CN114947144A - Preparation method of soluble corn bran dietary fiber - Google Patents

Abstract

The invention discloses a corn husk soluble dietary fiber, which is prepared by the following methods: taking corn husks, washing, drying, pulverizing and degreasing; carrying out twin-screw extrusion treatment on the treated corn husks; adding water to adjust pH to 4.5~5, add xylanase and cellulase, mix, heat to kill enzymes; adjust pH to 5.3~5.7, add α-amylase, slowly stir at 93~97°C; add alkaline protease, stir; add starch Glucosidase, adjust pH to 4～4.5, stir; Heat the mixture at 95～100 DEG C to kill enzyme; Centrifuge, collect supernatant, add 95% ethanol of 4 times the volume of the supernatant, at 0 Store at ~4°C for 7~9 hours; centrifuge, collect sediment, and dry to obtain corn soluble dietary fiber; the invention has the advantages that compared with traditional extraction, the physicochemical properties and functional properties of soluble dietary fiber are improved.

Description

Preparation method of corn husk soluble dietary fiber

technical field

The invention belongs to the technical field of dietary fiber preparation, in particular to a preparation method of corn husk soluble dietary fiber.

Background technique

As the seventh largest nutrient, dietary fiber is of great significance for promoting body health. According to its solubility, it is divided into soluble dietary fiber (fruit, algae, etc.) and insoluble dietary fiber (grains, beans, fruits and vegetables, etc.). Insoluble dietary fiber has basic The adsorption and swelling properties of soluble dietary fiber have a good effect in stimulating intestinal peristalsis and controlling body weight. Due to its looser structure, soluble dietary fiber has stronger hydration and adsorption properties, and is in regulating fat metabolism and carbohydrate metabolism. It plays an important physiological role in improving the intestinal environment. However, the low content of soluble dietary fiber in natural sources such as grains and vegetables limits its application in food. Therefore, it is of great significance to modify the dietary fiber and increase the proportion of soluble dietary fiber to improve the utilization value of dietary fiber. .

Corn is the second largest food crop in my country with extremely high yield. The consumption of corn mainly includes three aspects: feed field, industrial field, food and other fields. In recent years, with the rapid development of the corn industry, the proportion of the corn industry has continued to increase, resulting in a large number of corn processing by-products, and corn husks, as the main by-products, are mostly used in the feed or fertilizer industry, and have not been reasonably developed and utilized. As a result, the added value of the product is extremely low, resulting in a waste of resources. However, compared with other grain husks, the content of dietary fiber in corn husks is higher, reaching 40-60%, of which insoluble dietary fiber accounts for more than 95%. Small, is a good source of dietary fiber. Therefore, it is of great significance to modify the corn husk dietary fiber, increase the proportion of soluble dietary fiber, and realize the high-value transformation and utilization of corn husk to improve the economic value and application value of corn by-products.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problem of low added value of corn by-products and serious waste of resources caused in the corn processing process, and to overcome the problems of low soluble dietary fiber content and poor quality in the corn husk dietary fiber, and to provide a corn husk soluble dietary fiber. Preparation.

Corn husk soluble dietary fiber, which is prepared by the following method:

1) Take corn husks, wash, dry, pulverize, and degrease;

2) The treated corn husks are subjected to twin-screw extrusion treatment, and the conditions are: the barrel temperature is 150~200°C, the water addition amount is 25~30%, and the screw speed is 200~250 rpm;

3) Add water to the sample treated in step 2) to form a suspension, adjust the pH to 4.5~5, add xylanase and cellulase, mix, and heat at 95~100°C to kill the enzyme;

4) Adjust pH to 5.3~5.7, add α-amylase, and slowly stir for 0.5~1.5h at 93~97℃;

5) Add alkaline protease and stir at pH 9.3~9.7 and 50~60 °C for 1.5~2.5h;

6) Add amyloglucosidase, adjust the pH to 4~4.5, stir at 55~65°C for 0.5~1.5h; heat the mixture at 95~100°C to kill the enzyme;

7) Centrifuge, collect the supernatant, add 4 times the volume of 95% ethanol of the supernatant, and store at 0-4°C for 7-9 hours; centrifuge, collect the precipitate, and dry to obtain corn soluble dietary fiber;

The degreasing described in step 1) is degreasing with n-hexane;

Step 2) The barrel temperature is 160°C, the amount of water added is 29%, and the screw speed is 210 rpm;

In step 3), the pH is adjusted to 4.8, and the heating temperature is 100°C;

Adjust the pH to 5.5 as described in step 4) and slowly stir for 1 h at 95°C.

