Preparation method of heat-stable soybean protein mixture

Abstract

The invention discloses a preparation method of a soybean protein mixture with thermal stability, the mixture comprises the following components in parts by weight: 6.0-10.0 parts of soybean protein, 1.5-3.0 parts of beta-cyclodextrin and 95-105 parts of water, and the pH value is 6.0-8.0. Wherein the soybean protein is soybean protein isolate or modified soybean protein. The invention relates to a preparation method of a soybean protein mixture, which comprises the following steps: uniformly dispersing soybean protein powder in water according to a mass concentration of 6.0-10.0%, adjusting the pH value to 6.0-8.0, and uniformly dispersing beta-cyclodextrin in a protein solution according to a mass concentration of 1.5-3.0% to obtain the heat-stable soybean protein mixture. The prepared soybean protein mixture can be used for preparing food easy to swallow or high-protein and high-fiber beverages, so that the stability of related products in the hot processing process is improved while the protein content is increased.

Description

Technical Field

[0001] The invention belongs to the field of plant protein processing, and in particular relates to a method for preparing a heat-stable soybean protein mixture. Background Art

[0002] Dietary fiber has become a nutrient favored by consumers due to its many health benefits, such as promoting intestinal health and helping to control weight. At the same time, soy protein has been widely used in the field of food processing due to its rich nutritional value and excellent functional properties, especially in the fields of high-protein beverages and meal replacement foods. Therefore, the development of high-protein beverages or other related foods rich in dietary fiber based on soy protein has become a research hotspot in the field of food technology.

[0003] However, in the production process of high-protein products, high-temperature sterilization is usually required to ensure food safety and extend its shelf life. However, soy protein is prone to thermal denaturation when heated, resulting in excessive aggregation between protein molecules and the formation of larger aggregates. These aggregates can cause precipitation or gelation in the product, seriously affecting the texture and taste of the food, while significantly reducing its nutritional value. This problem is particularly evident in systems with high protein concentrations, and has become an unavoidable technical bottleneck in the production process of high-protein foods.

[0004] Patent CN110679725A discloses a process for preparing heat-stable soy protein isolate. In this invention, the heat stability of soy protein isolate is improved by adding modified starch. For specific groups of people, such as diabetic patients, special attention should be paid to the intake of starchy foods. Although modified starch is modified, it still belongs to starch. Excessive intake may lead to increased blood sugar, which is not conducive to disease control. Patent CN 109770041 A discloses a method for preparing heat-stable soy protein. The soy protein is modified by heat treatment to improve the heat stability of the soy protein, and the soy protein prepared by this method can maintain a certain heat stability at a concentration of 0.1-1.5% (w / w, g / g). However, in the actual study of the performance of soy protein, it was found that the soybean meal used to extract soy protein has a great influence on the stability of soy protein. The higher the degree of oxidation of the soybean meal, the better the stability of the extracted soy protein. The degree of oxidation of the soybean meal can be reflected by the total thiol content of the extracted soy protein, such as Figure 1As shown, the higher the degree of oxidation of soybean meal, the lower the total thiol content of the extracted soy protein. This may be because, in soybean meal with a higher degree of oxidation, the thiol groups are oxidized into disulfide bonds, resulting in a decrease in the total thiol content of the finally extracted soy protein. By studying the properties of soy protein from soybean meal with different degrees of oxidation, it was found that the lower the degree of oxidation of soybean meal, the higher the total thiol content in the extracted soy protein. When the total thiol content in soy protein is greater than 1.5 μmol / g, the thermal stability of soy protein is very poor. Even if the soy protein with a concentration of 1% is heat-treated and modified according to the method of patent CN 109770041 A, the modified soy protein dispersion will still gel when heated at a concentration of 10%. Therefore, how to improve the thermal stability of soy protein with a high thiol content has become a difficulty in the research.

[0005] In recent years, with the rapid development of functional foods, words such as high dietary fiber, no sucrose, low fat, and high calcium are increasingly sought after by consumers. However, for plant protein products, it is impossible to take into account high protein while also having the characteristics of high dietary fiber, low fat, and high calcium. The main reason is that polysaccharides such as dietary fiber are also prone to aggregation during high temperature treatment, further exacerbating the thermal instability of protein-polysaccharide mixtures. The interaction between dietary fiber and soy protein also accelerates the aggregation process of protein, exacerbating the occurrence of precipitation and gelation problems, thereby further deteriorating the processing performance and final quality of the product. For example, patent CN118489873A discloses a double network inulin / KGM-fish source protein gel and its preparation method. Inulin, as a kind of dietary fiber, promotes the formation of protein gel after being added to fish source protein, which is not conducive to the preparation of high-protein and high-fiber beverages.

