A preparation method of water-dispersible dietary fiber from cereal bran

Abstract

The present invention relates to the technical field of food processing, and discloses a preparation method of water-dispersible cereal bran dietary fiber, comprising the following steps: (1) pretreatment; (2) ultrafine grinding treatment; (3) molecular encapsulation treatment; (4) spray drying. The present invention discloses a method for converting insoluble dietary fiber from cereal bran into dietary fiber that can be uniformly dispersed in an aqueous solution. First, the cereal bran is processed into micron-sized dietary fiber particles by ultrafine grinding technology, and then a water-soluble macromolecule is coated on the surface of the micron-sized dietary fiber by molecular encapsulation technology, so that the prepared cereal bran dietary fiber particles can be stably and uniformly dispersed in the aqueous solution without stratification or precipitation, and are rich in nutrients such as dietary fiber, amino acids, vitamins, and minerals, with a delicate taste, and can be widely used as a raw material for beverage food production or eaten directly.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and particularly relates to a method for preparing water-dispersible dietary fiber from cereal bran. Background Art

[0002] At present, dietary fiber is a carbohydrate in plant-based foods that cannot be digested and absorbed by the human small intestine and can be completely or partially fermented in the large intestine, which is of health significance to the human body. Dietary fiber has various physiological functions such as lowering blood sugar and blood lipids, improving the intestinal flora structure, relieving constipation, facilitating weight loss, preventing coronary heart disease, and preventing colon cancer, and is listed as the essential "seventh nutrient" by modern nutrition.

[0003] Classified according to solubility in water, dietary fiber is usually divided into soluble dietary fiber and insoluble dietary fiber. Soluble dietary fiber can dissolve in water, absorb water and swell to form a colloidal state, and can be fermented by microorganisms in the large intestine to form substances such as short-chain fatty acids, which helps to maintain intestinal health, lower blood lipids and blood sugar, and is also beneficial to weight control and prevention of diseases such as colon cancer. Soluble dietary fiber includes pectin, gum, chitin, resistant dextrin, inulin, β-glucan, oligosaccharides, etc., and is mainly derived from foods such as oats, barley, beans, apples, citrus fruits, etc. A large amount of soluble dietary fiber is also contained in kelp and konjac. Insoluble dietary fiber is insoluble in water and cannot be fermented by microorganisms in the large intestine. It mainly has a great influence on the running and retention time of food in the stomach and intestines and the defecation process. It can promote intestinal peristalsis, increase the volume and softness of feces, relieve constipation, and also reduce the risk of colon cancer. Insoluble dietary fiber mainly comes from the components of plant cell walls, including cellulose, hemicellulose, lignin, etc., and is mainly present in foods such as coarse grains, cereal bran, beans, root and tuber vegetables, and fruit peels. Although there are certain differences in the functions of soluble dietary fiber and insoluble dietary fiber, both are necessary for maintaining human health. The recommended appropriate intake ratio of soluble dietary fiber and insoluble dietary fiber is 1:2 to 1:3.

