CN109349331B - Liquid nitrogen quick-freezing method for portunids - Google Patents
Liquid nitrogen quick-freezing method for portunids Download PDFInfo
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- CN109349331B CN109349331B CN201811328830.1A CN201811328830A CN109349331B CN 109349331 B CN109349331 B CN 109349331B CN 201811328830 A CN201811328830 A CN 201811328830A CN 109349331 B CN109349331 B CN 109349331B
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- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
- A23B4/00—General methods for preserving meat, sausages, fish or fish products
- A23B4/06—Freezing; Subsequent thawing; Cooling
- A23B4/08—Freezing; Subsequent thawing; Cooling with addition of chemicals or treatment with chemicals before or during cooling, e.g. in the form of an ice coating or frozen block
- A23B4/09—Freezing; Subsequent thawing; Cooling with addition of chemicals or treatment with chemicals before or during cooling, e.g. in the form of an ice coating or frozen block with direct contact between the food and the chemical, e.g. liquid N2, at cryogenic temperature
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- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
- A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
- A23L3/36—Freezing; Subsequent thawing; Cooling
- A23L3/37—Freezing; Subsequent thawing; Cooling with addition of or treatment with chemicals
- A23L3/375—Freezing; Subsequent thawing; Cooling with addition of or treatment with chemicals with direct contact between the food and the chemical, e.g. liquid nitrogen, at cryogenic temperature
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Abstract
The invention relates to the technical field of freezing and fresh-keeping of aquatic products, in particular to a liquid nitrogen quick-freezing method for swimming crabs, which comprises the following steps: (1) cleaning; (2) hole forming; (3) soaking; (4) plating ice clothes; (5) liquid nitrogen temperature equalization quick freezing; (6) and (7) vacuum packaging. The method has the advantages of simple process steps, stable and controllable process and strong operability, and the obtained frozen portunid product has low frost cracking rate, uniform thickness of ice coat, difficult shedding and good appearance quality.
Description
Technical Field
The invention relates to the technical field of freezing and fresh-keeping of aquatic products, in particular to a liquid nitrogen quick-freezing method for swimming crabs.
Background
The portunus trituberculatus meat is tender and tender, tastes delicious, has extremely high protein content and extremely rich essential fatty acid and vitamin A, D content, is popular with Chinese people and is one of the main aquatic products for earning foreign exchange in China. Swimming crabs are regarded as important aquatic resources in China, but because the muscles of the swimming crabs are rich in protein, fat and various mineral substances, the swimming crabs are extremely easy to decay after death, and the crab meat can also have the phenomenon of muscle gelatinization. In order to reduce the quality deterioration of portunids and to suppress the gelatinization of muscle fibers, a low-temperature freezing method is generally adopted. Common methods for freezing swimming crabs at low temperature include flat quick freezing, freezer freezing and liquid nitrogen quick freezing. The liquid nitrogen quick freezing mainly adopts liquid nitrogen to reduce the central temperature of the portunids, and stores the portunids in an environment below 18 ℃ below zero to inhibit the action of microorganisms and enzymes so as to achieve the aim of keeping the portunids fresh. Compared with flat quick freezing and freezer freezing, the liquid nitrogen quick freezing is more beneficial to maintaining the quality of the swimming crabs.
In practical application, however, the liquid nitrogen technology can cause low-temperature freezing damage to crack the swimming crab shells, so that the problem of product quality is seriously influenced, the commodity value of the product is reduced, and great economic loss is caused to enterprises.
