A cold chain logistics transportation method for maintaining the muscle quality of live crayfish after transport.

Abstract

This invention discloses a cold chain logistics transportation method for maintaining the muscle quality of fresh crayfish after transportation, belonging to the field of aquatic product preservation and logistics technology. The method includes the following steps in sequence: (1) raw material screening; (2) cleaning treatment: cleaning the screened fresh crayfish; (3) anti-stress treatment: mixing the fresh crayfish with anti-stress slow-release ice particles and placing them in a foam insulated box for anti-stress treatment; (4) insulated packaging and transportation: taking out the anti-stress treated fresh crayfish, mixing them with nutrient slow-release ice particles, and then placing them in an insulated transport box, while configuring a cold storage agent in the insulated transport box for gradient cold storage transportation. This invention effectively reduces the transportation stress response by combining anti-stress treatment with gradient cold storage, slows down the decrease in muscle pH and protein denaturation, thereby significantly improving the survival rate of fresh crayfish after transportation, and maintaining the excellent water retention, texture and shell integrity of the muscle.

Description

Technical Field

[0001] This invention belongs to the field of aquatic product preservation and logistics technology, specifically relating to a cold chain logistics transportation method suitable for live crayfish, and particularly a method for maintaining the muscle quality (such as water retention, elasticity, and freshness) of live crayfish after transportation through comprehensive pretreatment and gradient cooling technology. Background Technology

[0002] Even if live crayfish survive transportation, they will experience a strong stress response due to environmental stress. This stress response leads to metabolic disorders, causing a large consumption of energy-storing substances in the muscles (such as muscle glycogen) and the production of metabolic waste such as lactic acid. As a result, even if live crayfish are still alive when they arrive at their destination, their muscles often undergo potential biochemical changes, such as a decrease in pH, protein denaturation, reduced water-holding capacity, softening of texture, and deterioration of flavor. Ultimately, this results in the processed quality (such as taste and elasticity) of the crayfish muscles (including edible parts such as tail and claw meat) being significantly lower than that of live crayfish that have not experienced transportation stress, greatly affecting their commercial value and processing suitability.

[0003] Existing cold chain transportation methods for live crayfish primarily focus on simple low-temperature refrigeration, which has significant shortcomings. First, traditional methods often involve directly stacking live crayfish in a low-temperature environment, causing severe compression and low-temperature stress, directly leading to the internal quality deterioration mentioned above. Second, the lack of refined temperature management during transportation, while preventing ice crystal formation due to above-freezing temperatures, results in unstable dormancy states for the crayfish, causing them to repeatedly expend energy between "awakening" and "dormancy," further exacerbating the decline in muscle quality. Furthermore, existing methods generally neglect the pre-treatment stage of live crayfish. Although raw material screening is routine, targeted deep cleaning and anti-stress nutritional fortification treatments remain largely in the laboratory research stage and have not yet been standardized and integrated into cold chain logistics methods. This fails to effectively reduce the microbial load on the crayfish surface at the source and does not enhance the crayfish's resilience during transportation.

[0004] Therefore, there is an urgent need in this field for a comprehensive logistics and transportation method that can effectively reduce transportation stress, precisely control temperature changes, and comprehensively protect the health of shrimp from the source through cleaning and nutritional fortification, in order to solve the technical problem of declining muscle quality of live crayfish even if they survive after transportation. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides a cold chain logistics transportation method for maintaining the muscle quality of live crayfish after transportation. Through the synergistic effects of deep cleaning to reduce microbial invasion, anti-stress treatment to stabilize physiological state, and gradient cold storage and cooling to smoothly induce dormancy, the transportation stress of live crayfish is greatly reduced, thereby effectively maintaining the muscle quality of live crayfish after transportation and improving the survival rate during transportation.

[0006] The present invention is achieved through the following scheme.

[0007] A cold chain logistics transportation method for maintaining the muscle quality of fresh crayfish after transportation, characterized by comprising the following steps: (1) Raw material selection: Select fresh crayfish that are uniform in size, vigorous, intact, disease-free and undamaged; remove dead crayfish, diseased crayfish, damaged crayfish and individuals with obviously weak vitality; (2) Cleaning treatment: The selected live crayfish are cleaned to reduce the amount of bacteria on the surface; (3) Anti-stress treatment: Fresh crayfish were mixed with anti-stress slow-release ice pellets and placed in a foam insulated box for anti-stress treatment to reduce their metabolic rate and stress response; (4) Insulated packaging and transportation: After the stress-resistant treatment, the fresh crayfish are taken out and mixed with nutrient slow-release ice particles and then placed in an insulated transport box. At the same time, a cold storage agent is placed in the insulated transport box for gradient cold storage transportation.

[0008] Preferably, in step (2), the cleaning process is bubble cleaning, and the cleaning time is 20 to 40 minutes.

[0009] More preferably, in step (2), the cleaning agent is pre-cooled to 10-12°C before use. For live crayfish with high body temperature, by controlling the mass-to-volume ratio of the cleaning agent to the crayfish body to be 1:8-12, and using bubbling cleaning for 20-40 minutes, the forced convection heat exchange of the large-volume low-temperature cleaning agent can effectively reduce the crayfish body temperature to a temperature close to that of the cleaning agent during the cleaning process.

[0010] More preferably, the cleaning agent is any one of sodium chloride solution, chlorine dioxide solution, or sodium citrate solution; the concentration of the sodium chloride solution is 8-12 g / L, preferably 10 g / L; the concentration of the chlorine dioxide solution is 80-120 mg / L, preferably 100 mg / L; and the concentration of the sodium citrate solution is 15-25 g / L, preferably 20 g / L.

[0011] In this invention, by using bubbling cleaning and a cleaning agent, the silt and original bacteria attached to the surface of the shrimp can be effectively removed, significantly reducing the amount of bacteria on the surface. This reduces the destructive effect of microorganisms on muscle quality during subsequent storage and transportation, and improves the gloss of the surface. In addition, immersing live crayfish in a low-temperature cleaning agent at 10-12℃ can pre-regulate their body temperature to a stable lower level, reducing the activity of surface microorganisms while avoiding severe cold stress caused by excessive temperature difference when directly contacting anti-stress slow-release ice particles later.

