. Under this condition, the ultrasonic extraction treatment was timed for 1 hour. After the ultrasonic immersion was completed, the layers were separated and the upper organic hydrophobic layer was collected. The organic hydrophobic layer and an equal volume of 0.01 mol / L sulfuric acid of the organic hydrophobic layer were mixed and placed in a magnetic stirring chamber, and then the reaction temperature was controlled to 40°C. After stirring for 10 minutes, deionized water twice the volume of the organic hydrophobic layer was added and stirred for 10 minutes. After standing for stratification, the lower aqueous phase was retained. The aqueous phase was dialyzed with a 50 kDa dialysis bag and then freeze-dried to obtain oat β-glucan prebiotic powder. The calculated yield was 34.11%. The purity of the oat β-glucan prebiotic powder was detected by high performance liquid chromatography, and the purity was 87.41%.

[0049] Embodiment 2:

[0050] A method for preparing oat beta-glucan prebiotics, specifically comprising the following steps:

[0051] The oats were ground into bran powder by a grinder, 10 parts by weight of bran powder was added with 320 parts by weight of deionized water to form a suspended mucus, 320 parts by weight of the hydrophobic formaldehyde ionic liquid of Preparation Example 2 was mixed with the suspended mucus to form an extraction system, the extraction system was placed in an ultrasonic cleaning machine, and 65 parts by weight of methanesulfonic acid were added to the extraction system to mix and stir, and then the ultrasonic power was set to 420 W and the ultrasonic temperature was set to 32 ° C. Under this condition, the ultrasonic leaching treatment was timed for 1 hour. After the ultrasonic leaching was completed, the layers were separated and the upper organic hydrophobic layer was collected. The organic hydrophobic layer and an equal volume of 0.01 mol / L sulfuric acid of the organic hydrophobic layer were mixed and placed in a magnetic stirrer, and then the reaction temperature was controlled to 42°C. After stirring for 12 minutes, deionized water twice the volume of the organic hydrophobic layer was added and stirred for 12 minutes. After standing for stratification, the lower aqueous phase was retained. The aqueous phase was dialyzed with a 50 kDa dialysis bag and then freeze-dried to obtain oat β-glucan prebiotic powder. The calculated yield was 39.47%. The oat β-glucan prebiotic powder was subjected to high performance liquid chromatography to detect its purity, and the purity was 88.12%.

[0052] Embodiment 3:

[0053] A method for preparing oat beta-glucan prebiotics, specifically comprising the following steps:

[0054] The oats were ground into bran powder by a grinder, 10 parts by weight of bran powder was added with 340 parts by weight of deionized water to form a suspended mucus, 340 parts by weight of the hydrophobic formaldehyde ionic liquid of Preparation Example 3 was mixed with the suspended mucus to form an extraction system, the extraction system was placed in an ultrasonic cleaning machine, and 138 parts by weight of benzenesulfonic acid was added to the extraction system to mix and stir, and then the ultrasonic power was set to 440 W and the ultrasonic temperature was set to 34 ° C. Under this condition, the ultrasonic extraction treatment was timed for 1 hour. After the ultrasonic immersion was completed, the layers were separated and the upper organic hydrophobic layer was collected. The organic hydrophobic layer and an equal volume of 0.01 mol / L sulfuric acid of the organic hydrophobic layer were mixed and placed in a magnetic stirring chamber, and then the reaction temperature was controlled to 44°C. After stirring for 14 minutes, deionized water twice the volume of the organic hydrophobic layer was added and stirred for 14 minutes. After standing for stratification, the lower aqueous phase was retained. The aqueous phase was dialyzed with a 50 kDa dialysis bag and then freeze-dried to obtain oat β-glucan prebiotic powder. The calculated yield was 42.09%. The oat β-glucan prebiotic powder was subjected to high performance liquid chromatography to detect its purity, and the purity was 88.01%.

