A Quick-freezing and Fresh-keeping Method for Australian Freshwater Lobsters

Abstract

The present invention relates to the technical field of aquatic product preservation, and particularly to a quick-freezing preservation method for Australian freshwater crayfish. A quick-freezing preservation method for Australian freshwater crayfish comprises the following steps: (1) immersing the washed crayfish in an antifreeze protective solution for immersion pre-cooling; (2) performing pulsed ultrasound on the pre-cooled crayfish and then quick-freezing them using liquid nitrogen; (3) immersing the quick-frozen crayfish in an ice glaze solution to coat an ice glaze; (4) vacuum-packing the crayfish with an ice glaze and then storing them frozen. The Australian freshwater crayfish processed by the present invention has a long preservation period, can maintain its good flavor quality for a long time, and effectively solves the problems of the decline in freshness and difficulty in preservation after the Australian freshwater crayfish is captured.

Description

Technical Field

[0001] The present invention relates to the technical field of aquatic product preservation, and particularly to a quick-freezing preservation method for Australian freshwater crayfish. Background Art

[0002] Australian freshwater crayfish (Cherax quadricarinatus), scientifically named smooth-shelled southern crayfish with four ridges, also known as red-clawed crayfish, belongs to the family Parastacidae and the genus Cherax. It is native to Australia and is one of the shrimp species with relatively high economic value in the world. It is cultivated in Zhejiang, Jiangsu, Fujian, Guangdong and Hainan. This shrimp lives in fresh water throughout its life, is omnivorous, has a fast growth rate, can reproduce and hatch naturally in fresh water, has a high survival rate, strong disease resistance, weak aggressiveness, is tolerant of low oxygen and pollution, has strong adaptability, has a large body size, tender meat, rich nutrition, delicious taste, a high edible ratio (the abdomen accounts for 42% - 47% of the total weight), is tolerant of long-distance transportation, and can be sold live in the market. It has the advantages of simple artificial breeding equipment and low cost, so it is widely popular in the market.

[0003] Aquatic products are rich in various nutrient elements such as protein, have a high water content, and at the same time, the endogenous enzyme activity of their own tissues is also relatively strong, resulting in their easy decline in freshness or even spoilage due to the growth and reproduction of microorganisms and their own strong enzyme activity after being caught. At present, freezing technology has been widely used in the long-term preservation of aquatic products. However, due to the characteristics of tender muscle tissue and high water content of aquatic products, traditional slow freezing technology is likely to form large and irregular ice crystals inside aquatic products, thus causing serious mechanical damage to their cells, and further leading to problems such as juice loss, color deterioration, and poor texture characteristics, resulting in a decline in quality.

[0004] Therefore, how to provide a quick-freezing preservation method that can effectively prevent the formation of ice crystals during the freezing of crayfish and achieve the long-term preservation of freshwater crayfish is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a quick-freezing preservation method for Australian freshwater crayfish, aiming to solve the technical problem of how to achieve the long-term preservation of Australian freshwater crayfish.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a quick-freezing preservation method for Australian freshwater crayfish, including the following steps:

[0008] (1) Immerse the washed crayfish in an antifreeze protection solution for immersion pre-cooling;

[0009] (2) Perform pulsed ultrasound on the pre-cooled crayfish, and then use liquid nitrogen for quick freezing;

[0010] (3) Immerse the quick-frozen lobsters in an ice glazing solution to apply an ice glaze;

[0011] (4) After applying the ice glaze, vacuum package the lobsters and store them frozen.

[0012] Preferably, the cryoprotectant solution in step (1) comprises the following components: sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, trehalose, and sorbitol; the mass ratio of sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, trehalose, and sorbitol is 0.1 - 0.3: 0.2 - 0.4: 0.4 - 0.6: 1.5 - 2.5: 1.5 - 2.5.

[0013] Preferably, before use, the cryoprotectant solution in step (1) needs to be precooled to 1.5 - 2.5 °C; the time for immersion precooling is 25 - 35 min.

