Preparation method of pickled mustard preservative

Abstract

The application belongs to the field of food preservation, and particularly relates to a preparation method of a pickled mustard anticorrosive agent, wherein the components of the anticorrosive agent comprise: chitosan with a concentration of 75-125 mu g / mL; epsilon-polylysine with a concentration of 100-200 mu g / mL; cinnamyl aldehyde with a concentration of 75-125 mu g / mL; and streptococcal lactate with a concentration of 75-125 mu g / mL. The epsilon-polylysine, streptococcal lactate, chitosan and cinnamyl aldehyde are compounded and applied to the pickled mustard anticorrosive agent, which can produce a synergistic effect, can not only broaden the antibacterial spectrum, but also significantly prolong the shelf life of the food, and significantly inhibit the growth and reproduction of microorganisms on the premise of maintaining the original nutritional quality and flavor characteristics of the pickled mustard.

Description

Technical Field

[0001] This invention relates to the field of food preservation, specifically a method for preparing a preservative for pickled mustard greens. Background Technology

[0002] Pickled mustard greens are a traditional Chinese fermented food with a history of over two thousand years. Originally developed as a method of vegetable preservation, the high water content of mustard greens makes them an excellent substrate for microbial growth. With the popularization of healthy eating concepts and increased awareness of food safety, traditional high-salt pickling techniques are gradually shifting towards low-salt methods, which has become an important trend for the high-quality development of the mustard greens industry.

[0003] However, reduced salinity significantly increases the risk of microbial contamination, making products more susceptible to spoilage during processing and storage. Currently, the industry widely uses chemical preservatives such as sodium benzoate, which, while cost-effective, are often misused. Recent food safety inspections have revealed frequent instances of excessive levels of benzoic acid and its sodium salts, as well as recurring issues with sulfur dioxide residues, prompting regulatory authorities to strengthen their control over food additives.

[0004] Against this backdrop, developing a preservative technology that can both ensure the quality of low-salt pickled mustard greens and safely and effectively extend their shelf life has become a key issue that the industry urgently needs to address. Therefore, a method for preparing a preservative for pickled mustard greens is proposed to address the above issues. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art and solve at least one of the technical problems mentioned in the background art, the present invention proposes a method for preparing a preservative for pickled mustard greens.

[0006] The technical solution adopted by the present invention to solve its technical problem is: a method for preparing a preservative for pickled mustard greens, wherein the preservative comprises: chitosan, with a concentration of 75-125 μg / mL.

[0007] Preferably, the preservative further comprises ε-polylysine at a concentration of 100-200 μg / mL.

[0008] Preferably, the preservative further comprises cinnamaldehyde at a concentration of 75-125 μg / mL.

[0009] Preferably, the preservative further comprises nisin at a concentration of 75-125 μg / mL.

[0010] A method for preparing a preservative for pickled mustard greens involves preparing a solution containing the above-mentioned preservative components and thoroughly mixing the prepared solution.

[0011] Application of a preservative for pickled mustard greens, wherein the above-mentioned preservative for pickled mustard greens is used to prevent the spoilage of pickled mustard greens.

[0012] The advantages of this invention are:

[0013] 1. This invention utilizes chitosan, a natural preservative obtained by deacetylation of chitin, which combines antibacterial function with cost advantages. It has a good inhibitory effect on a variety of bacteria and fungi, and has high safety and significant antibacterial efficacy. At the same time, it exhibits better economy due to its low addition amount.

[0014] 2. This invention applies a compound of ε-polylysine, nisin, chitosan, and cinnamaldehyde to the preservation of pickled mustard greens. This compound can produce a synergistic effect, which can not only broaden the antibacterial spectrum, but also significantly extend the shelf life of food. It can significantly inhibit the growth and reproduction of microorganisms while maintaining the original nutritional quality and flavor characteristics of pickled mustard greens. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A schematic diagram of the combined MIC of preservatives determined using the checkerboard method.

