Peanut protein fibril-carrageenan-peanut oil body composite emulsion gel and preparation method and application thereof

Abstract

The application belongs to the technical field of plant protein deep processing and food colloid, and discloses a peanut protein fibril-carrageenan-peanut oil body composite emulsion gel and a preparation method thereof, specifically, the peanut protein fibril, the peanut oil body and the carrageenan are used as raw materials to construct the composite emulsion gel, the composite emulsion gel has a uniform and stable three-dimensional network structure, can effectively fix oil droplets and moisture, and improves the gel strength and water retention of the system. The peanut protein fibril is obtained by ultrasonic pretreatment of peanut protein isolate under acidic conditions and heating induction, and has a high aspect ratio and good interfacial activity. The application improves the problems of insufficient interfacial activity and limited network strength of traditional plant protein emulsion gel, and the composite emulsion gel can be applied to fat substitutes and plant-based functional foods.

Description

Technical Field

[0001] This invention belongs to the field of plant protein deep processing and food colloid technology, specifically relating to a peanut protein fibrillary-carrageenan-peanut oil composite emulsion gel, its preparation method and application. Background Technology

[0002] Emulsion gels are semi-solid systems composed of liquid oil droplets dispersed and immobilized in a three-dimensional gel network. They combine the interfacial properties of emulsions with the structural properties of gels, and have broad application prospects in mimicking fats, delivering active substances, and developing plant-based foods. Compared to animal-derived structured lipids, plant-based emulsion gels offer advantages in nutritional health, sustainability, and formulation flexibility.

[0003] However, traditional plant proteins, due to their naturally dense spherical structure, often suffer from insufficient interfacial activity, limited gel network strength, and weak ability to fix oil droplets and water, thus limiting their application in highly stable emulsion gels. Protein amyloid fibrous fibers are fibrous aggregates formed by the ordered self-assembly of denatured proteins or peptides. Due to their high aspect ratio, abundant intermolecular interaction sites, and strong viscoelastic behavior, they have been considered in recent years as novel assembly units for constructing food structures. Furthermore, protein protofibrils can improve the structural properties of composite systems through molecular entanglement, interfacial adsorption, and network reinforcement.

[0004] Peanut protein isolate is a widely available, highly nutritious, and low-cost plant protein resource with significant development potential. Under acidic and hot conditions, peanut protein isolate can denature, unfold, and self-assemble in an orderly manner to form peanut protein fibrils rich in β-sheet structures. However, single peanut protein fibril systems may still suffer from insufficient network density and limited oil droplet fixation capacity in gel construction. The journal "Research Progress on Fat Substitutes for Plant Protein-Based Emulsion Gels" (Zhu Xiuqing et al., Food Science) disclosed that plant protein-based emulsions and other interface-dominated foods face difficulties in preparation and are prone to instability under extreme environments, indicating that relying solely on plant proteins to construct stable interfacial films and dense network structures still faces challenges. Carrageenan, as an anionic polysaccharide, has excellent thickening and thermally induced gelling properties and can synergistically construct networks with protein systems through electrostatic and hydrogen bonding interactions. Peanut oil bodies are lipid storage particles naturally present in peanut kernels, possessing a natural emulsified structure composed of a triglyceride core and a phospholipid-protein interfacial membrane, exhibiting good interfacial stability and making them suitable for constructing naturally derived oil droplet phases. The journal "Research Progress on the Application of Oil Gels and Emulsion Gels in Alternating Animal Adipose Tissue" (Ye Shuxin et al., Food Science) published research progress on the application of common emulsion gel types (including protein matrix, polysaccharide matrix, protein-polysaccharide composite matrix and functional emulsion gel) as animal fat mimics in meat products. However, how to further improve the interfacial adsorption capacity, oil droplet fixation capacity, network density and oil and water retention stability of plant protein systems remains a key technical problem that needs to be solved in this field.

[0005] Therefore, developing a composite emulsion gel system with peanut protein fibrils enhancing the interfacial properties and network strength of oil droplets, carrageenan as the skeleton, and peanut oil as the filling phase is of great significance for improving the high-value utilization of peanut protein and constructing novel plant-based fat mimics. Summary of the Invention

