Soy protein isolate capable of forming low-hardness, high-water-retention gel and preparation method thereof

Abstract

The present invention discloses a soy protein isolate that can form a low-hardness, high-water-retention gel and a preparation method thereof. The present invention relates to the field of food processing technology, and specifically to a soy protein isolate that can form a low-hardness, high-water-retention gel and a preparation method thereof, including obtaining a soy protein precipitate from defatted soybean meal by an alkali-dissolution acid precipitation method, dispersing the soy protein precipitate with water and adjusting the pH value to 8.0-9.0, heating at 80-95°C for 5-10min, obtaining a soy reconstituted protein solution, wherein the soy reconstituted protein solution has a solid content of greater than or equal to 8%, sterilizing, spray drying, and obtaining a soy protein isolate. The present invention provides a preparation method for a soy protein isolate that can form a low-hardness, high-water-retention gel, which, while ensuring the product characteristics and gel properties, does not cause the flavor problem of the product, does not increase the cost, and can meet the actual needs of industrialized production.

Description

Technical Field

[0001] The invention relates to a soybean protein isolate capable of forming a gel with low hardness and high water retention and a preparation method thereof. Background Art

[0002] Soy protein isolate is a product with a protein content of more than 90% made from defatted soybean meal through an alkali-dissolution and acid-precipitation process. It has good gelling, dispersibility, emulsification and other functional properties and is widely used in meat, beverages and other products. With the global consumption boom of plant protein, the market for soy protein isolate gel products has gradually expanded, such as plant-based meat products, new dried tofu, Chiba tofu and other foods. Practice has found that products require soy protein isolate to provide different gel characteristics, such as hardness, elasticity, water retention, toughness, etc.

[0003] Water retention is the most important property in gel products, but in practice, it is found that while soy protein isolate meets the water retention requirements, it will lead to problems such as excessive hardness, poor toughness, and poor taste of gel products, and cannot meet consumers' demand for chewy taste. For example, in plant-based meat products, soy protein isolate provides gel formation and product water retention, and it is hoped that soy protein isolate will give plant-based meat products a chewy, juicy, and smooth taste. In addition, products such as Chiba tofu also need to use soy protein isolate with good water retention to improve the hardness and taste of the product, and the industry demand is huge.

[0004] At present, some studies have proposed methods to improve the water retention of soy protein. In CN112753846A, the finished soy protein isolate powder is pretreated with a high pressure field to improve the water retention of the prepared gel. This method starts from the perspective of modifying the finished soy protein powder, adding processes such as high pressure treatment, which is not only energy-intensive, but also difficult to industrialize. In patent CN106417887A, the gel water retention of soy protein is improved by adding modified enzymes, but enzymatic production will bring bitterness to the product and the application effect is not good. It can be seen that the methods currently proposed focus largely on the preparation method of soy protein isolate gel, and these methods also have the problem that technical operations are difficult to industrialize. Summary of the invention

[0005] The main problem to be solved by the present invention is how to prepare a soy protein isolate with low hardness and / or high water retention gel.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a soy protein isolate with low hardness and high water retention gel.

[0007] The method for preparing soy protein isolate provided by the present invention comprises the following steps:

[0008] Soy protein precipitate is obtained from defatted soybean meal by alkali dissolution and acid precipitation method, the soybean protein precipitate is dispersed with water and the pH value is adjusted to 8.0-9.0, and heated at 80-95° C. for 5-10 minutes to obtain a soybean reconstituted protein solution, wherein the solid content of the soybean reconstituted protein solution is greater than or equal to 8%, and sterilized to obtain a soybean protein isolate.

[0009] The above method further includes a drying step after the sterilization.

[0010] In the above method, the soy protein reconstituted solution is prepared according to a method comprising the following steps: dispersing soy protein precipitate with water and adjusting the pH value to 8.0, adding water to make the solid content 12%, heating at 80-95°C for 5-10 minutes, and then adding water to make the solid content 8% to obtain the soy protein reconstituted solution.

[0011] In the above method, the alkali dissolution and acid precipitation method is used to obtain soybean protein precipitate from defatted soybean meal according to the method comprising the following steps: mixing defatted soybean meal with water, alkaline extraction, filtering, collecting supernatant, adjusting the pH value of the supernatant to acidic, standing, washing, collecting precipitate, and obtaining soybean protein precipitate.

