Method for improving the frozen characteristics of a soy protein isolate plant-based meat

Abstract

The application belongs to the field of food processing, and particularly relates to a method for improving the freezing characteristics of soybean protein isolate plant protein meat. Soybean 7S globulin and soybean 11S globulin are mixed as soybean protein isolate at a 7S / 11S mass ratio of 0.8-1.2:1, other plant proteins and auxiliary materials including TG enzyme high-temperature-resistant microcapsules are compounded, and a high-moisture extrusion process is used for preparation; after forming, heat setting, gradient cooling pretreatment and ultra-high pressure freezing treatment are performed to obtain plant protein meat with good freezing characteristics. The soybean protein isolate plant protein meat prepared by the method has a water holding capacity of 3.5-4.5 g / g, a fiber integrity of 82-95%, an elastic modulus of 250-320 KPa, a freeze-thaw syneresis rate of 15-25%, a gel strength of 35-45 N, a cooking loss rate of 5-15%, and a weakly bound free water proportion of 78-97% after one freeze-thaw cycle.

Description

Technical Field

[0001] This invention belongs to the field of food processing, and specifically relates to a method for improving the freezing properties of soy protein isolate plant protein meat. Background Technology

[0002] With global population growth, increasing environmental and resource constraints, and the upgrading of healthy eating concepts, plant-based meat, as a sustainable alternative to traditional meat, has become a research hotspot and industry growth point in the food industry due to its advantages of low saturated fat, low carbon emissions, and efficient resource utilization. Plant-based meat uses plant proteins such as soy protein isolate and pea protein isolate as core raw materials, and is a functional food that mimics the fibrous structure, texture, and flavor characteristics of animal muscle through processing technologies such as high-moisture extrusion, thermal gelation, and fibrous remodeling. In recent years, its market size has continued to expand. In 2024, the global plant-based meat market size reached US$8.9 billion, of which frozen plant-based meat accounted for more than 60% due to its extended shelf life (storage period of more than 6 months at -18 ℃) and suitability for cold chain distribution, becoming the core category driving the large-scale development of the industry.

[0003] Frozen plant-based meat has a complex composition, consisting mainly of plant protein matrix, functional additives, and water. During the freezing and thawing cycles, the system of existing frozen plant-based meat is prone to physicochemical changes, leading to a series of quality deterioration problems, which has become a key bottleneck restricting the upgrading of the frozen plant-based meat industry.

[0004] Soy protein isolate (SPI) is a protein product obtained from soybean meal (a byproduct of soybean oil extraction) through extraction, separation, and purification, with a dry-basis protein content of ≥90%. As a core ingredient in plant-based meat protein, SPI dominates in mimicking the fibrous structure and textural properties of animal meat due to its excellent gelling, emulsifying, and processability. SPI molecules exist as spherical aggregates, with hydrophobic groups encapsulated internally and hydrophilic groups exposed on the surface, exhibiting good water solubility. Heating, pH changes, and the addition of salt ions cause protein depolymerization, exposing the hydrophobic groups, which then cross-link through hydrophobic interactions, hydrogen bonds, and disulfide bonds to form a three-dimensional network structure. However, ice crystal formation under freezing conditions disrupts the uniformity of protein aggregates, leading to the aggregation of some subunits, affecting functional properties, decreasing water-holding capacity (reducing by 5%-8% per cycle), increasing gel hardness, and resulting in a dry, loose product. Furthermore, the emulsifying stability of SPI decreases significantly after freezing, leading to oil precipitation and affecting product texture uniformity. This damage is irreversible for plant-based meat products. In practical applications, the most obvious manifestations are hardening, fragility, and easy leakage of juices. These problems directly lead to insufficient market acceptance of frozen plant-based meat, and the quality stability during the shelf life is difficult to meet the needs of industrial distribution. Systematic research is urgently needed from the perspective of composition mechanism and regulation technology. Summary of the Invention The main objective of this invention is to provide a method for improving the freezing properties of soy protein isolate plant-based meat by addressing the shortcomings of existing technologies. This invention improves the freezing properties of soy protein isolate plant-based meat by combining raw materials, formulation, and freezing treatment to reduce irreversible damage such as decreased water retention, texture hardening, and fiber breakage that occurs during freezing.