For example, chinese patent application publication No. CN106973975A, application publication No. 2017.07.25, discloses an ultra-low temperature liquid nitrogen deep freezing method for portunus trituberculatus, comprising: (1) cleaning; (2) soaking: soaking the portunus trituberculatus in a low-temperature protective agent solution; (3) quick-freezing: carrying out liquid nitrogen quick-freezing treatment on the portunus trituberculatus, wherein the liquid nitrogen quick-freezing treatment is divided into three stages; (4) plating ice clothes; (5) vacuum packaging; (6) and (5) freezing and storing. The quick-freezing method has the following defects: the whole body of the swimming crab is wrapped by the hard shell, and the low-temperature protective agent is difficult to enter the swimming crab through the crab shell during soaking, so the soaking and anti-freezing effects are poor; firstly, quickly freezing the portunid, then placing the quick-frozen portunid in ice water containing an ice coating agent to coat an ice coating on the surface of the portunid, wherein the portunid is firstly frozen from a shell to harden and become crisp (the mechanical strength of the portunid body is poor) so that the frozen portunid shell is difficult to bear the expansion pressure generated when the inside of the portunid is frozen by freezing firstly, thereby easily generating cracks or bulges and still having higher frost cracking rate (8%); thirdly, putting the frozen portunid into ice water containing an ice coating agent to plate ice coatings, wherein the thickness of the ice coatings is not easy to control, and the portunid can generate ice coating when being taken out of the ice water, so that the appearance quality of frozen portunid products is influenced; and (IV) the formed ice coat only has the function of isolating the swimming crabs from the outside and cannot prevent the color change of the swimming crabs.
Disclosure of Invention
The invention aims to solve the technical problems of the portunid quick-freezing method in the prior art, and provides the portunid liquid nitrogen quick-freezing method which adopts a liquid nitrogen uniform temperature quick-freezing method, has simple process steps, stable and controllable process and strong operability.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention relates to a liquid nitrogen quick freezing method for portunids, which comprises the following steps:
(1) cleaning: washing fresh swimming crabs with water, and draining. According to the invention, the swimming crabs are cleaned by clean water, impurities on the surfaces of the swimming crabs are removed, and the degree of draining is no water drops.
(2) Pore-forming: and (3) soaking the portunid in the step (1) in acid liquor for 1-2 h, taking out and draining. In the invention, the swimming crabs are soaked in the acid liquor, so that the acid liquor reacts with inorganic salt (mainly calcium carbonate) in the shells of the swimming crabs, and uniform micropores are formed on the shells of the swimming crabs, thereby being beneficial to the freezing protection liquid in the subsequent immersion step to enter the insides of the swimming crabs to exert the effect, and in addition, the generated micropores can disperse the internal pressure of the externally frozen crab shells when the swimming crabs are quickly frozen, thereby effectively preventing the crab shells from being frozen and cracked; the soaking time can not be too long, otherwise the crab shell is easy to soften, and the generated micropores can improve the roughness of the swimming crabs and are beneficial to the adhesion of the ice coating liquid in the subsequent ice coating process.
(3) Liquid immersion: and (3) soaking the portunid in the step (2) in the freezing protection liquid for 0.5-1 h, and then fishing out and draining. The portunids are soaked in the freezing protection liquid, the cell structures of the portunids are better preserved (the cell integrity is kept, the ice crystal destruction rate is reduced) through the freezing protection liquid, the damage of freezing to the portunids is reduced to the greatest extent, and the freezing quality of the portunids is guaranteed.
(4) Plating ice clothes: and putting the soaked swimming crabs into the icing liquid at 0-3 ℃, fishing out, draining until no liquid drops, putting into liquid nitrogen at-40 to-45 ℃, and immediately fishing out after the surfaces of the swimming crabs are coated with the icing. According to the invention, the portunid is subjected to pore-forming treatment, so that a plurality of uniform micropores are formed in the portunid shell, and when the portunid is frozen, the moisture and juice in the portunid can flow out of the micropores to generate a bubbling phenomenon, so that the appearance quality of the portunid frozen product is seriously affected.