[0006] The present invention aims to provide a peanut protein fibrillation-carrageenan-peanut oil composite emulsion gel and its preparation method. Specifically, peanut protein fibrillation, carrageenan, and peanut oil are used as raw materials to construct a composite emulsion gel. The resulting emulsion possesses a uniform and stable three-dimensional network structure, effectively fixing oil droplets and water, and improving the gel strength and water retention of the system. Furthermore, the peanut protein fibrillation is formed by ultrasonic pretreatment of peanut protein isolate under acidic conditions followed by heating induction, exhibiting a high aspect ratio and good interfacial activity. This solution overcomes the problems of insufficient interfacial activity, limited gel strength, and poor oil-water retention capacity in existing plant protein emulsion gels, and can be applied to fat substitutes and plant-based functional foods.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a peanut protein fibrillation-carrageenan-peanut oil composite emulsion gel, comprising the following steps: (1) Preparation of peanut protein fibrils: Peanut protein isolate was dispersed in water to obtain peanut protein isolate dispersion; the pH of the system was adjusted to 2.0 and then hydrated overnight at 4℃. The insoluble matter was removed by centrifugation, ultrasonic treatment was performed and then heat treatment was performed. After the heat treatment was completed, the solution was immediately cooled in an ice-water bath to obtain peanut protein fibrils solution, which was then freeze-dried and stored for later use. (2) Preparation method of composite emulsion gel: After freeze-drying the peanut protein fibrillary solution obtained in step (1), it was reconstituted with deionized water to prepare a protein concentration of 62.5 mg / mL. The protein solution was hydrated overnight at 4℃, and then peanut oil was added and homogenized to obtain mixed system 1. After adjusting the pH of mixed system 1 to 6.0, carrageenan was added to make the final mass concentration of carrageenan in the system reach 0.6% to obtain mixed system 2. The obtained mixed system 2 was heated and then cooled and allowed to stand to form a peanut protein fibrillary-carrageenan-peanut oil composite emulsion gel.

[0008] Further, the preparation method of peanut protein isolate in step (1) is as follows: peanut meal is taken and added to deionized water at a material-to-liquid ratio of 1g:15mL for dispersion. The pH is adjusted to 8.5 with 2M sodium hydroxide solution and stirred at room temperature until completely dissolved. The mixture is centrifuged at 4℃ and 4000×g for 30 min and the supernatant is collected. The pH of the supernatant is adjusted to 4.5 with 2M hydrochloric acid to precipitate the protein. The precipitate is collected after centrifugation again. The precipitate is washed with deionized water and the pH is adjusted to 7.0 with 2M sodium hydroxide solution. After dialysis for 48 h to remove salt, the mixture is freeze-dried to obtain peanut protein isolate. The concentration of the dispersion prepared using the above peanut protein isolate is preferably 40mg / mL. 6M hydrochloric acid is used to adjust the pH of the system to 2.0 before overnight hydration at 4℃.

[0009] Furthermore, the ultrasonic treatment conditions in step (1) are as follows: treatment power 30-300W; treatment time 10min; indirect ultrasonic method is used, preferably with a working mode of 5s on and 5s off, and the whole process is placed in an ice-water bath; heat treatment conditions are 85℃ for 6-12 h; after heat treatment, the ice-water bath is cooled for at least 30 min.

[0010] Further, in step (2), the peanut oil body is prepared as follows: after soaking peanut kernels, deionized water is added at a material-to-liquid ratio of 1g:8mL, and the mixture is crushed at 22,000 rpm for 2 min using a high-speed homogenizer; large particles are removed by filtration to obtain a slurry, and the pH is adjusted to 6.0 with 0.5 M hydrochloric acid. The slurry is then centrifuged at 4℃ and 7000×g for 30 min, and the upper white enrichment is collected; then the white enrichment is mixed with deionized water at a mass ratio of 1:5, and the pH is adjusted to 6.0 with 0.5 M hydrochloric acid. The mixture is then centrifuged again at 7000×g for 30 min, and the uppermost layer is collected as the peanut oil body. The peanut oil body is then separated for later use.

[0011] Furthermore, in step (2), the amount of peanut oil added accounts for 20% of the total mass of the mixture 2; Furthermore, the heating and cooling conditions of the mixed system 2 in step (2) are as follows: the heating temperature is 85°C and the time is 30 min; after cooling to room temperature, it is left to stand at 4°C for 12 h.

[0012] The second aspect of the present invention claims protection for the peanut protein fibrils-carrageenan-peanut oil composite emulsion gel prepared by the above preparation method, which has uniform moisture distribution and good texture and rheological properties.

[0013] A third aspect of the present invention claims the use of the above-mentioned composite emulsion gel in food processing, specifically, the composite emulsion gel can be used as one or more of the following: fat mimic, plant-based gel food, baked goods, meat substitute, and nutrient delivery carrier.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The formation of peanut protein protofibrils through acid-thermal-ultrasound synergistic induction improved the ordered assembly and structural functionality of protein molecules. Peanut protein protofibrils possess a high aspect ratio and abundant interfacial active sites, which facilitates bridging and entanglement in emulsion systems, enhancing network strength. 2. Carrageenan can form a synergistic network with peanut protein fibrils, further improving gel hardness, water retention, and moisture fixation capacity; 3. Peanut oil droplets, as natural emulsified lipid droplets, possess good interfacial film stability and can be uniformly embedded in a three-dimensional network, thereby improving system stability; 4. The composite emulsion gel constructed in this invention has good gelling properties and can be used to develop plant-based functional food products. Attached Figure Description

