Method for improving vegetable protein gel strength by using shrimp shell protein

Abstract

The invention belongs to the field of deep processing of food protein, and particularly relates to a method for improving the gel strength of vegetable protein by using shrimp shell protein. The method comprises the following steps: dispersing vegetable protein in a shrimp shell protein aqueous solution with the mass concentration of 4-8%, adding TGase enzyme, uniformly stirring and mixing at room temperature, heating for enzyme deactivation, and cooling to obtain the high-gel-property protein gel. According to the invention, the shrimp shell protein, which is a food processing byproduct, is utilized to enhance the gel strength of the vegetable protein, and the prepared gel network is more compact and better in water binding capacity. The operation steps are simple and easy to implement, and the method has good application prospects in the food industry.

Description

Technical Field

[0001] This invention relates to the preparation of plant-animal protein composite gels, belonging to the field of food protein deep processing, and specifically to a method for improving the strength of plant protein gels using shrimp shell protein. Background Technology

[0002] Plant protein boasts advantages such as wide availability, green and low-carbon characteristics, and rich nutrition, making it an effective way to meet human protein needs, achieve protein balance, and promote sustainable agricultural development in the future. Plant-based protein foods are a category of foods made primarily from plant protein, combined with other ingredients such as starch, TGase enzymes, and animal protein through processing. These include gel-based foods such as tofu, plant-based meats, and meatballs, and have broad market prospects.

[0003] Gel properties are a key indicator determining the quality of plant-based products. Gels formed from pure plant proteins exhibit poor performance in terms of strength, microstructure, rheological properties, and textural properties, and require high protein concentrations (soy protein isolate concentrations typically need to be greater than 10-15%), making it difficult to meet consumer demands for the texture of gelled foods. Research indicates that blended gels of animal and plant proteins can not only improve the amino acid profile but also enhance gel properties. Aquatic products are widely considered a healthy and nutritious source of high-quality animal protein. However, shrimp processing easily generates large amounts of byproducts such as shrimp shells and heads, which are currently only used as feed or discarded, leading to resource waste and environmental pollution. Studies have found that shrimp shells and other processing byproducts are rich in high-quality animal protein (content can reach over 30%), containing a complete range of amino acids, but their applications are currently rarely reported.

[0004] Improving the gelling properties of proteins effectively is a pressing issue for the development of the plant-based gel food industry. Exploring the preparation of combined animal and plant protein gels aligns with my country's "Dual Protein Engineering" development strategy and is of great significance for the processing of plant-based protein foods and aquatic products, possessing extremely high commercial application value. Summary of the Invention

[0005] This invention aims to provide a method for improving the strength of plant protein gels using shrimp shell protein. This method improves the performance of plant-based gels through the cross-linking of animal and plant proteins, thereby meeting market demands and consumer expectations for gelled foods. The preparation method includes the following steps:

[0006] S1: Preparation of shrimp shell protein. Shrimp shells were dried, pulverized, dissolved in water, and the pH was adjusted to 10.0–11.0. The mixture was heated and stirred for 2–4 hours, centrifuged, and the pH of the supernatant was adjusted to 4.0–5.0. The protein precipitate was obtained by centrifugation, reconstituted, and then freeze-dried to obtain shrimp shell protein.

[0007] S2: Disperse the shrimp shell protein obtained in S1 in an aqueous solution and stir until homogeneous;

[0008] S3: Dissolve the soy protein isolate in the shrimp shell protein solution obtained in S2 and stir until homogeneous;

[0009] S4: Add TGase enzyme to the protein mixture obtained in S3, stir, and react at a constant temperature of 37-50℃ for 2-4 hours. Then, heat in a water bath to inactivate the enzyme and cool to obtain a protein gel.

[0010] Preferably, in step S1, the ratio of shrimp shells to aqueous solution is 1:10-20; the heating and stirring temperature is 60-80℃; and the pH value for reconstitution is 7.5-8.5.

[0011] Preferably, the mass concentration of shrimp shell protein in step S2 is 4-8%.

[0012] Preferably, the plant protein in step S3 is soy protein isolate or walnut protein isolate, with a mass concentration of 6-10%.

[0013] Preferably, in step S4, the amount of TGase enzyme added is in the range of 10–80 U / g; and the enzyme is inactivated by heating in a water bath at 70–80°C for more than 10 minutes.

