Method for degrading nitrite and biogenic amine of fermented vegetables

Abstract

The invention relates to a method for degrading nitrite and biogenic amine of fermented vegetables. The method comprises the following steps: (1) pretreating raw materials; (2) preparing an organic acid solution; (3) adding an organic acid solution into the pretreated vegetable raw materials, stirring, standing and acidizing; (4) adding a microbial agent into the acidified raw material for fermentation, then adding malic acid and citric acid as a carbon source, and adding table salt; and (5) after fermentation is finished, packaging and refrigerating the product. And (6) taking all the remaining liquid as mother liquor after the pickles are packaged, and filtering to obtain acidic supernate, wherein the acidic supernate is used for secondary fermentation of the vegetables. Through the method, nitrite and biogenic amine in the plant raw materials can be efficiently degraded, so that the content of nitrite and biogenic amine is reduced to a safe level, the growth of harmful infectious microbes can be inhibited, and the safety of the pickled vegetables is improved; the secondary fermentation of the vegetables can also achieve the purpose of degrading nitrite. And moreover, cyclic utilization of resources is realized, and wastewater discharge is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of food fermentation, in particular to a method for degrading nitrite and biogenic amine in fermented vegetables. Background Art

[0002] Kimchi is a vegetable product made primarily from fresh vegetables, with or without additional ingredients, and processed through processes such as pickling in salt or brine. Kimchi is rich in active lactic acid bacteria, which inhibit the growth of putrefactive bacteria in the intestines and reduce their toxin production. It also aids digestion, prevents constipation, prevents cell aging, lowers cholesterol, and has anti-tumor effects. Kimchi has a long history and has played an important role in people's lives since ancient times. Common Sichuan kimchi ingredients include greens, radishes, cowpeas, cabbage, lettuce, peppers, cucumbers, and other traditional vegetables, making it a popular favorite.

[0003] Nitrite is toxic, with a poisoning dose of 0.1g and a lethal dose of 1.0-2.0g. On the one hand, it will undergo an oxidation reaction with the ferrous hemoglobin in the blood to produce methemoglobin, causing hypoxia and poisoning in the human body. Symptoms include cyanosis of the lips, fingers and toes, dull complexion, listlessness, rapid heartbeat, dizziness, vomiting, cold sweats, and even low blood pressure, convulsions, and coma. On the other hand, nitrite can also react with amines in the human body to form N-nitroso compounds called nitrosamines, which are highly carcinogenic.

[0004] In the production process of fermented vegetables, the nitrite content has always been a matter of great concern. Nitrite not only affects the quality of fermented vegetables, but excessive intake may also cause potential harm to human health. Traditional fermentation methods are difficult to effectively control the nitrite content and are easily contaminated by miscellaneous bacteria, resulting in fermentation failure or unstable product quality. Biogenic amines are a class of low-molecular-weight nitrogen-containing organic compounds with biological activity. Excessive intake can have adverse effects on human health, such as causing allergic reactions, headaches, and abnormal blood pressure. The degradation of nitrite and biogenic amines depends on an acidic environment and microbial metabolism, and existing processes make it difficult to achieve efficient synergy between the two. Therefore, it is of great significance to develop a method that can efficiently degrade nitrite and biogenic amines, inhibit the growth of miscellaneous bacteria, and at the same time ensure the flavor and quality of fermented vegetables. Summary of the Invention

[0005] The present invention aims to address the following issues in the prior art: 1) the long traditional natural fermentation cycle and the susceptibility to bacterial contamination in the early stages of fermentation; 2) the uncontrollable quality of natural fermentation, with microbial metabolism producing foreign odors that affect the sensory perception of kimchi; and 3) the high levels of nitrite and biogenic amines, which pose safety risks. By providing a method for degrading nitrite and biogenic amines in fermented vegetables, this method can efficiently degrade nitrite and biogenic amines in plant raw materials, reducing their levels to safe levels. It also inhibits the growth of harmful bacteria, improving the safety of kimchi.

