Water-retaining and anti-freezing method for frozen matured squid foot and product thereof

Abstract

The application discloses a water-retention and anti-freezing method for frozen mature squid feet and products, and belongs to the technical field of aquatic food processing. The method comprises the following steps: raw material pretreatment, composite water-retention agent directional injection, ultrasonic gradient diffusion, natural deep eutectic solvent directional penetration, high-temperature short-time cooking, ice-salt water rapid cooling and low-temperature frozen storage. The application realizes efficient penetration of functional components through the squid foot nerve cord channel, effectively solving the problem of insufficient central penetration in the traditional process. The natural deep eutectic solvent composed of betaine and lactic acid can construct a multifunctional protection system, and plays a molecular chaperone-like effect to stabilize the natural conformation of proteins during heat treatment, and delays heat-induced aggregation; under low-temperature freezing, hydrogen bond network is formed to bind water, and ice crystal nucleation and generation are inhibited. The squid feet processed by the method have greatly improved water retention, meat tenderness and frozen storage stability, and the product quality is excellent, and is suitable for industrialized large-scale production.

Description

Technical Field

[0001] This invention relates to aquatic food processing technology, and more particularly to a method and product for water retention and antifreeze of frozen cooked squid tentacles. Background Technology

[0002] The squid (Dosidicus gigas), commonly known as the Peruvian squid, is an important economically important cephalopod with abundant resources and low costs. The muscle tissue of its squid tentacles, from the inside out, consists of nerve cords, crisscrossing bundles of muscle fibers, spiral oblique muscles, circular muscles, and connective tissue. The tissue structure is dense, and the muscle fibers are tightly packed. Although this part is rich in high-quality protein and polyunsaturated fatty acids, making it highly nutritious, the high content of insoluble matrix protein in the muscle results in a tough, hardened texture and a dry, slightly sour taste after steaming or boiling. During freezing, ice crystal growth and recrystallization lead to mechanical damage to muscle fibers and protein denaturation, further exacerbating quality deterioration. Therefore, developing efficient water-retention, tenderizing, and antifreeze technologies is of significant industrial value in improving the edible quality of squid tentacles.

[0003] Currently, the water-retaining and tenderizing processing of aquatic products mostly adopts external soaking methods to add water-retaining agents. This process has problems such as long processing cycles and uneven penetration of functional components, resulting in poor water retention in the product, easy water loss during steaming and freezing, and low yield. Although ultrasonic-assisted treatment can shorten the soaking time to some extent, it still relies on the surface-to-inside diffusion path, and its effect on the product's interior is limited. In terms of cryoprotection, natural deep eutectic solvents (NADES) are often used as cryoprotectants. They mainly play a role in cryoprotection during frozen storage by inhibiting ice crystal nucleation and recrystallization and accelerating the thawing process through a hydrogen bond network enhanced at low temperatures. However, NADES itself has high viscosity and is currently mostly used in systems such as fish paste and meat paste. Because the muscle fiber structure of fish paste or meat paste is broken down after homogenization, the cell tissue barrier no longer exists. The high viscosity of NADES can be evenly dispersed in the entire system with simple stirring and mixing, completely avoiding penetration barriers. The operation is simple and the effect is uniform. The intact squid tentacle tissue has a dense structure, with tightly packed muscle fiber bundles surrounded by connective tissue, forming a natural mass transfer barrier. The high viscosity of NADES makes it difficult for it to overcome this physical barrier and effectively penetrate into the tissue. Therefore, in existing studies, NADES is mostly used in pulverized systems such as surimi, and no integrated heat-resistant and freeze-resistant processing schemes for intact squid tentacle tissue have been found. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preserving water and preventing freezing of frozen cooked squid tentacles that have good water retention, tender texture, and good stability during freezing.

[0005] To achieve the above objectives, the present invention provides a method for water retention and antifreeze preservation of frozen cooked squid tentacles, characterized by comprising the following steps: S1. Raw material pretreatment: Add salt to the thawed squid tentacles and roll them, then marinate them at low temperature, then wash them with water and drain them; S2. Targeted injection of compound water-retaining agent: Targeted needle puncture is performed from the middle of the squid tentacle sucker surface, and the compound water-retaining agent is injected into the squid tentacle nerve cord channel by the sudden drop in puncture resistance at the spatial position of the nerve cord. S3. Ultrasonic gradient diffusion: First, the squid tentacles treated with S2 are placed in a composite water-retaining agent solution for ultrasonic treatment; then the squid tentacles are soaked in ice water. S4. Directional penetration of natural deep eutectic solvent: Using the directional puncture combined with ultrasonic diffusion process described in S2 and S3, the composite water-retaining agent is replaced with a natural deep eutectic solvent composed of betaine and lactic acid to penetrate into the squid tentacle tissue. S5. High-temperature short-time steaming: After draining the water from the squid tentacles treated in S4, steam them at high temperature for a short time until they are cooked. S6. Rapid cooling with ice-salt water: Immediately transfer the steamed squid tentacles into ice-salt water to cool them down, so that the core temperature of the squid tentacles drops to 4-10℃; S7. Low-temperature freezing: After cooling, drain the surface moisture of the squid tentacles, vacuum pack them, and freeze them at low temperature to obtain frozen cooked squid tentacles.

[0006] Furthermore, in step S1, the weight ratio of squid tentacles to salt is 100:(3-8), and the mixture is tumbled for 10-20 minutes; preferably, the weight ratio of squid tentacles to salt is 100:5, and the mixture is tumbled for 15 minutes.

