A chitosan-gelatin composite preservative solution based on plasma-activated water modification, and a preparation method and application thereof

Abstract

The application belongs to the field of food preservation technology, and relates to a chitosan-gelatin composite preservative solution based on plasma-activated water modification and a preparation method and application thereof. First, PAW is used to prepare chitosan solution and gelatin solution respectively, and the composite preservative solution is obtained after mixing and homogenizing. The coating is dehydrated to form a preservative film. The PAW is prepared by treating deionized water with low-temperature plasma, and is rich in active ingredients such as hydroxyl radicals and hydrogen peroxide, which can effectively modify chitosan and gelatin, enhance intermolecular crosslinking, and form a composite film with a dense network structure. The composite film can be applied to fish preservation through coating or immersion, can effectively inhibit the growth of microorganisms, and can improve the color of fish fillets. In addition, the composite film has the function of delaying protein degradation by inhibiting endogenous protease activity, thereby maintaining the muscle tissue structure and prolonging the shelf life of chilled fish fillets. The application has the advantages of simple process, green safety, remarkable preservation effect, and wide market application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of food preservation, and particularly relates to a composite preservative solution, in particular, a chitosan-gelatin composite preservative solution based on PAW modification and a preparation method thereof, and application of the composite preservative solution in preservation of aquatic products, in particular, fish. BACKGROUND

[0002] Fish meat is prone to enzymatic hydrolysis, microbial spoilage and oxidative rancidity during storage and transportation due to its high water content, high protein and unsaturated fatty acid content, resulting in quality deterioration and shelf life shortening, causing huge economic losses. Therefore, developing green preservation technology that is efficient, safe and can replace chemical preservatives has become an urgent need for the aquatic product processing industry.

[0003] Traditional preservation methods such as physical low-temperature refrigeration, freezing, chemical preservatives (such as benzoate and sulfite) treatment, etc. have certain effects, but have problems such as high energy consumption, possible harmful residues, affecting product flavor and quality, and low consumer acceptance. Edible film preservation technology has become a research hotspot due to its green and safe advantages. Among them, chitosan and gelatin are two commonly used natural film-forming substrates. Chitosan has good film-forming properties and biocompatibility, and the formed film has good gas barrier and moisture barrier properties, but the mechanical strength is insufficient and the antibacterial performance is limited. Gelatin has good film-forming properties and oxygen barrier properties, but has weak antibacterial properties, is prone to water absorption and swelling, and has poor water vapor barrier ability. In the prior art, CN108586830A discloses a method for enhancing the antioxidant properties of a chitosan-gelatin composite film by adding antioxidant peptides; however, this method does not fundamentally modify the molecular structure of chitosan and gelatin, and the mechanical strength, compactness and other properties of the composite preservation film are insufficient, and the long-term preservation effect is still limited.

[0004] Low-temperature plasma-activated water is a functional water obtained by treating deionized water with low-temperature plasma, but the instability of the active components of PAW restricts its long-term antibacterial effect. However, there is no use of PAW to modify the chitosan-gelatin system in the prior art, and there is no related report on using the composite system to overcome the long-term antibacterial difficulty of PAW. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a preparation method of a chitosan-gelatin composite preservative solution based on PAW modification. The present application uses treated low-temperature plasma-activated water as a solvent and a physical modifier. The treated low-temperature plasma-activated water can directly dissolve gelatin at room temperature (15-30°C), which not only simplifies the process but also reduces energy consumption. It also directly proves that the low-temperature plasma-activated water has a unique modification ability for gelatin molecules, achieving the synergistic effect of low-temperature plasma-activated water, chitosan and gelatin.

[0006] To achieve the above object, the present application adopts the following technical solutions:

[0007] A preparation method of a chitosan-gelatin composite preservative solution based on PAW modification, comprising the following steps:

[0008] (1) Preparation of low-temperature plasma-activated water: using a low-temperature plasma generator to treat deionized water in an atmospheric environment, placing the plasma jet nozzle above the liquid surface of the deionized water for treatment, the treatment power is 0.3-0.8 kW, the treatment time is 10-40 min, and the treated low-temperature plasma-activated water is obtained.

