A gallic acid-mediated photodynamic antibacterial fresh-keeping solution and its fresh-keeping method

Abstract

The present invention provides a gallic acid-mediated photodynamic antibacterial preservative solution and its preservation method, belonging to the technical field of preservation materials. The photodynamic antibacterial preservative solution includes three components: a gallic acid microcapsule suspension treated with ultraviolet light, a chitosan quaternary ammonium salt-glycerol solution, and a carboxymethyl cellulose solution. In the present invention, biodegradable chitosan quaternary ammonium salt and carboxymethyl cellulose are used as the coating matrix, and the gallic acid microcapsule suspension treated with ultraviolet light is used as the active part of the coating. The present invention is fully biodegradable, easy to operate with less dosage, has excellent water vapor and oxygen barrier properties, good antioxidant and antibacterial properties, and can extend the shelf life of aquatic products.

Description

Technical Field

[0001] The present invention belongs to the technical field of preservation materials, and particularly relates to a gallic acid-mediated photodynamic antibacterial preservation solution and a preservation method thereof. Background Art

[0002] Aquatic products are characterized by high moisture and high protein. During storage and transportation, the degradation of biological macromolecules such as proteins they contain produces low-level products such as amines, hydrogen sulfide, and indole, and the muscle tissue loses its elasticity. When these products accumulate to a certain extent, it will cause off-flavors, and ultimately completely lose its edible value, resulting in huge waste in the aquatic industry.

[0003] Low temperature, chemical preservation, and coating with biological preservatives are common preservation methods for aquatic products. During the freezing process, adverse changes such as lipid oxidation, surface dehydration, and protein denaturation may occur, affecting the nutrition and sensory quality of aquatic products, and thus affecting the acceptability of aquatic products. Therefore, short-term storage generally chooses refrigeration. Although chemical preservation can control enzyme activity and microbial reproduction to a certain extent, it may also introduce some uncertain chemical pollutants into food. Summary of the Invention

[0004] To solve the above technical problems, the present invention proposes a gallic acid-mediated photodynamic antibacterial preservation solution and a preservation method thereof.

[0005] To achieve the above object, the present invention provides a gallic acid-mediated photodynamic antibacterial preservation solution, which includes three components: a gallic acid microcapsule suspension treated with ultraviolet light, a chitosan quaternary ammonium salt-glycerol solution, and a carboxymethyl cellulose solution.

[0006] Further, the preparation method of the gallic acid microcapsule suspension treated with ultraviolet light is as follows:

[0007] Dissolve gallic acid (GA) in absolute ethanol, and perform ultraviolet light treatment to obtain a gallic acid solution treated with ultraviolet light;

[0008] Add the ultraviolet light-treated gallic acid solution to a β-cyclodextrin solution for reaction. After the reaction is completed, wash with alcohol, vacuum filter to obtain a filter cake, and redissolve the filter cake in water to obtain a gallic acid (UVC-GA) microcapsule suspension treated with ultraviolet light.

[0009] Further, the preparation method of the GA solution is: dissolve 0.5 g of GA in 50 mL of absolute ethanol, and stir at 50 °C for 15 min to obtain a GA solution.

[0010] Further, the concentration of the β-cyclodextrin solution is 5 wt%.

[0011] Further, the preparation method of the β-cyclodextrin solution is as follows: Take 2.5 g of β-cyclodextrin and dissolve it in 50 mL of ultrapure water at 45 °C to obtain the β-cyclodextrin solution.

[0012] Further, the alcohol washing is as follows: Wash away the unencapsulated UVC-GA with absolute ethanol and wash away the excess β-cyclodextrin with distilled water.

[0013] Further, during the ultraviolet light treatment, the peak wavelength of the ultraviolet light is 250 nm, the average intensity is 2000 μW / cm 2 , the illumination distance is 3 cm, and the illumination time is 10 h.

[0014] Further, the reaction time for adding the gallic acid solution treated with ultraviolet light to the β-cyclodextrin solution for reaction is 1.5 h.

