Energy-saving quick-freezing method for golden pomfret

Abstract

A rapid freezing method for golden threadfin bream, comprising the steps of: putting the golden threadfin bream into a liquid nitrogen freezer with the temperature of the cavity being A; turning off the liquid nitrogen freezer when the central temperature of the fish body reaches -6 to -4°C; turning on the liquid nitrogen freezer when the temperature of the cavity of the liquid nitrogen freezer rises to B; turning off the liquid nitrogen freezer when the central temperature of the fish body reaches -19 to -17°C; and finally taking out the golden threadfin bream and storing it at -19 to -17°C, where A is -105 to -85°C, B is -95 to -65°C, and A < B. This rapid freezing method for golden threadfin bream not only reduces the consumption of liquid nitrogen to achieve energy conservation, but also reduces the hardness loss and stewing loss of the golden threadfin bream muscle, effectively guarantees the quality of the golden threadfin bream, and extends the storage period of the golden threadfin bream.

Description

[Technical field]

[0001] The present invention belongs to the field of golden pomfret storage technology, more particularly to an energy-saving quick-freezing method for golden pomfret. [Background technology]

[0002] Golden pomfret, scientific name Trachinotus ovatus, belongs to the Osteichthyes, Perciformes, Carangidae, and Trachinotus genus. It is one of the commercially important marine fishes in the southern coastal areas of China. Golden pomfret is loved by consumers for its tender flesh, delicious taste, high nutritional value, and lack of small bones in the muscle. As the scale of golden pomfret farming and production volume become larger and larger, the supply exceeds the demand, so it is very important to use a suitable quick-freezing method to extend the storage period. However, since it is mainly sold in the form of live fish and fresh fish in the market at present, a large amount of golden pomfret will spoil, especially when the production volume of golden pomfret reaches its peak, if it is not processed in a timely manner, it will lead to a large amount of resource waste.

[0003] At present, Gong Taoshuo et al. have disclosed four methods for freezing golden pomfret, including plate freezing, spiral freezing, ultra-low temperature freezing and refrigerator freezing (Gong Taoshuo, Lan Weiqing, Wang Meng, Xie Jing. Effect of different freezing methods on moisture, tissue structure and quality changes of golden pomfret [J]. Food Science, 2019, 40(23): 213-219.). However, the braised loss rate of golden pomfret using these methods is all above 16%, which means a certain amount of resource waste. Therefore, it is quite necessary to find a method that can effectively maintain the quality of golden pomfret and reduce the braised loss for the storage of golden pomfret. Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the defects and shortcomings of the above-mentioned existing golden pomfret freezing methods, the present invention aims to provide an energy-saving quick-freezing method for golden pomfret, so as to reduce the braised loss rate of golden pomfret muscle and thereby ensure the quality of golden pomfret. [Means for solving the problem]

[0005] The above object of the present invention is achieved by the following technical solutions.

[0006] The present invention provides a method for quick-freezing golden pomfret, Step S1: Put golden pomfret into a liquid nitrogen quick freezer with a cavity temperature of A, and when the core temperature of the fish body reaches -6 to -4°C, turn off the liquid nitrogen quick freezer; Step S2: when the temperature of the cavity of the liquid nitrogen quick freezer rises to B, start the liquid nitrogen quick freezer, and when the core temperature of the fish body reaches -19 to -17 ° C, turn off the liquid nitrogen quick freezer; Step S3 of extracting the golden pomfret and storing it at -19 to -17°C; Here, A is −105 to −85° C., B is −95 to −65° C., and A <Bである。

[0007] From the two perspectives of energy saving and the quality of golden pomfret, the present invention targets the quick-freezing method of golden pomfret, and creatively transforms the quick-freezing method of one-stage liquid nitrogen quick-freezing into two-stage liquid nitrogen quick-freezing. Through specific control of parameters such as freezing temperature and full utilization of liquid nitrogen, it not only reduces the consumption of liquid nitrogen and realizes energy saving, but also favors the rapid generation of a large amount of uniform small ice crystals in the body of golden pomfret, reduces the damage to fish tissue, reduces the hardness loss and braising loss of golden pomfret during freezing, effectively ensures the quality of golden pomfret, and extends the storage period of golden pomfret.

