阅读说明：本技术 一种金鲳鱼的节能速冻方法 (Energy-saving quick-freezing method for golden pomfret ) 是由 刘书成 杨作苗 孙钦秀 周结倩 魏帅 夏秋瑜 郑欧阳 于 2021-07-31 设计创作，主要内容包括：本发明提供了一种金鲳鱼的节能速冻方法。该方法是将金鲳鱼放入腔体温度为A的液氮速冻机内,当鱼体中心温度达到-6～-4℃时,关闭液氮速冻机；待液氮速冻机的腔体温度升至B时,启动液氮速冻机,当鱼体中心温度达到-19～-17℃时,关闭液氮速冻机；最后将金鲳鱼取出在-19～-17℃下贮藏；其中,所述A为-105～-85℃,所述B为-95～-65℃,且A≤B。本发明的金鲳鱼速冻方法不仅减少了液氮的消耗量,实现了节能,还减少了金鲳鱼肌肉的硬度损失和蒸煮损失,有效保证了金鲳鱼的品质,延长了金鲳鱼的货架期。(The invention provides an energy-saving quick-freezing method for golden pomfret. Putting golden pomfret into a liquid nitrogen quick freezing machine with the cavity temperature of A, and closing the liquid nitrogen quick freezing machine when the central temperature of the pomfret reaches-6 to-4 ℃; when the temperature of the cavity of the liquid nitrogen instant freezer rises to B, starting the liquid nitrogen instant freezer, and closing the liquid nitrogen instant freezer when the central temperature of the fish body reaches-19 to-17 ℃; finally, taking out golden pomfret and storing at the temperature of-19 to-17 ℃; wherein A is-105 to-85 ℃, B is-95 to-65 ℃, and A is not more than B. The method for quickly freezing golden pomfret reduces the consumption of liquid nitrogen, realizes energy conservation, reduces the hardness loss and the cooking loss of golden pomfret muscles, effectively ensures the quality of golden pomfret, and prolongs the shelf life of golden pomfret.)

1. A quick-freezing method of golden pomfret is characterized by comprising the following steps:

s1, putting golden pomfret into a liquid nitrogen quick freezing machine with a cavity temperature of A, and closing the liquid nitrogen quick freezing machine when the central temperature of the pomfret reaches-6 to-4 ℃;

s2, starting the liquid nitrogen instant freezer when the temperature of the cavity of the liquid nitrogen instant freezer is increased to B, and closing the liquid nitrogen instant freezer when the central temperature of the fish body reaches-19 to-17 ℃;

s3, taking out golden pomfret and storing at the temperature of-19 to-17 ℃;

wherein A is-105 to-85 ℃, B is-95 to-65 ℃, and A is not more than B.

2. The quick-freezing method according to claim 1, wherein A is-95 ℃.

3. The quick-freezing method according to claim 2, wherein B is-75 to-65 ℃.

4. The quick-freezing method as claimed in claim 1, wherein the center temperature of the fish body in step S1 is-5 ℃.

5. The quick-freezing method as claimed in claim 1, wherein the center temperature of the fish body in step S2 is-18 ℃.

6. The quick-freezing method as claimed in claim 1, wherein the storage temperature in step S3 is-18 ℃.

7. The quick-freezing method according to claim 1, wherein the liquid nitrogen quick-freezing machine comprises a spray type liquid nitrogen quick-freezing machine, a cold gas circulation type liquid nitrogen quick-freezing machine, and a dip type liquid nitrogen quick-freezing machine.

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

9. The quick-freezing method according to claim 8, wherein the spray-type liquid nitrogen quick-freezing machine comprises 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. The quick-freezing method as claimed in claim 1, wherein the temperature of the center of the fish body is the temperature of the geometric center of the fish body.

Technical Field

The invention belongs to the technical field of golden pomfret storage. More particularly, relates to an energy-saving quick-freezing method for golden pomfret.

