A soy protein isolate-serine protein emulsion gel and its application in lean-fat plant-based meat.

Abstract

This invention discloses a soy protein isolate-sericin emulsion gel and its application in plant-based meat with alternating lean and fatty layers, belonging to the field of plant-based food processing technology. The emulsion gel uses soy protein isolate, sericin, and vegetable oil as main raw materials. It is prepared through a process involving composite protein solution preparation, vegetable oil emulsification and homogenization, transglutaminase-catalyzed crosslinking, heat treatment, and cooling molding, resulting in stable fixation of vegetable oil in the form of oil droplets within the composite protein gel network. The introduction of sericin improves the uniformity of the single soy protein isolate gel network, enhances the system's water and oil holding capacity, thermal processing stability, and freeze-thaw stability, and reduces water and oil separation during processing and storage. The resulting emulsion gel can serve as the plant-based fatty phase, assembling in layers with a plant-based lean meat phase containing soy protein isolate. Through crosslinking and heat treatment, it can prepare plant-based meat with alternating red and white layers, clear layers, and a complete structure, suitable for the development of plant-based pork belly, bacon, and beef slices.

Description

Technical Field

[0001] This invention belongs to the field of plant-based food processing technology, specifically relating to a soy protein isolate-sericite emulsion gel and its preparation method, as well as the application of this emulsion gel as a plant-based fat mimic in lean-fat plant-based meat. This invention uses soy protein isolate, sericin, and vegetable oil as main raw materials, and prepares the emulsion gel through emulsification homogenization, enzymatic cross-linking, and heat treatment, fixing the vegetable oil in the form of oil droplets within a composite protein gel network. The resulting emulsion gel can serve as the plant-based fat phase, layered with the plant-based lean meat phase, to prepare plant-based meat products with a red-white appearance and a relatively complete layered structure. Background Technology

[0002] In recent years, with increasing consumer focus on healthy eating, resource utilization, and sustainable food, plant-based meat products have gradually become an important research direction in the food processing field. Plant-based meat typically uses soy protein, pea protein, wheat protein, vegetable oil, polysaccharides, and flavorings as raw materials, employing processes such as texturization, gelation, emulsification, and molding to simulate the color, texture, and edible quality of animal meat. Existing plant-based meat products are mostly in the form of minced meat, chunks, or fibrous materials, such as plant-based meat patties, meatballs, and chicken nuggets. These products primarily focus on simulating lean meat tissue, that is, constructing a certain fibrous texture and chewiness through plant proteins. However, for meat products with a distinct lean-fat structure, such as pork belly, bacon, and sliced ​​beef, simply simulating the lean portion is insufficient for product development needs. These products require not only a plant-based lean meat phase but also a plant-based fat phase with a white appearance, soft texture, and a certain degree of smoothness. Real animal fat in meat products not only acts as a filler but also affects the product's juiciness, flavor release, heat processing stability, and mouthfeel. In contrast, while vegetable oils can provide a certain degree of lubrication, their high fluidity makes them prone to migration, precipitation, or leakage during processing, storage, and reheating, making it difficult to form a stable fat layer structure. If only starch gels, polysaccharide gels, or ordinary protein gels are used to simulate fat, problems such as a hard texture, insufficient fat content, shrinkage or water separation after heating are likely to occur.

[0003] Emulsion gels are a type of structured system in which an oil phase is immobilized within a gel network. By pre-emulsifying and then gelling, vegetable oils can be dispersed into droplets and embedded and immobilized by a protein or polysaccharide network. Compared to directly adding liquid vegetable oils, emulsion gels offer better shape retention and processing stability; and compared to traditional solid fats, their oil composition can be controlled as needed. Therefore, emulsion gels are suitable for the development of plant-based fat mimics.

[0004] Soy protein isolate possesses good emulsifying, gelling, and nutritional value, making it a commonly used protein source in plant-based meat processing. Its molecules can adsorb at the oil-water interface, stabilizing oil droplets in the emulsion and forming a gel network under heating or enzymatic cross-linking conditions. However, single-soy protein isolate emulsion gels still have shortcomings in practical applications, such as insufficient gel network density, uneven oil droplet distribution, limited water and oil holding capacity, and susceptibility to water or oil separation or loose structure during cooking or freeze-thaw processes. Sericin, a natural protein produced during silk processing, contains numerous hydrophilic groups such as hydroxyl, carboxyl, and amino groups, exhibiting certain film-forming properties, hydrophilicity, and structural regulation. Introducing sericin into the soy protein isolate system may improve the complex protein network structure through hydrogen bonding, hydrophobic interactions, electrostatic interactions, and enzymatic cross-linking, thereby enhancing the stability of the emulsion gel.