[0014] Preferably, in step (2), when the mass of the lobster < 90 g, the method of liquid nitrogen quick-freezing is: first maintain at -105 to -95 °C for 3.5 - 4.5 min, then maintain at -125 to -115 °C for 3.5 - 4.5 min; the power of the pulsed ultrasound is 8 - 12 kHz, and the time is 1.5 - 2.5 s;

[0015] When the mass of the lobster is 90 - 100 g, the method of liquid nitrogen quick-freezing is: first maintain at -105 to -95 °C for 4.5 - 5.5 min, then maintain at -125 to -115 °C for 4.5 - 5.5 min; the power of the pulsed ultrasound is 14 - 16 kHz, and the time is 1.5 - 2.5 s;

[0016] When the mass of the lobster > 100 g, the method of liquid nitrogen quick-freezing is: first maintain at -105 to -95 °C for 5.5 - 6.5 min, then maintain at -125 to -115 °C for 5.5 - 6.5 min; the power of the pulsed ultrasound is 23 - 27 kHz, and the time is 4.5 - 5.5 s.

[0017] Preferably, the ice glazing solution in step (3) comprises the following components: rosmarinic acid, sodium alginate, and sodium erythorbate; the mass ratio of rosmarinic acid, sodium alginate, and sodium erythorbate is 0.05 - 0.15: 0.4 - 0.6: 0.5 - 1.5.

[0018] Preferably, before use, the ice glazing solution in step (3) needs to be precooled to 0.5 - 1.5 °C; the time for applying the ice glaze is 15 - 30 s.

[0019] Preferably, in step (4), the vacuum degree of the vacuum packaging is -0.07 to -0.11 MPa, and the vacuum time is 20 - 30 s.

[0020] Preferably, the temperature of the frozen storage in step (4) is -20 to -16 °C.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The components of the anti-freezing protective liquid provided by the present invention are used in combination, which can bind part of the water inside the shrimp body, reduce the ice crystals formed inside the shrimp tissue, and at the same time slow down the denaturation of proteins caused by the freezing process, thereby improving the quality of the quick-frozen lobster and playing the roles of crack prevention, color protection, and water retention.

[0023] For the ice-coating liquid provided by the present invention, rosmarinic acid is suitable for lobster meat products and can improve the flavor of the shrimp meat; sodium alginate has an anti-freezing effect, and sodium erythorbate has an antioxidant effect. Therefore, the ice-coating liquid prepared by the present invention can delay the oxidation of proteins and lipids during frozen storage of lobsters, maintain their freshness, and play the roles of color protection, anti-freezing, and antioxidant. At the same time, the ice coat formed on the surface of the lobster can prevent the spikes from damaging the packaging bag.

[0024] The liquid nitrogen quick-freezing used in the present invention is a rapid freezing technology. Its principle is that liquid nitrogen absorbs a large amount of latent heat and sensible heat of the material during the phase change process, so as to quickly freeze the food. Due to the relatively fast freezing rate, the ice crystals formed inside the samples processed by liquid nitrogen quick-freezing are uniform and fine, thus slowing down the mechanical damage of the ice crystals to the food and being able to better maintain the original flavor and quality of the food. Pulsed ultrasound, as a new processing technology in food freezing, can promote the formation of small ice crystals and improve the quality of frozen food. In addition, since nitrogen is an inert gas, the food will not undergo oxidation during the liquid nitrogen quick-freezing process. Compared with the traditional freezing technology, liquid nitrogen quick-freezing has the advantages of being green and environmentally friendly, having a fast freezing rate, small dry loss of frozen food, and effectively retaining the color, aroma, and taste of the food.

