Preparation method of high-solubility rice protein

Abstract

The invention provides a preparation method of high-solubility rice protein, which comprises the following steps: ultrasonically dispersing rice protein powder in deionized water, and treating by a pulsed magnetic field to obtain rice protein dispersion liquid; introducing liquid nitrogen into the rice protein dispersion liquid, immediately contacting high-pressure steam with the rice protein dispersion liquid, instantaneously releasing the pressure to normal pressure, naturally cooling to room temperature, adding a disulfide bond reducing agent, and stirring at room temperature for reaction to obtain depolymerized rice protein dispersion liquid; the disulfide bond reducing agent is prepared by mixing sodium sulfite, cysteine and tea polysaccharide-selenium nanoparticles in equal mass; and adding pullulan into the depolymerized rice protein dispersion liquid, carrying out electron beam irradiation and microwave irradiation, naturally cooling to room temperature, carrying out high-pressure homogenization treatment, and carrying out spray drying.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, in particular to a method for preparing highly soluble rice protein. Background Art

[0002] Currently, there are three main technical means to improve the solubility of rice protein: changing the protein conformation through physical action, modifying the molecular structure through chemical reaction, and specific modification with the help of biological enzyme catalysis. The details are as follows: (1) Physical modification Physical modification involves inducing conformational rearrangements in proteins by applying non-chemical means such as heat, mechanical stress, or electromagnetic fields, exposing internal hydrophilic amino acid residues to the surface. This structural remodeling process primarily relies on rebalancing intermolecular forces, improving functional properties such as protein solubility and surface activity without altering covalent bonds. Literature reports indicate that high-pressure homogenization can enhance the functional properties of rice protein, significantly increasing its water solubility and emulsification properties by 101% and 26%, respectively. Physical modification improves protein functional properties by inducing multiple structural changes. Physical treatment primarily affects the aggregation morphology of protein molecules while leaving their primary structure largely unchanged. Physical modification offers advantages such as high safety and controllability, low cost, and minimal damage to nutrients. However, it consumes significant energy and has limited effectiveness.

[0003] (2) Chemical modification Chemical modification of proteins is an important means of regulating their functional properties by altering the covalent structure of polypeptide chains or amino acid side chains. These modifications primarily include acylation, phosphorylation, methylation, glycosylation, and deamidation. These reactions can induce conformational rearrangements and restructure interaction networks within proteins, significantly improving their solubility, emulsification, and other functional properties. A study has structurally modified rice protein using citric acid-mediated deamidation, demonstrating that this treatment significantly enhances its water solubility and improves its emulsification properties. Chemical modification offers advantages such as short reaction times, low costs, and simple operation. However, with the exception of glycosylation, other chemical modification methods may generate harmful substances during the modification process due to the difficulty in removing the introduced chemical reagents, and amino acid loss may occur after acid-base treatment.

[0004] (3) Enzymatic modification Enzymatic hydrolysis uses endonucleases and exonucleases to specifically cleave protein molecules, breaking intact polypeptide chains into fragments of varying lengths. This enzymatic hydrolysis can reduce the average molecular weight of proteins while exposing more dissociable groups, thereby optimizing their functional properties such as solubility and surface activity. Researchers have hydrolyzed rice bran protein by controlling the degree of hydrolysis with papain. The results showed that the water solubility and in vitro digestibility of the enzymatically hydrolyzed protein samples were significantly improved, increasing by 46% and 23.91%, respectively, compared to unmodified rice bran protein. Enzymatic modification maintains the nutritional properties of proteins while offering advantages such as high specificity, mild reaction conditions, and environmental friendliness. However, the hydrophobic peptides formed during enzymatic hydrolysis (e.g., those containing leucine and phenylalanine) can produce a bitter taste, requiring additional debittering treatment. Furthermore, enzymatic modification alters the primary structure of the protein, significantly impacting its processing properties.

[0005] In summary, how to not destroy the primary structure of the protein during the preparation process and avoid the production of harmful substances and bad flavors is the current research difficulty in the preparation of soluble rice protein. Summary of the Invention

[0006] The present invention aims to provide a method for preparing highly soluble rice protein, so as to solve the technical problems that the existing preparation methods destroy the primary structure of the protein, and produce harmful substances and bad flavors.