[0005] The first aspect of this invention provides a method for improving the freezing properties of soy protein isolate plant-based meat. The method includes: selecting soy 7S globulin (β-conglycinin) and soy 11S globulin (soy globulin) mixed at a 7S / 11S mass ratio of 0.8-1.2:1 to form soy protein isolate; compounding other plant proteins and excipients including TG enzyme high-temperature resistant microcapsules; and preparing the mixture through a high-moisture extrusion process; after molding, the mixture undergoes heat setting, gradient cooling pretreatment, and ultra-high pressure freezing treatment to obtain plant-based meat with good freezing properties.

[0006] According to the above scheme, other plant proteins in the compound include: pea protein isolate, oat protein, and whey protein; the amount of each plant protein added is based on the mass of soy protein isolate: pea protein isolate 5-15%, oat protein 2-25%, whey protein 5-10% (the amount added is based on the mass of soy protein isolate).

[0007] According to the above scheme, the excipients also include vegetable oil, TG enzyme high-temperature resistant microcapsules, β-glucan, and konjac gum. The amount of each excipient added is based on the mass of soy protein isolate as follows: vegetable oil 3-6%, TG enzyme high-temperature resistant microcapsules 0.5-2.5%, β-glucan 2-7%, and konjac gum 0.1-0.3% (the amount added is based on the mass of soy protein isolate).

[0008] According to the above scheme, the TG enzyme and the wall material in the TG enzyme high-temperature resistant microcapsule are in a mass ratio of 1:4-5.

[0009] According to the above scheme, the TG enzyme high-temperature resistant microcapsules use whey protein isolate and low-denatured soy protein isolate at a mass ratio of 1:1.5-2.5 as wall materials. The TG enzyme and wall materials are mixed at a mass ratio of 1:4-5 to prepare a TG enzyme-protein mixed emulsion, which is then prepared by spray drying. Preferably, the solids content of the TG enzyme-protein mixed emulsion is 10%-12%.

[0010] Preferably, in the preparation of TG enzyme high-temperature resistant microcapsules, during spray drying, the inlet air temperature is 180-200℃, the outlet air temperature is 75-85℃, the feed rate is 10-15 mL / min, and the atomization pressure is 0.2-0.3 MPa.

[0011] According to the above scheme, the high-moisture extrusion process involves combining soybean protein isolate with other plant proteins and excipients including TG enzyme high-temperature resistant microcapsules in a specific subunit ratio, adding water to adjust the material moisture content to 55-65%, and then preparing it through a twin-screw extruder. During the extrusion protein preparation process, the temperature in the compression zone is 50-70℃, the temperature in the melting zone is 120-150℃, the temperature in the forming zone is 110-150℃, the screw speed is 250-300 RPM, and the material moisture content is 55-65%.

[0012] According to the above scheme, the heat setting is carried out at 70-85℃ for 20-30 minutes; the gradient cooling pretreatment and ultra-high pressure freezing treatment are carried out after the heat setting is cooled to 25-30℃, the heat setting is first placed in -1 to -4℃ for 1-2 hours for pretreatment, and then ultra-high pressure freezing treatment is carried out at -35 to -40℃ and 200-300 MPa pressure.

[0013] Specifically, the process can be as follows: the extruded protein meat is heat-set at 70-85℃ for 20-30 minutes, air-cooled to 25-30℃, then subjected to gradient cooling, pre-treated by refrigeration at -1 to -4℃ for 1-2 hours, and then frozen using ultra-high pressure freezing technology at -35 to -40℃ and 200-300 MPa.

[0014] According to the above scheme, after one freeze-thaw cycle, the water holding capacity of soy protein isolate plant protein meat is 3.5~4.5 g / g, the fiber integrity is 82-95%, the elastic modulus is 250-320 KPa, the freeze-thaw water separation rate is 15-25%, the gel strength is 35-45 N, the cooking loss rate is 5-15%, and the proportion of weakly bound free water is 78-97%.

