Method for enhancing solubility and completely retaining beta-glucan through ultrasonic-assisted enzymolysis of rice bran

Abstract

The invention discloses a method for enhancing solubility and completely retaining beta-glucan through ultrasonic-assisted enzymolysis of rice bran, and belongs to the technical field of food processing. The method comprises the following steps: grinding defatted rice bran, performing ultrasonic treatment, performing enzymolysis, drying and the like, specifically, performing enzymolysis on the rice bran by utilizing ultrasonic cavitation to assist trypsin, alpha-amylase and endo-xylanase, and converting insoluble dietary fibers in rice bran fibers into soluble dietary fibers through the endo-xylanase, meanwhile, beta-glucan and xylan which are in water-soluble mixed connection are generated, the dissolving capacity of the rice bran dietary fibers is remarkably improved, the rice bran beta-glucan is completely reserved, and the functional nutritive value of the rice bran dietary fibers is enhanced. The method is mild in reaction condition and low in energy consumption, efficiently retains nutritional ingredients, and provides important technical support for high-valued utilization of rice bran and production of functional rice bran dietary fibers.

Description

Technical Field

[0001] The present invention relates to a method for enhancing the solubility of rice bran by ultrasonic-assisted enzymatic hydrolysis and completely retaining β-glucan, belonging to the technical field of agricultural product processing. Background Art

[0002] Approximately 800 million people in China take rice as their staple food. China is the largest rice producer and consumer in the world. In the past decade, the annual average rice output in China has been 180 - 200 million tons, accounting for 1 / 3 of the total global rice output. As the most important by-product in rice processing, the bran extraction rate of rice bran is about 7%, and the annual output of rice bran is about 12 million tons. Rice bran mainly consists of parts such as the pericarp, seed coat, outer endosperm, aleurone layer, and embryo, which is the essence of rice and is known as the "soft gold of rice". Rice bran contains rich dietary fiber, unsaturated fatty acids, squalene, γ-oryzanol and other bioactive substances, and also contains a variety of essential vitamins and minerals, such as vitamin B group, vitamin E, potassium, magnesium, zinc, iron, etc. Although rice bran has such rich nutritional value, in reality, more than 80% of rice bran is used for feed or supplementary feed, and relatively few high-value-added products are developed for making biochar, rice bran oil, and food-grade rice bran fiber, etc. The overall comprehensive utilization rate is less than 20%, resulting in huge resource waste.

[0003] In recent years, with the increasing number of chronic patients and the pursuit of a healthy lifestyle by people, natural foods and plant-based ingredients have been highly regarded for their nutritional value and health benefits. Dietary fiber (DF) is considered an intervention diet beneficial to human health. High dietary fiber intake can effectively reduce the incidence of chronic diseases such as type II diabetes, cardiovascular diseases, colorectal cancer, and intestinal microbiota imbalance. Rice bran is a natural source of dietary fiber, with a content ranging from 25% to 40%. Its main components are non-starch polysaccharides such as insoluble dietary fiber (IDF) like cellulose and hemicellulose (xylan), and soluble dietary fiber (SDF) such as β-glucan and pectin. Among them, cereal cell wall β-glucan is an important physiologically functional active ingredient in rice bran, mainly playing physiological functions such as immunomodulation, anti-tumor, antioxidant, weight control, cholesterol level reduction, blood sugar stabilization, laxative effect, and improvement of intestinal microbiota, and is called "immune gold". β-glucan accounts for about 0.14% - 0.58% of rice bran, which is 4.5 times the content of β-glucan in the endosperm. Although the β-glucan content in rice bran is not high compared to that in grains such as oats, barley, and hulless barley, rice bran resources are abundant, and its output is hundreds of times the total of other cereal bran. Currently, based on the health benefits of dietary fiber, products such as high-fiber bread, cereals, snacks, and beverages are developed. By adding dietary fiber, not only the nutritional value of food is improved, but also the needs of consumers for healthy foods can be met. Dietary fiber supplements in the form of powders, tablets, and capsules also provide customized health solutions for different groups. Despite the rich nutritional value and broad market prospects of rice bran dietary fiber, in practical applications, due to the high content of insoluble dietary fiber and the soluble dietary fiber content accounting for less than 15% of the total rice bran dietary fiber, problems such as rough taste and poor solubility have always existed.