[0006] In order to achieve the above object of the invention, the technical solution of the present invention is as follows:

[0007] One of the objects of the present invention is to provide a Lactobacillus plantarum JXJ1 strain, which has been deposited in the General Microbiology Center of the China Culture Collection Administration on March 7, 2025, with a deposit number of CGMCC No. 33756. The depository address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences.

[0008] Furthermore, the Lactobacillus plantarum JXJ1 has the following characteristics:

[0009] 1) Salt tolerance, able to grow normally when the salt concentration is ≥8%;

[0010] 2) Acid-resistant, able to grow normally when pH ≤ 4;

[0011] 3) Rapid fermentation to produce acid, when the salt concentration is ≥8% and the pH is ≤4, the fermentation can produce acid rapidly, making the acidity ≥0.7%;

[0012] 4) It can inhibit the growth of harmful microorganisms, block the formation of nitrite, and has a strong ability to degrade biogenic amines.

[0013] The second purpose of the present invention is to protect the use of the above-mentioned Lactobacillus plantarum JXJ1 in degrading nitrite and biogenic amines in fermented vegetables.

[0014] The third object of the present invention is to protect a microbial agent for degrading nitrite and biogenic amines in fermented vegetables, wherein the microbial agent contains the aforementioned Lactobacillus plantarum JXJ1.

[0015] Furthermore, the preparation method of the microbial agent comprises the following steps:

[0016] After activation, Lactobacillus plantarum JXJ1 is inoculated into a culture medium at 2% of the total volume and further cultured to obtain a culture solution after culture; the culture solution after culture is centrifuged to obtain bacterial sludge; a protective agent is added to the bacterial sludge, and the bacterial powder is obtained by vacuum freeze-drying; the protective agent comprises the following raw materials in parts by weight: 12 parts of skim milk powder, 3 parts of sucrose, 2 parts of glycerol, and 2 parts of D-trehalose; the vacuum freeze-drying temperature is -50°C, the vacuum degree is 1 Pa, and the drying time is 30 hours; the freeze-drying survival rate reaches 85%, and the number of viable bacteria in the powder is approximately 3×10 11 CFU / g; by mass, the ratio of protective agent to bacterial sludge is 1:2.

[0017] Furthermore, in the preparation method of the microbial agent, the components of the expansion culture medium are: 4.0% glucose, 0.8% yeast powder, 0.6% beef extract, 1.0% peptone, and the remainder is water, and the sum of the total mass percentages is 100%; the culture conditions are: the initial pH of the culture medium is 6.5, the culture temperature is 35°C, the shaker speed is 120r / min, and the culture time is 16h; the centrifugal conditions are: temperature 4°C, speed 4500r / min, and centrifugation time is 15min.

[0018] A fourth object of the present invention is to provide a method for degrading nitrite and biogenic amines in fermented vegetables, which comprises the following steps:

[0019] (1) Raw material pretreatment: Select fresh vegetables that are free of pests and diseases, wash them, dry them, and cut them into pieces for later use;

[0020] (2) Preparation of organic acid solution: Malic acid and citric acid are mixed in a ratio of 1:4 to 4:1 to form an organic acid solution; by adjusting the type and ratio of organic acid, the acidification effect and the degradation rate of nitrite can be optimized.

[0021] (3) Acidification treatment: Add the organic acid solution prepared in step (2) to the vegetable raw material pretreated in step (1), and stir in a clean blender at a temperature of 25-35° C. and a speed of 10 r / min for 15-30 minutes, and then let it stand for 1-3 hours to fully acidify the raw material; the acidification conditions can promote the acidification and degradation of nitrite in the raw material, effectively reducing the initial content of nitrite.

[0022] Preferably, the mass ratio of the pretreated vegetable raw materials in step (1) to the organic acid solution prepared in step (2) is 1:1.5-1:3.

