Preparation method of oat beta-glucan and soothing, moisturizing and anti-aging effects of oat beta-glucan

Abstract

The invention provides a preparation method of oat beta-glucan, and belongs to the field of oat extracts. In the whole preparation process, the pH does not need to be adjusted for multiple times, the cost is reduced, the wall-breaking compound enzymes (cellulase, pectinase and xylanase) are added to treat the raw materials, the variant alpha-amylase is used for enzymolysis, the yield of beta-glucan is increased, the extraction efficiency is also improved, and the consumed time is short. According to the preparation method, beta-glucan is taken as a raw material, filter membranes with different molecular weight cutoff are subsequently adopted for graded filtration, beta-glucan with different molecular weights is specifically separated out to meet market requirements, and through deproteinization, decoloration and twice alcohol precipitation treatment, the purity of the beta-glucan is improved, and the beta-glucan has the effects of soothing, moisturizing and resisting aging on skin, and can be widely applied to the skin care product industry.

Description

Technical Field

[0001] This invention belongs to the field of oat extracts, specifically relating to a method for extracting oat β-glucan. Background Technology

[0002] β-glucan is a polysaccharide, a high-molecular-weight compound composed of glucose monomers linked by β-glycosidic bonds. Glycosidic bonds are chemical bonds that connect sugar molecules, and the way β-glycosidic bonds are linked gives β-glucan its unique structure and properties. Based on the position of the glycosidic bonds connecting the glucose units, β-glucan can be classified into several types, such as β-1,3-glucan, β-1,4-glucan, and β-1,6-glucan. For example, β-1,4-glucan is a major structural component of cellulose, while β-1,3-glucan is commonly found in biological structures such as yeast cell walls. β-glucan is typically derived from microorganisms, plants, and marine organisms. It can be added to food as dietary fiber for thickening and stabilizing purposes; secondly, β-glucan has immunomodulatory and antibacterial / antiviral effects, finding applications in the medical field. Finally, β-glucan possesses moisturizing and biocompatibility, promoting skin cell metabolism and facilitating skin nourishment and repair, making it used in the cosmetics industry.

[0003] Oats are one of the earliest cultivated grains on Earth and one of the richest sources of β-glucan, found in the endosperm and aleurone layer of oats. β-glucan content in oats is 6-8% of their total content. Besides its β-glucan functions, oat β-glucan also has effects such as lowering cholesterol, regulating blood sugar, and regulating gut microbiota, and has adjunctive therapeutic effects on cardiovascular disease, obesity, and certain cancers. Currently, there are two methods for extracting and preparing oat β-glucan: dry extraction and wet extraction. Dry extraction mainly involves grinding and sieving, using physical means to separate and concentrate β-glucan from oats, but the yield is usually low. Wet extraction mainly uses solvent extraction, including hot water extraction, alkali extraction, enzymatic extraction, and subcritical extraction, often supplemented by ultrasound and microwave to improve extraction efficiency. However, hot water extraction takes a long time and yields relatively low purity; while alkaline extraction improves the extraction rate, the extracted β-glucan has a low molecular weight and contains more impurities; enzymatic extraction is a commonly used method, typically using α-amylase, proteolytic enzymes, and xylanase to improve purity and extraction yield, but requires constant pH and temperature adjustment, leading to higher costs. Furthermore, the molecular weight of oat β-glucan is closely related to the extraction process, and its effects vary. For example, low molecular weight oat β-glucan has good anti-inflammatory and antioxidant effects, while high molecular weight oat β-glucan has good effects on cholesterol reduction and blood sugar lowering. Therefore, there is an urgent need to obtain a low-cost and efficient oat β-glucan preparation process to meet market demand. Summary of the Invention

[0004] To address the above problems, this invention provides a method for extracting and preparing oat β-glucan, specifically comprising the following steps:

[0005] (1) Wash the oat bran powder repeatedly 3-5 times in alkaline deionized water with pH 8-9, and then centrifuge to dry.