[0025] The quick-freezing process of the present invention is a gradually decreasing temperature process. This is different from the freezing process at a single temperature. If the freezing temperature is relatively high, the ice crystal formation time is long and the ice crystal size is large; if the freezing temperature is too low, the lobster will dehydrate severely, the surface will be brittle and cracked, and the energy consumption will be large. The gradient cooling method of the present invention can improve the temperature uniformity of the freshwater lobster, thereby preventing the lobster from being frozen and cracked due to the severe quick-freezing environment, and can enable the crayfish to quickly pass through the ice crystal formation area, thus ensuring the integrity and quality of the crayfish.

[0026] The Australian freshwater lobster processed by the present invention has a long shelf life and can maintain its good flavor and quality for a long time, effectively solving the problems of the decline in freshness and difficulty in preservation of the Australian freshwater lobster after capture. Brief Description of the Drawings

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to the provided drawings.

[0028] Figure 1 It is the flowchart of the present invention;

[0029] Figure 2 It is the lobster sample obtained by the method of Embodiment 3 of the present invention;

[0030] Figure 3 It is the quick-freezing temperature curve of Australian freshwater lobsters with different specifications processed by the method of Embodiment 3 of the present invention. Detailed implementation manners

[0031] The present invention provides a quick-freezing and fresh-keeping method for Australian freshwater lobsters, including the following steps:

[0032] (1) Immerse the cleaned lobsters in an antifreeze protection solution for immersion pre-cooling;

[0033] (2) Perform pulsed ultrasound on the pre-cooled lobsters, and then use liquid nitrogen for quick-freezing;

[0034] (3) Immerse the quick-frozen lobsters in an ice glaze solution to coat an ice glaze;

[0035] (4) Vacuum package the lobsters coated with an ice glaze and then store them frozen.

[0036] In the present invention, the antifreeze protection solution in step (1) includes the following components: sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, trehalose and sorbitol; the mass ratio of sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, trehalose and sorbitol is 0.1 - 0.3:0.2 - 0.4:0.4 - 0.6:1.5 - 2.5:1.5 - 2.5; preferably 0.2:0.3:0.4 - 0.6:1.5 - 2.5:1.5 - 2.5; further preferably 0.2:0.3:0.5:1:1.5 - 2.5; more preferably 0.2:0.3:0.5:1:2.

[0037] In the present invention, the antifreeze protection solution in step (1) needs to be pre-cooled to 1.5 - 2.5 °C before use; preferably 2 °C.

[0038] In the present invention, the time of immersion pre-cooling in step (1) is 25 - 35 min; preferably 27 - 33 min; further preferably 29 - 31 min; more preferably 30 min.

[0039] In the present invention, in step (2), when the mass of the lobster is < 90 g, the method of liquid nitrogen quick freezing is as follows: first, maintain at -105 to -95 °C for 3.5 to 4.5 min, and then maintain at -125 to -115 °C for 3.5 to 4.5 min; preferably, maintain at -103 to -97 °C for 4 min, and then maintain at -123 to -117 °C for 4 min; more preferably, maintain at -101 to -99 °C for 4 min, and then maintain at -121 to -119 °C for 4 min; most preferably, maintain at -100 °C for 4 min, and then maintain at -120 °C for 4 min.

[0040] The power of the pulsed ultrasound is 8 to 12 kHz, and the time is 1.5 to 2.5 s; preferably, the power of the pulsed ultrasound is 9 to 11 kHz, and the time is 2 s; more preferably, the power of the pulsed ultrasound is 10 kHz, and the time is 2 s.

[0041] When the mass of the lobster is 90 to 100 g, the method of liquid nitrogen quick freezing is as follows: first, maintain at -105 to -95 °C for 4.5 to 5.5 min, and then maintain at -125 to -115 °C for 4.5 to 5.5 min; preferably, maintain at -103 to -97 °C for 5 min, and then maintain at -123 to -117 °C for 5 min; more preferably, maintain at -101 to -99 °C for 5 min, and then maintain at -121 to -119 °C for 5 min; most preferably, maintain at -100 °C for 5 min, and then maintain at -120 °C for 5 min.

