A method for preparing soluble rice protein

Abstract

This invention provides a method for preparing soluble rice protein, comprising the following steps: using rice protein as raw material, adding water to form a uniform rice protein slurry, adjusting the pH, adding a structure modifier and stirring until uniformly mixed, and then spray-drying after high-pressure homogenization and high-temperature shearing to obtain soluble rice protein. This preparation method uses a combination of physical and chemical methods to inhibit protein aggregation. The combination of high-pressure homogenization and high-temperature shearing alters the structure of protein molecules, thereby improving hydrophilicity and significantly enhancing the solubility of rice protein. It also improves functional properties such as foaming and emulsifying properties. The resulting high-quality, highly soluble rice protein has a smooth and delicate texture and excellent quality, expanding the application of rice protein in beverages, baking, meat products, and plant-based meat.

Description

Technical Field

[0001] This invention belongs to the field of rice protein refining technology, specifically relating to a method for preparing soluble rice protein. Background Technology

[0002] Rice is an important food crop, with approximately 481 million tons produced globally in 2018. Demand for rice is projected to increase by 40% by 2030. Rice mainly contains about 80% starch and 8% protein. Rice protein contains 18 amino acids, including eight essential amino acids: methionine, proline, lysine, isoleucine, phenylalanine, leucine, tryptophan, and threonine. The amino acid composition of rice protein is well-balanced, possessing high nutritional value and closely resembling the nutritional pattern recommended by the WHO / FAO. Rice protein has a bioavailability of 77, similar to that of beef and fish, making it a high-quality plant-based protein.

[0003] Four proteins can be obtained from rice using the Osborne fractionation method. Glutelin and prolamins are the main components of rice. Glutelin accounts for over 80% of the total protein and is readily soluble in dilute alkalis and acids, but insoluble in water, alcohol, and neutral salt solutions. Prolamins account for 1-5% of the total protein, are soluble in 70-80% ethanol, insoluble in water, and are mostly found in plant seeds. Albumin and globulins, present in lower amounts, are the main physiologically active components. Albumin accounts for 2-5% of the total protein and is soluble in water, dilute acids, and dilute alkali solutions, and is found throughout organisms. Globulins account for 2-10% of the total rice protein, are slightly soluble in water, soluble in neutral dilute salt solutions, and are widely found in organisms.

[0004] Rice protein prepared by conventional methods contains more than 80% alkali-soluble glutelin, which is formed by many large molecular fragments linked by disulfide bonds and aggregated together. Water-soluble albumin accounts for only 2-5% of the rice protein. Therefore, rice protein prepared by conventional methods has poor solubility, which seriously restricts the functional development and application of rice protein.

[0005] Currently, the main methods for modifying rice protein include physical, chemical, and enzymatic methods, which modify it by changing its spatial structure and physicochemical properties, thereby improving its functional characteristics.

[0006] Physical modification can preserve the primary structure of proteins completely, with almost no loss to their nutritional value. Although physical modification methods can significantly improve the solubility of rice protein, the modification effect is often not significant.

[0007] Chemical modification is a method that improves the functional properties of proteins by introducing new groups into protein molecules, thereby altering their structure and physicochemical properties. This method can effectively increase the solubility of rice protein. However, the modification process is difficult to control and may produce undesirable byproducts, leading to food safety issues and significant nutrient loss.

[0008] Enzymatic modification primarily utilizes proteolytic enzymes to hydrolyze proteins into peptides and small amino acids. By reducing the molecular weight of the protein, its molecular structure and properties are altered, thereby improving its functional characteristics. Currently, enzymatic modification is the most commonly used modification method in China. However, the hydrolysis process produces bitter peptides, which can affect the flavor of food.

[0009] In view of this, the present invention is hereby proposed. Summary of the Invention

[0010] To address the problems existing in the prior art, this invention provides a method for preparing soluble rice protein. This method combines physical and chemical methods to inhibit protein aggregation, and combines high-pressure homogenization and high-temperature shearing treatment to change the structure of protein molecules, thereby improving hydrophilicity, significantly increasing the solubility of rice protein, and enhancing functional properties such as foaming and emulsifying properties. The resulting high-quality, highly soluble rice protein has a smooth and delicate taste and excellent quality, expanding the application of rice protein in beverages, baking, meat products, and plant-based meat.