Background

Golden pompano, the scientific name of Trachinotus ovatus, belongs to the class Osteichthyes, order Perciformes, family , genus Populus, and is one of the important marine economic fishes in southern coastal areas of China. The golden pomfret is tender in fish meat, delicious in taste, high in nutritional value, free of small thorns among muscles and deeply popular with consumers. With the increasing of the culture scale and the yield of the golden pomfret, the supply is greater than the demand, the adoption of a proper quick-freezing method is of great importance to prolong the shelf life, the golden pomfret is mainly sold in a fresh and ice fresh mode in the current market, so that the golden pomfret is rotten in a large amount, and particularly when the golden pomfret is at the peak of the yield of the golden pomfret, if the golden pomfret is not processed in time, a large amount of resources are wasted.

At present, consolidation and the like disclose four methods for freezing golden pomfret (consolidation, bluebeard green, king Mongolia, Schlemm, influence of different freezing modes on water, tissue structure and quality change of golden pomfret [ J ] food science, 2019,40(23):213 plus 219.) but the steaming loss rate of the methods on the golden pomfret is more than 16%, so that resource waste exists to a certain extent, therefore, a method capable of effectively maintaining the quality of the golden pomfret and reducing the steaming loss is found, and the method has considerable necessity for storage of the golden pomfret.

Disclosure of Invention

Aiming at the defects and shortcomings of the existing golden pompano freezing method, the invention aims to provide an energy-saving quick-freezing method for golden pompano to reduce the cooking loss rate of golden pompano muscles, thereby ensuring the quality of golden pompano.

The above purpose of the invention is realized by the following technical scheme:

the invention provides a quick-freezing method of golden pomfret, which comprises the following steps:

s1, putting golden pomfret into a liquid nitrogen quick freezing machine with a cavity temperature of A, and closing the liquid nitrogen quick freezing machine when the central temperature of the pomfret reaches-6 to-4 ℃;

s2, starting the liquid nitrogen instant freezer when the temperature of the cavity of the liquid nitrogen instant freezer is increased to B, and closing the liquid nitrogen instant freezer when the central temperature of the fish body reaches-19 to-17 ℃;

s3, taking out golden pomfret and storing at the temperature of-19 to-17 ℃;

wherein A is-105 to-85 ℃, B is-95 to-65 ℃, and A is not more than B.

The method is based on two aspects of energy conservation and golden pompano quality, a targeted research is carried out on the quick-freezing method of the golden pompano, the single-stage liquid nitrogen quick-freezing method is creatively converted into two-stage liquid nitrogen quick-freezing, and through specific control on parameters such as freezing temperature and the like and full utilization of the liquid nitrogen, the consumption of the liquid nitrogen is reduced, energy conservation is realized, a large amount of uniform small ice crystals are rapidly generated in the golden pompano body, damage to fish tissues is reduced, hardness loss and steaming loss in the freezing process of the golden pompano are reduced, the quality of the golden pompano is effectively guaranteed, and the shelf life of the golden pompano is prolonged.

The liquid nitrogen quick freezing has the advantages of large heat transfer coefficient, high freezing speed, low dry consumption, low energy consumption, good quality and the like, and absorbs a large amount of sensible heat and latent heat through the processes of low-temperature liquid nitrogen vaporization and subsequent cooling, so that the flesh of the golden pomfret is vitrified and frozen, and the damage of ice crystals to muscle cells is reduced.

Step S1 is the first stage (phase transition stage) of golden pomfret temperature, when the liquid nitrogen instant freezer is closed, the residual cold energy of the quick freezing is fully utilized to assist in completing the second stage (deep cooling process) of golden pomfret, namely, the residual cold energy of the phase transition stage continues to freeze the golden pomfret when the cavity temperature is increased from A to B, thereby reducing the consumption of liquid nitrogen and realizing energy conservation.

Most preferably, the A is-95 ℃.

Further preferably, the B is-75 to-65 ℃.

Most preferably, the central temperature of the fish body in step S1 is-5 ℃.

Most preferably, the central temperature of the fish body in step S2 is-18 ℃.

Most preferably, the temperature of the storage in step S3 is-18 ℃.

Preferably, the liquid nitrogen instant freezer comprises a spray type liquid nitrogen instant freezer, a cold air circulation type liquid nitrogen instant freezer and a dipping type liquid nitrogen instant freezer.

Further preferably, the liquid nitrogen instant freezer is a spray type liquid nitrogen instant freezer.