[0015] Figure 1 The moisture distribution diagram and gel appearance diagram of the composite emulsion gel prepared with different protein solutions or without protein solution in Experiment 1-1 are shown. Figure 2 Fourier transform infrared images and secondary structure distribution diagrams for Experimental Examples 1-2; Figure 3 Intermolecular force diagrams for Experimental Examples 1-3; Figure 4 Figures showing the hardness and gel strength of the emulsion gel in Experiment Examples 1-4; Figure 5 The strain scans and three-stage thixotropic recovery rheograms from Experimental Examples 1-5 are shown. Figure 6 This is a schematic diagram illustrating the effect of different fat replacement rates on the appearance of pork patties in Example 1 of the application examples; Figure 7 This is a schematic diagram illustrating the effect of different fat substitution rates on the water retention and cooking loss of pork patties in an application example. Detailed Implementation

[0016] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, 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 pertains.

[0017] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0018] The experimental materials used in the embodiments of this invention are all conventional experimental materials in the art, and can be purchased through commercial channels unless otherwise specified.

[0019] Example 1: Preparation of peanut protein fibrils-carrageenan-peanut oil composite emulsion gel (1) Preparation of peanut protein isolate: Peanut meal (Shandong Jinsheng Grain and Oil Food Co., Ltd.) was added to deionized water at a material-to-liquid ratio of 1g:15mL and dispersed. The pH was adjusted to 8.5 with 2M sodium hydroxide solution and extracted at room temperature at 300 rpm / min for 2 h. The supernatant was collected after centrifugation at 4℃ and 4000×g for 30 min. The pH of the supernatant was adjusted to 4.5 with 2M hydrochloric acid to precipitate the protein. The supernatant was centrifuged again (4000×g, 30 min) and the precipitate was collected. The precipitate was washed three times with deionized water and the pH was adjusted to 7.0 with 2M sodium hydroxide solution. After dialysis for 48 h to remove salt, the precipitate was freeze-dried to obtain peanut protein isolate powder. The protein content was found to be 89.72 wt%.

[0020] (2) Preparation of peanut protein fibrils: 4.5 g of the above-mentioned peanut protein isolate was dissolved in 100 mL of deionized water and stirred for 2 h to prepare a protein dispersion. Then, the pH of the system was adjusted to 2.0 with 6 M hydrochloric acid and hydrated overnight at 4℃. The solution was centrifuged (4000×g, 20 min) to remove insoluble components. Subsequently, it was pretreated with an ultrasonic processor with a power of 120W and a treatment time of 10 min. The working mode was 5 s on / 5 s off, and the entire process was carried out in an ice-water bath. After ultrasonic treatment, the sample was heated at 85℃ for 12 h. After heating, it was immediately cooled in an ice-water bath for 30 min to obtain the peanut protein fibrils dispersion. It was then processed by conventional freeze-drying process for three days to prepare peanut protein fibrils freeze-dried powder for later use. (3) Extraction of peanut oil: Peanut kernels (Shandong Luhua Agricultural Technology Promotion Co., Ltd.) were soaked for 12 h, and deionized water was added at a material-to-liquid ratio of 1 g: 8 mL. The mixture was then crushed at 22,000 rpm for 2 min using a high-speed homogenizer. After filtration, the slurry was obtained. The pH was adjusted to 6.0 with 0.5 M hydrochloric acid and then centrifuged at 4℃ and 7000×g for 30 min. The upper white concentrate was collected. The white concentrate was then mixed with deionized water at a mass ratio of 1:5 and the pH was adjusted to 6.0 with 0.5 M hydrochloric acid. The mixture was then centrifuged again at 7000×g for 30 min. The uppermost layer was collected as peanut oil. The peanut oil was then separated and set aside for later use. (4) Preparation of the composite emulsion gel: The lyophilized peanut protein fibrils obtained in step (2) were dissolved in deionized water to obtain a protein concentration of 62.5 mg / mL. The protein solution was hydrated overnight at 4°C. 12.5 g of peanut oil was dispersed in 40.0 mL of the above protein solution, and the pH was adjusted to 6.0 with 0.1 M sodium hydroxide solution. Subsequently, 10.0 g of carrageenan solution (4%, w / v) was added. The mixture was heated at 85°C for 30 min, then cooled to room temperature, and then allowed to stand at 4°C for 12 h to form a peanut protein fibrils-carrageenan-peanut oil composite emulsion gel. Based on a total system weight of approximately 62.5 g, the final protein concentration in the resulting gel was approximately 4%, the peanut oil mass fraction was 20%, and the final carrageenan concentration was approximately 0.6%.

