A preparation method for improving the thermal stability of ready-to-eat fish gelatin

Abstract

This invention discloses a method for improving the thermal stability of ready-to-eat fish gelatin jelly, belonging to the field of aquatic food product technology. The method includes: rehydrating dried fish gelatin at low temperature, heating and boiling, and filtering to obtain fish gelatin juice; adding calcium chloride to the fish gelatin juice to pre-regulate the fish gelatin system using calcium ions; mixing the ion-pre-regulated fish gelatin juice with κ-carrageenan sol, and promoting cross-linking of fish collagen protein and polysaccharides through the bridging effect of calcium ions; and finally, filling, sealing, high-temperature sterilization, and cooling to obtain ready-to-eat fish gelatin jelly. By combining ion pre-regulation with polysaccharide cross-linking modification, a uniform and dense composite gel structure is constructed, significantly improving the thermal stability, gel strength, and resistance to water separation of the ready-to-eat fish gelatin jelly. This allows the product to maintain its complete solid gel morphology at 37 ℃, effectively solving the problem of traditional fish gelatin jelly easily softening and liquefying after being removed from the cold chain. It is suitable for room temperature storage and transportation and industrial production of ready-to-eat fish gelatin products.

Description

Technical Field

[0001] This invention belongs to the field of aquatic food product technology, specifically relating to a preparation method for improving the thermal stability of ready-to-eat fish gelatin. Background Technology

[0002] Fish maw, a traditional aquatic product rich in natural collagen and various trace elements, possesses extremely high nutritional and health benefits. In recent years, ready-to-eat fish maw products have gradually gained market favor, with ready-to-eat fish maw jelly showing promising industry prospects due to its convenience. However, existing fish maw jelly systems primarily rely on the collagen released during the cooking process. Under low-temperature refrigeration conditions, this collagen cross-links with protein molecules through helical entanglement and hydrogen bonding to form a three-dimensional network gel structure. This network is highly sensitive to temperature changes, easily experiencing network relaxation, water separation, softening, and even liquefaction at room temperature, especially at higher ambient temperatures, resulting in insufficient product stability during storage, transportation, display, and consumption. Particularly when removed from strict cold chain conditions, traditional fish maw jelly struggles to maintain a stable appearance and texture, limiting its application in scenarios such as room-temperature distribution, convenient ready-to-eat consumption, travel, and e-commerce transportation.

[0003] To improve the thermal stability of gelatin systems, existing technologies typically involve adding polysaccharides and cross-linking agents. Current compounding processes usually involve mixing polysaccharides and proteins before adding calcium ions, or directly mixing all three. Because calcium ions rapidly promote the coagulation of carrageenan, direct contact in the complex gelatin solution easily leads to the rapid formation of uneven clumps (phase separation), preventing the polysaccharides from achieving uniform integration with the gelatin protein. This coarse network, when removed from refrigeration (e.g., at 37°C), is highly susceptible to severe dehydration and shrinkage due to uneven stress distribution. Furthermore, while simply adding polysaccharides like κ-carrageenan can enhance gel hardness to some extent, it can also make the product harder or produce a noticeable gelatinous texture, diminishing the original tender and smooth characteristics of gelatin jelly.

[0004] Therefore, how to break away from traditional compounding processes and construct a dynamic adaptive composite network that can maintain solid support at high temperatures and preserve the authentic taste of fish maw in a wide temperature range and multiple scenarios at a lower polysaccharide concentration is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] [Technical Issues] This invention aims to solve the technical problems of existing ready-to-eat fish gelatin, such as poor thermal stability, easy softening, collapse, liquefaction at room temperature or higher temperatures, and severe water separation during storage; at the same time, it also solves the problem that existing improvement technologies only improve the initial texture and fail to effectively reconstruct the thermal instability mechanism of the fish gel network.

[0006] [Technical Solution] This invention constructs a uniform and dense composite gel structure through ion pre-regulation combined with polysaccharide cross-linking modification, which significantly improves the thermal stability, gel strength and water resistance of ready-to-eat fish gelatin. The product can maintain its complete solid gel form even at a high ambient temperature of 37 ℃, effectively solving the problem of traditional fish gelatin softening and liquefying when removed from the cold chain.

[0007] This invention provides a method for improving the thermal stability of ready-to-eat fish gelatin, comprising the following steps: (1) Rehydration of fish maw raw materials and preparation of juice: The dried fish maw is soaked at low temperature to fully rehydrate, and then heated and boiled to prepare a uniform fish maw juice.

[0008] (2) Ion pre-regulation of fish glue system: Calcium chloride is added to fish glue juice, and calcium ions are used to pre-act on the fish glue protein system to achieve ion modification pretreatment of the protein matrix and enhance the cross-linking potential of the protein.