[0017] Figure 2 Line graph showing the antibacterial rate of ε-polylysine;

[0018] Figure 3 Line graph showing the antibacterial rate of nisin;

[0019] Figure 4 A line graph showing the antibacterial rate of chitosan;

[0020] Figure 5 A line graph showing the antibacterial rate of cinnamaldehyde;

[0021] Figure 6 A line graph showing the antibacterial rate of potassium sorbate;

[0022] Figure 7 Line graph showing the antibacterial rate of sodium benzoate;

[0023] Figure 8 Response surface plot and contour plot showing the effect of the interaction between ε-polylysine and nisin on total colony count;

[0024] Figure 9Response surface plot and contour plot showing the effect of the interaction between chitosan and ε-polylysine on total bacterial count;

[0025] Figure 10 The response surface plot and contour plot show the effect of the interaction between cinnamaldehyde and ε-polylysine on the total bacterial count.

[0026] Figure 11 Response surface plot and contour plot showing the effect of the interaction between chitosan and nisin on total bacterial count;

[0027] Figure 12 Response surface plot and contour plot showing the effect of the interaction between cinnamaldehyde and nisin on total bacterial count;

[0028] Figure 13 The response surface plot and contour plot show the effect of the interaction between cinnamaldehyde and chitosan on the total bacterial count. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Specific implementation examples are given below.

[0031] I. Preparation of Preservatives

[0032] Example 1

[0033] A preservative was prepared by mixing the following components: ε-polylysine 100 μg / mL, nisin 75 μg / mL, chitosan 100 μg / mL, and cinnamaldehyde 100 μg / mL.

[0034] Example 2

[0035] A preservative was prepared by mixing the following components: ε-polylysine 100 μg / mL, nisin 75 μg / mL, chitosan 75 μg / mL, and cinnamaldehyde 75 μg / mL.

[0036] Example 3

[0037] A preservative was prepared by mixing the following components: ε-polylysine 200 μg / mL, nisin 125 μg / mL, chitosan 125 μg / mL, and cinnamaldehyde 125 μg / mL.

[0038] Example 4

[0039] A preservative was prepared by mixing the following components: ε-polylysine 150 μg / mL, nisin 100 μg / mL, chitosan 100 μg / mL, and cinnamaldehyde 100 μg / mL.

[0040] Example 5

[0041] A preservative was prepared by mixing the following components: ε-polylysine 200 μg / mL, nisin 125 μg / mL, chitosan 100 μg / mL, and cinnamaldehyde 75 μg / mL.

[0042] Example 6

[0043] A preservative was prepared by mixing the following components: ε-polylysine 180 μg / mL, nisin 102 μg / mL, chitosan 121 μg / mL, and cinnamaldehyde 100 μg / mL.

[0044] A method for preparing a preservative for pickled mustard greens, comprising preparing a solution containing the preservative components described in any one of claims 1-3, and thoroughly mixing the prepared solution.

[0045] Application of a preservative for pickled mustard greens, the preservative for pickled mustard greens according to any one of claims 1-3 is used to prevent the spoilage of pickled mustard greens.

[0046] II. Verification of the antibacterial effect of preservatives

[0047] 1. Materials and Methods

[0048] 1.1 Materials and Reagents

[0049] Test strains: Pickled mustard greens provided by Hunan Haiba Food Co., Ltd., and the main spoilage bacteria isolated and purified (identified by molecular biological methods as Bacillus belye, Acinetobacter baumannii, Bacillus halophilus, and Bacillus pumilus).

[0050] McFarland turbidity tubes: Bickman Biotechnology Co., Ltd.; Nutrient agar medium, YPD medium, LB broth medium, YM broth medium, sterile phosphate buffer solution bags: Qingdao Haibo Biotechnology Co., Ltd.

[0051] ε-Polylysine (food grade): Jieheng Biotechnology Co., Ltd.; Nisin (food grade): Henan Zhongchen Biotechnology Co., Ltd.; Chitosan (food grade): Henan Wanbang Chemical Technology Co., Ltd.; Cinnamaldehyde (food grade): Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.; Sodium benzoate (food grade): Wuhan Organic Industry Co., Ltd.; Potassium sorbate (food grade): Shandong Kunda Biotechnology Co., Ltd.; Acetic acid (analytical grade): Sinopharm Chemical Reagent Co., Ltd.