[0005] Currently, the application of sericin in plant-based fat mimicry is relatively limited. In particular, there is no mature method for constructing a fat phase emulsion gel suitable for lean-fat layered plant-based meat by combining sericin with soy protein isolate. Therefore, developing a structurally stable, highly processable composite protein emulsion gel suitable for lean-fat layered plant-based meat has significant practical implications. Summary of the Invention

[0006] The purpose of this invention is to provide a soybean protein isolate-sericin emulsion gel and its preparation method, so as to improve the problems of insufficient water and oil holding capacity, poor thermal processing stability, easy structural damage after freeze-thaw, and difficulty in using it for layered plant-based meat.

[0007] Another objective of this invention is to provide the application of the above-mentioned emulsion gel in plant-based meat with alternating layers of fat and lean meat, so that the resulting plant-based meat product has a clearer fat-lean layer and a more complete tissue structure.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] Step 1: Preparation of soy protein isolate solution: Add soy protein isolate to deionized water, stir thoroughly to disperse and hydrate it evenly, and obtain soy protein isolate solution;

[0010] Step 2: Preparation of sericin solution: Add sericin to deionized water and stir until homogeneous to obtain sericin solution;

[0011] Step 3: Preparation of the composite protein solution: Add the sericin protein solution obtained in Step 2 to the soy protein isolate solution obtained in Step 1, mix and stir to obtain a soy protein isolate-sericin composite protein solution;

[0012] Step 4: Emulsion preparation. Vegetable oil is added to the composite protein solution obtained in Step 3, and the mixture is homogenized at high speed to obtain a soybean protein isolate-sericite emulsion.

[0013] Step 5: Preparation of emulsion gel: Add transglutaminase to the emulsion obtained in step 4, mix evenly, and then perform enzymatic cross-linking. After heat treatment and cooling, soybean protein isolate-sericite emulsion gel is obtained.

[0014] Preferably, in step one, the concentration of the soy protein isolate solution is 0.08~0.16 g / mL, more preferably 0.12 g / mL;

[0015] Preferably, in step two, the concentration of the sericin solution is 0.04~0.08 g / mL, more preferably 0.06 g / mL;

[0016] Preferably, in step three, the amount of sericin added is 5% to 25% of the total protein content of soy protein isolate and sericin;

[0017] More preferably, the amount of sericin added is 15% to 20%; more preferably, it is 20%.

[0018] Preferably, in step four, the vegetable oil is one or more of soybean oil, corn oil, rapeseed oil, sunflower seed oil, and peanut oil, and more preferably soybean oil;

[0019] Preferably, the volume ratio of the composite protein solution to the vegetable oil is 9:1;

[0020] Preferably, the high-speed homogenization process involves a rotation speed of 10,000 to 16,000 rpm and a homogenization time of 1 to 4 minutes; more preferably, it involves homogenization at 13,000 rpm for 2 minutes.

[0021] Preferably, the amount of transglutaminase added is 10-30 U / g protein, more preferably 20 U / g protein;

[0022] Preferably, the enzymatic cross-linking temperature is 45~60 ℃ and the cross-linking time is 40~90 min; more preferably, the cross-linking temperature is 55 ℃ for 60 min.

[0023] Preferably, the heat treatment temperature is 80~90 ℃ and the treatment time is 15~35 min; more preferably, the treatment is carried out at 85 ℃ for 25 min.

[0024] This invention also provides a method for preparing plant-based meat with alternating layers of fat and lean meat, comprising the following steps:

[0025] Step 1: The rehydrated soybean protein is de-spun and then mixed with protein gel, transglutaminase and red yeast rice pigment to obtain a red plant-based lean meat phase;

[0026] Step 2: Prepare the plant-based fat phase. Prepare soybean protein isolate-serine protein emulsion gel according to the above method and use it as the plant-based fat phase.

[0027] Step 3: Layered assembly. Place the plant-based lean meat phase and the plant-based fat phase into the mold in a certain proportion to form a red and white layered structure.

[0028] Step 4: Cross-linking and heat treatment molding. The molded sample is subjected to enzymatic cross-linking and heat treatment. After cooling and demolding, the lean and fatty plant-based meat is obtained.

[0029] Preferably, the mass ratio of plant-based lean meat phase to plant-based fat phase is 1:1;

[0030] Preferably, the crosslinking conditions are a water bath at 50-60 °C for 40-80 min, and more preferably a water bath at 55 °C for 1 h;

[0031] Preferably, the heat treatment conditions are 85~95 ℃ water bath for 10~25 min, and more preferably 90 ℃ water bath for 15 min.

[0032] Technical effects:

[0033] The present invention, by adopting the above-described technical solution, has the following beneficial effects:

[0034] 1. This invention constructs a composite protein system using soy protein isolate and sericin, and prepares an emulsion gel through emulsification, enzymatic cross-linking, and heat treatment, thereby immobilizing vegetable oil within the gel network. This structure reduces the migration of liquid vegetable oil during processing and storage, and facilitates the formation of a stable plant-based lipid phase.

[0035] 2. The addition of sericin improves the problem of uneven gel network in soy protein isolate emulsions. The hydrophilic groups in sericin molecules can interact with soy protein isolate and participate in gel network formation, making the oil droplet distribution and network structure of the emulsion gel more stable.