[0007] To achieve the above object, the present invention provides a method for preparing highly soluble rice protein, which comprises the following steps: S1. First, rice protein was crushed into rice protein powder, and then the rice protein powder was ultrasonically dispersed in deionized water and treated with a pulsed magnetic field to obtain a rice protein dispersion; S2. Liquid nitrogen is introduced into the rice protein dispersion, and the rice protein dispersion is immediately exposed to high-pressure steam. The pressure is then instantly released to normal pressure (0.1 MPa), and the mixture is naturally cooled to room temperature (25°C). A disulfide bond reducing agent is then added, and the mixture is stirred at room temperature to produce a depolymerized rice protein dispersion. The disulfide bond reducing agent is prepared by mixing sodium sulfite, cysteine, and tea polysaccharide-selenium nanoparticles in equal amounts. S3. Pullulan is added to the depolymerized rice protein dispersion, and the mixture is subjected to electron beam irradiation, microwave irradiation, natural cooling to room temperature, high pressure homogenization, and spray drying to obtain a highly soluble rice protein.

[0008] Preferably, in step S1, the average particle size of the rice protein powder is 40 to 50 μm.

[0009] Preferably, in step S1, the mass ratio of rice protein powder to deionized water is 1:18-20.

[0010] Preferably, in step S1, the process conditions of the pulsed magnetic field treatment are: pulse frequency 30-40 Hz, magnetic induction intensity 200-220 mT, duty cycle 25-35%, current 180-200 A, and treatment time 80-100 s.

[0011] Preferably, in step S2, liquid nitrogen is introduced at a rate of 10 to 12 kg / min for a time of 3 to 4 seconds.

[0012] Preferably, in step S2, the pressure of the high-pressure steam is 2-3 MPa, the temperature is 150-170° C., and the contact time is 50-70 s.

[0013] Preferably, in step S2, the amount of the disulfide bond reducing agent is 0.05 to 0.5% by mass of the rice protein dispersion, more preferably 0.1 to 0.3%.

[0014] Preferably, in step S2, the tea polysaccharide-selenium nanoparticles are prepared by the following method: first, tea polysaccharide is stirred and dissolved in 85-90°C water, and naturally cooled to room temperature to obtain a 2-4 mg / L tea polysaccharide solution, and then the tea polysaccharide solution is stirred and mixed with a 10-15 mmol / L sodium selenite solution, and then a freshly prepared 35-45 mmol / L ascorbic acid solution is added dropwise under vigorous stirring conditions, and the mixture is stirred and reacted at 40-50°C in the dark for 4-6 hours, and excess ascorbic acid and sodium selenite are dialyzed with deionized water to obtain the obtained nanoparticles; wherein the molar ratio of the tea polysaccharide contained in the tea polysaccharide solution, the sodium selenite contained in the sodium selenite solution, and the ascorbic acid contained in the ascorbic acid solution is 1:1:4.

[0015] More preferably, the dialysis molecular weight cut-off is 3500 kDa and the dialysis time is 4 days.

[0016] Preferably, in step S2, the stirring reaction time at room temperature is 60 to 80 minutes.

[0017] Preferably, in step S3, the amount of pullulan is 0.1 to 0.2% of the mass of the depolymerized rice protein dispersion.

[0018] Preferably, in step S3, before electron beam irradiation, the pH is adjusted to 5.0-6.5 using 1 mol / L hydrochloric acid solution.

[0019] Preferably, in step S3, a 10 MeV high energy electron accelerator is used as the radiation source, and the electron beam irradiation dose is 6 to 8 KGy.

[0020] Preferably, in step S3, the microwave irradiation conditions are: microwave power 400-500W, irradiation for 2-3 minutes, rest for 1 minute, and so on, until the cumulative irradiation time is 15-18 minutes.

[0021] Preferably, in step S3, the process conditions of the high-pressure homogenization treatment are: pressure 50-70 MPa, and 3-5 cycles.

[0022] Preferably, in step S3, the process conditions for spray drying are: feed rate 3-5 mL / min, inlet temperature 160-180°C, and outlet temperature 130-140°C.

[0023] The present invention has the following beneficial effects: The invention provides a preparation method of highly soluble rice protein. The method comprises the following steps: firstly, crushing rice protein into rice protein powder; then ultrasonically dispersing the rice protein powder in deionized water; and subjecting the rice protein dispersion to pulsed magnetic field treatment to obtain a rice protein dispersion liquid; introducing liquid nitrogen into the rice protein dispersion liquid, immediately contacting the rice protein dispersion liquid with high-pressure steam, instantly releasing the pressure to normal pressure, naturally cooling the mixture to room temperature, adding a disulfide bond reducing agent, and stirring and reacting the mixture at room temperature to obtain a depolymerized rice protein dispersion liquid; wherein the disulfide bond reducing agent is obtained by mixing sodium sulfite, cysteine, and tea polysaccharide-selenium nanoparticles in equal amounts; and adding pullulan into the depolymerized rice protein dispersion liquid, subjecting the mixture to electron beam irradiation and microwave irradiation, naturally cooling the mixture to room temperature, high-pressure homogenization treatment, and spray drying.