[0052] 1.2 Instruments and Equipment

[0053] HVA-85 Fully Automatic Pressure Steam Sterilizer: Jiangsu Kenfei Experimental Instrument Trading Co., Ltd.; BIOsafe12 Biosafety Cabinet: Shanghai Lishen Scientific Instrument Co., Ltd.; LRH-250 Biochemical Incubator: Shanghai Yiheng Technology Co., Ltd.; DKZ-450B Electric Thermostatic Shaking Water Bath: Shanghai Senxin Experimental Instrument Co., Ltd.; H1850 High-Speed ​​Benchtop Centrifuge: Xiangyi Centrifuge Instrument Co., Ltd.; SJ-142 Conductivity Meter: Shanghai Yidian Scientific Instrument Co., Ltd.; RT-2100C Microplate Reader: Shenzhen Leidu Life Science Co., Ltd.; UV-2600 Ultraviolet-Vis Spectrophotometer: Shimadzu Instruments (Suzhou) Co., Ltd.

[0054] 1.3 Experimental Methods

[0055] 1.3.1 Preparation of bacterial suspension: The bacteria were activated on nutrient agar medium at 38°C for 24 hours and then prepared for use. The activated bacteria were then prepared into a bacterial suspension with a concentration of 10⁷–10⁸ CFU / mL (McFarfell turbidimetric tube method) using sterile phosphate buffer and then prepared for use.

[0056] 1.3.2 Preparation of mixed bacteria: Four bacterial strains were inoculated into 5 mL of LB liquid medium and cultured at 37 °C for 24 h. 1 mL of bacterial suspension was taken from each strain and mixed. The mixture was centrifuged at 9000 r / min for 8 minutes. The precipitate was washed with sterile phosphate buffer and then resuspended with 0.5 mL of sterile phosphate buffer to obtain a mixed bacterial suspension of 107 CFU / mL.

[0057] 1.3.3 Preparation of relevant solutions

[0058] (1) 12.8g / L ε-polylysine, nisin, potassium sorbate and sodium benzoate stock solution: accurately weigh 0.64g of each, dissolve in sterile water and bring the volume to 50mL, filter under sterile conditions using a disposable 0.22μm needle filter, and store at 4℃ for later use.

[0059] (2) 12.8 g / L chitosan stock solution: accurately weigh 0.64 g chitosan, dissolve it in sterile water, add 0.2% glacial acetic acid to fully dissolve it, and make up to 50 mL. Filter it under sterile conditions using a disposable 0.22 μm needle filter and store it at 4 °C for later use.

[0060] (3) 12.8 g / L cinnamaldehyde stock solution: accurately weigh 0.64 g cinnamaldehyde, dissolve it in sterile water, add 0.2% volume fraction of anhydrous ethanol to fully dissolve it, and make up to 50 mL. Filter it under sterile conditions using a disposable 0.22 μm needle filter and store it at 4 °C for later use.

[0061] 1.3.4 Determination of the inhibitory effect of single preservatives on spoilage bacteria Preparation of single preservatives at different concentrations: In accordance with the maximum allowable range specified in the National Food Safety Standard for the Use of Food Additives (GB2760-2024)

[22] , preservative solutions containing different concentrations of nisin, ε-polylysine, chitosan, cinnamaldehyde (500, 400, 300, 200, 100, 75, 50, 25, 12.5, 0 μg / mL), potassium sorbate (1000, 800, 600, 400, 200, 100, 50, 25, 0 μg / mL), and sodium benzoate (1000, 800, 600, 400, 200, 100, 50, 25, 0 μg / mL) were prepared.

[0062] Add 100 μL of LB medium to each well of a cell culture plate, then add 100 μL of the prepared preservative, followed by 5 μL of bacterial suspension. After sample addition, measure the 0hOD630 using a microplate reader. Then, incubate the cell culture plate at 37°C with low-speed shaking for 12 hours. After incubation, measure the 12hOD630. Well 11 serves as the positive control without preservative, and well 12 serves as the negative control without bacterial suspension. If the negative control group is contaminated, the experiment fails. Each experiment is performed in triplicate. The antibacterial effect of the preservative on putrefactive bacteria is determined based on the inhibition rate.

