CN117617459B - Fresh-keeping method for processing freshwater fish - Google Patents

Abstract

The invention relates to the technical field of aquatic product processing, in particular to a method for processing and preserving freshwater fish; the method comprises the steps of stunning a live fish, removing mucus from the surface of the fish, removing a fishy odor layer from the surface of the fish, applying marine fish mucus to the fish, and packaging. The method has the beneficial effects of first removing mucus with fishy odor substances carried by the freshwater fish itself, then removing part of the tissues on the surface of the freshwater fish infiltrated by the fishy odor substances together with actinomycetes and blue-green algae attached to the surfaces of the tissues without destroying the integrity of the fish body, and finally applying marine fish mucus to the surface of the fish body, thereby obtaining a whole freshwater fish product which is conducive to preservation, has a lighter fishy odor, and the mucus does not increase the fishy odor as the preservation time increases.

Description

A kind of processing and preservation method of freshwater fish

Technical Field

The invention relates to the technical field of aquatic product processing, in particular to a method for processing and preserving freshwater fish.

Background Art

In recent years, people have found that fish surface mucus contains antioxidant and antibacterial substances (which can slow down the corruption of fish skin and fish meat), and the fish surface mucus is applied to the surface of the fish body that needs to be preserved to achieve the purpose of preservation, but it is currently limited to the preservation of marine fish and fish products (meat slices, minced meat). In the prior art, fish surface mucus is not suitable for the preservation of freshwater fish. The main reason is that most freshwater fish secrete more mucus, and the applied mucus is blocked by the mucus of the fish body and cannot contact the fish body, and cannot produce a substantial effect; one of the main sources of the fishy smell of freshwater fish is mucus. Applying more mucus means that a greater fishy smell may be produced. After the death of freshwater fish, the fishy substances in its mucus will continue to increase and easily penetrate into the fish skin and fish meat, seriously affecting the edible value.

Summary of the invention

In view of the deficiencies of the prior art, the present invention provides a method for processing and preserving freshwater fish, which uses mucus on the surface of fish as a whole fish preservative and does not increase the fishy smell of the fish body.

The technical solution of the present invention is:

A method for processing and preserving freshwater fish, comprising:

Procedure for stunning live fish; and,

Steps for removing mucus from the fish body surface; and,

The step of removing the fishy layer on the surface of the fish body; and,

The step of applying marine fish mucus to the fish body; and,

Packaging steps.

Preferably, the method of stunning live fish is: shocking live fish with pulses of 600-700V, 0.5-1.5A, with a pulse frequency of 0.5-2.0Hz and a shock duration of 1-3s. Generally, the weight of freshwater fish sold on the market is 2-5 kg. The above parameters of shock can ensure that most freshwater fish sold on the market will be stunned quickly (suffocated to death after stunning), avoiding struggling and scratching the fish body.

Preferably, the method for removing mucus from the fish body surface is: allowing sawdust to adhere to the fish body surface, scraping off the sawdust, allowing sawdust to adhere again, scraping off the sawdust again, repeating this operation until there is no mucus visible to the naked eye on the fish body surface, rinsing off the sawdust on the fish body surface, and draining for later use.

Preferably, the sawdust is Melaleuca alternifolia (Myrtaceae Melaleuca alternifolia) sawdust. Melaleuca alternifolia wood is soft and fluffy, and is not easy to scratch the fish skin. In addition, Melaleuca alternifolia contains deodorizing ingredients (eucalyptol, limonene, β-caryophyllene and α-pinene), and repeated rubbing of fish skin and fish scales can reduce the fishy smell of the fish body.

