Oyster-soybean compound protein gel constructed based on low-temperature synergy as well as preparation method and application of oyster-soybean compound protein gel

Abstract

The invention discloses oyster-soybean compound protein gel constructed based on low-temperature synergy as well as a preparation method and application of the oyster-soybean compound protein gel, and belongs to the technical field of functional foods. The composite gel is formed by oyster protein and soybean protein isolate through low-temperature stabilization, medium-temperature construction and thermal induction treatment. The preparation method comprises the following steps: preparing an oyster protein suspension; preparing a soybean protein isolate suspension; the oyster protein suspension and the soybean protein isolate suspension are mixed, stirred and left to stand, a gel structure is preliminarily constructed and then subjected to thermal induction curing treatment, and after the thermal induction curing treatment is finished, the oyster-soybean compound protein gel is formed through storage at low temperature and can be used in the field of food processing. The oyster protein and the soybean protein isolate are combined, so that the composite gel has excellent gel strength, smooth texture and long-acting storage stability, no organic chemical reagent or food additive is used in the preparation process, the formula safety is ensured, the process is simple and convenient, and the composite gel shows huge application value and industrialization prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional foods, in particular to an oyster-soy composite protein gel based on low-temperature synergistic construction and a preparation method and application thereof. BACKGROUND

[0002] With the global dietary concept shifting towards equal emphasis on nutrition and health, developing new protein products with complete amino acid composition and good functional properties has become an important direction for the food industry. Animal proteins have high nutritional value and excellent gel properties, but their production is often accompanied by high environmental load; plant proteins have advantages in resource sustainability, but their nutritional value and gel properties are often lower than animal proteins, limiting their application in high-quality products.

[0003] The gel properties of proteins are the basis for processing foods such as sausages, surimi, and tofu. Soy protein isolate, as the most widely used plant protein, can form a heat-irreversible gel after heating, but its single gel has defects such as hard texture and rough structure. More importantly, to achieve ideal gel strength, soy protein usually needs to be at high concentration (>10%) or rely on coagulants (such as gypsum, GDL, TG enzyme) to form a stable three-dimensional network structure. This leads to increased raw material costs, which is a key bottleneck restricting its high-value application. At the same time, tapping the value of marine protein resources has gradually become a research hotspot. Oysters are the highest-yielding economic shellfish in China, rich in high-quality protein, but their processing and utilization methods still rely on primary processing forms such as fresh food and drying, and the level of deep processing and comprehensive utilization needs to be improved.

[0004] Generally speaking, compounding animal proteins with plant proteins is an ideal way to achieve amino acid complementation and improve the gel properties of products. However, the field has long faced a core problem: the introduction of plant proteins often destroys the original gel network structure of animal proteins. Numerous studies and practices have shown that partial replacement of animal proteins with plant proteins can lead to a decrease in the gel properties of composite protein gels. Specifically, plant proteins are dispersed in the protein gel network, replacing gel components, weakening the effective cross-linking between proteins, and disrupting the formation of tight structures in proteins, ultimately weakening the quality of composite gels. Notably, this "performance deterioration" effect caused by protein incompatibility can be exacerbated sharply at low total protein concentrations, making "low concentration" and "high performance" a pair of contradictions. As a result, there is a general technical bias that "high-performance composite gels cannot be prepared without relying on high concentrations or external additives."

[0005] In the prior art, the preparation of composite protein gels is trapped in the conventional technical shackles that are difficult to break through. In order to overcome the compatibility barriers between proteins and ensure the texture of the product, one or more combination strategies of "high protein concentration (>10%)", "adding TG enzyme and other cross-linking agents", "using modified plant proteins", and "adjusting pH" are relied on as necessary compensation means. For example, the published patents CN120419630A and CN117413927A prepare composite gels by using high protein concentration and pH adjustment; CN118846203B prepares composite gels by adding TG enzyme; CN109700035A and CN118383450B use hydrolyzed or pH modified plant proteins to prepare composite protein gels. However, this "high concentration, enzyme addition, pH adjustment" technical mode increases the process complexity, production cost, and introduces exogenous additives, which deviates from the current market's pursuit of clean label, simplified process and low-cost healthy food.

