Rice protein extraction process

Abstract

The invention discloses a rice protein extraction process, particularly relates to the technical field of rice protein extraction, and realizes efficient dissociation of a starch-protein composite structure and accurate regulation and control of an extraction process through parameter cooperative control of a three-order coupling extraction process in combination with a dynamic impedance real-time monitoring and self-adaptive adjustment mechanism. A gradient centrifugal separation and transmembrane pressure control ultrafiltration technology is adopted to construct a complete protein purification system. The process core comprises an intelligent extraction system provided with a spiral guide plate and an annular electrode array, a three-stage temperature control centrifugal unit and a dynamic spray drying device. According to the extraction process disclosed by the invention, the rice protein extraction efficiency and the product functionality are remarkably improved, thermal denaturation damage is effectively controlled, meanwhile, excellent process adaptability and production stability are achieved, and reliable technical guarantee is provided for industrial continuous production of high-purity active rice protein.

Description

Technical Field

[0001] This invention relates to the field of rice protein extraction, and particularly to a rice protein extraction process. Background Technology

[0002] Currently, the industry commonly employs a combination of alkali dissolution and acid precipitation with multi-stage extraction processes for rice protein extraction. Typical processes include raw material crushing, alkaline solution extraction, and centrifugation. In mainstream technologies, the extraction temperature is typically controlled within the range of 50-55℃, with 2-3 repeated extractions to improve the extraction rate. Some improved processes introduce ultrasonic treatment or enzymatic hydrolysis, with treatment times generally controlled between 30-60 minutes. In the separation and purification stage, centrifugation at a force ranging from 2000-6000g is commonly used for multi-stage impurity separation, and some advanced methods incorporate membrane filtration technology for protein concentration.

[0003] However, existing technologies have the following drawbacks: First, the extraction process uses a fixed parameter mode, lacking a real-time response mechanism to changes in material state, leading to severe damage to the protein structure. Second, single-factor control strategies are insufficient to effectively dissociate starch-protein complexes, resulting in a low nitrogen solubility index. Third, the discrete parameter settings in the separation stage lead to insufficient impurity retention efficiency, resulting in high ash content in the final product and limited functional properties. Especially when processing different varieties of rice raw materials, the existing process has poor particle size adaptability; when the material fineness exceeds 100 mesh, over-extraction is easily triggered, increasing the starch residue in the product by more than 30%, severely restricting the industrial preparation of high-purity protein.

[0004] Therefore, we propose a rice protein extraction process. Summary of the Invention

[0005] The main objective of this invention is to provide a rice protein extraction process that solves the technical problems of low protein extraction rate, poor nitrogen solubility index, severe thermal denaturation, and high impurity residue in traditional processes by using a three-stage coupled extraction process parameter coordinated control, a dynamic impedance real-time monitoring triggering mechanism, and gradient centrifugation separation.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A rice protein extraction process, the specific steps of which are as follows: Step 1: After the raw rice is processed by the countercurrent rinsing process, it is fed into the wet grinding system for grinding. The particle size of the material is controlled within the range of 80-100 mesh, and the moisture content of the material is adjusted to the range of 45% to 50%. Step 2: The crushed material is conveyed to a three-stage coupled alkaline leaching tank equipped with a spiral guide plate, a pressure pulse generator and a regular hexagonal electrode array, wherein the electrode array is arranged in a regular hexagonal topology. Step 3: Perform a three-stage extraction operation. In the first stage, set the temperature to 45℃±0.5℃ and the pressure to 0.3MPa±0.02MPa, with a duration of 8min±15s. In the second stage, adjust the temperature to 52℃±0.8℃ and start the pressure pulse generator to perform a cyclic pressure change from 0.5MPa to 0.8MPa, with a single cycle time of 30s. In the third stage, increase the temperature to 60℃±1℃ and decrease the pressure to 0.2MPa, while simultaneously activating the 40kHz±2kHz ultrasonic generator. Step 4: Acquire impedance spectrum data in the 10Hz-10MHz band using an electrode array at a sampling interval of 50ms. When the phase angle offset of the characteristic frequency point of 2.48-2.52MHz reaches 12°±0.5°, trigger the dynamic adjustment mechanism of the extraction parameters. Step 5: The extracted mixture is processed by a three-stage disc centrifuge unit, with centrifugal forces of 3000g±50g, 5000g±80g, and 8000g±100g applied sequentially, and the separation temperature maintained at 55℃±2℃. Step 6: After centrifugation, the liquid phase is introduced into a pH adjustment tank, and the pH value is adjusted to the range of 6.8-7.2 using 0.5 mol / L hydrochloric acid solution, with the adjustment rate stabilized at 0.1 pH / s; Step 7: Pump the pH adjustment solution into an ultrafiltration membrane module with a molecular weight cutoff of 10 kDa, and concentrate the protein by controlling the transmembrane pressure at 0.6 MPa ± 0.05 MPa and the membrane surface flow rate at 1.5 m / s ± 0.1 m / s. Step 8: The concentrate is fed into the spray drying tower, the inlet air temperature is set to 180℃ and the outlet air temperature to 80℃, and the atomization pressure is 12MPa to obtain rice protein product with a moisture content of 5%.

