阅读说明：本技术 基于电场协同的水产品快速冷冻方法 (Aquatic product rapid freezing method based on electric field synergy ) 是由 苏来金 杨会成 徐仰丽 李瑞雪 吴明江 李光 吴士专 董恩和 陈云云 彭虹晖 于 2020-11-06 设计创作，主要内容包括：本发明公开了一种基于电场协同的水产品快速冷冻方法,包括下列步骤：(1)配制流化冰浆；(2)将制备好的流化冰浆平铺在泡沫箱底部,将冰温保存完毕的水产品按照层冰层鱼放置在流化冰浆上；(3)低电压冰温处理；(4)高电压冷冻处理；(5)冷冻长期保存。本发明采用冷冻结合电场的方法,得到一种冷冻成本低,保藏效果好的冷冻方法,其水产品体内冰晶粒度更小,数量比普通冷冻更少。(The invention discloses an aquatic product quick freezing method based on electric field synergy, which comprises the following steps: (1) preparing fluidized ice slurry; (2) flatly paving the prepared fluidized ice slurry at the bottom of a foam box, and placing the aquatic product with ice temperature preserved on the fluidized ice slurry according to the layer of ice fish; (3) low-voltage ice temperature treatment; (4) high-voltage freezing treatment; (5) freezing for long-term storage. The invention adopts a method of freezing and combining with an electric field to obtain a freezing method with low freezing cost and good preservation effect, and the ice crystal size in the aquatic product is smaller and the quantity is less than that of the aquatic product by common freezing.)

1. An electric field synergy-based aquatic product rapid freezing method is characterized by comprising the following steps:

(1) preparing a saline solution with the concentration of 1.5-4.5%, and preparing fluidized ice slurry from the prepared saline solution by using a fluidized ice machine;

(2) flatly paving the prepared fluidized ice slurry at the bottom of a foam box, placing aquatic products subjected to ice temperature preservation on the fluidized ice slurry according to ice layer fish, wherein the ice thickness at the bottommost part of the foam box is 2-5cm, each layer of ice covering the surface of the fish body is 2-3cm, the volume ratio of the ice fish is 0.5-1:1, and the fluidized ice completely embeds the fish body and isolates oxygen;

(3) low-voltage ice temperature treatment: placing the foam box in an electrostatic refrigerating machine, wherein the voltage of an electric field is 1.0-2.5KV, the temperature is adjusted to-2 to-5 ℃, and the treatment time is 1-8 h;

(4) high-voltage freezing treatment: adjusting the voltage of an electric field of the electrostatic refrigerating machine in the step (4) to 4.0-6.5 KV, adjusting the temperature to-18-20 ℃, and treating for 20-50 min;

(5) and (3) freezing for long-term storage: and (5) putting the electric field frozen aquatic product in the step (5) into a freezing environment, and storing for a long time.

2. The aquatic product rapid freezing method according to claim 1, wherein the aquatic product is first soaked in the preservative solution for 10-15min for pretreatment.

3. A quick freezing method of aquatic products according to claim 2, wherein the preservative is selected from Xanthomonas polysaccharide, guar gum and sodium alginate, and the mass ratio of the Xanthomonas polysaccharide to the guar gum to the sodium alginate is 1-10:1-3: 1.

4. The method for rapidly freezing aquatic products according to claim 1, wherein in the step (5) of high-voltage freezing treatment, carbon dioxide and nitrogen are filled in a freezing machine.

5. A method of rapidly freezing aquatic products according to claim 4 wherein the volume ratio of carbon dioxide to nitrogen is 75: 25.

Technical Field

The invention relates to an electric field synergy-based aquatic product rapid freezing method, and belongs to the technical field of aquatic product preservation and processing.

Background

Freezing is one of the most widely used food preservation methods, and can preserve food for a long time. The quick freezing can keep the quality, taste and nutrition of the food to the maximum extent, wherein the most influence on the food quality is the ice crystal forming stage, the ice crystals formed by the quick freezing are fine and have small damage to cell tissues, and the juice after being thawed flows out less and has high freshness. From the freezing method of food, the quick freezing technology mainly includes blast freezing, contact freezing, liquefied gas spray freezing, immersion freezing, and the like. According to the type of frozen products, different quick-freezing technologies are needed to achieve the best freezing effect.

