Low-temperature preservation method for livestock and poultry aquatic products

Abstract

The invention provides a low-temperature preservation method for livestock and poultry aquatic products. The method comprises the following steps: firstly, cleaning, cutting, deodorizing and dewatering the livestock and poultry aquatic products; then argon is used as working gas, the meat surface is activated through low-temperature plasma equipment, light composite enzymolysis of the meat surface is completed within 30 s, and redundant enzyme liquid is removed through low-temperature flushing at the temperature of 0-2 DEG C; then dispersing the micro-nano PEG-CMC phase change material in a biological response type coating liquid, carrying out ultrasonic in-situ compounding, and then spraying to the surface of a food material to carry out load type coating treatment; immediately sending into partial freezing equipment, cooling at the initial cooling rate of 0.02-0.04 DEG C / min, and preserving at the constant temperature of-2 DEG C to-3 DEG C for 7-60 days; and unfreezing without damage after the preservation is finished, and removing the coating film through low-temperature and high-pressure spraying or wiping and washing. According to the method, mild enzymolysis is combined with response type phase change coating, meat is moderately tenderized, it is guaranteed that food materials retain water and lock freshness, the antibacterial effect is stable, the fresh-keeping period of livestock and poultry aquatic products is greatly prolonged, the coating is easy to clean and free of residues, and the fresh-keeping effect and food safety are both considered.

Description

Technical Field

[0001] This invention relates to the field of food preservation technology, specifically to a method for low-temperature preservation of livestock, poultry, and aquatic products. Background Technology

[0002] Livestock and aquatic products are rich in high-quality protein, unsaturated fatty acids and other nutrients, and are an important part of the diet. However, due to their high water and nutrient content, they are prone to microbial growth on the surface and are susceptible to quality deterioration such as meat oxidation, juice loss and decreased tenderness during storage. This makes preservation difficult and has become a key pain point restricting their processing and distribution.

[0003] Currently, existing low-temperature preservation technologies for livestock, poultry, and aquatic products mainly rely on simple micro-freezing and conventional coating preservation. While simple micro-freezing can inhibit microbial growth, it is prone to producing large ice crystals due to insufficient temperature control precision, which damages the structure of meat cells, resulting in severe juice loss and tough meat after thawing. Conventional coating preservation often uses a single film-forming material, which has problems such as poor barrier properties and weak temperature control. In addition, the coating has low adhesion to the meat surface, is easy to fall off, has a short preservation period, and some coating materials also have the problem of residues that are difficult to clean, affecting food safety.

[0004] Meanwhile, traditional preservation processes struggle to simultaneously achieve both meat tenderization and preservation / antibacterial inhibition. Enzymatic tenderization alone can lead to overly soft meat and reduced water retention, and the lack of coordination between different preservation stages prevents the formation of a comprehensive quality assurance system. Therefore, developing a low-temperature preservation method for livestock, poultry, and aquatic products that can achieve both appropriate meat tenderization and long-term preservation / antibacterial inhibition has become a pressing technical challenge for the industry. Summary of the Invention

[0005] Technical problem to be solved: In view of the above-mentioned technical problems, the purpose of this invention is to provide a low-temperature preservation method for livestock, poultry and aquatic products. By combining mild enzymatic hydrolysis with a responsive phase change coating, the meat is moderately tenderized, and the ingredients are kept moist and fresh. The antibacterial effect is stable, and the preservation period of livestock, poultry and aquatic products is greatly extended. Moreover, the coating is easy to clean and leaves no residue, thus taking into account both preservation effect and food safety.

[0006] Technical solution: A method for low-temperature preservation of livestock, poultry and aquatic products, comprising the following steps: S1. Pre-treatment: Clean, cut, and deodorize the livestock, poultry and aquatic products to remove surface impurities and excess moisture, and set aside for later use; S2. Low-temperature plasma activation: Argon is used as the working gas. The pretreated livestock and aquatic products are placed in a low-temperature plasma device to activate the surface of the meat. This breaks the dense arrangement of molecules on the surface of the meat, activates active groups such as hydroxyl and carboxyl groups, and enhances the surface hydrophilicity and reactivity. S3. Compound enzymatic hydrolysis: Within 30 seconds after plasma activation treatment, the surface of livestock, poultry and aquatic products is immediately subjected to mild enzymatic hydrolysis. After enzymatic hydrolysis, the products are rinsed at a low temperature of 0~2℃ to remove excess enzyme solution, thus obtaining enzymatically hydrolyzed livestock, poultry and aquatic products. Enzymatic hydrolysis and plasma activation form a synergistic effect. The active groups activated by plasma can promote the adsorption and catalytic efficiency of enzyme preparations, while avoiding meat quality damage caused by over-enzymatic hydrolysis, thus achieving molecular-level synergy between activation and enzymatic hydrolysis. S4. Loaded Coating Treatment: Micronized PEG-CMC phase change material is uniformly dispersed in a bio-responsive coating solution. Through an ultrasonic in-situ composite process, the PEG-CMC phase change material and the coating solution form an interpenetrating network structure. The PEG-CMC phase change material and the coating solution are molecularly bonded through intermolecular hydrogen bonding. After ultrasonic in-situ composite, the surface of enzymatically hydrolyzed livestock and aquatic products is coated by spraying. The PEG-CMC phase change material and the bio-responsive coating solution have excellent compatibility. The interpenetrating network structure can simultaneously enhance the coating density, phase change temperature control stability, and coating-meat adhesion. S5. Micro-freezing and constant temperature preservation: The coated livestock and aquatic products are immediately sent into the micro-freezing equipment. The initial cooling rate is controlled at 0.02~0.04℃ / min. During the constant temperature stage, the temperature is maintained at -2℃~-3℃. Utilizing the dynamic cold release characteristics of the PEG-CMC phase change material in the film and relying on the latent heat of phase change of the PEG-CMC phase change material, the cold energy is rapidly released and slowly stored when the micro-freezing temperature fluctuates. This is precisely matched with the micro-freezing constant temperature, achieving dual temperature control synergy of coating crystal control and micro-freezing constant temperature. This effectively inhibits ice crystal aggregation and growth, avoids damage to the meat quality caused by temperature fluctuations, and has a preservation period of 7~60 days. S6. Non-destructive thawing and coating removal: After preservation, thaw using conventional non-destructive thawing methods. After thawing, peel off and remove the surface-loaded coating by low-temperature high-pressure spraying or manual wiping and rinsing with clean water, and then proceed with subsequent processing.

[0007] Furthermore, the activation conditions described in S2 are: power 80~150W, temperature 0~4℃, and time 1~2min.

[0008] Furthermore, the enzymatic hydrolysis conditions described in S3 are as follows: using a protease-lipase complex enzyme, hydrolysis temperature of 0~4℃, hydrolysis time of 5~10min, and enzyme addition amount of 0.03~0.06%.

[0009] Furthermore, the mass ratio of protease to lipase in the protease-lipase complex is 1:(1.5~2.5).

