Rice protein and method for preparing the same

Abstract

The present application relates to the field of food, especially to a rice protein and a preparation method thereof. The preparation method of the rice protein comprises the following steps: (1) grinding rice, adding a first amylase for enzymolysis, and separating to obtain a heavy phase to obtain a crude rice protein; (2) adding a glycerol triester lipase or a phospholipase to the crude rice protein obtained in step (1) for enzymolysis, and separating to obtain a heavy phase to obtain a defatted crude rice protein; (3) using a protease to perform enzymolysis on the defatted crude rice protein obtained in step (2) to obtain the rice protein, wherein the protease is one or two or more of a neutral protease, an alkaline protease and a papain. The present application successfully solves the problem of providing the protein content of the rice protein while improving the water holding capacity and oil holding capacity of the rice by adopting a whole enzymolysis combination technology, and improves the comprehensive performance of the rice protein.

Description

Technical Field

[0001] This invention relates to the food industry, and in particular to a rice protein and its preparation method. Background Technology

[0002] Among cereal proteins, rice protein has a higher biological value (BV) and protein value (PV) than other proteins. The amino acid composition of rice protein is balanced and its amino acid content is high, unmatched by other plant proteins. Rice protein is widely recognized as a high-quality food protein, conforming to the ideal model recommended by the WHO / FAO. Its high biological value and nutritional value are comparable to eggs, milk, and beef. Rice, rice bran, and other raw materials can be used to prepare rice protein. Researchers have proposed various preparation methods for rice protein development and utilization, mainly including solvent extraction, enzymatic extraction, alkaline extraction, and acid extraction. Among these, many studies both domestically and internationally have used the alkaline dissolution and acid precipitation method to increase protein content. However, this method incurs significant environmental treatment costs and leaves a relatively high amount of inorganic salt residue in the protein product, which can negatively impact product quality. Studies on enzymatic extraction of rice protein have yielded inconsistent results due to differences in raw materials, extraction processes, and various factors such as the type of protease, manufacturer, enzyme activity, and composition. Solvent extraction of rice protein has certain advantages, but the extraction solvent is not easy to remove, and there are safety issues with the application of the product, especially in food. In addition, the high cost of the extraction solvent increases the production cost.

[0003] Rice protein is a low-antigenic protein that does not cause allergic reactions, making it highly advantageous for the production of infant formula. In addition to its unique nutritional functions, rice protein also offers other health benefits. Recent studies have shown that rice protein can lower serum cholesterol levels. Therefore, rice protein is a high-quality plant protein with significant development value. However, rice protein is primarily a storage protein found in rice endosperm. The gluten extracted using alkali-soluble acid precipitation methods or the purified rice protein isolate have very poor solubility. Many of its processing properties, such as emulsification, foaming, water-holding capacity, and oil-holding capacity, fail to meet the needs of food processing, severely restricting the development and utilization of rice protein.

[0004] Chinese patent CN1900123A discloses a method for preparing rice starch and rice protein. The method includes crushing raw materials such as broken rice, old rice, indica rice, japonica rice or glutinous rice, followed by enzymatic hydrolysis with protease, and then centrifugation to obtain rice starch and rice protein. The obtained rice protein has a protein content of more than 65% and low purity. Summary of the Invention

[0005] The technical problem this invention aims to solve is to increase the protein content of rice protein while simultaneously enhancing its functional properties.

[0006] To address the aforementioned issues, the inventors employed a combined enzymatic hydrolysis technique based on the different mechanisms of action of various enzymes. Through long-term and repeated experimental research, they successfully solved the problem of improving the water-holding and oil-holding properties of rice while simultaneously increasing its protein content, thereby enhancing the overall performance of rice protein.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing rice protein, comprising the following steps:

[0009] (1) After grinding rice, add first amylase to hydrolyze it, separate the heavy phase and obtain crude rice protein;

[0010] (2) Add triglyceride or phospholipase to the crude rice protein obtained in step (1) for enzymatic hydrolysis, separate and take the heavy phase to obtain defatted crude rice protein;

[0011] (3) Rice protein is obtained by enzymatic hydrolysis of the defatted crude rice protein obtained in step (2) with a protease, wherein the protease is one or more of neutral protease, alkaline protease and papain.

[0012] In some embodiments of the present invention, step (1) after grinding further includes the step of preparing rice to 5-35 wt%.