[0008] Liquid nitrogen quick freezing has the advantages of large heat transfer coefficient, fast freezing speed, small drying consumption, low energy consumption, and good quality. Through the process of vaporization of low-temperature liquid nitrogen and subsequent cooling, a large amount of sensible heat and latent heat is absorbed, thereby vitrifying and freezing the golden pomfret muscle part and reducing the damage caused by ice crystals to muscle cells.

[0009] Step S1 is the first stage (phase change stage) of golden pomfret temperature, when the liquid nitrogen quick freezing machine is turned off, the remaining cold energy of quick freezing is fully utilized to help complete the second stage (deep cooling process) freezing of golden pomfret, i.e. while the temperature of the cavity rises from A to B, the remaining cold energy of phase change stage continues to freeze golden pomfret, thereby reducing the consumption of liquid nitrogen and realizing energy saving.

[0010] Most preferably, A is -95°C.

[0011] More preferably, B is -75 to -65°C.

[0012] Most preferably, the core temperature of the fish body described in step S1 is -5°C.

[0013] Most preferably, the core temperature of the fish body described in step S2 is -18°C.

[0014] Most preferably, the storage temperature described in step S3 is -18°C.

[0015] Preferably, the liquid nitrogen flash freezer includes a spray type liquid nitrogen flash freezer, a cold air circulation type liquid nitrogen flash freezer, and an immersion type liquid nitrogen flash freezer.

[0016] More preferably, the liquid nitrogen flash freezer is a spray type liquid nitrogen flash freezer.

[0017] Liquid nitrogen quick freezing can generally be classified into three types: cold air circulation freezing, immersion freezing, and spray freezing. Here, spray freezing is achieved by spraying liquid nitrogen from a nozzle into a mist and directly contacting the object to be frozen. After the liquid nitrogen evaporates, the food can be pre-cooled to improve the freezing efficiency. Therefore, spray freezing has a reputation of "magic freezing" and is widely used.

[0018] More preferably, the spray type liquid nitrogen flash freezer includes a large cabinet type spray liquid nitrogen flash freezer, a large tunnel type liquid nitrogen flash freezer, and a small cabinet type spray liquid nitrogen flash freezer.

[0019] Preferably, the core temperature of the fish is the temperature at the geometric centre of the fish.

[0020] In a preferred embodiment, the method for quick freezing golden pomfret comprises: Step S1: putting the golden pomfret into a spray-type liquid nitrogen quick-freezer with a cavity temperature of -95°C, and turning off the spray-type liquid nitrogen quick-freezer when the core temperature of the fish body reaches -5°C; Step S2: when the cavity temperature of the spray type liquid nitrogen quick freezer rises to -75 to -65 ° C, start the spray type liquid nitrogen quick freezer, and when the core temperature of the fish body reaches -18 ° C, turn off the spray type liquid nitrogen quick freezer; and step S3 of extracting the golden pomfret and storing it at -18°C. Effect of the Invention

[0021] The beneficial effects of the present invention are as follows: From the two perspectives of energy saving and the quality of golden pomfret, the present invention targets the quick-freezing method of golden pomfret, and creatively transforms the quick-freezing method of one-stage liquid nitrogen quick-freezing into two-stage liquid nitrogen quick-freezing. Through specific control of parameters such as freezing temperature and full use of liquid nitrogen, it not only reduces the consumption of liquid nitrogen and realizes energy saving, but also reduces the hardness loss and braising loss of golden pomfret muscle, effectively ensures the quality of golden pomfret, and extends the storage period of golden pomfret. [Brief description of the drawings]

