Improvement of network structure compactness of brine tofu by three different hydrocolloids

Abstract

The application discloses a preparation method of three different sources of hydrophilic colloid for improving network structure compactness of brine bean curd, and belongs to the technical field of bean product processing. On the basis of a traditional brine bean curd processing technology, seaweed-derived carrageenan, animal-derived chitosan and microbial-derived dextran are synchronously added into soybean milk at a final concentration of 0.4% in the cooling stage of soybean milk boiling. By utilizing the differentiated synergistic mechanism of ion cross-linking network increase of carrageenan, hydrogen bond compact bonding of chitosan and pore filling repair of dextran, the soybean protein gel micro network is reconstructed, and the technical problems of loose network, large pore, poor compactness and easy breaking and water separation of traditional brine bean curd are solved. The application has the advantages of simple process, safety compliance and large-scale production. The obtained brine bean curd has continuous and compact protein network and uniform pores, and the water retention and structural stability are significantly improved, and the product quality is excellent.

Description

Technical Field

[0001] This invention belongs to the field of traditional deep processing of soy products and modification of food colloids. Specifically, it relates to an industrial preparation technology that uses three different natural hydrophilic colloids—seaweed, animal, and microbial—at a uniform mass concentration of 0.4% to synergistically improve the microscopic protein network structure of brine tofu, enhance network density, and improve overall structural stability. Background Technology

[0002] Brine-cured tofu is a traditional plant-based protein gel food made from soybeans and using brine as a coagulant. It has the advantages of pure soybean aroma, chewy texture, and wide appeal. Traditional brine relies on magnesium and calcium cations to induce the denaturation and aggregation of soybean 7S and 11S globulins, but the natural soybean protein gel itself has limited cross-linking ability, resulting in microstructural defects such as loose protein network, large and uneven pores, many local voids, and poor network continuity after curing.

[0003] The aforementioned structural defects directly result in high water separation rate, poor water retention, and soft texture of the finished brine tofu. It is extremely easy to break and collapse during cutting, transportation, and storage, resulting in a short shelf life and making it difficult to meet the quality requirements of pre-made soy products and deep-processed soy products.

[0004] Existing tofu improvement technologies have significant shortcomings: they mostly use single colloids or arbitrarily proportioned compound colloids for modification, resulting in a single mechanism of action and poor synergy. They can only slightly improve gel strength and cannot fundamentally refine the pores and create a dense network structure. At the same time, existing technologies do not differentiate between the sources and complementary functions of carrageenan, chitosan, and dextran, nor have they established a standardized process for achieving an optimal modification concentration of 0.4% for all three colloids. This leads to problems such as unscientific proportions, unstable modification effects, and easy agglomeration and stratification.

[0005] Carrageenan, chitosan, and dextran have different sources and complementary, non-antagonistic mechanisms of action: carrageenan can undergo ionic cross-linking to strengthen the gel backbone, chitosan can form high-density hydrogen bonds to compress the intermolecular distances between protein molecules, and dextran can fill network micropores and repair structural defects. Currently, there is no complete process for using a 0.4% equal concentration of these three compounds to improve the network density of brine tofu. Therefore, this invention was developed to overcome the bottlenecks in existing technologies. Summary of the Invention Purpose of the invention

[0006] This invention aims to overcome the technical defects of traditional brine tofu, such as loose protein network, insufficient density, poor structural stability, and easy water release and breakage. It provides a method for preparing brine tofu by synergistic modification of three heterogeneous hydrophilic colloids. By fixing the addition concentration to 0.4%, the multiple synergistic modification effects of the three types of colloids are brought into play, and the micro-gel network of tofu is systematically optimized, thereby improving the density, uniformity and stability of the network. Technical solution

[0007] To achieve the above objectives, the present invention provides a method for preparing brine-cured tofu with improved network structure density, comprising the following steps: 1. Soybean pretreatment: Select high-quality dried soybeans that are free from mold and insect infestation, soak them in room temperature water for 8-10 hours until the soybeans have no hard core and are fully hydrated, then drain and set aside.

[0008] 2. Grinding and filtration: Add purified water at a ratio of 1:8 to 1:10 for grinding, and filter with a 100-mesh filter to remove residue, resulting in a fine and uniform pure soy milk.

[0009] 3. High-temperature cooking: Heat the soy milk to 95-100℃ and cook at a constant temperature for 8-12 minutes to remove the beany smell and promote the moderate and complete denaturation of soy protein, providing a basis for gel cross-linking.