Aquatic products have the characteristics of low fat and high protein, are indispensable important components in a reasonable dietary structure, and become an important source for people to take animal protein. Among them, the aquatic products such as fish, shrimp, crab, etc. have good meat quality and unique flavor, and are deeply favored by consumers. The freshness of aquatic products is the most important quality index of the aquatic products, and is the main factor for determining the price of the aquatic products. The aquatic products are rich in nutrient substances, but simultaneously are rich in a large amount of water, are extremely easy to rot, and have quality reduction and even rot caused by fresh-keeping problems in the transportation or storage process of a large amount of fish catches every year. In addition, because the marine fishery resources in China are increasingly deficient, and the demand of people for aquatic products is increasingly increased, the marine fishery in China has to expand the ship shape, the offshore fishery is gradually developed to the ocean, and the development of the ocean fishery not only requires to increase the production capacity, but also requires to keep the quality and the delicate flavor of fish products as far as possible in a long time, so that the diversified demands of the public can be met, and the aim of improving the fishery benefit is fulfilled. Therefore, the problem of keeping the fish fresh is always puzzling the development of the marine fishing industry.

At present, the preservation of the fishery products is mainly realized by adopting a low-temperature refrigeration and freezing method, and generally 3 temperature zones of refrigeration at 0-4 ℃, refrigeration at-4 to-1 ℃ and refrigeration at-40 to-18 ℃ are selected. Generally, the cold preservation and fresh-keeping period with higher temperature is short and can only be maintained for several days, and the fresh-keeping period of low-temperature freezing is long, but the quality deterioration of unpredictable protein denaturation, water retention capacity reduction, juice loss after thawing and the like can be caused by long-term low-temperature freezing, so that the freshness and the taste of the aquatic products are greatly reduced. Aquatic products are one of the most applied products subjected to freezing treatment in the field of foods due to the special physiological characteristics of the aquatic products.

The temperature of-18 ℃ is the optimal temperature for freezing preservation of aquatic products. The method for freezing the aquatic products to the temperature used at the earliest is direct freezing, namely, the aquatic products are directly put into an environment with the temperature of 18 ℃ below zero and are slowly frozen. However, it was found that 0 to-5 ℃ is a stage of ice crystal formation, which is called a maximum ice crystal formation zone. During this process, the temperature degradation is very slow, and extracellular water first crystallizes, causing an increase in the concentration of the extracellular solution, so that intracellular water continuously permeates out of the cell and continues to solidify, and finally larger ice crystals are formed in the extracellular space. The cells are deformed or broken due to the extrusion of the ice crystals, the tissue structure of the food is damaged, the loss rate of the juice after thawing is increased, the original appearance and freshness of the food cannot be maintained, the quality is obviously reduced, and the preservation of aquatic products is extremely unfavorable.

The traditional refrigerator has low freezing speed, large formed ice crystals and great influence on the quality of fishes, shrimps, crabs and the like. Although the immersion freezing has fast heat transfer, ice crystals with certain sizes can also be formed to destroy tissues. The formation of ice crystals can have adverse effects on the texture of aquatic products, and the hardness, stickiness, elasticity and recoverability after thawing can be reduced. The ice crystals can also damage muscle fibers and cells, and the thawing water loss rate and the cooking water loss rate are improved, so that the quality of aquatic products is influenced. Therefore, the research on the method for reducing the formation of ice crystals in the freezing process of the water product has important significance for maintaining the quality of the water product and improving the edible value and the economic value.

In the text of research on ice crystal morphology and auxiliary freezing method of quick-frozen food, the application of electric field in the field of food freezing is described in detail. In recent years, electric fields have been widely studied in the field of food freezing. Unlike high pressure to increase supercooling, the electric field primarily affects the nucleation rate of ice crystals to aid freezing. Under the condition of the electrostatic field, polar water molecules rotate and tend to be aligned with the direction of the electrostatic field, and the water molecules distributed along the direction of the electrostatic field by the electric dipole moment are most stable. Orlowska et al, in the study of high voltage DC electrostatic field to control ice crystal nucleation, point out that the mechanism of electric field assisted freezing is due to the reduction of free energy due to reorientation of water molecules and formation of more ordered cluster structure as the voltage increases the ice crystal nucleation temperature, but this mechanism needs to be further verified by experiments. Saideh et al also teach that the electrostatic field can increase the ice crystal nucleation temperature, but that further increases in electrostatic field intensity cause a decrease in ice crystal nucleation temperature. The optimum electric field intensity for electric field assisted freezing differs from food to food, and it is necessary to separately study the optimum conditions for obtaining various foods. Mok, etc., combines a pulse electric field and a magnetic field for food freezing, and under the combined action of the pulse electric field and the magnetic field, promotes the formation of ice crystals with smaller sizes, and obviously shortens the phase transition time. The electrostatic field can control the nucleation temperature of the ice crystals and improve the quality of frozen products, and is an auxiliary freezing mode with great prospect.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for quickly freezing aquatic products, which has the advantages of low freezing cost, long freezing preservation time, small ice crystal particle size in the aquatic products and high quality after thawing.

