A compound ice coating solution for frozen preservation of mussels and its preparation method

Abstract

This invention provides a compound ice coating liquid for frozen preservation of mussels and its preparation method. The preparation method of the compound ice coating liquid for frozen preservation of mussels includes the following steps: mixing sodium isoascorbate, alginate oligosaccharide, and a positively charged wall material in a solvent, followed by high-pressure homogenization to obtain an inner active emulsion with droplet size distribution between 120 nm and 180 nm and a Zeta potential of +15 mV to +30 mV; wherein the positively charged wall material is a compound of soy protein isolate and chitosan, with a mass ratio of soy protein isolate to chitosan of 9:1; and mixing sodium polyacrylate and citric acid in a solvent to obtain an outer shielding gel. This invention achieves high crack resistance in the ice coating for frozen preservation of mussels, deep penetration of preservative components, and high stability of the emulsion.

Description

Technical Field

[0001] This invention relates to an ice coating liquid and its preparation method, specifically to a compound ice coating liquid for frozen preservation of mussels and its preparation method, belonging to the field of aquatic product preservation and processing technology. Background Technology

[0002] If effective measures are not taken promptly after mussels are harvested, the residual active enzymes and microorganisms within them will rapidly degrade, causing problems such as protein degradation, lipid oxidation, and color deterioration. Freezing is currently a key method for extending the shelf life of mussels industrially, by lowering the temperature below freezing to inhibit enzyme activity and microbial growth. However, during conventional freezing and storage, mussel muscle tissue still faces risks of deterioration such as desiccation, ice recrystallization, lipid oxidation, and protein denaturation. Therefore, coating the surface of mussels with a protective ice layer before freezing has become a widely adopted quality maintenance method in the industry.

[0003] Early ice coating technology mainly involved immersing or spraying with pure water, sugar water, or salt water to form a thin layer of ice on the surface of the material. Although this method could isolate some oxygen and reduce water evaporation for a certain period of time, the bonding force between the ice layer and the material surface was limited, and pure water ice coatings were prone to ice crystal sublimation during long-term frozen storage, resulting in a porous and loose structure on the surface of the ice coating. As a result, its oxygen and water barrier performance rapidly decreased with the extension of frozen storage time.

[0004] To address this, researchers further explored adding antioxidants, antibacterial agents, and other preservative components to the ice coating solution, aiming to endow the ice coating with active preservation capabilities while providing passive protection. However, these simple solution immersion or crude emulsion mixing methods did not fundamentally solve the problem of effective retention and deep delivery of functional components. To further improve oxygen barrier effects and protective performance, double-layer ice coating technology has been gradually developed and applied.

[0005] However, existing double-layer ice coatings typically rely solely on physical freezing for adhesion. During temperature fluctuations in cold chain logistics, the difference in expansion coefficients between the inner and outer ice coatings, coupled with insufficient physical adhesion, easily leads to interlayer peeling and cracking, resulting in the failure of the protective effect. Even if the ice coating structure is temporarily maintained, effectively delivering preservatives to the deep tissues of the mussel, rather than merely remaining on the outermost surface, remains another challenge lacking effective solutions in current technology. In the frozen state, mussel myofibrils contract significantly due to the compression of intracellular ice crystals, forming numerous microscopic interstitial spaces below the muscle surface. In conventional technologies, preservatives are usually added to the ice coating liquid in the form of droplets or simple dissolutions, with particle sizes much larger than these microscopic interstitial spaces. These large-diameter functional droplets are blocked by the dense muscle membrane and connective tissue on the surface of the muscle, making it difficult to penetrate deeper and only allowing them to be distributed on the outermost surface of the material. During thawing, the preservatives are easily lost in large quantities with the juices, failing to achieve a deep and long-lasting antioxidant preservation effect.

[0006] Nanoemulsion technology is considered a potentially effective way to solve the problem of deep delivery of preservatives. By encapsulating functional ingredients in nano-sized droplets, their size effect is expected to enable penetration into deep muscle tissues. When preparing nano-emulsions as ice coats, soy protein isolate is commonly used as the wall material. Under high-pressure homogenization and strong shear forces, excessive aggregation and denaturation of molecules easily occur due to mechanical heating and strong shearing, leading to emulsion demulsification, uncontrolled particle size, and the inability to form a stable nano-scale protective system.