[0012] Preferably, in step (3), the particle size of the anti-stress slow-release ice particles is 5-10 mm, the anti-stress slow-release ice particles are pre-cooled to -10 to -5℃, the mass ratio of the live crayfish to the anti-stress slow-release ice particles is 1:0.3-0.5, and the anti-stress treatment time is 1-2 h.

[0013] More preferably, in step (3), the anti-stress sustained-release ice particles are prepared by mixing one or more of a vitamin C solution with a concentration of 50-150 mg / L and a vitamin A solution with a concentration of 0.5-2.0 mg / L.

[0014] In this invention, three objectives can be achieved by using anti-stress slow-release ice particles. First, the pre-cooling effect of the cleaning step is used to achieve a second precise cooling. Second, the continuous melting and heat absorption of the anti-stress slow-release ice particles allows the shrimp's body temperature to drop steadily from 12-15°C to 4-8°C within 1-2 hours, entering a shallow dormancy precursor state and avoiding low-temperature stress caused by a sudden drop in temperature. Secondly, it can create and maintain a low-temperature and high-humidity environment before the treatment in step (4), so that the shrimp can have a mild pre-cooling adaptation process before entering the gradient cold storage transportation. According to the test, during the continuous melting and heat absorption process of the anti-stress slow-release ice particles, the foam insulation box can maintain a low-temperature and humid environment with a temperature of 0-5℃ and a relative humidity of 85%-95%. The shrimp temperature gradually approaches the ambient temperature range during the heat transfer process, thereby achieving a mild gradient cooling and avoiding cold stress. Thirdly, the anti-stress slow-release ice particles can slowly release anti-stress agents through melting and come into contact with the shrimp. These anti-stress agents can enhance the antioxidant capacity of their cells, thereby directly alleviating metabolic disorders and muscle deterioration caused by environmental stress. Since transporting live crayfish with water will greatly increase the transportation cost, and in the off-water transportation, anti-stress agents can only be sprayed directly onto the shrimp. However, the anti-stress agent is added once. Adding too much can easily cause poisoning of live shrimp, and adding too little will not achieve the desired effect. The present invention can solve the above problems by slowly releasing anti-stress agents through the continuous melting process of the anti-stress slow-release ice particles.

[0015] Preferably, in step (4), the gradient cold storage transportation specifically includes: During the 0-6 hours of transportation, a cold storage agent A is pre-cooled to a temperature of 8-10℃ in the insulated transport box. When the temperature inside the box exceeds 10℃, cold storage agent A can be added or replaced. This stage is the initial adaptation stage, which allows the live crayfish that have completed the anti-stress treatment to be placed on a temperature buffer platform, further stabilizing their physiological state and avoiding continuous low temperature stress. During the 6-12 hours of transportation, the cold storage agent A in the insulated transport box is replaced with cold storage agent B pre-heated to 5-8℃. When the temperature inside the box exceeds 8℃, cold storage agent B can be added or replaced. This stage is a transitional dormancy stage, which can allow the live crayfish to enter a shallow dormancy state, reducing energy consumption and stress metabolism. After more than 12 hours of transportation, the cold storage agent B in the insulated transport box should be replaced with cold storage agent C pre-cooled to a temperature of 3-5℃. When the temperature inside the box exceeds 5℃, cold storage agent C can be replenished or replaced. This stage is the deep dormancy stage, which allows the live crayfish to enter a deep ecological dormancy state, thereby maximally inhibiting enzymatic reactions and microbial growth. Through this stable temperature transition, the dormancy state caused by temperature fluctuations is avoided, thus stabilizing the energy consumption of the crayfish and effectively maintaining the stability of the muscle tissue structure and water retention capacity. Specifically, the cold storage agent A, cold storage agent B, and cold storage agent C are all commercially available phase change cold storage materials. Organic (such as paraffin, fatty acids), inorganic (such as inorganic salt hydrates), or composite materials can be selected according to the required temperature range. In order to accurately control the temperature, organic paraffin-based cold storage agents with phase change temperature points matching the target temperature range are preferred. They have advantages such as low supercooling, stable performance, and no phase separation, which enable precise temperature control.

[0016] More preferably, in step (4), the particle size of the nutrient-releasing ice particles is 1-3 mm, the nutrient-releasing ice particles are pre-cooled to -5 to -3℃, the mass ratio of the live crayfish to the nutrient-releasing ice particles is 1:0.1-0.2, and the nutrient-releasing ice particles are prepared from a glucose solution with a concentration of 0.10% to 0.20%.

[0017] More preferably, the glucose solution contains a nutritional factor, which is one of an amino acid or an organic acid. The amino acid is selected from glycine, alanine, or glutamic acid, and the organic acid is selected from citric acid, lactic acid, or succinic acid.

[0018] More preferably, when amino acids are added to the glucose solution as a nutrient-supporting factor, the mass concentration of amino acids in the glucose solution is 0.005% to 0.10%, and when organic acids are added to the glucose solution as a nutrient-supporting factor, the mass concentration of organic acids in the glucose solution is 0.001% to 0.10%.

[0019] In this invention, by adding a small amount of slow-release nutrient ice particles, the slow-release nutrient ice particles continuously melt and slowly release liquid nutrients during transportation. This can supplement the nutrients of live shrimp during the initial adaptation stage of initial transportation, thereby improving the shrimp's resistance to low temperatures and its survival ability. At the same time, the small amount of slow-release nutrient ice particles will not affect the ambient temperature required by the cold storage agent to maintain the initial adaptation stage.