[0009] Preferably, in step (1), the plasma jet nozzle is placed 3-5 cm above the liquid surface of the deionized water; the treatment power is 0.6 kW.

[0010] (2) Structural modification of chitosan: using the low-temperature plasma-activated water treated in step (1) to prepare an acetic acid solution with a volume concentration of 3.0%-5.0% (v / v), then dissolving chitosan powder with a degree of deacetylation of ≥90% in the acetic acid solution, stirring and dissolving to obtain a chitosan-PAW solution with a mass concentration of 1.0%-3.0% (w / v);

[0011] Preferably, in step (2), the volume concentration of the acetic acid solution is 3.0%, and the mass concentration of the chitosan-PAW solution is 3.0%.

[0012] (3) Structural modification of gelatin: at room temperature, gelatin is added to the low-temperature plasma-activated water prepared in step (1), stirred and dissolved to obtain a gelatin-PAW solution with a mass concentration of 2.0%-4.0% (w / v);

[0013] Preferably, in step (2), the mass concentration of the gelatin-PAW solution is 3.0%.

[0014] (4) Preparation of a composite preservative solution: mixing the chitosan-PAW solution obtained in step (2) with the gelatin-PAW solution obtained in step (3), wherein the volume ratio of the chitosan-PAW solution to the gelatin-PAW solution is 1:0.5-4, and after mixing, stirring uniformly to obtain the composite preservative solution.

[0015] Preferably, in step (4), the volume ratio of the chitosan-PAW solution to the gelatin-PAW solution is 1:2.

[0016] Preferably, in step (4), the stirring is magnetic stirring for 0.5-1 h.

[0017] The application of the PAW modified chitosan-gelatin composite preservative solution prepared by the above method in water product preservation and bacterium inhibition is as follows: the water product is immersed in the composite preservative solution or the composite preservative solution is uniformly coated on the surface of the water product by spraying, and then the surface liquid drops are drained and the water product is refrigerated, so that the application of the PAW modified chitosan-gelatin composite preservative solution in water product preservation and bacterium inhibition is realized.

[0018] Preferably, the water product includes fresh fish and fish fillets, and the water product is immersed in the composite preservative solution for 1-3 min.

[0019] Preferably, the refrigeration is under the condition of 4-10°C. Beneficial effects

[0020] (1) The low-temperature plasma activated water (PAW) after treatment is used to replace ordinary water as a solvent, the active components (ROS, RNS) in the low-temperature plasma activated water can effectively modify the molecular structure of chitosan and gelatin, induce intermolecular crosslinking, combine to form a more compact three-dimensional network structure, improve the film-forming property of the preservative solution, and endow the preservative solution with the ability of long-acting and slow-releasing of active components (H2O2, O3, NO2⁻, NO3⁻, -NH3⁺, etc.). In addition, the active components after specific treatment can interact with biological macromolecules such as polysaccharides and proteins, improve the functional properties of the biological macromolecules by inducing polysaccharide structure hydrolysis or conformational change, and modifying the molecular structure of proteins (such as changing the secondary structure or promoting intramolecular crosslinking, etc.).

[0021] (2) The PAW, chitosan and gelatin are combined creatively in the application, and the advantages of the three are complementary and the functions of the three are synergistic. On the one hand, the active components in the PAW can modify the molecular structure of chitosan and gelatin by oxidation and other ways, make part of the chitosan and gelatin degrade or expose more active sites, enhance the intermolecular crosslinking, and promote the formation of a more compact network structure, so as to fundamentally improve the physical load performance of the film. On the other hand, the chitosan and gelatin can effectively embed and fix the active components in the PAW in the three-dimensional network structure during the film-forming process, protect the active components from rapid decay, and realize the long-acting and slow-releasing of the active components during the preservation process, so as to significantly prolong the duration of preservation. Thus, the instant sterilization effect of the PAW, the inherent antibacterial property and moisture resistance of the chitosan, and the good film-forming property and oxygen resistance of the gelatin are combined, through multi-dimensional synergistic effect, the growth of microorganisms on the surface of the fish fillets is effectively inhibited, and the protein degradation is delayed, so that the refrigerated shelf life of the snakehead fish fillets is significantly prolonged from 6 days to 12 days, and substantial technical effects are achieved.