[0007] Preferably, in step 1, the wet grinding system is equipped with an online particle size analyzer, and the moisture content is controlled using a near-infrared spectroscopy real-time feedback system.

[0008] Preferably, in step 3, during the third stage, the sound intensity density of the ultrasonic generator is 0.5 W / cm².

[0009] Preferably, in step 2, the spacing between adjacent units of the regular hexagonal electrode array is 15cm ± 0.5cm, the phase angle measurement error is ± 0.1°, and the impedance spectrum data sampling rate is 20kHz.

[0010] Preferably, when the hexagonal electrode array detects that the phase angle offset in the 2.48-2.52MHz frequency band reaches the threshold of 12°±0.5°, an adjustment is performed.

[0011] Preferably, the specific process of the parameter dynamic adjustment mechanism is as follows: First, the temperature is adjusted at a rate of 2℃ / min ± 0.5℃ / min, with the adjustment range being ± 3℃ ± 0.5℃ of the current set value, and maintained for 5min ± 30s after each adjustment; then, the pressure system generates fluctuations of ± 0.15MPa at a rate of 0.1MPa, with the fluctuation frequency controlled at 0.033Hz ± 0.002Hz; finally, the alkali flow rate is increased to 1.2m / s ± 0.05m / s within 2s ± 0.5s. After the flow rate adjustment is completed, the trend of phase angle offset change is monitored. If it does not fall back below the threshold within 30s ± 5s, the stepwise adjustment cycle of temperature-pressure-flow rate is repeated.

[0012] Preferably, in step 5, the material temperature is maintained at 55℃±2℃ during the three-stage centrifugal separation.

[0013] Preferably, the pH adjustment process in step 7 is performed using an online pH electrode, which is calibrated daily.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves a breakthrough improvement in protein extraction efficiency and product quality control through innovative process design and technology integration. The synergistic effect of parameters in the three-stage coupled extraction process significantly enhances the dissociation efficiency of the starch-protein complex structure. Combined with a dynamic impedance monitoring mechanism, it enables precise control of the extraction process, effectively overcoming the contradiction between insufficient extraction and protein denaturation in traditional processes. At the same time, the innovative application of gradient centrifugation technology greatly improves the efficiency of impurity separation.

[0015] 2. The implementation of this invention enables the final product to possess both high functional properties and stable quality, with the obtained protein powder exhibiting excellent solubility and thermal stability. The process system demonstrates outstanding adaptability, and through a real-time feedback adjustment mechanism, it can accommodate the processing requirements of raw materials with different physical properties, significantly reducing the frequency of equipment parameter adjustments and energy consumption costs, and providing reliable technical support for industrial continuous production. Detailed Implementation

[0016] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0017] This invention discloses a rice protein extraction process, the main equipment used in this process is as follows: 1. Three-stage coupled extraction tank This equipment is made of 316L stainless steel, and its main structure comprises three functional modules: a spiral guide plate, a pressure pulse generator, and a ring electrode array. The spiral guide plate is designed with a 45°±2° helix angle to achieve a synergistic effect of laminar flow propulsion and turbulent mixing of materials. The pressure pulse generator is equipped with a dual-cylinder servo system, capable of generating pressure fluctuations of 0.3-0.8MPa with a frequency adjustment range of 0.01~0.1Hz. The ring electrode array is arranged in a regular hexagonal topology, with adjacent electrodes spaced 15cm±0.5cm. Its built-in impedance analysis module supports a wide frequency band scanning of 10Hz-10MHz, with a phase angle detection accuracy of ±0.1°. The equipment integrates a PLC control system, enabling multi-parameter linkage adjustment of temperature (±0.5℃), pressure (±0.02MPa), and flow rate (±0.05m / s). The extraction tank uses sodium hydroxide for extraction; this part is existing technology and will not be described in detail.

[0018] 2. Wet grinding system The system is equipped with a two-stage turbine grinding chamber and an online particle size monitoring unit. The gap between the front-stage grinding teeth is adjustable from 2 to 5 mm, while the secondary grinding stage employs dynamic gap control technology (DGC). It integrates a near-infrared moisture analyzer (wavelength 1200-2400 nm) and an automatic water replenishment device to achieve closed-loop moisture content control (accuracy ±0.8%). The grinding chamber is equipped with a liquid nitrogen cooling circuit to ensure the material temperature is ≤35℃. The discharge particle size distribution control system uses acoustic resonance sieving technology to ensure that the proportion of 80-100 mesh particles is ≥90%.