[0024] The invention is simple to operate, and the obtained rice protein has good solubility and emulsification, does not destroy the primary structure of the protein, and does not produce harmful substances or bad flavors.

[0025] Rice protein is mainly composed of four kinds of proteins such as albumin, globulin, alcohol-soluble protein and gluten, and particularly alkali-soluble gluten content is the highest, and gluten is formed by many macromolecular fragments by disulfide bond, cross-linked and condensed each other, therefore, compared with wheat protein, soy protein, rice protein solubility, emulsification are relatively poor. The present invention is combined by means such as pulsed magnetic field processing, liquid nitrogen and high-pressure steam treatment, disulfide bond reducing agent, pulsed magnetic field processing helps to reduce the stability of protein tertiary structure, after liquid nitrogen instant cooling, high-pressure steam treatment promotes the abundant swelling of rice protein, pressure is released instantly, promotes rice protein depolymerization, in conjunction with the destruction of disulfide bond by reducing agent, reduce intermolecular crosslinking, promote the expansion of protein tertiary structure, the change of secondary structure, increase the flexibility and dynamics of protein molecule, this helps to improve solubility, because the structure expanded is easier to interact with water molecules, simultaneously, remove the polymerization of subunits in rice protein molecule, also improve the emulsification of rice protein.

[0026] Furthermore, the present invention introduces pullulan and performs electron beam irradiation, microwave irradiation and high-pressure homogenization treatment to cause a glycosylation reaction, further change the aggregation mode of protein molecules, reduce the particle size of rice protein microparticles, increase the specific surface area, and further improve the solubility of rice protein. DETAILED DESCRIPTION

[0027] The following is a detailed description of embodiments of the present invention, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0028] Example 1: A preparation method of highly soluble rice protein, comprising the following steps: S1. first crushing rice protein into rice protein powder, then ultrasonically dispersing the rice protein powder in deionized water and treating with a pulsed magnetic field to obtain a rice protein dispersion; The average particle size of rice protein powder is 40 μm.

[0029] The mass ratio of rice protein powder to deionized water is 1:18.

[0030] The process conditions of the pulsed magnetic field treatment are: pulse frequency 30 Hz, magnetic induction intensity 200 mT, duty cycle 25%, current 180 A, and treatment time 80 s.

[0031] S2. liquid nitrogen is introduced into the rice protein dispersion, the rice protein dispersion is immediately contacted with high-pressure steam, the pressure is instantly released to normal pressure (0.1MPa), and naturally cooled to room temperature (25°C), a disulfide bond reducing agent is added, and the reaction is stirred at room temperature to obtain a depolymerized rice protein dispersion; the disulfide bond reducing agent is obtained by mixing the quality of sodium sulfite, cysteine, tea polysaccharide-selenium nanoparticles; The pressure of the high-pressure steam is 2 MPa, the temperature is 150°C, and the contact time is 50 s.

[0032] The dosage of the disulfide bond reducing agent is 0.05% of the mass of the rice protein dispersion.

[0033] Tea polysaccharide-selenium nanoparticles are prepared by the following method: first, tea polysaccharide is stirred and dissolved in 85°C water, and naturally cooled to room temperature to obtain a 2 mg / L tea polysaccharide solution; then, the tea polysaccharide solution is stirred and mixed with a 10 mmol / L sodium selenite solution; then, a freshly prepared 35 mmol / L ascorbic acid solution is dropped into the solution under vigorous stirring conditions (18000 r / min); the mixture is stirred and reacted at 40°C in the dark for 4 hours; and excess ascorbic acid and sodium selenite are removed by dialysis with deionized water to obtain the tea polysaccharide-selenium nanoparticles; wherein the molar ratio of the tea polysaccharide contained in the tea polysaccharide solution, the sodium selenite contained in the sodium selenite solution, and the ascorbic acid contained in the ascorbic acid solution is 1:1:4; the dialysis cut-off molecular weight is 3500 kDa, and the dialysis time is 4 days.

[0034] The reaction time was 60 minutes with stirring at room temperature.

