Method for preparing functional bean dreg dietary fiber by utilizing ultrasonic coupling enzyme method

Abstract

The invention belongs to the technical field of food processing and comprehensive utilization of byproducts, and particularly relates to a method for preparing functional dietary fibers from soybean meal protein extraction residues by using an ultrasonic coupling enzyme method. The method comprises the following steps: (1) raw material pretreatment: carrying out deproteinization and starch removal treatment on soybean meal residues after protein extraction by using alkaline protease and high-temperature-resistant alpha-amylase; (2) ultrasonic treatment: modifying the dietary fibers of the bean dregs by adopting energy-gathered ultrasonic equipment; and (3) performing enzymatic treatment: adding cellulase into the bean dreg dietary fiber solution subjected to ultrasonic pretreatment for performing enzymolysis treatment, and performing high-temperature enzyme deactivation after the treatment is completed, so as to obtain the functional bean dreg dietary fiber. The method disclosed by the invention is mild in operation condition and high in process efficiency, contributes to retaining or enhancing the functional characteristics of the dietary fibers, is suitable for the development of functional foods, healthy foods and dietary supplements, and has a good industrial application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of food processing and comprehensive utilization of by-products, and in particular to a method for extracting functional dietary fiber from soybean meal protein residues by utilizing an ultrasonic coupled enzyme method. Background Art

[0002] Soybean meal is a major byproduct of the soybean oil extraction industry and is widely used in feed and plant protein extraction. During the soy protein extraction process, a large amount of insoluble residue (okara) is discarded or used at a low value, resulting in both resource waste and environmental pressure. Research has shown that this residue is rich in insoluble dietary fiber (IDF) and soluble dietary fiber (SDF) precursors, suggesting high development potential.

[0003] Traditional methods for preparing dietary fiber primarily rely on physical separation or single enzymatic hydrolysis, which can lead to low processing efficiency, poor fiber solubility, and severe structural damage. In recent years, ultrasound-assisted enzymatic hydrolysis has gained widespread attention in food processing due to its environmentally friendly, efficient, and gentle properties. Ultrasound can enhance the contact efficiency between enzymes and substrates through the cavitation effect, thereby promoting cell wall breakdown and fiber release, thereby improving functional properties (such as water holding capacity, adsorption, and prebiotic activity), and promoting the application of okara dietary fiber in food processing and functional foods. Summary of the Invention

[0004] The present invention aims to provide a method for preparing bean dregs dietary fiber that is efficient, environmentally friendly, and suitable for industrial application. Specifically, the method utilizes ultrasonic coupled enzymatic hydrolysis technology to firstly ultrasonicate and then enzymatically hydrolyze bean dregs to produce functional dietary fiber, thereby improving the utilization rate of bean dregs resources and enhancing the quality of dietary fiber.

[0005] Based on the above purpose, the technical solution of the present invention is as follows: A method for preparing functional bean dregs dietary fiber using an ultrasound-coupled enzyme method comprises the following steps: (1) Raw material pretreatment: Bean dregs were crushed to less than 60 mesh and added to deionized water at a mass ratio of 1:30 (g / mL) to form a bean dregs suspension. Alkaline protease and thermostable α-amylase were added to the bean dregs suspension to perform deproteinization and destarch treatment, respectively, to initially obtain crude dietary fiber.

[0006] (2) Ultrasonic pretreatment: The crude dietary fiber in step (1) was ultrasonically treated using a focused ultrasonic device. The ultrasonic treatment conditions were as follows: ultrasonic frequency 25 kHz, ultrasonic power 100-500 W, ultrasonic time 10-30 min, and temperature 30°C.