[0006] In addition, the applicant's prior patent (application number: CN202510536474.6) shows that oyster proteins can form high-strength gels under relatively mild, low concentration (1.5%), and without coagulant conditions. The huge difference in gel behavior between oyster proteins and soybean proteins leads to a technical bias among those skilled in the art: in a low total protein concentration system, without relying on the above-mentioned "high concentration, enzyme addition, pH adjustment" and other compensatory means, it is impossible to construct a uniform and high-performance composite system. Therefore, although there are successful solutions for pure oyster protein gels, how to overcome the inherent protein incompatibility under the extremely simplified process of not relying on high concentration, not adding exogenous coagulants, and not precisely controlling pH, and prepare composite protein composite gels with gel strength comparable to pure oyster protein gels, is still a technical problem that needs to be solved in the field.

[0007] Therefore, there is an urgent need in the field for an innovative technical solution to break the technical shackles of "low concentration" and "high performance" being incompatible, and under the premise of not relying on traditional compensatory strategies, to prepare high-performance oyster-soybean composite protein gels under the simplified conditions of low total protein concentration (<5%), without exogenous coagulants, and without the need for precise pH control, through a completely new technical path, to meet the market demand for diversified healthy foods, and to open up a new path for the high-value processing of oysters and soybeans. SUMMARY

[0008] The purpose of the present application is to provide an oyster-soybean composite protein gel based on low-temperature synergistic construction and its preparation method and application, so as to solve the problems existing in the prior art. The present application is based on a specific protein ratio, and constructs a gel system with a gel strength comparable to that of pure oyster protein gel, a controllable texture, and a dual-protein nutritional advantage by compounding oyster protein and soybean protein isolate under the condition of no coagulant. The present application aims to meet the market demand for diversified texture and balanced nutrition, and to provide an innovative way for promoting the high-value utilization of oysters and soybeans.

[0009] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0010] In a first aspect, the present application provides an oyster-soybean composite protein gel based on low-temperature synergistic construction, which is formed by oyster protein and soybean protein isolate through preliminary construction of gel structure and heat induction treatment.

[0011] Preferably, the volume ratio of the oyster protein and the soybean protein isolate is 90-99:1-10.

[0012] Preferably, the method for preliminary construction of gel structure is to perform preliminary construction of gel structure at 25-40℃, and the treatment time is ≥20h.

[0013] Preferably, the condition for heat induction treatment is 80-90℃ water bath for 20-30min.

[0014] In a second aspect, the present application also provides a preparation method of the oyster-soybean composite protein gel, comprising the following steps:

[0015] Formulating an oyster protein suspension;

[0016] Formulating a soybean protein isolate suspension;

[0017] Mixing the oyster protein suspension and the soybean protein isolate suspension, stirring, standing, preliminary construction of gel structure, heat induction treatment, and then storing at low temperature after the end to form the oyster-soybean composite protein gel.

[0018] Preferably, the concentration of the oyster protein suspension is 1.5%-2.0%.

[0019] Preferably, the concentration of the soybean protein isolate suspension is 1.5%-2.0%.

[0020] Preferably, the condition for low-temperature storage after heat induction treatment is 4-6℃ storage for 12-24h.

[0021] In a third aspect, the present application also provides an application of the oyster-soybean composite protein gel in preparing a protein gel food.

[0022] In a fourth aspect, the present application also provides a protein gel food, comprising the oyster-soy protein composite gel.