[0036] 3. The emulsion gel obtained by this invention has good water retention and thermal processing stability. An appropriate amount of sericin can enhance the system's water binding capacity, while the complex protein network can restrict the migration of oil droplets and water, thereby reducing water and oil separation during the heating process.

[0037] 4. The emulsion gel obtained by this invention has good freeze-thaw stability. During freezing and thawing, the complex protein network can reduce the damage to the gel structure caused by water migration and ice crystal formation, allowing the sample to maintain a relatively intact structure under refrigeration, freezing, and reheating conditions.

[0038] 5. This invention uses emulsion gel as the plant-based fat phase and assembles it in layers with the plant-based lean meat phase, which can prepare plant-based meat products with alternating red and white layers, clear layers, and relatively complete overall structure, providing a new technical solution for the development of plant-based pork belly, plant-based bacon, plant-based beef slices, and other products. Attached Figure Description

[0039] Figure 1 shows the Fourier transform infrared spectra of soybean protein isolate-sericite emulsion gels with different amounts of sericin added.

[0040] Figure 2 shows the microstructure of soybean protein isolate-serine emulsion gel with different amounts of sericin added;

[0041] Figure 3 shows the water-holding capacity of soy protein isolate-sericite emulsion gel with different amounts of sericin added;

[0042] Figure 4 shows the textural properties of soybean protein isolate-serine emulsion gel with different amounts of sericin added.

[0043] Figure 5 shows the cooking loss results of soy protein isolate-sericin emulsion gel under different amounts of sericin addition;

[0044] Figure 6 shows the freeze-thaw stability of soy protein isolate-sericin emulsion gel with different amounts of sericin added;

[0045] Figure 7 shows the appearance of the lean and fatty plant-based meat prepared using soy protein isolate-sericin emulsion gel. Detailed Implementation

[0046] The present invention will be further explained below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Percentages mentioned in the following embodiments are weight percentages. It should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the present invention, and these aspects of the invention can be implemented even without these specific details.

[0047] Example 1

[0048] This embodiment provides a method for preparing a soy protein isolate-sericite emulsion gel with a sericin content of 5%, comprising the following steps:

[0049] Step 1: Preparation of soy protein isolate solution: Weigh soy protein isolate, add it to deionized water, and stir until it is evenly dispersed to obtain a soy protein isolate solution with a concentration of 0.12 g / mL;

[0050] Step 2: Preparation of sericin solution: Weigh sericin, add it to deionized water, and stir until homogeneous to obtain a sericin solution with a concentration of 0.06 g / mL;

[0051] Step 3: Preparation of composite protein solution. Add the sericin protein solution obtained in step 2 to the soy protein isolate solution obtained in step 1, so that the sericin protein accounts for 5% of the total protein content. Continue stirring to obtain the composite protein solution.

[0052] Step 4: Emulsion preparation. Add soybean oil to the composite protein solution obtained in step 3, and control the volume ratio of composite protein solution to soybean oil to be 9:1. Homogenize at 13000 rpm for 2 min to obtain composite protein emulsion.

[0053] Step 5: Preparation of emulsion gel. Add 20 U / g protein transglutaminase to the emulsion obtained in step 4, crosslink at 55 ℃ for 60 min, then heat at 85 ℃ for 25 min, and after cooling, obtain an emulsion gel with 5% sericin added, named EG-SPS-5.

[0054] Example 2

[0055] This embodiment provides a method for preparing a soy protein isolate-sericite emulsion gel with a sericin content of 10%, comprising the following steps:

[0056] Step 1: Weigh out soy protein isolate and add it to deionized water, stir well to obtain a soy protein isolate solution with a concentration of 0.12 g / mL;

[0057] Step 2: Weigh the sericin and add it to deionized water, stir well to obtain a sericin solution with a concentration of 0.06 g / mL;

[0058] Step 3: Add the sericin solution to the soy protein isolate solution so that the sericin accounts for 10% of the total protein content, mix well, and obtain a composite protein solution;

[0059] Step 4: Mix the composite protein solution with soybean oil at a volume ratio of 9:1, and homogenize at 13000 rpm for 2 min to obtain a composite protein emulsion;

[0060] Step 5: Add 20 U / g protein transglutaminase to the composite protein emulsion, crosslink it at 55 ℃ for 60 min, then heat it at 85 ℃ for 25 min, and after cooling, obtain an emulsion gel with 10% sericin protein added, named EG-SPS-10.