(5) Liquid nitrogen temperature equalization and quick freezing: cooling the quick-frozen environment to-40 to-45 ℃ by spraying liquid nitrogen, keeping the environment temperature to ensure that the swimming crabs in the step (4) are pre-cooled to the central temperature of 0 to-1 ℃, then carrying out uniform temperature on the swimming crabs by cold air at the temperature of-15 to-20 ℃ until the internal and external temperatures of the swimming crabs tend to be consistent, then spraying liquid nitrogen to the swimming crabs to ensure that the quick-frozen environment temperature is reduced to-90 to-95 ℃, keeping the environment temperature until the central temperature of the swimming crabs reaches-10 to-15 ℃, finally carrying out uniform temperature on the swimming crabs by cold air at the temperature of-25 to-30 ℃ until the central temperature of the swimming crabs is reduced to below-18 ℃, and discharging. According to the invention, the portunids are pre-cooled by liquid nitrogen spraying, and the maximum ice crystal generation area of the portunids is about-5 ℃, so that the portunids are pre-cooled to 0-minus 1 ℃ so that the portunids can rapidly pass through the maximum ice crystal generation zone during liquid nitrogen quick freezing, in addition, the temperature difference between the surface and the interior of the portunids can be reduced by pre-cooling, the low-temperature fracture caused by overhigh thermal stress during the liquid nitrogen spraying quick freezing of the portunids is effectively reduced, and the frost cracking rate is reduced; the lower the liquid nitrogen quick-freezing environment temperature is, the faster the central temperature of the portunid is reduced, the shorter the time for the portunid to generate a zone through the maximum ice crystal is, the smaller the formed ice crystal is, the less the damage to the muscle tissue of the portunid is, the better the quality of the portunid is kept, but the too low liquid nitrogen quick-freezing environment temperature can increase the hardness and the cold brittleness of the shell, so that the frost cracking rate is gradually increased, and the comprehensive consideration is that the liquid nitrogen quick-freezing environment temperature of the portunid is controlled to be-90 to-95 ℃; the invention also changes the cooling condition to carry out uniform temperature treatment to lead the internal and external temperatures of the portunid to be consistent after precooling and liquid nitrogen spraying and quick freezing the portunid, and the invention reduces the temperature difference between the periphery and the center of the sample through secondary uniform temperature treatment to lead the shell with lower temperature at the outer side of the portunid to be softened and remove the stress stored in the sample, thereby achieving the effect of dispersing the internal pressure and preventing the portunid from being frozen and cracked.
(6) And (3) vacuum packaging: and (4) bagging the portunids in the step (5) according to the required weight, then carrying out vacuum packaging, and storing at the temperature of-18 ℃.
Preferably, in the step (2), the acid solution is an acetic acid solution with the mass concentration of 3-5%, and the mass ratio of the swimming crabs to the acid solution is 1: (5-10). The acetic acid is easy to obtain, the cost is low, and the concentration of the acetic acid and the addition amount of the acetic acid are strictly controlled in the invention to avoid softening the crab shells.
Preferably, the temperature of the acid solution is 0-10 ℃.
Preferably, in the step (3), the freezing protection liquid consists of the following components in percentage by mass: 3-5% of sucrose, 0.03-0.05% of sodium ascorbate, 0.03-0.05% of sorbitol and the balance of water, wherein the mass ratio of the swimming crabs to the freezing protection liquid is 1: (3-5). In the freezing protection liquid, the sucrose can reduce the generation of ice crystals in cells; the sodium ascorbate has the function of protecting color; the sorbitol can change the state of the bound water embedded in the protein molecules, replace the bound water on the surface of the protein molecules and be bound with the protein molecules, so that the denaturation of the protein is inhibited, and the freezing denaturation of the protein in the portunids is effectively prevented.
Preferably, the temperature of the freezing protection liquid is 0-10 ℃.