[0023] The core inventive concept of the present application is that it is first discovered that by precisely controlling the mass proportion of soy protein isolate in the total protein in the range of 1% to 10% and using a specific low-temperature synergistic construction process (i.e. a three-stage procedure combining low-temperature standing stability, medium-temperature construction and high-temperature heat-induced solidification), a composite protein gel with gel strength, water holding capacity and microstructure comparable to pure oyster protein gel can be successfully prepared under harsh conditions of no pH adjustment and without any exogenous coagulant at a low total protein concentration (0.5% to 4%). The breakthrough of this technical path has overturned the traditional industry recognition that high-performance composite gel can only be achieved by adding additives at low concentration. Based on the above concept, the present application aims to break the traditional technical shackles of "high concentration, enzyme addition, pH adjustment", and its specific purposes include: 1. Process innovation: providing a clean and simplified preparation path that does not rely on complex pH adjustment steps and exogenous additives; 2. Performance breakthrough: effectively overcoming the core technical problem of gel performance degradation caused by the inherent incompatibility of animal and plant proteins at low protein concentration.

[0024] The core of the method of the present application is that, rather than simply mixing two proteins, through the three indispensable physical procedures of "low-temperature stability, medium-temperature construction and high-temperature solidification", and in synergism with the specific critical range of 1% to 10% of soy protein isolate in the total protein, a unique double-protein composite gel with performance comparable to pure oyster protein gel is successfully constructed at a low total protein concentration (0.5% to 4%) under a clean label process without using any chemical additives, enzymes or pH adjusters. Among them, the protein ratio of 1% to 10% is a critical range for effective compounding, and exceeding this range will result in phase separation and significant deterioration of performance.

[0025] The present application discloses the following technical effects:

[0026] The present application uses oyster protein obtained by alkali dissolution and acid precipitation method and commercial soy protein isolate as raw materials, and through a low-temperature synergistic construction process with a specific ratio, the process includes three key stages of low-temperature stability, medium-temperature construction and heat-induced solidification, successfully constructing a rigid and stable double-protein composite gel at a low protein concentration without adding coagulants. The gel has excellent gel strength, smooth texture and long-term storage stability. The key of the present application is that by precisely regulating the protein ratio, the phase separation behavior of the gel can be directed regulated, thereby realizing flexible customization of the appearance and texture of the product. The entire preparation process does not use any organic chemical reagents and food additives, ensuring the cleanliness and safety of the formula, and the process is simple, showing great application value and industrialization prospect.

[0027] Compared with the prior art, the present application has the following remarkable advantages: 1. Process simplification: the whole process does not need to adjust pH, avoiding the problems of process complexity, cost increase and product flavor damage caused by adding acid and alkali reagents;

[0028] 2. Mildness and economy of conditions: high-strength gel can be achieved at low total protein concentration, greatly reducing the cost of raw materials;

[0029] 3. Natural and high-quality product: under the clean formula without exogenous coagulant and pH adjustment, the prepared composite gel can still maintain the gel strength, water retention and smooth texture comparable to pure oyster protein gel. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0031] Figure 1 Figure 1-4 and Comparative Example 1-4 are macroscopic appearance comparison charts of oyster protein-soybean protein isolate composite gels in Examples 1-4 and Comparative Example 1-4;

[0032] Figure 2 Figure 1-4 and Comparative Example 1-3 are gel strength comparison charts of oyster protein-soybean protein isolate composite gels in Examples 1-4 and Comparative Example 1-3; wherein different letters in the figure represent significant differences (P<0.05);

[0033] Figure 3 Figure 1-4 and Comparative Example 1-3 are hardness comparison charts of oyster protein-soybean protein isolate composite gels in Examples 1-4 and Comparative Example 1-3; wherein different letters in the figure represent significant differences (P<0.05);

[0034] Figure 4 Figure 1-4 and Comparative Example 1-3 are water retention comparison charts of oyster protein-soybean protein isolate composite gels in Examples 1-4 and Comparative Example 1-3; wherein different letters in the figure represent significant differences (P<0.05);

[0035] Figure 5 Figure 3-4 and Comparative Example 1-3 are scanning electron microscope comparison charts of oyster protein-soybean protein isolate composite gels in Examples 3-4 and Comparative Example 1-3; wherein the upper chart is a chart magnified by 300 times, and the lower chart is a chart magnified by 500 times;

[0036] Figure 6The laser confocal microscope contrast images of oyster protein-soy protein isolate composite gel in Examples 3-4 and Comparative Examples 1-3 are shown below; wherein the upper side scale = 100 μm, and the lower side scale = 20 μm. DETAILED DESCRIPTION

[0037] The detailed description set forth below of various illustrative embodiments explains the principles of the application and the best mode presently contemplated by the inventors for carrying out the application. It will be understood that the detailed description is merely meant to illustrate certain aspects of the application, and is not meant to limit the scope of the application.