The liquid nitrogen quick freezing can be generally divided into three types of cold air circulation freezing, dipping freezing and spray freezing, wherein the spray freezing is to spray liquid nitrogen into a mist product through a nozzle, the mist product is directly contacted with a freezing object to realize freezing, and the liquid nitrogen can be precooled after being gasified, so that the freezing efficiency is improved, therefore, the spray freezing enjoys the reputation of magic freezing and is widely applied.

More preferably, the spray-type liquid nitrogen instant freezer comprises a large cabinet-type spray liquid nitrogen instant freezer, a large tunnel-type liquid nitrogen instant freezer and a small cabinet-type spray liquid nitrogen instant freezer.

Preferably, the fish body center temperature is the temperature at the fish body geometric center.

As a preferred embodiment, the method for quickly freezing the golden pomfret comprises the following steps:

s1, putting golden pomfret into a spray type liquid nitrogen quick freezing machine with a cavity temperature of-95 ℃, and closing the spray type liquid nitrogen quick freezing machine when the central temperature of a fish body reaches-5 ℃;

s2, when the temperature of a cavity of the spray type liquid nitrogen instant freezer rises to-75 to-65 ℃, starting the spray type liquid nitrogen instant freezer, and when the central temperature of the fish body reaches-18 ℃, closing the spray type liquid nitrogen instant freezer;

s3, taking out golden pomfret and storing at-18 ℃.

The invention has the following beneficial effects:

the method is based on two aspects of energy conservation and golden pomfret quality, a targeted research is carried out on the quick-freezing method of golden pomfret, the single-stage liquid nitrogen quick-freezing method is creatively converted into two-stage liquid nitrogen quick-freezing, and through specific control of freezing temperature and other parameters and full utilization of liquid nitrogen, the consumption of liquid nitrogen is reduced, energy conservation is realized, the hardness loss and the cooking loss of golden pomfret muscles are reduced, the quality of golden pomfret is effectively guaranteed, and the shelf life of golden pomfret is prolonged.

Drawings

Figure 1 is a freezing curve for an air freezing battery.

FIG. 2 is a freezing curve of a single-stage liquid nitrogen flash freezing set.

FIG. 3 shows the effect of single-stage liquid nitrogen quick freezing group on the cooking loss rate of golden pomfret muscles.

FIG. 4 shows the effect of single-stage liquid nitrogen quick freezing group on the hardness of golden pomfret muscle.

FIG. 5 is a freezing curve of a two-stage liquid nitrogen flash freezing set.

FIG. 6 shows the results of the consumption of liquid nitrogen in the two-stage liquid nitrogen quick freezing group.

FIG. 7 shows the effect of two-stage liquid nitrogen quick freezing group on the cooking loss rate of golden pomfret muscles.

FIG. 8 shows the effect of two-stage liquid nitrogen quick freezing group on the hardness of golden pomfret.

Wherein, Fresh represents a Fresh group, namely a group which is not subjected to any freezing treatment after the equilibrium temperature of a refrigerator at 4 ℃ is 24 hours; RF denotes air freezing; LNF means liquid nitrogen flash freezing;

-35 ℃ RF denotes the air-freezing group at-35 ℃;

the-35 ℃ LNF group represents a single-stage liquid nitrogen flash freezing group that freezes at-35 ℃; the-55 ℃ LNF group represents a single-stage liquid nitrogen snap freezing group that freezes at-55 ℃; the-75 ℃ LNF group represents a single-stage liquid nitrogen quick freezing group that freezes at-75 ℃; the-85 ℃ LNF group represents a single-stage liquid nitrogen flash freezing group that freezes at-85 ℃; the-95 ℃ LNF group represents a single-stage liquid nitrogen flash freezing group that freezes at-95 ℃; the-105 ℃ LNF group represents a single-stage liquid nitrogen flash freezing group that freezes at-105 ℃; the-115 ℃ LNF group represents a single-stage liquid nitrogen flash freezing group that freezes at-115 ℃;