[0006] Therefore, how to ensure the intake of dietary fiber while improving the thermal stability of soy protein during the heating process and inhibiting the protein aggregation caused by heat treatment has become a technical problem that needs to be urgently solved in the current food processing field. Summary of the invention

[0007] The present invention aims to provide a method for preparing a heat-stable soy protein mixture to improve the stability of soy protein during heat treatment, and at the same time prepare a soy protein mixture containing dietary fiber to solve the problem that high-concentration soy protein is easy to aggregate when soy protein with high thiol content (-SH group content is greater than 1.5 μmol / g) is subjected to heat treatment and the soy protein mixture containing dietary fiber has poor heat stability.

[0008] The present invention uses soybean protein as a raw material, and adds soluble dietary fiber β-cyclodextrin thereto. Since β-cyclodextrin affects the spatial conformation, surface hydrophobicity and electrostatic interaction of soybean protein, the stability of the soybean protein dispersion during heat treatment is greatly improved. The heat-stable soybean protein mixture prepared by the present invention has better stability than the dispersion prepared by soybean protein isolate under the same conditions, has obvious fluidity after heating treatment, and has a simple process, which is conducive to industrialization.

[0009] The present invention first provides a heat-stable soybean protein mixture, which consists of 6.0-10.0 parts of soybean protein, 1.5-3 parts of beta-cyclodextrin and 95-105 parts of water in parts by weight, and the pH of the soybean protein mixture is 6.0-8.0; wherein the soybean protein is isolated soybean protein or modified soybean protein.

[0010] In one embodiment of the present invention, the method for preparing the modified soy protein comprises the following steps:

[0011] S1. Dispersion: Take soy protein isolate, evenly disperse it in water at a mass concentration of 0.5% to 2.0%, and adjust the pH to between 6.0 and 8.0 to obtain a protein dispersion 1;

[0012] S2, heat treatment: heat the protein dispersion 1 obtained in step S1 at 90-120° C. for 15-60 min to obtain a protein dispersion 2;

[0013] S3, acid precipitation, centrifugation and re-dissolution: The protein dispersion 2 obtained in step S2 is subjected to acid precipitation, re-dissolution and drying to obtain modified soy protein powder.

[0014] In one embodiment of the present invention, the soy protein isolate is dispersed in water for 2 to 4 hours in step S1.

[0015] In one embodiment of the present invention, the acid precipitation process is to adjust the pH of the protein dispersion 2 obtained in step S2 to 4-5 with HCl.

[0016] In one embodiment of the present invention, the centrifugal speed is 3000-15800 g, and the centrifugal time is 20-120 min.

[0017] In one embodiment of the present invention, the re-dissolution process is to add water to the precipitate obtained by centrifugation at a weight ratio of 1:5 to 8, and adjust the pH to 6.0 to 7.0 for dispersion and re-dissolution.

[0018] In one embodiment of the present invention, the drying is freeze drying or spray drying; the freeze drying parameters are -30 to -80°C, vacuum degree 0.01Pa to 50Pa, and drying for 24 to 72 hours; the spray drying parameters are: inlet air temperature 195°C, outlet air temperature 95°C, and feed rate 20mL / min.

[0019] In one embodiment of the present invention, the preparation method of the soy protein isolate comprises the following steps: adding deionized water to defatted soybean meal at a weight-to-volume ratio of 1:10, adjusting the pH to 7.0-8.5, stirring at room temperature for 1 hour, centrifuging at 15800g and 4°C for 30 minutes, and taking the supernatant; adjusting the pH of the supernatant to 4.0-5.0, centrifuging at 3000-15800g and 4°C for 5-120 minutes to obtain a precipitate; dissolving the precipitate with deionized water and adjusting the pH to 7.0-8.5 to obtain a protein solution, wherein the weight ratio of the precipitate to the deionized water is 1:(3-10); drying the protein solution to obtain soy protein; wherein the drying is freeze-drying or spray-drying; the freeze-drying parameters are -50--80°C, vacuum degree 0.01Pa-50Pa, and drying 24-72h; the spray-drying parameters are: inlet air temperature 195°C, outlet air temperature 95°C, and feed rate 20mL / min.

[0020] In one embodiment of the present invention, the total thiol content of the soy protein isolate is greater than 1.5 μmol / g, preferably 3-5 μmol / g.

[0021] In one embodiment of the present invention, HCl solution is used to adjust the pH of the soy protein mixture to 6.0-8.0.

