A compound color-protecting agent and method suitable for the freezing and thawing process of yellow catfish after slaughter.

Abstract

The application discloses a compound color protection agent suitable for postmortem yellow-bone fish freezing and thawing processes and a color protection method, and belongs to the technical field of yellow-bone fish post-freezing color protection. The compound color protection agent is composed of an antioxidant and a pH regulator; the compound color protection agent is composed of an antioxidant and a pH regulator; the antioxidant has a mass fraction of 40-45%, and the pH regulator has a mass fraction of 55-60%. The color protection agent is used for soaking yellow-bone fish, vacuum packaging, quick freezing, and thawing in a thawing solution; can effectively delay the shedding of slime on the surface of the yellow-bone fish after slaughtering, freezing and thawing, maintain the original color of the surface of the yellow-bone fish, and effectively solve the problems of small distribution radius and high transportation cost of fresh yellow-bone fish caused by logistics distribution and other problems.

Description

Technical Field

[0001] This invention relates to the field of color protection technology for frozen yellow catfish, specifically to a compound color-protecting agent and method suitable for the freezing and thawing process of yellow catfish after slaughter. Background Technology

[0002] Yellow catfish is prized for its tender texture, boneless nature, and delicious broth, making it a popular choice for both its nutritional and medicinal value. With increasing urbanization and the fast pace of modern life, pre-prepared, pre-washed dishes are gaining popularity in the catering industry. Yellow catfish, which undergoes pre-processing such as slaughtering, cleaning, and quick-freezing, is particularly favored by hot pot restaurants. However, it has also been observed that the surface mucus on quick-frozen yellow catfish easily detaches during the thawing process (freeze-thaw process), causing a change in its color. This, to some extent, affects consumer purchasing desire and reduces the product's perceived value.

[0003] Currently, research on color protection for yellow catfish mainly focuses on upstream aspects such as breeding, feed production, and disease control. Research on color protection during processing is rarely reported, and the few existing studies on yellow catfish preservation primarily focus on novel packaging materials such as polyvinyl alcohol / nano-silver films and composite biological preservatives such as those containing tea polyphenols, lysozyme, and ε-polylysine. For example, Chinese patent CN105077201B discloses a color-protecting agent for tuna and its preparation and application method, which utilizes multiple antioxidants, including sodium iso-VC and sodium citrate, to maintain a good appearance color of tuna. However, this method only addresses color changes caused by post-slaughter spoilage of tuna and does not address the retention and color protection of mucus on the fish surface during freeze-thaw cycles.

[0004] Therefore, delaying the discoloration caused by the shedding of mucus on the surface of frozen and thawed yellow catfish through specific methods has high practical application value and practical guiding significance. Summary of the Invention

[0005] In view of the defects and deficiencies of the existing technology, the present invention provides a compound color-protecting agent and a color-protecting method suitable for the freezing and thawing process of yellow catfish after slaughter, so as to delay the shedding of mucus on the surface of the fish after freezing and thawing and maintain its good surface color, which has high practical application value.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] The first objective of this invention is to provide a compound color-protecting agent suitable for the freezing and thawing process of yellow catfish after slaughter. The compound color-protecting agent is composed of an antioxidant and a pH adjuster. The antioxidant has a mass fraction of 40-45%, and the pH adjuster has a mass fraction of 55-60%.

[0008] In one embodiment, the antioxidant includes one or more of sodium D-isoascorbate, ascorbic acid, and sodium ascorbate.

[0009] In one embodiment, the pH adjuster is citric acid and sodium citrate.

[0010] In one embodiment, the citric acid has a mass fraction of 70-90% in the pH adjuster.

[0011] In one embodiment, the sodium citrate has a mass fraction of 10-30% in the pH adjuster.

[0012] In one embodiment, the compound color-protecting agent consists of an antioxidant and a pH adjuster; the antioxidant has a mass fraction of 40%, and the pH adjuster has a mass fraction of 60%.

[0013] In one embodiment, the compound color-protecting agent consists of an antioxidant and a pH adjuster; the antioxidant has a mass fraction of 45%, and the pH adjuster has a mass fraction of 55%.

[0014] In one embodiment, the compound color-protecting agent consists of 40% sodium D-isoascorbate, 55% citric acid, and 5% sodium citrate.

[0015] In one embodiment, the compound color-protecting agent consists of 20% sodium D-isoascorbate, 25% ascorbic acid, 47% citric acid, and 8% sodium citrate.