[0020] More preferably, in step (4), the cold storage agent A, cold storage agent B and cold storage agent C are pre-cooled to the target temperature and kept at a constant temperature for at least 2 hours before use; before use, the cold storage agent is placed in a programmable low temperature constant temperature bath or other temperature control device and pre-cooled to the target temperature, for example, pre-cooled to 9±1℃, 6.5±1.5℃ and 4±1℃ respectively, and kept at a constant temperature for at least 2 hours to ensure that the internal temperature of the cold storage agent is uniform and stable before use.

[0021] In a further preferred embodiment, the cold storage agent A, cold storage agent B, or cold storage agent C is arranged alternately in layers with the live crayfish in the packaging box. That is, a layer of pre-cooled cold storage agent is laid at the bottom of the box, followed by a layer of live crayfish mixed with slow-release ice particles. This alternating arrangement is repeated, and the top layer is covered with another layer of cold storage agent before the box is immediately sealed. This cycle is repeated. Each layer of live crayfish should be laid roughly flat to avoid excessive accumulation and to ensure uniform circulation of cold air.

[0022] Further optimization involves controlling the net weight of each box of live crayfish to 5-8 kg to ensure a uniform and stable temperature and sufficient cooling within the box.

[0023] More preferably, the insulated transport box adopts a three-layer composite structure: the outer layer is a corrugated cardboard box, the middle layer is a foam insulation box, and the inner layer is an inner packaging bag; the inner packaging bag is either a PE plastic bag or a composite bubble bag, preferably a composite bubble bag; the main function of the inner packaging bag is to separate the live crayfish from the middle foam box and the cold storage agent, on the one hand to prevent the crayfish from directly contacting the cold box wall and causing local frostbite, and on the other hand to prevent the crayfish shells or claws from puncturing the cold storage agent and causing leakage and pollution, while also playing a certain role in cushioning and shock absorption.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) Significantly Improved Survival Rate During Transportation: This invention significantly reduces transportation stress in live crayfish through the synergistic effects of deep cleaning to reduce microbial invasion, anti-stress treatment to stabilize physiological state, and gradient cooling to smoothly induce dormancy. As shown in Table 1, after 48 hours of simulated transportation, the survival rate of the experimental group using the method of this invention reached 97%-99%, significantly better than the control group transported by direct ice addition (see Test Example 5 for specific data). Simultaneously, this invention can significantly slow down the decrease in muscle pH during transportation and maintain the stability of proteins such as myosin. This results in a significantly lower centrifugal water loss rate in the muscle of the experimental group compared to the control group, maintaining muscle firmness and elasticity at levels closer to ideal for freshness, effectively avoiding quality deterioration problems such as dry and hard meat and juice loss.

[0025] 2) Ensuring shrimp health and enhancing stress resistance from the source: The present invention effectively removes the silt and original bacteria attached to the surface of the shrimp through deep cleaning in step (2), reducing the initial microbial load; through the anti-stress treatment in step (3), the shrimp are supplemented with anti-stress agents such as vitamin C and vitamin A, which enhances the antioxidant capacity of the cells. Moreover, the anti-stress agents are slowly released by the melting of anti-stress slow-release ice particles, which is more conducive to absorption and will not cause poisoning of the shrimp. This pretreatment method from the source significantly improves the adaptability of fresh crayfish to the subsequent low-temperature transportation environment, laying a solid foundation for maintaining muscle quality.

[0026] 3) Protecting the integrity of the shrimp's appearance and improving the product's quality: Optimized ice-shrimp ratios and alternating layered packaging effectively reduce physical compression and collision damage during transportation. In particular, the inner packaging bag's isolation function avoids the risk of localized frostbite or puncture of the refrigerant caused by direct contact between the shrimp shell and claws and the refrigerated container walls. Experimental results show that the shells of the live crayfish remained more intact after transportation, and the claws remained intact without significant detachment or damage, resulting in a significantly better overall product quality compared to traditional transportation methods.

[0027] 4) Provides standardized and replicable process solutions: This invention clarifies the key process parameters for each step (such as cleaning agent concentration, type and amount of anti-stress agent, temperature gradient and time nodes), forming a complete and controllable standardized operating procedure, which is conducive to industrial promotion and application.

[0028] Based on the above-mentioned technical solutions provided by this invention, in order to facilitate understanding of the advantages or innovations of this invention, the exploration or implementation process of this invention is described below. Attached Figure Description

[0029] Figure 1 The effect of different washing times and plastic baskets on the cleaning effect of live crayfish.

[0030] Figure 2The impact of different cleaning methods and times on the survival rate of live crayfish.

[0031] Figure 3 The effects of different cleaning agents and concentrations on the degree of cleaning (d) and survival rate (a: sodium chloride; b: chlorine dioxide; c: sodium citrate).

[0032] Figure 4 V of each processing group under different transportation times A Experimental group (a), V C Experimental group (b), V C Changes in the centrifugal water loss rate of shrimp meat in the control group (c) with the concentration of additives Figure 5 V of each processing group under different transportation times A Experimental group (a), V C Experimental group (b), V C The effect of shear force on shrimp meat in the control group (c).

[0033] Figure 6 Temperature changes of live crayfish placed at different times (a: 0 h; b: 12 h; c: 24 h; d: 36 h; e: 48 h).

[0034] Figure 7 Survival rate of live crayfish refrigerated at 4℃ for 48 hours. Detailed Implementation

[0035] The process parameters for each step in the method described in this invention were determined and optimized through the following comparative experiments. The selection criteria for each key parameter and the preferred embodiments of this invention are explained in detail below with reference to specific examples. It should be understood that these examples are used to more clearly illustrate the technical content of this invention and are not intended to limit the scope of protection of this invention. All changes and improvements made based on the core concept of this invention should be included within the scope of this invention.

[0036] The gradient cold storage design in step (4) of this invention is a continuous programmed temperature control strategy that is directly connected with the anti-stress treatment in step (3). Its core principle is that, based on the deep sedation and pre-cooling of the shrimp body in step (3) after the anti-stress treatment, the fresh crayfish are actively and gently guided into and maintained in a deep ecological dormancy state by the temperature environment provided by the cold storage agent in the packaging box that changes over time, thereby systematically solving the problem of balancing transportation stress and low temperature damage.

