Processing method of minced fillet gel

Abstract

The invention relates to the technical field of food processing, in particular to a processing method of minced fillet gel. According to the processing method of the surimi gel provided by the invention, the efficient embedding and targeted delivery of the blueberry anthocyanin are realized by adding the self-made active emulsion of the ovalbumin-chitosan loaded blueberry anthocyanin and by virtue of pH gradient regulation and the synergistic effect of protein-polysaccharide; meanwhile, an ultrasonic treatment technology and a pulsed electric field physical processing technology are combined to improve the quality of the minced fillet gel, so that the problems of poor water binding capacity, loose gel network, non-uniform pore size distribution of the gel network and the like in the traditional minced fillet processing technology are solved. The surimi gel prepared by the method has the advantages of high water binding capacity, moderate hardness and elasticity, uniform pore size distribution of a gel network, strong deformation resistance of the gel network and high quality stability, and is suitable for industrial production of high-quality surimi products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food processing, in particular to a processing method of surimi gel. BACKGROUND

[0002] Surimi products are prepared by processes such as meat picking, rinsing, fine filtering, dehydrating, grinding or chopping, shaping, heating and cooling. Surimi products occupy an important position in the food industry due to their tender taste and rich nutritional value, and are increasingly valued by Chinese consumers. However, the water-holding capacity and hardness of surimi gel products prepared by traditional surimi processing technology are difficult to meet the market demand, and the activity of active substances added to improve the functionality of surimi products during the processing process can easily affect the quality stability of surimi products.

[0003] Patent document CN110115349A discloses a method for improving the water-holding capacity of fresh and tender fish balls and prolonging the shelf life of the products. The method includes: air chopping, i.e., cutting semi-thawed surimi into small pieces, adding ice water and chopping; salt chopping, i.e., adding salt and chopping; mixed chopping, i.e., dissolving exogenous additives in a small amount of water and adding them to surimi and chopping; shaping, i.e., using a fish ball forming machine to shape; gelation, i.e., using a two-stage heating method to gel; cooling, i.e., cooling the gelled fish balls in cold water; chitosan coating, i.e., immersing the fish balls in a chitosan solution for coating; packaging, i.e., vacuum packaging the fish balls using retort pouches; heat sterilization treatment and cold storage. The products prepared by this method have white color, delicate and tender taste and convenient eating, not only meeting the needs of modern consumers for convenient and fast products, but also being conducive to the industrialized production of traditional surimi products.

[0004] Patent document CN119385278A discloses a method for improving the frozen storage stability of frozen low-salt surimi products. The method includes: step S1, chopping fish meat with polysaccharide, sodium chloride and water to obtain low-salt surimi; step S2, performing sausage processing on the low-salt surimi, then performing ultrasonic treatment under heating conditions, maturation treatment, cooling and frozen storage to obtain frozen low-salt surimi; the polysaccharide is one or more of curdlan, chitosan and kappa-carrageenan; the ultrasonic treatment conditions are a power of 200-600 W and a time of 10-30 min. This method can not only improve the gel quality of low-salt surimi products under the condition of reducing salt by 50%, but also improve the quality deterioration caused by temperature fluctuations, significantly improving the frozen storage stability of frozen low-salt surimi products.

[0005] However, the single ultrasonic physical processing technology currently used in the industry is difficult to achieve efficient combination of additives and surimi matrix, and cannot solve the problem of network uniformity during gel formation. At the same time, the direct coating method is also difficult to completely solve the rancidity problem caused by oxidation of fat and protein inside the surimi product. Therefore, developing an integrated process that can synergistically improve the quality of surimi gel and the retention rate of active substances has become a research hotspot in the field of aquatic processing. SUMMARY

[0006] In order to solve the defects of the prior art, the application provides a processing method of surimi gel. The application innovatively constructs an active emulsion of egg white-chitosan loaded with blueberry anthocyanins, which is a triple microcapsule system of acidic core-lipid barrier-biocompatible shell. The efficient embedding and targeted delivery of blueberry anthocyanins are achieved through pH gradient regulation and protein-polymer synergistic effect. At the same time, the combination of ultrasonic treatment technology and pulsed electric field physical processing technology enables the active emulsion droplets to be precisely embedded in the surimi protein matrix, which can significantly improve the water holding capacity, texture properties and stability of surimi, and is suitable for industrialized production of high-quality surimi products.

[0007] In order to achieve the above-mentioned goal, the technical scheme of the application is as follows:

[0008] The application provides a processing method of surimi gel, comprising the following steps:

[0009] Step S1, take ice-fresh surimi, thaw, rinse with salt water with a mass concentration of 0.5%, then perform ultrasonic treatment and chopping, to obtain an activated surimi matrix;

[0010] Step S2, add the active emulsion to the activated surimi matrix prepared in step S1, mix uniformly, then perform pulsed electric field treatment, to obtain a mixed surimi;

[0011] Step S3, after the mixed surimi prepared in step S2 is formed, perform ultrasonic treatment under the condition that the water bath control temperature is 35-40℃ for 20-30min, then stand still under the condition that the water bath control temperature is 35-40℃ for 30-40min, and solidify under the condition that the standing temperature is 85-90℃ for 28-33min, to obtain the product.

