Freezing and unfreezing method of tilapia meat

Abstract

The invention discloses a freezing and unfreezing method of tilapia meat, which comprises the following steps: pretreatment of tilapia meat: slaughtering fresh tilapia, and uniformly slicing tilapia spine meat with the size of 5cm * 5cm * 2cm; preparing an anti-freezing agent: accurately weighing sodium tripolyphosphate accounting for 0.16% of the total mass of the tilapia fillets, sodium pyrophosphate accounting for 0.08% of the total mass of the tilapia fillets, sodium hexametaphosphate accounting for 0.12% of the total mass of the tilapia fillets and trehalose accounting for 4% of the total mass of the tilapia fillets Liquid nitrogen rapid freezing treatment: soaking the treated tilapia fillets in an antifreeze agent, then taking out the tilapia fillets, packaging the tilapia fillets with a sealing bag, placing the tilapia fillets in a tray, rapidly freezing the tilapia fillets with liquid nitrogen, and then placing the tilapia fillets in a freezer for freezing And carrying out unfreezing treatment in a stable and constant magnetic field: putting the tray in a-20 DEG C magnetic-field-free environment for unfreezing treatment for 24 hours, and then putting the tray in a stable and constant magnetic field environment for unfreezing. By adopting the antifreeze agent, the liquid nitrogen quick freezing technology and the steady magnetic field thawing technology, the juice loss rate is remarkably reduced, the color, the smell and other sensory characteristics, the elasticity and the hardness of the thawed tilapia meat can be effectively maintained, and the quality and the fresh degree of the tilapia meat can be maintained.

Description

Technical Field

[0001] The invention relates to the technical field of aquatic product storage and processing, in particular to a freezing and thawing method of tilapia meat. Background Art

[0002] Tilapia, also known as African crucian carp, belongs to the family Cichlidae of the order Perciformes. It has a fast growth rate and a short maturity period, and is the main farmed aquatic product in my country. As a source of high-quality protein, tilapia has a complete range of amino acids and is easily digested and absorbed by the human body. It has a good taste and high economic and nutritional value, and is deeply loved by consumers. However, due to the high water content of tilapia itself and its delicate muscle tissue, it is easily affected by microorganisms and endogenous enzymes, and unsaturated fatty acids are very prone to fat oxidation, which shortens the shelf life. During the thawing process, protein decomposition to produce amino acids and nitrogen-containing compounds to produce alkaline nitrogen often occur simultaneously, resulting in changes in the color, smell and flavor of the fish, deterioration of the quality of the fish, loss of juice, reduced nutrition, production of harmful substances, rapid decline in freshness and quality, and corruption and deterioration.

[0003] In order to inhibit the growth and reproduction of microorganisms and the oxidation of fat and protein during the thawing process, reduce the activity of endogenous enzymes, maintain the quality and freshness of tilapia meat, and extend the shelf life, it has become a concern to explore an effective method. At present, the main thawing methods are chemical methods and physical methods. The chemical method is to improve the thawing quality by adding antifreeze. Common antifreezes include compound phosphates, sugars and protein hydrolysis. Compound phosphates have obvious effects on maintaining the color, shape, aroma and taste of food, and can increase the hydrophilicity of actomyosin to promote the stability of fish protein. Trehalose has also become a research hotspot as a low-sweetness, low-calorie antifreeze. Physical methods can be divided into two categories: traditional thawing technology and new thawing technology. The new thawing technology mainly includes magnetic field thawing method, ultrasonic thawing method, high-voltage electrostatic thawing method, microwave thawing method and radio frequency thawing method. Among them, magnetic field thawing method is a new thawing method with low energy consumption, convenient operation, green and environmental protection, and broad prospects. These methods provide new ideas for the development of frozen tilapia thawing methods.