the LNF group at minus 95 ℃ and minus 35 ℃ represents a two-stage liquid nitrogen quick-freezing group with the first-stage temperature of minus 95 ℃ and the second-stage temperature of minus 35 ℃; the LNF group at minus 95 ℃ and minus 55 ℃ represents a two-stage liquid nitrogen quick-freezing group with the first-stage temperature of minus 95 ℃ and the second-stage temperature of minus 55 ℃; the LNF group at minus 95 ℃ and minus 65 ℃ represents a two-stage liquid nitrogen quick-freezing group with the first-stage temperature of minus 95 ℃ and the second-stage temperature of minus 65 ℃; the LNF group at minus 95 ℃ and minus 75 ℃ represents a two-stage liquid nitrogen quick-freezing group with the first-stage temperature of minus 95 ℃ and the second-stage temperature of minus 75 ℃; the LNF group at minus 95 ℃ and minus 85 ℃ represents a two-stage liquid nitrogen quick-freezing group with the first-stage temperature of minus 95 ℃ and the second-stage temperature of minus 85 ℃.

Detailed Description

The invention is further described with reference to the drawings and the following detailed description, which are not intended to limit the invention in any way. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Unless otherwise indicated, reagents and materials used in the following examples are commercially available.

(1) Experimental Material

Fresh and alive golden pomfret (500 +/-50 g) is purchased from the market for wholesale of Dongfeng aquatic products in Zhanjiang, is sent to a laboratory within one hour, is killed by ice temperature, is cleaned and wiped dry by clear water, is weighed and bagged, and is kept at the equilibrium temperature of a refrigerator of 4 ℃ for 24 hours for later use.

(2) Laboratory apparatus

The DJL-QF60 cabinet type liquid nitrogen quick freezing machine is purchased from Shenzhen Shenjizhen Dejieli freezing science and technology Co., Ltd; XT PlusC texture analyzer was purchased from Stable Micro System, UK.

Example 1 Single-stage liquid nitrogen quick freezing treatment of golden pomfret

(1) Air freezing treatment:

s1, putting golden pompano into a refrigerator at-35 ℃ for freezing, inserting a probe of a paperless recorder into the geometric center of a fish body, simultaneously inserting a U disk, recording time and temperature changes in real time, and recording data changes every two seconds; after the central temperature of the fish body reaches-18 ℃, the U disk is pulled out after the freezing is finished, and the data is led into origin software to draw a freezing curve of air freezing at-35 ℃, as shown in figure 1;

s2, rapidly transferring the frozen golden pomfret to-18 ℃ for storage for 24h, then putting the golden pomfret into a refrigerator at 4 ℃ for unfreezing until the central temperature of the pomfret reaches 4 ℃, and taking muscles (8 cm in length, width and thickness, 3cm and 1cm in thickness) on two sides of the back of the pomfret for subsequent index measurement.

(2) Single-stage liquid nitrogen quick freezing treatment:

s1, placing golden pomfret on a tray in a cavity of a liquid nitrogen instant freezer with the cavity temperature of-35 ℃, 55 ℃, 75 ℃, 85 ℃, 95 ℃, 105 ℃ and 115 ℃, inserting a probe of a paperless recorder into the geometric center of a pomfret body, simultaneously inserting the probe into a U disk, recording time and temperature changes in real time, and recording data changes every two seconds; after the central temperature of the fish body reaches-18 ℃, the U disk is pulled out after the freezing is finished, and the data are led into origin software to draw a freezing curve of the single-section type liquid nitrogen quick freezing, as shown in figure 2;

s2, rapidly transferring the frozen golden pomfret to-18 ℃ for storage for 24h, then putting the golden pomfret into a refrigerator at 4 ℃ for unfreezing until the central temperature of the pomfret reaches 4 ℃, and taking muscles (8 cm in length, width and thickness, 3cm and 1cm in thickness) on two sides of the back of the pomfret for subsequent index measurement.

As can be seen from fig. 1 and 2, the time of the single-stage liquid nitrogen quick freezing treatment group is significantly shorter than that of the air freezing treatment group, indicating that the freezing speed of the liquid nitrogen quick freezing is significantly faster than that of the air freezing.