[0023] (4) Inoculation and fermentation: adding 1.5%-3% of the microbial agent or the microbial agent prepared by the method to the raw material after acidification in step (3), then adding 1‰-2‰ malic acid, 0.3‰-0.8‰ citric acid and 0.5%-1% glucose as carbon sources, adding 3%-6% of the total mass of kimchi salt, controlling the fermentation temperature to 20-30°C, and fermenting for 6-8 days; the plant lactobacillus can adapt to the acidic environment created by the previous acidification, and utilize the nutrients in the vegetable raw materials and the added malic acid, citric acid and glucose as carbon sources for growth and metabolism. During this process, it not only reproduces itself in large quantities, but also continuously produces acid, further reducing the pH value of the environment, so that nitrite is further degraded under the dual effects of acidity and microorganisms. At the same time, the acidic environment can effectively inhibit the growth of miscellaneous bacteria, ensuring the smooth progress of the fermentation process.

[0024] (5) Low temperature storage: After fermentation, the product is packaged and refrigerated at 2-6°C to maintain the active lactic acid bacteria in the kimchi and extend the shelf life of the product.

[0025] Furthermore, the method for degrading nitrite and biogenic amine in fermented vegetables further comprises step (6) of recovering and utilizing the acidified mother liquor: filtering all the liquid remaining after the kimchi is packaged as the mother liquor, centrifuging at 4000-6000 r / min to obtain an acidic supernatant, and the acidic supernatant is used for secondary fermentation of the vegetables.

[0026] Furthermore, in the method for degrading nitrite and biogenic amines in fermented vegetables, the specific operation steps of using the acidic supernatant for secondary fermentation of vegetables are as follows: after the fresh vegetables have been treated in steps (1) to (3), 0.8-1.2% of the microbial agent or the microbial agent prepared by the method is added, by weight percentage, to the fresh vegetables, and then 2.5%-3.5% of the acidic supernatant is added, the fermentation temperature is controlled at 20-30°C, and the fermentation is carried out for 6-8 days. The purpose of nitrite degradation can also be achieved. In addition, resource recycling is achieved and wastewater discharge is reduced.

[0027] Compared with the existing technology, the beneficial effects of the present invention are:

[0028] (1) A strain of plant lactobacillus with excellent performance was screened. The plant lactobacillus is salt-tolerant and can grow normally when the salt concentration is ≥8%; it is acid-tolerant and can grow normally when the pH is ≤4; it can quickly ferment and produce acid, and can quickly ferment and produce acid when the salt concentration is ≥8% and the pH is ≤4, so that the acidity is ≥0.7%; it can inhibit the growth of harmful microorganisms, block the formation of nitrite, and has a strong ability to degrade biogenic amines.

[0029] (2) The bacterial agent made from the screened strains can efficiently degrade nitrite and biogenic amines in plant raw materials, reducing their content to a safe level; it can also effectively inhibit the growth of harmful bacteria and improve the safety of kimchi.

[0030] (3) The acidifier is used as a carbon source, which reduces the addition of additional carbon sources and is low-cost; the acidified mother liquor can also be recycled to reduce wastewater discharge, reduce costs and increase efficiency.

[0031] (4) The operation is simple, no complicated equipment and process are required, and it is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic flow chart of a method for degrading nitrite and biogenic amines in fermented vegetables;

[0033] Figure 2 This is a graph showing the change in nitrite content of the finished pickled vegetable product over fermentation time in Example 3-8;

[0034] Figure 3 is a graph showing the change in total acid content of the finished pickled vegetable product over fermentation time in Examples 3-8;

[0035] Figure 4 is a graph showing changes in the number of lactic acid bacteria over fermentation time in Example 3-8;

[0036] Figure 5 Graph showing the content of biogenic amines in the finished pickles prepared in Examples 3-8. DETAILED DESCRIPTION

[0037] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0038] Any feature disclosed in this specification (including claims and abstract), unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0039] The features and properties of the present invention are further described in detail below with reference to the examples. % or ‰ not specifically marked in this application represent the percentage by mass.