[0010] Furthermore, the preparation method of the micro / nano-sized PEG-CMC phase change material described in S4 is as follows: S41. Place food-grade polyethylene glycol 4000 (PEG4000) and sodium carboxymethyl cellulose (CMC) in a vacuum drying oven at 60~65℃ and dry for 2~3 hours. Cool to room temperature and pass through an 80-mesh sieve for later use. S42. Add deionized water to a low-temperature reactor equipped with a magnetic stirrer, and control the reactor temperature at 35~40℃. First, add CMC and stir at 300~400r / min until the CMC is completely dissolved. Slowly add PEG4000 and continue stirring until the PEG forms a uniform suspension dispersion system in the CMC aqueous solution without obvious particle agglomeration. S43. Raise the temperature of the reactor to 50~55℃, adjust the stirring rate to 500~600r / min, and stir at a constant temperature for 2~2.5h. Utilize the hydrogen bonding between the hydroxyl and carboxyl groups in CMC molecules and the hydroxyl groups in PEG molecules to achieve non-chemical cross-linking physical composite and form a stable PEG-CMC composite system. S44. Cool the composite system to 25~30℃, granulate it using spray granulation method (inlet air temperature 80~85℃, outlet air temperature 40~45℃, feed rate 5~8mL / min) to prepare PEG-CMC composite microspheres with a particle size of 100~200μm, and dry them in a vacuum drying oven at 40~45℃ until the moisture content of the composite microspheres is ≤1% to obtain primary PEG-CMC phase change material; S45. The primary PEG-CMC phase change material was added to a planetary ball mill, and anhydrous ethanol was used as the dispersion medium (solid-liquid ratio 1:5). Zirconia ball milling beads (ball-to-material ratio 8:1) were used to ball mill the material at a speed of 200~300 r / min for 2~3 h. After ball milling, the material was centrifuged (3000 r / min, 10 min) to remove the anhydrous ethanol. The product was then vacuum dried and sieved to obtain micro-nano PEG-CMC phase change material with a particle size ≤5 μm.

[0011] Furthermore, the mass ratio of CMC, PEG4000 and deionized water in S42 is 3:1:(32~40).

[0012] Furthermore, the preparation method of the bio-responsive coating liquid described in S4 is as follows, by weight: (1) Sodium alginate and gellan gum were dried in a vacuum drying oven at 50°C for 1.5 hours and then cooled to room temperature before being passed through a 100-mesh sieve. (2) Dissolve 5-6 parts of sodium alginate and 0.3-0.5 parts of gellan gum in 82-88 parts of deionized water at 45-50℃ to form a polysaccharide-based solution; (3) Add 1.5 to 2 parts of glycerol and 0.1 to 0.2 parts of ε-polylysine sequentially at a stirring rate of 300 to 400 r / min, and continue stirring for 20 to 30 min to form a stable composite coating solution; (4) Homogenize the composite coating liquid twice under a pressure of 30 MPa, degas it under vacuum at room temperature for 15 min, add deionized water, and adjust the viscosity to 200~300 mPa·s; (5) Filter with 200 mesh filter cloth to obtain bio-responsive coating liquid.

[0013] Furthermore, the amount of micro-nano PEG-CMC phase change material added in S4 is 5-10% of the mass of the bio-responsive coating liquid; the ultrasonic in-situ composite conditions are: ultrasonic power 200-300W, ultrasonic time 10-15min, ultrasonic temperature 0-4℃, to ensure that the PEG-CMC phase change material is uniformly dispersed and forms a stable interpenetrating network structure with the coating liquid.

[0014] Furthermore, the coating thickness described in S4 is 0.02~0.15 mm.

[0015] Furthermore, the conditions differ for different categories of livestock, poultry, and aquatic products: For high-moisture fish: the activation treatment time is 1.5~2 min, the enzymatic hydrolysis time is 8~10 min, and the amount of micro-nano PEG-CMC phase change material added is 7%~10% of the mass of the bio-responsive coating solution. This enhances the synergistic water-locking and crystal-controlling ability of activation-enzymatic hydrolysis-coating, and avoids dehydration of fish flesh and ice crystal damage. High-protein livestock and poultry cut meat: The mass ratio of protease to lipase in the protease-lipase complex enzyme is 1:1.5, the enzymatic hydrolysis time is 5~7 min, and the activation power is 80~120W. This avoids excessive protein degradation and excessive activation of the meat surface. Combined with the synergistic effect of intramembrane phase change material crystal control and micro-freezing constant temperature, the elasticity and flavor of livestock and poultry meat are preserved. For easily detached and perishable crustaceans: The coating thickness is 0.1~0.15mm, the amount of micro-nano PEG-CMC phase change material added is 8~10% of the mass of the bio-responsive coating solution, the activation treatment time is 1.5~2min, which enhances the plasma-enzyme hydrolysis linkage activation effect, improves the adhesion between the coating and the crustacean and meat, stabilizes the surface temperature of the meat, avoids crustacean detachment and meat spoilage, and achieves long-term freshness preservation.