The invention provides corn husk soluble dietary fiber, which is prepared by the following methods: taking corn husks, washing, drying, pulverizing, and degreasing; carrying out twin-screw extrusion treatment on the treated corn husks; adding water, and adjusting pH to 4.5 ~5, add xylanase and cellulase, mix, heat to kill the enzyme; adjust pH to 5.3~5.7, add α-amylase, stir slowly at 93~97°C; add alkaline protease, stir; add amyloglucoside Enzyme, adjust the pH to 4~4.5, stir; heat the mixture at 95~100 ° C to kill the enzyme; centrifuge, collect the supernatant, add 4 times the volume of 95% ethanol of the supernatant, at 0~4 ℃ of preservation for 7-9 hours; centrifugation, collection of precipitation, and drying to obtain corn soluble dietary fiber; the advantages of the present invention are: compared with traditional extraction (without modification treatment), the product obtained through twin-screw extrusion-enzymatic modification treatment The yield of soluble dietary fiber was significantly improved, and the physicochemical properties (such as water and oil holding capacity) and functional properties (such as antioxidant activity, nitrite ion adsorption capacity) of soluble dietary fiber were also improved.

Description of drawings

Fig.1 SEM images; (A) SDF, (B) USDF, (C) UESDF, (D) ESDF, (E) EESDF magnification × 1000; (a) IDF, (b) UIDF, (c) SEM images of UEIDF, (d) EIDF and (e) EEIDF magnification × 1000; (IDF stands for unmodified corn husk insoluble dietary fiber, Ultrasonic-IDF (UIDF) stands for ultrasonically modified corn husk insoluble dietary fiber, Ultrasonic assist enzyme -IDF (UEIDF) means ultrasonic-enzymatically modified corn insoluble dietary fiber, Extrusion-IDF (UIDF) means twin-screw extrusion modified corn husk insoluble dietary fiber, Extrusionassist-enzyme-IDF (EEIDF) means twin-screw extrusion- Enzymatically modified corn husk insoluble dietary fiber)

Fig. 2 Liquid chromatograms of HPLC of SDF(A), USDF(B), UESDF(C), ESDF(D), EESDF(E);

Fig.3 DSC curves of SDF, USDF, UESDF, ESDF and EESDF;

Fig.4 FT-IR spectra of SDF, USDF, UESDF, ESDF and EESDF;

Figure 5 Extraction of soluble dietary fiber from corn husks using different X-ray diffraction analyses;

Figure 6 DPPH scavenging activity (A), ABTS scavenging activity (B), FRAP (C) and nitrite ion adsorption capacity (D) of SDF, USDF, UESDF, ESDF and EESDF.

Detailed ways

Example 1 Preparation of corn husk soluble dietary fiber

Preparation of corn husk soluble dietary fiber, which includes:

1) Take (Xianyu 335) corn husks, wash them with water for six times, remove part of the residual starch and protein, put them in an oven to dry at 60°C for 36 hours; crush the corn husks through an 80-mesh sieve, and use n-hexane to degrease 3 times ;

2) The treated corn husks are subjected to twin-screw extrusion modification treatment, and the conditions are: the barrel temperature is 160°C, the water content is 29%, and the screw speed is 210 rpm;

3) Disperse 10 g of the extruded sample in 120 mL of distilled water to form a suspension, adjust the pH to 4.8, add complex enzymes (120 U/g xylanase, 240 U/g cellulase), mix , the mixture was heated at 100 ° C for 15 min to inactivate the enzyme;

4) After inactivating the enzyme, adjust the pH to 5.5, add α-amylase (100U/g), and slowly stir for 1 hour at 95°C;

5) After stirring, add alkaline protease (100 U/g), and stir for 2 hours at pH 9.5 and 55 °C;

6) Add amyloglucosidase (200U/g), adjust the pH to 4.2, stir at 60°C for 1h; heat the mixture at 100°C for 15min to kill the enzyme;

7) Centrifuge at 5000 × g for 15 min to collect the supernatant; add 4 times the volume of 95% ethanol to the supernatant, and store at 4°C for 8 h; centrifuge, collect the precipitate, and dry to obtain corn soluble dietary fiber.