[0007] (3) enzymatic treatment: the dietary fiber after ultrasonic treatment is subjected to cellulase enzymatic treatment, and the treatment conditions are as follows: enzyme addition amount 0.1%~0.5%, pH 4~6, enzymatic treatment time 0.5~2.5 h, and enzymatic treatment temperature 45~65 ℃; (4) enzyme inactivation and drying treatment: the dietary fiber solution after enzymatic treatment is subjected to enzyme inactivation treatment (105 ℃, 10 min), and after enzyme inactivation, cooling and freeze-drying are carried out, and finally the functional dietary fiber product is obtained.

[0008] Further, in step (1), the mixing ratio of the bean dregs and deionized water is 1:30; the addition amount of alkaline protease is 30 U / g, and the enzyme treatment time is 30 min; the addition amount of thermostable alpha-amylase is 20 U / g, and the enzyme treatment time is 35 min.

[0009] Further, in step (2), the ultrasonic treatment conditions are preferably as follows: ultrasonic power 300 W, and ultrasonic time 20 min. Further, in step (3), the enzymatic treatment conditions are preferably as follows: enzyme addition amount 0.2%, pH 5.0, enzymatic treatment time 1 h, and enzymatic treatment temperature 60 ℃.

[0010] Further, in step (4), the enzyme inactivation treatment conditions are 105 ℃, 10 min.

[0011] Further, in step (3), during enzymolysis, glucomannan, mannitol and sorbitan laurate are added, and the mass ratio of the addition amount to cellulase is 1~2:2~5:1~2:100.

[0012] Further, in step (3), during enzymolysis, glucomannan, mannitol and sorbitan laurate are added, and the mass ratio of the addition amount to cellulase is 1:3:1:100.

[0013] Advantages of the present application: The present application uses the residue (bean dregs) after extracting protein from soybean meal as raw material, and adopts ultrasonic coupling enzyme method to prepare functional dietary fiber, realizes high-value utilization of bean dregs, improves the resource utilization rate of by-products, and meets the industrial demand of green and sustainable development. The prepared dietary fiber has good water holding capacity and oil holding capacity, which helps to improve its application performance in food system, such as improving the water retention, emulsification and taste stability of food. During enzymolysis, glucomannan, mannitol and sorbitan laurate are added, which is beneficial to the stability of enzymolysis and promotes enzymolysis. Compared with the traditional dietary fiber preparation method, the operation condition of the present application is mild, the process efficiency is high, which is helpful to retain or enhance the functional properties of dietary fiber, and is suitable for the development of functional food, health food and dietary supplements, and has good industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a functional dietary fiber product; Figure 2 Effects of different treatments on the yield of soluble dietary fiber in okara dietary fiber (CK: control; U: ultrasonic treatment; M: enzyme treatment; UM: ultrasound-coupled enzyme treatment); Figure 3 Effects of different treatments on the water holding capacity of dietary fiber from soybean dregs (CK: control; U: ultrasonic treatment; M: enzyme treatment; UM: ultrasound-coupled enzyme treatment); Figure 4 Effects of different treatments on the oil retention of dietary fiber in soybean dregs (CK: control; U: ultrasonic treatment; M: enzyme treatment; UM: ultrasound-coupled enzyme treatment); Figure 5 Effects of different treatments on the glucose adsorption capacity of okara dietary fiber (CK: control; U: ultrasonic treatment; M: enzyme treatment; UM: ultrasound-coupled enzyme treatment). DETAILED DESCRIPTION The technical solution of the present invention is further described below, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention shall be included in the scope of protection of the present invention.