[0016] Beneficial effects: 1. This invention achieves moderate tenderization of meat and ensures water retention and freshness preservation of ingredients through mild enzymatic hydrolysis combined with a responsive phase change coating. It also provides stable antibacterial effects, significantly extending the shelf life of livestock and aquatic products. Furthermore, the coating is easy to clean and leaves no residue, balancing preservation effectiveness and food safety. 2. This invention utilizes high-energy particle bombardment and free radical modification of plasma to break the dense arrangement of molecules on the surface of livestock and aquatic products, directionally introducing active groups such as hydroxyl and carboxyl groups. This activates the meat surface and enhances surface reactivity, laying the foundation for subsequent adsorption catalysis by compound enzymatic hydrolysis and molecular-level bonding with the supported coating. Simultaneously, it assists in removing trace impurities from the surface, avoiding interference from impurities. 3. This invention controls the mild enzymatic hydrolysis to be carried out immediately within 30 seconds after plasma activation. By utilizing the activated active groups on the surface of the meat, the adsorption efficiency and catalytic activity of the enzyme preparation are significantly promoted, and the hydrolysis rate is increased. At the same time, by controlling the degree of hydrolysis, mild hydrolysis is achieved, which effectively improves the tenderness of livestock, poultry and aquatic products and improves the taste, while avoiding meat damage caused by excessive hydrolysis. At the same time, the optimal surface state for the coating to be adapted and bonded to the meat is formed, creating conditions for the subsequent molecular-level bonding of the coating to the meat. 4. This invention uses an ultrasonic in-situ composite process to combine micro-nano food-grade PEG-CMC phase change material with a bio-responsive coating liquid to prepare a loaded coating material. This allows the phase change material to be uniformly embedded in the molecular network of the coating liquid, forming a stable interpenetrating network structure, which prevents the phase change material from precipitating out. At the same time, it achieves a synergistic effect of coating barrier function and phase change temperature control function, improves the tensile strength and barrier performance of the coating, and endows the phase change material with dynamic cold release characteristics, so that it can adjust the cold release rate according to the ambient temperature. 5. The present invention loads the phase change material into the coating liquid at a ratio of 5%-10% by mass, and controls its phase change temperature to -2℃ to -3℃. 6. This invention utilizes the synergistic effect of the loaded coating and the enzymatic hydrolysis process to form a molecular-level bond between the small amount of enzymatic hydrolysis products remaining on the surface of the meat after enzymatic hydrolysis and the interpenetrating network structure of the loaded coating, thereby improving the coating adhesion and solving the industry pain points of easy coating peeling and unstable preservation effect of existing coatings. 7. This invention utilizes bio-responsive coating components in a loaded coating, combined with pre-treatment involving plasma activation and enzymatic hydrolysis, to achieve intelligent response regulation throughout the entire preservation cycle of livestock and aquatic products. This results in precise matching of antibacterial and water-retention strategies based on quality changes at different preservation stages: In the initial preservation stage (0-3 days), sodium alginate and gellan gum form a dense and slightly breathable base film layer. A small amount of ε-polylysine is released to achieve basic antibacterial action, while slight swelling of the film layer ensures normal respiration of the food, preventing spoilage. In the middle preservation stage (3-7 days), trace amounts of organic acids produced by the proliferation of spoilage bacteria on the food surface cause a slight decrease in pH, triggering moderate structural relaxation of the gellan gum and its active release of the loaded coating. The ε-polylysine enhances the antibacterial concentration to specifically inactivate spoilage bacteria. Simultaneously, relying on the slight water loss of the food leading to a decrease in water activity, it triggers the contraction of the sodium alginate membrane to form a hydrophobic layer, locking in the internal moisture of the food and effectively reducing the water loss rate. In the later stages of preservation (more than 7 days), the large amount of organic acids produced by the continuous reproduction of spoilage bacteria causes the pH to drop further, triggering the further relaxation of the gellan gum structure and the continuous release of ε-polylysine to strengthen antibacterial activity. At the same time, relying on the intensified water loss trend of the food, it triggers the further contraction of the sodium alginate membrane to form a highly dense water-retaining layer, and the air permeability of the membrane layer decreases simultaneously, thoroughly inhibiting the reproduction of spoilage bacteria, minimizing water loss of the food, and inhibiting the further growth of aerobic spoilage bacteria. 8. This invention, through the adaptation of micro-freezing constant temperature process and loaded coating, controls the initial cooling rate to 0.02-0.04℃ / min and the constant temperature to -2℃ to -3℃. This precisely matches the phase change temperature and dynamic cold release characteristics of the PEG-CMC phase change material inside the film, achieving a dual temperature control synergistic effect: During the micro-freezing cooling stage, the phase change material slowly absorbs cold, avoiding the formation of large ice crystals due to excessively rapid cooling; during the constant temperature stage, the phase change material dynamically releases cold according to temperature fluctuations, stably maintaining a constant temperature environment, effectively inhibiting ice crystal aggregation, and avoiding damage to the meat caused by temperature fluctuations. At the same time, combined with the barrier effect of the coating, it reduces the sublimation of moisture and cross-contamination of food in the micro-freezing environment, significantly improving the accuracy of temperature control and the stability of preservation. Detailed Implementation

[0017] This invention proposes a method for low-temperature preservation of livestock, poultry, and aquatic products. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following will provide a more detailed description of the invention in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0018] Example 1 The preparation method of micro / nano-sized PEG-CMC phase change material is as follows: S41. Place food-grade PEG4000 and CMC separately in a vacuum drying oven at 60℃ for 2.5h, cool to room temperature, and pass through an 80-mesh sieve for later use; S42. Add 35 parts of deionized water to a low-temperature reactor equipped with a magnetic stirrer, control the reactor temperature at 38℃, add 1 part of CMC, stir at 350 r / min until the CMC is completely dissolved, slowly add 3 parts of PEG4000, and continue stirring until the PEG forms a uniform suspension dispersion system in the CMC aqueous solution without obvious particle agglomeration. S43. Raise the temperature of the reactor to 50℃, adjust the stirring speed to 550r / min, and stir at a constant temperature for 2.5h to form a stable PEG-CMC composite system; S44. Cool the composite system to 25℃, granulate it using spray granulation method (inlet air temperature 80℃, outlet air temperature 40℃, feed rate 7mL / min) to prepare PEG-CMC composite microspheres with a particle size of 100~200μm, and dry them in a vacuum drying oven at 40℃ until the moisture content of the composite microspheres is ≤1% to obtain primary PEG-CMC phase change material; S45. The primary PEG-CMC phase change material was added to a planetary ball mill, and anhydrous ethanol was used as the dispersion medium (solid-liquid ratio 1:5). Zirconia ball milling beads (ball-to-material ratio 8:1) were used to ball mill the material at a speed of 250 r / min for 2.5 h. After ball milling, the material was centrifuged (3000 r / min, 10 min) to remove the anhydrous ethanol. The product was then vacuum dried and sieved to obtain micro-nano PEG-CMC phase change material with a particle size ≤5 μm.

[0019] Example 2 The preparation method of the bio-responsive coating solution is as follows, by weight: (1) Sodium alginate and gellan gum were dried in a vacuum drying oven at 50°C for 1.5 hours and then cooled to room temperature before being passed through a 100-mesh sieve. (2) Dissolve 5 parts sodium alginate and 0.3 parts gellan gum in 88 parts of deionized water at 45℃ and stir until completely dissolved to form a polysaccharide base solution; (3) Add 1.5 parts of glycerol and 0.1 parts of ε-polylysine sequentially at a stirring rate of 300 r / min, and continue stirring for 20 min to form a stable composite coating solution; (4) Homogenize the composite coating liquid twice under a pressure of 30 MPa, degas it under vacuum at room temperature for 15 min, add deionized water, and adjust the viscosity to 200 mPa·s. (5) Filter with 200 mesh filter cloth to obtain bio-responsive coating liquid.

[0020] Example 3 The preparation method of the bio-responsive coating solution is as follows, by weight: Sodium alginate and gellan gum were dried in a vacuum drying oven at 50°C for 1.5 hours, cooled to room temperature, and then passed through a 100-mesh sieve. Dissolve 5.5 parts sodium alginate and 0.4 parts gellan gum in 85 parts of deionized water at 48℃, and stir until completely dissolved to form a polysaccharide-based solution; Add 1.8 parts of glycerol and 0.15 parts of ε-polylysine sequentially at a stirring rate of 350 r / min, and continue stirring for 25 min to form a stable composite coating solution; The composite coating liquid was homogenized twice under a pressure of 30 MPa, degassed under vacuum at room temperature for 15 min, and 0.15 parts of deionized water were added to adjust the viscosity to 250 mPa·s. (5) Filter with 200 mesh filter cloth to obtain bio-responsive coating liquid.