[0035] S3. Pullulan is added to the depolymerized rice protein dispersion, subjected to electron beam irradiation, microwave irradiation, naturally cooled to room temperature, high pressure homogenization, and spray drying to obtain a highly soluble rice protein.

[0036] The amount of pullulan used is 0.1% of the mass of the depolymerized rice protein dispersion.

[0037] Before electron beam irradiation, the pH was adjusted to 5.0 using 1 mol / L hydrochloric acid solution.

[0038] A 10MeV high-energy electron accelerator was used as the radiation source, and the electron beam irradiation dose was 6KGy.

[0039] The microwave irradiation conditions were as follows: microwave power 400 W, irradiation for 2 minutes, rest for 1 minute, and so on, until the cumulative irradiation time reached 15 minutes.

[0040] The process conditions of high-pressure homogenization treatment are: pressure 50 MPa, 3 cycles.

[0041] The process conditions of spray drying were: feed rate 3 mL / min, inlet temperature 160 °C, and outlet temperature 130 °C.

[0042] Example 2: A preparation method of highly soluble rice protein, comprising the following steps: S1. first crushing rice protein into rice protein powder, then ultrasonically dispersing the rice protein powder in deionized water and treating with a pulsed magnetic field to obtain a rice protein dispersion; The average particle size of rice protein powder is 50 μm.

[0043] The mass ratio of rice protein powder to deionized water is 1:20.

[0044] The process conditions of the pulsed magnetic field treatment are: pulse frequency 40 Hz, magnetic induction intensity 220 mT, duty cycle 35%, current 200 A, and treatment time 100 s.

[0045] S2. liquid nitrogen is introduced into the rice protein dispersion, the rice protein dispersion is immediately contacted with high-pressure steam, the pressure is instantly released to normal pressure (0.1MPa), and naturally cooled to room temperature (25°C), a disulfide bond reducing agent is added, and the reaction is stirred at room temperature to obtain a depolymerized rice protein dispersion; the disulfide bond reducing agent is obtained by mixing the quality of sodium sulfite, cysteine, tea polysaccharide-selenium nanoparticles; The pressure of the high-pressure steam is 3 MPa, the temperature is 170°C, and the contact time is 70 s.

[0046] The dosage of the disulfide bond reducing agent is 0.5% of the mass of the rice protein dispersion.

[0047] Tea polysaccharide-selenium nanoparticles are prepared by the following method: first, tea polysaccharide is stirred and dissolved in 90°C water, and naturally cooled to room temperature to obtain a 4 mg / L tea polysaccharide solution; then, the tea polysaccharide solution is stirred and mixed with a 15 mmol / L sodium selenite solution; then, a freshly prepared 45 mmol / L ascorbic acid solution is added dropwise under vigorous stirring conditions (18000 r / min); the mixture is stirred and reacted at 50°C in the dark for 6 hours; and excess ascorbic acid and sodium selenite are removed by dialysis with deionized water to obtain the tea polysaccharide-selenium nanoparticles; wherein the molar ratio of tea polysaccharide contained in the tea polysaccharide solution, sodium selenite contained in the sodium selenite solution, and ascorbic acid contained in the ascorbic acid solution is 1:1:4; the dialysis cut-off molecular weight is 3500 kDa, and the dialysis time is 4 days.

[0048] The reaction time was 80 minutes with stirring at room temperature.

[0049] S3. Pullulan is added to the depolymerized rice protein dispersion, subjected to electron beam irradiation, microwave irradiation, naturally cooled to room temperature, high pressure homogenization, and spray drying to obtain a highly soluble rice protein.

[0050] The amount of pullulan used is 0.2% of the mass of the depolymerized rice protein dispersion.

[0051] Before electron beam irradiation, the pH was adjusted to 6.5 using 1 mol / L hydrochloric acid solution.

[0052] A 10MeV high-energy electron accelerator was used as the radiation source, and the electron beam irradiation dose was 8KGy.

[0053] The microwave irradiation conditions were as follows: microwave power 500 W, irradiation for 3 minutes, rest for 1 minute, and this cycle was repeated until the cumulative irradiation time reached 18 minutes.

[0054] The process conditions of high-pressure homogenization treatment are: pressure 70 MPa, 5 cycles.

[0055] The process conditions of spray drying were: feed rate 5 mL / min, inlet temperature 180 °C, and outlet temperature 140 °C.

[0056] Example 3: A preparation method of highly soluble rice protein, comprising the following steps: S1. first crushing rice protein into rice protein powder, then ultrasonically dispersing the rice protein powder in deionized water and treating with a pulsed magnetic field to obtain a rice protein dispersion; The average particle size of rice protein powder is 40 μm.