[0015] Further, the preparation method of the chitosan quaternary ammonium salt-glycerol solution is as follows: Dissolve chitosan quaternary ammonium salt in water and add glycerol during the stirring and dissolving process to obtain the chitosan quaternary ammonium salt-glycerol solution.

[0016] Further, the mass-volume ratio of chitosan quaternary ammonium salt to glycerol is (1 - 1.5) g∶500 μL.

[0017] Furthermore, the preparation method of the chitosan quaternary ammonium salt-glycerol solution is as follows: Dissolve 1 g of chitosan quaternary ammonium salt in 100 mL of ultrapure water and gradually add 500 μL of glycerol dropwise during the stirring and dissolving process to enhance the mechanical properties of the coating formed during the preservation process.

[0018] Further, the preparation method of the carboxymethyl cellulose solution is as follows: Dissolve carboxymethyl cellulose in water and stir evenly to obtain the carboxymethyl cellulose solution.

[0019] Furthermore, the preparation method of the carboxymethyl cellulose solution is as follows: Dissolve 1 g of carboxymethyl cellulose in 100 mL of ultrapure water and stir for 15 min at 50 °C to prepare the carboxymethyl cellulose solution.

[0020] Application of the gallic acid-mediated photodynamic antibacterial preservative solution in the preservation of aquatic products.

[0021] A method for preserving aquatic products, using the above-mentioned gallic acid-mediated photodynamic antibacterial preservative solution. The specific method is as follows:

[0022] Soak the aquatic products in the chitosan quaternary ammonium salt-glycerol solution and air-dry to form a chitosan quaternary ammonium salt coating;

[0023] Soak the aquatic products covered with the chitosan quaternary ammonium salt coating in the carboxymethyl cellulose solution and air-dry to obtain the aquatic products covered with the carboxymethyl cellulose coating;

[0024] Soak the aquatic product coated with carboxymethyl cellulose in the suspension of ultraviolet-light-treated gallic acid microcapsules, and air-dry it to obtain an aquatic product coated with the ultraviolet-light-treated gallic acid microcapsule coating, thus completing the preservation of the aquatic product.

[0025] Gallic acid is a polyphenolic organic compound widely present in terrestrial plants and seaweeds. Under ultraviolet light irradiation, gallic acid absorbs the energy of light and is excited from the ground state of the singlet state into a higher energy orbital to form an excited singlet state. The excited singlet state of gallic acid is very unstable and easily loses energy and returns to the singlet state to form a more stable excited triplet state, which is more stable. In this process, reactive oxygen species are generated, which have a killing effect on a variety of bacteria. In the aquatic product preservation method, the present invention uses biodegradable chitosan quaternary ammonium salt and carboxymethyl cellulose as the coating matrix, and the suspension of ultraviolet-light-treated gallic acid microcapsules as the active part of the coating. The present invention is fully biodegradable, easy to operate with less dosage, has excellent water vapor and oxygen barrier properties, good antioxidant and antibacterial properties, and can extend the shelf life of aquatic products.

[0026] Using the gallic acid-mediated photodynamic antibacterial preservative solution of the present invention to preserve aquatic products, only the soaking treatment of the aquatic products is required, and a coating will be self-assembled on the surface of the aquatic products through electrostatic interaction. The coating is clear and transparent, and has little impact on the appearance of the aquatic products. The UVC-GA solution has antibacterial properties, thereby extending the storage time of aquatic products after leaving the natural low-temperature environment of seawater. The present invention utilizes the layer-by-layer self-assembly preservation coating technology to form an active antibacterial preservation coating on the surface of the aquatic products with the electrostatic interaction between ions as the film-forming driving force. The chitosan quaternary ammonium salt coating carries a positive charge, and the carboxymethyl cellulose coating carries a negative charge, and the two can form a dense coating, and use its semi-permeable barrier to oxygen, carbon dioxide and moisture to adjust the weight loss rate of the aquatic products and reduce cell respiration, etc. The coatings formed by the preservative solution are all edible and easily degradable materials, which are convenient to operate and environmentally friendly.