[0004] Therefore, to solve the above problems, researchers have carried out a large number of studies, mainly using physical methods, chemical methods, bio-enzymatic methods, and fermentation methods to improve the structural and dissolution properties of rice bran dietary fiber. Li Juan et al. used high-pressure microchannel jet technology to significantly reduce the content of insoluble fibers such as rice bran and bran. Wu Nana et al. modified defatted rice bran by steam explosion, increasing the SDF content from 3.22 g / 100 g to 6.28 g / 100 g, an increase of 95.03%; using extrusion cooking method, the SDF content of rice bran increased from 4.34% to 14.34%, significantly improving the solubility. Yang Duo et al. used high-pressure homogenization to improve the structure and physicochemical properties of IDF in millet bran, enhancing the stability of the water fiber dispersion, and also used Bacillus natto fermentation to increase the SDF content of millet bran dietary fiber from 5.17% to 19.36%. Ma Jiteng et al. used a multi-enzyme combination of cellulase, xylanase, and phytase to degrade non-starch polysaccharides in rice bran to improve the digestion and utilization efficiency of rice bran. Zhu Fengxia used ultrasonic-assisted cellulase enzymatic hydrolysis to prepare soluble dietary fiber from rice bran, with a high purity and good solubility of SDF in rice bran. In summary, the methods for improving rice bran dietary fiber still have problems such as severe treatment conditions, high energy consumption, and incomplete retention of nutrients. Therefore, developing a new method for modifying rice bran dietary fiber, efficiently retaining the physiological activity of nutrients in rice bran, and being easy for large-scale production is of great significance for enhancing the important position of rice bran as a source of dietary fiber functional raw materials.

[0005] The present invention uses ultrasonic-assisted trypsin, α-amylase, endo-xylanase, and endo-1,3(4)-β-glucanase to enzymatically hydrolyze rice bran, converting some insoluble dietary fiber into soluble dietary fiber, and converting β-glucan into water-soluble mixed-linkage β-glucan without destroying it, thereby enhancing the solubility and functional nutrition of rice bran. This method has mild conditions, low energy consumption, efficiently retains β-glucan in rice bran, and is easy for large-scale production, providing important technical support for the production of functional rice bran dietary fiber. Summary of the Invention

[0006] The present invention provides a method for ultrasonic-assisted enzymatic hydrolysis of rice bran to enhance solubility and completely retain β-glucan. This method improves the solubility of rice bran and increases soluble dietary fiber through controllable enzymatic hydrolysis while completely retaining functional β-glucan, providing a new method for the development of rice bran as a dietary fiber functional raw material.

[0007] The present invention relates to a method for ultrasonic-assisted enzymatic hydrolysis of rice bran to enhance solubility and completely retain β-glucan, and the specific technical solution is as follows:

[0008] A method for ultrasonic-assisted enzymatic hydrolysis of rice bran to enhance solubility and completely retain β-glucan, which comprises the following components:

[0009] Defatted rice bran powder, trypsin, α-amylase, endo-xylanase.

[0010] Preferably, defatted rice bran powder is mixed with hot water at a ratio of 1:10 (w / v), treated with ultrasound at 450 W for 2 h at a temperature of 55 °C.

[0011] Preferably, the amount of trypsin added for enzymatic hydrolysis is 0.00084 g of trypsin per 10 g of rice bran powder. The enzyme activity of trypsin is 250,000 U / g, the temperature is 37 °C, the pH is 8.0, and the time is 30 min to terminate the enzymatic hydrolysis reaction.

[0012] Preferably, the amount of α-amylase added for enzymatic hydrolysis is 0.0053 g of α-amylase per 10 g of rice bran powder. The enzyme activity of α-amylase is 400,000 U / g, the temperature is 50 °C, the pH is 5.5, and the time is 35 min to terminate the enzymatic hydrolysis reaction.

[0013] Preferably, the amount of endo-xylanase added is 0.02 g of endo-xylanase per 10 g of rice bran powder. The enzyme activity of endo-xylanase is 1,000,000 U / g, the temperature is 50 °C, the pH is 4.8, and the time is 35 min to terminate the enzymatic hydrolysis reaction.

[0014] Preferably, the amount of endo-β-1,3(4)-glucanase added is 0.00165 g per 10 g of rice bran powder. The enzyme activity of endo-β-1,3(4)-glucanase is 10,000 U / g, the temperature is 37 °C, the pH is 5.0, and the time is 35 min to terminate the enzymatic hydrolysis reaction.

[0015] The method for preparing the enzymatically hydrolyzed rice bran solution includes the following steps:

[0016] Ultrasonically treat a certain proportion of defatted rice bran powder solution in hot water, adjust the pH value of the mixed solution according to the optimal pH of the enzyme, and add trypsin, α-amylase, endo-xylanase, and β-1,3(4)-glucanase for enzymatic hydrolysis respectively. Finally, terminate the enzymatic hydrolysis reaction. The mixed solution and the precipitate are freeze-dried to obtain the enzymatically hydrolyzed product.