Preferably, the method for removing the fishy smell layer on the surface of the fish body is: the tender meat powder and water are mixed uniformly according to the weight ratio of 1:80-90 to obtain a deodorizing liquid, the fish body is soaked in the deodorizing liquid for 3-7 minutes, the fish body is taken out and immediately transferred to a 75wt% ethanol solution for 2-5 minutes, the fish body is taken out and soaked in clean water for 2-5 minutes, and the water is drained for standby use. The deodorizing liquid hydrolyzes the outer layer of the fish scales, fins, tails, heads, gills, mouths, front ends of the esophagus and partially exposed fish skin on the surface of the fish body. The principle is to use the tender meat powder to have a strong hydrolysis effect on elastin and collagen, but a weak hydrolysis effect on muscle protein, so that it can quickly hydrolyze some tissues on the surface of the fish body, and also make some actinomycetes and blue-green algae separate, and then obtain a fish body with a lighter taste. Then, the enzyme in the tender meat powder is denatured by ethanol, and then the deodorizing liquid is stopped to continue to hydrolyze the fish body, and the number of bacteria on the surface of the fish body is reduced.

Preferably, the temperature of the deodorizing liquid is controlled at 30-44°C. Theoretically, the optimal hydrolysis temperature of tenderizer is 50-60°C, but fish protein is prone to high-temperature denaturation at temperatures above 45°C. Therefore, a temperature is selected that is slightly slower in hydrolysis but less prone to high-temperature denaturation of fish protein.

Preferably, the method of applying marine fish mucus to the fish body is: the marine fish mucus scraped from the surface of fresh large yellow croaker is stirred with a food defoamer and glycerin in a weight ratio of 90:1-3:3-4 to obtain a mixed solution, the fish body is immersed in the mixed solution during stirring, and vacuuming is started after stirring for more than 5 minutes until the stirring is completed. Marine fish mucus is a waste product in large yellow croaker processing; the food defoamer is used to prevent excessive bubbles from being generated when the mixed solution is stirred, and facilitates the air in the gills, oral cavity, esophagus, etc. of the fish body to be separated from the fish body when vacuuming; glycerin can enhance the water retention capacity of marine fish mucus and avoid excessive water loss during vacuuming.

Preferably, the stirring rate is 30 to 50 r/min, the stirring time is 8 to 11 min, and low-speed stirring is used in combination with a defoaming agent to avoid the generation of a large number of tiny bubbles in the marine fish mucus, which is also beneficial to the discharge of air from the fish gills, mouth and esophagus of the fish body; the vacuum degree of vacuum extraction is -0.05 to -0.10 bar, and a smaller vacuum degree is used to induce the discharge of air from the fish gills, mouth and esophagus, slowing down the oxidation of the above-mentioned parts in the subsequent preservation process without causing damage to the fish's internal organs or mucous membranes.

Preferably, the food defoamer is DSA-5 defoamer, which is a food grade defoamer and can be used in food processing.

Preferably, the packaging method is: fish out the fish from the mixed liquid and put it into a packaging bag, and then vacuumize the packaging bag and seal the bag opening. This product is suitable for freezing and refrigeration.

Principle of the invention:

The fishy smell of marine fish comes from trimethylamine produced by muscle decomposition after the fish dies. Therefore, the fishy smell of marine fish mucus produced by processing fresh yellow croaker is lighter, and because it is separated from the fish body, the mucus will not increase in fishy smell over time. The fishy smell of freshwater fish comes from the actinomycetes and cyanobacteria in the mucus on the surface of the fish body and attached to the gills, scales, skin, fins, tail, mouth and esophagus. Freshwater fish mucus itself is rich in water and nutrients, which is suitable for the survival of actinomycetes and cyanobacteria. After the death of the fish, the skin and muscles decompose and release nutrients into the mucus, providing more sufficient nutrients for actinomycetes and cyanobacteria. Therefore, the mucus of freshwater fish will increase in fishy smell due to the rapid proliferation of actinomycetes and cyanobacteria for a period of time after the death of the fish. And it has been proven that the antibacterial substances in the mucus on the surface of the fish body have no effective inhibitory effect on actinomycetes and cyanobacteria. The invention removes mucus from the fish body surface and the outer tissues of the fish gills, fish scales, skin, fish fins, fish tail, oral cavity and esophagus on the fish body surface first, and then applies the marine fish mucus to the fish body surface which contains almost no actinomycetes and blue-green algae, thereby obtaining a whole freshwater fish product with a long shelf life and less fishy smell.