[0019] 3. Three-stage disc centrifuge unit The unit adopts a series layout, with each centrifuge equipped with an independent temperature control jacket (temperature control accuracy ±1.5℃). The first-stage centrifuge drum diameter is 600mm, with a maximum centrifugal force of 3000g; the second-stage drum diameter is 450mm, with a maximum centrifugal force of 5000g; and the third-stage drum diameter is 300mm, with a maximum centrifugal force of 8000g. The drum surface is coated with a tungsten carbide coating (thickness 50μm), and the disc gap is 0.2mm. The material transfer pipeline is equipped with a laminar flow maintenance device, with a flow rate control accuracy of ±5%. The centrifuge residue moisture content monitoring module adopts the microwave resonance method (frequency 2.45GHz), with a measurement error ≤0.3%.

[0020] 4. Ultrafiltration membrane module system The system employs hollow fiber membrane modules (molecular weight cutoff 10 kDa), with a membrane area of ​​200 m² and a fiber inner diameter of 0.8 mm. The transmembrane pressure control system includes a feedforward PID controller and a piezoelectric ceramic fine-tuning valve, with pressure fluctuations ≤ ±0.03 MPa. Membrane surface flow rate control utilizes magnetic coupling transmission technology, with a linear speed regulation range of 0.5–2.5 m / s. The online cleaning system is equipped with a reverse pulse device (pulse width 50 ms, frequency 0.5 Hz), achieving a flux recovery rate ≥98%.

[0021] 5. Dynamic spray drying tower The tower body adopts a cyclone separation structure design, and the atomizer is equipped with a dual-fluid nozzle (0.5mm orifice diameter) with an atomization pressure of 12MPa±0.2MPa. The air inlet system is equipped with three-stage heating (electric heating + gas-assisted heating + waste heat recovery), with a temperature control gradient ≤2℃ / m. The outlet air humidity is monitored using a dew point sensor (accuracy ±0.5℃), and the negative pressure control range inside the tower is -50~-100Pa. The finished product collection system integrates a fluidized bed cooling device, with an outlet temperature ≤40℃.

[0022] The present invention uses the above-mentioned equipment to extract rice protein. The present invention is further disclosed below with reference to specific embodiments and comparative examples.

[0023] Example 1 This embodiment discloses a rice protein extraction process, the specific steps of which are as follows: Step 1: After the raw rice is processed by the countercurrent rinsing process, it is fed into the wet grinding system for grinding. The particle size of the material is controlled at 80 mesh and the moisture content of the material is adjusted to 45%. The wet grinding system is equipped with an online particle size analyzer and the moisture content is controlled by a near-infrared spectroscopy real-time feedback system.

[0024] Step 2: The crushed material is conveyed to a third-order coupled alkaline extraction tank equipped with a spiral guide plate, a pressure pulse generator and a regular hexagonal electrode array, wherein the electrode array is arranged in a regular hexagonal topology; wherein the spacing between adjacent units of the regular hexagonal electrode array is 15cm, the phase angle measurement error is ±0.1°, and the impedance spectrum data sampling rate is 20kHz.

[0025] Step 3: Perform a three-stage extraction operation. In the first stage, set the temperature to 45℃ and the pressure to 0.3MPa for 8 minutes and 15 seconds. In the second stage, adjust the temperature to 52℃ and start the pressure pulse generator to perform a cyclic pressure change from 0.5MPa to 0.8MPa, with a single cycle time of 30 seconds. In the third stage, increase the temperature to 60℃ and decrease the pressure to 0.2MPa, while simultaneously activating the 40kHz ultrasonic generator. The sound intensity density of the ultrasonic generator is 0.5W / cm².

[0026] Step 4: Acquire impedance spectrum data in the 10Hz-10MHz band using an electrode array at a sampling interval of 50ms. When the phase angle offset at the 2.48MHz characteristic frequency point reaches 12°, trigger the dynamic adjustment mechanism of the extraction parameters. Specifically, when the hexagonal electrode array detects a phase angle offset of 12° in the 2.48-2.52MHz frequency band, the following adjustments are performed: First, the temperature is adjusted at a rate of 2℃ / min, with an adjustment range of ±3℃ from the current set value, and maintained for 5min30s after each adjustment; then, the pressure system generates fluctuations of ±0.15MPa at a rate of 0.1MPa / s, with the fluctuation frequency controlled at 0.033Hz; finally, the alkali flow rate is increased to 1.2m / s within 2s. After the flow rate adjustment is completed, the trend of phase angle offset change continues to be monitored. If it does not fall back below the threshold within 30s, the stepwise adjustment cycle of temperature-pressure-flow rate is repeated.

[0027] Step 5: The extracted mixture is processed by a three-stage disc centrifuge unit, with centrifugal forces of 3000g, 5000g and 8000g applied sequentially. The material temperature is maintained at 55℃ during the three-stage centrifugation separation. Step 6: After centrifugation, the liquid phase is introduced into a pH adjustment tank, and the pH value is adjusted to 6.8 using 0.5 mol / L hydrochloric acid solution, with the adjustment rate stabilized at 0.1 pH / s; Step 7: Pump the pH adjustment solution into the ultrafiltration membrane module with a molecular weight cutoff of 10 kDa, and concentrate the protein by controlling the transmembrane pressure at 0.6 MPa and the membrane surface flow rate at 1.5 m / s; the pH adjustment process is monitored by an online pH electrode, which is calibrated daily.