[0007] Furthermore, in step S2, the amount of the composite water-retaining agent injected is 10%-20% of the weight of the squid tentacles.

[0008] Further, in step S2, the composite water-retaining agent is formulated as follows (by weight percentage): 0.5-2.5% polyphosphate, 0.5-2.5% sodium citrate, 1-4% sodium carbonate, 0.5-1.0% trehalose, 0.3-0.4% sorbitol, 0.1-0.2% glucose, 0.2-0.3% glycine, 0.5-1.5% salt, with the remainder being water; preferably, the composite water-retaining agent is formulated as follows: 1.0-2.0% polyphosphate, 1.0-2.0% sodium citrate, 2.0-4.0% sodium carbonate, 0.5-1.0% trehalose, 0.3-0.4% sorbitol, 0.1-0.2% glucose, 0.2-0.3% glycine, 0.5-1.5% salt, with the remainder being water.

[0009] Furthermore, in step S3, the ratio of squid tentacles treated in step S2 to the composite water-retaining agent solution during ultrasonic treatment is 1:(1-2); the weight ratio of squid tentacles to ice water during ice water soaking is 1:(1-3).

[0010] Furthermore, in step S3, the ratio of squid tentacles treated in step S2 to the composite water-retaining agent solution during ultrasonic treatment is 1:1.5; the weight ratio of squid tentacles to ice water during ice water soaking is 1:2; the conditions for ultrasonic treatment are: frequency 40-50 kHz, power 200-300 W, temperature 15-20℃, and time 30-60 minutes.

[0011] Furthermore, in step S4, the method for preparing the natural deep eutectic solvent is as follows: betaine and lactic acid are mixed in a molar ratio of 1:(1-2), water accounting for 40-60% of the total mass of the mixture is added, and the mixture is heated and stirred at 60-80°C until a homogeneous and transparent liquid is formed.

[0012] Furthermore, in step S5, the conditions for high-temperature short-time steaming are steaming at 100-120°C for 4-10 minutes.

[0013] Furthermore, in step S6, the ice-salt water consists of 2-5% salt, 0.1-0.2% sodium isoascorbate, and the remainder is water by weight percentage; the cooling in the ice-salt water is 0-4°C for 10-30 minutes.

[0014] This invention also protects the frozen cooked squid tentacles prepared by the method.

[0015] This invention utilizes the unique nerve cord structure of squid tentacles as a natural permeation channel for functional components, combines targeted puncture injection with ultrasound-assisted diffusion technology, and constructs a multifunctional NADES protection system to solve problems such as poor permeation effect in existing technologies, thereby improving the overall quality and frozen storage stability of cooked squid tentacles.

[0016] This invention achieves efficient penetration of functional components through the neural cord pathways of squid tentacles, effectively solving the problem of insufficient center penetration in traditional processes. The natural deep eutectic solvent composed of betaine and lactic acid constructs a multifunctional protective system. During heat treatment, it exerts a molecular chaperone-like effect to stabilize the native conformation of proteins and delay heat-induced aggregation; under low-temperature freezing, it forms a hydrogen bond network to bind water, inhibiting ice crystal nucleation and formation. Squid tentacles treated with this method exhibit significantly improved water-holding capacity, tenderness, and frozen storage stability, resulting in superior product quality suitable for large-scale industrial production.

[0017] This invention obtained the optimal formulation of the composite water-retaining agent through orthogonal experiments, and verified the synergistic effect of nerve cord directional injection, ultrasonic gradient diffusion, and natural deep eutectic solvent directional penetration processes through comparisons in Examples 2-8. Frozen cooked squid tentacles treated with the complete method of this invention (Example 8) exhibited the highest water retention and lowest hardness, significantly superior to other treatment methods. This demonstrates that the method of this invention can effectively improve the water retention and tenderness of frozen cooked squid tentacles, significantly enhance the product's water retention and freeze resistance, and is highly operable, possessing promising prospects for industrial application. Attached Figure Description

[0018] Figure 1 This is a graph showing the effect of polyphosphate addition in a single-factor experiment.

[0019] Figure 2 This is a graph showing the effect of sodium citrate addition on the single-factor experiment.

[0020] Figure 3 This is a graph showing the effect of sodium carbonate addition in a single-factor experiment.

[0021] Figure 4 The graph shows the test results of the water-holding capacity of squid tentacles in Examples 2-8.

[0022] Figure 5 The image shows the test results of the hardness of squid tentacles in Examples 2-8.

[0023] Figure 6 The graph shows the moisture distribution test results of squid tentacles prepared in Examples 2-8. Detailed Implementation

[0024] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0025] A method for preserving water and preventing freezing of frozen cooked squid tentacles, characterized by comprising the following steps: S1. Raw material pretreatment: Add salt to the thawed squid tentacles and roll them, then marinate them at low temperature, then wash them with water and drain them; S2. Targeted injection of compound water-retaining agent: Targeted needle puncture is performed from the middle of the squid tentacle sucker surface, and the compound water-retaining agent is injected into the squid tentacle nerve cord channel by the sudden drop in puncture resistance at the spatial position of the nerve cord. S3. Ultrasonic gradient diffusion: First, the squid tentacles treated with S2 are placed in a composite water-retaining agent solution for ultrasonic treatment; then the squid tentacles are soaked in ice water. S4. Directional penetration of natural deep eutectic solvent: Using the directional puncture combined with ultrasonic diffusion process described in S2 and S3, the composite water-retaining agent is replaced with a natural deep eutectic solvent composed of betaine and lactic acid to penetrate into the squid tentacle tissue. S5. High-temperature short-time steaming: After draining the water from the squid tentacles treated in S4, steam them at high temperature for a short time until they are cooked. S6. Rapid cooling with ice-salt water: Immediately transfer the steamed squid tentacles into ice-salt water to cool them down, so that the core temperature of the squid tentacles drops to 4-10℃; S7. Low-temperature freezing: After cooling, drain the surface moisture of the squid tentacles, vacuum pack them, and freeze them at low temperature to obtain frozen cooked squid tentacles.