Preferably, in the step (4), the ice clothes liquid consists of the following components in percentage by mass: 1-2% of konjac mannan, 0.5-1% of sucrose ester, 0.1-0.2% of sodium polyacrylate, 0.03-0.06% of sodium dehydroacetate, 5-8% of propylene glycol and the balance of water. The ice coating liquid can form a uniform water film on the surface of the portunid, so that an ice coating with uniform thickness and good transparency is formed, the appearance quality of a frozen portunid product is improved, the shell of the portunid is hard and smooth, and after the portunid is soaked in the ice coating liquid, the ice coating liquid is not easy to adhere to the surface of the portunid (the water on the surface of the portunid is less) to form the ice coating with a certain thickness; the sucrose ester can uniformly disperse all components in the invention, and simultaneously, the formed ice coat is transparent and bright, thus being beneficial to improving the appearance quality of the swimming crabs; sodium dehydroacetate as preservative; the sodium polyacrylate can form a glassy transparent film which is the same as that of a clear water coat, the commodity value is obviously improved, the ice coating liquid has no foamability, the trouble of foaming can not occur during soaking, and meanwhile, the sodium polyacrylate has a blocking effect on metal ions, so that the color change of portunids due to the catalytic action of the metal ions can be prevented, the elasticity and the strength of the ice coating can be enhanced, and the falling-off phenomenon of the ice coating due to mechanical impact can be reduced; the propylene glycol is used for dispersing the sodium polyacrylate and has a wetting effect, so that the ice coating liquid can be uniformly attached to the shell of the swimming crab.
Preferably, in the step (5), the temperature of the quick freezing environment is reduced to-40 to-45 ℃ within 2-3 min by spraying liquid nitrogen.
Preferably, in the step (5), the temperature of the quick freezing environment is reduced to-90 to-95 ℃ within 3 to 4min by spraying liquid nitrogen. When the freezing rate exceeds a certain limit, the freezing rate is positively correlated with the low-temperature fracture of the portunid caused by thermal stress, and the higher the freezing rate is, the more serious the low-temperature fracture is. Therefore, in order to preserve the food quality to the maximum extent, the freezing rate is lower than the limit cooling rate of low-temperature breakage of the food, and within the rate, the cooling rate is as fast as possible, so that the temperature of the quick-freezing environment is limited to be reduced to-90 to-95 ℃ within 3-4 min by spraying liquid nitrogen.
Therefore, the invention has the following beneficial effects:
(1) limiting a pore-forming step, so that the acid liquor reacts with inorganic salt (mainly calcium carbonate) in the swimming crab shell to generate uniform micropores on the swimming crab shell, thereby being beneficial to the freezing protection liquid in the subsequent immersion step to enter the inside of the swimming crab to exert the effect, and in addition, the generated micropores can disperse the internal pressure of the externally frozen crab shell when the swimming crab is quickly frozen, thereby effectively preventing the crab shell from being frozen and cracked; the soaking time cannot be too long, otherwise the crab shell is easy to soften, and the generated micropores can improve the roughness of the swimming crabs and are beneficial to the adhesion of ice coating liquid in the subsequent ice coating process;
(2) the sequence of the step of plating the ice coating is limited so as to prevent the water and juice inside the portunid from flowing out of the micropores during quick freezing, and in addition, the ice coating can enhance the mechanical strength of the portunid shell and inhibit the portunid shell from cracking in the quick freezing process;
(3) the formula of the ice coating liquid is limited, and a uniform water film can be formed on the surface of the portunid, so that the ice coating with uniform thickness and good transparency is formed, and the appearance quality of frozen portunid products is improved;
(4) the specific process steps of liquid nitrogen uniform-temperature quick freezing are limited, and through the steps of precooling, uniform temperature, quick freezing and uniform temperature, the frost cracking rate is reduced while the swimming crabs can quickly pass through the maximum ice crystal generation zone;
(5) the method has the advantages of simple process steps, stable and controllable process and strong operability, and the obtained frozen portunid product has low frost cracking rate, uniform thickness of ice coating, difficult shedding and good appearance quality.
Detailed Description
The invention is further described below by means of specific embodiments.