[0010] 4. Precise compounding and modification of colloids: After the soy milk is cooked, the temperature is lowered to 75-80℃, and carrageenan, chitosan, and dextran, each with a final concentration of 0.4%, are added to the soy milk simultaneously; the mixture is stirred at a uniform speed for 3-5 minutes to ensure that the three types of colloids are evenly dispersed and completely blended, without clumping or layering.

[0011] 5. Brine coagulation: Cool to 70-75℃, add edible brine at 4% of the weight of soy milk, stir gently, seal and let stand for 20-30 minutes to coagulate, forming a protein-colloidal complex gel system.

[0012] 6. Gradient pressing molding: The tofu pudding is placed into a molding mold and pressed under gradient pressure: low pressure for pre-shaping and high pressure for solidifying the structure, which fully removes free water and solidifies a dense and continuous protein gel network. The finished product is then demolded. Core modification mechanism

[0013] The core innovation of this invention lies in the synergistic effect mechanism of three heterologous colloids at equal concentrations of 0.4%: 1. Seaweed-derived carrageenan: It contains anionic groups, which can ion bridge with brine metal cations, significantly increasing the number of cross-linking points of protein molecules, strengthening the gel network backbone, and improving the problem of network looseness; 2. Animal-derived chitosan: Rich in hydroxyl and active amino groups, it can form a large number of hydrogen bonds with soybean protein peptide chains, bringing protein molecules closer together, compressing gel pore size, and significantly improving the overall density of the network; 3. Microbial dextran: It has excellent water solubility and dispersibility, and can accurately fill the tiny gaps and structural defects caused by protein cross-linking, eliminate local voids, and make the network pores uniformly distributed and the structure continuous and regular.

[0014] The three components showed optimal compatibility and no functional antagonism at a concentration of 0.4%. This approach reconstructed the microstructure of tofu from three dimensions: skeleton enhancement, spacing compression, and pore repair, thereby achieving a systematic improvement in density. Beneficial effects

[0015] 1. Significantly optimized microstructure: Compared with traditional processes, this invention can greatly increase the cross-linking density of the protein network, refine the pores, eliminate large voids, and make the network continuous, uniform, and dense, thus thoroughly improving the loose structure defects of traditional tofu.

[0016] 2. High stability of finished product quality: The dense and stable composite network greatly improves the water retention, elasticity and resistance to breakage of tofu, with low water separation rate and less tendency to break and collapse, making it suitable for transportation, storage and deep processing scenarios.

[0017] 3. Controllable process standards: The three colloids are mixed at a fixed concentration of 0.4%, the parameters are standardized, the replicability is strong, the batch quality difference is small, and the problem of unstable effect of traditional compounding process is avoided.

[0018] 4. Safe and Authentic Flavor: All colloids used are natural food-grade raw materials, with compliant and safe addition amounts. They do not mask the original flavor of soybeans and retain the pure flavor of traditional brine tofu.

[0019] 5. Easy to promote industrialization: No complicated equipment is required. The colloid addition process is optimized based on traditional technology. It is easy to operate, cost controllable, and suitable for large-scale production in various soy product processing plants. Detailed Implementation Example 1

[0020] 1. Soak high-quality soybeans at room temperature for 9 hours, drain the water; grind them into a paste at a ratio of 1:9 (soybean paste to water), and filter through a 100-mesh screen to obtain pure soy milk.

[0021] 2. Boil the soy milk at a constant temperature of 98℃ for 10 minutes to fully denature and remove any fishy smell.

[0022] 3. Cool to 78 ℃, add 0.4% carrageenan, 0.4% chitosan and 0.4% dextran to a final concentration, and stir at 400 r / min for 4 min until completely homogeneous.

[0023] 4. Cool down to 72 ℃, add 3% of the weight of soy milk in brine, and let stand to coagulate for 25 minutes.

[0024] 5. Gradient pressing: Hold pressure at 0.03 MPa for 10 min, then at 0.07 MPa for 20 min, and demold to obtain the finished brine tofu.