[0013] In some embodiments of the present invention, the first amylase in step (1) is a high-temperature amylase or a medium-temperature amylase, preferably a high-temperature amylase.

[0014] Preferably, the amount of the first amylase added, based on the dry weight of rice, is 0.1-10‰, more preferably 0.5-6.0‰, and even more preferably 2-6‰;

[0015] More preferably, the temperature of the first amylase hydrolysis in step (1) is 90-130℃, preferably 90-110℃, and more preferably 105-110℃;

[0016] More preferably, in step (1), the pH of the first amylase hydrolysis is 3.0-7.0, preferably 3.0-6.0, and more preferably 4.0-6.0;

[0017] More preferably, the time for the first amylase hydrolysis in step (1) is 1-6 hours, preferably 3-5 hours.

[0018] In some embodiments of the present invention, the temperature of the enzymatic hydrolysis by triglyceride or phospholipase in step (2) is 40-70°C, preferably 50-70°C;

[0019] Preferably, the pH of the enzymatic hydrolysis by the triglyceride or phospholipase is 5.0-10.0, more preferably 6.0-9.0;

[0020] More preferably, the amount of triglyceride or phospholipase added, based on the dry weight of crude rice protein, is 0.5-10‰, preferably 0.5-6.0‰, and more preferably 4.0-6.0‰;

[0021] More preferably, the enzymatic hydrolysis time of the triglyceride or phospholipase in step (3) is 1-10 hours.

[0022] In some embodiments of the present invention, step (3) includes preparing the defatted crude rice protein into a 3-15 wt% dispersion before enzymatic hydrolysis.

[0023] In some embodiments of the present invention, the enzymatic hydrolysis temperature in step (3) is 40-70°C, preferably 55-70°C, and more preferably 55-65°C;

[0024] Preferably, the pH of the enzymatic hydrolysis in step (3) is 4.0-8.0, more preferably 4.0-6.0, and even more preferably 5.0-6.0;

[0025] More preferably, based on the dry weight of the defatted crude rice protein, the amount of protease added is 0.01-5‰, preferably 2.0-5.0‰, and more preferably 2.0-4.0‰;

[0026] More preferably, the enzymatic hydrolysis time is 1-10 hours, more preferably 4-8 hours.

[0027] In some embodiments of the present invention, step (1) further includes a step of secondary grinding of the coarse rice protein; preferably, it further includes a step of adding a second amylase to the secondary-ground coarse rice protein for enzymatic hydrolysis.

[0028] In some embodiments of the present invention, the step of preparing crude rice protein to a concentration of 3-15 wt% is included before the secondary grinding; preferably, the concentration is 4-12 wt%.

[0029] In some embodiments of the present invention, the secondary grinding temperature is 30-70℃, preferably 40-60℃, and preferably, the particle size of the coarse rice protein after secondary grinding is 5-30μm, preferably 10-20μm.

[0030] In some embodiments of the present invention, the second amylase is a high-temperature amylase or a medium-temperature amylase, preferably a medium-temperature amylase.

[0031] Preferably, the amount of the second amylase added is 0.1-10‰, more preferably 2.0-6.0‰, based on the dry weight of the crude rice protein.

[0032] More preferably, the enzymatic hydrolysis temperature of the second amylase is 40-90℃, more preferably 40-70℃;

[0033] More preferably, the pH of the second amylase hydrolysis is 3.0-8.0, preferably 4.0-7.0;

[0034] More preferably, the enzymatic hydrolysis time of the second amylase is 0.5-10 hours, more preferably 7-10 hours.

[0035] In some embodiments of the present invention, step (3) is followed by a step of drying rice protein, preferably the drying method being spray drying, vacuum drying or tube drying.

[0036] Secondly, the present invention also provides a rice protein, which is prepared by the above-mentioned preparation method. Preferably, the rice protein has a protein content of more than 80%, more preferably a fat content of less than 10%, and more preferably a water-holding capacity of more than 100% and an oil-holding capacity of more than 100%.

[0037] The beneficial effects of this invention are:

[0038] This invention uses a specific enzymatic hydrolysis method to obtain rice protein products with high protein content. The operation is simple and safe, and does not cause environmental pollution. At the same time, the rice protein obtained by this invention has low fat content and significantly improved water-holding and oil-holding properties. Detailed Implementation

[0039] To make the objectives, technical solutions, and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. The embodiments described below are some embodiments of the present invention, but not all embodiments. In conjunction with the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] As described in this article, mesophilic amylase refers to amylase whose enzyme activity is better at 70-90℃.