[0026] Furthermore, in step S1, the weight ratio of squid tentacles to salt is 100:(3-8), and the mixture is tumbled for 10-20 minutes; preferably, the weight ratio of squid tentacles to salt is 100:5, and the mixture is tumbled for 15 minutes.

[0027] Furthermore, in step S2, the amount of the composite water-retaining agent injected is 10%-20% of the weight of the squid tentacles.

[0028] Further, in step S2, the composite water-retaining agent is formulated as follows (by weight percentage): 0.5-2.5% polyphosphate, 0.5-2.5% sodium citrate, 1-4% sodium carbonate, 0.5-1.0% trehalose, 0.3-0.4% sorbitol, 0.1-0.2% glucose, 0.2-0.3% glycine, 0.5-1.5% salt, with the balance being water; preferably, the composite water-retaining agent is formulated as follows: 1.0-2.0% polyphosphate, 1.0-2.0% sodium citrate, 2.0-4.0% sodium carbonate, 0.5-1.0% trehalose, 0.3-0.4% sorbitol, 0.1-0.2% glucose, 0.2-0.3% glycine, 0.5-1.5% salt, with the balance being water.

[0029] Furthermore, in step S3, the ratio of squid tentacles treated in step S2 to the composite water-retaining agent solution during ultrasonic treatment is 1:(1-2); the weight ratio of squid tentacles to ice water during ice water soaking is 1:(1-3).

[0030] Furthermore, in step S3, the ratio of squid tentacles treated in step S2 to the composite water-retaining agent solution during ultrasonic treatment is 1:1.5; the weight ratio of squid tentacles to ice water during ice water soaking is 1:2; the conditions for ultrasonic treatment are: frequency 40-50 kHz, power 200-300 W, temperature 15-20℃, and time 30-60 minutes.

[0031] Furthermore, in step S4, the method for preparing the natural deep eutectic solvent is as follows: betaine and lactic acid are mixed in a molar ratio of 1:(1-2), water accounting for 40-60% of the total mass of the mixture is added, and the mixture is heated and stirred at 60-80°C until a homogeneous and transparent liquid is formed.

[0032] Furthermore, in step S5, the conditions for high-temperature short-time steaming are steaming at 100-120°C for 4-10 minutes.

[0033] Furthermore, in step S6, the ice-salt water consists of 2-5% salt, 0.1-0.2% sodium isoascorbate, and the remainder is water by weight percentage; the cooling in the ice-salt water is 0-4°C for 10-30 minutes.

[0034] Example 1: Formulation optimization experiment of composite water-retaining agent To determine the optimal addition amount of each component in the composite water-retaining agent, this invention first investigated the effects of polyphosphate, sodium citrate and sodium carbonate on the quality of squid tentacles through single-factor experiments, and then optimized the optimal formula through orthogonal experiments.

[0035] 1) Single-factor experiment The effects of polyphosphate, sodium citrate, and sodium carbonate additions on the cooking loss rate and firmness of squid tentacles were investigated. The addition amounts of polyphosphate and sodium citrate were set at 0.5%, 1.0%, 1.5%, 2.0%, and 2.5% (w / v), and the addition amounts of sodium carbonate were set at 1.0%, 1.5%, 2.0%, 3.0%, and 4.0% (w / v). In each experiment, only the addition amount of one additive was changed, while the other two additives were kept constant at 1.5% (w / v). Based on the results of the cooking loss rate and firmness measurements, the appropriate addition range for each additive was determined. The processing flow was standardized for all groups as follows: S1. Raw material pretreatment: Add 5% salt by weight to the thawed squid tentacles, roll and knead for 15 minutes, marinate at 4℃ for 1 hour, then rinse with running water and drain.

[0036] Prepare a compound water-retaining agent solution with corresponding concentration gradients; soak the marinated squid tentacles in the compound water-retaining agent solution for 12 hours at a material-to-liquid ratio of 1:1.5; then soak them in ice water for 1 hour at a material-to-liquid ratio of 1:2.

[0037] S5. High-temperature short-time steaming: Remove the squid tentacles, drain the surface water, and steam at 100℃ for 4 minutes.

[0038] S6. Rapid cooling with ice-salt water: Separately weigh 3.5% salt and 0.15% sodium isoascorbate by weight, dissolve them in pure water, and prepare ice-salt water. Immediately transfer the steamed squid tentacles into the ice-salt water to cool for 10 minutes, so that their core temperature drops below 10°C.

[0039] S7. Low-temperature freezing: Drain the surface moisture, vacuum pack and freeze at -18℃ to obtain frozen cooked squid tentacles.