[0027] Further, during the preservation of aquatic products, after obtaining the aquatic product coated with the ultraviolet-light-treated gallic acid microcapsule coating, repeat the process of soaking the aquatic product in the chitosan quaternary ammonium salt-glycerol solution and soaking it in the carboxymethyl cellulose solution to prepare a multi-layer preservation coating.

[0028] Further, in the aquatic product preservation method, the soaking time of the aquatic product in the chitosan quaternary ammonium salt-glycerol solution is 30-45 s, the air-drying temperature is 4 °C, and the air-drying time is 30 min;

[0029] The soaking time of the aquatic product in the carboxymethyl cellulose solution is 30-45 s, the air-drying temperature is 4 °C, and the air-drying time is 30 min;

[0030] The soaking time of aquatic products in the suspension of gallic acid microcapsules treated with ultraviolet light is 30 min, the air-drying temperature is 4 °C, and the air-drying time is 30 min.

[0031] Compared with the prior art, the present invention has the following advantages and technical effects:

[0032] 1. The preservation liquid and preservation method of the present invention extend the shelf life of aquatic products, greatly reduce the degree of lipid oxidation, and at the same time inhibit the growth and reproduction of bacteria, and have inhibitory effects on common foodborne pathogenic bacteria (such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa) and aquatic spoilage bacteria (such as Pseudomonas putida and Shewanella).

[0033] 2. The preservation method of the present invention is easy to operate, time-consuming, small in dosage, and easy to control. During the preservation process of the present invention, the preservation liquid is driven by electrostatic action to form a coating on the surface of aquatic products. The coating is delicate and smooth, has a self-healing function, is transparent light amber in appearance, has good water-holding effect, and the coating performance is stable.

[0034] 3. Compared with traditional food preservative films, the coating formed by the present invention is edible and easy to wash off, has high antibacterial and antioxidant properties, and can better guarantee the food quality. Gallic acid itself has antibacterial properties. When used as a photosensitizer, its antibacterial effect is greatly improved, and the shelf life of aquatic products (especially seafood products) is extended. Compared with traditional photosensitizers, gallic acid is cheap and easily available. A small amount of quinone compounds and reactive oxygen species generated by the photooxidation of gallic acid have a killing effect on bacteria, and at the same time will not cause too much damage to the aquatic product's own tissue and affect the flavor. The microcapsule structure blocks the oxidation and blackening caused by the contact of the gallic acid solution with air, and has little impact on the appearance of aquatic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0036] Figure 1 is a schematic diagram of the principle of the method of the present invention;

[0037] Figure 2 is the change of the oyster colony count during storage at 4 °C;

[0038] Figure 3 is the change of the salmon colony count during storage at 4 °C;

[0039] Figure 4 is the change of TVB-N of salmon during storage at 4 °C;

[0040] Figure 5 is the change of TVB-N of oyster during storage at 4 °C;

[0041] Figure 6 For the change of TBA in salmon during storage at 4°C;

[0042] Figure 7 For the change of TBA in oyster during storage at 4°C;

[0043] Figure 8 For the appearance change of oyster on the fifth day of storage at 4°C;

[0044] Figure 9 For the antibacterial effect of gallic acid irradiated with different wavelengths;

[0045] Figure 10 For the comparison of the content of active ingredients in the UVC-GA microcapsule suspension and the UVC-GA solution in the coating. Detailed implementation manners

[0046] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0048] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0049] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the specification of the present invention, which are obvious to those skilled in the art. Other implementation manners obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are only exemplary.

[0050] As used herein, terms such as "comprising", "including", "having", "containing", etc. are all open-ended terms, meaning including but not limited to.

[0051] Unless otherwise specified, each raw material in the present invention can be obtained by commercial purchase, and the equipment used in the present invention can be a conventional equipment in the field or can be referred to the existing technology in the field.

[0052] The chitosan quaternary ammonium salt in the examples of the present invention was purchased from Solarbio.

[0053] The schematic diagram of the method of the present invention is shown in Figure 1 .