[0063] Antibacterial rate (%) = [(Absorbance value of positive control group at 12h - Absorbance value of positive control group at 0h) - Absorbance value of group with added preservative at 12h - Absorbance value of group with added preservative at 0h)] / (Absorbance value of positive control group at 12h - Absorbance value of positive control group at 0h) × 100%.

[0064] 1.3.5 Determination of the combined antibacterial effect of preservatives

[0065] (1) Determination of the chessboard method

[0066] Using high-throughput sequencing and traditional culture methods, the main spoilage bacteria of pickled mustard greens were isolated, purified and identified as Bacillus belyssae and Acinetobacter baumannii, and the secondary spoilage bacteria were Bacillus halophilus and Bacillus pumilus.

[0067] Please see Figure 1 The checkerboard micro-liquid dilution method (checkerboard method) was used to test the inhibitory effect of synergistic use of preservatives (nisin + chitosan; nisin + cinnamaldehyde; nisin + ε-polylysine; chitosan + cinnamaldehyde; chitosan + ε-polylysine; cinnamaldehyde + ε-polylysine) on putrefactive bacteria.

[0068] Under aseptic conditions, a 64-well "chessboard" composed of Column 1 to Column 8 and Row A to Row H in a 96-well plate is used for sample adding. Aspirate 100 μL of the pre-prepared medium containing preservative A at different concentrations and add it to each row, so that the concentration of preservative A in each well of the same row is the same. The maximum concentration of the bacteriostatic agent in Row A is set to 4 times the MIC of a single bacteriostatic agent. The concentrations of preservative A contained in each well of Row B, C, D, E, F, G are 2MIC, MIC, 1 / 2MIC, 1 / 4MIC, 1 / 8MIC, and 1 / 16MIC respectively, and Row H is the control group without preservative A added; then aspirate 100 μL of medium containing preservative B at different concentrations, and add it to the wells of each column in turn. The sample adding principle is the same as above, wherein Column 8 is the control group without preservative B added. After the sample adding is completed, as Figure 1 shown, each well contains a total of 200 μL of LB medium containing preservatives A and B at different concentrations. Finally, 5 μL of bacterial suspension with a concentration of about 10⁵ to 10⁶ CFU / mL is inoculated into each well, mixed uniformly, and the OD₆₃₀ of each sample at 0 h is measured with a microplate reader, and the value is recorded. Cover the 96-well plate, place it in a 37°C environment for static culture for 24 h, then measure the OD₆₃₀ of each sample at 24 h, and record the value. Well 11 is the positive control group without preservative added, and Well 12 is the negative control group without bacterial suspension added. If the negative control group is contaminated, the experiment fails. Each group of experiments is performed in triplicate.

[0069] (2) Determination of Fractional Inhibitory Concentration Index (FICI)

[0070] The test results use the Fractional Inhibitory Concentration Index (FICI) as the judgment basis for the combined preservative test

[24] : FICI ≤ 0.5 indicates synergistic effect; 0.5 < FICI ≤ 1 indicates additive effect; 1 < FICI ≤ 2 indicates indifferent effect; FICI > 2 indicates antagonistic effect. The calculation formula is as follows:

[0071]

[0072] In the formula: FICI — Fractional Inhibitory Concentration Index; OIC — Minimum inhibitory concentration of the two preservatives in combination, μg / mL; MIC — Minimum inhibitory concentration of each of the two preservatives alone, μg / mL;

[0073] 1.3.6 Optimization of the proportion of each component in compound natural preservatives by response surface methodology According to the experimental results of the inhibitory effect of single preservative on spoilage bacteria, a four-factor three-level response surface is designed in this experiment. According to the level design, different dosages of ε-polylysine (Factor A), nisin (Factor B), chitosan (Factor C), and cinnamaldehyde (Factor D) are adopted, as shown in Table 1.

[0074]

[0075] Table 1 Box-Behnken Experimental Design and Coding Level

[0076] 1.3.7 Statistical Analysis: Origin2022 software was used for data statistics, analysis, and plotting.