[0022] [Figure 1] 1 is a refrigeration curve of an air refrigeration group. [Diagram 2] This is the freezing curve for the single-stage liquid nitrogen quick freezing group. [Diagram 3] The results show that one-stage liquid nitrogen quick freezing group affected the braised loss rate of golden pomfret muscle. [Figure 4] The results show that the single-stage liquid nitrogen quick freezing group affected the hardness of golden pomfret muscle. [Diagram 5] This is the freezing curve of the two-stage liquid nitrogen quick freezing group. [Figure 6] This shows the liquid nitrogen consumption in the two-stage liquid nitrogen quick freezing group. [Figure 7] The results show that two-stage liquid nitrogen quick freezing group affected the braised loss rate of golden pomfret muscle. [Figure 8]The results show that the two-stage liquid nitrogen quick freezing group affected the hardness of golden pomfret muscle. Here, "Fresh" refers to the fresh group, i.e., the group that was equilibrated in a 4℃ refrigerator for 24 hours and then no freezing treatment was performed, "RF" refers to air freezing, "LNF" refers to liquid nitrogen quick freezing, and "-35℃RF" refers to the group that was air frozen at -35℃. The -35°C LNF group indicates the single-stage liquid nitrogen quick-frozen group frozen at -35°C, the -55°C LNF group indicates the single-stage liquid nitrogen quick-frozen group frozen at -55°C, the -75°C LNF group indicates the single-stage liquid nitrogen quick-frozen group frozen at -75°C, the -85°C LNF group indicates the single-stage liquid nitrogen quick-frozen group frozen at -85°C, the -95°C LNF group indicates the single-stage liquid nitrogen quick-frozen group frozen at -95°C, the -105°C LNF group indicates the single-stage liquid nitrogen quick-frozen group frozen at -105°C, and the -115°C LNF group indicates the single-stage liquid nitrogen quick-frozen group frozen at -115°C. The -95℃ / -35℃LNF group indicates a two-stage liquid nitrogen quick-freezing group with a first stage temperature of -95℃ and a second stage temperature of -35℃; the -95℃ / -55℃LNF group indicates a two-stage liquid nitrogen quick-freezing group with a first stage temperature of -95℃ and a second stage temperature of -55℃; the -95℃ / -65℃LNF group indicates a two-stage liquid nitrogen quick-freezing group with a first stage temperature of -95℃ and a second stage temperature of -65℃; the -95℃ / -75℃LNF group indicates a two-stage liquid nitrogen quick-freezing group with a first stage temperature of -95℃ and a second stage temperature of -75℃; and the -95℃ / -85℃LNF group indicates a two-stage liquid nitrogen quick-freezing group with a first stage temperature of -95℃ and a second stage temperature of -85℃. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will be further described below with reference to the drawings and specific examples in the specification, but the examples are not intended to limit the present invention in any manner. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0024] Unless otherwise stated, all reagents and materials used in the following examples were commercially purchased.

[0025] (1) Experimental materials Live golden pomfret (500 ± 50 g) were purchased from Dongfeng Seafood Wholesale Market, Zhanjiang City, and transported to the laboratory within 1 h, killed at ice temperature, washed with clean water, wiped dry, weighed, bagged, and then equilibrated in a refrigerator at 4 °C for 24 h before use.

[0026] (2) Experimental equipment The DJL-QF60 cabinet-type liquid nitrogen quick freezer was purchased from Shenzhen Dejiali Refrigeration Technology Co., Ltd., and the TA.XT plusC texture analyzer was purchased from Stable Micro System, UK.

[0027] Example 1 Golden pomfret is flash frozen in one step using liquid nitrogen (1) Air refrigeration process: In S1, the golden pomfret is placed in a -35℃ refrigerator to be frozen, the paperless recorder probe is inserted into the geometric center of the fish body, and a USB is inserted to record the time and temperature changes in real time, and the data changes are recorded every 2 seconds. When the fish body center temperature reaches -18℃, the freezing is stopped, the USB is removed, and the data is imported into the origin software to plot the freezing curve of -35℃ air freezing, as shown in Figure 1. In S2, the frozen golden pomfret was quickly transferred to -18℃ and stored for 24h, then placed in a 4℃ refrigerator and thawed until the core temperature of the fish reached 4℃. Muscles (length*width*thickness 8cm*3cm*1cm) were taken from both sides of the back for subsequent index measurements.