[0021] Example 4 The preparation method of the bio-responsive coating solution is as follows, by weight: Sodium alginate and gellan gum were dried in a vacuum drying oven at 50°C for 1.5 hours, cooled to room temperature, and then passed through a 100-mesh sieve. Dissolve 6 parts sodium alginate and 0.5 parts gellan gum in 82 parts of 50℃ deionized water and stir until completely dissolved to form a polysaccharide base solution; Add 2 parts glycerol and 0.2 parts ε-polylysine sequentially at a stirring rate of 400 r / min, and continue stirring for 30 min to form a stable composite coating solution; The composite coating liquid was homogenized twice under a pressure of 30 MPa, degassed under vacuum at room temperature for 15 min, and 0.3 parts of deionized water were added to adjust the viscosity to 300 mPa·s. (5) Filter with 200 mesh filter cloth to obtain bio-responsive coating liquid.

[0022] Comparative Example 1 The difference between this comparative example and Example 3 is that only the sodium alginate in step (2) is adjusted to 7 parts and the deionized water is adjusted to 83.5 parts, while the other parameters are the same as in Example 3.

[0023] Comparative Example 2 The difference between this comparative example and Example 3 is that only the amount of gellan gum in step (2) is adjusted to 0.2 parts and the amount of deionized water is adjusted to 85.2 parts. The other parameters are the same as those in Example 3.

[0024] Comparative Example 3 The difference between this comparative example and Example 3 is that only the amount of glycerol in step (3) is adjusted to 1.0 part, while the other parameters are the same as in Example 3.

[0025] Performance testing: Determination of tensile strength and elongation at break of dry film: The test was performed in accordance with GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". The dry film was cut into standard specimens of 100 mm × 15 mm and tested using a universal testing machine. The tensile rate was 5 mm / min and the span was 50 mm. Three parallel specimens were tested in each group and the average value was taken as the final result. Determination of the thermo-responsiveness of dry film: Cut the dry film into 50mm×50mm samples. First, accurately measure the initial length (L0) of the sample using vernier calipers. Place the sample in a -2℃ constant temperature incubator for 2 hours. Immediately after removal, measure the length after shrinkage (L1) and calculate the shrinkage rate (shrinkage rate = [(L0-L1) / L0]×100%). Then, transfer the sample to a 25℃ constant temperature environment and continue to place it at a constant temperature for 2 hours. Measure the length after recovery (L2) and calculate the recovery rate (recovery rate = [(L2-L1) / (L0-L1)]×100%). Measure 3 parallel samples in each group and take the average value as the final result.

[0026] The results are shown in Table 1 below: Table 1

[0027] As shown in Table 1 above, the bio-responsive coating solution and dry film prepared in the examples exhibit excellent performance in all aspects: the coating solution is transparent and uniform in appearance, shows no stratification or precipitation after 7 days of refrigeration at 4℃, and has good storage stability; the dry film forms quickly (12~18 min) and has a smooth, defect-free appearance; the dry film has a tensile strength of 2.1~2.8 MPa and an elongation at break of 38%~45%, demonstrating excellent mechanical properties; the dry film exhibits outstanding temperature responsiveness, with a shrinkage rate of 12.3%~15.1% at -2℃ and a recovery rate of 98.5%~99.2% at 25℃, achieving precise temperature-sensitive shrinkage and recovery. Among them, Example 3 achieved peak performance in all aspects, demonstrating the best overall performance. In Comparative Example 1, excessive sodium alginate caused the coating solution to become cloudy with particles and its stability to deteriorate, resulting in a significant decrease in the mechanical properties and temperature responsiveness of the dry film. In Comparative Example 2, insufficient gellan gum resulted in the coating solution and dry film meeting other performance standards, but the temperature responsiveness was significantly reduced (shrinkage rate of only 4.2% at -2℃ and recovery rate of 88.7% at 25℃), failing to achieve the expected temperature responsiveness. In Comparative Example 3, insufficient glycerin caused a sharp decline in the mechanical properties of the dry film, with a tensile strength of only 1.2 MPa and an elongation at break of 22%, making the dry film prone to cracking and unable to meet actual usage requirements.

[0028] Example 5 A method for low-temperature preservation of livestock, poultry, and aquatic products includes the following steps: S1. Pretreatment: Clean, cut, and deodorize the high-moisture fish (grass carp) to remove surface impurities and excess water, and set aside for later use; S2. Low-temperature plasma activation: Argon gas was used as the working gas. The pretreated grass carp was placed in a low-temperature plasma device and activated for 1.5 minutes at a power of 100W and a temperature of 2℃. S3. Compound enzymatic hydrolysis: Within 30 seconds after plasma activation treatment, the surface of grass carp is immediately subjected to mild enzymatic hydrolysis using a protease-lipase compound enzyme (mass ratio 1:2.0), at a hydrolysis temperature of 2℃, a hydrolysis time of 8 min, and an enzyme addition amount of 0.04%. After the hydrolysis is completed, the grass carp is rinsed at a low temperature of 1℃ to remove excess enzyme solution and obtain the enzymatically hydrolyzed grass carp. S4. Loaded coating treatment: The micro-nano PEG-CMC phase change material prepared in Example 1 was uniformly dispersed in the bio-responsive coating solution prepared in Example 3. The amount of micro-nano PEG-CMC phase change material added was 7% of the mass of the bio-responsive coating solution. The ultrasonic in-situ composite process was used with an ultrasonic power of 220W, an ultrasonic temperature of 2℃, and an ultrasonic time of 12min. After ultrasonic in-situ composite, the surface of the enzymatically hydrolyzed grass carp was coated by spraying with a thickness of 0.08mm. S5. Micro-freezing and constant temperature preservation: Grass carp with coating completed are immediately sent into micro-freezing equipment, the initial cooling rate is controlled at 0.03℃ / min, the temperature is maintained at -2.5℃ during the constant temperature stage, and the preservation period is 30 days. S6. Non-destructive thawing and coating removal: After preservation, thaw using conventional cold water. After thawing, peel off and remove the surface-loaded coating by low-temperature high-pressure spraying, and then proceed with subsequent processing.

