Pre-assembled rice protein, its preparation method and high-expansion extruded rice protein particles

Abstract

This invention discloses a pre-assembled rice protein, which is a raw material that has undergone pre-assembly treatment to exhibit high extrusion puffing performance. The invention also provides a method for preparing this pre-assembled rice protein, as well as a high-puffing-degree extruded rice protein granule. This invention involves thorough pretreatment of the rice protein raw material before puffing, resulting in a very loose internal structure of the rice protein molecular chains. Modified starch is added before extrusion, forming a pre-assembled structure with the rice protein, masking the hydrophobic groups of the protein, inhibiting protein folding, and facilitating the formation of a complete molten sphere structure during extrusion. The extruded rice protein granules prepared using the pre-assembled rice protein of this application exhibit high puffing degree, crispness, and excellent taste.

Description

Technical Field

[0001] This invention relates to the field of rice protein processing technology, and in particular to a pre-assembled rice protein, a method for preparing the rice protein, and high-expansion extruded rice protein particles. Background Technology

[0002] Rice protein is a high-quality plant protein, mainly composed of albumin, globulin, prolamins, and glutenin, with glutenin accounting for over 70% and being the main component. Rice protein has a balanced and reasonable composition of essential amino acids, low allergenicity, and superior quality compared to other plant proteins.

[0003] Extrusion puffing can induce a series of chemical reactions in food processing raw materials. In the food processing industry, it is commonly used for starch ripening and protein denaturation through heat. Extrusion puffing can loosen the dense spatial structure of rice protein, significantly improving its digestibility and the antioxidant properties of its digestive products. It can also improve the palatability of the finished product, increase the solubility and water absorption of rice protein, and expand its application range. For example, puffed rice protein particles can be used in energy bars to create high-rice-protein products.

[0004] Because rice protein contains over 70% gluten, which has very low hydrophilicity, the high temperatures during extrusion puffing in actual processing cause severe breakage of the gluten structure, preventing the formation of a continuous network structure (the effect of heat processing on the structure and digestibility of wheat protein, Ma Mengyao et al.). Furthermore, high-pressure heat treatment destroys the intact network structure of the protein, and high-temperature moist heat treatment may further increase the surface tension of the gluten, forming irregular surfaces with depressions or even cracks / fragments (the effect of extrusion puffing on the physical properties and protein composition of soybean protein concentrate, Lin Huaxing et al.), leading to puffing failure. Therefore, rice protein has a low degree of puffing during extrusion, resulting in insufficiently crispy and unpalatable rice protein granules, thus limiting its applications. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a pre-assembled rice protein, which is a raw material that has undergone pre-assembly treatment to exhibit high extrusion puffing performance. This invention also provides a method for preparing the pre-assembled rice protein, as well as a high-puffing-degree extruded rice protein granule.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] The preparation method of pre-assembled rice protein includes the following steps:

[0008] (S1) Take rice protein raw material, add water to make a slurry to obtain protein solution;

[0009] (S2) The protein liquid obtained in step (S1) is subjected to high-pressure steam treatment. After treatment, the pressure is released to atmospheric pressure, cooled to room temperature, and dried to obtain pretreated protein liquid one.

[0010] (S3) The pretreated protein material one is pretreated in a eutectic solvent system to obtain pretreated protein material two;

[0011] (S4) The pretreated protein material II obtained in step (S3) is pre-assembled with starch to obtain pre-assembled rice protein.

[0012] Further, the rice protein raw material mentioned in step (S1) is rice protein powder, and the mass concentration of the slurry is 20-40%.

[0013] Further, the high-pressure steam treatment in step (S2) involves directly contacting the high-pressure steam with the protein liquid to form a high-temperature, high-pressure protein liquid. The pressure of the formed high-temperature, high-pressure protein liquid is 1-5 MPa, the temperature is 160-200°C, and the pressure is maintained for 30-70 seconds, and then the pressure is released instantaneously. During the high-pressure steam treatment, a pressure regulating valve can be used to control the steam pressure of the contacting protein liquid, so that the steam in contact with the protein liquid is maintained at 1-5 MPa and 160-200°C.

[0014] Furthermore, the eutectic solvent is a solvent with hydrogen bond donors and hydrogen bond acceptors, specifically betaine and lactic acid as hydrogen bond acceptors and hydrogen bond donors; the method for constructing the eutectic solvent system is as follows: betaine and lactic acid are heated and stirred at 50°C in a molar ratio of 1:2 until the solid is transformed into a mixed liquid.