[0014] The beneficial effects of this invention are as follows: by adding shrimp shell protein and TGase enzyme from aquatic product by-products as excipients, cross-linking occurs between the excipients and plant proteins, causing changes in the spatial structure of the protein molecules and reducing the gelling concentration of the plant proteins. This method has the advantages of simple steps and being environmentally friendly, and yields a protein gel with excellent gelling properties, including a dense network structure, high gel strength, and good water retention, showing broad application prospects in the plant-based gel food industry. Attached image description:

[0015] Figure 1 These are rheological properties of the protein gels in Examples 1-3 and Comparative Example 1 of the present invention;

[0016] Figure 2 These are scanning electron microscope images of the protein gels from Examples 1-3 and Comparative Example 1 of the present invention;

[0017] Figure 3 The diagram shows the water-holding capacity of the protein gels in Examples 1-3 and Comparative Example 1 of this invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0019] Unless otherwise specified, all techniques or conditions used in the examples were conventional methods or performed in accordance with techniques or conditions described in the literature in this field. All reagents and instruments used were readily available products from legitimate suppliers.

[0020] Example 1

[0021] This embodiment provides a method for improving the gel strength of walnut protein isolate using shrimp shell protein. The preparation method is as follows:

[0022] (1) Prepare shrimp shell protein: Dry and crush shrimp shells, dissolve them in water, adjust the pH value to 10.5, heat and stir for 2 hours, centrifuge, adjust the pH value of the supernatant to 4.0, centrifuge to obtain protein precipitate, reconstitute and freeze dry to obtain shrimp shell protein;

[0023] (2) Disperse the shrimp shell protein obtained above in an aqueous solution to prepare a shrimp shell protein solution with a concentration of 6%;

[0024] (3) Dissolve the walnut protein isolate in the shrimp shell protein solution obtained above, stir evenly, and the final total protein mass concentration is 20%;

[0025] (4) Add 50 U / g of TGase enzyme to the protein mixture obtained above, stir and react at 37°C for 2 hours, then heat in a water bath at 80°C for 10 minutes to inactivate the enzyme, and cool to obtain walnut protein isolate-shrimp shell protein composite gel, named protein gel A.

[0026] Example 2

[0027] This embodiment provides a method for improving the gel strength of soy protein isolate using shrimp shell protein. The preparation method is the same as in Example 1, thereby obtaining a soy protein isolate-shrimp shell protein composite gel, named protein gel B.

[0028] Example 3

[0029] This embodiment provides a method for improving the gel strength of soy protein isolate using shrimp shell protein. The only difference between this method and that of Example 1 is:

[0030] The concentration of the shrimp shell protein solution was set to 8%, thus obtaining a soy protein isolate-shrimp shell protein composite gel, named protein gel C.

[0031] Comparative Example 1

[0032] This comparative example provides a traditional method for preparing soy protein isolate gel, the preparation method is as follows:

[0033] (1) Disperse soy protein isolate in an aqueous solution at a mass concentration of 20% and stir until homogeneous;

[0034] (2) Add 50 U / g TGase enzyme to the soybean protein isolate solution obtained above, stir and react at 37°C for 2 hours, then heat in an 80°C water bath to inactivate the enzyme for 10 minutes, and cool to obtain soybean protein isolate-shrimp shell protein composite conventional gel, named protein gel D.

[0035] Experimental Example 1: Gel Rheological Properties Test

[0036] The prepared protein gels A, B, C, and D were tested for rheological properties using a rotational rheometer (DHR2, TA Instrument, USA). During the test, the protein hydrogels were placed on the parallel plates of the rheometer, and the distance between the parallel plates was set to 1 mm to fill the gap between the clamps. The tests were performed in two modes: frequency scanning and amplitude scanning. The specific parameters were as follows: (1) Frequency scanning range was set to 0.1-100 Hz, strain was fixed at 1%, and the temperature was maintained at 25 ℃ during the experiment. The storage modulus (G') and loss modulus (G”) of the protein hydrogels under different shear forces were measured. (2) Amplitude scanning oscillation strain range was set to 0.01–1000%, frequency was fixed at 1 Hz, and the temperature was maintained at 25 ℃ during the experiment. The storage modulus (G') and loss modulus (G”) of the protein hydrogels under different strains were measured.

[0037] The test results are as follows Figure 1 As shown, Figure 1 The diagram shows a comparison of the gel rheological properties of soy protein isolate gels prepared by traditional methods. The results show that, while maintaining a total protein concentration of 20%, the composite protein gels (protein gels A, B, and C) are stronger than the single plant protein gel (protein gel D) after the addition of shrimp shell protein. The composite protein gels exhibit stronger rheological properties, indicating that the addition of shrimp shell protein significantly improves the rheological properties of walnut protein isolate and soy protein isolate gels.

