Process for processing grass carp fillets by combining alkaline water with preservative

Abstract

The invention discloses a process for processing grass carp fillets by combining alkaline water with a preservative. The process comprises the following steps: putting pretreated grass carp slices into a purified water tank with water, controlling the working power of the purified water tank to be 380-550W, keeping the temperature of the water in the purified water tank to be 20 + / -10 DEG C, carrying out electrolytic treatment for 1-10 minutes, and draining the treated fish slices; and soaking the obtained grass carp slices in a preservative for 1-10 minutes, performing sterile packaging, and performing cold storage in a refrigerator. According to the invention, the fresh grass carp fillets are treated through the combination of the purification water tank pretreatment and the preservative, so that the content of microorganisms in the grass carp fillets is reduced, the long-time soaking of a single high-concentration preservative and the influence of the single high-concentration preservative on the appearance and color of the fillets are effectively avoided, the shelf life is effectively prolonged by 3-8 days, and the quality of the fillets is well protected.

Description

Technical Field

[0001] The invention relates to a method for processing fish fillets in food purification technology, and in particular to a process for processing grass carp fillets by combining alkaline water with a preservative. Background Art

[0002] my country is one of the world's major fishing countries. According to the statistics of the global aquaculture market from 2018 to 2022, the growth rate of fish consumption is 5.15%, which has exceeded the growth rate of the global population. Freshwater fish is rich in nutrition, with a water content of up to 80%, a protein content of 15-25%, and a relatively low fat content (1.3%), which is mainly composed of unsaturated fatty acids. In addition, fish meat is also rich in vitamins, such as V A 、V D and V E Therefore, accelerating the research on freshwater fish processing is crucial to maintaining the quality of freshwater fish, human health and the development of my country's aquaculture economy.

[0003] Grass carp (Ctenopharyngodon idellus), also known as white carp, is one of the famous "four major carps" in China and occupies an important economic position in China's fishery market. Grass carp has white and tender meat, good tenderness, few bones, and delicious taste. It is a high-protein, low-fat, high-quality protein food source. The unsaturated fatty acids in the muscle have important benefits for promoting blood circulation in the human body and improving cardiovascular diseases. In addition, the trace elements in grass carp have the effects of anti-aging, beauty care, and reducing the risk of tumors.

[0004] The pretreatment of fresh aquatic fish products is relatively time-consuming, including complex processes such as slaughtering, evisceration, descaling, and skinning. At present, consumers' eating habits have gradually changed from food and clothing-oriented to health and nutrition-oriented. As a new revolution in the kitchen, pre-packaged fresh aquatic food has become a new consumption model today, promoting social and economic development and consumption transformation. Pre-packaged fresh food solves the difficulty of consumers in choosing ingredients. Its convenient production greatly saves cooking time, improves work efficiency and food quality and safety, and brings a new revolution in the kitchen to consumers in a fast-paced life. In addition, the pre-prepared fresh food industry can boost agricultural product consumption, reduce agricultural product losses, better ensure food safety, and reduce pollutant emissions.

[0005] New antibacterial methods are widely used to avoid the adverse effects of heat treatment on food and better maintain the quality of food. At present, the application of electrolyzed water in fish preservation is mainly acidic electrolyzed water, and it mainly causes the level of active oxygen in fish to increase through oxidation reaction, so as to effectively inactivate the level of microorganisms and improve the quality of fish preservation. Studies have reported that alkaline water has limitations in fish preservation, such as poor stability. When the power is turned off, the alkalinity of the water is immediately reduced to the original water, which is very easy to lose its unique functional characteristics.

[0006] Chinese invention patent CN102960425B discloses a method for preserving American redfish using acidic electrolyzed water, comprising the following steps: 1) pretreatment of American redfish; 2) spraying treatment with acidic electrolyzed water; 3) soaking treatment with acidic electrolyzed water, the soaking time being 25 to 35 minutes; 4) freezing point injection treatment; 5) vacuum packaging; 6) ice temperature preservation. Chinese invention patent application CN113662036A discloses the use of acidic electrolyzed water in sterilization and preservation of small yellow croaker, the steps comprising: killing small yellow croaker, cleaning and standby; soaking small yellow croaker in acidic electrolyzed water with a pH value of 4 to 6 for 2 to 8 hours, and maintaining the ambient temperature at 4 to 25°C. However, the soaking time of Chinese invention patent CN102960425 is 25-35 minutes, and the soaking time used in Chinese invention patent application CN113662036A is as high as 2 to 8 hours, and the long-term soaking of fish meat in acidic electrolyzed water containing a large amount of sodium hypochlorite has certain damage to its appearance, color and fish meat quality.