[0028] Step 8: The concentrate is fed into the spray drying tower, the inlet air temperature is set to 180℃ and the outlet air temperature to 80℃, and the atomization pressure is 12MPa to obtain rice protein product with a moisture content of 5%.

[0029] Example 2 This embodiment discloses a rice protein extraction process, the specific steps of which are as follows: Step 1: After the raw rice is processed by the countercurrent rinsing process, it is fed into the wet grinding system for grinding. The particle size of the material is controlled at 100 mesh and the moisture content of the material is adjusted to 50%. The wet grinding system is equipped with an online particle size analyzer and the moisture content is controlled by a near-infrared spectroscopy real-time feedback system.

[0030] Step 2: The crushed material is conveyed to a third-order coupled alkaline extraction tank equipped with a spiral guide plate, a pressure pulse generator and a regular hexagonal electrode array, wherein the electrode array is arranged in a regular hexagonal topology; wherein the spacing between adjacent units of the regular hexagonal electrode array is 15cm, the phase angle measurement error is ±0.1°, and the impedance spectrum data sampling rate is 20kHz.

[0031] Step 3: Perform a three-stage extraction operation. In the first stage, set the temperature to 45.5℃ and the pressure to 0.28MPa for 7 minutes and 45 seconds. In the second stage, adjust the temperature to 52.8℃ and start the pressure pulse generator to perform a cyclic pressure change from 0.5MPa to 0.8MPa, with a single cycle time of 30 seconds. In the third stage, increase the temperature to 60℃ and decrease the pressure to 0.2MPa, while simultaneously activating the 42kHz ultrasonic generator. The sound intensity density of the ultrasonic generator is 0.5W / cm².

[0032] Step 4: Acquire impedance spectrum data in the 10Hz-10MHz band using an electrode array at a sampling interval of 50ms. When the phase angle offset at the 2.48MHz characteristic frequency point reaches 12°, trigger the dynamic adjustment mechanism of the extraction parameters. Specifically, when the hexagonal electrode array detects a phase angle offset of 12° in the 2.48-2.52MHz frequency band, the following adjustments are performed: First, the temperature is adjusted at a rate of 1.5℃ / min, with an adjustment range of ±3℃ from the current set value, and maintained for 5min30s after each adjustment; then, the pressure system generates fluctuations of ±0.15MPa at a rate of 0.1MPa / s, with the fluctuation frequency controlled at 0.031Hz; finally, the alkali flow rate is increased to 1.25m / s within 2s. After the flow rate adjustment is completed, the trend of phase angle offset change continues to be monitored. If it does not fall back below the threshold within 30s, the stepwise adjustment cycle of temperature-pressure-flow rate is repeated.

[0033] Step 5: The extracted mixture is processed by a three-stage disc centrifuge unit, with centrifugal forces of 3000g, 5000g and 8000g applied sequentially. The material temperature is maintained at 55℃ during the three-stage centrifugation separation. Step 6: After centrifugation, the liquid phase is introduced into a pH adjustment tank, and the pH value is adjusted to 7.2 using 0.5 mol / L hydrochloric acid solution, with the adjustment rate stabilized at 0.1 pH / s; Step 7: Pump the pH adjustment solution into the ultrafiltration membrane module with a molecular weight cutoff of 10 kDa, and concentrate the protein by controlling the transmembrane pressure at 0.6 MPa and the membrane surface flow rate at 1.5 m / s; the pH adjustment process is monitored by an online pH electrode, which is calibrated daily.

[0034] Step 8: The concentrate is fed into the spray drying tower, the inlet air temperature is set to 180℃ and the outlet air temperature to 80℃, and the atomization pressure is 12MPa to obtain rice protein product with a moisture content of 5%.

[0035] Example 3 This embodiment discloses a rice protein extraction process, the specific steps of which are as follows: Step 1: After the raw rice is processed by the countercurrent rinsing process, it is fed into the wet grinding system for grinding. The particle size of the material is controlled at 80 mesh, and the moisture content of the material is adjusted to 48%. The wet grinding system is equipped with an online particle size analyzer, and the moisture content is controlled by a near-infrared spectroscopy real-time feedback system.

[0036] Step 2: The crushed material is conveyed to a third-order coupled alkaline extraction tank equipped with a spiral guide plate, a pressure pulse generator and a regular hexagonal electrode array, wherein the electrode array is arranged in a regular hexagonal topology; wherein the spacing between adjacent units of the regular hexagonal electrode array is 15.5cm, the phase angle measurement error is ±0.1°, and the impedance spectrum data sampling rate is 20kHz.

