Method for improving quality stability of minced fillet by using natural deep eutectic solvent and application of method

Abstract

The invention discloses a method for improving the quality stability of minced fillet by using a natural deep eutectic solvent and application thereof, and the preparation method comprises the following steps: mixing the natural deep eutectic solvent with minced fillet to prepare a minced fillet composition, and performing 3D printing to obtain a minced fillet 3D printed product; wherein the natural deep eutectic solvent comprises natural polysaccharide and water, and the natural polysaccharide comprises trehalose and fructo-oligosaccharide. The natural deep eutectic solvent adopted by the invention is green, healthy and non-toxic, trehalose and fructo-oligosaccharide are natural substances conforming to the food health concept, the nutritional value of the food can be improved, the freezing resistance is ensured, the preparation process is simple, the raw materials are green and natural, and the natural deep eutectic solvent can be widely applied to the field of food and has broad market prospects. And certain theoretical guiding significance is provided for wide development and quality improvement of various novel surimi 3D printing products.

Description

Technical Field

[0001] The present application belongs to the technical field of food preservation, and in particular relates to a method for improving the quality stability of fish paste using a natural deep eutectic solvent and its application. Background Art

[0002] As a rapidly developing new technology, food 3D printing has been widely used in the food field due to its advantages such as customization, personalized nutrition, and reduced raw material waste. The development of new products using fish paste as 3D printing raw materials has also become one of the current hot research topics in food 3D printing.

[0003] As the surimi 3D printing technology matures, the storage problem of its printed products is becoming a difficult problem that must be solved. Frozen storage technology is a common method for food storage and preservation, but in the process of frozen storage and transportation, it is inevitable that the product will be repeatedly thawed and frozen due to temperature fluctuations, which will seriously affect the quality of surimi 3D printed products, such as the destruction of complex three-dimensional structures, water loss, protein and fat oxidation, etc. This seriously restricts the development of food 3D printing. Therefore, how to prevent and solve the problem of reduced three-dimensional structure stability and quality stability of surimi 3D printing during frozen storage is a top priority.

[0004] At present, in the field of food freezing and storage, some new physical field assisted freezing technologies or the addition of some food antifreeze agents are usually used to inhibit the quality deterioration of products during freezing and thawing. The new physical field assisted freezing technology equipment is expensive and power-intensive, while traditional commercial antifreeze agents (4% sorbitol + 4% sucrose) will bring high calorific value to the product, which is not in line with the concept of food health. Some new antifreeze agents such as antifreeze proteins, ice nucleation proteins, and antifreeze peptides nowadays have complex preparation processes and high costs, and are difficult to use in actual production. Therefore, it is crucial to develop a green, healthy, and low-cost antifreeze agent to improve the freeze-thaw stability of the quality of surimi 3D printed products. Summary of the invention

[0005] The technical problem to be solved by this application is to overcome the defects of the prior art in that the three-dimensional structural stability and quality stability of surimi 3D printing are reduced during frozen storage, the traditional antifreeze agents cannot meet the quality requirements in terms of function, and the existing new antifreeze agents are complex and costly to prepare and difficult to popularize, and to provide a method and application of a natural deep eutectic solvent to improve the quality stability of surimi. This application utilizes a natural deep eutectic solvent in combination with natural polysaccharides such as oligofructose and trehalose to synthesize an antifreeze agent that can fix water, lower the freezing point, and control the size of ice crystals, thereby achieving excellent antifreeze performance, thereby ensuring quality stability and structural stability during the freeze-thaw process.

[0006] This application adopts the following technical solutions to solve the above technical problems:

[0007] First aspect:

[0008] 1. A method for improving the quality stability of surimi using a natural deep eutectic solvent and its application, wherein the preparation method comprises: mixing the natural deep eutectic solvent with surimi to prepare a surimi composition, and performing 3D printing to obtain a surimi 3D printed product;

[0009] Wherein, the natural deep eutectic solvent is composed of trehalose, oligofructose and water.

[0010] Preferably, in the natural deep eutectic solvent, the mass ratio of trehalose to oligofructose is 1:3 to 3:1, preferably 3:2.