[0007] The prior art also uses preservatives or similar measures to preserve fish, but there is also the problem of affecting the texture of fish meat. For example, Chinese invention patent CN110915887B discloses a composite biological preservative and its application, the composite biological preservative includes Lactobacillus rhamnosus and tea polyphenols, and uses Lactobacillus rhamnosus SCB0119 and 0.01% to 2.0% tea polyphenols for composite preservation, but studies have shown that the L* value of fish meat after soaking in tea polyphenols decreases significantly, and the a* value is relatively high, which has a huge impact on the appearance and color of the fish meat, which may be caused by soaking in a high concentration of tea polyphenols. Chinese invention patent application CN107494697A discloses a whole fish preservation method for grass carp, firstly, the fresh fish body to be processed is placed in a packaging bag containing Nisin and ε-polylysine aqueous solution, and after sealing, an ultra-high pressure of 100 to 300 MPa is applied and the pressure is maintained for 5 to 20 minutes, and after the pressure is released, the water is first extracted, and then vacuum-sealed and refrigerated at 0 to 4°C. The polylysine used in this method can extend the shelf life of grass carp by 3 to 5 days, but this technology also has the limitation that ultra-high pressure treatment can cause the fish meat to become hard or white in color. Summary of the invention

[0008] In order to solve the current technical defects such as the long soaking time of acidic electrolyzed water and the damage of sodium hypochlorite produced to the texture of fish meat and the impact on human health, as well as the impact of soaking in a composite preservative on the appearance and color of fish meat, the purpose of the present invention is to provide a green, safe, low-energy consumption process for processing grass carp fillets using alkaline water combined with a preservative, which can maintain the color of the fillets while reducing the total number of colonies in the fish meat and significantly extend the shelf life.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0010] A process for processing grass carp fillets using alkaline water combined with a preservative comprises the following steps:

[0011] Pre-process the fresh grass carp, clean it and collect the grass carp fillets;

[0012] Put the grass carp fillet into a purification tank with water, control the working power of the purification tank to 380-550W, maintain the temperature of the water in the purification tank to 20±10℃, electrolyze for 1-10min, and drain the treated fish fillet;

[0013] The obtained grass carp fillets are soaked in a preservative for 1 to 10 minutes, aseptically packaged, and refrigerated in a refrigerator.

[0014] To further achieve the purpose of the present invention, preferably, the pretreatment is to slaughter, eviscerate, descale and skin the fresh grass carp.

[0015] Preferably, the cleaning is to clean the grass carp fillets obtained by pretreatment with running water.

[0016] Preferably, the body of the purified water tank is made of titanium dioxide material, and an electrolytic water generator and an LED ultraviolet lamp are installed on the side of the tank; the electrolytic water generator is provided with an array of cathode and anode exchange electrodes and a filter.

[0017] Preferably, the electrolytic treatment time is 3 to 8 minutes.

[0018] Preferably, the draining of water is achieved by aseptic ventilation.

[0019] Preferably, the preservative is ε-polylysine or tea polyphenols.

[0020] Preferably, the mass concentration of the ε-polylysine is 0.10-1.00%; the mass concentration of the tea polyphenols is 0.02%-0.08%.

[0021] Preferably, the soaking time is 3 to 5 minutes.

[0022] Preferably, the refrigeration temperature of the refrigerator is 4°C to 8°C.

[0023] Compared with the prior art, the present invention has the following advantages, disadvantages and beneficial effects:

[0024] 1) The present invention utilizes alkaline water prepared in a purified water tank in combination with a preservative to treat grass carp fillets, which can significantly reduce the concentration of a simple composite preservative, and has a better control effect on microorganisms, maintains the original color of the fresh fish fillets, and slows down the change in the quality of the fish fillets.