[0022] The present invention also provides a method for preparing the above-mentioned heat-stable soybean protein mixture, comprising the following steps:

[0023] 1. Dispersion: Disperse soybean protein powder evenly in water at a mass concentration of 6.0% to 10.0%, and adjust the pH to 6.0 to 8.0 to obtain a protein dispersion;

[0024] 2. Adding β-cyclodextrin: uniformly dispersing β-cyclodextrin in the protein dispersion of step S1 at a mass concentration of 1.5% to 3.0% to obtain a heat-stable soybean protein mixture;

[0025] Wherein, the soy protein is soy protein isolate or modified soy protein; HCl is used to adjust the concentration of the protein dispersion in step S1 to 6.0-8.0.

[0026] In one embodiment of the present invention, the dispersion time of the soy protein in water in step 1 is 2 to 4 hours.

[0027] In one embodiment of the present invention, the method for preparing the modified soy protein comprises the following steps:

[0028] S11, dispersion: taking soy protein isolate, uniformly dispersing it in water at a mass concentration of 0.5% to 2.0%, and adjusting the pH to between 6.0 and 8.0 to obtain a protein dispersion 1;

[0029] S12, heat treatment: heat the protein dispersion 1 obtained in step S11 at 90-120° C. for 15-60 min to obtain a protein dispersion 2;

[0030] S13, acid precipitation, centrifugation and redissolution: the protein dispersion 2 obtained in step S12 is subjected to acid precipitation, redissolution and drying to obtain modified soy protein powder.

[0031] In one embodiment of the present invention, the extraction method of the soy protein isolate is as follows: defatted soybean meal is added with deionized water in a weight-to-volume ratio of 1:10, the pH is adjusted to 7.0-8.5, stirred at room temperature for 1 hour, centrifuged at 15800g and 4°C for 30 minutes, and the supernatant is taken; the supernatant is adjusted to pH 4.0-5.0, 3000-15800g, and centrifuged at 4°C for 5-120 minutes to obtain a precipitate; the precipitate is dissolved with deionized water and the pH is adjusted to 7.0-8.5 to obtain a protein solution, and the weight ratio of the precipitate to deionized water is 1:(3-10); the protein solution is dried to obtain soy protein; wherein the drying is freeze-drying or spray-drying; the freeze-drying parameters are -50--80°C, vacuum degree 0.01Pa-50Pa, and drying 24-72h; the spray-drying parameters are: inlet air temperature 195°C, outlet air temperature 95°C, and feed rate 20mL / min.

[0032] The present invention also provides an application of the soybean protein mixture in preparing easy-to-swallow food or high-protein and high-fiber food.

[0033] In one embodiment of the present invention, the application includes preparing the soy protein mixture into a protein beverage, sterilizing it, and then filling it.

[0034] Beneficial effects:

[0035] 1. The present invention prepares a soy protein mixture with thermal stability by mixing β-cyclodextrin and soy protein. The mixture of the present invention contains high concentrations of soy protein and dietary fiber and has excellent thermal stability. The mixture can be diluted or undiluted, sterilized and then filled to prepare easy-to-swallow food or high-protein beverages.

[0036] 2. The thermal stability of soy protein is improved by adding soluble dietary fiber β-cyclodextrin, so that high-concentration soy protein still has fluidity after heating; as an experimental example, by using this method, 3% β-cyclodextrin was added to a soy protein isolate dispersion with a thiol content of 3.46 μmol / g and a mass concentration of 10%, a soy protein mixture with good thermal stability was prepared. The mixture had good fluidity after heating at a protein concentration of 10% (w / v), had better thermal stability than natural soy protein, and can be used to improve the texture of high-protein and high-fiber foods.

[0037] 3. By heat-treating and modifying the soy protein isolate, and then adding β-cyclodextrin to the heat-treated modified soy protein, even if the soy protein isolate at a concentration of 2% is heat-treated, the resulting mixture of soy protein and β-cyclodextrin still has good thermal stability, and the mixture has good fluidity after heating at a protein concentration of 10% (w / v). BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 These are the measurement results of total thiol content of soy protein isolate extracted from soybean meal with different oxidation degrees, where soybean meal 1 is soybean meal with a low oxidation degree, and soybean meal 2 is soybean meal with a high oxidation degree.

[0039] Figure 2 The elastic modulus measurement result of the heat-stable soy protein mixture obtained in Example 1 of the present invention after heating.

[0040] Figure 3 The viscosity measurement result of the heat-stable soy protein mixture after heating obtained in Example 1 of the present invention is shown.