[0006] (2) Add the oat bran powder from step (1) to water with a weight of 10-15 times that of the oat bran powder raw material, add the cell wall breaking compound enzyme, and react with ultrasound at 55-65℃ for 5-10 hours.

[0007] (3) After the reaction, inactivate the enzyme, centrifuge, and collect the supernatant;

[0008] (4) After letting the supernatant from step (3) stand overnight at 4°C, centrifuge and collect the supernatant;

[0009] (5) After heating the supernatant to 50-80℃, add heat-resistant α-amylase, stir and react for 0.5-1h, then heat to boiling to inactivate the enzyme, keep warm for 30min, and then centrifuge to collect the supernatant.

[0010] (6) After letting the supernatant from step (5) stand overnight at 4°C, centrifuge and collect the supernatant;

[0011] (7) Filter the supernatant from step (6) through filter membranes with different molecular weight cutoffs, collect the retentate, concentrate it and cool it to room temperature;

[0012] (8) Slowly stir the concentrated solution from step (7) into ethanol to make its final concentration 60%, and let it stand for 1 hour to precipitate.

[0013] (9) Centrifuge, remove the supernatant, and collect the precipitate;

[0014] (10) Add 5 times the amount of water to redissolve the precipitate, slowly stir and add ethanol to make the final concentration 60%, and let it stand to precipitate for 1 hour;

[0015] (11) Centrifuge, remove the supernatant, and collect the precipitate;

[0016] (12) Drying to obtain oat β-glucan of different low molecular weights.

[0017] The centrifugation conditions in step (1) are 4000 r / min for 30 min.

[0018] In step (2), the composite cell wall breaking enzyme is cellulase, pectinase and xylanase in a volume ratio of 1:1:1. The amount of the composite cell wall breaking enzyme added is 0.02-0.05 times the weight of the raw materials. The ultrasonic conditions are 80W.

[0019] In step (3), the enzyme inactivation step is boiling for 15 minutes and centrifugation at 4000 r / min for 15 minutes.

[0020] The centrifugation conditions in step (4) are 4000 r / min for 30 min.

[0021] The amino acid sequence of the thermostable α-amylase in step (5) is shown in SEQ ID No. 2. The centrifugation conditions are 4000 r / min for 30 min.

[0022] The centrifugation conditions in step (6) are 4000 r / min for 30 min.

[0023] In step (7), the molecular weight cutoffs of the filter membranes selected are 300,000 Da, 100,000 Da, 50,000 Da, 10,000 Da, 5,000 Da and 1,000 Da.

[0024] The centrifugation conditions for steps (9) and (11) are 4000 r / min and 30 min.

[0025] In step (12), the drying process is freeze drying.

[0026] The extraction and preparation method of the present invention further includes steps of deproteinization and decolorization.

[0027] The deproteinization step involves adjusting the pH of the supernatant to 4.5-5 at room temperature after step (5), letting it stand overnight, and then centrifuging to remove the protein precipitate.

[0028] The decolorization step is carried out after deproteinization. Specifically, activated charcoal is added at room temperature and reacted for 30-60 minutes. The amount of activated charcoal added is 1%-5% of the volume of the enzymatic hydrolysate.

[0029] Application of oat beta-glucan in the preparation of skin care products with soothing, moisturizing and anti-aging effects.

[0030] Beneficial effects: This invention utilizes an enzymatic method to extract β-glucan from oats. The entire process eliminates the need for multiple pH adjustments, reducing costs. Furthermore, the addition of a complex of cellulase-breaking enzymes (cellulase, pectinase, and xylanase) to treat the raw materials, along with enzymatic hydrolysis using a variant α-amylase, not only improves the yield of β-glucan but also increases extraction efficiency and shortens the extraction time. Subsequent filtration using membranes with different molecular weight cutoffs allows for the targeted separation of β-glucan at different molecular weights to meet market demands. Additionally, deproteinization, decolorization, and two alcohol precipitation processes further enhance the purity of the β-glucan, resulting in soothing, moisturizing, and anti-aging effects on the skin, making it widely applicable in the skincare industry. Attached Figure Description

[0031] Figure 1 : Flowchart of the extraction process of oat β-glucan in this invention;

[0032] Figure 2 Skin moisture content 2 hours after using 0.1% oat beta-glucan;

[0033] Figure 3 Skin moisture content 2 hours after using 0.2% oat beta-glucan;

[0034] Figure 4 : Inhibition rate of inflammatory factor secretion. Detailed Implementation

[0035] The specific implementation methods provided by the present invention will be described in detail below with reference to the embodiments.