[0077] 2 Results and Analysis

[0078] 2.1 Antibacterial effect of a single preservative against putrefactive bacteria

[0079] Please see Figure 2-7 This application used *Bacillus bellsii*, *Acinetobacter baumannii*, and four mixed bacterial strains—the main spoilage bacteria in pickled mustard greens—as test strains. A simulated acidic system for pickled vegetables was constructed by adding 0.02% anhydrous acetic acid, and the antibacterial effects of different preservatives were systematically evaluated. Figure 2 It can be seen that natural preservatives generally exhibit significantly better antibacterial performance than chemical preservatives: ε-polylysine, at an optimal concentration of 150 μg / mL, showed an inhibition rate of 64.5% against mixed spoilage bacteria; nisin (100 μg / mL) showed a high inhibition rate of 86.3% against Bacillus belyceca, but its inhibitory effect on Acinetobacter baumannii and mixed bacterial groups was poor; chitosan (100 μg / mL) and cinnamaldehyde (100 μg / mL) showed significant inhibitory effects of 86.1% and 83.4% against mixed bacterial groups, respectively. In contrast, although conventional chemical preservatives showed an increasing inhibition rate with increasing concentration, their overall inhibitory efficacy against the target spoilage bacteria was still insufficient. It is worth noting that although chemical preservatives are widely used in the pickled vegetable industry, their actual antibacterial efficiency in this application system was significantly lower than that of the tested natural preservatives. Therefore, the use of natural preservatives not only has high safety and significant antibacterial efficacy, but also exhibits better economic efficiency due to the low addition amount.

[0080] 2.2 Antibacterial effect of two preservatives combined

[0081] The interaction relationship of preservatives can be measured by calculating the fractional inhibitory concentration index (FICI) using the checkerboard method

[28] . As shown in Table 2, after compounding the preservatives, there are 3 combinations that have an additive effect on Bacillus belyssus, namely Nisin and ε-polylysine, chitosan and ε-polylysine, and cinnamaldehyde and ε-polylysine, while the rest have no effect; all of them have an additive effect on Acinetobacter baumannii; and there are 4 combinations that have an additive effect on mixed bacteria, namely Nisin and chitosan, Nisin and ε-polylysine, chitosan and cinnamaldehyde, and cinnamaldehyde and ε-polylysine, among which chitosan and ε-polylysine show a good synergistic effect. The combined minimum inhibitory concentrations (MICs) of chitosan and ε-polylysine exhibiting a synergistic effect against mixed bacteria were 25 μg / mL and 100 μg / mL, respectively, while their respective MICs against mixed bacteria alone were 100 μg / mL and 1600 μg / mL. These results indicate that the combined use of the preservatives reduced the MICs by 75% and 94%, respectively, compared to using the preservatives alone. Although ε-polylysine alone was not very effective against mixed bacteria, the combination of the two preservatives showed a better synergistic antibacterial effect. This may be because ε-polylysine can disrupt the cell wall structure, causing the dissolution of cell contents, while the protonation of chitosan's amino groups can generate electrostatic interactions with the negative charge on the cell membrane surface and rapidly bind to membrane proteins, thereby accelerating the complete release of cell contents and achieving a better synergistic antibacterial effect. Both chitosan and ε-polylysine can inhibit the growth of Clostridium botulinum through mechanisms such as disrupting the cell wall and cell membrane and inducing oxidative stress.

[0082]

[0083]

[0084] Table 2. Combined antibacterial effects of different preservatives against putrefactive bacteria.

[0085] 2.3 Optimization of the proportions of components in a compound natural preservative using response surface methodology

[0086] As shown in Table 3, 29 sets of experiments were obtained by using the Box-Behnken design with DesignExpert 8.0.6trial software. Specific experiments were conducted based on this 29-set experimental design, with each set of experiments having 3 replicates. The total number of colonies (CFU / mL) was used as the response value (R1). The experimental results were analyzed by DesignExpert 8.0.6trial software to obtain the regression equation of R1 with the three factors (A, B, C, D). The extreme value of R1 is the expected total number of colonies, and the corresponding values ​​of the four factors are the optimal ratio of each component in the compound preservative.

[0087] Table 3 Box-Behnken Experimental Design and Results

[0088]

[0089]

[0090]

[0091] The experimental data were fitted using multiple regression analysis with Design-Expert 13 software. The regression equation with the total number of colonies as the objective function was obtained after fitting the four factors:

[0092] Y=173.90A2+232.96B2+322.65C2+375.46D2+160.00AB-72.50AC-158.75AD- 247.50BC+174.38BD-306.25CD-237.08A+66.04B-492.08C-67.29D+812.00.