[0015] A second aspect of the present invention provides soy protein isolate plant protein meat prepared by the above method.

[0016] This invention utilizes a 7S / 11S controlled ratio of soy protein isolate, along with appropriate amounts of other plant protein components including pea protein isolate, oat protein, whey protein, and excipients including β-glucan, transglutaminase (TG enzyme), and konjac gum. By leveraging the interactions between these components, a multi-layered protein network and moisture-locking mechanism are constructed. Combined with process control of ice crystal morphology and freeze-thaw kinetics, this enhances the water-holding capacity, elasticity, chewiness, and freeze-thaw resistance of soy protein isolate plant-based meat products. It significantly improves the gel strength and water-holding capacity of the plant-based meat products, resulting in frozen plant-based meat products with excellent firmness, elasticity, and freeze-thaw resistance. Specifically: 11S globulin has good gelling and film-forming properties, a higher proportion of hydrophobic amino acids, and a denser gel network formed after heat denaturation. It can lock in a large amount of water through capillary action and hydrogen bonding. 7S protein has excellent emulsifying activity and foaming properties, which can evenly disperse oil and water, improve product elasticity, alleviate the problem of excessive hardness of 11S gel, and optimize the texture. However, a high amount used may lead to an inability to support the chewy texture of meat, poor freezing stability, and a loose structure after thawing.

[0017] Through extensive research, this invention has discovered that, based on a specific 7S / 11S ratio (mass ratio of 0.8-1.2:1), the use of soy protein isolate in a synergistic system with other added protein components (pea protein isolate, oat protein, whey protein) and excipients forms a composite three-dimensional structure that is both soft and strong. This structure has a multi-layered protein network structure and multiple moisture-locking mechanisms, significantly improving the overall texture, juiciness, oil and water retention, and freeze-thaw stability of the product. This invention incorporates several key components, including 7S, which can form a mixed gel network with other proteins through non-covalent interactions. Additionally, the helical network formed by polysaccharide chains (such as konjac gum) during heating and cooling allows 7S molecules to fill, entangle, or attach to the polysaccharide network, ultimately forming an interpenetrating or coupled flexible and elastic gel network through non-covalent interactions. Furthermore, the combined effects of other plant protein molecules and excipients effectively buffer the expansion pressure of ice crystals during freezing. This gel network also possesses a degree of "stretchability," making it less susceptible to complete puncture or collapse by ice crystals. During thawing, the gel network can retract and recombine some of the melted water, reducing dripping loss, maintaining juiciness, and significantly improving freezing properties. This invention, based on the addition of other protein components and excipients to a 7S / 11S ratio soy protein isolate system, enables the constructed mixed gel network to possess superior flexibility, elasticity, and hardness. This addresses the problem in existing plant protein meat systems where the gel network is too rigid and easily torn or develops irreversible cracks due to the physical force of ice crystals, leading to easy leakage of water after thawing and resulting in poor frozen quality.

[0018] Pea protein is rich in hydrophilic amino acids. Its loose molecular conformation acts as a "water storage cavity," forming an elastic gel network to buffer the pressure of ice crystals. This stabilizes free water and reduces water loss during processing. At low temperatures, it binds tightly to water molecules to reduce free water content. This buffers the mechanical pressure from ice crystal growth during freeze-thaw cycles, inhibits ice crystal damage to the structure, and reduces water loss and texture deterioration after freeze-thaw cycles. The gel formed by β-lactoglobulin in whey protein has good flexibility, mitigating the damage to the plant protein network caused by ice crystal compression, and significantly improving the overall water retention and freeze-thaw resistance of plant-based meat. Furthermore, oat protein has significantly better water retention at room temperature than soybean and pea protein. Combined with the addition of β-glucan, it forms an interpenetrating network structure—the hydroxyl groups (-OH) of β-glucan can form multiple hydrogen bonds with protein molecules and water, locking in free water (reducing ice crystal formation) and buffering the mechanical damage to the protein network caused by ice crystals during freeze-thaw cycles. Building upon the aforementioned foundation, the use of TG enzyme heat-resistant microcapsules and konjac gum has resulted in a highly efficient "bio-physical" synergistic strategy. Konjac gum, with its excellent water-holding and gelling properties, can fill the gaps in the protein network during the early stages of processing, binding free water to quickly form a soft physical gel network, enhancing structural elasticity, instantly locking in water, improving lubricity, and providing basic support. Meanwhile, the TG enzyme heat-resistant microcapsules protect the TG enzyme from thermal processing damage, allowing it to be precisely released during extrusion, catalyzing the formation of a strong covalent cross-linked network between plant protein molecules, and strengthening the density and stability of the gel network. This synergy constructs a composite three-dimensional structure that combines softness and strength, significantly improving the overall texture, juiciness, oil and water retention, and freeze-thaw stability of the product. This makes it particularly suitable for developing high-quality plant protein meat products that require high-temperature processing and frozen storage.