[0004] Cereal brans such as wheat bran, rice bran, and corn husk are by-products in cereal processing. They are rich in dietary fiber and are important sources of dietary fiber. Recently, a number of foreign studies have shown that cereal dietary fiber has higher health value compared to dietary fiber from food sources such as vegetables and fruits. Increasing the intake of cereal dietary fiber can more effectively reduce the risk of diseases such as cardiovascular diseases and rectal cancer. China is a major grain-producing country, and the amount of wheat bran produced annually from wheat processing alone can reach 20 million tons. In addition to dietary fiber, cereal brans also contain abundant minerals, trace elements, amino acids, and phytochemicals, and have high nutritional value. However, since the dietary fiber in cereal brans is mainly insoluble dietary fiber and contains a lot of crude fiber, the edible taste is poor, resulting in most brans being used as feed and unable to become widely consumed materials. Even when added to flour to make foods such as high-fiber bran bread and biscuits, the addition amount is limited, causing great waste. With the increasing market demand for low-sugar, low-calorie, low-fat, and high-fiber foods and beverages, dietary fiber beverages are an inevitable trend in the future development of foods and beverages. The main dietary fiber added to dietary fiber beverages is water-soluble dietary fiber, including resistant dextrin, isomaltooligosaccharide, pectin, glucan, and inulin, etc. Cereal dietary fiber is mainly insoluble dietary fiber such as cellulose, hemicellulose, and lignin (more than 90%), and it is difficult to dissolve and disperse after being added to beverages. The finished product presents a thick slurry-like state, with high consistency and many suspended substances, and it is very easy to produce stratification and precipitation phenomena, which cannot meet the requirements of beverages for solubility, stability, and taste. Therefore, it is less used in beverages. In order to improve the solubility and stability of cereal dietary fiber in beverages, the commonly used methods at present include: reducing the particle size of cereal dietary fiber particles through ultrafine comminution processing; using physical, chemical, or biological methods to increase the content of soluble dietary fiber in cereal dietary fiber; or adding emulsifiers and thickeners in the beverage formula. Chinese Patent CN103750147A discloses a method for improving the solubility of cereal dietary fiber. By jointly applying lactic acid bacteria fermentation and ultra-high pressure homogenization treatment, the content of soluble dietary fiber in cereal dietary fiber can be increased (≥30%), and the particle size of dietary fiber can be reduced (<40um). Chinese Patent CN103371309A discloses an emulsifying stabilizer for cereal dietary fiber beverages, which mainly includes components such as monoglyceride, sodium stearoyl lactate, carrageenan, agar, and sodium tripolyphosphate, and can effectively inhibit the precipitation phenomenon of cereal dietary fiber beverages and prevent the water separation phenomenon caused by starch retrogradation. Chinese Patent CN101642205A discloses a nano-processing and deagglomeration method for cereal dietary fiber. By comprehensively applying processes such as ultrafine comminution, nano comminution, and surface modification, the weakness that dietary fiber is difficult to be comminuted to the nano level is solved, and the defect that nano dietary fiber is easy to agglomerate is improved. The surfactants selected for surface modification are monoglyceride, sucrose ester, or sodium dodecyl sulfate, and the dispersants selected are carboxymethyl cellulose or sodium carboxymethyl cellulose.However, the current methods for improving the solubility and stability of cereal dietary fiber in beverages cannot meet the requirements of the beverage industry. The specific reasons are as follows: (1) The water-holding capacity and dispersibility of dietary fiber in water do not always increase with the decrease in the particle size of dietary fiber. When the particle size of dietary fiber is less than a certain range (e.g., less than 200 mesh), the water-holding capacity and dispersibility of dietary fiber in water will instead decrease. (2) The current physical, chemical, or biological methods of treatment can only convert a small part of the insoluble dietary fiber in cereal dietary fiber into soluble dietary fiber, which is not very helpful for improving the overall water solubility of cereal dietary fiber. (3) The method of adding emulsifiers and thickeners to improve the stability of dietary fiber beverages requires the use of a large amount of food additives, which will increase production costs and pose certain health risks.

[0005] Therefore, how to effectively utilize cereal bran to prepare cereal dietary fiber with good water solubility or dispersibility, which can be widely used in beverage foods, and the preparation process is green, environmentally friendly, with low production costs, and can better maintain the nutrition of cereal bran and the health functions of dietary fiber, is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0006] The object of the present invention is to overcome the shortcomings of the existing technology and provide a method for preparing water-dispersible cereal bran dietary fiber. By combining the ultrafine grinding technology with the molecular encapsulation technology, the ultrafine grinding technology is used to shorten the length of cereal dietary fiber, make the fiber bundles fluffy, increase the specific surface area, and then a water-soluble macromolecule is coated on the surface of the fiber bundles through the molecular encapsulation technology. By using the hydrophilicity, steric hindrance, and electrostatic repulsion of the water-soluble macromolecule, the fiber bundles are prevented from approaching and flocculating with each other in water, and the dispersibility and stability of dietary fiber particles in water are improved, so that the prepared cereal dietary fiber can be stably and uniformly dispersed in water and can be widely used in the production of beverage foods. The preparation method is simple, green, efficient, has a high conversion efficiency for bran, low production costs, does not damage the natural molecular structure and functions of cereal dietary fiber, and greatly retains the nutrients such as vitamins, trace elements, and amino acids rich in cereal bran.