[0040] Index determination: The following indexes were determined for the obtained frozen cooked squid tentacles product: (1) Cooking loss rate: Weigh the squid tentacles after soaking (M1), steam for 4 min, cool in crushed ice for 10 min, drain the surface moisture, and weigh again (M2). The calculation formula is as follows: (1) In the formula, M1 represents the mass of the squid tentacles before steaming, in g; M2 represents the mass of the squid tentacles after steaming, in g.

[0041] (2) Texture: The hardness of squid tentacles was measured using a TA-XT Plus texture analyzer with a P / 0.5 probe.

[0042] (3) Water retention: Cut the sample into 5 mm thick slices, weigh them (M3), wrap them in filter paper, place them in a 50 mL centrifuge tube, centrifuge at 4℃ and 1000×g for 15 min, and weigh them again (M4). The calculation formula is as follows: (2) In the formula, M3 represents the mass of the sample before centrifugation, in g; M4 represents the mass of the sample after centrifugation, in g.

[0043] The effect of polyphosphate addition amount is shown in Figure 1 .Depend on Figure 1 It was found that with the increase of polyphosphate addition, the hardness and cooking loss rate of squid tentacles showed a trend of first decreasing and then increasing, reaching a minimum at an addition of 1.5%, indicating that the water retention and texture of squid tentacles were optimal under this condition. This is mainly because an appropriate amount of polyphosphate can increase the pH and ionic strength of the system, increase the electrostatic repulsion between protein molecules, and promote the binding of muscle protein and water molecules, thereby improving the product's water retention and tenderness. However, excessive addition of polyphosphate will lead to excessively high pH and ionic strength, which will make the squid tentacles harder and increase the cooking loss rate. Therefore, the polyphosphate levels in the orthogonal experiment were set at 1.0%, 1.5%, and 2.0%.

[0044] The effect of sodium citrate addition is shown in the figure. Figure 2 .like Figure 2As shown, with the increase of sodium citrate addition, the hardness and cooking loss rate of squid tentacles also showed a trend of first decreasing and then increasing, reaching the lowest value when the addition amount was 1.5%. Sodium citrate can not only increase the pH value of the system, but also chelate divalent metal ions in the muscle, making the protein structure loose and enhancing the charge repulsion, thereby improving water retention and achieving a tenderizing effect. However, excessive sodium citrate will weaken the water-holding and deformation capacity of muscle cells, leading to hardening of the meat and decreased water retention. Therefore, the sodium citrate levels were set at 1.0%, 1.5%, and 2.0% in the orthogonal experiment.

[0045] The effect of sodium carbonate addition is shown in the figure. Figure 3 .Depend on Figure 3 It was found that sodium carbonate at an addition level of 3.0% had the best effect on improving squid tentacles. This may be because sodium carbonate can increase the pH of the system, causing it to deviate from the isoelectric point of myofibrillar proteins, increasing the negative charge on the protein surface and the intermolecular repulsion, promoting the swelling of myofibrillar fibers, thereby enhancing the water retention and tenderizing effect. However, when excessive sodium carbonate is added, the excessively high pH may damage the protein structure, thus weakening its water retention capacity. Therefore, the sodium carbonate levels selected in the orthogonal experiment were 2.0%, 3.0%, and 4.0%.

[0046] 2) Orthogonal experiment Based on the results of single-factor experiments, the addition amounts of polyphosphate (A), sodium citrate (B), and sodium carbonate (C) were selected as influencing factors. Each factor was set with three levels, and L9 (3) experiments were conducted. 4 Orthogonal experiment. Using cooking loss rate and hardness as evaluation indicators, a weighted scoring method was employed to calculate the comprehensive score, with each indicator accounting for 50% of the total score. This determined the optimal ratio of the composite water-retaining agent. The factor level design is shown in Table 1. The treatment process flow for each group is standardized as follows: S1. Raw material pretreatment: Add 5% salt by weight to the thawed squid tentacles, roll and knead for 15 minutes, marinate at 4℃ for 1 hour, then rinse with running water and drain.

[0047] Prepare a compound water-retaining agent solution with corresponding concentration gradients; soak the marinated squid tentacles in the compound water-retaining agent solution for 12 hours at a material-to-liquid ratio of 1:1.5; then soak them in ice water for 1 hour at a material-to-liquid ratio of 1:2.

[0048] S5. High-temperature short-time steaming: Remove the squid tentacles, drain the surface water, and steam at 100℃ for 4 minutes.

[0049] S6. Rapid cooling with ice-salt water: Separately weigh 3.5% salt and 0.15% sodium isoascorbate by weight, dissolve them in pure water, and prepare ice-salt water. Immediately transfer the steamed squid tentacles into the ice-salt water to cool for 10 minutes, so that their core temperature drops below 10°C.

[0050] S7. Low-temperature freezing: Drain the surface moisture, vacuum pack and freeze at -18℃ to obtain frozen cooked squid tentacles.

[0051] Table 1. Factors and Levels of Orthogonal Experiment

[0052] The indicator detection is the same as that of the single-factor experiment.

[0053] The results of the orthogonal experiment are shown in Table 2.

[0054] The range analysis results in Table 2 show that the order of influence of each factor on the cooking loss rate and hardness of squid tentacles is: sodium carbonate > polyphosphate > sodium citrate, indicating that sodium carbonate is the key factor affecting the quality of squid tentacles. K-value analysis revealed that when the addition amounts of polyphosphate are 2.0% (k1=87.13), sodium citrate is 2.0% (k2=83.58), and sodium carbonate is 3.0% (k3=94.93), the theoretically highest comprehensive score is achieved, corresponding to the theoretically optimal combination A3B3C2. This combination is consistent with the 9th group of experiments with the highest comprehensive score; therefore, it is determined to be the final optimal formula.