[0017] Preferably, the centrifugation speed is 3000 r, and the centrifugation time is 15 min; the rotary evaporation temperature is 55 °C, the rotation speed is 80 revolutions, concentrated to 1 / 3 of the original volume, add 2 volumes of 95% ethanol to the concentrated volume, stir and then let stand for 12 h to measure the β-glucan content.

[0018] Preferably, the Congo red method is used to measure the β-glucan content of the product, and an ion chromatograph is used to determine the monosaccharide composition, so as to verify the purity of β-glucan in the product.

[0019] The beneficial effects of the present invention are as follows:

[0020] The present invention uses ultrasonic-assisted enzymatic hydrolysis of rice bran to obtain dietary fiber instead of high-energy-consuming methods such as blasting and high pressure, and the biological enzymatic hydrolysis method is milder.

[0021] The present invention uses trypsin, α-amylase, and endo-xylanase for controlled enzymatic hydrolysis, which can improve the solubility of rice bran and increase soluble dietary fiber while completely retaining functional β-glucan, improving the availability of rice bran dietary fiber, and providing a new method for the development of dietary fiber functional raw materials. Brief Description of the Drawings

[0022] Figure 1 : Process flow of ultrasonic-assisted enzymatic hydrolysis of rice bran

[0023] Figure 2 : Content of β-glucan in different enzymatic hydrolysis products Detailed Embodiments

[0024] The present invention will be further described below in conjunction with specific implementation examples.

[0025] Example 1

[0026] Pretreatment of defatted rice bran raw material: Weigh an appropriate amount of defatted rice bran, crush it and pass through a 60-mesh sieve. Add the rice bran powder to hot water according to a solid-liquid ratio of 1:10 (w / v), stir evenly, and perform ultrasonic treatment at 450 W for 2 h at a temperature of 55°C.

[0027] Controlled enzymatic hydrolysis: After ultrasonic treatment, adjust the pH of the solution to 8.0, add trypsin to the ultrasonic-treated rice bran solution. Based on 10 g of rice bran, the enzyme addition amount is 0.00084 g. Enzymatic hydrolysis is carried out in a water bath at 37°C for 30 min, and then the enzyme is inactivated; then adjust the pH of the solution to 5.5, add α-amylase to the rice bran solution, with an addition amount of 0.0053 g, and perform enzymatic hydrolysis at 50°C for 35 min, and inactivate the enzyme. Centrifuge the mixture of the enzymatic hydrolysate, take the supernatant, perform rotary evaporation, alcohol precipitation, and freeze-drying, and measure the content of β-glucan.

[0028] Example 2

[0029] Pretreatment of defatted rice bran raw material: Weigh an appropriate amount of defatted rice bran, crush it and pass through a 60-mesh sieve. Add the rice bran powder to hot water according to a solid-liquid ratio of 1:10 (w / v), stir evenly, and perform ultrasonic treatment at 450 W for 2 h at a temperature of 55°C.

[0030] Controlled enzymatic hydrolysis: After ultrasonic treatment, adjust the pH of the solution to 8.0. Add trypsin to the ultrasonicated rice bran solution. Based on 10 g of rice bran, the enzyme addition amount is 0.00084 g. Enzymatically hydrolyze in a water bath at 37 °C for 30 min, and then inactivate the enzyme. Then adjust the pH of the solution to 5.5, add α-amylase to the rice bran solution, with an addition amount of 0.0053 g, and enzymatically hydrolyze at 50 °C for 35 min, and then inactivate the enzyme. After enzymatic hydrolysis, adjust the pH of the solution to 4.8, add endo-xylanase to the enzymatically hydrolyzed rice bran solution, with an addition amount of 0.02 g, and enzymatically hydrolyze at 50 °C for 35 min, and then inactivate the enzyme. Centrifuge the mixture of the enzymatic hydrolysate, take the supernatant, perform rotary evaporation, alcohol precipitation, freeze-dry, and measure the β-glucan content.

[0031] Example 3

[0032] Pretreatment of defatted rice bran raw material: Weigh an appropriate amount of defatted rice bran, crush it and pass through a 60-mesh sieve. Add the rice bran powder to hot water at a solid-liquid ratio of 1:10 (w / v), stir evenly, and perform ultrasonic treatment at 450 W for 2 h at a temperature of 55 °C.