Example 2 Screening of the best modification process for corn husk soluble dietary fiber

1. Method

1. Twin-screw extrusion modified corn husk soluble dietary fiber (ESDF)

The corn husk soluble dietary fiber is prepared by twin-screw extrusion. The specific method is as follows: washing the corn husk with distilled water to remove residual starch and protein, drying the sample and degreasing with n-hexane, grinding and passing through an 80-mesh sieve. Then, under the conditions of feeding speed 16 kg/h, extrusion temperature 160 °C, screw speed 210 rpm, and water addition 29%, the sample was subjected to twin-screw extrusion treatment. After the treatment, the pH was adjusted to 5.5, and α-starch was added. The enzyme (100 U/g) was slowly stirred at 95 °C for 1 h; then, alkaline protease (100 U/g) was added, and the mixture was stirred at pH 9.5 and 55 °C for 2 h; then amyloglucosidase (200 °C) was added. U/g), adjust the pH to 4.2, stir at 60 °C for 1 h; heat the mixture at 100 °C for 15 min to inactivate the enzyme; centrifuge at 5000 × g for 15 min to collect the supernatant; add 4 times the volume of the supernatant 95% ethanol, stored at 4 °C for 8 h; centrifuged, collected the precipitate, dried, and the obtained dietary fiber sample was expressed by ESDF;

2. Twin-screw extrusion-assisted enzymatically modified corn husk soluble dietary fiber (EESDF)

The corn husk soluble dietary fiber was prepared by twin-screw extrusion-assisted enzymatic treatment. The specific method was as follows: washing the corn husk with distilled water to remove residual starch and protein, drying the sample and degreasing with n-hexane, grinding and passing through an 80-mesh sieve. Then, under the conditions of feeding speed 16 kg/h, extrusion temperature 160 °C, screw speed 210 rpm, and water addition 29%, the sample was subjected to twin-screw extrusion treatment, and the extruded sample (10 g) was dispersed in distilled water ( 120mL), adjust the pH to 4.8, add compound enzymes (120 U/g xylanase, 240 U/g cellulase) for enzymatic hydrolysis for 2.5 hours, and then heat the mixture at 100°C for 15min to kill the enzyme; Then, adjust the pH to 5.5, add α-amylase (100 U/g), and stir slowly at 95 °C for 1 h; then, add alkaline protease (100 U/g), and stir at pH 9.5 and 55 °C for 2 h ; Then add amyloglucosidase (200U/g), adjust the pH to 4.2, stir at 60°C for 1h; heat the mixture at 100°C for 15min to kill the enzyme; centrifuge at 5000×g for 15min, collect the supernatant; add 4 times the volume of 95% ethanol to the supernatant, store at 4°C for 8 hours; centrifuge, collect the precipitate, and dry, and the obtained dietary fiber sample is represented by EESDF;

3. Ultrasonic modified corn husk soluble dietary fiber (USDF)

The corn husk soluble dietary fiber was prepared by ultrasonic treatment. The specific method was as follows: washing the corn husk with distilled water to remove residual starch and protein, drying the sample and degreasing with n-hexane, grinding and passing through an 80-mesh sieve. Then, the solid-liquid ratio was 1:31 and the ultrasonic power was 480W for 38 min. After the treatment, the pH was adjusted to 5.5, α-amylase (100 U/g) was added, and the stirring was carried out at 95 °C for 1 h; then , add alkaline protease (100 U/g), and stir at pH 9.5 and 55 °C for 2 h; then add amyloglucosidase (200 U/g), adjust the pH to 4.2, and stir at 60 °C for 1 h; The mixture was heated at 100 °C for 15 min to inactivate the enzyme; centrifuged at 5000 × g for 15 min, and the supernatant was collected; 4 times the volume of 95% ethanol was added to the supernatant, and stored at 4 °C for 8 h; centrifuged, the precipitate was collected, and dried to obtain The dietary fiber samples are expressed in USDF;

