A composite method for high-quality quick freezing and high-recovery thawing of oily fresh fish

Abstract

The present invention discloses a composite method for high-quality quick freezing and high-recovery thawing of oily fresh fish, which belongs to the technical field of food freezing and processing. The present invention uses oily fresh fish as the main raw material, and undergoes raw material preparation, physical field assisted freezing and high-recovery thawing processes. In this method, rosemary extract and gallic acid are added in the raw material preparation stage and assisted by the effect of electrostatic field, so as to delay the fat oxidation of oily fresh fish. At the same time, ultrasonic and magnetic field combined immersion freezing, microwave combined with nano zinc oxide and graphene particles thawing can minimize the quality loss of fresh samples after freezing and thawing, thereby achieving high-quality freezing and high-recovery thawing. After using the above-mentioned treatment, the quality of subsequent fresh fish is significantly improved, such as reducing thawing loss, retaining nutrients, improving sensory quality, delaying fat oxidation, high recovery, etc., and extending the sales period to achieve the purpose of increasing revenue.

Description

Technical Field

[0001] The invention relates to a composite method for high-quality quick freezing and high-recovery thawing of oily fresh fish, belonging to the technical field of food freezing processing. Background Art

[0002] Because the muscles of aquatic products such as fish, shrimp, crab, and shellfish contain over 70% water, their tissues are fragile, low in natural immune substances, easily oxidized unsaturated fatty acids, and high in soluble protein, they are more susceptible to spoilage than typical animal meat tissue and difficult to store. Fresh fish, shrimp, crab, and shellfish require very stringent storage and transportation conditions, requiring low-temperature preservation from the moment they are caught to delay spoilage. Currently, the low-temperature cold chain storage and transportation used globally generally falls within four temperature ranges: refrigerated preservation at 0-4°C, frozen preservation at 0-2°C, slightly frozen preservation at -2-4°C, and frozen preservation at -18-40°C. Frozen preservation is the most widely used method for aquatic product preservation. "Frozen aquatic products" obtained at -18-40°C are popular among consumers because they maintain flavor and nutrients, allow for long-term storage, and meet the seafood needs of inland consumers.

[0003] Freezing aquatic products and keeping them at low temperatures allows for long-term storage. When stored below -20°C after quick freezing, the effects of bacteria are almost negligible; however, some chemical reactions, such as fat oxidation, protein denaturation, enzyme action, changes in muscle tissue, and water evaporation, can also occur slowly during storage, affecting the quality of frozen products. These changes are usually related to the freezing method (such as rapid freezing and slow freezing). The change that has the greatest impact on the quality of oily fresh fish during frozen storage is the denaturation of fat and protein. The denaturation of frozen fish fat protein is determined by many factors, including freezing temperature and storage time, packaging, freeze-thaw rate, temperature fluctuations, and repeated freeze-thaw cycles.

[0004] Tian Fang et al. (2022) disclosed a graphene-assisted radiofrequency thawing technology (CN115299488 A) for improving the thawing quality of fish meat. The method comprises the following steps: the frozen fish meat is plastic-sealed and then immersed in a thawing medium solution for radiofrequency thawing, wherein the thawing medium is one or more of graphene nanoparticles, graphene oxide nanoparticles, and magnetic graphene oxide nanoparticles. The present invention effectively improves the heat transfer efficiency of frozen fish fillets during radiofrequency thawing by using a thawing medium, improves the problem of uneven thawing, thereby reducing water loss, protein denaturation, and microbial contamination of the fish meat, and slows down the deterioration of the sensory quality of the fish meat. The radiofrequency thawing used in this patent will cause fat oxidation, thereby affecting the quality of the product, and is also unable to highly restore high-fat fresh fish. The present invention adds a fat oxidation inhibitor and synergistically acts with an electric field, and at the same time uses a magnetic field combined with ultrasonic immersion freezing, and nano zinc oxide combined with pulsed microwave thawing to reduce product damage and achieve high-restoration thawing.

[0005] Jiang Qiyong et al. (2021) disclosed a static magnetic field assisted liquefied CO2 pulse spraying quick freezing and efficient freezing method (CN114659316 A). Liquefied CO2 is used as the freezing medium, and pulse spraying is provided to make thick piles of materials freeze evenly and quickly. A static magnetic field generating device is provided to assist in freezing, which can reduce the size of ice crystals. The freezing method includes vacuuming, pre-cooling and CO2 pressurization, magnetic field-assisted quick freezing, and deep freezing. This method combines CO2 pressurization pretreatment and pulse spraying to significantly reduce the freezing time, the ice nucleation process is regulated, and the freezing is uniform. The conditions required for the freezing process involved in this invention are complex, and there may be a risk of carbon dioxide leakage. The freezing and thawing conditions used in the present invention are highly safe.