[0040] The relevant raw materials mentioned are all commercially available products; the process steps or devices not specified are all existing technologies.

[0041] Example 1:

[0042] Samples were collected from fermented vegetables in Yinchuan, Ningxia Hui Autonomous Region, China, and then inoculated and cultured. The samples were then tested for salt tolerance, acid resistance, and acid production. Finally, a strain of Lactobacillus plantarum, designated JXJ1, was obtained and deposited with the General Microbiology Center of the China Culture Collection of Microorganisms on March 7, 2025, under the deposit number CGMCC No. 33756. The depository address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences. This strain has the following characteristics:

[0043] 1) Salt tolerance, able to grow normally when the salt concentration is ≥8%;

[0044] 2) Acid-resistant, able to grow normally when pH ≤ 4;

[0045] 3) Rapid fermentation and acid production: when the salt concentration is ≥8% and the pH is ≤4, the fermentation can produce acid quickly within 24 hours, with the acidity reaching ≥0.7%;

[0046] 4) It can inhibit the growth of harmful microorganisms, block the formation of nitrite, and has a strong ability to degrade biogenic amines.

[0047] Example 2: Preparation of a microbial agent for degrading nitrite and biogenic amines in fermented vegetables

[0048] After activation, the Lactobacillus plantarum JXJ1 strain screened and preserved in Example 1 was inoculated into an expansion culture medium at 2% of the total volume and continued to be cultured. The expansion culture medium components were: 4.0% glucose, 0.8% yeast powder, 0.6% beef extract, and 1.0% peptone. The culture conditions were: an initial pH of 6.5, a culture temperature of 35°C, a shaker speed of 120 rpm, and a culture time of 16 hours. The culture solution after the expansion was centrifuged at a temperature of 4°C and a speed of 4500 rpm for 15 minutes to obtain a bacterial slurry. A protective agent was added at a mass ratio of 1:2 to the bacterial slurry, and the culture was vacuum freeze-dried to obtain bacterial powder (i.e., a microbial agent for degrading nitrites and biogenic amines in fermented vegetables). The protective agent includes the following raw materials in parts by weight: 12 parts skim milk powder, 3 parts sucrose, 2 parts glycerol, and 2 parts D-trehalose; the drying temperature is -50°C, the vacuum degree is 1Pa, and the time is 30 hours. After freeze-drying, the powders are prepared respectively. The freeze-dried survival rate reaches 85%, and the number of viable bacteria in the powder is about 3×10 11 CFU / g.

[0049] Example 3:

[0050] A method for degrading nitrite and biogenic amines in fermented vegetables comprises the following steps:

[0051] (1) Raw material pretreatment: Use cabbage as raw material, select fresh cabbage without pests and diseases, wash it, dry it, and cut it into pieces for later use.

[0052] (2) Preparation of organic acid solution: malic acid and citric acid were mixed in a mass ratio of 2:1 to form an organic acid solution.

[0053] (3) Acidification treatment: Add the organic acid solution prepared in step (2) to the pretreated cabbage, with the mass ratio of cabbage to organic acid solution being 1:1.5. In a clean blender, stir at a temperature of 20°C and a speed of 10 r / min for 20 minutes, and then let it stand for 1.5 hours to fully acidify the cabbage.

[0054] (4) Inoculation and fermentation: 2% Lactobacillus plantarum inoculum was added to the cabbage acidified in step (3) by weight percentage, 1.5‰ malic acid, 0.6‰ citric acid and 0.8% glucose were added as carbon sources, and 3% salt of the total mass of the kimchi was added. The fermentation temperature was controlled at 25° C. and the fermentation was carried out for 7 days.