[0055] Embodiment 4:

[0056] A method for preparing oat beta-glucan prebiotics, specifically comprising the following steps:

[0057] The oats were ground into bran powder by a grinder, 10 parts by weight of bran powder was added with 360 parts by weight of deionized water to form a suspended mucus, 360 parts by weight of the hydrophobic formaldehyde ionic liquid of Preparation Example 4 was mixed and stirred with the suspended mucus to form an extraction system, the extraction system was placed in an ultrasonic cleaning machine, and 146 parts by weight of p-toluenesulfonic acid was added to the extraction system to mix and stir, and then the ultrasonic power was set to 460 W and the ultrasonic temperature was set to 36 ° C. Under this condition, the ultrasonic extraction treatment was timed for 2 hours, and after the ultrasonic immersion was completed, the layers were statically separated, and the upper organic hydrophobic layer was collected. , the organic hydrophobic layer and an equal volume of 0.01 mol / L sulfuric acid of the organic hydrophobic layer were mixed and placed in a magnetic stirring chamber, and then the reaction temperature was controlled to 48°C. After stirring for 18 minutes, deionized water twice the volume of the organic hydrophobic layer was added and stirred for 18 minutes. After standing and stratification, the lower aqueous phase was retained. The aqueous phase was dialyzed through a 50 kDa dialysis bag and then freeze-dried to obtain oat β-glucan prebiotic powder. The calculated yield was 45.38%. The purity of the oat β-glucan prebiotic powder was detected by high performance liquid chromatography, and the purity was 88.61%.

[0058] Embodiment 5:

[0059] A method for preparing oat beta-glucan prebiotics, specifically comprising the following steps:

[0060] Oats were ground into bran powder by a grinder, 10 parts by weight of bran powder was added with 400 parts by weight of deionized water and stirred to form a suspended mucus, 400 parts by weight of the hydrophobic formaldehyde ionic liquid of Preparation Example 5 was mixed and stirred with the suspended mucus to form an extraction system, the extraction system was placed in an ultrasonic cleaning machine, 162 parts by weight of p-toluenesulfonic acid was added to the extraction system and mixed and stirred, and then the ultrasonic power was set to 500 W and the ultrasonic temperature was set to 40° C. Under this condition, the ultrasonic extraction treatment was timed for 2 hours, and after the ultrasonic immersion was completed, the layers were separated and the upper organic hydrophobic layer was collected, and the organic hydrophobic layer and the organic hydrophobic layer were mixed with 0. 0.1 mol / L sulfuric acid was mixed and placed in a magnetic stirrer, and then the reaction temperature was controlled to 50°C. After stirring for 20 minutes, deionized water twice the volume of the organic hydrophobic layer was added and stirred for 20 minutes. After standing for stratification, the lower aqueous phase was retained, and the recovered upper hydrophobic formaldehyde ionic liquid was repeatedly rinsed with deionized water and then vacuum dried at 60°C to remove water for standby use; the aqueous phase was dialyzed with a 50 kDa dialysis bag and then freeze-dried to obtain oat β-glucan prebiotic powder, with a calculated yield of 50.92%. The oat β-glucan prebiotic powder was subjected to high performance liquid chromatography to detect its purity, and the purity was 89.01%.

[0061] Embodiment 6:

[0062] A method for preparing oat beta-glucan prebiotics, specifically comprising the following steps:

[0063] The hydrophobic aldehyde-containing ionic liquid recovered in Example 5 was used to replace the hydrophobic aldehyde-containing ionic liquid in Example 5, and the hydrophobic aldehyde-containing ionic liquid was recovered. The other conditions were kept consistent with those in Example 5, and the yield of oat β-glucan prebiotics was 46.58% and the purity was 88.43%.

[0064] Embodiment 7:

[0065] A method for preparing oat beta-glucan prebiotics, specifically comprising the following steps:

[0066] The hydrophobic aldehyde-containing ionic liquid recovered in Example 6 was used to replace the hydrophobic aldehyde-containing ionic liquid in Example 5. The other conditions were kept the same as those in Example 5. The yield of oat β-glucan prebiotic was 40.09% and the purity was 87.81%.

[0067] Comparative Example 1:

[0068] A method for preparing oat beta-glucan prebiotics, specifically comprising the following steps:

[0069] The oats were ground into bran powder by a grinder, 10 parts by weight of bran powder was added to 400 parts by weight of deionized water and stirred to form a suspended mucus, 400 parts by weight of the hydrophobic formaldehyde ionic liquid of Preparation Example 5 was mixed and stirred with the suspended mucus to form an extraction system, 162 parts by weight of p-toluenesulfonic acid was added to the extraction system and mixed and stirred, and then 0.01 parts by weight of α-amylase and 0.01 parts by weight of pectinase were added to the extraction system and stirred at 40°C for 40 minutes, and after enzymatic hydrolysis, the temperature was further raised to 80°C for inactivation treatment for 10 minutes, and the upper organic layer was collected. The organic hydrophobic layer and the organic hydrophobic layer were mixed with an equal volume of 0.01 mol / L sulfuric acid and placed in a magnetic stirring chamber, and then the reaction temperature was controlled to be 50°C. After stirring for 20 minutes, deionized water twice the volume of the organic hydrophobic layer was added and stirred for 20 minutes. After standing for stratification, the lower aqueous phase was retained. The aqueous phase was dialyzed with a 50 kDa dialysis bag and then freeze-dried to obtain oat β-glucan prebiotic powder. The calculated yield was 10.11%. The oat β-glucan prebiotic powder was subjected to high performance liquid chromatography to detect its purity, and the purity was 68.19%.