[0041] Figure 4 The elastic modulus measurement result of the heat-stable soy protein mixture obtained in Example 2 of the present invention after heating.

[0042] Figure 5 The viscosity measurement result of the heat-stable soy protein mixture after heating obtained in Example 2 of the present invention is shown.

[0043] Figure 6 The elastic modulus measurement result of the heat-stable soy protein mixture obtained in Example 3 of the present invention after heating.

[0044] Figure 7 The viscosity measurement result of the heat-stable soy protein mixture after heating obtained in Example 3 of the present invention is shown.

[0045] Figure 8 This is the elastic modulus measurement result of the heat-stable soy protein mixture obtained in Comparative Example 1 of the present invention after heating.

[0046] Fig. 9The viscosity measurement result of the heat-stable soy protein mixture obtained in Comparative Example 1 of the present invention after heating.

[0047] Fig.10 The elastic modulus measurement result of the soy protein dietary fiber mixture after heating obtained in Comparative Example 2 of the present invention.

[0048] Fig.11 The viscosity measurement result of the soy protein dietary fiber mixture after heating obtained in Comparative Example 2 of the present invention.

[0049] Fig.12 This is a schematic diagram of the fluidity of the heat-stable soy protein mixture obtained in Example 1 of the present invention after heating.

[0050] Fig.13 This is a schematic diagram of the fluidity of the heat-stable soy protein mixture obtained in Example 2 of the present invention after heating.

[0051] Fig.14 This is a schematic diagram of the fluidity of the heat-stable soy protein mixture obtained in Example 3 of the present invention after heating.

[0052] Fig.15 This is a schematic diagram of the fluidity of the heat-stable soy protein mixture obtained in Comparative Example 1 of the present invention after heating.

[0053] Fig.16 This is a schematic diagram of the fluidity of the soy protein dietary fiber mixture obtained in Comparative Example 2 of the present invention after heating. DETAILED DESCRIPTION

[0054] The present invention is further introduced and illustrated by means of specific embodiments, comparative examples and accompanying drawings.

[0055] Example 1

[0056] A heat-stable soybean protein mixture comprises, by weight, 10.0 parts of soybean protein, 1.5 parts of beta-cyclodextrin and 100 parts of water, and the pH value of the mixture is 7; wherein the soybean protein is modified soybean protein.

[0057] The preparation method of the modified soy protein is as follows:

[0058] S1. Dispersion: Take soy protein isolate and evenly disperse it in water at a mass concentration of 1.0% for 3 h, and adjust the pH to 7.0 with 2 mol / L NaOH to obtain protein dispersion 1;

[0059] S2, heat treatment: heat the protein dispersion 1 obtained in step S1 at 100° C. for 30 min to obtain protein dispersion 2;

[0060] S3, acid precipitation: the pH of the protein dispersion 2 obtained in step S2 is adjusted to 4.5 with 1 mol / L HCl;

[0061] S4, centrifugation: centrifuge the product obtained in step S3 at 3000 g for 60 min to collect the precipitate;

[0062] S5, redissolution: add water to the precipitate obtained in step S4 at a weight ratio of 1:5, adjust the pH to 7.0 with 2 mol / L NaOH, and disperse and redissolve to obtain protein dispersion 3;

[0063] S6, drying: the protein dispersion 3 obtained in step S5 is subjected to vacuum freeze drying (-30°C, 0.01Pa, 48h) to obtain modified soybean protein;

[0064] Wherein, the total thiol content of the soy protein isolate in step S1 is 3.46 μmol / g, and the preparation method of the soy protein isolate in step S1 is:

[0065] Deionized water was added to defatted soybean meal at a ratio of 1:10 (w / v, g / mL), the pH was adjusted to 8.5 with 2mol / LNaOH solution, the mixture was stirred at room temperature for 1h, and centrifuged at 15800g and 4°C for 30min to obtain a supernatant; the supernatant was adjusted to pH 5.0 with 2mol / LHCl, and centrifuged at 6000g and 4°C for 15min to obtain a soybean protein precipitate; the soybean protein precipitate was dissolved with deionized water for 3h, and the pH of the protein solution was adjusted to 8.5 with 2mol / LNaOH, and the protein solution was freeze-dried to obtain soybean protein isolate, and the freeze-drying was specifically -50°C, 0.01Pa, and 24h.