The invention discloses an aquatic product quick freezing method based on electric field synergy, which comprises the following steps:

(1) preparing 1.5-4.5% saline solution, and preparing fluidized ice slurry from the prepared saline solution by a fluidized ice machine.

(2) The prepared fluidized ice slurry is flatly paved at the bottom of a foam box, aquatic products stored at ice temperature are placed on the ice slurry according to ice layers of fish, the ice thickness at the bottommost part of the foam box is 2-5cm, each ice layer covering the surface of the fish body is 2-3cm, the volume ratio of the ice fish is 0.5-1:1, and the fluidized ice completely embeds the fish body and isolates oxygen.

(3) Low-voltage ice temperature treatment: the foam box is placed in an electrostatic refrigerating machine, the voltage of an electric field is 1.0-2.5KV, the temperature is adjusted to-10 to-13 ℃, and the treatment time is 2-8 h.

The invention is improved from the prior art in that the aquatic product is pretreated by a low-voltage electric field, and the function of the pretreatment is to form a layer of ice coat on the surface of the aquatic product together with a preservative, so that the problem of zero-gravity dry loss of the aquatic product in the freezing process is solved.

The invention uses the fluidization ice slurry to pre-cool the aquatic product, and the pre-freezing temperature is selected from-10 to-13 ℃ during the pre-cooling, the temperature is lower than the conventional refrigeration temperature, the temperature of the fluidization ice is lower than the conventional refrigeration temperature, and the temperature is higher than the conventional refrigeration temperature, and the low-voltage electric field treatment is carried out at the temperature, thereby achieving the obvious effect.

(4) High-voltage freezing treatment: and (4) adjusting the voltage of an electric field of the electrostatic refrigerating machine in the step (4) to 4.0-6.5 KV, adjusting the temperature to-18-20 ℃, and treating for 10-50 min.

After the low-voltage electric field treatment, the temperature is adjusted to-18 ℃ for short-time high-voltage electric field treatment, and the temperature is the most common temperature for freezing, so that ice crystals formed in aquatic products are endured, and the quality of the aquatic products cannot be influenced by changes in the later preservation process.

(5) And (3) freezing for long-term storage: and (5) putting the electric field frozen aquatic product in the step (5) into a freezing environment, and storing for a long time.

Preferably, the fresh aquatic product (fish and shrimp) fluidized ice slurry is placed into a preservative solution for soaking for 10-15min for pretreatment before precooling the aquatic product.

Preferably, the preservative is selected from Xanthomonas polysaccharide, guar gum and sodium alginate, and the mass ratio of the Xanthomonas polysaccharide to the guar gum to the sodium alginate is 1-10:1-3: 1. The selected preservative has the effects of volatilizing internal water, delaying fat oxidation and inhibiting microorganism growth to prolong the shelf life of fish bodies on one hand, and is easy to be ionized to carry charges when being treated by a later electric field and acts together with the electric field on the other hand, so that the water in aquatic products can increase the nucleation temperature of ice crystals and reduce the particle size of the ice crystals.

Furthermore, based on the same principle and purpose, the research discovers that sodium alginate with the mass fraction of 0.5-5% is added when the fluidized ice slurry is prepared in the step (1), and the sodium alginate in the fluidized ice slurry is easily ionized to carry charges in electric field freezing, so that the sodium alginate in the fluidized ice slurry and the electric field act together to increase the nucleation temperature of ice crystals, so that the frozen ice crystals in the aquatic product can more quickly pass through the maximum ice crystal generation zone, and meanwhile, the particle size of the ice crystals is reduced.