[0070] Comparative Example 2:

[0071] A method for preparing oat beta-glucan prebiotics, specifically comprising the following steps:

[0072] The amount of α-amylase and pectinase in Comparative Example 1 was increased from 0.01 parts by weight to 0.02 parts by weight of α-amylase and pectinase, and the other conditions remained unchanged. The yield of oat β-glucan prebiotics was 11.68% and the purity was 68.97%.

[0073] It can be seen from Comparative Examples 1 and 2 that:

[0074] On the one hand, the hydrophobic formaldehyde ionic liquid with strong hydrophobicity may interact with the hydrophobic region of the enzyme, causing the conformation of the enzyme to change, interfering with the normal structure of the enzyme, resulting in reduced stability of the enzyme, and further affecting its activity. This conformational change may destroy the tertiary and quaternary structures of the enzyme, causing it to lose its activity, resulting in poor enzymatic cell wall breaking effect using α-amylase and pectinase, and difficulty in releasing oat β-glucan; on the other hand, since the proton acid used is strongly acidic, α-amylase and pectinase may be destroyed by the proton acid and inactivated, and cannot exert the enzyme catalytic function. Even if the amount of enzyme is increased, the effect is still poor. Therefore, the extraction system constructed by the present invention combines the extraction method of acid catalysis and ultrasonic extraction. In the cell wall breaking treatment, ultrasonic extraction cannot be abandoned and enzymatic hydrolysis is adopted, which has the characteristics of specific application.

[0075] The above-described embodiments provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected.

Claims

1. A method for preparing oat β-glucan prebiotic, characterized in that: The preparation method comprises the following steps: Oat bran is ground to obtain bran powder; The bran powder, deionized water and hydrophobic aldehyde-containing ionic liquid are mixed and stirred to form an extraction system, protonic acid is added to the extraction system and mixed and stirred to form a reaction solution, and the reaction solution is ultrasonically immersed for 1 h to 2 h in an environment with an ultrasonic power of 400 W to 500 W and an ultrasonic temperature of 30° C. to 40° C. to obtain an organic hydrophobic layer; The organic hydrophobic layer is acidified with an equal volume of inorganic acid to obtain oat β-glucan prebiotics; The preparation method of the hydrophobic formaldehyde ionic liquid comprises the following steps: The nitrogen-containing imidazole compound and the aldehyde halide are mixed and dissolved in a solvent and then heated under reflux to obtain a mixture, and the mixture is subjected to rotary evaporation to obtain the hydrophobic aldehyde-containing ionic liquid; The nitrogen-containing imidazole compound includes N-methylimidazole, 2-methylimidazole or 4-methylimidazole; The aldehyde halide includes chloroacetaldehyde; The molar ratio of the nitrogen-containing imidazole compound to the aldehyde halide is 1:1-3; The inorganic acid is 0.01 mol / L sulfuric acid; The conditions of the inorganic acid acidification treatment are a reaction temperature of 40° C. to 50° C. and a reaction time of 10 min to 20 min.

2. The method for preparing oat β-glucan prebiotic according to claim 1, characterized in that: The heating reflux conditions include a heating temperature of 60° C. to 70° C. and a reflux time of 5 h to 8 h.

3. The method for preparing oat β-glucan prebiotic according to claim 1, characterized in that: The weight ratio of the bran powder: deionized water: hydrophobic formaldehyde ionic liquid is 1:30-40:30-40.

4. The method for preparing oat β-glucan prebiotic according to claim 1, characterized in that: The protonic acid includes methanesulfonic acid, benzenesulfonic acid or p-toluenesulfonic acid.

5. The method for preparing oat β-glucan prebiotic according to claim 1, characterized in that: The weight ratio of the extraction system to the protonic acid is 1:0.1-0.

2.

6. Use of the method for preparing an oat β-glucan prebiotic as claimed in any one of claims 1 to 5 in the field of preparing plant polysaccharide prebiotics.

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