[0055] Table 2. Results of Orthogonal Experiments

[0056] Example 2 S1. Raw material pretreatment: Add 5% salt by weight to the thawed squid tentacles, roll and knead for 15 minutes, marinate at 4℃ for 1 hour, then rinse with running water and drain.

[0057] Soak the marinated squid tentacles in pure water for 12 hours at a ratio of 1:1.5 (marinade to liquid); then soak them in ice water for 1 hour at a ratio of 1:2 (marinade to liquid).

[0058] S5. High-temperature short-time steaming: Remove the squid tentacles, drain the surface water, and steam at 100℃ for 6 minutes.

[0059] S6. Rapid cooling with ice-salt water: Immediately transfer the steamed squid tentacles into ice water to cool for 10 minutes, so that the core temperature drops below 10°C.

[0060] S7. Low-temperature freezing: Drain the surface moisture, vacuum pack and freeze at -18℃ to obtain frozen cooked squid tentacles.

[0061] Example 3 S1. Raw material pretreatment: Add 5% salt by weight to the thawed squid tentacles, roll and knead for 15 minutes, marinate at 4℃ for 1 hour, then rinse with running water and drain.

[0062] Weigh out 1.5% polyphosphate, 1.5% sodium citrate, 2% sodium carbonate, 0.5% trehalose, 0.3% sorbitol, 0.1% glucose, 0.2% glycine, and 0.5% salt by weight percentage, dissolve in pure water, and prepare a compound water-retaining agent solution. Soak the marinated squid tentacles in the compound water-retaining agent solution at a material-to-liquid ratio of 1:1.5 for 12 hours; then soak them in ice water at a material-to-liquid ratio of 1:2 for 1 hour.

[0063] S5. High-temperature short-time steaming: Remove the squid tentacles, drain the surface water, and steam at 100℃ for 4 minutes.

[0064] S6. Rapid cooling with ice-salt water: Separately weigh 2% salt and 0.1% sodium isoascorbate by weight, dissolve them in pure water, and prepare ice-salt water. Immediately transfer the steamed squid tentacles into the ice-salt water to cool for 10 minutes, so that their core temperature drops below 10°C.

[0065] S7. Low-temperature freezing: Drain the surface moisture, vacuum pack and freeze at -18℃ to obtain frozen cooked squid tentacles.

[0066] Example 4 S1. Raw material pretreatment: Add 5% salt by weight to the thawed squid tentacles, roll and knead for 15 minutes, marinate at 4℃ for 1 hour, then rinse with running water and drain.

[0067] Weigh out 2.0% polyphosphate, 2.0% sodium citrate, 3.0% sodium carbonate, 0.75% trehalose, 0.35% sorbitol, 0.15% glucose, 0.25% glycine, and 1.0% salt by weight percentage, dissolve in pure water, and prepare a compound water-retaining agent solution. Soak the marinated squid tentacles in the compound water-retaining agent solution at a material-to-liquid ratio of 1:1.5 for 12 hours; then soak them in ice water at a material-to-liquid ratio of 1:2 for 1 hour.

[0068] S5. High-temperature short-time steaming: Remove the squid tentacles, drain the surface water, and steam at 100℃ for 4 minutes.

[0069] S6. Rapid cooling with ice-salt water: Separately weigh 3.5% salt and 0.15% sodium isoascorbate by weight, dissolve them in pure water, and prepare ice-salt water. Immediately transfer the steamed squid tentacles into the ice-salt water to cool for 10 minutes, so that their core temperature drops below 10°C.

[0070] S7. Low-temperature freezing: Drain the surface moisture, vacuum pack and freeze at -18℃ to obtain frozen cooked squid tentacles.

[0071] Example 5 S1. Raw material pretreatment: Add 5% salt by weight to the thawed squid tentacles, roll and knead for 15 minutes, marinate at 4℃ for 1 hour, then rinse with running water and drain.

[0072] Weigh out 2.5% polyphosphate, 2.5% sodium citrate, 4.0% sodium carbonate, 1.0% trehalose, 0.4% sorbitol, 0.2% glucose, 0.3% glycine, and 1.5% salt by weight percentage, dissolve in pure water, and prepare a compound water-retaining agent solution. Soak the marinated squid tentacles in the compound water-retaining agent solution at a material-to-liquid ratio of 1:1.5 for 12 hours; then soak them in ice water at a material-to-liquid ratio of 1:2 for 1 hour.

[0073] S5. High-temperature short-time steaming: Remove the squid tentacles, drain the surface water, and steam at 100℃ for 4 minutes.

[0074] S6. Rapid cooling with ice-salt water: Separately weigh 5.0% salt and 0.2% sodium isoascorbate by weight, dissolve them in pure water, and prepare ice-salt water. Immediately transfer the steamed squid tentacles into the ice-salt water to cool for 10 minutes, so that their core temperature drops below 10°C.

[0075] S7. Low-temperature freezing: Drain the surface moisture, vacuum pack and freeze at -18℃ to obtain frozen cooked squid tentacles.

[0076] Example 6 S1. Raw material pretreatment: Add 5% salt by weight to the thawed squid tentacles, roll and knead for 15 minutes, marinate at 4℃ for 1 hour, then rinse with running water and drain.