[0036] Example 1: Preparation of oat β-glucan

[0037] (1) Wash the oat bran powder repeatedly 5 times in alkaline deionized water with pH 8, centrifuge at 4000 r / min for 30 min, and then dry it.

[0038] (2) Add the oat bran powder from step (1) to water with 10 times the weight of the oat bran powder raw material, add 0.02 times the weight of the raw material of the cell wall breaking complex enzyme (cellulase: pectinase: xylanase in a ratio of 1:1:1), and react with ultrasound (80W) at 55℃ for 10h.

[0039] (3) After the reaction, boil for 15 min to inactivate the enzyme, centrifuge at 4000 r / min for 15 min, and collect the supernatant;

[0040] (4) After letting the supernatant from step (3) stand overnight at 4°C, centrifuge at 4000 r / min for 30 min and collect the supernatant;

[0041] (5) After heating the supernatant to 50°C, add the thermoresistant α-amylase (SEQ ID No.2), stir and react for 1 hour, then heat to boiling to inactivate the enzyme, keep warm for 30 minutes, and then centrifuge to collect the supernatant.

[0042] (6) After letting the supernatant from step (5) stand overnight at 4°C, centrifuge at 4000 r / min for 30 min and collect the supernatant;

[0043] (7) The supernatant from step (6) is filtered through a filter membrane with different molecular weight cutoffs (300000Da, 100000Da, 50000Da, 10000Da, 5000Da and 1000Da), the retentate is collected, concentrated and cooled to room temperature.

[0044] (8) Slowly stir the concentrated solution from step (7) into ethanol to make its final concentration 60%, and let it stand for 1 hour to precipitate.

[0045] (9) Centrifuge at 4000 r / min for 30 min, remove the supernatant and collect the precipitate;

[0046] (10) Add 5 times the amount of water to redissolve the precipitate, slowly stir and add ethanol to make the final concentration 60%, and let it stand to precipitate for 1 hour;

[0047] (11) Centrifuge at 4000 r / min for 30 min, remove the supernatant and collect the precipitate;

[0048] (12) Freeze-drying to obtain oat β-glucan of different low molecular weights.

[0049] Example 2: Preparation of oat β-glucan

[0050] (1) Wash the oat bran powder repeatedly 5 times in alkaline deionized water with pH 9, centrifuge at 4000 r / min for 30 min, and then spin dry;

[0051] (2) Add the oat bran powder from step (1) to water at 15 times the weight of the oat bran powder raw material, add 0.05 times the weight of the raw material of the cell wall breaking complex enzyme (cellulase: pectinase: xylanase in a ratio of 1:1:1), and react with ultrasound (80W) at 65℃ for 5 hours.

[0052] (3) After the reaction, boil for 15 min to inactivate the enzyme, centrifuge at 4000 r / min for 15 min, and collect the supernatant;

[0053] (4) After letting the supernatant from step (3) stand overnight at 4°C, centrifuge at 4000 r / min for 30 min and collect the supernatant;

[0054] (5) After heating the supernatant to 80°C, add the thermoresistant α-amylase (SEQ ID No.2), stir and react for 30 min, then heat to boiling to inactivate the enzyme, keep warm for 30 min, and then centrifuge to collect the supernatant.

[0055] (6) After letting the supernatant from step (5) stand overnight at 4°C, centrifuge at 4000 r / min for 30 min and collect the supernatant;

[0056] (7) The supernatant from step (6) is filtered through a filter membrane with different molecular weight cutoffs (300000Da, 100000Da, 50000Da, 10000Da, 5000Da and 1000Da), the retentate is collected, concentrated and cooled to room temperature.