[0025] 2) Compared with simple soaking in ordinary alkaline water, the alkaline water in the purified water tank promotes the hydrophobic interaction between proteins, forming a more ordered structure, making it easier for low-concentration tea polyphenols or preservatives represented by ε-polylysine to combine with free amino acids on the protein surface, thereby effectively inhibiting the growth of microorganisms during storage.

[0026] 3) The alkaline water used in the present invention is prepared from original tap water in a purified water tank with a certain catalytic effect. A short period of electrolysis can obtain stable weak alkaline reduced water, and its pH value is maintained at about 9.30; no sodium hypochlorite is produced during the treatment process, and compared with acidic electrolyzed water, the sterilization time is short, the energy consumption is low, and it is green and safer.

[0027] 4) The process of processing grass carp fillets with alkaline water combined with a preservative of the present invention has the characteristics of safety, environmental protection, high efficiency, etc., and the shelf life can be extended by 3 to 8 days.

[0028] 5) The preservatives used in the present invention are all from my country's additive standards (GB2760-2014 National Food Safety Standard Food Additives Usage Standard), are non-toxic, low-priced, simple and convenient to process, and are green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Changes in the total bacterial count of grass carp during storage in the Examples and Comparative Examples.

[0030] Figure 2 Changes in volatile basic nitrogen (TVB-N) of grass carp during storage in the Examples and Comparative Examples.

[0031] Figure 3 Changes of thiobarbituric acid (TBARS) in grass carp during storage in Examples and Comparative Examples. DETAILED DESCRIPTION

[0032] In order to better understand the present invention, the present invention is further described below in conjunction with specific drawings and embodiments, but the embodiments of the present invention are not limited thereto.

[0033] In view of the problems of heat treatment sterilization, the equipment currently used for fish preservation often adopts non-thermal sterilization methods such as ozone, ultra-high pressure or acidic electrolyzed water to improve the shelf life of fresh fish. Among them, electrolyzed water has low equipment requirements, low cost, simple processing steps and has a significant effect on improving the quality of fish. The working principle of a general electrolytic cell is to place the positive and negative electrodes in a generator prepared by an anion and cation exchange membrane, use electrolyte as a solvent, and electrolyze it under power-on state to produce electrolyzed water with different acidity and alkalinity at the positive and negative electrodes. In recent years, acidic water prepared by electrolysis has been used as the main sterilization method for fish preservation. However, the soaking time of electrolyzed water for fish preservation in the prior art varies greatly. At a lower temperature, it takes up to 2 to 8 hours to improve its quality (CN113662036A), which greatly increases the working time, and long-term soaking causes the fish to be exposed to light and oxygen environment, which may cause lipid oxidation and damage the appearance and color of the fish to a certain extent.

[0034] At present, alkaline water has been used to remove free radicals, enhance human metabolism, reduce the level of pathogenic microorganisms in food, remove pesticide residues in fruits and vegetables, etc. However, alkaline electrolyzed water has problems such as easy oxidation and instability. In particular, fish treated with ordinary alkaline water is rich in microorganisms. During storage, microorganisms continuously use nutrients such as protein and water in fish to provide conditions for their own growth. This process promotes the corruption of fish protein and produces nitrogen compounds such as amines and biogenic amines.