[0042] The power of the pulsed ultrasound is 14 to 16 kHz, and the time is 1.5 to 2.5 s; preferably, the power of the pulsed ultrasound is 15 kHz, and the time is 1.5 to 2.5 s; more preferably, the power of the pulsed ultrasound is 15 kHz, and the time is 2 s.

[0043] When the mass of the lobster is > 100 g, the method of liquid nitrogen quick freezing is as follows: first, maintain at -105 to -95 °C for 5.5 to 6.5 min, and then maintain at -125 to -115 °C for 5.5 to 6.5 min; preferably, maintain at -103 to -97 °C for 6 min, and then maintain at -123 to -117 °C for 6 min; more preferably, maintain at -101 to -99 °C for 6 min, and then maintain at -121 to -119 °C for 6 min; most preferably, maintain at -100 °C for 6 min, and then maintain at -120 °C for 6 min.

[0044] The power of the pulsed ultrasound is 23 to 27 kHz, and the time is 4.5 to 5.5 s; preferably, the power of the pulsed ultrasound is 24 to 26 kHz, and the time is 5 s; more preferably, the power of the pulsed ultrasound is 25 kHz, and the time is 5 s.

[0045] In the present invention, the ice-coating liquid in step (3) comprises the following components: rosmarinic acid, sodium alginate, and sodium erythorbate; the mass ratio of rosmarinic acid, sodium alginate, and sodium erythorbate is 0.05 - 0.15:0.4 - 0.6:0.5 - 1.5; preferably 0.07 - 0.13:0.5:0.7 - 1.3; more preferably 0.09 - 0.11:0.5:0.9 - 1.1; still more preferably 0.1:0.5:1.

[0046] In the present invention, the ice-coating liquid in step (3) needs to be precooled to 0.5 - 1.5 °C before use; preferably 1 °C

[0047] In the present invention, the time for ice-coating in step (3) is 15 - 30 s; preferably 17 - 27 s; more preferably 19 - 25 s; still more preferably 20 s.

[0048] In the present invention, the vacuum degree of the vacuum packaging in step (4) is -0.07 - -0.11 MPa; preferably -0.08 - -0.10 MPa; more preferably -0.09 MPa.

[0049] In the present invention, the vacuum time of the vacuum packaging in step (4) is 20 - 30 s; preferably 22 - 28 s; more preferably 24 - 26 s; still more preferably 25 s.

[0050] In the present invention, the freezing storage temperature in step (4) is -20 - -16 °C; preferably -19 - -17 °C; more preferably -18 °C.

[0051] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0052] Example 1

[0053] (1) Experimental materials and reagents

[0054] Australian freshwater crayfish were purchased from a certain market in Nansha, Guangzhou.

[0055] (2) Experimental instruments

[0056] The DJL-QFL liquid nitrogen tunnel freezer was purchased from Shenzhen Dejieli Cryogenic Technology Co., Ltd.; the LT502 electronic balance was purchased from Changshu Tianliang Instrument Co., Ltd.

[0057] (3) Cleaning and classification

[0058] 1) Wash the lobsters in a drum cleaning tank to remove foreign objects and sediment completely, and then classify the lobsters according to their mass into extra-large sized lobsters (>100 g), large sized lobsters (90 - 100 g), and medium sized lobsters (<90 g).

[0059] (4) Impregnation precooling with antifreeze protection liquid

[0060] 1) Put the washed lobsters into the 1.5 °C antifreeze protection liquid for impregnation precooling for 25 min to achieve the effects of stunning the lobsters, precooling, and cryoprotection.

[0061] 2) The formula of the antifreeze protection liquid uses water as the solvent and includes the following components in mass percentages: 0.1% sodium tripolyphosphate, 0.2% sodium pyrophosphate, 0.4% sodium hexametaphosphate, 1.5% trehalose, and 1.5% sorbitol.