[0011] To achieve the above objectives, the present invention employs the following technical solution.

[0012] This invention provides a method for preparing soluble rice protein, comprising the following steps:

[0013] Soluble rice protein is prepared by mixing rice protein with water to form a uniform rice protein slurry, adjusting the pH, adding a structure modifier, stirring and mixing evenly, and then spray drying after high-pressure homogenization and high-temperature shearing.

[0014] Furthermore, the dry-basis protein content of the rice protein is 80-85%.

[0015] Furthermore, the solids content of the rice protein slurry is 6-20%.

[0016] Furthermore, the pH of the rice protein slurry is adjusted to 6.0-11.0.

[0017] Furthermore, the structural modifier includes at least one of fructose, granulated sugar, stachyose, and fructooligosaccharides.

[0018] Furthermore, the amount of the structural modifier added is 0.05-0.5% of the rice protein content.

[0019] Furthermore, the pressure of the high-pressure homogenization is 20–55 MPa; and / or, the number of homogenization cycles is 1–2.

[0020] Furthermore, the temperature of the high-temperature shearing is set to 125-175℃; and / or, the time of the high-temperature shearing is 30-60s; and / or, the flow rate of the high-temperature shearing is 1-3T / h.

[0021] Furthermore, the inlet temperature of the spray dryer is 140-190℃, and the outlet temperature is 60-90℃.

[0022] Further, the rice protein includes either rice protein residue or low-soluble rice protein; preferably, the rice protein residue is produced during the production of rice starch sugar from rice or broken rice; preferably, the low-soluble rice protein is selected from at least one of spray-dried rice protein, tubular rice protein, or air-jet rice protein.

[0023] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0024] The preparation method of the present invention combines physical and chemical methods to disrupt the interaction forces between proteins, hindering protein aggregation. Combined with a modifier, the protein molecules are altered through high-pressure homogenization and high-temperature shearing treatment, enhancing hydrophilicity and significantly improving the solubility of rice protein, thereby preparing highly soluble rice protein and further altering the foaming, emulsifying and other functional properties of rice protein.

[0025] Highly soluble rice protein is prepared by combining physical and chemical methods with spray drying. The operation is simple, time-saving, and highly efficient. It can continuously produce high-quality, highly soluble rice protein with a yield (or production rate) of over 90% and a rice protein content of over 80% in the product. The product has a smooth and delicate taste and excellent quality.

[0026] Compared with existing technologies, the preparation method of the present invention avoids the defects of poor results of pure physical modification methods, as well as the impact of chemical modification and enzymatic modification on the quality of rice protein, thus expanding the application of rice protein in beverages, baking, meat products, and plant-based meat. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0028] Figure 1 SEM image of rice protein obtained in Example 2;

[0029] Figure 2 SEM image of rice protein from airflow;

[0030] Figure 3 SEM image of rice protein in tubular bundles;

[0031] Figure 4 SEM image of spray-dried rice protein;

[0032] Figure 5 This is a schematic diagram of the shearing equipment used in the high-temperature shearing process of this invention;

[0033] Figure 6 This is a top view of the rotating drum structure proposed in this invention.

[0034] Explanation of reference numerals in the attached diagram: 1. Hopper; 2. Evaporator; 3. Rotating drum; 4. Annular channel; 5. Feed pipe; 6. Steam pipe; 31. Through hole. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0036] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0037] According to a first aspect of the present invention, a method for preparing soluble rice protein includes the following steps:

[0038] Soluble rice protein is prepared by mixing rice protein with water to form a uniform rice protein slurry, adjusting the pH, adding a structure modifier, stirring and mixing evenly, and then spray drying after high-pressure homogenization and high-temperature shearing.

[0039] As an optional embodiment of the present invention, the rice protein includes either rice protein residue or low-soluble rice protein; preferably, the rice protein residue is produced during the production of rice starch sugar from rice or broken rice.