[0035] The purified water tank used in the present invention is a new type of non-thermal sterilization electrolysis device; the tank body of the purified water tank is made of titanium dioxide material, and an electrolytic water generator and an LED ultraviolet lamp are installed on the side of the tank body; the electrolytic water generator is provided with an array and a filter screen for exchanging cathode and anode electrodes. The titanium dioxide purified water tank has excellent photocatalytic properties, can absorb light energy in the ultraviolet light region, excite electron-hole pairs, and drive the cracking of water. In addition, the titanium dioxide material has high durability, reduces the maintenance and replacement costs of the equipment, and can also effectively reduce the overall energy consumption of the treatment process. After water is injected into the purified water tank, the power is turned on, that is, the electrolysis process is started. As the electrolysis time increases, the water in the purified water tank is bombarded by the LED photocatalysis and electric energy, causing it to undergo continuous cracking, resulting in a gradually increasing trend in the pH value of the tap water in the tank, and the free hydroxide ions in the tank gradually reach a saturated state, so that its pH value is stabilized in an alkaline environment, but the alkaline pH value is within 9.3 and is not high. The electrolytic treatment process of the present invention not only avoids lipid oxidation of fish meat during the treatment process, but also effectively shortens the processing time of raw materials. Moreover, the electrolytic solute is only tap water, so no substances such as hypochlorous acid are produced during the entire electrolytic process, which greatly improves the safety of the raw materials. Conventional electrolysis is a process in which electric current is used to decompose water into hydrogen and oxygen, which increases the cost of the reaction driven by external electric energy and has relatively high energy consumption. In addition, conventional electrolysis technology requires the addition of complex reaction substances to effectively achieve the cleaning effect, and the alkalinity is relatively high, with a pH value generally exceeding 9.3.

[0036] Compared with simple soaking in ordinary alkaline water, the alkaline water in the purification tank promotes the hydrophobic interaction between proteins and forms a more ordered structure, making it easier for low-concentration tea polyphenols or ε-polylysine as preservatives to bind to free amino acids on the surface of proteins, effectively inhibiting the growth of microorganisms during storage. In addition, the fish fillets are treated in the purification tank, and the weak alkaline environment modifies the protein macromolecules, making the arrangement of the protein molecules more compact, which is conducive to improving the quality of the fish; and the compact structure makes the tea polyphenols or ε-polylysine as preservatives soaking in the fish more uniform, which further enhances the stability of the protein structure.

[0037] Based on the synergistic effect of alkaline water and preservatives in the purification tank, the present invention proposes a process for processing grass carp fillets with alkaline water combined with preservatives, using fresh grass carp fillets as raw materials, pre-treating fresh grass carp, collecting grass carp fillets after cleaning; putting grass carp fillets into a purification tank with water, controlling the working power of the purification tank to 380-550W, maintaining the temperature of the water in the purification tank to 20±10℃, electrolyzing for 1 to 10 minutes, draining the treated fillets; soaking the obtained grass carp fillets in the preservative for 1 to 10 minutes, aseptically packaging, and refrigerating in a refrigerator. The core feature of this process is the synergistic effect of alkaline water from the purification tank and the preservative on the fillets, and the specific quantification of the preservative can be determined by testing in combination with the purpose of the present invention.

[0038] Moreover, the process of the present invention is also beneficial to improving the storage shelf life of meat; on the one hand, electrolytic treatment in a purified water tank containing water can remove microorganisms and other substances on the surface of fish meat, so as to achieve the purpose of purifying fish fillets; on the other hand, alkaline water treatment from the purified water tank can promote the orderly three-dimensional spatial arrangement of fish protein structure; on this basis, further immersion in a preservative can also inhibit the reproduction of harmful microorganisms during the storage period, effectively improving the storage shelf life of fish meat.

[0039] The process of the present invention not only reduces the problem of long soaking time in single preservative treatment, but also more effectively solves the effect of high concentration preservative on the appearance and color of fish meat. The low dose of additives is conducive to eliminating consumers' psychological concerns about the health and safety risks of food additives.

[0040] The relevant testing methods involved in the present invention are as follows:

[0041] Determination of L* value: Use a handheld colorimeter to measure its L* value.

[0042] Total colony count: The total live bacterial count of fish fillets during storage was determined according to the method of GB4789.2-2016.

[0043] Volatile basic nitrogen: The volatile basic nitrogen content was determined according to the method of GB 5009.228-2016.

[0044] Thiobarbituric acid: The thiobarbituric acid content was determined according to the method of GB 5009.181-2016.