[0057] The mass ratio of rice protein powder to deionized water is 1:20.

[0058] The process conditions of the pulsed magnetic field treatment are: pulse frequency 30 Hz, magnetic induction intensity 220 mT, duty cycle 25%, current 200 A, and treatment time 80 s.

[0059] S2. liquid nitrogen is introduced into the rice protein dispersion, the rice protein dispersion is immediately contacted with high-pressure steam, the pressure is instantly released to normal pressure (0.1MPa), and naturally cooled to room temperature (25°C), a disulfide bond reducing agent is added, and the reaction is stirred at room temperature to obtain a depolymerized rice protein dispersion; the disulfide bond reducing agent is obtained by mixing the quality of sodium sulfite, cysteine, tea polysaccharide-selenium nanoparticles; The pressure of the high-pressure steam is 3 MPa, the temperature is 150°C, and the contact time is 70 s.

[0060] Tea polysaccharide-selenium nanoparticles are prepared by the following method: first, tea polysaccharide is stirred and dissolved in 85°C water, and naturally cooled to room temperature to obtain a 4 mg / L tea polysaccharide solution; then, the tea polysaccharide solution is stirred and mixed with a 10 mmol / L sodium selenite solution; then, a freshly prepared 45 mmol / L ascorbic acid solution is added dropwise under vigorous stirring conditions (18000 r / min); the mixture is stirred and reacted at 40°C in the dark for 6 hours; and excess ascorbic acid and sodium selenite are removed by dialysis with deionized water to obtain the tea polysaccharide-selenium nanoparticles; wherein the molar ratio of the tea polysaccharide contained in the tea polysaccharide solution, the sodium selenite contained in the sodium selenite solution, and the ascorbic acid contained in the ascorbic acid solution is 1:1:4; the dialysis cut-off molecular weight is 3500 kDa, and the dialysis time is 4 days.

[0061] The dosage of the disulfide bond reducing agent is 0.1% of the mass of the rice protein dispersion.

[0062] The reaction time was 80 minutes with stirring at room temperature.

[0063] S3. Pullulan is added to the depolymerized rice protein dispersion, subjected to electron beam irradiation, microwave irradiation, naturally cooled to room temperature, high pressure homogenization, and spray drying to obtain a highly soluble rice protein.

[0064] The amount of pullulan used is 0.1% of the mass of the depolymerized rice protein dispersion.

[0065] Before electron beam irradiation, the pH was adjusted to 6.5 using 1 mol / L hydrochloric acid solution.

[0066] A 10MeV high-energy electron accelerator was used as the radiation source, and the electron beam irradiation dose was 6KGy.

[0067] The microwave irradiation conditions were as follows: microwave power 500 W, irradiation for 2 minutes, rest for 1 minute, and so on, until the cumulative irradiation time reached 18 minutes.

[0068] The process conditions of high-pressure homogenization treatment are: pressure 50 MPa, 5 cycles.

[0069] The process conditions of spray drying were: feed rate 3 mL / min, inlet temperature 180 °C, and outlet temperature 130 °C.

[0070] Example 4: A preparation method of highly soluble rice protein, comprising the following steps: S1. first crushing rice protein into rice protein powder, then ultrasonically dispersing the rice protein powder in deionized water and treating with a pulsed magnetic field to obtain a rice protein dispersion; The average particle size of rice protein powder is 50 μm.

[0071] The mass ratio of rice protein powder to deionized water is 1:18.

[0072] The process conditions of the pulsed magnetic field treatment are: pulse frequency 40 Hz, magnetic induction intensity 200 mT, duty cycle 35%, current 180 A, and treatment time 100 s.

[0073] S2. liquid nitrogen is introduced into the rice protein dispersion, the rice protein dispersion is immediately contacted with high-pressure steam, the pressure is instantly released to normal pressure (0.1MPa), and naturally cooled to room temperature (25°C), a disulfide bond reducing agent is added, and the reaction is stirred at room temperature to obtain a depolymerized rice protein dispersion; the disulfide bond reducing agent is obtained by mixing the quality of sodium sulfite, cysteine, tea polysaccharide-selenium nanoparticles; The pressure of the high-pressure steam is 2 MPa, the temperature is 170°C, and the contact time is 50 s.

[0074] The dosage of the disulfide bond reducing agent is 0.3% of the mass of the rice protein dispersion.