[0040] As an optional embodiment of the present invention, the low-soluble rice protein is selected from at least one of spray-dried rice protein, tube-dried rice protein, or air-dried rice protein. Solubility is mainly based on the determination of nitrogen solubility index. Unmodified rice protein dried by spray, tube, or airflow methods typically has a nitrogen solubility index of less than 5%, and is therefore labeled as low-soluble rice protein.

[0041] As an optional embodiment of the present invention, the dry-based protein content of the rice protein is 80%-85% (e.g., 80%, 81%, 82%, 83%, 84% or 85%).

[0042] In the process of producing starch sugar from rice, enzymatic hydrolysis breaks down the cross-links between the main components of rice, such as starch, fat, and protein, decomposing the starch into small-molecule starch sugars. After plate and frame extrusion separation and multiple washings, rice protein residue with a dry basis protein content of 80%-85% is obtained.

[0043] The rice protein residue can be dried directly by spraying, tube bundles and airflow to obtain low soluble rice protein. Using this low soluble rice protein as raw material, water is directly added to prepare rice protein slurry with a solid content of 6-20%.

[0044] As an optional embodiment of the present invention, the solids content of the rice protein slurry is 6-20% (e.g., 7%, 8%, 9%, 10%, 12%, 14%, 15%, 17%, 18%, or 19%). Based on the water absorption characteristics of protein, a solids content greater than 20% will cause the liquid to become viscous and less fluid, making spray drying difficult. Too low a solids concentration will reduce spray drying efficiency and increase production costs. Therefore, the optimal solids concentration of the present invention has been determined.

[0045] As an optional embodiment of the present invention, the pH of the rice protein slurry is adjusted to 6.0-11.0 (e.g., 7.0, 8.0, 9.0, 10.0, or 10.5). The pH value directly affects the solubility and color of rice protein. Too low or too high a pH value will cause protein denaturation and will also affect the color of the protein by darkening it.

[0046] In one optional embodiment of the present invention, the structural modifier includes at least one selected from fructose, sucrose, stachyose, and fructooligosaccharides. By adding the structural modifier, under high-pressure homogenization, rice protein molecules undergo depolymerization and extension, increasing the contact area between the protein and water. Due to hydrogen bonds, intermolecular interactions, and hydrophobic interactions, polar and hydrophobic groups within the protein are exposed to a certain extent, altering the surface charge distribution of the protein molecules, enhancing hydration, and thus improving solubility.

[0047] As an optional embodiment of the present invention, the amount of the structure modifier added is 0.05-0.5% (e.g., 0.1%, 0.2%, 0.3%, 0.4%, or 0.45%) of the rice protein mass. The amount of structure modifier added should be sufficient to improve the solubility of the protein by changing its structure. Too much addition will affect the effective exposure of the active groups of the protein, while too little will result in poor modification effect.

[0048] As an optional embodiment of the present invention, the high-pressure homogenization pressure is 20–55 MPa (e.g., 25 MPa, 30 MPa, 35 MPa, 40 MPa, 45 MPa, or 50 MPa), and the homogenization is performed 1–2 times. Too low a homogenization pressure will cause uneven particle size, affecting product quality; too high a homogenization pressure will affect the particle size, morphology, and aggregation state of the protein.

[0049] As an optional embodiment of the present invention, the temperature of the high-temperature shearing is set to 125-175℃ (e.g., 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, or 170℃). The duration of the high-temperature shearing is 30-60s (e.g., 30s, 40s, 50s, or 60s). The flow rate of the high-temperature shearing is 1-3T / h.

[0050] As an optional embodiment of the present invention, the inlet temperature of the spray dryer is 140-190°C (e.g., 142°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, or 188°C), and the outlet temperature is 60-90°C (e.g., 62°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 88°C).