[0041] As mentioned in this article, high-temperature amylase refers to amylase whose enzyme activity is better at temperatures above 95℃, and the suitable temperature is generally between 100-130℃.

[0042] The purpose of this invention is to provide a method for producing rice protein with a protein content of over 80%, a fat content of less than 10%, and a water-holding and oil-holding capacity of over 100% by using rice as raw material through full enzymatic hydrolysis technology.

[0043] In a first aspect, in one specific embodiment of the present invention, the present invention provides a method for preparing rice protein, comprising the following steps:

[0044] (1) After grinding rice, add first amylase to hydrolyze it, separate the heavy phase and obtain crude rice protein;

[0045] (2) Add lipase or phospholipase to the crude rice protein obtained in step (1) for enzymatic hydrolysis, separate and take the heavy phase to obtain defatted crude rice protein.

[0046] (3) Rice protein is obtained by enzymatic hydrolysis of the defatted crude rice protein obtained in step (2) with a protease, wherein the protease is one or more of alkaline protease, neutral protease and papain.

[0047] According to the present invention, the rice in step (1) is not limited in type and grade, and can be, for example, at least one of japonica rice, indica rice, glutinous rice or broken rice.

[0048] The grinding described in this invention can be performed in a manner known to those skilled in the art, such as by using a pestle and mortar, or a colloid mill.

[0049] In some embodiments of the present invention, the method for preparing the above-mentioned rice protein includes the following steps:

[0050] (1) After grinding rice, prepare a dispersion, add first amylase for enzymatic hydrolysis, separate and take the heavy phase to obtain crude rice protein;

[0051] (2) The crude rice protein obtained in step (1) is prepared into a dispersion and then ground twice, and then a second amylase is added for enzymatic hydrolysis.

[0052] (3) Add triglyceride or phospholipase to the enzymatic hydrolysate obtained in step (2) and separate the heavy phase to obtain defatted crude rice protein.

[0053] (4) Prepare a dispersion of the defatted rice protein obtained in step (3) and hydrolyze it with a protease to obtain rice protein, wherein the protease is one or more of alkaline protease, neutral protease and papain.

[0054] In some embodiments of the invention, the concentration of the dispersion in step (1) is 5-35 wt%, the first amylase hydrolysis is carried out at a temperature of 90℃-130℃ and pH 3.0-7.0 for 1-6 h, and the heavy phase is separated to obtain crude rice protein, preferably carried out at a temperature of 90℃-110℃ and pH 2.0-6.0 for 3-5 h, and the amount of the first amylase added is 0.1-10 wt‰ (based on the dry weight of rice), preferably 0.5-6.0 wt‰.

[0055] In some embodiments of the present invention, in the above preparation method, the amount of the first amylase added, based on the dry weight of rice, is 0.1-9 wt‰, 0.1-8 wt‰, 0.1-7 wt‰, 0.1-6 wt‰, 0.1-5 wt‰, 0.1-4 wt‰, 0.5-10 wt‰, 1-10 wt‰, 2-10 wt‰, 3-10 wt‰, 4-10 wt‰, 5-10 wt‰, or 6-10 wt‰. In some embodiments of the present invention, in the above preparation method, the amount of the first amylase added, based on the dry weight of rice, is 0.1 wt‰, 0.5 wt‰, 1.0 wt‰, 2.0 wt‰, 3.0 wt‰, 4.0 wt‰, 5.0 wt‰, 6.0 wt‰, 7.0 wt‰, 8.0 wt‰, 9.0 wt‰, or 10.0 wt‰, or falls within the numerical range defined by any two of the above specific values ​​as endpoints. It should be understood that, in specific embodiments, any of the above ranges can be combined with any other ranges, as long as the rice protein of the present invention can be obtained.

[0056] In some embodiments of the invention, the concentration of the dispersion in step (2) is 4-12 wt%, the temperature of the secondary grinding is 30-70°C, preferably 40-60°C, and the grinding is carried out to a particle size of 5-30 μm, preferably 10-20 μm.