The beneficial effects of the present invention are as follows: firstly, the mucus with fishy smell substances carried by the freshwater fish itself is removed, and then, without destroying the integrity of the fish body, part of the tissues on the surface of the freshwater fish body that are infiltrated by the fishy smell substances together with the actinomycetes and blue-green algae attached to the surface of these tissues are removed, and finally, marine fish mucus is applied to the surface of the fish body, thereby obtaining a whole freshwater fish product that is conducive to preservation, has a lighter fishy smell, and the mucus will not increase the fishy smell as the preservation time increases; the method is environmentally friendly and healthy, will not leave toxic substances in the fish body, is simple and easy to operate, and is suitable for batch processing of freshwater fish.

DETAILED DESCRIPTION

The specific embodiments of the present invention are further described below in conjunction with comparative examples:

Example 1

S1: Put freshwater fish into a water tank, and use an electric fish machine to shock the live fish with pulses of 620V and 0.6A, with a pulse frequency of 0.8Hz and a shock duration of 1.2s, to obtain a dead fish body. The freshwater fish described in Examples 1-3 and Comparative Examples 1-4 are all carp (Cypriniformes, Cyprinidae, Cyprinus) weighing 2 jin ± 10%.

S2 makes sawdust adhere to the fish body surface, scrapes off the sawdust, makes sawdust adhere again, scrapes off the sawdust again, repeats this operation until there is no mucus visible to the naked eye on the fish body surface, rinses off the sawdust on the fish body surface, drains and sets aside, the sawdust is Melaleuca sawdust.

S3: Evenly mix the tenderizing powder and water in a weight ratio of 1:82 to obtain a deodorizing liquid, soak the fish body in the deodorizing liquid for 4 minutes, the temperature of the deodorizing liquid is controlled at 31°C, stir the fish body to make it fully contact with the deodorizing liquid, take out the fish body and immediately transfer it to a 75wt% ethanol solution and soak it for 2.5 minutes, stir the fish body to make it fully contact with the ethanol solution, take out the fish body and soak it in clean water for 2.5 minutes, drain and set aside.

S4: The marine fish mucus scraped from the surface of fresh yellow croaker is stirred with a food defoamer and glycerin in a weight ratio of 90:1.2:3.2 to obtain a mixed liquid, wherein the food defoamer is DSA-5 defoamer. The fish body is immersed in the mixed liquid during stirring. The stirring rate is 32 r/min, and the stirring time is 8.5 min. After stirring for more than 5 min, vacuuming is started, and the vacuum degree of vacuuming is -0.07 bar, until the stirring is completed.

S5 takes the fish body out of the mixed liquid and puts it into a packaging bag, and then evacuates the packaging bag and seals the bag opening.

Example 2

S1 puts freshwater fish into a water tank and uses an electric fish machine to shock the live fish with pulses of 680V and 1.4A. The pulse frequency is 1.8Hz and the shock duration is 2.5s, resulting in a stunned fish body.

S2 makes sawdust adhere to the fish body surface, scrapes off the sawdust, makes sawdust adhere again, scrapes off the sawdust again, repeats this operation until there is no mucus visible to the naked eye on the fish body surface, rinses off the sawdust on the fish body surface, drains and sets aside, the sawdust is Melaleuca sawdust.

S3: Evenly mix the tenderizing powder and water in a weight ratio of 1:88 to obtain a deodorizing liquid, soak the fish body in the deodorizing liquid for 6 minutes, the temperature of the deodorizing liquid is controlled at 42°C, stir the fish body to make it fully contact with the deodorizing liquid, take out the fish body and immediately transfer it to a 75wt% ethanol solution and soak it for 4 minutes, stir the fish body to make it fully contact with the ethanol solution, take out the fish body and soak it in clean water for 4 minutes, drain and set aside.

S4: The marine fish mucus scraped from the surface of fresh large yellow croaker is stirred with a food defoamer and glycerin in a weight ratio of 90:2.8:3.8 to obtain a mixed liquid, wherein the food defoamer is DSA-5 defoamer. The fish body is immersed in the mixed liquid during stirring. The stirring rate is 48 r/min, and the stirring time is 10 min. After stirring for more than 5 min, vacuuming is started, and the vacuum degree of vacuuming is -0.09 bar, until the stirring is completed.