[0038] It is to be understood that the terminology used in the disclosure of the application is for the purpose of describing the particular embodiments only and is not intended to be limiting of the application. Additionally, for a range of values of a parameter, unless otherwise stated, each intervening value of the parameter, as well as each other stated value or intervening value in that stated range is expressly contemplated. In each stated range, any other stated values of that parameter and any other stated ranges of that parameter are also expressly contemplated. The inclusion of a stated value or range of values for a parameter is not a limitation on the same parameter or other parameters disclosed.

[0039] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All documents mentioned in this specification are incorporated herein by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict between the specification and any document incorporated herein by reference, the specification will control.

[0040] Various modifications and changes can be made to the specific embodiments of the application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0041] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional, unrecited elements or method steps.

[0042] The oyster protein preparation method in the examples and comparative examples of the present application refers to the method disclosed in the patent document with the application number CN202510536474.6, and the soy protein isolate is commercially available.

[0043] Example 1 - Preparation of an oyster-soy composite protein gel

[0044] This example demonstrates a specific embodiment at a total protein concentration of 1.5% (w / v), which is within the range of 0.5-4% required by the present application.

[0045] (1) The oyster protein was dispersed in deionized water to prepare a protein suspension with a mass fraction of 1.5%. The suspension was stirred at a speed of 500 rpm for 10 minutes using a magnetic stirrer, and then was left to stand at 4°C for 12 hours to ensure that the protein was fully hydrated.

[0046] (2) A (natural) soybean protein isolate suspension with a mass fraction of 1.5% was prepared, and was also left to stand at 4°C for 12 hours to hydrate.

[0047] (3) The hydrated oyster protein solution and the soybean protein isolate solution were mixed in a volume ratio of 99:1 (under this ratio, the mass fraction of the soybean protein isolate in the total protein was about 1%). The mixture was stirred at a speed of 500 rpm for 5 minutes using a magnetic stirrer in an ice bath at 2-10°C, and then was left to stand at 4°C for 1 hour to stabilize the system.

[0048] (4) Preliminary construction of the gel structure: The uniformly mixed protein suspension was dispensed into a mold and sealed, and was left to stand at 25°C for no less than 20 hours.

[0049] (5) Heat-induced treatment: The sample after standing was heated in a water bath at 80°C for 20 minutes for heat-induced gelation to solidify the network structure, and then was cooled with flowing cold water and stored at 4°C for 12 hours.

[0050] (6) After the prepared composite gel was returned to room temperature, an oyster-soybean composite protein gel was obtained, and the performance was characterized.

[0051] Example 2: A method for preparing an oyster-soybean composite protein gel

[0052] The steps were completely the same as in Example 1, except that in step (3), the volume mixing ratio of the oyster protein solution and the soybean protein isolate solution was 95:5 (under this ratio, the mass fraction of the soybean protein isolate in the total protein was about 5%). After the prepared gel was returned to room temperature, the performance was characterized.

[0053] Example 3: A method for preparing an oyster-soybean composite protein gel

[0054] The steps were completely the same as in Example 1, except that in step (3), the volume mixing ratio of the oyster protein solution and the soybean protein isolate solution was 90:10 (under this ratio, the mass fraction of the soybean protein isolate in the total protein was about 10%). After the prepared gel was returned to room temperature, the performance was characterized.