[0015] Example 1 10 g of bean dregs were added to 300 mL of deionized water and dispersed thoroughly. The pH was adjusted to 8.0 and the temperature was 60°C. 30 U / g alkaline protease was added for 30 min to deproteinize the solution. After the reaction, the solution was incubated in a boiling water bath for 10 min to inactivate the enzyme. After cooling, the pH of the bean dregs solution was adjusted to 4.5 and the temperature was 95°C. 20 U / g thermostable α-amylase was added for 35 min to destarch the solution. After the reaction, the solution was incubated in a boiling water bath for 10 min to inactivate the enzyme. The crude dietary fiber solution was obtained after cooling. The crude dietary fiber solution was treated with ultrasound (frequency 25 kHz, power 300 W, time 20 min), and then 0.1% cellulase by mass of the crude dietary fiber solution was added. The reaction was incubated at 50 °C for 1 h, and the enzyme was inactivated by heating. After cooling, a functional dietary fiber product was obtained. The results showed that the purity of dietary fiber in the dietary fiber product was 86.11%±5.71%, the SDF yield was 6.87%±0.87%, the water holding capacity was 11.62±0.21 g / g, the oil holding capacity was 8.68±1.04 g / g, and the glucose adsorption capacity was 9.276±0.001 mmol / g.

[0016] Example 2 10 g of bean dregs were added to 300 mL of deionized water and dispersed thoroughly. The pH was adjusted to 8.0 and the temperature was 60°C. 30 U / g alkaline protease was added for 30 min to deproteinize the solution. After the reaction, the solution was incubated in a boiling water bath for 10 min to inactivate the enzyme. After cooling, the pH of the bean dregs solution was adjusted to 4.5 and the temperature was 95°C. 20 U / g thermostable α-amylase was added for 35 min to destarch the solution. After the reaction, the solution was incubated in a boiling water bath for 10 min to inactivate the enzyme. The crude dietary fiber solution was obtained after cooling. The crude dietary fiber solution was ultrasonically treated (frequency 25 kHz, power 200 W, time 25 min), and then 0.2% cellulase by mass of the crude dietary fiber solution was added. The reaction was carried out at 60 °C for 1.5 h. After the reaction, the enzyme was heated to inactivate the enzyme and cooled to obtain a functional dietary fiber product. The results showed that the dietary fiber purity of the dietary fiber product was 87.43%±3.94%, the SDF yield was 8.00%±1.04%, the water holding capacity was 12.07±0.20 g / g, the oil holding capacity was 9.45±0.47 g / g, and the glucose adsorption capacity was 9.202±0.004 mmol / g.

[0017] Example 3 10 g of bean dregs were added to 300 mL of deionized water and dispersed thoroughly. The pH was adjusted to 8.0 and the temperature was 60°C. 30 U / g alkaline protease was added for 30 min to deproteinize the solution. After the reaction, the solution was incubated in a boiling water bath for 10 min to inactivate the enzyme. After cooling, the pH of the bean dregs solution was adjusted to 4.5 and the temperature was 95°C. 20 U / g thermostable α-amylase was added for 35 min to destarch the solution. After the reaction, the solution was incubated in a boiling water bath for 10 min to inactivate the enzyme. The crude dietary fiber solution was obtained after cooling. The crude dietary fiber solution was ultrasonically treated (frequency 25 kHz, power 400 W, time 15 min), and then 0.3% cellulase by mass of the crude dietary fiber solution was added. The reaction was carried out at 55 °C for 2 h. After the reaction, the enzyme was heated to inactivate the enzyme and cooled to obtain a functional dietary fiber product. The results showed that the dietary fiber purity of the dietary fiber product was 87.91%±9.15%, the SDF yield was 7.08%±0.64%, the water holding capacity was 10.98±0.34 g / g, the oil holding capacity was 7.94±0.52 g / g, and the glucose adsorption capacity was 9.311±0.003 mmol / g.

[0018] Comparative Example 1 10 g of soybean dregs were added to 300 mL of deionized water and thoroughly dispersed. The solution was then adjusted to pH 8.0 and heated to 60°C. 30 U / g alkaline protease was added for 30 minutes to deproteinize the solution. The enzyme was then inactivated by boiling in a water bath for 10 minutes. After cooling, the pH of the dregs solution was adjusted to 4.5 and heated to 95°C. 20 U / g thermostable α-amylase was added for 35 minutes to destarch the solution. The enzyme was then inactivated by boiling in a water bath for 10 minutes. The crude dietary fiber solution was then cooled. The results showed a dietary fiber purity of 84.55% ± 7.66%, an SDF yield of 3.07% ± 0.31%, a water holding capacity of 10.62 ± 0.02 g / g, an oil holding capacity of 7.97 ± 0.63 g / g, and a glucose adsorption capacity of 9.150 ± 0.001 mmol / g.