[0057] In one embodiment of the invention, in step (3), the second amylase hydrolyzes the food at a temperature of 40℃-90℃ and a pH of 3.0-8.0 for 0.5h-10h, preferably at a temperature of 40℃-70℃ and a pH of 4.0-7.0 for 7h-10h, and the amount of the second amylase added is 0.1-10wt‰ (based on the dry weight of crude rice protein), preferably 2.0-6.0wt‰.

[0058] In some embodiments of the present invention, in the above preparation method, the amount of the second amylase added, based on the dry weight of rice, is 0.1-9 wt‰, 0.1-8 wt‰, 0.1-7 wt‰, 0.1-6 wt‰, 0.1-5 wt‰, 0.1-4 wt‰, 0.5-10 wt‰, 1-10 wt‰, 2-10 wt‰, 3-10 wt‰, 4-10 wt‰, 5-10 wt‰, or 6-10 wt‰. In some embodiments of the present invention, in the above preparation method, the amount of the second amylase added, based on the dry weight of rice, is 0.1 wt‰, 0.5 wt‰, 1.0 wt‰, 2.0 wt‰, 3.0 wt‰, 4.0 wt‰, 5.0 wt‰, 6.0 wt‰, 7.0 wt‰, 8.0 wt‰, 9.0 wt‰, or 10.0 wt‰, or falls within the numerical range defined by any two of the above specific values ​​as endpoints. It should be understood that, in specific embodiments, any of the above ranges can be combined with any other ranges, as long as the rice protein of the present invention can be obtained.

[0059] In one embodiment of the invention, in step (4), the triglyceride or phospholipase hydrolysis is carried out at a temperature of 40℃-70℃ and a pH of 5.0-10.0 for 1-10 hours, preferably at a temperature of 50℃-70℃ and a pH of 6.0-9.0 for 3-9 hours. The amount of triglyceride or phospholipase added is 0.5-10 wt‰ (based on the dry weight of the hydrolysate), preferably 0.5-6.0 wt‰, and more preferably 4.0-6.0 wt‰.

[0060] In one embodiment of the invention, the concentration of the dispersion in step (5) is 3-15 wt%, preferably 5-10 wt%, and the protease hydrolysis is carried out at a temperature of 40℃-70℃ and a pH of 4.0-8.0 for 1-10 hours, preferably at a temperature of 55℃-70℃ and a pH of 4.0-6.0 for 4-8 hours. The amount of protease added is 0.01-5.0 wt‰ (based on the dry weight of defatted rice protein), preferably 2.0-5.0 wt‰.

[0061] In some embodiments of the present invention, in the above preparation method, the amount of protease added, based on the dry weight of defatted rice protein, is 0.01-4.0 wt‰, 0.01-3.0 wt‰, 0.01-2.0 wt‰, 0.01-1.0 wt‰, 0.05-4.0 wt‰, 0.1-4.0 wt‰, 0.5-4.0 wt‰, or 1.0-4.0 wt‰. In some embodiments of the present invention, the amount of protease added, based on the dry weight of defatted rice protein, is 0.01 wt‰, 0.05 wt‰, 0.1 wt‰, 0.5 wt‰, 1.0 wt‰, 2.0 wt‰, 3.0 wt‰, 4 wt‰, or 5 wt‰, or falls within a numerical range defined by any two of the above specific values ​​as endpoints. It should be understood that, in specific embodiments, any of the above ranges can be combined with any other range, as long as the rice protein of the present invention can be obtained.

[0062] In some embodiments of the present invention, the protease is two or more of alkaline protease, neutral protease and papain, and more preferably, the protease includes 1-2 wt‰ alkaline protease and 1-2 wt‰ papain and / or 1-2 wt‰ neutral protease.

[0063] In some embodiments of the invention, the above preparation method further includes a step of drying rice protein, preferably the drying method being one of vacuum drying, tube drying or spray drying.

[0064] According to the present invention, the first amylase or the second amylase is selected from mesophilic amylases and / or thermophilic amylases.

[0065] Secondly, the present invention also provides rice protein prepared by the above-described preparation method.

[0066] In some embodiments of the present invention, the rice protein has a protein content of more than 80%, a fat content of less than 10%, and a water-holding capacity and an oil-holding capacity of more than 100%; preferably, the rice protein has a protein content of more than 85%, a fat content of less than 5%, and a water-holding capacity and an oil-holding capacity of more than 150%.

[0067] The beneficial effects of the present invention will be further illustrated below through specific embodiments.