[0012] In the above method, the mass ratio of the defatted soybean meal to water in step 1) is 1:10-15, specifically 1:15.

[0013] In the above method, the alkaline extraction pH is 7.5-8.5, specifically 8.0, and can be adjusted to the desired pH using food alkali; the extraction temperature is between 25-50°C, specifically 30°C, and the stirring extraction time can be 20-30min, specifically 30min.

[0014] In the above method, the pH value of the supernatant is adjusted to an acidic pH of 4.5-5.0, and the standing time is 15-20 minutes.

[0015] In the above method, in step 1), the pH value of the supernatant is adjusted to an acidic pH of 4.5-5.0, with an optimal pH of 4.5, and the acid precipitation is allowed to stand for 15-20 minutes; the addition of the food-grade alkali / acid and the temperature heating method are combined with the actual production needs and equipment capacity requirements, and the pH and temperature are achieved according to the conventional industry production method.

[0016] In the above method, before dispersing the soybean protein precipitate with water, the step of washing the obtained soybean protein precipitate with water is also included.

[0017] In the above method, the washing with water is to prepare a suspension of the soybean protein precipitate and water in a mass ratio of 1:3, wash the precipitate twice, and then centrifuge for separation.

[0018] In the above method, the heating treatment at 80-95°C for 5-10 min is heating and keeping warm at 90°C for 8 min.

[0019] In the above method, the drying step also includes a dilution step, and the dilution must be performed after the heating treatment. The appropriate solid concentration is determined according to the production capacity of the ultra-high temperature instantaneous sterilization equipment and the spray drying equipment, and the dilution is performed to a concentration suitable for processing. The high-temperature heating and dilution methods can be performed according to various conventional methods.

[0020] In the above method, the sterilization is an ultra-high temperature instantaneous sterilization treatment at 125-150°C for 3-8s, and specifically at 135°C for 8s.

[0021] In the above method, the drying is spray drying, and the process parameters of the spray drying are: inlet air temperature is 170°C; outlet air temperature is 65°C; wind speed is 0.3m 3 / min and wind pressure is 100Kpa.

[0022] In the above method, the "ultra-high temperature sterilization and spray drying" steps can be carried out according to various conventional methods; the equipment selected can be processed according to conventional industrial production equipment and modes.

[0023] The low-hardness and high-water-retention gel soy protein isolate product prepared according to the above method also belongs to the protection scope of the present invention.

[0024] The present invention also provides the use of the preparation method in improving the water retention of gel prepared from soy protein isolate and / or in reducing the hardness of gel prepared from soy protein isolate.

[0025] The present invention makes full use of the high-temperature heating treatment method of alkaline high-concentration protein liquid, accurately controls the exposure degree of active sites of soybean protein, regulates the aggregation mode of protein subunits during heat sterilization and spray drying, and produces a soybean protein isolate product with low hardness and high water retention, which not only meets the water retention requirements of gel products, but also effectively solves the product texture problem of excessive hardness of gel formation. From the production perspective of soybean protein isolate, this method does not increase materials, equipment, energy consumption, etc., nor does it bring other flavor problems to the product. It is a method for preparing soybean protein isolate with strong feasibility and good applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The thermal gel rheology diagrams of the soy protein isolates prepared in Example 1 and Comparative Examples 1, 2, and 3. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0028] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels.

[0029] The quantitative experiments in the following examples were performed in triplicate unless otherwise specified.

[0030] Example 1. Method for preparing a soy protein isolate having low hardness and high water retention gel

[0031] 1. The specific steps for preparing soy protein are as follows:

[0032] 1. Mix low-temperature defatted soybean meal (from Shandong Yuwang Ecological Food Co., Ltd.; 901E soybean meal) and water in a mass ratio of 1:15, stir, heat to 30°C, adjust the pH to 8.0 with sodium hydroxide, stir for 30 minutes, centrifuge at 4000r / min for 20 minutes to remove the residue, and obtain the supernatant extract;

[0033] 2. Adjust the pH of the supernatant extract to 4.5 with hydrochloric acid, let it stand for 15 minutes, and centrifuge at 2000r / min for 5 minutes to remove the supernatant to obtain the precipitate of soy protein;