[0011] Preferably, the method for preparing the natural deep eutectic solvent comprises: when the natural deep eutectic solvent comprises trehalose or oligofructose, mixing the natural polysaccharide with the water, and heating and stirring until a uniform and transparent liquid natural deep eutectic solvent is formed;

[0012] The heating and stirring temperature is 40-80°C, preferably 60°C;

[0013] The heating and stirring rotation speed is 80-120 rpm, preferably 100 rpm.

[0014] Preferably, the method for preparing the fish paste comprises: crushing the fish meat, rinsing it, adding water to stir it, filtering it, and dehydrating it.

[0015] Preferably, the method for preparing surimi satisfies at least one of the following conditions:

[0016] The pulverized hole diameter is 2 to 6 mm, preferably 4 mm;

[0017] During the rinsing process, the mass ratio of the crushed fish meat to the water is 1:3 to 1:5, preferably 1:3;

[0018] The water temperature needs to be controlled during the rinsing process, and the water temperature is 3-5°C, for example 4°C;

[0019] The stirring time is 4 to 6 minutes, preferably 5 minutes;

[0020] The stirring speed is 2800-3500 rpm, preferably 3200 rpm;

[0021] The number of rinsing is 2 to 4 times; preferably 3 times;

[0022] Sodium chloride needs to be added in the last rinsing, and the added amount of the sodium chloride is 0.5% of the volume of the water.

[0023] Preferably, the mass ratio of the natural deep eutectic solvent to the surimi is 4%;

[0024] Preferably, the 3D printing method comprises the following steps:

[0025] S1.3D printing model was modeled and designed in the software AUTODESK 123D DESING. First, a cuboid of 30×30×20 mm was constructed, and then a cylinder with a diameter of 15 mm was dug out from the cuboid. The obtained hollow three-dimensional structure was the basic model for 3D printing.

[0026] S2. In the slicing software RepetierHost, set the printing parameters: nozzle diameter; layer height value; fill percentage; printing speed.

[0027] Preferably, the 3D printing adopts a single nozzle extrusion type food 3D printer, and the 3D printing method meets at least one of the following conditions:

[0028] The nozzle diameter is 1.2mm;

[0029] The layer height value is 1.0mm;

[0030] The fill percentage is 75%;

[0031] The printing speed is 30mm / s.

[0032] The present application also provides a method for improving the quality stability of surimi using a natural deep eutectic solvent and its application in frozen surimi products, wherein the frozen surimi products include freshwater fish such as mirror carp, carp, grass carp, and black carp.

[0033] Second aspect:

[0034] The present application found in the study that natural deep eutectic solvent (NADES) is a type of liquid mixture formed by natural molecules through hydrogen bonds found in some cold-resistant plants and animals. Its biggest feature is a high-viscosity supramolecular network formed by a large number of hydrogen bonds. Inspired by this, some natural substances are used to synthesize NADES by heating and stirring, and it is applied in the food field. The special supramolecular network structure of NADES, when added to fish paste, can fix water, lower the freezing point, and control the size of ice crystals, thereby playing an excellent antifreeze performance. Trehalose is a natural non-reducing disaccharide with strong stability and a sweetness of 45% of sucrose. Fructo-oligosaccharide is a short-chain carbohydrate composed of a small amount of fructose units and belongs to the class of prebiotics. Trehalose and oligofructose both contain a large number of hydroxyl groups in their chemical structures, which makes them ideal raw materials for synthesizing NADES. Therefore, NADES prepared with trehalose and oligofructose as raw materials is used in fish paste 3D printing, and has the potential to improve the quality stability of its products during freeze-thaw processes.

[0035] On the basis of conforming to the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present application.

[0036] The reagents and raw materials used in this application are commercially available.

[0037] The positive effects of this application are:

[0038] (1) The method and application of the natural deep eutectic solvent for improving the quality stability of fish paste in the present application uses green and natural substances in the preparation process and has extremely high health and safety:

[0039] (2) The natural deep eutectic solvent used in this application is green, healthy and non-toxic. The selected trehalose and oligofructose are natural substances that conform to the concept of food health, which help to improve the nutritional value of food, ensure antifreeze properties, and at the same time improve the quality stability of fish paste 3D products in freeze-thaw cycles; and the preparation process is simple, the raw materials are green and natural, and can be widely used in the food field. It is a new type of green and healthy antifreeze agent. Adding this natural deep eutectic solvent to fish paste can improve the quality stability of fish paste 3D products in freeze-thaw cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present application can be better understood by referring to the description given below in conjunction with the accompanying drawings. The accompanying drawings, together with the following detailed description, are included in this specification and form a part of this specification, and are used to further illustrate the preferred embodiments of the present application and explain the principles and advantages of the present application.