[0066] A method for preparing a heat-stable soy protein mixture is as follows:

[0067] 1. Dispersion: Disperse the modified soybean protein powder in water at a mass concentration of 10.0% for 3 hours, and adjust the pH to 7.0 to obtain a protein dispersion;

[0068] 2. Adding β-cyclodextrin: uniformly dispersing β-cyclodextrin at a mass concentration of 1.5% in the protein dispersion obtained in step 1 to obtain a soy protein mixture with improved thermal stability;

[0069] The heat-stable soy protein mixture prepared in this example was taken, and the solution was heated at 100°C for 30 minutes, cooled and placed in a 4°C refrigerator for 24 hours, and then the elastic modulus and viscosity were measured; at the same time, untreated soy protein isolate was taken as a control (soy protein group), and the solution was heated at 100°C for 30 minutes at the same protein concentration, cooled and placed in a 4°C refrigerator for 24 hours, and then the elastic modulus and viscosity were measured; the elastic modulus measurement results are shown in FIG. Figure 2As shown in FIG. 1 , the elastic modulus of the untreated soy protein isolate after heating is significantly higher than that of the heat-stable soy protein mixture prepared in this example. Figure 3 As shown in FIG. 1 , the viscosity of the heat-stable soy protein mixture prepared in this example after heating is much lower than that of the untreated soy protein isolate. Fig.12 As shown, the bottle on the left-hand side-soy protein isolate forms a hot gel after heating, and the bottle on the right-soy protein mixture prepared in this embodiment is still fluid after heating. In summary, the heat-stable soy protein mixture prepared in this embodiment has high thermal stability and still has fluidity even after being heated at 100°C for 30 minutes, and can be used to prepare easy-to-swallow foods and protein beverages.

[0070] Example 2

[0071] A heat-stable soybean protein mixture comprises, by weight, 8.0 parts of soybean protein, 3.0 parts of beta-cyclodextrin and 100 parts of water, and the pH value of the mixture is 7; wherein the soybean protein is modified soybean protein.

[0072] The preparation method of the modified soy protein is as follows:

[0073] S1. Dispersion: Take soy protein isolate, evenly disperse it in water at a mass concentration of 2.0%, and adjust the pH to 6.0 to obtain protein dispersion 1;

[0074] S2, heat treatment: heat the protein dispersion 1 obtained in step S1 at 120° C. for 15 min to obtain protein dispersion 2;

[0075] S3, acid precipitation: the pH of the protein dispersion 2 obtained in step S2 is adjusted to 4.5 with 1 mol / L HCl;

[0076] S4, centrifugation: centrifuge the product obtained in step S3 at 3000 g for 60 min to collect the precipitate;

[0077] S5, re-dissolving: adding water to the precipitate obtained in step S4 at a weight ratio of 1:3, adjusting the pH to 7.0 for dispersion and re-dissolution, to obtain a protein dispersion 3;

[0078] S6, drying: the protein dispersion 3 obtained in step S5 is subjected to vacuum freeze drying (-80° C., 0.01 Pa, 24 h) to obtain modified soybean protein;

[0079] Wherein, the total thiol content of the soy protein isolate in step S1 is 3.46 μmol / g, and the preparation method of the soy protein isolate in step S1 is:

[0080] Deionized water was added to defatted soybean meal at a ratio of 1:10 (w / v, g / mL), the pH was adjusted to 8.5 with 2mol / LNaOH solution, the mixture was stirred at room temperature for 1h, and centrifuged at 15800g and 4°C for 30min to obtain a supernatant; the supernatant was adjusted to pH 5.0 with 2mol / LHCl, and centrifuged at 6000g and 4°C for 15min to obtain a soybean protein precipitate; the soybean protein precipitate was dissolved with deionized water for 3h, and the pH of the protein solution was adjusted to 8.5 with 2mol / LNaOH, and the protein solution was freeze-dried to obtain soybean protein isolate, and the freeze-drying was specifically -50°C, 0.01Pa, and 24h.

[0081] A method for preparing a heat-stable soy protein mixture is as follows:

[0082] 1. Dispersion: Disperse the modified soybean protein powder evenly in water at a mass concentration of 8.0%, and adjust the pH to 7.0 to obtain a protein dispersion;

[0083] 2. Adding β-cyclodextrin: uniformly disperse β-cyclodextrin at a mass concentration of 3.0% in the protein dispersion obtained in step 1 to obtain a soybean protein mixture with improved thermal stability.