[0037] Step 3: Perform a three-stage extraction operation. In the first stage, set the temperature to 45℃ and the pressure to 0.3MPa for 8 minutes and 15 seconds. In the second stage, adjust the temperature to 52℃ and start the pressure pulse generator to perform a cyclic pressure change from 0.5MPa to 0.8MPa, with a single cycle time of 30 seconds. In the third stage, increase the temperature to 61℃ and decrease the pressure to 0.2MPa, while simultaneously activating the 40kHz ultrasonic generator. The sound intensity density of the ultrasonic generator is 0.5W / cm².

[0038] Step 4: Acquire impedance spectrum data in the 10Hz-10MHz band using an electrode array at a sampling interval of 50ms. When the phase angle offset at the 2.48MHz characteristic frequency point reaches 12°, trigger the dynamic adjustment mechanism of the extraction parameters. Specifically, when the hexagonal electrode array detects a phase angle offset of 11.5° in the 2.48-2.52MHz frequency band, the following adjustments are performed: First, the temperature is adjusted at a rate of 2℃ / min, with an adjustment range of ±3℃ from the current set value, and maintained for 5min30s after each adjustment; then, the pressure system generates fluctuations of ±0.15MPa at a rate of 0.1MPa / s, with the fluctuation frequency controlled at 0.033Hz; finally, the alkali flow rate is increased to 1.2m / s within 2s. After the flow rate adjustment is completed, the trend of phase angle offset change continues to be monitored. If it does not fall back below the threshold within 30s, the stepwise adjustment cycle of temperature-pressure-flow rate is repeated.

[0039] Step 5: The extracted mixture is processed by a three-stage disc centrifuge unit, with centrifugal forces of 2950g, 4920g, and 7900g applied sequentially. The material temperature is maintained at 57℃ during the three-stage centrifugation separation. Step 6: After centrifugation, the liquid phase is introduced into a pH adjustment tank, and the pH value is adjusted to 6.8 using 0.5 mol / L hydrochloric acid solution, with the adjustment rate stabilized at 0.1 pH / s; Step 7: Pump the pH adjustment solution into the ultrafiltration membrane module with a molecular weight cutoff of 10 kDa, and concentrate the protein by controlling the transmembrane pressure at 0.65 MPa and the membrane surface flow rate at 1.6 m / s; the pH adjustment process is monitored by an online pH electrode, which is calibrated daily.

[0040] Step 8: The concentrate is fed into the spray drying tower, the inlet air temperature is set to 180℃ and the outlet air temperature to 80℃, and the atomization pressure is 12MPa to obtain rice protein product with a moisture content of 5%.

[0041] Example 4 This embodiment discloses a rice protein extraction process, the specific steps of which are as follows: Step 1: After the raw rice is processed by the countercurrent rinsing process, it is fed into the wet grinding system for grinding. The particle size of the material is controlled at 80 mesh and the moisture content of the material is adjusted to 45%. The wet grinding system is equipped with an online particle size analyzer and the moisture content is controlled by a near-infrared spectroscopy real-time feedback system.

[0042] Step 2: The crushed material is conveyed to a third-order coupled alkaline extraction tank equipped with a spiral guide plate, a pressure pulse generator and a regular hexagonal electrode array, wherein the electrode array is arranged in a regular hexagonal topology; wherein the spacing between adjacent units of the regular hexagonal electrode array is 14.5cm, the phase angle measurement error is ±0.1°, and the impedance spectrum data sampling rate is 20kHz.

[0043] Step 3: Perform a three-stage extraction operation. In the first stage, set the temperature to 45℃ and the pressure to 0.32MPa for 8 minutes. In the second stage, adjust the temperature to 52.8℃ and start the pressure pulse generator to perform a cyclic pressure change from 0.5MPa to 0.8MPa, with a single cycle time of 30 seconds. In the third stage, increase the temperature to 59℃ and decrease the pressure to 0.2MPa, while simultaneously activating the 40kHz ultrasonic generator. The sound intensity density of the ultrasonic generator is 0.5W / cm².

[0044] Step 4: Acquire impedance spectrum data in the 10Hz-10MHz band using an electrode array at a sampling interval of 50ms. When the phase angle offset at the 2.48MHz characteristic frequency point reaches 12°, trigger the dynamic adjustment mechanism of the extraction parameters. Specifically, when the hexagonal electrode array detects a phase angle offset of 12.5° in the 2.48-2.52MHz frequency band, the following adjustments are performed: First, the temperature is adjusted at a rate of 2℃ / min, with an adjustment range of ±3℃ from the current set value, and maintained for 5min30s after each adjustment; then, the pressure system generates fluctuations of ±0.15MPa at a rate of 0.1MPa / s, with the fluctuation frequency controlled at 0.035Hz; finally, the alkali flow rate is increased to 1.15m / s within 2s. After the flow rate adjustment is completed, the trend of phase angle offset change continues to be monitored. If it does not fall back below the threshold within 35s, the stepwise adjustment cycle of temperature-pressure-flow rate is repeated.