Example 1
(1) Cleaning: cleaning fresh swimming crabs with water, and draining;
(2) pore-forming: putting the portunid in the step (1) into an acid liquor at the temperature of 0 ℃ for soaking for 1h, taking out and draining, wherein the acid liquor is an acetic acid solution with the mass concentration of 3%, and the mass ratio of the portunid to the acid liquor is 1: 10;
(3) liquid immersion: putting the swimming crabs in the step (2) into a freezing protection liquid at the temperature of 0 ℃, soaking for 0.5h, taking out and draining, wherein the freezing protection liquid consists of the following components in percentage by mass: 3% of sucrose, 0.03% of sodium ascorbate, 0.03% of sorbitol and the balance of water, wherein the mass ratio of the swimming crabs to the freezing protection liquid is 1: 5;
(4) plating ice clothes: putting the soaked swimming crabs into an ice coating liquid at 0-3 ℃, fishing out, draining to remove liquid drops, putting into liquid nitrogen at-40 to-45 ℃, and immediately fishing out after the surfaces of the swimming crabs are coated with ice coatings, wherein the ice coating liquid comprises the following components in percentage by mass: 1% of konjak mannan, 0.5% of sucrose ester, 0.1% of sodium polyacrylate, 0.03% of sodium dehydroacetate, 5% of propylene glycol and the balance of water;
(5) liquid nitrogen temperature equalization and quick freezing: reducing the temperature of the quick-frozen environment to-40 ℃ within 2min by spraying liquid nitrogen, keeping the environment temperature to pre-cool the swimming crabs in the step (4) until the central temperature is 0 ℃, then carrying out uniform temperature on the swimming crabs by cold air at the temperature of-15 ℃ until the temperature inside and outside the swimming crabs is consistent, then spraying liquid nitrogen to the swimming crabs to reduce the temperature of the quick-frozen environment to-90 ℃ within 3min, keeping the environment temperature until the central temperature of the swimming crabs reaches-10 ℃, finally carrying out uniform temperature on the swimming crabs by the cold air at the temperature of-25 ℃ until the central temperature of the swimming crabs is reduced to below-18 ℃, and discharging;
(6) and (3) vacuum packaging: and (4) bagging the portunids in the step (5) according to the required weight, then carrying out vacuum packaging, and storing at the temperature of-18 ℃.
Example 2
(1) Cleaning: cleaning fresh swimming crabs with water, and draining;
(2) pore-forming: putting the portunid in the step (1) into acid liquor at the temperature of 5 ℃, soaking for 1.5h, taking out and draining, wherein the acid liquor is an acetic acid solution with the mass concentration of 4%, and the mass ratio of the portunid to the acid liquor is 1: 7. (ii) a
(3) Liquid immersion: putting the swimming crabs in the step (2) into a freezing protection liquid at the temperature of 2 ℃, soaking for 0.7h, taking out and draining, wherein the freezing protection liquid consists of the following components in percentage by mass: 4% of sucrose, 0.04% of sodium ascorbate, 0.04% of sorbitol and the balance of water, wherein the mass ratio of the swimming crabs to the freezing protection liquid is 1: 3.5;
(4) plating ice clothes: putting the soaked swimming crabs into a liquid icing coat at 0-3 ℃, fishing out, draining to remove liquid drops, putting into liquid nitrogen at-42 ℃, and immediately fishing out after the surfaces of the swimming crabs are plated with the liquid icing coat, wherein the liquid icing coat comprises the following components in percentage by mass: 1.5% of konjak mannan, 0.8% of sucrose ester, 0.15% of sodium polyacrylate, 0.05% of sodium dehydroacetate, 7% of propylene glycol and the balance of water;
(5) liquid nitrogen temperature equalization and quick freezing: reducing the temperature of the quick-frozen environment to-42 ℃ within 2.5min by spraying liquid nitrogen, keeping the environment temperature to pre-cool the swimming crabs in the step (4) to the central temperature of-0.5 ℃, then carrying out temperature equalization on the swimming crabs by cold air at-18 ℃ until the temperature inside and outside the swimming crabs is consistent, then spraying liquid nitrogen to the swimming crabs to reduce the temperature of the quick-frozen environment to-92 ℃ within 3.5min, keeping the environment temperature until the central temperature of the swimming crabs reaches-12 ℃, finally carrying out temperature equalization on the swimming crabs by the cold air at-28 ℃ until the central temperature of the swimming crabs is reduced to below-18 ℃, and discharging;
(6) and (3) vacuum packaging: and (4) bagging the portunids in the step (5) according to the required weight, then carrying out vacuum packaging, and storing at the temperature of-18 ℃.