[0037] Specifically, in step (3) of the anti-stress treatment, the live crayfish that maintains a stable body temperature are in full contact with the anti-stress slow-release ice particles. The anti-stress slow-release ice particles continue to melt to create a humid and low-temperature environment for the live crayfish while releasing anti-stress agents. The metabolism of the live crayfish is significantly inhibited, and the core temperature drops to the low-temperature range, thus achieving deep sedation. Subsequently, in step (4) of heat preservation packaging and transportation, the gradient cold storage transportation does not start from room temperature, but is based on the pre-cooling state of step (3) for fine management. That is, in the initial 0-6 hours of transportation, a cold storage agent of 8~10℃ is used. The purpose is to provide a plateau period slightly higher than the pretreatment temperature, so that the shrimp body avoids the stress of being constantly close to the freezing point, and thus smoothly transitions to a more stable dormant preparation state. During this process, the crayfish that have not yet gone dormant are mixed with nutrient slow-release ice particles. The nutrient slow-release ice particles continue to melt and release nutrient solution, which can improve the shrimp body's resistance to low temperature and survival ability. During the 6-12 hours of transportation, the cold storage agent is changed to 5~8℃, which aims to actively induce and consolidate shallow dormancy. In this temperature range, the shrimp body's metabolism and energy consumption are reduced to extremely low levels, effectively reducing lactic acid production and winning a key window for maintaining muscle pH. After more than 12 hours of transportation, a cold storage agent of 3~5℃ is used. This temperature can maximize the inhibition of enzyme and microbial activity while ensuring that the temperature is strictly higher than the tissue freezing point, thereby completely avoiding the physical damage risk of ice crystal formation and achieving quality lock-in during long-distance transportation.

[0038] Based on the above, this invention provides a complete temperature program from "deep sedation" to "stable transition," then to "light sleep induction," and finally to "deep sleep protection," demonstrating a progressive management of the shrimp's physiological state. Its effectiveness has been verified through the comparative experiment in Test Example 5 (see Table 1). Data shows that the experimental group using this gradient path significantly outperformed traditional methods in key indicators such as survival rate, muscle pH, water retention, and texture. This proves that this invention, through the synergistic design of temperature at each stage, achieves unexpected technical results superior to conventional constant temperature or abrupt cooling.

[0039] The technical solution and its effects of the present invention will be further illustrated below through specific embodiments. Example 1

[0040] A cold chain logistics transportation method for maintaining the muscle quality of live crayfish after transportation includes the following steps: (1) Raw material screening and pretreatment Select live crayfish that are uniform in size, vigorous, intact, and free from disease or injury; remove dead, diseased, damaged, and obviously weak individuals. (2) Cleaning treatment The selected live crayfish were bubbled and cleaned. The cleaning agent, which was pre-cooled to 10-12℃, was used at a mass-volume ratio of 1:10 between the live crayfish and the cleaning agent. The cleaning agent was a sodium chloride solution with a concentration of 10 g / L. The live crayfish were ensured to be completely submerged in the cleaning agent and cleaned for 30 minutes. After cleaning, the surface water was drained. (3) Stress relief treatment Six kg of cleaned live crayfish were mixed with 2.4 kg of anti-stress slow-release ice granules and placed in a foam insulated box for 1 hour of anti-stress treatment. The anti-stress slow-release ice granules had a particle size of 5-10 mm and were pre-cooled to -10 to -5°C. The anti-stress slow-release ice granules were prepared by using an ice maker with a vitamin C solution of 100 mg / L. (4) Thermal packaging and transportation Cold storage agent A, cold storage agent B, and cold storage agent C (commercially available phase change cold storage materials) are placed in a programmable low-temperature constant temperature bath, pre-cooled to 9±1℃, 6.5±1.5℃, and 4±1℃ respectively, and kept at the same temperature for at least 2 hours for later use. Fresh crayfish that have undergone stress-resistant treatment are taken out and mixed with 0.6 kg of slow-release nutrient ice granules before being placed in an insulated transport box. The slow-release nutrient ice granules have a particle size of 1-3 mm and are pre-cooled to -5 to -3℃. The slow-release nutrient ice granules are prepared by using an ice maker with a concentration of 0.15% glucose. During the 0-6 hours of transportation, a pre-cooled refrigerant A is placed in the insulated transport box to a temperature of 9±1℃. When the temperature inside the box exceeds 10℃, a new pre-cooled refrigerant A to a temperature of 9±1℃ is added or replaced. During the 6-12 hour transportation period, replace the refrigerant A in the insulated transport box with refrigerant B pre-cooled to a temperature of 6.5±1.5℃. When the temperature inside the box exceeds 8℃, replenish or replace with new refrigerant B pre-cooled to a temperature of 6.5±1.5℃. After 12 hours of transport, replace the refrigerant B in the insulated transport box with refrigerant C that has been pre-cooled to a temperature of 4±1℃. When the temperature inside the box exceeds 5℃, replenish or replace with new refrigerant C that has been pre-cooled to a temperature of 4±1℃. The fresh crayfish and the pre-cooled refrigerant are packed in layers. First, a layer of refrigerant is laid at the bottom of the box, then a layer of fresh crayfish and slow-release ice pellets are laid out, and so on alternately. The top layer is covered with another layer of refrigerant and then the box is immediately sealed. The packaging uses a three-layer composite structure: the outer layer is a corrugated cardboard box, the middle layer is a foam insulated box (box No. 3, 410×270×190 mm), and the inner layer is a composite bubble bag. Example 2