[0045] Step 5: The extracted mixture is processed by a three-stage disc centrifuge unit, with centrifugal forces of 3050g, 5080g and 8100g applied sequentially. The material temperature is maintained at 53℃ during the three-stage centrifugation separation. Step 6: After centrifugation, the liquid phase is introduced into a pH adjustment tank, and the pH value is adjusted to 7 using 0.5 mol / L hydrochloric acid solution, with the adjustment rate stabilized at 0.1 pH / s; Step 7: Pump the pH adjustment solution into the ultrafiltration membrane module with a molecular weight cutoff of 10 kDa, and concentrate the protein by controlling the transmembrane pressure at 0.55 MPa and the membrane surface flow rate at 1.5 m / s; the pH adjustment process is monitored by an online pH electrode, which is calibrated daily.

[0046] Step 8: The concentrate is fed into the spray drying tower, the inlet air temperature is set to 180℃ and the outlet air temperature to 80℃, and the atomization pressure is 12MPa to obtain rice protein product with a moisture content of 5%.

[0047] Example 5 This embodiment discloses a rice protein extraction process, the specific steps of which are as follows: Step 1: After the raw rice is processed by the countercurrent rinsing process, it is fed into the wet grinding system for grinding. The particle size of the material is controlled at 80 mesh and the moisture content of the material is adjusted to 46%. The wet grinding system is equipped with an online particle size analyzer and the moisture content is controlled by a near-infrared spectroscopy real-time feedback system.

[0048] Step 2: The crushed material is conveyed to a third-order coupled alkaline extraction tank equipped with a spiral guide plate, a pressure pulse generator and a regular hexagonal electrode array, wherein the electrode array is arranged in a regular hexagonal topology; wherein the spacing between adjacent units of the regular hexagonal electrode array is 15cm, the phase angle measurement error is ±0.1°, and the impedance spectrum data sampling rate is 20kHz.

[0049] Step 3: Perform a three-stage extraction operation. In the first stage, set the temperature to 44.5℃ and the pressure to 0.28MPa for 8 minutes and 15 seconds. In the second stage, adjust the temperature to 51.2℃ and start the pressure pulse generator to perform a cyclic pressure change from 0.5MPa to 0.8MPa, with a single cycle time of 30 seconds. In the third stage, increase the temperature to 60℃ and decrease the pressure to 0.2MPa, while simultaneously activating the 38kHz ultrasonic generator. The sound intensity density of the ultrasonic generator is 0.5W / cm².

[0050] Step 4: Acquire impedance spectrum data in the 10Hz-10MHz band using an electrode array at a sampling interval of 50ms. When the phase angle offset at the 2.48MHz characteristic frequency point reaches 12°, trigger the dynamic adjustment mechanism of the extraction parameters. Specifically, when the hexagonal electrode array detects a phase angle offset of 12° in the 2.48-2.52MHz frequency band, the following adjustments are performed: First, the temperature is adjusted at a rate of 2℃ / min, with an adjustment range of ±3℃ from the current set value, and maintained for 4min30s after each adjustment; then, the pressure system generates fluctuations of ±0.15MPa at a rate of 0.1MPa / s, with the fluctuation frequency controlled at 0.033Hz; finally, the alkali flow rate is increased to 1.2m / s within 2s. After the flow rate adjustment is completed, the trend of phase angle offset change continues to be monitored. If it does not fall back below the threshold within 30s, the stepwise adjustment cycle of temperature-pressure-flow rate is repeated.

[0051] Step 5: The extracted mixture is processed by a three-stage disc centrifuge unit, with centrifugal forces of 3000g, 5000g and 8000g applied sequentially. The material temperature is maintained at 55℃ during the three-stage centrifugation separation. Step 6: After centrifugation, the liquid phase is introduced into a pH adjustment tank, and the pH value is adjusted to 6.8 using 0.5 mol / L hydrochloric acid solution, with the adjustment rate stabilized at 0.1 pH / s; Step 7: Pump the pH adjustment solution into the ultrafiltration membrane module with a molecular weight cutoff of 10 kDa, and concentrate the protein by controlling the transmembrane pressure at 0.6 MPa and the membrane surface flow rate at 1.4 m / s; the pH adjustment process is monitored by an online pH electrode, which is calibrated daily.

[0052] Step 8: The concentrate is fed into the spray drying tower, the inlet air temperature is set to 180℃ and the outlet air temperature to 80℃, and the atomization pressure is 12MPa to obtain rice protein product with a moisture content of 5%.

[0053] Comparative Example 1 This comparative example is based on Example 1. The similarities between this comparative example and Example 1 will not be described again. The differences are as follows: Step 1 involves dry pulverization to 60 mesh; Step 2 involves ordinary alkaline extraction (without electrode array); Step 3 involves single-stage constant-temperature extraction at 50°C; Step 4 involves no dynamic adjustment mechanism; Step 5 involves single-stage centrifugation (2000g); Step 7 involves atmospheric pressure filtration. The remaining steps are exactly the same as in Example 1.