[0015] Furthermore, the solvent pretreatment process described in step (S3) is as follows:

[0016] (S31) Under heating conditions, add the powdered pretreated protein material obtained in step (S2), i.e., 1g of powdered rice protein raw material and 10-30mL of eutectic solvent to the eutectic solvent at a solid-liquid ratio of 1:10-30. After reacting for a certain period of time, centrifuge and take the supernatant, i.e., protein extract.

[0017] (S32) Add 2-5 times the volume of ethanol to the protein extract obtained in step (S31), mix well, let stand and centrifuge, the precipitate is the pretreated protein, wash the protein with water and collect it to obtain pretreated protein material II.

[0018] (S33) The washing liquid is mixed with the ethanol solution, and the ethanol and water are evaporated off using a rotary evaporator to recover the eutectic solvent, namely the betaine-lactic acid system.

[0019] Furthermore, in step (S31), the heating temperature is 40-60°C and the reaction time is 1-3 hours.

[0020] Further, the pre-assembly method described in step (S4) is as follows: the obtained pretreated protein material is slurried with water, the pH is adjusted to alkalinity, a certain amount of starch is added, the pH is adjusted to neutral after stirring for a certain time, and then dried to obtain pre-assembled rice protein.

[0021] Further, in step (S4), the mass ratio of the pretreated protein material II to starch is 7-15:1, that is, 7-15 parts by mass of the pretreated protein material II are pre-assembled and combined with 1 part by mass of starch.

[0022] Furthermore, in step (S4), the pH is 9.0-11.0, the temperature is controlled at 30-40℃ during stirring, and the stirring time is 1-2 hours.

[0023] Furthermore, the starch mentioned in step (S4) is modified glutinous rice starch, and its preparation method is as follows:

[0024] Glutinous rice starch reacts with sodium chloroacetate under high temperature and alkaline conditions to produce sodium carboxymethyl glutinous rice starch, which is modified glutinous rice starch.

[0025] The reaction conditions are: pH 8.5-9.5, reaction at 40-50℃ for 40-80 min, and chloroacetic acid is 40-50% of the starch mass. Under alkaline conditions, the macromolecular glycosidic bonds of glutinous rice starch break, and new reducing chain groups appear, which is conducive to the substitution reaction between glutinous rice starch and chloroacetic acid.

[0026] This invention provides a pre-assembled rice protein, which is prepared by the above-described method for preparing pre-assembled rice protein.

[0027] The present invention also provides a highly expanded extruded rice protein granule prepared using the above-mentioned pre-assembled rice protein.

[0028] Furthermore, the preparation method of the high-expansion extruded rice protein granules is as follows: the obtained pre-assembled rice protein is placed in an extruder and extruded. The extrusion conditions are controlled as follows: sleeve temperature 120-160℃, screw speed 200-300r / min, and material moisture content 25%-35%.

[0029] The protein used in this invention is rice protein. Because the main component of rice protein is insoluble glutenin, it has low hydrophilicity and numerous internal cross-linked structures. Therefore, it exhibits almost no puffing properties during high-temperature extrusion, and the dried product is extremely hard, making it difficult to apply in practice. This application pre-assembles heat-denatured rice protein, giving it excellent hot-extrusion puffing properties and expanding its application range.

[0030] In this application, the rice protein raw material is first subjected to a short-term high-temperature and high-pressure treatment, which fully denatures and swells the rice protein, allowing the molecular chains to come into full contact with water. Then, the pressure is released instantaneously, which depolymerizes or breaks the rice protein molecular chains, reducing the β-sheet in the rice protein molecules and exposing some groups inside the rice protein molecules. The molecular structure of the rice protein changes from a stacked shape to a spherical shape. Then, the rice protein is pretreated in a eutectic solvent system. A polar eutectic solvent is used to break the hydrogen bonds in the rice protein, making it easier to present a molten state under the high temperature and high pressure environment in the extruder. This changes the molecular structure configuration of the rice protein: the protein structure unfolds, the proportion of β-sheet in the secondary structure of the rice protein changes, the protein rearranges, and the internal hydrophilic groups can fully combine with water molecules, resulting in higher puffing degree of the extruded and expanded particles.