[0006] The frozen meat thawing method invented by Liu Ye et al. (2022) (CN 115176835 A) includes ohmic heating of frozen meat placed between paired electrode plates in a conductive thawing liquid, wherein the electrode plates are not in contact with the frozen meat during the heating and thawing process, and the gap between them is filled with thawing liquid as a conductive medium, and wherein the electric field strength between the electrode plates is gradually reduced as the frozen meat is partially thawed during the heating and thawing process to maintain a predetermined thawing power range. This invention is conducive to achieving uniform thawing of frozen meat, but the thawing liquid used therein may contaminate the product and cause quality deterioration, which cannot achieve good recovery. The freezing conditions used in this patent are safe and controllable, and efficient freezing is achieved while preserving product quality.

[0007] Therefore, the high-fat fresh fish storage and transportation industry urgently needs a method that can reduce fat oxidation, achieve rapid high-quality freezing, and high-recovery thawing. Summary of the Invention

[0008] The present invention aims to prevent fat oxidation by adding fat oxidation protective agents, and rapid immersion freezing in an ultrasonic magnetic field, and microwave combined with nanoparticle thawing to achieve high-quality freezing and high-recovery thawing. Common high-fat fresh fish is used as the main raw material, and the process goes through raw material preparation, freezing, and thawing. The present invention uses rosemary extract and gallic acid combined with electric field synergy as pretreatment, ultrasonic and magnetic field combined immersion freezing, and microwave combined with nanoparticle thawing to minimize the quality loss of fresh samples after freezing and thawing, thereby achieving high-quality freezing and high-recovery thawing. After using the above-mentioned treatment, the quality of subsequent fresh fish is significantly improved, such as reducing thawing loss, retaining nutrients, improving sensory quality, and delaying fat oxidation.

[0009] In order to achieve the above technical objectives, the technical solution of the present invention is:

[0010] A composite method for high-quality quick freezing and high-recovery thawing of oily fresh fish mainly comprises the following steps:

[0011] (1) Sample pre-freezing treatment: Fresh fish were cut into even-sized pieces, and the samples were pre-treated with a mixture of rosemary extract and gallic acid, supplemented with electrostatic field treatment, and then pre-cooled at 4°C;

[0012] (2) Sample freezing: placing the pre-cooled fresh fish sample obtained in step (1) into a magnetic field ultrasonic freezing device, and freezing by immersion in a magnetic field combined with pulsed ultrasound;

[0013] (3) Sample thawing: Nanographene and nanozinc oxide were evenly applied on the surface of frozen fresh fish and placed in a pulse microwave device for thawing.

[0014] In the step (1), the fresh fish is cut into pieces with a length of 3-5 cm.

[0015] The rosemary extract and gallic acid in step (1) are both naturally extracted powders, and the two are mixed into a mixed solution in a ratio of 1:3 to 1:5 w / w; the mixed solution is directly added to the fresh fish and mixed for 10-20 minutes, and then the treated fresh fish is placed in a polyethylene ziplock bag; the amount of the rosemary extract and gallic acid is 0.01% to 0.03% of the mass of the fresh fish sample.

[0016] During the pretreatment process, an electrostatic field is used to assist the antioxidant action. The intensity of the electric field is 100kV / m to 500kV / m. The electric field generating device is a thorn electrode with a generating voltage of 220V.

[0017] Step (2) uses magnetic field combined with pulsed ultrasonic immersion freezing, the freezing temperature is -80°C, and the immersion freezing liquid medium used is a mixture of 90% ethanol, 5% ethylene glycol, and 5% glycerol v / v. The mixed immersion freezing liquid is directly placed in the freezing chamber of the magnetic field ultrasonic freezing equipment.

[0018] The magnetic field strength used in step (2) is 100-500 mT, the voltage is 220 V, and the frequency range of the magnetic field generated by the magnetic field generating unit is 0-100 kHz.

[0019] The power of the ultrasound used in step (2) is 1000-1500W, the ultrasound frequency is 28-40kHz; the ultrasound is pulsed, and the pulse period is 60s, that is, 40s on and 20s off; the voltage is 220V.

[0020] In the step (3), the concentration of graphene and nano zinc oxide is 0.1 mg / kg, and the particle size of graphene and zinc oxide is 0.5-5 nm.