[0055] (5) Low temperature storage: After the fermentation is completed, the product is packaged and the obtained kimchi product 1 is refrigerated at 4°C to maintain the active lactic acid bacteria in the kimchi and extend the shelf life of the product.

[0056] (6) Recovery and utilization of acidified mother liquor: The mother liquor remaining after kimchi packaging is filtered and centrifuged at 5000 r / min to obtain an acidic supernatant.

[0057] Example 4:

[0058] The vegetable raw materials in Example 1 were replaced with radish, and the other parameters remained unchanged. The pickled radish was prepared according to the method in Example 3, and finally the pickled vegetable product 2 was obtained.

[0059] Example 5:

[0060] The vegetable raw materials in Example 1 were replaced with cowpeas, and the other parameters remained unchanged. The pickled cowpeas were prepared according to the method in Example 3, and finally the pickled vegetable product 3 was obtained.

[0061] Example 6:

[0062] The pickled cabbage was prepared by the method and steps of Example 3, except that, after the cabbage was treated in steps (1) to (3), 1% Lactobacillus plantarum inoculum was added, and then 2.5% acidic supernatant (prepared in Example 3) was added. The fermentation temperature was controlled at 25° C. and fermented for 7 days to obtain the pickled cabbage product 4.

[0063] Example 7:

[0064] (1) Raw material pretreatment: Use cabbage as raw material, select fresh cabbage without pests and diseases, wash it, dry it, and cut it into pieces for later use.

[0065] (2) Preparation of organic acid solution: malic acid and citric acid were mixed in a mass ratio of 2:1 to form an organic acid solution.

[0066] (3) Acidification treatment: Add the organic acid solution prepared in step (2) to the pretreated cabbage, with the ratio of cabbage to organic acid solution being 1:2.5. In a clean blender, stir at a temperature of 20°C and a speed of 10 r / min for 20 minutes, and then let it stand for 1.5 hours to fully acidify the cabbage.

[0067] (4) Inoculation and fermentation: 1.5‰ malic acid, 0.6‰ citric acid and 0.8% glucose were added as carbon sources to the cabbage acidified in step (3), and the fermentation temperature was controlled at 25°C and fermented for 7 days.

[0068] (5) Low temperature storage: After the fermentation is completed, the product is packaged and the obtained kimchi product 5 is refrigerated at 4°C to maintain the active lactic acid bacteria in the kimchi and extend the shelf life of the product.

[0069] Example 8: Preparation of naturally fermented pickled cabbage

[0070] Fresh, pest-free cabbage was selected, washed, dried, and cut into pieces for later use. Salt was added, accounting for 3% of the total mass of the kimchi. The fermentation temperature was controlled at 25°C and fermented for 7 days to obtain kimchi product 6.

[0071] experiment

[0072] Experiment 1: Comparison of nitrite content

[0073] According to the national standard determination method, the nitrite content of the pickled vegetables No. 1-6 prepared in Examples 3-8 at 0, 1, 3, 5, 7, and 9 days of fermentation was determined. The results are as follows: Figure 2 shown.

[0074] Depend on Figure 2It can be seen that the nitrite peaks in the finished kimchi products in Examples 3-7 all appeared early, with low content, and were gradually degraded after 3 days. The results of nitrite content in Example 3-5 show that this method is applicable to various types of fermented vegetables and can degrade the nitrite content during their fermentation process. The nitrite content in the finished kimchi product in Example 6 shows that recycling the acidified mother liquor can also achieve the effect of degrading nitrite. The nitrite content in the finished kimchi product in Example 7 shows that the effect of only using organic acid acidification on nitrite degradation is weaker than that of the solution in Example 3. The nitrite content in the finished kimchi product in Example 8 is relatively high, close to the national limit standard (20 mg / kg), and there is a certain risk of nitrite exceeding the standard. It can be seen that the method used in the present invention can effectively block the formation of nitrite and ensure the edible safety of fermented vegetables.