[0012] Further, the ultrasonic treatment condition in step S1 is that the temperature is 5-10℃, the power is 200-300W, the frequency is 20-40kHz, and the ultrasonic treatment time is 5-8min.

[0013] Further, the chopping treatment in step S1 is that the rotation speed is 2000-3000rpm, and the chopping time is 4-6min, then the rotation speed is 3000-4000rpm, and the high-speed chopping time is 4-6min.

[0014] Further, the amount of the active emulsion added in step S2 is 5-15% of the total mass of the activated surimi matrix.

[0015] Further, the preparation method of the active emulsion in step S2 is as follows:

[0016] Step A: Dissolve the blueberry anthocyanin extract in an ice acetic acid aqueous solution with a pH of 3.0-4.0, and centrifuge at a speed of 3000-5000 rpm for 5-10 min to obtain an inner water phase;

[0017] Step B: Mix the inner water phase obtained in step A with soybean oil, and the volume ratio of the inner water phase to soybean oil is 1:4, and shear homogenize at a speed of 10000-12000 rpm for 2-4 min to obtain a water-in-oil primary emulsion; the primary emulsion is a uniform emulsion, the oil droplet particle size D50 is 3.2±0.5 μm, and there is no obvious stratification;

[0018] Step C: Dissolve the egg white protein and chitosan in deionized water, adjust the pH to 5.00±0.02 with 1 mol / L HCl, so that the total concentration is 3-6 wt%, and stir until completely dissolved to obtain an outer water phase; the outer water phase composite system constructs a three-dimensional protection network through the anchoring of egg white protein to the oil-water interface-chitosan to form a synergistic stable structure.

[0019] Step D: Add the water-in-oil primary emulsion obtained in step B dropwise to the outer water phase, and premix at a speed of 500-1000 rpm for 5-10 min, and then homogenize at 60 MPa, with the outlet temperature controlled at 10-20°C. The egg white-chitosan loaded blueberry anthocyanin active emulsion is finally formed into a uniform purple W / O / W emulsion with a particle size distribution of 1-3 μm and a zeta potential of -32±2 mV.

[0020] Further, the mass ratio of egg white protein to chitosan in step C is 3:1-5:1.

[0021] Further, the volume ratio of the water-in-oil primary emulsion to the outer water phase in step D is 1:3-1:5.

[0022] Further, the mixing process in step S2 is as follows: coat at a temperature of 5-10°C and a speed of 2500-3000 rpm for 1-2 min, and then fuse at a temperature of 5-10°C and a speed of 4500-5000 rpm for 3-5 min.

[0023] Further, the pulse electric field treatment conditions in step S2 are as follows: treat 3-5 times at a temperature of 10-15°C, an electric field strength of 20-30 kV / cm, and a pulse width of 2-5 μs.

[0024] Furthermore, the ultrasonic treatment conditions in step S3 are as follows: ultrasonic treatment for 20 to 30 minutes at a power of 150 to 200 W and a frequency of 30 to 50 kHz.

[0025] To address the problems of poor water retention, loose gel networks, and uneven pore size distribution in traditional surimi processing, the inventors have proposed for the first time a W / O / W dual emulsion-loaded with blueberry anthocyanins for addition to surimi products. This active emulsion effectively reduces the inactivation and leakage of blueberry anthocyanins during processing, improving the functionality and quality stability of surimi products. Simultaneously, the synergistic effect of ultrasonic treatment and pulsed electric field technology increases the exposure of hydrophobic sites in surimi proteins and the uniformity of emulsion droplet dispersion, resolving the issues of loose gel networks and uneven additive distribution in traditional processes. Furthermore, the inventors utilize ultrasound-assisted technology during the gelation stage of surimi products to effectively accelerate the cross-linking rate of surimi proteins, improve the uniformity of gel network pore size distribution, and enhance the water retention, hardness, and other textural properties of the surimi products.

[0026] Specifically, experiments have shown that the ultrasonic treatment in the pretreatment of surimi gel provided by this invention can increase the exposure of hydrophobic sites of surimi proteins by 15-20% on the basis of salt washing. After salt washing and ultrasonication, gradient chopping results in a matrix viscosity of 2300-2600 mPa·s. The pulsed electric field treatment in the mixing step of the activated surimi matrix and the active emulsion can induce the conformational unfolding of surimi protein molecules, promote the hydrophobic interaction between ovalbumin and surimi proteins in the outer layer of the emulsion, and the cross-linking of chitosan. This increases the dispersion uniformity of active emulsion droplets in the surimi matrix to over 95%. Simultaneously, the hydrophobic interaction between ovalbumin and surimi proteins and the film-forming properties of chitosan can reduce the precipitation of water and oil during processing, controlling the juice loss rate to within 5%. The ultrasonic treatment in the surimi gelation stage can increase the cross-linking rate of surimi proteins by 20-25% and improve the uniformity of gel network pore size distribution by 15%. Compared with surimi without added active emulsion, the surimi gel prepared by this invention has 18-25% higher water retention, 25-40% higher hardness, 35-50% higher storage modulus (G'), and significantly enhanced resistance to deformation of the gel network, making it a high-quality surimi product.