[0031] Based on the eutectic solvent pretreatment of rice protein in step (S3), the pretreated protein material II is pre-assembled with starch. When the pretreated protein-starch assembly structure is extruded, the protein and starch combine to form a non-Newtonian fluid with increased viscosity, exhibiting better water absorption and water retention. At the same time, the starch is added before extrusion to form an assembly structure with the protein, masking the hydrophobic groups of the protein, inhibiting protein folding, and forming a molten globular protein structure. The starch is sodium carboxymethyl glutinous rice starch. In an alkaline environment, the modified glutinous rice starch fully absorbs water and gelatinizes. The glutinous rice starch micelle molecules expand outwards in the system and connect with each other in the rice protein system, which exhibits a unfolded structure, to form a network of hydrophilic colloids. During this process, the carboxymethyl modified glutinous rice starch has more hydrophilic groups attached to its molecular branches, increasing the steric hindrance of the starch molecular chains. At the same time, the glutinous rice starch sugar chains with more branches are entangled and bound with the protein chains. When the pH of the system is adjusted to neutral, the unfolded rice protein molecular structure tends to refold. The network of hydrophilic colloids formed by the modified glutinous rice starch with a large water absorption rate in the system will generate steric hindrance to inhibit the folding of rice protein molecules. The starch sugar chains are entangled and bound with the protein chains, and the starch chains inhibit the folding of the protein chains, so that the rice protein maintains the loose internal structure after treatment with a eutectic solvent, making it easier to form a complete molten sphere state during extrusion processing.

[0032] In the preparation of high-expansion extruded rice protein granules, the high-temperature extrusion process, with its high temperature and high pressure processing conditions, transforms the plant starch raw material into gelatinized starch. The fully permeated modified glutinous rice starch acts as a binder during the extrusion and puffing process. Under high temperature, high pressure, and high shear force, the structure of the rice protein changes. During extrusion, the protein undergoes intermolecular rearrangement, surface charge redistribution tends towards homogenization, and some hydrogen bonds and disulfide bonds between molecules break, resulting in a molten state. As the pressure is instantly released after the raw material passes through the extruder, the modified glutinous rice starch, acting as a binder, also instantly puffs up. The pre-assembled rice protein with its loose internal structure becomes molten, and the protein further rearranges. The hydrophilic groups within the molecular structure can fully combine with the expanded modified glutinous rice starch molecules and water molecules, producing porous, foamed, expanded granules. Numerous micropores burst open inside, causing rapid volume expansion, resulting in granules with a high degree of puffing obtained through extrusion puffing.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] This invention involves thoroughly pre-treating the rice protein raw material before extrusion, resulting in a very loose internal structure of the rice protein molecular chains. Modified starch is added before extrusion, forming a pre-assembled structure with the rice protein. This pre-assembles the hydrophobic groups of the protein, inhibiting protein folding and facilitating the formation of a complete molten sphere structure during extrusion. The extruded rice protein granules prepared using this pre-assembled rice protein exhibit high extrusion degree, crispness, and excellent taste. Attached Figure Description

[0035] Figure 1 This is a SEM image of the pre-assembled rice protein from Example 1.

[0036] Figure 2 This is a SEM image of the pre-assembled rice protein in Comparative Example 1.

[0037] Figure 3 This is a SEM image of the pre-assembled rice protein from Comparative Example 2.

[0038] Figure 4 This is a SEM image of the pre-assembled rice protein in Comparative Example 4.

[0039] Figure 5 This is a SEM image of the pre-assembled rice protein in Comparative Example 5.

[0040] Figure 6 This is a photograph of the rice protein particles from Example 1.

[0041] Figure 7This is a photograph of the rice protein particles in Comparative Example 6. Detailed Implementation

[0042] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0043] Example 1: A method for preparing pre-assembled rice protein, comprising the following steps:

[0044] (S1) Take rice protein powder, add water to make a slurry with a mass concentration of 30%, and obtain protein solution;

[0045] (S2) The protein liquid obtained in step (S1) is subjected to high-pressure steam treatment. The high-pressure steam is directly contacted with the protein liquid to form a high-temperature and high-pressure protein liquid. The pressure of the high-temperature and high-pressure protein liquid is 3MPa and the temperature is 180℃. The pressure is maintained for 50s and then the pressure is released instantly. After treatment, the pressure is released instantly to atmospheric pressure, cooled to room temperature, and dried to obtain pretreated protein liquid one.

[0046] (S3) The pretreated protein material one is pretreated in a eutectic solvent system to obtain pretreated protein material two;

[0047] (S4) The pretreated protein material II obtained in step (S3) is pre-assembled with modified glutinous rice starch to obtain pre-assembled rice protein.

[0048] Furthermore, the eutectic solvent is a solvent with hydrogen bond donors and hydrogen bond acceptors, specifically betaine and lactic acid as hydrogen bond acceptors and hydrogen bond donors; the method for constructing the eutectic solvent system is as follows: betaine and lactic acid are heated and stirred at 50°C in a molar ratio of 1:2 until the solid is transformed into a mixed liquid state. In the following embodiments, the eutectic solvent involved is the same as in this embodiment.