[0007] In summary, existing mussel freezing and preservation technologies have shortcomings in terms of ice coat structure stability, effectiveness of preservative deep delivery, and nanoemulsion processing stability. Denaturation of the protein wall material makes it difficult to stably prepare nanoemulsions, uncontrolled particle size prevents preservatives from penetrating deep into the muscle tissue, and the lack of binding force between ice coat layers causes the entire protective system to rapidly fail during cold chain fluctuations. Therefore, there is an urgent need to develop a compound ice coat solution for mussel freezing and preservation that can effectively prevent ice coat cracking, reduce preservative loss, and possess high stability, along with its preparation method. Summary of the Invention

[0008] Based on the above background, the purpose of this invention is to provide a compound ice coating liquid for frozen storage and preservation of mussels and its preparation method, so as to achieve high crack resistance of the ice coating for frozen storage and preservation of mussels, deep penetration of the preservation ingredients and high stability of the emulsion, and solve the technical problems of easy cracking of ice coating, easy loss of preservatives and easy denaturation and precipitation of protein wall material under high pressure homogenization in the prior art.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] A method for preparing a compound ice coating solution for frozen preservation of mussels, the compound ice coating solution comprising a separate inner active emulsion and an outer shielding adhesive solution, the method comprising the following steps:

[0011] Sodium isoascorbate, alginate oligosaccharide, and a positively charged wall material were mixed in a solvent and homogenized under high pressure to obtain an inner-layer active emulsion with a droplet size distribution between 120 nm and 180 nm and a Zeta potential of +15 mV to +30 mV; wherein the positively charged wall material is a compound of soy protein isolate and chitosan, and the mass ratio of soy protein isolate to chitosan is 9:1;

[0012] Sodium polyacrylate and citric acid are mixed in a solvent to prepare an outer shielding adhesive.

[0013] The inner active emulsion prepared using the above method possesses specific nanoscale particle size and a specific positive charge property. This specific particle size can form a steric hindrance match with the myofibril gaps in the frozen state of mussels, allowing the emulsion droplets to target and penetrate deep into the mussel muscle layer, preventing the loss of preservative components during thawing. Simultaneously, the introduction of the positively charged wall material provides a charge basis for subsequent interfacial complexation with the negatively charged outer shielding adhesive. A specific 9:1 ratio of soy protein isolate and chitosan can form a structurally stable composite wall material, effectively encapsulating the active ingredients. The mixture of sodium polyacrylate and citric acid in the outer shielding adhesive provides a strongly negatively charged environment, undergoing a polyelectrolyte complexation reaction upon contact with the inner active emulsion, generating a dense and resilient cross-linked network, effectively preventing cracking and peeling of the ice coating during cold chain fluctuations.

[0014] Preferably, the inner active emulsion comprises, by mass fraction: 0.5% to 2.0% sodium isoascorbate and 0.2% to 1.0% alginate oligosaccharide.

[0015] By controlling the content of sodium isoascorbate and alginate oligosaccharides within the aforementioned specific ranges, sufficient antioxidant and antibacterial activities can be ensured, while avoiding damage to the colloidal stability of the emulsion due to excessive concentration.

[0016] Preferably, the outer shielding adhesive comprises, by mass fraction: 0.05%~0.2% sodium polyacrylate and 0.3%~1.2% citric acid.

[0017] The above ratio of sodium polyacrylate and citric acid not only provides sufficient negatively charged groups to ensure efficient interfacial crosslinking, but also plays a synergistic role in anti-oxidation and maintaining the acid-base buffer system.

[0018] Preferably, sodium isoascorbate, alginate oligosaccharides, and positively charged wall materials are mixed in a solvent, specifically including:

[0019] Soy protein isolate and chitosan were hydrated and dissolved in a water bath at 40℃~50℃ to obtain a wall material solution.

[0020] Sodium isoascorbate and alginate oligosaccharide were added to the wall material solution and mixed.

[0021] Hydration and dissolution under mild water bath conditions of 40℃~50℃ can promote the full expansion and uniform dispersion of soy protein isolate and chitosan molecules, which is beneficial for subsequent encapsulation and modification, while avoiding thermal denaturation of proteins caused by high temperature.