[0051] In addition, the high-temperature shearing of the mixture liquid with added structural modifier in this invention can be performed as shown in the attached figure. Figure 5 , 6 The shearing device shown includes a hopper 1 and an evaporator 2, with the outlet of the hopper 1 connected to the evaporator 2; a rotating drum 3 is installed inside the hopper 1, and the inner wall of the hopper 1 and the outer wall of the rotating drum 3 form an annular channel 4; a feed pipe 5 is installed on the side wall of the hopper 1, and the outlet of the feed pipe 5 is connected to the annular channel 4, with the discharge direction tangential to the side wall of the rotating drum 3;

[0052] The top of the rotating drum 3 is provided with a steam pipe 6, and the steam outlet of the steam pipe 6 is connected to the interior of the rotating drum 3; the side wall of the rotating drum 3 is provided with a through hole 31.

[0053] The material enters the annular channel 4 rapidly through the feed pipe 5, tangential to the side wall of the rotating drum 3. Under the thrust of the material, the rotating drum 3 begins to rotate rapidly, and the material forms a thin film layer on the inner wall of the chamber 1. At the same time, pressurized saturated steam comes into rapid contact with the material through the through hole 31 from the inside of the rotating drum 3. The material heats up rapidly and expands quickly. The dispersed steam shears the material in an orderly manner. The material after shearing enters the evaporator 2 to remove some of the water. The evaporator 2 concentrates the sheared liquid.

[0054] The temperature of high-temperature shearing refers to the temperature of the steam entering the shearing equipment;

[0055] The high-temperature shearing time refers to the duration of contact between the material and steam;

[0056] The flow rate of high-temperature shearing refers to the feed rate at the inlet.

[0057] The present invention will now be described in further detail with reference to specific embodiments and comparative examples. It should be noted that the spray drying equipment used in the following embodiments and comparative examples 1-13 is a spray drying tower, and the high-temperature shearing equipment used in the embodiments and comparative examples 1-12 is the aforementioned shearing equipment, as shown in the attached figures. Figure 5 , 6 As shown.

[0058] Example 1

[0059] A method for preparing soluble rice protein includes the following steps: using rice protein residue produced during the production of rice starch from broken rice as raw material, it is mixed into a uniform rice protein slurry, the pH is adjusted, a structure modifier is added and stirred until homogenized, and then the homogenized rice protein slurry is subjected to high-temperature shearing using high-temperature shearing technology. Finally, the rice protein slurry, after being evaporated and concentrated using a high-temperature shearing device, is spray-dried to obtain highly soluble rice protein with a yield of 92%.

[0060] The dry-basis protein content of the protein residue obtained during the production of rice starch sugar is 81%.

[0061] The solids content of the rice protein slurry is 12%; the pH of the rice protein slurry is adjusted to 8.0.

[0062] The structural modifier is fructose, and its addition amount is 0.06% of the protein residue mass;

[0063] The homogenization pressure for homogenizing the rice protein slurry was 45 MPa, and the homogenization was performed once.

[0064] The high-temperature shearing temperature was set at 150℃, the shearing time at 30s, and the flow rate at 3T / h; the inlet temperature of the spray dryer was 175℃, and the outlet temperature was 82℃.

[0065] Example 2

[0066] A method for preparing soluble rice protein includes the following steps: using air-flow rice protein as raw material, it is prepared into a uniform rice protein slurry; the pH is adjusted; a structure modifier is added and stirred until homogenized; the homogenized rice protein slurry is subjected to high-temperature shearing technology; and then the rice protein slurry, which has been evaporated and concentrated using a high-temperature shearing device, is spray-dried to obtain highly soluble rice protein with a yield of 93%.

[0067] Airflow-dried rice protein is a low-soluble rice protein obtained by directly drying the rice protein residue produced during the production of rice starch sugar through airflow. The dry basis protein content of airflow-dried rice protein is 80%.

[0068] The solids content of the rice protein slurry is 8%; the pH of the rice protein slurry is adjusted to 10.5.

[0069] The structural modifier is white sugar, and its addition amount is 0.2% of the protein content of air-flow rice;

[0070] The homogenization pressure for homogenizing the rice protein slurry was 50 MPa, and the homogenization was performed twice.

[0071] The high-temperature shearing temperature was set at 160℃, the shearing time at 45s, and the flow rate at 2T / h; the inlet temperature of the spray dryer was 170℃, and the outlet temperature was 80℃.