[0019] In terms of processing, heat setting, gradient cooling pretreatment, and ultra-high pressure freezing technology are used to freeze the extruded plant protein meat. Heat setting further enhances the strength of the plant protein meat, while gradient cooling and ultra-high pressure freezing reduce the impact of freezing on the network and water-holding capacity of the plant protein meat. During freezing, free water in the plant protein meat first forms ice crystals. As the ice crystals grow, they compress the protein fiber network, causing network breakage. During thawing, the water generated by the melting of ice crystals cannot be reabsorbed by the protein matrix (the hydrophobic groups of the protein aggregate after being exposed, reducing water-holding sites), resulting in "drip water loss". Repeated freeze-thaw cycles also cause ice crystal recrystallization (small ice crystals fuse into large ice crystals), further aggravating structural damage, ultimately manifesting as decreased water-holding capacity, poor texture, and broken fiber structure. This invention reduces ice crystal formation through formulation and improves the freezing properties of plant-based meat by controlling ice crystal morphology and freeze-thaw rates. Before freezing, the protein is fully denatured at 70-85°C, a temperature conducive to gel formation, to form a dense gel network, which better resists ice crystal damage during freezing. During freezing, pre-crystallization, along with inhibiting ice crystal growth under high pressure and low temperature, reduces stress concentration during ice crystal formation and creates uniform, fine ice crystals, minimizing damage to the protein network. During thawing, the stable network reabsorbs moisture, preventing "drip water loss." This multi-layered protein network and moisture-locking mechanism based on the formulation, combined with process-controlled ice crystal morphology and freeze-thaw kinetics, enhance the product's water retention, elasticity, chewiness, and freeze-thaw resistance, effectively preventing deterioration of frozen plant-based meat and ensuring stable performance during processing, storage, and transportation.

[0020] The beneficial effects of this invention are: This invention focuses on improving the frozen quality of soy protein isolate plant-based meat. Through the selection and modification of plant-based meat raw materials and improvements to the freezing process, and by regulating protein network stability, ice crystal morphology, and freeze-thaw kinetics, a multi-layered protein network and moisture-locking mechanism are constructed based on the formulation. Furthermore, process control of ice crystal morphology and freeze-thaw kinetics enhances the product's water retention, elasticity, chewiness, and freeze-thaw resistance, effectively preventing the deterioration of the frozen plant-based meat's texture. It significantly improves the freezing characteristics and product quality of frozen plant-based meat.

[0021] The soy protein isolate plant protein meat of the present invention has a water holding capacity of 3.5~4.5 g / g, fiber integrity of 82-95%, elastic modulus of 250-320 KPa, freeze-thaw water separation rate of 15-25%, gel strength of 35-45 N, cooking loss rate of 5-15%, and weakly bound free water ratio of 78-97% after one freeze-thaw cycle. Attached Figure Description