[0022] (3) The application also provides the composite preservative solution prepared by the above method, which combines the antibacterial property of chitosan, the film forming property of gelatin and the instant sterilization and molecular modification function of PAW, and forms a dense and uniform coating film with long-acting and slow-release preservative properties. Meanwhile, the application further provides the application method of the above composite preservative solution in aquatic product preservation, especially in fish preservation, which can significantly inhibit the growth of microorganisms and the deterioration caused by protease, and effectively prolong the refrigerated shelf life. The application cleverly plays the advantages of PAW and overcomes its shortcomings based on the synergistic mechanism of "modified film-embedded slow release", and finally effectively maintains the quality of refrigerated fish fillet products.

[0023] (4) The application has a simple preparation process, does not need to use chemical cross-linking agents or modifiers, and can be used in situ after the preparation of PAW. The whole process is simple and fast, and easy to scale up production. Meanwhile, all components (acetic acid, chitosan, gelatin and PAW) are safe and edible or green and environmentally friendly components, without toxic and harmful residues, which meets the development needs of modern food industry. Meanwhile, the preservative solution is in the form of liquid, easy to store and convenient to use. It can be conveniently applied to the surface of fish meat by immersion or spraying, and the operation is very simple, which is suitable for different processing production lines and various occasions, and has a wide market application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The change of total bacterial count (TVC) of fish fillets treated by different composite preservative solutions under 4℃ storage is shown in Table 1;

[0025] Figure 2 The change of total bacterial count (TVC) of fish fillets treated by different preservative solutions under 4℃ storage is shown in Table 2;

[0026] Figure 3 The change of total volatile basic nitrogen (TVB-N) content of fish fillets treated by different preservative solutions under 4℃ storage is shown in Table 3;

[0027] Figure 4 The influence of different preservative solutions on the activity of crude protease of fresh fish meat is shown in Table 4;

[0028] Figure 5 The microstructure of fish fillets treated by different preservative solutions under 4℃ storage for 12 days is shown in Table 5;

[0029] Figure 6 The microstructure of the film of different gel-forming preservative solutions is shown in Table 6;

[0030] Figure 7 The change of whiteness value of fish fillets treated by different preservative solutions under 4℃ storage is shown in Table 7;

[0031] Figure 8 The change of redness value of fish fillets treated by different preservative solutions under 4℃ storage is shown in Table 8;

[0032] Figure 9 Color changes of fish fillets treated with different preservative solutions for 12 days under 4℃ storage. DETAILED DESCRIPTION

[0033] The acetic acid, chitosan (deacetylation degree ≥ 90%, 600 kDa) and gelatin used in the following examples are all food grade. Example 1:

[0034] (1) Preparation of PAW: 600 mL of deionized water was treated by an atmospheric jet type low-temperature plasma equipment under atmospheric environment, the treatment power was 0.6 kW, and the treatment time was 10 min, to obtain the low-temperature plasma activated water (PAW), which was prepared and used within 6 h.

[0035] (2) Structural modification of chitosan: the PAW prepared in step (1) was used to prepare an acetic acid solution with a volume concentration of 3.0% (v / v), and then the chitosan powder with a deacetylation degree of ≥ 90% was added into the acetic acid solution, and the magnetic stirring was performed for 2 h until the chitosan was completely dissolved, to obtain a chitosan-PAW solution with a mass concentration of 3.0% (w / v).

[0036] (3) Structural modification of gelatin: the gelatin particles were added into the plasma activated water prepared in step (1) under stirring at room temperature, and the gelatin was completely dissolved within 1 h by stirring, to obtain a gelatin-PAW solution with a mass concentration of 3.0% (w / v).