[0072] Example 3

[0073] A method for preparing soluble rice protein includes the following steps: using tubular rice protein as raw material, preparing a uniform rice protein slurry, adjusting the pH, adding a structure modifier, stirring and mixing evenly, homogenizing, subjecting the homogenized rice protein slurry to high-temperature shearing using instantaneous high-temperature shearing technology, and then spray-drying the rice protein slurry that has been evaporated and concentrated using a high-temperature shearing device to obtain highly soluble rice protein with a yield of 92%.

[0074] Tubular rice protein is a low-soluble rice protein obtained by directly drying the rice protein residue produced during the production of rice starch sugar through a tubular method. The dry basis protein content of tubular rice protein is 81%.

[0075] The solids content of the rice protein slurry is 16%; the pH of the rice protein slurry is adjusted to 9.5.

[0076] The structural modifier is fructooligosaccharide, and its addition amount is 0.3% of rice protein;

[0077] The homogenization pressure for homogenizing the rice protein slurry was 35 MPa, and the homogenization was performed twice.

[0078] The high-temperature shearing temperature was set at 130℃, the shearing time at 30s, and the flow rate at 1.5T / h; the inlet temperature of the spray dryer was 145℃, and the outlet temperature was 62℃.

[0079] Example 4

[0080] A method for preparing soluble rice protein includes the following steps: using spray-dried rice protein as raw material, preparing a uniform slurry, adjusting the pH, adding a structure modifier, stirring and mixing evenly, homogenizing, subjecting the homogenized rice protein slurry to high-temperature shearing technology, and then spray-drying the rice protein slurry that has been evaporated and concentrated using a high-temperature shearing device to obtain highly soluble rice protein, with a yield of 91%.

[0081] Spray-dried rice protein is a low-soluble rice protein obtained by directly drying the rice protein residue produced during the production of rice starch sugar through spray drying. The dry basis protein content of spray-dried rice protein is 83%.

[0082] The solids content of the rice protein slurry is 14%; the pH of the rice protein slurry is adjusted to 6.5.

[0083] The structural modifier is stachyose, and its addition amount is 0.08% of the spray-dried rice protein;

[0084] The homogenization pressure for homogenizing the rice protein slurry was 55 MPa, and the homogenization was performed once.

[0085] The high-temperature shearing temperature was set at 145℃, the shearing time at 60s, and the flow rate at 1T / h; the spray drying inlet temperature was 180℃, and the outlet temperature was 86℃.

[0086] Comparative Example 1

[0087] A method for preparing soluble rice protein includes the following steps: using air-jet rice protein as raw material, preparing a uniform slurry, adjusting the pH, adding a structure modifier, stirring and mixing evenly, homogenizing, and spray drying to obtain highly soluble rice protein with a yield of 89%.

[0088] The dry-basis protein content of air-flow rice protein is 80%.

[0089] The solids content of the rice protein slurry is 8%, and the pH of the rice protein slurry is adjusted to 10.5;

[0090] The structural modifier is fructooligosaccharide; its addition amount is 0.2% of rice protein;

[0091] The homogenization pressure for homogenizing the rice protein slurry was 50 MPa, and the homogenization was performed twice.

[0092] The spray dryer has an inlet temperature of 170℃ and an outlet temperature of 80℃.

[0093] Comparative Example 2

[0094] A method for preparing soluble rice protein includes the following steps: using spray-dried rice protein as raw material, preparing a uniform slurry, adjusting the pH, adding a structure modifier and stirring until uniformly mixed, performing high-temperature shearing on the rice protein slurry using high-temperature shearing technology, and then spray-drying the high-temperature sheared rice protein slurry to obtain highly soluble rice protein with a yield of 90%.

[0095] The dry-basis protein content of the spray-dried protein is 83%.

[0096] The solids content of the rice protein slurry is 14%, and the pH of the rice protein slurry is adjusted to 6.5;

[0097] The rice protein structure modifier is white granulated sugar; its addition amount is 0.08% of the rice protein.

[0098] The high-temperature shearing temperature was set at 145℃, the shearing time at 60s, and the flow rate at 1T / h; the spray drying inlet temperature was 180℃, and the outlet temperature was 86℃.