[0075] Tea polysaccharide-selenium nanoparticles are prepared by the following method: first, tea polysaccharide is stirred and dissolved in 88°C water, and naturally cooled to room temperature to obtain a 3 mg / L tea polysaccharide solution; then, the tea polysaccharide solution is stirred and mixed with a 12 mmol / L sodium selenite solution; then, a freshly prepared 40 mmol / L ascorbic acid solution is added dropwise under vigorous stirring conditions (18000 r / min); the mixture is stirred and reacted at 45°C in the dark for 5 hours; and excess ascorbic acid and sodium selenite are removed by dialysis with deionized water to obtain the tea polysaccharide-selenium nanoparticles; wherein the molar ratio of the tea polysaccharide contained in the tea polysaccharide solution, the sodium selenite contained in the sodium selenite solution, and the ascorbic acid contained in the ascorbic acid solution is 1:1:4; the dialysis cut-off molecular weight is 3500 kDa, and the dialysis time is 4 days.

[0076] The reaction time was 60 minutes with stirring at room temperature.

[0077] S3. Pullulan is added to the depolymerized rice protein dispersion, subjected to electron beam irradiation, microwave irradiation, naturally cooled to room temperature, high pressure homogenization, and spray drying to obtain a highly soluble rice protein.

[0078] The amount of pullulan used is 0.2% of the mass of the depolymerized rice protein dispersion.

[0079] Before electron beam irradiation, the pH was adjusted to 5.0 using 1 mol / L hydrochloric acid solution.

[0080] A 10MeV high-energy electron accelerator was used as the radiation source, and the electron beam irradiation dose was 8KGy.

[0081] The microwave irradiation conditions were as follows: microwave power 400 W, irradiation for 3 minutes, rest for 1 minute, and this cycle was repeated until the cumulative irradiation time reached 15 minutes.

[0082] The process conditions of high-pressure homogenization treatment are: pressure 70 MPa, 3 cycles.

[0083] The process conditions of spray drying were: feed rate 5 mL / min, inlet temperature 160 °C, and outlet temperature 140 °C.

[0084] Comparative Example 1 The pulse magnetic field treatment is omitted, and the rest is the same as in Example 1.

[0085] Comparative Example 2 The liquid nitrogen and high-pressure steam treatments were omitted, and the remainder was the same as in Example 1.

[0086] Comparative Example 3 A preparation method of soluble rice protein, comprising the following steps: S1. first crushing rice protein into rice protein powder, then ultrasonically dispersing the rice protein powder in deionized water and treating with a pulsed magnetic field to obtain a rice protein dispersion; The average particle size of rice protein powder is 40 μm.

[0087] The mass ratio of rice protein powder to deionized water is 1:18.

[0088] The process conditions of the pulsed magnetic field treatment are: pulse frequency 30 Hz, magnetic induction intensity 200 mT, duty cycle 25%, current 180 A, and treatment time 80 s.

[0089] S2. liquid nitrogen is introduced into the rice protein dispersion, the rice protein dispersion is immediately contacted with high-pressure steam, the pressure is released to normal pressure (0.1MPa) in an instant, and naturally cooled to room temperature (25°C), a disulfide bond reducing agent is added, and the reaction is stirred at room temperature to obtain a depolymerized rice protein dispersion; the disulfide bond reducing agent is obtained by mixing qualities such as sodium sulfite and cysteine; The pressure of the high-pressure steam is 2 MPa, the temperature is 150°C, and the contact time is 50 s.

[0090] The dosage of the disulfide bond reducing agent is 0.05% of the mass of the rice protein dispersion.

[0091] The reaction time was 60 minutes with stirring at room temperature.

[0092] S3. Pullulan is added to the depolymerized rice protein dispersion, subjected to electron beam irradiation, microwave irradiation, naturally cooled to room temperature, high pressure homogenization, and spray drying to obtain a soluble rice protein.

[0093] The amount of pullulan used is 0.1% of the mass of the depolymerized rice protein dispersion.

[0094] Before electron beam irradiation, the pH was adjusted to 5.0 using 1 mol / L hydrochloric acid solution.

[0095] A 10MeV high-energy electron accelerator was used as the radiation source, and the electron beam irradiation dose was 6KGy.

[0096] The microwave irradiation conditions were as follows: microwave power 400 W, irradiation for 2 minutes, rest for 1 minute, and so on, until the cumulative irradiation time reached 15 minutes.

[0097] The process conditions of high-pressure homogenization treatment are: pressure 50 MPa, 3 cycles.