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a freezing and thawing method for tilapia meat, which adopts liquid nitrogen rapid freezing technology, antifreeze agent and constant magnetic field thawing technology, has low energy consumption, convenient operation, and is green and environmentally friendly. It can effectively reduce the juice loss rate of frozen tilapia fillets after thawing, maintain its elasticity and hardness, and maintain the quality and freshness of the tilapia fillets after thawing. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a freezing and thawing method for tilapia meat.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A freezing and thawing method for tilapia meat comprises the following steps:

[0008] (1) Pretreatment of tilapia meat: fresh tilapia was slaughtered and the fish spine was evenly sliced ​​into slices of 5 cm × 5 cm × 2 cm in size;

[0009] (2) Preparation of antifreeze agent: accurately weigh 0.16% of sodium tripolyphosphate, 0.08% of sodium pyrophosphate, 0.12% of sodium hexametaphosphate and 4% of trehalose based on the total weight of tilapia fillet to prepare antifreeze agent;

[0010] (3) Liquid nitrogen rapid freezing treatment: soak the tilapia fillets treated in step (1) in an antifreeze agent, take them out, package them in a sealed bag, place them in a tray, quickly freeze them with liquid nitrogen, and then place them in a freezer for freezing treatment;

[0011] (4) Thawing treatment in a steady magnetic field: The tray of step (3) is placed in a -20°C non-magnetic field environment for 24 hours for thawing, and then placed in a steady magnetic field environment for thawing.

[0012] Preferably, in step (2), 0.16% sodium tripolyphosphate, 0.08% sodium pyrophosphate, 0.12% sodium hexametaphosphate and 0.04% water are first mixed into a composite phosphate solution, and then 4% trehalose is added to obtain the antifreeze agent.

[0013] Preferably, the antifreeze soaking time of the tilapia fillets in step (3) is 1-2 minutes.

[0014] Preferably, the tray in step (3) is a food-grade PET tray, and the sealed bag is a food-grade PE sealed bag.

[0015] Preferably, the freezer in step (3) is an ultra-low temperature refrigerator with a non-magnetic field at -80°C.

[0016] Preferably, in step (3), the tilapia fillets are sealed in a sealed bag to prevent a large amount of water loss.

[0017] Preferably, in step (4), the magnetic field strength is 3-5 mT, the thawing temperature is 8-10° C., and the thawing time is 140-160 min.

[0018] Preferably, the constant magnetic field in step (4) utilizes a Helmholtz coil, and the magnitude of the magnetic field is controlled by adjusting the current of the coil.

[0019] Compared with the related art, the beneficial effects of the present invention are:

[0020] (1) The present invention provides a new method for freezing and thawing tilapia meat, which has low energy consumption, convenient operation, and is green and environmentally friendly.

[0021] (2) The liquid nitrogen rapid freezing technology of the present invention and the antifreeze agent combinedly process tilapia meat, which can rapidly freeze tilapia, increase the hydrophilicity of actomyosin, and promote the stability of fish protein, and can effectively maintain the color, smell and other sensory characteristics of the fish meat after thawing, making it bright and shiny.

[0022] (3) The present invention utilizes a steady magnetic field thawing technology to significantly reduce the juice loss rate of frozen tilapia fillets after thawing, and the juice loss rate is reduced by 60%-80% compared with that of the fillets not treated by the method. At the same time, the elasticity and hardness of the tilapia fillets are maintained, and the muscle tissue is made tight, thereby maintaining its quality and freshness. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Process flow chart of the freezing and thawing method for tilapia.

[0024] Figure 2 These are the juice loss rate, hardness, and elasticity curves of thawed tilapia fillets under different gradient magnetic field intensities.

[0025] Figure 3 Radar chart of sensory scores of thawed tilapia fillets under different gradient magnetic field intensities. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] Experimental materials and instruments:

[0028] Tilapia fillets: Select live tilapia of similar weight from the same manufacturer and batch, slaughter them quickly after purchase, and slice them evenly to a size of 5cm×5cm×2cm. Antifreeze: Accurately weigh 0.16% of sodium tripolyphosphate, 0.08% of sodium pyrophosphate, 0.12% of sodium hexametaphosphate and 4% of trehalose to prepare antifreeze. Soak the treated tilapia fillets in the antifreeze for 1-2 minutes, take them out, seal them in a sealed bag, place them in a tray, quickly freeze them with liquid nitrogen, and place them in a -80 freezer for freezing.

[0029] Refrigeration system and equipment: ordinary freezer; 0-10mT magnetoelectric coupling freezer and refrigerator.