[0009] (3) Polysaccharide system dissolution treatment: κ-carrageenan was added to water and heated to dissolve it, so that it was fully dispersed and hydrated to prepare κ-carrageenan sol system.

[0010] (4) Protein-polysaccharide composite cross-linking modification: The fish glue juice after ion pretreatment is mixed with κ-carrageenan sol and stirred evenly. Through the bridging effect of calcium ions, the fish glue protein and κ-carrageenan polysaccharide interact to synergistically construct a dense and stable composite gel structure.

[0011] (5) Sterilization, cooling and shaping: After the mixture is filled and sealed, it is sterilized at high temperature and then cooled at low temperature to promote the stable formation of the composite system gel, thus producing ready-to-eat fish jelly.

[0012] In one embodiment of the present invention, in step (1), dried fish glue and water are soaked at 3-5 °C for 54-56 h in a mass ratio of 1:19 to 1:21, and then the water is removed and dried with filter paper.

[0013] In one embodiment of the present invention, in step (1), the soaked fish glue and water are mixed in a mass ratio of 1:3 to 1:5 and heated at 70 to 90 °C for 2.5 to 3.5 h, and the fish glue juice is filtered out with 80 mesh gauze.

[0014] In one embodiment of the present invention, the concentration of κ-carrageenan in the fish gelatin is 0.5-0.7 wt%, the concentration of CaCl2 is 0.07-0.09 wt%, and the concentration of fish glue is 5.8-6.0 wt%.

[0015] In one embodiment of the present invention, the mixed system is dispensed into 25 mL glass jars and sterilized at 120-122°C for 14-16 min, and then refrigerated at 3-5°C for 11-13 h to form ready-to-eat fish jelly.

[0016] In one embodiment of the present invention, the prepared ready-to-eat fish gelatin retains good solid form and sensory quality after being stored at 37 °C for 28 days.

[0017] The present invention provides ready-to-eat fish gelatin prepared by the method described above.

[0018] The present invention also provides the application of the above method in the preparation of highly stable ready-to-eat fish gelatin.

[0019] Beneficial effects: (1) This invention pre-regulates the fish gelatin system using calcium ions and then mixes it with independently dissolved κ-carrageenan to promote the cross-linking modification of proteins and polysaccharides, which can significantly improve the thermal stability and high-temperature storage retention of ready-to-eat fish gelatin. The product obtained by this invention still maintains a solid gel form after being stored at 37 ℃ for 28 days, with a texture retention rate as high as 88.34%, a hardness of 109.62 g, and a gel strength of 52.73 g; while the comparative sample softened, collapsed, and liquefied in a short time, indicating that this invention can effectively solve the technical problem of the instability of traditional ready-to-eat fish gelatin when it is removed from the cold chain.

[0020] (2) The present invention preferably uses 0.5% κ-carrageenan and 0.07% CaCl2 to construct a composite network, which can significantly improve the wide temperature range applicability of the system without the need for adding a large amount of polysaccharides, thus expanding fish gelatin from a low-temperature product dependent on the cold chain to a ready-to-eat product that can be distributed at room temperature and at higher temperatures. The results of the examples show that the overall acceptability of the sample of the present invention after storage at 37 ℃ for 28 days is 324% higher than that of the comparative example 1, and the taste, texture, flavor and color are significantly better than those of the comparative example, indicating that it still has good edible quality and consumer acceptance under higher temperature storage conditions, providing a technical basis for the application of fish gelatin products in room temperature storage, shelf display and non-strict cold chain conditions.

[0021] (3) The product prepared by this invention has excellent thermal stability and sensory quality, mainly due to the ion pre-regulation combined with proteoglycan composite cross-linking modification, which enables it to form a dense, uniform, and strongly cohesive composite network structure in the early stage of gelation. The results of the examples show that the sample of this invention has higher initial hardness (1062.77 g) and gel strength (372.48 g), a more uniform and dense network structure, and the wavenumber of amide A band is reduced to 3419 cm⁻¹. -1 This indicates that hydrogen bonding within the system is enhanced. This is because, by first treating the fish glue system with Ca... 2+Pretreatment and regulation, followed by mixing with κ-carrageenan, promote stronger intermolecular interactions between protein and polysaccharide segments through calcium ion bridging, thereby reducing local aggregation and structural defects and forming a more uniform, dense, and stable composite gel network. Attached Figure Description

[0022] Figure 1 These are visualizations of Example 1 and Comparative Examples 1-3.

[0023] Figure 2 Flavor score diagrams for Example 1 and Comparative Examples 1-3.