[0055] Example 4: A method for preparing an oyster-soybean composite protein gel

[0056] The steps are exactly the same as Example 3, the only difference is that in step (2), the protein suspension is prepared using preheated soy protein isolate. After the prepared gel is restored to room temperature, the performance is characterized.

[0057] Comparative Example 1

[0058] To provide a performance comparison benchmark, this example prepares a pure oyster protein gel. Referring to the preferred method disclosed in application number CN202510536474.6: oyster protein is prepared into a 1.5% suspension, after hydration, pre-coagulation and heat induction, a pure oyster protein gel is obtained. This gel will serve as a performance reference benchmark for subsequent examples and comparative examples.

[0059] Comparative Example 2

[0060] The difference between this comparative example and Example 3 is that in step (3), the volume mixing ratio of oyster protein solution to soy protein isolate solution is 80:20 (under this ratio, the mass ratio of soy protein isolate in the total protein is about 20%), and the rest of the steps and conditions are the same as Example 3.

[0061] Comparative Example 3

[0062] The difference between this comparative example and Example 3 is that in step (3), the volume mixing ratio of oyster protein solution to soy protein isolate solution is 70:30 (under this ratio, the mass ratio of soy protein isolate in the total protein is about 30%), and the rest of the steps and conditions are the same as Example 3.

[0063] Comparative Example 4

[0064] This comparative example aims to illustrate the gel-forming performance of single soy protein isolate in this system. The difference between its preparation method and Comparative Example 1 is that no oyster protein is added, only soy protein isolate is used to prepare a suspension with a mass fraction of 1.5%, and an attempt is made to form a gel according to the same steps.

[0065] The gel materials prepared in Examples 1-4 and Comparative Examples 1-4 are comprehensively characterized and analyzed, and the analysis results are as follows:

[0066] 1. Appearance analysis

[0067] Figure 1 The appearance comparison chart of the composite protein gel in Examples 1-4 and Comparative Examples 1-4.

[0068] The results show that the appearance of the composite gels with the addition of natural soybean protein isolate (Examples 1-3) or 10% pre-heat treated soybean protein isolate (Example 4) is comparable to that of the pure oyster protein gel (Comparative Example 1), both showing a stable and smooth state, proving the feasibility of the technical solution of the present application and the inclusiveness of the heat treatment of soybean protein isolate. When the proportion of soybean protein isolate is 20% and 30% (Comparative Examples 2-3), the composite gel shows a delamination phenomenon, and the edge appears transparent, indicating that the composite protein gel becomes unstable and the appearance quality deteriorates. The results directly reveal the incompatibility between proteins beyond a certain proportion. In addition, the results of Comparative Example 4 show that under the same process conditions, a single soybean protein isolate solution cannot form a self-supporting gel and always remains in a liquid state. This indicates that in the low-temperature co-construction process of the present application, oyster protein is an indispensable gel matrix, while soybean protein can only be effectively accommodated as a functional auxiliary material at a specific proportion (≤10%), indicating the necessity of a double-protein composite system.

[0069] 2. Gel strength analysis

[0070] The gel strength of the composite gel was determined using a texture analyzer. The test parameters were: trigger force 5g, test speed 2.0mm / s, and compression distance 5mm.

[0071] Figure 2 A comparison chart of the gel strength of the composite protein gel in Examples 1-4 and Comparative Examples 1-3.

[0072] The results show that when the addition proportion of soybean protein isolate is within the range of 1% to 10% as described in the present application (Examples 1-3), the strength of the composite gel can be maintained at about 200g, which is not significantly different from that of the pure oyster protein gel (Comparative Example 1). This result shows that within this specific proportion range, the composite system successfully forms a gel strength comparable to that of the high-strength pure oyster protein gel. This proves that the present application successfully reduces the total protein concentration of high-performance gels from >10% in traditional technology to 0.5%-4%, achieving high-strength construction at very low concentrations and breaking through the raw material cost bottleneck. In addition, even with pre-heat treated soybean protein isolate (Example 4), the high gel strength can still be maintained at an addition proportion of 10%, which shows that the present application is not sensitive to the heat treatment of soybean protein isolate and has good industrial adaptability. However, when the addition proportion increases to 30% (Comparative Example 3), the gel strength decreases significantly to 155.02g, proving that "1%-10%" is not an arbitrary proportion range, but a precise critical range that achieves the synergistic effect of the two proteins and avoids phase separation, which clearly defines the effective ratio boundary for achieving high-strength composite protein gel.