[0061] Example 3

[0062] This embodiment provides a method for preparing a soy protein isolate-sericite emulsion gel with a sericin content of 15%, comprising the following steps:

[0063] Step 1: Prepare a soy protein isolate solution with a concentration of 0.12 g / mL;

[0064] Step 2: Prepare a sericin solution with a concentration of 0.06 g / mL;

[0065] Step 3: Add the sericin solution to the soy protein isolate solution so that the sericin accounts for 15% of the total protein content, stir well to obtain a composite protein solution;

[0066] Step 4: Add soybean oil to the composite protein solution, controlling the volume ratio of composite protein solution to soybean oil to be 9:1, and homogenize at 13000 rpm for 2 min to obtain composite protein emulsion;

[0067] Step 5: Add transglutaminase to the emulsion at a rate of 20 U / g protein, crosslink at 55 ℃ for 60 min, then heat at 85 ℃ for 25 min, and after cooling, obtain an emulsion gel with a sericin content of 15%, named EG-SPS-15.

[0068] Example 4

[0069] This embodiment provides a method for preparing a soy protein isolate-sericite emulsion gel with a sericin content of 20%, comprising the following steps:

[0070] Step 1: Preparation of soy protein isolate solution: Weigh soy protein isolate, add it to deionized water, and stir at room temperature until fully hydrated to obtain a soy protein isolate solution with a concentration of 0.12 g / mL;

[0071] Step 2: Preparation of sericin solution: Weigh sericin, add it to deionized water, and stir until homogeneous to obtain a sericin solution with a concentration of 0.06 g / mL;

[0072] Step 3: Preparation of the composite protein solution: Add the sericin solution obtained in Step 2 to the soy protein isolate solution obtained in Step 1, so that sericin accounts for 20% of the total protein content, mix thoroughly, and obtain a soy protein isolate-sericin composite protein solution.

[0073] Step 4: Emulsification treatment. Add soybean oil to the composite protein solution obtained in Step 3, and control the volume ratio of composite protein solution to soybean oil to be 9:1. Homogenize at 13000 rpm for 2 min to obtain composite protein emulsion.

[0074] Step 5: Enzymatic cross-linking treatment. Add transglutaminase to the emulsion obtained in step 4 at a rate of 20 U / g protein. After mixing, react in a 55 ℃ water bath for 60 min.

[0075] Step 6: Heat treatment for shaping. The sample obtained in Step 5 was heated in an 85 ℃ water bath for 25 min. After heating, it was cooled to room temperature to obtain a soybean protein isolate-sericite emulsion gel with a sericin content of 20%, named EG-SPS-20.

[0076] The emulsion gel obtained in this embodiment has a uniform appearance, complete gel formation, relatively flat cut surface, and relatively uniform oil droplet distribution, making it suitable as a fat simulation phase in plant-based meat with alternating lean and fatty parts.

[0077] Example 5

[0078] This embodiment provides a method for preparing a soy protein isolate-sericite emulsion gel with a sericin content of 25%, comprising the following steps:

[0079] Step 1: Prepare a soy protein isolate solution with a concentration of 0.12 g / mL;

[0080] Step 2: Prepare a sericin solution with a concentration of 0.06 g / mL;

[0081] Step 3: Add the sericin solution to the soy protein isolate solution so that the sericin accounts for 25% of the total protein content, thus obtaining a complex protein solution;

[0082] Step 4: Mix the composite protein solution with soybean oil at a volume ratio of 9:1, and homogenize at 13000 rpm for 2 min to obtain a composite protein emulsion;

[0083] Step 5: Add 20 U / g protein transglutaminase to the composite protein emulsion, crosslink it at 55 ℃ for 60 min, then heat it at 85 ℃ for 25 min, and after cooling, obtain an emulsion gel with 25% sericin added, named EG-SPS-25.

[0084] In this embodiment, the amount of sericin added was relatively high. The sample could still be formed, but the local uniformity was not as good as in Example 5, indicating that excessive sericin may cause local aggregation of protein molecules, affecting the uniformity of the gel network.

[0085] Example 6

[0086] This embodiment provides a method for preparing lean and fatty plant-based meat using soy protein isolate-sericite emulsion gel, comprising the following steps:

[0087] Step 1: Pretreatment of plant-based lean meat raw materials: Weigh out soy protein fibers, add an appropriate amount of water for rehydration treatment, and allow it to fully absorb water and soften. After rehydration, de-silk the fibers to obtain a plant protein base with a certain fibrous texture;

[0088] Step 2: Add protein gel, transglutaminase and red yeast rice pigment to the soybean textured protein obtained in Step 1, mix well, so that the red yeast rice pigment is distributed in the lean meat phase, and obtain a red plant-based lean meat phase;

[0089] Step 3: Preparation of plant-based fat phase. Soy protein isolate-sericite emulsion gel with 20% sericin content was prepared according to the method in Example 5 and used as the plant-based fat phase.

[0090] Step 4: Layering lean and fat phases. Place the lean meat phase and fat phase from the plant-based substrate into the mold in a 1:1 mass ratio. When filling the mold, alternately lay the lean meat and fat phases and compact them appropriately to ensure full contact between the two phases.

[0091] Step 5: Crosslinking and shaping. Place the molded sample in a 55 ℃ water bath for 1 h for crosslinking to form a more stable bond between the lean meat phase and the fat phase.