Example 3
(1) Cleaning: cleaning fresh swimming crabs with water, and draining;
(2) pore-forming: putting the portunid in the step (1) into acid liquor at the temperature of 10 ℃ for soaking for 2h, taking out and draining, wherein the acid liquor is an acetic acid solution with the mass concentration of 5%, and the mass ratio of the portunid to the acid liquor is 1: 5;
(3) liquid immersion: soaking the portunid in the step (2) in a freezing protection liquid at the temperature of 10 ℃ for 1h, taking out and draining, wherein the freezing protection liquid comprises the following components in percentage by mass: 5% of sucrose, 0.05% of sodium ascorbate, 0.05% of sorbitol and the balance of water, wherein the mass ratio of the swimming crabs to the freezing protection liquid is 1: 5;
(4) plating ice clothes: putting the soaked swimming crabs into the ice coating liquid at 3 ℃, fishing out the swimming crabs, draining the liquid until no liquid drops, putting the swimming crabs into liquid nitrogen at the temperature of minus 45 ℃, and immediately fishing out the swimming crabs after the ice coatings are plated on the surfaces of the swimming crabs, wherein the ice coating liquid comprises the following components in percentage by mass: 2% of konjak mannan, 1% of sucrose ester, 0.2% of sodium polyacrylate, 0.06% of sodium dehydroacetate, 8% of propylene glycol and the balance of water;
(5) liquid nitrogen temperature equalization and quick freezing: cooling the quick-frozen environment temperature to-45 ℃ within 3min by spraying liquid nitrogen, keeping the environment temperature to pre-cool the swimming crabs in the step (4) to the central temperature of-1 ℃, then carrying out uniform temperature on the swimming crabs by cold air at-20 ℃ until the internal and external temperatures of the swimming crabs tend to be consistent, then spraying liquid nitrogen on the swimming crabs to cool the quick-frozen environment temperature to-95 ℃ within 4min, keeping the environment temperature until the central temperature of the swimming crabs reaches-15 ℃, finally carrying out uniform temperature on the swimming crabs by the cold air at-30 ℃ until the central temperature of the swimming crabs is reduced to below-18 ℃, and discharging;
(6) and (3) vacuum packaging: and (4) bagging the portunids in the step (5) according to the required weight, then carrying out vacuum packaging, and storing at the temperature of-18 ℃.
Selecting 100 fresh portunids with the same specification, freezing the portunids by adopting the methods in the embodiments 1 to 3, finally taking out and counting the number of the frozen portunids, and calculating the frost cracking rate according to the following formula:
the frost cracking rate (%) is N/N100%, wherein N is the number of the portunids, and N is the total number of the portunids.
Obvious cracks can be seen through visual observation, the internal frost cracking of the portunid can be seen through the cracks, the frost cracking condition is not seen under other conditions, and the obtained statistical results are shown in table 1:
TABLE 1 statistic results of freezing crack rate of portunid in each example
| Item | Number of portunid frost crack | Freezing crack Rate (%) |
| Example 1 | 1 | 1 |
| Example 2 | 2 | 2 |
| Example 3 | 1 | 1 |
As can be seen from table 1, the frost cracking rate of the portunid frozen product obtained by the method of each embodiment is lower than 2%, and is significantly reduced compared with that obtained by a conventional rapid liquid nitrogen freezing method (freezing temperature is about-35 ℃, freezing time is more than 2 h) (the frost cracking rate of the portunid is more than 15%), which indicates that the method of the present invention can significantly reduce the frost cracking rate of the portunid, is favorable for improving the quality of the portunid frozen product, and provides a certain technical support for the liquid nitrogen quick freezing processing of the portunid.