[0033] Controlled enzymatic hydrolysis: After ultrasonic treatment, adjust the pH of the solution to 8.0. Add trypsin to the ultrasonicated rice bran solution. Based on 10 g of rice bran, the enzyme addition amount is 0.00084 g. Enzymatically hydrolyze in a water bath at 37 °C for 30 min, and then inactivate the enzyme. Then adjust the pH of the solution to 5.5, add α-amylase to the rice bran solution, with an addition amount of 0.0053 g, and enzymatically hydrolyze at 50 °C for 35 min, and then inactivate the enzyme. After enzymatic hydrolysis, adjust the pH of the solution to 4.8, add endo-xylanase to the enzymatically hydrolyzed rice bran solution, with an addition amount of 0.02 g, and enzymatically hydrolyze at 50 °C for 35 min, and then inactivate the enzyme. Then add endo-1,3(4)-β-glucanase, with an addition amount of 0.00165 g, at a temperature of 37 °C, for a time of 35 min, and a pH of 5.0. Centrifuge the mixture of the enzymatic hydrolysate, take the supernatant, perform rotary evaporation, alcohol precipitation, freeze-dry, and measure the β-glucan content. The content of β-glucan decreases mainly because endo-β-1,3(4)-glucanase enzymatically hydrolyzes glucan to finally produce glucose.

Claims

1. A method for ultrasonic-assisted enzymatic hydrolysis of defatted rice bran to enhance solubility and completely retain β-glucan, characterized in that: (1) Weigh an appropriate amount of defatted rice bran powder, mix it with hot water at a certain ratio, and then perform ultrasonic treatment; (2) After ultrasonic treatment, adjust the pH value of the solution, and sequentially add trypsin, α-amylase, endo-xylanase, and endo-1,3(4)-β-glucanase for enzymatic hydrolysis.

2. The method for enhancing the solubility of ultrasonic-assisted enzymolysis of rice bran and completely retaining β-glucan according to claim 1, characterized in that, The defatted rice bran powder is pulverized and sieved through a 60-mesh sieve to obtain micronized rice bran powder.

3. A method for enhancing the solubility of ultrasonic-assisted enzymolysis of rice bran and completely retaining β-glucan according to claim 1, characterized in that, The defatted rice bran powder is mixed with hot water at a ratio of 1:10 (w / v), and ultrasonic treatment is carried out at 450 W for 2 h at a temperature of 55 °C.

4. A method for enhancing the solubility of ultrasonic-assisted enzymatically hydrolyzed rice bran and completely retaining β-glucan according to claim 1, characterized in that The addition amount of the trypsin is 0.00084 g per 10 g of rice bran powder, the enzyme activity of the trypsin is 250000 U / g, the temperature of enzymatic hydrolysis is 37 °C, the pH is 8.0, and the time is 30 min to terminate the enzymatic hydrolysis reaction. Then, the addition amount of α-amylase is 0.0053 g per 10 g of rice bran powder, the enzyme activity is 400000 U / g, the temperature is 50 °C, the pH is 5.5, and the time is 35 min to terminate the enzymatic hydrolysis reaction. Then, the addition amount of endo-xylanase is 0.02 g per 10 g of rice bran powder, the enzyme activity is 1000000 U / g, the temperature is 50 °C, the pH is 4.8, and the time is 35 min to terminate the enzymatic hydrolysis reaction. Finally, add endo-β-1,3(4)-glucanase, the addition amount is 0.00165 g per 10 g of rice bran powder, the enzyme activity is 10000 U / g, the temperature is 37 °C, the pH is 5.0, and the time is 35 min to terminate the enzymatic hydrolysis reaction.

5. The method for enhancing the solubility of ultrasonic-assisted enzymolysis of rice bran and completely retaining β-glucan according to claim 1, characterized in that, The mixture of the enzymatic hydrolysate and the enzymatic hydrolysis solution is collected, rotary evaporated, and freeze-dried. The rotary evaporation temperature is 55 °C, the rotation speed is 80 r / min, and the concentrated solution is freeze-dried to obtain the rice bran enzymatic hydrolysis product.

6. The method for enhancing the solubility of ultrasonic-assisted enzymolysis of rice bran and completely retaining β-glucan according to claim 1, wherein The enzymatic hydrolysis solution is centrifuged at 3000 r / min for 15 min to take the supernatant, rotary evaporated at 55 °C, the volume of the concentrated solution is added with 2 times the volume of 95% ethanol, stirred, and then allowed to stand for 12 h for alcohol precipitation. After freeze-drying, the β-glucan content is measured.

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