[0041] A cold chain logistics transportation method for maintaining the muscle quality of live crayfish after transportation includes the following steps: (1) Raw material screening and pretreatment Select live crayfish that are uniform in size, vigorous, intact, and free from disease or injury; remove dead, diseased, damaged, and obviously weak individuals. (2) Cleaning treatment The selected live crayfish were bubbled and cleaned. The cleaning agent, which was pre-cooled to 10-12℃, was used at a mass-volume ratio of 1:12 between the live crayfish and the cleaning agent. The cleaning agent was a chlorine dioxide solution with a concentration of 100 mg / L. The live crayfish were ensured to be completely submerged in the cleaning agent and cleaned for 30 minutes. After cleaning, the surface water was drained. (3) Stress relief treatment Six kg of cleaned live crayfish were mixed with 3.0 kg of anti-stress slow-release ice granules and placed in a foam insulated box for 2 hours of anti-stress treatment. The anti-stress slow-release ice granules had a particle size of 5-10 mm and were pre-cooled to -10 to -5°C. The anti-stress slow-release ice granules were prepared using an ice maker with a concentration of 1.0 mg / L vitamin A solution. (4) Thermal packaging and transportation Cold storage agent A, cold storage agent B, and cold storage agent C (commercially available phase change cold storage materials) are placed in a programmable low-temperature constant temperature bath, pre-cooled to 9±1℃, 6.5±1.5℃, and 4±1℃ respectively, and kept at the same temperature for at least 2 hours for later use. Fresh crayfish treated to resist stress were removed and mixed with 1.0 kg of slow-release nutrient ice granules before being placed in an insulated transport box. The slow-release nutrient ice granules had a particle size of 2-5 mm and were pre-cooled to -5 to -3°C. The slow-release nutrient ice granules were prepared using an ice maker from a 0.10% glucose solution, with glycine added as a nutritional aid. The mass concentration of glycine in the glucose solution was 0.02%. During the 0-6 hours of transportation, a pre-cooled refrigerant A is placed in the insulated transport box to a temperature of 9±1℃. When the temperature inside the box exceeds 10℃, a new pre-cooled refrigerant A to a temperature of 9±1℃ is added or replaced. During the 6-12 hour transportation period, replace the refrigerant A in the insulated transport box with refrigerant B pre-cooled to a temperature of 6.5±1.5℃. When the temperature inside the box exceeds 8℃, replenish or replace with new refrigerant B pre-cooled to a temperature of 6.5±1.5℃. After 12 hours of transport, replace the refrigerant B in the insulated transport box with refrigerant C that has been pre-cooled to a temperature of 4±1℃. When the temperature inside the box exceeds 5℃, replenish or replace with new refrigerant C that has been pre-cooled to a temperature of 4±1℃. The fresh crayfish and the pre-cooled refrigerant are packed in layers. First, a layer of refrigerant is laid at the bottom of the box, then a layer of fresh crayfish and slow-release ice pellets are laid out, and so on alternately. The top layer is covered with another layer of refrigerant and then the box is immediately sealed. The packaging uses a three-layer composite structure: the outer layer is a corrugated cardboard box, the middle layer is a foam insulated box (box No. 3, 410×270×190 mm), and the inner layer is a composite bubble bag. Example 3

[0042] A cold chain logistics transportation method for maintaining the muscle quality of live crayfish after transportation includes the following steps: (1) Raw material screening and pretreatment Select live crayfish that are uniform in size, vigorous, intact, and free from disease or injury; remove dead, diseased, damaged, and obviously weak individuals. (2) Cleaning treatment The selected live crayfish were bubbled and cleaned. The cleaning agent, which was pre-cooled to 10-12℃, was used at a mass-volume ratio of 1:8 between the live crayfish and the cleaning agent. The cleaning agent was a sodium citrate solution with a concentration of 20 g / L. The live crayfish were ensured to be completely submerged in the cleaning agent and cleaned for 30 minutes. After cleaning, the surface water was drained. (3) Stress relief treatment Six kg of cleaned live crayfish were mixed with 2.4 kg of anti-stress slow-release ice granules and placed in a foam insulated box for 1.5 h of anti-stress treatment. The anti-stress slow-release ice granules had a particle size of 5-10 mm and were pre-cooled to -10 to -5℃. The anti-stress slow-release ice granules were prepared by mixing a 1.0 mg / L vitamin A solution and a 100 mg / L vitamin C solution using an ice maker. (4) Thermal packaging and transportation Cold storage agent A, cold storage agent B, and cold storage agent C (commercially available phase change cold storage materials) are placed in a programmable low-temperature constant temperature bath, pre-cooled to 9±1℃, 6.5±1.5℃, and 4±1℃ respectively, and kept at the same temperature for at least 2 hours for later use. After stress-resistant treatment, the live crayfish were removed and mixed with 0.9 kg of slow-release nutrient ice granules, which were then placed in an insulated transport box. The slow-release nutrient ice granules had a particle size of 1-3 mm and were prepared by an ice maker using a 0.15% glucose solution. Citric acid was also added to the glucose solution as a nutritional aid, and the mass concentration of citric acid in the glucose solution was 0.01%. During the 0-6 hours of transportation, a pre-cooled refrigerant A is placed in the insulated transport box to a temperature of 9±1℃. When the temperature inside the box exceeds 10℃, a new pre-cooled refrigerant A to a temperature of 9±1℃ is added or replaced. During the 6-12 hour transportation period, replace the refrigerant A in the insulated transport box with refrigerant B pre-cooled to a temperature of 6.5±1.5℃. When the temperature inside the box exceeds 8℃, replenish or replace with new refrigerant B pre-cooled to a temperature of 6.5±1.5℃. After 12 hours of transport, replace the refrigerant B in the insulated transport box with refrigerant C that has been pre-cooled to a temperature of 4±1℃. When the temperature inside the box exceeds 5℃, replenish or replace with new refrigerant C that has been pre-cooled to a temperature of 4±1℃. The fresh crayfish and the pre-cooled refrigerant are packed in layers. First, a layer of refrigerant is laid at the bottom of the box, then a layer of fresh crayfish and slow-release ice pellets are laid out, and so on alternately. The top layer is covered with another layer of refrigerant and then the box is immediately sealed. The packaging uses a three-layer composite structure: the outer layer is a corrugated cardboard box, the middle layer is a foam insulated box (box No. 3, 410×270×190 mm), and the inner layer is a composite bubble bag. Test Example 1

[0043] To determine a cleaning method and cleaning time that can effectively remove dirt from the surface of live crayfish while maximizing their survival rate, this test case compares and verifies the cleaning effect and survival of live crayfish under different cleaning methods and different durations.

