Water-soluble dietary fiber-phenolic substance structure and method for processing the same

Abstract

The present application belongs to the field of functional food processing, and particularly relates to a water-soluble dietary fiber-phenolic substance structure and a processing method thereof. The present application comprises the following steps: subjecting cereal particles to airflow pulverization and screening to obtain a skin product; mixing the skin product with water at a weight ratio of 1:(20-200) to obtain a mixed system by adding a composite enzyme, the mass fraction of the composite enzyme in the mixed system being 0.1%-8%, and the composite enzyme being obtained by compounding heat-resistant alpha-amylase, glucoamylase, alkaline protease and cellulase at a mass ratio of 1:(0.1-5):(0.5-5):(0.1-10); subjecting the mixed system to physical field-assisted reaction at 40-80 DEG C for 0.2-10 h, and then fractionally precipitating the reaction product with an ethanol aqueous solution with a volume fraction of 60%-95%, and drying the precipitate to obtain the water-soluble dietary fiber-phenolic substance structure; wherein the average molecular weight of the water-soluble dietary fiber-phenolic substance structure is 10 4 -10 6 Da, the content of arabinoxylan is >50wt%, and the content of bound polyphenol is 8-18mg GAE / g, and the bound polyphenol is one or a combination of caffeic acid, cinnamic acid and coumaric acid.

Description

Technical Field

[0001] This invention belongs to the field of functional food processing technology, and in particular relates to a water-soluble dietary fiber-phenolic substance structure and its processing method. Background Technology

[0002] With the development of my country's economy and society, people are paying more and more attention to dietary health. Dietary fiber has been recognized as the "seventh essential nutrient" that can balance the body's nutritional status. People also fully recognize the importance of supplementing dietary fiber for human health. For example, dietary fiber can slow down the rise in postprandial blood sugar levels; promote gastrointestinal motility and prevent constipation; and lower blood cholesterol levels. In addition, dietary fiber deficiency is often associated with an increased risk of chronic diseases such as type 2 diabetes, cardiovascular disease, and colon cancer. The World Health Organization recommends an intake of 25 grams of dietary fiber per day.

[0003] Water-soluble dietary fiber is composed of β-glucan, hemicellulose, glucan, pectin, oligosaccharides, etc., and has high viscosity and good gel-forming ability, thus it can be used as a stabilizer, gelling agent, and thickener. For example, existing technologies have extracted dietary fiber from soybean, wheat bran, apple, beet, and carrot by-products, and used it in the food industry for puffed foods, snacks, noodles, biscuits, bread, dairy products, and meat products. However, the current industrialized preparation process of water-soluble dietary fiber mainly uses the alkaline extraction process. This process causes significant environmental pollution, and the resulting water-soluble dietary fiber suffers a large loss of its main physiologically active substances. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a safe, efficient, and functionally nutritious water-soluble dietary fiber-phenolic substance structure and its processing method. This method offers a solution to the current problems of low added value of dietary fiber activity and heavy pollution during processing. Its application scope can involve special dietary foods, health foods, special medical foods, infant formula foods, and other fields.