[0024] Figure 3 The color score diagrams are for Example 1 and Comparative Examples 1-3.

[0025] Figure 4 The image shows the taste score charts for Example 1 and Comparative Examples 1-3.

[0026] Figure 5 The images show the tissue state scores for Example 1 and Comparative Examples 1-3.

[0027] Figure 6 The graph shows the overall acceptability scores for Example 1 and Comparative Examples 1-3.

[0028] Figure 7 The diagram shows the microstructure of Example 1 and Comparative Examples 1-3.

[0029] Figure 8 The Fourier transform infrared spectra are of Example 1 and Comparative Examples 1-3.

[0030] Figure 9 This is a visualization of comparison figures 4-5. Detailed Implementation

[0031] Test methods (1) Visualization experiment: Samples stored for different times were placed in a photography box and photographed under the same light.

[0032] (2) Texture characteristics test: The texture characteristics of different samples were determined using a physical property tester. A P0.5 probe was used, and the speed before, during and after the test was set to 1 mm / s, 2 mm / s and 2 mm / s, respectively. The pressure was 40% and the trigger force was 2 g.

[0033] (3) Gel strength test: The texture was determined using a physical property analyzer. A cylindrical probe with P0.5 was selected. The speed before the test was 1.5 mm / s, and the speed during and after the test was 1 mm / s. The maximum force applied when the probe entered the sample to a depth of 4 mm was the gel strength.

[0034] (4) Water separation rate test: Under different storage times, take the sample out of the 37 ℃ constant temperature box, gently tilt the sample container to let the free water flow out naturally into the pre-weighed weighing dish.

[0035] Water separation rate (%) =

[0036] Where m1 is the mass of water precipitated at the corresponding storage time point, and m0 is the mass of the initial sample.

[0037] (5) Sensory evaluation: A sensory evaluation team of 10 people was established to conduct sensory evaluation in five aspects: flavor, color, taste, texture, and overall acceptability. The team members were composed of professionally trained personnel. Different samples were labeled using a random numbering method, and each indicator was quantitatively evaluated using a 20-point scale. The scoring criteria are as follows: Table 1 Sensory Rating Table

[0038] (6) Scanning electron microscopy test: Fix the freeze-dried sample on a dedicated SEM sample kit and place the sample under vacuum for surface gold plating. After the gold plating process is completed, place the sample in a scanning electron microscope for observation. The working voltage is 5 kV and the magnification of the sample is 100x.

[0039] (7) Fourier transform infrared spectroscopy test: Take 1 mg of sample and grind it with potassium bromide at a ratio of 1:100. Compress the mixture into tablets using a tablet press and press at 4000-400 cm⁻¹. -1 Interval scanning with a resolution of 4 cm -1 The scanning frequency is 16 times.

[0040] Example 1 A method for improving the thermal stability of ready-to-eat fish gelatin includes the following steps: (1) Soak dried fish maw and water at a mass ratio of 1:20 at 4 ℃ for 55 h to allow the fish maw to fully expand; control the concentration of fish maw in the final product system to be 5.8%.

[0041] (2) After soaking, remove the fish maw, drain off the excess water, mix it with water at a mass ratio of 1:4, and heat at 80 ℃ for 3 h to promote the full dissolution of collagen in the fish maw. After boiling, filter it through 80 mesh gauze to obtain fish maw juice.

[0042] (3) Add calcium chloride to the fish gelatin juice and stir until fully dissolved. Utilize the pre-treatment of the fish gelatin protein system by the action of calcium ions to achieve ion modification of the protein matrix and enhance the cross-linking potential of the protein. Control the concentration of calcium chloride in the final product system to 0.07%.

[0043] (4) Add κ-carrageenan to water and heat to dissolve it, so that it is fully dispersed and hydrated to prepare a κ-carrageenan sol system. Control the concentration of κ-carrageenan in the final product system to be 0.5%.

[0044] (5) Mix the fish glue juice obtained after ion pretreatment in step (3) with the κ-carrageenan sol obtained in step (4) and stir evenly. Through the bridging effect of calcium ions, fish glue protein and κ-carrageenan polysaccharide interact and synergistically construct a dense and stable composite gel structure.

[0045] (6) The obtained mixture was filled and sealed, sterilized at 121 °C for 15 min, and then placed at 4 °C for 12 h to allow the composite system to stabilize and form a gel, thus obtaining ready-to-eat fish jelly. The obtained sample was stored at a constant temperature of 37 °C and measured at 0, 7, 14, 21 and 28 days.