[0057] (8) Slowly stir the concentrated solution from step (7) into ethanol to make its final concentration 60%, and let it stand for 1 hour to precipitate.

[0058] (9) Centrifuge at 4000 r / min for 30 min, remove the supernatant and collect the precipitate;

[0059] (10) Add 5 times the amount of water to redissolve the precipitate, slowly stir and add ethanol to make the final concentration 60%, and let it stand to precipitate for 1 hour;

[0060] (11) Centrifuge at 4000 r / min for 30 min, remove the supernatant and collect the precipitate;

[0061] (12) Freeze-drying to obtain oat β-glucan of different low molecular weights.

[0062] Example 3: Preparation of oat β-glucan

[0063] (1) Wash the oat bran powder repeatedly 5 times in alkaline deionized water with pH 9, centrifuge at 4000 r / min for 30 min, and then spin dry;

[0064] (2) Add the oat bran powder from step (1) to water at 15 times the weight of the oat bran powder raw material, add 0.05 times the weight of the raw material of the cell wall breaking complex enzyme (cellulase: pectinase: xylanase in a ratio of 1:1:1), and react with ultrasound (80W) at 65℃ for 5 hours.

[0065] (3) After the reaction, boil for 15 min to inactivate the enzyme, centrifuge at 4000 r / min for 15 min, and collect the supernatant;

[0066] (4) After letting the supernatant from step (3) stand overnight at 4°C, centrifuge at 4000 r / min for 30 min and collect the supernatant;

[0067] (5) After heating the supernatant to 80°C, add the thermoresistant α-amylase (SEQ ID No.2), stir and react for 30 min, then heat to boiling to inactivate the enzyme, keep warm for 30 min, and then centrifuge to collect the supernatant.

[0068] (6) Adjust the pH of the supernatant from step (5) to 4.5 at room temperature, let it stand overnight, and then centrifuge to remove the protein precipitate.

[0069] (7) Add activated carbon at room temperature and react for 60 min. The amount of activated carbon added is 5% of the volume of the enzyme hydrolysate.

[0070] (8) After letting the treatment solution from step (7) stand at 4°C overnight, centrifuge at 4000 r / min for 30 min and collect the supernatant.

[0071] (9) The supernatant from step (8) is filtered through a filter membrane with different molecular weight cutoffs (300000 Da, 100000 Da, 50000 Da, 10000 Da, 5000 Da and 1000 Da), the retentate is collected, concentrated and cooled to room temperature.

[0072] (10) Slowly stir the concentrated solution from step (9) into ethanol to make its final concentration 60%, and let it stand for 1 hour to precipitate.

[0073] (11) Centrifuge at 4000 r / min for 30 min, remove the supernatant and collect the precipitate;

[0074] (12) Add 5 times the amount of water to redissolve the precipitate, slowly stir and add ethanol to make the final concentration 60%, and let it stand for 1 hour to precipitate;

[0075] (13) Centrifuge at 4000 r / min for 30 min, remove the supernatant and collect the precipitate;

[0076] (14) Freeze-dry to obtain oat β-glucan of different low molecular weights.

[0077] Comparative Example 1

[0078] The difference from Example 3 is the addition of 0.05 times the amount of cellulase; the rest of the method is the same.

[0079] Comparative Example 2

[0080] The difference from Example 3 is the addition of 0.05 times the amount of pectinase; the rest of the method is the same.

[0081] Comparative Example 3

[0082] The difference from Example 3 is the addition of 0.05 times xylanase; the rest of the method is the same.

[0083] Comparative Example 4

[0084] The difference from Example 3 is the addition of 0.05 times the amount of cell wall breaking complex enzyme (cellulase: pectinase ratio of 1:1), the rest of the methods are the same.

[0085] Comparative Example 5

[0086] The difference from Example 3 is the addition of 0.05 times the amount of cell wall-breaking complex enzyme (cellulase: xylanase in a 1:1 ratio), the rest of the methods are the same.