[0007] In order to achieve the above object, the technical solution of the present invention is: a method for preparing water-dispersible cereal bran dietary fiber, characterized by comprising the following steps:

[0008] (1) Pretreatment: Screen, remove impurities, and crush cereal bran, pass through a 20-60 mesh sieve, then add drinking water to the cereal bran, mix evenly, and incubate at 50-60 °C for 1-2 hours;

[0009] (2) Ultrafine grinding treatment: Add drinking water to the pretreated cereal bran material, stir evenly, and then add it to a colloid mill for grinding until the particle size of the dietary fiber particles is 20 - 50 microns;

[0010] (3) Molecular encapsulation treatment: Add water-soluble macromolecules to the ground dietary fiber material, stir evenly to form a mixed water suspension. The water-soluble macromolecules are plant-derived water-soluble macromolecules or animal-derived water-soluble macromolecules. Perform high-pressure homogenization treatment on the mixed water suspension to fully mix the water-soluble macromolecules with the dietary fiber particles and evenly adsorb them on the surface of the fiber bundles;

[0011] (4) Spray drying: Perform spray drying on the dietary fiber material after molecular encapsulation treatment to obtain a water-dispersible cereal bran dietary fiber dry powder.

[0012] Further; the cereal bran in step (1) is selected from one of wheat bran, rice bran, and corn bran.

[0013] Further; the mass ratio of the cereal bran to the drinking water in step (1) is 1∶1 - 3.

[0014] Further; the mass ratio of the drinking water to the cereal bran in step (2) is 5 - 10∶1.

[0015] Further; the mass ratio of the water-soluble macromolecules to the cereal bran in step (3) is 0.1 - 0.5∶1.

[0016] Further; the water-soluble macromolecules in step (3) are selected from one of wheat albumin, soy protein, β-glucan, and pectin; the animal-derived water-soluble macromolecules are selected from one of whey protein and sodium caseinate.

[0017] Further; in the high-pressure homogenization treatment in step (3), the pressure is 20 - 60 MPa, and the cyclic treatment is carried out 1 - 3 times.

[0018] The technical solution of the present invention is: The application of a water-dispersible cereal bran dietary fiber dry powder in the preparation of a beverage, and the beverage is a liquid beverage, a solid beverage, or yogurt.

[0019] The beneficial effects of the present invention:

[0020] (1) The present invention provides a method for converting insoluble dietary fiber into dietary fiber that can be stably and uniformly dispersed in an aqueous solution, which preferably solves the problems in the prior art that cereal dietary fiber is difficult to dissolve and disperse in beverages and is prone to layering, precipitation, etc. Moreover, there is no need to add food additives such as emulsifiers and stabilizers, providing an effective way for the wide application of cereal dietary fiber in beverage foods and also providing a new solution for the high-value utilization of cereal bran resources.

[0021] (2) Compared with the prior art: By physical, chemical or biological treatment to increase the content of soluble dietary fiber in cereal dietary fiber, the content of soluble dietary fiber in the cereal dietary fiber treated by these technologies usually can only reach about 10 - 30%, the utilization rate of raw materials is very low, and the operation process is relatively complex with high costs, unable to meet the production requirements of beverage foods. The preparation method of the present invention is simple, green, and efficient, with a high conversion efficiency of bran, can convert all the dietary fiber in bran into water-dispersible cereal dietary fiber without generating waste, has low production costs, does not damage the natural molecular structure and function of cereal dietary fiber, and greatly retains the nutritional components such as vitamins, trace elements, and amino acids rich in cereal bran, and can be widely applied to the production of beverage foods.

[0022] (3) The present invention provides a solution for evenly providing soluble dietary fiber and insoluble dietary fiber in beverage foods. These two types of dietary fiber have different functions in the human body and are both beneficial to health. The recommended optimal intake ratio of soluble dietary fiber and insoluble dietary fiber is 1∶2. In the prior art, only a single soluble dietary fiber can be added to beverages, unable to meet the requirement of providing both types of dietary fiber simultaneously. The water-dispersible cereal bran dietary fiber (micrometer-sized cereal dietary fiber particles wrapped by water-soluble macromolecules) prepared by the technology of the present invention, on the one hand, can be added to beverage foods like soluble dietary fiber, maintaining good dispersibility, stability, and taste quality; on the other hand, it can play the health function of insoluble dietary fiber in the human body, and an appropriate amount of soluble dietary fiber can be additionally added in proportion. Thus, the purpose of evenly providing soluble dietary fiber and insoluble dietary fiber in beverage foods is achieved.