[0045] Example 1

[0046] A process for processing grass carp fillets using alkaline water combined with a preservative comprises the following steps: slaughtering the fresh grass carp, removing the internal organs, scales and skin, washing it thoroughly with running water, collecting the grass carp fillets, and cutting them into 5*4*3cm 3(length * width * thickness) large and small fish pieces. Place the fish pieces in a purified water tank (professional food purification water tank for food safety) filled with 10℃ tap water and a working power of 380W, and take out the fish pieces after power treatment for 1 minute. Take out the treated fish meat, rinse it again with sterile water to remove residual impurities on the surface; soak it in 0.02% tea polyphenols and let it stand for 1 minute, drain the surface water on the sterile operating table, put it into sterile packaging, and refrigerate it in the refrigerator at 4℃. Take Example 1 at different storage times and measure its volatile basic nitrogen and thiobarbituric acid content. The results are shown in the figure. Figure 2 and 3 .

[0047] Example 2

[0048] A process for processing grass carp fillets using alkaline water combined with a preservative comprises the following steps: slaughtering the fresh grass carp, removing the internal organs, scales and skin, and then thoroughly washing it with running water, collecting the grass carp fillets, and cutting them into 5*4*3cm 3 (length * width * thickness) large and small fish pieces. Place the fish pieces in a purified water tank (food safety professional food purification water tank) filled with 20℃ tap water and its working power is 550W, and take out the fish pieces after power treatment for 5 minutes. Take out the treated fish meat, rinse it again with sterile water to remove residual impurities on the surface; soak it in 0.08% tea polyphenols and let it stand for 10 minutes, drain the surface water on the sterile operating table, put it into sterile packaging, and place it in a refrigerator at 6℃. Take Example 2 at different storage times to measure its L* value, total colony count and thiobarbituric acid content.

[0049] Example 3

[0050] A process for processing grass carp fillets using alkaline water combined with a preservative comprises the following steps: slaughtering the fresh grass carp, removing the internal organs, scales and skin, and then thoroughly washing it with running water, collecting the grass carp fillets, and cutting them into 5*4*3cm 3 (length * width * thickness) large and small fish pieces. Place the fish pieces in a purified water tank (food safety professional purified water tank) filled with 30℃ tap water and a working power of 450W, and take out the fish pieces after power treatment for 10 minutes. Take out the treated fish meat, rinse it again with sterile water to remove residual impurities on the surface; soak it in 0.04% tea polyphenols and let it stand for 5 minutes, drain the surface water on the sterile operating table, put it into sterile packaging, and place it in a refrigerator at 4℃. Take Example 3 at different storage times to measure its total colony count and volatile basic nitrogen content.

[0051] Example 4

[0052] A process for processing grass carp fillets using alkaline water combined with a preservative comprises the following steps: slaughtering the fresh grass carp, removing the internal organs, scales and skin, and then thoroughly washing it with running water, collecting the grass carp fillets, and cutting them into 5*4*3cm 3 (length * width * thickness) large and small fish pieces. Place the fish pieces in a purified water tank (food safety professional food purification water tank) filled with 20℃ tap water and a working power of 450W, and take out the fish pieces after power treatment for 5 minutes. Take out the treated fish meat, rinse it again with sterile water to remove residual impurities on the surface; soak it in 0.1% ε-polylysine and let it stand for 1 minute, drain the surface water on the sterile operating table, put it into sterile packaging, and refrigerate it in a refrigerator at 8℃. Take Example 4 at different storage times to measure its volatile basic nitrogen content.

[0053] Example 5

[0054] A process for processing grass carp fillets using alkaline water combined with a preservative comprises the following steps: slaughtering the fresh grass carp, removing the internal organs, scales and skin, and then thoroughly washing it with running water, collecting the grass carp fillets, and cutting them into 5*4*3cm 3 (length * width * thickness) large and small fish pieces. Place the fish pieces in a clean water tank (food safety professional food purification water tank) filled with 20℃ tap water and a working power of 450W, and take out the fish pieces after power treatment for 1 minute. Take out the treated fish meat, rinse it again with sterile water to remove residual impurities on the surface; soak it in 0.5% ε-polylysine and let it stand for 5 minutes, drain the surface water on the sterile operating table, put it into sterile packaging, and refrigerate it in a refrigerator at 8℃. Take Example 5 at different storage times to measure its L* value, total colony count and thiobarbituric acid content.