[0073] 3. Hardness analysis

[0074] The hardness of the composite gel was measured using a full texture profile mode with the following parameters: compression ratio 30%, test speed 2.0 mm / s.

[0075] Figure 3 A comparison chart of the hardness of the composite protein gels in Examples 1-4 and Comparative Examples 1-3 is shown in FIG. 1. The results show that the hardness test results further verify the effectiveness of the present application: when the addition ratio of soybean protein isolate is 1% to 10% (Examples 1-3), the hardness of the composite gel is maintained at a high level of 131.72 g or more, which is comparable to Comparative Example 1. In addition, Example 4, which adds 10% of pre-heated soybean protein isolate, also achieves this hardness level. This shows that the composite gel also has excellent texture characteristics under the ratio protected by the present application. When the addition ratio reaches 20% (Comparative Example 2) and above, the hardness decreases significantly, again confirming that 10% is the upper limit for achieving high hardness in the present application.

[0076] 4. Water retention analysis

[0077] A certain mass (W0) of gel sample was accurately weighed and centrifuged at 3000 r / min for 10 min. After removal, the surface water was wiped off and weighed again (W1). The water holding capacity (WHC) was calculated according to the following formula: WHC (%) = (W1 / W0) x 100%.

[0078] Figure 4 A comparison chart of the water retention of the composite protein gels in Examples 1-4 and Comparative Examples 1-3 is shown in FIG. 2. The results are highly consistent with the strength and hardness results: at an addition ratio of 1% to 10% (Examples 1-3), the water retention of the composite gel is higher than 68.91%, which is no different from the pure oyster protein gel (Comparative Example 1). In addition, even if pre-heated soybean protein isolate is used (Example 4), there is no negative impact on water retention. This proves that the gel network structure formed within this range also has excellent water holding capacity. However, when the proportion of soybean protein isolate exceeds 10% (Comparative Examples 2-3), the water retention decreases significantly, indicating that the gel network structure has been destroyed, which is in sharp contrast to the technical effect of the present application. This further shows that exceeding the critical ratio not only leads to macroscopic phase separation, but also fundamentally deteriorates the microscopic network structure.

[0079] 5. Scanning electron microscope image

[0080] The microstructure of the composite gel was observed using a scanning electron microscope. The sample was fixed with 2.5% glutaraldehyde solution, then dehydrated with ethanol gradient, freeze-dried and gold-coated, and then observed and photographed under the electron microscope.

[0081] Figure 5The scanning electron microscope contrast images of the composite protein gels in Examples 3-4 and Comparative Examples 1-3 are shown. The test results show that, whether 10% natural soybean protein isolate (Example 3) or 10% preheated soybean protein isolate (Example 4) is added, the microstructure of the composite gel is similar to that of the pure oyster protein gel (Comparative Example 1), and both present a continuous and uniform three-dimensional network structure. This result explains the reason for the high gel strength exhibited in the macroscopic level. More importantly, the results of Example 4 show that, even if the soybean protein isolate is preheated, its dispersion state and network structure remain excellent, which indicates that the core process of the present application is not sensitive to the heat treatment of the raw material, showing strong industrial adaptability and universality. In contrast, the microscopic images of Comparative Examples 2-3 clearly show that when the proportion of soybean protein isolate exceeds 10%, the gel microstructure becomes disordered, rough and uneven, which directly explains the fundamental reason for the deterioration of its macroscopic performance.

[0082] 6. Laser confocal microscope images

[0083] The microstructure of the composite gel was observed by laser confocal microscope. After being dyed with rhodamine B, the sample was placed under the laser confocal microscope, observed under 561 nm excitation light and the image was collected.