Sodium alginate is a byproduct after iodine and mannitol are extracted from brown algae such as kelp or gulfweed, the molecules of sodium alginate are connected by beta-D-mannuronic acid (beta-D-mannuronic, M) and alpha-L-guluronic acid (alpha-L-guluronic, G) according to a (1 → 4) bond, the sodium alginate is a natural polysaccharide, and xanthomonas polysaccharide (xanthan gum) and guar gum are also natural polysaccharides.

Further, in the step (5) of high voltage freezing treatment, the freezing machine is filled with carbon dioxide and nitrogen. The volume ratio of carbon dioxide to nitrogen was 75: 25. Modified atmosphere preservation is also a common preservation and refrigeration method in the field, the invention can also select to fill fresh-keeping gas during high-pressure treatment, and the conventional modified atmosphere in the field is the combination of carbon dioxide and nitrogen. In order to improve the economy of the freezing preservation, a modified atmosphere method can be selected.

In the existing research, the main focus is on electric field assisted ice temperature preservation (-1 +/-1 ℃), and the specific research on electric field assisted freezing (-below 18 ℃) is less, and the applicant of the invention explores an electric field assisted freezing preservation method on the basis of the research on the preservation and fresh-keeping agent by combining the pre-cooling with fluidized ice and the biological ice temperature in the early stage.

At present, frozen aquatic products are mainly quick-frozen at minus 30 ℃, food passes through the largest ice crystal to generate a zone within 30min, the central temperature is below minus 18 ℃ after freezing, and the size of the formed ice crystal is about 100 mu m. The quick-freezing mode at minus 30 ℃ has higher requirements on a refrigeration house and freezing equipment, and the freezing economy is poorer.

The research on the freezing theory of electric field for food has been carried out in a large number of researches and reports in the prior art, the theory is relatively perfect, the main conclusion is that the high-voltage electric field has a good effect on the fresh-keeping of aquatic products, however, the related researches mainly stay on the basis of theoretical researches, the popularization rate of practical industrialized fresh-keeping application is not high, firstly, the cost problem is that the high-voltage electric field needs to consume a large amount of electric power, and the time for the high-voltage electric field to be treated is often more than ten hours, except for fish with high economic value, for common water products, the method for freezing preservation by the high-voltage electric field is not feasible, secondly, the safety problem is that related journal documents report: the thawing development of the high-voltage electrostatic field still has problems and defects so far, and the safety problem needs to be studied. There is still a risk that higher voltages are required in the high voltage electrostatic field. If the environment humidity is too high, the air in the electrostatic field can be punctured, and certain potential safety hazards are caused. And the operation under the condition of the high-voltage electrostatic field has no influence on human body, and the high-voltage electrostatic refrigerator is applied to meat thawing in Japan, so the high-voltage electrostatic preservation is safer and more reliable, but more research is needed for domestic application. "

In addition, the aquatic products are put into a freezing environment for freezing and are frozen by an auxiliary electric field, the improvement of the granularity of ice crystals is not greatly improved, and the degradation of the quality such as protein denaturation, reduction of water holding capacity, juice loss after unfreezing and the like still occurs after long-term freezing preservation, so that the freshness and the taste of the aquatic products are reduced. In addition, the preservation method of the freezing auxiliary electric field generally needs to apply the electric field for a long time, so the cost is high, and the main factor for greatly limiting the freezing method is also high. The invention is to explore a method for small ice crystal nucleation and low freezing cost in aquatic products on the basis of the existing research theory.

The invention has the beneficial effects that:

in the technical field of freezing preservation of aquatic products, the reduction of the ice crystal size in the aquatic products is an important index for preserving the aquatic products.

Drawings

FIG. 1 is a microstructure diagram of a freezing experiment of a large yellow croaker according to example 3.

FIG. 2 is the microstructure observation of the freezing experiment of the weever in example 4.