[0019] Comparative Example 2 10 g of bean dregs were added to 300 mL of deionized water and dispersed thoroughly. The pH was adjusted to 4.5 and the temperature was 60°C. 30 U / g alkaline protease was added for 30 min to deproteinize the solution. After the reaction, the solution was incubated in a boiling water bath for 10 min to inactivate the enzyme. After cooling, the pH of the bean dregs solution was adjusted to 4.5 and the temperature was 95°C. 20 U / g thermostable α-amylase was added for 35 min to destarch the solution. After the reaction, the solution was incubated in a boiling water bath for 10 min to inactivate the enzyme. The crude dietary fiber solution was obtained after cooling. The crude dietary fiber solution was treated with ultrasonic waves (frequency 25 kHz, power 300 W, time 20 min) to obtain a functional dietary fiber product. The results showed that the dietary fiber purity was 83.23%±1.54%, the SDF yield was 6.20%±1.10%, the water holding capacity was 14.88±0.29 g / g, the oil holding capacity was 9.67±0.85 g / g, and the glucose adsorption capacity was 9.137±0.020 mmol / g.

[0020] Comparative Example 3 10 g of bean dregs were added to 300 mL of deionized water and dispersed thoroughly. The pH was adjusted to 8.0 and the temperature was 60°C. 30 U / g alkaline protease was added for 30 min to deproteinize the solution. After the reaction, the solution was incubated in a boiling water bath for 10 min to inactivate the enzyme. After cooling, the pH of the bean dregs solution was adjusted to 4.5 and the temperature was 95°C. 20 U / g thermostable α-amylase was added for 35 min to destarch the solution. After the reaction, the solution was incubated in a boiling water bath for 10 min to inactivate the enzyme. The crude dietary fiber solution was obtained after cooling. 0.2% cellulase (by mass of the crude dietary fiber solution) was added to the crude dietary fiber solution, and the reaction was carried out at 50 °C for 1 h. After the reaction, the enzyme was heated to inactivate the enzyme, and the functional dietary fiber product was obtained after cooling. The results showed that the dietary fiber purity of the dietary fiber product was 85.18%±3.76%, the SDF yield was 3.73%±1.10%, the water holding capacity was 12.97±0.04 g / g, the oil holding capacity was 14.57±0.56 g / g, and the glucose adsorption capacity was 9.142±0.001 mmol / g.

[0021] The dietary fibers prepared in Examples 1-3 and Comparative Examples 1-3 were tested for purity according to the national standard GB 5009.88-2023. Water holding capacity was tested as follows: 1 g of sample (recorded as m) was weighed and placed in a test tube (recorded as M1). 30 mL of distilled water was added, and the mixture was incubated at 37°C and shaken at 150 rpm for 4 h. After centrifugation at 4000 rpm and 25°C for 10 min, the supernatant was discarded. The test tube and the precipitate were weighed together and recorded as M2. The calculation formula is: WHC (g / g) = (M2 - M1) / m. Oil holding capacity was tested as follows: 1 g of IDF sample (recorded as m) was mixed with 25 mL of soybean oil (recorded as W1), and incubated on a shaker at 37°C and 180 rpm for 4 h. After centrifugation at 3000 g and 25°C for 10 min, the supernatant was discarded and recorded as W2. The calculation formula is as follows: OHC (g / g) = (W2 - W1) / m. Glucose adsorption capacity was determined by mixing 1 g (M) of sample with 100 mL of 100 mmol / L (C1) glucose solution and incubating at 37°C for 6 h. The sample was then centrifuged at 4000 g for 20 min. The glucose content (C2) in the supernatant (V) was measured using a glucose assay kit (Solarbio, BC2500, Beijing, China). GAC (mmol / g) = (C1 - C2) / M × V. The results are shown in Table 1.