[0037] (4) Preparation of the composite preservative solution: the chitosan-PAW solution obtained in step (2) and the gelatin-PAW solution obtained in step (3) were mixed according to a volume ratio of 2:1, and the magnetic stirring was performed for 0.5 h to fully mix them, to obtain the composite preservative solution. Example 2:

[0038] (1) Preparation of PAW: 5000 mL of deionized water was treated by a low-temperature plasma equipment, the treatment power was 0.6 kW, and the treatment time was 40 min, to obtain the low-temperature plasma activated water (PAW), which was prepared and used within 6 h.

[0039] (2) Structural modification of chitosan: the PAW prepared in step (1) was used to prepare an acetic acid solution with a volume concentration of 3.0% (v / v), and then the chitosan powder with a deacetylation degree of ≥ 90% was added into the acetic acid solution, and the magnetic stirring was performed for 1-2 h until the chitosan was completely dissolved, to obtain a chitosan-PAW solution with a mass concentration of 3.0% (w / v).

[0040] (3) Structure modification of gelatin: At room temperature, gelatin particles were added into the plasma-activated water prepared in step (1) under stirring, and the gelatin was completely dissolved within 1 h by stirring to obtain a gelatin-PAW solution with a mass concentration of 3.0% (w / v).

[0041] (4) Preparation of the composite preservative solution: The chitosan-PAW solution obtained in step (2) and the gelatin-PAW solution obtained in step (3) were mixed at a volume ratio of 1:1, and were fully mixed by magnetic stirring for 0.5 h to obtain the composite preservative solution. Example 3:

[0042] (1) Preparation of PAW: 600 mL of deionized water was treated by a low-temperature plasma device at a treatment power of 0.6 kW for 10 min to obtain low-temperature plasma-activated water (PAW), which was prepared and used within 6 h.

[0043] (2) Structure modification of chitosan: The PAW prepared in step (1) was used to prepare an acetic acid solution with a volume concentration of 3.0% (v / v), and then deacetylation degree ≥ 90% chitosan powder was added into the acetic acid solution, and was completely dissolved by magnetic stirring for 1-2 h to obtain a chitosan-PAW solution with a mass concentration of 3.0% (w / v).

[0044] (3) Structure modification of gelatin: At room temperature, gelatin particles were added into the plasma-activated water prepared in step (1) under stirring, and the gelatin was completely dissolved within 1 h by stirring to obtain a gelatin-PAW solution with a mass concentration of 3.0% (w / v).

[0045] (4) Preparation of the composite preservative solution: The chitosan-PAW solution obtained in step (2) and the gelatin-PAW solution obtained in step (3) were mixed at a volume ratio of 1:2, and were fully mixed by magnetic stirring for 0.5 h to obtain the composite preservative solution. Example 4:

[0046] (1) Preparation of PAW: 5000 mL of deionized water was treated by a low-temperature plasma device at a treatment power of 0.6 kW for 40 min to obtain low-temperature plasma-activated water (PAW), which was prepared and used within 6 h.

[0047] (2) Structure modification of chitosan: The PAW prepared in step (1) was used to prepare an acetic acid solution with a volume concentration of 4.0% (v / v), and then deacetylation degree ≥ 90% chitosan powder was added into the acetic acid solution, and was completely dissolved by magnetic stirring for 2 h to obtain a chitosan-PAW solution with a mass concentration of 3.0% (w / v).

[0048] (3) Gelatin structure modification: At room temperature, gelatin particles were added into the plasma-activated water prepared in step (1) while stirring, and the gelatin was completely dissolved within 1 h by stirring, to obtain a gelatin-PAW solution with a mass concentration of 3.0% (w / v).