[0028] (2) One-stage liquid nitrogen quick-freezing process: In S1, golden pomfret is placed on the tray in the cavity of liquid nitrogen flash freezer with cavity temperatures of -35℃, -55℃, -75℃, -85℃, -95℃, -105℃, and -115℃, respectively. The paperless recorder probe is inserted into the geometric center of the fish body, and a USB is inserted to record the time and temperature changes in real time. The data changes every 2 seconds. When the core temperature of the fish body reaches -18℃, the freezing is stopped, the USB is removed, and the data is imported into the origin software to plot the freezing curve of one-stage liquid nitrogen flash freezing, as shown in Figure 2. In S2, the frozen golden pomfret was quickly transferred to -18℃ and stored for 24h, then placed in a 4℃ refrigerator and thawed until the core temperature of the fish reached 4℃. Muscles (length*width*thickness 8cm*3cm*1cm) on both sides of the back were taken for subsequent index measurements.

[0029] As can be seen with reference to Figures 1 and 2, the times of the single-stage liquid nitrogen quick freezing treatment group were all shorter than those of the air freezing treatment group, which indicates that the freezing speed of liquid nitrogen quick freezing is significantly faster than that of air freezing.

[0030] Example 2 Measurement of steaming loss rate and hardness of single-stage liquid nitrogen quick-freezing treatment group (1) Measurement of steaming loss rate The thawed samples (one of two back muscles with length*width*thickness of 8cm*3cm*1cm) of the two groups in Example 1 were weighed (W1), and then heated in a water bath at 85°C until the center temperature of the sample reached 75°C. The moisture on the surface of the sample was then absorbed with filter paper, and the mass of the sample was accurately weighed and recorded as W2. The braising loss rate was calculated according to the formula [braising loss rate (%)=(W1-W2) / W1*100%], and Figure 3 was obtained.

[0031] As can be seen from Figure 3, the braising loss rate of the fresh group was the lowest, at about 10%, while the braising loss rate of the air-frozen group was the highest, at 19.18%, and that of the -95℃LNF group (single-stage liquid nitrogen quick-frozen group frozen at -95℃) was 10.48%, which was not significantly different from the fresh group. The braising loss rates of the -85℃LNF group (single-stage liquid nitrogen quick-frozen group frozen at -85℃) and -105℃LNF groups (single-stage liquid nitrogen quick-frozen group frozen at -105℃) were all significantly lower than the remaining groups (single-stage liquid nitrogen quick-frozen groups frozen at -35℃, -55℃, -75℃, -115℃).

[0032] Liquid nitrogen quick freezing at temperatures between -105 and -85℃ reduced the braising loss of golden pomfret muscle, making it closer to fresh, and the effect was especially good at -95℃. This is because the freezing speed of liquid nitrogen quick freezing at -105 to -85℃ is fast, producing fine and uniform ice crystals, which causes less damage to the muscle, resulting in less braising loss; on the other hand, air freezing has a slow freezing speed, which tends to produce large ice crystals, which presses the muscle cells, causing irreversible damage to the muscle cells, which weakens the muscle's ability to retain moisture, making it easier to lose moisture and nutrients during braising, resulting in greater braising loss. In addition, the braising loss rate of the -115℃ LNF group (single-stage liquid nitrogen quick freezing group frozen at -115℃) was higher than that of the -95℃ LNF group, which may be due to the liquid nitrogen temperature being too low, which causes parts of the fish meat to break at low temperatures, resulting in increased braising loss.