[0027] Meanwhile, in preparing the ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion, this invention constructs an acidic microenvironment, allowing the anthocyanins to exist in a stable flavonoid form, improving the initial solubility stability by 22% compared to the neutral system, and the transmittance of the supernatant after centrifugation is ≥95%. Through the synergistic effect of the protein anchoring interface of ovalbumin-chitosan and the polysaccharide network, the absolute value of the zeta potential of the active emulsion reaches 32±2mV, and the particle size increase rate after 15 days of storage is ≤15%, which can effectively improve the stability of the active substance blueberry anthocyanins, thereby effectively inhibiting the oxidation of fats and proteins inside the surimi gel and extending the shelf life of the surimi gel.

[0028] In summary, compared with existing technologies, the surimi gel processing method provided by this invention utilizes an ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion within a triple microcapsule system of an acidic core-lipid barrier-biocompatible shell. This achieves efficient encapsulation and targeted delivery of blueberry anthocyanins through pH gradient regulation and the synergistic effect of proteins and polysaccharides. Furthermore, the quality of the surimi gel is improved by combining ultrasonic processing and pulsed electric field physical processing techniques. The surimi gel prepared by this invention possesses advantages such as high water retention, moderate hardness and elasticity, uniform pore size distribution in the gel network, strong resistance to deformation of the gel network, and high quality stability, meeting the demands of industrial production for high-quality, functional aquatic products. Detailed Implementation

[0029] The present invention will be further described below through specific embodiments, but this is not intended to limit the invention. Those skilled in the art can make various modifications or improvements based on the basic ideas of the invention, but as long as they do not depart from the basic ideas of the invention, they are all within the scope of the invention. The raw materials and components involved in the present invention can all be obtained through commercially available or conventional techniques in the art. For example, the blueberry anthocyanin extract (36% purity) was purchased from Shaanxi Haolin Biotechnology Co., Ltd., a food raw material, product model: KT-H16. The chitosan is food-grade acid-soluble chitosan (CS, degree of deacetylation ≥85%), purchased from Shandong Weikang Biomedical Technology Co., Ltd. (Linyi, Shandong, China).

[0030] Example 1: Preparation of an active emulsion of ovalbumin-chitosan loaded with blueberry anthocyanins

[0031] Step A: Dissolve blueberry anthocyanin extract (36% purity) in glacial acetic acid aqueous solution with pH 3.0. The ratio of blueberry anthocyanin extract to glacial acetic acid aqueous solution is 1g:10mL. Stir magnetically for 30min until a bright purple clear liquid is formed. Centrifuge at 4000rpm for 10min to obtain the inner aqueous phase.

[0032] Step B: Mix the aqueous phase obtained in step A with soybean oil, wherein the volume ratio of the aqueous phase to soybean oil is 1:4. Place the mixture in a high-speed shear homogenizer and shear homogenize it for 3 minutes at a speed of 10,000 rpm to obtain a water-in-oil type primary emulsion.

[0033] Step C: Dissolve ovalbumin and chitosan in deionized water, wherein the mass ratio of ovalbumin to chitosan is 3:1. Adjust the pH to 5.00±0.02 with 1mol / L HCl to make the total concentration 3wt%. Stir until completely dissolved to obtain the external aqueous phase.

[0034] Step D: Add the water-in-oil pre-emulsion obtained in step B to the external aqueous phase. The volume ratio of the water-in-oil pre-emulsion to the external aqueous phase is 1:3. Premix for 10 minutes at a speed of 800 rpm, then homogenize for 2 cycles at 60 MPa. The outlet temperature is controlled at 15°C to obtain the final product.

[0035] Example 2: Preparation of an active emulsion of ovalbumin-chitosan loaded with blueberry anthocyanins

[0036] Step A: Dissolve blueberry anthocyanin extract (36% purity) in glacial acetic acid aqueous solution with pH 3.0. The ratio of blueberry anthocyanin extract to glacial acetic acid aqueous solution is 1g:10mL. Stir magnetically for 30min until a bright purple clear liquid is formed. Centrifuge at 5000rpm for 8min to obtain the inner aqueous phase.

[0037] Step B: Mix the aqueous phase obtained in step A with soybean oil, wherein the volume ratio of the aqueous phase to soybean oil is 1:4. Place the mixture in a high-speed shear homogenizer and shear homogenize it for 3 minutes at a speed of 10,000 rpm to obtain a water-in-oil type primary emulsion.

