Aquatic product preservation method based on Pickering emulsion of natural nanoparticles

Abstract

The invention belongs to the technical field of aquatic product preservation, and relates to a natural nanoparticle-based Pickering emulsion aquatic product preservation method, which comprises: soaking an aquatic product in a natural nanoparticle-based Pickering emulsion to form a film layer on the surface of the aquatic product; the Pickering emulsion based on the natural nano particles is formed by mixing a chitosan-sodium alginate-calcium chloride nano particle solution and cinnamon essential oil according to the mass ratio of 1: (0.1-10) and dispersing the mixture at a high speed, and the Pickering emulsion contains composite nano particles loaded with the cinnamon essential oil. Chitosan and sodium alginate form stable nano particles with a three-dimensional network structure through an ionic cross-linking effect with calcium ions, so that efficient loading of active ingredients of cinnamon essential oil is realized; and the Pickering emulsion based on the natural nanoparticles has good stability, can form a stable film layer on the surface of the aquatic product, effectively prevents sulfydryl exposure and oxidation, delays growth and reproduction of putrefying bacteria, and further effectively prolongs the preservation time of the aquatic product.

Description

Technical Field

[0001] The invention belongs to the technical field of aquatic product preservation, and relates to a method for preserving aquatic products based on a Pickering emulsion of natural nanoparticles. Background Art

[0002] Aquatic products are susceptible to microbial contamination and oxidation during processing and storage, which leads to a decline in quality and a shortened shelf life. Therefore, extending the shelf life of aquatic products while maintaining their freshness, flavor and nutritional value has become a major challenge in food preservation technology. Although traditional preservation methods, such as refrigeration and vacuum packaging, can appropriately extend the shelf life, they are still ineffective in the face of microbial growth, lipid oxidation and flavor changes caused by improper storage. Moreover, solid preservatives are mostly used for non-sealed products such as fruits and vegetables, and are not suitable for aquatic products. Furthermore, conventional preservation methods may also affect the sensory quality and nutritional content of aquatic products, so there is an urgent need to explore new and more effective preservation technologies.

[0003] The main active ingredients in cinnamon essential oil, such as cinnamaldehyde, have strong antibacterial and antioxidant effects, which can effectively inhibit the growth of microorganisms and lipid oxidation in aquatic products, thereby delaying the spoilage process. However, cinnamon essential oil faces multiple challenges when used alone. First, cinnamon essential oil is highly volatile, and its active ingredients may evaporate in a short period of time, reducing the preservation effect. Secondly, cinnamon essential oil has poor water solubility and is difficult to be evenly distributed on the surface of aquatic products, resulting in uneven preservation effect. In addition, too high a concentration of cinnamon essential oil may change the flavor of aquatic products.

[0004] Existing studies have shown that by compounding natural antibacterial ingredients such as cinnamon essential oil with a film-forming matrix, a functional fresh-keeping coating can be constructed on the surface of aquatic products. However, this technology has significant limitations in practical applications: first, the coating construction requires the use of special film coating equipment for quantitative spraying, which not only increases the cost of facility investment, but also requires precise control of the film thickness to avoid uneven coating affecting the fresh-keeping effect; second, for high-fat aquatic products, the film layer formed on the surface is easily interfered by oil, resulting in a decrease in the bonding strength between the coating and the matrix, making it difficult to effectively block the penetration of oxygen and microorganisms, thereby losing the fresh-keeping effect. Summary of the invention

[0005] The purpose of the present invention is to solve the above problems existing in the prior art and propose a method for preserving aquatic products by using a Pickering emulsion containing composite nanoparticles loaded with cinnamon essential oil. In an environment with a pH value of 5.5-6.8, the swelling degree of the nanoparticles is increased, the pH-responsive release of cinnamaldehyde is achieved, and the shelf life of the aquatic products is effectively extended.

[0006] One object of the present invention is achieved by the following technical solutions:

[0007] A method for preserving aquatic products based on a Pickering emulsion of natural nanoparticles, the method comprising: immersing the aquatic products in the Pickering emulsion based on natural nanoparticles to form a film layer on the surface of the aquatic products;

[0008] The Pickering emulsion based on natural nanoparticles is formed by mixing a chitosan-sodium alginate-calcium chloride nanoparticle solution with a mass ratio of 1:(0.1-10) and cinnamon essential oil, and dispersing the mixture at high speed, and contains composite nanoparticles loaded with cinnamon essential oil.

[0009] Preferably, the concentration of the chitosan-sodium alginate-calcium chloride nanoparticle solution is 0.1-2% (w / v).