[0046] Comparative Example 1 The only difference from Example 1 is that κ-carrageenan and CaCl2 are not added to the fish maw juice. Instead, the filtered fish maw juice is directly dispensed, sterilized, and cooled to form a gel to obtain a pure fish maw jelly sample.

[0047] Comparative Example 2 The only difference from Example 1 is that only κ-carrageenan is added, and CaCl2 is not added; the other process conditions are the same as in Example 1.

[0048] Comparative Example 3 The only difference from Example 1 is that only CaCl2 is added, and κ-carrageenan is not added; the other process conditions are the same as in Example 1.

[0049] Comparative Example 4 The preparation method is the same as in Example 1, except that calcium chloride is added after mixing κ-carrageenan and fish glue juice, and the amounts of each are the same as in Example 1.

[0050] Comparative Example 5 The preparation method is the same as in Example 1, except that the amounts of κ-carrageenan, fish glue juice, and calcium chloride are directly mixed and remain the same as in Example 1.

[0051] The prepared ready-to-eat fish gelatin was tested, and the results are as follows: Figure 1 These are visualizations of Example 1 and Comparative Examples 1-3. From Figure 1It can be seen that all samples formed a gel state at the beginning of storage. However, with the extension of storage time, the gel structure stability of pure fish gelatin and samples with κ-carrageenan or CaCl2 added alone decreased significantly, and softening, collapse, and liquefaction occurred to varying degrees within a short period of time. In contrast, the compound sample obtained in Example 1 maintained a relatively intact solid gel morphology after storage at 37 ℃ for 28 days. This result indicates that relying solely on the gel network of fish gelatin itself, adding κ-carrageenan alone, or adding calcium chloride alone are all insufficient to effectively maintain the structural stability of fish gelatin under high temperature conditions. In contrast, this invention constructs a more stable composite network structure by pre-regulating the fish gelatin system with calcium ions and generating a composite cross-linking effect with κ-carrageenan.

[0052] Table 2. Texture properties, gel strength, and water separation rate of ready-to-eat fish gelatin at different storage times.

[0053] Note: Different capital letters in the same column indicate significant differences. P <0.05, different lowercase letters in the same row indicate significant differences ( P <0.05).

[0054] Table 2 shows the changes in texture, gel strength, and water separation rate of Example 1 and Comparative Examples 1-3 at different storage times. Example 1 achieved an initial hardness of 1062.77 g and a gel strength of 372.48 g at 0 days, significantly higher than the pure fish gelatin and the single modified group, indicating that a denser and stronger gel network was formed in the early stages of gelation. Although the hardness and gel strength of Example 1 decreased with prolonged storage at 37°C, they remained at a certain level in the later stages of storage. At 28 days, the hardness was 109.62 g, the gel strength was 52.73 g, and the water separation rate was only 11.66%, demonstrating good storage stability. In contrast, the comparative sample lost its complete gel state in a shorter time, making it difficult to maintain subsequent texture tests. These results demonstrate that the composite network constructed in this invention can significantly improve the structure retention and water separation resistance of ready-to-eat fish gelatin.

[0055] Figure 2 The image shows the flavor scores for Example 1 and Comparative Examples 1-3. At day 0, the initial flavor scores of all samples were at a high level. With prolonged storage, the sensory scores of Comparative Examples 1, 2, and 3 decreased and remained at a low level. Example 1, however, exhibited strong stability, with its sensory score significantly better than the other three groups during a storage period of up to 28 days. P <0.05).

[0056] Figure 3The image shows the color score diagrams for Example 1 and Comparative Examples 1-3. At day 0, there were no significant differences between the sample groups. P >0.05), with prolonged storage time, only the color score of Example 1 remained at a high level.

[0057] Figure 4 The image shows the taste scores for Example 1 and Comparative Examples 1-3. At 0 days, all samples had high taste scores, with Example 1 having the highest initial sensory score of 16.10. As storage time increased, the sensory scores of Comparative Examples 1, 2, and 3 decreased sharply, mainly due to liquefaction of the samples. In contrast, Example 1 had the highest taste score at 28 days, at 13.30.

[0058] Figure 5 The diagram shows the tissue state scores for Example 1 and Comparative Examples 1-3. The results indicate that all samples had high tissue state scores at 0 days, with Example 1 having the highest score. With prolonged storage, the tissue state scores of Comparative Examples 1, 2, and 3 decreased significantly after 7 days and remained at a low level during subsequent storage, mainly due to liquefaction and structural damage. However, Example 1 maintained a relatively stable score throughout the storage period, with its score at 28 days still significantly higher than the other groups, at 14.20 points.