[0021] Example 2: Preparation of peanut protein fibrils-carrageenan-peanut oil composite emulsion gels under different power conditions The difference from Example 1 lies in the ultrasonic power used to prepare the composite emulsion gel. In this example, the peanut protein fibrils were treated with 60 W ultrasonic power and then heated for 12 h according to the scheme of Example 1 to form peanut protein fibrils (60 W, 12 h). The rest of the process is the same. The final preparation steps of the peanut protein fibrils (60 W, 12 h)-carrageenan-peanut oil composite emulsion gel are as follows: The peanut protein fibrillation lyophilized powder (60 W, 12 h) obtained in step (2) was dissolved in deionized water to obtain a protein concentration of 62.5 mg / mL. The protein solution was hydrated overnight at 4°C. 12.5 g of peanut oil was dispersed in 40.0 mL of the above protein solution, and the pH was adjusted to 6.0 with 0.1 M sodium hydroxide solution. Then, 10.0 g of carrageenan solution (4%, w / v) was added. The mixture was heated at 85°C for 30 min, then cooled to room temperature, and then allowed to stand at 4°C for 12 h to form a peanut protein fibrillation cellulose (60 W, 12 h)-carrageenan-peanut oil composite emulsion gel. The final protein concentration in the resulting gel was approximately 4%, the peanut oil mass fraction was 20%, and the final carrageenan concentration was approximately 0.6%.

[0022] Comparative Example 1: Preparation of Carrageenan-Peanut Oil Composite Emulsion Gel The difference between this comparative example and Example 1 is that peanut protein isolate was not added during the preparation of the composite emulsion gel; otherwise, the steps are the same. 12.5 g of peanut oil was dispersed in 40.0 g of deionized water, and the pH was adjusted to 6.0 with 0.1 M sodium hydroxide solution. Then, 10.0 g of carrageenan solution (4%, w / v) was added. The mixture was heated at 85 °C for 30 min, then cooled to room temperature, and finally allowed to stand at 4 °C for 12 h to form a carrageenan-peanut oil composite emulsion gel. The resulting gel contained 20% peanut oil by mass, and the final carrageenan concentration was approximately 0.6%.

[0023] Comparative Example 2: Preparation of peanut protein isolate-carrageenan-peanut oil complex emulsion gel The difference between this comparative example and Example 1 is that, in the preparation of the composite emulsion gel, the peanut protein fibrils are replaced with the peanut protein isolate prepared in step (1), while the rest are the same. The specific steps are as follows: Peanut protein isolate lyophilized powder was dissolved in deionized water to obtain a protein concentration of 62.5 mg / mL. The protein solution was hydrated overnight at 4°C. 12.5 g of peanut oil was dispersed in 40.0 mL of the protein solution, and the pH was adjusted to 6.0 with 0.1 M sodium hydroxide solution. Subsequently, 10.0 g of carrageenan solution (4%, w / v) was added, and the mixture was heated at 85°C for 30 min, then cooled to room temperature, and then allowed to stand at 4°C for 12 h to form a peanut protein isolate-carrageenan-peanut oil composite emulsion gel. The final concentration of peanut protein isolate in the resulting gel was approximately 4%, the peanut oil content was 20%, and the carrageenan concentration was approximately 0.6%.

[0024] Comparative Example 3: Peanut protein fibrils were prepared under different conditions. The difference between this comparative example and Example 1 is that the preparation conditions of the peanut protein fibrils used in the preparation of the composite emulsion gel are different. In this comparative example, peanut protein fibrils formed by heating with 60 W ultrasonic power for 8 hours are added. The rest are the same. The specific steps are as follows: The peanut protein fibrillation lyophilized powder (60 W, 8 h) obtained in step (2) was dissolved in deionized water to obtain a protein concentration of 62.5 mg / mL. The protein solution was hydrated overnight at 4°C. 12.5 g of peanut oil was dispersed in 40.0 mL of the above protein solution, and the pH was adjusted to 6.0 with 0.1 M sodium hydroxide solution. Then, 10.0 g of carrageenan solution (4%, w / v) was added. The mixture was heated at 85°C for 30 min, then cooled to room temperature, and then allowed to stand at 4°C for 12 h to form a peanut protein fibrillation cellulose (60 W, 8 h)-carrageenan-peanut oil composite emulsion gel. The final protein concentration in the resulting gel was approximately 4%, the peanut oil mass fraction was 20%, and the final carrageenan concentration was approximately 0.6%.

[0025] Test case performance testing The peanut protein fibrils (120 W, 12 h)-carrageenan-peanut oil composite emulsion gel of Example 1, the peanut protein fibrils (60 W, 12 h)-carrageenan-peanut oil composite emulsion gel of Example 2, the carrageenan-peanut oil composite emulsion gel of Comparative Example 1, the peanut protein isolate-carrageenan-peanut oil composite emulsion gel of Comparative Example 2, and the peanut protein fibrils (60 W, 8 h)-carrageenan-peanut oil composite emulsion gel of Comparative Example 3 were used as samples, and their low-field nuclear magnetic resonance, Fourier transform infrared, intermolecular interaction forces, textural properties, and rheological properties were detected.