[0022] Preferably, during the hydration and dissolution of soy protein isolate and chitosan, L-arginine is added and ultrasonic-assisted modification is performed; the amount of L-arginine added is 1% to 3% of the soy protein isolate; the parameters of the ultrasonic-assisted modification are: ultrasonic power 200 to 300 W, ultrasonic time 10 to 15 min, and the treatment temperature is maintained at 45℃ to 50℃.

[0023] By introducing a specific proportion of L-arginine and combining it with ultrasonic treatment at specific power and temperature, the cavitation effect of ultrasound can be used to moderately expand the dense spherical structure of soy protein isolate, allowing positively charged L-arginine to insert and anchor into the protein molecular chain. This significantly increases the positive charge density and steric hindrance on the protein surface, effectively preventing disordered aggregation and precipitation of soy protein isolate due to mechanical shear heating during subsequent high-pressure homogenization, and significantly improving the processing stability and physical stability of the emulsion.

[0024] Preferably, before high-pressure homogenization, the mixed liquid is subjected to high-shear pre-emulsification. The parameters of the high-shear pre-emulsification are: shear speed 8000~10000 r / min, processing time 5~10 min.

[0025] Preferably, the homogenization pressure of the high-pressure homogenization process is 40~45 MPa, and the number of homogenization cycles is 2~3.

[0026] Preferably, the solvent is sterile deionized water.

[0027] Preferably, the preparation method of the compound ice-coating solution further includes the following steps:

[0028] The prepared inner active emulsion and outer shielding adhesive are packaged separately and then combined to obtain a complete set of the compound ice coating liquid.

[0029] Separate packaging is used to prevent the two liquids from undergoing a complexation reaction during storage; cross-linking only occurs when they are coated together on the surface of the mussels.

[0030] A compound ice coating liquid for frozen storage and preservation of mussels is prepared by the method described above.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The present invention discloses a method for preparing a compound ice coating liquid for frozen preservation of mussels. The method involves placing a positively charged inner active emulsion and a negatively charged outer shielding adhesive liquid separately and coating them sequentially on the surface of the mussels. The polyelectrolyte complexation reaction that occurs when the two liquids meet at the interface generates a dense and tough three-dimensional polymer cross-linked network between the two ice coating layers. This network has a bonding effect and a stress buffering effect, effectively alleviating the expansion stress caused by temperature fluctuations in the cold chain, and significantly improving the crack resistance and integrity of the ice coating.

[0033] This invention limits the particle size of the inner active emulsion to 120 nm to 180 nm. This particle size range is exactly matched with the 100 nm to 200 nm interstitial space generated by the contraction of myofibrils in the frozen state of mussels, which forms a spatial steric hindrance. This allows the nano-emulsion droplets to penetrate smoothly into the deep layer of the mussel, significantly reducing the loss rate of thawed juice and achieving deep anti-oxidation.

[0034] This invention utilizes ultrasound and L-arginine to synergistically modify soy protein isolate. The ultrasonic cavitation effect unfolds the protein molecular chain, and the introduction of L-arginine increases charge repulsion and steric hindrance, effectively solving the problem of disordered aggregation and precipitation of soy protein isolate under high pressure, homogenization, and strong shear force, thereby improving the stability of the nanoemulsion. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0036] Figure 1 This is a schematic flowchart of a method for preparing a compound ice coating liquid for frozen preservation of mussels according to the present invention.

[0037] Figure 2 This is a test report on the thawing water loss rate of frozen mussel products prepared using the ice coating liquid in Example 3 of this invention;

[0038] Figure 3 These are photos of the frozen mussel products prepared using the ice coating liquid in Example 3 of this invention after a crack resistance test.

[0039] Figure 4These are photos of the frozen mussel products prepared using the ice coating liquid in Comparative Example 3 after a crack resistance test.

[0040] Figure 5 These are photos of the frozen mussel products prepared using the ice coating liquid in Comparative Example 4 in this invention after a crack resistance test. Detailed Implementation

[0041] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any modifications and / or alterations made to the present invention will fall within the protection scope of the present invention.

[0042] In this invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art. Unless otherwise specified, the components or equipment in the following embodiments are general standard parts or components known to those skilled in the art, and their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods.