[0062] (5) Pulse ultrasonic-assisted gradient cooling and liquid nitrogen quick freezing

[0063] 1) Perform pulse ultrasound on the precooled lobsters and then use liquid nitrogen for quick freezing;

[0064] For medium sized lobsters (<90 g), adopt the quick freezing process of -95 °C (held for 3.5 min), then -115 °C (held for 3.5 min), with a pulse ultrasonic frequency of 8 kHz and a time of 1.5 s;

[0065] For large sized lobsters (90 - 100 g), adopt the quick freezing process of -95 °C (held for 4.5 min), then -115 °C (held for 4.5 min), with a pulse ultrasonic frequency of 14 kHz and a time of 1.5 s;

[0066] For extra-large sized lobsters (>100 g), adopt the quick freezing process of -95 °C (held for 5.5 min), then -115 °C (held for 5.5 min), with a pulse ultrasonic frequency of 23 kHz and a time of 4.5 s.

[0067] (6) Coating with ice glaze

[0068] 1) Precool the ice glaze liquid to 0.5 °C in advance, and immediately immerse the quickly frozen lobsters in the ice glaze liquid for 15 s so that a layer of ice glaze covers the surface of the lobsters.

[0069] 2) The formula of the ice glaze liquid is: using water as the solvent and including the following components in mass percentages: 0.05% rosmarinic acid, 0.4% sodium alginate, and 0.4% sodium erythorbate.

[0070] (7) Vacuum packaging

[0071] 1) Immediately perform vacuum packaging on the quickly frozen crayfish, with a vacuum time of 20 s and a vacuum degree of -0.08 MPa.

[0072] 2) The packaging material is polyethylene composite nylon, which can maintain good properties in ultra-low temperature environment and can withstand the mechanical extrusion of the lobster on the packaging after vacuum pumping.

[0073] (8) Frozen storage

[0074] The vacuum-packed lobster is immediately placed in a foam box and quickly transferred to a -17°C cold storage for frozen storage.

[0075] Example 2

[0076] (1) Experimental materials and reagents

[0077] Australian freshwater lobsters were purchased from a market in Nansha, Guangzhou.

[0078] (2) Experimental instruments

[0079] The DJL-QFL liquid nitrogen tunnel quick-freezing machine was purchased from Shenzhen Dejieli Low Temperature Technology Co., Ltd.; the LT502 electronic balance was purchased from Changshu Tianliang Instrument Co., Ltd.

[0080] (3) Cleaning and classification

[0081] 1) Use a drum cleaning tank to clean the lobsters, remove foreign objects and sediment, and then classify the lobsters according to their mass into extra-large-sized lobsters (>100 g), larger-sized lobsters (90 - 100 g), and medium-sized lobsters (<90 g).

[0082] (4) Immersion pre-cooling with anti-freezing protective liquid

[0083] 1) Put the cleaned lobsters into a 2.5°C anti-freezing protective liquid for immersion pre-cooling for 35 min to achieve the effects of stunning the lobsters, pre-cooling, and freezing protection.

[0084] 2) The anti-freezing protective liquid formula uses water as a solvent and includes the following components in mass percentage: 0.3% sodium tripolyphosphate, 0.4% sodium pyrophosphate, 0.6% sodium hexametaphosphate, 2.5% trehalose, and 2.5% sorbitol.

[0085] (5) Pulse ultrasonic-assisted gradient cooling liquid nitrogen quick-freezing

[0086] 1) Perform pulse ultrasound on the pre-cooled lobsters and then use liquid nitrogen for quick-freezing

[0087] For medium-sized lobsters (<90 g), adopt a quick-freezing process of -105°C (maintained for 4.5 min), and then -125°C (maintained for 4.5 min), with a pulse ultrasound frequency of 12 kHz and a time of 2.5 s;

[0088] For larger-sized lobsters (90 - 100 g), a quick-freezing process is adopted: -105°C (held for 5.5 min), then -125°C (held for 5.5 min), with a pulsed ultrasonic frequency of 16 kHz and a time of 2.5 s;

[0089] For extra-large-sized lobsters (> 100 g), a quick-freezing process is adopted: -105°C (held for 6.5 min), then -125°C (held for 6.5 min), with a pulsed ultrasonic frequency of 27 kHz and a time of 5.5 s.