[0041] in:

[0042] Figure 1 Appearance of surimi 3D printed samples prepared in Example 2 and Comparative Examples 1-2;

[0043] Figure 2 Structural stability of surimi 3D printed samples prepared in Example 2 and Comparative Examples 1-2;

[0044] Figure 3 Moisture content of surimi 3D printed samples prepared in Example 2 and Comparative Examples 1-2;

[0045] Figure 4 Thawing loss of surimi 3D printed samples prepared in Example 2 and Comparative Examples 1-2;

[0046] Figure 5 Freshness of the surimi 3D printed samples prepared in Example 2 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0047] The present application is further described below by way of examples, but the present application is not limited to the scope of the examples. The experimental methods without specific conditions in the following examples are selected according to conventional methods and conditions, or according to the product instructions.

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0049] The raw materials in the following examples and comparative examples are all commercially available.

[0050] The food 3D printer model in the following embodiments and comparative examples is FOOD D0T-D1, purchased from Hangzhou Shiyin Technology Co., Ltd.

[0051] Example 1

[0052] Preparation of natural deep eutectic solvents:

[0053] Trehalose and oligofructose were mixed at a mass ratio of 3:2, and 14.52% of water was added. The mixture was heated to 60°C using a magnetic stirrer equipped with a heating plate and stirred at a constant speed of 100 rpm per minute until a uniform and transparent liquid natural deep eutectic solvent was formed.

[0054] Example 2

[0055] A method for improving the quality stability of surimi using a natural deep eutectic solvent and its application comprises the following steps:

[0056] Step 1: Preparation of fish paste containing natural deep eutectic solvent:

[0057] S1. Remove the head, skin, bones, and internal organs of fresh mirror carp, and collect the fish meat. Use a meat grinder with a pore size of 4mm to mince the fish meat and rinse it. During the rinsing process, the ratio of fish meat to water is 1:3, the water temperature is controlled at 4℃, and it is stirred slowly for 5 minutes. The rinsing liquid is filtered out with a filter cloth, and repeated twice. In the third rinse water, 0.5% of the water volume of sodium chloride is added, and then dehydrated to obtain fish paste;

[0058] S2. 4% (based on the weight of the surimi) of water-adjusted natural deep eutectic solvent was added to the surimi prepared in S1, and the mixture was thoroughly mixed to obtain a surimi containing water-adjusted deep eutectic solvent;

[0059] Step 2: 3D printing of surimi containing natural deep eutectic solvent:

[0060] S1.3D printing model was modeled and designed in the software AUTODESK 123D DESING. First, a cuboid of 30×30×20 mm was constructed, and then a cylinder with a diameter of 15 mm was dug out from the cuboid. The obtained hollow three-dimensional structure was the basic model for 3D printing.

[0061] S2. Set the parameters in the slicer software RepetierHost: nozzle diameter is 1.2mm; layer height is 1.0mm; fill percentage is 75%; print speed is 30mm / s. Print temperature is 25+1℃;

[0062] S3. Use a single nozzle extrusion type food 3D printer) for printing.

[0063] Comparative Example 1:

[0064] Step 1: Preparation of fish paste containing water-containing deep eutectic solvent:

[0065] Remove the head, skin, bones, and internal organs of fresh mirror carp, and collect the fish meat. Use a meat grinder with a pore size of 4mm to mince the fish meat and rinse it. During the rinsing process, the ratio of fish meat to water is 1:3, the water temperature is controlled at 4℃, and it is stirred slowly for 5 minutes. The rinsing liquid is filtered out with a filter cloth, and repeated twice. In the third rinse water, 0.5% of the water volume of sodium chloride is added, and then dehydrated to obtain fish paste;

[0066] Step 2: 3D printing of surimi without natural deep eutectic solvent:

[0067] S1.3D printing model was modeled and designed in the software AUTODESK 123D DESING. First, a cuboid of 30×30×20 mm was constructed, and then a cylinder with a diameter of 15 mm was dug out from the cuboid. The obtained hollow three-dimensional structure was the basic model for 3D printing.