[0010] Preferably, the concentration of the chitosan-sodium alginate-calcium chloride nanoparticle solution is 2% (w / v).

[0011] Preferably, the mass ratio of the chitosan-sodium alginate-calcium chloride nanoparticle solution to cinnamon essential oil is 1:(0.5-5).

[0012] More preferably, the mass ratio of the chitosan-sodium alginate-calcium chloride nanoparticle solution to the cinnamon essential oil is 1:(0.8-2).

[0013] Preferably, the high-speed dispersion comprises: stirring at 10,000 to 30,000 rpm in a high-speed disperser.

[0014] Preferably, the method for preparing the chitosan-sodium alginate-calcium chloride nanoparticle solution comprises:

[0015] (1) dissolving chitosan in 0.1-3% acetic acid solution and adjusting the pH value to 5.4±0.2 to obtain a chitosan solution;

[0016] (2) adding sodium alginate to water under continuous magnetic stirring, and adjusting the pH to 5.2±0.2 to obtain a sodium alginate solution; adding calcium chloride solution dropwise until the mass ratio of sodium alginate to calcium chloride is (3-8):1, and stirring to obtain a sodium alginate-calcium chloride composite solution;

[0017] (3) The chitosan solution and the sodium alginate-calcium chloride composite solution are stirred and mixed to obtain nanoparticles; the mass ratio of chitosan, sodium alginate and calcium chloride in the nanoparticles is (1-1.9):(3-8):1; then the mixture is centrifuged and washed, and redispersed in water to obtain a chitosan-sodium alginate-calcium chloride nanoparticle solution with a concentration of 0.1-2% (w / v).

[0018] Preferably, the chitosan has a deacetylation degree of 86-95% and a molecular weight of 10-40 kDa.

[0019] Preferably, the mass ratio of sodium alginate to calcium chloride in (2) is (4-6):1.

[0020] Preferably, the average particle size of the (3) nanoparticles is 100 to 260 nm.

[0021] More preferably, the average particle size of the (3) nanoparticles is 150 to 200 nm.

[0022] Preferably, the mass ratio of chitosan, sodium alginate and calcium chloride in the (3) nanoparticles is 1.5:5:1.

[0023] Preferably, the aquatic product preservation method comprises: soaking the aquatic product in a 2% (w / v) Pickering emulsion based on natural nanoparticles for 5 to 60 minutes to form a film layer on the surface of the aquatic product; after taking out the aquatic product, sealing it and storing it in a refrigerator at 4°C for 8 to 12 days.

[0024] Further preferably, the preparation method of the Pickering emulsion based on natural nanoparticles with a concentration of 2% (w / v) comprises: mixing the chitosan-sodium alginate-calcium chloride nanoparticle solution with a concentration of 2% (w / v) and cinnamon essential oil in a mass ratio of 1:1 and dispersing at high speed to form.

[0025] More preferably, the Pickering emulsion based on natural nanoparticles with a concentration of 2% (w / v) is left to stand at room temperature for 0 to 40 days, and the Pickering emulsion has no stratification phenomenon.

[0026] A Pickering emulsion based on natural nanoparticles, comprising composite nanoparticles loaded with cinnamon essential oil.

[0027] Preferably, the average particle size of the composite nanoparticles loaded with cinnamon essential oil is 100-260 nm.

[0028] Preferably, the content of cinnamon essential oil in the composite nanoparticles loaded with cinnamon essential oil is 20-60wt%.

[0029] A BP neural network prediction model was constructed to predict the TVB-N, TVC, sensory evaluation, thiol, and juice loss rate parameters of salmon by inputting storage days and emulsion information to evaluate whether it met the shelf life standards.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention uses a Pickering emulsion containing composite nanoparticles loaded with cinnamon essential oil for the preservation of aquatic products. Under an environment with a pH value of 5.5-6.8 (consistent with the spoilage characteristics of aquatic products), the swelling degree of the nanoparticles increases, thereby achieving the pH-responsive release of cinnamaldehyde.

[0032] 2. In the present invention, chitosan and sodium alginate form stable nanoparticles with a three-dimensional network structure through ionic crosslinking with calcium ions, and achieve efficient loading of active ingredients of cinnamon essential oil through the dual action mechanism of physical loading (hydrogen bonding) and chemical bonding (ionic bonding), and construct a "adsorption-sustained release" dual controlled release system: on the one hand, the volatility of cinnamaldehyde is significantly reduced through the steric hindrance effect of the three-dimensional network; on the other hand, relying on the pH response characteristics of the crosslinked structure, the intelligent controlled release of cinnamaldehyde during the storage of aquatic products can be achieved.