[0044] Fresh crayfish from the same batch were selected as experimental subjects and placed in containers filled with clean water. They were treated using both bubbling and static soaking methods, with different cleaning durations. The cleaning effect and survival rate were comprehensively evaluated. The cleanliness of the crayfish's abdomen and gills was specifically examined, and the survival rate of the fresh crayfish after cleaning was recorded. The experimental results are shown below. Figure 1 and Figure 2 .

[0045] like Figure 1 As shown, under the same cleaning time conditions, bubbling cleaning is significantly more effective than soaking cleaning in cleaning the abdomen and gills of live crayfish. Especially at cleaning times of 30 and 40 minutes, bubbling cleaning effectively removes attached mud and impurities, significantly improving the cleanliness of the crayfish's appearance. Soaking cleaning, on the other hand, shows no significant difference in cleaning effect across different cleaning durations, and its overall cleaning ability is weaker. Meanwhile, as... Figure 2 As shown, a comparison of the survival rates of fresh crayfish under different cleaning methods revealed that, under the bubbling cleaning method, the survival rate of crayfish decreased slightly with the extension of cleaning time, but the survival rate remained above 97% when the cleaning time was 30 min and 40 min, and the difference between the two was not significant; under the soaking cleaning method, the survival rate changed unstablely with time and tended to be close at different time points.

[0046] Based on both cleaning effectiveness and survival rate, the bubbling cleaning method, with a cleaning time of 30 minutes, can significantly improve the cleanliness of the surface of live crayfish and maintain a high survival rate. Its overall performance is significantly better than other treatment methods and time combinations.

[0047] Therefore, the present invention preferably adopts a bubbling cleaning method with a cleaning time of 30 minutes as a standard cleaning pretreatment step before transporting live crayfish, so as to achieve a synergistic guarantee of efficient decontamination and high survival rate. Test Example 2

[0048] In order to screen for cleaning agents that combine high cleaning efficiency with good biocompatibility and their suitable concentrations, this invention compared and verified different cleaning agents and their concentration combinations under the aforementioned preferred cleaning method of bubbling cleaning and a cleaning time of 30 minutes.

[0049] Live crayfish were selected as the treatment subjects. Under the same water environment conditions, sodium chloride solution, chlorine dioxide solution, and sodium citrate solution were used as cleaning agents, with different concentration gradients for cleaning treatment. The cleaning effect on easily accumulated dirt areas such as the abdomen and gills of the crayfish was evaluated. The survival of the live crayfish after cleaning treatment under low-temperature storage conditions was continuously monitored to comprehensively reflect the cleaning ability of the cleaning agents and their impact on the physiological state of the live crayfish. The experimental results are shown in [Figure number missing]. Figure 3 .

[0050] like Figure 3 As shown, the type and concentration of cleaning agents significantly affect the cleaning effect on the surface of live crayfish. Within the investigated concentration range, the removal effect of dirt attached to the gills and abdomen of live crayfish was significantly enhanced with increasing cleaning agent concentration, resulting in a significant improvement in the cleanliness of the crayfish's appearance. Although there were some differences in the initial degree of dirt adhesion among different individuals, the overall cleaning effect maintained a consistent trend with increasing concentration. Regarding biosafety, a comparison of the survival rates of cleaned live crayfish under medium- and long-term storage conditions at low temperatures revealed that cleaning agent treatment within the appropriate concentration range can maintain good cleaning effects while avoiding significant stress on live crayfish. Specifically, live crayfish treated with sodium chloride solution maintained a high survival rate after 36 hours of refrigeration; live crayfish treated with medium- and low-concentration chlorine dioxide solution maintained a stable survival level after 72 hours of refrigeration; and live crayfish treated with high-concentration sodium citrate solution showed good survival even after 60 hours of refrigeration.

[0051] Based on two key indicators—immediate cleaning effect and long-term storage survival rate—this invention screened out the following three cleaning agents that combine cleaning performance and biosafety, along with their preferred concentrations: sodium chloride solution, with a preferred concentration of 10 g / L; chlorine dioxide solution, with a preferred concentration of 100 mg / L; and sodium citrate solution, with a preferred concentration of 20 g / L.

[0052] Pre-treating live crayfish with the above-mentioned preferred concentration of cleaning agent can significantly improve the cleanliness of the body surface while minimizing the physiological stress on the live crayfish, ensuring that they maintain a high survival rate during subsequent low-temperature treatment and simulated storage stages, and providing a technical basis for determining the pre-treatment process parameters of this invention. Test Example 3

[0053] Under simulated cold chain transportation conditions, different anti-stress slow-release ice particles were compared to verify the effect of the present invention in improving the muscle quality of fresh crayfish using anti-stress slow-release ice particles.

[0054] Experimental group: 1.2 kg of anti-stress slow-release ice pellets and 3 kg of fresh crayfish were placed in alternating layers in a foam insulated box for 1 h of anti-stress treatment. The anti-stress slow-release ice pellets were made by using an ice-making machine with different concentrations of vitamin A solution and vitamin C solution. The particle size of the anti-stress slow-release ice pellets was 5-10 mm. The anti-stress slow-release ice pellets were pre-cooled to -8℃±1℃. Control group: Anti-stress agents were applied in the conventional way, and ice treatment was used at the same time. Specifically, 3 kg of fresh crayfish were taken, and vitamin C solutions of different concentrations were sprayed on their surface. The amount of spraying was 2% of the crayfish's body weight. Then, the fresh crayfish and 1.2 kg of ordinary ice made of water pre-cooled to -8℃±1℃ were placed in a foam insulated box in alternating layers for anti-stress treatment for 1 h. The fresh crayfish from the experimental and control groups that underwent anti-stress treatment were transported for 48 hours using the method described in step (4) of Example 1. The centrifugal water loss rate and shear force of the crayfish muscle were measured, and the results are shown in […]. Figure 4 and Figure 5 ; As Figure 4 , Figure 5 As shown, with the extension of simulated transportation time, the centrifugal water loss rate of crayfish muscle in the control group increased significantly, and the water-holding capacity decreased rapidly; while the increase in centrifugal water loss rate of crayfish treated with anti-stress slow-release ice particles was significantly slowed down, indicating that anti-stress slow-release ice particle treatment can effectively delay muscle water loss during transportation. Within the range investigated, the higher the concentration of vitamin A solution and vitamin C solution, the more obvious their effect on maintaining muscle water-holding capacity.