[0092] Step 6: Heat treatment molding. Place the cross-linked sample in a 90 ℃ water bath and heat for 15 min. After removing it and cooling, demold it to obtain the lean and fatty plant-based meat.

[0093] The plant-based meat obtained in this embodiment has clear red and white layers, an intact overall structure, and is not easily broken or separated between layers after cutting, thus presenting a good appearance characteristic of meat products with alternating layers of fat and lean meat.

[0094] Comparative Example 1

[0095] This embodiment provides a method for preparing a soy protein isolate emulsion gel without added sericin, comprising the following steps:

[0096] Step 1: Preparation of soy protein isolate solution: Weigh soy protein isolate, add it to deionized water, stir at room temperature to fully disperse and hydrate it, and obtain a soy protein isolate solution with a concentration of 0.12 g / mL;

[0097] Step 2: Preparation of emulsion. The soy protein isolate solution obtained in Step 1 is mixed with soybean oil at a volume ratio of 9:1 and homogenized at 13000 rpm for 2 min to disperse the soybean oil in the protein aqueous phase, thus obtaining soy protein isolate emulsion.

[0098] Step 3: Enzymatic cross-linking treatment. Add transglutaminase to the emulsion obtained in step 2 at a rate of 20 U / g protein. Mix well and react in a 55 ℃ water bath for 60 min.

[0099] Step 4: Heat treatment molding. The emulsion treated in step 3 is heated in an 85 ℃ water bath for 25 min. After cooling to room temperature, a soy protein isolate emulsion gel without added sericin is obtained, named EG-SPI.

[0100] Experimental results:

[0101] Experimental Example 1: Color Analysis of Soy Protein Isolate Emulsion Gel with Different SS Addition Amounts

[0102] This experiment investigated the color development of soy protein isolate emulsion gels with different SS (suspended solids) addition levels by testing color. The method involved taking emulsion gel samples of specific volumes and areas from Examples 1-5 and Comparative Example 1. A handheld colorimeter was used to detect color changes on the emulsion gel surface, and the L*, a*, and b* values ​​were recorded. The instrument was calibrated using a black calibration cup before analysis. The L* value represents the brightness range from 0 (black) to 100 (white), the a* value represents the degree of green (-a*) or red (+a*), and the b* value represents the degree of blue (-b*) or yellow (+b*). Measurements were repeated three times, and the average value was used to calculate the color change.

[0103] Table 1. Color Measurement Results

[0104] Fatty pork belly <![CDATA[69.23 ± 0.79 f ]]> <![CDATA[-0.24 ± 0.14 c ]]> <![CDATA[7.65 ± 0.61 e ]]> EG-SPI <![CDATA[83.07 ± 0.99 a ]]> <![CDATA[0.75 ± 0.11 a ]]> <![CDATA[8.66 ± 0.23 d ]]> EG-SPS-5 <![CDATA[81.43 ± 0.60 b ]]> <![CDATA[0.57 ± 0.04 a ]]> <![CDATA[9.07 ± 0.03 cd ]]> EG-SPS-10 <![CDATA[77.10 ± 0.40 c ]]> <![CDATA[0.23 ± 0.19 b ]]> <![CDATA[9.22 ± 0.40 c ]]> EG-SPS-15 <![CDATA[74.04 ± 0.38 d ]]> <![CDATA[-0.29 ± 0.04 cd ]]> <![CDATA[9.57 ± 0.04 c ]]> EG-SPS-20 <![CDATA[72.78 ± 0.32 d ]]> <![CDATA[-0.42 ± 0.02 cd ]]> <![CDATA[10.31 ± 0.09 b ]]> EG-SPS-25 <![CDATA[71.05 ± 1.23 e ]]> <![CDATA[-0.49 ± 0.10 d ]]> <![CDATA[11.35 ± 0.19 a ]]>

[0105] As shown in Table 1, with the increase of SS addition, the L* value of the emulsion gel gradually decreased from 83.07 ± 0.99 to 71.05 ± 1.23, indicating a significant decrease in system brightness and a gradual approach to the L* value of fatty pork belly (69.23 ± 0.79). This result suggests that the introduction of an appropriate amount of SS helps to adjust the appearance of the emulsion gel, making its brightness closer to that of real adipose tissue. The a* value of the emulsion gel generally showed a decreasing trend with the increase of SS addition, gradually decreasing from 0.75 ± 0.11 to -0.49 ± 0.10. The a* values ​​of all treatment groups were close to zero, and the changes were small, indicating that none of the emulsion gel samples had a strong red-green color, and were relatively close to the overall color characteristics of real adipose tissue. Among them, when the SS addition was 15%, its a* value was -0.29, which was closest to the a* value of commercially available fatty pork belly (-0.24). In addition, the b* value of the emulsion gel gradually increased from 8.66 ± 0.23 to 11.35 ± 0.19, showing a significant upward trend, indicating that the yellowness of the system gradually increased and gradually deviated from the b* value of pork belly (7.65 ± 0.61).