[0093] Analysis of variance was performed on the regression equation. As shown in Table 4, the established regression model for total colony count reached a highly significant level (F = 40.16, P < 0.0001); the difference in the lack-of-fit term was not significant (P = 0.2698 > 0.05), indicating that the model fit well and the experimental model is reasonable. In addition, the correlation coefficient of the equation was R2 = 0.9757 and the adjusted correlation coefficient was R2Adj = 0.9514, indicating that the model can explain the change of total colony count caused by preservatives, indicating that the model fits well and can be used for theoretical prediction of the optimization of compound preservative formulations. Analysis of variance of the regression model can determine the degree of influence of the independent variable on the dependent variable

[32] . Further analysis showed that the linear terms A and C had a significant impact on the response value, reaching a highly significant level (P < 0.01), while the effects of B and D on the response value were significant (P < 0.05). The interaction terms AB, AD, BC, BD, and CD in the model had a significant impact on the response value, reaching a highly significant level (P < 0.01), while the effect of AC was not significant (P > 0.05). The quadratic terms A², B², C², and D² had a significant impact on the response value, all reaching a highly significant level (P < 0.01). Comparing the F-values ​​of each factor, the influence of preservatives on the total bacterial count of pickled vegetables was in the following order: chitosan (C) > ε-polylysine (A) > cinnamaldehyde (D) > nisin (B).

[0094]

[0095] Table 4 shows the analysis of variance for the regression equations. "*" indicates significant (P<0.05); "**" indicates highly significant (P<0.01); "—" indicates not significant (P<0.1). The correlation coefficient of the equations is R² = 0.9757, and the adjusted correlation coefficient is R²Adj = 0.9514.

[0096] Please refer to section 8-13. The 3D surface plot and contour plot of the response surface optimization model for the effect of preservatives on the total bacterial count in pickled vegetables show that the response value changes relatively little with the concentrations of both ε-polylysine and chitosan, indicating that the interaction between ε-polylysine and chitosan has a relatively small impact on the total bacterial count in pickled vegetables. However, the concentrations of both chitosan and cinnamaldehyde change significantly, indicating that the interaction between chitosan and cinnamaldehyde has a significant impact on the total bacterial count in pickled vegetables. Furthermore, based on the optimization results of the quadratic multiple regression equation, the optimal formulation concentrations of this compound natural preservative are: ε-polylysine 180 μg / mL, nisin 102 μg / mL, chitosan 121 μg / mL, and cinnamaldehyde 100 μg / mL (the predicted values ​​have been corrected for actual production requirements). Under these formulation conditions, the predicted total bacterial count in pickled vegetables is 508 CFU / mL. To verify the reliability of the response surface model, six replicate experiments were conducted under the given formulation conditions. The actual total bacterial count of the pickled vegetables was 533 CFU / mL, which deviated from the theoretical prediction of the model by approximately 4.92%. This indicates that the response surface regression model has accuracy and reliability and can be used to determine the proportion of each component in a compound natural preservative.

[0097] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0098] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A preservative for pickled mustard greens, characterized in that: The preservative contains chitosan at a concentration of 75-125 μg / mL.

2. The preservative for pickled mustard greens according to claim 1, characterized in that: The preservative also contains ε-polylysine at a concentration of 100-200 μg / mL.

3. The preservative for pickled mustard greens according to claim 2, characterized in that: The preservative also contains cinnamaldehyde at a concentration of 75-125 μg / mL.

4. The preservative for pickled mustard greens according to claim 3, characterized in that: The preservative also includes nisin at a concentration of 75-125 μg / mL.

5. A method for preparing a preservative for pickled mustard greens, characterized in that: Prepare a solution containing the preservative component as described in any one of claims 1-3, and thoroughly mix the prepared solution.

6. The application of a preservative for pickled mustard greens, characterized in that: The preservative for pickled mustard greens according to any one of claims 1-3 is used to prevent the spoilage of pickled mustard greens.

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