Detailed Description

Example 1

The method for quickly freezing the aquatic product based on electric field synergy comprises the following steps:

(1) preparing a saline solution with the concentration of 3%, and preparing fluidized ice slurry from the prepared saline solution by using a fluidized ice machine;

(2) the prepared fluidized ice slurry is flatly paved at the bottom of a foam box, aquatic products with ice temperature preserved are placed on the fluidized ice slurry according to ice layer fish, the ice thickness at the bottommost part of the foam box is 5cm, each layer of ice covering the surface of the fish body is 3cm, the volume ratio of the ice fish is 1:1, the fluidized ice completely embeds the fish body, and oxygen is isolated;

(3) low-voltage ice temperature treatment: placing the foam box in an electrostatic refrigerating machine, wherein the voltage of an electric field is 1.5KV, the temperature is adjusted to-2 ℃, and the processing time is 2 h;

(4) high-voltage freezing treatment: adjusting the voltage of an electric field of the electrostatic refrigerating machine in the step (4) to 4.0 KV, adjusting the temperature to-18 ℃, and treating for 20 min;

(5) and (3) freezing for long-term storage: and (5) putting the electric field frozen aquatic product in the step (5) into a freezing environment, and storing for a long time.

Example 2

The method for quickly freezing the aquatic product based on electric field synergy comprises the following steps:

(1) preparing a saline solution with the concentration of 3%, and preparing fluidized ice slurry from the prepared saline solution by using a fluidized ice machine;

(2) the prepared fluidized ice slurry is flatly paved at the bottom of a foam box, aquatic products with ice temperature preserved are placed on the fluidized ice slurry according to ice layer fish, the ice thickness at the bottommost part of the foam box is 5cm, each layer of ice covering the surface of the fish body is 3cm, the volume ratio of the ice fish is 1:1, the fluidized ice completely embeds the fish body, and oxygen is isolated;

(3) low-voltage ice temperature treatment: placing the foam box in an electrostatic refrigerating machine, wherein the voltage of an electric field is 1.5KV, the temperature is adjusted to-2 ℃, and the processing time is 2 h;

(4) high-voltage freezing treatment: adjusting the voltage of an electric field of the electrostatic refrigerating machine in the step (4) to 4.0 KV, adjusting the temperature to-18 ℃, and treating for 20 min;

(5) and (3) freezing for long-term storage: and (5) putting the electric field frozen aquatic product in the step (5) into a freezing environment, and storing for a long time.

The aquatic product is put into the preservative solution to be soaked for 10min for pretreatment. The preservative is selected from Xanthomonas polysaccharide, guar gum and sodium alginate, and the mass ratio of the Xanthomonas polysaccharide to the guar gum to the sodium alginate is 2:1: 1.

When the fluidized ice slurry is prepared in the step (1), sodium alginate with the mass fraction of 2% is added, and in electric field freezing, the sodium alginate in the fluidized ice slurry is easily ionized to carry charges and acts with an electric field together, so that the water in the aquatic product body increases the nucleation temperature of ice crystals, the frozen ice crystals in the aquatic product can more quickly pass through the maximum ice crystal generation zone, and meanwhile, the particle size of the ice crystals is reduced.

Example 3 control of freezing experiment of large yellow croaker

1. The experimental fish: the fresh large yellow croaker is purchased from seafood wholesale market in Wenzhou city, and fresh and alive individuals with uniform body state, bright color and full spirit are selected.

2. Experiment design: the experiment is divided into 4 groups, and the preservation treatment method of each group is as follows:

a first group: cryopreservation was performed as provided in example 1. After high-voltage freezing treatment, the electric field is closed, and the temperature is kept at-18 ℃ for storage.

Second group: cryopreservation was performed as provided in example 2. After high-voltage freezing treatment, the electric field is closed, and the temperature is kept at-18 ℃ for storage.

Example 1 differs from example 2 in that example 2 was pretreated with an antistaling agent and sodium alginate was added to the fluidized ice slurry.

Third group: directly starting freezing according to the high-voltage freezing treatment in the step (4) of the embodiment 1, adjusting the voltage of an electric field to 4.0 KV, adjusting the temperature to-18 ℃, and treating for 140 min; after high-voltage freezing treatment, the electric field is closed, and the temperature is kept at-18 ℃ for storage.

And a fourth group: directly storing large yellow croaker in a freezing environment at-18 ℃.

3. Main instruments for experiments:

the main apparatus of this embodiment is a multifunctional electrostatic freezing tester, manufactured by defles technologies, ltd, taiwan.

The first and second groups of samples required the electrostatic function to be turned on, and the third group of samples turned on only the freezing function.

After freezing for 90 days, the sample was taken out and microstructure observation was performed.