[0075] Experiment 2: Comparison of total acid content

[0076] According to the national standard determination method, the total acid content of the pickled vegetables No. 1-6 prepared in Examples 3-8 at 0, 1, 3, 5, 7, and 9 days of fermentation was determined. The results are as follows: Figure 3 shown.

[0077] Depend on Figure 3 As can be seen, the fermentation speed and total acid content of Examples 3-7 were higher than those of Example 8. Among the different vegetable raw materials, the total acid content of cowpeas > cabbage > radish was the highest. In Example 6, fermentation using acidified mother liquor also achieved a higher total acid content. Since Example 7 was not inoculated, the total acid content was lower than that of the inoculated fermentation group. This shows that the method of the present invention is applicable to different types of vegetables and can achieve rapid fermentation.

[0078] Experiment 3: Lactic acid bacteria count

[0079] According to the national standard determination method, the number of lactic acid bacteria in the pickled vegetable products No. 1-6 prepared in Examples 3-8 was determined at 0, 1, 3, 5, 7, and 9 days of fermentation. The results are as follows: Figure 4 shown.

[0080] Depend on Figure 4 It can be seen that in Examples 3-6, the lactic acid bacteria grew rapidly and in high numbers in the early stage of fermentation. In Example 8, the lactic acid bacteria grew relatively slowly and decreased in number after 5 days of fermentation.

[0081] Experiment 4: Determination of biogenic amine content

[0082] As people's living standards improve, the safety of fermented vegetables has received widespread attention, but the focus has mainly been on nitrites while ignoring the presence of biogenic amines. Biogenic amines are a class of low-molecular-weight nitrogen-containing organic compounds. Excessive intake can cause adverse reactions such as migraines and poisoning. Biogenic amines can also react to form carcinogenic nitrosamines, which can cause certain harm to the human body. The biogenic amine content of the finished pickles No. 1-6 prepared in Examples 3-8 was measured, and the results are as follows: Figure 5 shown.

[0083] Depend on Figure 5 As can be seen, the biogenic amine content in kimchi product No. 6 was 309 mg / kg, with tyramine, histamine, and putrescine being the highest. In contrast, the biogenic amine content in kimchi products Nos. 1-4 was lower, reaching a maximum of only 68.1 mg / kg. The biogenic amine content in kimchi product No. 5 was 141.79 mg / kg. This comparison reveals that inoculation with Lactobacillus plantarum has a histamine-degrading effect. Overall, the method used in the present invention is significantly effective in reducing the biogenic amine content in fermented vegetables.

[0084] The above-described embodiments merely represent specific implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of protection of the present application. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the technical concept of the present application, and all such variations and improvements fall within the scope of protection of the present application.

[0085] This background section is provided to generally present the context of the invention, and the work of the presently named inventors, the work to the extent described in this background section, and aspects of the description in this section that did not constitute prior art at the time of filing are neither explicitly nor implicitly admitted to be prior art to the present invention.

Claims

1. A strain of Lactobacillus plantarum JXJ1 was deposited in the General Microbiology Center of the China Culture Collection Administration on March 7, 2025, with the deposit number CGMCC No. 33756. The depository address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences.

2. The Lactobacillus plantarum JXJ1 according to claim 1, wherein The plant lactobacillus has the following characteristics: 1) Salt tolerance, able to grow normally when the salt concentration is ≥8%; 2) Acid-resistant, able to grow normally when pH ≤ 4; 3) Rapid fermentation to produce acid, when the salt concentration is ≥8% and the pH is ≤4, the fermentation can produce acid rapidly, making the acidity ≥0.7%; 4) It can inhibit the growth of harmful microorganisms, block the formation of nitrite, and has a strong ability to degrade biogenic amines.

3. Use of Lactobacillus plantarum JXJ1 as claimed in claim 1 or 2 in degrading nitrite and biogenic amines in fermented vegetables.