[0049] Furthermore, the solvent pretreatment process described in step (S3) is as follows:

[0050] (S31) Under heating at 50°C, add the powdered pretreated protein material obtained in step (S2) to the eutectic solvent at a solid-liquid ratio of 1:20. After reacting for 2 hours, centrifuge and take the supernatant, which is the protein extract.

[0051] (S32) Add 3 times the volume of ethanol to the protein extract obtained in step (S31), mix well, let stand and centrifuge, the precipitate is the pretreated protein, wash the protein with water and collect it to obtain pretreated protein material II.

[0052] (S33) The washing liquid is mixed with the ethanol solution, and the ethanol and water are evaporated off using a rotary evaporator to recover the eutectic solvent, namely the betaine-lactic acid system.

[0053] Further, the pre-assembly method described in step (S4) is as follows: the obtained pretreated protein material II is slurried with water, the pH is adjusted to 10.0, a certain amount of modified glutinous rice starch is added at a controlled temperature of 35°C, so that the mass ratio of pretreated protein material II to modified glutinous rice starch is 10:1, the mixture is stirred for 1.5 hours, the pH is adjusted to neutral, and the mixture is dried to obtain pre-assembled rice protein.

[0054] Furthermore, the modified glutinous rice starch mentioned in step (S4) is prepared by the following method:

[0055] Glutinous rice starch reacts with sodium chloroacetate under high temperature and alkaline conditions to produce sodium carboxymethyl glutinous rice starch, which is modified glutinous rice starch.

[0056] The reaction conditions were: pH 9.0, reaction at 45℃ for 60 min, and chloroacetic acid at 45% of the starch mass. Under alkaline conditions, the macromolecular glycosidic bonds of glutinous rice starch break, and new reducing chain groups appear, which is conducive to the substitution reaction between glutinous rice starch and chloroacetic acid.

[0057] In the following embodiments, the modified glutinous rice starch involved is the same as in this embodiment.

[0058] Example 2: A method for preparing pre-assembled rice protein, comprising the following steps:

[0059] (S1) Take rice protein powder, add water to make a slurry with a mass concentration of 20%, and obtain protein solution;

[0060] (S2) The protein liquid obtained in step (S1) is subjected to high-pressure steam treatment. The high-pressure steam is directly contacted with the protein liquid to form a high-temperature and high-pressure protein liquid. The pressure of the high-temperature and high-pressure protein liquid is 1 MPa and the temperature is 160°C. The pressure is maintained for 30 seconds and then the pressure is released instantly. After treatment, the pressure is released instantly to atmospheric pressure, cooled to room temperature, and dried to obtain pretreated protein liquid one.

[0061] (S3) The pretreated protein material one is pretreated in a eutectic solvent system to obtain pretreated protein material two;

[0062] (S4) The pretreated protein material II obtained in step (S3) is pre-assembled with modified glutinous rice starch to obtain pre-assembled rice protein.

[0063] Furthermore, the solvent pretreatment process described in step (S3) is as follows:

[0064] (S31) Under heating at 40°C, add the powdered pretreated protein material obtained in step (S2) to the eutectic solvent at a solid-liquid ratio of 1:10. After reacting for 1 hour, centrifuge and take the supernatant, which is the protein extract.

[0065] (S32) Add 2 times the volume of ethanol to the protein extract obtained in step (S31), mix well, let stand and centrifuge, the precipitate is the pretreated protein, wash the protein with water and collect it to obtain pretreated protein material II.

[0066] (S33) The washing liquid is mixed with the ethanol solution, and the ethanol and water are evaporated off using a rotary evaporator to recover the eutectic solvent, namely the betaine-lactic acid system.

[0067] Further, the pre-assembly method described in step (S4) is as follows: the obtained pretreated protein material II is slurried with water, the pH is adjusted to 9.0, a certain amount of modified glutinous rice starch is added at a controlled temperature of 30°C, so that the mass ratio of pretreated protein material II to modified glutinous rice starch is 7:1. After stirring for 1 hour, the pH is adjusted to neutral, and the mixture is dried to obtain pre-assembled rice protein.

[0068] Example 3: A method for preparing pre-assembled rice protein, comprising the following steps:

[0069] (S1) Take rice protein powder, add water to make a slurry with a mass concentration of 40%, and obtain protein solution;

[0070] (S2) The protein liquid obtained in step (S1) is subjected to high-pressure steam treatment. The high-pressure steam is directly contacted with the protein liquid to form a high-temperature and high-pressure protein liquid. The pressure of the high-temperature and high-pressure protein liquid is 5MPa and the temperature is 200℃. The pressure is maintained for 70s and then the pressure is released instantly. After treatment, the pressure is released instantly to atmospheric pressure, cooled to room temperature, and dried to obtain pretreated protein liquid one.