[0084] The heat-stable soy protein mixture prepared in this example was taken, and the solution was heated at 100°C for 30 minutes, cooled and placed in a 4°C refrigerator for 24 hours, and then the elastic modulus and viscosity were measured; at the same time, untreated soy protein isolate was taken as a control (soy protein group), and the solution was heated at 100°C for 30 minutes at the same protein concentration, cooled and placed in a 4°C refrigerator for 24 hours, and then the elastic modulus and viscosity were measured; the elastic modulus measurement results are shown in FIG. Figure 4 As shown in FIG. 1 , the elastic modulus of the untreated soy protein isolate after heating is significantly higher than that of the heat-stable soy protein mixture prepared in this example. Figure 5 As shown in FIG. 1 , the viscosity of the heat-stable soy protein mixture prepared in this example after heating is much lower than that of the untreated soy protein isolate. Fig.13 As shown, the soy protein isolate in the left bottle forms a hot gel after heating, and the heat-stable soy protein mixture prepared in this embodiment is still in a fluid state after heating in the right bottle. In summary, the heat-stable soy protein mixture prepared in this embodiment has a high thermal stability.

[0085] Example 3

[0086] A heat-stable soybean protein mixture comprises, by weight, 10.0 parts of soybean protein, 3.0 parts of beta-cyclodextrin and 100 parts of water, and the pH value of the mixture is 7; wherein the soybean protein is soybean protein isolate.

[0087] The total thiol content of the soy protein isolate is 3.46 μmol / g, and the preparation method of the soy protein isolate is as follows:

[0088] Deionized water is added to defatted soybean meal at a ratio of 1:10 (w / v, g / mL), the pH is adjusted to 7.0 with a 2mol / L NaOH solution, the mixture is stirred at room temperature for 1 hour, and the insoluble matter is removed by centrifugation (15800g, 30min, 4°C) to obtain a supernatant; the supernatant is adjusted to pH 4.0 with 2mol / L HCl, and the mixture is centrifuged (15800g, 5min, 4°C) to obtain a precipitate; the precipitate is dissolved in deionized water for 3 hours, and the pH of the solution is adjusted to 7.0 with 2mol / L NaOH, and the solution is freeze-dried to obtain soy protein isolate; the freeze-drying parameters are -80°C, 50Pa, and 72h;

[0089] A method for preparing a heat-stable soy protein mixture is as follows:

[0090] 1. Dispersion: Soybean protein isolate was uniformly dispersed in water at a mass concentration of 10% (w / w, g / g) for 3 h, and the pH was adjusted to 6.0 with 2 mol / L HCl to obtain protein dispersion 1;

[0091] 2. Adding β-cyclodextrin: uniformly disperse β-cyclodextrin in the protein dispersion 1 obtained in step 1 at a mass concentration of 3.0% to obtain a soybean protein mixture with improved thermal stability.

[0092] The heat-stable soy protein mixture prepared in this example was taken, and the solution was heated at 100°C for 30 minutes, cooled and placed in a 4°C refrigerator for 24 hours, and then the elastic modulus and viscosity were measured; at the same time, untreated soy protein isolate was taken as a control (soy protein group), and the solution was heated at 100°C for 30 minutes at the same protein concentration, cooled and placed in a 4°C refrigerator for 24 hours, and then the elastic modulus and viscosity were measured; the elastic modulus measurement results are shown in FIG. Figure 6 As shown in FIG. 1 , the elastic modulus of the untreated soy protein isolate after heating is significantly higher than that of the heat-stable soy protein mixture prepared in this example. Figure 7 As shown in FIG. 1 , the viscosity of the heat-stable soy protein mixture prepared in this example after heating is much lower than that of the untreated soy protein isolate. Fig.14 As shown, the soy protein isolate in the left bottle forms a hot gel after heating, and the heat-stable soy protein mixture prepared in this embodiment is still in a fluid state after heating in the right bottle. In summary, the heat-stable soy protein mixture prepared in this embodiment has a high thermal stability.

[0093] Comparative Example 1

[0094] The method for preparing preheated modified soybean protein comprises the following steps:

[0095] S1. Dispersion: Soybean protein isolate was uniformly dispersed in water at a mass concentration of 1%, and the pH was adjusted to 7.0 with 2 mol / L HCl to obtain a protein dispersion 1;

[0096] S2, heat treatment: heat the protein dispersion 1 obtained in step S1 at 100° C. for 60 min to obtain protein dispersion 2;

[0097] S3, acid precipitation: cool the protein dispersion 2 obtained in step S2 to room temperature, and adjust the pH to 4.0 using 2 mol / L HCl;

[0098] S4, centrifugation: centrifuge the product obtained in step S3 at 10000 g for 30 min to collect the precipitate;

[0099] S5, re-dissolving: adding water to the precipitate obtained in step S4 at a weight ratio of 1:8, adjusting the pH to 8.0 with 2 mol / L NaOH for dispersion and re-dissolution to obtain a protein solution;