[0049] (4) Preparation of the composite preservative solution: The chitosan-PAW solution obtained in step (2) was mixed with the gelatin-PAW solution obtained in step (3) at a volume ratio of 1:3, and they were fully mixed by magnetic stirring for 0.5 h, to obtain the composite preservative solution. Example 5:

[0050] (1) Preparation of PAW: 1000 mL of deionized water was treated by a low-temperature plasma device at a treatment power of 0.6 kW for 15 min, to obtain low-temperature plasma-activated water (PAW), which was used within 6 h.

[0051] (2) Chitosan structure modification: A chitosan-PAW solution with a mass concentration of 3.0% (w / v) was obtained by adding deacetylation degree ≥ 90% chitosan powder into the acetic acid solution prepared from the PAW prepared in step (1) and stirring magnetically for 2 h until complete dissolution.

[0052] (3) Gelatin structure modification: At room temperature, gelatin particles were added into the plasma-activated water prepared in step (1) while stirring, and the gelatin was completely dissolved within 1 h by stirring, to obtain a gelatin-PAW solution with a mass concentration of 3.0% (w / v).

[0053] (4) Preparation of the composite preservative solution: The chitosan-PAW solution obtained in step (2) was mixed with the gelatin-PAW solution obtained in step (3) at a volume ratio of 1:4, and they were fully mixed by magnetic stirring for 0.5 h, to obtain the composite preservative solution.

[0054] Application Example 1:

[0055] Comparison of effects of composite preservative solutions with different formulations: Fresh snakehead fish fillets were treated by immersion for 2 min using the composite preservative solutions prepared in the above Examples 1, 2, 3, 4, and 5, respectively, and then the surface water drops were drained and the fish fillets were placed in sterile trays and wrapped with preservative film, and then stored at 4°C. Figure 1The total number of colonies (TVC) of the fish fillets treated by the preservative solutions of different embodiments under storage at 4°C (1-5 in the figure represent the preservative solutions prepared in embodiments 1, 2, 3, 4, and 5, respectively) is shown in the figure. The results show that the preservative solutions prepared in different embodiments can achieve the preservation effect, but the total number of colonies (TVC) of the snakehead fillets treated by the composite preservative solutions in different embodiments also has significant differences during cold storage, indicating that the selection of the mixing ratio of the chitosan-PAW solution and the gelatin-PAW solution has a direct impact on the effect. The TVC value of the fish fillets treated by the preservative solution of embodiment 3 (the volume ratio of the chitosan-PAW solution to the gelatin-PAW solution is 1:2) reaches the critical value on the 12th day; while the TVC values of the fish fillets treated by embodiments 1, 2, 4, and 5 reach the critical value on the 8th-10th day of cold storage. The results show that the selection of the mixing ratio of the chitosan-PAW solution and the gelatin-PAW solution has an important impact on the effect, and the composite preservative solution of embodiment 3 achieves a more significant effect at a specific ratio, which can more effectively inhibit the growth of microorganisms and prolong the shelf life by 2-4 days; because aquatic products are extremely prone to spoilage and deterioration, prolonging the shelf life by ≥2 days is a very significant technical improvement.

[0056] Application Example 2:

[0057] (1) Verify the synergistic effect of the composite preservative solution of the application: fresh snakehead fillets are randomly divided into six groups: ① blank control group (not treated); ② PAW treatment group (immersed for 2 min); ③ 3.0% chitosan-PAW solution group (immersed for 2 min); ④ 3.0% gelatin-PAW solution group (immersed for 2 min); ⑤ ordinary combination group (except that deionized water is used instead of PAW, the remaining steps and conditions are the same as those of embodiment 3, and the immersion time of the preservative solution is 2 min); ⑥ the application group (immersed in the composite preservative solution prepared in embodiment 3 for 2 min). After draining, they are placed in sterile trays and wrapped with preservative film, and stored at 4°C. The effect of different preservative solutions on fish proteinase activity during cold storage is determined, and the total number of colonies (TVC) and the volatile base nitrogen content (TVB-N) of the fish fillets are determined periodically.