EXAMPLE 2 measurement of cooking loss ratio and hardness in Single-stage liquid Nitrogen quick freezing treatment group

(1) Measurement of cooking loss ratio

Two groups of thawed samples from example 1 (one of two back muscles 8cm by 3cm by 1cm in length by width) were each weighed (W₁) Heating in water bath at 85 deg.C until the central temperature of the sample reaches 75 deg.C, sucking off water on the surface of the sample with filter paper, and accurately weighing the sample mass as W₂And according to the formula [ cooking loss rate (%) ] [ (W) ]₁-W₂)/W₁100% the loss rate of cooking was calculated to give figure 3.

As can be seen from fig. 3, the cooking loss of the fresh group is the lowest, about 10%; the highest cooking loss rate of the air freezing group is 19.18 percent; the-95 ℃ LNF group (single-stage liquid nitrogen quick freezing group frozen at-95 ℃) is 10.48%, and has no significant difference compared with the fresh group; the boil-off loss rate of the-85 ℃ LNF group (single-stage liquid nitrogen quick-freezing group frozen at-85 ℃) and the-105 ℃ LNF group (single-stage liquid nitrogen quick-freezing group frozen at-105 ℃) were significantly lower than those of the remaining groups (single-stage liquid nitrogen quick-freezing group frozen at-35 ℃, -55 ℃, -75 ℃, -115 ℃).

The result shows that the liquid nitrogen quick freezing is carried out at the temperature of-105 to-85 ℃, the steaming loss of the golden pomfret muscles is small, the golden pomfret muscles are close to the fresh state, and the effect is optimal particularly at the temperature of-95 ℃. The method is characterized in that the liquid nitrogen quick-freezing at the temperature of minus 105 to minus 85 ℃ has high freezing speed, generates fine and uniform ice crystals, and has small damage to muscles, so the cooking loss is less; the air freezing has a slow freezing speed, large ice crystals are easily generated, and the large ice crystals cause irreversible damage to muscle cells by extruding the muscle cells, so that the water retention capacity of the muscle is weak, water and nutrient substances are more easily lost in the cooking process, and the cooking loss is serious; in addition, the cooking loss rate of the-115 ℃ LNF group (one-stage liquid nitrogen quick freezing group in which freezing is performed at-115 ℃) was higher than that of the-95 ℃ LNF group, probably because the liquid nitrogen temperature was too low, resulting in low-temperature breakage of the fish meat portion, thereby increasing the cooking loss.

(2) Measurement of hardness

The test probe was tested using P10 using the TPA measurement mode of the texture analyzer, and the test results are shown in fig. 4, where the probe was measured on 3cm x 1cm fish (obtained by cutting another back muscle of 8cm x 3cm x 1cm thick, with length x width x 8 cm) of the two groups of example 1, and the rate before measurement was 1mm/s, the rate after measurement was 1mm/s, and the amount of compression deformation was 50%.

As can be seen from FIG. 4, the hardness value of the fresh group is the greatest, 2627.63 g; the minimum for the air-cooling group, 1256.79 g; 2104.33g in the-95 ℃ LNF group, significantly higher than the remaining groups (single-stage liquid nitrogen quick-frozen group frozen at-35 ℃, -55 ℃, -75 ℃, -85 ℃, -105 ℃, -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.

The result shows that the liquid nitrogen quick freezing is carried out at the temperature of-115 to-35 ℃, which is beneficial to keeping the hardness of the golden pomfret muscles, and the effect is optimal particularly at the temperature of-95 ℃. The reason is that the liquid nitrogen quick freezing at the temperature of between 115 ℃ below zero and 35 ℃ below zero has high freezing speed, generates fine and uniform ice crystals, and has small damage to muscles, thereby inhibiting the reduction of muscle hardness values; the air freezing speed is slow, large ice crystals are easy to generate, and the large ice crystals cause irreversible damage to muscle cells by extruding the muscle cells, so that the water holding capacity of the muscle is weak, and the hardness value in the muscle is reduced.

As can be seen from the combination of the figure 3 and the figure 4, the steaming loss and the hardness loss of the golden pomfret muscles are less when the liquid nitrogen quick freezing is carried out at the temperature of-105 to-85 ℃, so that the temperature of-105 to-85 ℃ is selected as the temperature of the first stage of the two-stage liquid nitrogen quick freezing treatment, and the optimal temperature of the temperature is-95 ℃ for carrying out subsequent experiments.

