Liquid nitrogen quick-freezing process for procambarus clarkii
Through the liquid nitrogen quick-freezing process, including rapid pre-cooling, low-temperature protection and multi-stage deep-cold quick-freezing, the problem of high shell freezing rate of Crayfish in the fast-freezing process is solved, and the improvement of freezing quality and economic value is achieved.
Patent Information
- Application Number
- CN202411715431.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-27
- Publication Date
- 2025-03-04
AI Technical Summary
During the fast freezing process, the Chrissian carcinoma is prone to high shell freezing rate, resulting in a decrease in freezing quality and loss of economic value.
The liquid nitrogen quick-freezing process is adopted, including rapid pre-cooling, low-temperature protection and multi-stage deep-cooling quick-freezing. Rapid pre-cooling reduces the temperature difference between the inside and the surface of the shrimp body, low-temperature protective agents increase the glass transition temperature, reduce the content of frozen water, and achieve ultra-low-temperature freezing through liquid nitrogen in multi-stage deep-cold and quick-freezing.
It effectively reduces the freezing rate of Crayfish, improves the freezing quality, and improves the economic value of the product.
Smart Images
Figure CN119547810A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of crayfish preservation, in particular to a liquid nitrogen quick-freezing process for crayfish. Background Art
[0002] my country has abundant shrimp resources, among which Procambarus clarkii, or crayfish, is one of the most important freshwater economic aquatic species. The production of Procambarus clarkii accounts for 8.27% of the total freshwater aquaculture production in China, ranking sixth among my country's freshwater aquaculture varieties. In 2021, my country's Procambarus clarkii production was 2.6336 million tons, a year-on-year increase of 10.02%. It is estimated that the Procambarus clarkii industry will continue to maintain rapid growth in 2022, with production reaching 3.255 million tons. With its own social attributes, Procambarus clarkii has not only become a super internet celebrity in the catering industry, but also driven the development of the entire industry. However, the supply of Procambarus clarkii raw materials is cyclical. They have been listed on the market since late March, and are in peak season from May to August. After August, most of the products sold in catering are processed from frozen products, and the contradiction between seasonal supply and demand is very prominent. In addition, its protein and water content is high, and it is easy to be used by microorganisms and spoil after inactivation, which makes its nutritional value very easy to lose. Therefore, the storage and preservation of Procambarus clarkii is crucial in the aquatic processing industry.
[0003] Quick freezing is currently the most commonly used method for preserving crayfish with good quality. Among them, liquid nitrogen ultra-low temperature quick freezing technology can significantly improve the water holding capacity and texture quality characteristics of aquatic products. However, for crayfish covered with a hard shell, if an inappropriate ultra-low temperature rapid freezing procedure is used, as the temperature drops sharply, the hardness and brittleness of its shell increase, while the plasticity and toughness decrease, resulting in severe low-temperature freezing and cracking, which leads to a high shell freezing and cracking rate of quick-frozen crayfish. The freezing and cracking rate is generally around 15%, and can be as high as 40% in severe cases, which seriously affects the appearance quality of frozen products, greatly reduces the commodity value of the product, and causes great economic losses. Therefore, the technical problem of low-temperature freezing and cracking faced by crayfish needs to be solved urgently. Summary of the invention
[0004] The invention aims to solve the problem that the shell cracking rate of existing crayfish is very high during quick freezing, and provides a liquid nitrogen quick freezing process for crayfish, which has simple process, strong operability and can effectively reduce the shell cracking rate of crayfish during quick freezing.
[0005] In order to achieve the above object, the present invention adopts the following technical scheme: A liquid nitrogen quick-freezing process of crayfish of the present invention comprises the following steps: (1) Rapid precooling: cooling the crayfish to below 0°C. In the present invention, by precooling the crayfish, the temperature difference between the surface and the interior of the crayfish can be reduced, so as to effectively eliminate the low-temperature cracking caused by excessive thermal stress; on the other hand, precooling advances the time when the volume expansion of the central part of the crayfish due to phase change occurs to the time when the shrimp shell has not yet completely hardened and become brittle, so that the crayfish can withstand greater internal pressure and is not prone to cracking; precooling also reduces the temperature difference between the crayfish and the freezing medium (liquid nitrogen), thereby reducing the freezing speed, which is also conducive to reducing the occurrence of freeze cracking.
[0006] (2) Low temperature protection: spray a cryoprotectant uniformly on the surface of the crayfish, wherein the cryoprotectant is made of the following components in percentage by weight: 1-1.5% trehalose, 3-4% glycerol, 1.5-2% sorbitol, 12-15% glycerol, and the balance water. The present invention can increase the glass transition temperature (Tg') of the crayfish by soaking in the cryoprotectant, and more importantly, can also reduce the content of freezable water in the crayfish, thereby reducing the volume expansion caused by the phase change of water into ice during the freezing process, thereby improving the resistance to low temperature cracking and inhibiting cracking.
[0007] (3) Multi-stage deep freezing: The crayfish prepared in step (2) is placed in a tunnel-type liquid nitrogen quick freezer for deep freezing. After freezing to a central temperature of -75°C, the crayfish is taken out and stored at -18°C.
[0008] Preferably, in step (1), the temperature of the crayfish is reduced to -5 to -1°C. This temperature is the center temperature of the crayfish. Considering both efficiency and effect, it is more appropriate to reduce the temperature to -5 to -1°C.
[0009] Preferably, the temperature of the crayfish is lowered to -5~-1°C within 20~30 minutes.
[0010] Preferably, in step (2), the mass ratio of Procambarus clarkii to the cryoprotectant is 1:(10-15), the soaking temperature is -5--1°C, and the soaking time is 20-30 min.