[0099] Comparative Example 3

[0100] A method for preparing soluble rice protein includes the following steps: using rice protein residue produced during the production of rice starch from broken rice as raw material, mixing it into a uniform rice protein slurry, adjusting the pH, adding a structure modifier and stirring until uniform, and then spray-drying the rice protein slurry to obtain soluble rice protein with a yield of 89%.

[0101] The dry-basis protein content of the protein residue obtained during the production of rice starch sugar is 81%.

[0102] The solids content of the rice protein slurry is 12%; the pH of the rice protein slurry is adjusted to 8.0.

[0103] The structural modifier is fructose, and its addition amount is 0.06% of the protein residue mass;

[0104] The spray dryer has an inlet temperature of 175℃ and an outlet temperature of 82℃.

[0105] Comparative Example 4

[0106] A method for preparing soluble rice protein includes the following steps: using rice protein residue produced during the production of rice starch from broken rice as raw material, it is mixed into a uniform rice protein slurry, the pH is adjusted, homogenized, and the homogenized rice protein slurry is subjected to high-temperature shearing using high-temperature shearing technology. Then, the high-temperature sheared rice protein slurry is spray-dried to obtain highly soluble rice protein with a yield of 90%.

[0107] The dry-basis protein content of the protein residue obtained during the production of rice starch sugar is 81%.

[0108] The solids content of the rice protein slurry is 12%; the pH of the rice protein slurry is adjusted to 8.0.

[0109] The structural modifier is fructose, and its addition amount is 0.06% of the protein residue mass;

[0110] The homogenization pressure for homogenizing the rice protein slurry was 45 MPa, and the homogenization was performed once.

[0111] The high-temperature shearing temperature was set at 150℃, the shearing time at 30s, and the flow rate at 3T / h; the inlet temperature of the spray dryer was 175℃, and the outlet temperature was 82℃.

[0112] Comparative Example 5

[0113] A method for preparing soluble rice protein, the specific steps of which are basically the same as those in Example 2, except that the pH of the rice protein slurry is adjusted to 5 in the latter step.

[0114] Comparative Example 6

[0115] A method for preparing soluble rice protein, the specific steps of which are basically the same as those in Example 2, except that the pH of the rice protein slurry is adjusted to 12 in the latter step.

[0116] Comparative Example 7

[0117] A method for preparing soluble rice protein, the specific steps of which are basically the same as those in Example 1, except that the structural modifier is fructose, and its addition amount is 0.8% of the mass of the protein residue.

[0118] Comparative Example 8

[0119] A method for preparing soluble rice protein, the specific steps of which are basically the same as those in Example 1, except that the structural modifier is fructose, and its addition amount is 0.02% of the mass of the protein residue.

[0120] Comparative Example 9

[0121] A method for preparing soluble rice protein, the specific steps of which are basically the same as those in Example 2, except that the homogenization pressure for homogenizing the rice protein slurry in the latter step is 15 MPa.

[0122] Comparative Example 10

[0123] A method for preparing soluble rice protein, the specific steps of which are basically the same as those in Example 2, except that the homogenization pressure for homogenizing the rice protein slurry in the latter step is 60 MPa.

[0124] Comparative Example 11

[0125] A method for preparing soluble rice protein, the specific steps of which are basically the same as those in Example 2, except that the high-temperature shearing temperature in the latter step is set to 180°C.

[0126] Comparative Example 12

[0127] A method for preparing soluble rice protein, the specific steps of which are basically the same as those in Example 2, except that the high-temperature shearing temperature in the latter step is set to 120°C.

[0128] Comparative Example 13

[0129] A method for preparing soluble rice protein, the specific steps of which are the same as those in Example 2, the difference being that the high-temperature shearing in the latter step uses a commercially available product (high-shear high-speed disperser AYF-220, Nantong Bolide Machinery Technology Co., Ltd.), and the shearing conditions are: shearing speed of 1400 rpm, shearing temperature of room temperature, and shearing time of 5 min.