[0043] Example 1

[0044] like Figure 1 As shown in the figure, this embodiment discloses a method for preparing a compound ice coating solution for frozen preservation of mussels. The specific steps are as follows:

[0045] S1. Mix soy protein isolate and chitosan at a mass ratio of 9:1, add to sterile deionized water at 40℃ for hydration and dissolution to obtain a wall material solution. During the dissolution process, add 1% L-arginine of soy protein isolate and start ultrasonic-assisted modification treatment with an ultrasonic power of 200 W for 15 min and maintain the treatment temperature at 45℃.

[0046] S2. Based on the mass fraction of the inner layer active emulsion, add 0.5% sodium isoascorbate and 1.0% alginate oligosaccharide to the modified wall material solution, mix well, and make up to volume with sterile deionized water.

[0047] S3. The above-mentioned mixed liquid is subjected to high-shear pre-emulsification treatment at a shearing speed of 8000 r / min and a treatment time of 10 min.

[0048] S4. Pump the pre-emulsion into a high-pressure homogenizer and homogenize it three times under a homogenization pressure of 40 MPa to obtain an inner active emulsion with a droplet size distribution between 120 nm and 150 nm and a Zeta potential of +18 mV.

[0049] S5. Based on the mass fraction of the outer shielding adhesive, mix 0.05% sodium polyacrylate and 1.2% citric acid in sterile deionized water and stir evenly to obtain the outer shielding adhesive.

[0050] S6. The prepared inner active emulsion and outer shielding adhesive are packaged separately and combined to obtain a complete set of compound ice coating liquid.

[0051] Example 2

[0052] This embodiment discloses a method for preparing a compound ice coating solution for frozen storage and preservation of mussels. The specific steps are as follows:

[0053] S1. Mix soy protein isolate and chitosan at a mass ratio of 9:1, add to sterile deionized water at 50℃ for hydration and dissolution to obtain a wall material solution. During the dissolution process, add 3% L-arginine of soy protein isolate and start ultrasonic-assisted modification treatment with an ultrasonic power of 300 W for 10 min and maintain the treatment temperature at 50℃.

[0054] S2. Based on the mass fraction of the inner layer active emulsion, add 2.0% sodium isoascorbate and 0.2% alginate oligosaccharide to the modified wall material solution, mix well, and make up to volume with sterile deionized water.

[0055] S3. The above-mentioned mixed liquid is subjected to high-shear pre-emulsification treatment at a shearing speed of 10000 r / min and a treatment time of 5 min.

[0056] S4. Pump the pre-emulsion into a high-pressure homogenizer and homogenize it twice under a homogenization pressure of 45 MPa to obtain an inner active emulsion with a droplet size distribution between 140 nm and 180 nm and a Zeta potential of +26 mV.

[0057] S5. Based on the mass fraction of the outer shielding adhesive, mix 0.2% sodium polyacrylate and 0.3% citric acid in sterile deionized water and stir evenly to obtain the outer shielding adhesive.

[0058] S6. The prepared inner active emulsion and outer shielding adhesive are packaged separately and combined to obtain a complete set of compound ice coating liquid.

[0059] Example 3

[0060] This embodiment discloses a method for preparing a compound ice coating solution for frozen storage and preservation of mussels. The specific steps are as follows:

[0061] S1. Soy protein isolate and chitosan were mixed at a mass ratio of 9:1 and added to sterile deionized water at 45°C for hydration and dissolution to obtain a wall material solution. During the dissolution process, 2% L-arginine of the soy protein isolate was added, and ultrasonic-assisted modification treatment was initiated. The ultrasonic power was 250 W, the ultrasonic time was 12 min, and the treatment temperature was maintained at 48°C.

[0062] S2. Based on the mass fraction of the inner layer active emulsion, add 1.2% sodium isoascorbate and 0.6% alginate oligosaccharide to the modified wall material solution, mix well, and make up to volume with sterile deionized water.

[0063] S3. The above-mentioned mixed liquid is subjected to high-shear pre-emulsification treatment at a shearing speed of 9000 r / min and a treatment time of 8 min.

[0064] S4. Pump the pre-emulsion into a high-pressure homogenizer and homogenize it twice under a homogenization pressure of 42 MPa to obtain an inner active emulsion with a droplet size distribution between 130 nm and 165 nm and a Zeta potential of +22 mV.