[0098] The process conditions of spray drying were: feed rate 3 mL / min, inlet temperature 160 °C, and outlet temperature 130 °C.

[0099] Comparative Example 4 A preparation method of soluble rice protein, comprising the following steps: S1. first crushing rice protein into rice protein powder, then ultrasonically dispersing the rice protein powder in deionized water and treating with a pulsed magnetic field to obtain a rice protein dispersion; The average particle size of rice protein powder is 40 μm.

[0100] The mass ratio of rice protein powder to deionized water is 1:18.

[0101] The process conditions of the pulsed magnetic field treatment are: pulse frequency 30 Hz, magnetic induction intensity 200 mT, duty cycle 25%, current 180 A, and treatment time 80 s.

[0102] S2. liquid nitrogen is introduced into the rice protein dispersion, the rice protein dispersion is immediately contacted with high-pressure steam, the pressure is instantly released to normal pressure (0.1MPa), and naturally cooled to room temperature (25°C), a disulfide bond reducing agent is added, and the reaction is stirred at room temperature to obtain a depolymerized rice protein dispersion; the disulfide bond reducing agent is obtained by mixing the quality of sodium sulfite, cysteine, tea polysaccharide-selenium nanoparticles; The pressure of the high-pressure steam is 2 MPa, the temperature is 150°C, and the contact time is 50 s.

[0103] The dosage of the disulfide bond reducing agent is 0.05% of the mass of the rice protein dispersion.

[0104] Tea polysaccharide-selenium nanoparticles are prepared by the following method: first, tea polysaccharide is stirred and dissolved in 85°C water, and naturally cooled to room temperature to obtain a 2 mg / L tea polysaccharide solution; then, the tea polysaccharide solution is stirred and mixed with a 10 mmol / L sodium selenite solution; then, a freshly prepared 35 mmol / L ascorbic acid solution is dropped into the solution under vigorous stirring conditions (18000 r / min); the mixture is stirred and reacted at 40°C in the dark for 4 hours; and excess ascorbic acid and sodium selenite are removed by dialysis with deionized water to obtain the tea polysaccharide-selenium nanoparticles; wherein the molar ratio of the tea polysaccharide contained in the tea polysaccharide solution, the sodium selenite contained in the sodium selenite solution, and the ascorbic acid contained in the ascorbic acid solution is 1:1:4; the dialysis cut-off molecular weight is 3500 kDa, and the dialysis time is 4 days.

[0105] The reaction time was 60 minutes with stirring at room temperature.

[0106] S3. The depolymerized rice protein dispersion is subjected to electron beam irradiation and microwave irradiation, naturally cooled to room temperature, high pressure homogenization treatment, and spray drying to obtain a soluble rice protein.

[0107] Before electron beam irradiation, the pH was adjusted to 5.0 using 1 mol / L hydrochloric acid solution.

[0108] A 10MeV high-energy electron accelerator was used as the radiation source, and the electron beam irradiation dose was 6KGy.

[0109] The microwave irradiation conditions were as follows: microwave power 400 W, irradiation for 2 minutes, rest for 1 minute, and so on, until the cumulative irradiation time reached 15 minutes.

[0110] The process conditions of high-pressure homogenization treatment are: pressure 50 MPa, 3 cycles.

[0111] The process conditions of spray drying were: feed rate 3 mL / min, inlet temperature 160 °C, and outlet temperature 130 °C.

[0112] Comparative Example 5 The electron beam irradiation is omitted, and the rest is the same as in Example 1.

[0113] Comparative Example 6 Omit microwave irradiation, and otherwise remain the same as in Example 1.

[0114] The soluble rice proteins obtained in Examples 1 to 4 and Comparative Examples 1 to 6 were subjected to performance tests, respectively, including: 1. Solubility Disperse soluble rice protein in phosphate buffer (0.01 mol / L, pH 7.0) to prepare a 10 mg / mL rice protein dispersion. Stir at 25°C for 1 hour and centrifuge at 3000 rpm for 20 minutes. Carefully remove the supernatant fraction and determine the protein content using the Lowry method. Calculate the solubility using the following formula: Solubility (%) = protein content in supernatant / total protein content in raw material × 100.