[0033] 3. The amino groups of chitosan in the present invention can destroy bacterial cell membranes after protonation, and the cinnamaldehyde in cinnamon essential oil penetrates the lipid bilayer membrane through hydrophobic action. At the same time, cinnamon essential oil continues to exert antibacterial and antioxidant effects through the sustained release effect of nanoparticles. Sodium alginate chelates metal ions calcium, blocks the Fenton reaction, reduces the peroxide value of lipids in aquatic products, and maintains the color, flavor and nutritional components of aquatic products, thereby achieving a synergistic effect of antibacterial and antioxidant effects.

[0034] 4. The present invention controls the ratio of nanoparticles to cinnamon essential oil. An appropriate concentration of nanoparticles can improve the stability of the Pickering emulsion and effectively delay the volatilization of cinnamon essential oil. Too high or too low concentration of nanoparticles affects the stability of the Pickering emulsion and even reduces the loading capacity of the nanoparticles.

[0035] 5. The Pickering emulsion based on natural nanoparticles of the present invention has good stability, can maintain the Pickering emulsion texture after standing for a long time, can form a stable film layer on the surface of aquatic products, effectively prevent the exposure and oxidation of thiol groups, delay the growth and reproduction of spoilage bacteria, reduce protein degradation, and thus effectively reduce the total colony count, TVB-N value, and thiol groups; combined with the pH-responsive sustained release of cinnamaldehyde, the shelf life of aquatic products is effectively extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The stability results of CS-ALG-Pickering with a concentration of 0 to 2% (w / v) in Example 1 of the present invention after standing at room temperature for 0 days (a) and 10 days (b).

[0037] Figure 2This is a graph showing the total colony count of the fish pieces in Example 1 of the present invention after being immersed in CS-ALG-Pickering at a concentration of 0 to 2% (w / v) and then sealed and refrigerated for 0 to 12 days.

[0038] Figure 3 The graph is a volatile basic nitrogen test result of the fish block in Example 1 of the present invention after being immersed in CS-ALG-Pickering with a concentration of 0 to 2% (w / v) and then sealed and refrigerated for 0 to 12 days.

[0039] Figure 4 This is a graph showing the juice loss rate of the fish pieces in Example 1 of the present invention after being immersed in CS-ALG-Pickering with a concentration of 0 to 2% (w / v) and then sealed and refrigerated for 0 to 12 days.

[0040] Figure 5 This is a graph showing the change in total thiol content of the fish pieces in Example 1 of the present invention after being immersed in CS-ALG-Pickering at a concentration of 0 to 2% (w / v) and then sealed and refrigerated for 0 to 12 days.

[0041] Figure 6 This is a diagram showing the sensory evaluation results of the fish pieces in Example 1 of the present invention after being immersed in CS-ALG-Pickering with a concentration of 0 to 2% (w / v) and then sealed and refrigerated for 0 to 12 days.

[0042] Figure 7 A prediction model is constructed for the BP neural network of the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further described below through specific embodiments and drawings. It should be understood that the specific embodiments described herein are only used to help understand the present invention and are not specifically limited to the present invention. The drawings used herein are only for better illustrating the disclosed content of the present invention and do not have a limiting effect on the scope of protection.

[0044] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0045] Herein, the preparation method of the Pickering emulsion based on natural nanoparticles comprises:

[0046] (1) dissolving chitosan in 0.1-3% acetic acid solution, adjusting the pH value to 5.4±0.2, and obtaining a chitosan solution with a concentration of 1-10 g / L;

[0047] (2) Under continuous magnetic stirring, sodium alginate is added to water, and the pH is adjusted to 5.2±0.2 to obtain a sodium alginate solution with a concentration of 1 to 5 g / L; a calcium chloride solution with a concentration of 0.1 to 0.5 g / L is added dropwise until the mass ratio of sodium alginate to calcium chloride is (3 to 8):1, and the mixture is stirred to obtain a sodium alginate-calcium chloride composite solution;

[0048] (3) stirring and mixing the chitosan solution and the sodium alginate-calcium chloride composite solution to obtain nanoparticles; the mass ratio of chitosan, sodium alginate and calcium chloride in the nanoparticles is (1-1.9):(3-8):1; then centrifuging and washing, and redispersing in water to obtain a chitosan-sodium alginate-calcium chloride nanoparticle solution with a concentration of 0.1-2% (w / v);

[0049] (4) mixing a chitosan-sodium alginate-calcium chloride nanoparticle solution with cinnamon essential oil in a mass ratio of 1:(0.1-10), and stirring the mixture in a high-speed disperser at 10,000-30,000 rpm to form a Pickering emulsion based on natural nanoparticles;

[0050] The Pickering emulsion based on natural nanoparticles contains composite nanoparticles loaded with cinnamon essential oil and with an average particle diameter of 100-260nm.