[0084] Figure 6 The laser confocal microscope contrast images of the composite protein gels in Examples 3-4 and Comparative Examples 1-3 are shown. The test results show that, at a proportion of 10% soybean protein isolate, the composite protein forms a uniform and continuous network structure. In Example 3 (natural soybean protein isolate), the soybean protein isolate is uniformly dispersed in the oyster protein network in the form of small particles. However, in Example 4, although the soybean protein isolate is preheated, its distribution in the gel network is similar to that in Example 3, and no obvious large-size aggregation occurs. This proves that, under the specific proportion and process of the present application, the gel behavior of the composite protein is not sensitive to the preheating of the soybean protein isolate, further confirming the universality and stability of the technical solution of the present application. On the contrary, in Comparative Example 2 (20% soybean protein isolate added) and Comparative Example 3 (30% soybean protein isolate added), the soybean protein isolate aggregates to form large aggregates, thereby seriously damaging the uniformity and continuity of the composite gel network.

[0085] Based on the analysis of all the above data and compared with the prior art which relies on "high concentration, enzyme addition, pH adjustment", the present application has made an unexpected technical progress: under the conditions of lower total protein concentration (0.5%-4% vs >10%) and simpler process (no pH adjustment, no exogenous coagulant), a product with gel strength, water holding capacity and microstructure comparable to pure oyster protein gel or high-concentration traditional composite gel has been successfully prepared.

[0086] The present application successfully breaks the technical prejudice that "under such a low protein concentration, high-performance animal-plant composite protein gel cannot be constructed without relying on pH adjustment or exogenous cross-linking agent" by discovering the specific protein ratio critical range of "1%-10%" and cooperating with the temperature program of "low-temperature stabilization, medium-temperature construction, and high-temperature solidification". This not only realizes the construction of high performance under low concentration, but also establishes a new and clean-label composite protein gel preparation mode.

[0087] The above examples and comparative examples specifically show the implementation effect under the preferred condition of a total protein concentration of 1.5%, and the results fully support the universal feasibility of the present application in the concentration range of 0.5%-4%.

[0088] The above examples only describe the preferred mode of the present application and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. An oyster-soybean composite protein gel based on low-temperature synergistic construction, characterized in that, The composite gel is formed by initially constructing a gel structure from oyster protein and soy protein isolate, followed by heat-induced treatment.

2. The oyster-soybean composite protein gel according to claim 1, characterized in that, The volume ratio of oyster protein to soy protein isolate is 90-99:1-10.

3. The oyster-soybean composite protein gel according to claim 1, characterized in that, The method for initially constructing the gel structure is as follows: the gel structure is initially constructed at 25-40℃ for a processing time of ≥20h.

4. The oyster-soybean composite protein gel according to claim 1, characterized in that, The conditions for the heat-induced treatment are: 80-90℃ water bath for 20-30 minutes.

5. A method for preparing oyster-soybean composite protein gel according to any one of claims 1-4, characterized in that, Includes the following steps: Prepare oyster protein suspension; Prepare a soy protein isolate suspension; Oyster protein suspension and soy protein isolate suspension were mixed, stirred, and allowed to stand. After preliminary gel structure construction, thermal induction treatment was performed. After completion, the mixture was stored at low temperature to form the oyster-soybean composite protein gel.

6. The preparation method according to claim 5, characterized in that, The concentration of the oyster protein suspension is 1.5%-2.0%.

7. The preparation method according to claim 5, characterized in that, The concentration of the soy protein isolate suspension is 1.5%-2.0%.

8. The preparation method according to claim 5, characterized in that, The conditions for low-temperature storage after heat-induced treatment are 4-6℃ for 12-24 hours.

9. The application of the oyster-soybean composite protein gel according to any one of claims 1-4 in the preparation of protein gel foods.

10. A protein gel food product, characterized in that, Includes the oyster-soybean composite protein gel according to any one of claims 1-4.

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