[0106] Experimental Example 2: Fourier Transform Infrared Spectroscopy Analysis of Soy Protein Isolate Emulsion Gel with Different SS Addition Amounts

[0107] This experiment investigated the interaction between soy protein isolate emulsion gels under different SS (saturated superoxide dismutase) addition levels using Fourier transform infrared (FTIR) spectroscopy. The method involved taking samples of specific volumes and areas from Experiments 1-5 and Comparative Example 1 and freeze-drying them. After freeze-drying, each sample was ground into powder. The FTIR spectra of the complex were then measured using a Fourier transform infrared spectrometer, with a wavenumber range of 500–4000 cm⁻¹. The instrument resolution was set to 4 cm⁻¹, the number of scans was 32, and the ambient temperature was 25 °C. Furthermore, Peakfit v4.12 software was used to fit the FTIR spectra to calculate the changes in protein secondary structure content. The results were the average of three parallel experiments.

[0108] The results of Fourier transform infrared spectroscopy measurements are as follows: Figure 1 As shown. By Figure 1It can be seen that with the increase of SS addition, the peak positions and intensities of the main characteristic absorption peaks in the emulsion gel samples (EG-SPI and EG-SPS) changed to some extent, reflecting the differences in intermolecular interactions. Specifically, the emulsion gel exhibited a broad absorption peak in the range of 3200~3400 cm⁻¹, corresponding to the stretching vibrations of -OH and -NH. Compared with the EG-SPI emulsion gel (approximately 3412 cm⁻¹), the peak value of the EG-SPS emulsion gel gradually shifted towards lower wavenumbers (3286.96~3385.85 cm⁻¹), accompanied by a broadening of the absorption band, exhibiting a typical redshift phenomenon, indicating enhanced hydrogen bonding interactions. This helps to improve gel strength. The absorption peaks of the emulsion gel at 2925 cm⁻¹ and 2854 cm⁻¹ correspond to the asymmetric and symmetric stretching vibrations of -CH₂, respectively, and their changes were not significant, indicating that the aliphatic chain structure was relatively stable. The peak at 3008 cm⁻¹... -1 The absorption peak at that point is related to the CH stretching vibration of the unsaturated carbon (HC=C) in the fatty acid chain.

[0109] Experiment Example 3: Microstructural Analysis of Soy Protein Isolate Emulsion Gel with Different SS Addition Amounts

[0110] This experiment investigated the microstructure of soy protein isolate emulsion gels with different SS (suspended solids) addition levels using laser confocal microscopy. The method was as follows: A certain volume of emulsion gel samples from Experiments 1-5 and Comparative Example 1 were taken. The microstructure of the emulsion gels was observed using confocal laser scanning microscopy. The oil phase was stained with Nile Red (0.1%, w / v), and the aqueous phase was stained with Nile Blue (0.1%, w / v), and then homogenized. A small amount of sample was transferred to a glass slide, covered with a coverslip, and sealed. Subsequently, observation was performed under a 20× objective lens using a laser confocal microscope. Each sample was measured in triplicate.

[0111] Microscopic analysis results as follows Figure 2As shown in the figure, green represents the aqueous phase and red represents the oil phase. It can be seen that the red oil phase is dispersed within the green aqueous phase in the emulsion gel, indicating that the emulsion gel is an oil-in-water type. In EG-SPI and EG-SPS-5 emulsion gels, the red protein phase and green oil phase are unevenly distributed, and there are many dark areas within the system, which seems to be caused by phase separation. At the same time, the droplet size is relatively large, and there is a tendency for them to aggregate and form larger droplets, indicating that the emulsion gels without SS or with a small amount of SS have constructed an incomplete network structure, resulting in weak system continuity and stability. The distribution of the protein and oil phases in EG-SPS-10 is improved compared to EG-SPS-5, but some oil droplet aggregation and relatively obvious phase separation can still be observed. With the SS addition further increased to 15% and 20%, a significant increase in the yellow overlapping areas in C4 and C5 was observed, and magnified images D4 and D5 show that the oil droplet size tends to decrease and the distribution is more uniform, indicating enhanced emulsion gel continuity. SPS complexes, acting as interface stabilizers, adsorb and stabilize oil droplets at the oil / water interface, leading to the formation of an emulsion gel network structure. This network structure enhances the physical stability of the emulsion gel. However, when excessive SS is added, although the overall network remains relatively compact, oil droplet aggregation occurs in localized areas, indicating that excessive SS has a negative impact on the structure of the emulsion gel. This is because the aggregation of SPS complexes restricts their adsorption behavior at the oil / water interface, resulting in increased instability of the emulsion gel.

[0112] Experiment Example 4: Water-holding capacity analysis of soy protein isolate emulsion gels with different SS addition levels

[0113] This experiment investigated the absorbable and retained water content of soy protein isolate emulsion gels under different SS (suspended solids) addition levels by measuring water-holding capacity (WHC). The method was as follows: 5 g of emulsion gel samples from Experiments 1-5 and Comparative Example 1 were placed in centrifuge tubes and centrifuged at 4000×g for 10 min at 25 °C. Residual moisture on the sample surface and centrifuge tube walls was then removed with dry filter paper. WHC was calculated using the following formula, and the result was the average of three parallel experiments.