[0055] Example 6

[0056] A process for processing grass carp fillets using alkaline water combined with a preservative comprises the following steps: slaughtering the fresh grass carp, removing the internal organs, scales and skin, and then thoroughly washing it with running water, collecting the grass carp fillets, and cutting them into 5*4*3cm 3 (length * width * thickness) large and small fish pieces. Place the fish pieces in a purified water tank (food safety professional food purification water tank) filled with 10℃ tap water and a working power of 380W, and take out the fish pieces after power treatment for 10 minutes. Take out the treated fish meat, rinse it again with sterile water to remove residual impurities on the surface; soak it in 1.0% ε-polylysine and let it stand for 10 minutes, drain the surface water on the sterile operating table, put it into sterile packaging, and refrigerate it in a refrigerator at 4℃. Take Example 6 at different storage times to measure its L* value and volatile basic content.

[0057] Comparative Example 1

[0058] A process for processing grass carp fillets using alkaline water combined with a preservative comprises the following steps: slaughtering the fresh grass carp, removing the internal organs, scales and skin, and then thoroughly washing it with running water, collecting the grass carp fillets, and cutting them into 5*4*3cm 3 (length * width * thickness) large and small fish pieces. Soak the fish meat in alkaline electrolyzed water produced on the market (tap water ionized by Xinkang Fu hydrogen electrolyzed water machine, pH value of 9.5 prepared at the anode) for 10 minutes. Soak in 0.04% tea polyphenols for 5 minutes. Drain the surface water on the sterile operating table, put it into sterile packaging and refrigerate it in a refrigerator at 4°C. Take comparative example 1 at different storage times to determine its L* value, total colony count, volatile basic nitrogen and thiobarbituric acid content.

[0059] Comparative Example 2

[0060] A process for processing grass carp fillets with a preservative, comprising the following steps: slaughtering fresh grass carp, removing the internal organs, scales and skin, washing thoroughly with running water, collecting the grass carp fillets, and cutting them into 5*4*3cm 3 (length * width * thickness) large and small fish pieces. Soak the fish meat in 1.0% ε-polylysine for 10 minutes. Drain the surface moisture on a sterile operating table, put it into sterile packaging, and then refrigerate it in a refrigerator at 6°C. Take comparative example 2 at different storage times to determine its L* value and thiobarbituric acid content.

[0061] Microorganisms are an important indicator of fish quality. Microorganisms promote the degradation of fish protein, causing it to produce unpleasant and unacceptable odors. Figure 1The changes in the total viable counts in the fish meat were compared by soaking in ordinary alkaline electrolyzed water with pH = 9.5 for 10 minutes combined with soaking in 0.04% tea polyphenols for 10 minutes (Comparative Example 1), treating in a purified water tank for 5 minutes combined with soaking in 0.08% tea polyphenols for 10 minutes (Example 2), treating in a purified water tank for 10 minutes combined with soaking in 0.04% tea polyphenols for 5 minutes (Example 3), and treating in a purified water tank for 1 minute combined with soaking in 0.5% ε-polylysine for 5 minutes (Example 5). The results showed that compared with Comparative Example 1, the total viable counts of the fish meat treated in Examples 2, 3 and 5 decreased significantly when stored for 1 day. Among them, the total viable count of Example 5, which had a poor effect in the examples, was 3.20Log CFU / g when stored for 1 day, which was significantly reduced by 1.11Log CFU / g compared with Comparative Example 1, indicating that the effect of ordinary alkaline water soaking treatment combined with preservatives was poor compared with the electrolytic reduced water of the present invention. Compared with simple soaking in ordinary alkaline water, the purified water tank is more conducive to cleaning the microorganisms on the surface of the fish meat, which is conducive to reducing the microorganisms on the surface of the fish meat and further reducing the growth of microorganisms in the fish meat during storage. With the increase of storage time, the total number of colonies in the fish meat of different treatment groups showed an overall upward trend. After the 6th day of Comparative Example 1, the total number of viable bacteria in the fish meat exceeded the standard limit of the total number of colonies of fresh fish meat (7Log CFU / g), which was 7.61Log CFU / g. Among them, the total number of viable bacteria in Example 5 at the time of storage for 6 days was 5.85Log CFU / g, which was significantly reduced by 1.76Log CFU / g compared with Comparative Example 1. Compared with Comparative Example 1, the total number of colonies in the fish meat of each embodiment increased slowly within the 12th day of storage, indicating that the electrolyzed water treatment adopted by the present invention has a better effect of delaying the shelf life of fish meat than general alkaline water soaking. Among them, the total viable count of Example 5 after 12 days of storage was 8.13Log CFU / g, which was significantly reduced by 1.38Log CFU / g compared with Comparative Example 1. In addition, the viable count of Example 2 after 12 days of storage was still lower than 7Log CFU / g, which delayed the unacceptable state by about 8 days compared with the total colony count in Comparative Example 1. The test results confirmed that the alkaline water produced by the purified water tank combined with the preservative can effectively inhibit the growth of microorganisms before and after storage, improve the preservation effect of grass carp during storage, and extend the shelf life of grass carp fillets.