[0054] Example 1

[0055] (1) Take 1 g of chitosan quaternary ammonium salt and dissolve it in 100 mL of ultrapure water. During the stirring and dissolving process, gradually add 500 μL of glycerol to increase the mechanical properties of the coating formed during preservation, and obtain a chitosan quaternary ammonium salt-glycerol solution (Solution A).

[0056] (2) Take 0.5 g of GA and dissolve it in 50 mL of absolute ethanol. Stir at 50 °C for 15 min to obtain a GA solution. Incubate for 10 h under the conditions that the peak wavelength of ultraviolet light is 250 nm, the average intensity is 2000 μW / cm 2 , and the illumination distance is 3 cm to prepare a UVC-GA solution. Take 2.5 g of β-cyclodextrin and dissolve it in 50 mL of ultrapure water at 45 °C to obtain a 5 wt% β-cyclodextrin solution. Gradually add the UVC-GA solution dropwise to the above 5 wt% β-cyclodextrin solution, react for 1.5 h, and shake well. Place it in an environment at 4 °C, precipitate overnight, wash away the unencapsulated UVC-GA with absolute ethanol, and wash away the excess β-cyclodextrin with distilled water. After vacuum filtration, obtain a filter cake, and redisperse the filter cake in 100 mL of ultrapure water to obtain a UVC-GA microcapsule suspension (Suspension B).

[0057] (3) Take 1 g of carboxymethyl cellulose and dissolve it in 100 mL of ultrapure water. Stir at 50 °C for 15 min to obtain a carboxymethyl cellulose solution (Solution C).

[0058] (4) After standing the chitosan quaternary ammonium salt-glycerol solution, the UVC-GA microcapsule suspension, and the carboxymethyl cellulose solution for 30 min respectively, completely immerse the salmon slices in Solution A, soak for 30 s, form a cationic coating on the surface of the fish body, and air-dry at 4 °C for 30 min to obtain salmon slices covered with Coating A.

[0059] (5) Immerse the salmon slices covered with Coating A in Solution C for 30 s, and then air-dry at 4 °C for 30 min again to obtain salmon slices covered with Coating A and Coating C.

[0060] (6) Immerse the salmon slices coated with coating A and coating C in suspension B for 30 min, and then place them in a 4°C environment to air-dry for 30 min again.

[0061] (7) Repeat the coating of coating A and C on the above-treated fish slices once each. After air-drying, a fresh-keeping coating is formed on the surface of the fish meat, denoted as the UVC-GA group. Store at 4°C, observe the fresh-keeping effect, and evaluate the fresh-keeping efficacy of this coating.

[0062] Example 2

[0063] (1) Dissolve 1.5 g of quaternary ammonium salt of chitosan in 100 mL of ultrapure water, and gradually add 500 μL of glycerol dropwise during the stirring and dissolving process to increase the mechanical properties of the coating formed during fresh-keeping, to obtain a quaternary ammonium salt of chitosan-glycerol solution (solution A).

[0064] (2) Take 0.5 g of GA and dissolve it in 50 mL of absolute ethanol, stir at 50°C for 15 min to obtain a GA solution. Incubate for 10 h under the conditions of an ultraviolet light peak wavelength of 250 nm, an average intensity of 2000 μW / cm 2 , and a light distance of 3 cm to prepare a UVC-GA solution. Take 2.5 g of β-cyclodextrin and dissolve it in 50 mL of ultrapure water at 45°C to obtain a 5 wt% β-cyclodextrin solution. Gradually add the UVC-GA solution dropwise to the above 5 wt% β-cyclodextrin solution, react for 1.5 h, and mix well by shaking. Place it in a 4°C environment, precipitate overnight, and then wash away the unencapsulated UVC-GA with absolute ethanol and wash away the excess β-cyclodextrin with distilled water. After vacuum filtration, obtain a filter cake, and redisperse the filter cake in 100 mL of ultrapure water to obtain a UVC-GA microcapsule suspension (suspension B).

[0065] (3) Dissolve 1 g of carboxymethyl cellulose in 100 mL of ultrapure water, and stir at 50°C for 15 min to obtain a carboxymethyl cellulose solution (solution C).