[0033] (2) Hardness measurement Using the TPA measurement mode of texture analyzer, the test is carried out using P10 as the test probe, the probe measures 3cm*3cm*1cm of fish meat (cut from another back muscle of 8cm*3cm*1cm length*width*thickness in two groups of example 1), the speed before the test is 1mm / s, the test speed is 1mm / s, the speed after the test is 5mm / s, the compression deformation amount is 50%, and the measurement result is as shown in Figure 4.

[0034] As can be seen from Figure 4, the hardness value of the fresh group was the highest, 2627.63g, and the air-frozen group was the lowest, 1256.79g, followed by the -95℃LNF group at 2104.33g, which was significantly higher than the remaining groups (single-stage liquid nitrogen quick-frozen groups frozen at -35℃, -55℃, -75℃, -85℃, -105℃, and -115℃). The hardness values ​​of the remaining groups were not significantly different from each other, and were all significantly higher than the air-frozen group.

[0035] Liquid nitrogen quick freezing at temperatures between -115 and -35°C is advantageous in maintaining the hardness of golden pomfret muscle, with -95°C being the most effective. This is because liquid nitrogen quick freezing at temperatures between -115 and -35°C has a fast freezing speed, produces fine, uniform ice crystals, and causes little damage to the muscle, preventing a decrease in muscle hardness. On the other hand, air freezing has a slow freezing speed, which tends to produce large ice crystals, which press on the muscle cells, causing irreversible damage to the muscle cells and weakening the muscle's ability to retain water, thereby decreasing the muscle hardness.

[0036] As can be seen from FIG. 3 and FIG. 4 , when liquid nitrogen quick-freezing is performed at a temperature of −105 to −85°C, both the braising loss and the hardness loss of golden pomfret muscle are small. Therefore, the present invention selects −105 to −85°C as the temperature of the first stage of the two-stage liquid nitrogen quick-freezing process, and conducts subsequent experiments at the optimal temperature of −95°C.

[0037] Example 3 Golden pomfret two-stage liquid nitrogen quick-freezing process In S1, the golden pomfret is placed on a tray in the cavity of a liquid nitrogen flash freezer with a cavity temperature of -95℃, the paperless recorder probe is quickly inserted into the geometric center of the fish body, and a USB is inserted to record the time and temperature changes in real time, and the data changes every 2 seconds. The door of the flash freezer is closed, and the start button is activated to start spraying liquid nitrogen onto the fish. When the temperature of the center of the fish body reaches -5℃, the liquid nitrogen flash freezer is immediately turned off to stop using liquid nitrogen; In S2, when the cavity temperature of the liquid nitrogen flash freezer rises from -95℃ to -35℃, -55℃, -65℃, -75℃, -85℃ and -95℃, respectively, the liquid nitrogen flash freezer is started again, and liquid nitrogen spraying continues until the core temperature of the fish reaches -18℃, then the liquid nitrogen flash freezer is turned off, freezing is terminated, the USB is removed, and the data is imported into the origin software to plot the freezing curve of the two-stage liquid nitrogen flash freezing, as shown in Figure 5. In S3, the frozen golden pomfret was quickly transferred to -18℃ and stored for 24h, then placed in a 4℃ refrigerator and thawed until the core temperature of the fish reached 4℃. Muscles (length*width*thickness 8cm*3cm*1cm) on both sides of the back were taken for subsequent index measurements.

[0038] As can be seen by referring to Figures 1 and 5, the times of the two-stage liquid nitrogen quick freezing treatment group were all significantly shorter than those of the air freezing treatment group, which indicates that the freezing speed of the two-stage liquid nitrogen quick freezing treatment is significantly faster than that of the air freezing treatment group.

[0039] Example 4 Measurement of liquid nitrogen consumption in two-stage liquid nitrogen quick-freezing treatment groups The weighing method was used to calculate the liquid nitrogen consumption of the two-stage liquid nitrogen quick-freezing treatment group, that is, a scale was placed under the liquid nitrogen tank of the liquid nitrogen quick-freezing machine, and the initial mass of liquid nitrogen m1 was recorded before the liquid nitrogen spraying began, and when the core temperature of the fish body reached -18℃, the remaining mass of liquid nitrogen m2 was recorded. The initial mass of the golden pomfret was taken as m3, and the liquid nitrogen consumption was calculated according to the formula [liquid nitrogen consumption [kg(LN2) / kg(fish)]=(m1-m2) / m3], and Figure 6 was obtained.