[0090] (6) Coating with ice glaze

[0091] 1) The ice glaze solution is pre-cooled to 1.5°C in advance. The quickly frozen lobsters are immediately immersed in the ice glaze solution for 30 s, so that a layer of ice glaze covers the surface of the lobsters.

[0092] 2) The formula of the ice glaze solution is: using water as the solvent, including the following components in mass percentage: 0.15% rosmarinic acid, 0.6% sodium alginate, and 1.5% sodium erythorbate.

[0093] (7) Vacuum packaging

[0094] 1) The quickly frozen crayfish are immediately vacuum-packed, with a vacuum time of 30 s and a vacuum degree of -0.11 MPa.

[0095] 2) The packaging material is polyethylene composite nylon, which can maintain good properties in an ultra-low temperature environment and can withstand the mechanical extrusion of the lobsters on the packaging after vacuum pumping.

[0096] (8) Frozen storage

[0097] The vacuum-packed lobsters are immediately placed in a foam box and quickly transferred to a -20°C cold storage for frozen storage.

[0098] Example 3

[0099] (1) Experimental materials and reagents

[0100] Australian freshwater lobsters are purchased from a certain market in Nansha, Guangzhou.

[0101] (2) Experimental instruments

[0102] The DJL-QFL liquid nitrogen tunnel quick-freezing machine is purchased from Shenzhen Dejieli Low Temperature Technology Co., Ltd.; the LT502 electronic balance is purchased from Changshu Tianliang Instrument Co., Ltd.; the WST-491-SGN digital display temperature indicator is purchased from Anhui Jixun Automation Instrument Co., Ltd.

[0103] (3) Cleaning and classification

[0104] 1) Wash the lobsters in a drum cleaning tank to remove foreign matters and sediment completely, and then classify the lobsters according to their mass into extra-large-sized lobsters (>100 g), large-sized lobsters (90 - 100 g), and medium-sized lobsters (<90 g).

[0105] (4) Immersion pre-cooling with anti-freezing protective liquid

[0106] 1) Put the washed lobsters into a 2°C anti-freezing protective liquid and immerse them for 30 minutes for stunning, pre-cooling, and cryoprotection effects.

[0107] 2) The formula of the anti-freezing protective liquid is 0.2% sodium tripolyphosphate, 0.3% sodium pyrophosphate, 0.5% sodium hexametaphosphate, 2% trehalose, and 2% sorbitol.

[0108] (5) Pulse ultrasonic-assisted gradient cooling and liquid nitrogen quick-freezing

[0109] 1) Conduct pulse ultrasound on the pre-cooled lobsters and then use liquid nitrogen for quick-freezing

[0110] For medium-sized lobsters (<90 g), adopt a quick-freezing process of -100°C (held for 4 minutes) and then -120°C (held for 4 minutes), with a pulse ultrasonic frequency of 10 kHz and a time of 2 s;

[0111] For large-sized lobsters (90 - 100 g), adopt a quick-freezing process of -100°C (held for 5 minutes) and then -120°C (held for 5 minutes), with a pulse ultrasonic frequency of 15 kHz and a time of 2 s;

[0112] For extra-large-sized lobsters (>100 g), adopt a quick-freezing process of -100°C (held for 6 minutes) and then -120°C (held for 6 minutes), with a pulse ultrasonic frequency of 25 kHz and a time of 5 s.

[0113] (6) Coating with ice glaze

[0114] 1) Pre-cool the ice glaze liquid to 1°C in advance, and immediately immerse the quickly frozen lobsters in the ice glaze liquid for 25 s so that a layer of ice glaze covers the surface of the lobsters.