[0066] (4) After allowing the quaternary ammonium salt of chitosan-glycerol solution, UVC-GA microcapsule suspension, and carboxymethyl cellulose solution to stand for 30 min respectively, completely immerse the oyster meat in solution A, soak for 30 s, and form a cationic coating on the surface of the oyster meat. Let it stand and air-dry at 4°C for 30 min.

[0067] (5) Immerse the oyster meat covered with coating A in solution C for 30 s, and then air-dry at 4°C for 30 min again.

[0068] (6) Immerse the oyster meat covered with coatings A and C in suspension B for 30 min, and then air-dry at 4°C for 30 min again.

[0069] (7) Repeat the above-treated oyster meat by coating with Coating A and Coating C once each. After air-drying, a fresh-keeping coating is formed on the surface of the oyster meat, denoted as the UVC-GA group. Store at 4°C, observe the fresh-keeping effect, and evaluate the fresh-keeping efficacy of this coating.

[0070] Comparative Example 1

[0071] Set up a blank control group of salmon slices without any treatment and store them in the same environment. Observe and record their changes.

[0072] Set up a blank control group of oyster meat without any treatment and store it in the same environment. Observe and record its changes.

[0073] Comparative Example 2

[0074] Compared with Example 1, in Comparative Example 2, the photodynamic effect of gallic acid was cancelled, and the gallic acid solution was not treated with ultraviolet light.

[0075] (1) Dissolve 1 g of quaternary ammonium salt of chitosan in 100 mL of ultrapure water. During the stirring and dissolving process, gradually add 500 μL of glycerol to increase the mechanical properties of the coating formed during fresh-keeping, and obtain a quaternary ammonium salt of chitosan-glycerol solution (Solution A).

[0076] (2) Dissolve 0.5 g of GA in 50 mL of absolute ethanol, stir at 50°C for 15 min to obtain a GA solution. Take 2.5 g of β-cyclodextrin and dissolve it in 50 mL of ultrapure water at 45°C to obtain a 5 wt% β-cyclodextrin solution. Gradually add the GA solution dropwise to the above β-cyclodextrin solution, react for 1.5 h, and shake well. Place it in a 4°C environment, precipitate overnight, and then wash away the unencapsulated GA with absolute ethanol and wash away the excess β-cyclodextrin with distilled water. After vacuum filtration, obtain a filter cake, and redisperse the filter cake in 100 mL of ultrapure water to obtain a GA microcapsule suspension (Suspension B).

[0077] (3) Dissolve 1 g of carboxymethyl cellulose in 100 mL of ultrapure water and stir at 50°C for 15 min to obtain a carboxymethyl cellulose solution (Solution C).

[0078] (4) After allowing the quaternary ammonium salt of chitosan-glycerol solution, GA microcapsule suspension, and carboxymethyl cellulose solution to stand for 30 min each, completely immerse the salmon slices in Solution A, soak for 30 s, form a cationic coating on the surface of the fish body, and air-dry at 4°C for 30 min to obtain salmon slices covered with Coating A.

[0079] (5) Immerse the salmon slices covered with Coating A in Solution C for 30 s, and then air-dry at 4°C for 30 min again to obtain salmon slices covered with Coating A and Coating C.

[0080] (6) Immerse the salmon slices coated with coating A and coating C in suspension B for 30 min, and then place them in the air to dry for 30 min at 4°C again.

[0081] (7) Repeat the coating of coating A and C on the above-treated fish slices once each. After air-drying, a fresh-keeping coating is formed on the surface of the fish meat, denoted as the GA coating group. Store at 4°C, observe the fresh-keeping effect, and evaluate the fresh-keeping efficacy of this coating.

[0082] Comparative Example 3

[0083] Compared with Example 2, Comparative Example 3 cancels the photodynamic effect of gallic acid and does not perform ultraviolet treatment on the gallic acid solution.

[0084] (1) Dissolve 1.5 g of quaternary ammonium chitosan in 100 mL of ultrapure water, and gradually add 500 μL of glycerol dropwise during the stirring and dissolving process to increase the mechanical properties of the coating formed during fresh-keeping, obtaining a quaternary ammonium chitosan-glycerol solution (solution A).