[0051] In this article, the aquatic product preservation method includes: soaking the aquatic product in a 2% (w / v) Pickering emulsion based on natural nanoparticles for 5 to 60 minutes to form a film layer on the surface of the aquatic product; after the aquatic product is taken out, it is sealed and stored in a refrigerator at 4°C for 8 to 12 days.

[0052] Example 1

[0053] (1) dissolving chitosan (deacetylation degree 90%, molecular weight 20 kDa) in 1% acetic acid solution, adjusting the pH value to 5.4, to obtain a chitosan solution with a concentration of 5 g / L;

[0054] (2) under continuous magnetic stirring, sodium alginate was added to pure water, and the pH was adjusted to 5.2 with 1M NaOH to obtain a sodium alginate solution with a concentration of 2 g / L; a calcium chloride solution with a concentration of 0.2 g / L was added dropwise so that the mass ratio of sodium alginate to calcium chloride was 5:1; and then stirred to obtain a sodium alginate-calcium chloride composite solution;

[0055] (3) Mixing a chitosan solution with a volume ratio of 2:11 and a sodium alginate-calcium chloride composite solution (the mass ratio of chitosan, sodium alginate, and calcium chloride is 1.5:5:1), stirring at room temperature for 1 hour, and centrifuging at 12000 x g for 30 minutes to separate nanoparticles, the average particle size of the nanoparticles is 190 nm, and removing unreacted chitosan and sodium alginate; the separated nanoparticles are washed three times with deionized water, and then the nanoparticles are re-dispersed in deionized water using ultrasound to obtain a nanoparticle solution (suspension) with a concentration of 0-2% (w / v);

[0056] (4) The nanoparticle solution was mixed with cinnamon essential oil in a volume ratio of 1:1 to prepare nanoparticle mixed solutions containing cinnamon essential oil of different concentrations, and stirred at 12000 rpm for 2 min in a high-speed disperser to form a Pickering emulsion based on natural nanoparticles containing composite nanoparticles loaded with cinnamon essential oil, which was recorded as CS-ALG-Pickering.

[0057] Performance Testing:

[0058] 1. Pickering emulsion stability test

[0059] The Pickering emulsions based on natural nanoparticles with concentrations of 0%, 0.5%, 1%, 1.5%, and 2% (w / v) were placed in test tubes, sealed, transferred to a test tube rack, and allowed to stand at room temperature.

[0060] The stability of nanoparticle emulsions with different concentrations was observed every day and recorded continuously for 40 days to evaluate the effect of nanoparticle concentration on emulsion formation and stability.

[0061] Pickering emulsion stability results are shown in Figure 1 It can be seen that after 10 days, when the concentration is 0.5%, the composite nanoparticles cannot completely cover the surface of the droplets, resulting in stratification; when the concentration is 1%, although there are no excess composite nanoparticles dispersed in the continuous phase, as time goes by, the composite nanoparticle film cannot effectively prevent the droplets from agglomerating, and stratification will still occur; when the concentration reaches 1.5%, the excess particles are dispersed in the continuous phase, which significantly reduces the aggregation between the droplets, and the stratification phenomenon is not obvious; when the concentration is further increased to 2%, the composite nanoparticles can effectively form a film, and the remaining composite nanoparticles are fully dispersed in the continuous phase, thereby greatly enhancing the stability of the emulsion, and there is almost no stratification. Continue to stand, after 40 days, only the CS-ALG-Pickering with a concentration of 2% (w / v) remains stable.

[0062] 2. Freshness preservation performance test

[0063] (1) Remove the head, viscera and skin of the salmon, take two slices of dorsal meat from both sides of the fish body, wash with sterile water, and use sterile filter paper to wipe the surface moisture; cut the fish fillets into 15.0±0.5g pieces, a total of 36 pieces.

[0064] (2) The fish pieces were divided equally into a control group and an experimental group.

[0065] Experimental group (CS-ALG-2%): fish pieces were immersed in 2% (w / v) concentration of natural nanoparticle-based Pickering emulsion for 30 min;

[0066] Control group (Control): The fish pieces were immersed in sterile water for 30 minutes.