[0062] Volatile basic nitrogen is an indicator for evaluating the freshness of fish meat. Figure 2It can be seen that on the first day of storage, there is no difference in the content of TVB-N between each embodiment and comparative example 1, but as the storage time increases, the TVB-N in the grass carp fillets increases; according to GB 5009.228, the TVB-N limit for freshwater fish is 20 mg / 100 g. The TVB-N of comparative example 1 reached 18.39 mg / 100 g on the sixth day of storage, and exceeded the limit when the storage day reached the ninth day, with its TVB-N reaching 23.66 mg / 100 g. All embodiments delayed reaching the freshness limit value compared with the comparative example. Among them, the TVB-N in the fish meat after treatment in Example 1 was significantly reduced during the storage period, but when the storage day reached 9 days, the TVB-N reached 19.68 mg / 100g, and its quality maintenance effect was lower than that of Example 3 (17.43 mg / 100g), Example 4 (11.94 mg / 100g) and 6 (15.30 mg / 100g). The concentration of ε-polylysine in Example 4 was only 0.1%, and its TVB-N value within 12 days of storage was the lowest. The test results show that the TVB-N content of the examples of the present invention meets the standards within 9 days, which is significantly better than comparative example 1. The time for each group to reach the freshness limit value is divided into 10 days (Example 1), 11 days (Example 3) and more than 12 days (Example 3 and Example 4).

[0063] The test results of the changes of thiobarbituric acid in grass carp fillets treated with comparative examples 1 and 2 and examples 1, 2 and 5 during storage are shown in Figure 3 . In general, as the treatment time increases, the lipid oxidation degree of the grass carp fillets in the examples and comparative examples deepens. After 1 day of storage, the thiobarbituric acid value of the fish meat in Example 2 is higher than that in Comparative Example 1, and its value is 0.057 MDA / Kg. After 6 days of storage, the thiobarbituric acid value of the fish meat in Comparative Example 1 (0.085 MDA / Kg) increases sharply and exceeds the thiobarbituric acid value of Example 2 (0.078 MDA / Kg) stored for 9 days. Within 6 days of storage, the thiobarbituric acid values ​​of the fish meat in Example 5 (0.053 MDA / Kg) and Example 1 (0.050 MDA / Kg) were significantly lower than those in Comparative Example 1 (0.070 MDA / Kg) and Comparative Example 2 (0.062 MDA / Kg), indicating that soaking in 0.02% tea polyphenols or 0.5% ε-polylysine after alkaline water treatment effectively inhibited lipid oxidation of fish meat during storage. However, during the entire storage period, the thiobarbituric acid of each group of fish meat was less than 0.5 mg MDA / Kg, indicating that during storage, the oxidation of fish meat between different treatment groups was within an acceptable range.