[0068] S2. Set the parameters in the slicer software RepetierHost: nozzle diameter is 1.2mm; layer height is 1.0mm; fill percentage is 75%; print speed is 30mm / s. Print temperature is 25+1℃;

[0069] S3. Use a single nozzle extrusion type food 3D printer for printing.

[0070] Comparative Example 2:

[0071] Step 1: Preparation of fish paste containing commercial antifreeze:

[0072] The fresh mirror carp was headed, skinned, boned, and visceral, and the fish meat was collected. The fish meat was minced with a meat grinder with a pore size of 4 mm, and rinsed. During the rinsing process, the ratio of fish meat to water was 1:3, the water temperature was controlled at 4°C, and it was slowly stirred for 5 minutes. The rinsing liquid was filtered out with a filter cloth, and repeated twice. In the third rinse water, 0.5% of the volume of the water was added to sodium chloride, followed by dehydration, and the obtained fish paste was added with a commercial antifreeze agent (4% sorbitol + 4% sucrose).

[0073] Step 2: 3D printing of surimi containing commercial antifreeze:

[0074] S1.3D printing model was modeled and designed in the software AUTODESK 123D DESING. First, a cuboid of 30×30×20 mm was constructed, and then a cylinder with a diameter of 15 mm was dug out from the cuboid. The obtained hollow three-dimensional structure was the basic model for 3D printing.

[0075] S2. Set the parameters in the slicer software RepetierHost: nozzle diameter is 1.2mm; layer height is 1.0mm; fill percentage is 75%; print speed is 30mm / s. Print temperature is 25+1℃;

[0076] S3. Use a single nozzle extrusion type food 3D printer for printing.

[0077] Effect Example 1

[0078] Appearance changes of surimi 3D printed samples

[0079] The changes of surimi 3D printed samples during freeze-thaw cycles were evaluated by viewing the top view and side view of the surimi 3D printed samples.

[0080] Analysis of the appearance changes of surimi 3D printed samples

[0081] like Figure 1 , the surimi without antifreeze added in Comparative Example 1, the surimi with commercial antifreeze (4% sorbitol + 4% sucrose) added in Comparative Example 2, and the surimi with 4% natural deep eutectic solvent added in Example 2 can all be successfully printed, and the 3D printed sample of Example 2 is more refined in appearance than the comparative example. After freeze-thaw treatment, it can be found that with the increase in the number of freeze-thaw cycles, the three-dimensional structure of all samples has undergone varying degrees of deformation. In particular, after 5 freeze-thaw cycles, the structure of Comparative Example 1 was severely deformed, and dumping and collapse occurred; Comparative Example 2 was still able to maintain a three-dimensional structure, but the sample had obvious defects such as cracks and tilting. Only the sample in Example 2 showed only slight deformation, and was still able to maintain a three-dimensional structure without obvious defects.

[0082] Effect Example 2

[0083] Determination of structural stability of surimi 3D printed samples;

[0084]

[0085] Where H is the height of the designed shape, H0 is the product height measured immediately after printing, and H2 is the product height measured after 1 to 5 freeze-thaw cycles after printing. The height is measured using a handheld digital micrometer with an accuracy of 0.01 mm.

[0086] Structural stability analysis of surimi 3D printed samples;

[0087] like Figure 2 , the structural stability of the surimi 3D printed samples in the freeze-thaw cycle was quantified. With the increase in the number of freeze-thaw cycles, the stability of all samples decreased significantly (P<0.05). After 5 freeze-thaw cycles, the surimi 3D printed samples in Comparative Example 1 without the addition of antifreeze had the lowest structural stability, and the structural stabilities of Comparative Example 2 and Example 2 were significantly higher than those of Comparative Example 1 (P<0.05), indicating that the addition of antifreeze can effectively improve the structural stability of the surimi 3D printed samples. However, compared with Example 2, the structural stability of Example 2 was significantly higher than that of Comparative Example 2 (P<0.05), which indicates that the addition of 4% natural deep eutectic solvent is more excellent in improving the shape retention ability of surimi 3D printed samples than traditional commercial antifreeze. ( Figure 2 Capital letters indicate significant differences in structural stability among different surimi treatment groups at the same freeze-thaw times (P<0.05); lowercase letters indicate significant differences in structural stability among different freeze-thaw times among the same surimi treatment group (P<0.05).