[0067] All the fish pieces were taken out and placed in sterilized sealed packaging bags to ensure good sealing, and stored in a refrigerator at 4°C. After 0, 1, 3, 5, 8, and 12 days of storage, 3 samples were randomly taken each time to measure their freshness indicators, including total bacterial colony count (TVC), volatile basic nitrogen (TVB-N), juice loss rate, thiol content, and sensory evaluation.

[0068] 2.1. Total Viable Count Test (TVC):

[0069] The experiment was conducted according to GB4789.2-2022. Weigh 1g of untreated fish pieces stored at 4°C as the control group, place it in a sterile bag containing 1mL of 0.9% saline, and pat for 2 minutes to make a 1:10 sample solution. Use a pipette to take the above sample solution for gradient dilution to prepare 1:1000 and 1:10000 sample solutions. Pipette 1mL of the sample solution into a sterile plate, pour 15mL of plate count agar medium cooled to 46°C into the plate, and rotate the plate to mix it evenly. Incubate the culture plate at 37°C for 48 hours; calculate the number of colonies grown on the culture medium, and then deduce the total number of colonies per gram of sample.

[0070] According to the hygienic standards for raw salmon and lobster (DB46 / 118-2008), the total colony count of raw salmon reaches 7lg (CFU / g), which is the acceptable limit.

[0071] The total colony count results are shown in Figure 2 And Table 1,

[0072] Table 1. Results of total colony count TVC lg (CFU / g) of fish meat in Example 1

[0073] Day 0 1 day 3 days 5 days 8 days 12 days CS-ALG - 2% 3 3.85 4.88 6.11 7.02 8.24 Control 3.18 4.5 5.45 7.19 8.4 9.75

[0074] It can be seen that the total number of colonies in the control group (Control) exceeded the standard on the 5th day of storage, while the total number of colonies in the experimental group (CS-ALG-2%) did not exceed the standard until the 8th day. This shows that the Pickering emulsion of the present invention has a good antibacterial effect and can continue to exert the antibacterial effect during the storage process, significantly extending the shelf life of salmon.

[0075] 2.2, Volatile Basic Nitrogen (TVB-N) Test:

[0076] Refer to GB 5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food". Cut the fish block sample and mix it evenly, take an appropriate amount of sample and grind it, and extract the volatile basic nitrogen by distillation. The nitrogen content of the extract is measured by a trace nitrogen analyzer to obtain the TVB-N content.

[0077] According to GB / T 18108-2019 "General Rules for Fresh Marine Fish", the TVB-N value of high-quality marine fish should be ≤15mg / 100g, and the TVB-N value of qualified products should be between 15 and 30mg / 100g.

[0078] Volatile basic nitrogen test results are shown in Figure 3 And Table 2.

[0079] Table 2. Results of the volatile basic nitrogen TVB-N (mg / 100g) of fish meat in Example 1

[0080] Day 0 1 day 3 days 5 days 8 days 12 days CS-ALG - 2% 6.89 10.36 12.34 15.78 27.38 35.38 Control 7.93 12.75 17.92 22.34 33.75 37.82

[0081] It can be seen that the TVB-N value of the control group (Control) exceeded 30 mg / 100 g on the 8th day of storage, indicating that the fish meat had become corrupted and could not be sold any more. However, the TVB-N value of the fish meat in the experimental group (CS-ALG-2%) treated with CS-ALG-2% Pickering emulsion containing cinnamon essential oil did not exceed 30 mg / 100 g until the 12th day, indicating that the Pickering emulsion can significantly slow down the formation of TVB-N in fish meat. The Pickering emulsion may act as an oxygen barrier, delay the growth and reproduction of spoilage bacteria, reduce protein degradation, and thus effectively reduce the TVB-N value, thereby extending the shelf life of fish meat.

[0082] 2.3. Juice loss rate

[0083] Samples were taken and weighed regularly to calculate the juice loss rate.

[0084] The formula is: juice loss rate (%) = (initial weight - current weight) / initial weight × 100.

[0085] The results of juice loss rate are shown in Figure 4 It can be seen that the juice loss rate of the fish fillets in the control group (Control) decreased significantly on the 12th day, which may be due to the degradation of the cytoskeleton gradually alleviating the impact of protein hydrolysis, making it possible for the originally discharged water to re-enter the tissue. Compared with the control group (Control), the fish juice loss rate of the experimental group (CS-ALG-2%) treated with Pickering emulsion was lower and changed more slowly, which may be because Pickering emulsion can effectively inhibit the metabolism of microorganisms and reduce their damage to proteins, thereby reducing the loss of fish juice and effectively extending the storage time.