[0087] Comparative Example 6

[0088] The difference from Example 3 is the addition of 0.05 times the amount of cell wall breaking complex enzyme (pectinase: xylanase in a 1:1 ratio), the rest of the methods are the same.

[0089] Comparative Example 7

[0090] The difference from Example 3 is that wild-type α-amylase (SEQ ID No. 1) was used for enzymatic hydrolysis, while the rest of the methods are the same.

[0091] The yield, extraction rate, and purity of oat β-glucan from Examples 1-3 and Comparative Examples 1-7 were determined, and the results are shown in Table 1:

[0092] Table 1

[0093]

[0094]

[0095] Therefore, it can be seen that using three compound enzymes during cell wall breaking resulted in better yield and extraction rate than using a single enzyme or two compound enzymes (Example 3 and Comparative Examples 1-6); adding deproteinization and decolorization steps during the extraction preparation process can improve its purity (Example 3 and Examples 1-2); using a variant α-amylase in the enzymatic hydrolysis process significantly improved the yield and extraction rate (Example 3 and Comparative Example 7).

[0096] Therefore, the extraction and preparation process of oat β-glucan of the present invention reduces the number of pH adjustments, uses a cell-wall breaking complex enzyme and a thermoresistant amylase for enzymatic hydrolysis, thereby improving extraction efficiency, and employs deproteinization, decolorization, and multiple alcohol precipitation treatments to improve purity. Furthermore, oat β-glucan with different molecular weights (100,000-300,000 Da, 50,000-100,000 Da, 10,000-50,000 Da, 5,000-10,000 Da, 1,000-5,000 Da, and below 1,000 Da) can be obtained by using filter membranes with different molecular weight cutoffs.

[0097] Example of effect

[0098] The low molecular weight (1000-300000 Da) oat β-glucan obtained in Example 3 was mixed and its effect was verified.

[0099] 1. Cell proliferation experiment

[0100] Reference standard: SN / T 2328-2009 "Keratinocyte Test for Acute Toxicity of Cosmetics". Human keratinocyte cell line was used, and the relative cell viability after 24 hours of treatment with the test substance was detected using the CCK8 assay, serving as a reference for the acute toxicity evaluation of oat β-glucan in Example 3. Logarithmic growth phase cells were seeded in 96-well plates, 2*10 cells per well. 4100 μL of complete culture medium was used to prepare 100 viable cells per well. The cells were incubated in a CO2 incubator for 24 h. The test substance diluted with complete culture medium was added to each well according to the concentrations in Table 2, at a rate of 100 μL per well. The cells were incubated in a CO2 incubator for 24 h. The supernatant was discarded, and the cells were washed once with PBS. Then, 100 μL of 10% CCK8 working solution prepared with DMEM was added, and the cells were incubated in a CO2 incubator for 1.5 h. After incubation, the absorbance at 450 nm was measured using a microplate reader, and the relative cell viability was calculated. Relative cell viability (%) = 100% * (OD200%) 实验组 -OD 空白对照组 ) / (OD 溶剂对照组 -OD 空白对照组 When the relative cell viability is ≥100% and higher than the control, it is considered to have cell proliferation activity.

[0101] The results showed that when the added concentration was 8-10%, oat β-glucan had a certain promoting effect on the proliferation of human keratinocytes (Table 2).

[0102] Table 2

[0103]

[0104]

[0105] 2. DPPH Antioxidant Experiment

[0106] According to T / SHRH 006-2018 "Cosmetics - Experimental Method for Free Radical (DPPH) Scavenging", the DPPH antioxidant activity of oat β-glucan in Example 3 was tested. The oat β-glucan sample and DPPH solution from Example 3 were added according to Table 3.