[0071] (S3) The pretreated protein material one is pretreated in a eutectic solvent system to obtain pretreated protein material two;

[0072] (S4) The pretreated protein material II obtained in step (S3) is pre-assembled with modified glutinous rice starch to obtain pre-assembled rice protein.

[0073] Furthermore, the solvent pretreatment process described in step (S3) is as follows:

[0074] (S31) Under heating at 60°C, add the powdered pretreated protein material obtained in step (S2) to the eutectic solvent at a solid-liquid ratio of 1:30. After reacting for 3 hours, centrifuge and take the supernatant, which is the protein extract.

[0075] (S32) Add 5 times the volume of ethanol to the protein extract obtained in step (S31), mix well, let stand and centrifuge, the precipitate is the pretreated protein, wash the protein with water and collect it to obtain pretreated protein material II.

[0076] (S33) The washing liquid is mixed with the ethanol solution, and the ethanol and water are evaporated off using a rotary evaporator to recover the eutectic solvent, namely the betaine-lactic acid system.

[0077] Further, the pre-assembly method described in step (S4) is as follows: the obtained pretreated protein material II is slurried with water, the pH is adjusted to 11.0, a certain amount of modified glutinous rice starch is added at a controlled temperature of 40°C, so that the mass ratio of pretreated protein material II to modified glutinous rice starch is 15:1, the pH is adjusted to neutral after stirring for 2 hours, and the mixture is dried to obtain pre-assembled rice protein.

[0078] Comparative Example 1: A method for preparing pre-assembled rice protein, comprising the following steps:

[0079] (S1) Take rice protein powder, add water to make a slurry with a mass concentration of 30%, and obtain protein solution;

[0080] (S2) The protein liquid obtained in step (S1) is subjected to high-pressure steam treatment. The high-pressure steam is directly contacted with the protein liquid to form a high-temperature and high-pressure protein liquid. The pressure of the high-temperature and high-pressure protein liquid is 3MPa and the temperature is 180℃. The pressure is maintained for 50s and then the pressure is released instantly. After treatment, the pressure is released instantly to atmospheric pressure, cooled to room temperature, and dried to obtain pretreated protein liquid one.

[0081] (S3) The pretreated protein material is pretreated in a eutectic solvent system to obtain pre-assembled rice protein.

[0082] Furthermore, the solvent pretreatment process described in step (S3) is as follows:

[0083] (S31) Under heating at 50°C, add the powdered pretreated protein material obtained in step (S2) to the eutectic solvent at a solid-liquid ratio of 1:20. After reacting for 2 hours, centrifuge and take the supernatant, which is the protein extract.

[0084] (S32) Add 3 times the volume of ethanol to the protein extract obtained in step (S31), mix well, let stand and centrifuge, the precipitate is the pretreated protein, wash the protein with water and collect it to obtain pretreated protein material II.

[0085] (S33) The washing liquid is mixed with the ethanol solution, and the ethanol and water are evaporated off using a rotary evaporator to recover the eutectic solvent, namely the betaine-lactic acid system.

[0086] Comparative Example 2: A method for preparing pre-assembled rice protein, comprising the following steps:

[0087] (S1) Take rice protein powder, add water to make a slurry with a mass concentration of 30%, and obtain protein solution;

[0088] (S2) The protein liquid obtained in step (S1) is subjected to high-pressure steam treatment. The high-pressure steam is directly contacted with the protein liquid to form a high-temperature and high-pressure protein liquid. The pressure of the high-temperature and high-pressure protein liquid is 3MPa and the temperature is 180℃. The pressure is maintained for 50s and then the pressure is released instantly. After treatment, the pressure is released instantly to atmospheric pressure, cooled to room temperature, and dried to obtain pretreated protein liquid one.

[0089] (S3) The pretreated protein material one is pretreated in a eutectic solvent system to obtain pretreated protein material two;

[0090] (S4) The pretreated protein material II obtained in step (S3) is pre-assembled with glutinous rice starch to obtain pre-assembled rice protein.

[0091] Furthermore, the solvent pretreatment process described in step (S3) is as follows:

[0092] (S31) Under heating at 50°C, add the powdered pretreated protein material obtained in step (S2) to the eutectic solvent at a solid-liquid ratio of 1:20. After reacting for 2 hours, centrifuge and take the supernatant, which is the protein extract.