[0026] Experimental Example 1-1 Low-field nuclear magnetic resonance 5.0 g of each of the composite emulsion gel samples obtained in the examples and comparative examples were weighed and placed in glass tubes. The T2 signal of the samples was acquired using a CPMG pulse sequence. Parameter settings: resampling wait time (TW) was 2000 ms, number of resampling attempts (NS) was 8, echo time (TE) was 0.5 ms, and echo number (NECH) was 4000. The obtained attenuation signal curves were inverted and analyzed using software (Niumag Invert), and the results are as follows. Figure 1 As shown: T2 is divided into three regions: T 21 (0.1-10 ms, tightly bound water), T 22 (10-100 ms, fixed water) and T 23 (100-1000 ms, free water). Generally, a higher ratio of bound water to fixed water and a lower ratio of free water indicate that the gel network has a stronger ability to bind water.

[0027] from Figure 1 It can be seen that the peanut protein fibrils-carrageenan-peanut oil composite emulsion gel prepared by treating peanut protein fibrils with 120 W ultrasonic power and heating for 12 h (Example 1) has the most uniform moisture distribution; followed by the peanut protein fibrils (60 W, 12 h)-carrageenan-peanut oil composite emulsion gel (Example 2). The composite emulsion gel composed only of carrageenan and peanut oil (Comparative Example 1) has the least uniform moisture distribution; the composite emulsion gel with peanut protein isolate instead of peanut protein fibrils (Comparative Example 2) and the composite emulsion gel prepared by treating peanut protein fibrils with 60 W ultrasonic power and heating for 8 h (Comparative Example 3) both have weaker moisture distribution than Examples 1 and 2. The above results indicate that suitable ultrasonic-heat treatment conditions are beneficial to the formation of a protein fibril network that can bind water, thereby enhancing the ability of the composite emulsion gel to fix free water and improving the uniformity of the system.

[0028] Experimental Example 1-2 Fourier Transform Infrared Spectroscopy The lyophilized gel sample was ground and mixed with potassium bromide at a ratio of 1:100, and then pressed into thin sheets. The protein structure of the gel was determined by Fourier transform infrared spectroscopy in the wavenumber range of 4000-500 cm⁻¹. -1 The internal characterization was performed, and the results are as follows: Figure 2 As shown.

[0029] Fourier transform infrared spectroscopy is mainly composed of COC (1163 cm⁻¹) generated by polysaccharides and lipids, respectively. -1 ) and C=O (1747 cm) -1Vibration-dominated. Example 1 showed the highest β-turn content at 31.8%. No amide I band was observed in Comparative Example 1, indicating a lack of quantifiable protein secondary structure in this system. The composite emulsion gels prepared in Comparative Examples 2 and 3 had β-sheet contents of 30.96% and 36.4%, respectively, and β-turn contents of 9.04% and 25.8%, respectively. This reflects the unfolding of the protein induced by 8 h heat treatment and 60 W sonication, which favors a transition to a flexible conformation. Carrageenan further disrupted β-sheet stacking through hydrogen bonding and electrostatic interactions, increasing the β-turn content. This indicates that 12 h heat treatment and 120 W sonication promoted the unfolding and orderly rearrangement of some proteins, resulting in a more stable structure. This demonstrates that prolonged heating time and moderate sonication synergistically regulate protein conformation, promoting the formation of a more stable gel network.

[0030] Experimental Examples 1-3: Intermolecular Forces 0.5 g of emulsion gel was mixed with 5 mL of aqueous solutions A through E, respectively. Solution A contained 0.05 M sodium chloride; solution B contained 0.6 M sodium chloride; solution C contained 0.6 M sodium chloride and 1.5 M urea; solution D contained 0.6 M sodium chloride and 8 M urea; and solution E contained 0.6 M sodium chloride, 8 M urea, and 0.5 M dithiothreitol. The mixtures were homogenized at 10,000 rpm for 1 min using a high-speed disperser, followed by stirring for 1 h. The mixtures were then centrifuged at 6000 × g for 20 min. The protein content in the supernatant was determined using the Coomassie Brilliant Blue method. Electrostatic interactions, hydrogen bonds, hydrophobic interactions, and covalent interactions were calculated based on the differences in protein concentration between solutions B and A, C and B, D and C, and E and D, respectively. The results are shown below. Figure 3 As shown.