[0068] All raw materials or reagents used in this invention are purchased from mainstream manufacturers on the market. Those without specified manufacturers or concentrations are all analytical grade raw materials or reagents that can be obtained routinely. There are no special restrictions as long as they can achieve the expected effect.

[0069] Unless otherwise specified in this embodiment, the techniques or conditions described in the literature in this field or in accordance with the product manual shall apply.

[0070] The present invention will now be described in more detail with reference to examples and comparative examples, but the scope of the present invention is not limited to these examples. It should be noted that, unless otherwise specified, all percentages, parts, and ratios used in the present invention are based on mass.

[0071] The sources of the reagents and instruments used in the following examples are shown in Table 1.

[0072] Table 1. Raw material information used in the embodiments.

[0073]

[0074] Example 1

[0075] Prepare rice protein using the following steps:

[0076] (1) The broken rice was ground and prepared into a 5wt% concentration dispersion. 0.1‰ high-temperature amylase (based on the dry weight of the broken rice) was added and reacted at 95℃ and pH 3.0 for 6 hours. The heavy phase was separated to obtain the crude rice protein.

[0077] (2) Prepare a 5.0 wt% dispersion of the crude rice protein from step (1). Grind it evenly using a colloid mill at 30°C until the particle size of the crude rice protein is 5 μm.

[0078] (3) Add 0.5wt‰ of medium-temperature amylase (based on the dry weight of crude rice protein) to the crude rice protein solution obtained in step (2) and act at 50℃ and pH 3.0 for 8 hours;

[0079] (4) Add 0.5‰ triglyceride to the enzymatic hydrolysate obtained in step (3), and react at 50℃ and pH 6.0 for 8 hours. Separate the heavy phase to obtain defatted rice protein.

[0080] (5) Prepare a 5wt% concentration dispersion of defatted rice protein obtained in step (4), add 0.05wt‰ neutral protease (based on the dry weight of defatted rice protein), and react at 50℃ and pH 6.0 for 4h.

[0081] (6) The enzymatic hydrolysate obtained in step (5) is dried under vacuum to obtain powdered rice protein.

[0082] The protein content, fat content, water-holding capacity, and oil-holding capacity of rice protein were determined using the following methods, and the results are shown in Table 3.

[0083] The protein content was determined according to Method 1, Kjeldahl method, in the National Food Safety Standard for Determination of Protein in Food (GB5009.5-2016).

[0084] The fat content was determined according to the first method, Soxhlet extraction, in the National Food Safety Standard for Determination of Fat in Food (GB5009.6-2016).

[0085] Water retention test method:

[0086] Accurately weigh 0.500g of rice protein sample, place it in a centrifuge tube, add 5ml of water, stir well, centrifuge at 2200rpm / min for 15min, discard the supernatant, and weigh the amount of rice protein after water absorption. The water-holding capacity of rice protein is calculated using the following formula:

[0087] Water-holding capacity (%) = Mass of rice protein after water absorption / Mass of rice protein before water absorption * 100%.

[0088] Test method for oil retention:

[0089] Accurately weigh 0.500g of rice protein sample and place it in a centrifuge tube. Add 5mL of soybean salad oil, centrifuge at 2200rpm / min for 15min, remove the unabsorbed oil from the upper layer, and weigh the amount of rice protein after oil absorption. The oil-holding capacity of rice protein is calculated using the following formula:

[0090] Oil retention (%) = Mass of rice protein after oil absorption / Mass of rice protein before oil absorption * 100%.

[0091] Examples 2-9

[0092] Examples 2-9 were prepared according to the method in Example 1, following the process conditions in Table 2.

[0093] Table 2 Process conditions for Examples 2-9

[0094]

[0095]

[0096]

[0097] The protein content, fat content, water-holding capacity, and oil-holding capacity of rice protein were determined using the method described in Example 1. The results are shown in Table 3.

[0098] Example 10

[0099] The difference from Example 1 is that steps (2) and (3) are omitted. The specific method is as follows:

[0100] (1) The broken rice was ground and prepared into a 5wt% concentration dispersion. 0.1‰ high temperature amylase (based on the dry weight of the broken rice) was added and reacted at 95℃ and pH 3.0 for 6 hours. The heavy phase was separated to obtain crude rice protein.

[0101] (2) Add 0.5‰ triglyceride to the crude rice protein obtained in step (1), and react at 50℃ and pH 6.0 for 8 hours. Separate and take the heavy phase to obtain defatted rice protein.