[0040] The following can be seen from Figure 6: (1) The liquid nitrogen consumption in the -95℃ LNF group was the highest, at 3.38 kg(LN2) / kg(fish). (2) The liquid nitrogen consumption in the -95℃ / -35℃ LNF group was the lowest, at only 1.66kg(LN2) / kg(fish), saving 1.72kg(LN2) / kg(fish) compared to the -95℃ LNF group, a saving of 50.89%. (3) The liquid nitrogen consumption in the -95℃ / -55℃ LNF group was 2.05 kg(LN2) / kg(fish), which was 1.33 kg(LN2) / kg(fish) less than the -95℃ LNF group, a saving of 39.35%. (4) The liquid nitrogen consumption in the -95℃ / -65℃ LNF group was 2.33 kg(LN2) / kg(fish), which was 1.05 kg(LN2) / kg(fish) less than the -95℃ LNF group, a saving of 31.07%. (5) The liquid nitrogen consumption in the -95℃ / -75℃ LNF group was 2.44 kg(LN2) / kg(fish), which was 0.94 kg(LN2) / kg(fish) less than the -95℃ LNF group, a saving of 27.81%. (6) The liquid nitrogen consumption in the -95℃ / -85℃ LNF group was 2.87 kg(LN2) / kg(fish), which was 0.51 kg(LN2) / kg(fish) less than the -95℃ LNF group, representing a saving of 15.10%.

[0041] To sum up, it can be seen that the two-stage liquid nitrogen quick-freezing process of golden pomfret is more energy-saving, and the higher the temperature of the second-stage liquid nitrogen quick-freezer, the less liquid nitrogen is consumed, because the cold energy of the remaining liquid nitrogen in the first stage can be fully utilized to different degrees during the second-stage freezing, thus reducing the liquid nitrogen consumption and realizing energy saving.

[0042] Example 5 Measurement of steaming loss rate and hardness of two-stage liquid nitrogen quick-freezing treatment groups (1) Measurement of steaming loss rate The thawed sample of Example 3 (one of two back muscles with length*width*thickness 8cm*3cm*1cm) was weighed (W1), then heated in a water bath at 85℃ until the central temperature of the sample reached 75℃, and then the moisture on the surface of the sample was absorbed with filter paper. The mass of the sample was accurately weighed and recorded as W2. The braising loss rate was calculated according to the formula [braising loss rate (%)=(W1-W2) / W1*100%], and the braising loss rate data of the air-frozen group of Example 2 was used to obtain Figure 7.

[0043] As can be seen from Figure 7, the braised loss rate of the fresh group was the lowest, 9.99%, and the braised loss rate of the air-frozen group was the highest, 19.18%. The braised loss rates of the -95℃ / -65℃LNF group, -95℃ / -75℃LNF group, -95℃ / -85℃LNF group, and -95℃LNF group were 11.24%, 11.21%, 10.60%, and 10.48%, respectively, which were significantly lower than the remaining groups (-95℃ / -35℃LNF group, -95℃ / -55℃LNF group), and these four groups had no significant difference with each other. This shows that setting the temperature of the second stage of the two-stage liquid nitrogen quick-freezing process at -95~-65℃ can effectively reduce the braised loss rate of golden pomfret muscle.

[0044] (2) Hardness measurement Using the TPA measurement mode of the texture analyzer, the test was carried out using P10 as the test probe, and the probe was used to measure a 3cm*3cm*1cm piece of fish meat (cut from another back muscle of length*width*thickness 8cm*3cm*1cm in Example 3), the speed before the test was 1mm / s, the test speed was 1mm / s, the speed after the test was 5mm / s, and the compression deformation amount was 50%. The hardness data of the air-frozen group in Example 2 was reused, and the measurement result is shown in Figure 8.