[0100] S6, drying: spray drying the protein solution obtained in step S5 (inlet air temperature 195°C, outlet air temperature 95°C, feed rate 20 mL / min) to obtain heat-stable soy protein;

[0101] Wherein, the total thiol content of the soy protein isolate in step S1 is 3.46 μmol / g, and the preparation method of the soy protein isolate in step S1 is:

[0102] Deionized water is added to defatted soybean meal at a ratio of 1:10 (w / v, g / mL), the pH is adjusted to 8.5 with a 2mol / L NaOH solution, the mixture is stirred at room temperature for 1 hour, and the mixture is centrifuged at 15800g and 4°C for 30 minutes to obtain a supernatant; the supernatant is adjusted to pH 5.0 with 2mol / L HCl, and the mixture is centrifuged at 6000g and 4°C for 15 minutes to obtain a soybean protein precipitate; the soybean protein precipitate is dissolved with deionized water for 3 hours, and the pH of the protein solution is adjusted to 8.5 with 2mol / L NaOH, and the protein solution is freeze-dried to obtain soybean protein isolate, and the freeze-drying is specifically performed at -50°C, 0.01Pa, and 24 hours;

[0103] The modified soy protein prepared in this comparative example was prepared into an aqueous solution with a protein concentration of 10% (w / v, g / mL), and the aqueous solution was heated at 100°C for 30 minutes, cooled and placed in a 4°C refrigerator for 24 hours, and the elastic modulus and viscosity were measured; at the same time, soy protein isolate was taken as a control (soy protein group), prepared into an aqueous solution with a protein concentration of 10% (w / v, g / mL), heated at 100°C for 30 minutes, cooled and placed in a 4°C refrigerator for 24 hours, and the elastic modulus and viscosity were measured; the elastic modulus measurement results are as follows Figure 8 The viscosity measurement results are shown in Fig. 9As shown, the modified protein prepared in this comparative example gelled after heat treatment, and the elastic modulus and viscosity values ​​were slightly lower than those of the soy protein isolate solution after heating; Fig.15 It is intuitively shown that both the soy protein isolate on the left and the modified soy protein dispersion on the right are gelled, indicating that the modified soy protein prepared in this comparative example has poor thermal stability.

[0104] Comparative Example 2

[0105] A soybean protein dietary fiber mixture comprises, by weight, 10.0 parts of soybean protein, 3.0 parts of resistant dextrin and 100 parts of water, and the pH value of the mixture is 7; wherein the soybean protein is soybean protein isolate.

[0106] The total thiol content of the soy protein isolate is 3.46 μmol / g, and the preparation method of the soy protein isolate is as follows:

[0107] Deionized water was added to defatted soybean meal at a ratio of 1:10 (w / v, g / mL), the pH was adjusted to 8.5 with 2mol / LNaOH solution, the mixture was stirred at room temperature for 1h, and centrifuged at 15800g and 4°C for 30min to obtain a supernatant; the supernatant was adjusted to pH 5.0 with 2mol / LHCl, and centrifuged at 6000g and 4°C for 15min to obtain a soybean protein precipitate; the soybean protein precipitate was dissolved with deionized water for 3h, and the pH of the protein solution was adjusted to 8.5 with 2mol / LNaOH, and the protein solution was freeze-dried to obtain soybean protein isolate, and the freeze-drying was specifically -50°C, 0.01Pa, and 24h.

[0108] A method for preparing a soybean protein dietary fiber mixture is as follows:

[0109] 1. Dispersion: Disperse the soy protein isolate powder evenly in water at a mass concentration of 10.0%, and adjust the pH to 7.0 to obtain a protein dispersion;

[0110] 2. Add β-cyclodextrin: Take resistant dextrin at a mass concentration of 3.0% and evenly disperse it in the protein dispersion obtained in step 1 to obtain a soybean protein mixture rich in dietary fiber.

[0111] The soy protein dietary fiber mixture prepared in this comparative example was taken, and the solution was heated at 100°C for 30 minutes, cooled and placed in a 4°C refrigerator for 24 hours, and the elastic modulus and viscosity were measured; at the same time, untreated soy protein isolate was taken as a control, and the elastic modulus and viscosity were measured after heating at 100°C for 30 minutes at the same protein concentration and cooling and placing in a 4°C refrigerator for 24 hours; the elastic modulus measurement results are as follows Fig.10 As shown in FIG. 1 , the elastic modulus of the soy protein dietary fiber mixture prepared in this comparative example is significantly higher than that of the untreated soy protein isolate after heating. Fig.11 As shown in FIG. 1 , the viscosity of the soy protein dietary fiber mixture prepared in this comparative example after heating is much higher than that of the untreated soy protein isolate. Fig.16 As shown, the bottle on the left-hand side-soy protein isolate forms a hot gel after heating, and the bottle on the right-soy protein dietary fiber mixture prepared in this comparative example forms a strong gel after heating. In summary, the resistant dextrin added in this comparative example will enhance the gel properties of soybean protein and reduce its thermal stability.