[0034] 3. Mix water and soy protein precipitate in a mass ratio of 3:1 to prepare a suspension to wash the precipitate, centrifuge at 2000r / min for 5 minutes to remove the supernatant, and wash twice with water. Mix water and soy protein precipitate in a mass ratio of 2:1, crush and homogenize to form a particle-free suspension, adjust the pH to 8.0 with sodium hydroxide, adjust the solid concentration to 12% with water, and heat at 90°C for 8 minutes. Then dilute with water to a solid content of 8% to obtain a soy protein reconstituted solution;

[0035] 4. The soy protein solution was sterilized at 135°C for 8s and then spray dried to prepare soy protein isolate. The specific conditions were as follows: the air inlet temperature was 170°C; the air outlet temperature was 65°C; the wind speed was 0.3m / s. 3 / min; wind pressure is 100Kpa.

[0036] Comparative Example 1

[0037] 1. Mix low-temperature defatted soybean meal and water in a mass ratio of 1:15, stir, heat to 30°C, adjust the pH to 8.0 with sodium hydroxide, stir for 30 minutes; centrifuge at 4000r / min for 20 minutes to remove the residue and obtain the supernatant extract;

[0038] 2. Adjust the pH of the supernatant extract to 4.5 with hydrochloric acid, let it stand for 15 minutes, and centrifuge at 2000r / min for 5 minutes to remove the supernatant to obtain the soybean protein precipitate;

[0039] 3. Mix water and soy protein precipitate in a mass ratio of 3:1 to prepare a suspension to wash the precipitate, centrifuge at 2000r / min for 5 minutes to remove the supernatant, and wash twice with water. Mix water and soy protein precipitate in a mass ratio of 2:1 to homogenize into a particle-free suspension, adjust the pH to 7.0 with sodium hydroxide, adjust the solid concentration to 12% with water, and heat at 90°C for 8 minutes. Then dilute to a solid concentration of 8% to obtain a soy protein reconstituted solution;

[0040] 4. The soy protein solution was sterilized at 135°C for 8s, and then spray-dried to prepare soy separated eggs. The specific conditions were as follows: the air inlet temperature was 170°C; the air outlet temperature was 65°C; the wind speed was 0.3m / s. 3 / min; wind pressure is 100Kpa.

[0041] Comparative Example 2

[0042] 1. Mix low-temperature defatted soybean meal and water in a mass ratio of 1:15, stir, heat to 30°C, adjust the pH to 8.0 with sodium hydroxide, stir for 30 minutes; centrifuge at 4000r / min for 20 minutes to remove the residue and obtain the supernatant extract;

[0043] 2. Adjust the pH of the supernatant extract to 4.5 with hydrochloric acid, let it stand for 15 minutes, and centrifuge at 2000r / min for 5 minutes to remove the supernatant to obtain the soybean protein precipitate;

[0044] 3. Mix water and soybean protein precipitate in a mass ratio of 3:1 to prepare a suspension to wash the precipitate, centrifuge at 2000r / min for 5 minutes to remove the supernatant, and wash twice with water. Mix water and soybean protein precipitate in a mass ratio of 2:1 to homogenize into a particle-free suspension, adjust the pH to 8.0 with sodium hydroxide, adjust the solid concentration to 4% with water, heat at 90°C for 8 minutes to obtain a soybean reconstituted protein solution;

[0045] 4. The soy protein solution was sterilized at 135°C for 8s and then spray dried to prepare soy protein isolate. The specific conditions were as follows: the air inlet temperature was 170°C; the air outlet temperature was 65°C; the wind speed was 0.3m / s. 3 / min; wind pressure is 100Kpa.