[0088] Effect Example 3

[0089] Determination of moisture content of surimi 3D printed samples;

[0090] The moisture content was determined by drying 2 g of sample in a DHG-9240A heated air drying oven (Yiheng Scientific Instrument Co., Ltd., Shanghai, China) until constant weight.

[0091] Analysis of moisture content changes in surimi 3D printed samples

[0092] like Figure 3 , the moisture content of all surimi 3D printed samples decreased to varying degrees with the increase of freeze-thaw cycles. After one freeze-thaw cycle, the moisture content of the surimi 3D printed samples of Comparative Example 2 and Example 2 did not change significantly (P>0.05). Compared with Comparative Example 1, Comparative Example 2 and Example 2 with the addition of antifreeze can effectively inhibit the loss of water. After 5 freeze-thaw cycles, the moisture content of Example 2 was 77.88%, which was significantly higher than that of Comparative Example 1 (73.50%) and Comparative Example 2 (76.59%) (P<0.05). ( Figure 3 Capital letters indicate significant differences in water content among different surimi treatment groups at the same freeze-thaw times (P<0.05); lowercase letters indicate significant differences in water content among different freeze-thaw times among the same surimi treatment group (P<0.05).

[0093] Effect Example 4

[0094] Determination of thawing loss of surimi 3D printed samples

[0095] The surimi 3D printed samples were weighed before and after thawing and marked as W0 and W1. The calculation formula is as follows:

[0096]

[0097] Thawing loss analysis of surimi 3D printed samples

[0098] like Figure 4 , with the increase of freeze-thaw cycles, the thawing loss of all samples increased significantly (P<0.05), which is consistent with the change in moisture content. After 5 freeze-thaw cycles, the thawing loss of comparative example 1 increased to 18.28%, which was significantly higher than that of comparative example 2 (14.11%) and example 2 (11.51%) (P<0.05). All these indicate that the surimi 3D printing sample with 4% NADES added in example 2 has a better water retention capacity and is better than traditional commercial antifreeze agents. Figure 4 (Capital letters indicate significant differences in thawing loss among different surimi treatment groups at the same freeze-thaw times (P<0.05); lowercase letters indicate significant differences in thawing loss among different freeze-thaw times among the same surimi treatment group (P<0.05).

[0099] Effect Example 5

[0100] Freshness determination of surimi 3D printed samples

[0101] The volatile basic nitrogen value (TVB-N) of surimi 3D printed samples was determined according to the Kjeldahl method.

[0102] Analysis of freshness changes of surimi 3D printed samples

[0103] The change of volatile basic nitrogen value (TVB-N) of surimi 3D printed samples can reflect the change of freshness of surimi products. The increase of TVB-N value indicates that the freshness of the product is deteriorating. Figure 5 , with the increase of the number of freeze-thaw cycles, the TVB-N values ​​of all samples showed a significant increase trend (P<0.05). After 5 freeze-thaw cycles, the TVB-N values ​​of Comparative Example 1 and Comparative Example 2 increased to 23.78 mg / 100 g and 15.67 mg / 100 g, respectively, which exceeded the acceptable range of freshwater fish products (15 mg / 100 g). However, the TVB-N value of Example 2 with the addition of 4% NADES can still be maintained at a low level (13.65 mg / 100 g), which shows that 4% NADES can effectively inhibit the decline in the freshness of surimi 3D printing samples, and the effect is better than traditional commercial antifreeze. Figure 5Capital letters indicate significant differences in the volatile basic nitrogen content among different surimi treatment groups at the same freeze-thaw times (P<0.05); lowercase letters indicate significant differences in the volatile basic nitrogen content among the same surimi treatment group at different freeze-thaw times (P<0.05).