[0114]

[0115] Where W0, W1, and W2 represent the mass (g) of an empty centrifuge tube, a centrifuge tube containing fresh emulsion gel before centrifugation, and a centrifuge tube containing dehydrated gel after centrifugation, respectively.

[0116] The results of the water-holding capacity test are as follows Figure 3 As shown. By Figure 3It was found that all emulsion gels with added SS exhibited significantly enhanced water-holding capacity (WHC) compared to those without SS. This is because SS contains more polar groups, which can bind the movement of free water molecules within the system. With increasing SS content (5–15%), the WHC of the EG-SPS emulsion gel gradually increased, reaching its strongest water-holding capacity (97.14 ± 0.4%) at a 20% addition level, an increase of 7.31% compared to the control group. However, when the SS addition level was further increased to 25%, the WHC of the EG-SPS-25 emulsion gel decreased to 94.58 ± 0.45%, indicating that SS addition can have a positive effect on the water-holding capacity of emulsion gels within a certain range.

[0117] Example 5: Textural Properties Analysis of Soy Protein Isolate Emulsion Gels with Different SS Addition Amounts

[0118] This experiment investigated the hardness, elasticity, cohesiveness, and chewiness of soy protein isolate emulsion gels with different SS (soybean sorbitol) addition levels by measuring their textural properties. The method was as follows: 5 g of emulsion gel samples from Examples 1-5 and Comparative Example 1 were placed in centrifuge tubes. After equilibration at room temperature for 30 min, the textural properties of the gel samples were measured using a texture analyzer. A P / 0.5 cylindrical probe was used for measurement, with a probe forward speed of 1 mm / s and 2 downward presses, a trigger force of 5 g, and detection and retraction speeds both set to 5 mm / s. The results were the average of three parallel experiments.

[0119] The results of the determination of textural properties are as follows: Figure 4 As shown. By Figure 4 It can be seen that compared with EG-SPI, EG-SPS exhibits increased hardness, elasticity, cohesiveness, and chewiness. This indicates that the introduction of SS effectively enhances the textural properties of the emulsion gel. Furthermore, with increasing SS content, the elasticity of the EG-SPS emulsion gel gradually increases, while hardness, cohesiveness, and chewiness show a trend of first increasing and then decreasing. Specifically, at SS addition levels of 5-15%, the EG-SPS emulsion gel exhibits relatively weak textural properties. Combined with confocal microscopy observations, this is because a small amount of SS is insufficient to maintain a stable distribution of the oil and aqueous phases in the system, leading to phase separation and weakening the structural integrity and density of the system, resulting in a loose and fragile gel structure. At an SS addition level of 20%, EG-SPS-20 reaches its maximum hardness, cohesiveness, and chewiness. Meanwhile, EG-SPS-25 shows a decrease in chewiness and cohesiveness.

[0120] Experimental Example 6: Analysis of Cooking Loss of Soy Protein Isolate Emulsion Gel under Different SS Addition Amounts

[0121] This experiment investigated the cooking loss rate of soy protein isolate emulsion gels under different SS (suspended solids) addition levels by measuring the mass loss of the emulsion gel samples before and after cooking. The method was as follows: Appropriate amounts of emulsion gel samples from Experiments 1-5 and Comparative Example 1 were weighed into 15 mL centrifuge tubes (a), heated in a 90 ℃ water bath for 1 h, and the surface moisture was absorbed with filter paper. The mass of the sample after cooking was then measured (b). The cooking loss (%) was calculated using the following formula, and the result was the average of three parallel experiments.

[0122]

[0123] Where a and b are the masses (g) of the emulsion gel before and after cooking, respectively.

[0124] The results of the cooking loss determination are as follows: Figure 5 As shown in the figure, except for the emulsion gel with 5% SS, the cooking loss of the other emulsion gels with different SS additions was significantly lower than that of the control group (P < 0.05). This indicates that the amount of SS added has a positive effect on the water retention of the emulsion gel system. This is related to the water-holding capacity (SS). Figure 3 The analysis results correspond to those of the previous analysis. Notably, EG-SPS-20 exhibited the lowest cooking loss rate (5.41 ± 0.18%). This is attributed both to the binding ability of the polar groups carried by SS itself to water molecules, resulting in reduced water loss during cooking, and to the effective binding of water and oil molecules by the dense structure formed by the intermolecular cross-linking between SPS and SPI, which also leads to reduced cooking loss. A lower cooking loss rate indicates higher system stability and a positive effect on the processing adaptability of meat simulants.