[0107] Table 3

[0108]

[0109] After reacting at room temperature in the dark for 30 minutes, the absorbance at 517 nm was measured using a microplate reader. The free radical scavenging rate was calculated using the following formula:

[0110] In the formula:

[0111] • T - Absorbance of the sample well, i.e., the absorbance of the solution after the sample reacts with DPPH;

[0112] •T0 - Sample background absorbance;

[0113] • C-DPPH well absorbance, i.e., the absorbance of the DPPH solution without sample;

[0114] •C0 - Solvent background absorbance.

[0115] The results showed that oat β-glucan had a certain scavenging effect on DPPH free radicals at concentrations of 5% and 10% (Table 4).

[0116] Table 4

[0117] Group Blank control group 10％ 5％ DPPH removal rate 0.00％±2.37％ 19.94％±0.93％ 11.78％±1.66％

[0118] 3. Moisturizing Experiment

[0119] According to QB / T 4256-2011 Guidelines for Evaluating the Moisturizing Efficacy of Cosmetics, a moisturizing experiment was conducted on the oat β-glucan in Example 3.

[0120] The oat β-glucan from Example 3 was prepared into 0.1% and 0.2% solutions using purified water. A total of 30 subjects were included, including 12 males and 18 females, aged 20-57 years. Subjects were selected based on the voluntary participation criteria.

[0121] The test area was the inner side of both forearms. Three test product areas and three blank control areas were randomly selected on each of the right and left forearms. Each area was 16 square centimeters (4cm × 4cm). Subjects used the test sample and underwent a 2-hour double-blind trial. Test time points: Skin moisture content was measured with a probe before use and 2 hours after use.

[0122] Note: To use, take an appropriate amount of the aqueous solution of this product, apply it to the skin, and massage until absorbed.

[0123] The results showed that under the test conditions, the skin moisture content of the test areas of the subjects increased significantly after using solutions of 0.1% and 0.2% dextran, indicating a moisturizing effect (Table 5). Figures 2-3 ).

[0124] Table 5

[0125] product base value After using the product for 2 hours Product improvement rate after 2 hours p-value Significance Glucan - 0.1% 36.58±1.24 39.08±0.90 9.81％ <0.001 *** Glucan - 0.2% 35.58±1.24 41.42±1.56 14.08％ <0.001 ***

[0126] 4. In vitro soothing experiment

[0127] According to T-SHRH034-2021 "Test Method for Soothing Efficacy of Cosmetics - In Vitro Determination of TNF-α Inflammatory Factor Content in Lipopolysaccharide-Induced Macrophages RAW264.7", an in vitro soothing experiment was conducted on the oat β-glucan in Example 3. The test principle was to use mouse macrophages Ana-1, co-stimulate them with bacterial lipopolysaccharide and the test substance, collect the cell supernatant, and detect the secretion of inflammatory factors using enzyme-linked immunosorbent assay (ELISA).

[0128] Test materials:

[0129] Cells: Mouse macrophages Ana-1 P6;

[0130] Reagents: Complete culture medium, LPS, PBS, dexamethasone, mouse TNF-α enzyme-linked immunosorbent assay kit, mouse IL-6 enzyme-linked immunosorbent assay kit;

[0131] Test steps:

[0132] Logarithmic growth phase cells were seeded into 96-well plates, 1 x 10⁶ cells per well. 5 Live cells were cultured in 100 μL of complete culture medium in a CO2 incubator for 6 h. Then, according to the experimental groups, 0.1% and 0.2% of the oat β-glucan sample from Example 3, 40 μg / mL dexamethasone, and 1 μg / mL LPS were added to each well (100 μL per well), and the mixture was incubated in a CO2 incubator for 24 h. After incubation, 200 μL of cell culture supernatant was collected in a 1.5 mL sterile centrifuge tube, centrifuged at 500g for 5 min to remove cell components, and the ELISA kit was analyzed according to the instructions. A standard curve was constructed according to the ELISA kit instructions, and the corresponding concentrations were determined based on the OD450 values ​​of the samples.