[0011] Preferably, in step (3), the quick freezing program of the tunnel-type liquid nitrogen quick freezing machine is: 8 min to -20°C, 3 min to -30°C, 3 min to -50°C, 4 min to -70°C, 10 min to -85°C; PID duty cycle 25%, exhaust fan 75%. The inventors combined the liquid nitrogen energy consumption and comprehensively optimized the liquid nitrogen quick freezing program suitable for Procambarus clarkii to obtain the best liquid nitrogen quick freezing program for Procambarus clarkii. By setting this quick freezing program, the freezing and cracking rate of Procambarus clarkii can be effectively reduced.
[0012] Therefore, the present invention has the following beneficial effects: through the rapid precooling process and the cryoprotectant technology, combined with the liquid nitrogen multi-stage ultra-low temperature quick freezing technology, they are jointly applied to inhibit the deep cold quick freezing process of the crayfish, thereby comprehensively improving its low-temperature freezing and cracking resistance, reducing and inhibiting the freezing and cracking rate, helping to improve the freezing quality of the crayfish and increasing its economic value. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 This is a real picture of the deep-frozen quick-frozen Procambarus clarkii in Example 1.
[0014] Figure 2 This is a real picture of the crayfish after deep freezing and quick freezing in Comparative Example 1.
[0015] Figure 3 This is a real picture of the crayfish after deep freezing and quick freezing in Comparative Example 2.
[0016] Figure 4 This is a real picture of the crayfish after deep freezing and quick freezing in Comparative Example 3. DETAILED DESCRIPTION
[0017] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.
[0018] Example 1 (1) Rapid precooling: cool the crayfish to -1°C within 20 min; (2) Cryoprotection: The crayfish was immersed in a cryoprotectant, the mass ratio of crayfish to cryoprotectant was 1:10, the immersion temperature was -1°C, and the immersion time was 30 min. The cryoprotectant was made of the following components in percentage by mass: 1.5% trehalose, 3.8% glycerol, 1.8% sorbitol, 12% glycerol, and the balance was water; (3) Multi-stage deep freezing: Place the crayfish prepared in step (2) in a tunnel-type liquid nitrogen quick freezer for deep freezing and take it out after freezing to a core temperature of -75°C (e.g. Figure 1 The quick freezing program of the tunnel type liquid nitrogen quick freezing machine is as follows: 8 min to -20 °C, 3 min to -30 °C, 3 min to -50 °C, 4 min to -70 °C, and 10 min to -85 °C; the PID duty cycle is 25%, and the exhaust fan is 75%.
[0019] Comparative Example 1 Comparative Example 1 is different from Example 1 in that step (1) of rapid precooling is omitted, and the rest is the same as Example 1. The deep-frozen Procambarus clarkii is Figure 2 shown.
[0020] Comparative Example 2 Comparative Example 2 is different from Example 1 in that step (2) of low temperature protection is omitted, and the rest is the same as Example 1. The deep-frozen Procambarus clarkii is Figure 3 shown.
[0021] Comparative Example 3 Comparative Example 3 is different from Example 1 in that, in step (3), the quick freezing program of the tunnel type liquid nitrogen quick freezing machine is: 10 min to -20°C, 4 min to -30°C, 4 min to -50°C, 4 min to -70°C, and 16 min to -90°C; the PID duty cycle is 30%, the exhaust fan is 80%, and the rest is the same as Example 1. The deep-frozen crayfish is as follows: Figure 4 shown.
[0022] from Figure 1~Figure 4 It can be seen that Figure 1 After deep freezing, the crayfish did not crack. Figure 2~Figure 4 The crayfish after deep freezing all have different degrees of cracking, which shows that the present invention can effectively inhibit the cracking phenomenon of crayfish during deep freezing, which is beneficial to improving the freezing quality of crayfish and increasing its economic value.
[0023] The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.
Claims
1. A liquid nitrogen quick freezing process for crayfish, characterized in that: The following steps are involved: (1) Rapid precooling: cool the crayfish to below 0°C; (2) Cryoprotection: soaking the crayfish in a cryoprotectant, wherein the cryoprotectant is made of the following components in percentage by weight: 1-1.5% trehalose, 3-4% glycerol, 1.5-2% sorbitol, 12-15% glycerol, and the balance water; (3) Multi-stage deep freezing: The crayfish prepared in step (2) is placed in a tunnel-type liquid nitrogen quick freezer for deep freezing. After freezing to a central temperature of -75°C, the crayfish is taken out and stored at -18°C.
2. The liquid nitrogen quick freezing process of Procambarus clarkii according to claim 1, characterized in that: In step (1), the temperature of the crayfish is lowered to -5 to -1°C.
3. The liquid nitrogen quick freezing process for crayfish according to claim 2, characterized in that: Cool the crayfish to -5~-1℃ within 20~30 minutes.
4. The liquid nitrogen quick freezing process for crayfish according to claim 1, characterized in that: In step (2), the mass ratio of Procambarus clarkii to the cryoprotectant is 1:(10-15), the soaking temperature is -5--1°C, and the soaking time is 20-30 min.
5. The liquid nitrogen quick freezing process of Procambarus clarkii according to claim 1, characterized in that: In step (3), the quick freezing program of the tunnel type liquid nitrogen quick freezing machine is: 8 minutes to reduce to -20°C, 3 minutes to reduce to -30°C, 3 minutes to reduce to -50°C, 4 minutes to reduce to -70°C, and 10 minutes to reduce to -85°C; PID duty cycle is 25%, and exhaust fan is 75%.