Example 3 two-stage liquid nitrogen quick freezing treatment of golden pomfret

S1, placing golden pomfret on a tray in a cavity of a liquid nitrogen instant freezer with the cavity temperature of-95 ℃, quickly inserting a probe of a paperless recorder into the geometric center of a fish body, simultaneously inserting a U disk, recording time and temperature changes in real time, recording data changes every two seconds, closing a door of the instant freezer, starting a start button, and spraying the fish by liquid nitrogen; when the temperature of the center of the fish body reaches-5 ℃, immediately closing the liquid nitrogen instant freezer and stopping using the liquid nitrogen;

s2, when the cavity temperature of the liquid nitrogen instant freezer is respectively raised to-35 ℃, 55 ℃, 65 ℃, 75 ℃, 85 ℃ and-95 ℃ from-95 ℃, the liquid nitrogen instant freezer is started again, liquid nitrogen is sprayed continuously until the central temperature of the fish body reaches-18 ℃, the liquid nitrogen instant freezer is closed, the U disk is pulled out after freezing is finished, and data are led into origin software to draw a two-stage liquid nitrogen quick-freezing curve, as shown in figure 5;

s3, rapidly transferring the frozen golden pomfret to-18 ℃ for storage for 24h, then putting the golden pomfret into a refrigerator at 4 ℃ for unfreezing until the central temperature of the pomfret reaches 4 ℃, and taking muscles (8 cm in length, width and thickness, 3cm and 1cm in thickness) on two sides of the back of the pomfret for subsequent measurement indexes.

As can be seen from fig. 1 and 5, the time of the two-stage liquid nitrogen quick freezing treatment group is significantly shorter than that of the air freezing treatment group, which indicates that the freezing speed of the two-stage liquid nitrogen quick freezing is significantly faster than that of the air freezing.

Example 4 measurement of liquid nitrogen consumption in two-stage liquid nitrogen quick freezing treatment group

Calculating the liquid nitrogen consumption of the two-section type liquid nitrogen quick-freezing treatment group by adopting a weighing method, namely placing a scale below a liquid nitrogen tank of a liquid nitrogen quick-freezing machine, and recording the initial mass m of the liquid nitrogen before the liquid nitrogen starts to be sprayed₁(ii) a Recording the residual mass m of liquid nitrogen until the central temperature of the fish body reaches-18 DEG C₂(ii) a And the initial mass of the golden pomfret is recorded as m₃And according to the formula [ liquid nitrogen consumption [ kg (LN)₂)/kg(fish)]＝(m₁-m₂)/m₃Liquid nitrogen consumption was calculated to obtain fig. 6.

As can be seen from fig. 6:

(1) the maximum liquid nitrogen consumption of the-95 ℃ LNF group was 3.38kg (LN)₂)/kg(fish)；

(2) The liquid nitrogen consumption of the-95 ℃/-35 ℃ LNF group is minimal, only 1.66kg (LN2)/kg (fish), saving 1.72kg (LN) over the-95 ℃ LNF group₂) The amount of the material is saved by 50.89 percent per kg (fish);

(3) the liquid nitrogen consumption of the-95 ℃ and/or-55 ℃ LNF group was 2.05kg (LN2)/kg (fish), which is a 1.33kg (LN) savings over the-95 ℃ LNF group₂) The saving of/kg (fish) is 39.35 percent;

(4) the liquid nitrogen consumption of the-95 ℃ and 65 ℃ LNF group is 2.33kg (LN2)/kg (fish), which is 1.05kg (LN) less than that of the-95 ℃ LNF group₂) The material is saved by 31.07 percent per kg (fish);

(5) the liquid nitrogen consumption of the-95 ℃/-75 ℃ LNF group was 2.44kg (LN2)/kg (fish), which is a saving of 0.94kg (LN) over the-95 ℃ LNF group₂) The material is saved by 27.81 percent by/kg (fish);

(6) the liquid nitrogen consumption of the-95 ℃/-85 ℃ LNF group was 2.87kg (LN2)/kg (fish), which is a saving of 0.51kg (LN) over the-95 ℃ LNF group₂) And/kg (fish), 15.10% of the saving.