[0133]

[0134] In the formula:

[0135] T—The average content of inflammatory factors in the test substance;

[0136] C—The average content of inflammatory factors in the negative control;

[0137] The results showed that at concentrations of 0.2% and 0.1%, dextran inhibited the secretion of inflammatory factors in mouse macrophages Ana-1, with significant differences (p<0.001) (Tables 6-7). Figure 4 ).

[0138] Table 6

[0139] concentration Dexamethasone: 40ug / mL Glucan - 0.2% Glucan - 0.1% IL-6 75.36％±0.04％ 25.61％±2.96％ 22.86％±6.30％ TNF-α 56.90％±0.69％ 32.05％±0.03％ 22.17％±2.14％

[0140] Table 7

[0141]

[0142] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A method for preparing oat β-glucan, characterized in that, The preparation method includes the following steps: (1) Wash the oat bran powder repeatedly 3-5 times in alkaline deionized water with pH 8-9, and then centrifuge to dry. (2) Add the oat bran powder from step (1) to water with a weight of 10-15 times that of the oat bran powder raw material, add the cell wall breaking compound enzyme, and react with ultrasound at 55-65℃ for 5-10 hours. (3) After the reaction, inactivate the enzyme, centrifuge, and collect the supernatant; (4) After letting the supernatant from step (3) stand overnight at 4°C, centrifuge and collect the supernatant; (5) After heating the supernatant to 50-80℃, add heat-resistant α-amylase, stir and react for 0.5-1h, then heat to boiling to inactivate the enzyme, keep warm for 30min, and then centrifuge to collect the supernatant. (6) After letting the supernatant from step (5) stand overnight at 4°C, centrifuge and collect the supernatant; (7) Filter the supernatant from step (6) through a filter membrane with different molecular weight cutoffs, collect the retentate, concentrate it and cool it to room temperature; (8) Slowly stir the concentrated solution from step (7) into ethanol to make its final concentration 60%, and let it stand for 1 hour to precipitate. (9) Centrifuge, remove the supernatant, and collect the precipitate; (10) Add 5 times the amount of water to redissolve the precipitate, slowly stir and add ethanol to make the final concentration 60%, and let it stand to precipitate for 1 hour; (11) Centrifuge, remove the supernatant, and collect the precipitate; (12) Drying to obtain oat β-glucan of different low molecular weights.

2. The preparation method according to claim 1, characterized in that, The complex enzyme in step (2) is composed of pectinase, xylanase and cellulase in a ratio of 1:1:1, and the amount of complex enzyme added is 0.02-0.05 times the weight of the raw materials.

3. The preparation method according to claim 1, characterized in that, The ultrasound conditions in step (2) are 80W.

4. The preparation method according to claim 1, characterized in that, The amino acid sequence of the thermostable α-amylase in step (5) is shown in SEQ ID No.

2.

5. The preparation method according to claim 1, characterized in that, The process also includes deproteinization and decolorization steps.

6. The preparation method according to claim 5, characterized in that, The deproteinization step involves adjusting the pH of the enzymatic hydrolysate to 4.5-5 at room temperature after step (5), letting it stand overnight, and then centrifuging to remove the protein precipitate.

7. The preparation method according to claim 5, characterized in that, The decolorization step is carried out after deproteinization. Specifically, activated charcoal is added at room temperature and reacted for 30-60 minutes. The amount of activated charcoal added is 1%-5% of the volume of the enzymatic hydrolysate.

8. The preparation method according to claim 1, characterized in that, The molecular weight cutoffs of the filter membranes selected in step (7) are 300,000 Da, 100,000 Da, 50,000 Da, 10,000 Da, 5,000 Da and 1,000 Da, respectively. The molecular weight ranges of the obtained oat β-glucan are 100,000-300,000 Da, 50,000-100,000 Da, 10,000-50,000 Da, 5,000-10,000 Da, 1,000-5,000 Da and below 1,000 Da.

9. The preparation method according to claim 1, characterized in that, The drying process described is freeze-drying.

10. The use of oat β-glucan prepared by the preparation method according to any one of claims 1-9 in the preparation of skin care products with soothing, moisturizing and anti-aging effects on the skin.

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