[0077] S2. Targeted Injection of Composite Water-Retaining Agent: Weigh out 2.0% polyphosphate, 2.0% sodium citrate, 3.0% sodium carbonate, 0.75% trehalose, 0.35% sorbitol, 0.15% glucose, 0.25% glycine, and 1.0% salt by weight percentage, dissolve in pure water, and prepare a composite water-retaining agent solution. After pretreatment, puncture the squid tentacle sucker surface from the middle. When the resistance encountered during needle insertion decreases by ≥50%, the needle has entered the nerve cord channel. Immediately inject the composite water-retaining agent solution into this channel, with a total injection volume of 10% of the squid tentacle weight.

[0078] S3. Ultrasonic gradient diffusion: After injection, the squid tentacles were placed in a composite water-retaining agent solution at a material-to-liquid ratio of 1:1.5 and ultrasonically treated for 30 minutes at a frequency of 45 kHz, a power of 300 W, and a temperature of 18℃. After treatment, ice water was added at a material-to-liquid ratio of 1:2 and the mixture was soaked for 1 hour.

[0079] S5. High-temperature short-time steaming: Remove the squid tentacles, drain the surface water, and steam at 100℃ for 4 minutes.

[0080] S6. Rapid cooling with ice-salt water: Separately weigh 3.5% salt and 0.15% sodium isoascorbate by weight, dissolve them in pure water, and prepare ice-salt water. Immediately transfer the steamed squid tentacles into the ice-salt water to cool for 10 minutes, so that their core temperature drops below 10°C.

[0081] S7. Low-temperature freezing: Drain the surface moisture, vacuum pack and freeze at -18℃ to obtain frozen cooked squid tentacles.

[0082] Example 7 S1. Raw material pretreatment: Add 5% salt by weight to the thawed squid tentacles, roll and knead for 15 minutes, marinate at 4℃ for 1 hour, then rinse with running water and drain.

[0083] S3. Weigh out 2.0% polyphosphate, 2.0% sodium citrate, 3.0% sodium carbonate, 0.75% trehalose, 0.35% sorbitol, 0.15% glucose, 0.25% glycine, and 1.0% salt by weight percentage, add them to pure water to dissolve, and prepare a composite water-retaining agent solution.

[0084] Soak the marinated squid tentacles in a compound water-retaining agent solution at a ratio of 1:1.5 for 12 hours; then soak them in ice water at a ratio of 1:2 for 1 hour.

[0085] S4. Directional infiltration of natural deep eutectic solvent: Betaine and lactic acid are mixed in a molar ratio of 1:1, and water accounting for 50% of the total mass of the mixture is added. The mixture is heated and stirred in a 60°C water bath until a homogeneous and transparent liquid is formed. After cooling, the natural deep eutectic solvent is obtained.

[0086] Squid tentacles were soaked in a natural deep eutectic solvent at a material-to-liquid ratio of 1:1.5 for 12 hours to allow them to penetrate into the tissue.

[0087] S5. High-temperature short-time steaming: Remove the squid tentacles, drain the surface water, and steam at 100℃ for 4 minutes.

[0088] S6. Rapid cooling with ice-salt water: Weigh out 3.5% salt and 0.15% sodium isoascorbate by weight, dissolve them in pure water, and prepare ice-salt water. Immediately transfer the steamed squid tentacles into the ice-salt water to cool for 10 minutes, so that their core temperature drops below 10°C.

[0089] S7. Low-temperature freezing: Drain the surface moisture, vacuum pack and freeze at -18℃ to obtain frozen cooked squid tentacles.

[0090] Example 8 S1. Raw material pretreatment: Add 5% salt by weight to the thawed squid tentacles, roll and knead for 15 minutes, marinate at 4℃ for 1 hour, then rinse with running water and drain.

[0091] S2. Targeted Injection of Composite Water-Retaining Agent: Weigh out 2.0% polyphosphate, 2.0% sodium citrate, 3.0% sodium carbonate, 0.75% trehalose, 0.35% sorbitol, 0.15% glucose, 0.25% glycine, and 1.0% salt by weight percentage, dissolve in pure water, and prepare a composite water-retaining agent solution. After pretreatment, puncture the squid tentacle sucker surface from the middle. When the resistance encountered during needle insertion decreases by ≥50%, the needle has entered the nerve cord channel. Immediately inject the composite water-retaining agent solution into this channel, with a total injection volume of 10% of the squid tentacle weight.

[0092] S3. Ultrasonic gradient diffusion: After injection, the squid tentacles were placed in a composite water-retaining agent solution at a material-to-liquid ratio of 1:1.5 and ultrasonically treated for 30 minutes at a frequency of 45 kHz, a power of 300 W, and a temperature of 18℃. After treatment, ice water was added at a material-to-liquid ratio of 1:2 and the mixture was soaked for 1 hour.

[0093] S4. Directional infiltration of natural deep eutectic solvent: Betaine and lactic acid are mixed in a molar ratio of 1:1, and water accounting for 50% of the total mass of the mixture is added. The mixture is heated and stirred in a 60°C water bath until a homogeneous and transparent liquid is formed. After cooling, the natural deep eutectic solvent is obtained.

[0094] Using the same directional puncture and ultrasonic diffusion process as described above, the natural deep eutectic solvent was injected into the squid foot nerve cord channel and allowed to penetrate into the tissue.

[0095] That is, repeat steps S2 and S3, except that the composite water-retaining agent is replaced with a natural deep eutectic solvent.