[0031] In this emulsion-gel system, hydrophobic interactions are the main driving force for protein aggregation and network formation, while hydrogen bonds and electrostatic interactions also participate in maintaining the gel structure. Example 1 exhibits the strongest hydrophobic interactions and hydrogen bonds, followed by Example 2; Comparative Example 1, due to the absence of added protein, shows the lowest levels of all interaction forces. Although Comparative Examples 2 and 3 exhibit some intermolecular forces due to the introduction of protein components, these forces are lower than those of Example 1. These results indicate that peanut protein protofibrils formed by 120 W ultrasonic treatment combined with 12 h of heat induction have a larger specific surface area and more structural sites that can participate in interactions, which can promote entanglement and synergistic effects between protein protofibrils and between them and the interfaces of carrageenan and peanut oil bodies, thereby improving the stability of the gel network.

[0032] Experimental Examples 1-4: Texture Properties Texture profile analysis of the gel samples was performed using a TA / 0.5 gel probe. The initial test speed was set to 0.5 mm / s and maintained throughout the evaluation process, including the post-test phase. The test trigger point was set to 3.0 gf, with an interval of 3.0 s between consecutive tests. The required displacement was determined to be 7.0 mm, while the trigger force was configured to 5.0 gf, and a return distance of 10 mm was applied. The results are as follows: Figure 4 As shown.

[0033] In Example 1, both the hardness and gel strength were at their maximum values, 232.50 gf and 20.50 g / cm, respectively. 2 Example 2: Hardness and gel strength were 146.84 gf and 15.15 g / cm, respectively. 2 Comparative Example 1 had a hardness of 9.18 gf and a gel strength of 1.12 g / cm. 2 The hardness of Comparative Example 2 and Comparative Example 3 were 26.51 gf and 112.17 gf, respectively; the gel strength was 3.22 g / cm. 2 and 13.02 g / cm 2 The above results indicate that the protein components play a crucial supporting role in the strength of the composite emulsion gel network; compared with unfibrillated peanut protein isolate, fibrillation treatment significantly improves the system's hardness and gel strength. As the heat treatment time increased from 8 h to 12 h, the peanut protein fibrillary structure further elongated, leading to increased gel hardness and gel strength. Under 120 W ultrasonic conditions, Example 1 exhibited the highest hardness and gel strength, demonstrating that the synergistic effect of appropriate ultrasonic treatment and thermal induction can enhance oil droplet interface stability and gel network strength.

[0034] Experimental Examples 1-5 Rheological Properties In the strain scanning test, the frequency was fixed at 1 Hz, and the shear strain increased logarithmically from 0.1% to 100%, with five data points per decade. The three-stage thixotropic test was used to evaluate the sample in three consecutive shear rate intervals (1 s). -1 Lasting 120 seconds, 100 s -1 Lasting 180 seconds, 1 second -1 The thixotropic recovery behavior (lasting 120 seconds) was as follows: Figure 5 As shown.

[0035] Within the low-strain region (approximately 0.1-1%), the storage modulus G′ of each sample was significantly higher than the loss modulus G″, and both remained relatively stable, indicating that the system was in the linear viscoelastic region (LVR), with a relatively stable gel structure exhibiting typical elastic-dominated characteristics. Example 1 exhibited the highest storage modulus G′, the widest linear viscoelastic region, and the highest structural recovery rate. The remaining samples were in the order of Example 2 > Comparative Example 3 > Comparative Example 2 > Comparative Example 1. This demonstrates that the three-dimensional network structure formed by the composite emulsion gel made of protein fibrils in Example 1 was more dense and stable.

[0036] In summary, compared to Example 1, the composite emulsion gels prepared without peanut protein fibrils (Comparative Example 1), with direct addition of peanut protein isolate (Comparative Example 2), and with addition of peanut protein fibrils formed by ultrasonic treatment at 60 W and heating for 8 h (Comparative Example 3) all exhibited varying degrees of uneven moisture distribution, weak intermolecular interactions, low hardness and gel strength, and insufficient rheological stability. Example 1, by preparing peanut protein fibrils with appropriate ultrasonic power and heat treatment time, effectively enhanced the synergistic effect between the fibrils, carrageenan, and peanut oil, thereby improving the structural stability and gel performance of the composite emulsion gel.

[0037] Application Examples Using Example 1 as a fat simulant, it was added to pork patties at different rates of pork back fat replacement (0%, 25%, 50%, 75%, 100%). The effects of different replacement rates on the texture, flavor, cooking loss, storage stability, and other quality characteristics of the pork patties were systematically investigated to determine the optimal fat replacement rate.

[0038] 1. Appearance: Pork patties with added emulsion gel have a more uniform color than those without. Figure 6 The 0% and 25% fat replacement samples had loose and uneven tissues, while the 50% and 75% replacement samples had fewer pores and a denser, finer texture. This may be because the addition of the emulsion gel interacts with the meat proteins, making the protein network structure more compact. The 100% fat replacement pork patty had a rougher surface, indicating that a higher fat replacement rate is not necessarily better; adding too much emulsion gel makes the pork patty loose and porous.