[0064] The changes in the brightness values ​​of the appearance of grass carp fillets in each group of Comparative Examples 1, 2 and Examples 2, 5 and 6 were recorded by a colorimeter after storage for 0, 6 and 12 days. The results show that the alkaline electrolyzed water produced on the market and the use of preservatives alone in the general market cannot significantly improve the brightness of the fish meat, but the brightness value of the alkaline water washing from the purification tank combined with the preservative soaking in the present invention is significantly increased. At 0 days of storage, compared with Comparative Examples 1 and 2, the brightness values ​​of Examples 5 and 6 increased significantly, indicating that ordinary alkaline water or ε-polylysine (representing preservatives) soaking alone cannot obtain a better brightness of the fillet appearance. With the increase of storage time, the L* value of each treatment group decreased significantly. However, compared with Comparative Example 1, when stored for 6 days, the brightness values ​​of Examples 5 and 6 increased by 2.6 and 3.2, respectively, indicating that the alkaline water treatment from the purification tank combined with 0.5% ε-polylysine or 1.0% ε-polylysine is beneficial to maintain the brightness of the fish meat. As the storage time increases further, compared with comparative example 2 (immersed in 1.0% ε-polylysine for 10 minutes), the brightness value of the fish meat treated with alkaline water from the purified water tank and then immersed in 1.0% ε-polylysine for 10 minutes significantly increases by 3.7. It can be seen that the fish meat combined with the ε-polylysine preservative and the alkaline water from the purified water tank has a better appearance, and has a significant effect on maintaining the surface brightness value of the fish meat during the entire storage period, and the appearance color of the fish meat is well maintained during the entire storage stage.

[0065] Table 2 Changes in L* value during storage of fresh grass carp fillets

[0066]

[0067] ** indicates p<0.05 compared with the blank group; *** indicates p<0.01 compared with the blank group; **** indicates p<0.001 compared with the blank group.

[0068] In summary, compared with commercially available fresh fish fillets, the fresh grass carp fillets prepared by the present invention can reduce the total number of colonies in the fish meat while maintaining its color and significantly prolong its shelf life by using alkaline water from a purified water tank with an appropriate negative redox potential combined with a preservative.

[0069] It should be noted that the processing method of the present invention is not limited to the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A process for processing grass carp fillets using alkaline water combined with a preservative, characterized in that The steps include: Pre-process the fresh grass carp, clean it and collect the grass carp fillets; Put the grass carp fillet into a purification tank with water, control the working power of the purification tank to 380-550W, maintain the temperature of the water in the purification tank to 20±10℃, electrolyze for 1-10min, and drain the treated fish fillet; The obtained grass carp fillets are soaked in a preservative for 1 to 10 minutes, aseptically packaged, and refrigerated in a refrigerator.

2. The process for processing grass carp fillets using alkaline water combined with a preservative according to claim 1, characterized in that: The pretreatment is to slaughter, eviscerate, descale and skin the fresh grass carp.

3. The process for processing grass carp fillets using alkaline water combined with a preservative according to claim 1, characterized in that: The cleaning is to clean the grass carp fillets obtained by pretreatment by washing with running water.

4. The process for processing grass carp fillets using alkaline water combined with a preservative according to claim 1, characterized in that: The tank body of the water purification tank is made of titanium dioxide material, and an electrolytic water generator and an LED ultraviolet lamp are installed on the side of the tank; the electrolytic water generator is provided with an array of cathode and anode electrode exchange and a filter screen.

5. The process for processing grass carp fillets using alkaline water combined with a preservative according to claim 1, characterized in that: The electrolytic treatment time is 3 to 8 minutes.

6. The process for processing grass carp fillets using alkaline water combined with a preservative according to claim 1, characterized in that: The draining of water is achieved through aseptic ventilation.

7. The process for processing grass carp fillets using alkaline water combined with a preservative according to claim 1, characterized in that: The preservative is ε-polylysine or tea polyphenols.

8. The process for processing grass carp fillets using alkaline water combined with a preservative according to claim 7, characterized in that: The mass concentration of the epsilon-polylysine is 0.10-1.00%; the mass concentration of the tea polyphenols is 0.02%-0.08%.

9. The process for processing grass carp fillets using alkaline water combined with a preservative according to claim 1, characterized in that: The soaking time is 3 to 5 minutes.

10. The process for processing grass carp fillets using alkaline water combined with a preservative according to claim 1, characterized in that: The refrigeration temperature of the refrigerator is 4°C to 8°C.

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