[0045] As can be seen from Figure 8, the hardness value of the fresh group was the largest, the hardness value of the air-frozen group was the smallest, 1256.79g, the hardness value of the -95℃LNF group was the largest, 2104.33g, next to the fresh group, and there was no significant difference between the -95℃ / -75℃LNF group (hardness value is 1917.95g) and the -95℃ / -85℃LNF group (hardness value is 2072.92g), and there was no significant difference between the -95℃ / -65℃LNF group (hardness value is 1832.11g) and the -95℃ / -75℃LNF group. This shows that the hardness of golden pomfret muscle can be effectively maintained by setting the temperature of the second stage of the two-stage liquid nitrogen quick-freezing process at -95 to -65℃.

[0046] Referring to Figures 6 to 8, from the comprehensive perspective of the two angles of energy saving and the quality of golden pomfret, -95 to -65℃ is the preferred selection of the temperature for the second stage of the two-stage liquid nitrogen quick-freezing process, and -75 to -65℃ is the optimal.

[0047] To sum up, the present invention studies the quick-freezing method of golden pomfret from the two aspects of energy saving and the quality of golden pomfret, creatively transforming the quick-freezing method of one-stage liquid nitrogen quick-freezing into two-stage liquid nitrogen quick-freezing, through specific control of parameters such as temperature and full utilization of liquid nitrogen, not only reducing the consumption of liquid nitrogen and realizing energy saving, but also favorably generating a very large number of uniform small ice crystals in the body of golden pomfret, and causing less damage to the fish meat, thereby reducing the hardness loss and braising loss of golden pomfret during freezing, effectively ensuring the quality of golden pomfret, and extending the storage period of golden pomfret.

[0048] The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention are equivalent replacement forms, and all fall within the protection scope of the present invention.

Claims

1. Step S1: Put golden pomfret into a liquid nitrogen quick freezer with a cavity temperature of A, and when the core temperature of the fish reaches −6 to −4° C., turn off the liquid nitrogen quick freezer; Step S2: when the temperature of the cavity of the liquid nitrogen quick freezer rises to B, start the liquid nitrogen quick freezer, and when the core temperature of the fish reaches −19 to −17° C., turn off the liquid nitrogen quick freezer; Step S3 of extracting the golden pomfret and storing it at −19 to −17° C.; Here, A is −105 to −85° C., B is −95 to −65° C., and A<B. The method for quick freezing golden pomfret is characterized by the above.

2. 2. The method for quick freezing according to claim 1, wherein A is −95° C.

3. 3. The method for quick freezing according to claim 2, wherein B is −75 to −65° C.

4. 2. The method for quick freezing according to claim 1, wherein the core temperature of the fish in step S1 is -5°C.

5. 2. The method for quick freezing according to claim 1, wherein the core temperature of the fish in step S2 is -18°C.

6. The quick-freezing method according to claim 1, wherein the storage temperature in step S3 is -18°C.

7. 2. The method for quick freezing according to claim 1, wherein the liquid nitrogen quick freezing machine includes a spray type liquid nitrogen quick freezing machine, a cold air circulation type liquid nitrogen quick freezing machine, and an immersion type liquid nitrogen quick freezing machine.

8. 8. The method for rapid freezing according to claim 7, wherein the liquid nitrogen rapid freezing machine is a spray type liquid nitrogen rapid freezing machine.

9. The quick freezing method according to claim 8, wherein the spray type liquid nitrogen quick freezing machine includes a large cabinet type spray liquid nitrogen quick freezing machine, a large tunnel type liquid nitrogen quick freezing machine, and a small cabinet type spray liquid nitrogen quick freezing machine.

10. 2. The method of claim 1, wherein the central temperature of the fish body is the temperature at the geometric center of the fish body.

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