[0039] 2. Color difference: Use absorbent paper to dry the surface of the pork patty, and use a colorimeter to measure the brightness value of the pork patty ( L * ), redness value ( a * ) and yellowness value ( b * The measurement was performed using a whiteboard or blackboard before testing. L * The value represents brightness. a* The value represents whether it leans towards red or green. b * The values ​​represent whether the color leans towards yellow or blue, and the results are shown in Table 1: Table 1. Color difference of pork patties with different fat replacement rates As the fat replacement rate increases from 0% to 100%, pork patties... L * The overall increase in values ​​indicates that the product's brightness is improved after the emulsion gel replaces the pig's back fat, and its appearance is closer to the light-colored, milky-white gel fat phase. a * The value decreased overall as the substitution ratio increased, indicating that a high substitution rate would weaken the red color of the pork patty; b * The overall yellowness of the product was higher in the substitution group than in the control group, indicating a slight increase in yellowness. The above color difference changes suggest that the composite emulsion gel of this invention can improve the color uniformity and fat-mimicking appearance of pork patties. However, an excessively high substitution rate may result in excessively high product brightness and reduced redness. Therefore, it is advisable to select an appropriate substitution ratio based on appearance, texture, and water retention.

[0040] 3. Water retention: Cut the pork patties into 1 cm pieces. 3 After recording the mass (m1 / g) of the cube, wrap it with filter paper, place it in a centrifuge tube, and centrifuge at 4℃ and 5000 r / min for 15 min. Remove the meat cake, blot the surface moisture with filter paper, and record the mass (m2 / g). Each sample was measured three times.

[0041] The water retention of pork patties is calculated according to formula (1): In the formula: m 1 This is the initial weight (g) of the sample before centrifugation. m 2 It is the weight (g) of the sample after centrifugation to remove moisture.

[0042] like Figure 7 As shown, the water retention of pork patties at all substitution rates was above 70.00%, reaching its maximum (82.95%) at a substitution rate of 75%.

[0043] 4. Cooking loss: Accurately weigh 5.0 g of pork patty, seal it in a glass sample bottle, and boil for 15 min. After removing surface moisture, reweigh the sample. The cooking loss rate is calculated according to formula (2): In the formula: A 1 This is the initial weight of the sample before cooking; A2 The weight of the sample after removing moisture.

[0044] Lower cooking loss generally means the product has better moisture retention, which helps improve the texture and tenderness of meat products. For example... Figure 7 As shown, the water retention of pork patties with all replacement rates remained above 70.00%, reaching its highest at 75% replacement rate (82.95%), indicating that the appropriate addition of the composite emulsion gel can enhance the system's ability to bind water. Compared with the 0% replacement rate, the cooking losses of the 25%, 50%, and 75% replacement groups were all at a lower level, indicating that at these replacement levels, the emulsion gel can form a relatively dense gel network with meat proteins, effectively preventing the loss of water and fat during heating, thereby maintaining the juiciness and processing stability of the pork patties. When the fat replacement rate increased to 100%, the cooking loss rebounded, possibly because excessive emulsion gel weakened the continuous binding between myofibril proteins and gel particles, making the network structure looser and thus reducing water retention.

[0045] 5. Texture properties of pork patties: Texture profile analysis was performed on the gel samples using a TA / 0.5 gel probe. The initial test speed was set to 0.5 mm / s and maintained throughout the evaluation process, including the post-test phase. The test trigger point was set to 5.0 gf, and the interval between consecutive tests was 5.0 s. The required displacement was determined to be 7.0 mm, while the trigger force was configured to be 5.0 gf, and a return distance of 10 mm was applied. The results are shown in Table 2.

[0046] Table 2. Texture properties of pork patties with different fat substitution rates Hardness and chewiness initially increased and then decreased with increasing fat replacement rate. The highest value was achieved at a fat replacement rate of 50%, likely because the emulsion gel itself is less hard than pork fat. When pork back fat is ground up, its tissue structure is disrupted and collapses, while the emulsion gel, even after being ground up, remains as intact gel particles, maintaining its original gel structure and textural properties. This results in relatively high hardness and chewiness in the fat-replaced pork patties. There were little difference in elasticity and cohesion among pork patty samples with different fat replacement rates, indicating that the replacement of the fat mimic did not have a significant impact. Overall, pork patties with replacement rates between 50% and 75% exhibited good combined textural and water-retention properties.

[0047] In summary, the peanut protein fibrils-carrageenan-peanut oil composite emulsion gel prepared by this invention can form a stable three-dimensional network structure and play a role in fat simulation and moisture retention in pork patty systems. When used as a fat substitute in pork patties, an appropriate substitution ratio can improve the uniformity of the product's texture, reduce moisture and oil loss during cooking, and maintain good textural properties; among them, the 50% and 75% substitution groups showed better overall effects in terms of appearance, water retention, cooking loss, and textural performance. This indicates that the product of this invention can not only be used for fat reduction and quality improvement of meat products, but can also be further extended to the development of functional food products such as plant-based gel foods, low-fat baked goods, and nutrient delivery carriers, demonstrating significant application value.