[0038] Step C: Dissolve ovalbumin and chitosan in deionized water, with a mass ratio of ovalbumin to chitosan of 5:1. Adjust the pH to 5.00±0.02 with 1 mol / L HCl to make the total concentration 6 wt%. Stir until completely dissolved to obtain the external aqueous phase.

[0039] Step D: Add the water-in-oil pre-emulsion obtained in step B to the external aqueous phase. The volume ratio of the water-in-oil pre-emulsion to the external aqueous phase is 1:5. Premix for 8 minutes at a speed of 1000 rpm, then homogenize for 2 cycles at 60 MPa. The outlet temperature is controlled at 10℃ to obtain the final product.

[0040] Example 3: A processing method for surimi gel

[0041] Step S1: Take fresh tilapia surimi, thaw at 4℃ for 8 hours, rinse twice with 0.5% brine (the brine is twice the mass of the surimi), and then perform ultrasonic treatment. The ultrasonic treatment conditions are: ultrasonic treatment for 6 minutes at 8℃ in an ice water bath with a power of 250W and a frequency of 30kHz, followed by chopping at 2000rpm for 5 minutes and then chopping at 3000rpm for 5 minutes to obtain activated surimi matrix.

[0042] Step S2: Add an active emulsion to the activated fish paste matrix obtained in step S1. The active emulsion is the ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion obtained in Example 1. The amount of active emulsion added is 10% of the total mass of the activated fish paste matrix. Mix evenly. The mixing treatment is as follows: coat for 1 min under the condition of ice water bath temperature controlled at 8°C and rotation speed of 3000 rpm, fuse for 4 min under the condition of ice water bath temperature controlled at 8°C and rotation speed of 5000 rpm, and then perform pulsed electric field treatment. The pulsed electric field treatment conditions are: treatment 4 times under the condition of temperature of 12°C, electric field strength of 25kV / cm, and pulse width of 3μs to obtain mixed fish paste.

[0043] Step S3: Pack the mixed fish paste obtained in step S2 into a 5cm×5cm×2cm mold, compact it to remove air bubbles, and sonicate it for 25 minutes at a water bath temperature of 40℃, a power of 180W, and a frequency of 40kHz. Then, let it stand for 35 minutes at a water bath temperature of 40℃ and solidify it for 30 minutes at a temperature of 90℃.

[0044] Example 4: A processing method for fish paste gel

[0045] Step S1: Take fresh tilapia surimi, thaw at 4℃ for 6 hours, rinse twice with 0.5% brine (the brine is twice the mass of the surimi), and then perform ultrasonic treatment. The ultrasonic treatment conditions are: ultrasonic treatment for 8 minutes at 8℃ in an ice water bath with a power of 200W and a frequency of 20kHz, followed by chopping at 2000rpm for 5 minutes and then chopping at 3000rpm for 5 minutes to obtain activated surimi matrix.

[0046] Step S2: Add an active emulsion to the activated fish paste matrix obtained in step S1. The active emulsion is the ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion obtained in Example 1. The amount of active emulsion added is 5% of the total mass of the activated fish paste matrix. Mix evenly. The mixing treatment is as follows: coat for 1 min under the condition of ice water bath temperature controlled at 8°C and rotation speed of 3000 rpm, fuse for 3 min under the condition of ice water bath temperature controlled at 8°C and rotation speed of 5000 rpm, and then perform pulsed electric field treatment. The pulsed electric field treatment conditions are: treatment 5 times under the condition of temperature of 10°C, electric field strength of 20kV / cm, and pulse width of 2μs to obtain mixed fish paste.

[0047] Step S3: Pack the mixed fish paste obtained in step S2 into a 5cm×5cm×2cm mold, compact it to remove air bubbles, and sonicate it for 30 minutes at a water bath temperature of 40℃, a power of 150W, and a frequency of 30kHz. Then, let it stand for 30 minutes at a water bath temperature of 40℃, and then cure it at a temperature of 90℃ for 30 minutes to obtain the final product.

[0048] Example 5: A processing method for fish paste gel

[0049] Step S1: Take fresh tilapia surimi, thaw at 4℃ for 12 hours, rinse twice with 0.5% brine (the brine is twice the mass of the surimi), and then perform ultrasonic treatment. The ultrasonic treatment conditions are: ultrasonic treatment for 5 minutes at 8℃, 300W, and 40kHz in an ice water bath, followed by chopping at 2000rpm for 5 minutes and then chopping at 3000rpm for 5 minutes to obtain activated surimi matrix.

[0050] Step S2: Add an active emulsion to the activated fish paste matrix obtained in step S1. The active emulsion is the ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion obtained in Example 2. The amount of active emulsion added is 15% of the total mass of the activated fish paste matrix. Mix evenly. The mixing treatment is as follows: coat for 1 min under the condition of ice water bath temperature controlled at 8°C and rotation speed of 3000 rpm, fuse for 5 min under the condition of ice water bath temperature controlled at 8°C and rotation speed of 5000 rpm, and then perform pulsed electric field treatment. The pulsed electric field treatment conditions are: treatment 3 times under the condition of temperature of 15°C, electric field strength of 30kV / cm, and pulse width of 5μs to obtain mixed fish paste.