[0085] (2) Take 0.5 g of GA and dissolve it in 50 mL of absolute ethanol, stir at 50°C for 15 min to obtain a GA solution. Take 2.5 g of β-cyclodextrin and dissolve it in 50 mL of ultrapure water at 45°C to obtain a 5 wt% β-cyclodextrin solution. Gradually add the GA solution dropwise to the above β-cyclodextrin solution, react for 1.5 h, and shake well. Place it in an environment at 4°C, precipitate overnight, and then wash away the unencapsulated GA with absolute ethanol and the excess β-cyclodextrin with distilled water. After vacuum filtration, obtain the filter cake, and redisperse the filter cake in 100 mL of ultrapure water to obtain a GA microcapsule suspension (suspension B).

[0086] (3) Take 1 g of carboxymethyl cellulose and dissolve it in 100 mL of ultrapure water, stir at 50°C for 15 min to obtain a carboxymethyl cellulose solution (solution C).

[0087] (4) After each of solution A, suspension B, and solution C stands for 30 min, completely immerse the oyster meat in solution A and soak for 30 s to form a cationic coating on the surface of the oyster meat. Let it stand and air-dry at 4°C for 30 min.

[0088] (5) Immerse the oyster meat covered with coating A in solution C for 30 s, and then air-dry at 4°C for 30 min again.

[0089] (6) Immerse the oyster meat covered with coatings A and C in suspension B for 30 min, and then air-dry at 4°C for 30 min again.

[0090] (7) Repeat the coating of coatings A and C on the above-treated oyster meat once each. After air-drying, a fresh-keeping coating is formed on the surface of the oyster meat, denoted as the GA coating group. Store at 4°C, observe the fresh-keeping effect, and evaluate the fresh-keeping efficacy of this coating.

[0091] Comparative Example 4

[0092] Set up an uncoated group of salmon slices, only soak them in UVC-GA solution for 30 min, store them in the same environment, and observe and record their changes.

[0093] Comparative Example 5

[0094] Set up an uncoated group of oyster meat, only soak it in UVC-GA solution for 30 min, store it in the same environment, and observe and record its changes.

[0095] Comparative Example 6

[0096] UVC-GA solution group:

[0097] (1) Dissolve 1 g of quaternary ammonium salt of chitosan in 100 mL of ultrapure water, and gradually add 500 μL of glycerol dropwise during the stirring and dissolving process to increase the mechanical properties of the coating formed during preservation, and obtain a quaternary ammonium salt of chitosan-glycerol solution (solution A).

[0098] (2) Dissolve 0.5 g of GA in 50 mL of absolute ethanol, stir at 50 °C for 15 min to obtain a GA solution. Incubate for 10 h under the conditions of an ultraviolet light peak wavelength of 250 nm, an average intensity of 2000 μW / cm 2 , and a light distance of 3 cm to prepare a UVC-GA solution (solution B).

[0099] (3) Dissolve 1 g of carboxymethyl cellulose in 100 mL of ultrapure water, and stir at 50 °C for 15 min to obtain a carboxymethyl cellulose solution (solution C).

[0100] (4) After standing the quaternary ammonium salt of chitosan-glycerol solution, UVC-GA solution and carboxymethyl cellulose solution for 30 min respectively, completely immerse the salmon slices in solution A, soak for 30 s, form a cationic coating on the fish body surface, and air-dry at 4 °C for 30 min to obtain salmon slices covered with coating A.

[0101] (5) Immerse the salmon slices covered with coating A in solution C for 30 s, and air-dry again at 4 °C for 30 min to obtain salmon slices covered with coating A and coating C.

[0102] (6) Immerse the salmon slices covered with coating A and coating C in solution B for 30 min, and air-dry again at 4 °C for 30 min.

[0103] Repeat covering coating A and C once for the above-treated fish slices, and a fresh-keeping coating is formed on the surface of the fish meat after air-drying, denoted as the basic coating group, and stored at 4 °C.