[0005] The technical concept of this invention is as follows: Using bulk grain grains as the main raw material, the grains undergo sequential processing including airflow milling, sieving, enzymatic hydrolysis with a specific complex enzyme composition (heat-resistant α-amylase, saccharifying enzyme, alkaline protease, and cellulase in a mass ratio of 1:(0.1-5):(0.5-5):(0.1-10)) and alcohol precipitation to obtain water-soluble dietary fiber-phenolic compounds. The seed coat of bulk grain grains has a complex composition, and the main components interfering with the extraction and purity of the water-soluble dietary fiber-phenolic compounds are starch, protein, and cellulose. This invention utilizes a physical field-assisted reaction with a specific complex enzyme (a mass ratio of heat-resistant α-amylase, saccharifying enzyme, alkaline protease, and cellulase of 1:(0.1-5):(0.5-5):(0.1-10)) to moderately depolymerize cellulose and hemicellulose in the outer layer of solid grains while precisely preserving the arabinoxylan-polyphenol complex structure. The combination of heat-resistant α-amylase and saccharifying enzyme efficiently removes starch components, while alkaline protease and cellulase decompose protein and cellulose components. The four enzymes work in a way that balances the effects of heat-resistant α-amylase, saccharifying enzyme, alkaline protease, and cellulase. Synergistic treatment with a specific ratio of enzymes (1:(0.1-5):(0.5-5):(0.1-10) to alkaline protease and cellulase improves the extraction rate of water-soluble dietary fiber-phenolic compounds and reduces interference from impurities. Compared to existing methods for extracting water-soluble dietary fiber using alkaline methods, this invention employs a green and gentle method—physical field-assisted enzymatic hydrolysis—which not only improves the extraction rate of water-soluble dietary fiber-phenolic compounds but also helps to increase the content and activity of phenolic substances.

[0006] This invention is achieved through the following technical solution:

[0007] On the one hand, a method for processing water-soluble dietary fiber-phenolic substance structures is provided, which includes the following steps:

[0008] (1) The grain particles are pulverized and sieved by airflow to obtain the outer skin product;

[0009] (2) Mix the outer skin product with water at a weight ratio of 1:(20-200), add the complex enzyme to obtain a mixed system, wherein the mass fraction of the complex enzyme in the mixed system is 0.1%-8%, and the complex enzyme is prepared by combining heat-resistant α-amylase, saccharifying enzyme, alkaline protease and cellulase in a mass ratio of 1:(0.1-5):(0.5-5):(0.1-10);

[0010] (3) The mixed system was placed in a physical field-assisted reaction at 40-80℃ for 0.2-10 h. After the reaction, it was precipitated by fractional precipitation with a 60%-95% ethanol aqueous solution. The precipitate was dried to obtain the water-soluble dietary fiber-phenolic substance structure; wherein, the average molecular weight of the water-soluble dietary fiber-phenolic substance structure is 10. 4 -10 6 Da contains >50wt% arabinoxylan and 8-18mgGAE / g of bound polyphenols, which are one or more combinations of caffeic acid, cinnamic acid, and coumaric acid.

[0011] In some embodiments, the grain kernels are at least one of corn, rice, wheat, oats, and buckwheat.

[0012] In some embodiments, the corn kernels are of any one of the following types: waxy, sweet, sweet-glutinous, or high amylose (amylose > 50%).

[0013] In some embodiments, the working pressure of the airflow pulverizer in step (1) is 0.5-0.9 MPa.

[0014] In some embodiments, the sieving fineness in step (1) is 0.5-50 μm.

[0015] In some embodiments, the physical field in step (3) is one or a combination of microwave field and ultrasonic field.

[0016] In some embodiments, the power of the microwave field or ultrasonic field is 80-1000W.

[0017] On the other hand, a water-soluble dietary fiber-phenolic substance structure prepared by the aforementioned method is provided.

[0018] On the other hand, the aforementioned water-soluble dietary fiber-phenolic substance structure is provided for use in one of the following: special dietary foods, health foods, special medical foods, and infant formula foods.

[0019] On the other hand, the aforementioned water-soluble dietary fiber-phenolic substance structure is provided for use in the preparation of products with antioxidant effects.

[0020] On the other hand, the aforementioned water-soluble dietary fiber-phenolic substance structure is provided for its application in the preparation of foods that regulate gut health.

[0021] The present invention has the following beneficial effects:

[0022] (1) This invention makes full use of by-products generated from grain processing as raw materials. The raw materials are widely available and inexpensive. At the same time, it also solves the technical problems of waste of resources and low added value of by-products generated from grain processing.