[0051] Step S3: Pack the mixed fish paste obtained in step S2 into a 5cm×5cm×2cm mold, compact it to remove air bubbles, and sonicate it for 20 minutes at a water bath temperature of 40℃, a power of 200W, and a frequency of 50kHz. Then, let it stand for 40 minutes at a water bath temperature of 40℃, and then cure it for 30 minutes at a temperature of 90℃.

[0052] Comparative Example 1: A processing method for surimi gel

[0053] The difference from Example 3 is that there is no ultrasonic treatment or pulsed electric field treatment. The specific steps are as follows:

[0054] Step S1: Take fresh tilapia surimi, thaw at 4℃ for 8 hours, rinse twice with 0.5% brine (the brine is twice the mass of the surimi), then chop at 2000 rpm for 5 minutes and at 3000 rpm for 5 minutes to obtain activated surimi matrix.

[0055] Step S2: Add an active emulsion to the activated fish paste matrix obtained in step S1. The active emulsion is the ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion obtained in Example 1. The amount of active emulsion added is 10% of the total mass of the activated fish paste matrix. Mix evenly. The mixing process is as follows: coating for 1 minute under the condition of ice water bath temperature controlled at 8°C and rotation speed of 3000 rpm, and then fusing for 4 minutes under the condition of ice water bath temperature controlled at 8°C and rotation speed of 5000 rpm to obtain mixed fish paste.

[0056] Step S3: Fill the mixed fish paste obtained in step S2 into a 5cm×5cm×2cm mold, press it to remove air bubbles, shape it in a water bath at a controlled temperature of 40℃ for 1 hour, and then cure it at a temperature of 90℃ for 30 minutes to obtain the final product.

[0057] Comparative Example 2: A processing method for surimi gel

[0058] The difference from Example 3 is that ultrasonic treatment is performed only in the pretreatment stage, and the specific steps are as follows:

[0059] Step S1: Take fresh tilapia surimi, thaw at 4℃ for 8 hours, rinse twice with 0.5% brine (the brine is twice the mass of the surimi), and then perform ultrasonic treatment. The ultrasonic treatment conditions are: ultrasonic treatment for 6 minutes at 8℃ in an ice water bath with a power of 250W and a frequency of 30kHz, followed by chopping at 2000rpm for 5 minutes and then chopping at 3000rpm for 5 minutes to obtain activated surimi matrix.

[0060] Step S2: Add an active emulsion to the activated fish paste matrix obtained in step S1. The active emulsion is the ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion obtained in Example 1. The amount of active emulsion added is 10% of the total mass of the activated fish paste matrix. Mix evenly. The mixing process is as follows: coating for 1 minute under the condition of ice water bath temperature controlled at 8°C and rotation speed of 3000 rpm, and then fusing for 4 minutes under the condition of ice water bath temperature controlled at 8°C and rotation speed of 5000 rpm to obtain mixed fish paste.

[0061] Step S3: Fill the mixed fish paste obtained in step S2 into a 5cm×5cm×2cm mold, press it to remove air bubbles, shape it in a water bath at a controlled temperature of 40℃ for 1 hour, and then cure it at a temperature of 90℃ for 30 minutes to obtain the final product.

[0062] Comparative Example 3: A processing method for surimi gel

[0063] The difference from Example 3 is that only pulsed electric field processing is used, and the specific steps are as follows:

[0064] Step S1: Take fresh tilapia surimi, thaw at 4℃ for 8 hours, rinse twice with 0.5% brine (the brine is twice the mass of the surimi), then chop at 2000 rpm for 5 minutes and at 3000 rpm for 5 minutes to obtain activated surimi matrix.

[0065] Step S2: Add an active emulsion to the activated fish paste matrix obtained in step S1. The active emulsion is the ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion obtained in Example 1. The amount of active emulsion added is 10% of the total mass of the activated fish paste matrix. Mix evenly. The mixing treatment is as follows: coat for 1 min under the condition of ice water bath temperature controlled at 8°C and rotation speed of 3000 rpm, fuse for 4 min under the condition of ice water bath temperature controlled at 8°C and rotation speed of 5000 rpm, and then perform pulsed electric field treatment. The pulsed electric field treatment conditions are: treatment 4 times under the condition of temperature of 12°C, electric field strength of 25kV / cm, and pulse width of 3μs to obtain mixed fish paste.

[0066] Step S3: Fill the mixed fish paste obtained in step S2 into a 5cm×5cm×2cm mold, press it to remove air bubbles, shape it in a water bath at a controlled temperature of 40℃ for 1 hour, and then cure it at a temperature of 90℃ for 30 minutes to obtain the final product.