[0115] 2) The formula of the ice glaze liquid is: using water as the solvent, including the following components by mass percentage: 0.1% rosmarinic acid, 0.5% sodium alginate, and 1% sodium erythorbate.

[0116] (7) Vacuum packaging

[0117] 1) Immediately conduct vacuum packaging on the quickly frozen crayfish, with a vacuum time of 25 s and a vacuum degree of -0.09 MPa.

[0118] (2) The packaging material is polyethylene composite nylon, which can maintain good properties in ultra-low temperature environments and can withstand the mechanical extrusion of the packaging by the lobster after vacuum pumping.

[0119] (8) Frozen storage

[0120] The vacuum-packaged lobsters are immediately placed in a foam box and quickly transferred to a -18°C cold storage for frozen storage.

[0121] Experimental example 1

[0122] During the process of pulsed ultrasound-assisted gradient cooling and liquid nitrogen quick-freezing of freshwater lobsters of different specifications in Example 3, the central temperature of the lobsters was monitored, and the results are as Figure 3 shown.

[0123] It can be seen from Figure 3 that the central temperature of the freshwater lobsters has dropped below -18°C under different freezing conditions.

[0124] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A quick-freezing and fresh-keeping method for Australian freshwater crayfish, characterized in that, It includes the following steps: (1) Immerse the cleaned lobsters in an antifreeze protective solution for impregnation and precooling for 25 - 35 min; (2) Perform pulsed ultrasound on the precooled lobsters, and then use liquid nitrogen for quick freezing; (3) Immerse the quickly frozen lobsters in an ice glaze solution to apply an ice glaze for 15 - 30 s; (4) Vacuum package the lobsters with an ice glaze and then store them frozen; The antifreeze protective solution described in step (1) includes the following components: sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, trehalose, and sorbitol, with a mass ratio of 0.1 - 0.3:0.2 - 0.4:0.4 - 0.6:1.5 - 2.5:1.5 - 2.5; The antifreeze protective solution described in step (1) needs to be precooled to 1.5 - 2.5 °C before use; In step (2), when the mass of the lobster < 90 g, the method of quick freezing with liquid nitrogen is: first maintain at -105 - -95 °C for 3.5 - 4.5 min, and then maintain at -125 - -115 °C for 3.5 - 4.5 min; the power of the pulsed ultrasound is 8 - 12 kHz, and the time is 1.5 - 2.5 s; When the mass of the lobster is 90 - 100 g, the method of quick freezing with liquid nitrogen is: first maintain at -105 - -95 °C for 4.5 - 5.5 min, and then maintain at -125 - -115 °C for 4.5 - 5.5 min; the power of the pulsed ultrasound is 14 - 16 kHz, and the time is 1.5 - 2.5 s; When the mass of the lobster > 100 g, the method of quick freezing with liquid nitrogen is: first maintain at -105 - -95 °C for 5.5 - 6.5 min, and then maintain at -125 - -115 °C for 5.5 - 6.5 min; the power of the pulsed ultrasound is 23 - 27 kHz, and the time is 4.5 - 5.5 s; The ice glaze solution described in step (3) includes the following components: rosmarinic acid, sodium alginate, and sodium erythorbate, with a mass ratio of 0.05 - 0.15:0.4 - 0.6:0.5 - 1.5; The ice glaze solution described in step (3) needs to be precooled to 0.5 - 1.5 °C before use.

2. The quick-freezing and fresh-keeping method for Australian freshwater crayfish according to claim 1, wherein In step (4), the vacuum degree of the vacuum packaging is -0.07 - -0.11 MPa, and the vacuum time is 20 - 30 s.

3. A quick-freezing and fresh-keeping method for Australian freshwater crayfish according to claim 1, characterized in that, In step (4), the temperature of the frozen storage is -20 - -16 °C.

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