In conclusion, the two-stage liquid nitrogen quick-freezing treatment of the golden pomfret is more energy-saving, and the higher the temperature of the second-stage liquid nitrogen quick-freezing machine is, the less the liquid nitrogen consumption is, because the cold energy of the residual liquid nitrogen in the first stage is fully utilized in the second stage in different degrees, the consumption of the liquid nitrogen is reduced, and the energy conservation is realized.

Example 5 measurement of cooking loss ratio and hardness in two-stage liquid nitrogen quick-freezing treatment group

(1) Measurement of cooking loss ratio

The thawed sample from example 3 (one of two dorsal muscles 8cm by 3cm by 1cm in length by width) was weighed (W₁) Heating in water bath at 85 deg.C until the central temperature of the sample reaches 75 deg.C, sucking off water on the surface of the sample with filter paper, and accurately weighing the sample mass as W₂And according to the formula [ cooking loss rate (%) ] [ (W) ]₁-W₂)/W₁100% cooking loss rate was calculated and the cooking loss rate data for the air-cooled group of example 2 was followed to obtain figure 7.

As can be seen from fig. 7, the cooking loss rate of the fresh group was the lowest, 9.99%; the highest cooking loss rate of the air freezing group is 19.18 percent; and the boiling loss rates of the-95 ℃ and/or-65 ℃ LNF group, the-95 ℃ and/or-75 ℃ LNF group, the-95 ℃ and/or-85 ℃ LNF group and/or-95 ℃ LNF group are respectively 11.24%, 11.21%, 10.60% and 10.48% which are significantly lower than those of the remaining groups (the-95 ℃ and/or-35 ℃ LNF group and/or-95 ℃ and/or-55 ℃ LNF group), and the four groups have no significant difference from each other. The temperature of the second stage of the two-stage liquid nitrogen quick-freezing treatment is set to be-95 to-65 ℃, so that the cooking loss rate of the golden pomfret muscles can be effectively reduced.

(2) Measurement of hardness

The test probe was tested using P10 in the TPA measurement mode using a texture analyzer, and the test results are shown in fig. 8, using a probe measured on 3cm x 1cm fish (cut from another piece of back muscle of example 3, 8cm x 3cm x 1cm long x wide), at a rate of 1mm/s before measurement, at a rate of 1mm/s after measurement, at a rate of 5mm/s after measurement, and at a compression deformation amount of 50%, and using the hardness data of the air-frozen portion of example 2.

As can be seen from fig. 8, the hardness values of the fresh group are the greatest; the air-freezing group had the smallest hardness value of 1256.79 g; the hardness value of the-95 ℃ LNF group is 2104.33g which is the largest, is only next to the fresh group, and has no significant difference from the-95 ℃ and the-75 ℃ LNF group (the hardness value is 1917.95g), and the-95 ℃ and the-85 ℃ LNF group (the hardness value is 2072.92 g); the-95 ℃/-65 ℃ LNF group (hardness value 1832.11g) was not significantly different from the-95 ℃/-75 ℃ LNF group. The temperature of the second stage of the two-stage liquid nitrogen quick freezing treatment is set to be-95 to-65 ℃, so that the hardness of the golden pomfret muscles can be effectively maintained.

With the combination of the figures 6-8, the temperature of-95 to-65 ℃ is the better choice of the temperature of the second stage of the two-stage liquid nitrogen quick freezing treatment, and the temperature of-75 to-65 ℃ is the best, from the two aspects of energy conservation and golden pomfret quality.

In conclusion, the invention carries out targeted research on the quick-freezing method of the golden pomfret from two aspects of energy conservation and golden pomfret quality, creatively converts the single-stage liquid nitrogen quick-freezing method into two-stage liquid nitrogen quick-freezing, and not only reduces the consumption of liquid nitrogen and realizes energy conservation, but also is beneficial to quickly generating a great number of uniform small ice crystals in the golden pomfret body and has small damage to fish meat by specifically controlling parameters such as temperature and fully utilizing the liquid nitrogen, thereby reducing the hardness loss and the cooking loss in the freezing process of the golden pomfret, effectively ensuring the quality of the golden pomfret and prolonging the shelf life of the golden pomfret.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.