[0125] Experiment Example 7: Freeze-thaw stability analysis of soy protein isolate emulsion gels with different SS addition levels

[0126] This experiment investigated the freeze-thaw stability of soy protein isolate emulsion gels with different SS (suspended solids) addition levels through repeated freeze-thaw cycles. The method was as follows: 5 g of emulsion gel samples from Examples 1-5 and Comparative Example 1 were placed in petri dishes and frozen at -20°C for 20 h, then thawed at room temperature for 4 h. Subsequently, the samples were centrifuged at 10000×g for 15 min to remove precipitated free water from the emulsion gel. The freeze-thaw cycle was repeated five times, and the permeability was calculated using the following formula. The result was the average of three parallel experiments.

[0127]

[0128] Where A is the weight (g) of the emulsion gel before freeze-thaw treatment, and B is the weight (g) of the emulsion gel after freeze-thaw treatment.

[0129] The results of the freeze-thaw stability test are as follows: Figure 6 As shown. From Figure 6 As can be seen, the freeze-thaw stability of the emulsion gel system was significantly enhanced after the addition of SS. With the increase of SS addition (0–20%), the freeze-thaw stability of the emulsion gel gradually increased from 53.15 ± 1.43% to 64.62 ± 0.93%. This indicates that the amount of SS added is positively correlated with the inhibition of ice crystal formation. The highest freeze-thaw stability of EG-SPS-20 is attributed to the positive effects of its gel strength, water-holding capacity, and other factors. However, at an SS addition of 25%, the freeze-thaw stability of EG-SPS-25 decreased. Its weaker water-holding capacity led to the formation of larger ice crystals, which, upon melting, disrupted the network structure of the emulsion gel, thus reducing the freeze-thaw stability of the system.

[0130] Experiment Example 8: Analysis of the Appearance Characteristics of Plant-Based Meat with Alternating Fat and Lean Texture

[0131] This experiment examines the appearance characteristics of plant-based meat with alternating layers of fat and lean meat by comparing it with commercially available pork belly. The method was as follows: 25 g of the alternating layers of fat and lean meat from Example 6 was taken, cut into pieces, and fried in soybean oil at 180℃ for 1.5 minutes. The pieces were then turned over and fried for another 1.5 minutes. The meat was then removed and its appearance was compared with that of commercially available pork belly after frying.

[0132] Appearance picture as follows Figure 7 As shown, the lean meat matrix of plant-based meat is tightly integrated with the adipose tissue, exhibiting a complete overall structure and dense texture. The lean meat matrix shows stable coloring, while the adipose tissue is clear and white, displaying a distinct red and white alternating lean and fat appearance. Therefore, based on hydrogel-based lean plant-based meat and emulsion gel-based fatty plant-based meat, it is possible to create pork belly analogs with similar appearance and texture.

Claims

1. A method for preparing lean and fatty plant-based meat using a soy protein isolate-sericite emulsion gel, characterized in that, Includes the following steps: (1) Add the sericin solution to the soy protein isolate solution, mix and stir to obtain a soy protein isolate-sericin complex protein solution; (2) The composite protein solution is mixed with vegetable oil and homogenized to obtain an emulsion; (3) Add transglutaminase to the emulsion, stir evenly, perform water bath crosslinking treatment, then heat and cool to obtain soybean protein isolate-sericin emulsion gel. (4) The plant-based lean meat and the soy protein isolate-sericite emulsion gel are layered in a mold, cross-linked and heated to set, and then cooled and demolded to obtain the lean and fatty plant-based meat.

2. The method according to claim 1, characterized in that, In step (1), the proportion of sericin to the total protein content of the system is 5% to 25%, the concentration of sericin solution is 0.06 g / mL, and the concentration of soy protein isolate solution is 0.12 g / mL.

3. The method according to claim 1, characterized in that, In step (2), the vegetable oil is soybean oil, and the volume ratio of the compound protein solution to the vegetable oil is 9:

1.

4. The method according to claim 1, characterized in that, In step (2), the rotation speed of the homogenization process is 13000 rpm and the homogenization time is 2 min.

5. The method according to claim 1, characterized in that, In step (3), the amount of glutamine transaminase added is 20 U / g (based on the protein mass in the emulsion); the water bath crosslinking temperature is 55 °C and the time is 60 min; the heat treatment temperature is 85 °C and the time is 25 min.

6. The method according to claim 1, characterized in that, In step (4), the mass ratio of plant-based lean meat to emulsion gel is 1:1, and it is crosslinked at 55 °C for 1 h, and then heated at 90 °C for 15 min.

7. The soybean protein isolate-serine protein emulsion gel prepared by the method according to any one of claims 1 to 6, characterized in that, Oil droplets are uniformly dispersed in the emulsion gel and form a continuous gel network structure.

8. The lean-fat plant-based meat prepared by the method according to any one of claims 1 to 6, characterized in that, Plant-based meat with alternating layers of fat and lean meat consists of a plant-based lean meat phase and an emulsion gel fat phase, which are combined in a layered structure.

9. The method according to any one of claims 1 to 8, characterized in that, The prepared plant-based meat with alternating layers of fat and lean meat is suitable for frozen storage and heating cooking, and can maintain good texture and flavor.

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