[0048] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a peanut protein fibrils-carrageenan-peanut oil composite emulsion gel, characterized in that, Includes the following steps: (1) Preparation of peanut protein fibrils: Peanut protein isolate was dispersed in water to obtain peanut protein isolate dispersion; the pH of the system was adjusted to 2.0 and then hydrated overnight at 4℃. The insoluble matter was removed by centrifugation, ultrasonic treatment was performed and then heat treatment was performed. After the heat treatment was completed, the solution was immediately cooled in an ice-water bath to obtain peanut protein fibrils solution, which was then freeze-dried and stored for later use. (2) Preparation method of composite emulsion gel: After freeze-drying the peanut protein fibrillary solution obtained in step (1), it was reconstituted with deionized water to prepare a protein concentration of 62.5 mg / mL. The protein solution was hydrated overnight at 4℃, and then peanut oil was added and homogenized to obtain mixed system 1. After adjusting the pH of mixed system 1 to 6.0, carrageenan was added to make the final mass concentration of carrageenan in the system 0.6% to obtain mixed system 2. The obtained mixed system 2 was heated and then cooled and allowed to stand to form a peanut protein fibrillary-carrageenan-peanut oil composite emulsion gel.

2. The preparation method of the peanut protein fibrils-carrageenan-peanut oil composite emulsion gel as described in claim 1, characterized in that, The preparation method of peanut protein isolate in step (1) is as follows: Take peanut meal, add it to deionized water at a material-to-liquid ratio of 1g:15mL, adjust the pH of the solution to 8.5 with alkali, and stir at room temperature until completely dissolved; centrifuge at 4℃ and 4000×g for 30 min, and collect the supernatant; adjust the pH of the supernatant to 4.5 with acid to precipitate the protein, centrifuge again and collect the precipitate; wash the precipitate with deionized water and adjust the pH to 7.0 with alkali, dialyze for 48 h to remove salt, and freeze dry to obtain peanut protein isolate.

3. The preparation method of the peanut protein fibrils-carrageenan-peanut oil composite emulsion gel as described in claim 1, characterized in that, In step (1), the concentration of the dispersion prepared using the above-mentioned peanut protein isolate was 40 mg / mL; when adjusting the pH, sodium hydroxide with a concentration of 2 M and hydrochloric acid with a concentration of 2 M were used.

4. The preparation method of the peanut protein fibrils-carrageenan-peanut oil composite emulsion gel as described in claim 1, characterized in that, In step (1), the ultrasonic treatment power is 30-300 W, the treatment time is 10 min, the intermittent ultrasonic method is used, and the whole process is placed in an ice water bath.

5. The preparation method of the peanut protein fibrils-carrageenan-peanut oil composite emulsion gel as described in claim 1, characterized in that, In step (1), the heat treatment conditions are heating at 85℃ for 6 to 12 hours; after the heat treatment is completed, the water bath is cooled for at least 30 minutes.

6. The preparation method of the peanut protein fibrils-carrageenan-peanut oil composite emulsion gel as described in claim 1, characterized in that, In step (2), after soaking the peanut kernels, deionized water was added at a ratio of 1g:8mL. The mixture was then crushed at 22,000 rpm for 2 min using a high-speed homogenizer. Large particles were removed by filtration to obtain a slurry. The pH was adjusted to 6.0 with 0.5 M hydrochloric acid, and the slurry was centrifuged at 4℃ and 7000×g for 30 min. The upper white concentrate was collected. The white concentrate was then mixed with deionized water at a mass ratio of 1:5, and the pH was adjusted to 6.0 with 0.5 M hydrochloric acid. The mixture was centrifuged again at 7000×g for 30 min. The uppermost layer was collected as peanut oil. The peanut oil was then separated for later use.

7. The preparation method of the peanut protein fibrils-carrageenan-peanut oil composite emulsion gel as described in claim 1, characterized in that, In step (2), the amount of peanut oil added accounts for 20% of the total mass of the mixture 2.

8. The preparation method of the peanut protein fibrils-carrageenan-peanut oil composite emulsion gel as described in claim 1, characterized in that, In step (2), the heating temperature is 85℃ and the time is 30 min; after cooling to room temperature, it is left to stand at 4℃ for 12 h.

9. A peanut protein fibrils-carrageenan-peanut oil composite emulsion gel obtained by the preparation method according to any one of claims 1 to 8.

10. The application of the composite emulsion gel according to claim 9 in food processing, characterized in that: The applications include compound emulsion gels as one or more of the following: fat mimics, plant-based gel foods, baked goods, meat substitutes, and nutrient delivery carriers.

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