[0055] Meanwhile, the shear force of the shrimp meat in the control group continued to decrease with transportation time, showing that the muscle tissue structure gradually loosened; while the shear force of the fresh crayfish treated with anti-stress slow-release ice pellets showed a significantly slower decline, and under some treatment conditions, the shear force even increased in the early stage of transportation. This indicates that appropriate concentrations of anti-stress agents vitamin A and vitamin C help maintain the stability of muscle structure, thereby maintaining good textural properties.

[0056] This demonstrates that the anti-stress slow-release ice particles used in this invention have significant technical effects under cold chain transportation conditions, and can effectively improve the product quality and stability of fresh crayfish after transportation. Test Example 4

[0057] To screen suitable thermal insulation packaging materials for cold chain transportation of live crayfish, the thermal insulation performance of different thermal insulation bag materials and their impact on the survival rate of live crayfish were compared and verified.

[0058] Two common insulation materials, PE plastic bags and composite bubble wrap bags, were selected as comparison objects. Equal amounts of ice were placed into both types of insulation bags and then placed in foam boxes of the same size. Temperature detection probes were placed at different locations inside the foam boxes. Subsequently, live crayfish of similar weight and quantity were packed into the boxes and left to stand at room temperature for 48 hours. Temperature changes and the survival rate of the live crayfish were continuously monitored. The results are shown in [Figure number missing]. Figure 6 and Figure 7 .

[0059] The results showed that both insulation materials could maintain the internal temperature of the box within the range of 12-16℃ during the initial 16 hours of transportation. However, as the transportation time increased, the insulation performance of the PE plastic bag decreased rapidly, and the internal temperature began to rise significantly after 16 hours, while the composite bubble bag only showed a significant temperature increase trend after 26 hours. In comparison, the effective insulation time of the composite bubble bag was approximately 10 hours longer than that of the PE plastic bag, indicating that its thermal insulation performance was significantly superior.

[0060] Further comparison of survival rates revealed that after 48 hours of simulated transportation, the survival rate of live crayfish insulated with PE plastic bags was less than 90%, while the survival rate of live crayfish insulated with composite bubble bags was significantly higher, remaining above 95% overall. This indicates that composite bubble bags can effectively reduce the impact of temperature fluctuations during transportation on the physiological state of live crayfish.

[0061] In summary, composite bubble wrap exhibits superior insulation performance and a more significant survival rate retention effect compared to traditional PE plastic bags. Based on these results, this invention preferentially uses composite bubble wrap as the insulation packaging material for the cold chain transportation of live crayfish, thereby significantly improving the survival rate and stability of live crayfish during transportation. Test Example 5

[0062] To verify the technical advantages of the stress-resistant treatment and gradient cold storage transportation strategy proposed in this invention in maintaining the muscle quality of fresh crayfish after transportation compared with traditional constant temperature or rapid cooling methods, this embodiment conducted a systematic comparative study on the physiological state and muscle quality changes of fresh crayfish under different transportation methods under simulated long-distance cold chain transportation conditions.

[0063] Experimental Group 1: The transportation was simulated for 48 hours using the method in Example 1.

[0064] Experimental Group 2: The transportation was simulated for 48 hours using the method in Example 2.

[0065] Experimental Group 3: The transportation was simulated for 48 hours using the method in Example 3.

[0066] Control group 1: The traditional method was used to simulate transportation for 48 hours, that is, live shrimp were packed with ordinary ice (made from water using an ice maker) at a mass ratio of 2:1, without any anti-stress treatment or gradient cold storage treatment.

[0067] Control group 2: Step (3) anti-stress treatment was omitted, and other steps were the same as in Example 1, with simulated transportation for 48 hours.

[0068] Control group 3: Step (4) was carried out at a constant temperature of 4°C without the use of nutrient-releasing ice particles. Other steps were carried out in the same manner as in Example 1 for 48 hours of simulated transportation.

[0069] After transportation, the survival rate of each group of live crayfish was tested, and the muscle quality was measured by pH, centrifugal water loss rate, and firmness. The physiological state and muscle quality indicators of each group of live crayfish after a simulated 48-hour transportation period are shown in Table 1.

[0070] As shown in Table 1, the gradient cold storage temperature control path (experimental groups 1-3) adopted in this invention exhibits good comprehensive effects in all key indicators. Experimental group 1 consists of slow-release nutrient ice pellets containing only glucose, while experimental groups 2 and 3 are further supplemented with glycine and citric acid, respectively. After transportation (48 h), the survival rates of experimental groups 1-3 were 97%, 98%, and 99%, respectively, all higher than those of the traditional control group 1 (85%) and the control group 2 (92%) without anti-stress treatment, indicating that the method of this invention can effectively alleviate transportation stress. Among them, experimental groups 2 and 3, with the addition of glycine and citric acid, showed a certain upward trend in survival rate compared to experimental group 1. pH results showed that at 24 h and 48 h of transportation, the pH values ​​of experimental groups 1-3 were higher than those of the control groups, indicating that the method of this invention can mitigate acidification caused by glycolysis during transportation. In this study, the pH value of experimental group 2, which added glycine, was slightly higher than that of experimental group 1, indicating a better stabilizing effect. Experimental group 3, which added citric acid, also showed a relatively gradual decrease in pH, suggesting that it helps maintain muscle environment stability. Regarding centrifugal water loss, after 24 and 48 hours of transport, experimental groups 1-3 were significantly lower than the control groups, indicating that the method of this invention can effectively improve muscle water retention. The water loss rates of experimental groups 2 and 3 were slightly lower than those of experimental group 1, indicating that the addition of amino acids or organic acids to glucose can further reduce water loss. Internal hardness results showed that all groups increased with prolonged transport time, but the increase in experimental groups 1-3 was significantly lower than that in the control groups. In contrast, the internal hardness of experimental groups 2 and 3 was generally lower than that of experimental group 1, indicating that the addition of glycine or citric acid helps slow down the hardening process of muscle structure. Regarding external hardness, all groups decreased over time, but experimental groups 1-3 were generally higher than the control groups, indicating that it has a good protective effect on the carapace structure. Among them, experimental groups 2 and 3 were comparable to or slightly better than experimental group 1 in maintaining shell hardness, demonstrating a more stable ability to maintain appearance quality.