[0067] Experiment Example 1: Stability Experiment of Ovalbumin-Chitosan-Loaded Blueberry Anthocyanin Active Emulsion

[0068] 1. Experimental Method:

[0069] 1.1 Traditional single emulsion preparation:

[0070] Blueberry anthocyanin extract (36% purity) was directly dispersed in an aqueous solution containing Tween-80 at a concentration of 2% of the total emulsion mass, and then magnetically stirred at 500 rpm for 30 minutes.

[0071] 1.2 Storage stability testing:

[0072] (1) 4℃ light-protected storage experiment: The ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion prepared in Example 1 and the traditional single emulsion were stored in a 4℃ light-protected environment. Samples were taken at 0 days, 5 days, 10 days and 15 days of storage, and the blueberry anthocyanin content was determined by high performance liquid chromatography (HPLC) and the retention rate was calculated.

[0073] (2) 60℃ gelation treatment experiment: The ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion prepared in Example 1 and the traditional single emulsion were subjected to 60℃ gelation treatment respectively. After the treatment, the blueberry anthocyanin content was determined by high performance liquid chromatography (HPLC) and the retention rate was calculated.

[0074] 2. Experimental Results:

[0075] 2.1 Results of storage at 4℃ in the dark: Testing showed that the ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion prepared in Example 1 retained 80.2% of its blueberry anthocyanins after 15 days of storage at 4℃ in the dark; while the traditional single emulsion retained only 51.8% of its blueberry anthocyanins after 15 days of storage under the same conditions. Compared with the traditional single emulsion, the active emulsion prepared in this invention improved the blueberry anthocyanin retention rate by approximately 28.4%.

[0076] 2.2 Results of 60℃ Gelation Treatment: After gelation treatment at 60℃, the ovalbumin-chitosan-loaded blueberry anthocyanin active emulsion prepared in Example 1 still retained 72.3% of its active components; while the system using the traditional method of directly adding blueberry anthocyanins retained only 35.2% of the anthocyanins after gelation treatment at 60℃. Compared with the traditional direct addition method, the active emulsion prepared by this invention has an increased blueberry anthocyanin retention rate of approximately 37.1%. This indicates that the technical solution of this invention can effectively improve the stability of blueberry anthocyanins during storage and processing, and alleviate the problem of easy degradation of natural active ingredients.

[0077] Experimental Example 2: Performance Testing of Surimi Gel

[0078] 1. Experimental Method:

[0079] The performance of the surimi gels prepared in Examples 3, 4, 5, Comparative Examples 1, 2, and 3 was tested. Among them:

[0080] 1.1 Water-holding capacity test:

[0081] Water holding capacity (WHC) was determined by wrapping 2g of fish paste gel (m1) in three layers of filter paper and placing it at the bottom of a 50mL centrifuge tube. The sample was centrifuged at 4℃ and 1000r / min for 15min using a centrifuge (Hu Kang, W21R, Hunan, China). The mass (m2) of the centrifuged sample was weighed and recorded. The WHC of the fish paste gel was calculated according to equation (2).

[0082] WHC is calculated by pressing the formula.

[0083]

[0084] 1.2 Hardness testing:

[0085] Texture analysis (TPA) of the surimi gel was performed using a texture analyzer with a P50 cylindrical probe, following a slightly modified method described in the reference (Tong et al., 2018). The test conditions were: trigger force 5g, velocity before and after the test 1mm / s, velocity after the test 5mm / s, compression ratio 30%, residence time 5s, and two compressions. The hardness of the surimi gel was recorded.

[0086] 1.3 Rheological property testing:

[0087] Surimi gel samples were uniformly distributed between parallel plates with a diameter of 40 mm (gap = 1 mm). Temperature scanning of the surimi gel was performed from 4 °C to 90 °C (heating rate = 2 °C / min, oscillation frequency = 0.1, strain = 1%). Frequency scanning of the surimi gel was conducted at 25 °C with a strain of 1%, in the frequency range of 0–20 Hz. Storage modulus (G') and loss modulus (G”) were recorded during heating.

[0088] 1.4 Detection of hydrophobic site exposure in surimi protein:

[0089] First, the fish surimi protein was salt-washed (using a NaCl solution of a certain concentration to remove soluble proteins, etc.), and then the 8-aniline-1-naphthalenesulfonic acid (ANS) fluorescent probe method was used. The treated protein was mixed with the ANS solution, and the fluorescence intensity was measured using a fluorescence spectrophotometer. The fluorescence intensity was positively correlated with the exposure of hydrophobic sites. The increase in fluorescence intensity based on salt washing was expressed as the percentage of the difference between the experimental group and the control group fluorescence intensity compared to the control group fluorescence intensity.

[0090] 1.5. Detection of emulsion droplet dispersion uniformity:

[0091] A laser particle size analyzer was used in conjunction with a microscope for observation. The laser particle size analyzer was used to determine the particle size distribution of the emulsion droplets and calculate the distribution uniformity (usually measured by indicators such as the coefficient of variation of particle size distribution); at the same time, the dispersion of the droplets was observed through an optical microscope to comprehensively evaluate the dispersion uniformity of the emulsion droplets.