[0130] Performance testing

[0131] (1) Sensory evaluation: Take an appropriate amount of sample and place it in a white porcelain dish. Observe the color and state under natural light, and check for any impurities. Smell the aroma, rinse your mouth with warm water, and taste the flavor. Use a scoring method, 1-5 points. The higher the score, the better the taste. The evaluation includes color, state, aroma, graininess, smoothness, and bitterness.

[0132] (2) Nitrogen solubility index determination: Weigh 5g of sample into a stoppered Erlenmeyer flask with a ground glass stopper, add 200mL of water, and then place it in a 200rpm, 30℃ vortex water bath for 2 hours. After shaking, transfer the sample solution in the Erlenmeyer flask to a 250mL volumetric flask, cool to room temperature, and then make up to volume and shake well for 5 minutes. Then, shake the made-up sample solution well and centrifuge at 1500r / min for 10 minutes. Filter with rapid filter paper and keep the filtrate for later use. Protein content was determined by the Kjeldahl method according to GB 5009.5-2016.

[0133]

[0134] (3) Determination of emulsifying properties and emulsion stability:

[0135] Weigh 2.5g of sample, disperse it in 50mL of water, add 50mL of salad oil, stir in a tissue homogenizer for 1min, take an appropriate amount and pour it into a graduated centrifuge tube, centrifuge at 2500rpm for 5min, and record the liquid height and emulsion layer height in the graduated centrifuge tube respectively.

[0136]

[0137] (4) Determination of foaming properties and foam stability: Weigh 8g of protein sample, dissolve it in 92mL of water, pour it into a small bottle, and measure and record the height of the sample solution (H1). Shear the sample at 12000rpm for 5min using a high-speed shearing machine, and then immediately measure and record the height of the sample solution (H2). After 30min, record the sample height (H3). The formula for calculating the foaming ability (FC) of the sample is as follows:

[0138] FC (%) = (H2 - H1) / H1 × 100%

[0139] (5) Determination of water-holding capacity: Weigh the labeled mass of the protein sample as m1 and place it in a 10 mL centrifuge tube. The total weight of the sample and the centrifuge tube is m2. Add distilled water until the water just covers the sample. Shake for 5 min to mix well. Centrifuge at 5000 rpm for 15 min. Then, remove the water from the upper layer of the centrifuge tube with filter paper. Accurately weigh the total mass of the sample and the centrifuge tube and record it as m3.

[0140]

[0141] (6) The rice protein powder sample was attached to the sample stage with conductive adhesive and sputtered with gold, and then observed with a scanning electron microscope.

[0142] Results data

[0143] Table 1. Properties of different types of rice protein

[0144] Sensory evaluation Nitrogen solubility index Water retention emulsifying Foaming properties Airflow rice protein 2.0 1.94 1.8 38 23 Tubular rice protein 1.0 1.85 1.6 35 25 Spray-dried rice protein 1.8 2.52 1.9 40 20 Example 1 4.8 72 3.1 81 75 Example 2 4.6 85 3.4 85 83 Example 3 4.5 76 3.2 78 75 Example 4 4.4 65 3.1 75 71

[0145] Table 2 shows the performance of highly soluble rice protein in Comparative Examples 1-13.

[0146] Sensory evaluation Nitrogen solubility index Water retention emulsifying Foaming properties Comparative Example 1 2.4 11 2.0 42 37 Comparative Example 2 3.8 48 2.4 58 53 Comparative Example 3 2.4 10 2.0 30 28 Comparative Example 4 4.1 50 2.8 65 58 Comparative Example 5 4.0 59 2.3 65 62 Comparative Example 6 2.8 88 3.1 89 85 Comparative Example 7 4.0 70 3.0 82 76 Comparative Example 8 4.3 68 2.9 75 68 Comparative Example 9 3.9 64 2.6 72 66 Comparative Example 10 4.3 63 2.8 70 63 Comparative Example 11 4.1 53 2.5 67 61 Comparative Example 12 4.2 58 2.7 69 63 Comparative Example 13 2.7 15 2.1 45 41