[0115] 2. Emulsification Soluble rice protein was dispersed in phosphate buffer (0.2 mol / L, pH 7.0) to prepare a 0.1% rice protein dispersion. 150 mL of the rice protein dispersion was added to 50 mL of soybean oil and homogenized at 10,000 rpm for 2 minutes. A 50 μL sample was taken from the bottom of the container and 5 mL of a 0.1% sodium dodecyl sulfate solution was added. The mixture was mixed thoroughly and the absorbance (A0) was measured at a wavelength of 500 nm, using a 0.1% sodium dodecyl sulfate solution as a blank. After 10 minutes (t), the absorbance (At) was measured. Emulsification and emulsion stability were calculated according to the following formula: Emulsification activity index EAI = (2 × 2.303 × A0 × dilution factor) / (0.001 × (1-φ) × 10000), where φ is the volume ratio of oil (v / v); Emulsion stability ESI = A0 × t × (A0-At).

[0116] The test results are shown in Table 1.

[0117] Table 1. Soluble protein performance test results As shown in Table 1, the soluble rice proteins obtained in Examples 1 to 4 have excellent solubility and emulsification properties.

[0118] Comparative Example 1 omits pulsed magnetic field treatment, Comparative Example 2 omits liquid nitrogen and high-pressure steam treatment, the disulfide bond reducing agent of Comparative Example 3 omits tea polysaccharide-selenium nanoparticles, Comparative Example 4 omits pullulan, Comparative Example 5 omits electron beam irradiation, and Comparative Example 6 omits microwave irradiation. The solubility and emulsification of the gained soluble rice protein all obviously deteriorate, illustrating that the synergistic effects such as pulsed magnetic field treatment, liquid nitrogen and high-pressure steam treatment, and disulfide bond reducing agent composition of the present invention have improved the solubility and emulsification of rice protein without changing the primary structure of rice protein.

[0119] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing highly soluble rice protein, characterized in that, The specific steps are as follows: S1. First, rice protein was crushed into rice protein powder, and then the rice protein powder was ultrasonically dispersed in deionized water and treated with a pulsed magnetic field to obtain a rice protein dispersion; S2. liquid nitrogen is introduced into the rice protein dispersion, the rice protein dispersion is immediately contacted with high-pressure steam, the pressure is instantly released to normal pressure, and the mixture is naturally cooled to room temperature, a disulfide bond reducing agent is added, and the reaction is stirred at room temperature to obtain a depolymerized rice protein dispersion; the disulfide bond reducing agent is obtained by mixing sodium sulfite, cysteine, and tea polysaccharide-selenium nanoparticles; S3. Pullulan is added to the depolymerized rice protein dispersion, and the mixture is subjected to electron beam irradiation, microwave irradiation, natural cooling to room temperature, high pressure homogenization, and spray drying to obtain a highly soluble rice protein.

2. The preparation method according to claim 1, characterized in that In step S1, the average particle size of the rice protein powder is 40 to 50 μm.

3. The preparation method according to claim 1, characterized in that In step S1, the mass ratio of rice protein powder to deionized water is 1:18-20.

4. The preparation method according to claim 1, characterized in that In step S1 , the process conditions of the pulsed magnetic field treatment are: pulse frequency 30-40 Hz, magnetic induction intensity 200-220 mT, duty cycle 25-35%, current 180-200 A, and treatment time 80-100 s.

5. The preparation method according to claim 1, characterized in that In step S2, liquid nitrogen is introduced at a rate of 10 to 12 kg / min for a time of 3 to 4 seconds.

6. The preparation method according to claim 1, characterized in that In step S2, the pressure of the high-pressure steam is 2-3 MPa, the temperature is 150-170° C., and the contact time is 50-70 s.

7. The preparation method according to claim 1, characterized in that In step S2, the amount of the disulfide bond reducing agent is 0.05 to 0.5% of the mass of the rice protein dispersion; The reaction time is 60 to 80 minutes with stirring at room temperature.

8. The preparation method according to claim 1, characterized in that In step S3, the amount of pullulan is 0.1-0.2% of the mass of the depolymerized rice protein dispersion.

9. The preparation method according to claim 1, characterized in that In step S3, before electron beam irradiation, the pH is adjusted to 5.0-6.5 using 1 mol / L hydrochloric acid solution.

10. The preparation method according to claim 1, characterized in that In step S3, a 10 MeV high energy electron accelerator is used as a radiation source, and the electron beam irradiation dose is 6 to 8 KGy; The microwave irradiation conditions are as follows: microwave power 400-500W, irradiation for 2-3 minutes, rest for 1 minute, and so on, until the cumulative irradiation time is 15-18 minutes; The process conditions of high-pressure homogenization treatment are: pressure 50-70 MPa, 3-5 cycles; The process conditions of spray drying are: feed rate 3-5 mL / min, inlet temperature 160-180°C, and outlet temperature 130-140°C.

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