4. Ultrasonic-assisted enzymatic modification of corn husk soluble dietary fiber (UESDF)

The corn husk soluble dietary fiber was prepared by ultrasonic-assisted enzymatic treatment. The specific method was as follows: washing the corn husk with distilled water to remove residual starch and protein, drying the sample and degreasing with n-hexane, grinding and passing through an 80-mesh sieve. Then, the sonicated sample (10 g) was dispersed in distilled water (120 mL) under the conditions of a solid-liquid ratio of 1:31 and an ultrasonic power of 480 W for 38 min, the pH was adjusted to 4.8, and a composite enzyme (120 U/g xylan) was added. Enzyme, 240 U/g cellulase) enzymatic hydrolysis for 2.5 hours, then the mixture was heated at 100 °C for 15 min to kill the enzyme; after the enzyme was killed, adjust the pH to 5.5, add α-amylase (100 U/g), at 95 Stir slowly for 1 h at ℃; then, add alkaline protease (100 U/g), stir at pH 9.5, 55 ℃ for 2 h; then add amyloglucosidase (200 U/g), adjust the pH to 4.2, Stir at 60 °C for 1 h; heat the mixture at 100 °C for 15 min to inactivate the enzyme; centrifuge at 5000 × g for 15 min, collect the supernatant; add 4 times the volume of 95% ethanol to the supernatant, and store at 4 °C for 8 h ; Centrifuge, collect the precipitate, dry, and the obtained dietary fiber sample is represented by UESDF.

2. Yield and physicochemical properties of corn soluble dietary fiber

The samples were prepared by the above four processes respectively, and the yield of the samples was measured. The results are shown in Table 1. The twin-screw extrusion assisted enzymatic treatment, the yield of corn soluble dietary fiber was 10.53%, and the ultrasonic assisted enzymatic modified diet was 10.53%. The yield of fiber was 6.98%, the yield of dietary fiber treated by twin-screw extrusion was 6.54%, the yield of ultrasonic-treated dietary fiber was 4.58%, and the yield of untreated dietary fiber was 2.42%; this shows that twin-screw extrusion treatment is more beneficial than ultrasonic treatment. Enzymatic hydrolysis; in the table SDF means unmodified corn husk soluble dietary fiber, Ultrasonic-SDF (USDF) means ultrasonically modified corn husk soluble dietary fiber, Ultrasonic assist enzyme-SDF (UESDF) means ultrasonic-enzymatic modified corn husk soluble dietary fiber Dietary fiber, Extrusion-SDF (ESDF) stands for twin-screw extrusion modified corn husk soluble dietary fiber, Extrusion assist-enzyme-SDF (EESDF) stands for twin-screw extrusion-enzymatically modified corn husk soluble dietary fiber;

As shown in Table 1, compared with the untreated group, all four treatments significantly improved the water and oil holding capacity of dietary fiber, with EESDF having the highest water holding capacity and UESDF having the highest oil holding capacity.

Table 1 Chemical composition, yield (%) and average molecular weight of corn soluble dietary fiber (SDF)

Samples SDF Ultrasonic-SDF Ultrasonic assist enzyme-SDF Extrusion-SDF Extrusion assist-enzyme-SDF Extraction yield % 2.42±0.14e 4.58±0.08d 6.98±0.15b 6.54±0.13c 10.53±0.24a WHC(g/g) 0.81 ±0.02e 1.40 ±0.13d 2.89 ±0.14b 2.06 ±0.07c 3.22±0.23a OHC(g/g) 1.57±0.06d 2.27±0.12c 2.87±0.06a 2.28±0.08c 2.55±0.07b Average molecular weight (Da) 1.58×10⁵ 3.07×105 6.41×104 1.22×10⁵ 4.00×104

NOTE: Results are expressed as mean ± standard deviation (n = 3); a, b, c, d, e values in the same row are significantly different from each other ( p < 0.05).

3. Structural characteristics

1. Scanning Electron Microscope

The microstructures of four modified corn husk dietary fiber samples (soluble dietary fiber and insoluble dietary fiber) were observed by scanning electron microscopy. The results are shown in Figure 1. IDF(a) showed a dense network structure; UIDF(b) Under the cavitation of ultrasonic waves, many cavities were formed on the surface, and the specific surface area increased, but the overall structure did not change much; EIDF (d) under the action of twin-screw extrusion, the dense layered structure was destroyed , the structure becomes loose, the internal structure is exposed, and it has a larger specific surface area and porous structure, which increases the binding site with enzymes, which is conducive to the enzymatic hydrolysis reaction; on the basis of ultrasonic and twin-screw extrusion, cellulose Further treatment with enzymes and xylanase further disrupted the structures of UEIDF(c) and EEIDF(e), resulting in corrosion-like areas around insoluble dietary fibers and more open fiber structures. Compared with SDF, USDF and ESDF have larger specific surface area, and UESDF and EESDF have smaller particle size. It can be seen from the above results that the four treatment methods have an effect on the structure of insoluble dietary fiber, which is the reason for increasing the yield of soluble dietary fiber and improving the physicochemical and functional properties.