[0025] The tofu produced in this embodiment has a dense and complete microstructure with uniform and fine pores. Its water retention and structural toughness are significantly better than traditional tofu, and it does not have problems such as looseness, voids, water separation, or breakage. Comparative Example 1 (Blank control group, no colloid added)

[0026] Using the exact same process, without adding any hydrophilic colloids, the finished protein network is loose and disordered, with large and uneven pores, a soft structure, severe water separation, and is extremely fragile with very poor density. Comparative Example 2 (single 0.4% carrageenan group)

[0027] With only 0.4% carrageenan added, and the rest of the process remaining the same, the gel strength was only slightly improved, the pore refinement and defect repair effects were poor, the network uniformity was insufficient, and the effect on improving density was limited. Comparative Example 3 (Non-equivalent concentration compound group)

[0028] A mixture of 0.3% carrageenan, 0.35% chitosan, and 0.45% dextran in non-equilibrium concentrations was used. The colloid synergistic matching was unbalanced, resulting in localized aggregation and phase separation, uneven network density, and poor structural stability. The improvement effect was significantly inferior to the solution of this invention.

[0029] The comparative results demonstrate that the 0.4% equal concentration of three heterogeneous colloid compounding scheme of the present invention has the best synergistic modification effect and is the optimal technical solution for improving the network density of brine tofu. Attached Figure Description

[0030] Figure 1 Animation diagram of protein network in tofu brine, including blank control group, carrageenan, chitosan and dextran; Figure 2 This is the overall process flow diagram of the present invention; Figure 3 The effect of adding different hydrocolloids on the texture of brine tofu; Figure 4 The effects of adding different hydrocolloids on the water content and water retention of brine tofu; Figure 5 SEM microstructure of protein networks in tofu brine from blank control group, carrageenan, chitosan, and dextran brine; Figure 6 Secondary structure analysis of blank control group, carrageenan, chitosan and dextran brine tofu; Figure 7 Sensory evaluation of blank control group, carrageenan, chitosan and dextran brine tofu; Figure 8 Comparison of blank control group, carrageenan, chitosan and dextran brine tofu: physical comparison images. Patent protection scope description

[0031] The core protected aspect of this invention is the molecular mechanism by which three colloids from different sources differentially regulate the density of the protein network in brine tofu, under a fixed hydrophilic colloid addition amount of 0.4%, and the corresponding standardized preparation process. Any minor adjustments to the conventional process made by those skilled in the art without changing the fixed 0.4% addition amount and the core process will fall within the scope of protection of this invention.

Claims

1. A method for preparing brine-cured tofu with improved network structure density, comprising soybean pretreatment, grinding and filtering, high-temperature boiling, coagulation with brine, and pressing and molding steps, characterized in that: In the soy milk system during the cooling stage after boiling, three food-grade hydrocolloids from different sources were added simultaneously: carrageenan, chitosan, and dextran. The final mass concentration of each of the three hydrocolloids in the soy milk was 0.4%. The carrageenan was an algae-derived colloid, the chitosan was an animal-derived colloid, and the dextran was a microbial-derived colloid. Through the synergistic effect of the differential action mechanism of the three types of colloids, the density and structural uniformity of the brine tofu protein gel network were improved.

2. The preparation method for improving the density of the network structure of brine tofu according to claim 1, characterized in that: The hydrophilic colloids are all food-grade powders of 80 mesh or above, which comply with the GB 2760 standard for the use of food additives, and are free from lumps, impurities, and odors.

3. The preparation method for improving the density of the network structure of brine tofu according to claim 1, characterized in that: The cooking process parameters are as follows: heat the soy milk to 95-100 ℃ and cook at a constant temperature for 8-12 minutes; add the colloid at 75-80 ℃, using a multi-stage feeding method, and stir at 300-500 r / min for 3-5 minutes until completely dispersed and uniform.

4. The preparation method for improving the density of the network structure of brine tofu according to claim 1, characterized in that: The coagulation process uses edible brine as a coagulant, with the amount of brine added being 4% of the mass of the soy milk. The coagulation temperature is 70–75 ℃, and the mixture is allowed to stand and coagulate for 20–30 minutes.

5. The preparation method for improving the density of the network structure of brine tofu according to claim 1, characterized in that: The compression molding process employs a gradient pressure stabilization process. First, it is pre-molded at a low pressure of 0.02–0.04 MPa for 8–12 min, and then solidified at a high pressure of 0.06–0.08 MPa for 18–22 min to solidify the dense protein network structure.

6. A highly dense brine tofu prepared by the method according to any one of claims 1-5, characterized in that: The protein gel network inside the tofu has a high cross-linking density, small and uniform pores, and no large voids or loose flocculent structure. Its network continuity, water retention and resistance to mechanical damage are significantly better than those of traditional brine tofu.

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