[0046] Comparative Example 3

[0047] 1. Mix low-temperature defatted soybean meal and water in a mass ratio of 1:15, stir, heat to 30°C, adjust the pH to 8.0 with sodium hydroxide, stir for 30 minutes; centrifuge at 4000r / min for 20 minutes to remove the residue and obtain the supernatant extract;

[0048] 2. Adjust the pH of the supernatant extract to 4.5 with hydrochloric acid, let it stand for 15 minutes, and centrifuge at 2000r / min for 5 minutes to remove the supernatant to obtain the soybean protein precipitate;

[0049] 3. Mix water and soybean protein precipitate in a mass ratio of 3:1 to prepare a suspension to wash the precipitate, centrifuge at 2000r / min for 5 minutes to remove the supernatant, and wash twice with water. Mix water and soybean protein precipitate in a mass ratio of 2:1 to homogenize into a particle-free suspension, adjust the pH to 7.0 with sodium hydroxide, and adjust the solid concentration to 12% with water to obtain a soybean reconstituted protein solution;

[0050] 4. The soy protein solution was sterilized at 135°C for 8s and then spray dried to prepare soy protein isolate. The specific conditions were as follows: the air inlet temperature was 170°C; the air outlet temperature was 65°C; the wind speed was 0.3m / s. 3 / min; wind pressure is 100Kpa.

[0051] Example 2: Preparation of gel using soy protein isolate powder and testing of gel rheology and hardness

[0052] 1. Rheological determination method of soy protein isolate gel

[0053] The soy protein isolate prepared in Example 1 and the soy protein isolate prepared in Comparative Examples 1-3 were dissolved in a mass ratio of soy protein isolate powder to water of 1:8, mixed and stirred for 1h, and the state of room temperature (25°C) was ensured. The bubbles were removed by centrifugation at 1000r / min to obtain a soy protein isolate solution. The soy protein isolate solution was added to a DHR-1 rheometer for measurement, equipped with parallel plates (diameter 25mm, gap 1mm). The edges were sealed with silicone oil to prevent evaporation during the heating process. The time scanning analysis program was set: the first stage was heated from 25°C to 95°C, and the heating was heated at a frequency of 2°C / min; the second stage was kept at 95°C for 30min; the third stage was cooled from 95°C to 25°C, and the cooling was cooled at a frequency of 2°C / min. The strain was 0.5%, and the scanning frequency range was 0.1-100Hz. The storage modulus (G0) was recorded. All samples were measured three times.

[0054] The gelation process of soy protein isolate Figure 1As shown, by comparing Comparative Examples 1, 2, and 3 with Example 1, the gel formation rate of the soy protein isolate prepared by the method shown in the example slows down during the heating and cooling processes, indicating that the coupling of the processing methods of the present invention can achieve different degrees of control over the gel formation performance of the soy protein isolate.

[0055] 2. Determination method of soy protein isolate gel hardness texture

[0056] 1) Preparation of soy protein isolate gel

[0057] The soy protein isolate prepared in Example 1 and the soy protein isolate prepared in Comparative Examples 1-3 were dissolved in a soy protein isolate powder and water mass ratio of 1:7, mixed and stirred for 1 hour, and kept at room temperature (25°C). Centrifuged at 1000r / min to remove bubbles, poured into a 10ml plastic syringe (inner diameter 10mm), kept warm in a 95°C water bath for 1 hour, and immediately cooled to room temperature to obtain a soy protein isolate gel prepared from the soy protein isolate in Example 1 (at Figure 1 , referred to as Example 1 in Table 1 and Table 2), a soy protein isolate gel prepared from the soy protein isolate of Comparative Example 1 (in Figure 1 , referred to as Comparative Example 1 in Table 1 and Table 2), and the soy protein isolate gel prepared from the soy protein isolate powder of Comparative Example 2 (in Figure 1 , referred to as Comparative Example 2 in Tables 1 and 2), and a soy protein isolate gel prepared from the soy protein isolate powder of Comparative Example 3 (in Figure 1 , referred to as Comparative Example 3 in Tables 1 and 2), and stored at 4°C for later use.

[0058] 2) Using a texture analyzer TA-XI2i, two compression tests were performed to determine the gel texture of the above soy protein isolate gel under the conditions of probe model TA3 / 100, pre-test speed 0.5 mm / s, test speed 0.5 mm / s, post-test speed 0.5 mm / s, and downward pressure distance 40%.

[0059] Table 1 Comparison of gel hardness of soy protein isolate prepared from Example and Comparative Example

[0060] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Gel hardness / g 69.10 87.16 82.51 113.50

[0061] 3. Determination of water retention of soy protein isolate gel

[0062] 1) The method for preparing the soy protein isolate gel is the same as step 2 of this embodiment.