[0096] S5. High-temperature short-time steaming: Remove the squid tentacles, drain the surface water, and steam at 100℃ for 4 minutes.

[0097] S6. Rapid cooling with ice-salt water: Weigh out 3.5% salt and 0.15% sodium isoascorbate by weight, dissolve them in pure water, and prepare ice-salt water. Immediately transfer the steamed squid tentacles into the ice-salt water to cool for 10 minutes, so that their core temperature drops below 10°C.

[0098] S7. Low-temperature freezing: Drain the surface moisture, vacuum pack and freeze at -18℃ to obtain frozen cooked squid tentacles.

[0099] Example 9: Effect Verification Experiment The indicator detection is the same as that of the single-factor experiment.

[0100] Figure 4 , Figure 5 The results show the water-holding capacity and hardness of the squid tentacles prepared in Examples 2-8.

[0101] Example 2 showed the lowest water retention and the highest hardness, indicating that without any water retention treatment, the squid tentacle muscle protein is prone to freezing denaturation during frozen storage, leading to easy water loss and meat hardening, resulting in the worst product quality.

[0102] Examples 3-5 involved prolonged soaking with different concentrations of composite water-retaining agents. Compared to Example 2, an appropriate concentration of composite water-retaining agent could improve the water retention and tenderness of squid tentacles to some extent. However, relying solely on surface soaking and penetration, the water-retaining agent could not easily penetrate deeper tissues, resulting in limited quality improvement.

[0103] Compared with Example 4, Example 6, through targeted injection and ultrasonic gradient diffusion treatment of the natural nerve cord of squid tentacles, showed improved water retention and reduced hardness, indicating that targeted injection and ultrasonic diffusion can more effectively deliver the composite water-retaining agent into the squid tentacles tissue, thereby improving the water retention and tenderness of the squid tentacles.

[0104] The water retention and hardness of Example 7 are better than those of Example 2 but worse than those of Example 6, indicating that the natural deep eutectic solvent has a certain water retention capacity and can bind free water, but its effect is limited and it is difficult to penetrate into the tissue.

[0105] Example 8, employing the complete method of this invention, exhibits significantly superior water retention and hardness compared to other examples. P<0.05 This invention primarily involves the targeted injection of a composite water-retaining agent through neural cord channels, followed by ultrasonic gradient diffusion. This allows the composite water-retaining agent to penetrate deep into the squid tentacle tissue, altering the myofibril structure and thus enhancing the muscle's water-holding capacity and tenderness. Subsequently, a natural deep eutectic solvent penetrates along the same neural cord channels, further inhibiting ice crystal formation and growth during frozen storage, binding free water, and slowing down moisture loss and quality deterioration in the squid tentacle. The combined use of this method achieves water-retaining and antifreeze effects far exceeding those of a single process, ensuring that the squid tentacle retains high water retention and a tender texture even after frozen storage.

[0106] Low-field NMR and imaging analysis: An approximately 8 mm thick sample was wrapped in plastic wrap and placed in an NMR tube. The relaxation time T2 was measured using a Carr-Purcell-Meiboom-Gill sequence with the following parameters: echo interval 3.0 ms, echo number 2048, repetition time 2.0 s, and 20 accumulations. Simultaneously, a spin-echo sequence was used to acquire a proton density-weighted image with the following imaging parameters: gain 64, pulse width 16, pulse interval 1, gradient destruction time 20 ms, and repetition time 1 ms. The resulting images were displayed in pseudo-color.

[0107] Figure 6 The graph shows the moisture distribution detection results of squid tentacles prepared in Examples 2-8.

[0108] T 21(10~100 ms) corresponds to water inside the myofibrils and water in the protein structure, T 22 (100~1000 ms) represents the interstitial water in the myofibrils, T 23 (1000~10000 ms) represents the free water released after heating. Figure 6 The relaxation time plot of (a) shows that the water in squid tentacles is mainly in the form of T. 21 T 22 Representing non-flowing water and T 23 It exists in the form of free water. Figure 6 (b) Peak area ratio analysis showed that Example 2 had the lowest proportion of non-flowing water and the highest proportion of free water, indicating that most of the water in the squid leg muscle without water-retention and antifreeze treatment existed in a free state, which was easily lost during freezing and processing. Furthermore, this free water easily formed ice crystals during freezing, causing irreversible mechanical damage to the muscle fibers, resulting in a significant decrease in water retention and tenderness. In Example 6, after nerve cord injection and ultrasonic gradient diffusion, the proportion of non-flowing water was higher than in Examples 3-5, indicating that this treatment could effectively enhance the water-binding ability within the muscle fibers. The improvement in the proportion of non-flowing water in Example 7 was limited, while Example 8 had the highest proportion of non-flowing water and the lowest proportion of free water. This indicates that the method of the present invention can strengthen the hydrogen bond network under low-temperature freezing conditions, effectively bind free water, inhibit ice crystal nucleation and growth, and allow water to exist in a more compact state within the squid leg tissue, thereby reducing the mechanical damage to the muscle fiber structure caused by freezing and exhibiting excellent cryopreservation stability. Magnetic resonance imaging (MRI) Figure 6 The brightness and color of different regions in (c) directly reflect the distribution of water. Red regions indicate high water signals, typically representing bound water or non-flowing water, while blue regions indicate low water signals, corresponding to relatively free water. In Examples 2-5, the water signals were mostly concentrated at the edges of the squid tentacles, with weak and unevenly distributed signals inside. In Examples 6-8, the internal water signals were enhanced, with Example 8 showing the highest intensity. This indicates that the treatment in Example 8 not only increased the proportion of non-flowing water but also promoted the uniform penetration and distribution of water into the muscle tissue, thereby improving overall water retention.