[0022] Table 1 is the test results of Examples 1-3 and Comparative Examples 1-3 Example 4 10 g of soybean dregs were added to 300 mL of deionized water and dispersed thoroughly. The pH was adjusted to 8.0 and the temperature was 60°C. 30 U / g alkaline protease was added for 30 minutes to deproteinize the dregs. After the reaction, the enzyme was inactivated by boiling in a water bath for 10 minutes. After cooling, the pH of the dregs solution was adjusted to 4.5 and the temperature was 95°C. 20 U / g thermostable α-amylase was added for 35 minutes to destarch the dregs. After the reaction, the enzyme was inactivated by boiling in a water bath for 10 minutes. The crude dietary fiber solution was then cooled and ultrasonically treated (frequency 25 kHz, power 400 W, time 15 minutes). Cellulase (0.3% by weight of the crude dietary fiber solution) was then added. Glucomannan, mannitol, and sorbitan laurate were added in a mass ratio of 1:3:1:100 to the mass of the crude dietary fiber solution. The mixture was reacted at 55°C for 2 hours. After the reaction, the enzymes were inactivated by heating. The functional dietary fiber product was obtained after cooling.

[0023] Comparative Example 4 10 g of soybean dregs were added to 300 mL of deionized water and thoroughly dispersed. The pH was then adjusted to 8.0 and the temperature to 60°C. 30 U / g alkaline protease was added for 30 minutes to deproteinize the dregs. The enzyme was then inactivated by boiling in a water bath for 10 minutes. After cooling, the pH of the dregs solution was adjusted to 4.5 and the temperature was adjusted to 95°C. 20 U / g thermostable α-amylase was added for 35 minutes to destarch the dregs. The enzyme was then inactivated by boiling in a water bath for 10 minutes. The crude dietary fiber solution was then cooled and ultrasonically treated (frequency 25 kHz, power 400 W, time 15 minutes). Cellulase (0.3% by weight of the crude dietary fiber solution) and sorbitan laurate (a weight ratio of 1:100) were then added. The reaction was incubated at 55°C for 2 hours. After the reaction, the enzyme was inactivated by heating. The functional dietary fiber product was obtained after cooling.

[0024] Comparative Example 5 10 g of soybean dregs were added to 300 mL of deionized water and dispersed thoroughly. The pH was adjusted to 8.0 and the temperature was 60°C. 30 U / g alkaline protease was added for 30 minutes to deproteinize the dregs. After the reaction, the enzyme was inactivated by boiling in a water bath for 10 minutes. After cooling, the pH of the dregs solution was adjusted to 4.5 and the temperature was 95°C. 20 U / g thermostable α-amylase was added for 35 minutes to destarch the dregs. After the reaction, the enzyme was inactivated by boiling in a water bath for 10 minutes. The crude dietary fiber solution was then cooled and ultrasonically treated (frequency 25 kHz, power 400 W, time 15 minutes). Cellulase (0.3% by weight of the crude dietary fiber solution) was then added. Mannitol and sorbitan laurate were added in a mass ratio of 3:1:100 to the mass of the crude dietary fiber solution. The reaction was incubated at 55°C for 2 hours. After the reaction, the enzymes were inactivated by heating. The functional dietary fiber product was obtained after cooling.