[0023] (4) The water-soluble macromolecules added in the preparation method of the present invention are different from the food additives such as emulsifying stabilizers usually added in the existing beverage formulations. They are mainly natural nutritional components such as water-soluble proteins and water-soluble dietary fibers of plant or animal origin, have high health value, and can be used as auxiliary nutritional components of beverage foods.

[0024] (5) The present invention discloses a method for converting insoluble dietary fiber into dietary fiber that can be evenly dispersed in an aqueous solution. First, the cereal bran is processed into micrometer-sized dietary fiber particles by ultrafine comminution technology, and then a layer of water-soluble macromolecules is wrapped on the surface of the micrometer-sized dietary fiber by molecular encapsulation technology, so that the prepared cereal bran dietary fiber particles can be stably and evenly dispersed in the aqueous solution without stratification or precipitation, and are rich in dietary fiber, amino acids, vitamins, minerals and other nutrients, with a delicate taste, and can be widely used as raw materials for the production of beverage foods or eaten directly. Description of the Drawings

[0025] Figure 1It is the centrifugal sedimentation rate diagram of the wheat bran dietary fiber beverage with different treated products in Example 1;

[0026] Figure 2 In it, A is the scanning electron micrograph of the product obtained in step (2) of Example 1 after drying, and B is the scanning electron micrograph of the water-dispersible cereal bran dietary fiber powder of Example 1;

[0027] Figure 3 It is the schematic diagram of the technical principle of the present invention. Detailed implementation manners

[0028] Example 1:

[0029] A preparation method of water-dispersible cereal bran dietary fiber, comprising the following steps:

[0030] (1) Pretreatment: Select fresh wheat bran produced in wheat flour processing, sieve, remove impurities, and crush the wheat bran, pass through a 40-mesh sieve, weigh 100 g of the wheat bran passing through the 40-mesh sieve, add 200 g of drinking water, mix evenly, incubate at 55 °C for 2 hours, and use the endogenous phytase in the wheat bran to remove the phytic acid therein;

[0031] (2) Ultrafine grinding treatment: Add 700 g of drinking water to the pretreated wheat bran material, stir evenly, and then add a colloid mill for grinding until the particle size of the wheat bran dietary fiber particles is about 30 microns;

[0032] (3) Molecular encapsulation treatment: Add 30 g of wheat albumin to the ground wheat bran dietary fiber material, stir evenly into a mixed water suspension, perform high-pressure homogenization treatment on the mixed water suspension, the pressure is 40 MPa, and cycle the treatment 2 times to further reduce the particle size of the dietary fiber particles, so that the wheat albumin and the dietary fiber particles are fully mixed and evenly adsorbed on the surface of the fiber bundle;

[0033] (4) Spray drying: Perform spray drying on the material after molecular encapsulation treatment to obtain 130 g of water-dispersible cereal bran dietary fiber powder. The scanning electron micrograph is as Figure 2 shown in B. As can be seen from Figure 2 it, a layer of adhesion layer (wheat albumin) is adsorbed on the surface of the wheat bran dietary fiber particles after molecular encapsulation treatment, and the dispersion degree between the particles is better.

[0034] Example 2:

[0035] A preparation method of water-dispersible cereal bran dietary fiber, comprising the following steps:

[0036] (1) Pretreatment: Select fresh rice bran produced during rice processing. Screen, remove impurities, and pulverize the rice bran, then pass it through a 40-mesh sieve. Weigh 100 g of the rice bran passing through the 40-mesh sieve, add 150 g of drinking water, mix evenly, incubate at 55 °C for 2 hours, and use the endogenous phytase in the rice bran to remove the phytic acid therein;

[0037] (2) Ultrafine pulverization treatment: Add 700 g of drinking water to the pretreated rice bran material, stir evenly, and then add it to a colloid mill for grinding until the particle size of the rice bran dietary fiber particles is about 30 microns;

[0038] (3) Molecular encapsulation treatment: Add 300 g of wheat albumin to the ground rice bran dietary fiber material, stir evenly to form a mixed water suspension, and perform high-pressure homogenization treatment on the mixed water suspension at a pressure of 40 MPa for 2 cycles to further reduce the particle size of the dietary fiber particles, so that the wheat albumin and the dietary fiber particles are fully mixed and evenly adsorbed on the surface of the fiber bundle;

[0039] (4) Spray drying: Perform spray drying on the material after molecular encapsulation treatment to obtain 130 g of water-dispersible cereal bran dietary fiber dry powder.