[0054] Comparative Example 2 This comparative example is based on Example 1. The similarities between this comparative example and Example 1 will not be described again. The differences are as follows: In step 1, the particle size is controlled to 110 mesh; in step 3, the temperature of the third stage is 65°C; in step 4, the phase angle threshold is set to 15°; in step 5, the centrifugation temperature is 48°C. The remaining steps are exactly the same as in Example 1.

[0055] Comparative Example 3 This comparative example is based on Example 1. The similarities between this comparative example and Example 1 will not be repeated. The differences are: the equipment is simplified in this comparative example, specifically: the spiral guide plate is removed from the extraction tank in step 2; and the pressure pulse generator is removed from step 3. The remaining steps are exactly the same as in Example 1.

[0056] The samples prepared in Examples 1-5 and Comparative Examples 1-3 were tested as follows: I. Protein Extraction Rate Determination This test was conducted in accordance with GB5009.5-2016, "National Food Safety Standard - Determination of Protein in Food". A sample of 1.000 g ± 0.001 g was weighed, and digestion and distillation were performed using the Kjeldahl method. The sample was then titrated with 0.1 mol / L hydrochloric acid standard solution to calculate the total nitrogen content.

[0057] II. Protein Purity Analysis SDS-PAGE electrophoresis was performed according to GB / T28720-2012 "Electrophoresis Method for Determination of Protein Purity". A 12% separating gel and a 5% stacking gel were prepared, with a sample volume of 10 μg. Electrophoresis was performed at a constant voltage of 120V for 90 minutes. After staining with Coomassie Brilliant Blue R-250, grayscale analysis was performed using Gel-ProAnalyzer software. A target protein band coverage of ≥90% was considered high purity. The experimental temperature was controlled at 25℃±1℃.

[0058] III. Nitrogen Solubility Index (NSI) Determination The method was modified according to GB / T22427.11-2008 "Determination of Nitrogen Content in Starch and its Derivatives". Accurately weigh 0.500 g of sample, add 50 mL of 0.2 mol / L phosphate buffer (pH 7.0), and incubate at 25°C with shaking for 1 hour. After centrifugation, collect the supernatant and determine the soluble nitrogen content using the Kjeldahl method. Calculate: NSI (%) = soluble nitrogen content / total nitrogen content × 100%. Centrifugation parameters were 8000 g for 15 min, and centrifuge tubes were pre-cooled to 4°C.

[0059] IV. Product Solubility Test The optimized method was performed according to GB / T5413.29-1997, "Determination of Solubility of Infant Formula and Milk Powder". 2.00 g of sample was added to 40 mL of distilled water and magnetically stirred at 200 rpm for 30 minutes at 25°C. The sample was immediately filtered through a 0.45 μm filter membrane, and the filter residue was dried at 105°C to constant weight. The solubility (g / 100 g) was calculated as: (1 - filter residue mass / sample mass) × 100. The experiment was repeated 5 times, and the RSD value was ≤1.2%.

[0060] V. Determination of Moisture Content and Ash Content Moisture content: According to the first method of GB5009.3-2016 "Determination of Moisture in Food", take 3g of sample and dry it in an oven at 105℃ until constant weight; Ash content: According to GB5009.4-2016 "Determination of Ash in Food", the ash was ignited in a muffle furnace at 550℃ for 4 hours, and the residue was weighed after cooling. Both tests were conducted using a 0.01 g analytical balance (METTLERTOLEDOME 204), with a desiccant consisting of both silica gel and molecular sieve.

[0061] The results of the above five tests are shown in Table 1.

[0062] Table 1: Results of protein extraction rate, protein purity, NSI index, product solubility, moisture content and ash content of samples from Examples 1-5 and Comparative Examples 1-3.

[0063] Experimental data show that the protein extraction rate (86.5%–89.2%) of Examples 1–5 of this invention is significantly improved compared to the comparative example (72.3%–81.2%), and the key indicators NSI (83.1%–86.3%) and solubility (86.2–89.7 g / 100 g) are significantly better than those of the comparative example. This is attributed to the synergistic effect of parameters in the three-stage coupled extraction process: ① precise particle size control (80–100 mesh) ensures sufficient enzymatic hydrolysis; ② dynamic impedance monitoring (2.48–2.52 MHz phase angle) enables precise control of the extraction process; ③ three-stage gradient centrifugation (3000–8000 g) effectively separates impurities. In particular, the stepwise adjustment mechanism triggered when the phase angle offset reaches 12° significantly reduces the protein denaturation rate, which is key to obtaining high NSI.