[0086] 2.4. Thiol content

[0087] Mix salmon myofibrillar protein with Tris-glycine buffer and Ellman's reagent, and react in the dark for 30 minutes. Then use a UV spectrophotometer to measure the absorbance at 412nm. Calculate the thiol content based on the absorbance value and the standard curve. A higher thiol content usually indicates a higher degree of oxidation and degradation of the aquatic product. The calculation formula is as follows:

[0088] Thiol content (μmol / g protein) = (73.53×A412×D) / C

[0089] Note: A412 is the absorbance at 412 nm; C is the protein concentration in mg / mL; D is the dilution factor;

[0090] The change of total thiol content in fish meat stored at 4°C between the control group (Control) and the experimental group (CS-ALG-2%) is shown in Figure 5 It can be seen that most of the thiol groups in the fish meat of the control group (Control) were oxidized, and the rate of decrease of their content gradually accelerated; the total thiol content of the fish meat treated with emulsion in the experimental group (CS-ALG-2%) was significantly higher than that of the control group (Control), and the rate of decrease was slower. The results show that the Pickering emulsion forms a protective film on the surface of the fish meat, which effectively prevents the exposure and oxidation of thiol groups.

[0091] In summary, the Pickering emulsion of the present invention significantly improves the freshness-keeping ability of fish meat and can extend the shelf life of fish meat by 3 to 5 days.

[0092] 2.5 Sensory evaluation

[0093] Eight well-trained assessors were selected to score the color, appearance, impurities, smell, and tissue structure (25 points each) of the salmon samples according to the standard scoring table. After each assessor scored independently, the final result was the average score of all assessors, which was used to comprehensively judge the sensory quality of the samples and reflect the effect of the preservation treatment.

[0094] The sensory evaluation results are shown in Figure 6 . It can be seen that the sensory score of the fish meat gradually decreased during the entire storage process. Fresh fish meat is bright in color, has no odor, is orange-red in color, has rich texture in muscle tissue, and has good elasticity. After storage for 3 days, the sensory score of the control group dropped sharply. Compared with untreated fish meat, the sensory score of fish meat decreased more slowly after being treated with Pickering emulsion containing cinnamon essential oil. On the 5th day of storage, the fish meat in the control group exuded an unpleasant odor, reaching an unacceptable limit and could not be eaten. The fish meat treated with the emulsion had no odor, but the meat was loose, the elasticity decreased, and the color darkened. It was not until the 8th day that it reached the unacceptable limit.

[0095] The analysis shows that the amino groups of chitosan are positively charged and can interact electrostatically with the carboxyl groups of sodium alginate, making the nanoparticles more compact and thus enhancing the gas barrier properties. In addition, chitosan, sodium alginate and cinnamon essential oil have antibacterial and antioxidant properties, which can effectively inhibit the growth of microorganisms and fat oxidation, thereby delaying the decline in the sensory quality of fish meat. Therefore, Pickering emulsion can better maintain the sensory quality of fish meat in terms of appearance, color, smell, tissue structure and texture. The emulsion can effectively extend the shelf life of salmon by 3 to 5 days.

[0096] 2.7. Artificial Intelligence Shelf Life Evaluation:

[0097] The prediction model was constructed using BP neural network. By inputting different storage days, the TVB-N, TVC, sensory evaluation, sulfhydryl, juice loss rate and other parameters of salmon were predicted to evaluate whether it met the shelf life standard. Figure 7 The model can predict the freshness of aquatic products based on these parameters, and help evaluate the effect of the Pickering emulsion of the present invention on extending the shelf life of salmon in mass production applications.

[0098] The model adopts a three-layer structure (7A), in which the middle hidden layer is optimized through multiple experiments, and the final result is shown in 7B. In order to balance the mean absolute error (MAE), mean absolute percentage error (MAPE), mean square error (MSE), root mean square error (RMSE) and parameter quantity (determines the calculation time), an 11-layer structure is selected as the best solution. The data set contains 120 samples. After 210 iterations, 7C shows the error values ​​and their average statistical values ​​of the training samples (96) and the test samples (24). The results show that the prediction accuracy reaches the decimal point level, with high accuracy, which is suitable for actual prediction.