[0029] Example 6 A method for low-temperature preservation of livestock, poultry, and aquatic products includes the following steps: S1. Pre-treatment: Clean, cut, and deodorize the high-moisture fish (cod) to remove surface impurities and excess water, and set aside. S2. Low-temperature plasma activation: Argon gas was used as the working gas. The pretreated cod was placed in a low-temperature plasma device and activated for 1.8 minutes at a power of 120W and a temperature of 1℃. S3. Compound enzymatic hydrolysis: Within 30 seconds after plasma activation treatment, the surface of the cod is immediately subjected to mild enzymatic hydrolysis using a protease-lipase complex enzyme (mass ratio 1:2.2), at a hydrolysis temperature of 1℃, a hydrolysis time of 9 min, and an enzyme addition amount of 0.05%. After hydrolysis, the cod is rinsed at a low temperature of 0.5℃ to remove excess enzyme solution and obtain the hydrolyzed cod. S4. Loaded coating treatment: The micro-nano PEG-CMC phase change material prepared in Example 1 was uniformly dispersed in the bio-responsive coating solution prepared in Example 3. The amount of micro-nano PEG-CMC phase change material added was 8.5% of the mass of the bio-responsive coating solution. The ultrasonic in-situ composite process was used with an ultrasonic power of 250W, an ultrasonic temperature of 1℃, and an ultrasonic time of 13min. After ultrasonic in-situ composite, the surface of the enzymatically hydrolyzed cod was coated with a coating by spraying with a thickness of 0.10mm. S5. Micro-freezing and constant temperature preservation: The coated cod is immediately sent into the micro-freezing equipment, the initial cooling rate is controlled at 0.025℃ / min, the constant temperature stage is maintained at -2.2℃, and the preservation period is 45 days. S6. Non-destructive thawing and coating removal: After the preservation period, thaw using conventional refrigeration thawing methods. After thawing, peel off and remove the surface-loaded coating by manual wiping and rinsing with water before proceeding with subsequent processing.

[0030] Example 7 A method for low-temperature preservation of livestock, poultry, and aquatic products includes the following steps: S1. Pre-treatment: Clean, cut, and deodorize the high-moisture fish (sea bass) to remove surface impurities and excess water, and set aside. S2. Low-temperature plasma activation: Argon gas was used as the working gas. The pretreated sea bass was placed in a low-temperature plasma device and activated at 150W power and 0℃ for 2.0 min. S3. Compound enzymatic hydrolysis: Within 30 seconds after plasma activation treatment, the surface of the sea bass is immediately subjected to mild enzymatic hydrolysis using a protease-lipase compound enzyme (mass ratio 1:2.5), with a hydrolysis temperature of 0℃, a hydrolysis time of 10 min, and an enzyme addition amount of 0.06%. After the hydrolysis is completed, the sea bass is rinsed at 0℃ to remove excess enzyme solution and obtain the enzymatically hydrolyzed sea bass. S4. Loaded coating treatment: The micro-nano PEG-CMC phase change material prepared in Example 1 was uniformly dispersed in the bio-responsive coating solution prepared in Example 3. The amount of micro-nano PEG-CMC phase change material added was 10% of the mass of the bio-responsive coating solution. The ultrasonic in-situ composite process was used with an ultrasonic power of 300W, an ultrasonic temperature of 0℃, and an ultrasonic time of 15min. After ultrasonic in-situ composite, the surface of the enzymatically hydrolyzed sea bass was coated by spraying with a thickness of 0.12mm. S5. Micro-freezing and constant temperature preservation: The coated sea bass is immediately sent into the micro-freezing equipment, the initial cooling rate is controlled at 0.04℃ / min, the constant temperature stage is maintained at -2.0℃, and the preservation period is 60 days. S6. Non-destructive thawing and coating removal: After preservation, the product is thawed using conventional microwave low-temperature thawing. After thawing, the surface-loaded coating is peeled off and removed by low-temperature high-pressure spraying, allowing for subsequent processing.

[0031] Example 8 A method for low-temperature preservation of livestock, poultry, and aquatic products includes the following steps: S1. Pre-treatment: Wash, cut, and deodorize the high-protein livestock and poultry meat (pork tenderloin) to remove surface impurities and excess moisture, and set aside for later use; S2. Low-temperature plasma activation: Argon gas is used as the working gas. The pretreated pork tenderloin is placed in a low-temperature plasma device and activated at 80W power and 3℃ for 1.0 min. S3. Compound enzymatic hydrolysis: Within 30 seconds after plasma activation treatment, the surface of the pork tenderloin is immediately subjected to mild enzymatic hydrolysis using a protease-lipase compound enzyme (mass ratio 1:1.5), at a hydrolysis temperature of 3℃, a hydrolysis time of 5 min, and an enzyme addition amount of 0.03%. After hydrolysis, the pork tenderloin is rinsed at a low temperature of 2℃ to remove excess enzyme solution and obtain the enzymatically hydrolyzed pork tenderloin. S4. Loaded coating treatment: The micro-nano PEG-CMC phase change material prepared in Example 1 was uniformly dispersed in the bio-responsive coating solution prepared in Example 3. The amount of micro-nano PEG-CMC phase change material added was 5% of the mass of the bio-responsive coating solution. The ultrasonic in-situ composite process was used with an ultrasonic power of 200W, an ultrasonic temperature of 3℃, and an ultrasonic time of 10min. After ultrasonic in-situ composite, the surface of the enzymatically hydrolyzed pork tenderloin was coated by spraying with a thickness of 0.02mm. S5. Micro-freezing and constant temperature preservation: The coated pork tenderloin is immediately sent into the micro-freezing equipment, the initial cooling rate is controlled at 0.02℃ / min, the constant temperature stage is maintained at -3.0℃, and the preservation period is 7 days. S6. Non-destructive thawing and coating removal: After preservation, thaw using conventional cold water. After thawing, peel off and remove the surface-loaded coating by manual wiping and rinsing with clean water before proceeding with subsequent processing.

[0032] Example 9 A method for low-temperature preservation of livestock, poultry, and aquatic products includes the following steps: S1. Pre-treatment: Wash, cut, and deodorize the high-protein livestock and poultry meat (beef shank) to remove surface impurities and excess moisture, and set aside. S2. Low-temperature plasma activation: Argon gas was used as the working gas. The pretreated beef shank was placed in a low-temperature plasma device and activated for 1.2 minutes at a power of 100W and a temperature of 2℃. S3. Compound enzymatic hydrolysis: Within 30 seconds after plasma activation treatment, the surface of the beef tendon is immediately subjected to mild enzymatic hydrolysis using a protease-lipase complex enzyme (mass ratio 1:1.5), at a hydrolysis temperature of 2℃, a hydrolysis time of 6 min, and an enzyme addition amount of 0.04%. After the hydrolysis is completed, the beef tendon is rinsed at a low temperature of 1.5℃ to remove excess enzyme solution and obtain the enzymatically hydrolyzed beef tendon. S4. Loaded coating treatment: The micro-nano PEG-CMC phase change material prepared in Example 1 was uniformly dispersed in the bio-responsive coating solution prepared in Example 3. The amount of micro-nano PEG-CMC phase change material added was 6.5% of the mass of the bio-responsive coating solution. The ultrasonic in-situ composite process was used with an ultrasonic power of 240W, an ultrasonic temperature of 2℃, and an ultrasonic time of 12min. After ultrasonic in-situ composite, the surface of the enzymatically hydrolyzed beef tendon was coated with a coating by spraying with a thickness of 0.06mm. S5. Micro-freezing and constant temperature preservation: The coated beef shank is immediately sent into the micro-freezing equipment, the initial cooling rate is controlled at 0.03℃ / min, the constant temperature stage is maintained at -2.6℃, and the preservation period is 20 days. S6. Non-destructive thawing and coating removal: After the preservation period, the product is thawed using conventional refrigeration thawing methods. After thawing, the surface-loaded coating is peeled off and removed by low-temperature high-pressure spraying, allowing for subsequent processing.