[0021] In the step (3), the ratio of graphene to nano zinc oxide is 1:2-1:5 w / w.

[0022] The microwave power of the thawing process in step (3) is 100-500W, and the microwave frequency is 2450MHz; the microwave action process mode is pulse action, and the pulse period is 60s, that is, working for 45s and stopping for 15s.

[0023] Beneficial effects of the present invention:

[0024] The active ingredients in rosemary extract and gallic acid work by quenching singlet oxygen, scavenging free radicals and terminating lipid auto-oxidation. Adding antioxidants to oils and fats not only provides a strong antioxidant effect, ensuring oil quality, but also has antibacterial and antiviral properties. High-voltage electric fields inactivate enzymes, and combining natural compound antioxidants with high-voltage electric fields can more effectively delay fat oxidation during the freeze-thaw process.

[0025] Magnetic fields are a common physical field. Research has shown that, due to the magnetic effect of living organisms, magnetic field assistance can significantly impact the frozen storage process of foods. Appropriate magnetic field strength can alter the physical and chemical properties of biomacromolecules and cell membranes, effectively scavenging free radicals, improving food preservation and extending shelf life. Magnetic fields can also influence the freezing process of water, reducing the size of ice crystals formed during food freezing, effectively minimizing freezing losses and improving the quality of frozen foods. Pulsed magnetic fields can alter the cell membrane structure of meat products, altering cell metabolism, thereby effectively inhibiting cell apoptosis and extending food shelf life. Magnetic fields can significantly lower the freezing point, reduce ice crystal size, and achieve more uniform ice crystal distribution, beneficially maintaining the freshness and flavor of meat during micro-freezing. Ultrasound can also reduce ice crystal size and minimize freezing damage. Microwave thawing utilizes the electrical properties of the material itself, heating the food being thawed under the influence of an alternating electric field. Due to the deep penetration of microwaves, heating angle effects, energy attenuation, temperature unevenness, and localized overheating can occur during the thawing process. Graphene nanoparticles and magnetic nano-zinc oxide are used as thawing media and combined with microwave technology to thaw frozen fish. Compared with traditional thawing technology, the thawing technology has high heat transfer efficiency and can greatly shorten the thawing time of frozen fish. The improvement of heat transfer efficiency by the thawing medium can also balance the heat distribution of various parts of the frozen fish. Therefore, compared with the single radio frequency thawing technology, it effectively solves the problem of uneven thawing and local overheating. The freezing and thawing technology can effectively reduce water loss, protein denaturation, lipid oxidation and microbial contamination of fish, that is, it slows down the deterioration of the sensory quality of fish and improves the thawing quality of fish.

[0026] The frozen-thawed fresh fish obtained by the method of the present invention has significantly improved thawing efficiency and product quality due to the synergistic effect of rosemary extract and gallic acid combined with an electric field before freezing, the use of a magnetic field and ultrasound in the freezing process, and the use of nanoparticles combined with microwaves in the thawing process. During the freezing and thawing process, the increase of TBA value, TVB-N value, and K value slows down, microorganisms grow slowly, the color difference value does not change significantly compared with fresh samples, the protein and amino acid contents are well preserved, the retention rate of minerals such as iron, zinc, and potassium is greater than 95%, the product hardness is increased by 10%-15% compared with ordinary transportation and sales, and is closer to the hardness of fresh products, and the retention rate of fatty acids such as unsaturated fatty acids is greater than 95% compared with fresh samples. The method is a method for improving the quality of oily fresh fish with slow spoilage, low microbial level, good color, aroma and taste preservation, perfect quality protection, high recovery degree, simple process flow, and suitable for industrial production. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] Example 1: High-quality quick freezing and high-recovery thawing of hairtail