[0104] In summary, the present invention designs a method for preparing a natural deep eutectic solvent based on trehalose / oligofructose and introducing an appropriate amount of water. All raw materials are of natural origin and it is a new green and healthy antifreeze agent. Adding the natural deep eutectic solvent to fish paste can improve the quality stability of fish paste 3D products in the freeze-thaw cycle, thereby ensuring the widespread development of various new fish paste 3D printing products.

[0105] Finally, it should be noted that in this application, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0106] Although the present application has been disclosed above through the description of the specific embodiments of the present application, it should be understood that those skilled in the art can design various modifications, improvements or equivalents to the present application within the spirit and scope of the attached scheme. These modifications, improvements or equivalents should also be considered to be included in the scope of protection claimed in the present application.

Claims

1. A method for improving the quality stability of surimi using a natural deep eutectic solvent and its application, characterized in that: The preparation method comprises: mixing a natural deep eutectic solvent with surimi to prepare a surimi composition, and performing 3D printing to obtain a surimi 3D printed product; Wherein, the natural deep eutectic solvent is composed of trehalose, oligofructose and water.

2. The method for improving the quality stability of surimi using a natural deep eutectic solvent as claimed in claim 1 and its application, characterized in that: In the natural deep eutectic solvent, the mass ratio of the trehalose to the oligofructose is 1:3 to 3:1, preferably 3:

2.

3. The method for improving the quality stability of surimi using the natural deep eutectic solvent according to claim 1 or 2 and its application, characterized in that: The preparation method of the natural deep eutectic solvent comprises: when the natural deep eutectic solvent comprises trehalose or oligofructose, the natural polysaccharide is mixed with the water, and heated and stirred until a uniform and transparent liquid natural deep eutectic solvent is formed; The heating and stirring temperature is 50-80°C, preferably 60°C; The heating and stirring rotation speed is 80-120 rpm, preferably 100 rpm.

4. The method for improving the quality stability of surimi using a natural deep eutectic solvent as claimed in claim 3 and its application, characterized in that: The method for preparing the fish paste comprises: crushing the fish meat, rinsing it, adding water to stir it, filtering it, and dehydrating it.

5. The method for improving the quality stability of surimi using a natural deep eutectic solvent as claimed in claim 4 and its application, characterized in that: The method for preparing surimi satisfies at least one of the following conditions: The pulverized hole diameter is 2 to 6 mm, preferably 4 mm; During the rinsing process, the mass ratio of the crushed fish meat to the water is 1:3 to 1:5, preferably 1:3; The water temperature needs to be controlled during the rinsing process, and the water temperature is 3-5°C, for example 4°C; The stirring time is 4 to 6 minutes, preferably 5 minutes; The stirring speed is 2800-3500 rpm, preferably 3200 rpm; The number of rinsing is 2 to 4 times; preferably 3 times; Sodium chloride needs to be added in the last rinsing, and the added amount of the sodium chloride is 0.5% of the volume of the water.

6. The method for improving the quality stability of surimi using a natural deep eutectic solvent as claimed in claim 1 and its application, characterized in that: The mass ratio of the natural deep eutectic solvent to the surimi is 4%.

7. The method for improving the quality stability of surimi using a natural deep eutectic solvent as claimed in claim 1 and its application, characterized in that: The 3D printing method comprises the following steps: S1.3D printing model was modeled and designed in the software AUTODESK 123D DESING. First, a cuboid of 30×30×20 mm was constructed, and then a cylinder with a diameter of 15 mm was dug out from the cuboid. The obtained hollow three-dimensional structure was the basic model for 3D printing. S2. In the slicing software RepetierHost, set the printing parameters: nozzle diameter; layer height value; fill percentage; printing speed.

8. The method for improving the quality stability of surimi using a natural deep eutectic solvent as claimed in claim 7 and its application, characterized in that: The 3D printing adopts a single nozzle extrusion type food 3D printer, and the 3D printing method meets at least one of the following conditions: The nozzle diameter is 1.2mm; The layer height value is 1.0mm; The fill percentage is 75%; The printing speed is 30mm / s.

9. A method for improving the quality stability of surimi using a natural deep eutectic solvent and its application, characterized in that: The invention is applied to frozen surimi products, wherein the frozen surimi products are freshwater fish such as mirror carp, carp, grass carp, black carp, etc.

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