2. Molecular weight determination

The molecular weights of the four modified corn husk soluble dietary fiber samples were determined by high performance liquid chromatography. It can be seen from Figure 2 that there are significant differences in the molecular weights of the four samples. The relative molecular weights are arranged in descending order: USDF (3.07×10 ⁴ Da), SDF (1.58×10 ⁴ Da), ESDF (1.22×10 ⁴ Da), UESDF (6.41×10 ³ Da), EESDF (4.00×10 ³ Da). Compared with SDF, the high molecular weight dietary fiber content of UESDF, ESDF, and EESDF samples decreased, and the low molecular weight dietary fiber content increased, resulting in a decrease in the average molecular weight; due to the cavitation effect of ultrasonic waves, the average molecular weight of the USDF sample was the highest. .

3. Monosaccharide composition analysis

The monosaccharide (mannose, rhamnose, galacturonic acid, glucose, xylose and arabinose) compositions of four modified corn husk soluble dietary fiber samples were analyzed by high performance liquid chromatography, and the results are shown in Table 2 , SDF contains rhamnose and higher galacturonic acid, USDF and ESDF treatment significantly increased xylose and arabinose content compared with untreated group, UESDF and EESDF treatment significantly increased glucose content, the above results show that , twin-screw extrusion and ultrasonic treatment destroy the connection between cellulose and hemicellulose and increase the solubility of hemicellulose; twin-screw extrusion and ultrasonic-assisted enzyme treatment promote the hydrolysis of cellulose, and the four treatments make dietary fiber structure changes, resulting in changes in the monosaccharide composition.

Table 2 Monosaccharide composition of SDF (%)

Monosaccharides (%) SDF USDF UESDF ESDF ESDF Mannose 2.41 ± 0.01^c 2.57 ± 0.01^b 0.00 1.56 ± 0.01^d 3.69 ± 0.01^a Rhamnose 1.39 ± 0.01 0.00 0.00 0.00 0.00 Galacturonic acid 15.04 ± 0.02^a 7.79 ± 0.01^b 3.36 ± 0.02^e 6.36 ± 0.01^c 5.83 ± 0.03^d Glucose 13.79 ± 0.01^d 3.33 ± 0.01^e 57.53 ± 0.01^a 16.70 ± 0.01^c 24.45 ± 0.01^b Xylose 35.77 ± 0.02^c 37.98 ± 0.01^a 19.08 ± 0.01^e 36.32 ± 0.02^b 30.85 ± 0.03^d Arabinose 31.59 ± 0.02^a 48.32 ± 0.01^a 20.01 ± 0.01^e 39.06 ± 0.04^b 35.17 ± 0.04^c

NOTE: Results are expressed as mean ± standard deviation (n = 3); a, b, c, d, e represent values in the same row that are significantly different from each other ( p < 0.05).

4. Differential Scanning Calorimetry

The thermal properties of four modified corn husk soluble dietary fiber samples were determined by differential scanning calorimetry. The results are shown in Figure 3. Compared with the untreated group, all four treatments improved the thermal stability of dietary fiber. The endothermic peak of ESDF is shifted to the right, and the movement of EESDF is more obvious. This is because the twin-screw extrusion treatment destroys the hydrogen bonds in the molecule, making the molecular structure more stable, resulting in a decrease in bound water and an increase in the endothermic temperature.

5. Fourier infrared spectroscopy

Fourier transform infrared spectroscopy was used to characterize the chemical functional groups and structural changes of the four modified corn husk soluble dietary fiber samples. Internal hydrogen bonds. Among them, the structure of the EESDF sample was severely damaged, and the carboxyl group content increased.

6. Crystal structure detection

The crystal structures of the four modified corn husk soluble dietary fiber samples were analyzed by X-ray diffractometer. The results are shown in Figure 5. SDF has an obvious diffraction peak at the 2θ value of 22°, and the four modification treatments did not change the dietary fiber. The crystal structure of , the diffraction peak at 26° showed that SDF coexisted in crystalline and amorphous states, and all four treatments significantly reduced the crystallinity of dietary fiber, indicating that twin-screw extrusion and ultrasonic treatment destroyed the crystal structure of dietary fiber, Change the crystal structure from ordered to disordered and increase the amorphous composition.