[0023] (2) Existing technologies mainly extract water-soluble dietary fiber through vigorous methods such as strong alkalis or strong acids. Due to the violent reaction process, phenolic substances are easily lost or deactivated. The processing of the product of this invention is a physical field-assisted compound enzymatic process. Through optimization, a compound enzyme composed of four enzymes, namely heat-resistant α-amylase, saccharifying enzyme, alkaline protease and cellulase, in a mass ratio of 1:(0.1-5):(0.5-5):(0.1-10), can directionally and efficiently depolymerize the solid structure of the outer skin of grain particles, accurately remove impurities (starch, protein, cellulose and hemicellulose) that interfere with the extraction of water-soluble dietary fiber-phenolic substances. Moreover, the enzymatic reaction conditions are mild, the operation is simple, green and efficient. It can not only obtain water-soluble dietary fiber-phenolic substances with high purity, but also the retention rate of phenolic substances in the water-soluble dietary fiber-phenolic substances structure is greater than 90%. Compared with the common alkaline extraction process for water-soluble dietary fiber, which is cumbersome and easily causes the loss of phenolic substances in the structure. This invention utilizes a combination of compound enzymes and physical and thermal fields to treat water-soluble structures. The mechanical force or thermal effect of the physical and thermal fields is used to increase the dissolution of water-soluble structures. The method of extracting water-soluble dietary fiber by combining compound enzymes with physical and thermal fields is not only simple to operate, but also yields water-soluble structures with high purity and an arabinoxylan content of more than 50%.

[0024] (3) The processing method of the present invention yields a water-soluble dietary fiber-phenolic substance structure with an average molecular weight of 10. 4 -10 6 The product contains >50 wt% arabinoxylan and 8-18 mg GAE / g of bound polyphenols, which are one or more combinations of caffeic acid, cinnamic acid, and coumaric acid. This water-soluble dietary fiber-phenolic structure exhibits excellent antioxidant properties, with a free radical scavenging rate exceeding 60%. The product is not easily digested by the stomach and small intestine, but can be broken down and utilized by microorganisms in the large intestine to produce short-chain fatty acids, especially butyric acid (butyric acid content of 2-10 mmol / L produced by in vitro anaerobic fermentation), which can regulate human intestinal health. Therefore, the product obtained by the method of this invention helps maintain human health and can be used as a raw material for health food processing, which is of great significance for improving health levels. Attached Figure Description

[0025] Figure 1 The average molecular weight of the water-soluble dietary fiber-phenolic substance structure obtained in Example 1 is as follows. Detailed Implementation

[0026] Test method:

[0027] Average molecular weight determination:The average molecular weight of the samples was determined using a high-performance liquid chromatography-size exclusion chromatography system coupled with a multi-angle laser light scattering detector and a differential refractive index detector. A Shodx Ohpak SB-805HQ gel chromatography column was used, with 0.1 mol / L sodium nitrate aqueous solution as the mobile phase, a flow rate of 0.7 mL / min, and a refractive index of dn / dc = 0.138.

[0028] Determination of arabinoxylan content: The content of arabinoxylan was determined using the lichenol-hydrochloric acid method. The specific method is as follows: 0.01 g of sample was added to 1 mL of 4 mol / L hydrochloric acid aqueous solution and hydrolyzed in a boiling water bath for 2 h to obtain a polysaccharide hydrolysate. This hydrolysate was then diluted with water to 100 μg / mL. 3 mL of the 100 μg / mL polysaccharide hydrolysate was placed in a stoppered test tube, and 3 mL of 0.1% FeCl3-concentrated hydrochloric acid solution and 0.3 mL of 1% lichenol-anhydrous ethanol solution were added respectively. The mixture was stirred and reacted in a boiling water bath for 30 min. After cooling to room temperature, the absorbance was measured at wavelengths of 580 nm and 670 nm to obtain the A content. 580 and A 670 Simultaneously, using arabinoxylan solutions of different concentrations as the x-axis, the absorbance difference (A) was calculated. 670 –A 580 Plot a standard curve for arabinoxylan using A(A) as the ordinate. The formula for calculating the arabinoxylan content in the sample is as follows: arabinoxylan content (%) = [(A) / [A] 670 –A 580 –b) / a]×0.88, where a and b are the fitting constants of the arabinoxylan standard curve, and 0.88 is the pentosan conversion factor.