[0038] Experimental Example 2: Gel Scanning Electron Microscopy Test

[0039] The gel samples were cut into 4mm × 4mm × 1mm pieces and then freeze-dried. The dried gels were then fixed onto a sample stage and sputter-coated with gold. Finally, the microstructures of protein gels A, B, C, and D were observed and photographed using a scanning electron microscope.

[0040] The test results are as follows Figure 2 As shown, the network structure of protein gel D formed by plant protein alone has large pores and low cross-linking degree. However, with the addition of shrimp shell protein, the network structure of protein gels A to C is more compact. Especially when the shrimp shell protein content is 6%, soy protein isolate and shrimp shell protein show a phenomenon of tight protein cross-linking.

[0041] Experimental Example 3: Determination of water-holding capacity (WHC) of gel

[0042] Cut the gel into uniform rectangular blocks, each weighing approximately 3g. Place each block in a centrifuge tube and centrifuge at 10000 rpm and 4°C for 20 minutes. After blotting the water from the centrifuge tube and the surface of the gel with filter paper, weigh the gel and calculate the weight using the following formula:

[0043] WHC(%)=(W2-W0) / (W1-W0)×100%

[0044] In the formula, W2 is the weight (g) of the tube and gel after centrifugation and water absorption; W0 is the weight (g) of the centrifuge tube; and W1 is the weight (g) of the tube and gel before centrifugation.

[0045] The test results are as follows Figure 3 As shown, with the addition of shrimp shell protein, the composite gel has a stronger water-holding capacity. This may be because shrimp shell protein, as an animal protein, has a stronger hydrophilicity, thus enhancing the binding force between it and water molecules and forming a denser network structure, thereby achieving higher protein water-holding capacity.

[0046] Experimental Example 4: Determination of gel loss during cooking

[0047] Approximately 3g of sample was cut into standard cuboids (2×2×1cm), and then boiled in 800mL of water for 10 minutes. The cooking loss of the protein gel was calculated using the following formula:

[0048]

[0049] In the formula, W1 and W2 are the sample weights (g) before and after cooking, respectively.

[0050] The cooking losses of the protein gels prepared in Examples 1-3 and Comparative Example 1 are shown in Table 1 below. The results show that with the addition of shrimp shell protein, the cooking losses of protein gels A to C gradually decrease, while the cooking loss of gel D formed by plant protein alone is the greatest. This indicates that the addition of shrimp shell protein makes it less likely for water to precipitate out of the gel.

[0051] Table 1. Protein gel cooking loss

[0052]

[0053] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for improving the gel strength of plant protein using shrimp shell protein, characterized in that, Includes the following steps: S1: Preparation of shrimp shell protein. Shrimp shells were dried, pulverized, dissolved in water, and the pH was adjusted to 10.0–11.

0. The mixture was heated and stirred for 2–4 hours, centrifuged, and the pH of the supernatant was adjusted to 4.0–5.

0. The protein precipitate was obtained by centrifugation and freeze-dried to obtain shrimp shell protein. S2: Disperse the shrimp shell protein obtained in S1 in an aqueous solution and stir until homogeneous; S3: Dissolve the plant protein in the shrimp shell protein solution obtained in S2 and stir until homogeneous; S4: Add TGase enzyme to the protein mixture obtained in S3, stir, and react at a constant temperature of 37-50℃ for 2-4 hours. Then, heat in a water bath to inactivate the enzyme and cool to obtain a protein gel.

2. The method according to claim 1, characterized in that, In step S1, the ratio of shrimp shells to aqueous solution is 1:10-20; the heating and stirring temperature is 60-80℃; and the pH value for reconstitution is 7.5-8.

5.

3. The method according to claim 1, characterized in that, In step S2, the mass concentration of shrimp shell protein is 4-8%.

4. The method according to claim 1, characterized in that, In step S3, the plant protein includes common plant proteins such as soy protein isolate and walnut protein isolate, with a mass concentration of 6-15%.

5. The method according to claim 1, characterized in that, In step S4, the amount of TGase enzyme added ranges from 10 to 80 U / g; the enzyme is inactivated by heating in a water bath at 70 to 80°C for more than 10 minutes.

6. A plant protein gel prepared using shrimp shell protein, characterized in that, It is prepared by the method of any one of claims 1 to 5 for preparing plant protein gel.

7. The application of the plant protein gel as described in claim 6 in plant-based gel foods.

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