[0030] Detection method:

[0031] Determination of juice loss rate

[0032] Weigh the samples before thawing (M0). After thawing, use absorbent paper to gently absorb the surface moisture of the samples until there is no obvious water sheen on the surface, and weigh them immediately (M1). Each group of samples was tested in parallel three times. The calculation formula for the juice loss rate (Driploss, DL) is as follows:

[0033] DL(%)=(m0-m1) / m0×100%

[0034] Among them, m0 and m1 are the mass of the sample before thawing and after thawing and water absorption, respectively (in g).

[0035] Determination of texture:

[0036] The texture (hardness) of thawed tilapia fillets was measured using a P / 36R cylindrical probe. The test rate and return rate were both 1 mm / s, the deformation was 50%, and the trigger force was 25 g. The sample was tested 6 times, and the average value was taken after removing the maximum and minimum values.

[0037] Sensory evaluation

[0038] The sensory evaluation was conducted by 10 trained professionals to evaluate the quality of tilapia fillets after thawing under different thawing conditions based on color, tissue morphology, smell and muscle elasticity. The specific scoring rules are shown in Table 1.

[0039] Table 1 Criteria of sensory evaluation for tilapia fillets

[0040]

[0041] The technical solution, its implementation process and principle, etc. will be further explained in conjunction with several embodiments as follows. However, it should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described in the following (embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here.

[0042] Example 1

[0043] The quality and freshness of tilapia meat are maintained by using antifreeze, liquid nitrogen rapid freezing technology and constant magnetic field thawing technology. The specific method includes the following steps:

[0044] (1) Pretreatment of tilapia meat: fresh tilapia was slaughtered and the fish spine was evenly sliced ​​into slices of 5 cm × 5 cm × 2 cm in size;

[0045] (2) Preparation of antifreeze: Accurately weigh 0.16% sodium tripolyphosphate, 0.08% sodium pyrophosphate, 0.12% sodium hexametaphosphate and 4% trehalose, accounting for the total weight of tilapia fillets, to prepare the antifreeze. First, 0.16% sodium tripolyphosphate, 0.08% sodium pyrophosphate, 0.12% sodium hexametaphosphate and 0.04% water are mixed into a composite phosphate solution, and then 4% trehalose is added, and the balance is distilled water, and stirred to blend, and the antifreeze is prepared.

[0046] (3) Liquid nitrogen rapid freezing treatment: soak the tilapia fillets treated in step (1) in an antifreeze for 1-2 min, take them out, package them in a sealed bag, place them in a tray, quickly freeze them with liquid nitrogen, and place them in a -80°C freezer for freezing treatment;

[0047] (4) Steady magnetic field thawing treatment: After placing the tray in step (3) in a non-magnetic field environment at -20°C for 24 hours, thawing it in a static magnetic field of 1 mT and a temperature of 8°C for 150 minutes;

[0048] The juice loss rate, hardness, elasticity and sensory score of the thawed tilapia fillets were measured. The results showed that the juice loss rate of the thawed tilapia fillets was 5.63%, the hardness was 13.58, the elasticity was 5.73, and the sensory score was 8.58.

[0049] Example 2

[0050] The specific implementation method is the same as Example 1, except that the magnetic field strength is adjusted to 3 mT. The thawed tilapia fillets were subjected to juice loss rate detection, hardness, elasticity measurement, and sensory evaluation, and the results are shown as follows:

[0051] The juice loss rate of thawed tilapia fillets was 4.50%, the hardness was 13.20, the elasticity was 5.17, and the sensory score was 9.36.

[0052] Example 3

[0053] The specific implementation is the same as that of Example 1, except that the magnetic field strength is adjusted to 5 mT.

[0054] The thawed tilapia fillets were tested for juice loss rate, hardness, elasticity, and sensory evaluation, and the results are as follows:

[0055] The juice loss rate of thawed tilapia fillets was 5.30%, the hardness was 10.22, the elasticity was 4.39, and the sensory score was 8.69.

[0056] Example 4

[0057] The specific implementation method is the same as Example 1, except that the magnetic field strength is adjusted to 7 mT. The thawed tilapia fillets were subjected to juice loss rate detection, hardness, elasticity measurement, and sensory evaluation, and the results are shown as follows:

[0058] The juice loss rate of thawed tilapia fillets was 4.74%, the hardness was 10.11, the elasticity was 5.12, and the sensory score was 7.92.