[0058] (2) Result analysis: In the application example of the application, a series of physicochemical index determinations are performed on the fish fillets treated by different preservative solutions, including the total number of colonies (TVC) Figure 2 , the volatile base nitrogen (TVB-N) content Figure 3 , and the crude protease activity Figure 4). The results showed that the TVC of the untreated fish sample reached the critical value after only 6 days of storage at 4°C. In contrast, the TVB-N content of the samples treated with PAW, chitosan or gelatin alone reached the critical value on the 9th day, while the TVB-N content of the samples treated with the ordinary combination reached the critical value on the 10th day. Among all the preservative solutions tested, the TVC value of the fish sample treated with the preservative solution of the application was 5.89 log CFU / g and the TVB-N value was 19.73 mg / 100g on the 12th day of storage, both of which were lower than the food microbiological safety threshold (6 log CFU / g) and the freshness acceptable range (less than 20 mg / 100g), effectively delaying the increase of the TVC and TVB-N values and showing a significant preservation effect. At the same time, the importance of the components and conditions of the application was also reflected, and the components and conditions were indispensable.

[0059] In addition, the sample treated with the application exhibited the lowest protease activity among all the test groups ( Figure 4 ). This finding indicates that the preservative solution of the application not only effectively inhibits microbial growth, but also significantly reduces the activity of protease, achieving an unexpected technical effect, thereby delaying the degradation process of fish protein and being particularly suitable for the preservation and storage of fish, which can effectively improve the cold storage quality of fish.

[0060] Further, the fish fillets treated with different preservative solutions prepared in the application examples were observed by scanning electron microscopy (SEM), and the results are shown in Figure 5 . The tissue structure of the blank group (Figure ①) appeared loose, with uneven structure fragmentation and high porosity. It is possible that without the protection of the preservative solution, the texture of the fish meat was significantly degraded during storage. Compared with the blank group, the tissue structure of the samples in the PAW treatment group (Figure ②), the chitosan-PAW solution group (Figure ③) and the gelatin-PAW solution group (Figure ④) was slightly compact, and the tissue structure fragmentation was reduced, indicating that PAW, chitosan or gelatin alone may have a certain protective effect on the fish fillet tissue, slowing down the degradation of the tissue, but the effect is not significant. The fiber structure of the ordinary combination group (Figure ⑤) was relatively complete and arranged in order, indicating that the combination of chitosan and gelatin can synergistically promote the preservation of fish meat, so that the microstructure of the fish fillet is well maintained. However, the fiber structure is still partially fragmented. The tissue structure of the implementation example group (Figure ⑥) is not significantly different from that of fresh fish meat, and the fiber structure is smooth and continuous, arranged most closely and orderly, providing the best protection effect for fish preservation, so that the microstructure of the fish fillet is maintained most completely during storage.

[0061] Meanwhile, the microstructure of the dried preservative film of the application examples was observed by SEM, and the results are shown inFigure 6 The blank group was used as a control. The PAW treatment group did not form a gel, so only the microstructure of the gelled chitosan film (Figure ③), the gelatin film (Figure ④), the ordinary combination group film (Figure ⑤), and the composite film of the embodiment of the present application (Figure ⑥) was characterized. The results show that the chitosan film (Figure ③) has a rough and uneven structure; in contrast, the gelatin film (Figure ④), the ordinary combination group film (Figure ⑤), and the composite film of the embodiment 3 of the present application (Figure ⑥) all exhibit a more dense and uniform morphology. In particular, the composite film prepared by the embodiment 3 of the present application (Figure ⑥) has the smoothest and densest surface and the lowest porosity, indicating that PAW may expose more active groups through oxidation, degradation, and the like, thereby promoting the crosslinking between chitosan and gelatin molecules, ultimately improving the microstructure of the film, making it form a more complete and strong dense network, which provides an ideal structural basis for the long-acting and slow release of the active components of PAW.