[0022] Figure 1The figures show the microstructure of the soy protein isolate plant-based meat from Examples 1-4 and Comparative Examples 1-4 after a single freeze-thaw cycle. As can be seen from the figures, the plant-based meat in the examples retains a relatively dense structure with few voids after freeze-thaw. In contrast, the plant-based meat in the comparative examples exhibits a sparse network structure after freeze-thaw treatment. This indicates that the growth of ice crystals generates significant localized mechanical stress, directly piercing or compressing the surrounding protein network, leading to network breakage and pore deformation. The formulation and process of this invention enable the prepared plant-based meat to possess better freeze-thaw characteristics. Detailed Implementation To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0023] Example 1 A method for improving the freezing properties of soy protein isolate plant-based meat includes the following steps: 7S (β-conglycinin) and 11S (glycinin) were mixed at a mass ratio of 1.0:1.0 to form soy protein isolate, which was then compounded with 10% pea protein isolate, 15% oat protein, and 8% whey protein (based on the mass of soy protein isolate). In addition, 5% vegetable oil, 2.2% heat-resistant microcapsules, 5% β-glucan, and 0.2% konjac gum (based on the total mass of the above proteins) were added. The mixture was then mixed with water and processed into plant protein meat using a twin-screw extruder. During extrusion, the temperature of the compression zone was controlled at 60℃, the temperature of the melting zone at 145℃, the temperature of the forming zone at 150℃, the screw speed at 300 RPM, and the moisture content of the material at 60%. After forming, the protein meat was first heat-set at 80-85℃ for 20-30 min, then air-cooled to 25-30℃, and then subjected to gradient cooling treatment (refrigerated at -1 to -4℃ for 2 hours, then transferred to -35 to -40℃) and frozen at 250 MPa pressure. The high-temperature resistant TG enzyme microcapsules used in this invention are prepared by using whey protein isolate and low-denatured soy protein isolate as wall materials (mass ratio 1:2.0). The TG enzyme and protein wall material are mixed in a ratio of 1:4 to form a TG enzyme-protein mixed emulsion with a solid content of 10%-12%. The microcapsules are prepared by spray drying. During drying, the inlet air temperature is 180-200℃, the outlet air temperature is 75-85℃, the feed rate is 12 mL / min, and the atomization pressure is 0.25 MPa.

[0024] Example 2 A method for improving the freezing properties of soy protein isolate plant-based meat includes the following steps: 7S (β-conglycinin) and 11S (glycinin) were mixed at a mass ratio of 0.8:1.0 to form soy protein isolate, which was then compounded with 12% pea protein isolate, 5% oat protein, and 10% whey protein (based on the mass of soy protein isolate). In addition, 6% vegetable oil, 2.5% heat-resistant microcapsules, 2% β-glucan, and 0.3% konjac gum (based on the total mass of the above proteins) were added. The mixture was then mixed with water and processed into plant protein meat using a twin-screw extruder. During extrusion, the temperature of the compression zone was controlled at 50℃, the temperature of the melting zone at 125℃, the temperature of the forming zone at 111℃, the screw speed at 280 RPM, and the moisture content of the material at 65%. After forming, the protein meat was first heat-set at 70-75℃ for 20-30 min, then air-cooled to 25-30℃, and then subjected to gradient cooling treatment (refrigerated at -1 to -4℃ for 1.2 hours, then transferred to -35 to -40℃) and frozen at 300 MPa pressure. The high-temperature resistant TG enzyme microcapsules used in this invention are prepared by using whey protein isolate and low-denatured soy protein isolate as wall materials (mass ratio 1:1.7). The TG enzyme and protein wall material are mixed at a ratio of 1:4.5 to form a TG enzyme-protein mixed emulsion with a solid content of 10%-12%. The microcapsules are prepared by spray drying. During drying, the inlet air temperature is 180-200℃, the outlet air temperature is 75-85℃, the feed rate is 14 mL / min, and the atomization pressure is 0.27 MPa.