4. A microbial agent for degrading nitrite and biogenic amines in fermented vegetables, characterized in that: Contains the Lactobacillus plantarum JXJ1 according to claim 1 or 2.

5. The method for preparing the microbial agent according to claim 4, wherein The following steps are involved: After activation, Lactobacillus plantarum JXJ1 was inoculated into a culture medium at 2% of the total volume and continued to be cultured to obtain a culture solution after expansion; the culture solution after expansion was centrifuged to obtain a bacterial slurry; a protective agent was added to the bacterial slurry, and the bacterial powder was obtained by vacuum freeze-drying; the protective agent included the following raw materials in parts by weight: 12 parts of skim milk powder, 3 parts of sucrose, 2 parts of glycerol, and 2 parts of D-trehalose; the vacuum freeze-drying temperature was -50°C, the vacuum degree was 1 Pa, and the drying time was 30 hours; the freeze-drying survival rate was 85%, and the number of viable bacteria in the powder was 3×10 11 CFU / g.

6. The method for preparing the microbial agent according to claim 5, wherein: The components of the expansion culture medium are: 4.0% glucose, 0.8% yeast powder, 0.6% beef extract, 1.0% peptone, and the balance is water, and the sum of the total mass percentages is 100%; the culture conditions are: the initial pH of the culture medium is 6.5, the culture temperature is 35°C, the shaker speed is 120 r / min, and the culture time is 16 hours; the centrifugation conditions are: temperature 4°C, speed 4500 r / min, and centrifugation time 15 minutes; and the ratio of the protective agent to the bacterial sludge is 1:2 by mass.

7. A method for degrading nitrite and biogenic amines in fermented vegetables, characterized in that The following steps are involved: (1) Raw material pretreatment: Select fresh vegetables that are free of pests and diseases, wash them, dry them, and cut them into pieces for later use; (2) Preparation of organic acid solution: malic acid and citric acid are mixed in a ratio of 1:4 to 4:1 to form an organic acid solution; (3) Acidification treatment: Add the organic acid solution prepared in step (2) to the vegetable raw material pretreated in step (1), stir in a clean blender at a temperature of 25-35° C. and a speed of 10 r / min for 15-30 minutes, and then let it stand for 1-3 hours to fully acidify the raw material; (4) Inoculation and fermentation: adding 1.5%-3% of the microbial agent according to claim 5 or the microbial agent prepared by the method according to claim 6 or claim 7 to the raw material acidified in step (3), adding 1‰-2‰ malic acid and 0.3‰-0.8‰ citric acid and 0.5%-1% glucose as carbon sources, adding 3%-6% of salt based on the total mass of the kimchi, controlling the fermentation temperature at 20-30°C, and fermenting for 6-8 days; (5) Low temperature storage: After fermentation, the product is packaged and refrigerated at 2-6°C.

8. The method for degrading nitrite and biogenic amines in fermented vegetables according to claim 7, wherein: The mass ratio of the pretreated vegetable raw materials in step (1) to the organic acid solution prepared in step (2) is 1:1.5-1:

3.

9. The method for degrading nitrite and biogenic amine in fermented vegetables according to claim 7, characterized in that The method further comprises step (6) of recovering and utilizing the acidified mother liquor: filtering all the liquid remaining after the kimchi is packaged as the mother liquor, and centrifuging at 4000-6000 r / min to obtain an acidic supernatant, which is used for secondary fermentation of vegetables.

10. The method for degrading nitrite and biogenic amine in fermented vegetables according to claim 9, characterized in that The specific operation steps of using the acidic supernatant for secondary fermentation of vegetables are as follows: after the fresh vegetables are treated in steps (1) to (3), 0.8-1.2% of the microbial agent according to claim 5 or the microbial agent prepared by the method according to claim 6 or claim 7 is added, calculated as a percentage by mass, and then 2.5%-3.5% of the acidic supernatant is added, the fermentation temperature is controlled at 20-30° C., and the fermentation is carried out for 6-8 days.

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