[0102] (3) Prepare a 5wt% concentration dispersion of defatted rice protein obtained in step (2), add 0.05wt‰ neutral protease (based on the dry weight of defatted rice protein), and react at 50℃ and pH 6.0 for 4h.

[0103] (4) The enzymatic hydrolysate obtained in step (3) is vacuum dried to obtain powdered rice protein.

[0104] The protein content, fat content, water-holding capacity, and oil-holding capacity of rice protein were determined using the method described in Example 1. The results are shown in Table 3.

[0105] Comparative Example 1

[0106] The difference from Example 10 is that step (3) uses a medium-temperature amylase instead of a neutral protease for enzymatic hydrolysis. Everything else is the same as in Example 10.

[0107] The protein content, fat content, water-holding capacity, and oil-holding capacity of rice protein were determined using the method described in Example 1. The results are shown in Table 3.

[0108] Comparative Example 2

[0109] The difference from Example 10 is that in step (3), pepsin is used instead of neutral protease for enzymatic hydrolysis. Everything else is the same as in Example 10.

[0110] The protein content, fat content, water-holding capacity, and oil-holding capacity of rice protein were determined using the method described in Example 1. The results are shown in Table 3.

[0111] Table 3. Test results of various indicators of rice protein in Examples 1-10 and Comparative Example 1.

[0112] serial number Protein content, % Fat content, % Water retention, % Oil retention, % Example 1 83.2 6.7 142 132 Example 2 86.5 7 165 154 Example 3 90.9 3.9 174 169 Example 4 90.2 4 198 184 Example 5 88.5 5.1 181 172 Example 6 86.4 5.4 189 178 Example 7 87.4 6.3 175 177 Example 8 84.3 7.6 155 156 Example 9 82.1 8.3 146 137 Example 10 80.1 7.1 155 144 Comparative Example 1 83.5 7.8 78 65 Comparative Example 2 84.9 6.1 89 84

[0113] As shown in Table 3, the rice protein prepared by the methods in Examples 1-10 of this invention has a protein content of 80.1-90.2%, all above 80%, a water-holding capacity of 142-198%, and an oil-holding capacity of 132-184%, all exceeding 100%. Compared with Example 10, Example 1 uses double grinding and double amylase hydrolysis, which further increases the protein content in the rice protein.

[0114] As can also be seen from Table 3, by selecting specific enzymatic hydrolysis conditions, the rice protein obtained in Examples 2-7 has a protein content of 86.5-90.2%, which exceeds 86%, a water holding capacity of 165-198%, and an oil holding capacity of 154-184%. Both water holding capacity and oil holding capacity exceed 150%, and the overall performance of rice protein is significantly improved.

[0115] Compared to Example 10, Comparative Example 1 used a medium-temperature amylase instead of a protease for enzymatic hydrolysis in step (3). Although the protein content was increased, the water-holding and oil-holding properties of the resulting rice protein were significantly reduced. This may be because the protein molecular structure could not be opened, and the hydrophilic and hydrophobic amino acids could not be exposed, thus preventing an increase in their hydrophilicity and lipophilicity. Furthermore, compared to Example 10, Comparative Example 2 used pepsin instead of a neutral protease for enzymatic hydrolysis, which also resulted in a significant decrease in water-holding and oil-holding properties. This may be because pepsin has an excessively strong ability to degrade rice protein, leading to excessive protein hydrolysis and the production of large amounts of amino acids and short peptides, which in turn cause the rice protein to lose its protein characteristics.

[0116] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing rice protein, characterized by, The method comprises the following steps: (1) grinding rice, adding high-temperature amylase for enzymolysis, separating and taking the heavy phase to obtain crude rice protein, adding medium-temperature amylase for enzymolysis of the crude rice protein after secondary grinding, and obtaining the crude rice protein after medium-temperature amylase enzymolysis, wherein the addition amount of the high-temperature amylase is 2.0-6.0 ‰ based on the dry basis mass of rice, and the high-temperature amylase enzymolysis temperature is 105-110 ℃; the addition amount of the medium-temperature amylase is 2.0-6.0 ‰ based on the dry basis mass of the crude rice protein, and the medium-temperature amylase enzymolysis temperature is 40-70 ℃; (2) adding phospholipase for enzymolysis to the crude rice protein after medium-temperature amylase enzymolysis obtained in step (1), and separating and taking the heavy phase to obtain defatted crude rice protein, wherein the addition amount of the phospholipase is 4.0-6.0 ‰ based on the dry basis mass of the crude rice protein; (3) using protease for enzymolysis of the defatted crude rice protein obtained in step (2) to obtain rice protein, wherein the addition amount of the protease is 2.0-4.0 ‰ based on the dry basis mass of the defatted crude rice protein, and the protease is alkaline protease.