[0025] Example 3 A method for improving the freezing properties of soy protein isolate plant-based meat includes the following steps: 7S (β-conglycinin) and 11S (glycinin) were mixed at a mass ratio of 1.1:1 to form soy protein isolate, which was then compounded with 5% pea protein isolate, 22% oat protein, and 5% whey protein (based on the mass of soy protein isolate). In addition, 3% vegetable oil, 0.5% heat-resistant microcapsules, 7% β-glucan, and 0.1% konjac gum (based on the total mass of the above proteins) were added. The mixture was then mixed with water and processed into plant protein meat using a twin-screw extruder. During extrusion, the temperature of the compression zone was controlled at 50℃, the temperature of the melting zone at 145℃, the temperature of the forming zone at 130℃, the screw speed at 250 RPM, and the moisture content of the material at 58%. After forming, the protein meat was first heat-set at 78-83℃ for 20-30 min, then air-cooled to 25-30℃, and then subjected to gradient cooling treatment (refrigerated at -1 to -4℃ for 2 hours, then transferred to -35 to -40℃) and frozen at 200 MPa pressure. The high-temperature resistant TG enzyme microcapsules used in this invention are prepared by using whey protein isolate and low-denatured soy protein isolate as wall materials (mass ratio 1:2.5). The TG enzyme and protein wall material are mixed in a ratio of 1:5 to form a TG enzyme-protein mixed emulsion with a solid content of 10%-12%. The microcapsules are prepared by spray drying. During drying, the inlet air temperature is 180-200℃, the outlet air temperature is 75-85℃, the feed rate is 13 mL / min, and the atomization pressure is 0.2 MPa.

[0026] Example 4 A method for improving the freezing properties of soy protein isolate plant-based meat includes the following steps: 7S (β-conglycinin) and 11S (glycinin) were mixed at a mass ratio of 1.2:1 to form soy protein isolate, which was then compounded with 8% pea protein isolate, 15% oat protein, and 9% whey protein (based on the mass of soy protein isolate). In addition, 4% vegetable oil, 1.5% heat-resistant microcapsules, 5% β-glucan, and 0.15% konjac gum (based on the total mass of the above proteins) were added. The mixture was then mixed with water and processed into plant protein meat using a twin-screw extruder. During extrusion, the temperature of the compression zone was controlled at 60℃, the temperature of the melting zone at 145℃, the temperature of the forming zone at 120℃, the screw speed at 280 RPM, and the moisture content of the material at 60%. After forming, the protein meat was first heat-set at 72-77℃ for 20-30 min, then air-cooled to 25-30℃, and then subjected to gradient cooling treatment (refrigerated at -1 to -4℃ for 2 hours, then transferred to -35 to -40℃) and frozen at 280 MPa pressure. The high-temperature resistant TG enzyme microcapsules used in the invention are prepared by using whey protein isolate and low-denatured soy protein isolate as wall materials (mass ratio 1:1.5, mixed at a ratio of 1:4.8 of TG enzyme to protein wall material to form a TG enzyme-protein mixed emulsion with a solid content of 10%-12%). The preparation is carried out by spray drying, with an inlet air temperature of 180-200℃, an outlet air temperature of 75-85℃, a feed rate of 15 mL / min, and an atomization pressure of 0.3 MPa.

[0027] The 7S (β-conglycinin) and 11S (glycinin) in this invention can be obtained by separating soy protein isolate through sedimentation, and the obtained 7S (β-conglycinin) and 11S (glycinin) can be mixed and used as soy protein isolate.

[0028] Comparative Example 1 7S (β-conglycinin) and 11S (glycinin) were mixed at a mass ratio of 1.0:1.0 to form soy protein isolate (without any other plant protein or whey protein added). Additionally, 5% vegetable oil, 2.2% heat-resistant microcapsules, 5% β-glucan, and 0.2% konjac gum (based on soy protein isolate content) were added. Protein meat was prepared using a high-moisture extrusion process with the same process parameters as in Example 1. The heat setting and freezing procedures after molding were also the same as in Example 1.

[0029] After freezing-thawing cycles, the resulting protein meat exhibited significant textural degradation, a coarse chewiness, a marked decrease in elasticity, and a juice loss rate far exceeding that of Example 1. This indicates that soy protein isolate controlled solely by a 7S / 11S ratio, even with the addition of other modifiers, cannot form a stable and dense fiber network under high-pressure freezing conditions. The combination of pea protein, oat protein, and whey protein plays a crucial synergistic role in constructing a composite protein matrix that combines toughness and water retention under specific extrusion and freezing conditions.