[0093] (S32) Add 3 times the volume of ethanol to the protein extract obtained in step (S31), mix well, let stand and centrifuge, the precipitate is the pretreated protein, wash the protein with water and collect it to obtain pretreated protein material II.

[0094] (S33) The washing liquid is mixed with the ethanol solution, and the ethanol and water are evaporated off using a rotary evaporator to recover the eutectic solvent, namely the betaine-lactic acid system.

[0095] Further, the pre-assembly method described in step (S4) is as follows: the obtained pretreated protein material II is mixed with water to make a slurry, the pH is adjusted to 10.0, a certain amount of glutinous rice starch is added at a controlled temperature of 35°C, so that the mass ratio of pretreated protein material II to glutinous rice starch is 10:1, the mixture is stirred for 1.5 hours, the pH is adjusted to neutral, and the mixture is dried to obtain pre-assembled rice protein.

[0096] Comparative Example 3: A method for preparing pre-assembled rice protein, comprising the following steps:

[0097] (S1) Take rice protein powder, add water to make a slurry with a mass concentration of 30%, and obtain protein solution;

[0098] (S2) The protein liquid obtained in step (S1) is subjected to high-pressure steam treatment. The high-pressure steam is directly contacted with the protein liquid to form a high-temperature and high-pressure protein liquid. The pressure of the high-temperature and high-pressure protein liquid is 3MPa and the temperature is 180℃. The pressure is maintained for 50s and then the pressure is released instantly. After treatment, the pressure is released instantly to atmospheric pressure, cooled to room temperature, and dried to obtain pretreated protein liquid one.

[0099] (S3) The pretreated protein material one is pretreated in a eutectic solvent system to obtain pretreated protein material two;

[0100] (S4) The pretreated protein material II obtained in step (S3) is pre-assembled with rice starch to obtain pre-assembled rice protein.

[0101] Furthermore, the solvent pretreatment process described in step (S3) is as follows:

[0102] (S31) Under heating at 50°C, add the powdered pretreated protein material obtained in step (S2) to the eutectic solvent at a solid-liquid ratio of 1:20. After reacting for 2 hours, centrifuge and take the supernatant, which is the protein extract.

[0103] (S32) Add 3 times the volume of ethanol to the protein extract obtained in step (S31), mix well, let stand and centrifuge, the precipitate is the pretreated protein, wash the protein with water and collect it to obtain pretreated protein material II.

[0104] (S33) The washing liquid is mixed with the ethanol solution, and the ethanol and water are evaporated off using a rotary evaporator to recover the eutectic solvent, namely the betaine-lactic acid system.

[0105] Further, the pre-assembly method described in step (S4) is as follows: the obtained pretreated protein material II is slurried with water, the pH is adjusted to 10.0, a certain amount of rice starch is added at a controlled temperature of 35°C, so that the mass ratio of pretreated protein material II to rice starch is 10:1, the mixture is stirred for 1.5 hours, the pH is adjusted to neutral, and the mixture is dried to obtain pre-assembled rice protein.

[0106] Comparative Example 4: A method for preparing pre-assembled rice protein, comprising the following steps:

[0107] (S1) Take rice protein powder;

[0108] (S2) Rice protein powder is pretreated in a eutectic solvent system to obtain pretreated protein material;

[0109] (S3) The pretreated protein material obtained in step (S2) is pre-assembled with modified glutinous rice starch to obtain pre-assembled rice protein.

[0110] Furthermore, the solvent pretreatment process described in step (S2) is as follows:

[0111] (S21) Under heating at 50°C, add the powdered rice protein raw material obtained in step (S1) to the eutectic solvent at a solid-liquid ratio of 1:20. After reacting for 2 hours, centrifuge and take the supernatant, which is the protein extract.

[0112] (S22) Add 3 times the volume of ethanol to the protein extract obtained in step (S21), mix well, let stand and centrifuge, the precipitate is the pretreated protein, wash the protein with water and collect it to obtain the pretreated protein material.

[0113] (S23) The washing liquid is mixed with the ethanol solution, and the ethanol and water are evaporated off using a rotary evaporator to recover the eutectic solvent, namely the betaine-lactic acid system.

[0114] Further, the pre-assembly method described in step (S3) is as follows: the obtained pretreated protein material II is slurried with water, the pH is adjusted to 10.0, a certain amount of modified glutinous rice starch is added at a controlled temperature of 35°C, so that the mass ratio of pretreated protein material II to modified glutinous rice starch is 10:1, the mixture is stirred for 1.5 hours, the pH is adjusted to neutral, and the mixture is dried to obtain pre-assembled rice protein.