S5 takes the fish body out of the mixed liquid and puts it into a packaging bag, and then evacuates the packaging bag and seals the bag opening.

Example 3

S1 puts freshwater fish into a water tank, and uses an electric fish machine to shock the live fish with pulses of 650V and 1.0A. The pulse frequency is 1.5Hz and the shock duration is 1.5s, so that the fish is stunned.

S2 makes sawdust adhere to the fish body surface, scrapes off the sawdust, makes sawdust adhere again, scrapes off the sawdust again, repeats this operation until there is no mucus visible to the naked eye on the fish body surface, rinses off the sawdust on the fish body surface, drains and sets aside, the sawdust is Melaleuca sawdust.

S3: Evenly mix the tenderizing powder and water in a weight ratio of 1:85 to obtain a deodorizing liquid, soak the fish body in the deodorizing liquid for 5 minutes, the temperature of the deodorizing liquid is controlled at 39°C, stir the fish body to make it fully contact with the deodorizing liquid, take out the fish body and immediately transfer it to a 75wt% ethanol solution and soak it for 3 minutes, stir the fish body to make it fully contact with the ethanol solution, take out the fish body and soak it in clean water for 3 minutes, drain and set aside.

S4: The marine fish mucus scraped from the surface of fresh large yellow croaker is stirred with a food defoamer and glycerin in a weight ratio of 90:1.5:3.5 to obtain a mixed liquid, wherein the food defoamer is DSA-5 defoamer. The fish body is immersed in the mixed liquid during stirring. The stirring rate is 40 r/min, and the stirring time is 10 min. After stirring for more than 5 min, vacuuming is started, and the vacuum degree of vacuuming is -0.07 bar, until the stirring is completed.

S5 takes the fish body out of the mixed liquid and puts it into a packaging bag, and then evacuates the packaging bag and seals the bag opening.

Comparative Example 1

Step S2 is cancelled, and the other steps are the same as those in Example 3.

Comparative Example 2

The meat tenderizer is replaced with deodorizing powder, which is a powder obtained by uniformly mixing star anise, pepper and cinnamon powder in a weight ratio of 5:4:3. The other steps are the same as those in Example 3.

Comparative Example 3

The marine fish mucus was replaced with mucus scraped from the body surface of raw fish (Channa genus, Channa family, Perciformes), and the other steps were the same as those in Example 3.

Comparative Example 4

The marine fish mucus was replaced with mucus scraped from the body surface of grass carp (Cypriniformes, Cyprinidae, genus Ctenopharyngodon), and the other steps were the same as those in Example 3.

Fishy smell experiment

The purpose of the experiment is to test whether the product obtained by the present invention will increase the fishy smell after being refrigerated for a certain period of time.

Experimental method: 9 experimenters conducted independent experiments. Each experimenter took one freshly prepared product of Examples 1-3 and Comparative Examples 1-4, opened the bag and smelled it, and marked it with 1-5 points according to the intensity of the fishy smell from light to heavy. After marking, the bag was sealed again and placed in a refrigerator at 4°C for 5 days. Then the product was taken out, opened the bag and smelled it, and marked it with 1-5 points according to the intensity of the fishy smell from light to heavy. The scores of the 9 experimenters on the fishy smell of each product before and after refrigeration were added together to obtain the scores for comparison and recording.

The experimental results are shown in Table 1.

Table 1 Record of fishy odor scores of each product before and after refrigeration

The products obtained in Examples 1-3 had a light taste, and the fishy smell did not increase significantly after 5 days of cold storage. Comparative Examples 1, 3 and 4 had a slightly stronger taste because of the presence of freshwater fish mucus on the surface. After 5 days of cold storage, the actinomycetes in the freshwater fish mucus multiplied in large quantities, causing the fishy smell to become stronger. Comparative Example 2 had a light taste because of the use of deodorizing powder to remove the fishy smell, but because it contained freshwater fish mucus on the surface, it produced a strong fishy smell after 5 days of cold storage.

Fresh-keeping effect experiment

The purpose of the experiment is to verify that the product obtained by the present invention has a preservation function.