[0112] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A heat-stable soy protein mixture, characterized in that: The components are composed of 6.0-10.0 parts of soybean protein, 1.5-3 parts of beta-cyclodextrin and 95-105 parts of water in parts by weight, and the pH of the soybean protein mixture is 6.0-8.0; wherein the soybean protein is isolated soybean protein or modified soybean protein.

2. The heat-stable soybean protein mixture according to claim 1, characterized in that: The preparation method of the modified soybean protein comprises the following steps: S1. Dispersion: Take soy protein isolate and evenly disperse it in water at a mass concentration of 0.5% to 2.0% for 2 to 4 hours, and adjust the pH to between 6.0 and 8.0 to obtain protein dispersion 1; S2, heat treatment: heat the protein dispersion 1 obtained in step S1 at 90-120° C. for 15-60 min to obtain a protein dispersion 2; S3, acid precipitation, centrifugation and re-dissolution: The protein dispersion 2 obtained in step S2 is subjected to acid precipitation, re-dissolution and drying to obtain modified soy protein powder.

3. The heat-stable soybean protein mixture according to claim 2, characterized in that: In step S3, the acid precipitation process is to adjust the pH of the protein dispersion 2 obtained in step S2 to 4-5 with HCl, the centrifugal speed is 3000-15800g, and the centrifugal time is 20-120min. The re-dissolution process is to add water to the precipitate obtained by centrifugation at a weight ratio of 1:5-8, adjust the pH to 6.0-7.0 for dispersion and re-dissolution.

4. The heat-stable soybean protein mixture according to claim 2, characterized in that: In step S3, the drying is freeze drying or spray drying; the freeze drying parameters are -30 to -80°C, vacuum degree 0.01Pa to 50Pa, and drying for 24 to 72 hours; the spray drying parameters are: inlet air temperature 195°C, outlet air temperature 95°C, and feed rate 20mL / min.

5. The heat-stable soybean protein mixture according to any one of claims 1 to 4, characterized in that: The extraction method of the soy protein isolate is as follows: defatted soybean meal is added with deionized water in a weight-to-volume ratio of 1:10, the pH is adjusted to 7.0-8.5, the mixture is stirred at room temperature for 1 hour, and the mixture is centrifuged at 15800g and 4°C for 30 minutes to obtain a supernatant; the supernatant is adjusted to pH 4.0-5.0, and the mixture is centrifuged at 3000-15800g and 4°C for 5-120 minutes to obtain a precipitate; the precipitate is dissolved with deionized water and the pH is adjusted to 7.0-8.5 to obtain a protein solution, wherein the weight ratio of the precipitate to the deionized water is 1:(3-10); the protein solution is dried to obtain soy protein; wherein the drying is freeze drying or spray drying; the freeze drying parameters are -50--80°C, vacuum degree 0.01Pa-50Pa, and drying for 24-72 hours; the spray drying parameters are: inlet air temperature 195°C, outlet air temperature 95°C, and feed rate 20mL / min.

6. The heat-stable soybean protein mixture according to any one of claims 1 to 4, characterized in that The total thiol content of the soy protein isolate is greater than 1.5 μmol / g.

7. A method for preparing a heat-stable soybean protein mixture according to claim 1, characterized in that: The following steps are involved: (1) Dispersion: Dispersing soybean protein powder in water at a mass concentration of 6.0% to 10.0%, and adjusting the pH to 6.0 to 8.0 to obtain a protein dispersion; (2) adding β-cyclodextrin: taking β-cyclodextrin at a mass concentration of 1.5% to 3.0% and uniformly dispersing it in the protein dispersion described in step S1 to obtain a heat-stable soy protein mixture; Wherein, the soy protein is soy protein isolate or modified soy protein; and HCl is used to adjust the concentration of the protein dispersion in step 1 to 6.0-8.

0.

8. The preparation method according to claim 7, characterized in that: The dispersion time of the soy protein in water in step 1 is 2 to 4 hours.

9. Use of the soybean protein mixture according to claim 1 in preparing easy-to-swallow food or high-protein and high-fiber food.

10. The use according to claim 9, characterized in that: The application comprises preparing the soybean protein mixture into a protein beverage and filling the beverage after sterilization.

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