[0092] 1.6 Detection of increased cross-linking rate of surimi protein:

[0093] A chemical method combining sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with the determination of protein cross-linking degree was employed. SDS-PAGE analysis was used to analyze changes in the molecular weight distribution of proteins to determine the degree of cross-linking; alternatively, the cross-linking rate could be calculated by measuring changes in the content of free amino groups in proteins (e.g., the trinitrobenzenesulfonic acid (TNBS) method). The cross-linking rate was expressed as the percentage of the difference between the cross-linking rates of the experimental group and the control group.

[0094] 1.7 Improved detection of gel network pore size distribution uniformity:

[0095] The microstructure of the fish paste gel was observed using cryo-scanning electron microscopy (Cryo-SEM), and images of the gel network were captured. Then, image analysis software (such as ImageJ) was used to perform statistical analysis on the pore size of the gel network and calculate the uniformity of the pore size distribution (e.g., measured by the ratio of the standard deviation to the mean of the pore size). The improvement was expressed as the percentage of the difference in uniformity between the experimental group and the control group compared to the uniformity of the control group.

[0096] 2. Experimental Results:

[0097] The experimental results are shown in Table 1.

[0098] Table 1. Performance test results of fish paste gel

[0099]

[0100]

[0101] As shown in Table 1, the fish paste gel prepared by this invention exhibits significantly better properties than the comparative example. Specifically:

[0102] (1) The improved water retention of the surimi gel prepared by the present invention is due to the densification of the protein network promoted by ultrasound and the emulsion stability enhanced by the pulsed electric field, which is 83.3% to 100% higher than that of Comparative Example 1.

[0103] (2) The hardness and storage modulus of the surimi gel prepared by the present invention are due to the efficient cross-linking of proteins induced by the three-stage process, which is 30% to 45% higher than that of Comparative Example 2 and Comparative Example 3 treated by a single technology.

[0104] (3) The synergistic improvement of the hydrophobic site exposure and emulsion dispersion uniformity of the surimi gel prepared by the present invention proves that the combination of multiple technologies can overcome the control limitations of a single physical field.

[0105] Furthermore, during the experimental process, the inventors discovered that: During the high-pressure homogenization process, the outlet temperature must be strictly controlled to ≤20℃ to avoid protein denaturation; a segmented heating temperature gradient is crucial to ensuring gel quality, as skipping the low-temperature shaping step leads to a coarse network and a 10-15% decrease in hardness. Ultrasound during the gelation stage must be strictly matched to the heating temperature: it should only be applied during the 40℃ low-temperature shaping period, avoiding use during the 90℃ high-temperature curing stage, as high-temperature ultrasound can easily cause gel network breakage and a 5-8% decrease in hardness. Ultrasonic power needs precise control: exceeding 200W will cause localized overheating, potentially exceeding 45℃ and leading to uncontrolled protein thermal denaturation; below 150W, it cannot effectively promote molecular cross-linking, resulting in insignificant process gains. The duration of ultrasonic treatment is related to gel thickness: for surimi products with a thickness exceeding 2cm, the ultrasonic time can be appropriately extended to 30 minutes, but temperature uniformity must be enhanced through a circulating water bath.

[0106] Experiment Example 3: Stability Experiment of Fish Paste Gel

[0107] 1. Experimental Method:

[0108] 1.1 Sample Preparation:

[0109] The fish paste gel prepared in Example 3.

[0110] Comparative Example 4: The difference between this active emulsion and that of Example 3 is that this is an active emulsion with ovalbumin loaded with blueberry anthocyanins and without added chitosan.

[0111] Comparative Example 5: The difference between this active emulsion and that of Example 3 is that it is a chitosan-loaded blueberry anthocyanin-free active emulsion.

[0112] Comparative Example 6: The difference from Example 3 is that 10% of the total mass of blueberry anthocyanin extract (36% purity) was directly added to the surimi matrix.

[0113] Comparative Example 7: The difference from the active emulsion in Example 3 is that 10% of the total mass of the active emulsion containing only lipid barrier-loaded blueberry anthocyanins was added to the surimi matrix.

[0114] Control group: The difference from Example 3 is that no active emulsion was added to the surimi matrix.

[0115] 1.2 Storage and Testing:

[0116] The fish paste gel samples prepared above were stored at 4°C for 14 days. During this period, the degree of lipid oxidation rancidity of the samples was detected every 2 days using the thiobarbituric acid (TBA) method, and the result was expressed by measuring the malondialdehyde content.

[0117] The TBA assay kit was purchased from Nanjing Jiancheng Bioengineering Institute. The sample pretreatment involved precipitating proteins with trichloroacetic acid and using distilled water as the extraction solvent.

[0118] 2. Experimental Results:

[0119] The experimental results are shown in Table 2.