[0063] 2) Water retention test:

[0064] Prepare a clean aluminum box (mass M1) that has been dried to constant weight, cut the gel obtained in step 1) into 10mm×10mm cylindrical blocks and place them in the aluminum box (the mass of the aluminum box + gel is M2), place the aluminum box in a 105°C oven and dry to constant weight (M3); use a 50mL centrifuge tube with an internal cannula to measure the water retention of the gel. Place filter paper of the same size at the bottom of the cannula (the mass of the filter paper + cannula is M4), cut the gel into 10mm×10mm gels and place them in the cannula (the mass of the filter paper + cannula + gel is M5). After centrifugation at 1500×g for 5 minutes, the mass of the filter paper + cannula + gel is measured as M6. The water retention of the gel is calculated as follows: WHC (%) = 1-(M5-M6) / ((M5-M4)×(M2-M3) / (M2-M1))×100%.

[0065] The results of the gel water retention test of the embodiment and comparative examples 1-3 are shown in Table 2.

[0066] Table 2 Comparison of water retention of gel prepared by soy protein isolate obtained in Example and Comparative Example

[0067] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Water retention (%) 53.21 44.17 42.38 39.20

[0068] It can be seen from Tables 1 and 2 that, compared with the gels prepared from the soy protein isolate obtained in Example 1, Comparative Examples 1, 2, and 3, the hardness decreased by 20.72%, 16.25%, and 39.12%, respectively, and the water retention increased by 20.46%, 25.55%, and 35.74%, respectively. It can be seen that in the preparation process of soy protein isolate, alkaline high concentration re-dissolution and high temperature heat treatment can effectively reduce the hardness of the soy protein isolate gel and improve the water retention.

[0069] This method starts from the perspective of producing soy protein isolate products. It is based on the traditional alkali dissolution and acid precipitation process, focuses on the re-dissolution pH of the acid-precipitated protein, the re-dissolution solid content, the heat treatment of the protein re-solution solution, and other links. A preparation method for soy protein isolate with low hardness and high water retention is invented. While ensuring the product characteristics and its gel properties, it will not cause product flavor problems, will not increase costs, and can meet the actual needs of industrial production.

[0070] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, and without the need to carry out unnecessary experimental conditions, the present invention can be implemented in a wide range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principles of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departure from the disclosed scope in the application, and changes made with conventional techniques known in the art.

Claims

1. A method for preparing soy protein isolate, comprising the steps of: Soybean protein precipitate is obtained from defatted soybean meal by alkali dissolution and acid precipitation method, the soybean protein precipitate is dispersed with water and the pH value is adjusted to 8.0-9.0, water is added to make the solid content 12%, heating treatment is performed at 80-95°C for 5-10 minutes, and then water is added to make the solid content equal to or less than 8% to obtain soybean reconstituted protein solution, sterilization is performed, and then drying treatment is performed to obtain soybean protein isolate.

2. The method according to claim 1, characterized in that: The soy protein precipitate is obtained from defatted soybean meal by using an alkali dissolution and acid precipitation method according to a method comprising the following steps: mixing defatted soybean meal with water, alkaline extraction, filtering, collecting the supernatant, adjusting the pH value of the supernatant to acidic, standing, collecting the precipitate, and obtaining the soy protein precipitate.

3. The method according to claim 2, characterized in that: The alkaline leaching is carried out in a system with a pH of 7.5-8.5 and a temperature of 25-50° C.; the alkaline leaching time is 20-30 minutes.

4. The method according to claim 2, characterized in that: The pH value of the supernatant is adjusted to an acidic pH of 4.5-5.0, and the standing time is 15-20 minutes.

5. The method according to any one of claims 1 to 4, characterized in that: The method further comprises the step of washing the obtained soybean protein precipitate with water before dispersing the soybean protein precipitate with water.

6. The method according to any one of claims 1 to 4, characterized in that: The heating treatment at 80-95° C. for 5-10 min is heating and keeping at 90° C. for 8 min; and the drying is spray drying.

7. A soy protein isolate prepared by the method according to any one of claims 1 to 6.

8. Use of the soy protein isolate according to claim 7 in the preparation of a soy protein isolate gel with high water retention and / or a soy protein isolate gel with low hardness.

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