The above-described embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention in any way, and other variations and modifications may be made without departing from the spirit of the invention as set forth in the claims.
Claims (6)
1. A liquid nitrogen quick-freezing method for portunids is characterized by comprising the following steps:
(1) cleaning: cleaning fresh swimming crabs with water, and draining;
(2) pore-forming: soaking the portunid in the step (1) in acid liquor for 1-2 h, taking out and draining; the acid solution is an acetic acid solution with the mass concentration of 3-5%, and the mass ratio of the swimming crabs to the acid solution is 1: (5-10);
(3) liquid immersion: soaking the portunid in the step (2) in a freezing protection solution for 0.5-1 h, taking out and draining;
(4) plating ice clothes: putting the soaked swimming crabs into a 0-3 ℃ icing coat liquid, fishing out, draining until no liquid drops, putting into liquid nitrogen at the temperature of minus 40 to minus 45 ℃, and immediately fishing out after the surfaces of the swimming crabs are coated with the icing coat; the ice clothes liquid comprises the following components in percentage by mass: 1-2% of konjac mannan, 0.5-1% of sucrose ester, 0.1-0.2% of sodium polyacrylate, 0.03-0.06% of sodium dehydroacetate, 5-8% of propylene glycol and the balance of water;
(5) liquid nitrogen temperature equalization and quick freezing: cooling the quick-frozen environment to-40 to-45 ℃ by spraying liquid nitrogen, keeping the environment temperature to ensure that the swimming crabs in the step (4) are precooled to the central temperature of 0 to-1 ℃, then carrying out uniform temperature on the swimming crabs by cold air at-15 to-20 ℃ until the internal and external temperatures of the swimming crabs tend to be consistent, then spraying liquid nitrogen on the swimming crabs to ensure that the quick-frozen environment temperature is reduced to-90 to-95 ℃, keeping the environment temperature until the central temperature of the swimming crabs reaches-10 to-15 ℃, finally carrying out uniform temperature on the swimming crabs by the cold air at-25 to-30 ℃ until the central temperature of the swimming crabs is reduced to below-18 ℃, and discharging;
(6) and (3) vacuum packaging: and (4) bagging the portunids in the step (5) according to the required weight, then carrying out vacuum packaging, and storing at the temperature of-18 ℃.
2. The method for liquid nitrogen quick freezing of swimming crabs according to claim 1, wherein the temperature of the acid solution in the step (2) is 0-10 ℃.
3. The method for liquid nitrogen quick-freezing of swimming crabs according to claim 1, wherein in the step (3), the freezing protection liquid consists of the following components in percentage by mass: 3-5% of sucrose, 0.03-0.05% of sodium ascorbate, 0.03-0.05% of sorbitol and the balance of water, wherein the mass ratio of the swimming crabs to the freezing protection liquid is 1: (3-5).
4. The method for liquid nitrogen quick freezing of the swimming crabs according to claim 1 or 3, wherein the temperature of the freezing and protecting liquid is 0-10 ℃.
5. The method for quickly freezing the swimming crabs by using the liquid nitrogen according to claim 1, wherein in the step (5), the temperature of a quick freezing environment is reduced to-40 to-45 ℃ within 2 to 3min by spraying the liquid nitrogen.
6. The method for quickly freezing the swimming crabs by using the liquid nitrogen according to claim 1, wherein in the step (5), the temperature of a quick freezing environment is reduced to-90 to-95 ℃ within 3 to 4min by spraying the liquid nitrogen.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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