[0016] The second objective of this invention is to provide a method for color preservation in the freezing and thawing process of yellow catfish after slaughter, the method comprising the following steps:

[0017] (1) Dissolve the above-mentioned compound color-protecting agent in water to form a color-protecting agent solution;

[0018] (2) After killing the live yellow catfish, remove the internal organs and gills, clean it, and drain it briefly.

[0019] (3) After draining, the yellow catfish are soaked in a color-protecting agent solution; after soaking, they are taken out, put into bags, and vacuum-packed.

[0020] (4) Place the vacuum-packed yellow catfish from step (3) into a quick-freezing room for quick-freezing;

[0021] (5) Take the quick-frozen yellow catfish from the vacuum bag in step (4) and thaw it in the thawing solution.

[0022] In step (1), the color-protecting agent accounts for 4.0-8.0% of the mass concentration of the color-protecting agent solution, the pH value of the color-protecting agent solution is between 2 and 4, and the temperature of the color-protecting agent solution is 15-25℃.

[0023] In one embodiment, the soaking time in step (3) is 1.0 to 1.5 hours.

[0024] In one embodiment, the mass ratio of the color-protecting agent solution in step (3) to the yellow catfish is 1:1 to 2:1.

[0025] In one embodiment, after soaking the yellow catfish in step (3), care should be taken to handle it gently to reduce the damage to the mucus on the surface of the fish by external force. At the same time, attention should be paid to the vacuum time to avoid excessive squeezing of the yellow catfish.

[0026] In one embodiment, the temperature of the quick-freezing chamber in step (4) is -30 to -32°C, and the quick-freezing time is 6.0 to 8.0 hours.

[0027] In one embodiment, the thawing solution in step (5) is an alkaline solution of food-grade sodium bicarbonate or sodium carbonate with a mass fraction of 0.1 to 0.2%.

[0028] In one embodiment, the thawing solution in step (5) is 1 to 1.5 times the mass of the yellow catfish.

[0029] In one embodiment, the temperature of the thawing solution in step (5) is 4-6°C, and the thawing time is 20-40 min.

[0030] A third objective of this invention is to provide a method for increasing the mucus adhesion rate on the surface of yellow catfish during freezing and thawing, the method comprising the following steps:

[0031] (1) Dissolve the above-mentioned compound color-protecting agent in water to form a color-protecting agent solution;

[0032] (2) After killing the live yellow catfish, remove the internal organs and gills, clean it, and drain it briefly.

[0033] (3) After draining, the yellow catfish are soaked in a color-protecting agent solution; after soaking, they are taken out, put into bags, and vacuum-packed.

[0034] (4) Place the vacuum-packed yellow catfish from step (3) into a quick-freezing room for quick-freezing;

[0035] (5) Take the quick-frozen yellow catfish from the vacuum bag in step (4) and thaw it in the thawing solution.

[0036] In step (1), the color-protecting agent accounts for 4.0-8.0% of the mass concentration of the color-protecting agent solution, and the pH value of the color-protecting agent solution is between 2 and 4; the temperature of the color-protecting agent solution is 15-25℃; and the thawing solution in step (5) is an alkaline solution of food-grade sodium bicarbonate or sodium carbonate with a mass fraction of 0.1-0.2%.

[0037] The beneficial effects of this invention are:

[0038] (1) The raw materials of the compound color-protecting agent of the present invention are inexpensive, easy to obtain, and simple to prepare, and have high food safety. The pH adjuster in the compound color-protecting agent makes the overall pH value of the color-protecting agent solution between 2 and 4. When used for soaking yellow catfish, it is beneficial for the yellow catfish surface mucus, whose main component is hyaluronic acid, to form a gel that is not easy to fall off. At the same time, during the thawing process, soaking the quick-frozen yellow catfish in an alkaline solution for low-temperature thawing can weaken the hyaluronic acid gel on the surface of the yellow catfish to form a natural hydrogel, restoring the fresh yellow catfish to its post-slaughter state; thus achieving the purpose of protecting the surface mucus of the yellow catfish.

[0039] (2) This invention employs a compound agent for color protection during the freezing and thawing process of yellow catfish after slaughter. An antioxidant is used to reduce the oxidative browning of lutein, the coloring substance on the yellow catfish's skin, and vacuum packaging is used to reduce the risk of contact with oxygen during the quick-freezing process. This color protection method is simple to operate and highly practical; the color-protecting agent can be dissolved in water to soak the yellow catfish. After quick-freezing, the yellow catfish can be simply soaked in the thawing solution to thaw and then eaten. It is suitable for various catering establishments, offering immediate and convenient use.