[0025] Comparative Example 6 10 g of soybean dregs were added to 300 mL of deionized water and dispersed thoroughly. The pH was adjusted to 8.0 and the temperature was 60°C. 30 U / g alkaline protease was added for 30 minutes to deproteinize the dregs. After the reaction, the enzyme was inactivated by boiling in a water bath for 10 minutes. After cooling, the pH of the dregs solution was adjusted to 4.5 and the temperature was 95°C. 20 U / g thermostable α-amylase was added for 35 minutes to destarch the dregs. After the reaction, the enzyme was inactivated by boiling in a water bath for 10 minutes. The crude dietary fiber solution was then cooled and ultrasonically treated (frequency 25 kHz, power 400 W, time 15 minutes). Cellulase (0.3% by weight of the crude dietary fiber solution) was then added. Glucomannan and sorbitan laurate were added in a mass ratio of 1:1:100 to the cellulase, respectively. The reaction was incubated at 55°C for 2 hours. After the reaction, the enzymes were inactivated by heating. The functional dietary fiber product was obtained after cooling.

[0026] The dietary fibers prepared in Example 4 and Comparative Examples 4-6 were tested, and the results are shown in Table 2.

[0027] Table 2 is the test results of Example 4 and Comparative Examples 4-6 The above detailed description is a specific description of a feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the patent scope of this case.

Claims

1. A method for preparing functional dietary fiber from bean dregs using an ultrasound-coupled enzyme method, characterized in that: The following steps are involved: (1) Raw material pretreatment: crush the soybean dregs to less than 60 mesh, add deionized water at a mass ratio of 1:30 (g / mL) to form a soybean dregs suspension; add alkaline protease and thermostable α-amylase to the soybean dregs suspension for deproteinization and destarch treatment, respectively, to preliminarily obtain crude dietary fiber; (2) Ultrasonic pretreatment: The crude dietary fiber in step (1) was ultrasonically treated using a focused ultrasonic device. The ultrasonic treatment conditions were as follows: ultrasonic frequency 25 kHz, ultrasonic power 100-500 W, ultrasonic time 10-30 min, and temperature 30 °C. (3) Enzymatic hydrolysis: The dietary fiber after ultrasonic treatment was subjected to cellulase enzymatic hydrolysis. The treatment conditions were: enzyme addition amount 0.1%-0.5%, pH 4-6, enzymatic hydrolysis time 0.5-2.5 h, and enzymatic hydrolysis temperature 45-65 °C; (4) Enzyme inactivation and drying treatment: The enzymatically hydrolyzed dietary fiber solution is subjected to enzyme inactivation treatment (105 °C, 10 min), and then cooled and freeze-dried to finally obtain a functional dietary fiber product.

2. The method for preparing functional dietary fiber from bean dregs by using ultrasound-coupled enzyme method according to claim 1, characterized in that: The mixing ratio of the bean dregs and deionized water is 1:30; the addition amount of alkaline protease is 30 u / g, and the enzyme treatment time is 30 min; the addition amount of high-temperature resistant α-amylase is 20 u / g, and the enzyme treatment time is 35 min.

3. The method for preparing functional dietary fiber from bean dregs by utilizing ultrasound-coupled enzymatic method according to claim 2 or 3, characterized in that: The ultrasonic treatment conditions were as follows: ultrasonic power 300 W, ultrasonic time 20 min; and enzymatic hydrolysis conditions were as follows: enzyme addition amount 0.2%, pH 5.0, enzymatic hydrolysis time 1 h, and enzymatic hydrolysis temperature 60°C.

4. The method for preparing functional dietary fiber from bean dregs by utilizing ultrasound-coupled enzymatic method according to claim 1, characterized in that: In step (3), during enzymatic hydrolysis, glucomannan, mannitol and sorbitan laurate are added, and the mass ratio of the added amount to the cellulase is 1-2:2-5:1-2:

100.

5. The method for preparing functional dietary fiber from bean dregs by utilizing ultrasound-coupled enzymatic method according to claim 4, characterized in that: In step (3), during enzymatic hydrolysis, glucomannan, mannitol and sorbitan laurate are added, and the mass ratio of the added amount to the cellulase is 1:3:1:100.

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