Experimental method: the volatile basic nitrogen of the products obtained in Examples 1-3 and Comparative Examples 1-4 was tested after being refrigerated at 4°C for 5 days; the national standard stipulates the TVB-N value: first-grade fresh meat <15mg/100g; second-grade fresh meat 15-25mg/100g; spoiled meat >25mg/100g.

The experimental results are shown in Table 2.

Table 2 TVB-N value record of volatile basic nitrogen test of each product after refrigeration

It is well known that bacteria such as Pseudomonas, Moraxella, Acinetobacter, Flavobacterium and Shewanella are the main microorganisms that cause the corruption of low-temperature stored fish. Combining Tables 1 and 2, it can be seen that the intensity of the fishy smell is not directly related to the corruption rate. Examples 1-3 and Comparative Example 2 have better antibacterial properties (for the above-mentioned types of corruption bacteria) because they apply the marine fish mucus scraped from the surface of large yellow croaker; Comparative Example 3 applies the mucus scraped from the surface of raw fish, which also has better antibacterial properties; while Comparative Example 1 retains the mucus on the surface of carp, and it is difficult to protect the fish body even if the marine fish mucus scraped from the surface of large yellow croaker is applied; Comparative Example 4 is coated with the mucus scraped from the surface of grass carp, which cannot inhibit corruption. The experiments of Comparative Examples 1 and 4 found that not all fish mucus have the characteristics of inhibiting corruption to achieve the preservation effect.

The above embodiments and descriptions are only for illustrating the principles and best embodiments of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, all of which fall within the scope of the present invention to be protected.

Claims (7)

1. A method for processing and preserving freshwater fish, characterized in that it comprises: Procedure for stunning live fish; and, Steps for removing mucus from the fish body surface; and, The step of removing the fishy layer on the surface of the fish body; and, The step of applying marine fish mucus to the fish body; and, Packaging steps: The method for removing mucus from the fish body surface comprises: allowing sawdust to adhere to the fish body surface, scraping off the sawdust, adhering sawdust again, scraping off the sawdust again, repeating this operation until there is no mucus visible to the naked eye on the fish body surface, washing off the sawdust on the fish body surface, and draining for later use; The method for removing the fishy smell layer on the surface of the fish body is as follows: tenderizing meat powder and water are mixed evenly at a weight ratio of 1:80-90 to obtain a deodorizing liquid, the fish body is soaked in the deodorizing liquid for 3-7 minutes, the fish body is taken out and immediately transferred to a 75wt% ethanol solution for soaking for 2-5 minutes, the fish body is taken out and soaked in clean water for 2-5 minutes, and the water is drained for later use; The method for applying marine fish mucus to the fish body is as follows: the marine fish mucus scraped from the surface of fresh large yellow croaker is stirred with a food defoamer and glycerin in a weight ratio of 90:1-3:3-4 to obtain a mixed liquid, the fish body is immersed in the mixed liquid during stirring, and vacuuming is started after stirring for more than 5 minutes until the stirring is completed. 2. The freshwater fish processing and preservation method according to claim 1 is characterized in that the method of stunning the live fish is: using a pulse electric shock of 600-700V, 0.5-1.5A for the live fish, with a pulse frequency of 0.5-2.0Hz and a duration of 1-3s. 3. The processing and preservation method of freshwater fish according to claim 1, wherein the wood chips are Melaleuca alternifolia sawdust. 4. The method for processing and preserving freshwater fish according to claim 1, characterized in that the temperature of the deodorizing liquid is controlled at 30-44°C. 5. The method for processing and preserving freshwater fish according to claim 1, characterized in that the stirring rate is 30-50 r/min, the stirring time is 8-11 min, and the vacuum degree of vacuuming is -0.05-0.10 bar. 6. The method for processing and preserving freshwater fish according to claim 1, characterized in that the food defoamer is a DSA-5 defoamer. 7. The method for processing and preserving freshwater fish according to claim 1 is characterized in that the packaging method is: taking the fish body out of the mixed liquid and putting it into a packaging bag, and then vacuumizing the packaging bag and sealing the bag opening.