[0030] Comparative Example 2 The protein formulation and additives were exactly the same as in Example 1, but without the addition of heat-resistant TG enzyme microcapsules. The high-moisture extrusion process and subsequent heat setting and freezing steps were also consistent with those in Example 1.

[0031] The resulting protein meat was soft in texture and lacked sufficient fibrous strength before freezing. After high-pressure freezing, the damage to the protein network caused by internal ice crystals intensified, resulting in significant structural collapse, reduced water-holding capacity, and a loose texture after thawing. This indicates that using heat-resistant microcapsules of TG enzyme protects the TG enzyme from heat processing damage. Combined with soy protein isolate and other protein components, along with excipients, the TG enzyme can be precisely released during extrusion, catalyzing the formation of a strong covalent cross-linked network between plant protein molecules. This, combined with the effects of other excipients, imparts the final product with elasticity, chewiness, and excellent freezing properties.

[0032] Comparative Example 3 The protein compounding scheme was the same as in Example 1, with the addition of 5% vegetable oil and 2.2% heat-resistant microcapsules, but without the addition of β-glucan and konjac gum. The high-moisture extrusion process and subsequent heat setting and freezing treatment steps were consistent with those in Example 1.

[0033] The resulting protein meat exhibited poor water retention after freezing, resulting in significant juice loss upon thawing and a dry, tough texture. The gel strength and viscoelasticity of the product were significantly lower than in Example 1. This indicates that the addition of β-glucan and konjac gum can form an interpenetrating, complex gel system with the protein network, effectively binding water and reducing cell damage caused by ice crystal formation and growth during freezing. Their water-retention and texture-improving effects are synergistic, which cannot be achieved by relying solely on the protein network.

[0034] Comparative Example 4 The protein compounding scheme, additives, high-moisture extrusion process, and heat setting steps were exactly the same as in Example 1. However, in the freezing stage, the gradient cooling treatment was omitted (i.e., the -1 to -4°C refrigeration stage was skipped), and the air-cooled protein meat was directly placed in an environment of -35 to -40°C and frozen at 250 MPa pressure.

[0035] After thawing, the resulting protein meat exhibited large ice crystal pores, uneven texture, and fiber breakage in some areas, resulting in poor overall integrity. Its water retention and elasticity were significantly lower than those of Example 1, which employed gradient cooling. This indicates that gradient cooling (refrigeration near the freezing point) is a crucial pre-treatment step for high-pressure assisted freezing. It helps promote uniform water distribution within the protein network and the formation of numerous small ice crystal nuclei, thereby enabling the formation of fine, uniform ice crystals during subsequent ultra-high-pressure deep freezing, maximizing the protection of the protein fiber structure's integrity.

[0036] The soy protein isolates prepared in the examples and comparative examples were thawed and subjected to one freeze-thaw cycle. Their water-holding capacity, fiber integrity, elastic modulus, freeze-thaw water separation rate, gel strength, cooking loss rate, and proportion of weakly bound free water were measured. The results are shown in Table 1, and the microstructure diagram is shown in [Figure number missing]. Figure 1 As can be seen from the table, the prepared plant protein meat in the examples exhibits high water-holding capacity (3.7-4.1 g / g), fiber integrity (87-95%), elastic modulus (269-310 KPa), gel strength (38-45 N), and a low proportion of weakly bound water (92-95%), as well as low freeze-thaw separation rate (16-22%) and cooking loss rate (7-14%). Even after freeze-thaw cycles, the plant protein meat retains a relatively compact structure with few voids, while the trend in the comparative examples is the opposite of that in the examples. A comparison between the comparative examples and the examples reveals that the combination of proteins from different sources (peas, oats, whey) with a specific proportion of soy protein provides a functionally complementary matrix, which is the basis for forming a freeze-resistant structure. The heat-resistant TG enzyme microcapsules undergo in-situ protein cross-linking during extrusion, significantly strengthening the network and enabling it to resist freezing stress. The combined use of β-glucan and konjac gum stabilizes the system's moisture state through water retention and thickening effects, reducing the content of freezeable water and ice crystal breakage based on water retention and texture improvement. The combination of gradient cooling and high-pressure freezing processes, working synergistically with the above-mentioned optimized formulation, achieves precise control over ice crystal size. In this embodiment of the invention, the protein compound system, the heat-resistant microcapsule TG enzyme, the hydrophilic colloids (β-glucan and konjac gum), and the gradient cooling and high-pressure freezing process are four interconnected and indispensable elements, forming a complete technical solution for significantly improving the freezing properties of plant-based meat protein, achieving synergistic technical effects superior to conventional methods or those lacking any one of the elements.