[0104] To explore the assembly ability of the microcapsule active coating and the base coating, a comparison was made between the base coating group of the UVC-GA solution and the coating group of the UVC-GA microcapsules:

[0105] The coatings of the UVC-GA solution group and the UVC-GA microcapsule group of Example 1 were washed three times with PBS to ensure that there was no extra UVC-GA interfering with the experiment. The content of the active ingredient in the coating was determined using 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (DPBA). A 0.2% (w / v) DPBA solution was prepared, and 10 mL of the DPBA solution was taken to react with the two groups in the dark for 5 min. The fluorescence absorbance value was measured using a fluorescence spectrophotometer under the condition of (λex / λem = 405 / 465 nm). The results are shown in Figure 10 .

[0106] Explore the adsorption and assembly ability of the microcapsule active coating and the chitosan quaternary ammonium salt-carboxymethyl cellulose coating.

[0107] The fresh-keeping effects of the films made from the fresh-keeping solutions in each group of examples and comparative examples were evaluated. The specific results are shown in the following table.

[0108] The water loss was calculated according to the following formula, where m 0 is the initial weight and m x is the weight on the xth day:

[0109] Water loss rate = (m 0 - m x ) / m 0 * 100%

[0110] The fresh-keeping situation of the salmon slices is shown in Table 1.

[0111] Table 1 Results table of water loss rate

[0112]

[0113] The fresh-keeping situation of the oyster meat is shown in Table 2.

[0114] Table 2 Results table of water loss rate

[0115]

[0116]

[0117] Note: (No more records are made after the water loss rate exceeds 10%)

[0118] According to the experimental results, the water loss in the uncoated group was severe. This might be because the UVC-GA solution directly caused tissue damage to the fish and oyster meat, accelerating the reaction between air and tissue, resulting in a high water loss rate, affecting their flavor and sensory properties. Therefore, it is meaningless to study its preservation effect. The water retention of the GA coating and the UVC-GA coating was higher than that of the blank group. Thus, it can be seen that the coating formed by the preservation liquid of the present invention has excellent effects.

[0119] Colony change

[0120] The total number of colonies can be used as a standard to judge the shelf life of aquatic products. When the total number of colonies reaches 6.0 lg (CFU / mL), it is the unacceptable limit for aquatic products. As Figure 2 and 3 shown, the UVC-GA preservation coating has good antibacterial effects and can extend the shelf life of aquatic products.

[0121] TVB-N change

[0122] The TVB-N value, as one of the indicators for evaluating the spoilage of marine fish, can effectively reflect the degree of decomposition of seafood protein during storage.

[0123] As Figure 4 and 5 shown, the UVC-GA preservation coating has good protein protection effects.

[0124] Lipid oxidation situation

[0125] The TBA value is one of the important standards for evaluating lipid oxidation in aquatic products. During the storage of aquatic products, due to the accumulation of secondary products of lipid oxidation, the TBA value increases. As Figure 6 and 7 shown, the UVC-GA preservation coating has good lipid antioxidant effects.

[0126] Based on the above indicators, it can be found that the coating formed by the preservation liquid of the present invention can significantly extend the shelf life of seafood and has antibacterial and antioxidant properties.

[0127] To further illustrate the staining situation of the coated and uncoated samples, the uncoated group of oyster meat was only treated with the UVC-GA solution for 30 min (comparative example 5), and the coated group (example 2) and the blank group (oyster meat group of comparative example 1) were stored in the same environment, and their changes were observed and recorded.

[0128] According to Figure 8 it can be seen that the uncoated group was severely stained and had severe water loss. The coated group was slightly stained. The blank group without preservation treatment showed spoilage spots.

[0129] Photodynamic wavelength screening

[0130] Taking the common foodborne pathogenic bacteria Escherichia coli (Gram-negative bacteria) and Staphylococcus aureus (Gram-positive bacteria) as models, the photodynamic wavelengths were screened. Since the maximum absorption peak of gallic acid is at 250 - 260 nm, irradiation treatments at 250 nm, 260 nm, and 300 nm were respectively carried out to explore its antibacterial effect. The turbidimetric method was used to represent the bacterial concentration by the absorbance value at OD 600 The absorbance value at this point represents the bacterial concentration.