[0059] Example 5

[0060] The specific implementation method is the same as Example 1, except that the magnetic field strength is adjusted to 9 mT. The thawed tilapia fillets were subjected to juice loss rate detection, hardness, elasticity measurement, and sensory evaluation, and the results are shown as follows:

[0061] The juice loss rate of thawed tilapia fillets was 4.73%, the hardness was 7.73, the elasticity was 4.87, and the sensory score was 8.48.

[0062] Comparative Example 1

[0063] Specific implementation method is the same as Example 1, except that the magnetic field treatment is not used, and the frozen tilapia fillets are directly thawed in an environment with a temperature of 8° C. for 150 minutes.

[0064] The same method as in Example 1 was used to test the juice loss rate, hardness, elasticity, and sensory evaluation, and the results were as follows:

[0065] The juice loss rate of thawed tilapia fillets was 5.81%, the hardness was 13.49, the elasticity was 5.53, and the sensory score was 8.56.

[0066] Comparative Example 2

[0067] Specific implementation method is the same as Example 1, except that the frozen tilapia fillet is thawed for 240 minutes, and the temperature and magnetic field strength remain unchanged, still at 8° C. and 5 mT.

[0068] The same method as in Example 1 was used to test the juice loss rate, hardness, elasticity, and sensory evaluation, and the results were as follows:

[0069] The juice loss rate of thawed tilapia fillets was 8.86%, the hardness was 12.68, the elasticity was 4.36, and the sensory score was 7.66.

[0070] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A freezing and thawing method for tilapia meat, characterized in that: The following steps are involved: (1) Pretreatment of tilapia meat: fresh tilapia was slaughtered and the fish spine was evenly sliced ​​into slices of 5 cm × 5 cm × 2 cm in size; (2) Preparation of antifreeze agent: accurately weigh 0.16% of sodium tripolyphosphate, 0.08% of sodium pyrophosphate, 0.12% of sodium hexametaphosphate and 4% of trehalose based on the total weight of tilapia fillet to prepare antifreeze agent; (3) Liquid nitrogen rapid freezing treatment: soak the tilapia fillets treated in step (1) in an antifreeze agent, take them out, package them in a sealed bag, place them in a tray, quickly freeze them with liquid nitrogen, and then place them in a freezer for freezing treatment; (4) Thawing treatment in a steady magnetic field: The tray of step (3) is placed in a -20°C non-magnetic field environment for 24 hours for thawing, and then placed in a steady magnetic field environment for thawing.

2. The freezing and thawing method of tilapia meat according to claim 1, characterized in that: In the step (2), 0.16% sodium tripolyphosphate, 0.08% sodium pyrophosphate, 0.12% sodium hexametaphosphate and 0.04% water are first mixed into a composite phosphate solution, and then 4% trehalose is added, and the balance is distilled water, and the mixture is stirred and blended to obtain an antifreeze agent.

3. The freezing and thawing method of tilapia meat according to claim 1, characterized in that: In the step (3), the tilapia fillets are soaked in antifreeze for 1-2 minutes.

4. The freezing and thawing method of tilapia meat according to claim 1, characterized in that: The tray in step (3) is a food-grade PET tray, and the sealed bag is a food-grade PE sealed bag.

5. The freezing and thawing method of tilapia meat according to claim 1, characterized in that: The freezing box in step (3) is an ultra-low temperature refrigerator with a temperature of -80°C and no magnetic field.

6. The freezing and thawing method of tilapia meat according to claim 1, characterized in that: In the step (3), the tilapia fillets are sealed with a sealing bag to prevent a large amount of water loss.

7. The freezing and thawing method of tilapia meat according to claim 1, characterized in that: In step (4), the magnetic field strength is 3-5 mT, the thawing temperature is 8-10° C., and the thawing time is 140-160 min.

8. The freezing and thawing method of tilapia meat according to claim 1, characterized in that: The step (4) uses a Helmholtz coil to stabilize the magnetic field, and the magnitude of the magnetic field is controlled by adjusting the current of the coil.

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