[0037] Table 1. Characteristics of soy protein isolate plant-based meat after one freeze-thaw cycle.

[0038] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for improving the freezing properties of soy protein isolate plant-based meat, characterized in that: Soybean 7S globulin and soybean 11S globulin were mixed at a 7S / 11S mass ratio of 0.8-1.2:1 to form soy protein isolate. Other plant proteins and excipients, including TG enzyme high-temperature resistant microcapsules, were then combined and prepared using a high-moisture extrusion process. After molding, the mixture underwent heat setting, gradient cooling pretreatment, and ultra-high pressure freezing to obtain plant protein meat with good freezing properties.

2. The method according to claim 1, characterized in that: Other plant proteins in the blend include: pea protein isolate, oat protein, and whey protein. Measured by soy protein isolate, the amount of each plant protein added is based on the mass of soy protein isolate: pea protein isolate 5-15%, oat protein 2-25%, whey protein 5-10%.

3. The method according to claim 1, characterized in that: The excipients also include vegetable oil, TG enzyme high-temperature resistant microcapsules, β-glucan, and konjac gum. The amount of each excipient added is based on the mass of soy protein isolate as follows: vegetable oil 3-6%, TG enzyme high-temperature resistant microcapsules 0.5-2.5%, β-glucan 2-7%, and konjac gum 0.1-0.3%.

4. The method according to claim 3, characterized in that: The TG enzyme in the high-temperature resistant microcapsule is in a mass ratio of 1:4-5 to the wall material.

5. The method according to claim 4, characterized in that: Using whey protein isolate and low-denatured soy protein isolate at a mass ratio of 1:1.5-2.5 as wall materials, TG enzyme and wall materials were mixed at a mass ratio of 1:4-5 to prepare a TG enzyme-protein mixed emulsion, which was then prepared by spray drying.

6. The method according to claim 5, characterized in that: In the preparation of TG enzyme high-temperature resistant microcapsules, during spray drying, the inlet air temperature is 180-200℃, the outlet air temperature is 75-85℃, the feed rate is 10-15 mL / min, and the atomization pressure is 0.2-0.3 MPa.

7. The method according to claim 1, characterized in that: The high-moisture extrusion process involves mixing soy protein isolate with other plant proteins and excipients including TG enzyme high-temperature resistant microcapsules, adjusting the material moisture content to 55-65%, and then extruding the mixture using a twin-screw extruder. During the extrusion process, the temperature in the compression zone is 50-70℃, the temperature in the melting zone is 120-150℃, the temperature in the forming zone is 110-150℃, the screw speed is 250-300 RPM, and the material moisture content is 55-65%.

8. The method according to claim 1, characterized in that: The heat setting is performed at 70-85℃ for 20-30 minutes; the gradient cooling pretreatment and ultra-high pressure freezing treatment are performed after the heat setting is cooled to 25-30℃, then placed in a refrigerator at -1 to -4℃ for 1-2 hours for pretreatment, and then subjected to ultra-high pressure freezing treatment at -35 to -40℃ and 200-300 MPa pressure.

9. The method according to claim 1, characterized in that: Soy protein isolate plant protein meat, after one freeze-thaw cycle, has a water holding capacity of 3.5~4.5 g / g, fiber integrity of 82-95%, elastic modulus of 250-320 KPa, freeze-thaw water separation rate of 15-25%, gel strength of 35-45 N, cooking loss rate of 5-15%, and weakly bound free water ratio of 78-97%.

10. Soy protein isolate plant-based meat prepared by any of the methods in claims 1-9.

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