4. Microstructure observation

Taking muscle tissue of the large yellow croaker, cutting the muscle tissue into cuboid blocks with the size of 1 mm multiplied by 2 mm, and immediately fixing. Firstly, putting the mixture into 2.5% glutaraldehyde for fixation for more than 2h, taking out the mixture for rinsing by using a phosphate buffer, then putting 1% osmic acid fixing solution for fixation for 1-2 h, and after the fixation is finished, rinsing by using the buffer for 20min and then dehydrating; dehydrating with 70% acetone for 15min, sequentially dehydrating with 80% acetone for 15min, 90% acetone for 15min, and 100% acetone for 10min (twice); placing the dehydrated tissue block in an epoxy resin embedding agent, soaking, then placing in an oven for drying, and placing in the oven at 45 ℃ for more than 12 h; ultrathin section, staining, observing microstructure under transmission electron microscope.

5. The transmission electron microscope image of muscle fiber of large yellow croaker treated by different freezing modes is shown in FIG. 1, and the images A-D respectively show the experimental results of the first to fourth groups.

By observing the organization scheme of the large yellow croaker of the 4 groups of freezing treatment methods in fig. 1, it can be seen that the organization mechanism is more complete because of the small ice crystal size in the organization mechanism in the electric field assisted freezing mode. In panel D, the cell space is greatest in the fish meat and ice crystals are most damaging to the cells.

The figure C shows the direct electric field freezing mode, the number and the range of the ice crystal particles are larger than those of the figures A and B, which proves that the improved freezing mode of the invention has better effect, and the number and the particle diameter of the ice crystal in the figure B are smaller than those of the figure A.

Example 4 control of freezing experiment of weever

1. The experimental fish: the fresh weever is purchased from seafood wholesale market in Wenzhou city, and fresh and alive individuals with uniform body state, bright color and full spirit are selected.

2. Experiment design: the experiment is divided into 4 groups, and the preservation treatment method of each group is as follows:

a first group: cryopreservation was performed as provided in example 1. After high-voltage freezing treatment, the electric field is closed, and the temperature is kept at-18 ℃ for storage.

Second group: cryopreservation was performed as provided in example 2. After high-voltage freezing treatment, the electric field is closed, and the temperature is kept at-18 ℃ for storage.

Example 1 differs from example 2 in that example 2 was pretreated with an antistaling agent and sodium alginate was added to the fluidized ice slurry.

Third group: directly starting freezing according to the high-voltage freezing treatment in the step (4) of the embodiment 1, adjusting the voltage of an electric field to 4.0 KV, adjusting the temperature to-18 ℃, and treating for 140 min; after high-voltage freezing treatment, the electric field is closed, and the temperature is kept at-18 ℃ for storage.

And a fourth group: directly storing large yellow croaker in a freezing environment at-18 ℃.

3. Main instruments for experiments:

the main apparatus of this embodiment is a multifunctional electrostatic freezing tester, manufactured by defles technologies, ltd, taiwan.

The first and second groups of samples required the electrostatic function to be turned on, and the third group of samples turned on only the freezing function.

After freezing for 90 days, the sample was taken out and microstructure observation was performed.

4. Microstructure observation

Taking muscle tissue of the large yellow croaker, cutting the muscle tissue into cuboid blocks with the size of 1 mm multiplied by 2 mm, and immediately fixing. Firstly, putting the mixture into 2.5% glutaraldehyde for fixation for more than 2h, taking out the mixture for rinsing by using a phosphate buffer, then putting 1% osmic acid fixing solution for fixation for 1-2 h, and after the fixation is finished, rinsing by using the buffer for 20min and then dehydrating; dehydrating with 70% acetone for 15min, sequentially dehydrating with 80% acetone for 15min, 90% acetone for 15min, and 100% acetone for 10min (twice); placing the dehydrated tissue block in an epoxy resin embedding agent, soaking, then placing in an oven for drying, and placing in the oven at 45 ℃ for more than 12 h; ultrathin section, staining, observing microstructure under transmission electron microscope.

5. The results of transmission electron microscopy of muscle fibers of weever treated by different freezing modes are shown in FIG. 2, and FIGS. A-D show the results of the experiments of the first to fourth groups, respectively.

By observing the organization structure diagram of the weever in the 4 groups of freezing treatment methods in the figure 2, the result is the same as that of the example 3, the ice crystals formed in the weever are small in granularity and more regular, and the organization structure is more complete by adding the electric field to assist the freezing mode. And the improved freezing mode of example 2 is more effective than that of example 1.