[0115] Comparative Example 5: A method for preparing pre-assembled rice protein, comprising the following steps:

[0116] (S1) Take rice protein powder, add water to make a slurry with a mass concentration of 30%, and obtain protein solution;

[0117] (S2) The protein liquid obtained in step (S1) is subjected to high-pressure steam treatment. The high-pressure steam is directly contacted with the protein liquid to form a high-temperature and high-pressure protein liquid. The pressure of the high-temperature and high-pressure protein liquid is 3MPa and the temperature is 180℃. The pressure is maintained for 50s and then the pressure is released instantly. After treatment, the pressure is released instantly to atmospheric pressure, cooled to room temperature, and dried to obtain pretreated protein.

[0118] (S3) The pretreated protein material obtained in step (S2) is pre-assembled with modified glutinous rice starch to obtain pre-assembled rice protein.

[0119] Further, the pre-assembly method described in step (S3) is as follows: the obtained pretreated protein material is mixed with water to form a slurry, the pH is adjusted to 10.0, and modified glutinous rice starch is added at a controlled temperature of 35°C so that the mass ratio of pretreated protein material II to modified glutinous rice starch is 10:1. After stirring for 1.5 hours, the pH is adjusted to neutral, and the mixture is dried to obtain pre-assembled rice protein.

[0120] The pre-assembled rice proteins prepared using the preparation methods of Examples 1-3 and Comparative Examples 1-5 are respectively the pre-assembled rice proteins of Examples 1-3 and Comparative Examples 1-5. For example, the pre-assembled rice protein prepared using the preparation method of Example 1 is the pre-assembled rice protein of Example 1.

[0121] Rice protein particles were prepared by extruding the pre-assembled rice protein from Examples 1-3 and Comparative Examples 1-5, respectively. For example, the rice protein particles prepared by extruding the pre-assembled rice protein from Example 1 are the rice protein particles of Example 1. The extrusion process used in all cases was as follows: the obtained pre-assembled rice protein was placed in an extruder and extruded. The extrusion conditions were controlled as follows: sleeve temperature 140℃, screw speed 250 r / min, and material moisture content 30%. The rice protein particles of Comparative Example 6 were prepared by directly extruding the rice protein powder from step (S1) in an extruder under the same extrusion conditions as described above.

[0122] SEM image of pre-assembled rice protein after spray drying in Example 1 is shown below. Figure 1 As shown, the pre-assembled rice protein in Examples 2 and 3 and Figure 1 Similarly, protein samples that underwent instantaneous high-pressure steam treatment, eutectic solvent pretreatment, and modified glutinous rice starch assembly pretreatment showed that the surface structure of the protein particles was relatively smooth and expansive, and the fragment structure indicated that the spherical interior was a loose hollow structure. Figure 2 The image shows the SEM image of the pre-assembled rice protein in Comparative Example 1. The hollow spherical protein without the addition of modified glutinous rice starch has a higher degree of surface fragmentation and more groove-like wrinkles. Figure 3 The SEM image shows the pre-assembled rice protein of Comparative Example 2. It can be seen that the rice protein pre-assembled with glutinous rice starch has a significantly smoother and more continuous particle surface compared to rice protein pre-assembled without added starch. However, its surface shell is also noticeably thinner and more fragile. In Comparative Example 3, rice starch was used instead of modified glutinous rice starch for pre-assembly of rice protein. However, due to the lack of the branched chain content and strong hydrophilicity of glutinous rice starch, its pre-assembly effect was significantly weaker than that of glutinous rice starch, but stronger than that of rice starch. Figure 2 The hollow spherical protein structure shown is pre-assembled without the addition of modified glutinous rice starch; Figure 5 The image shows a SEM image of the pre-assembled rice protein in Comparative Example 5. It is evident that the surface of the protein without eutectic solvent treatment is not smooth, exhibiting numerous grooved and wrinkled structures. This contrasts with the pre-assembled rice protein in Comparative Example 4. Figure 4As shown, due to the lack of instantaneous high-pressure steam treatment, the rice protein molecular chains were not depolymerized or broken, and some groups inside the rice protein molecules were difficult to be exposed before the eutectic solvent pretreatment. Therefore, the surface of the pre-assembled rice protein in Comparative Example 4 was not smooth and had more groove-like wrinkles.