[0109] In summary, this invention determined the optimal formulation of the composite water-retaining agent through orthogonal experiments, and verified the synergistic effect of nerve cord directional injection, ultrasonic gradient diffusion, and natural deep eutectic solvent directional penetration processes through comparisons in Examples 2-8. The frozen cooked squid tentacles treated with the complete method of this invention (Example 8) exhibited the highest water retention, lowest hardness, and highest proportion of non-flowing water, significantly outperforming other treatment methods. This indicates that the method of this invention can effectively improve the water retention, tenderness, and frozen storage stability of frozen cooked squid tentacles, significantly enhancing the product's water retention and freeze-resistance quality. Furthermore, the process is highly operable and possesses promising prospects for industrial application.

[0110] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for water retention and freeze protection of frozen cooked squid tentacles, characterized in that, Includes the following steps: S1. Raw material pretreatment: Add salt to the thawed squid tentacles and roll them, then marinate them at low temperature, then wash them with water and drain them; S2. Targeted injection of compound water-retaining agent: Targeted needle puncture is performed from the middle of the squid tentacle sucker surface, and the compound water-retaining agent is injected into the squid tentacle nerve cord channel by the sudden drop in puncture resistance at the spatial position of the nerve cord. S3. Ultrasonic gradient diffusion: First, the squid tentacles treated with S2 are placed in a composite water-retaining agent solution for ultrasonic treatment; then the squid tentacles are soaked in ice water. S4. Directional penetration of natural deep eutectic solvent: Using the directional puncture combined with ultrasonic diffusion process described in S2 and S3, the composite water-retaining agent is replaced with a natural deep eutectic solvent composed of betaine and lactic acid to penetrate into the squid tentacle tissue. S5. High-temperature short-time steaming: After draining the water from the squid tentacles treated in S4, steam them at high temperature for a short time until they are cooked. S6. Rapid cooling with ice-salt water: Immediately transfer the steamed squid tentacles into ice-salt water to cool them down, so that the core temperature of the squid tentacles drops to 4-10℃; S7. Low-temperature freezing: After cooling, drain the surface moisture of the squid tentacles, vacuum pack them, and freeze them at low temperature to obtain frozen cooked squid tentacles.

2. The method for water retention and antifreeze treatment of frozen cooked squid tentacles as described in claim 1, characterized in that, In step S1, the weight ratio of squid tentacles to salt is 100:(3-8), and the mixture is tumbled for 10-20 minutes.

3. The method for water retention and antifreeze treatment of frozen cooked squid tentacles as described in claim 1, characterized in that, In step S2, the amount of the composite water-retaining agent injected is 10%-20% of the weight of the squid tentacles.

4. The method for water retention and antifreeze treatment of frozen cooked squid tentacles as described in claim 1, characterized in that, In step S2, the composite water-retaining agent is formulated as follows: 0.5-2.5% polyphosphate, 0.5-2.5% sodium citrate, 1-4% sodium carbonate, 0.5-1.0% trehalose, 0.3-0.4% sorbitol, 0.1-0.2% glucose, 0.2-0.3% glycine, 0.5-1.5% sodium chloride, with the remainder being water. Preferably, the compound water-retaining agent is formulated as follows: 1.0-2.0% polyphosphate, 1.0-2.0% sodium citrate, 2.0-4.0% sodium carbonate, 0.5-1.0% trehalose, 0.3-0.4% sorbitol, 0.1-0.2% glucose, 0.2-0.3% glycine, 0.5-1.5% salt, with the balance being water.

5. The method for water retention and antifreeze treatment of frozen cooked squid tentacles as described in claim 1, characterized in that, In step S3, during ultrasonic treatment, the ratio of squid tentacles treated in step S2 to the composite water-retaining agent solution is 1:(1-2); during ice water soaking, the ratio of squid tentacles to ice water is 1:(1-3).

6. The method for water retention and antifreeze treatment of frozen cooked squid tentacles as described in claim 1, characterized in that, In step S3, the ultrasonic conditions are: frequency 40-50 kHz, power 200-300 W, temperature 15-20℃, and time 30-60 minutes.

7. The method for water retention and antifreeze preservation of frozen cooked squid tentacles as described in claim 1, characterized in that, In step S4, the natural deep eutectic solvent is prepared by mixing betaine and lactic acid in a molar ratio of 1:(1-2), adding water accounting for 40-60% of the total mass of the mixture, and heating and stirring at 60-80°C until a homogeneous and transparent liquid is formed.

8. The method for water retention and antifreeze treatment of frozen cooked squid tentacles as described in claim 1, characterized in that, In step S5, the conditions for high-temperature short-time steaming are steaming at 100-120℃ for 4-10 minutes.

9. The method for water retention and antifreeze treatment of frozen cooked squid tentacles as described in claim 1, characterized in that, In step S6, the ice-salt water consists of 2-5% salt, 0.1-0.2% sodium isoascorbate, and the remainder is water, by weight percentage. Cooling in ice-salt water involves cooling in ice-salt water at 0-4°C for 10-30 minutes.

10. Frozen cooked squid tentacles prepared by the method described in claims 1-9.

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