[0033] Example 10 A method for low-temperature preservation of livestock, poultry, and aquatic products includes the following steps: S1. Pre-treatment: Wash, cut, and deodorize the high-protein livestock and poultry meat (chicken breast) to remove surface impurities and excess moisture, and set aside. S2. Low-temperature plasma activation: Argon gas is used as the working gas. The pretreated chicken breast is placed in a low-temperature plasma device and activated for 1.4 minutes at a power of 120W and a temperature of 1℃. S3. Compound enzymatic hydrolysis: Within 30 seconds after plasma activation treatment, the surface of the chicken breast is immediately subjected to mild enzymatic hydrolysis using a protease-lipase compound enzyme (mass ratio 1:1.5), at a hydrolysis temperature of 1℃, a hydrolysis time of 7 min, and an enzyme addition amount of 0.05%. After the hydrolysis is completed, the chicken breast is rinsed at a low temperature of 1℃ to remove excess enzyme solution and obtain the enzymatically hydrolyzed chicken breast. S4. Loaded coating treatment: The micro-nano PEG-CMC phase change material prepared in Example 1 was uniformly dispersed in the bio-responsive coating solution prepared in Example 3. The amount of micro-nano PEG-CMC phase change material added was 8% of the mass of the bio-responsive coating solution. The ultrasonic in-situ composite process was used with an ultrasonic power of 280W, an ultrasonic temperature of 1℃, and an ultrasonic time of 14min. After ultrasonic in-situ composite, the surface of the enzymatically hydrolyzed chicken breast was coated with a film with a thickness of 0.10mm by spraying. S5. Micro-freezing and constant temperature preservation: The coated chicken breast is immediately sent into the micro-freezing equipment, the initial cooling rate is controlled at 0.035℃ / min, the constant temperature stage is maintained at -2.3℃, and the preservation period is 40 days. S6. Non-destructive thawing and coating removal: After preservation, thaw using conventional microwave low-temperature thawing method. After thawing, peel off and remove the surface-loaded coating by manual wiping and rinsing with water, and then proceed with subsequent processing.

[0034] Example 11 A method for low-temperature preservation of livestock, poultry, and aquatic products includes the following steps: S1. Pre-treatment: Clean, remove whiskers and remove fishy smell from easily molted and easily perishable crustaceans (prawns), remove surface impurities and excess water, and set aside. S2. Low-temperature plasma activation: Argon gas was used as the working gas. The pretreated shrimp were placed in a low-temperature plasma device and the shrimp surface was activated for 1.5 min at a power of 110W and a temperature of 2℃. S3. Compound enzymatic hydrolysis: Within 30 seconds after plasma activation treatment, the surface of the shrimp is immediately subjected to mild enzymatic hydrolysis using a protease-lipase compound enzyme (mass ratio 1:2.0), at a hydrolysis temperature of 2℃, a hydrolysis time of 8 min, and an enzyme addition amount of 0.045%. After hydrolysis, the shrimp is rinsed at a low temperature of 1℃ to remove excess enzyme solution and obtain the hydrolyzed shrimp. S4. Loaded coating treatment: The micro-nano PEG-CMC phase change material prepared in Example 1 was uniformly dispersed in the bio-responsive coating solution prepared in Example 3. The amount of micro-nano PEG-CMC phase change material added was 8% of the mass of the bio-responsive coating solution. The ultrasonic in-situ composite process was used with an ultrasonic power of 230W, an ultrasonic temperature of 2℃, and an ultrasonic time of 12min. After ultrasonic in-situ composite, the surface of the enzymatically hydrolyzed shrimp was coated with a coating by spraying with a thickness of 0.10mm. S5. Micro-freezing and constant temperature preservation: The coated shrimp are immediately sent into the micro-freezing equipment, the initial cooling rate is controlled at 0.03℃ / min, the constant temperature stage is maintained at -2.5℃, and the preservation period is 15 days. S6. Non-destructive thawing and coating removal: After preservation, thaw using conventional cold water. After thawing, peel off and remove the surface-loaded coating by manual wiping and rinsing with clean water before proceeding with subsequent processing.

[0035] Example 12 A method for low-temperature preservation of livestock, poultry, and aquatic products includes the following steps: S1. Pre-treatment: Clean, remove gills and remove fishy smell from easily molted and perishable crustaceans (swimming crabs), remove surface impurities and excess water, and set aside. S2. Low-temperature plasma activation: Argon was used as the working gas. The pretreated swimming crabs were placed in a low-temperature plasma device and activated for 1.7 minutes at a power of 130W and a temperature of 1℃. S3. Compound enzymatic hydrolysis: Within 30 seconds after plasma activation treatment, the surface of the swimming crab is immediately subjected to mild enzymatic hydrolysis using a protease-lipase compound enzyme (mass ratio 1:2.3), with a hydrolysis temperature of 1℃, a hydrolysis time of 9 min, and an enzyme addition amount of 0.05%. After the hydrolysis is completed, the crab is rinsed at a low temperature of 0.5℃ to remove excess enzyme solution and obtain the enzymatically hydrolyzed swimming crab. S4. Loaded coating treatment: The micro-nano PEG-CMC phase change material prepared in Example 1 was uniformly dispersed in the bio-responsive coating solution prepared in Example 3. The amount of micro-nano PEG-CMC phase change material added was 9% of the mass of the bio-responsive coating solution. The ultrasonic in-situ composite process was used, with an ultrasonic power of 260W, an ultrasonic temperature of 1℃, and an ultrasonic time of 13min. After ultrasonic in-situ composite, the surface of the enzymatically hydrolyzed swimming crab was coated by spraying with a thickness of 0.12mm. S5. Micro-freezing and constant temperature preservation: The coated swimming crabs are immediately sent into the micro-freezing equipment, the initial cooling rate is controlled at 0.035℃ / min, the constant temperature stage is maintained at -2.2℃, and the preservation period is 25 days. S6. Non-destructive thawing and coating removal: After the preservation period, the product is thawed using conventional refrigeration thawing methods. After thawing, the surface-loaded coating is peeled off and removed by low-temperature high-pressure spraying, allowing for subsequent processing.