[0029] Fresh hairtail fish were cut into uniformly sized pieces and treated with a powder mixture (rosemary extract and gallic acid (1:3)) at a concentration of 0.01% of the sample's mass. After packaging and sealing, the samples were pre-cooled in an electric field at 150 kV / m for 2 hours. Once the core temperature reached 4°C, the pre-cooled samples were placed in an ultrasonic magnetic field freezing device with a constant magnetic field, ultrasonic pulses, and a pulse cycle of 60 seconds (40 seconds on, 20 seconds off). The ultrasonic power was 1000 W, the frequency was 28 kHz, the magnetic field intensity was 100 mT, and the freezing temperature was -80°C. When the core temperature reached -20°C, the ultrasonic and magnetic fields were turned off, and the samples were stored in a -20°C freezer. During the subsequent thawing process, 0.1 mg / kg of graphene and nano-zinc oxide were added. Microwave power was 200 W, and the microwave application mode was pulsed (60 seconds on, 45 seconds off, 15 seconds off). Thawing was considered complete when the sample center temperature reached 4°C. Thawing time and sample quality before and after thawing were recorded. Physical and chemical properties of hairtail, including total colony count, TBA value, TVB-N value, K value, color, iron and zinc content, texture, cooking loss, and low-field nuclear magnetic resonance, were measured and compared with fresh samples, control group 1 (no pretreatment, conventional freezing and thawing), control group 2 (only antioxidant combined with electrostatic field pretreatment, conventional freezing and thawing), control group 3 (magnetic field combined with ultrasonic immersion freezing, no pretreatment, conventional thawing), and control group 4 (microwave combined with nano-zinc oxide and graphene particle thawing, no pretreatment, conventional freezing) to explore the effect of the combined method.

[0030] The results showed that the TVB-N, TBA and K values ​​of the treated group were significantly lower than those of the untreated group. The total colony count after treatment was reduced by 60% compared with ordinary transportation. The retention rate of minerals such as iron and zinc was greater than 96% compared with fresh products. The retention rate of protein content was greater than 95% compared with fresh samples. The retention rate of minerals such as iron, zinc and potassium was greater than 95%. The retention rate of fatty acids such as unsaturated fatty acids was greater than 95% compared with fresh samples. The hardness was increased by 11% compared with ordinary treatment, which was closer to the hardness of fresh samples.

[0031] Table 1 Total colony counts and physical and chemical indicators of hairtails treated with different methods

[0032]

[0033] Example 2: High-quality quick freezing and high-recovery thawing of salmon

[0034] Fresh salmon was cut into uniformly sized pieces and treated with a powder mixture (rosemary extract and gallic acid (1:4)) at a concentration of 0.015% of the sample weight. After packaging and sealing, the samples were pre-cooled for 2 hours at 300 kV / m. Once the core temperature reached 4°C, the pre-cooled samples were placed in an ultrasonic magnetic field freezer with a constant magnetic field, 1200 W ultrasonic pulses, a 60-second pulse cycle (40 seconds on, 20 seconds off), an ultrasonic power of 1,200 W, a frequency of 20 kHz, and a magnetic field intensity of 300 mT. The freezing temperature was -80°C. When the core temperature reached -20°C, the ultrasonic and magnetic fields were turned off and the samples were stored in a -20°C freezer. During the subsequent thawing process, 0.23 mg / kg of graphene and nano-zinc oxide were added. Microwave power was 350 W, and the microwave application mode was pulsed (60 seconds on, 45 seconds off, 15 seconds off). Thawing was considered complete when the center temperature of the sample reached 4°C. Thawing time and sample quality before and after thawing were recorded. Physical and chemical properties of the salmon, including total colony count, TBA value, TVB-N value, K value, color, iron and zinc content, texture, cooking loss, and low-field nuclear magnetic resonance, were measured and compared with fresh samples, control group 1 (no pretreatment, conventional freezing and thawing), control group 2 (only antioxidant combined with electrostatic field pretreatment, conventional freezing and thawing), control group 3 (magnetic field combined with ultrasonic immersion freezing, no pretreatment, conventional thawing), and control group 4 (microwave combined with nano-zinc oxide and graphene particle thawing, no pretreatment, conventional freezing) to explore the effect of the combined method.

[0035] The results showed that the TVB-N, TBA and K values ​​of the treated group were significantly lower than those of the untreated group. The total colony count after treatment was reduced by 65% ​​compared with ordinary transportation, the protein content was retained at a rate of greater than 96% compared with fresh products, the retention rate of minerals such as iron, zinc and potassium was greater than 95%, the hardness was increased by 12% compared with ordinary treatment, closer to the hardness of fresh samples, and the content of fatty acids such as unsaturated fatty acids was retained at a rate of greater than 96% compared with fresh samples.