[0065] S5. Based on the mass fraction of the outer shielding adhesive, mix 0.12% sodium polyacrylate and 0.8% citric acid in sterile deionized water and stir evenly to obtain the outer shielding adhesive.

[0066] S6. The prepared inner active emulsion and outer shielding adhesive are packaged separately and combined to obtain a complete set of compound ice coating liquid.

[0067] Comparative Example 1

[0068] This comparative example discloses a method for preparing a compound ice coating solution for frozen storage and preservation of mussels. The method steps are the same as in Example 3, except that:

[0069] In step S1, no L-arginine was added and no ultrasonic-assisted modification was performed; the soy protein isolate and chitosan were simply dissolved by stirring at 45°C. The remaining steps and process parameters were completely consistent with those in Example 3.

[0070] Comparative Example 2

[0071] This comparative example discloses a method for preparing a compound ice coating solution for frozen storage and preservation of mussels. The method steps are the same as in Example 3, except that:

[0072] Without performing the high-pressure homogenization process in step S4, the high-shear pre-emulsification process in step S3 was performed at a shear speed of 8000 r / min for 5 min, resulting in an average droplet size of 350 nm for the inner active emulsion. All other steps and process parameters were completely consistent with those in Example 3.

[0073] Comparative Example 3

[0074] This comparative example discloses a method for preparing a compound ice coating solution for frozen storage and preservation of mussels. The method steps are the same as in Example 3, except that:

[0075] In step S5, the outer layer adhesive is prepared by replacing sodium polyacrylate with an equal mass of chitosan, so that the outer layer adhesive also carries a positive charge; the remaining steps and process parameters are completely consistent with those in Example 3.

[0076] Comparative Example 4

[0077] This comparative example discloses a method for preparing a conventional ice coating solution for frozen storage and preservation of mussels, which directly uses sterile deionized water as the ice coating solution.

[0078] To verify the technical effectiveness of the compound ice coating liquid and its preparation method of the present invention, the performance of the emulsions prepared in the above embodiments and comparative examples, as well as various indicators after application to mussel preservation, were tested. The tests included emulsion stability testing, water-holding capacity and antioxidant testing, and anti-cracking testing, and the test methods are as follows.

[0079] The emulsion stability test determined the average particle size, polydispersity index, and centrifugal sedimentation rate (calculated as the mass fraction of sediment after centrifugation at 4000 r / min for 15 min) of the inner layer emulsion after high-pressure homogenization in each group, and observed the state of the emulsion after being placed at room temperature for 24 hours.

[0080] The water-holding capacity and antioxidant tests were conducted by washing fresh mussels and coating them with the ice-coating solutions used in each example and comparative example using a double-layer dip-coating method (first dipping in the inner active emulsion, draining and freezing, then dipping in the outer shielding adhesive; comparative example 4 was directly immersed in water and frozen). The mussels were then frozen at -20°C for 90 days. The loss rate of thawed juices after thawing was measured, and the thiobarbituric acid reactive substance value in the deep muscle layer (2-3 mm below the surface) of the mussels was measured to evaluate the deep antioxidant effect.

[0081] The anti-cracking test involved placing mussels coated with ice in a high-low temperature alternating chamber to simulate temperature fluctuations (maintaining the temperature at -20℃ for 12 hours, then raising it to -4℃ and maintaining it for 12 hours, which constitutes one cycle). After 10 cycles, the integrity rate and shedding rate of the ice coating were observed and calculated.

[0082] The test results are shown in Table 1-3.

[0083] Table 1 Results of physical stability test of emulsion

[0084]

[0085] Table 2. Results of water-holding capacity and deep-sea antioxidant tests of mussels after 90 days of frozen storage.

[0086]

[0087] Table 3. Results of ice coat crack resistance test after 10 temperature fluctuation cycles.