[0040] (3) The color protection method of the present invention can effectively improve the color performance of yellow catfish after slaughter and freezing and thawing, delay the shedding of mucus from the body surface of yellow catfish after freezing and thawing, and retain the original color of yellow catfish to a certain extent, thereby improving its freeze resistance. On the other hand, the color protection method provided by the present invention can effectively solve the problems of small delivery radius and high transportation cost of fresh yellow catfish caused by logistics and distribution issues. Attached Figure Description

[0041] Figure 1 This is a comparison image of freshly slaughtered yellow catfish in this invention and yellow catfish treated in Example 1.

[0042] Figure 2 This is a comparison image of freshly slaughtered yellow catfish in this invention and yellow catfish treated in Example 2.

[0043] Figure 3 This is a comparison image of freshly slaughtered yellow catfish in this invention and yellow catfish treated in Comparative Example 1.

[0044] Figure 4 This is a comparison image of freshly slaughtered yellow catfish in this invention and yellow catfish treated in Comparative Example 2.

[0045] Figure 5 This is a comparison image of freshly slaughtered yellow catfish in this invention and yellow catfish treated in Comparative Example 3.

[0046] Figure 6This is a comparison image of freshly slaughtered yellow catfish in this invention and yellow catfish treated in Comparative Example 4.

[0047] Figure 7 This is a comparison image of freshly slaughtered yellow catfish in this invention and yellow catfish treated in Comparative Example 5. Detailed Implementation

[0048] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0049] Unless otherwise specified, all percentages in this invention are in units of weight, and all equipment and materials are commercially available or commonly used in this industry.

[0050] The measurement methods involved in the embodiments and comparative examples of this invention are as follows:

[0051] 1. Determination of mucus adhesion rate on the surface of yellow catfish:

[0052] 1.1 Materials and Instruments: Digital camera, standard coordinate paper grid (1mm×1mm scale, waterproofed with a sealing film).

[0053] 1.2 Methods: Yellow catfish were placed on graph paper, one side facing up and the other side down. Digital images of the fish were taken and imported into a computer. The images were then printed in color. Areas where mucus had sloughed off the fish's surface were marked with a marker. The number of squares representing the fish's body and the mucus-sloughed areas was counted (squares less than half the area were counted as 0, and squares exceeding half the area were counted as 1). The number of squares occupied by the fish's body was counted as N1, and the number of squares occupied by the mucus-sloughed areas was counted as N2. The mucus adhesion rate on the yellow catfish's surface was determined as W. When taking the photos, the lens should be perpendicular to the plane of the graph paper, and the viewfinder should be parallel to the plane of the graph paper. The experiment was repeated three times, and the average value was taken.

[0054]

[0055] 2. Determination of the color reproduction of yellow catfish

[0056] Digital images of the fish after slaughter and freeze-thaw were obtained using a digital camera. The images were imported into a computer and digital photos of the fish were printed in color. Ten trained personnel were invited to score the color reproduction of the yellow catfish after freeze-thaw. The scoring criteria for the color reproduction of the yellow catfish are shown in Table 1. The above experiment was repeated three times and the average value was taken.

[0057] Table 1. Scoring Criteria for Color Reproduction of Yellow Catfish

[0058]

[0059]

[0060] Example 1

[0061] A compound color-protecting agent suitable for use in the freezing and thawing process of yellow catfish after slaughter, is composed of the following raw materials in the indicated mass fractions: 40% antioxidant sodium D-isoascorbate, 55% pH adjuster citric acid and 5% sodium citrate.

[0062] A method for color preservation in yellow catfish during the freezing and thawing process after slaughter includes the following steps:

[0063] (1) Dissolve the color-protecting agent composed of antioxidant and pH adjuster in an appropriate amount of water to prepare a 5% color-protecting agent solution with a pH value of 2.2;

[0064] (2) After killing the live yellow catfish, remove the internal organs and gills, clean it, and drain it briefly.

[0065] (3) After draining, the yellow catfish was soaked in a color-protecting agent solution for 1.5 hours. The temperature of the color-protecting agent solution was 20℃, and the mass ratio of the color-protecting agent solution to the yellow catfish was 1:1.

[0066] (4) Take out the yellow catfish that have been soaked in the color-protecting agent solution, put them in a bag, and vacuum pack them;

[0067] (5) Place the packaged yellow catfish in a -30℃ quick-freezing room and freeze for 8 hours;

[0068] (6) Take the fully frozen yellow catfish out of the vacuum bag and place it in a sodium bicarbonate solution with a mass of 0.15% at 5°C for 30 minutes to thaw.