[0029] Determination of bound polyphenol content: The sample and NaOH aqueous solution (2 mol / L, 40 mL) were placed in a brown bottle and mixed thoroughly until completely dissolved. The air in the bottle was replaced with sufficient nitrogen to avoid oxidation of phenolic acid. The sample was then stirred evenly under dark conditions at room temperature. The sample was then acidified to pH 1.5-2.0 with HCl aqueous solution (6 mol / L), centrifuged (4000 g, 20 min), and the supernatant was extracted five times with 2 volumes of ethyl acetate. The resulting extract was concentrated by rotary evaporation at 40-50 °C and finally dissolved in methanol to obtain the alkali-soluble acidified extract. The polyphenol content (mg GAE / g) was calculated and converted using the Folin-Ciocalteu colorimetric method with the gallic acid standard curve.

[0030] Free radical scavenging rate determination:The antioxidant activity of the water-soluble dietary fiber-phenolic compound structure releasing bound polyphenols was evaluated using ABTS free radical scavenging rate as an indicator. The specific test method for ABTS free radical scavenging rate is as follows: 67 μL of the above-mentioned alkali-soluble acidified extract was mixed thoroughly with 133.5 μL of ABTS working solution, and reacted at 25°C for 30 min in the dark. The absorbance was measured at 734 nm (A1). 67 μL of methanol was mixed thoroughly with 133.5 μL of ABTS working solution, and the absorbance was measured at 734 nm (A0). 67 μL of the above-mentioned alkali-soluble acidified extract was mixed thoroughly with 133.5 μL of methanol, and the absorbance was measured at 734 nm (A2). Standard curves were prepared by repeating the above steps using different concentrations of water-soluble vitamin E (Trolox) instead of the above-mentioned alkali-soluble acidified extract.

[0031] The formula for calculating the free radical scavenging rate is as follows: Free radical scavenging rate (%) = [A0 - (A1 - A2)] / A0 × 100.

[0032] Performance determination of butyric acid production by simulated in vitro anaerobic fermentation: An anaerobic fermentation medium with the following composition was prepared using dietary fiber-phenolic compound structure as the carbon source: 2.5g dietary fiber-phenolic compound structure, 2.0g yeast extract, 2.0g peptone, 2.0g sodium bicarbonate, 0.5g porcine bile salts, 0.5g L-cysteine, 0.45g potassium chloride, 0.1g sodium chloride, 0.04g potassium dihydrogen phosphate, 0.01g magnesium sulfate heptahydrate, 0.01g calcium chloride hexahydrate, 1.0mg resazurin, 2.0mL Tween 80, and 10μL vitamin K. The medium was autoclaved at 121℃ for 30min and then cooled. Human intestinal flora solution was added to the medium at 10wt%, and the medium was incubated at 37℃ for anaerobic fermentation for 12h. The resulting fermentation broth was centrifuged (10000g, 10min), and the butyric acid content in the supernatant was determined by gas chromatography. The human gut microbiota solution was obtained from fecal samples provided by 10 volunteers aged 23-29. Volunteers were required to be in good health and not have taken antibiotics or prebiotics within two months prior to sampling. The fecal samples were mixed with phosphate buffer (1M, pH 7) at a ratio of 1:3 (w / v), stirred, and filtered through an 800-mesh filter to remove large particles, thus obtaining the human gut microbiota solution.