[0071] Table 1. Physiological state and quality changes of live crayfish under different transportation methods

[0072] Note: Different capital letters in the superscript of data in the same column indicate that the same group has significant differences at different time points. p<0.05 Different lowercase letters in the superscript of peer data indicate significant differences between different groups at the same time point. p<0.05 Data are expressed as mean ± standard deviation.

[0073] In summary, this invention, through the synergistic effect of gradient cold storage temperature control and anti-stress treatment, can effectively maintain a high survival rate, slow down pH decline, reduce water loss rate, and stabilize texture indicators during transportation. At the same time, the nutrient-release ice granules, with the addition of glycine or citric acid to glucose, can further improve the transportation quality of live crayfish to a certain extent, demonstrating a good synergistic enhancement effect.

Claims

1. A cold chain logistics transportation method for maintaining the muscle quality of fresh crayfish after transportation, characterized in that, Includes the following steps: (1) Raw material screening; (2) Cleaning: Clean the selected live crayfish; (3) Anti-stress treatment: Fresh crayfish were mixed with anti-stress slow-release ice pellets and placed in a foam insulated box for anti-stress treatment; (4) Insulated packaging and transportation: After the stress-resistant treatment, the fresh crayfish are taken out and mixed with nutrient slow-release ice particles and then placed in an insulated transport box. At the same time, a cold storage agent is placed in the insulated transport box for gradient cold storage transportation.

2. The cold chain logistics transportation method according to claim 1, characterized in that, In step (2), the cleaning process is carried out by bubbling cleaning, and the cleaning time is 20 to 40 minutes.

3. The cold chain logistics transportation method according to claim 2, characterized in that, In step (2), during the bubbling cleaning, a cleaning agent pre-cooled to 10-12°C is used and injected at a mass-to-volume ratio of 1:8-12 between the live crayfish and the cleaning agent to ensure that the live crayfish are completely submerged in the cleaning agent.

4. The cold chain logistics transportation method according to claim 3, characterized in that, The cleaning agent is any one of sodium chloride solution, chlorine dioxide solution, or sodium citrate solution; the concentration of the sodium chloride solution is 8-12 g / L, the concentration of the chlorine dioxide solution is 80-120 mg / L, and the concentration of the sodium citrate solution is 15-25 g / L.

5. The cold chain logistics transportation method according to claim 1, characterized in that, In step (3), the particle size of the anti-stress slow-release ice particles is 5-10 mm, the anti-stress slow-release ice particles are pre-cooled to -10 to -5℃, the mass ratio of the live crayfish to the anti-stress slow-release ice particles is 1:0.3-0.5, and the anti-stress treatment time is 1-2 h.

6. The cold chain logistics transportation method according to claim 5, characterized in that, In step (3), the anti-stress sustained-release ice particles are prepared by mixing one or more of the following: a vitamin C solution with a concentration of 50-150 mg / L and a vitamin A solution with a concentration of 0.5-2.0 mg / L.

7. The cold chain logistics transportation method according to claim 1, characterized in that, In step (4), the gradient cold storage transportation specifically refers to: During the 0-6 hour transportation period, a cold storage agent A is pre-cooled to a temperature of 8-10℃ in the insulated transport box; During the 6-12 hour transportation period, the refrigerant A in the insulated transport box should be replaced with refrigerant B pre-heated to 5-8℃. After more than 12 hours of transportation, replace the refrigerant B in the insulated transport box with refrigerant C, which has been pre-cooled to a temperature of 3-5℃.

8. The cold chain logistics transportation method according to claim 1, characterized in that, In step (4), the particle size of the nutrient-releasing ice pellets is 1-3 mm, the nutrient-releasing ice pellets are pre-cooled to -5 to -3℃, the mass ratio of the live crayfish to the nutrient-releasing ice pellets is 1:0.1-0.2, and the nutrient-releasing ice pellets are prepared from a glucose solution with a concentration of 0.10% to 0.20%.

9. The cold chain logistics transportation method according to claim 8, characterized in that, The glucose solution contains a nutritional factor, which is one of an amino acid or an organic acid. The amino acid is selected from glycine, alanine, or glutamic acid, and the organic acid is selected from citric acid, lactic acid, or succinic acid.

10. The cold chain logistics transportation method according to claim 9, characterized in that, When amino acids are added to a glucose solution as a nutrient-supporting factor, the mass concentration of amino acids in the glucose solution is 0.005% to 0.10%. When organic acids are added to a glucose solution as a nutrient-supporting factor, the mass concentration of organic acids in the glucose solution is 0.001% to 0.10%.

11. The cold chain logistics transportation method according to claim 7, characterized in that, In step (4), the cold storage agent A, cold storage agent B and cold storage agent C are pre-cooled to the target temperature and kept at a constant temperature for at least 2 hours before use; the cold storage agent A, cold storage agent B or cold storage agent C and the fresh crayfish are arranged alternately in layers in the packaging box.

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