[0131] As Figure 9 It can be seen that irradiation at different wavelengths endows gallic acid with photodynamic efficacy and enhances its antibacterial property. The antibacterial effects of 250 nm and 260 nm are similar, and the photodynamic effect of GA irradiated at 250 nm is slightly better than that at 260 nm, and the photodynamic antibacterial effects of both are better than that at 300 nm. Therefore, 250 nm was selected as the optimal irradiation wavelength.

[0132] Determination of the adsorption capacity of the coating

[0133] Using the specific property of 2-(4'-dimethylaminophenyl)-6-methylbenzoxazole (DPBA) and flavonoid compounds, the fluorescence absorbance value was measured under the condition of (λex / λem = 405 / 465 nm) to determine the active content of the overall coating. According to Figure 10 It can be seen that the microcapsule suspension has a higher content in the total fresh-keeping coating, which proves that after being prepared into a microcapsule suspension, it combines more closely with the coating material and carries more antibacterial active factors.

[0134] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for preserving aquatic products, characterized in that, the specific method is: Soak the aquatic products in a chitosan quaternary ammonium salt - glycerol solution, and air-dry to form a chitosan quaternary ammonium salt coating; Soak the aquatic products covered with the chitosan quaternary ammonium salt coating in a carboxymethyl cellulose solution, and air-dry to obtain aquatic products covered with a carboxymethyl cellulose coating; Soak the aquatic products covered with the carboxymethyl cellulose coating in a suspension of ultraviolet-light-treated gallic acid microcapsules, and air-dry to obtain aquatic products covered with a coating of ultraviolet-light-treated gallic acid microcapsules, thus completing the preservation of aquatic products; The preparation method of the suspension of ultraviolet-light-treated gallic acid microcapsules is: Dissolve gallic acid in absolute ethanol, perform ultraviolet-light treatment to obtain an ultraviolet-light-treated gallic acid solution; Add the ultraviolet-light-treated gallic acid solution to a β-cyclodextrin solution and react for 1.5 h. After the reaction, wash with alcohol and perform vacuum filtration to obtain a filter cake. Redissolve the filter cake in water to obtain the suspension of ultraviolet-light-treated gallic acid microcapsules; When the ultraviolet light treatment is carried out, the peak wavelength of the ultraviolet light irradiation is 250 nm, and the average intensity is 2000 μW / cm 2 , the irradiation distance is 3 cm, and the irradiation time is 10 h.

2. The method for preserving aquatic products according to claim 1, characterized in that, the preparation method of the chitosan quaternary ammonium salt - glycerol solution is: Dissolve chitosan quaternary ammonium salt in water, and add glycerol during the stirring and dissolving process to obtain the chitosan quaternary ammonium salt - glycerol solution.

3. The method for preserving aquatic products according to claim 1, characterized in that, the preparation method of the carboxymethyl cellulose solution is: Dissolve carboxymethyl cellulose in water and stir evenly to obtain the carboxymethyl cellulose solution.

4. The method for preserving aquatic products according to claim 1, characterized in that, During the preservation of aquatic products, after obtaining the aquatic products covered with a coating of ultraviolet-light-treated gallic acid microcapsules, repeat the process of soaking the aquatic products in the chitosan quaternary ammonium salt - glycerol solution and soaking in the carboxymethyl cellulose solution to prepare a multi-layer preservation coating.

5. The method for preserving aquatic products according to claim 1, characterized in that, The soaking time of the aquatic products in the chitosan quaternary ammonium salt - glycerol solution is 30 - 45 s, the air-drying temperature is 4 °C, and the air-drying time is 30 min; The soaking time of the aquatic products in the carboxymethyl cellulose solution is 30 - 45 s, the air-drying temperature is 4 °C, and the air-drying time is 30 min; The soaking time of the aquatic products in the suspension of ultraviolet-light-treated gallic acid microcapsules is 30 min, the air-drying temperature is 4 °C, and the air-drying time is 30 min.

Images