[0062] In addition, in the 12-day storage experiment, the treatment group of the embodiment 3 showed a significant advantage in color retention of the fish fillets. As shown in Figures Figure 7 and Figure 8 , the present application group effectively delayed the increase in the whiteness of the white meat and improved the redness of the red meat, showing good color protection ability. The color sensory evaluation results of the present application group were significantly better than those of other groups (p<0.05). Figure 9

[0063] The results of the present study show that the present application group is significantly better than the treatment groups using PAW, chitosan solution, or gelatin solution alone, and the ordinary combination group in terms of inhibiting spoilage and preserving quality and freshness. In particular, the present application group, through the synergistic effect of PAW, chitosan, and gelatin, extends the shelf life of snakehead fillets by more than 50%, and shows significant superiority (p<0.05) in all key quality indicators, achieving more efficient product quality preservation and market value improvement. P <0.05)

[0064] Note: The above embodiments are only used to illustrate the present application and do not limit the technical solutions described in the present application; therefore, although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present application can still be modified or replaced equivalently; and all technical solutions and improvements that do not deviate from the spirit and scope of the present application should be covered within the scope of the claims of the present application.​

Claims

1. A method for preparing a chitosan-gelatin composite preservative solution based on plasma-activated water modification, characterized in that, Includes the following steps: (1) Preparation of low-temperature plasma activated water: Deionized water was treated in an atmospheric environment using a low-temperature plasma generator. The plasma jet nozzle was placed above the surface of the deionized water for treatment. The treatment power was 0.3~0.8 kW and the treatment time was 10~40 min to obtain the treated low-temperature plasma activated water. (2) Structural modification of chitosan: Prepare an acetic acid solution with a volume concentration of 3.0%~5.0% using the low-temperature plasma activated water after step (1), and then dissolve chitosan powder with a deacetylation degree ≥90% in the acetic acid solution, stir to dissolve, and obtain a chitosan-PAW solution with a mass concentration of 1.0%~3.0%; (3) Structural modification of gelatin: At room temperature, gelatin is added to the low-temperature plasma-activated water prepared in step (1), stirred and dissolved to obtain a gelatin-PAW solution with a mass concentration of 2.0%~4.0%; (4) Preparation of composite preservative solution: The chitosan-PAW solution obtained in step (2) is mixed with the gelatin-PAW solution obtained in step (3), wherein the volume ratio of chitosan-PAW solution to gelatin-PAW solution is 1:0.5~4. After mixing, the mixture is stirred evenly to obtain the composite preservative solution. In step (4), the volume ratio of chitosan-PAW solution to gelatin-PAW solution is 1:2; The stirring described in step (4) is magnetic stirring for 0.5~1 h.

2. The method for preparing a chitosan-gelatin composite preservative solution based on plasma-activated water modification according to claim 1, characterized in that, In step (1), the plasma jet nozzle is placed 3-5 cm above the surface of the deionized water; the processing power is 0.6 kW.

3. The method for preparing a chitosan-gelatin composite preservative solution based on plasma-activated water modification according to claim 1, characterized in that, In step (2), the volume concentration of the acetic acid solution is 3.0%, and the molar concentration of the chitosan-PAW solution is 3.0%.

4. The method for preparing a chitosan-gelatin composite preservative solution based on plasma-activated water modification according to claim 1, characterized in that, The mass concentration of the gelatin-PAW solution in step (2) is 3.0%.

5. The chitosan-gelatin composite preservative solution based on plasma-activated water modification prepared according to any one of claims 1-4.

6. The application of the chitosan-gelatin composite preservative solution based on plasma-activated water modification according to claim 5 in the preservation and antibacterial effects of aquatic products, characterized in that... The steps are as follows: Immerse the aquatic products in the composite preservative solution or spray the composite preservative solution evenly onto the surface of the aquatic products. After draining the surface droplets, refrigerate. This realizes the application of the chitosan-gelatin composite preservative solution modified by plasma-activated water in the preservation and antibacterial properties of aquatic products.

7. The use according to claim 6, characterized in that, The aquatic products include fresh fish and fish fillets; the aquatic products are immersed in the compound preservation solution for 1 to 3 minutes.

8. The use according to claim 6, characterized in that, The refrigeration is carried out at a temperature of 4~10°C.

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