[0033] Example 1

[0034] A method for processing a water-soluble dietary fiber-phenolic substance structure includes the following steps:

[0035] (1) 50g of corn kernels were pulverized by airflow (working pressure 0.6MPa) and sieved to obtain a 12μm outer skin product;

[0036] (2) Mix the outer skin product with water at a weight ratio of 1:20, and add a complex enzyme (heat-resistant α-amylase: saccharifying enzyme: alkaline protease: cellulase in a mass ratio of 1:0.1:0.5:1) to obtain a mixed system, wherein the mass fraction of the complex enzyme in the mixed system is 0.5%;

[0037] (3) The mixture was placed in an ultrasonic physical field (200W) at 45°C for 0.5h to assist the reaction. After the reaction was completed, it was fractionally precipitated with a 75% ethanol aqueous solution. The precipitate was dried to obtain the water-soluble dietary fiber-phenolic substance structure.

[0038] After measurement, according to Figure 1 The average molecular weight of the water-soluble dietary fiber-phenolic compound structure obtained in Example 1 was 5.1 × 10⁻⁶. 5 The product, Da, contains 62 wt% arabinoxylan and 9.6 mg GAE / g of bound polyphenols. The bound polyphenols are identified as caffeic acid, cinnamic acid, and coumaric acid. The water-soluble dietary fiber-phenolic compound structure prepared in Example 1 exhibits an ABTS free radical scavenging rate as high as 73.2%; the butyric acid content produced during 12 hours of in vitro anaerobic fermentation is 5.6 mmol / L.

[0039] Example 2

[0040] A method for processing a water-soluble dietary fiber-phenolic substance structure includes the following steps:

[0041] (1) Weigh 50g of sweet and glutinous wheat grains and pulverize them by airflow (working pressure 0.5MPa) and sieve to obtain a 23μm outer skin product;

[0042] (2) Mix the outer skin product with water at a weight ratio of 1:150, and add a complex enzyme (heat-resistant α-amylase: saccharifying enzyme: alkaline protease: cellulase in a mass ratio of 1:1:1:3) to obtain a mixed system, wherein the mass fraction of the complex enzyme in the mixed system is 6%.

[0043] (3) The mixture was placed in a microwave physical field (800W) at 60℃ for 1 hour to assist the reaction. After the reaction was completed, it was precipitated by fractional precipitation with 90% ethanol aqueous solution. The precipitate was dried to obtain the water-soluble dietary fiber-phenolic substance structure.

[0044] The average molecular weight of the water-soluble dietary fiber-phenolic compound structure prepared in Example 2 was determined to be 8.5 × 10⁻⁶. 4The product, Da, contains 54 wt% arabinoxylan and 14.2 mg GAE / g of bound polyphenols. The bound polyphenols are identified as caffeic acid and coumaric acid. The water-soluble dietary fiber-phenolic structure obtained in Example 2 exhibits an ABTS free radical scavenging rate as high as 64.9%; the butyric acid content produced during 12 hours of in vitro anaerobic fermentation is 4.8 mmol / L.

[0045] Example 3

[0046] A method for processing a water-soluble dietary fiber-phenolic substance structure includes the following steps:

[0047] (1) 50g of oat grains were pulverized by airflow (working pressure 0.9MPa) and sieved to obtain a 1.7μm outer skin product;

[0048] (2) Mix the outer skin product with water at a weight ratio of 1:200, and add a complex enzyme (heat-resistant α-amylase: saccharifying enzyme: alkaline protease: cellulase in a mass ratio of 1:3:2:5) to obtain a mixed system, wherein the mass fraction of the complex enzyme in the mixed system is 3%.

[0049] (3) The mixture was placed in a microwave physical field (420W) at 45°C for 2 hours to assist the reaction. After the reaction was completed, it was precipitated by fractional precipitation with 70% ethanol aqueous solution. The precipitate was dried to obtain the dietary fiber-phenolic substance structure.

[0050] The average molecular weight of the water-soluble dietary fiber-phenolic compound structure prepared in Example 3 was determined to be 1.3 × 10⁻⁶. 6 The product, Da, contains 82 wt% arabinoxylan and 17.5 mg GAE / g of bound polyphenols, which are identified as caffeic acid and coumaric acid. The water-soluble dietary fiber-phenolic structure prepared in Example 3 exhibits an ABTS free radical scavenging rate as high as 75.1%; the butyric acid content produced during 12 hours of in vitro anaerobic fermentation is 7.4 mmol / L.