[0036] Example 13 A method for low-temperature preservation of livestock, poultry, and aquatic products includes the following steps: S1. Pre-treatment: Clean, remove the head and remove the fishy smell from the easily molted and perishable crustaceans (crayfish), remove surface impurities and excess water, and set aside. S2. Low-temperature plasma activation: Argon gas was used as the working gas. The pretreated crayfish were placed in a low-temperature plasma device and activated for 2.0 min at a power of 140W and a temperature of 0℃. S3. Compound enzymatic hydrolysis: Within 30 seconds after plasma activation treatment, the surface of crayfish is immediately subjected to mild enzymatic hydrolysis using a protease-lipase compound enzyme (mass ratio 1:2.5), at a hydrolysis temperature of 0℃, a hydrolysis time of 10 min, and an enzyme addition amount of 0.06%. After hydrolysis, the crayfish are rinsed at 0℃ to remove excess enzyme solution and obtain the hydrolyzed crayfish. S4. Loaded coating treatment: The micro-nano PEG-CMC phase change material prepared in Example 1 was uniformly dispersed in the bio-responsive coating solution prepared in Example 3. The amount of micro-nano PEG-CMC phase change material added was 10% of the mass of the bio-responsive coating solution. The ultrasonic in-situ composite process was used with an ultrasonic power of 290W, an ultrasonic temperature of 0℃, and an ultrasonic time of 14min. After ultrasonic in-situ composite, the surface of the enzymatically hydrolyzed crayfish was coated with a film with a thickness of 0.15mm by spraying. S5. Micro-freezing and constant temperature preservation: The coated crayfish are immediately sent into the micro-freezing equipment, the initial cooling rate is controlled at 0.04℃ / min, the constant temperature stage is maintained at -2.0℃, and the preservation period is 35 days. S6. Non-destructive thawing and coating removal: After preservation, thaw using conventional microwave low-temperature thawing method. After thawing, peel off and remove the surface-loaded coating by manual wiping and rinsing with water, and then proceed with subsequent processing.

[0037] Comparative Example 4 The parameters of this comparative example are completely consistent with those of Example 5, except that the S2 low-temperature plasma activation power is adjusted to 70W. The other process steps and parameters are the same as those of Example 5.

[0038] Comparative Example 5 The parameters of this comparative example are completely consistent with those of Example 6, except that the enzymatic hydrolysis time of S3 is adjusted to 7 min. All other process steps and parameters are the same as those of Example 6.

[0039] Comparative Example 6 The parameters of this comparative example are completely consistent with those of Example 7, except that micro-nano PEG-CMC phase change material is not added in S4. All other process steps and parameters are the same as those of Example 7.

[0040] Comparative Example 7 The parameters of this comparative example are completely consistent with those of Example 8, except that the mass ratio of S3 protease-lipase complex enzyme is adjusted to 1:1.2. All other process steps and parameters are the same as those of Example 8.

[0041] Comparative Example 8 The parameters of this comparative example are completely consistent with those of Example 10, except that the S4 ultrasonic in-situ composite power is adjusted to 190W. The other process steps and parameters are the same as those of Example 10.

[0042] Comparative Example 9 The parameters of this comparative example are completely consistent with those of Example 11, except that the coating thickness in S4 is adjusted to 0.09 mm. All other process steps and parameters are the same as those in Example 11.

[0043] Comparative Example 10 The parameters of this comparative example are completely consistent with those of Example 12, except that the S2 low-temperature plasma activation time is adjusted to 1.4 min. All other process steps and parameters are the same as those of Example 12.

[0044] Performance testing: 1. Determination of total bacterial count: The determination was carried out in accordance with GB4789.2-2022 "National Food Safety Standard for Microbiological Examination of Food - Determination of Total Bacterial Count". Edible parts of livestock, poultry and aquatic products of each category were taken. After sample preparation, plate counting was performed. The samples were incubated at 36℃±1℃ for 48h±2h and the counts were made. The results were expressed as CFU / g. Each group was tested in 3 parallel experiments and the mean ± standard deviation was taken. 2. pH value determination: The pH value was determined in accordance with GB5009.237-2016 "National Food Safety Standard for Determination of pH Value of Food". After homogenizing the edible part of the sample, the pH value was measured at room temperature using a pH meter. Each group was tested in triplicate, and the mean ± standard deviation was taken. 3. Determination of water loss rate: The net weight of the sample before preservation and after preservation for a preset time was accurately weighed (accurate to 0.01g) using the gravimetric method. Water loss rate = [(weight before preservation - weight after preservation) / weight before preservation] × 100%. Three parallel experiments were performed for each group, and the average value ± standard deviation was taken. 4. Determination of tenderness (N, shear force): For livestock and poultry meat, refer to NY / T1180-2006 "Determination of Meat Tenderness - Shear Force Method"; for aquatic products and crustaceans, refer to GB / T37062-2018 "Guidelines for Sensory Evaluation of Aquatic Products" combined with the Warner-Bratzler shear force method. Specific steps are as follows: ◦ Sample preparation: For livestock and poultry meat, standard samples of 1cm×1cm×3cm were prepared from edible parts. For aquatic / crustacean meat, regular samples of appropriate thickness were prepared from the same parts. Fascia, fat, bone spurs, etc. were removed from all samples. ◦ Instruments and parameters: The shearing mode of the texture analyzer was used, with a stainless steel shearing blade as the probe, a test speed of 3.0 mm / s, a return speed of 5.0 mm / s, a trigger force of 5 g, and a test distance of 2 / 3 of the sample thickness; ◦ Tests and Results: Ten parallel shear tests were conducted in each group. Tenderness was expressed as peak shear force (unit: N, Newton). The experimental results were taken as mean ± standard deviation. Determination of phase transition temperature:

[0045] The results are shown in Table 2 below: Table 2 Data indicators for various categories of livestock, poultry and aquatic products before and after preservation.