[0059] Figure 6 The graph shows the overall acceptability of Example 1 and Comparative Examples 1-3. The results indicate that all samples showed the highest overall acceptability at day 0, with Example 1 scoring the highest. Example 1 maintained a relatively stable score throughout the storage period, achieving a sensory score of 14.0 at day 28. Compared to Comparative Example 1, the overall sensory acceptability improved by 324%.

[0060] Figure 7 The diagram shows the microstructural changes of Example 1 and Comparative Examples 1-3. To further analyze the reason for the high stability of the composite crosslinking system, scanning electron microscopy was performed on the samples at 0 days. The results showed that Example 1 exhibited a more uniform and dense network structure, while the pure fish gelatin group (Comparative Example 1) had larger pore sizes and uneven pore distribution. In addition, the gel network structure of the group with only κ-carrageenan added (Comparative Example 2) and CaCl2 added (Comparative Example 3) showed an irregular honeycomb-like pore structure. These results indicate that the present invention, through ion pre-regulation of fish gelatin juice, independent dissolution pretreatment of κ-carrageenan, and then crosslinking the two phases, enables the mixed system to form a more uniform and stable composite network, thereby improving the macroscopic gel stability.

[0061] Figure 8The images show the FT-IR spectra of Example 1 and Comparative Examples 1-3. The results indicate that the wavenumbers of amide A in Comparative Examples 1 and 2 are 3436 cm⁻¹. -1 and 3435 cm -1 The wavenumber of amide A in Example 1 decreased to 3419 cm⁻¹. -1 The wavenumber of amide A band is negatively correlated with hydrogen bond strength. In Example 1, the amide A band shifted towards lower wavenumbers, indicating enhanced hydrogen bonding within the system and more robust intermolecular interactions between protein and polysaccharide segments. Combined with scanning electron microscopy results, it is evident that the fish gelatin obtained in this invention forms a more dense and stable composite network structure.

[0062] Figure 9 The figures show visualizations of Comparative Examples 4 and 5. The results indicate that Comparative Examples 4 and 5 softened, collapsed, and separated water during storage, significantly reducing the stability of the gel structure. Changing the order of addition of polysaccharides, gelatin, and CaCl2 affected the degree of ionic interaction and protein-polysaccharide cross-linking: neither the method of "mixing polysaccharides and gelatin before adding calcium ions" (Comparative Example 4) nor "directly mixing the three" (Comparative Example 5) could achieve effective and uniform pre-regulation of calcium ions in the system, leading to insufficient cross-linking between the protein matrix and κ-carrageenan. This, in turn, made the network structure more prone to disintegration and water release under thermal stress.

[0063] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for improving the thermal stability of ready-to-eat fish gelatin, characterized in that, Includes the following steps: (1) Rehydration and preparation of fish glue raw material: The dried fish glue is soaked at low temperature to fully rehydrate, and then heated and boiled to prepare fish glue juice; (2) Ion pre-regulation of fish glue system: Calcium chloride was added to fish glue juice to obtain fish glue juice after ion pretreatment; (3) Polysaccharide system dissolution treatment: κ-carrageenan was added to water and heated to dissolve, thus preparing κ-carrageenan sol; (4) Protein-polysaccharide composite cross-linking modification: The fish glue juice after ion pretreatment is mixed with κ-carrageenan sol and stirred evenly. Through the bridging effect of calcium ions, the fish glue protein and κ-carrageenan polysaccharide interact and synergistically construct a dense and stable composite gel structure. (5) Sterilization, cooling and shaping: Finally, the ready-to-eat fish jelly is made by filling, sterilization and shaping.

2. The method according to claim 1, characterized in that, In step (1), the dried fish glue and water are soaked at 3-5 ℃ for 54-56 h in a mass ratio of 1:19 to 1:21, and then the water is removed and dried.

3. The method according to claim 1, characterized in that, In step (1), the soaked fish maw and water are mixed in a mass ratio of 1:3 to 1:5 and heated at 70 to 90 °C for 2.5 to 3.5 h, and the fish maw juice is filtered out.

4. The method according to claim 1, characterized in that, In the fish gelatin, the concentration of κ-carrageenan is 0.5-0.7 wt%, the concentration of CaCl2 is 0.07-0.09 wt%, and the concentration of fish glue is 5.8-6.0 wt%.

5. The method according to claim 1, characterized in that, In step (5), after sterilization at 120~122 ℃ for 14~16 min, the fish gelatin is then refrigerated at 3~5 ℃ for 11~13 h to form ready-to-eat fish gelatin.

6. Ready-to-eat fish gelatin prepared by any one of claims 1 to 5.

7. The application of the method according to any one of claims 1 to 5 in the preparation of highly stable ready-to-eat fish gelatin.

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