[0051] Comparative Example 1

[0052] A method for processing dietary fiber-phenolic substances, referring to Example 1, differs only in that the dietary fiber-phenolic substances are obtained without airflow pulverization.

[0053] Comparative Example 2

[0054] A method for processing dietary fiber-phenolic substances is described in Example 1, except that the complex enzyme treatment is omitted in step (2), and the dietary fiber-phenolic substances are obtained.

[0055] Comparative Example 3

[0056] A method for processing water-soluble dietary fiber-phenolic substances is described, referring to Example 1, except that the dietary fiber-phenolic substances are obtained without ultrasonic treatment.

[0057] Comparative Example 4

[0058] A method for processing dietary fiber-phenolic substances is described, referring to Example 1, except that the dietary fiber-phenolic substances are obtained without ethanol fractionation precipitation.

[0059] Comparative Example 5

[0060] A method for processing dietary fiber-phenolic substances is described in Example 1, except that the complex enzyme used in step (2) is adjusted to a mass ratio of heat-resistant α-amylase: alkaline protease: cellulase of 1:0.5:1, i.e. no saccharifying enzyme is added, and dietary fiber-phenolic substances are obtained.

[0061] Comparative Example 6

[0062] A method for processing water-soluble dietary fiber-phenolic substances is described in Example 1, except that the complex enzyme used in step (2) is adjusted to a mass ratio of saccharifying enzyme: alkaline protease: cellulase of 0.1:0.5:1, i.e. no heat-resistant α-amylase is added, and dietary fiber-phenolic substances are obtained.

[0063] Comparative Example 7

[0064] A method for processing dietary fiber-phenolic substances, referring to Example 1, differs only in that the complex enzyme used in step (2) is adjusted to have a mass ratio of heat-resistant α-amylase: saccharifying enzyme: alkaline protease: cellulase of 1:10:0.01:15.

[0065] The molecular weight, arabinoxylan content, bound polyphenol content, ABTS free radical scavenging, and butyric acid content of the dietary fiber-phenolic substances obtained in Comparative Examples 1–7 are shown in Table 1.

[0066] Table 1. Comparison of the functional qualities of dietary fiber-phenolic compound structures in the examples and comparative examples.

[0067]

[0068]

[0069] As shown in Table 1, the functional quality of the dietary fiber-phenolic substance structure obtained by grain particles without airflow pulverization, physical field-assisted complex enzyme reaction, ethanol graded precipitation, or by changing the composition of the complex enzyme (not using the combination of heat-resistant α-amylase, saccharifying enzyme, alkaline protease and cellulase, or changing the mass ratio of the four enzymes) is far lower than that of Example 1.

[0070] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A processing method for a water-soluble dietary fiber-phenolic substance structure, characterized in that, Includes the following steps: (1) 50 g of oat grains were pulverized and sieved by airflow milling to obtain a 1.7 μm outer skin product; the working pressure of airflow milling was 0.9 MPa; (2) Mix the outer skin product with water at a weight ratio of 1:200, add the compound enzyme to obtain a mixed system, wherein the mass fraction of the compound enzyme in the mixed system is 3%; the mass ratio of heat-resistant α-amylase: saccharifying enzyme: alkaline protease: cellulase in the compound enzyme is 1:3:2:

5. (3) The mixture was placed in a microwave-assisted reaction at 45 °C for 2 h with a microwave power of 420 W. After the reaction, it was precipitated by fractional precipitation with a 70% ethanol aqueous solution. The precipitate was dried to obtain the dietary fiber-phenolic substance structure; wherein the average molecular weight of the water-soluble dietary fiber-phenolic substance structure was 1.3 × 10⁻⁶. 6 The content of Da is 82 wt% arabinoxylan and 17.5 mg GAE / g of bound polyphenols, which are caffeic acid and coumaric acid.

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