[0069] Example 2

[0070] A compound color-protecting agent suitable for the freezing and thawing process of yellow catfish after slaughter, is composed of the following raw materials in the indicated mass fractions: 20% D-isoascorbic acid sodium salt and 25% ascorbic acid antioxidants, 47% citric acid and 8% sodium citrate pH adjuster;

[0071] A method for color preservation in yellow catfish during the freezing and thawing process after slaughter includes the following steps:

[0072] (1) Dissolve the color-protecting agent composed of antioxidant and pH adjuster in an appropriate amount of water to prepare a color-protecting agent solution with a concentration of 8% and a pH value of 3.0;

[0073] (2) After killing the live yellow catfish, remove the internal organs and gills, clean it, and drain it briefly.

[0074] (3) After draining, the yellow catfish was soaked in a color-protecting agent solution for 1.5 hours. The temperature of the color-protecting agent solution was 20°C, and the mass ratio of the color-protecting agent solution to the yellow catfish was 2:1.

[0075] (4) Take out the yellow catfish that have been soaked in the color-protecting agent solution, put them in a bag, and vacuum pack them;

[0076] (5) Place the packaged yellow catfish in a -30℃ quick-freezing room and quick-freeze for 6 hours;

[0077] (6) Take the fully frozen yellow catfish out of the vacuum bag and place it in a sodium bicarbonate solution with a mass of 0.1% at 5°C for 40 minutes to thaw.

[0078] Comparative Example 1

[0079] After the live yellow catfish are slaughtered and cleaned, they are directly vacuum-packed, placed in a -30℃ quick-freezing room for 6 hours, and then thawed in 25℃ water.

[0080] Comparative Example 2

[0081] A compound color-protecting agent suitable for use in the freezing and thawing process of yellow catfish after slaughter, is composed of the following raw materials in the indicated mass fractions: 90% antioxidant sodium D-isoascorbate and 10% pH adjuster citric acid.

[0082] A method for color preservation in yellow catfish during the freezing and thawing process after slaughter includes the following steps:

[0083] (1) Dissolve the color-protecting agent in an appropriate amount of water to prepare a 5% color-protecting agent solution with a pH value of 5.2;

[0084] (2) After killing the live yellow catfish, remove the internal organs and gills, clean it, and drain it briefly.

[0085] (3) After draining, the yellow catfish was soaked in a color-protecting agent solution for 1.5 hours. The temperature of the color-protecting agent solution was 20℃, and the mass ratio of the color-protecting agent solution to the yellow catfish was 1:1.

[0086] (4) Take out the yellow catfish that have been soaked in the color-protecting agent solution, put them in a bag, and vacuum pack them;

[0087] (5) Place the packaged yellow catfish in a -30℃ quick-freezing room and freeze for 8 hours;

[0088] (6) Take the fully frozen yellow catfish out of the vacuum bag and place it in a sodium bicarbonate solution with a mass of 0.15% at 5°C for 30 minutes to thaw.

[0089] Comparative Example 3

[0090] A compound color-protecting agent suitable for use in the freezing and thawing process of yellow catfish after slaughter, is composed of the following raw materials in the indicated mass fractions: 10% antioxidant sodium D-isoascorbate, 80% pH adjuster citric acid, and 10% sodium citrate.

[0091] A method for color preservation in yellow catfish during the freezing and thawing process after slaughter includes the following steps:

[0092] (1) Dissolve the color-protecting agent in an appropriate amount of water to prepare a 5% color-protecting agent solution with a pH value of 1.5;

[0093] (2) After killing the live yellow catfish, remove the internal organs and gills, clean it, and drain it briefly.

[0094] (3) After draining, the yellow catfish was soaked in a color-protecting agent solution for 1.5 hours. The temperature of the color-protecting agent solution was 20℃, and the mass ratio of the color-protecting agent solution to the yellow catfish was 1:1.

[0095] (4) Take out the yellow catfish that have been soaked in the color-protecting agent solution, put them in a bag, and vacuum pack them;

[0096] (5) Place the packaged yellow catfish in a -30℃ quick-freezing room and freeze for 8 hours;

[0097] (6) Take the fully frozen yellow catfish out of the vacuum bag and place it in a sodium bicarbonate solution with a mass of 0.15% at 5°C for 30 minutes to thaw.

[0098] Comparative Example 4

[0099] The only difference from Example 1 is that step (4) vacuum packaging is omitted, and the soaked yellow catfish is directly placed in a -30℃ quick-freezing room for 8 hours; the other parameters and conditions are the same as in Example 1.