[0147] From Table 1, Table 2 and Figure 1 , 2 3 and 4 (of which, Figure 1 The soluble rice protein obtained in Example 2 Figure 2 It is an airflow protein. Figure 3It is a tubular protein. Figure 4 It is a spray protein. Figure 2 , 3 The proteins in samples 4 and 5 are obtained by washing the protein residue obtained after plate and frame extrusion of starch sugar and then drying it using conventional methods such as airflow, tube bundle, and spray drying. It can be seen that the preparation process of this invention avoids the shortcomings of purely physical modification methods, such as poor results, and the negative impact of chemical and enzymatic modifications on rice protein quality. This preparation process combines physical and chemical methods to disrupt the interaction forces between proteins, thus hindering protein aggregation. Conventional airflow proteins, tubular proteins, and spray proteins exhibit a continuous, tightly packed lamellar structure. In Example 2, the protein is loosely spherical with a rich porous structure on its surface. This indicates that by combining a modifier and undergoing high-pressure, high-temperature treatment, the structure of the protein molecules can be altered, exposing more hydrophilic groups, enhancing hydrophilicity, and significantly improving the solubility of rice protein. This allows for the preparation of soluble rice protein, thereby altering functional properties such as foaming and emulsifying properties. The spray drying method is simple, time-efficient, and highly effective, enabling continuous production of high-quality, highly soluble rice protein with a yield of over 90% and a rice protein content of over 80% in the product, resulting in a smooth, delicate texture and excellent quality.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing soluble rice protein, characterized in that, Includes the following steps: Soluble rice protein is prepared by mixing rice protein with water to form a uniform rice protein slurry, adjusting the pH, adding a structure modifier, stirring and mixing evenly, and then spray drying after high-pressure homogenization and high-temperature shearing. The pH of the rice protein slurry was adjusted to 6.5-11.0; The structural modifier includes at least one of granulated sugar and stachyose; The amount of the structural modifier added is 0.05-0.5% of the rice protein content; The pressure of the high-pressure homogenization is 20-55 MPa; the number of homogenization cycles is 1-2. The temperature for the high-temperature shearing is set to 125-175℃; The high-temperature shearing equipment includes a hopper and an evaporator. The outlet of the hopper is connected to the evaporator. A rotating drum is installed inside the hopper. The inner wall of the hopper and the outer wall of the rotating drum form an annular channel. A feed pipe is installed on the side wall of the hopper. The outlet of the feed pipe is connected to the annular channel, and the discharge direction is tangent to the side wall of the rotating drum. A steam pipe is provided at the top of the rotating drum, and the steam outlet of the steam pipe is connected to the interior of the rotating drum. A through hole is opened on the side wall of the rotating drum. The material enters the annular channel quickly through the feed pipe along the tangent direction to the side wall of the rotating drum. The rotating drum starts to rotate rapidly under the thrust of the material. The material forms a thin film layer on the inner wall of the chamber. At the same time, pressurized saturated steam comes from the inside of the rotating drum through the through hole and comes into rapid contact with the material. The material heats up rapidly and expands rapidly. The dispersed steam shears the material in an orderly manner. The material after shearing enters the evaporator to remove some of the moisture. The evaporator plays the role of concentrating the sheared liquid. The flow rate of the high-temperature shearing is 1-3 T / h.

2. The preparation method according to claim 1, characterized in that, The dry-basis protein content of the rice protein is 80-85%.

3. The preparation method according to claim 1, characterized in that, The solids content of the rice protein slurry is 6-20%.

4. The preparation method according to claim 1, characterized in that, The high-temperature shearing time is 30-60 seconds.

5. The preparation method according to claim 1, characterized in that, The spray dryer has an inlet temperature of 140-190℃ and an outlet temperature of 60-90℃.

6. The preparation method according to claim 1, characterized in that, The rice protein includes either rice protein residue or low-soluble rice protein.

7. The preparation method according to claim 6, characterized in that, The rice protein residue is produced during the production of rice starch sugar from rice or broken rice.

8. The preparation method according to claim 6, characterized in that, The low-soluble rice protein is selected from at least one of spray-dried rice protein, tubular rice protein, or air-dried rice protein.

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