[0099] The results of the fresh-keeping test showed that the shelf life of untreated salmon was 5 days, while the shelf life of salmon treated with fresh-keeping emulsion was extended to 8 days. By inputting information such as the number of days the salmon was stored and whether emulsion was added, the model can effectively predict and reflect the quality indicators of salmon, which are highly correlated with the actual indicators, thus providing a basis for judging the quality of salmon.

[0100] Example 2

[0101] Compared with Example 1, the difference is that the chitosan used has a deacetylation degree of 85% and a molecular weight of 50 kDa, and the average particle size of the prepared nanoparticles is 270 nm.

[0102] The fish meat was immersed in CS-ALG-Pickering with a concentration of 2% (w / v) in this example for 30 minutes and then sealed and refrigerated for 0 to 12 days. The results of total colony count and volatile basic nitrogen are shown in Table 3 below.

[0103] Table 3. Total colony count and volatile basic nitrogen results of fish meat in Example 2

[0104]

[0105] Example 3

[0106] (1) dissolving chitosan (deacetylation degree 90%, molecular weight 20 kDa) in 1% acetic acid solution, adjusting the pH value to 5.0, to obtain a chitosan solution with a concentration of 5 g / L;

[0107] (2) under continuous magnetic stirring, sodium alginate was added to pure water, and the pH was adjusted to 5.2 with 1M NaOH to obtain a sodium alginate solution with a concentration of 2 g / L; a calcium chloride solution with a concentration of 0.2 g / L was added dropwise so that the mass ratio of sodium alginate to calcium chloride was 5:1; and then stirred to obtain a sodium alginate-calcium chloride composite solution;

[0108] Then, according to the steps of Example 1 (3-4), a Pickering emulsion based on natural nanoparticles containing composite nanoparticles loaded with cinnamon essential oil was formed.

[0109] In this embodiment, the average particle size of the nanoparticles is 320 nm.

[0110] The fish meat was immersed in CS-ALG-Pickering of the present embodiment at a concentration of 2% (w / v) for 30 minutes and then sealed and refrigerated for 0 to 12 days. The results of total colony count and volatile basic nitrogen are shown in Table 4 below.

[0111] Table 4. Total colony count and volatile basic nitrogen results of fish meat in Example 2

[0112]

[0113] Comparative Example 1

[0114] Cinnamon essential oil and sterile water were mixed in a volume ratio of 1:1, and stirred in a high-speed disperser at 12000 rpm for 2 minutes to obtain a fresh-keeping emulsion. Fish meat was preserved in the manner of Example 1. The total colony count and volatile basic nitrogen results after storage for 0 to 12 days are shown in Table 5 below.

[0115] Table 5. Results of total colony count and volatile basic nitrogen in fish meat in Comparative Example 1

[0116]

[0117] In this comparative example, cinnamon essential oil volatilizes within 5 days, resulting in obvious changes in the later preservation performance.

[0118] Comparative Example 2

[0119] The nanoparticle solution in Example 1 (3) was stirred in a high-speed disperser at 12000 rpm for 2 minutes to form a fresh-keeping emulsion. The fish meat was preserved in the same manner as in Example 1. The total colony count and volatile basic nitrogen results after storage for 0 to 12 days are shown in Table 6 below.

[0120] Table 6. Results of total colony count and volatile basic nitrogen in fish meat in Comparative Example 2

[0121]

[0122] In this comparative example, the preservation performance of the nanoparticles without cinnamon essential oil was significantly reduced, which was attributed to the fact that chitosan could only achieve limited antibacterial effect and easily induce muscle tissue dehydration, further affecting the preservation effect.

[0123] In summary, the present invention constructs three-dimensional network structure nanoparticles through the calcium ion cross-linking effect of chitosan and sodium alginate, and efficiently loads cinnamon essential oil by means of hydrogen bonds and ionic bonds, significantly reduces its volatility loss and realizes slow release and controlled release; the Pickering emulsion stabilized by the nanoparticles has both hydrophobic-hydrophilic balance characteristics, and its micro / nano solid particles inhibit oil migration through interface anchoring, prevent coating stratification, and form a dense protective film on the surface of fat-rich aquatic products; the film layer reduces sulfhydryl oxidation and protein degradation through physical barrier, cooperates with the pH-responsive slow release characteristics of cinnamaldehyde to inhibit microbial proliferation, effectively reduces the total colony count, TVB-N value and sulfhydryl loss during storage, thereby significantly extending the shelf life of aquatic products.

[0124] The various aspects, embodiments, and features of the present invention should be considered to be illustrative in all aspects and not limiting of the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0125] In the preparation method of the present invention, the order of each step is not limited to the order listed. For those skilled in the art, without creative work, the order of each step is also within the protection scope of the present invention. In addition, two or more steps or actions can be performed simultaneously.