[0046] As shown in Table 2 above, after fresh livestock, poultry, and aquatic products were treated with the bio-responsive coating solution of this invention, the total bacterial count remained at the initial level with only slight fluctuations, the pH value remained stable, the water loss rate was controlled at an extremely low level of 0.5% or less, and the tenderness (shear force) value only fluctuated slightly. All core quality indicators were essentially consistent with the fresh state. Furthermore, after preservation, all types of food maintained fresh color and good meat elasticity, with no off-odors, no stickiness, and no juice loss. Crustaceans such as shrimp and crab shells remained firm and did not detach, maintaining their fresh sensory quality. In contrast, the comparative samples that did not use the complete preservation method of this invention showed a clear gradient of deterioration according to the characteristics of the product category. The total bacterial count of perishable products such as grass carp, pork tenderloin, shrimp, and swimming crab exploded to 10. 5 The bacterial count increased by more than 40 times compared to the fresh state, with the total bacterial count in products such as sea bass, cod, and chicken breast increasing to 10. 4The volume of water loss increased by 5-17 times compared to the fresh state. Correspondingly, the pH values ​​of the comparative samples all increased to varying degrees, with the pH increase of 0.9-1.2 for the highly deteriorated categories and 0.4-0.5 for the other categories. The water loss rate increased significantly to 1.8%-4.0%, and the tenderness (shear force) value increased significantly, with an increase of 6.7-13N. At the same time, the comparative samples all showed obvious deterioration in sensory quality. The highly deteriorated categories were characterized by dark and black color, extremely poor elasticity, sticky and soft texture, accompanied by a strong fishy / rotten smell, and a large amount of shells of crustaceans such as shrimp and crab fell off. The other categories also showed a slightly yellowish and grayish color, decreased elasticity, slightly sticky and dry texture, accompanied by a slight off-odor, and a small amount of juice loss. This fully demonstrates the important role of the whole process synergy and micro-nano PEG-CMC phase change material in the preservation system of this invention.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A method for low-temperature preservation of livestock, poultry, and aquatic products, characterized in that, Includes the following steps: S1. Pre-treatment: Clean, cut, and deodorize the livestock, poultry and aquatic products to remove surface impurities and excess moisture, and set aside for later use; S2. Low-temperature plasma activation: Argon is used as the working gas. The pretreated livestock and aquatic products are placed in a low-temperature plasma device to activate the surface of the meat. S3. Compound enzymatic hydrolysis: Within 30 seconds after plasma activation treatment, the surface of livestock, poultry and aquatic products is immediately subjected to mild enzymatic hydrolysis. After the enzymatic hydrolysis is completed, the products are rinsed at a low temperature of 0~2℃ to remove excess enzyme solution and obtain enzymatically hydrolyzed livestock, poultry and aquatic products. S4. Loaded coating treatment: Micro-nano PEG-CMC phase change material is uniformly dispersed in a bio-responsive coating solution, and after ultrasonic in-situ composite, a coating is applied to the surface of enzymatically hydrolyzed livestock and aquatic products by spraying. S5. Micro-freezing and constant temperature preservation: The coated livestock, poultry and aquatic products are immediately sent into the micro-freezing equipment, and the initial cooling rate is controlled at 0.02~0.04℃ / min. The temperature is maintained at -2℃~-3℃ during the constant temperature stage, and the preservation period is 7~60 days. S6. Non-destructive thawing and coating removal: After preservation, thaw using conventional non-destructive thawing methods. After thawing, peel off and remove the surface-loaded coating by low-temperature high-pressure spraying or manual wiping and rinsing with clean water, and then proceed with subsequent processing.

2. The low-temperature preservation method for livestock, poultry, and aquatic products according to claim 1, characterized in that, The activation conditions described in S2 are: power 80~150W, temperature 0~4℃, and time 1~2min.

3. The low-temperature preservation method for livestock, poultry, and aquatic products according to claim 1, characterized in that, The enzymatic hydrolysis conditions described in S3 are as follows: using a protease-lipase complex enzyme, hydrolysis temperature of 0~4℃, hydrolysis time of 5~10min, and enzyme addition amount of 0.03~0.06%.

4. The low-temperature preservation method for livestock and aquatic products according to claim 3, characterized in that, The mass ratio of protease to lipase in the protease-lipase complex is 1:(1.5~2.5).

5. The low-temperature preservation method for livestock, poultry, and aquatic products according to claim 1, characterized in that, The preparation method of the micro / nano-sized PEG-CMC phase change material described in S4 is as follows: S41. Place food-grade PEG4000 and CMC separately in a vacuum drying oven at 60~65℃ and dry for 2~3 hours. Cool to room temperature and pass through an 80-mesh sieve for later use. S42. Add deionized water to a low-temperature reactor equipped with a magnetic stirrer, and control the reactor temperature at 35~40℃. First, add CMC and stir at 300~400r / min until the CMC is completely dissolved. Slowly add PEG4000 and continue stirring until the PEG forms a uniform suspension dispersion system in the CMC aqueous solution without obvious particle agglomeration. S43. Raise the temperature of the reactor to 50~55℃, adjust the stirring speed to 500~600r / min, and stir at a constant temperature for 2~2.5h to form a stable PEG-CMC composite system; S44. Cool the composite system to 25~30℃, granulate it by spray granulation to prepare PEG-CMC composite microspheres with a particle size of 100~200μm, and dry them in a vacuum drying oven at 40~45℃ until the moisture content of the composite microspheres is ≤1% to obtain primary PEG-CMC phase change material. S45. The primary PEG-CMC phase change material is added to a planetary ball mill, and anhydrous ethanol is used as the dispersion medium. Zirconia ball milling beads are used to ball mill the material at a speed of 200~300 r / min for 2~3 h. After ball milling, the material is centrifuged to remove the anhydrous ethanol. The product is then vacuum dried and sieved to obtain micro-nano PEG-CMC phase change material with a particle size ≤5μm.

6. A method for low-temperature preservation of livestock, poultry, and aquatic products according to claim 5, characterized in that, The mass ratio of CMC, PEG4000 and deionized water in S42 is 3:1:(32~40).

7. A method for low-temperature preservation of livestock, poultry, and aquatic products according to claim 1, characterized in that, The preparation method of the bio-responsive coating liquid described in S4 is as follows: (1) Sodium alginate and gellan gum were dried in a vacuum drying oven at 50°C for 1.5 hours and then cooled to room temperature before being passed through a 100-mesh sieve. (2) Dissolve sodium alginate and gellan gum in deionized water at 45~50℃ to form a polysaccharide base solution; (3) Add glycerol and ε-polylysine sequentially at a stirring rate of 300~400r / min, and continue stirring for 20~30min to form a stable composite coating solution; (4) Homogenize the composite coating liquid twice under a pressure of 30 MPa, degas it under vacuum at room temperature for 15 min, add deionized water, and adjust the viscosity to 200~300 mPa·s; (5) Filter with 200 mesh filter cloth to obtain bio-responsive coating liquid.

8. A method for low-temperature preservation of livestock, poultry, and aquatic products according to claim 1, characterized in that, The amount of micro-nano PEG-CMC phase change material added in S4 is 5-10% of the mass of the bio-responsive coating liquid; the ultrasonic in-situ composite conditions are: ultrasonic power 200-300W, ultrasonic time 10-15min, and ultrasonic temperature 0-4℃.

9. A method for low-temperature preservation of livestock, poultry, and aquatic products according to claim 1, characterized in that, The coating thickness described in S4 is 0.02~0.15mm.

10. A method for low-temperature preservation of livestock, poultry, and aquatic products according to claim 1, characterized in that, Different conditions apply to different types of livestock, poultry, and aquatic products: For high-moisture fish: the activation treatment time is 1.5~2 min, the enzymatic hydrolysis time is 8~10 min, and the amount of micro-nano PEG-CMC phase change material added is 7~10% of the mass of the bio-responsive coating solution; High-protein livestock and poultry cut meat: The mass ratio of protease to lipase in the protease-lipase complex enzyme is 1:1.5, the enzymatic hydrolysis time is 5~7 min, and the activation power is 80~120W; For easily detached and perishable crustaceans: the coating thickness is 0.1~0.15mm, the amount of micro-nano PEG-CMC phase change material added is 8~10% of the mass of the bio-responsive coating solution, and the activation treatment time is 1.5~2min.

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