[0123] The circular dichroism chromatographic secondary structure data of the intermediate and final product proteins obtained in Example 1 are shown in the table below:

[0124] Percentage / % α-helix β-fold β-turn irregular curl Rice protein powder 0 33.3 26.6 40.9 After step (S3) of Example 1 12.3 25.4 21.4 41.4 Before pre-assembly of modified glutinous rice starch and rice protein 13.5 20.3 23.5 43.2 After pre-assembly of modified glutinous rice starch and rice protein 22.3 20.8 19.6 37.8

[0125] Data comparison reveals that after treatment with a eutectic solvent, the protein defolds, the β-sheet content decreases, and the protein structure gradually unfolds. Following eutectic solvent treatment, rice protein underwent alkali treatment, and after assembly with modified glutinous rice starch, the branched sugar chains of the glutinous rice starch intertwined with the protein chains. Secondary structure data indicate that modified glutinous rice starch significantly inhibited protein chain folding upon pH adjustment.

[0126] The bulk density of rice protein particles obtained in Examples 1-3 and Comparative Examples 1-6 was tested, and the results are shown in the table below:

[0127]

[0128] It should be noted that the above description is only an illustrative description of the technical solution of the present invention, and not a limitation on the scope of protection of the present invention. Those skilled in the art can make many modifications or equivalent changes without departing from the spirit and scope defined by the claims, but all such modifications or equivalent changes will fall within the scope of protection of the present invention.

Claims

1. A method for preparing pre-assembled rice protein, characterized in that, Includes the following steps: (S1) Take rice protein raw material, add water to make a slurry to obtain protein solution; (S2) The protein liquid obtained in step (S1) is subjected to high-pressure steam treatment. After treatment, the pressure is released to atmospheric pressure, cooled to room temperature, and dried to obtain pretreated protein liquid one. (S3) The pretreated protein material one is pretreated in a eutectic solvent system to obtain pretreated protein material two; (S4) The pretreated protein material II obtained in step (S3) is pre-assembled with starch to obtain pre-assembled rice protein; The eutectic solvent system is a betaine-lactic acid system; the solvent pretreatment process in step (S3) is as follows: (S31) Under heating conditions, add the powdered pretreated protein material obtained in step (S2) to the eutectic solvent at a solid-liquid ratio of 1:10-30. After reacting for a certain period of time, centrifuge and take the supernatant, which is the protein extract. (S32) Add 2-5 times the volume of ethanol to the protein extract obtained in step (S31), mix well, let stand and centrifuge, the precipitate is the pretreated protein, wash the protein with water and collect it to obtain pretreated protein material II. The pre-assembly method described in step (S4) is as follows: the obtained pretreated protein material II is slurried with water, the pH is adjusted to alkaline, a certain amount of starch is added, the pH is adjusted to neutral after stirring for a certain time, and then dried to obtain pre-assembled rice protein. The starch mentioned is sodium carboxymethyl glutinous rice starch.

2. The method for preparing pre-assembled rice protein according to claim 1, characterized in that: The rice protein raw material mentioned in step (S1) is rice protein powder, and the mass concentration of the slurry is 20-40%.

3. The method for preparing pre-assembled rice protein according to claim 1, characterized in that: The high-pressure steam treatment described in step (S2) involves directly contacting the high-pressure steam with the protein liquid to form a high-temperature and high-pressure protein liquid. The pressure of the formed high-temperature and high-pressure protein liquid is 1-5 MPa, the temperature is 160-200℃, and the pressure is maintained for 30-70 seconds before the pressure is released instantly.

4. The method for preparing pre-assembled rice protein according to claim 1, characterized in that: In step (S31), the heating temperature is 40-60℃ and the reaction time is 1-3h.

5. The method for preparing pre-assembled rice protein according to claim 1, characterized in that: The mass ratio of the pretreated protein material II to starch in step (S4) is 7-15:

1.

6. The method for preparing pre-assembled rice protein according to claim 5, characterized in that: The pH value mentioned in step (S4) is 9.0-11.0, the temperature is controlled at 30-40℃ during stirring, and the stirring time is 1-2 hours.

7. A pre-assembled rice protein, said pre-assembled rice protein being prepared by the method for preparing pre-assembled rice protein according to any one of claims 1-6.

8. A high-expansion extruded rice protein granule, characterized in that: The rice protein was prepared using the pre-assembled rice protein as described in claim 7.

9. The high-expansion extruded rice protein granules according to claim 8, characterized in that: The method for preparing high-expansion extruded rice protein granules is as follows: pre-assembled rice protein is placed in an extruder and extruded. The extrusion conditions are controlled as follows: sleeve temperature 120-160℃, screw speed 200-300r / min, and material moisture content 25%-35%.

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