[0064] Furthermore, it can be seen that in Comparative Example 1, dry grinding resulted in uneven particle size (60 mesh), the lack of an electrode array rendered the dynamic adjustment mechanism ineffective, and single-stage centrifugation (2000g) increased the amount of residual impurities (ash content 2.5%), resulting in a final extraction rate of only 72.3%. In Comparative Example 2, excessively fine grinding (110 mesh) damaged the starch-protein complex structure, and the high temperature of 65℃ led to an increase in the β-sheet structure, reducing the NSI to 72.1%. DSC analysis showed a decrease in denaturation temperature of 6.2℃ and a deterioration in thermal stability. In Comparative Example 3, the removal of the spiral guide plate resulted in uneven material distribution, the lack of pressure pulses led to a decrease in extraction efficiency, insufficient membrane flow rate caused concentration polarization, and the final product solubility was only 82.4g / 100g.

[0065] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A rice protein extraction process, characterized in that, The specific steps are as follows: Step 1: After the raw rice is processed by the countercurrent rinsing process, it is fed into the wet grinding system for grinding. The particle size of the material is controlled within the range of 80-100 mesh, and the moisture content of the material is adjusted to the range of 45% to 50%. Step 2: The crushed material is conveyed to a three-stage coupled alkaline leaching tank equipped with a spiral guide plate, a pressure pulse generator and a regular hexagonal electrode array, wherein the electrode array is arranged in a regular hexagonal topology. Step 3: Perform a three-stage extraction operation. In the first stage, set the temperature to 45℃±0.5℃ and the pressure to 0.3MPa±0.02MPa, with a duration of 8min±15s. In the second stage, adjust the temperature to 52℃±0.8℃ and start the pressure pulse generator to perform a cyclic pressure change from 0.5MPa to 0.8MPa, with a single cycle time of 30s. In the third stage, increase the temperature to 60℃±1℃ and decrease the pressure to 0.2MPa, while simultaneously activating the 40kHz±2kHz ultrasonic generator. Step 4: Acquire impedance spectrum data in the 10Hz-10MHz band using an electrode array at a sampling interval of 50ms. When the phase angle offset of the characteristic frequency point of 2.48-2.52MHz reaches 12°±0.5°, trigger the dynamic adjustment mechanism of the extraction parameters. Step 5: The extracted mixture is processed by a three-stage disc centrifuge unit, with centrifugal forces of 3000g±50g, 5000g±80g, and 8000g±100g applied sequentially, and the separation temperature maintained at 55℃±2℃. Step 6: After centrifugation, the liquid phase is introduced into a pH adjustment tank, and the pH value is adjusted to the range of 6.8-7.2 using 0.5 mol / L hydrochloric acid solution, with the adjustment rate stabilized at 0.1 pH / s; Step 7: Pump the pH adjustment solution into an ultrafiltration membrane module with a molecular weight cutoff of 10 kDa, and concentrate the protein by controlling the transmembrane pressure at 0.6 MPa ± 0.05 MPa and the membrane surface flow rate at 1.5 m / s ± 0.1 m / s. Step 8: The concentrate is fed into the spray drying tower, the inlet air temperature is set to 180℃ and the outlet air temperature to 80℃, and the atomization pressure is 12MPa to obtain rice protein product with a moisture content of 5%.

2. The rice protein extraction process according to claim 1, characterized in that: In step 1, the wet grinding system is equipped with an online particle size analyzer, and the moisture content is controlled using a near-infrared spectroscopy real-time feedback system.

3. The rice protein extraction process according to claim 1, characterized in that: In step 3, during the third stage, the sound intensity density of the ultrasonic generator is 0.5 W / cm².

4. The rice protein extraction process according to claim 1, characterized in that: In step 2, the spacing between adjacent units of the regular hexagonal electrode array is 15cm ± 0.5cm, the phase angle measurement error is ± 0.1°, and the impedance spectrum data sampling rate is 20kHz.

5. The rice protein extraction process according to claim 4, characterized in that: When the hexagonal electrode array detects that the phase angle offset in the 2.48-2.52MHz band reaches the threshold of 12°±0.5°, an adjustment is performed.

6. The rice protein extraction process according to claim 5, characterized in that: The specific process of the parameter dynamic adjustment mechanism is as follows: First, the temperature is adjusted at a rate of 2℃ / min ± 0.5℃ / min, with the adjustment range being ± 3℃ ± 0.5℃ of the current set value, and maintained for 5min ± 30s after each adjustment; then, the pressure system generates fluctuations of ± 0.15MPa at a rate of 0.1MPa, with the fluctuation frequency controlled at 0.033Hz ± 0.002Hz; finally, the alkali flow rate is increased to 1.2m / s ± 0.05m / s within 2s ± 0.5s. After the flow rate adjustment is completed, the trend of phase angle offset change is monitored. If it does not fall back below the threshold within 30s ± 5s, the stepwise adjustment cycle of temperature-pressure-flow rate is repeated.

7. The rice protein extraction process according to claim 1, characterized in that: In step 5, the material temperature is maintained at 55℃±2℃ during the three-stage centrifugal separation.

8. The rice protein extraction process according to claim 1, characterized in that: The pH adjustment process in step 7 is monitored using an online pH electrode, which is calibrated daily.

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