[0036] Table 2 Total colony counts and physicochemical indicators of salmon treated with different methods

[0037]

[0038] Example 3: High-quality quick freezing and high-recovery thawing of eels

[0039] Fresh eels were cut into uniformly sized pieces and treated with a powder mixture (rosemary extract and gallic acid (1:5)) at a concentration of 0.02% of the fresh fish sample mass. After packaging and sealing, the samples were pre-cooled in an electric field at 450 kV / m for 2 hours. Once the core temperature reached 4°C, the pre-cooled samples were placed in an ultrasonic magnetic field freezer with a constant magnetic field, ultrasonic pulses operating for a 60-second pulse cycle (40 seconds on, 20 seconds off). The ultrasonic power was 1600 W, the frequency was 40 kHz, the magnetic field intensity was 500 mT, and the freezing temperature was -80°C. When the core temperature reached -20°C, the ultrasonic and magnetic fields were turned off and the samples were stored in a -20°C freezer. During the subsequent thawing process, 0.32 mg / kg of graphene and nano-zinc oxide were added. Microwave power was 450 W, and the microwave application mode was pulsed for 60 seconds (45 seconds on, 15 seconds off). Thawing was considered complete when the center temperature of the sample reached 4°C. Thawing time and sample quality before and after thawing were recorded. Physical and chemical properties of the eels, including total colony count, TBA value, TVB-N value, K value, color, iron and zinc content, texture, cooking loss, and low-field nuclear magnetic resonance, were measured and compared with fresh samples, control group 1 (no pretreatment, conventional freezing and thawing), control group 2 (only antioxidant combined with electrostatic field pretreatment, conventional freezing and thawing), control group 3 (magnetic field combined with ultrasonic immersion freezing, no pretreatment, conventional thawing), and control group 4 (microwave combined with nano-zinc oxide and graphene particle thawing, no pretreatment, conventional freezing) to explore the effect of the combined method.

[0040] The results showed that the TVB-N, TBA and K values ​​of the treated group were significantly lower than those of the untreated group. The total colony count after treatment was reduced by 65% ​​compared with ordinary transportation, the protein content was retained at a rate of more than 96% compared with fresh products, the retention rate of minerals such as iron, zinc and potassium was more than 95%, the hardness was increased by 12% compared with ordinary treatment, closer to the hardness of fresh samples, and the content of fatty acids such as unsaturated fatty acids was retained at a rate of more than 97% compared with fresh samples.

[0041] Table 3 Total colony counts and physical and chemical indicators of eels treated with different methods

[0042]

[0043]

Claims

1. A composite method for high-quality quick freezing and high-recovery thawing of oily fresh fish, characterized in that: The main steps include: (1) Sample pre-freezing treatment: Fresh fish were cut into even-sized pieces, and the samples were pre-treated with a mixture of rosemary extract and gallic acid, supplemented with electrostatic field treatment, and then pre-cooled at 4°C; The rosemary extract and gallic acid are both naturally extracted powders, and the two are mixed into a mixed solution in a ratio of 1:3 to 1:5 w / w; the mixed solution is directly added to the fresh fish and mixed for 10-20 minutes, and then the treated fresh fish is placed in a polyethylene ziplock bag; the amount of the rosemary extract and gallic acid is 0.01% to 0.03% of the mass of the fresh fish sample; The electrostatic field treatment has an electric field strength of 100 kV / m to 500 kV / m, an electric field generating device is a thorn electrode, and a generating voltage of 220V; (2) Sample freezing: the pre-cooled fresh fish sample obtained in step (1) is placed in a magnetic field ultrasonic freezing device, and is frozen by immersion in a magnetic field combined with pulsed ultrasound; the freezing temperature is -80°C, and the immersion freezing liquid medium used is a mixture of 90% ethanol, 5% ethylene glycol, and 5% glycerol v / v, and the mixed immersion freezing liquid is directly placed in the freezing chamber of the magnetic field ultrasonic freezing device; The magnetic field strength is 100-500 mT, the voltage is 220 V, and the frequency range of the magnetic field generated by the magnetic field generating unit is 0-100 kHz; The ultrasonic power is 1000-1500 W, the ultrasonic frequency is 28-40 kHz; the ultrasonic action is pulsed, the pulse period is 60s, that is, 40s on and 20s off; the voltage is 220V; (3) Sample thawing: Nano-graphene and nano-zinc oxide were evenly spread on the surface of frozen fresh fish and placed in a pulse microwave device for thawing; the concentration of the graphene and nano-zinc oxide was 0.1 mg / kg, and the particle size of the graphene and zinc oxide was 0.5-5 nm; the ratio of graphene to nano-zinc oxide was 1:2-1:5 w / w; the microwave power during the thawing process was 100-500 W, and the microwave frequency was 2450 MHz; the microwave action process mode was pulse action, and the pulse period was 60 s, that is, working for 45 s and stopping for 15 s.

2. A composite method for high-quality quick freezing and high-recovery thawing of oily fresh fish according to claim 1, characterized in that: In the step (1), the fresh fish is cut into pieces with a length of 3-5 cm.

Images