[0126] Finally, it should be noted that the specific embodiments described herein are merely examples of the present invention, and are not intended to limit the implementation methods of the present invention. A person skilled in the art of the present invention may make various modifications or supplements to the specific embodiments described, or replace them in a similar manner. It is not necessary and impossible to provide all examples of all implementation methods here. However, these obvious changes or modifications derived from the essential spirit of the present invention still fall within the scope of protection of the present invention, and interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A method for preserving aquatic products based on a Pickering emulsion of natural nanoparticles, characterized in that: The preservation method comprises: immersing the aquatic product in a Pickering emulsion based on natural nanoparticles to form a film layer on the surface of the aquatic product; The Pickering emulsion based on natural nanoparticles is formed by mixing a chitosan-sodium alginate-calcium chloride nanoparticle solution with a mass ratio of 1:(0.1-10) and cinnamon essential oil, and dispersing the mixture at high speed. The Pickering emulsion based on natural nanoparticles contains composite nanoparticles loaded with cinnamon essential oil.

2. The method for preserving aquatic products using a Pickering emulsion based on natural nanoparticles according to claim 1, characterized in that: The concentration of the chitosan-sodium alginate-calcium chloride nanoparticle solution is 0.1-2% (w / v).

3. The method for preserving aquatic products using a Pickering emulsion based on natural nanoparticles according to claim 1, characterized in that: The preparation method of the chitosan-sodium alginate-calcium chloride nanoparticle solution comprises: (1) dissolving chitosan in 0.1-3% acetic acid solution and adjusting the pH value to 5.4±0.2 to obtain a chitosan solution; (2) adding sodium alginate to water under continuous magnetic stirring, and adjusting the pH to 5.2±0.2 to obtain a sodium alginate solution; adding calcium chloride solution dropwise until the mass ratio of sodium alginate to calcium chloride is (3-8):1, and stirring to obtain a sodium alginate-calcium chloride composite solution; (3) stirring and mixing the chitosan solution and the sodium alginate-calcium chloride composite solution to obtain nanoparticles; The mass ratio of chitosan, sodium alginate and calcium chloride in the nanoparticles is (1-1.9):(3-8):1; the nanoparticles are then centrifuged and washed, and redispersed in water to obtain a chitosan-sodium alginate-calcium chloride nanoparticle solution with a concentration of 0.1-2% (w / v).

4. The method for preserving aquatic products using a Pickering emulsion based on natural nanoparticles according to claim 3, characterized in that: The average particle size of the (3) nanoparticles is 100 to 260 nm.

5. The method for preserving aquatic products using a Pickering emulsion based on natural nanoparticles according to claim 1, characterized in that: The aquatic product preservation method comprises: soaking the aquatic product in a 2% (w / v) Pickering emulsion based on natural nanoparticles for 5 to 60 minutes to form a film layer on the surface of the aquatic product; taking out the aquatic product, sealing it, and storing it in a refrigerated state at 4°C for 8 to 12 days.

6. The method for preserving aquatic products using a Pickering emulsion based on natural nanoparticles according to claim 5, characterized in that: The preparation method of the 2% (w / v) concentration of the Pickering emulsion based on natural nanoparticles comprises: mixing the 2% (w / v) concentration of the chitosan-sodium alginate-calcium chloride nanoparticle solution with cinnamon essential oil in a mass ratio of 1:1 and dispersing at high speed to form.

7. The method for preserving aquatic products using a Pickering emulsion based on natural nanoparticles according to claim 5, characterized in that: The Pickering emulsion based on natural nanoparticles with a concentration of 2% (w / v) is left to stand for 0 to 40 days at room temperature, and the Pickering emulsion has no stratification phenomenon.

8. A Pickering emulsion based on natural nanoparticles as claimed in claim 1, characterized in that: The invention comprises composite nanoparticles loaded with cinnamon essential oil.

9. The Pickering emulsion based on natural nanoparticles according to claim 8, characterized in that The content of cinnamon essential oil in the composite nanoparticles loaded with cinnamon essential oil is 20-60wt%.

10. A BP neural network prediction model, characterized in that: The BP neural network prediction model predicts the TVB-N, TVC, sensory evaluation, thiol, and juice loss rate parameters of salmon by inputting the storage days and the Pickering emulsion information as described in any one of claims 8 to 9, and evaluates whether it meets the shelf life standards.

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