4. Features

1. Antioxidant ability

The antioxidant activities of four modified corn husk soluble dietary fiber samples were compared by measuring ABTS+ scavenging capacity, DPPH scavenging capacity and iron reduction antioxidant activity (FRAP). As shown in Fig. 6A, in the sample concentration range of 1.5-3.5 mg/mL, all samples showed a certain DPPH scavenging activity, among which, EESDF showed the highest DPPH scavenging activity at different concentrations. As shown in Fig. 6B, in the sample concentration range of 3-7 mg/mL, the ABTS+ scavenging activity of the four samples was higher than that of the untreated group, and the ABTS+ scavenging activity of EESDF was the highest. As shown in Figure 6C, as the sample concentration increased, the FRAP activity of the four treated samples was continuously enhanced, and all were significantly stronger than the untreated group.

2. Nitrite ion (NO2-) adsorption activity

The nitrite ion adsorption activities of the four modified corn husk soluble dietary fiber samples were analyzed, and the results are shown in Figure 6D, SDF has a strong adsorption capacity at pH 2, indicating that it mainly adsorbs nitrous acid in the stomach root ion. Compared with SDF, the adsorption capacity of dietary fiber obtained by four treatments on nitrite ions was significantly improved, and EESDF had the highest adsorption capacity for nitrite ions.

To sum up, the results show that, compared with other methods, the corn husk soluble dietary fiber prepared by twin-screw extrusion-assisted enzymatic method has a high yield, good water and oil holding capacity, good structural properties, and strong oxidation resistance.

Example 3 Application of modified corn husk soluble dietary fiber

Natural corn starch is easily retrograded, which limits the processing and food production of corn starch. Improving the processing properties of starch by adding dietary fiber is one of the research hotspots in recent years.

The present invention prepares a modified corn husk soluble dietary fiber with good physical and chemical properties and functional properties. In order to further investigate its practical application value, the present invention adds the modified corn husk soluble dietary fiber to corn starch, and evaluates its effect on The effects of corn starch processing characteristics and digestion characteristics were found. It was found that the modified corn husk soluble dietary fiber could inhibit the starch gelatinization, reduce the gelatinization viscosity, increase the gelatinization temperature and improve the shear of the blend system of starch and dietary fiber. stability, while inhibiting the short-term and long-term retrogradation of starch. In addition, the modified corn husk soluble dietary fiber reduced the proportion of rapidly digestible starch in corn starch, inhibited the digestion of corn starch, and reduced the degree of starch hydrolysis and the glycemic index. In conclusion, the modified soluble dietary fiber prepared by the present invention has good effects in delaying corn starch retrogradation, improving corn starch processing characteristics and inhibiting starch digestion.

Claims (5)

1. The soluble corn bran dietary fiber is characterized in that: it is prepared by the following method:

1) taking corn bran, washing, drying, crushing and degreasing;

2) carrying out double-screw extrusion treatment on the treated corn bran under the conditions as follows: the temperature of the machine barrel is 150-200 ℃, the water adding amount is 25-30%, and the rotating speed of the screw is 200-250 rpm;

3) adding water into the sample treated in the step 2) to form a suspension, adjusting the pH to 4.5-5, adding xylanase and cellulase, mixing, and heating at 95-100 ℃ to inactivate enzymes;

4) adjusting the pH value to 5.3-5.7, adding alpha-amylase, and slowly stirring for 0.5-1.5 h at the temperature of 93-97 ℃;

5) adding alkaline protease, and stirring for 1.5-2.5 h under the conditions of pH 9.3-9.7 and 50-60 ℃;

6) adding amyloglucosidase, adjusting the pH to 4-4.5, and stirring at 55-65 ℃ for 0.5-1.5 h; heating the mixture at 95-100 ℃ to inactivate enzyme;

7) centrifuging, collecting supernatant, adding 95% ethanol with 4 times volume of the supernatant, and storing at 0-4 ℃ for 7-9 h; centrifuging, collecting the precipitate, and drying to obtain the corn soluble dietary fiber.

2. The corn bran soluble dietary fiber of claim 1, wherein: degreasing in the step 1) is carried out by using n-hexane.

3. The corn bran soluble dietary fiber of claim 2, characterized in that: the temperature of the cylinder in the step 2) is 160 ℃, the water adding amount is 29 percent, and the rotating speed of the screw is 210 rpm.

4. The corn bran soluble dietary fiber of claim 3, characterized in that: adjusting the pH value to 4.8 in the step 3), and heating to 100 ℃.

5. The corn bran soluble dietary fiber of claim 4, wherein: adjusting the pH value to 5.5 in the step 4), and slowly stirring for 1h at the temperature of 95 ℃.

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