[0088]

[0089] As can be seen from the data in Table 1, the inner-layer active emulsions prepared in Examples 1-3 exhibited high physical stability, with an average particle size distribution in the range of 120 nm to 180 nm, a low polydispersity index, and a near-zero centrifugal sedimentation rate. No demulsification or stratification was observed after 24 hours. In contrast, Comparative Example 1, which did not contain L-arginine and was not subjected to ultrasonic modification, showed a rapid increase in particle size to 520 nm, a significantly higher polydispersity index, a centrifugal sedimentation rate as high as 18.50%, and experienced severe demulsification and protein denaturation precipitation within 24 hours.

[0090] The reason for this is that soy protein isolate molecules naturally exhibit a highly dense and folded spherical structure, containing a large number of hydrophobic groups. During high-pressure homogenization, the mechanical shear force and the instantaneous release of pressure generate significant localized mechanical heat. For the unmodified natural soy protein isolate in Comparative Example 1, the strong shear and thermal effects force its structure to unfold disorderedly, exposing a large number of hydrophobic groups. This leads to disordered hydrophobic association and excessive aggregation between molecules, ultimately causing protein denaturation and precipitation, resulting in complete demulsification of the emulsion system.

[0091] In Examples 1-3, by introducing 1%-3% L-arginine into the soybean protein isolate during the hydration process and supplementing it with ultrasonic treatment at 200-300 W, the resulting cavitation effect gently breaks the hydrogen bonds and weak hydrophobic interactions within the soybean protein isolate molecules, causing the protein molecular chains to unfold in a moderate and controllable manner. The strongly positively charged basic amino acids in the medium can insert into these unfolded protein molecular chains, anchoring them to the protein side chains through electrostatic interactions and strong hydrogen bonds. This increases the positive charge density on the surface of the soybean protein isolate molecules, generating strong electrostatic repulsion; furthermore, the protein structure anchored by arginine becomes more flexible, forming strong steric hindrance, thus enabling the modified protein wall material to withstand the mechanical heat and shear forces during subsequent high-pressure homogenization, preventing disordered aggregation and denaturation precipitation of protein molecules.

[0092] According to the test results in Table 2, the ice coating liquid prepared in Examples 1-3 had a thawing juice loss rate of 3.5%-4.2% at a low level, and the thiobarbituric acid reactant value of the deep muscle of mussels was only 0.18-0.24 mg / kg, showing excellent water retention and anti-oxidation effects. Figure 2The report on the thawing water loss rate of frozen mussel products prepared using the ice coating liquid of Example 3 is shown.

[0093] In contrast, Comparative Example 2, with an inner emulsion particle size of 350 nm, experienced a thawing juice loss rate as high as 12.8%, and the thiobarbituric acid reactive substance value in the deep muscle also significantly increased to 0.58 mg / kg. For Comparative Example 2, the emulsion particle size is much larger than the microscopic gaps in the mussel muscle, preventing the nano-droplets from penetrating deep into the muscle layer; they remain only on the outermost surface of the mussel. During thawing, due to the lack of physical anchoring to the muscle tissue, these outer surface preservatives are easily washed away as the ice coating melts and juices flow out, failing to provide water retention and antioxidant protection for the deep muscle, leading to rapid quality deterioration.

[0094] As can be seen from the data in Table 3, after undergoing 10 severe temperature fluctuation cycles, the integrity rate of the ice coating in Examples 1 to 3 of the present invention remained above 95.5% to 97.5%, with almost no shedding. Figure 3 The images show the appearance of frozen mussel products prepared using the ice coating liquid of Example 3 after a crack resistance test. In contrast, Comparative Example 3, whose outer layer also carries a positive charge and cannot undergo charge cross-linking, had an ice coating shedding rate as high as 32.4% and an integrity rate of only 67.6%. Figure 4 The images show the appearance of frozen mussel products prepared using the ice coating solution of Comparative Example 3 after a crack resistance test. Comparative Example 4 performed the worst, with an ice coating shedding rate as high as 48.5% and an integrity rate of only 51.5%. Figure 5 Photographs of frozen mussel products prepared using the ice coating liquid of Comparative Example 4 after anti-cracking tests are shown.