[0040] Example 3:

[0041] A method for preparing water-dispersible cereal bran dietary fiber, comprising the following steps:

[0042] (1) Pretreatment: Select fresh corn husks produced during deep corn processing. Screen, remove impurities, and pulverize the corn husks, then pass it through a 40-mesh sieve. Weigh 100 g of the corn husks passing through the 40-mesh sieve, add 200 g of drinking water, mix evenly, incubate at 55 °C for 2 hours, and use the endogenous phytase in the corn husks to remove the phytic acid therein;

[0043] (2) Ultrafine pulverization treatment: Add 700 g of drinking water to the pretreated corn husk material, stir evenly, and then add it to a colloid mill for grinding until the particle size of the corn husk dietary fiber particles is about 30 microns;

[0044] (3) Molecular encapsulation treatment: Add 30 g of wheat albumin to the ground corn husk dietary fiber material, stir evenly to form a mixed water suspension, and perform high-pressure homogenization treatment on the mixed water suspension at a pressure of 40 MPa for 2 cycles to further reduce the particle size of the dietary fiber particles, so that the wheat albumin and the dietary fiber particles are fully mixed and evenly adsorbed on the surface of the fiber bundle;

[0045] (4) Spray drying: Perform spray drying on the material after molecular encapsulation treatment to obtain 130 g of water-dispersible cereal bran dietary fiber dry powder.

[0046] Example 4:

[0047] Application of water-dispersible cereal bran dietary fiber in the preparation of liquid beverages: Respectively take 15 g of the water-dispersible cereal dietary fiber dry powder prepared in Example 1, Example 2, and Example 3, and add them to 240 mL of beverages respectively. Stir evenly to obtain approximately 250 mL of cereal dietary fiber beverages respectively. Each 250 mL of cereal dietary fiber beverage can meet about 30% of the daily dietary fiber requirement of adults.

[0048] Example 5:

[0049] Application of water-dispersible cereal bran dietary fiber in the preparation of solid beverages: Respectively take 150 g of the water-dispersible cereal dietary fiber dry powder prepared in Example 1, Example 2, and Example 3, and add them to 350 g of solid beverage dry powder respectively. Mix evenly to make granules, and 500 g of cereal dietary fiber solid beverage powder can be obtained respectively. Each 50 g of cereal dietary fiber solid beverage powder can meet about 30% of the daily dietary fiber requirement of adults.

[0050] Example 6:

[0051] Application of water-dispersible cereal bran dietary fiber in the preparation of yogurt products: Respectively take 15 g of the water-dispersible cereal dietary fiber dry powder prepared in Example 1, Example 2, and Example 3, and add them to 110 g of fermented yogurt respectively. Mix evenly to obtain 125 g of cereal dietary fiber yogurt respectively. Each 125 g of cereal dietary fiber yogurt can meet about 30% of the daily dietary fiber requirement of adults.

[0052] Detection test

[0053] 1. Determination of the reconstitution stability of the products after different treatments in Examples 1-3

[0054] Determination method: Sampling is carried out on the products obtained by pretreatment, ultrafine grinding treatment, and molecular encapsulation treatment in Examples 1-3 in sequence, drying, and respectively weighing 10 g of the dried samples and adding 90 mL of normal temperature water. Stir immediately and let stand for 3 minutes, 30 minutes, and 1 hour, and respectively conduct reconstitution property evaluations. The evaluation results are shown in Table 1.

[0055] Table 1

[0056]

[0057] It can be seen from Table 1 that the dispersibility and dispersion stability of the water-dispersible cereal bran dietary fiber prepared by pretreatment + ultrafine grinding + molecular encapsulation treatment in Examples 1-3 of the present invention are better than those of the samples treated by pretreatment and pretreatment + ultrafine grinding treatment, indicating that the present invention can significantly improve the reconstitution performance of cereal dietary fiber and make the reconstituted beverage more stable, and it is not easy to appear layering and precipitation.