[0100] Comparative Example 5

[0101] The only difference from Example 1 is that the sodium bicarbonate solution in step (6) is replaced with water, while the other parameters and conditions are the same as in Example 1.

[0102] Results Measurement

[0103] The surface properties of frozen and thawed yellow catfish from Examples 1 and 2, as well as Comparative Examples 1-5, were measured, and the results are shown in Table 2.

[0104] Table 2. Mucus adhesion rate and color reproduction of yellow catfish surface

[0105] Case Actual product image Surface slime adhesion rate / % Color reproduction Example 1 Figure 1 92 86 Example 2 Figure 2 96 91 Comparative Example 1 Figure 3 10 10 Comparative Example 2 Figure 4 53 65 Comparative Example 3 Figure 5 70 70 Comparative Example 4 Figure 6 82 75 Comparative Example 5 Figure 7 85 53

[0106] The data in the table show that soaking freshly slaughtered yellow catfish in an acidic color-protecting solution containing antioxidants can effectively reduce the oxidative browning of lutein, the coloring substance on the yellow catfish's skin. It also promotes the formation of a gel from the yellow catfish's surface mucus, whose main component is hyaluronic acid, making it less likely to detach after thawing (Examples 1 and 2). Furthermore, analysis of the data from Example 1 and Comparative Example 4 shows that vacuum-packing and then quick-freezing the yellow catfish after soaking in the color-protecting solution effectively reduces its contact with air during the quick-freezing process, thus reducing oxidative discoloration of the yellow catfish's skin.

[0107] As shown by the data from Example 1 and Comparative Example 5, soaking the yellow catfish in the color-protecting agent solution and then quick-freezing it before thawing it in an alkaline solution at low temperature weakens the hyaluronic acid gel on the surface of the yellow catfish, forming a natural hydrogel and restoring the fresh yellow catfish to its post-slaughter state. The color-protecting method of this invention can effectively improve the color appearance of yellow catfish after slaughter and freezing / thawing, delay the shedding of surface mucus after freezing and thawing, and to a certain extent preserve the original color of the yellow catfish, thus improving its freeze resistance. The entire color-protecting process is simple in terms of color-protecting agent solution preparation, readily available materials, and straightforward operation, making it suitable for various catering establishments.

[0108] The above examples are merely specific embodiments of the present invention, and the comparative examples are intended to illustrate the technical points and positive effects of the present invention. The present invention is not limited to the above embodiments; any methods derived directly from or modified from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for increasing the rate of slime adhesion to the surface of yellow bone fish during freezing and thawing, characterized in that, The method comprises the following steps: (1) dissolving the compound color protection agent in water to form a color protection agent solution; The compound color protection agent is composed of an antioxidant and a pH regulator; the mass fraction of the antioxidant is 40-45%, and the mass fraction of the pH regulator is 55-60%; the antioxidant is one or more of D-sodium isoascorbate, ascorbic acid, and sodium ascorbate; The pH regulator is citric acid and sodium citrate; The mass fraction of the citric acid in the pH regulator is 70-90%; The mass fraction of the sodium citrate in the pH regulator is 10-30%; (2) after the fresh and live yellow bone fish is slaughtered, the internal organs and gills are removed, washed clean, and simply drained; (3) the drained yellow bone fish is soaked in the color protection agent solution; after soaking treatment, it is taken out, placed in a bag, and vacuum packaged; (4) the vacuum packaged yellow bone fish of step (3) is placed in a quick freezing library for quick freezing; (5) the quick frozen yellow bone fish of step (4) is taken out of the vacuum bag, soaked in a thawing solution for thawing, and then it is ready; In step (1), the mass concentration of the color protection agent in the color protection agent solution is 4.0-8.0%, the pH value of the color protection agent solution is between 2 and 4, and the temperature of the color protection agent solution is 15-25℃; In step (5), the thawing solution is an alkaline solution of food-grade sodium bicarbonate or sodium carbonate with a mass fraction of 0.1-0.2%.

2. The method of claim 1, wherein, In step (3), the soaking time is 1.0-1.5h.

3. The method of claim 1, wherein, In step (3), the mass ratio of the color protection agent solution to the yellow bone fish is 1:1-2:

1.

4. The method of claim 1, wherein, In step (4), the temperature of the quick freezing library is -30--32℃, and the quick freezing time is 6.0-8.0h.

5. The method of claim 1, wherein, In step (5), the temperature of the thawing solution is 4-6℃, and the thawing time is 20-40min.

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