[0095] The reason for this lies in the unique design of separating positive and negative charges and interfacial complexation in this invention. The inner active emulsion, due to the combined effect of chitosan and modified soy protein isolate, carries a significant positive charge on its surface, while the sodium polyacrylate in the outer shielding emulsion dissociates into a large number of free carboxyl groups in aqueous solution, exhibiting a strong negative charge. Separating and packaging the two ensures the stability of their respective charges during storage. When these two liquid layers are successively coated onto the mussel surface, at the extremely thin interface between the inner and outer liquid layers, the positively charged ammonium groups from chitosan and L-arginine-modified protein meet the negatively charged carboxyl groups from sodium polyacrylate, resulting in a vigorous polyelectrolyte complexation reaction. This strong electrostatic attraction between charges constructs a tough and elastic three-dimensional polymer cross-linked network at the interface of the double-layered ice coating. This in-situ generated cross-linked network acts as double-sided tape in space, pulling the inner and outer ice layers together. At the same time, the cross-linked network has excellent viscoelasticity, which can serve as a stress buffer layer to effectively absorb and buffer the recrystallization expansion stress caused by temperature fluctuations in the cold chain, thereby preventing interlayer peeling and cracking of the ice layer and maintaining the long-term integrity of the ice layer.

[0096] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a compound ice coating solution for frozen preservation of mussels, characterized in that: The compound ice-coating solution comprises a separate inner layer of active emulsion and an outer layer of shielding adhesive. The preparation method of the compound ice-coating solution includes the following steps: Sodium isoascorbate, alginate oligosaccharide, and a positively charged wall material were mixed in a solvent and homogenized under high pressure to obtain an inner-layer active emulsion with a droplet size distribution between 120 nm and 180 nm and a Zeta potential of +15 mV to +30 mV; wherein the positively charged wall material is a compound of soy protein isolate and chitosan, and the mass ratio of soy protein isolate to chitosan is 9:1; Sodium polyacrylate and citric acid are mixed in a solvent to prepare an outer shielding adhesive.

2. The method for preparing a compound ice coating solution for frozen preservation of mussels according to claim 1, characterized in that: The inner active emulsion comprises, by mass fraction: 0.5% to 2.0% sodium isoascorbate and 0.2% to 1.0% alginate oligosaccharides.

3. The method for preparing a compound ice coating solution for frozen preservation of mussels according to claim 1, characterized in that: The outer shielding adhesive comprises, by mass fraction: 0.05%~0.2% sodium polyacrylate and 0.3%~1.2% citric acid.

4. The method for preparing a compound ice coating solution for frozen preservation of mussels according to claim 1, characterized in that: Sodium isoascorbate, alginate oligosaccharides, and positively charged wall materials are mixed in a solvent, specifically including: Soy protein isolate and chitosan were hydrated and dissolved in a water bath at 40℃~50℃ to obtain a wall material solution. Sodium isoascorbate and alginate oligosaccharide were added to the wall material solution and mixed.

5. The method for preparing a compound ice coating solution for frozen preservation of mussels according to claim 4, characterized in that: During the hydration and dissolution of soy protein isolate and chitosan, L-arginine is added and ultrasonic-assisted modification is performed; the amount of L-arginine added is 1% to 3% of the soy protein isolate; the parameters of the ultrasonic-assisted modification are: ultrasonic power 200 to 300 W, ultrasonic time 10 to 15 min, and the processing temperature is maintained at 45℃ to 50℃.

6. The method for preparing a compound ice coating solution for frozen preservation of mussels according to claim 1, characterized in that: Before high-pressure homogenization, the mixed liquid is subjected to high-shear pre-emulsification. The parameters of the high-shear pre-emulsification are: shear speed 8000~10000 r / min, processing time 5~10 min.

7. The method for preparing a compound ice coating solution for frozen preservation of mussels according to claim 1, characterized in that: The homogenization pressure of the high-pressure homogenization process is 40~45 MPa, and the number of homogenization cycles is 2~3.

8. The method for preparing a compound ice coating solution for frozen preservation of mussels according to claim 1, characterized in that: All solvents used are sterile deionized water.

9. The method for preparing a compound ice coating solution for frozen preservation of mussels according to claim 1, characterized in that: The preparation method of this compound ice-coating solution also includes the following steps: The prepared inner active emulsion and outer shielding adhesive are packaged separately and then combined to obtain a complete set of the compound ice coating liquid.

10. A compound ice coating solution for frozen preservation of mussels, characterized in that: It is prepared by any one of the compound ice coating solutions for frozen preservation of mussels as described in any one of claims 1-9.

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