[0058] 2. Determination of the Stability of the Dietary Fiber Beverage from Wheat Bran Treated in Example 1

[0059] Sample Preparation: Samples were taken from the three products obtained in Example 1 after pretreatment, ultrafine grinding, and molecular encapsulation treatment in sequence, dried, and 50 g was weighed respectively. Then they were added into 450 mL of beverage respectively and stirred evenly to obtain three kinds of cereal dietary fiber beverages of about 500 mL respectively.

[0060] Method for Determining the Centrifugal Sedimentation Rate: Weigh the three kinds of prepared cereal dietary fiber beverages respectively, three portions for each kind, 100 g for each portion. Then they were centrifuged to remove the supernatant after standing for 0 h, 2 h, and 24 h respectively. The centrifugal speed was 1500 r / min and the centrifugation time was 3 min. The precipitate was dried and the mass of the dried precipitate g1 (g) was weighed. The centrifugal sedimentation rate was calculated to characterize the stability of the beverage. The test results were the average values of two detections. The formula for calculating the centrifugal sedimentation rate is as follows:

[0061] C% = g1 / 10×100

[0062] In the formula, C is the centrifugal sedimentation rate, %;

[0063] g1 is the mass of the precipitate, g.

[0064] The larger the centrifugal sedimentation rate, the more the precipitate, indicating that the stability of the solid beverage after preparation is worse. On the contrary, the stability is better. The results are as Figure 1 shown. The centrifugal sedimentation rates of the wheat bran dietary fiber beverages obtained after pretreatment + ultrafine grinding + molecular encapsulation treatment are significantly lower than those of the sample beverages after pretreatment and pretreatment + ultrafine grinding, and are less affected by the standing time, indicating that the water-dispersible cereal bran dietary fiber prepared by the present invention has good stability after being added to the beverage.

[0065] The above-described embodiments are only preferred solutions of the present invention, and do not impose any form of limitation on the present invention. There are other variations and modifications without exceeding the technical solutions recorded in the claims.

Claims

1. A preparation method of water-dispersible cereal bran dietary fiber, characterized in that, It includes the following steps: (1) Pretreatment: Sieving, impurity removal, and pulverization of cereal bran are carried out, passing through a 20-60 mesh sieve, then adding drinking water to the cereal bran, mixing evenly, and incubating at 50-60 °C for 1-2 hours; (2) Ultrafine pulverization treatment: Adding drinking water to the pretreated cereal bran material, stirring evenly, and then adding a colloid mill for grinding until the particle size of the dietary fiber particles is 20-50 microns; (3) Molecular encapsulation treatment: Adding a water-soluble macromolecule to the ground dietary fiber material, stirring evenly to form a mixed water suspension. The water-soluble macromolecule is one of whey protein, wheat albumin, and soy protein. The mixed water suspension is subjected to high-pressure homogenization treatment to fully mix the water-soluble macromolecule with the dietary fiber particles and evenly adsorb them on the surface of the fiber bundle. The pressure of the high-pressure homogenization treatment is 40-60 MPa, and the cyclic treatment is carried out 1-3 times; (4) Spray drying: Spray drying the dietary fiber material after molecular encapsulation treatment to obtain a water-dispersible cereal bran dietary fiber dry powder.

2. The preparation method of the water-dispersible cereal bran dietary fiber according to claim 1, characterized in that: In step (1), the cereal bran is selected from one of wheat bran, rice bran, and corn husk.

3. The preparation method of the water-dispersible cereal bran dietary fiber according to claim 1, characterized in that: In step (1), the mass ratio of the cereal bran to the drinking water is 1:1-3.

4. The preparation method of the water-dispersible cereal bran dietary fiber according to claim 1, characterized in that: In step (2), the mass ratio of the drinking water to the cereal bran is 5-10:

1.

5. The preparation method of the water-dispersible cereal bran dietary fiber according to claim 1, characterized in that: In step (3), the mass ratio of the water-soluble macromolecule to the cereal bran is 0.1-0.5:

1.

6. Use of the water-dispersible cereal bran dietary fiber dry powder prepared according to claim 1 in the preparation of a drink, wherein the drink is a liquid beverage, a solid beverage, or yogurt.

Images