[0120] Table 2. Changes in TBA in fish paste gel

[0121]

[0122] As shown in Table 2, the TBA value of the control group increased rapidly, reaching 0.042 mg / g on day 8. Since the sample TBA value exceeded the linear detection range of the kit (the kit's upper detection limit is 0.045 mg / g), accurate quantification was still impossible after dilution and retesting; therefore, the recording for subsequent days was terminated. Comparative Example 6 reached 0.043 mg / g on day 10, also exceeding the kit's upper detection limit, so the recording for subsequent days was terminated. In contrast, the surimi gel prepared in Example 3 of this invention reached 0.025 mg / g on day 14, Comparative Example 7 reached 0.036 mg / g on day 14, Comparative Example 4 reached 0.038 mg / g on day 14, and Comparative Example 5 reached 0.031 mg / g on day 14. This indicates that the active emulsion of the acidic core-lipid barrier-biocompatible shell triple microcapsule system constructed in this invention can more significantly inhibit lipid oxidation inside the surimi gel, thereby effectively extending the shelf life of the surimi gel, compared with microcapsule systems with only a single biocompatible shell (Comparative Example 4, Comparative Example 5) and microcapsule systems with only a lipid barrier (Comparative Example 7).

[0123] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for processing fish paste gel, characterized in that, Includes the following steps: Step S1: Take frozen fish paste, thaw it, rinse it with 0.5% saline solution, then sonicate it, chop and mix it to obtain activated fish paste matrix. Step S2: Add active emulsion to the activated fish paste matrix obtained in step S1, mix evenly, and then perform pulsed electric field treatment to obtain mixed fish paste. Step S3: After the mixed fish paste obtained in step S2 is shaped, it is ultrasonically treated for 20-30 minutes under the condition of water bath temperature control at 35-40℃, then left to stand for 30-40 minutes under the condition of water bath temperature control at 35-40℃, and then cured for 28-33 minutes under the condition of placement temperature at 85-90℃ to obtain the final product.

2. The processing method of fish paste gel as described in claim 1, characterized in that, The ultrasonic treatment conditions in step S1 are as follows: ultrasonic treatment for 5 to 8 minutes at a temperature of 5 to 10°C, a power of 200 to 300W, and a frequency of 20 to 40kHz.

3. The processing method of fish paste gel as described in claim 1, characterized in that, The chopping process in step S1 is as follows: chopping at a speed of 2000-3000 rpm for 4-6 minutes, followed by high-speed chopping at a speed of 3000-4000 rpm for 4-6 minutes.

4. The processing method of fish paste gel as described in claim 1, characterized in that, In step S2, the amount of active emulsion added is 5-15% of the total mass of the activated fish paste matrix.

5. The processing method of fish paste gel as described in claim 1, characterized in that, The method for preparing the active emulsion in step S2 is as follows: Step A: Dissolve the blueberry anthocyanin extract in an aqueous solution of glacial acetic acid with a pH of 3.0–4.0, and centrifuge at 3000–5000 rpm for 5–10 min to obtain the inner aqueous phase; Step B: Mix the aqueous phase obtained in step A with soybean oil, wherein the volume ratio of the aqueous phase to soybean oil is 1:

4. Shear and homogenize at a speed of 10000-12000 rpm for 2-4 minutes to obtain a water-in-oil type primary emulsion. Step C: Dissolve ovalbumin and chitosan in deionized water, adjust the pH to 5.00±0.02 with 1mol / L HCl to make the total concentration 3-6wt%, stir until completely dissolved to obtain the external aqueous phase; Step D: Add the water-in-oil type primary emulsion obtained in step B to the external aqueous phase, premix for 5 to 10 minutes at a speed of 500 to 1000 rpm, then homogenize at 60 MPa, and control the outlet temperature at 10 to 20°C to obtain the final product.

6. The processing method of fish paste gel as described in claim 5, characterized in that, In step C, the mass ratio of ovalbumin to chitosan is 3:1 to 5:

1.

7. The processing method of fish paste gel as described in claim 5, characterized in that, In step D, the volume ratio of the water-in-oil primary emulsion to the external aqueous phase is 1:3 to 1:

5.

8. The processing method of the fish paste gel as described in claim 1, characterized in that, The mixing process in step S2 is as follows: coating for 1 to 2 minutes at a temperature of 5 to 10°C and a rotation speed of 2500 to 3000 rpm, followed by fusion for 3 to 5 minutes at a temperature of 5 to 10°C and a rotation speed of 4500 to 5000 rpm.

9. The processing method of fish paste gel as described in claim 1, characterized in that, The pulsed electric field processing conditions in step S2 are as follows: the process is repeated 3 to 5 times under the conditions of a temperature of 10 to 15°C, an electric field strength of 20 to 30 kV / cm, and a pulse width of 2 to 5 μs.

10. The processing method of fish paste gel as described in claim 1, characterized in that, The ultrasonic treatment conditions in step S3 are as follows: ultrasonic treatment for 20 to 30 minutes at a power of 150 to 200 W and a frequency of 30 to 50 kHz.

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