2. The production method according to claim 1, characterized by, The secondary grinding before step (1) further comprises preparing a dispersion liquid of 3-15 wt% of the crude rice protein.

3. The production method according to claim 1, characterized by, The pH of the high-temperature amylase enzymolysis in step (1) is 3.0-7.

0.

4. The production method according to claim 3, characterized by, The pH of the high-temperature amylase enzymolysis in step (1) is 3.0-6.

0.

5. The preparation method according to claim 4, characterized in that, The pH of the high-temperature amylase enzymolysis in step (1) is 4.0-6.

0.

6. The method of claim 1, wherein, The time of the high-temperature amylase enzymolysis in step (1) is 1-6 h.

7. The production method according to claim 6, wherein The time of the high-temperature amylase enzymolysis in step (1) is 3-5 h.

8. The method of claim 1, wherein, The temperature of the phospholipase enzymolysis in step (2) is 40-70 ℃.

9. The production method according to claim 8, characterized by, The temperature of the phospholipase enzymolysis in step (2) is 50-70 ℃.

10. The method of claim 1, wherein, The pH of the phospholipase enzymolysis in step (2) is 5.0-10.

0.

11. The method of claim 10, wherein, The pH of the phospholipase enzymolysis in step (2) is 6.0-9.

0.

12. The method of claim 1, wherein, The time of the phospholipase enzymolysis in step (2) is 1-10 h.

13. The method of claim 1, wherein, The step (3) before enzymolysis comprises preparing a dispersion liquid of 3-15 wt% of the defatted crude rice protein.

14. The method of claim 1, wherein, The enzymolysis temperature in step (3) is 40-70 ℃.

15. The preparation method according to claim 14, characterized in that, The enzymolysis temperature in step (3) is 55-70 ℃.

16. The method of claim 15, wherein, The enzymolysis temperature in step (3) is 55-65 ℃.

17. The method of claim 1, wherein, The pH of the enzymolysis in step (3) is 4.0-8.

0.

18. The method of claim 17, wherein, The pH of the enzymolysis in step (3) is 4.0-6.

0.

19. The method of claim 18, wherein, The pH of the enzymolysis in step (3) is 5.0-6.

0.

20. The method of claim 1, wherein, The time of the enzymolysis in step (3) is 1-10 h.

21. The method of claim 20, wherein, The time of the enzymolysis in step (3) is 4-8 h.

22. The method of claim 1, wherein, The secondary grinding before step (1) further comprises preparing a dispersion liquid of 3-15 wt% of the crude rice protein.

23. The method of claim 22, wherein, The secondary grinding before step (1) further comprises preparing a dispersion liquid of 4-12 wt% of the crude rice protein.

24. The method of claim 1, wherein, The secondary grinding temperature is 30-70 ℃.

25. The method of claim 24, wherein, The secondary grinding temperature is 40-60 ℃.

26. The method of claim 1, wherein, The particle size of the crude rice protein after secondary grinding is 5-30 μm.

27. The method of claim 26, wherein, The particle size of the crude rice protein after secondary grinding is 10-20 μm.

28. The method of claim 1, wherein, The pH of the medium-temperature amylase enzymolysis is 3.0-8.

0.

29. The method of claim 28, wherein, The mesophilic amylase enzymolysis is performed at a pH of 4.0-7.

0.

30. The method of claim 1, wherein, The mesophilic amylase enzymolysis is performed for 0.5-10 hours.

31. The method of claim 30, wherein, The mesophilic amylase enzymolysis is performed for 7-10 hours.

32. The method of making according to any one of claims 1-31, wherein, The step (3) further comprises a step of drying the rice protein, which is one of spray drying, vacuum drying or tube bundle drying.

33. A rice protein, characterized in that, The rice protein prepared by the preparation method in any one of claims 1-32 has a protein content of 90.9% or more, a fat content of 3.9% or less, a water holding capacity of more than 100%, and an oil holding capacity of more than 100%.

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